bluuebunny/crossref_metadata_2025_split huggingface dataset:
Advance toward S phase and retreat toward deeper “GO” states in resting 3Y1 cells with environmental changes
Authors: Zaitsu Hirokazu , Kimura Genki 
Published: February 2005

AbstractTo elucidate conditions which affect the lag time for resting cells to enter S phase after serum stimulation, we used a wild‐type 3Y1 rat fibroblast line and four temperature‐sensitive mutants of 3Y1 (3Y1tsD123, 3Y1tsF121, 3Y1tsG125, and 3Y1tsH203). Among these five lines, in only tsG125 cells was there an obviously prolonged lag time with increase in time in resting state at 33.8°C. The resting wild‐type 3Y1 cells, preexposed to 39.8°C, also showed a prolongation of lag time. The prolongation in tsG125 had a certain limit. Preexposure to 39.8°C before serum stimulation accelerated such prolongation in tsG125 to its limit, but did not change the limit, per se. Resting tsG125 cells stimulated by serum at 39.8°C, did not enter S phase, yet they did advance toward S phase. When they were kept at 39.8°C, they retreated toward a deeper resting state (“GO”) with time. These retreats correlated with the decrease in stimulating activity in the culture media. About 20% of the resting tsG125 cells stimulated by serum at 39.8°C were committed to enter S phase, when the extent of commitment was examined at 33.8°C. Most of the tsG125 cells committed at 33.8°C did not enter S phase, when the extent of commitment was examined at 39.8°C. More cells were committed after stimulation at 33.8°C than at 39.8°C, when the test was done at 33.8°C. We suggest that resting cells may be reversibly changed within range of resting states, in either direction, that is, advance toward S phase or retreat toward deeper “GO”. These changes may be determined by alterations in the balance between synthesis and decay of the preparedness for the initiation of DNA synthesis caused by cellular response to environmental changes (e.g., medium activity, temperature, etc.). The ts defect in tsG125 may affect the cell cycle progression, both before and after commitment by serum.
Cell growth and differentiation in vitro in mouse macrophages transformed by a tsA mutant of simian virus 40. II. Changes in the distribution of DNA content during the reversible transition between macrophage and nonmacrophage states in the cultures of tsA 640‐transformed macrophages
Authors: Tanigawa Takahiko , Okuda Atsuyuki , Takayama Hisao , Yamada Koji , Takagi Atsushi , Kimura Genki 
Published: February 2005

AbstractCultures of mouse macrophage cell lines transformed by wild‐type or the tsA640 mutant of simian virus 40 (SV40) show a reversible phenotypic transition between the nonmacrophage (proliferating phase) and the macrophage (stationary phase) states (Takayama, 1980; Tanigawa et al., 1983). Distribution of DNA content in the cultures of the tsA640‐transformed macrophage lines in the process of the phenotypic transition was determined by flow cytometry. Taking the mean DNA content of mouse peritoneal macrophages as 1 unit in the scale of fluorescence intensity in the flow cytogram, the transformed macrophages showed, at 33°C, two peaks, one located around the 1.0‐unit position (peak 1.0) and the other around the 1.6‐unit position (peak 1.6), and a plateau distribution continuing to 3.2 units. Peak 1.0 was predominant in the stationary‐phase culture, whereas peak 1.6 was predominant in the proliferating‐phase culture. Almost the entire population of the strictly resting culture, which was obtained by culturing the stationary‐phase culture for a further 5 days at nonpermissive temperature (39°C), was phagocytic, and had accumulated at peak 1.0. Cells in peak 1.0 moved to peak 1.6 and to higher positions, after the strictly resting culture was sparsely reseeded and incubated at 33°C. In contrast, the DNA content distribution of the successively proliferating cells, which were obtained by repeated passage of an extensively proliferating culture and none of which were phagocytic, was similar to that of proliferating hypotetraploid BALB/c3T3 fibroblasts with a G1 peak at 1.6 unit followed by a plateau containing S‐ and G2‐phase cells. The peak 1.0 cell population appeared from the recloned population of the successively proliferating cells in company with the restoration of the culture condition‐dependent phagocytic ability when cocultured with primary macrophages. Each peak in the flow cytogram reflected fairly well DNA content per cell as determined by other methods.
Cystamine augments the stimulation of DNA synthesis by peptide growth factors and microtubule‐disrupting agents in cultures of 3T3 mouse fibroblasts
Authors: Fong Steven , Friedkin Morris 
Published: February 2005

