bluuebunny/crossref_metadata_2025_split huggingface dataset:
Subcellular structures involved in internalization and degradation of epidermal growth factor
Authors: Fine Richard E. , Goldenberg Richard , Sorrentino Joseph , Herschman Harvey R. 
Published: May 2005

AbstractEpidermal Growth Factor (EGF), a small polypeptide which acts as a mitogen for many cell types, has previously been shown to bind to a specific plasma membrane receptor on 3T3 cells. If 125I‐EGF is bound to 3T3 cells for one hour at 4°C, it remains predominantly associated with the plasma membrane‐containing fractions obtained by subjecting cell supernatants to equilibrium sedimentation on sucrose gradients. When binding is followed by a 10‐minute incubation at 37°C, over 50% of the 125I‐EGF is associated with two internal membrane‐containing peaks having higher densities than the plasma membrane. After one hour at 37°C, over 80% of the 125I‐EGF is degraded and removed from the cells.The most rapidly labeled internal peak corresponds in density to brain‐coated vesicles (CVs). Antiserum prepared against coated vehicles from brain precipitates the 125I‐EGF in this peak. In addition, CVs containing 125I‐EGF can be co‐purified from 3T3 cells exposed to 125I‐EGF, using brain as a carrier. Several lines of evidence suggest that the other 125I‐EGF‐labeled intracellular peak is 125I‐EGF in lysosomes.These results provide kinetic and biochemical evidence for a unidirectional pathway for EGF catabolism by 3T3 cells. EGF first binds to the plasma membrane bound receptors, is then moved to the cytoplasm in CVs, and finally appears in lysosomes, where it is degraded and released from the cells. Ten‐millimolar NH4Cl blocks lysosomal hydrolysis of EGF almost completely. Subsequently, EGF internalization is inhibited. This finding suggests that the pathway for EGF internalization and degradation is tightly coupled.
Sulfated glycoproteins and extracellular matrix of cultured human pulmonary endothelial cells
Authors: Heifetz Aaron , Johnson Alice R. 
Published: May 2005

AbstractEndothelial cells derived from human pulmonary arteries incorporate (3H)‐glucosamine and 35SO4 into glycosaminoglycans and into the carbohydrate side chains of glycoproteins. These 3H/35S‐carbohydrate chains were isolated from cells and culture medium after Pronase digestion. The 3H/35S‐glycosaminoglycans were separated from the 3H/35S glycopeptides by chromatography on Sephadex G‐50. The distribution of cellular glycosaminoglycans and glycopeptides indicated that 30–60% of the cellular 35S‐glycopeptides may be associated with the matrix components that are synthesized by the cell and attached to a plastic substratum. Human pulmonary arterial endothelial cells were grown on collagen or on a matrix derived from vascular smooth muscle cells in order to investigate how smooth muscle cell extracellular matrix components may regulate the synthesis of endothelial cell glycoconjugates. Endothelial cells grown on plastic release various proportions of the glycoconjugates they synthesize into the culture medium. However, these same cells, when grown on substratum composed of extracellular matrix materials, synthesized altered proportions of cell‐associated glycosaminoglycans and reduced the levels of total glycosaminoglycans they released into the culture medium. Thus the growth of endothelial cells on a matrix of smooth muscle cell components indicates that the glycosaminoglycan materials released into the culture medium by cells grown on a plastic substratum may not be an accurate reflection of the levels or composition of extracellular matrix materials made by endothelial cells in vivo.
Heparin‐inhibitable lectins: Marked similarities in chicken and rat
Authors: Roberson Marie M. , Ceri Howard , Shadle Paula J. , Barondes Samuel H. 
Published: May 2005

AbstractExtracts 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 behave as high molecular weight aggregates that can be dissociated into two peptides with apparent molecular weights of 13,000 and 16,000 by gel electrophoresis in SDS. Samples of purified lectin contained up to 20% DNA by weight, and the degree of lectin aggregation and hemagglutination activity was greatly reduced by treatment with micrococcal nuclease without inhibiting heparin‐binding activity. Association of lectin with DNA is an artifact of homogenization in high salt, since only 2% of the lectin is found associated with a purified nuclear fraction.
Stimulation of DNA polymerase α by a nuclear DNA/protein complex
Authors: Balabanova Henny , Fridlender Berthold R. , Anderer F. Alfred 
Published: May 2005

