id stringlengths 4 8 | title stringlengths 1 642 | abstract stringlengths 50 17.9k |
|---|---|---|
940769 | Histone dimers: a fundamental unit in histone assembly. | Histone interactions which occur, at moderate ionic strengths, when several types of purified, renatured histones are mixed at equimolar ratios have been studied. The four histones H2A,H2B,H3 and H4 complex and form dimers. Histone H1 does not interact with the other four histone types and does not form dimers. Mixing ... |
820236 | Inner ear degeneration in acoustic neurinoma. | The temporal bones of three cases of acoustic neurinoma are described to illustrate histopathological features of inner ear lesions due to chronic partial obstruction of blood circulation by the tumor in the internal auditory meatus. Degenerative changes in the inner ear due to acoustic neurinoma were evaluated and com... |
932939 | Controlled drug permeation I: controlled release of butamben through silicone membrane by complexation. | The effects of caffeine, beta-cyclodextrin, and povidone on the permeation behavior of butamben from saturated solutions in these complexing agents through a dimethyl polysiloxane membrane were investigated at 30 degrees. In all systems, these agents increased the rate of release over the plain saturated drug solution.... |
1278182 | Complementation of subunits from glycogen phosphorylases of frog and rabbit skeletal muscle and rabbit liver. | Activity can be induced in potentially active rabbit skeletal muscle phosphorylase monomers covalently bound to Sepharose by noncovalent interaction with soluble subunits carrying inactive pyridoxal 5'-phosphate analogs or even salicyladlehyde. These analogs are themselves incapable of reconstituting active holophorpho... |
179813 | Metallocytochromes c: characterization of electronic absorption and emission spectra of Sn4+ and Zn2+ cytochromes c. | Tin (Sn4+) and zinc (Zn2+) derivatives of horse heart cytochrome c have been prepared and their optical spectra have been characterized. Zinc cytochrome c has visible absorption maxima at 549 and 585 nm and Soret absorption at 423 nm. Tin cytochrome c shows visible absorption maxima at 536 and 574 nm and Soret absorpti... |
1276897 | Type 1 and 2 synaptic junctions: differences in distribution of concanavalin A binding sites and stability of the junctional adhesion. | Two classes of synaptosomes have been distinguished in subcellular fractions from rat forebrain. They differ in morphology and distribution of concanavalin A binding sites. Morphological examination suggests that the two classes correspond to the type 1 (excitatory) and type 2 (inhibitory) synapses of intact brain tiss... |
945023 | Methoxyflurane biotransformation and renal function following methoxyflurane administration for vaginal delivery or cesarean section. | Methoxyflurane (MOF) administration for conscious analgesia during vaginal delivery (range 5 to 70 min, mean 23 min) or for anesthesia following delivery of the infant at cesarean section (range 25 to 70 min, mean 44 min) was studied in 18 healthy parturients. Serum ionic fluoride increased significantly in both groups... |
1275037 | Myelinated nerve fibers and severe myopia. | Two 4-year-old boys, one white and one black, had unilateral extensive myelinization of retinal nerve fibers associated with severe myopia, esotropia, and amblyopia. The finding of unilateral extensive myelinization of the nerve head and retinal fibers in a child may indicate a potentially remediable anisometropic ambl... |
179091 | Hormone and neurotransmitter receptors in an established vascular endothelial cell line. | A cell line from the intima of the rabbit aorta has been established. This cell line exhibits strict contact inhibition, and morphologically resembles intimal endothelial cells. B-type blood group antigens and the presence of fibrinolytic activity also distinguish these cells from smooth muscle cells and from fibroblas... |
58417 | Human pituitary growth hormone: restoration of full biological activity by noncovalent interaction of two fragments of the hormone. | The NH2-terminal 134 amino-acid fragment of the reduced-carbamidomethylated human somatropin molecule is found to react noncovalently with the COOH-terminal 51 amino-acid fragment in solutions of pH 8.4 at 2 degrees to restore full biological activity as evidenced by the rat tibia and pigeon crop-sac assays. In additio... |
1268254 | Complex mitochondrial DNA in animal thyroids. A comparative study. | 1. The frequency of circular dimers and catenanes was determined in thyroid mitochondrial DNA (mtDNA) from rabbits, mice, pigs, sheep and cattle. 2. The mtDNA from freshly removed thyroids was isolated by buoyant density centrifugation in ethidium bromide/CsCl gradients after DNAase treatment of the mitochondrial pelle... |
1266946 | Cyclodextrin nephrosis in the rat. | The renal toxicity of the Schardinger dextrins, alpha and beta-cyclodextrin, is manifested as a series of alterations in the vacuolar organelles of the proximal convoluted tubule. These changes begin as an increase of apical vacuoles and the appearance of giant lysosomes. The giant lysosomes characteristic of cyclodext... |