AbstractCystamine together with colchicine markedly enhanced the uptake of [3H]‐thymidine into DNA of quiescent cultures of insulin‐stimulated Swiss 3T3 mouse fibroblasts. Flow cytofluorometric analyses showed an increased rate of transition of cells from G0/G1 → S + G2 in response to combinations of insulin, colchicine, and cystamine. Cystamine, the most effective of several thiol compounds, gave maximal augmentation at 200 μM and was toxic at 300–500 μM. Amplification of DNA synthesis by cystamine was also obtained with epidermal growth factor, vasopressin, and 0.5% fetal bovine serum. Combinations of cystamine and other microtubule‐disrupting agents such as nocodazole, maytansine, and podophyllotoxin enhanced DNA synthesis in insulin‐stimulated cells. In experiments involving sequential addition of agents, significant enhancement of DNA synthesis was observed when the addition of colchicine to cystamine‐treated cells was delayed or conversely when the addition of cystamine to colchicine‐treated cultures was delayed. This reciprocal interaction between cystamine and colchicine suggests that a prereplicative intermediate accumulates in response to the action of these dissimilar compounds. We consider the possibility that cystamine may act by forming mixed disulfides with thiol groups of unknown protein(s) that regulate DNA replication.
3‐Aminobenzamide is lethal to MMS‐damaged human fibroblasts primarily during s phase
Authors: Boorstein Robert J. , Pardee Arthur B. 
Published: February 2005

Abstract3‐Aminobenzamide (3‐AB) interferes with DNA repair and enhances lethality in growing MMS (methyl methane sulfonate)‐treated human fibroblasts. This sensitivity to 3‐AB disappears slowly; MMS‐treated cells are sensitive to 3‐AB for up to 36 hours (Boorstein and Pardee, 1984). Evidence is now presented that 3‐AB potentiates the effects of MMS primarily during S phase. When cells were synchronized at the G1/S boundary, released, and then treated with MMS, 3‐AB caused very substantial lethality in only 4 hours, and a 12‐hour treatment gave maximum lethality. These cells also lost sensitivity to 3‐AB within 12 hours of growth minus 3‐AB. In contrast, MMS‐treated quiescent (G0) cells did not lose sensitivity to 3‐AB nor did 3‐AB cause lethality during G0. Enhanced lethality occurred when damaged G0‐arrested cells were subsequently allowed to proceed through S phase in the presence of 3‐AB; this 3‐AB sensitivity was removed only during growth in the absence of 3‐AB. The lethality of 3‐AB to a population of asynchronously cycling cells treated with MMS is thus the summation of effects on the cells as they traverse S phase. Aphidicolin prevenced lethality of 3‐AB to cells released from G1/S and treated with MMS. It also inhibited the loss of sensitivity to added 3‐AB later. Correlation with the inhibition of DNA synthesis by this drug suggests that DNA synthesis is essential for the lethality enhancement by 3‐AB. Cells treated first with MMS and then with 3‐AB accumulated in G2. This G2 arrest depended on S‐phase events and correlated with cell lethality. Cells treated with a nonlethal dose of MMS at the G1/S boundary were delayed briefly (3 hours) in their passage through S and G2. These cells, when also exposed to 3‐AB, were delayed 6–9 hours in S and they became arrested in G2. There was no G2 arrest when 3‐AB was added only after these cells had reached G2. Treatment with 3‐AB during S phase thus resulted in both enhanced lethality and G2 arrest. 3‐AB inhibited repair of DNA single‐strand damage, shown by alkaline elution analysis, in both S‐phase and quiescent cells. Aphidicolin inhibited disappearance of breaks and eliminated the difference between 3‐AB‐treated and untreated cells. Lethality did not correlate well with the measured single‐strand damage. We propose that there is a class of MMS‐induced lesions whose repair occurs during normal replicative DNA synthesis. When this repair is interrupted by 3‐AB, during S phase, sublethal damage is converted to lesions which arrest the cells in G2 phase and prevent them from forming colonies. DNA synthesis is required to reach the step in DNA repair at which 3‐AB causes lethality.
Induction of microvillar hydrolase activities by cell density and exogenous differentiation inducers in an established kidney epithelial cell line (LLC‐PK1)
Authors: Yoneyama Yoshitaka , Lever Julia E. 
Published: February 2005

