bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bromodeoxyuridine‐induced reversion of transformed characteristics in BHK21 cells: Changes at the plasma membrane level
Authors: Lage‐Davila A. , Krust B. , Hofmann‐Clerc F. , Torpier G. , Montagnier L. 
Published: February 2005

AbstractWhen BHK21 cells transformed by hamster sarcoma virus aregrown in the presence of 5‐Bromodeoxyuridine (BUdr), several in vitro properties of the transformed cells such as morphology, adhesiveness, and alignment, revert towards a state close to that of untransformed cells. We have studied plasma membrane changes associated with this phenotypic reversion by several different biochemical methods. Reversion is accompanied by a reappearance of Fibronectin, an increase in a membrane‐associated protein of M. W. 195,000, a decrease in glycosylation and exposure of a glycoprotein M. W. 100,000 which is increased in transformed cells and a decrease in Con A‐agglutinability. On the other hand, several membrane changes associated with malignant transformation namely, the increase in an integral membrane protein M. W. 177,000, the higher rate of hexose uptake, the increase in high molecular weight surface glycopeptides and, to some extent, the increase in the density of intramembrnous particles, did not revert under BUdr treatment. Thus, membrane properties of transformed cells may be dissociated into two main groups by BUdr treatment. In addition, the exposure and glycosylation of a growth‐regulated membrane protein M. W. 160,000 was highly sensitive to BUdr.
The effect of homologous localanesthetics of the 4‐alkoxy‐ and 4‐alkylamino‐benzoicacid‐diethylamino‐ethylester‐hydrochloride‐series on the glucose transport in human erythrocytes
Authors: Lacko L. , Wittke B. , Lacko I. 
Published: February 2005

AbstractThe homologous compounds of the 4‐alkoxy‐ and 4‐alkylamino‐series inhibit the exchange transport of glucose in human erythrocytes; they show a competitive inhibition with one or two inhibitor molecules which become bound to a singular site of the transport system for glucose. The importance of length of hydrocarbon chain of the localanesthetics for the mode of their action is discussed.
Cell cycle analysis of sodium butyrate and hydroxyurea, inducers of ectopic hormone production in HeLa cells
Authors: Fallon Robert J. , Cox Rody P. 
Published: February 2005

AbstractSodium butyrate and hydroxyurea, effective inhibitors of DNA synthesis in HeLa cells, cause these cells to produce increased levels of the ectopic glycopeptide hormones human chorionic gonadotropin (hCG), follicle stimulating hormone (FSH), and free α chains for these hormones. The objective of this study was an assessment of the role of modulation of cell cycle events in the action of these two chemical agents. A variety of experimental approaches was employed to obtain a clear view of the drugs' effects on cells located initially in all phases of the cell cycle. Cells in early G1, G2, or M phase at time of addition of either inhibitor were not arrested at early time points, but by 48 hours became collected at a location characteristic for each drug, near the G1‐S phase boundary. Flow microfluorometry (FMF) and thymidine labeling index revealed that butyrate‐treated cells arrested late in G1 phase very close to S phase, while hydroxyurea‐blocked cells continued to early S phase. Both inhibitors prevented cells originally in S phase from reaching mitosis. S cells exposed to hydroxyurea were killed by 48 hours, but those growing in 5 mM butyrate progressed to the end of S or G2 phase where they became irreversibly arrested although not removed from the monolayer. Analysis of the cell cycle location and viability of each subpopulation resulting from 48 hour exposure to butyrate or hydroxyurea is important for the study of the function of each cellular subset. Treatment of HeLa cells with lower concentrations of butyrate (1 mM) resulted in slowed yet exponential growth. Fraction labeled mitosis (FLM) analysis shows that this is a result of prolongation of the G1 phase.
Hemicyst formation stimulated by cyclic AMP in dog kidney cell line MDCK
Authors: Valentich J. D. , Tchao R. , Leighton J. 
Published: February 2005

