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Glucuronidation and deglucuronidation reactions in hepatic and extrahepatic tissues during perinatal development.
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The relative activities of uridine diphosphoglucuronyltransferase (UDPGT) and beta-glucuronidase (betaG) were measured during perinatal development of hepatic and extrahepatic tissues to determine the balance between glucuronidation and deglucuronidation reactions at different developmental stages. Liver, lung, kidney, intestine, and placenta were studied in guinea pigs and rabbits. In general, betaG activities exceeded those of UDPGT in fetal tissues, whereas the converse was evident in adults. There were significant species and age differences in the onset of betaG and UDPGT activities and the occurrence of developmental peaks. A dramatic betaG developmental peak was observed in fetal guinea pig intestine and newborn rabbit intestine. Both microsomal and lysosomal betaG exhibited similar developmental patterns in all tissues tested. Hepatic nonsteroid UDPGT activities were higher at parturition than in adult animals, whereas no such developmental peak occurred for steroid UDPGT. Triton X-100 activated fetal UDPGT in vitro by approximately the same factor as it did for adult UDPGT.
| 17,527
|
In vitro pharmacology of the opioid peptides, enkephalins and endorphins.
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In the guinea-pig ileum methionine-enkephalin, normorphine and morphine are equipotent in depressing electrically evoked contractions; leucine-enkephalin has about 25% of the activity. The mouse vas deferens is more sensitive to the enkephalins which are 30 to 60 times more potent than morphine. Fragments of beta-lipotropin61-91 (beta-endorphin) having sequences up to LPH76 are more potent in the mouse vas deferens than in the guinea-pig ileum but beta-endorphin is about equipotent in the two preparations. None of the peptides has antagonist activity. Methionine-enkephalin and normorphine are equipotent in inhibiting [3H]-naloxone binding by homogenate of guinea-pig brain in the absence of Na+ while leucine-enkephalin has only 25% of this activity. In the guinea-pig ileum, naloxone antagonises normorhine and the enkephalins equally well whereas in the mouse vas deferens about ten times more naloxone is required for the enkophalins that for normorphine. Methionine-enkephalin depresses output of acetylcholine in the guinea-pig ileum and of noradrenaline in the mouse vas deferens.
| 17,538
|
Jejunal mucosal gamma glutamyl transferase activity in coeliac disease.
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In view of data suggesting that deficiency of gamma glutamyl transferase (GGT) may be the primary abnormality in the small-intestinal mucosa of patients with coeliac disease, this enzyme was measured in mucosal biopsies from coeliac patients at different stages of treatment. Activity was only slightly reduced in only one of nine well-treated patients, suggesting that deficiency of this enzyme has no primary role in the aetiology of coeliac disease.
| 17,564
|
Nursing education in crisis: a computer alternative.
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The impact of computer-assisted instruction upon the educational process is having its effect. The computer is being used in nursing education today to manage the educational environment, to instruct, to evaluate, to identify problem areas, to gather data, to manipulate data for research purposes and for continued education. As we struggle in our efforts for quality individualized education, we are minutely scrutinizing every aspect of the teaching learning process. We are not only examining how we teach but what we teach and why we are teaching it! Our deeper understanding of the process of education has helped us to delineate nursing process as content. Higher levels of instructional goals -- cognitive, affective and conative -- are resulting in education of the whole individual. The systematization of the learning process with the greater ease of accountability is leading nursing education to blaze promising new trails into the twenty-first century.
| 17,585
|
In vitro reconstitution of demolybdosulfite oxidase by molybdate.
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Reconstitution of purified demolybdosulfite oxidase from rat liver has been achieved using inorganic molybdate as the source of molybdenum. The activation process has a pH optimum of 7.4 and is dependent on concentrations of molybdate and demolybdoenzyme. The reaction is inhibited by high concentrations of anions and by reduction of the demolybdoenzyme and requires incubation temperatures higher than 30 degrees. A reconstitution mechanism involving loss of tungsten and concomitant replacement with molybdenum in those demolybdo molecules which contain tungsten is supported by the following observations: (a) the extent of activation achieved by molybdate corresponds to the proportion of molecules in the preparation which contain tungsten. (b) Incubation of the demolybdoenzyme preparation at 37 degrees in the absence of molybdate results in progressive and concentration-dependent loss of ability to be reconstituted by molybdate and a corresponding but more rapid loss of tungsten from the enzyme. The reconstituted enzyme displays the molybdenum EPR signal characteristic of native enzyme and is inactivated by incubation at 42 degrees in a manner identical to native sulfite oxidase.
| 17,611
|
Mullerian inhibiting substance in human testes after birth.
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Tiny testicular biopsies from humans were assayed for Mullerian inhibiting Substances using a graded organ culture technique. Mullerian Inhibiting Substance activity was high during the first year of life, declined during the second year of life, and then disappeared. Mullerian Inhibiting Substance activity is lower in boys with undescended testis than in children with normal or intersex testes at comparable ages under two years. It is possible that Mullerian Inhibiting Substance affects testicular descent as well as causing Mullerian duct regression.
| 17,665
|
The in vitro bioavailability of various drugs formulated as hard gelatin capsules.
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A factorially designed experiment has been carried out to study the influence of various additives on the in vitro release of drug from hard gelatin capsules. Analysis of variance confirms previous findings that, although the main factors of diluent type, diluent concentration, the absence and presence of both magnesium stearate and sodium lauryl sulphate, were highly significant, the existence of interactions between the factors prevented exact quantitative prediction of the influence of each factor. There appears however, to be a strong indication that the in vitro drug release of capsule formulations (y), expressed as the % of the drug content of the capsule which dissolves, can be related to the solubility of the drug (cs) by the expression y = 21-2 log cs + 31.2.
| 17,668
|
The interaction between clonidine and various neuroleptic agents and some benzodiazepine tranquillizers.
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The central hypotensive action of clonidine, infused into the vertebral artery of chloralose-anaesthetized cats was antagonized by several phenothiazine-neuroleptics (chlorpromazine, promazine, promethazine, thiethylperazine, thioridazine), by chlorprothixene and to a limited extent by haloperidol administered via the same route. Pimozide and some benzodiazepines (chlordiazepoxide, diazepam and flurazepam) hardly influenced the central hypotensive response to clonidine. The antagonism between clonidine and the psychotropic drugs is probably associated with central alpha-adrenoceptors, clonidine being the agonist and the neuroleptic agents the antagonists at these receptors. Virtually the same type of antagonism was observed in conscious, spontaneously hypertensive rats where both clonidine and the neuroleptic drugs were injected intravenously. The phenothiazines and also piperoxane effectively diminished the centrally induced hypotensive response to clonidine, whereas the initial pressor effect to clonidine was not reduced.
| 17,673
|
The enkephalins and opiates: structure-activity relations.
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The X-ray structures of 9 "opiate" drugs which exhibit a range of pharmacological activity have been examined in detail leading to the theory that one of the reasons why the enkephalins and related peptides possess morphine-like activity is because they have a tyrosine, and hence a "tyramine", residue at the amino terminal position. This residue or a conformationally similar moiety, can be shown to be present in many opiates and analogues.
| 17,687
|
The identification and analysis of mexiletine and its metabolic products in man.
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Sensitive and specific gas-liquid chromatographic methods were developed for the analysis of mexiletine and its metabolites in urine of man. The identity of the g.l.c. peaks was established by mass-spectrometry. The hydroxylamine (Va) was qualitatively identified and determined quantitatively after conversion to the more stable oxime (Vb). Selective extraction procedures, t.l.c. and derivatization with hexamethyldisilazane (HMDS) and trifluoroacetic anhydride (TFA) were used in the qualitative identification of the major metabolites (VI-IX), particularly in distinguishing the basic products VI and VII from their corresponding alcoholic products VIII and IX. The limit of detection of the g.l.c. method was 6 to 12 ng ml-1 for compounds I-IV, and 40 to 50 ng ml-1 for compounds Vb-IX.
| 17,691
|
Determination of aqueous solubility and pKa values of estrogens.
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Reported estrone pKa and solubility data show wide variation. Improved experimental procedures were designed and used to obtain reproducible results. The pKa values for several estrogens and related compounds also were determined to assess the effects of structural differences on ionization. No evidence was obtained for long-range D to A ring electronic transmission affecting pKa. Significant differences in pKa values resulted only when conjugated unsaturation was added into the B ring of estrone or estradiol. The aqueous solubilities of estrone and 17alpha-estradiol were 0.8 and 3.9 microgram/ml, respectively, at 25degrees.
| 17,710
|
Determination of meclizine hydrochloride by ion-pair extraction with methyl orange.
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A method, based on ion-pair extraction, is described for the quantification of meclizine hydrochloride in various pharmaceutical dosage forms, for content uniformity determination, and for concentration monitoring in dissolution and bioavailability studies. Methyl orange, dissolved in pH 2.8 MacIlvaine buffer, gave excellent recovery of meclizine after its isolation from aqueous solutions of gelatin, urine, and blood serum. The chloroform-extracted molecular species appeared to be a 1:1 ion-pair. Beer's law was obeyed for a wide concentration range. Because the extracted species seemed well defined and stable and since a surface or an interphase adsorption phenomenon was not a problem, the reported method is considered sensitive, accurate, precise, rapid, and simple.
| 17,714
|
Recording pH method of characterizing composition and monitoring dissolution profile of an anhydride-acid copolymer and its salt derivatives.
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A sensitive potentiometric monitoring method was developed that permits the continuous measurement of the disolution profiles of methyl vinyl ether-maleic anhydride-acid copolymers and salt derivatives. Three distinct rate periods were observed in the dissolution rate of the anhydride copolymer, expressed as percent anhydride dissolved, was independent of sample weight over the weight range studied. The acid form of the copolymer showed only one dissolution rate period, with dissolution being very rapid. The rapid initial pH decrease observed during the first stage of dissolution for a series of anhydride-acid copolymer powder samples correlated closely with the anhydride-acid ratio, permitting chemical characterization of the copolymer functionality simultaneously with the analysis of dissolution profiles. Similarly, the extent of copolymer alkaline salt conversion was inversely proportional to the initial maximum pH increase observed during the first stage of dissolution of these salts. Mechanisms of dissolution of copolymer powder materials are discussed and compared to the dissolution of compressed disks and films reported previously.
| 17,715
|
Kinetics of luminal acidification in cortical tubules of the rat kidney.