AbstractSeveral hydrolase activities characteristic of the apical brush border membrane of renal proximal tubule, leucine aminopeptidase, γ‐ glutamyl transpeptidase, alkaline phosphatase, maltase, and trehalase, were identified in cultures of the LLC‐PK1 kidney epithelial cell line. A coordinate increase in activities of these enzymes was observed upon development of a confluent cell density and functional membrane polarization. Further large progressive increases in individual hydrolase activities were induced after the addition of compounds known as differentiation inducers. Hexamethylene bisacetamide preferentially induced increased trehalase and maltase activities. Induced trehalase activity exhibited an increased Vmax but a similar Km compared with activity in control extracts. Induction required protein synthesis and was dependent on inducer concentration and exposure time. Treatment of confluent cultures with N,N′‐dimethylformamide triggered an induction of maltase, trehalase, alkaline phosphatase, and γ‐glutamyl transpeptidase activities, whereas dimethylsulfoxide induced trehalase and γ‐glutamyl transpeptidase activities. Increased leucine aminopeptidase and maltase activities were observed after addition of the phosphodiesterase inhibitor 1‐methyl‐3‐isobutylxanthine. Induction of trehalase activity by N,N′‐dimethylformamide was reversible over a 4‐day period after removal of inducer, but effects of hexamethylene bisacetamide were irreversible. These results suggest that the LLC‐PK1 cell line reproducibly develops differentiation‐specific characteristics under defined conditions in cell culture, which can be individually modulated by chemicals known as inducers of cell differentiation.
An acellular human amnionic membrane model for in vitro culture of type ii pneumocytes: The role of the basement membrane in cell morphology and function
Authors: Lwebuga‐Mukasa Jamson S. , Thulin Gunilla , Madri Joseph A. , Barrett Carolyn , Warshaw Joseph B. 
Published: February 2005

AbstractTo determine whether a preformed basement membrane contributes to the maintenance of morphology and function of type II pneumocytes, we cultured isolated adult rat type II pneumocytes on the basement membrane and stromal surfaces of an acellular human amnionic membrane and on plastic. The presence of lamellar bodies on transmission electron microscopy and epithelial morphology in culture and a characteristic phospholipid profile after incubation with 3H‐acetate identified the cells as type II. When type II cells were cultured on a preexisting basement membrane, they formed a well‐organized monolayer with polarity, centrally located surface microvilli, and more basally located nuclei. Individual cells maintained a cuboidal morphology for 8–10 days. Intracellularly, there were numerous mitochondria, endoplasmic reticulum (ER), and lamellar bodies. The cells secreted a new basal lamina of their own. When cultured on the stromal side of the amnion, the cells became flattened within 48–60 hours, formed small lamellar bodies, and had scanty surface microvilli; they formed clumps and appeared less ordered. These cells did not secrete a visible basement membrane, and the majority detached from the stromal surface after 7–8 days in culture. In addition, culture on the basement membrane aspect of the amnion prevented the rapid decline in the percentage of 3H‐acetate label incorporated in phosphatidylcholine after 72 hours of culture. We conclude that a preformed basement membrane influences the function and morphology of type II pneumocytes, organizes them into a monolayer in culture, and influences deposition of a visible basal lamina. Thus, the acellular human amnion provides an excellent model for the systematic study of basement membrane influence on the biology and pathology of these cells.
Transcriptional induction of urokinase in cultured human kidney carcinoma cells by tetradecanoyl‐phorbol‐acetate
Authors: Ferraiuolo Rosa , Stoppelli M. Patrizia , Verde P. , Bullock Sarah , Lazzaro Pasquale , Blasi Francesco , Pietropaolo Tina C. 
Published: February 2005

AbstractA cell line derived from a human kidney carcinoma produces in vitro the urinary type of plasminogen activator (urokinase). The synthesis of plasminogen activator is enhanced by 12‐O‐tetradecanoyl‐phorbol‐13‐acetate(TPA); the increase can be followed both in the cell lysate and in the culture medium. The effect requires RNA and protein synthesis as well as the continuous presence of the inducer. Immunofluorescence and immunoprecipitation experiments with monospecific antiurokinase IgG show that kidney carcinoma cells synthesize a 50,000‐dalton urokinase and TPA enhances the synthesis of the same molecular species. Hybridization of the total cellular RNA to a human urokinase cDNA probe shows that TPA increases the urokinase mRNA level.
Ca2+ and hormones interact synergistically to stimulate rapidly both prolactin production and overall protein synthesis in pituitary tumor cells
Authors: Brostrom Margaret A. , Brostrom Charles O. , Bocckino Stephen B. , Green Susan S. 
Published: February 2005