1262399 | Pressure-induced depolymerization of spindle microtubules. III. Differential stability in HeLa cells. | Evidence from light microscopy (principally polarization microscopy) has demonstrated that hydrostatic pressure can reversibly inhibit mitosis by rapidly depolymerizing the spindle fiber microtubules. We have confirmed this finding in ultrastructural studies of mitotic HeLa cells incubated at 37 degrees C and pressuriz... |
5438 | Acetyl coenzyme A carbosylase. Circular dichroism studies of Escherichia coli biotin carboxyl carrier protein. | The biotin carboxyl carrier protein (BCCP) component of Escherichia coli acetyl coenzyme A carboxylase and three peptides derived from BCCP by proteolytic digestion have been examined by circular dichroism spectroscopy. BCCP, which has a peptide molecular weight of 22,500, has a spectrum typical of globular proteins wi... |
5436 | Kinetic study of the action of snake venom phospholipase A2 on human serum high density lipoprotein 3. | The hydrolysis of the phospholipids of intact human serum high density lipoprotein 3 (HDL3) by pure alpha-phospholipase A2 from Crotalus adamanteus was studied by pH-stat titration. The enzyme quantitatively hydrolyzed phosphatidylcholine and phosphatidylethanolamine and left sphinogomyelin intact, yielding a stable an... |
816775 | Chemical characterization of the regularly arranged surface layers of Clostridium thermosaccharolyticum and Clostridium thermohydrosulfuricum. | Clostridum thermosaccharolyticum and Clostridium thermohydrosulfuricum possess as outermost cell wall layer a tetragonal or hexagonal ordered array of macromolecules. The subunits of the surface layer can be detached from isolated cell walls with urea (8M) or guanidine-HCl (4 to 5 M). Triton X-100, dithiothreitol, ethy... |
67116 | Supramolecular structure of polymorphic collagen fibrils. | Reconstituted cartilage collagen fibrils with an oblique banding pattern or with two types of symmetrical patterns, and reconstituted rattail tendon fibrils with a third type of symmetrical pattern were examined by electron microscopy and found to consist of narrow subfibrils having native-type cross-striations. Analys... |
950340 | Studies on cyclodextrin glycosyltransferase. IV. Enzymatic synthesis of 3-O-alpha-D-glucopyranosyl-L-sorbose and 4-O-alpha-D-glucopyranosyl-D-xylose using cyclodextrin glycosyltransferase. | The acceptor specificity of the transglycosylation reaction of cyclodextrin glycosyltransferase[EC 2.4.1.19] was investigated using various sugars and sugar alcohols. L-Sorbose, D-xylose, and D-galactose, which contain configurational or structural changes relative to the D-glucopyranose unit at positions other than po... |
1268877 | Comb-like derivatives of amylose having (1-6)-linked malto-oligosaccharide side-chains. | The preparation of acetylated glycosyl bromide derivatives of the higher malto-oligosaccharides was studied by using beta-cyclodextrin or linear malto-oligosaccharides of d.p. 6 and 7. The products were treated with 2,3-di-O-phenylcarbamoyl-6O-tritylamylose in the presence of silver perchlorate (reaction A), and with 2... |
1062794 | Inactivation of catalase monolayers by irradiation with 100 keV electrons. | A catalase monolayer adsorbed on a layer of arachidic acid deposited on a solid support was irradiated with 100 keV electrons simulating the conditions of electron microscopic imaging. Effective doses were calculated taking into account the angular and energy distribution of backscattered electrons. Enzymatic inactivat... |
1254570 | Ribonuclease S-peptide. A model for molecular recognition. | The relationship of structure to function in the recognition of ribonuclease S-peptide by S-protein was studied by several methods. Liquid phase peptide synthesis was employed to generate analogs of S-peptide in which from 1 to 8 residues were deleted from the NH2-terminal end of the S-peptide. Additional derivatives w... |
5431 | Interaction of cyclodextrins with fluorescent probes and its application to kinetic studies of amylase. | It was found that 6-p-toluidinylnaphthalene-2-sulfonate (TNS) showed pronounced fluorescence enhancement when it was added to alpha-, beta-, and gamma-cyclodextrin solutions. 2. The following results were obtained by quantitative study of the interactions of three kinds of cyclodextrins with TNS by following TNS fluore... |
4840 | Synthesis of corrins and related macrocycles based on pyrrolic intermediates. | Intermediate in structure between porphyrins and corrins are the corroles and 1-methyltetradehydrocorrins. These ring systems, like the porphyrins, can be obtained by cyclization of linear tetrapyrrolic compounds, reactions which have been shown to proceed by orbital symmetry-allowed electrocyclic processes, and exampl... |
4835 | Biosynthesis of porphyrins and corrins. | Haem, chlorophyll and vitamin B12 are all derived ultimately from four molecules of the pyrrole porphobilinogen (PBG) and the initial enzyme catalysed condensation of PBG leads to the unsymmetrical type III isomer of uroporphyrinogen. On the basis of straightforward chemical considerations the type I isomer should be f... |
54923 | A molecular concept of the properdin pathway. | The sequential events of the properdin system were analyzed. Properdin-depleted serum allows the formation of a Factor B- and D-dependent C3 convertase. This enzyme, called the properdin-receptor-forming enzyme, was shown to utilize a novel serum component, the initiating factor. The protein is a beta-globulin in precu... |