AbstractA 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 a activity about 10‐fold. The complex contained 4 major proteins with molecular weights of 46, 54, 76, and 94 kilodalton (KD). The stimulation activity was retained by protein A–Sepharose loaded with specific IgG from SV40‐tumor bearer serum, or from antisera against the 94 KD and 76 KD components and was partially inhibited in the presence of these antisera. The stimulation activity was completely abolished by treatment of the complex with trypsin or DNase I.
Two chick embryonic adhesion systems: Molecular vs tissue specificity
Authors: Thomas William A. , Edelman Bruce A. , Lobel Susan M. , Breitbart Arnold S. , Steinberg Malcom S. 
Published: May 2005

AbstractWe 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‐day hmb bud) displayed both Ca++‐dependent (CD) and Ca++‐independent (CI) aggregation, the relative rates of which differed from tissue to tissue In every case, cells prepared so as to display one mode of aggregation or the other cross‐adhered readily to cells—regardless of tissue origin—displaying the same mode of aggregation. Cross adhesion was negligible between cells—even from the same tissue—prepared so as to display different modes of aggregation. Anti‐retinal Fab molecules which inhibit selectively either the CI or CD aggregation of retina cells strongly inhibited the corresponding aggregation of optic tectum cells, but had no effect upon the aggregation (CI or CD) of heart cells. These results demonstrate the exis‐tence in the tissues examined of dual adhesion mechanisms similar in Ca++ dependence and recognition properties to those of the retina, but showing certain immunological distinctions from the latter. The imrmunological relationship among the adhesion mechanisms from the various tissues is under continuing investigation.
Bacterial attachment as related to cellular recognition in the rhizobium‐legume symbiosis
Authors: Dazzo Frank B. 
Published: May 2005

AbstractBacterial 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 interactions on the surfaces of the symbionts. An understanding of host specificity may lead to ways to broaden the host range of nitrogen‐fixing symbioses.
Specific reversal of cytolytic T lymphocyte – target cell interaction
Authors: Balk Steven P. , Mescher Matthew F. 
Published: May 2005

AbstractA 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 specific; only cells of the same H‐2 type as the bound target cell could induce reversal. In all cases, tumor cells were substantially more efficient than spleen cells in inducing specific reversal.
Expression of glial antigens C1 and M1 in developing and adult neurologically mutant mice
Authors: Sommer I. , Schachner M. 
Published: May 2005

AbstractThe distribution of two glial antigens (C1 and M1) has been studied by indi‐rect 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 antigen is expressed in ependyma, Bergmann glial fibers (BG), and astrocytes of the internal granular layer and white matter. After day 10, C1 antigen is restricted to BG and ependymal cells. During the sec‐ond and third week, BG undergo a transient loss of C1 antigen that starts in medioventral areas and spreads in a gradient dorsally and laterally.In reeler, weaver, and staggerer, C1 antigen expression is normal during the first postnatal week, and subsides in BG in a similar spatial gra‐ dient as described for the normal littermates. However, the loss of C1 anti‐gen in BG occurs earlier (first in reeler, then in weaver, and last in staggerer) and is not reversible as it is in normal mice. In Purkinje cell de‐generation, C1 antigen expression is diminished in BG after the onset of be‐havioral abnormalities. Wobbler is normal with respect to C1 antigen ex‐pression at adult ages.M1 antigen is detectable in white matter astrocytes from postnatal day 7 on, and persists in these cells into adulthood. Astrocytes of the internal granular layer and BG express M1 antigen only transiently in normal mice during the second and third weeks. The appearance of M1 antigen in BG occurs in a spatiotemporal gradient, matching the one in which C1 antigen disappears. M1 antigen expression is abnormally maintained in BG of reeler, staggerer, and weaver. In Purkinje cell degeneration, M1 antigen is ex‐pressed abnormally at the onset of behavioral abnormalities first in.astro‐cytes of the internal granular layer and, with growing age, increasingly also in BG. In wobbler, BG do not express M1 antigen. However, astrocytes of the granular layer are abnormally M1 antigen‐positive.
Suppression of tumorigenicity in cybrids
Authors: Shay Jerry W. , Lorkowski Gay , Clark Mike A. 
Published: May 2005

AbstractWe investigated cytoplasmic control of tumorigenicity in cybrids. Cytoplasts derived from nontumorigenic cells were fused to the highly tumorigenic 984 Cl 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 demonstrated the ability to differentiate into skeletal muscle. The results of these experiments indicate a heritable suppression of the tumorigenic phenotype by nontumorigenic cytoplasm. These findings are in contrast to our previous experiments in which we used a different experimental system and demonstrated a nuclear control of tumorigenicity in cybrids.
The in vivo formation and repair of DNA adducts from 1′‐hydroxysafrole
Authors: Phillips David H. , Hanawalt Philip C. , Miller James A. , Miller Elizabeth C. 
Published: May 2005