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1. Some kinetic aspects of renal tubular acidification were studied in proximal and distal tubules of the rat kidney by combining stationary microperfusion methods and continuous measurements of luminal pH changes of phosphate or bicarbonate buffers by means of antimony electrodes. The analysis included the measurement of steady-state pH, steady-state buffer concentrations and acidification half-times. From these data, net rates of tubular bicarbonate reabsorption and of H ion secretion were obtained since it was shown that the rate of phosphate acidification provides a realistic estimate of H ion secretion. 2. Experiments were performed in control rats, in animals undergoing metabolic acidosis or alkalosis and in control and acidotic rats receiving the carbonic anydrase inhibitor Diamox. 3. In all experiments, the rates of tubular bicarbonate reabsorption and of phosphate acidification (H ion secretion) were proportional to luminal buffer levels. The changes of luminal acid concentrations followed first-order kinetics. 4. Steady-state transepithelial pH differences were reduced in metabolic alkalosis and after diamox but augmented during metabolic acidosis. 5. Acidification half-times were prolonged in metabolic acidosis and after Diamox but remained similar to control levels in metabolic alkalosis. 6. From the observation that both bicarbonate reabsorption and phosphate acidification are similarly affected by these experimental manoeuvres, it is concluded that H ion secretion plays a key role in both transport processes.
| 17,736
|
Hyperpolarizing effects of dopamine on chemoreceptor nerve endings from cat and rabbit carotid bodies in vitro.
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1. The effects of dopamine on DC potential changes recorded from the carotid sinus nerve were studied in vitro using carotid bodies and associated sinus nerves removed from anaesthetized cats and rabbits.2. The carotid body was placed in one compartment of a superfusion chamber and was superfused with buffered salt solution. The carotid sinus nerve was led into an adjoining compartment, containing lightweight mineral oil, for recording DC potential changes with chlorided silver electrodes.3. Dopamine injected into the superfusing solution in amounts of 50-250 mug caused hyperpolarization of the DC potential. This effect occurred repeatedly in each preparation, the maximum number of tests in any one preparation being twenty-seven.4. In the same preparations, acetylcholine (50-100 mug) and NaCN (10-20 mug) caused depolarizations of the DC potential, effects that have been described by others.5. The hyperpolarizing effects of dopamine were reduced or abolished by the alpha-adrenergic antagonists, dihydroergotamine (10-100 mug/ml.) and phenoxybenzamine (5 mug/ml.) and the dopamine antagonist droperidol (10-25 mug/ml.).6. The results indicate that the inhibitory effects of dopamine on the frequency of carotid body chemosensory discharges in cats and rabbits are due to hyperpolarization of chemoreceptor afferent nerve endings and not necessarily to local vascular effects in the carotid body.
| 17,742
|
[Study of the nature of the associated microflora in the prolonged substrateless cultivation of beet plants].
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The purpose of the present investigation was to study variations in the population density of microorganisms, their qualitative and quantitative composition during substrate-free cultivation of beats. The results obtained show that the microbial number in the nutrient solution increased by the time of intensive growth of beats and decreased by the time of harvesting. The number of root microorganisms was much greater than the total number of microorganisms in the nutrient solution. Oligonitrophils and nitrogen fixing bacteria were found in the solution. This may be associated with a transient decrease of nitrogen in the solution. The number of ammonifiers and denitrifiers in the solution increased significantly by the end of plant vegetation; the amount of denitrifiers inhabiting the roots decreased during vegetation and that of ammonifiers increased. In the middle of vegetation cellulose decomposing aerobes appeared; this might occur since root hairs began to die off. By the end of vegetation an insignificant amount of fungi was also found. Nitrifying and spore-forming microorganisms were not detected. The identification of predominant microbial species showed them to be bacteria of the genera Pseudomonas and Mycobacterium. Besides, microorganisms of the genera Bacterium, Micrococcus, Mycococcus, Chromobacterium and Pseudobacterium also occurred.
| 17,774
|
[Thoracic injury and fat embolism].
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The authors state that fat embolism occurs rather frequently following thoracic injuries. It is difficult to make a diagnosis because of the complexity of the symptoms. The correct evaluation of the characteristic clinical and laboratory signs arising after a period free of symptoms is essential. The authors outline the brief case history of a successfully treated patient, who recovered, owing to the use of the respirator in the intensive care unit.
| 17,782
|
[Management of mass injuries in railway accidents].
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Authors write up the experiences they gained at repeated train accidents on the same section of railway line. The circumstances of the two accidents are evaluated and analysed. The experiences they obtained at the first accident were put to use the second time. The authors stress that the growing number of mass accidents makes it necessary to prepare an alarm and provision plan for every institution.
| 17,788
|
Non-equilibrium freezing behaviour of aqueous systems.
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The tendencies to non-equilibrium freezing behaviour commonly noted in representative aqueous systems derive from bulk and surface properties according to the circumstances. Supercooling and supersaturation are limited by heterogeneous nucleation in the presence of solid impurities. Homogeneous nucleation has been observed in aqueous systems freed from interfering solids. Once initiated, crystal growth is ofter slowed and, very frequently, terminated with increasing viscosity. Nor does ice first formed always succeed in assuming its most stable crystalline form. Many of the more significant measurements on a given systeatter permitting the simultaneous representation of thermodynamic and non-equilibrium properties. The diagram incorporated equilibrium melting points, heterogeneous nucleation temperatures, homogeneous nucleation temperatures, glass transition and devitrification temperatures, recrystallization temperatures, and, where appropriate, solute solubilities and eutectic temperatures. Taken together, the findings on modle systems aid the identification of the kinetic and thermodynamic factors responsible for the freezing-thawing survival of living cells.
| 17,872
|
[Proof of guanylate cyclase activity in the coronary artery of cattle].
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Guanylate cyclase activities were identified in a soluble fraction and a particular fraction obtained from the Arteria coronaria of cattle. The Km-value was 1.0 +/- 0.7 - 10(-4) M for the enzyme substrate complex of the guanylate cyclase of the soluble fraction and 9.2 +/- 1.5 - 10(-4) M for the particular fraction. For the enzyme activity of the soluble fraction Mn++ cannot be replaced by Ca++ or Mg++, whereas for the enzyme activity of the particulate fraction Mn++ can be replaced by Mg++ but not by Ca++. The guanylate cyclase of the particulate fraction can be activated by acetylcholine. This activation can be cancelled by atropine. Acetylcholine exerts no influence on the guanylate cyclase activity of the soluble fraction. ATP inhibits the enzyme activities of both fractions whereas cAMP shows no influence on the guanylate cyclase activity.
| 17,986
|
Bacteremia in hospitalized children.
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The results of 6,951 blood cultures taken from hospitalized children are reviewed. One or more organisms grew from 6% (399) of the cultures, of which 189 (two thirds) were considered to represent confirmed bacteremia. The most common organisms associated with bacteremia were Haemophilus influenzae, Streptococcus pneumoniae, enterobacteriaceae, and Staphylococcus aureus. Patients with deficient host defenses (newborns, oncology patients) with bacteremia had a higher mortality than normal children. Laboratory techniques allowing more rapid detection of positive blood cultures resulted in major alterations in therapy in almost one half of all bacteremic patients.
| 18,005
|
Function of human platelets during extracorporeal circulation.
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The interaction between human platelets and nonbiologic surfaces was studied during in vitro recirculation of 500 ml of fresh, heparinized human blood in four different perfusion circuits. Circuits differed in surface area (0.1 m2 or 0.9 m2) and in surface composition. No important differences were observed between standard silicone-rubber and filler-free, silicone-rubber surfaces. Platelet counts decreased to 85% of control in 0.1- m2 circuits, but retained normal sensitivity to aggregating agents and released only small amounts of platelet factor 4 (PF4). In contrast, platelet counts in 0.9-m2 circuits decreased to 20% of control within 2 min and platelet sensitivity was depressed out of proportion to the fall in platelet count. Plasma PF4 progressively increased and platelet PF4 content progressively decreased during 6 h of recirculation. The results indicate that human platelets may exist in three conditions during extracorporeal circulation. Some platelets are unaltered, some are less sensitive to aggregating agents, and others have undergone extensive release. The ratio of blood volume to surface area appears to be an important determinant of platelet-surface interaction.
| 18,017
|
[Dependence of diverticulosis on age (author's transl)].
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The diverticulosis of the gastrointestinal tract is a widespread senile disease. The dependence of the diverticulosis on age is investigated on the basis of 1 000 proven cases of this disease. The importance of the anatomicomorphological lesions of the organs at old age as its cause is pointed out. The males seem to be affected by the diverticulosis somewhat more than the females, whereas its percental manifestation in the different organs is about equal for both sexes. It prevails in the colon with 48.4% and in the duodenum with 35.4% of all cases of organ diverticulosis. The existence of constitutional associations with other diseases, such as diabetes mellitus, is discussed. Finally, the therapeutic problems of the diverticulitis and their dependence on age are examined.
| 18,032
|
Age-dependent alterations of the rate of RNA synthesis in rat brain cell nuclei.
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Endogenous Mn2+ and Mg2+ activated RNA polymerase activity was measured in isolated cell nuclei of brain from rats of different age-groups. It was established that the activity of the nucleoplasmic RNA polymerase is maintained at the level of young animals up to an age of 16 months but is decreased after 24 months. The nucleolar RNA polymerase activity decreases already at 16 months and a higher ratio of the Mn2+:Mg2+ activated RNA polymerase activities has been found to be characteristic for the older animals. By means of stepwise sucrose density gradient centrifugation fractions were obtained from the nuclear preparations highly enriched in cell nuclei of neuronal and glial origin respectively. By measuring the activity of the nucleoplasmic and nucleolar RNA polymerases in these fractions it was found that the elevated ratio of the nucleoplasmic to nucleolar RNA polymerase activity at 16 months of age is a characteristic of the neuronal nuclei while the glial nuclei behave by the opposite manner. A parallelism existing between the age-dependent change of the endogenous RNA polymerase activity and that of perichromatic granules of rat brain cortical cells is discussed.
| 18,035
|
[Hydroxylation of skin collagen in relation to age: analyses of the human skin].
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The results of human skin analysis are demonstrated. It has been pointed out, that the content of hydroxyproline and hydroxylysine, in addition to the usual variation as the other aminoacids varies extensively. The extent of hydroxylation was estimated from the relation of OH-aminoacids to (not hydroxylated) each other. The determined variation of the results is most probably due to a different collagen hydroxylation within the biological dispersion. An age-related degree of hydroxylation could not be detected.
| 18,040
|
[Behavior therapy in disorders of dietary behavior].