1028329 | Folding crystallization of DNA. Circular dichroism studies. | CD spectra of DNA monocrystals are extremely different from spectra of psi-DNA or DNA-histone H1 or DNA-polylysine complexes. They are discussed to be dependent on the supramolecular organization of DNA in the condensed form, and they are not in contradiction to the previously proposed seven folding model of DNA in chr... |
1027923 | Effects of RNase and RNA on in vitro aster assembly. | RNase alters the in vitro assembly of spindle asters in homogenates of meiotically dividing surf clam (Spisula solidissima) oocytes. Some effects of RNase, such as reduced astral fiber length, appear nonenzymatic and probably result from RNase binding to tubulin. However, RNase-induced changes in the microtubule organi... |
800621 | Measurement of the lateral mobility of cell surface components in single, living cells by fluorescence recovery after photobleaching. | The use of fluorescence recovery after photobleaching (FRAP) techniques to monitor the lateral mobility of plant lectin-receptor complexes on the surface of single, living mammalian cells is described in detail. FRAP measurements indicate that over 75% of the wheat germ agglutinin receptor (WGA-receptor) complexes on t... |
1036193 | Ricinus communis toxin-mediated inhibition of protein synthesis in cell-free extracts of a toxin-resistant variant mouse lymphoma cell line. | Ricinus communis agglutinin II (RCAII, ricin, toxin) at low concentrations inhibits protein synthesis in cell-free extracts, but not in intact cells, of an RCAII-resistant mouse lymphoma variant cell line. The concentration dependence of the inhibition by RCAII was the same in cell-free extracts of both RCAII-resistant... |
800619 | Structure and control of assembly of cytoplasmic microtubules in normal and transformed cells. | Indirect immunofluorescence analyses using antibodies directed against 6S tubulin have shown an elaborate cytoplasmic microtubule complex (CMTC) in nontransformed cells in culture. The CMTC is strikingly altered in cells that have been transformed spontaneously by viruses or by chemicals. Assembly of microtubules in vi... |
1027922 | Comparison of the structural and chemical composition of giant T-even phage heads. | A study has been made of the structure of the capsids of T4D giant phage produced from mutants in gene 23 and temperature-sensitive mutants in gene 24, and T4D and T2L giant phage formed by the addition of L-canavanine followed by an Larginine chase in the growth medium. All the giant phage capsids have been shown to b... |
1027921 | The gating currents of sodium channels: pore-population-size effects. | Sodium-channel behavior has been modeled in order to determine the answer to the following question: How large must a population of "on-off" sodium pores be before the inherently random behavior of the individual channels becomes smoothed to yield the expected gating current-conductance relationships which would be pre... |
1027920 | Central nervous system antigen (NS-5) and its presence during murine ontogenesis. | An antiserum raised by immunization of C3H.SW/Sn mice with cerebellum from 4-day-old C57BL/6J mice recognizes a cell surface component(s) [NS-5] present in different degrees on various parts of the mouse central nervous system. When analyzed by an antiserum- and complement-mediated cell cytotoxicity test and by the abi... |
1030937 | [Quantitative studies on the regeneration of myelinated nerve fibers. II. Variations of the number and size of regenerating nerve fibers after localized crushing or total section]. | 1. The number and size of myelinated nerve fibers have been determined at standard levels, in the nerve to medial head of right and left gastrocnemius muscles of 112 rats in which the left sciatic nerve had suffered an experimental lesion according one of the following four modalities: localized crushing, total section... |
1022124 | Circular dichroism studies on DNA condensed in NaCl cetyltrimethyl ammonium bromide solutions. | It is shown by means of circular dichroism studies of variously condensed forms of DNA that the specific supramolecular structure of DNA determines the type of CD spectra. DNA, condensed (crystallized) slowly in the presence of cetyltrimethyl ammonium bromide yields a spectrum very similar to that of DNA in solution in... |
1024124 | Interaction of charged lipid vesicles with planar bilayer lipid membranes: detection by antibiotic membrane probes. | A technique has been developed for monitoring the interaction of charged phospholipid vesicles with planar bilayer lipid membranes (BLM) by use of the antibiotics Valinomycin, Nonactin, and Monazomycin as surface-charge probes. Anionic phosphatidylserine vesicles, when added to one aqueous compartment of a BLM, are sho... |
1024123 | Interactions of neurotoxins with the action potential NA + ionophore. | Four neurotoxins that activate the action potential Na+ionophore of electrically excitable neuroblastoma cells interact with two distinct classes of sites, one specific for the alkaloids veratridine, batrachotoxin, and aconitine, and the second specific for scorpion toxin. Positive heterotropic cooperativity is observe... |