AbstractCertain epithelial cell lines have morphologic, physiologic, biochemical and pharmacologic characteristics of transporting epithelia from intact organs. In this paper we show that dibutyryl cyclic AMP, 5′ AMP, adenosine and cyclic AMP phosphodiesterase inhibitors stimulate hemicyst formation by the dog kidney cell line MDCK. It is suggested that this effect is explained by elevation of intracellular cyclic AMP levels by means of an exogenous non‐metabolizable source of cyclic AMP, phosphodiesterase inhibition or adenyl cyclase stimulation. Since hemicyst formation is in part due to transepithelial fluid transport, these findings raise the possibility that this fraction might be modulated by cAMP in an established cell line. We believe that cultured epithelial cells may provide an exploitable model system to investigate at the cellular and subcellular levels, the mechanism by which cyclic AMP modifies water and solute movements across epithelia.
Presence of epidermal growth factor receptors and influence of epidermal growth factor on proliferation and aging in cultured smooth muscle cells
Authors: Bhargava Girija , Rifas Leonard , Makman Maynard H. 
Published: February 2005

AbstractEpidermal growth factor (EGF) at nanomolar concentrations stimulated DNA synthesis in confluent, serum‐starved cultures of calf aorta and human uterine smooth muscle cells. Stimulation of DNA synthesis in lens epithelial cells was studied for comparison. L and D‐ascorbic acid potentiated the effect of serum and EGF on DNA synthesis in calf aorta cells. In contrast L‐ascorbic acid had minimal potentiating effect with serum and no effect with EFG present along with serum on DNA synthesis in human uterine smooth muscle and rabbit lens epithelial cells. EGF and ascorbic acid increased cell number when added to stationary phase cultures. Specific binding of 125I‐labelled EGF to smooth muscle cells was demonstrated. Receptor concentration in calf‐aorta smooth muscle cells was higher in dense cultures compared to sparse cultures. The time course of binding and dissociation of 125I‐labelled EGF was similar in “dense” and “sparse” cultures.Human uterine smooth muscle cells in culture exhibited a finite lifespan. There was no stimulation of DNA synthesis in response to serum and EGF in cells of high population doubling level (PDL); although 125I‐labeled EGF binding was higher in old cells (high PDL) compared to young cells (low PDL). This increase in binding was shown to be due to changes in the concentration of receptors without changes in their affinity for EGF.
Estrogen receptors and effects of estrogen on membrane electrical properties of coronary vascular smooth muscle
Authors: Harder David R. , Coulson Patricia B. 
Published: February 2005

AbstractThe effect of estrogen stimulation in vitro on the electrical properties of vascular smooth muscle (VSM), and the concentration of estrogen receptors in VSM were measured in isolated coronary arteries. Microelectrode measurements of the dog coronary artery membrane potential (Em) showed quiescent values of −51 millivolts (mV) and an input resistance (rin) of 10 megohms. Addition of diethylstibestrol (DES) at 10−6 M hyperpolarized the membrane to −64 mV and reduced in resistance (rin) to 5 megohms within 15 minutes. Extrapolation of the Em vs. log [K]o curve to zero potential gave similar values of [K]i of around 170 mM in both normal and DES treated muscles suggesting that the DES induced hyperpolarization is not due to increased Na‐K pump activity. The 0.5% ethanol vehicle alone had no effect on the membrane potentials. Tetraethylammonium ion (TEA) induced action potentials in the previously quiescent tissue. When DES was applied in the presence of TEA, the membrane potential increased and the action potential were abolished. Scatchard analysis of the estrogen receptor binding demonstrated both a high and a low affinity receptor for estrogen in the VSM. These data indicate that DES hyperpolarizes the VSM cells by a mechanism other than an increased Na‐K pump activity. The mechanism of this increased Em may be due to factors which increase K+ conductance either mediated directly through estrogen interaction with its cytosolic receptors or through some unidentified second mechanism.
Inhibition by aphidicolin of cell cycle progression and DNA replication in sea urchin embryos
Authors: Ikegami Susumu , Amemiya Shonan , Oguro Mieko , Nagano Hiroshi , Mano Yoshitake 
Published: February 2005

AbstractWe have recently found that aphidicolin, a tetracyclic diterpene‐tetraol produced by several fungi, blocks DNA synthesis of sea urchin embryos by interfering with the activity of DNA polymerase α. These cells fail to proliferate in the presence of aphidicolin.In continuation of these studies, we determined the drug‐sensitive stage in the first cell cycle of the sea urchin Clypeaster japonicus embryo.In continuous exposure to aphidicolin (2 μg/ml) from five minutes after fertilization, mitotic division of the embryo was completely suppressed. Embryos were exposed to the drug at progressively later intervals and their capability for cytokinesis was examined. Evidence was thereby obtained that aphidicolin acts at the S‐period to inhibit DNA synthesis resulting in developmental arrest of the embryo.
Oxocarboxylic acids, pyridine nucleotide‐linked oxidoreductases and serum factors in regulation of cell proliferation
Authors: McKeehan Wallace L. , McKeehan Kerstin A. 
Published: February 2005

