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6263487 | Homologous pairing and topological linkage of DNA molecules by combined action of E. coli RecA protein and topoisomerase I. | E. coli RecA protein and topoisomerase I, acting on superhelical DNA and circular single strands in the presence of ATP and Mg2+, topologically link single-stranded molecules to one another, and single-stranded molecules to duplex DNA. When superhelical DNA is relaxed by prior incubation with topoisomerase, it is a poo... |
7228895 | Dictyostelium myosin: characterization of chymotryptic fragments and localization of the heavy-chain phosphorylation site. | Chymotrypsin cleaves Dictyostelium myosin in half, splitting the heavy chain (210,000 daltons) into two fragments of 105,000 daltons each. One of the two major fragments is soluble at low ionic strength and has a native molecular weight of 130,000. As judged by SDS polyacrylamide gel electrophoresis, this soluble fragm... |
7013831 | Calcium-calmodulin-dependent phosphorylations in the control of muscular contraction? | Muscular contraction is triggered by the increase in free calcium concentration and modulated by cyclic nucleotide-dependent phosphorylation. Beside a direct trigger of sarcomeric muscle contraction through binding of troponin C, calcium ions trigger or modulate contractility through calcium-calmodulin-dependent myosin... |
7013719 | Significance of fibronectin in rheumatoid arthritis and osteoarthrosis. | Fibronectin is a glycoprotein secreted by connective tissue cells into their environment and into the blood. Plasma fibronectin has been isolated and used to prepare an antiserum. This has been shown to be specific for fibronectin and unreactive with fibrin(ogen) and collagen, to which fibronectin binds in vitro. The a... |
6261143 | Selective antagonists of benzodiazepines. | Benzodiazepines produce most, if not all, of their numerous effects on the central nervous system (CNS) primarily by increasing the function of those chemical synapses that use gamma-amino butyric acid (GABA) as transmitter. This specific enhancing effect on GABAergic synaptic inhibition is initiated by the interaction... |
7217003 | Recovery of competence in calcium-limited Azotobacter vinelandii. | Azotobacter vinelandii cells required 0.5 mM calcium in the iron-limited competence induction medium. This requirement also was fulfilled by strontium, but not by magnesium. Cells pregrown in competence medium lacking calcium rapidly recovered competence with the addition of 0.5 mM calcium, provided they were suspended... |
7012113 | Role of the supX gene in ultraviolet light-induced mutagenesis in Salmonella typhimurium. | Salmonella typhimurium strains with supX mutations are more sensitive than wild type to killing by ultraviolet (UV) irradiation. Studies with strains bearing the leuD21 mutation revealed that inactivation of the supX locus by a nonsense mutation or a deletion results in a complete lack of ability to produce induced Leu... |
7012112 | Reconstitution of maltose transport in malB mutants of Escherichia coli through calcium-induced disruptions of the outer membrane. | The barrier function of the Escherichia coli outer membrane against low concentrations of maltose in strains missing the lambda receptor was partially overcome by treating the cells for 3 h with 25 mM Ca2+. Kinetic analysis of maltose-transport revealed a Ca2+-induced shift of the apparent Km of the system from about 1... |
6940182 | Use of lectins and polyethylene glycol for fusion of glycolipid-containing liposomes with eukaryotic cells. | Efficient fusion of phospholipid vesicles with monolayer cultures of eukaryotic cells was accomplished by attaching glycolipid-containing vesicles to the cell surface by using a lectin displaying binding for both the cell surface and the glycolipid, followed by treatment with polyethylene glycol. Fusion was inferred fr... |
6262822 | Spectroscopic characterization of compound C and related derivatives of cytochrome oxidase. | Magnetic circular dichroism and resonance Raman spectra have been obtained for three "oxygenated" derivatives of cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.1). The spectra are interpreted and four alternatives for the states of cytochrome a3 and Cuu are evaluated. |
6262821 | Structural and functional domains of the Rous sarcoma virus transforming protein (pp60src). | The transforming protein (pp60src) of the Rous sarcoma virus (RSV) is a phosphoprotein with the enzymatic ability to phosphorylate tyrosine in protein substrates. Previous work has indicated that the bulk of pp60src may be attached to the plasma membrane of infected cells. In an effort to better understand the mechanis... |
7225362 | Differences in iron-fluoride bonding between the isolated subunits of human methemoglobin fluoride and sperm whale metmyoglobin fluoride as measured by resonance Raman spectroscopy. | The heme geometries of the isolated alpha and beta subunits of human methemoglobin fluoride (HbIIIF) and sperm whale metmyoglobin fluoride (MbIIIF) have been examined by exciting their Raman spectra within their ca. 6000-A charge-transfer absorption bands. The Fe-F stretching vibration at 471 cm-1 in the beta subunits ... |
