bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dissociation of plasminogen activator from the transformed phenotype in a 5‐Bromodeoxyuridine dependent mutant of syrian hamster melanoma cells
Authors: Rosenthal S. L. , Zucker D. , Davidson R. L. 
Published: February 2005

AbstractThe relationship between plasminogen activator levels and the expression of the transformed phenotype was studied in a 5‐bromodeoxyuridine (BrdUrd) dependent mutant of Syrian hamster melanoma cells. In terms of cell morphology and cellular interactions, the BrdUrd dependent cells resemble transformed cells when grown in the presence of BrdUrd but resemble untransformed cells when grown in the absence of BrdUrd. It was found that the BrdUrd dependent cells release significant levels of plasminogen activator only when cultured in the absence of BrdUrd. In the presence of BrdUrd, the release of plasminogen activator by the dependent cells is suppressed, and the decreased level of plasminogen activator released in the presence of BrdUrd seems to be due to decreased production of active enzyme. Growth tests revealed that the BrdUrd dependent cells, when attached to a substrate, required BrdUrd in order to attain high densities. Furthermore, the cells are able to grow well in soft agar only in the presence of BrdUrd. These results suggest that the production and release of high levels of plasminogen activator are not related (either as cause or effect) to the expression of the transformed phenotype in the BrdUrd dependent cellsThe effect of dog serum (as a plasminogen source) on the BrdUrd dependent cells also was tested. It was found that cells cultured in medium containing dog serum exhibit a morphological alteration, but only in the absence of BrdUrd. The morphological response of the cells to dog serum resembles that previously observed with virus‐transformed cells. In the BrdUrd dependent cells, the morphological response to dog serum appears correlated with the release of plasminogen activator but separated from other transformed characteristics.
Microtubule inhibitors alter the secretion of β‐glucuronidase by human blood platelets: Involvement of microtubules in release reaction II
Authors: Kenney Dianne M. , Chao Francis C. 
Published: February 2005

AbstractThe effects of the antimicrotubular drugs colchicine and vinblastine on the blood platelet release reaction were studied by measuring release of 14C‐5‐hydroxytryptamine (14C‐5‐HT, release I) and β‐glucuronidase (release II) from gel‐filtered human platelets. β‐glucuronidase release induced by thrombin was significantly inhibited by colchicine (0.01‐1 mM) or vinblastine (0.05–0.1 mM). Release of 14C‐5‐HT, however, was unaffected at low concentrations of colchicine and only slightly inhibited at higher concentrations. Inhibition of β‐glucuronidase release depended on colchicine or vinblastine concentrations and decreased with longer time intervals (1′, 5′, 20′) after thrombin stimulation. Levels of the cytoplasmic enzyme, lactic acid dehydrogenase, in supernatants of colchicine treated platelets were not significantly different from controls. Colchicine also inhibited β‐glucuronidse release, but not 14C‐5‐HT release, induced by trypsin and sodium arachidonate. Binding of 14C‐colchicine by platelets was measured and it was found that platelet aggregation and release of 5‐HT induced by adenosine diphosphate, epinephrine and collagen proceeded without any alteration in colchicine binding. However, significant increases in the rate and degree of colchicine binding were observed when platelets were stimulated by thrombin, trypsin and arachidonic acid which induced aggregation, release of both 5‐HT and β‐glucuronidase. The results suggest that an alteration in platelet microtubules is correlated with the physiologic response resulting in release II and that the cellular mechanisms effecting release I and II by platelets differ qualitatively in that the microtubules may facilitate release II.
Neoplasms produced from C3H/10T 1/2 cells attached to plastic plates; saturation density, anchorage dependence and serum requirement of in vitro lines correlated with growth aggressiveness in vivo
Authors: Paranjpe Meera S. , del Ande Eaton Sol , Boone Charles W. 
Published: February 2005

AbstractThe C3H/10T 1/2 embryo cell line, which is nontumorigenic when inoculated subcutaneously in saline suspension, produces tumors when implanted subcutaneously attached to 1 × 5 × 10 mm plastic plates. Under these in vivo conditions there is direct selection for “spontaneous” transformants that have undergone the specific cellular alterations required for neoplastic behavior. This is in contrast to the conventional situation where transformants are obtained in vitro and are only secondarily tested in vivo for neoplastic behavior. Early passages of cell lines from four different C3H/10T 1/2 tumors explanted back in culture were quantitatively examined for tumorigenicity and for alteration in the properties of density inhibition, anchorage dependence, serum requirement, and plasminogen activator production. A fairly consistent quantitative relationship was found between the degree of growth aggressiveness in vivo and the degree of expression of these phenotypic markers of the transformed state in vitro during early passages of the cell lines after tumor explantation.
Spontaneous mutation rate to thioguanine resistance is decreased in polyploid hamster cells
Authors: Morrow John , Stocco Douglas , Barron Emily 
Published: February 2005