AbstractWhen serum is made rate‐limiting for clonal multiplication of human diploid fibroblasts, the presence of a 2‐oxocarboxylic acid in the medium becomes essential. The requirement is independent of the 20 amino acids and glucose. Glyoxylic, pyruvic, 2‐oxoglutaric, and oxalacetic acids are most effective. The types of 2‐oxocarboxylic acids that support multiplication are oxidized substrates for several, pyridine nucleotide‐linked intracellular oxidoreductases. The requirement is not satisfied by carboxylic acids, oxidized substrates for oxidoreductases that are not linked to pyridine nucleotides, or by nonspecific electron acceptors. The quantitative requirement for 2‐oxocarboxylic acids in cell multiplication is markedly affected by the concentration of serum proteins in the medium. Therefore, 2‐oxocarboxylic acid metabolism may be related to the mechanism by which serum growth factors regulate cell multiplication.
Effect of cytosine arabinoside triphosphate on the incorporation of 3H‐thymidine in mitochondria isolated from HeLa cells
Authors: Mattoccia L. Pica , Sorrentino R. 
Published: February 2005

AbstractHeLa cell mitochondria were allowed to incorporate 3H‐thymidine in a cell free system and the effect of ethidium bromide, cytosine arabinoside and cytosine arabinoside triphosphate on the labeling of mitochondrial DNA was studied. The labeled products, isolated by sedimentation velocity in CsCl‐ethidium bromide two‐step gradients, showed similar sedimentation profiles as in vivo labeled mtDNA. Cytosine arabinoside triphosphate and ethidium bromide strongly inhibited the labeling of mitochondrial DNA, whereas cytosine arabinoside appeared to be much less effective. Tritiated deoxycytidine was found to be incorporated by isolated mitochondria, whereas cytosine arabinoside was shown to enter the mitochondrial acid‐soluble pool but not to be incorporated in acid‐insoluble form. These results are in agreement with the previously reported findings of in vivo experiments.
Effects of depletion of K+, Na+, or Ca2+ on DNA synthesis and cell cation content in chick embryo fibroblasts
Authors: Moscatelli David , Sanui Hisashi , Rubin A. Harry 
Published: February 2005

AbstractDecreasing the K+ concentration of the medium from 5 mM to 0.59 mM decreased the K+ content of chick embryo fibroblasts to 22% of control values and increased the Na+ content to 820% of control values. The alteration of monovalent cation content occurred within two hours but had no effect on the rate of DNA synthesis, as measured by 3H‐thymidine incorporation, for at least 16 hours. By decreasing the Na+ concentration in the medium, a 50% reduction in cellular Na+ could be obtained with no effect on thymidine incorporation. Since these changes in cellular Na+ and K+ are much larger than any known to occur under physiological conditions but have no effect on thymidine incorporation, we conclude that Na+ and K+ do not play a critical role in determining multiplication rate.Addition of 1.8 mM EGTA to cells in media containing 1.7 mM Ca2+ and 0.8 mM Mg2+ inhibited thymidine incorporation and sharply decreased cellular K+ and increased cellular Na+ content. However, there was no reduction in total cellular Ca2+ levels. Likewise, decreasing the Ca2+ concentration of the medium below 0.01 mM inhibited thymidine incorporation, decreased cellular K+ and Mg2+, and increased cellular Na+ but did not affect total cellular Ca2+ levels. Inhibition of DNA synthesis, therefore, could not be correlated with changes in cellular Ca2+ levels.
Replicative activity of isolated chromatin from proliferating and quiescent early passage and aging cultured mouse cells
Authors: Weisman‐Shomer P. , Kaftory A. , Fry M. 
Published: February 2005