AbstractEffects of Ca2+ and hormones on short‐term protein synthesis were examined utilizing intact Ca2+‐depleted and Ca2+‐restored GH3 pituitary tumor cells as a model system. Amino acid incorporation by cells in complete growth medium during short incubations was markedly reduced by EGTA concentrations in excess of Ca2+. Thyrotropin‐releasing hormone (TRH) rapidly enhanced amino acid incorporation and prolactin production, with both effects being reserved by EGTA in excess of extracellular Ca2+ or prevented by cellular Ca2+ depletion. Epidermal growth factor and phorbol myristate acetate (PMA) also stimulated amino acid incorporation and prolactin production; absolute increases in protein synthesis provided by these agents were significantly greater in Ca2+‐restored than in Ca2+‐depleted preparations. TRH and PMA concentrations which raised prolactin production were identical to those increasing the rate of amino acid incorporation into overall protein. The extracellular Ca2+ concentration dependencies of amino acid incorporation and prolactin production were similar and were unchanged by hormone. PMA, the most efficacious of the agents tested, and Ca2+ promoted incorporation of amino acid into the same spectrum of proteins. Stimulation of protein synthesis by hormones was not attributable to alterations in amino acid uptake, attachment to substrata, hormone binding, protein catabolism or transcription. Trifluoperazine selectively prevented the stimulation by Ca2+ of amino acid incorporation and prolactin production. Unlike total prolactin, the total protein content of GH3 cells during these short incubations was not altered by Ca2+, hormones or trifluoperazine. It is proposed that hormones and Ca2+, which have been demonstrated to regulate prolactin secretion and prolactin mRNA transcription in GH3 cells, also exert translational controls which serve to facilitate the overall expression of the prolactin gene.
Control of DNA synthesis in polyploid mammalian cells
Authors: Graves Jennifer A. Marshall , McMillan Julie 
Published: February 2005

AbstractTo test the hypothesis that the duration of DNA synthesis is an inverse function of nuclear size or DNA content, the S phase was calculated from PLM analysis for pseudodiploid, tetraploid, and octaploid lines of Chinese hamster cells growing as a monolayer or in suspension. S phase times were found not to be significantly different between polyploid lines and the diploid lines from which they were derived, regardless of the conformation of the nucleus. There is no evidence, therefore, that would implicate the nuclear membrane, or nuclear surface area/volume relationships, in the control of DNA synthesis.
Stimulation of DNA‐mediated transformation by UV irradiation of recipient (mouse FM3A) cells
Authors: Nagata Yoshiho , Takagi Hideki , Morita Toshimi , Oishi Michio 
Published: February 2005

AbstractDNA‐mediated transformation for thymidine autotrophs (Tk+) was stimulated severalfold when the recipient (mouse FM3A) (Tk−) cells were preirradiated by UV light. The effect was most prominently seen with the cells irradiated 12–16 hours prior to DNA addition. A similar stimulatory effect was observed when the cells were treated with novobiocin or mitomycin C. The effect, however, was blocked when cycloheximide was present during postirradiation period, suggesting that de novo protein synthesis is required for producing the effect. Most of the Tk+ transformants arised from the UV‐irradiated cells carried the donor DNA sequences in their chromosomes.
The effect of the extracellular matrix on the detachment of human endothelial cells
Authors: Gordon Portia B. , Levitt Mindy A. , Jenkins C. S. P. , Hatcher Victor B. 
Published: February 2005

AbstractHuman umbilical vein endothelial cells can be serially passaged by supplementing medium with a partially purified growth factor. Cell‐substratum detachment of early and late passage endothelial cells was examined using trypsin, collagenase, or homocysteine. Late‐passage cells detached more rapidly than early passage cells under all conditions tested. The rate of detachment was dependent upon the specific agent used. Protease‐mediated detachment was most rapid, occurring over minutes, in contrast to homocysteine‐induced detachment, which occurred over hours. When detached cells were collected and replated in the absence of the detaching agent, these cells reattached spread, and continued to proliferate. No significant difference was observed in the rate of adhesion of either early or late passage cells to a gelatin matrix. When early or late‐passage endothelial cells were plated and grown to confluence on a matrix synthesized by the opposite cell type, the rate of protease‐mediated cell detachment resembled the cell type from which the matrix was derived. The ease of endothelial cell detachment was determined by the origin of the extracellular matrix. Examination of the extracellular matrices from early and late passage cells revealed significant differences in the amounts of glycosaminoglycans and sulfated proteins present. These studies demonstrate the importance of the endothelial cell extracellular matrix in protease‐mediated cell detachment. The rate of cell detachment was controlled by the extracellular matrices and not altered by the endothelial cells.
Mitogen‐independent activation of Na+/H+ exchange in human epidermoid carcinoma A431 cells: Regulation by medium osmolarity
Authors: Cassel Dan , Whiteley Brian , Zhuang Ying Xin , Glaser Luis 
Published: February 2005

