bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cell antigens recognized by rabbit antibodies specific for oligomannosyl determinants
Authors: Sarkar Siddhartha , Menge Alan C. 
Published: May 2005

AbstractRabbit antibodies to cell wall mannans of various microbial strains and their mutants were found to be cross‐reactive to cell carbohydrates of mammalian sperm and 4–6‐day‐old blastocysts. Immunochemical studies indicate that oligomers of α1→2, α1→3, α1→6, and probably also α→4 linked mannose residues of sperm carbohydrates are available for antibody binding. At least 80% of binding activity of a yeast mannan antibody to sperm can be effectively inhibited by specific haptens or digestion with exo‐α‐D‐mannosidase, an enzyme activity highest in testicular tissue. In order to determine the role of this enzyme in the metabolism of the cross‐reactive mannan antigens of sperm, the relative amount of a specific α‐linked oligomannosyl determinant of bovine sperm from homozygous normals was compared to that of heterozygous carriers of α‐mannosidase deficiency.Extensive cross‐reactivity between the microbial and mammalian oligomannosyl determinants suggest that these are conserved structures in cell carbohydrates, although the organization of these units in the microbial cell wall lipopolysaccharide has very little similarity to the carbohydrate moieties of mammalian glycoproteins.
Distribution of glycoconjugates in mouse fibroblasts with varying degrees of tumorigenicity
Authors: Winterbourne D. J. , Mora P. T. 
Published: May 2005

AbstractAnalysis of glucosamine labeled glycoconjugates in cultured cells has been made comparing 2 clones and the parent embryonic mouse cell line. Hyaluronic acid, heparan sulphate, and chondroitin sulphate as well as a complex mixture of glycopeptides were found in the medium, the trypsinate, and the trypsinized cells, although the distribution was not uniform. The 3 cell lines had very similar in vitro growth properties, including their plating efficiency in viscous medium. However, the tumorigenicity of the cells, determined in syngeneic mice, was found to differ. All 3 cell lines were found to have similar glycoconjugate distributions, although a slight relative increase in labeled hyaluronic acid was found in the more tumorigenic mass cell line than either of the clones. The possible significance of this increase is discussed.
Interaction of cartilage proteoglycans with hyaluronic acid
Authors: Hascall Vincent C. 
Published: May 2005

AbstractMost proteoglycans are present in hyaline cartilage matrices as aggregates with as many as 100 molecules, each with average molecular weight of about 2 × 106, bound through specific, noncovalent interactions to individual strands of hyaluronic acid (HA). The interactions with HA are mediated by the HA‐binding region of the core protein, which is located at one end of each of the interactive proteoglycans. A fragment of the core protein, average molecular weight of about 6 × 104, which contains the HA‐binding site, can be isolated in an active form from trypsin digests of proteoglycan aggregates. The “active” HA‐binding site in this preparation interacts strongly with HA‐10 but weakly with HA‐8, (oligomers of HA derived from partial digests of HA with testicular hyaluronidase); HA‐9 derived from β‐glucuronidase digestion of HA‐10 also interacts strongly. No polysaccharide other than HA has been found to interact. Christner, Brown, and Dziewiatkowski (personal communication) modified the carboxyls on glucuronic acid groups in mixture of HA‐10 to HA‐30, and they found that the interaction with proteoglycan no longer occurred if about 60% of the total carboxyls were (a) methyl esterified, (b) reduced to glucose, or (c) substituted with glycine in amide linkage. Saponification of the methyl esters restored activity. Dansylation of lysine residues in the HA‐binding region preparation abolished binding activity. However, when the dansylation reaction was done in the presence of HA, the HA‐binding activity was protected. Acetylation of the same residues did not abolish binding activity but did prevent subsequent inactivation by dansylation. Hardingham, Ewins, and Muir (Biochem J 157:127–143, 1976) studied the effect of various amino acid modifiers on the interaction of intact proteoglycans with HA and showed that reaction of arginine residues with low concentrations of 2,3‐butanedione was particularly effective in destroying binding. In sum, the data above suggests that the HA‐binding region (a) contains accessible arginine residues necessary for activity, (b) contains lysine residues near the binding site which, when substituted with bulky groups such as dansyl, but not acetyl, sterically block interaction, and (c) requires a length of HA with at least 4.5 repeat disaccharides containing 3, and possibly 4, unmodified glucuronic acid carboxyls for interaction. The possible relevance of proteoglycan‐hyaluronic acid interaction to the observations that hyaluronic acid specifically inhibits proteogly can synthesis by cultured chondrocytes is discussed.
Glycosylation of VSV glycoprotein is similar in cystic fibrosis, heterozygous carrier, and normal human fibroblasts
Authors: Hunt Lawrence A. , Summers Donald F. 
Published: May 2005