7218012 | Neurogenesis in olfactory epithelium: loss and recovery of transepithelial voltage transients following olfactory nerve section. | 1. Unilateral olfactory nerve section was performed on the salamander, Ambystoma tigrinum. Physiological recordings and macroscopic observations were made to investigate the physiological correlates of functional recovery in the olfactory epithelium. 2. Slow transepithelial voltage transients, Veog, evoked by several o... |
6111566 | A permeabilized cell model for studying cell division: a comparison of anaphase chromosome movement and cleavage furrow constriction in lysed PtK1 cells. | After lysis in a Brij 58-polyethylene glycol medium, PtK1 cells are permeable to small molecules, such as erythrosin B, and to proteins, such as rhodamine-labeled FAB, myosin subfragment-1, and tubulin. Holes are present in the plasma membrane, and the mitochondria are swollen and distorted, but other membrane-bounded ... |
7217202 | Distribution of proteins between nucleus and cytoplasm of Amoeba proteus. | By transplanting nuclei between labeled and unlabeled cells, we determined the localization of the major proteins of amebas and described certain features of their intracellular distributon. We identified approximately 130 cellular proteins by fluorography of one-dimensional polyacrylamide electrophoretic gels and foun... |
7204671 | Fate of the hippocampal mossy fiber projection after destruction of its postsynaptic targets with intraventricular kainic acid. | Intraventricular injections of kainic acid were used to create a model of selective cell death in order to study the fate of afferent projections that are deprived of their postsynaptic targets. This treatment rapidly destroyed hippocampal CA3 pyramidal cells, but not those neurons that give rise to their mossy fiber a... |
7009573 | Growth rate-dependent control of chromosome replication initiation in Escherichia coli. | The initiation mass, defined as cell mass per origin of deoxyribonucleic acid replication (optical density units at 460 nm of culture/origins per milliliter of culture), reflects the intracellular concentration or activity of a hypothetical factor that controls initiation of chromosome replication in bacteria. In Esche... |
21289692 | Resolving the sore throat dilemma. | Many physicians ignore the traditional dictum that throat culture is the only tool of value in assessing sore throat. A review of the literature supports this skepticism. Evidence indicates that clinical assessment has been underestimated and the significance of positive culture exaggerated.An approach to managing phar... |
7028150 | Improved technique for investigation of cell metabolism by 31P NMR spectroscopy. | 31P NMR studies on microorganisms have been carried out with the cells embedded in agarose gel. The novel use of the gel for the NMR studies has advantages over the usual liquid suspensions in terms of improved reproducibility of data and cell viability, with no net loss of spectral quality. Polyphosphate formation in ... |
7277200 | Protective effects of cyclodextrins on drug-induced hemolysis in vitro. | beta-Cyclodextrin (beta-CyD) significantly protected the human erythrocytes from hemolysis and shape changes induced with chlorpromazine and flufenamic acid in isotonic solution. A good correlation between the stability constants of inclusion complexes (beta- greater than gamma- greater than alpha-CyD) and the inhibito... |
6262776 | Catenation and knotting of duplex DNA by type 1 topoisomerases: a mechanistic parallel with type 2 topoisomerases. | Escherichia coli omega protein, a type 1 topoisomerase, can catenate and knot duplex DNA circles. Previously, these activities were thought to be limited to type 2 topoisomerases. Catenation by omega requires a nick in one of the participating molecules, but it is not necessary that both be nicked. Catenation does not ... |
7204503 | Self-assembly of spectrin oligomers in vitro: a basis for a dynamic cytoskeleton. | Purified human erythrocyte spectrin is able to form large oligomeric species without the collaboration of any other proteins. This reversible self-assembly process is both temperature and concentration dependent and seems to be mediated by the same kinds of low affinity noncovalent associations between spectrin monomer... |
6894149 | Involvement of contractile proteins in the changes in consistency of oocyte nucleoplasm of the newt Pleurodeles waltlii. | In the present work, we show that actin is present in considerable quantities in the oocyte nucleus of the newt Pleurodeles waltlii. The nuclear sap, extracted in saline buffer containing Ca++, is fluid. DNAase I inhibition assays have shown that 90% of actin is under a globular state in such conditions. Chelation of C... |
7462426 | Effects of hepatectomy, nephrectomy, and nephrectomy/uremia on the metabolism of parathyroid hormone in the rat. | Reports from several laboratories, showing extensive hepatic extraction of circulating parathyroid hormone, led us to examine the effect of near-total hepatectomy on the metabolism of the hormone to circulating fragments, and on its clearance from plasma. The rate of disappearance of (125)I-labeled and unlabeled bovine... |
7007337 | Incomplete flagellar structures in Escherichia coli mutants. | Escherichia coli mutants with defects in 29 flagellar genes identified so far were examined by electron microscopy for possession of incomplete flagellar structures in membrane-associated fractions. The results are discussed in consideration of the known transcriptional interaction of flagellar genes. Hook-basal body s... |