66419 | Does a bacterial elongation factor share a common evolutionary ancestor with actin? | Protein synthesis elongation factor Tu from E. coli shares several physical, chemical, and functional properties with actin-like proteins. Limited tryptic degradation indicates that the two polypeptides have a similar molecular architecture. These observations suggest that they could have evolved from a common ancestor... |
799216 | Genetic control of membrane mosaicism. | The mosaic and dynamic character of cellular membranes is illustrated by the specific intramembrane particle array, the fusion rosette, found to be essential for membrane fusion and secretion in the ciliated protozoa, Tetrahymena and Paramecium. The rosette is not a permanent site within the membrane. When secretion of... |
1024122 | Nature and origin of patterns of changes in cell shape in embryos. | Spatial patterns of the future elongation of cells exist in the early embryo. In the newt, such a pattern of changes of cell shape contributes to the formation of the neural plate. Regardless of where neural plate cells are transplanted, they change shape as prescribed by the pattern. Embryonic induction has a role in ... |
1035781 | The surface events of fertilization: the movements of the spermatozoon through the sea urchin egg surface and the roles of the surface layers. | The sea urchin egg surface at fertilization has been examined with the scanning electron microscope to reveal the movements of the spermatozoon from the exterior, through the surface layers, and into the egg cytoplasm. The layers that the spermatozoon encounter have been studied to determine their physical and chemical... |
139505 | Suppression of stimulating cell activity by microtubule-disrupting alkaloids. | Microtubule-disrupting alkaloids and protein fixatives were used to investigate the nature of an active process that must occur within stimulator cells in order for them to initiate a unidirectional mixed lymphocyte response (MLR). Brief treatment of the stimulator cells (SC) with glutaraldehyde (0.15%), formalin (0.6%... |
799215 | Cytoskeletal functions of cytoplasmic contractile proteins. | This is a review of the evidence that the cytoplasmic contractile proteins function as a cytoskeletal system in the cytoplasmic matrix. Biochemical experiments show that cycoplasmic actin filaments can form a solid gel under conditions likely to exist in living cells. The actin filaments are associated with other prote... |
191699 | The correlation of plasma membrane microvilli and intracellular cyclic AMP content in a rat epitheloid kidney cell line. | Modulation of the intracellular concentration of cyclic AMP has been associated with a regulatory role in cell division, cell morphology, and physical properties of the plasma membrane. Untransformed rat kidney cells in culture exhibit epitheloid morphology, high intracellular cyclic AMP levels, and contact inhibition ... |
828690 | Changes in E. coli cell envelope structure caused by uncouplers of active transport and colicin E1. | It is of interest to inquire whether agents that uncouple or deenergize membranes cause concomitant structural changes. The agents considered here are the uncoupler carbonyl cyanide-p-trifluoromethoxyphenylhydrazone and the bacteriocidal protein colicin E1, agents for which there is some precedent for believing that th... |
1024121 | Surface architecture of the plant cell: biogenesis of the cell wall, with special emphasis on the role of the plasma membrane in cellulose biosynthesis. | Cell wall structure and biogenesis in the unicellular green alga, Oocystis apiculata, is described. The wall consists of an outer amorphous primary layer and an inner secondary layer of highly organized cellulosic microfibrils. The primary wall is deposited immediately after cytokinesis. Golgi-derived products contribu... |
1035780 | Microtubules and actin filaments in teleost visual cone elongation and contraction. | Teleost retinal cones contract in light and elongate in darkness. This paper describes the disposition of microtubules and cytoplasmic filaments in cone cells of 2 species of fish (Haemulon sciurus and Lutjanus griseus). In Haemulon, the neck-like "myoid" region of the cone changes in length from 5 mu to 75 mu. Maximal... |
1019260 | Kinetics of the light flash of the living firefly: a supramolecular process. | The light intensity vs. time curve of the light flash of the living firefly has been measured. Unlike the purified firefly enzyme system in aqueous solution, the living system does not show light decay conforming to a double exponential time curve, to simple first or second order decay, or to solid-state Elovich kineti... |
1003970 | Molecular composition and origin of substrate-attached material from normal and virus-transformed cells. | The proteins and polysaccharides which are left adherent to the tissue culture substrate after EGTA-mediated removal of normal, virus-transformed, and revertant mouse cells (so-called SAM, or substrate-attached material), and which have been implicated in the cell-substrate adhesion process, have been characterized by ... |
1034176 | Morphological and biochemical abnormalities in hearts of cardiac mutant salamanders (Ambystoma mexicanum). | The effect of homozygosity for recessive gene c in Ambystoma mexicanum is the absence of a heartbeat even though initially heart development appears normal. Mutant embryos (c/c) are first distinguishable from their normal siblings (+/+;+/c) at stage 34 (7 days after fertilization) when the normals develop contracting h... |