AbstractThe single envelope glycoprotein of vesicular stomatitis virus was used as a specific probe of glycosyltransferase activities in fibroblasts from two cystic fibrosis patients, an obligate heterozygous carrier and a normal individual. Gel filtration of pronasedigested glycopeptides from both purified virions and infected cell‐associated VSV glycoprotein which had been labeled with [3H] glucosamine did not reveal any significant differences in the glycosylation patterns between the different cell cultures. All 4 cell lines were apparently able to synthesize the mannose‐ and glucosamine‐containing core structure and branch chains terminating in sialic acid which are characteristic of asparagine‐linked carbohydrate side chains in cellular glycoproteins. Analysis of tryptic glycopeptides by anion‐exchange chromotography indicated that the same 2 major sites on the virus polypeptide were recognized and glycosylated in all 4 VSV‐infected cell cultures. These studies suggest that the basic biochemical defect(s) in cystic fibrosis is not an absence or deficiency in enzymes responsible for the biosynthesis of complex carbohydrate side chains.
Biochemical characteristics, metabolism, and antitumor activity of several acetylated hexosamines
Authors: Bernacki R. J. , Sharma M. , Porter N. K. , Rustum Y. , Paul B. , Korytnyk W. 
Published: May 2005

AbstractWe have synthesized several potential inhibitors and/or modifiers of the carbohydrate portion of plasma membrane glycoconjugates. These include fluorinated and actylated analogs of D‐glucosamine, D‐galactosamine, and D‐mannosamine. These compounds have been tested to determine their effects on both [14C] glucosamine and [3H] leucine incorporation into glycoconjugate and on cell growth and viability using P‐288 murine lymphoma cells maintained in tissue culture. The most cytotoxic agent tested was 2‐acetamido‐2‐deoxy‐1,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranose or simply β‐pentaacetylglucosamine which prevented cell growth at 10−4–10−3 M. β‐Pentaacetylglucosamine cytotoxicity was correlated with its high lipid solubility, having an octanol/water partition coefficient of 0.424 as compared with 0.278 for the β‐anomer and 0.017 for N‐acetylglucosamine. In vitro metabolism studies with [14C]‐and/or [3H]‐labeled pentaacetylglucosamine have indicated intracellular de‐O‐acetylation leading to the biosynthesis of UDP‐N‐acetylglucosamine, followed by the incorporation of this sugar into cellular glycoprotein. Concomitant with the formation of increased amounts of this nucleotide sugar, intracellular UTP and CTP pools fell to one third normal within 3 h after the administration of 1 mM pentaacetylglucosamine. At present it is unclear whether the cytotoxicity of β‐pentaacetylglucosamine or other similar agents is due to alterations in nucleotide and nucleotide‐sugar pools causing a decrease in energy charge and polynucleotide biosynthesis or is due to a direct effect on membrane glycoconjugate biosynthesis.
Cell surface changes accompanying myoblast differentiation
Authors: Furcht L. T. , Wendelschafer‐Crabb G. , Woodbridge P. A. 
Published: May 2005

AbstractMyoblasts are mononucleated cells and associated with differentation undergo cell fusion and become multinucleated. The current studies have examined cell surface dynamic changes of Concanavalin A lectin receptor mobility and the role of hormones in modulating myoblast differentiation. A uniform distribution of Con‐A receptors is observed in undifferentiated cells when reacted with Con‐A at 37°C. Cells from differentiating cultures or fully differentiated myotubes reacted similarly at 37°C show a significant redistribution of Con‐A into patches, “caps,” and endocytic vesicles containing Con‐A. If undifferentiated and differentiated cells are first prefixed with glutaraldehyde then reacted with Con‐A continuous distribution of Con‐A is seen across the cell surface. This suggests redistribution of Con‐A and its receptors occurs in differentiated cells reacted with lectin at 37°C. It is further shown that insulin (10 μg/ml) significantly enhances myoblast differentiation but that this occurs after an apparent stimulation of proliferation. In contrast to insulin, dexamethasone (10 μM and 100 μM) profoundly inhibits myoblast differentiation while having different effects on proliferation; 10 μM dex stimulates cell growth while 100 μM dex suppresses cell proliferation. Lastly, an extracellular filamentous matirix which binds Con‐A is observed at the ultrastructural level in high density cultures. No significant redistribution of Con‐A is observed on this matrix in distinction to the redistribution observed on the cell membrane in differentiated cells.
Purification and characteristics of hydrophobic membrane protein(s) required for DCCD sensitivity of ATPase in mycobacterium phlei
Authors: Cohen Natalie S. , Lee Soon‐Ho , Brodie Arnold F. 
Published: May 2005