Abstract1′‐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′‐hydroxysafrolc with those formed by reaction of deoxyribonucleo‐sides with electrophilic derivatives of 1′‐hydroxysafrole indicated that the four in vivo adducts studied were derived from an ester of 1′‐hydroxysafrole. Three of the four adducts comigrated with products of the reaction of 1′‐acetoxysafrole with deoxyguanosine, whereas the fourth adduct comigrated with the major reaction product of the ester with deoxyadenosine. Analysis of the three deoxyguanosine ad‐ducts indicated that all three involve substitution on the 2‐amino group of guanine. A sample of the major adduct prepared from deoxyguanylic acid has been charac‐terized from its NMR spectrum as N2‐(trans‐isosafrol‐3′‐Y1)‐deoxyguanosine, and the deoxyadenosine adduct has been similarly characterized as N6‐(trans‐isosafrol‐3′‐yl)‐deoxyadenosine.Repair replication was measured in cultured human T98G cells exposed to 1′‐acetoxysafrole using the combined 5‐bromodcoxyuridine density label and radioiso‐topic label metnod. At a concentration of 1 mM 1′‐acetoxysafrole, the amount of repair synthesis approached maximum values only about 15% of those obtained af‐ter saturating doses of ultraviolet light. Repair patch size distribution was found to be similar in cells treated with ultraviolet light or 1′‐acetoxysafrole as determined by the density of repair‐labeled DNA relative to that of parental DNA.
Lymphocyte recognition of H‐2 antigen in liposomes
Authors: Herrmann Steven H. , Mescher Matthew F. 
Published: May 2005

AbstractLiposomes 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 fourfold more activity than those prepared using just lipid and H‐2.
Endogenous lectins in chickens and slime molds: Transfer from intracellular to extracellular sites
Authors: Barondes Samuel H. , Beyer Eric C. , Springer Wayne R. , Cooper Douglas N. 
Published: May 2005

AbstractEndogenous 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 these organisms may be externalized and become associated with the cell surface and/or extracellular materials. In chicken intestine, chicken‐lactose‐lectin‐II is shown to be localized in the secretory granules of the goblet cells, along with mucin, and to be secreted onto the intestinal surface. In embryonic muscle, chicken‐lactose‐lectin‐I is shown to be externalized with differentiation, ultimately becoming localized on the surface of myotubes and in the extracellular spaces. In a cellular slime mold, Dictyostelium purpureum, externalization of lectin is elicited by either polyvalent glycoproteins that bind the small amount of endogenous cell surface lectin, or by slime mold or plant lectins that bind unoccupied complementary cell surface oligosaccharides. These results suggest that externalization of endogenous lectin may be a response to specific external signals. We conclude that lectins are frequently held in intracellular reserves awaiting release for specific external functions.
Effects of nicotinamide on NAD and poly (ADP‐ribose) metabolism in DNA‐damaged human lymphocytes
Authors: Sims James L. , Berger Sosamma J. , Berger Nathan A. 
Published: May 2005

AbstractThe 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 burst of poly(ADP‐ribose) synthesis caused by MNNG treat‐ment. Thus under conditions that it enhances unscheduled DNA synthesis, nicotinamide causes marked effects on the metabolism of NAD+ and poly(ADP‐ribose). The effect of nicotinamide on unscheduled DNA synthesis was shown to be independent of protein or polyamine synthesis.
Cellular transformation by radiation: Induction, promotion, and inhibition
Authors: Borek Carmia 
Published: May 2005

AbstractMammalian 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 induced transformation in both rodent and human cells requires initial replication for fixation of transformation as a hereditary property of the cells and further clonal expansion for full expression. Early events (fixation) are inhibited by cell–cell contact and high cell density but can be modified at low temperature where repair processes are slowed. Cell–cell contact and communication in tissue organization may be in part responsible for our findings that radiation oncogenesis induced in utero in hamsters is expressed at a lower frequency than that induced in vitro.Quantitative studies carried out on hamster embryo cells indicate that neutrons are more effective in their carcinogenic potential than x‐rays but also more toxic, that splitting the dose of x‐rays at low doses leads to enhanced transformation, but that at high doses protracted radiation has a sparing effect. At all dose ranges survival was increased by protracting the radiation dose, thus suggesting that different repair processes must be involved for survival and transformation. Similar observations were seen when the protease inhibitor Antipain was found to enhance transformation in rodent and human cells when present at the time of radiation, but was protective when added after radiation. Survival was not modified under any of those conditions, and Antipain did not affect DNA replication and repair. In our qualitative studies, once cells are transformed by radiation, they exhibit a wide range of structural and functional phenotypic changes, some of which are membrane‐associated and are expressed within days after induction.Our current studies on nutritional and hormonal influences on radiation transformation indicate the following: Pyrolysate products from broiled protein foods act in synergism with radiation to produce transformation, whereas vitamin A analogs are powerful, preventive agents. Retinoids inhibit both x‐ray‐induced transformation and its promotion by TPA: these modifications (enhancement by TPA, inhibition by retinoids) are not reflected in sister chromatid exchanges, but are reflected in the level of membrane associated enzymes Na/K ATPase. Whereas retinoids modify late events (expression, promotion), we find that thyroid hormone plays a crucial role in the early phases of radiation and chemically induced transformation. Under hypothyroid conditions no transformation is observed. The addition of triiodothyronine at physiological levels results in a transformation rate that is dose‐related.Our recent success in transforming human skin fibroblasts will enable quantitative and qualitative studies of radiation carcinogenesis in a system relevant to man.
Flagellar adhesion and deadhesion in chlamydomonas gametes: Effects of tunicamycin and observations on flagellar tip morphology
Authors: Snell William J. 
Published: May 2005