187878 | Cyclic nucleotides, thioldisulfide status of proteins, and cellular control processes. | It is shown that cyclic nucleotides can have a variety of effects on cell division, cell shape, cell adhesion, and cell movement, depending on the cells selected and the conditions under which they are used. For example, while CHO cells elongate under the influence of exogenous dibutyryl CAMP, Y-1 adrenal tumor cells r... |
1003969 | Fine structural localization of Concanavalin A binding sites on hamster spermatozoa. | The plasma membrane of epididymal spermatozoa of the golden hamster (Mesocricetus auratus) exhibits morphological differences over various parts of the head and tail as detected by air-dried replicas and freeze-etching techniques. In an attempt to ascertain whether any topographical differences exist in the number or d... |
794589 | Localization and organization of microfilaments and related proteins in normal and virus-transformed cells. | The localization and organization of actin-like microfilaments in normal, SV-40 and adenovirus transformed cells are determined by the coordinated use of light optical, electron optical and biochemical techniques. In adenovirus-type 5 transformed hamster embryo cells, microfilament meshworks appear to be the predominan... |
1087366 | Immunospecific labeling of mouse lymphocytes in the scanning electron microscope. | Bone marrow-derived (B) and thymus-derived (T) Balb/c mouse lymphocytes were identified in the scanning electron microscope (SEM) by the immunospecific attachment of one of several kinds of large-molecular-weight markers distinguishable in SEM. These markers (tobacco mosaic virus, keyhole limpet hemocyanin, bushy stunt... |
1003968 | Sarcomas routinely produced from putatively nontumorigenic Balb/3T3 and C3H/10T1/2 cells by subcutaneous inoculation attached to plastic platelets. | The Balb/3T3 and C3H/10T1/2 lines, noted for their marked postconfluence inhibition of proliferation and anchorage dependence, and frequently studied as non-tumorigenic lines that are compared with tumorigenic sublines transformed with various agents, produced tumors within two to four months at low-cell dosage (3 X 10... |
1034175 | Cytoskeletal elements of chick embryo fibroblasts revealed by detergent extraction. | Treatment of chick embryo fibroblasts with 0.5% Triton X-100 extracts most of the cell protein, leaving an organized part of the cell structure attached to the tissue culture dish. This "Triton cytoskeleton" consists largely of intermediate-sized filaments and bundles of microfilaments. SDS polyacrylamide gel electroph... |
1003967 | Trapping at low temperature of oriented chloroplasts: application to the study of antenna pigments and of the trap of photosystem-1. | A technique is described for the preparation of oriented samples from spinach chloroplasts whose linear dichroism is then studied by (flash) absorption spectroscopy. The chloroplasts are suspended in a glycerol-containing medium, oriented in a magnetic field, and slowly cooled in the magnet until the medium is rigid en... |
186666 | A study of adenosine 3'-5' cyclic monophosphate binding sites of human erythrocyte membranes using 8-azidoadenosine 3'-5' cyclic monophosphate, a photoaffinity probe. | An earlier report (1a) has shown the utility of 8-N3cAMP (8-azidoadenosine-3', 5'-cyclic monophosphate) as a photoaffinity probe for cAMP binding sites in human erythrocyte membranes. The increased resolution obtained using a linear-gradient SDS polyacrylamide gel system now shows that: 1) both cAMP and 8-N3cAMP stimul... |
1033438 | The action of cytochalasin A on the in vitro polymerization of brain tubulin and muscle G-actin. | The presence of cytochalasin A inhibits the self-assembly of beef brain tubulin and rabbit muscle G-actin in vitro and also decreases the colchicine binding of tubulin. Prior reaction of cytochalasin A with 2-mercaptoethanol destroys its inhibitory effects. It is shown that cytochalasin A exerts its actions by reacting... |
994501 | Control of membrane morphogenesis in bacteriophage PM2. | The regulation of membrane formation in bacteriophage PM2 serves as a simple model for changes in membrane structure in eukaryotic cells. Prior to Pseudomonas host lysis, wild-type virions mature to an icosahedral morphology at the inner face of the cytoplasmic membrane. The preliminary characterization of two temperat... |
792570 | Cell shape changes and transmembrane receptor uncoupling induced by tertiary amine local anesthetic. | Tertiary amine local anesthetics (dibucaine, tetracaine, procaine, etc.) modify cell morphology, concanavalin A (Con A)-mediated agglutinability and redistribution of Con A receptors. Con A agglutination of untransformed mouse 3T3 cells was enhanced at low concentrations of local anesthetics, and the dynamics of fluore... |
994500 | Purification of plasma membranes from rat mammary gland by a density perturbation procedure. | A highly purified plasma membrane fraction was obtained from a microsomal subfraction of rat mammary gland after treatment with digitonin to increase its density. The purified membranes were enriched 70-fold overall in 5'-nucleotidase with essentially no contamination from glactosyltransferase, succinate-ING reductase,... |