AbstractThe energy‐transducing N,N′‐dicyclohexylcarbodiimide‐sensitive (DCCD‐sensitive) ATPase complex consists of two parts, a soluble catalytic protein (F1), and an intrinsic membrane protein (F0). The bacterial coupling factor complex, BCF0‐BCF1, has recently been purified from Mycobacterium phlei, and used to reconstitute oxidative phosphorylation in detergent‐extracted membranes. The BCF0 moiety has been purified by being recovered from the purified BCF0‐BCF1 complex by affinity chromatography. BCF0 is a lipoprotein or lipoprotein complex with an approximate molecular weight of 60,000. The preparation contained 0.15 mg of phospholipid per milligram protein. There appear to be three polypeptides, with approximate molecular weights of 24,000, 18,000, and 8,000 as determined by sodium dodecylsulfate a crylamide gel electrophoresis. Purified BCF0 conferred DCCD sensitivity on a purified BCF1 preparation. Reconstitution of oxidative phosphorylation was achieved after incubation of detergent‐extracted membranes with purified BCF0 and purified BCF1.
Quantitative analysis of the microtubule system in isolated fish melanophores
Authors: Schliwa Manfred , Euteneuer Ursula 
Published: May 2005

AbstractIsolated melanophores of the angelfish, Pterophyllum scalare, have been used in a morphometric analysis and a quantitative study of their microtubule system. Using transverse sections spaced at regular intervals, the changes associated with the process of pigment aggregation have been determined. Upon the concentration of pigment granules in the central cell region, almost half of the cytoplasmic portion is also withdrawn from the peripheral cell regions. Counts of microtubules within a cell sector in cells with pigment aggregated and dispersed, respectively, reveal (a) a constancy of the number of microtubules in this sector regardless of the distance from the cell center, and (b) a reduction of microtubule number in cells with pigment aggregated by about 58%. On the basis of these counts, the total number of microtubules has been calculated. In the dispersed state, about 2,400 microtubules extend between the center and the periphery of the cell, while their number is about 1,000 in the aggregated state.Using a 13‐protofilament model of a microtubule and relevant data on size and molecular weight of microtubule subunits, the amount of tubulin present as microtubules is calculated. In the average, the cells contain 1.95·108 monomers corresponding to 1.78·10−8 mg tubulin. A tentative estimation of the concentration of tubulin inside a melanophore yields values of 6.1 mg/ml for the whole cell and 16.5 mg/ml for the cytoplasm alone (excluding membrane‐bound organelles). Based on this estimation, a comparison, with microtubule assembly in vitro is made.
Topology of amino‐phospholipids in the red cell membrane
Authors: Marinetti Guido V. , Crain Richard C. 
Published: May 2005