AbstractThe mutation rate to thioguanine resistance was 3.11 × 10−6 in a near diploid V79 hamster cell line and 7.58 × 10−8 in a near tetraploid derivative produced with colchicine. The specific activities of glucose‐6‐phosphate dehydrogenase and phosphoglycerate kinase of the tetraploid line were greater than that of the diploid which suggests that twice the number of active X chromosomes were present in the tetraploid. These results are compatible with the hypothesis that spontaneous variants resistant to thioguanine arise through mutation and chromosomal segregation, as has been suggested for induced mutations in tetraploid hamster cells.
Effect of phosphate esters, nucleotides and nucleosides on 5′‐nucleotidase of cultured mouse macrophages
Authors: Lazdins Janis , Karnovsky Manfred L. 
Published: February 2005

AbstractMouse peritoneal macrophages elicited by intraperitoneal injection of sodium caseinate exhibit low levels of ecto‐5′‐nucleotidase (E. C. 3.1.3.5) activity in contrast to macrophages obtained by peritoneal lavage. When elicited cells were cultured under standard conditions in the presence of serum, a 2.5‐fold increase in 5′‐nucleotidase activity was observed over a period of 48 hours. Addition of adenosine monophosphate to the culture medium led to an augmented (5‐fold) increase in the specific activity (per unit cell protein) as well as an absolute increase (per culture plate) of 5′‐nucleotidase. Other adenosine‐containing compounds also had stimulatory effects. The levels of this enzyme thus appear to be regulated by the extracellular levels of adenosine nucleotides. The product of the enzymatic reaction–adenosine–when added to the medium exhibited a toxic effect on these cells–as did adenosine monophosphate. However, the former substance did not augment the increase in enzyme activity during culture. The toxic effect could be suppressed when the cells were cultured in the presence of uridine 5′‐monophosphate. The latter substance also depressed the stimulation of enzyme activity due to AMP.
Peritoneal exudate cells. V. Influence of age, sex, strain and species on the induction and the growth of macrophage colony forming cells
Authors: Lin Hsiu‐San , Kuhn Charles , Stewart Carleton C. 
Published: February 2005

AbstractWe investigated the effects of age, sex and strain in the induction of peritoneal exudate colony‐forming cells (PE‐CFC) in mice. Sex and age (ranging from 3 weeks to 12 months) had no significant effect on the induction of PE‐CFC. However, we found significant difference between strains in terms of the number of nucleated cells and the proportion of PE‐CFC in exudate cells. When we investigated the mechanisms behind this strain difference, we found that it was due to neither the type of colony‐stimulating factor employed in culture, nor the type of stimulants used to induce the exudate, nor the difference in the kinetics of appearance of PE‐CFC in the peritoneal cavity.We also studied the induction of PE‐CFC in rats and hamsters and the growth of these cells in vitro. Unlike mouse cells, PE‐CFC from rats and hamsters could also use media conditioned by cells from other species as a source of colony‐stimulating factor.
Binding and internalization of 125I thrombin in chick embryo fibroblasts: Possible role in mitogenesis
Authors: Martin Bernice M. , Quigley James P. 
Published: February 2005

AbstractHuman α thrombin acts as a mitogen for cultures of resting chick embryo fibroblasts (CEF) in serum free medium. The use of 125I‐labeled thrombin shows that thrombin specifically binds to CEF and that after a lag of approximately 30 to 60 minutes it can not be removed by subsequent exposure to trypsin. The entry of 125I thrombin into the trypsin‐insensitive domain is not inhibited to any great extent by excess unlabelled thrombin. The cell‐associated thrombin retains its native molecular weight and its catalytic activity toward synthetic amide substrates. It appears to be located in the crude nuclear fraction of homogenized CEF cells. The association of thrombin with CEF is specific, since the non‐mitogenic serine protease chymotrypsin is internalized to a much lesser extent than thrombin. The data are discussed in terms of a possible intracellular site for thrombin's mitogenic action.
Culture pH, CO2 tension, and cell division in Euglena gracilis Z
Authors: Jones C. R. , Cook J. R. 
Published: February 2005