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Behaviour therapies using conditioning principles have been successful in the treatment of some psychopatological eating behaviours. Such have been the cases for anorexia nervosae in adolescents and adults, refusal to eat in the young child and difficulties of swallowing. Some of these cases are described. Research has been done in different countries on the applications of these methods to the treatment of obesity caused by overeating which appears very frequently in our societies. Systematic and covert desensitization and operant conditioning using positive reinforcements are more frequently used in these behaviour modification procedures than aversive methods. More recently, researches on self-control (self-reward and self-punishment) have shown it as a very efficient tool for inducing weight loss. These methods using self-control have been applied to large populations: after a first, careful examination of the patient's eating behaviour, the program of reinforcement is established. It can be partially controlled by written instructions and letters. Results are already encouraging although they need to be followed up. But more research should be done on overeating behaviours, the way they appear and are maintained and on different programs of reinforcement for weight loss.
| 18,079
|
Azlocillin: in vitro studies of a new semisynthetic penicillin.
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The activity of azlocillin, a new semisynthetic penicillin, was determined against 582 clinical isolates of gram-negative bacilli and gram-positive cocci. Over 75% of the isolates of Pseudomonas aeruginosa were inhibited at a concentration of 12.5 mug or less per ml. Azlocillin is also active against indole-negative and -positive Proteus spp., inhibiting 98 and 71%, respectively, at a concentration of 12.5 mug or less per ml. Isolates of Klebsiella spp. and Enterobacter spp. showed less susceptibility than isolates of Escherichia coli and Serratia spp. Gram-positive cocci except penicillin G-resistant Staphylococcus aureus were susceptible to azlocillin. Azlocillin failed to inhibit the growth of gram-negative bacilli when large inocula were used. It was more active in alkaline pH, but the type of medium used had little effect on its activity. Azlocillin was more active than mezlocillin, ticarcillin, and carbenicillin and as active as BLP-1654 against isolates of P. aeruginosa. It was not as active as mezlocillin against the majority of the other gram-negative bacilli.
| 18,083
|
Inheritance of muscle and liver types of supernatant NADP-dependent isocitrate dehydrogenase in rainbow trout (Salmo gairdneri).
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The genetics of allelic variation for NADP-dependent isocitrate dehydrogenase (IDH-s) found in the supernatant of liver and white muscle extracts of rainbow trout (Salmo gairdneri) was examined. Twenty progeny from each of 50 controlled matings were examined for IDH phenotypes. Progeny data clearly indicated that the IDH-s variation in the muscle is controlled by two loci--one fixed and one with two alleles producing molecules of different electrophoretic mobilities. IDH-s variation in the liver is controlled by two disomic loci which code for four alleles. No linkage between the loci controlling IDH-s in the liver and the loci controlling it in the muscle was detected.
| 18,132
|
Purification and properties of urease from bovine rumen.
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Urease (urea amidohydrolase, EC 3.5.1.5) was extracted from the mixed rumen bacterial fraction of bovine rumen contents and purified 60-fold by (NH4)2SO4 precipitation, calcium phosphate-gel adsorption and chromatography on hydroxyapatite. The purified enzyme had maximum activity at pH 8.0. The molecular weight was estimated to be 120000-130000. The Km for urea was 8.3 X 10(-4) M+/-1.7 X 10(-4) M. The maximum velocity was 3.2+/-0.25 mmol of urea hydrolysed/h per mg of protein. The enzyme was stabilized by 50 mM-dithiothreitol. The enzyme was not inhibited by high concentrations of EDTA or phosphate but was inhibited by Mn2+, Mg2+, Ba2+, Hg2+, Cu2+, Zn2+, Cd2+, Ni2+ and Co2+. p-Chloromercuribenzenesulfphonate and N-ethylmaleimide inhibited the enzyme almost completely at 0.1 mM. Hydroxyurea and acetohydroxamate reversibly inhibited the enzyme. Polyacrylamide-gel electrophoresis showed that the mixed rumen bacteria produce ureases which have identical molecular weights and electrophoretic mobility. No multiple forms of urease were detected.
| 18,137
|
Purification and properties of the NAD(P)H:nitrate reductase of the yeast Rhodotorula glutinis.
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The assimilatory nitrate reductase from the yeast Rhodotorula glutinus has been purified 740-fold, its different catalytic activities have been characterized and some inhibitors studied. The purified enzyme (150 units per mg protein) contains a cytochrome of the b-557 type. An S20,w of 7.9 S was found by the use of sucrose density gradient centrifugation, and a Stokes radius of 7.05 nm was determined by gel filtration. From these values, a molecular weight of 230 000 was estimated for the native enzyme. The purified preparation consisted of two electrophoretically distinguishable proteins, both of which exhibited nitrate reductase activity. The species with the higher electrophoretic mobility which represented the great majority of the total nitrate reductase gave a positive stain for heme and was shown to be composed of subunits with a molecular weight of about 118 000. Thus the molecule contains two subunits of the same size.
| 18,182
|
On the determination of isozyme levels in preparations containing cytoplasmic and mitochondrial aspartate aminotransferase.
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A spectrophotometric assay has been developed for the determination of the content of each isozyme of aspartate transaminase (L-aspartate:2-oxoglutarate aminotransferase, EC 2.6.1.1) in physiological fluids or tissue extracts. The methods relies on the ability of adipate, at low pH and ionic strength to inhibit the cytoplasmic isozyme but not the one from mitochondria. Two assays are necessary, one at pH 8.0 which measures the content of both isozymes and another at low pH which measures primarily the amount of mitochondrial isozyme. Results obtained by this simple procedure match those in which each isozyme is inhibited by its antibody. The validity of the results obtained by the new method was tested at different ratios of cytoplasmic:mitochondrial isozyme and with tissue extracts. Since the amounts of each isozyme determined by radial immunodiffusion match those values gathered by following enzymatic activity, it is concluded that the quantity of each isozyme obtained from its respective catalytic activity must represent the total protein content of each isozyme in a given sample.
| 18,183
|
Concerted inhibition of NADP+-specific isocitrate dehydrogenase by oxalacetate and glyoxylate. I. Oxalomalate formation and stability, and nature of the enzyme inhibition.
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Oxalacetate and glyoxylate are each weak inhibitors of NADP+-specific isocitrate dehydrogenase (threo-DS-isocitrate:NADP+ oxidoreductase (decarboxylating), EC 1.1.1.42)9 Together, however, they act in a concerted manner and strongly inhibit the enzyme. The rates of formation and dissociation of the enzyme inhibitor complex, and the rate of formation and the stability of the aldol condensation product of oxalacetate and glyoxylate, oxalomalate, were examined. The data obtained do not support the often suggested possibility that oxalomalate, per se, formed non-enzymatically in isocitrate dehydrogenase assay mixtures containing oxalacetate and glyoxylate, is responsible for the observed inhibition of the enzyme. Rather, the data presented in this communication suggest that oxalacetate binds to the enzyme first, and that the subsequent binding of glyoxylate leads to the formation of a catalytically inactive enzyme-inhibitor complex.
| 18,195
|
Partial purification and some properties of gamma-glutamyl transpeptidase from human bile.
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1. Gamma-Glutamyl transpepetidase ((5-glutamyl)-peptide: amino acid 5-glutamyltransferase, EC 2.3.2.2) from human bile has been partially purified using protamine sulphate treatment, DEAE-cellulose chromatography and Sephadex G-200 filtration. The procedure resulted in 150-fold increase in specific acitivity with a 37% yield. 2. The partially purified enzyme showed a single zone of enzyme activity by polyacrylamide gel electrophoresis and eluted in the inner volume of Sephadex G-200. 3. The enzyme had a pH optimum of 8.1 and Km of 1.52 mM using gamma-glutamyl p-nitroanilide as substrate. 4. The effects of cations and different gamma-glutamyl acceptors on the activity of the enzyme are reported. 5. As bile gamma-glutamyl transpeptidase appears to be soluble in the absence of detergents, it is suggested that bile may prove to be a useful source for further studies of the kinetic properties and physiological role of human gamma-glutamyl transpeptidase.
| 18,198
|
Purification and properties of a triacylglycerol lipase from Mycobacterium phlei.
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In order to study the metabolism of triacylglycerol in mycobacteria, an intracellular particulate triacylglycerol lipase (EC 3.1.1.3) was purified 800-fold from stationary phase cells of Mycobacterium phlei. Extraction of whole cell suspensions with 5% Triton X-100, followed by ion-exchange chromatography of the extract on two successive DEAE-cellulose columns produced a preparation which was nearly homogeneous by the criterion of analytical isoelectric focusing in acrylamide gels (one band, pI. 3.8) and by polyacrylamide gel electrophoresis. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis resolved the preparation into six protein bands. Lipase activity stable to electrophoresis in sodium dodecyl sulfate was extracted from the 40 000 molecular weight region of the gels. ith phosphate or maleate buffer the enzyme exhibits a broad pH optimum around 6.0 with sigmoid saturation kinetics (Hill number 2), and an apparent Km of 8.8 mM for tripalmitoylglycerol. Citrate and other carboxylic acids increase the apparent V up to 3-fold with the Hill number approaching 1.0. In a series of p-nitrophenyl esters tested (C2-C18), p-nitrophenylmyristate was hydrolyzed most rapidly. The saturation curve for p=nitrophenylmyristate was sigmoid and unaffected by citrate. The role of this activity in the metabolism of triacylglycerols by Mycobacteria is discussed.
| 18,200
|
Characteristics of a cytochrome P-450-dependent fatty acid omega-2 hydroxylase from bacillus megaterium.
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The fatty acid (omega-2) hydroxylase from Bacillus megaterium ATCC 14581 was examined with respect to some general enzymatic properties attributed to an intact complex isolated in a partially purified state. Hydroxylase specific activity was found to increase with increasing protein concentration in a manner consistent with a reversible association of the components in the complex. There was a substantial kinetic lag phase for palmitate hydroxylation which was abolished by a substrate preincubation in the absence of NADPH. The substrate bound and presumably activated the hydroxylase complex without the formation of a substrate-derived intermediated. The oxidation of NADPH and the hydroxylation of palmitate were found to occur in a one to one molar ration, independent of the protein concentration. Finally, a cytochrome P-450 component of the complex was identified on the basis of its CO-binding difference spectrum. It appears, that this cytochrome P-450 component is not identical to P-450 meg of the steroid hydroxylase system of B. megaterium ATCC 13368, since progesterone, an active substrate for the latter, is not hydroxylated by the preparation from B. megaterium ATCC 14581.
| 18,202
|
Amperometric assay of coenzyme-dependent oxidoreductase enzymes in a flow-through cell.