AbstractPrevious studies have documented the activation of Na+/H+ exchange in A431 cells by the addition of epidermal growth factor or serum (Rothenberg et al., 1983b). Here we show that exposure of A4 31 cells to medium of increased osmolarity also leads to activation of Na+/H+ exchange and to an increase in intracellular pH (pHi), which under a variety of conditions displays similar kinetics to that observed upon addition of mitogens to the cells. Measurements of cell volume using the 3–0‐methylglucose equilibration technique clearly show that mitogens do not activate Na+/H+ exchange by an osmotic mechanism (i.e., a decrease in cell volume). In fact, mitogens can induce further intracellular alkalinization if added to cells which have been shrunken in hypertonic medium. Activation of the Na+/H+ antiport does not lead to an obligatory change in pHi. Addition of epidermal growth factor of hypertonic solution to A431 cells in bicarbonate buffer activates Na+/H+ exchange without a concomitant increase in pHi. Under these conditions the increased proton efflux via Na+/H+ exchange must therefore be compensated by other mechanisms that control cytoplasmic pH.
Effect of oxygen and endotoxin on lactate dehydrogenase release, 5‐hydroxytryptamine uptake, and antioxidant enzyme activities in endothelial cells
Authors: Block Edward R. , Patel Jawaharlal M. , Sheridan Norman P. 
Published: February 2005

AbstractWe compared the effects of 95% O2 (hyperoxia) alone, endotoxin (20 ng/ml) alone, and 95% O2 plus endotoxin on the release of lactate dehydrogenase (LDH), uptake of 5‐hydroxytryptamine (5‐HT), and antioxidant enzyme activities in porcine pulmonary arterial and aortic endothelial cells in monolayer culture. Hyperoxia increased LDH release and decreased 5‐HT in both endothelial cell types. Hyperoxia also caused a decrease in catalase (CAT) activity and an increase in total superoxide dismutase (SOD) and glutathione reductase (GSH‐Red) activities in both cell types. Endotoxin alone had no effect on LDH release, 5‐HT uptake, or antioxidant enzyme activities. However, endotoxin prevented the hyperoxic increase in LDH release and the hyperoxia decrease in 5‐HT uptake. Endotoxin plus 95% O2 had no consistent effect on the antioxidant enzyme profile in pulmonary artery or aortic endothelial cells. These results indicate that (1) hyperoxia injures both pulmonary artery and aortic endothelial cells in culture and causes changes in the antioxidant enzyme profile that are similar in the two cell types; (2) hyperoxia‐induced decreases in CAT activity and increases in SOD activity may be responsible for increased sensitivity of endothelial cells to O2 toxicity; and (3) endotoxin protects against hyperoxic injury to endothelial cells in vitro, but increases in antioxidant enzyme activities are not the mechanism for this protection.
The osmotic response of human erythrocytes and the membrane cytoskeleton
Authors: Heubusch Philip , Jung Chan Y. , Green Floyd A. 
Published: February 2005

AbstractThe volumes of human erythrocytes suspended in solutions of varying concentrations of sodium chloride and sucrose were measured by a Coulter Channelyzer® Model H4 with appropriate corrections. The cells showed greatly restricted volume changes at osmolarities between 200–700 mOsm. At osmolarities outside this limit, on the other hand, the cells showed nonrestricted volume changes following essentially the predictions of an ideal osmometer. This unexpected volume response was not spuriously due to changes in shape or to a changing orientation of the cells as they traversed the aperture. The restricted volume change observed was abolished when the cells had previously been treated with diamide or had been heated for 60 minutes at 50°C, conditions that are known to disturb the spectrin‐actin network. The possibility must be considered that the osmotic behavior of human erythrocytes may be nonideal and that this nonideal behavior is primarily due to mechanical restriction provided by the spectrin‐actin network of the membrane cytoskeleton.