AbstractGrowth characteristics of Euglena gracilis Z as functions of culture pH, CO2 tension, temperature, and lighting regime were investigated. The results are consistent with the possibility that cell division is preceded by a lowered intracellular pH. Also consistent with this possibility is the finding that division rhythmicity can be induced by periodic changes in CO2 tension. It is suggested that the rhythmicity is induced by changes in intracellular pH produced by carbonic acid.
Amphibian cells in culture. II. Isolation of drug‐resistant variants and an asparagine‐independent variant
Authors: Chinchar Giovina D. , Sinclair John H. 
Published: February 2005

AbstractWith L‐15 as the base medium, drug‐resistant variants were isolated from two amphibian tissue culture strains: the Xenopus laevis A8 diploid cell line and the ICR 2A cell line of Rana pipiens. Four different classes of variants were obtained: (1) A8 cells resistant to chloramphenicol, an inhibitor of mitochondrial protein synthesis; (2) A8 cells resistant to ouabain, an inhibitor of the Na+/K+‐activated ATPase of the plasma membrane; (3) ICR 2A cells resistant to low (20 μg/ml) and high (300 μg/ml) levels of bromodeoxyuridine (BUdR), a thymidine analog which interferes with the pyrimidine salvage pathway; and (4) ICR 2A cells resistant to 2,6‐diaminopurine (DAP), an adenine analog which interferes with the purine salvage pathway.Unlike the other variants, isolation of BUdR resistant cells is a 2‐step process. Resistance to low levels of BUdR is phenotypically expressed by a reduction in thymidine transport activities while resistance to high levels of this compound is evidenced by greatly reduced levels of thymidine kinase activity.DAP‐resistant cells, which are characterized by reduced levels of adenine phosphoribosyl transferase (APRT) activity, do not die in AAT (adenine, aminopterin, thymidine) selection medium. This suggests that these cells utilize adenine efficiently.With MEM as the base medium, an asparagine independent clone was isolated from the ICR 2A cell line. When compared with the wild type, this variant exhibited a slightly reduced growth rate in the presence or absence of asparagine.
Effects of acidified fetal bovine serum on the fibrinolytic activity and growth of cells in culture
Authors: Loskutoff David J. 
Published: February 2005

AbstractThe fibrinolytic activity of cells in culture varied with the type of serum employed in the growth medium. Degradation of iodinated fibrin occurred slowly when Rous sarcoma virus‐transformed chick embryo fibroblasts were grown in medium containing fetal bovine serum (FBS), and rapidly when chicken serum was employed. This difference reflected the low plasminogen and high inhibitor content of FBS. The inhibitors were found to be serum macromolecules that were precipitated with ammonium sulfate or polyethylene glycol, and were inactivated by boiling or upon exposure to acidic conditions. No inhibitor activity was detected in fetuin, one of the major proteins present in FBS. Acidified FBS was similar to chicken serum in that both supported high rates of cell‐mediated fibrinolytic activity. Although virally transformed hamster, mouse and chicken cells grew well in acid‐treated FBS, their normal counter‐parts did not. Apparently, acidification resulted in the formation of materials that were toxic to normal cells. These agents rapidly blocked cellular DNA synthesis.
Glucocorticoid induction of proline oxidase in LLC‐RK1 cells
Authors: Kowaloff Edward M. , Phang James M. , Granger Alnora S. , Downing Sylvia J. 
Published: February 2005

AbstractDexamethasone induced proline oxidase in cultured LLC‐RK1 cells, an epithelial cell line derived from rabbit kidney. The dexamethasone‐mediated increase in enzyme activity was concentration and time dependent. Although the effect could be dissociated from cell growth and cell density, it was dependent on protein and RNA synthesis. A comparison of the enzyme isolated from control and dexamethasone‐treated cells showed that the increased activity was not due to an alteration in the affinity of the enzyme for proline. These findings suggest that glucocorticoids induce the synthesis of proline oxidase in mammalian cells.
Amino acid transport in thymic‐ and spleen‐derived lymphocytes
Authors: Wise W. C. 
Published: February 2005