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We have demonstrated that a simple electrochemical cell can serve as a detector of NADH concentration in a flow system thereby providing an assay technique for NADH dependent enzymes. When this is applied to NADH produced by enzymatic reaction, then a reproducible measure of enzyme activity is obtained. This method of enzyme activity assay is applicable to a number of oxidoreductase enzymes which employ NAD+ or NADP+ as coenzymes to achieve substrate modification. The presence of electroactive species in samples of human serum has proved a serious problem in the electrochemical analysis of serum activity. These species produce a large background anode current at the anode voltage appropriate for NADH oxidation. The presence of this high current limits the usefulness of amplification of the current output to detect small changes in NADH concentration.
| 18,231
|
[Inactivation of stem cells by allogenic lymphocytes: competition between T1- and T2-subpopulations].
|
Transplantation of the bone marrow cells with allogeneic T-lymphocytes to the irradiated hosts was accompanied by inactivation of the stem elements of the graft. The lymph node cells of T-mice (those deprived of B cells) were more active than the spleen cells of these mice. The stem cells inactivation was weakly expressed or absent in case of a combined acti-n of T-cells from the lymph nodes and the spleen.
| 18,238
|
The use of functional antagonism to determine whether beta-adrenoceptor agonists must have a lower efficacy than isoprenaline to be trachea-atria selective in vitro in guinea-pigs.
|
1 The relative efficacies of three trachea-atria selective beta-adrenoceptor agonists, fenoterol, Me 506 and Me 454, compared to isoprenaline, were determined on both trachea and atria of guinea-pigs. 2 On tracheal preparations the beta-adrenoceptor agonists were used as functional antagonists of carbachol and a comparison of the maximum shifts in the carbachol concentration-response line produced by each of the beta-adrenoceptor agonists provided a comparison of their efficacies. 3 On atrial preparations carbachol was used as a functional antagonist of the beta-adrenoceptor agonists and comparison of the maximum responses to the beta-adrenoceptor agonists in the presence of carbachol provided a comparison of their efficacies. 4 On trachea and atria the order of efficacy of the compounds was Me454 greater than Me506 greater than or equal to isoprenaline=fenoterol. 5. The results indicated that high efficacy in a non-catechol beta-adrenoceptor agonist is possible provided there is a favourable N-substituent group. 6 Since Me 454, Me 506 and fenoterol, which are trachea-atria selective, have effficacies equal to or greater than that of isoprenaline, which is non-selective, it is concluded that low efficacy in a compound is not essential for it to show trachea-atria selectivity in vitro in guinea-pigs.
| 18,249
|
Characteristics of potassium ion transport in pea cotyledon mitochondria isolated by a zonal technique.
|
Methodology was developed for measurement of K+ transport in pea cotyledon mitochondria isolated by zonal centrifugation. The valinomycin-mediated transport process required respiratory energy from Krebs cycle intermediates and was completely reversible in the absence of oxygen. The rate and extent of uptake were dependent on the presence of proton-conducting anions (with acetate plus phosphate being most effective), well-coupled mitochondria, and on the K+ concentration.
| 18,268
|
The tricarboxylic and acid pathway in Desulfovibrio.
|
Strains of two species of Desulfovibrio were examined for enzymes of the tricarboxylic acid cycle and related pathways. Pyruvate carboxylase (EC6.4.1.1) is present, and alpha-ketoglutarate is formed via the tricarboxylic acids. Glutamate, but not succinyl-CoA, arises from alpha-ketoglutarate. A pathway exists from pyruvate by malic enzyme (EC 1.1.1.39) activity to malate, then fumarate and succinate, again with no evidence of succinyl-CoA formation. The enzymes concerned with metabolism of these dicarboxylic acids show greater activity in the strains that can grow by fumarate dismutation. Glutamate (or glutamine), alpha-ketoglutarate, and yeast extract repress the enzymes that metabolize the tricarboxylic acids. There appears to be no glyoxylate cycle in Desulfovibrio vulgaris or D. desulfuricans.
| 18,274
|
Weekly methotrexate-calcium leucovorin rescue: effect of alkalinization on nephrotoxicity; pharmacokinetics in the CNS; and use in CNS non-Hodgkin's lymphoma.
|
Urinary alkalinization with oral sodium bicarbonate has decreased the incidence of acute nephrotoxicity and subsequent myelotoxicity in 18 adults receiving high-dose methotrexate with calcium leucovorin rescue (MTX-LCV) weekly in doses of 1-7.5 g/m2. Close monitoring of 24-hour serum creatinine and MTX levels can predict patients at risk for serious toxicity. By a prompt (24-36 hours) increase in the LCV dose rate, hematologic and biochemical evidence of myelosuppression has been prevented. Kinetic parameters in serum and lumbar cerebrospinal fluid (CSF) were studied in two patients following iv injection of 3 and 7.5 g/m2 respectively. Lumbar CSF MTX concentrations greater than 1 muM are achieved. The half-life of MTX in the CSF (11.95 hours) is twice as long as the serum half-life. In the presence of carcinomatous meningitis, further delay in the clearance of MTX from the CSF was seen. With weekly MTX-LCV, there have been four objective responses in six patients with non-Hodgkin's lymphoma in CNS relapse, including complete regression in two. It is suggested that therapeutic concentrations can be achieved in the central nervous system following MTX-LCV.
| 18,282
|
[Interaction of thymic cells and hemopoietic stem cells. Enhancing effect on irradiated thymus repopulation].
|
In irradiated mice engrafted with hemopoietic cells, the thymus is repopulated more rapidly by bone marrow-derived than by spleen-derived cells. Admixing thymic cells with the restorative suspension stimulates the thymic repopulation by spleen-derived cells whereas it has no effect on the repopulation by bone marrow-derived cells.
| 18,294
|
Properties of the thyroxine (T4) monodeiodinating system in rat liver homogenate.
|
The monodeiodination of T4 in rat liver homogenate was studied. The two possible products of this reaction show very different properties. The metabolically very active T3 is rather stable in this system whereas the biological inactive reverse T3 (rT3) disappears very rapidly. This explains the low apparent rT3 production in the incubation mixture even under optimal conditions and the peculiar pH profile. The T4 to T3 converting reaction can be increased by the addition of mercaptoethanol to the medium; no further activation is possible by several cofactors tested. The apparent KM of the reaction is 1.6 x 10(-6) M. Reverse T3 does inhibit the reaction non competitive; Ki = 2 x 10 (10-8) M. Alpha-methyl-para-tyrosine, a specific inhibitor of tyrosine hydroxylase, has no significant effect on the reaction.
| 18,299
|
A new method for peptidase activity measurement in serum and tissues, using L-Leu-L-Leu as substrate.
|
Peptidase-free L-amino-acid oxidase was purified from venom of Agkistrodon caliginosus and was used for the determination of serum peptidase (EC 3.4.1.-) activity with L-Leu-L-Leu as substrate. The peptidase activity in human serum rose remarkably in liver diseases, and had a significant correlation with serum transaminase activity. The peptidase activity in serum of rats treated with CCl4 was higher than that of normal rats. After Cellogel electrophoresis the zymogram of peptidase from human liver using di- or tripeptide as substrate appeared with three active bands; however, peptidase in serum of a patient with acute hepatitis showed only one active band.
| 18,304
|
Testicular androgen binding protein (ABP) - a parameter of Sertoli cell secretory function.
|
Using ABP as an index of Sertoli cell secretory function, several important features of the Sertoli cell have emerged: 1. The stimulation of ABP production by FSH clearly points to the Sertoli cell as a target cell for FSH (3,4,9-16,21,24). 2. The dramatic effects of androgens on ABP production both in immature and mature rats also suggest that the Sertoli cell is a target cell for androgen (3,12,14,16,25). 3. The striking reduction in ABP production in the cryptorchid testis raises the question whether impairment of Sertoli cell function is the primary reason for the loss of germ cells that occurs in this condition (20). 4. Drugs like nitrofurazone or ethionine, or X-irradiation only slightly affect the secretory function of the Sertoli cells (ABP production), indicating that these treatments most probably have direct effects on the germ cells as well. Thus, measurement of ABP production rate is a very important tool in order to evaluate how hormones, drugs and physical injuries might affect the secretory function of the Sertoli cell. This test system might be of great use in order to study the physiology and hormonal regulation of the Sertoli cells. It might also be valuable in pharmacological and toxicological studies.
| 18,322
|
Nickel cytochrome c. Effect of protein moiety on the metal ion coordination.
|
Nickel cytochrome c has been synthesized by the reaction of metal-free porphyrin cytochrome c with Ni(II) ions in 0.6 Mglycylglycine and 4 M KSCN. Electronic spectra and susceptibility measurement showed the nickel to be in a high-spin octahedral configuration exemplifying the strong influence of the protein moiety as a macrocyclic ligand on the coordination chemistry of the metal ion. Nickel cytochrome c has the same electrophoretic mobility, helicity and pK values of conformational transitions as the native enzyme. At high pH, the partially denatured nickel cytochrome c becomes dimeric. Nitric oxide reacts with nickel cytochrome c to form the nitrosyl derivative with (formula: see text). Reaction of NO with nickel protoporphyrin IX dimethyl ester in toluene, pyridine, or methylthioethanol produced no stable nitrosyl products, clearly demonstrating the effect of protein on metal ion ligation.
| 18,352
|
Phosphate uptake and involvement of binding protein in Tween-80 supplemented culture of Aspergillus fumigatus.
|
Tween-80 supplementation in submerged culture of Aspergillus fumigatus resulted in an increase of phosphate uptake. The uptake system was characterized as saturable, energy-dependent and operating against the concentration gradient. Control and Tween 80 cultures showed similar Km values for phosphate uptake (50 micrometer). Cold osmotic shock treatment of the cultures was found to cause considerable reduction in the ability to take up phosphorus with concomitant release of the binding protein into the shock fluid. Binding protein preparation from Tween-80 supplemented cells showed more activity than that from control cells.
| 18,385
|
[Purification and properties of the tetrahydropteroylglutamate methyltransferase from green beans (Phaseolus vulgaris) (author's transl)].
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The tetrahydropteroylglutamate methyltransferase from green beans (Phaseolus vulgaris) has been purified 80-fold by ion exchange chromatography and gel filtration. Optimal methyl transfer is found at pH 6.5 and 39 degrees C. Even at 0 degrees C, however, a considerable catalytic rate is observed. The Michaelis-Menten constants for homocysteine and 5-methyltetrahydropteroylglutamate are 0.43mM and 2.4 mM, respectively. Magnesium ions enhance the activity. Even purified preparations appear to contain traces of magnesium ions firmly bound, since a residual activity is found without addition of magnesium salts. Though the reaction requires anaerobiosis, an excess of reducing agents is inhibitory. The molecular weight of the transferase, determined by gel filtration, is 40 000 +/- 6%.
| 18,397
|
Testosterone production and metabolism in laboratory-maintained male rhesus monkeys.
|
Plasma production rates (PR), metabolic clearance rates (MCR) and plasma levels of testosterone were determined in 10 male, laboratory-maintained rhesus monkeys on two occasions out-of-season (April and August) and once in-season (October). Plasma testosterone levels in October were higher than those in April and August. The plasma PR was unchanged in August, but markedly increased in October, as compared to April. The MCR showed a parallel increase betueen August and October. Thus changes in testosterone production and metabolism can be observed between in- and out-of-season male rhesus monkeys, maintained under strict laboratory conditions. These changes must be taken into consideration when the male rhesus minkey is used as an experimental model for human reproductive endocrinology.
| 18,415
|
Pituitary and ovarian response to acute stimulation with LH-RH in normal and anovulatory women.