136550 | Functional organization of the outer membrane of escherichia coli: phage and colicin receptors as components of iron uptake systems. | The functional interaction of outer membrane proteins of E. coli can be studied using phage and colicin receptors which are essential components of penetration systems. The uptake of ferric iron in the form of the ferrichrome complex requires the ton A and ton B functions in the outer membrane of E. coli. The ton A gen... |
11368 | Isolated cortical granules: a model system for studying membrane fusion and calcium-mediated exocytosis. | Cortical granules are secretory vesicles bound to the inner surface of the plasma membrane of sea urchin eggs. Intact granules can be isolated by shearing away the cytoplasm of eggs which have been bonded to a protamine-coated surface. When Ca2+ is added to preparations of isolated granules the granules fuse with each ... |
136549 | Some changes in the properties of dynein ATPase in situ and after extraction following heat treatment of cilia. | Glycerol-extracted cilia from Tetrahymena pyriformis were demembranated by treatment with Triton X-100 and then heated for up to 30 min at temperatures between 34-38 degrees C. Heat treatment caused an uncoupling of the ATPase from motility as indicated by an increase in ATPase activity and a loss of pellet height resp... |
792569 | Topography of outer membrane assembly in Salmonella. | The topography of lipopolysaccharide insertion into the outer membrane of Salmonella is discussed in context with a review of recent findings pertaining to general properties of the outer membrane, such as asymmetry and lateral mobility of surface components. |
994499 | Hexagonal packing of lipid acyl chains and membrane plasticity. | Electron microscope and electron diffraction observations on microcrystals of pure lipids (a phosphatidylethanolamine, two phosphatidylcholines, a phosphatidic acid, and a galactocerebroside) reveal an extreme flexibility of lipid layers when the acyl chains are hexagonally packed (d100 = 4.17 A). This is corroborated ... |
823744 | Life cycle patterns and their genetic control: an attempt to reconcile evolutionary and mechanistic speculation. | A model is proposed which implicates molecular recognition systems as the major controlling factors in life cycle expression. It is envisaged that such systems are important in immune functioning and catabolic, metabolic molecule recognition at both inter- and intra-cellular level. These recognition systems have the fo... |
933540 | A scanning electron microscope study of concanavalin A receptors on retinal rod cells labeled with latex microspheres. | Con A-methacrylate microsphere conjugates prepared by a two-step glutaraldehyde reaction were used to label Con A-binding sites on bovine rod photoreceptor cells for visualization by scanning electron microscopy. A dense distribution of markers was observed on the surface of the rod outer segment, the inner segment, an... |
933539 | Protein transport: a selective membrane mechanism. | Proteins are selectively sequestered by a number of cell types. However, only in oocytes is the process sufficiently aggravated and specific to be readily studied. In these cells certain serum proteins are taken up in proportions different from those found in the serum. In vitro incubations of hormonally stimulated and... |
933538 | Drug-resistant mutants of Chinese hamster ovary cells possess an altered cell surface carbohydrate component. | Surface label experiments using the galactose oxidase-]3H]-borohydride technique reveal that cells from drug-resistant Chinese hamster ovary clones possess a surface carbohydrate component of apparent molecular weight 165,000 which is absent from wild-type cells. The component may also be demonstrated by [14C]glucosami... |
1084445 | Light-induced tetracycline accumulation by Rhodopseudomonas sphaeroides. | Light has been used as a primary energy source in studies of tetracycline transport by Rhodopseudomonas sphaeroides. Accumulation of the antibiotic occurs in light, while efflux occurs in dark. Both fluorescence enhancement and radioisotopic tracing have been used to monitor transport. Km's obtained from both technique... |
1084444 | Estimation of cell surface associated protease activity and its application to lymphocytes. | A new method has been developed to estimate proteolytic activity available at the cell surface. Radioiodinated protein substrates are covalently linked to modified polystyrene-divinylbenzene beads with various diameters. These beads are presented to viable cells. Secreted enzyme activity is estimated when no contact oc... |
180356 | Avian tumor virus interactions with chicken fibroblast plasma membranes. | A method is described which will rapidly measure the binding of avian tumor viruses (ATV) to plasma membrane receptors. With this procedure it may be shown that Rous sarcoma virus pseudotypes bind to protease-labile, heat-stable structures on the surface of chicken embryo fibroblast (CEF) plasma membranes. The binding ... |