AbstractWe have examined the transport of amino acids by the sodium‐dependent “A” and “ASC” system in thymic‐ and splenic‐derived lymphocytes from the Long‐Evans rat. Lymphocytes derived from the thymus transport amino acids by both the “A” and “ASC” systems, whereas lymphocytes from the spleen transport amino acids by the “ASC” system only. Thymic lymphocytes are capable of establishing a steady state distribution ratio of 7.9 for 2‐aminoisobutyric acid, but splenic lymphocytes can attain only 3.5. The steady state distribution ratio of alanine was the same in both cell types. Sodium‐independent transport is also different in splenic and thymic lymphocytes. But both cells move amino acids by a Na+‐independent system for mediated exchange‐diffusion. The studies show that lymphocytes derived from the spleen and thymus transport amino acids differently, and that the “T” lymphocytes from the spleen have membrane transport systems different from “T” lymphocytes from the thymus.
Isolation of mutant mammalian cells altered in polyamine transport
Authors: Mandel Jean‐Louis , Flintoff Wayne F. 
Published: February 2005

AbstractChinese hamster ovary and rat myoblast cells resistant to the toxic action of methylglyoxal bis guanylhydrazone (MGBG), an antimitotic agent and inhibitor of polyamine synthesis, have been isolated by single step selection. Mutagenesis with ethyl methanesulfonate increases the recovery of the variants at least 30‐fold. Intracellular accumulation of MGBG is greatly reduced in resistant cells. This property is accompanied by a 99% decrease in the uptake of all three naturally occurring polyamines. Both the resistant phenotype and the defect in polyamine transport behave recessively in somatic cell hybrids.
Cell surface‐associated ribonuclease activities
Authors: Fuller Frederick J. , Marcus Philip I. 
Published: February 2005

AbstractThe ribonuclease (RNase) activity associated with the surface of cells (primarily the Vero line of Green monkey kidney) was assayed under conditions where all cells remained viable as members of colonies or monolayers. RNase activity associated with individual clones was revealed as clear zones of hydrolyzed (acid‐soluble) RNA against an opaque background of acidprecipitated RNA in an isotonic agarose‐yeast RNA overlay. High resolution assays for single‐ and double‐stranded RNase were achieved by measuring the loss in activity of infectious Sindbis virus RNA, and of the antiviral state induced by poly(rI). poly(rC), respectively.Experiments using these assay procedures revealed that virtually all of the RNase activity associated with viable (intact) vertebrate cells in culture was contributed by the serum in the growth medium, and was superficially adsorbed to the cell surface, rendering it relatively easy to remove by extensive washing.A confluent monolayer of 2 × 106 unwashed Vero cells contained the equivalent of 500 ng of pancreatic RNase, representing about 5% of the total activity initially present in the serum of the growth medium. In terms of serum nuclease activity, only 0.45 ng equivalents of pancreatic RNase in 500 μl were required to destroy 50% of the activity of an infectious Sindbis virus RNA preparation in 15 minutes at 37°C.Cells grown in the absence of serum and cells washed about ten times had comparably low levels of RNase activity–about 100‐fold less than unwashed cells grown in the presence of 6% calf serum.The isotonic yeast RNA:agarose overlay procedure may be useful to identify and isolate cell mutants with different endogenous levels, or binding capacities, of surface RNase activity.Operationally, these studies describe the assay of cell surface‐associated RNase activity under conditions where all cells remain viable as members of individual colonies or monolayer populations. Specifically, the assay measures the solubilization of yeast RNA in an isotonic agarose mixture overlaying the cells. We describe its use to determine how much of the total RNase activity in viable cell monolayers or colonies is contributed by serum in the growth medium. In addition, we describe the results of two biological assays used as higher resolution probes for cell surface ribonuclease activity: (i) single‐strand (ss) RNA, in the form of infectious RNA from Sindbis virus, and (ii) double‐stranded(ds)‐RNA, in the form of poly(rI). poly(rC) as an inducer of an interferon‐mediated antiviral state.
Growth and electron microscopic studies on an experimentally established bacterial endosymbiosis in amoebae
Authors: Ahn T. I. , Jeon K. W. 
Published: February 2005