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The LH FSH estradiol and progesterone responses to acute stimulation with LH-RH were studied in 12 normal women with ovulatory cycles (4 in the initial follicular phase, 4 in the mid-follicular phase and 4 in the late follicular phase) and in two castrated women, two under hormonal contraception, two with ovarian amenorrhea, twelve with central amenorrhea of no detectable origin (6 with normal and 6 with low basal gonadotrophins), eleven anovulatory patients with pseudomenstruation, two with anorexia nervosa, and two with pituitary amenorrhea. Each woman received a rapid i.v. injection of 100 microgram synthetic LH-RH at 9:00 a.m. Serum levels of LH, FSH, estradiol and progesterone were determined by radioimmunoassay in samples collected before and 60, 120, 240 and 480 minutes after injection. The findings were : 1) A significant rise in estradiol and progesterone levels, in addition to LH and FSH elevation, in normal women; 2) A lack of ovarian steroid response in the castrated women and in ovarian amenorrheas, which suggests that the source of steroid response to stimulation is not extragonadal; 3) Significant differences in the responses of the four hormones to LH-RH in the women with central amenorrhea in comparison with the normal group with great variability of results; the steroid response in the presence of a positive LH response might correlate with the severity and/or prognosis of the disorder, a point deserving further study; 4) In anovulatory women with pseudomenstruation, LH responses for the most part normal, and particularly, progesterone responses.
| 18,416
|
Interpretation of thermal perturbation spectra of proteins.
|
The thermal perturbation difference spectrum of reduced lysozyme has a long wave length extremum at 304 nm at pH 6.15 and a very small extremum at 306 nm at pH 1.5. These results differ from those of Leach & Smith (1972), which showed an extremum at 293 nm, the same as for model tryptophyl compounds. Our result may arise from a conformational difference between the two sample temperatures. The interpretation of thermal perturbation spectra of proteins is discussed. Contributions from thermally induced concentration differences, buried chromophores, and chromophores in crevices are considered in the interpretation of the thermal perturbation spectrum of bovine serum albumin. It is suggested that chromophores in pauci-aqueous crevices may appear buried toward thermal perturbation spectroscopy but accessible toward solvent perturbation and chemical reagents.
| 18,420
|
Chemical modifications of ribonuclease U1.
|
In order to obtain information on the nature of the amino acid residues involved in the activity of ribonuclease U1 [EC 3.1.4.8], various chemical modifications of the enzyme were carried out. RNase U1 was inactivated by reaction with iodoacetate at pH 5.5 with concomitant incorporation of 1 carboxymethyl group per molecule of the enzyme. The residue specifically modified by iodoacetate was identified as one of the glutamic acid residues, as in the case of RNase T1. The enzyme was also inactivated extensively by reaction with iodoacetamide at pH 8.0 with the loss of about one residue each of histidine and lysine. When RNase U1 was treated with a large excess of phenylglyoxal, the enzymatic activity and binding ability toward 3'-GMP were lost, with simultaneous modification of about 1 residue of arginine. The reaction of citraconic anhydride with RNase U1 led to the loss of enzymatic activity and modification of about 1 residue of lysine. The inactivated enzyme, however, retained binding ability toward 3'-GMP. These results indicate that there are marked similarities in the active sites of RNases T1 and U1.
| 18,450
|
The activity of the pneumococcal autolytic system and the fate of the bacterium during ingestion by rabbit polymorphonuclear leukocytes.
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The extent to which autolytic microbial enzymes are involved in the fate of microorganisms ingested by phagocytes has not been determined. It is known, however, that activation of degradative enzymes occurs during certain microbicidal events. We examined the possible role of the pneumococcal autolytic enzyme (an N-acetylmuramyl-L-alanine amidase) in the loss of viability and degradation of pneumococci during phagocytosis by rabbit polymorphonuclear leukocytes. Three bacterial systems were compared: (a) wild type pneumococci with an active autolytic system; (b) wild type bacteria grown under conditions that block the endogenous autolytic activity and (c) a mutant strain defective in the major autolytic enzyme of this bacterium. No differences could be detected between the autolysis-positive and negative bacteria in the rate of killing and in the fate of macromolecular cell constituents during ingestion by rabbit peritoneal polymorphonuclear leukocytes.
| 18,480
|
Hypopotassemia following open heart surgery by cardio-pulmonary bypass.
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1. In this study where potassium concentration of perfusate of heart-lung machine was made high and no potassium was given until two hours after by-pass, the fall of plasma potassium level due to heart-lung bypass occurred in two stages, namely one hour of complete bypass and two hours after the end of bypass. 2. Regarding to the decrease of these plasma potassium level, increase of potassium excretion into urine and the movement of potassium from extracellular fluid into cells are presumed to be causes. Their genesis was discussed. 3. To prevent hypopotassemia following bypass, it is recommended to add KCl in the perfusate of heart-lung machine and to give intravenous drip of KCl immediately after bypass.
| 18,478
|
An analysis of the professional performance of physician's assistants.
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The job performance of a national sample of 939 physician's assistants has been assessed by means of a self-rating scale as well as by a rating scale completed by supervising physicians. Three-quarters of the participating supervising physicians are greatly satisfied with the work of their physician's assistants and a similar proportion indicate that they would definitely hire the same assistant if they "had it to do over again." The influences of background and work environment characteristics upon performance were assessed by means of multiple regression. Graduating from a military-sponsored physician's assistant program appears to have a beneficial effect upon performance. Performance during training exerts only a weak effect upon job performance. Amount of education and medical experience prior to beginning physician's assistant training do not affect job performance.
| 18,608
|
Nephropathia epidemica. The Scandinavian form of hemorrhagic fever with renal syndrome.
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We report epidemiologic, clinical, laboratory, and biopsy findings in 14 cases of nephropathia epidemica. The patients were between 19 and 49 years of age. The onset of the disease was characterized by high fever, nausea, headache, backache, abdominal pain, proteinuria, oliguria, hematuria, and uremia. The symptoms subsided rapidly during the polyuria phase, which followed the oliguria stage. Because of renal failure, hemodialysis was required in eight cases. Edema of eyelids, conjunctival injection and hemorrhages, transitory myopia, and acute glaucoma were the most common eye abnormalities. Renal biopsy specimens showed glomerular changes, with mild swelling of the epithelial cells of Bowman's capsule, thickening of the basement membrane of glomerular capillaries, glomerular adhesions, inflammatory cell infiltration, leukocytoclasis and hemorrhages in the interstitium, and eosinophilic hyaline degeneration and vacuolization of the epithelial cells of the proximal tubuli.
| 18,620
|
Porphyrin biosynthesis. Immobilized enzymes. IV. Studies on aminolaevulate dehydratase attached to Sepharose.
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Bovine liver aminolaevulate dehydratase (ALA-D) has been chemically attached to Sepharose 4B and its properties have been studied. The optimal conditions for coupling have been determined. It was found that the immobilized enzyme retained a significant percentage of the activity of the free enzyme. The coupling yield was rather high. The insolubilized enzyme requires both anaerobiosis and a thiol activator for maximal activity. It can be stored at 4 degrees C for long periods with little loss of activity and it can be repeatedly used without alteration of its enzymic capacity. Attachment of ALA-D to the gel has led to an enhanced thermal stability. pH optima of free and bound enzyme was the same while a small decrease in the Km of the matrix bonded ALA-D as compared to that of the soluble enzyme was observed. The use of the fixed-ALA-D for the preparation of PBG is described.
| 18,669
|
Phosphohistone and glycogen synthase D phosphatase activities in a liver glycogen pellet preparation.
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A liver glycogen pellet preparation previously found to contain synthase D phosphatase activity was shown to contain also phosphohistone phosphatase activity. Pellet phosphohistone phosphatase and synthase D phosphatase competed for the same substrates and appeared to be the same enzyme. ATP, a potent inhibitor, and G-6-P, a potent activator of the synthase phosphatase reaction, had little effect on the phosphohistone phosphatase reaction. These observations suggest that the ATP and G-6-P effects are relatively specific and are probably caused by binding to the synthase D substrate. The observed effects of NaCl and KCl were more complex. They stimulated phosphohistone phosphatase activity but strikingly inhibited synthase phosphatase activity. Sodium fluoride inhibited both reactions.
| 18,746
|
Assay and characterization of serum-stimulated lipolytic activity in homogenates of human adipose tissue.
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An assay of lipolytic activity in human adipose tissue is described, in which native homogenates of the adipose tissue yield the enzyme, as well as the triglyceride substrate, and the emulsifying phospholipids. The lipolytic activity in the presence of serum is characterized mainly as lipoprotein lipase activity by a pH-optimum of 8.0, by the fact that serum is necessary for full activity, and that it is inhibited by 1 M NaCl and by protamine. At serum concentrations of higher than 50% a marked inhibition of the lipolysis is observed. Noradrenaline, insulin, and heparin have no effect on the serum-stimulated lipolytic activity.
| 18,766
|
A deficient pyruvate kinase with an electrophoretically slow-moving component.
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A deficient erythrocyte pyruvate kinase observed in a patient with congenital non-spherocytic anaemia was characterized by the following properties: very low activity in haemolysates, decreased thermal stability, slightly increased urea denaturation, high affinity for PEP, poor FDP activation, normal ATP inhibition, decreased affinity for ADP, normal pH of optimal activity, and presence of an abnormal slow-moving component in this layer polyacrylamide gel electrophoresis. The patient was probably double heterozygous for two different deficient mutants of erythrocyte pyruvate kinase.
| 18,793
|
[Immunosuppressive properties of vinblastine and colchicine].
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The action of vinblastine and colchicine on the populations of antibody-forming cells, their precursors and stem cells using a model of primary immune response and in the transplantation system was studied using techniques by Jerne and Nordin (1963), Kennedy et al. (1965), and Till and McCulloch (1961). It was discovered that vinblastine and colchicine, at single administration 48 hours after immunization, inhibited immune response completely. The administration of colchicine and vinblastine to a donor gave an exponential decrease of in foci-forming cell number in a recipient in the system of syngenic transfer. But at the same time, vinblastine at small doses stimulated population of antibody-forming and stem cells, whereas at large doses it was not effective. Colchicine, in contrast, strongly inhibited both antibody-forming and haemopoietic cells in the recipient.
| 18,824
|
[Properties of chymotrypsin proteinase from Aspergillus oryzae].