6100956 | Murine teratocarcinoma: a model for virus-cell interaction in a differentiating cell system. | The stem cell of the murine teratocarcinoma is refractory to infection with Simian virus 40 and polyoma. Utilizing various procedures, we attempted to alter this block to infection by modifying the infection procedure. Multiple infections with high-titer SV40 and pretreatment of cells with DEAE-dextran or the carcinoge... |
6965091 | Neonatal imprinting and hepatic cytochrome P-450. II. Partial purification of a sex-dependent and neonatally imprinted form(s) of cytochrome P-450. | A new form of cytochrome P-450 was partially purified from hepatic microsomes of neonatally imprinted rats (adult male and adult male castrated at four weeks of age). This new form of cytochrome P-450 appears to have an apparent molecular weight of approximately 50,000 daltons as judged by sodium dodecyl sulfate polyac... |
6086006 | Purification and characterization of multiplication-stimulating activity (MSA) carrier protein. | The rat liver cell line, BRL-3A, is known to produce a family of polypeptides referred to as multiplication-stimulating-activity (MSA). Serum-free conditioned medium from this cell line is a rich source for the purification of these somatomedin-like molecules. Somatomedins in serum, as well as MSA produced by BRL-3A ce... |
6100955 | Release of erythropoietin from macrophages by treatment with silica. | An erythropoietic stimulating factor (ESF) can be shown to be released from preincubated macrophage-containing cell suspensions from mice by the macrophage-specific, cytotoxic agent, silica. A concentrated silica-treated spleen cell supernatant containing ESF is shown to cause a dose-dependent increase in 59Fe incorpor... |
6965248 | Cell cycle activation and ouabain-sensitive ion movements of 3T3 and C3H-10T1/2 fibroblasts. | The introduction of either PGF2 alpha-(10(-7) M) or TPA (10(-7) M) stimulated, ouabain-sensitive 86Rb+ influx at 30 min in postconfluent 3T3-4 mouse fibroblast cultures by 117% and 124%, respectively. Both TPA and PGF2 alpha at these concentrations stimulated the incorporation of 3H-TdR into DNA. TPA had the greatest s... |
6100954 | Effects of guanine nucleotides on CNS neuropeptide receptors. | The effect of nucleotides on central nervous system neuropeptide receptor binding was investigated. The guanine nucleotides, guanosine-5'-triphosphate and guanylyl-5'-imidodiphosphate, significantly inhibited the binding of radiolabeled vasoactive intestinal polypeptide but not that of [Tyr4]bombesin to rat brain membr... |
6965090 | In vitro characteristics of metastatic variant subclones of restricted genetic origin. | We have studied several metastatic variant cell lines derived from a common clonal origin and their transformed and untransformed parental cell lines. A number of in vitro characteristics were examined for each tumor line and these properties were correlated with the ability of the tumor cells to form pulmonary nodules... |
6965089 | Spectrin-4.1-actin complex of the human erythrocyte: molecular basis of its ability to bind cytochalasins with high-affinity and to accelerate actin polymerization in vitro. | The spectrin-4.1-actin complex isolated from the cytoskeleton of human erythrocyte was found to be similar to muscle F-actin in several aspects: Both the complex and F-actin nucleate cytochalasin-sensitive actin polymerization; both bind dihydrocytochalasin B with similar binding contrasts; both can be depolymerized by... |
6100953 | Effect of exogenous fatty acids on growth, membrane fluidity, and phospholipid fatty acid composition in yeast. | The growth response of a double-mutant fatty acid auxotroph of yeast Saccharomyces cerevisiae to exogenous saturated fatty acids of a homologous series from 12:0 to 16:0, each supplied with oleate, linoleate, linolenate, or cis-delta 11-eicosenoate, cannot be explained in terms of the efficiency of incorporation of the... |
6965088 | The hatching enzyme from Xenopus laevis: limited proteolysis of the fertilization envelope. | Hatching in the amphibian Xenopus laevis involves release of an embryo-secreted hatching enzyme, a protease, which weakens the envelope surrounding the embryo. The envelope is not totally solubilized, which infers that only selected envelope components are hydrolyzed by the enzyme. The susceptibility of the glycoprotei... |
7342601 | The existence of a precursor of cathepsin D: evidence from autolysis, denaturation and activation studies. | This report evidences that the single polypeptide chain of cathepsin D undergoes in vitro autolysis resulting in heavy (Mr about 30000) and light (Mr about 15000) polypeptide chains. These two chains are held together through non-covalent interaction, thus constituting a stable active conformation. Fluorescence and cir... |
6276574 | Long-term epidermal growth factor-receptor internalization and processing in quiescent human fibroblasts. | Epidermal growth factor is internalized into cells and concomitantly induces a massive clearance of up to 90% of its total surface receptors. The hormone-receptor complex is delivered to lysosomes and degraded or inactivated. Lysosomotropic alkylamines block the degradation but not the binding or internalization of lig... |