AbstractReplicative activity of isolated chromatin from late passage cultured mouse cells has been compared to the activities of chromatin preparations from dividing and quiescent early passage cells. Rates of endogenous DNA synthesis are similar for chromatin from growing or resting cells but this activity is stimulated 2.5‐fold in senescent cell chromatin. Chromatin from growing young cells copies exogenously added single stranded DNA at the highest efficiency. Chromatin of senescent cells copies this template at a lower rate and resting young cell chromatin replicates single stranded DNA at the lowest efficiency. Similar relative rates are obtained when activated DNA is copied by the various chromatin preparations. Total activity of DNA polymerase extracted by salt from chromatin is similar for dividing and quiescent young cells but the proportion of DNA polymerase β is higher in the latter. Elevated activities of DNA polymerases are extracted from chromatin of old cells. It is concluded, therefore, that chromatin‐directed replication is differently arrested in nondividing senescent cells and in quiescent early passage cells. The possible regulatory mechanisms of DNA replication in quiescence and aging are discussed.
Specific cellular defects in patients with Fanconi anemia
Authors: Weksberg Rosanna , Buchwald Manuel , Sargent Patricia , Thompson Margaret W. , Siminovitch Louis 
Published: February 2005

AbstractMeasurements of plating efficiency, accumulation of metaphases and generation times have shown that fibroblast from patients with Fanconi anemia (FA) have decreased probability of completing a further division after successful mitosis. Thus FA cells show decreased growth rates and increased generation times. We have also measured the survival of FA fibroblasts and lymphoblasts after treatment with a variety of mutagens. All FA cells show an increased sensitivity to drugs such as MMC and psoralen plus long wave length UV which cause DNA interstrand crosslinks. FA strains show varying degrees of sensitivity to these drugs and the extent of this sensitivity seems to be characteristic of each patient. FA cells are equal to controls in their sensitivity to other alkylating agents such as ethyl methane sulfonate, N‐methyl‐N1‐nitro‐N‐nitrosoguanidine and actinomycin D. Both the decreased growth and increased drug sensitivity may result from defect in DNA replication or repair.
Defect in polyamine metabolism in a BHK cell mutant temperature‐sensitive for rRNA maturation
Authors: Levin Eugene G. , Clark Jeffrey L. 
Published: February 2005

AbstractA mutant of BHK cells (ts422E) temperature‐sensitive for processing 32S rRNA to 28S rRNA (Toniolo et al., '73) also loses the ability to synthesize polyamines and 5.8S rRNA when shifted to the non‐permissive temperature (39°). The activity of several enzymes not involved with polyamine synthesis, methylation of 32S rRNA, and small nuclear RNA production are apparently unaffected after at least 24 hours at 39°. When cultures are returned to the permissive temperature (33°), polyamine synthesizing capacity returns to normal as mature rRNA production resumes.
A variant vascular endothelial cell line with altered growth characteristics
Authors: McAuslan B. R. , Reilly W. 
Published: February 2005

AbstractA variant endothelial cell type was found to arise spontaneously from cultures of bovine aortal endothelial cells. This variant showed no contact inhibition and overgrew confluent cultures of wild‐type endothelial cells. Unlike other reported variants of this cell type produced by chemical mutagenesis or by withdrawal of polypeptide growth factor, this variant retained the capacity to synthesise factor VIII antigen, but showed no alteration from wild‐type in capacity to adsorb platelets. The variant also had an increased capacity to bind FITC‐conjugated con A to its surface.
Induction of an oligodendroglial enzyme in C‐6 glioma cells maintained at high density or in serum‐free medium
Authors: Maltese William A. , Volpe Joseph J. 
Published: February 2005

AbstractThe relationship between cell density and the activity of 2′:3′‐cyclic nucleotide 3′‐phosphohydrolase (CNP), an enzyme believed to be specific to oligodendroglial cells and myelin in the brain, has been studied in cultured C‐6 glioma cells. Over a 12‐day period, the specific activity of CNP underwent a 4‐fold increase in conjunction with an increase in the cell density (total protein/flask) and a decline in the growth rate of the cultures. In contrast, the specific activity of Na+, K+‐ATPase was not influenced by cell density. Experiments with cultures seeded at different initial densities indicated that the increase in CNP activity coincided with the attainment of a specific cell density rather than with the length of time that the cells were maintained in culture. Arrest of cell proliferation in non‐confluent C‐6 cells by means of thymidine blockade was not sufficient to cause an increase in the activity of CNP; however, removal of serum from the culture medium resulted in a 3‐fold induction of the enzyme in the absence of a high degree of cell contact. The induction of CNP in cells maintained in serum‐free medium paralleled the development of a series of distinct morphological changes reminiscent of glial differentiation, which occurred within 48 hours after removal of the serum. Inhibition of protein synthesis by cycloheximide prevented the induction of CNP in serum‐free cultures. The demonstration that an enhancement of an oligodendroglial characteristic in C‐6 glioma cells can be obtained by growing the cells to high density or by removing serum from the medium, provides further support for the suggestion that these cells may be analogous to the glial stem cells present in the developing brain.
A synergistic effect of glucocorticoids and insulin on the differentiation of myoblasts
Authors: Ball Eric H. , Sanwal B. D. 
Published: February 2005