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Chymotrypsin-type proteinase is detected in the proteolytic system of Asp. oryzae. The action of it and chymotrypsin is shown to depend on formaldehyde. Hydrolysis of substrates, p-nitrophenyl acetate (p-NPA) and N-benzoyl-tyrosine methyl ether (BTME), by both preparations is almost the same. The obtained activity pH-optimum for the studied proteinase esterolytic activity is located in the alkaline zone as well as for crystalline chymotrypsin (substrate p-NPA). It concerns pH of both enzymes stability as well. The enzyme under study is relatively labile. At 50 degrees C there are only traces of the activity in the medium with p-NPG. Its considerable decrease is observed at 40 degrees C. This type activity is more stable on the substrate BTME. 10 min later it disappears completely in the enzymic preparation at a temperature of 60 degrees C at 40 degrees C it is 96.8%. For 24 h at 25 degrees C the activity lowers only by 8%. Crystalline chymotrypsin is stable under these conditions. DEAE-cellulose chromatography (different types of elution) detected multiple forms of proteinase differing in solubility chromatographic properties and specific activity when splitting the substrates p-NPA, BTME and casein.
| 18,830
|
[Detection and quantitative estimation of 2,2-diethyl-4-pentenamide in a fatal case of poisoning (author's transl)].
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Toxicological investivation in a fatal case of poisoning by Novo-DolestanR and DoromaR is presented with methods for identification and quantitative estimation of 2,2-diethyl-4-pentenamide especially. The findings confirm 2,2-diethyl-4-pentenamide as the main toxic agent in this case.
| 18,861
|
[Behavior therapy of fear of flying in professional pilots].
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The theorical frame proposed by behaviour principles seems to have an explanatory value in the genesis of some troubles of traumatic origin. This is the case for fear of flying which can appear suddenly in airline personnel following accidents, troubles or problems while flying and which could bring a definitive incapacity of flying. The use of behaviour therapy, like systematic desensibilisation, is then being considered. It is illustrated by examples taken from the literature and by two clinical cases.
| 18,875
|
Syntheses of virus-induced thymidine kinase and viral DNA in herpes simplex type 1 virus-infected chick embryo fibroblasts.
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Herpes simplex virus type 1, strain Kupka, did not replicate in chick embryo fibroblasts (CEF), but the infection was followed by the development of cytopathic changes. This effect could be abolished by UV irradiation of the virus. Virus-induced thymidine kinase was synthesized in the infected cells reaching a maximum level at 24 hours post infection (p.i.). In the presence of cytosine arabinoside, thymidine kinase synthesis was enhanced. This suggested that the late (post-replicative) viral function, which turns off thymidine kinase synthesis, was expressed in the infected CEF untreated with the drug. HSV type 1 laboratory strains Kupka and KOS were capable of inducing the synthesis of virus-specific DNA in CEF. But in CEF infected with fresh type 1 virus isolates replication of viral DNA was not observed.
| 18,914
|
Differential expression of D and R components of Epstein-Barr virus early antigen after superinfection and after induction with 5-iododeoxyuridine.
|
Three non-productive human lymphoblastoid cell lines, NC-37, RAJI and L-1, either superinfected with Epstein-Barr (EB) virus from P3HR-1 cells or treated with 5-iododexyuridine (IUDR), were studied for the development of early antigen (EA) of EB virus. In all three superinfected cell lines, both the restricted (R) and diffuse (D) componets of EA were synthesized, with R-component formation preceding D-component synthesis. After IUDR treatment both components of EA were only formed in RAJI cells, while in NC37 and L-1 cells only the R-component was synthesized.
| 18,915
|
Analysis of antibody response and immunoglobulins in sera of rabbits and guinea pigs immunized with Coxiella burnetii.
|
Rabbit and guinea pig sera and their immunoglobulin fractions (IgM and IgG) were examined by complement-fixation (CF), microagglutination (MA), opsonization-phagocytosis (OP) and serum protection (SP) tests at intervals after immunization with live phase I and phase II Coxiella burnetii suspensions. In general, MA antibodies, but also decreased, earlier than CF antibodies. The anamnestic immune response was higher with lower primary doses. Both phase II and phase I CF and MA antibodies as well as phase I opsonins and protective antibodies were found in either immunoglobulin fraction depending on post-immunization intervals. At later intervals and especially after the second immunizing dose the levels of protective antibodies in whole sera, but mainly in the IgG fractions, showed a better agreement with those of phase I opsonins rather than of phase I CF and MA antibodies.
| 18,924
|
The effects of purified cathepsin D infusions in intact animals.
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Cathepsin D, a potent acid proteinase, has been implicated in the pathogenesis of circulatory shock. The infusion of purified preparations of cathepsin D into intact animals resulted in significant depressions in core body temperature but failed to reproduce the cardiovascular disturbances seen in shock states.
| 18,942
|
[Toxico-pharmacological study of lyophilized sodium nitroprusside (SNP)].
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Sodium nitroprusside (SNP) shows a strong hypotensive activity not only in normotensive animals but also in the presence of experimentally induced arterial hypertension. Its use in intravenous perfusion produces the rapid induction of arterial hypotension lasting or only slightly exceeding the time of its administration. Most investigators consider this hypotensive activity related to the fall in peripheral resistance, as is supported by the considerable fall in diastolic blood pressure. However, an effect of SNP on heart function cannot be ruled out. After four weeks' treatment at dosages corresponding to one tenth of the LD 50, no local or general toxicity could be demonstrated.
| 18,961
|
[Changes in serum and urinary magnesium during and after extracorporeal circulation in cardiac surgery in children].
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Magnesium plays an essential role in the processes of myocardial contraction and conduction. In cardiovascular surgery, extracorporeal circulation (ECC) in haemodilution results in various electrolyte distrubances, with invariably hypomagnesaemia. A group of 13 children undergoing open heart surgery was compared with a group of 17 children operated upon under the same conditions but with the addition of magnesium to the filling solution for the extracorporeal circulation. Changes in blood and urinary electrolytes during and after ECC were studied. Hypomagnesaemia was seen in both groups after surgery but the provision of magnesium supplements shortened the duration. In addition, blood phosphate levels remained significantly higher in the group receiving magnesium. The significance of these various findings is discussed and a technique for the provision of magnesium supplements is proposed.
| 18,967
|
Rapid induction of alpha-amylase by nongrowing mycelia of Aspergillus oryzae.
|
A rapid induction system for synthesis of alpha-amylase by the funga Aspergillus oryzae M-13 was established. The mycelia were prepared from 20-h cultures grown on a peptone-glycerol medium and starved for 5 h; maltose was the optimum inducer tested. During h 1 of induction, formation of both intra- and extracellular alpha-amylases occurred at an almost identical rate (70 to 80 microgram/g of cells-h) without a detectable lag period. After a 1-h induction period, a remarkable increase in the extracellular concentration of the enzyme occurred, and a maximum rate (330 microgram/g of cells-h) was reached after 1.5 h of induction. During h 2 of induction, no significant change in mycelial weight was observed. Purified samples of intra- and extracellular enzymes formed in the induction system showed identical properties as examined by behavior in diethylaminoethyl-cellulose column chromatography, gel filtration, discontinuous gel electrophoresis, electrofocusing, optimal conditions for the reaction, heat stability, and molecular weight.
| 18,989
|
[Studies on the thiamine transport system in Bacillus cereus (author's transl)].
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The thiamine transport system in Bacillus cereus exhibits rhythmical changes of resorption- and excretion-phases lasting 1-2 h. These main phases are subdivided in shorter ones with an average duration of 45 s. The velocity of the thiamine uptake is influenced by pH, temperature, age of cells, energy and substrate supply and thiamine concentration of the medium. The Michaelis-Menten-Kinetic can be used to describe the uptake: Km = 1.98 x 10(-8) M; Vmax = 1.19 x 10(-6) mol/g dry weight x min. The rate is enhanced by K+, Ca2+ and Mg2+, and inhibited by Pyrithiamin, EDTA, H+-ions, proton donors and proton acceptors; OH(-)-ions cause a change in the direction of transport. A theoretical explanation can be given by assuming a coupling of the thiamine permeation with proton movements in the membrane.
| 19,001
|
Substitute and alternative neurotransmitters in neuropsychiatric illness.
|
The accumulation of structural analogs of normal synaptic neurotransmitters (substitute or "false" neurotransmitters) can have profound behavioral and neurologic consequences. Such abnormalities of the metabolism of amines and amino acids may explain behavioral and neurologic changes in hepatic failure. Accumulations of substitute transmitters may mediate other neuropsychiatric phenomena in states of inborn or acquired metabolic error or after certain drugs associated with psychosis. In developing hypotheses concerning relationships between neuropsychiatric disorders and neurotransmitter metabolism, this mechanism might be considered as a novel approach.
| 19,004
|
Respiratory effects and amnesia after premedication with morphine or lorazepam.