7328679 | Rejoining of DNA double-strand breaks in human fibroblasts and its impairment in one ataxia telangiectasia and two Fanconi strains. | Using the technique of neutral elution through polycarbonate filters as a measure of DNA length, and hence of the number of double-strand breaks incurred as a result of radiation damage, we found that normal human fibroblasts rejoin 50% of all breaks within only 3 min (37 degrees C). This fast rejoining was impaired in... |
7328678 | Developmental regulation of glycoprotein biosynthesis in Dictyostelium. | We have examined the glycoprotein-linked oligosaccharides assembled during the life cycle of Dictyostelium discoideum, and found their expression to be dramatically dependent upon the stage of development. During early development mature glycans have a high mannose character, and a substantial proportion acquire a fuco... |
6977040 | Cell interactions in the bone marrow microenvironment: role of endogenous colony-stimulating activity. | Adherent stromal cells from mouse bone marrow inhibited the formation of granulocyte/monocyte (G/M) colonies induced in vitro by colony-stimulating factor (CSF). This inhibition occurred both when crude conditioned media obtained from various sources were used to induce colony formation or when a pure CSF preparation f... |
7328677 | The resolution of two populations of lysosomal organelles containing endocytosed Wistaria floribunda agglutinin from murine fibroblasts. | Subcellular fractionation of Balb/c 3T3 fibroblasts exposed to Wistaria floribunda agglutinin was performed to localize fractions containing internalized lectin. Employing two sequential self-generating silica sol density gradients, the postnuclear supernatant of cell homogenates was resolved into five distinct cellula... |
7328676 | The role of glycoconjugates in metastatic melanoma blood-borne arrest and cell surface properties. | The role of glycoconjugates in cell surface and blood-borne implantation properties of murine metastatic melanoma sublines of low (B16-F1) or high (B16-F10) potential to colonize lungs was investigated by treating melanoma cells with the antibiotic tunicamycin. This drug prevents glycosylation of glycoproteins by inhib... |
6977039 | Involvement of fibronectin, Von Willebrand factor, and fibrinogen in platelet interaction with solid substrata. | The proteins fibronectin (FN), Von Willebrand factor (VWF), and fibrinogen are believed to play a role in platelet function. They are distributed between the plasma and the platelet pool in the resting state and undergo redistribution upon platelet activation. We have studied their expression on the surface of the plat... |
6799655 | Anomalous cell surface structure of sickle cell anemia erythrocytes as demonstrated by cell surface labeling and endo-beta-galactosidase treatment. | Erythrocyte surface glycoproteins from patients with various types of sickle cell anemia have been analyzed and compared with those from normal individuals. By hemagglutination with various anti-carbohydrate antibodies, sickle cells showed profound increase of i antigens and moderate increase of GlcNAc beta 1 leads to ... |
7328675 | Spectrin oligomers: a structural feature of the erythrocyte cytoskeleton. | Spectrin reversibly self-associates to high molecular weight oligomers through a concentration-driven process characterized by association constants of about 10(5) mol(-1). This association if prominent under physiological conditions of pH, ionic strength, and temperature. It is disrupted by urea, but not Triton X-100.... |
7328674 | Alkylation of DNA and tissue specificity in nitrosamine carcinogenesis. | A peculiarity of nitrosamines is the high degree of cell and organ specificity in inducing tumors. There is substantial evidence that the initiation of the carcinogenesis process by carcinogens of this group is linked to the metabolic competence of the target tissue or cell to convert these carcinogens into mutagenic m... |
7328673 | Initiator and promoter induced specific changes in epidermal function and biological potential. | Mouse epidermal basal cells can be selectively cultivated in medium with a calcium concentration of 0.01--9.09 mM. Terminal differentiation and sloughing of mature keratinocytes occur when the calcium concentration is increased to 1.2--1.4 mM. When basal cell cultures are exposed to chemical initiators of carcinogenesi... |
7328672 | Alternative conformations of DNA modified by N-2-acetylaminofluorene. | Modification of DNA by the carcinogen N-acetoxy-N-2-acetylaminofluorene gives two adducts, a major one at the C-8 position of guanine and a minor one at the N-2 position with differing conformations. Binding at the C-8 position results in a large distortion of the DNA helix referred to as the "base displacement model" ... |
7328670 | Effects of multiple membranes on measurements of cell surface dynamics by fluorescence photobleaching. | Fluorescence photobleaching recovery curves on a pair of membranes at various separations were calculated from a detailed knowledge of the variation in relative illumination areas and intensities as well as in relative contributions to the collected intensity with membrane separation. The observed diffusion coefficient... |