AbstractThe 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 inhibitor cycloheximide, there is a concomitant change in flagellar tip morphology from the activated bulbous form to the nonactivated tapered shape. The requirement of protein‐synthetic activity for the maintenance of flagellar adhesiveness during aggregation may be due in part to turnover of proteins involved in formation or stabilization of activated flagellar tips.Incubation of aggregating gametes with tunicamycin indicates that, like protein synthesis inhibitors, this inhibitor of glycosylation also causes adhering gametes to deadhere. The results suggest that protein glycosylation may be essential for maintenance of adhesiveness during aggregation.
Effect of serum, fibronectin, and laminin on adhesion of rabbit intestinal epithelial cells in culture
Authors: Burrill Peter H. , Bernardini Isa , Kleinman Hynda K. , Kretchmer Norman 
Published: May 2005

AbstractRabbit 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 with medium containing purified laminin or purified fibronectin. Cells did not attach in significant numbers to untreated bacteriological plastic, even in the presence of serum. Cells did attach to collagen‐coated dishes, and were judged viable on the basis of their incorporation of radiolabeled leucine into cell protein. Cell adhesion to the collagen substrate increased in proportion to the concentration of serum in the medium, with maximal attachment at 5% serum or greater. Pretreatment of plain or collagen‐coated dishes with increasing amounts of fibronectin enhanced cell adhesion in a concentration‐dependent manner. Either serum, or fibronectin‐free serum in the medium enhanced cell attachment to substrates pretreated with cither fibronectin or laminin. Thus, intestinal epithelial cells appear to possess surface receptors for both laminin and fibronectin. The evidence further suggests that calf serum may contain factors, other than fibronectin, capable of enhancing intestinal epithelial cell attachment to collagen substrates.
Antigen‐specific mouse lymphocyte stimulation by DNP‐conjugated T‐independent antigens studied by photobleaching recovery
Authors: Peacock James S. , Barisas B. George 
Published: May 2005

AbstractFluorescence 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 upon the antigen dose and epitope density. These factors also determine the mobility of antigen bound to B cell surfaces. For DNP‐POL bound to DNP‐specific cells, the observed diffusion constants D decrease monotonically with increasing antigen dose and epitope density. Values of D range from 10.4 × 10−11 cm2 sec−1 for DNP0.4‐POL at 0.15 μg/ml to 0.8 × 10−11cm2 sec−1for DNP3.5‐POL at 30 μg/ml. For receptor‐bound DNP‐DEX, D depends strongly on antigen epitope density but not observably on antigen concentration. For epitope densities of 1.2 or less, D is close to the value of 21 × 10−11cm2sec−1 observed for single slg receptors. By an epitope density of 4.8, D has fallen to 2.1 × 10−11cm2sec−1. Peak immunogenicities for DNP‐POL and DNP‐DEX arc observed when antigen‐ receptor aggregates have mobilities 14‐fold and 3‐fold lower, respectively, than a single slg molecule.
Glycoprotein differences among cells of the 14‐day embryonic chick neural retina
Authors: Sheffield Joel B. 
Published: May 2005

AbstractIn 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 differ in associative behavior and intramembrane particle content. We now report that these cells differ in cell surface glycoproteins. Proteins were labeled with two different extrinsic labels and one metabolic label. We used enzymatic transfer of galactose from UDP‐gal to cellular acceptors, and borotritide reduction after galactose oxidation as extrinsic labels. Glucosamine incorporation was used as the metabolic label. In all these cases, we were able to identify bands on electrophoretic gels which were unique to individual populations.