AbstractThe red cell membrane has an asymmetric arrangement of phospholipids. The amino‐phospholipids are localized primarily on the inner surface of the membrane and the choline phospholipids are localized to a large extent on the outer surface of the membrane. Evidence is presented based on the use of covalent chemical probes in sequence that the red cell membrane contains heterogeneous domains of PE and PS and that the transport systems for Pi and K+ are asymmetrically arranged. Certain amino groups of PE, PS, and/or protein localized on the outer membrane surface are involved in Pi transport and certain amino groups of PE, PS, and/or protein localized on the inner surface of the membrane are involved in K+ transport.Cross‐linking studies with DFDNB show that the cross‐linked PE‐PE molecules are rich in plasmalogens. This suggests that clusters of plasmalogen forms of PE occur in the membrane. Both PE and PS are cross‐linked to membrane protein. These PE and PS molecules contain 24–28% 16:0 and 18:0 fatty acids and 12% fatty aldehydes. PE and PS molecules are cross‐linked to a spectrin‐rich fraction. It is proposed that the binding of spectrin to membrane PE and PS may help anchor spectrin to the inner surface of the membrane and regulate shape changes in the cell.K+‐valinomycin forms a complex with TNBS and converts it from a non‐penetrating proble to a penetrating probe. Valinomycin enhances K+ leak and Pi leak in the red cells. SITS inhibits completely the valinomycin‐induced Pi leak and inhibits partially the valinomycin induced K+ leak. Valinomycin and IAA have additive effects on Pi leak. Ouabin has no effect on basal or valino‐mycin‐induced Pi leak. These data suggest that Pi leak and K+ leak occur by separate transport systems.In summary, the amino‐phospholipids in the red cell membrane are asymmetrically arranged; some occur in clusters and some are closely associated with membrane proteins. Amino‐phospholipids also are believed to bind spectrin to the inner surface of the membrane and also may play a role in cation and anion leak.
Mitogens for murine embryo cell lines
Authors: Herschman Harvey R. , Passovoy Dennis S. , Pruss Rebecca M. , Aharonov Aharon 
Published: May 2005

AbstractThe growth‐promoting activities of fetal bovine serum, cortisol, phorbol myristate acetate, prostaglandin F2α, insulin, epidermal growth factor, and fibroblast growth factor were evaluated on four murine embryo cell lines (Swiss 3T3, Balb 3T3, M2, and C3H10T1/2). Each cell had an unique response spectrum to this collection of reported mitogens. Phorbol myristate acetate and prostaglandin F2α were active only on selected cell lines; cortisol was inactive on all four lines. Serum, epidermal growth factor, and fibroblast growth factor were able to stimulate cell division in all four lines, albeit to varying degrees for the different target cells.
The band 3 protein of the human red cell membrane: A review
Authors: Steck Theodore L. 
Published: May 2005

AbstractBand 3 is the predominant polypetide and the purported mediator of anion transport in the human erythrocyte membrane. Against a background of minor and apparently unrelated polypeptides of similar electrophoretic mobility, and despite apparent heterogeneity in its glycosylation, the bulk of band 3 exhibits uniform and characteristic behavior. This integral glycoprotein appears to exist as a noncovalent dimer of two ∼ 93,000‐dalton chains which span the membrane asymmetrically. The protein is hydrophobic in its composition and in its behaviour in aqueous solution and is best solubilized and purified in detergent. It can be cleaved while membrane‐bound into large, topographically defined segments. An integral, outer‐surface, 38,000‐dalton fragment bears most of the band 3 carbohydrate. A 17,000‐dalton, hydrophobic glycopeptide fragment spans the membrane. A ∼ 40,000‐dalton hydrophilic segment represents the cytoplasmic domain. In vitro, glyceraldehyde 3‐P dehydrogenase and aldolase bind reversibly, in a metabolite‐sensitive fashion, to this cytoplasmic segment. The cytoplasmic domain also bears the amino terminus of this polypetide, in contrast to other integral membrane proteins. Recent electron microscopic analysis suggests that the poles of the band 3 molecule can be seen by freezeetching at the two original membrane surfaces, while freeze‐fracture reveals the transmembrane disposition of band 3 dimer particles.There is strong evidence that band 3 mediates 1:1 anion exchange across the membrane through a conformational cycle while remaining fixed and asymmetrical. Its cytoplasmic pole can be variously perturbed and even excised without a significant alteration of transport function. However, digestion of the outer‐surface region leads to inhibition of transport, so that both this segment and the membrane‐spanning piece (which is slectively labeled by covalent inhibitors of transport) may be presumed to be involved in transport. Genetic polymorphism has been observed in the structure and immunogenicity of the band 3 polypeptide but this feature has not been related to variation in anion transport or other band 3 activities.
Molecular characteristics of the transferrin‐receptor complex of the rabbit reticulocyte
Authors: Hu Hsiang‐Yun Yang , Aisen Philip 
Published: May 2005