7328669 | Immunological analysis of glycoprotein (contact sites A) involved in intercellular adhesion of Dictyostelium discoideum. | We have prepared antisera in rabbits to the "contact sites A" glycoprotein (gp80) purified from Dictyostelium discoideum. IgG isolated these antisera reacts with a number of different proteins in D discoideum lysates, as analyzed by immune precipitation and by antibody staining of gel electropherograms transferred to n... |
7321059 | Factors implicated in determining the structure of zinc tubulin-sheets: lateral tubulin-tubulin interaction is promoted by the presence of zinc. | Addition of increasing amounts of zinc to a cold microtubule protein solution results in the disappearance of 30 S oligomer found in the absence of that cation and in the appearance of new tubulin oligomers, 90 S and 23 S. When a microtubule protein solution is warmed in the presence of zinc, tubulin-sheets are assembl... |
7321058 | Member-associated changes during erythropoiesis. On the mechanism of maturation of reticulocytes to erythrocytes. | The mature mammalian erythrocyte has a unique membranoskeleton, the spectrin-actin complex, which is responsible for many of the unusual membrane properties of the erythrocyte. Previous studies have shown that in successive stages of differentiation of the erythropoietic series leading to the mature erythrocyte there i... |
7321057 | Structural analysis of fibronectin with monoclonal antibodies. | The reactivity of six monoclonal antibodies with fragments of fibronectin produced with trypsin, chymotrypsin, and Staphylococcus aureaus V8 protease is described. All these antibodies reacted with fragments derived from the C-terminal one-third of fibronectin. This region probably contains sites for the binding of fib... |
6172592 | Quantitation of changes in cell surface determinants during skeletal muscle cell differentiation using monospecific antibody. | The differentiation of skeletal muscle is characterized by recognition, alignment, and subsequent fusion of myoblast cells at their surfaces to form large, multinucleated myotubes. Monoclonal antibodies were used to investigate antigenic changes in the cell surface membrane specific for various stages of myogenesis. Ch... |
6275090 | Simian virus 40 as a probe for studying inducible repair functions in mammalian cells. | We describe the use of Simian Virus 40 (SV40) as a molecular probe for studying the cellular functions induced in cultured monkey kidney cells in response to DNA damaging agents. (a) Ultraviolet (UV) irradiation of SV40-infected cells inhibits viral DNA replication. Replication forks are blocked by the first pyrimidine... |
7198692 | Fibronectin expression on the platelet surface occurs in concert with secretion. | Thrombin stimulation of human platelets causes increased cellular adhesiveness for other platelets (aggregation) and surfaces and increased surface expression of platelet fibronectin antigen. Aggregation occurs concurrently with secretion. In these studies, the threshold thrombin dose for surface expression of fibronec... |
7321056 | Unscheduled synthesis of DNA and poly(ADP-ribose) in human fibroblasts following DNA damage. | Unscheduled DNA synthesis has been measured in human fibroblasts under conditions of reduced rates of conversion of NAD to poly)ADP-ribose). Cells heterozygous for the xeroderma pigmentosum genotype showed normal rates of UV induced unscheduled DNA synthesis under conditions in which the rate of poly(ADP-ribose) synthe... |
7321055 | Neuronal differentiation in cultures of weaver (wv) mutant mouse cerebellum. | In the present study we report for the first time a weaver (wv) gene dose effect on neuron survival and neurite formation in vitro. Dissociated cerebellar cells from postnatal 7- and 8-day-old normal (+/+), heterozygous weaver (+/wv) and homozygous weaver (wv/wv) mice were cultured as monolayers on poly-L-lysine coated... |
6895651 | The synthesis of a proteinase inhibitor, alpha-1-antichymotrypsin, by human breast epithelial cells. | The synthesis and release of glycoproteins were studied in organ cultures of human breast surgical specimens and in established breast epithelial cell lines, MCF-7 and MDA-MB-231. Biosynthesis was monitored by the incorporation of 14C-glucosamine. Labeled macromolecules in the culture supernatants were analyzed by bioc... |
7321054 | Association dynamics and lateral transport in biological membranes. | A theoretical analysis is presented for the interrelated effects of lateral diffusion and a simple form of molecular association (A + B in equilibrium with C) in biological membranes. Expression are derived for the characteristic functions measured in fluorescence redistribution after photobleaching experiments, corres... |
7321053 | Glycoprotein differences among cells of the 14-day embryonic chick neural retina. | In order to test the hypothesis that the progressive layering and differentiation of cell types during the development of the neural retina are associated with cell surface alterations we have separated distinct cell populations from the 14-day embryonic chick retina. Cells of these populations have been shown to diffe... |
6172591 | Antigen-specific mouse lymphocyte stimulation by DNP-conjugated T-independent antigens studied by photobleaching recovery. | Fluorescence photobleaching recovery techniques have allowed us to measure the lateral mobility of T-independent antigens bound to antigen-specific mouse B cells. The in vitro immunogenicity or tolerogenicity of antigens we have examined, DNP-polymerized flagellin (DNP-POL), and DNP-linear dextran (DNP-DEX), depend upo... |