AbstractA strain of nonsymbiotic A. proteus was infected with endosymbiotic bacteria isolated from another strain of amoeba which had become dependent on the symbionts after a few years of spontaneously established symbiosis. In the newly infected amoebae, the bacteria avoided digestion and multiplied at a faster rate than the hosts, reaching the maximum carrying number (about 42,000 per amoeba) in fewer than ten cell generations of the hosts. The experimentally infected amoebae were also examined under the electron microscope, and the development of bacteria‐containing vesicles was followed. The results show that the infective bacteria that were initially harmful to host amoebae have become harmless and that they have changed in their mode of multiplication during the course of establishing a stable symbiosis with their hosts.
Effect of amino acid deprivation on DNA synthesis in BHK‐21/C13 cells
Authors: Melvin William T. , Burke Julian F. , Slater Alison A. , Keir Hamish M. 
Published: February 2005

AbstractRemoval of serum from BHK‐21/C13 cells in culture results in a decline in thymidine incorporation extending over five days. Additional removal of any of several amino acids results in a rapid decrease in incorporation of thymidine to negligible levels by 24 hours. Replacement by complete medium then provokes a synchronous wave of DNA synthesis after only ten hours with DNA synthesis first increased at six hours. Starvation for glutamine results in a rapid decline in protein synthesis over the 24 hour period when DNA synthesis is falling. However, there is considerable degradation of total protein during this period, and RNA degradation is also greatly increased. Concurrently, synthesis of RNA falls to less than 10% of that in control cells.
Lipid‐saccharide intermediates and glycoprotein biosynthesis in a temperature‐sensitive Chinese hamster cell mutant
Authors: Tenner Andrea J. , Scheffler Immo E. 
Published: February 2005

AbstractThe characterization of a temperature‐sensitive Chinese hamster cell mutant has been continued with the aim of localizing the apparent defect in glycoprotein synthesis (Tenner et al., 1977). Although the mutation is lethal, a demonstration of the ability of the mutant cells to support proliferation of Mengo virus at the nonpermissive temperature indicates that the general metabolic processes of the cells remain intact at a time when glycoprotein synthesis is severely depressed. A quantitative study of protein synthesis on membrane‐associated polysomes suggests that the synthesis of the polypeptide portion of the glycoproteins at 40.8°C may be normal. The investigation of lipidsaccharide molecules which have been implicated in the formation and transfer of the oligosaccharide „core„ to polypeptide acceptors shows that mutaant cells at the nonpermissive temperature are capable of synthesizing these lipid saccharides normally, and that the pool of the dolichyl oligosaccharide is maintained at a constant level independent of the temperature. The rate of formation of the lipid‐oligosaccharide, however, is reduced in intact mutant cells at the nonpermissive temperature. Further investigations show this decreased rate to be the result of an increased half life of the lipid‐oligosaccharide at 40.8°C. These data indicate that the temperature‐sensitive step in glycoprotein biosynthesis is the transfer of the oligosaccharide core from the lipid‐oligosaccharide intermediates to the nascent polypeptide chain. The data presented also provide evidence that the lipid‐saccharide intermediates, previously described mainly in in vitro systems, are in fact involved in the glycosylation of a majority, if not all, of the mannose‐containing glycoproteins in intact, growing hamster cells.
In Vitro studies of the effect of intermittent compressive forces on cartilage cell proliferation
Authors: Veldhuijzen J. P. , Bourret L. A. , Rodan G. A. 
Published: February 2005

AbstractIntermittent compressive (IC) forces (96 mm Hg, 0.3 Hz) inhibit by 35–60% the serum stimulated increase in ornithine decarboxylase activity (ODC) in chick embryo epiphyseal cartilage cells and rat chondrosarcoma cells. IC had no effect on mouse fibroblast L‐cells ODC. The dose‐response pattern of the IC effect indicated an all‐or‐none response with a threshold at 80 mm Hg, a pressure roughly equivalent to the in vivo weight bearing force. The km of the cartilage cell ODC, measured at four hours, was about 0.1 mM and was not affected by IC. The Vmax, on the other hand, was significantly reduced by IC which is consistent with less enzyme or non‐competitive inhibition. IC also produced a significant increase in cAMP levels in both cartilage explants and isolated cells in the presence and absence of serum and a significant reduction in 3H‐thymidine incorporation into DNA. The findings show that cellular cAMP, on one hand, and ODC and DNA synthesis, on the other hand, change in opposite directions following exposure to serum and/or IC. Investigation of the IC effect on DNA synthesis in serum‐deprived synchronized cartilage cells revealed that IC reduced the number of cells going into S but did not lengthen the G1 phase. Exposure to IC early in G1 (0–13 hours) produced the full effect, whereas IC application between 13 to 24 hours (pre S) had no effect. IC had no effect on 3H‐thymidine incorporation in L‐cells.