180355 | Effect of essential fatty acid deficiency on activity of liver plasma membrane enzymes in the rat. | Liver plasma membranes (LPM) were isolated from rats fed an essential fatty acid-supplemented diet (+EFA) or from rats fed an essential fatty acid-deficient diet (-EFA). The proportions of linoleate and arachidonate in membrane total fatty acids in the -EFA preparations were one-half or less than the values for the +EF... |
933537 | Substrate heterogeneity of component a of the human erythrocyte membrane. | Component a of the erythrocyte membrane is a specific substrate for endogenous protein kinase activity and its phosphorylation is significantly decreased under assay conditions in myotonic muscular dystrophy (Roses, A.D., and Appel, S.H.J. Membr. Biol 20:51-58 (1975)). We have demonstrated substrate heterogeneity of tw... |
933536 | Effect of polyamines on the uptake of poly (2'-fluoro-2'-deoxyuridylic acid) by a mammalian cell line. | VERO cells can take up poly(dUfl)1 from the medium. The uptake involves surface adsorption and, most probably, intracellular penetration. Part of the poly(dUfl) is hydrolyzed during incubation with the cells but the hydrolysis products are not incorporated into de novo synthesized nucleic acids. The uptake is reduced b... |
778494 | The role of cell membrane in the antiviral effect of interferon. | The mechanism of interferon action in human fibroblasts has been studied by use of both antisera to human fibroblast interferon and the antisera to the surface of human fibroblast cell. The anti-interferon serum completely neutralized the antiviral effect of human fibroblast interferon. Interferon antiserum prevented t... |
778493 | Conjugated polyene fatty acids as fluorescent membrane probes: model system studies. | The use of conjugated polyene fatty acids as probes of membrane structure is examined, alpha- and beta-parinaric acid (cis, trans, trans, cis- and all trans-9, 11, 13, 15-octadecatetraenoic acid) and synthetic lecithins containing an alpha-parinaric acid chai in position 2 have been prepared, and their absorption and f... |
180354 | Transport of amino acids in intact 3T3 and SV3T3 cells. Binding activity for leucine in membrane preparations of ehrlich ascites tumor cells. | Transport of amino acids into 3T3 and SV3T3 (SV40 virus-transformed 3T3) cells was measured on glass cover slips. The 3T3 and SV3T3 cells contain both A (alanine preferring) and L (leucine prefferring) systems for neutral amino acid transport. Initial rates of uptake of amino acids are about twofold higher in SV3T3 tha... |
180353 | The existance of a group translocation transport mechanism in animal cells: uptake of the ribose moiety of inosine. | After exposure to inosine, transport-competent plasma membrane vesicles isolated from SV-40-transformed Bal/c 3T3 cells accumulate intravesicular ribose 1-PO4 at a concentration 200-fold greater than the extravesicular concentration. An analysis of the purine nucleoside phosphorylase activity distribution in various su... |
1263516 | Reconstitution of a purified acetylcholine receptor. | Dialysis of the purified acetylcholine receptor from Torpedo californica electroplax with lipids from the same organ results in a vesicular membrane system in which the receptor is embedded in the bilayer and oriented so that most of the neurotoxin-binding sites appear to be on the outer surface. The reconstituted vesi... |
1263515 | The regulatory control of beta-receptor dependent adenylate cyclase. | The characteristics of the beta-receptor in turkey erythrocyte adenylate cyclase were studied using both kinetics of enzyme activation and direct binding measurement of the beta-agonists and antagonists to the beta-receptor. The regulatory ligands Gpp(NH)p and Ca2+ do not have any direct effect on the beta-receptor, bu... |
817087 | Immunological studies of acetylcholine receptors. | Immunochemical techniques for the study of acetylcholine receptors are described. Immunization of rabbits, rats, guinea pigs, and goats with acetylcholine receptor protein purified from Electrophorus electric organ tissue results in muscular weakness and death due to impaired neuromuscular transmission. Serum from immu... |
772316 | Appearance of acetylcholine receptors in cultured myoblasts prior to fusion. | The development of the acetylcholine receptors in chick embryo myoblasts from 11-day old embryos was studied in vitro. Using the purified alpha-bungarotoxin labeled with radioactive iodide, a high concentration of acetylcholine receptors was found in the prefusing myoblasts; most of these receptors were located in the ... |
1263514 | Effect ofcholinergic ligands on the lipids of acetylcholine receptor-rich membrane preparations from Torpedo californica. | Ion permeation, triggered by ligand-receptor interaction, is associated with the primary events of membrane depolarization at the neuromuscular junction and synaptic connections. To explore the possible sites of ion permeation, the long-lived fluorescent probe pyrene (fluorescence lifetime approximately 400 nsec) has b... |
1263513 | Binding of agonists and antagonists to muscarinic receptors. | The binding of one irreversible and two reversible radioactive antagonists to muscarinic receptors in synaptosome preparations of rat cerebral cortex has been studied. The ligands all bind to the same receptor pool and directly and competitively yield self-consistent binding constants closely similar to those obtained ... |