7321052 | Microchemical instrumentation. | A number of cell surface molecules of great theoretical and practical importance simply cannot be obtained in amounts sufficient for molecular analysis using conventional methods and instrumentation. Because of our interest in such studies, we began about eight years ago to explore the possibility of developing new ins... |
7321051 | Macrophages and methylthio groups in lymphocyte proliferation. | Macrophages are shown to replace methylthio disulfides in supporting in vitro proliferation of three cell lines previously characterized as methylthio-dependent. Macrophages have the capacity to generate methylthio groups from methylthioadenosine. It is hypothesized that macrophages stimulate cell proliferation both in... |
6798219 | Aggregation of sponge cells: immunological characterization of the species-specific Geodia aggregation factor. | Antibodies were raised against the purified aggregation factor from Geodia cydonium in order to clarify its function during cell aggregation in the homologous and heterologous system. These antibodies inhibited only cell aggregation in the homologous Geodia system and were inactive in the heterologous Tethya lyncurium ... |
7310902 | Effect of serum, fibronectin, and laminin on adhesion of rabbit intestinal epithelial cells in culture. | Rabbit intestinal epithelial cells, obtained after a limited hyaluronidase digestion, were incubated in medium with or without calf serum, on bacteriological plastic dishes. The dishes, either plain or coated with an air-dried type I collagen film, were pretreated with medium alone or eith medium containing purified la... |
7310901 | Flagellar adhesion and deadhesion in Chlamydomonas gametes: effects of tunicamycin and observations on flagellar tip morphology. | The aggregation-dependent loss of flagellar adhesiveness in chlamydomonas reinhardi has been correlated with changes in flagellar tip morphology during adhesion and deadhesion. As aggregating mt- and impotent (able to adhere, but not fuse) mt+ gametes begin to disaggregate in the presence of the protein synthesis inhib... |
6975828 | Antigenic and genetic parameters in the stimulation and in the lytic phases of anti-hapten + self cytotoxic T cells and their derived clones: role of the T helper cell. | Requirements for stimulation of cytotoxic T cells (CTL) and for their lytic recognition have been compared in T cell lines repeatedly stimulated with trinitrobenzene sulfonate-treated syngeneic murine spleen cells. Differences were observed between the requirements for cells to stimulate or to be lysed by the CTL, whic... |
6273596 | The structure of fibronectin and its role in cellular adhesion. | Fibronectin is a large, adhesive glycoprotein which is found in a number of locations, most notably on cell surfaces, in extracellular matrixes, and in blood. Fibronectin had been detected in all vertebrates tested and in many invertebrates. Its presence in sponges is significant because this suggests that fibronectin ... |
6273595 | Double-strand breaks in DNA caused by repair of damage due to ultraviolet light. | DNA DSBs are formed in normal human IMR-90 cells during repair incubation after 100 and 300 J.m-2 of UVL. By contrast, no DSBs are formed after UVL in human XPA cells that are unable to excise pyrimidine dimers. The DSBs are not due to immediate cell death since all the cells excluded trypan blue at the time of assay a... |
7310900 | Cellular transformation by radiation: induction, promotion, and inhibition. | Mammalian cell cultures offer powerful tools for evaluating qualitatively and quantitatively the oncogenic potential of radiation over a wide range of doses with particular importance at the low dose range that is relevant to human exposure and risk. Our studies have shown that early events in the process of radiation ... |
6171650 | Repair of Bleomycin-damaged DNA by human fibroblasts. | The ability of human fibroblasts to repair bleomycin-damaged DNA was examined in vivo. Repair of the specific lesions caused by bleomycin (BLM) was investigated in normal cell strains as well as those isolated from patients with apparent DNA repair defects. The diseases ataxia telangiectasia (AT), Bloom syndrome (BS), ... |
7310899 | An immunochemical approach for the analysis of membrane protein alterations in Ca2+-loaded human erythrocytes. | An increase in the intracellular concentration of Ca2+ in human erythrocytes results in the formation of gamma-glutamyl-epsilon-lysine cross-linked membrane protein polymers. Following solubilization of the membranes with SDS, these polymers can be isolated on a Lubrol-containing sucrose gradient. Immunoelectrophoresis... |
6458707 | Effects of nicotinamide on NAD and poly(ADP-ribose) metabolism in DNA-damaged human lymphocytes. | The effect of nicotinamide on unscheduled DNA synthesis was studied in resting human lymphocytes. In cells treated with UV irradiation or with MNNG, nicotinamide caused a two-fold stimulation of unscheduled DNA synthesis and retarded the rate of NAD+ lowering caused by these treatments. Nicotinamide also reduced the bu... |
6273594 | Identifying human cells capable of metabolizing various classes of carcinogens. | Human cells that appear capable of metabolizing various classes of carcinogens have been identified using one of two methods: metabolism of tritiated benzo(a)pyrene to aqueous-acetone soluble forms or inhibition of cellular DNA synthesis. Each of the assay systems was optimized and the results on 15 human epithelial ce... |