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Lorazepam, a new benzodiazepine, was compared with morphine for premedication. Ten patients received morphine 10 mg/70 kg i.m. and 10 received lorazepam 4 mg/70 kg i.m. Respiratory effects were assessed from the change in slope (S) and intercept (B) of the carbon dioxide response line, using a development of Read's rebreathing method. Morphine depressed S by 47% (P less than 0.01), but after lorazepam S increased by 27% (P less than 0.05), neither drug altering B significantly. In two volunteers lorazepam was assessed by both the rebreathing and the steady-state methods; after lorazepam S was smaller by the steady-state than by the rebreathing technique. The findings for lorazepam are consistent with the known effects of sleep on carbon dioxide sensitivity. Amnesia lasting 4-8 h occurred in all patients who received lorazepam so that pain and nausea during this period were not recalled, but no patient who received morphine experienced amnesia. We conclude that lorazepam merits further study, particularly where sedation without respiratory depression is needed, as in obstetrics, and where amnesia for uncomfortable procedures is required.
| 19,025
|
Circular dichroism and conformation of human alpha1-antitrypsin.
|
The solution conformation of alpha 1-antitrypsin from human blood plasma was studied by the circular dichroism (CD) probe. The CD spectra revealed in this glycoprotein approximately 16-20% of alpha-helix, the rest of the main polypeptide chain possessing the pleated sheet (beta) and the aperiodic structures. The conformation was stable between pH 4.7 and 8.8. Reversible change in conformation was observed at pH 10.3, and more dratic denaturation occurred at pH 11.6. The environment of the side chain chromophores was strongly affected by acid at pH 2.5, whereas the main chain conformation was changed slightly. A drastic change in the CD spectra, indicating denaturation, was observed in 3.5 M guanidine hydrochloride. Sodium dodecyl sulfate was effective in disorganizing the tertiary structure and in enhancing the helix content. The phenylalanine band fine structure was observed in the native protein and also after denaturation with acid, guanidine hydrochloride and sodium dodecyl sulfate.
| 19,086
|
[Malic acid induction of decarboxylating NADP-malate dehydrogenase synthesis in C3-plant leaves].
|
The activity of decarboxylating NADP-malatedehydrogenase (E. C. 1.1.1.40) in green ethiolated pea and barley leaves and in green leaves of a pea mutant lacking photosystem II is found to be 3-fold increased after the injection of malic acid into cut plants. Protein synthesis inhibitors depressed malic acid-induced increase of the activity of "malic"-enzyme, the effect of chloramphenicol being more pronounced in ethiolated green leaves, and that of cycloheximide--in leaves of a mutant with formed photosynthetic apparatus. Possible dependence of malate-induced biosynthesis of "malic"-enzyme on the degree of NADP reduction in chloroplasts is discussed.
| 19,098
|
Structure and fragmentation mechanisms of some ions in the mass spectrum of ephedrine.
|
This paper describes the use of gas chromatography mass spectrometry for the confirmation of ephedrine in adulterated powdered ipecac and ipecac fluid extract. Deuteration studies of ephedrine hydrochloride and some related compounds were also performed in an attempt to postulate structures for some of the fragment ions appearing in the spectrum of ephedrine.
| 19,109
|
Process engineering studies on immobilized trypsin using molecular sieves as carriers.
|
In the present investigation molecular sieve has been found to be a suitable carrier for the immobilization of enzymes. From the present study it may be specifically found that trypsin and pappain can be immobilized by molecular sieve type 4a following a very simple techniqure. The immobilized enzyme can be used both in packed as well as in a continuous stirred tank reactor (CSTR).
| 19,110
|
The inhibition of calcium oxalate crystal growth by multidentate organic phosphonates.
|
The effect of a number of structurally related multidentate organic phosphonates on the rate of crystal growth of calcium oxalate was studied as a function of pH. Rate constants were obtained at various concentrations for the phosphonates ethane-1-hydroxy-1,1-diphosphonate (EHDP), nitrilotri(methylenephosphonic acid) (NTMP), N,N,N',N'-ethylene-diaminetetra(methylenephosphonic acid) (ENTNP), and N,N,N',N'-hexamethylenediaminetetra(methylenephosphonic acid (HMTMP), at pH 5.00, 6.00, and 7.00. The effect of pH on the inhibitory activity of each of the phosphonates was considerable with effective concentrations of inhibitor decreasing two orders of magnitude, in some cases, as the pH was increased. At a given pH the potentially hexadentate ligands, ENTMP and HMTMP, were generally the most effective inhibitors. The results suggested that EHDP, at currently administered doses, provides only a moderate increase in the capacity of human urine to inhibit calcium oxalate crystal growth.
| 19,137
|
Future of anesthesia.
|
The authors present an account of some of the problems facing the specialty of anesthesia, which suggests that the interdependence of these problems and of their solutions should be recognized. Recruitment, job satisfaction and clinical standards will be improved as a result of greater involvement by anesthetists in preanesthetic care as part of the health care team. Teaching programs require appropriate expansion and modification. The incorporation of a physician-assistant program is essential to the future of anesthesia.
| 19,147
|
Desensitization therapy for body image anxiety.
|
A newly devised therapy technique to desensitize individuals for body image anxiety arising from conversion symptoms and psychophysiologic disorders is outlined. One application involves the projective use of inkblots with high anatomical content which provide a source of visual input to stimulate somatic images in consciousness. When these are activated in a state of relaxation the anxiety content of the pathologic anatomical imagery is reduced. A case history involving desensitization treatment for a psychoneurotic patient's psychophysiologic symptom of premature ejaculation is cited. It is primarily designed to alert interested clinical investigators to this technical innovation in treatment.
| 19,149
|
The nature of the rate-limiting step in aniline hydroxylation involving cytochrome p-450 rat liver microsomes.
|
The kinetics of aniline hydroxylation was studied with: (1) rat liver microsomes involving NADPH and O2 (system 1), (2) hepatic microsomes and tert-butylhydroperoxide (system 2) and (3) microsomes and cumyl hydroperoxide (system 3) at 15--37 degrees C. The reactions were characterized by the values of the aniline oxidation rate constants, k2 = V/E0, where E0 is the initial concentration of cytochrome P-450: K 1/2 = 1.60 - 10(8) EXP (-13 400/RT) sec-1, k 2/2 = 1.66 - 10(9) exp (-14 500/RT) sec-1, k 3/2 = 6.83 - 10(9) exp (-15 300/RT) sec-1. The values of delta H0 and delta S0, were calculated and compared for the three systems. The evidence suggests that oxygen insertion into the substrate molecule is the rate-limiting step in the reaction of aniline oxidation for the mentioned systems. The nature of aniline binding to cytochrome P-450 and that of the hydroxylating agent have been discussed.
| 19,154
|
Creatine kinase: re-examination of optimum reaction conditions.
|
I have re-examined optimum reaction conditions for measurement of creatine kinase (EC 2.7.3.2). The optimum pH is 6.45, and 2,2-bis(hydroxymethyl)-2,2',2''-nitrotriethanol acetate, 200 mmol/liter, is the buffer of choice. Thioglycerol, 20 mmol/liter, is superior for both in-assay reactivation and for storage stability of sera. Fluoride, 25 mmol/liter, a broad inactivator of adenylate kinase (EC 2.7.4.3), has little effect on creatine kinase and is superior to AMP for adenylate kinase inhibition in the assay of creatine kinase. Magnesium ion, ADP, and buffer concentrations are interdependent and their optima must be determined together. The hexokinase/glucose-6-phosphate dehydrogenase activity ratio should not exceed 1.6. The range of linearity is limited by the glucose-6-phosphate dehydrogenase and NAD+ concentrations. Glucose-6-phosphate dehydrogenase, ADP, and NAD+ are the constituents most likely to result in unacceptable blanks. Creatine kinase is inhibited noncompetitively by anions: acetate and fluoride inhibit slightly, but sulfates, nitrates, and excessive chlorides should be avoided.
| 19,166
|
Calcium in bile and calcium salts in gallstones.
|
In gallbladder and common duct bile from patients undergoing cholecystectomy, usually because of gallstones, calcium was found to exist in at least 2 forms. Ultrafiltration showed some calcium was bound to substances with a molecular weight greater than 10 000, and the chief binding agent is likely to be the mixed micelle. Bound calcium was significantly less in common duct bile than in bile from functioning gallbladders, but the amount of ultrafiltrable calcium was the same. Furthermore, ultrafiltrable calcium in gallbladder bile from patients with cholesterol or some calcium carbonate in their gallstones was almost constant for a range of total calcium concentrations of 2.40--9.70 mmol/l. Comparison of ultrafiltrable and total calcium values for the different types of stone-formers showed that the deposition of calcium carbonate in gallstones was not related to any calcium measurement made. However, the presence of calcium phosphate and/or calcium bilirubinate in gallstones could be related to a significant increase in ultrafiltrable calcium in gallbladder bile.
| 19,175
|
Equine angiotensin converting enzyme: a zinc metalloenzyme.
|
1. Angiotensin I converting enzyme from horse plasma has been extensively purified and shown to be homogeneous by disc-gel electrophoresis. 2. The metal ion involved in the catalytic reaction of the enzyme has been identified for the first time as zinc by atomic absorption spectrometry. 3. A number of other physicochemical properties of the enzyme are described and compared with results obtained by other investigators. The molecular weight was determined by gel filtration to be 113 000 daltons. The pH maximum was found to be 7-4. The chloride activation of the enzyme appears to act by facilitation of substrate binding to the enzyme. 4. By use of enzyme inhibitors, tyrosine has been implicated as a functional residue at the active site of the enzyme. 5. The enzyme shows a fairly high degree of specificity towards its substrates.
| 19,186
|
The interrelationship between the metabolism of (S)-continine-N-oxide and (S)-cotinine.
|
The metabolism of (S)-cotinine-N-oxide was studied in the rabbit and the dog. The pattern of Koenig-positive substances in the urine of the animals suggested the presence of cotinine, demethylcotinine, hydroxycotinine, and allohydroxycotinine, compounds already previously identified as metabolites of (S)-cotinine and (S)-nicotine in many mammalian species. In the dog, 34% of the administered oral dose of (S)-cotinine-N-oxide was recovered from the urine, and 21% was recovered from the urine of the rabbit. Confirmation of the presence of (S)-cotinine, (S)-demethulcotinine, hydroxycotinine, and allohydroxycotinine in the urine of the rabbits was obtained by isolation of the metabolites as themselves of as derivatives. The data, although establishing the possibilities of an intermediary role for (S)-cotinine-N-oxide in the metabolism of nicotine, do not clearly indicate whether the metabolites such as demethylcotinine arise via the route (S)-cotinine-N-oxide leads to (S)-cotinine leads to (S)-demethylcotinine or via the alternate route (S)-cotinine-N-oxide leads to (S)-demethylcotinine-N-oxide leads to (S)-demethylcotinine.
| 19,214
|
Estradiol binding capacity in the cryptorchid rat testis.
|
Mature male Sprague-Dawley rats were made surgically cryptorchid at 47--50 days of age. Animals were sacrificed as controls and at 7, 14, and 21 days post-surgery. The testes were removed and utilized to determine the effects of cryptorchidism on tissue weight loss, histological changes, and cytoplasmic estradiol binding capacity. Testis weight decreased from a mean +/- SE of 1.1 +/- 0.09 to .41 +/- 0.02 g during the 21 day period, a 66% decrease in weight. Light microscopy revealed that the process of spermatogenesis was inhibited, the germinal epithelium had degenerated, and the tubules had become smaller in diameter. The interstitial tissue volume progressively increased through day 21 post-surgery. The cytoplasmic estradiol binding capacity, expressed as fmoles [3H]-estradiol/mg cytosol protein, increased markedly from a control of 16 +/- 1.1 to 36 +/- 8.0 at day 7 after surgery; this represented a 126% increase in binding capacity in one week. Binding capacity was equivalent to 54 +/- 7.4 and 58 +/- 10.5 fmol/mg on days 14 and 21 post-surgery, respectively. Testicular content of cytoplasmic estrogen receptors was shown to increase from 349 to a maximum of 575 fmoles/testis at day 7. Receptor content then declined slowly to a value of 481 at day 21. Testicular content of receptor is presumed to reflect an alteration in the Leydig cells induced by cryptorchidism.