AbstractGlucocorticoids and insulin were found to act synergistically to promote differentiation in some clones of the L6 rat myoblast cell line. Other hormone effects on these cells were investigated to determine the extent of the synergism. The insulin stimulation of sugar transport was unaffected by glucocorticoids although they did by themselves slightly enhance transport. Glucocorticoids were found to increase the adhesiveness of the cells–an effect not influenced by insulin. Cyclic AMP levels were found to peak just prior to the time of the onset of fusion and insulin broadened this peak, while the combination of both hormones further lengthened the time for which cyclic AMP levels remained elevated.
Studies of morphologically atypical (“sprouting”) cultures of bovine aortic endothelial cells. Growth characteristics and connective tissue protein synthesis
Authors: Cotta‐Pereira Gerson , Sage Helene , Bornstein Paul , Ross Russell , Schwartz Stephen 
Published: February 2005

AbstractMorphologic and biochemical studies were performed on cultures of bovine aortic endothelial cells which had developed a second growth pattern that has been referred to as “sprouting” (Gospodarowicz and Mecher, '78; Schwartz, '78). These morphologically atypical cells undergrew the intact endothelial cell monolayer and appeared only after the cells had reached confluence. They were ultra‐structurally very similar to endothelial cells, but synthesized reduced amounts of fibronectin and a predominance of type I procollagen, rather than the types III and IV procollagens synthesized by monolayer endothelial cells.It is suggested that these cells represent phenotypically altered endothelial cells that differ in biosynthesis of secreted proteins and display a reduced contact‐inhibition.
Induction of both rat and mouse lactate dehydrogenase in hybrids between inducible rat glioma and uninducible mouse neuroblastoma cells
Authors: Meyer Robert D. , McMorris F. Arthur 
Published: February 2005

AbstractThe specific activity of lactate dehydrogenase (LDH; EC 1.1.1.27) is induced two‐fold by l‐norepinephrine (NE) in C6TK− rat glioma cells, but not in NA mouse neuroblastoma cells or various other nonglial cells. Previous reports have shown that the induction is mediated by cyclic AMP (cAMP) and possibly protein phosphorylation, and that it requires RNA and protein synthesis. To study the block to LDH induction in nonglial cells, we hybridized C6TK− cells with NA cells and isolated a hybrid clone in which LDH is inducible by NE. Mouse and rat LDH from hybrid cells were separated by electrophoresis and quantitated by two independent methods, and it was found that mouse and rat LDH were induced equally when cells were exposed to NE. The results suggest that inducibility of LDH is not determined by a cis‐acting control at the gene level, but rather by the presence or absence of an earlier component in the cAMP‐mediated induction system, and that the induction system acts indiscriminately on all active LDH gene copies in the cell.
Multinucleation in mouse fibroblasts cultured in methocel medium
Authors: Ishii Kazuhiro 
Published: February 2005

Abstract3T3‐4E cells formed multinucleate cells with high frequency when incubated in methocel medium. The experiment with hydroxyurea and the cytological observation of mitoses showed that multinucleate cells were produced by nuclear division in the absence of cytokinesis. When transferred onto a solid substratum, most of the multinucleate cells divided within seven hours into mononucleate cells through the process of cytoplasmic division, indicating that cell spreading induced cytokinesis. Other mouse fibroblast lines examined so far showed only the low frequency of multinucleation. These findings indicate that in 3T3‐4E cells cultivated in methocel, nuclear division occurred independently of cytokinesis, and that cytokinesis was also anchorage‐dependent. This system will be available for studying cytoplasmic division of mammalian cells.