AbstractA macromolecular complex of transferrin and a membrane component was isolated by gel filtration chromatography from Triton X‐100‐solubilized ghosts of reticulocytes previously incubated with 125I‐labeled transferrin. This complex is believed to be transferrin specifically associated with its primary receptor. Following the procedures of Clark [14], the complex in Triton X‐100 was found to behave as an asymmetric molecule with a molecular weight of approximately 250,000 and an axial ratio of 9:1. On SDS‐polyacrylamide gel electrophoresis the complex displays, in addition to transferrin, components of molecular weights 176,000 and 95,000, respectively. The larger component may be a dimer of the smaller. Each appears to crosslink, with dimethyl suberimidate, to transferrin. These results are compatible with the hypothesis that the transferrin receptor itself has a molecular weight near 175,000 and may be a dimer of two smaller components each of molecular weight near 95,000.
The program of friend cell erythroid differentiation: Early changes in Na+/K+ ATPase function
Authors: Mager Dixie , Bernstein Alan 
Published: May 2005

AbstractTreatment of Friend erythroleukemia cells with several different chemical agents causes an early decrease in the 86Rb+ influx mediated by Na+/K+ adenosine triphosphatase (ATPase). These agents, which induced Friend cells to differentiate, include dimethylsulfoxide (DMSO), ouabain, hypoxanthine, and actinomycin D. The magnitude of the early decrease in 86Rb+ influx correlates with the proportion of cells in cultures of inducible Friend cell clones which later go on to synthesize hemoglobin. Compounds which do not incude differentiation in these cells, such as xanthine, exogenous hematin, and erythropoietin, do not cause a change in 86Rb+ influx. A change in the intracellular K+ ion concentration does not occur during induction by DMSO because, although there is a decrease in K+ content per cell soon after induction, there is a parallel decrease in cell volume. These results and previous observations from this laboratory are discussed in terms of the posible involvement of the Na+/K+ ATPase in Friend cell differentiation.
Analysis of the major polypeptides of spectrin by tryptic digestion
Authors: Maddy Alun H. , Dunn Michael J. 
Published: May 2005

AbstractThe two major polypeptides of erythrocyte membrane spectrin have been isolated by preparative polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The tryptic peptide maps of the two polypeptides have been prepared by thin‐layer chromatography and electrophoresis. Radioactive peptides have been prepared by 14C‐carboxymethylation and chloramine T‐catalysed 125I iodination. Maps of both sets of peptides demonstrate a marked similarity between the two parent polypeptides.
Metabolic stability of the nucleoside transport system of novikoff rat hepatoma cells
Authors: Marz Richard , Wohlhueter Robert M. , Plagemann Peter G. W. 
Published: May 2005

AbstractRates of transport of uridine and thymidine, estimated with a rapid sampling technique, did not change with culture age. Inhibition of cellular RNA and protein synthesis for periods up to 6 h, did not lead to a loss of nucleoside transport activity. Mild treatment of cell suspensions with trypsin or neuraminidase had no effect on the kinetics of thymidine transport. Thus we conclude, contrary to previous reports, that nucleoside transporters are metabolically stable and that the decreases in nucleoside uptake rates observed with decreased protein synthesis reflect loss of nucleoside kinase activities. These kinases (which have narrow substrate specificity) rather than the membrane‐associated, transport apparatus (which has broad substrate specificity) are the most likely sites for regulation of nucleoside uptake.
Properties and action mechanism of the toxic lectin modeccin: Interaction with cell lines resistant to modeccin, abrin, and ricin
Authors: Olsnes Sjur , Sandvig Kirsten , Eiklid Kristin , Pihl Alexander 
Published: May 2005

AbstractThe toxic lectin modeccin, which inhibits protein synthesis in eukaryotic cells, is cleaved upon treatment with 2‐mercaptoethanol into two peptide chains which move in polyacrylamide gels at rates corresponding to molecular weights 28,000 and 38,000. After reduction, the toxin loses its effect on cells, while its ability to inhibit cell‐free protein synthesis increases. Like abrin and ricin it inhibits protein synthesis by inactivating the 60S ribosomal subunits.Modeccin binds to surface receptors containing terminal galactose residues. Competition experiments with various glycoproteins indicate that the modeccin receptors are different from the abrin receptors. In addition, they were present on HeLa cells in much smaller numbers. Moreover, mutant lines resistant to abrin and ricin were not resistant to modeccin and vice‐versa.The toxin resistance of various mutant cell lines could not be accounted for by a reduced number of binding sites on cells. The data are consistent with the view that the cells possesss different populations of binding sites with differences in ability to facilitate the uptake of the toxins and that in the resistant lines the most active receptors have been reduced or eliminated.