| 19,233
|
Possible role of calcium-dependent protein phosphorylation in mediating neurotransmitter release and anticonvulsant action.
|
The results demonstrate that calcium and phenytoin have antagonistic actions on the net level of endogenous phosphorylation of specific rat brain proteins. These specific phosphoproteins were shown to be present in synaptosome preparations, and evidence is presented for the localization of these phosphoproteins within the presynaptic nerve terminal. The data are compatible with the hypothesis that the antagonistic actions of calcium and phenytoin on the phosphorylation of synaptosome proteins may be the underlying molecular mechanism mediating the opposing actions of these agents on the release of neurotransmitter from the presynaptic nerve terminal.
| 19,235
|
Bacteriorhodopsin-mediated photophosphorylation in Halobacterium halobium.
|
The rate of halobacterial photophosphorylation was found to be a linear function of light intensity over a wide range (between 1 and 20 mW/cm2). At higher light intensities (above 25 mW/cm2) the ATP-synthesizing system itself limits the maximal rate of photophosphorylation. The optimal external pH range for this type of photophosphorylation is between pH 6.2 and 7.2 external. The photophosphorylation rate is directly proportional to the bacteriorhodopsin content of the cells. The quantum requirement for photophosphorylation was found to be 22 +/- 5 photons per ATP molecule synthesized. According to Mitchell's chemiosmotic hypothesis of energy coupling phosphorylation can be driven by a membrane potential or a pH gradient or a combination of both. From the results of experiments with drugs which abolish or reduce either one of the two components we conclude that the major driving force for photophosphorylation above an external pH value of 6.5 is the membrane potential, while at more acidic pH value the pH gradient becomes dominating. We did not observe a correlation between a transient alkalinization of the medium and ATP-synthesis upon illumination under certain conditions.
| 19,249
|
Hemoglobin S Travis: a sickling hemoglobin with two amino acid substitutions [beta6(A3)glutamic acid leads to valine and beta142 (h20) alanine leads to valine).
|
Hb S Travis is a previously undescribed sickling hemoglobin with two amino acid substitutions in the beta chain: beta6 Glu leads to Val and beta142 Ala leads to Val. The beta6 Glu leads to Val mutation imparts to Hb S Travis the characteristic properties of sickling hemoglobin, namely its association with erythrocyte sickling, the insolubility of the hemoglobin in the reduced form, and a minimum gelling concentration value identical to Hb S. Unlike Hb S, Hb S Travis exhibits an increased oxygen affinity and a decreased affinity for 2,3-bisphosphoglycerate and inositol hexakisphosphate. In addition, the variant hemoglobin's tendency to autoxidize and its mechanical precipitability suggest that there are conformational differences between Hb S and Hb S Travis.
| 19,257
|
Regional effects of neuroleptics on dopamine metabolism and dopamine-sensitive adenylate cyclase activity.
|
The effect of haloperidol, chlorpromazine, thioridazine and sulpride on the levels of DOPAC and HVA, as an index of DA turnover, and on the activity of DA-stimulated adenylate cyclase was investigated inthe striatum, the nucleus accumbens and the tuberculum olfactorium of the rat brain. Haloperidol, chlorpromazine and thioridazine caused a more marked increase in DA turnover in the striatum than in the mesolimbic areas, while the reverse was true for sulpiride. In contrast, although the relative potency of these compounds varied greatly, the Ki of each drug for the DA-sensitive adenylate cyclase was similar in three structures of rat brain. The results indicate that in the three brain structures investigated there was no correlation between the differential effects of neuroleptics on dopamine turnover in vivo and the blockade by these drug of the DA-sensitive adenylate cyclase activity in vitro.
| 19,266
|
Interaction of extrinsic fluorescent probes with E. coli glutamine synthetase.
|
Binding of 2-p-toluidinylnaphthalene-6-sulfonate (TNS) to adenylylated (E--11) glutamine synthetase is cooperative and time-dependent, with 3 dye sites per subunit. In fluorescence polarization experiments TNS and pyrene butyrate give normalized Perrin plots that indicate a symmetrical arrangement of dye excited state dipoles, relative to the rotational axis of the oblate ellipsoid of the dodecameric native enzyme.
| 19,281
|
Chemical studies of marine invertebrates. XXVII. On the absolute configuration of aromadendrane sesquiterpenes from the soft coral Cespitularia aff. subviridis.
|
Allo-aromadendrene, (-)viridiflorol and (+)ledol have been identified as minor constituents of the soft coral Cespitularia aff. subviridis.
| 19,283
|
Hydrogen ion and carbon dioxide content of the oviductal fluid of the rhesus monkey (Macaca mulatta).
|
The pH in the oviduct lumen of adult female rhesus monkey (Macaca mulatta) during the menstrual cycle was measured by means of miniaturized pH electrodes. Two types were used: one was a flexible electrode 1.4 mm in diameter; the other was a rigid electrode 0.8 mm in diameter. The same results were obtained with both types. For PCO2 measurements, the pH electrodes was converted to a Severinghaus tyep electrode covered with a Teflon membrane. During the follicular phase, the pH remains constant in the range 7.1 to 7.3. In association with ovulation, there is a sudden increase in the pH to the range 7.5 to 7.8. The pH remains high through the luteal phase. The PCO2 values obtained showed no evident changes with day of cycle. The range of values estimated was wide because of drift in electrode calibration, with the average level about 89 Torr, compared with 40 Torr for blood. At the average pH of 7.2 in the follicular phase, this value of PCO2 corresponds to 35 mM HCO3-; at the average pH of 7.6 of the secretory phase, this value corresponds to 90 mM HCO3-. This increase in pH and HCO3- after ovulation would be expected to enhance dispersal of corona cells during fertilization and to provide a favorable environment for the developing embryo.
| 19,307
|
Antihypertensive effect and tolerability of metoprolol during long-term treatment: a multicentre study.
|
One hundred and forty-seven patients with essential hypertension participated in this multicentre study. The results indicate that metoprolol in a dosage of 150-450 mg daily is an effective and well tolerated therapy both in patients previously untreated and in patients unsatisfactorily treated with other antihypertensive agents.
| 19,328
|
Crohn's disease involving the colon: an audit of clinical management.
|
This paper describes the clinical management of 204 patients with Crohn's disease involving the colon who have been reviewed regularly for many years. The results have been analyzed to define the morbidity, mortality, and long term prognosis of the disorder. Despite a high morbidity, the long term prognosis is good. Although the mean interval since the onset of symptoms is more than 13 years, 77% of the patients are symptom-free and 60% have normal laboratory indices. This analysis suggests that until the etiology of Crohn's disease is established and a specific therapy is developed, good results can be obtained with regular medical review and appropriate surgical treatment with the limited use of immunosuppressive agents or total parenteral nutrition.
| 19,340
|
Effect of acetylsalicylic acid on the amphibian gastric mucosa. I. Electrophysiological and permeability changes.
|
The effects of acetylsalicylic acid on the in vitro bullfrog gastric mucosa were defined. After mucosal exposure of 10 or 20 mM acetylsalicylic acid, a characteristic series of changes evolved. The potential difference and resistance rose initially. After 15 to 30 min the potential difference declined to zero. Transmucosal resistance remained elevated considerably longer but began to decline toward zero after 30 to 60 min of exposure. Mucosal permeability to mannitol increased as transmucosal resistance declined, but was not markedly elevated until the 2nd hr of exposure to acetylsalicylic acid. The initial rise of potential difference was associated with inhibition of H+ secretion whereas the later decline of potential difference was due to inhibition of Cl- transport. The abolition of short circuit current could not be attributed to mucosal to serosal flux of acetylsalicylate.
| 19,341
|
Interaction of colchicine with DNA molecules.
|
Colchicine (7.5 X 10-6M or 3.3 X 10-5M) was incubated at pH 7.0, 10.0, or 12.0 with high-molecular DNA from salmon sperm (7 X 10-5M or 3.5 X 10-5M DNA-P) at 40 degrees C. Interaction was monitored by UV spectrophotometry; Amax/Amin ratios, difference and additive spectra, and the quantity of colchicine bound to DNA were presented as functions of time, ionic strength and DNA concentration. Using NMR techniques, delta deltav 1/2/deltac values, chemical shifts and half-line widths of colchicine protons were analyzed as a function of the DNA/colchicine ratio, thus proving the interaction between alkaloid and DNA. An intercalation of the tropolone moiety of colchicine between the nitrogenous bases of DNA is suggested.
| 19,350
|
Some properties of hemoglobin Gun Hill.
|
Hb Gun Hill has been found in an asymptomatic black female living in Alabama; neither her parents nor her two siblings carry the variant. The deletion of five amino acid residues in the beta chain of Hb Gun Hill (alpha2beta2 91-95 deleted) causes this variant to have a high oxygen affinity, an interaction coefficient of unity and an absence of the Bohr effect. The rate of oxidation of liganded Hb Gun Hill by the ferricyanide ion follows first-order kinetics. Hb Gun Hill is to a great extent dissociated into dimers over a wide range of pH values.
| 19,375
|
Aminoglycoside nephrotoxicity. I. Effects of aminoglycoside antibiotics on iodohippurate accumulation in rabbit renal cortical slices.
|
The effects of aminoglycoside antibiotics on the accumulation of O-125I-hippurate (OIH) in rabbit renal cortical slices were assessed in an attempt to establish an in vitro model for aminoglycoside nephrotoxicity. Accumulation of OIH was measured after incubation of cortex slices in media containing aminoglycosides in different concentrations. All aminoglycosides depressed OIH accumulation in the following minimum concentrations: Dihydrostreptomycin and kanamycin, 2,000 microgram/ml (P less than 0.01); streptomycin and neomycin, 1,000 microgram/ml (P less than 0.05 and P less than 0.01); amikacin and tobramycin, 300 microgram/ml (P less than 0.05); gentamicin, 100 microgram/ml (P less than 0.05). A concentration of 2,000 microgram/ml caused the following reduction in OIH accumulation: Dihydrostreptomycin, 19.3%; streptomycin, 28.9%; kanamycin, 23.8%; neomycin, 62.5%; gentamicin, 68.0%; amikacin and tobramycin, 100%. Changes in pH of the incubation media after addition of aminoglycosides were only partially responsible for the observed depression of OIH accumulation and there was no evidence of substrate competition between aminoglycosides and OIH. The in vitro model described here appears to be inadequate as a sole predictor of aminoglycoside nephrotoxicity, but may provide a supplementary tool in the investigation of aminoglycoside proximal tubular cell toxicity.
| 19,410
|
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