4659 | Preliminary characterization of the acetylcholine receptor in human erythrocytes. | The response of human erythrocytes to cholinergic ligands was studied with an electron spin resonance assay. The membrane response to carbamyl choline was found to be antagonized by atropine and, in the absence of calcium, by tetrodotoxin. Experiments with resealed ghosts showed that the membrane response to carbamyl c... |
1263512 | Perturbation of the chemotactic tumbling of bacteria. | The bacterial sensing system has been studied on three levels. First, a quantitative method has been devised for measuring the "action spectrum" of the bacterium in response to a sudden addition of attractant. Second, a technique has been developed for the rapid isolation of mutants defective in the transmission part o... |
772315 | Studies of bacterial chemotaxis in defined concentration gradients. A model for chemotaxis toward L-serine. | The details of the chemotactic response of Salmonella typhimurium to gradients of L-serine have been examined in some detail. Two relatively macroscopic techniques have been employed to measure the bacterial response. These include measurements of the average velocity as the bacterial population moves toward attractant... |
4658 | Lesion-induced synaptogenesis in brain: a study of dynamic changes in neuronal membrane specializations. | When incoming fibers to a given brain region are damaged and degenerate, the remaining undamaged fibers can, in some cases, form new synapses, and restore physiologically functional circuitry. Synaptic membrane events underlie this reconstruction: the connection between membranes is broken and reformed. |
772314 | Chemotaxis in bacteria. | Bacterial chemotaxis, the movement of motile bacteria toward or away from chemicals, was discovered nearly a century ago by Engelmann (1) and Pfeffer (2,3). The subject was actively studied for about 50 years, but then there were very few reports until quite recently. For reviews of the literature up to about 1960, see... |
177820 | Vasopressin-sensitive kidney adenylate cyclase: modulation of the hormonal response. | Vasopressin-sensitive pig kidney adenylate cyclase is sensitive to several effectors, such as Mg2+, other divalent cations, and guanyl nucleotides. The purpose of the present study was to compare the main characteristics of adenylate cyclase activation by vasopressin, Mg2+, and GMPPNP, respectively. Mg2+ ions were show... |
177819 | Cyclic nucleotides and cell growth. | Growth induction in resting fibroblast cultures by serum or growth factors induces a fast, transient cGMP peak which may constitute the intracellular signal for growth. A similar cGMP peak occurs when 3T3 cells arrested at the restriction point or in G0 by starvation for certain amino acids are induced for growth by re... |
177818 | Regulation of SV40-induced cell division and tumor antigen by dibutyryl adenosine 3'-5'-monophosphate. | Simian virus 40 (SV40) induces cell division in microcultures of sparsely plated nongrowing mouse BALB/3T3 cells during acute infection at moderate multiplicities of infection (MOI = 10-100). The infected cells are killed when a MOI of 1,000 is used. SV40 tumor (T) antigen is synthesized in the infected cells, but vira... |
177817 | Hormone receptor mobility and catecholamine binding in membranes. A theoretical model. | [3H]-Catecholamine binding to intact cells, isolated cell membranes, and to several isolated macromolecules has been shown by several laboratories to be neither stereospecific nor inhibited by known beta-antagonists. Since additional evidence indicates that this binding is not an artifact (i.e. due neither to the bindi... |
177816 | Cooperative properties of hormone receptors in cell membranes. | The binding of many polypeptide hormones to cell surface receptors does not appear to follow the law of mass action. While steady-state binding data are consistent in many cases with either heterogeneous populations of binding sites or interactions of the type known as negative cooperativity, study of the kinetics of d... |
177815 | Insulin binding and glucose transport in the R3230AC mammary adenocarcinoma. | Cells dissociated from the R3230AC mammary adenocarcinoma from intact and diabetic rats were examined for insulin binding and glucose transport. The Kd for insulin binding, approximately 10(--10) M, was similar in all tumors studied. However, the apparent number of receptor sites per cell increased in cells from diabet... |
1263511 | The HLB dependency for detergent solubilization of hormonally sensitive adenylate cyclase. | The HLB dependency for the solubilization of membrane proteins and adenylate cyclase activity from a plasma membrane-enriched fraction from rat liver has been determined. The HLB (hydrophilic/lipophilic/balance) number of a detergent is an empirical measure of its relative hydrophobicity. Detergent HLB numbers vary sys... |
1263510 | Some kinetic and chromatographic properties of detergent-dispersed adenylate cyclase. | Studies on the reaction kinetics and chromatographic properties of detergent-dispersed adenylate cyclase are described. Detergent-dispersed enzyme was prepared from whole rat cerebellum and from partially purified plasma membranes from rat liver. Data were simulated to fit kinetic models for which an inhibitor is added... |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.