7031274 | Monoclonal antibody covalently coupled to liposomes: specific targeting to cells. | We have evaluated optimal conditions for coupling monoclonal antibody to small unilamellar liposomes. Coupling of an IgG2 alpha monoclonal anti-beta 2-microglobulin antibody, which reacts with human cells, was examined in detail. Liposomes were composed of dipalmitoyl lecithin and cholesterol, and variable quantities o... |
7031273 | Endogenous lectins in chickens and slime molds: transfer from intracellular to extracellular sites. | Endogenous lectins in both cellular slime molds and chicken tissues have been localized primarily intracellularly, in contrast with the predominantly extracellular localization of the glycoproteins, glycolipids, and glycosaminoglycans with which they might interact. Here we present evidence that lectins in both of thes... |
6273593 | The dynamic state of liver gap junctions. | By the use of a simple, rapid method for the isolation of gap junctions from small amounts of rat liver (2-3 g), we have followed the incorporation of the radiolabeled amino acid precursors 3H-leucine and 35S-methionine into the gap junction protein. In timed studies with 35S-methionine as precursor, the specific activ... |
7198152 | Microfilament reorganization in normal and cytochalasin B treated adherent thrombocytes. | Thrombocyte adhesion following activation by a Formvar surface involves a morphologic transition resulting in a fully spread cell. Correlative SEM and whole mount TEM were used to study the cytoskeletal alterations that accompany changes in surface morphology during adhesion. Following initial adhesion, thrombocytes ex... |
7299843 | Reorganization and orientation of regenerating nerve fibres, perineurium, and epineurium in preformed mesothelial tubes - an experimental study on the sciatic nerve of rats. | Regeneration of severed peripheral nerves is unfortunately often incomplete, due to loss of nerve fibers and neuroma formation. A new approach is presented with the intention of improving the conditions for nerve repair. In the first of the two stages, a pseudosynovial tube is formed around a silicone rubber rod, surro... |
6271982 | The transforming sequences of avian myelocytomatosis virus (MC29). | Avian myelocytomatosis virus (MC29), a defective acute leukemia virus, has a broad oncogenic spectrum in vivo, and transforms fibroblasts and hematopoietic target cells in vitro, We have used recombinant DNA technology to isolate and characterize the sequences that are essential in the transformation process. Integrate... |
6170760 | The contribution of the calcium-dependent interaction of aggregation factor molecules to recognition: a system providing additional specificity forces? | Cells from the sponge Microciona prolifera display on their surfaces large but defined proteoglycan complexes (Microciona aggregation factor = MAF) that mediate species-specific cell aggregation by a process requiring high calcium ion concentrations. An analysis of MAF-MAF interactions based on binding studies of MAF t... |
7299842 | Biochemical analysis of an MHC-linked hematopoietic cell surface antigen, Qa-2. | The region of the murine 17th chromosome telomeric to H-2D encodes a group of serologically defined cell surface antigens termed Qa-1-5. These antigens are of interest because their expression is restricted to hematopoietic cells. In addition, the molecular weight and subunit structure (ie, association with beta-2 micr... |
6795360 | Tannic acid-glutaraldehyde fixation reveals calcium ionophore-induced changes in rabbit polymorphonuclear leukocyte membranes. | TAG fixation of normal and Ca2+ ionophore-treated rabbit polymorphonuclear leukocytes (PMN) has revealed membrane components not apparent with conventional glutaraldehyde fixation. These included a 30 A external electron-dense coating on untreated cells. A somewhat thicker coat (40 A) was observed in ionophore-treated,... |
7299841 | Ligatin binds phosphohexose residues on acidic hydrolases. | Ligatin, a receptor that recognizes phosphorylated sugars, was isolated from plasma membranes of mouse macrophages, rat ileum, and rat brain. Several acidic hydrolases including N-acetyl beta-D-glucosaminidase (beta-NAG) were solubilized with this receptor. The solubilized beta-NAG bound to ligatin in vitro as demonstr... |
7029001 | Presence of trifoliin A, a Rhizobium-binding lectin, in clover root exudate. | Trifoliin A, a Rhizobium-binding glycoprotein from white clover, was detected in sterile clover root exudate by a sensitive immunofluorescence assay employing encapsulated cells of Rhizobium trifolii 0403 heat-fixed to microscope slides. Its presence in root exudate was further examined by immunoaffinity chromatography... |
6170759 | Lymphocyte recognition of H-2 antigen in liposomes. | Liposomes containing purified H-2Kk will specifically stimulate generation of a secondary allogeneic cytolytic T lymphocyte response. Effective recognition was found to depend on the structure of the liposomes. Including detergent-insoluble plasma membrane matrix during formation resulted in liposomes having two- to fo... |
6170758 | I-A mutation resulted in a selective loss of an antigen-specific Ir gene function. | The immune responses to several antigens were compared in the I-A mutant mouse strain B6.C-H-2bm12 and the wild-type strain C57BL/6. With a lymph node cell proliferation assay, the response to two of these antigens, beef insulin and (TG)A-L, was demonstrated to be controlled by a gene in the I-Ab region. B6.C-H-2bm12 m... |
6271981 | The repair of DNA damage: recent developments and new insights. | This brief review presents the salient features of new developments in the enzymatic repair of base damage to DNA. DNA glycosylases and apurinic/apyrimidinic (AP) endonucleases are reviewed and evidence is presented that in at least two prokaryote systems incision of UV-irradiated DNA occurs by the sequential action of... |
7299840 | The in vivo formation and repair of DNA adducts from 1'-hydroxysafrole. | 1'-Hydroxysafrole is a proximate carcinogenic metabolite of the naturally occurring hepatocarcinogen safrole. Comparison by high-performance liquid chromatography of the nucleoside adducts obtained from hepatic DNA of adult female mice treated with [2',3'-3H]1'-hydroxysafrole with those formed by reaction of deoxyribon... |
7029000 | Suppression of tumorigenicity in cybrids. | We investigated cytoplasmic control of tumorigenicity in cybrids. Cytoplasts derived from nontumorigenic cells were fused to the highly tumorigenic 984 C1 10-15 cell line derived from a murine teratoma. The resultant cybrids did not retain the tumorigenicity of the original cell line. In addition, the majority demonstr... |
7028999 | Expression of glial antigens C1 and M1 in developing and adult neurologically mutant mice. | The distribution of two glial antigens (C1 and M1) has been studied by indirect immunofluorescence during postnatal development of the cerebella of normal and neurologically mutant mice (weaver, staggerer, reeler, Purkinje cell degeneration, and wobbler). During the first postnatal week of normal development, C1 antige... |
6795359 | Specific reversal of cytolytic T lymphocyte--target cell interaction. | A functional assay is described that measures the reversal of specific cytolytic T cell (CTL)-target cell binding. Binding of 51Cr-labeled P815 cells was stable in suspension but could be readily reversed by the addition of unlabeled P815 cells. The reversal of CTL-tumor cell and CTL-spleen cell binding was H-2 specifi... |
7299839 | Bacterial attachment as related to cellular recognition in the Rhizobium-legume symbiosis. | Bacterial attachment is viewed as a cellular recognition event during the infection of legumes by the nitrogen-fixing symbiont, Rhizobium. Studies on the biochemical basis of selective attachment are reviewed, and suggest that this recognition process is accomplished by specific glycoprotein lectin-polysaccharide inter... |
7299838 | Two chick embryonic adhesion systems: molecular vs tissue specificity. | We have investigated the adhesive properties of cells from several neural and nonneural chick embryonic tissues dissociated using modifications of the standard dissociation procedures employed routinely in this laboratory to obtain retinal cells. Each of these tissues (7-day optic tectum, retina, and heart, and 3.75-da... |
7028998 | Genetics of receptors for bioactive polypeptides: a variant of Swiss/3T3 fibroblasts resistant to a cytotoxic insulin accumulates lysosome-like vesicles. | Recently we have isolated six variants of Swiss/3T3 mouse fibroblasts that are resistant to the cytotoxic insulin-diphtheria toxin A fragment. All of the variants proved to have greatly reduced or no insulin binding capacity, and several variants showed altered morphologies and growth characteristics. We now report on ... |
6271980 | Stimulation of DNA polymerase alpha by a nuclear DNA/protein complex. | A nuclear DNA complex containing DNA polymerase and SV40 T-antigen was isolated from nuclei of SV40-transformed mouse fibroblasts. DNA polymerase could be separated from the complex. The remaining DNA/T-antigen-containing complex stimulated DNA polymerase alpha activity about 10-fold. The complex contained 4 major prot... |
7299837 | Heparin-inhibitable lectins: marked similarities in chicken and rat. | Extracts of young rat lung contain a heparin-inhibitable lectin that closely resembles one recently purified from chicken liver. Both lectins interact with heparin and N-acetyl-D-galactosamine, and were purified by gel filtration on Sepharose CL-2B followed by affinity chromatography on heparin-Sepharose. They both beh... |
7299836 | Isolation of a high molecular weight glycoconjugate derived from the surface of S purpuratus eggs that is implicated in sperm adhesion. | Sea urchin sperm-egg adhesion is mediated by bindin, a sperm surface protein that has lectin-like activity. Bindin agglutinates eggs, and this interaction has been shown to be inhibited by glycopeptides released from the egg surface by protease treatment. In this study, we report the purification and properties of such... |
6271979 | Phosphoproteins in Dictyostelium discoideum. | The phosphoproteins of Dictyostelium discoideum were compared at different stages of development of polyacrylamide gel electrophoresis. Certain phosphoproteins of vegetative amoebae were conserved while others appeared and disappeared during development. Four major phosphoproteins with apparent subunit molecular weight... |
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