bluuebunny/crossref_metadata_2025_split huggingface dataset:
Related effects of calcium and serum on the G1 phase of the human WI38 fibroblast
Authors: Tupper Joseph T. , Kaufman Lydia , Bodine Peter V. 
Published: February 2005

AbstractDeprivation of extracellular Ca or serum inhibits the proliferation of WI38 human diploid fibroblasts. Under these conditions, the cells become quiescent at a point in the cell cycle typical of early G1 or Go phase‐arrested cells. Exit of the cells from this point in the cycle appears to require both the presence of serum and Ca simulataneously. If quiescent cells are serum‐stimulated in low Ca medium (0.01 mM), they do not progress through G1 to the S phase, which normally requires 14–18 hr. However, they remain competent to do so. Addition of Ca for up to 48 hr after serum stimulation results in an equal fraction of the cells progressing G1 phase as compared to the presence of Ca at the time of serum addition. In contrast, if quiescent cells are serum‐stimulated in the presence of Ca, which is then removed, the cells can remain competent to enter S phase for only 10–12 hr. Re‐addition of Ca beyond this time does not allow G1 progression on a normal schedule.These data suggest that Ca and serum are both required to trigger, in whole or in part, the pleiotypic response. Ca appears also to render the cells competent to enter S phase, but this competence is labile; an observation consistent with the PDGF‐induced competence observed previously in the 3T3 cell. These observations are in contrast to previous data from other cell types which suggest that Ca is required only in late G1 phase for successful entrance to S phase.
Intracellular concentration of potassium and other elements in vaginal epithelial cells stimulated by estradiol administration
Authors: Cameron Ivan L. , Pool Thomas B. , Smith Nancy K. R. 
Published: February 2005

AbstractElectron probe x‐ray microanalysis was used to measure cytoplasmic elemental content (in mmoles/kg dry weight) of the basal layer of cells of the vaginal epithelium of ovariectomized rats. Measurements were made both before estradiol injection and at 2 hr, 17 hr, and 24 hr after estradiol administration. Mitotic figures first appeared in the basal cell layer at 24 hr. During the course of the study significant time‐dependent differences were seen in the content of all elements measured. A pattern of change in cytoplasmic content was seen for Na, P, S, and Cl; all of which decrease significantly by 17 hr and then return to approximately the nonstimulated concentration by 24 hr. On the other hand K, and to a lesser extent Mg, show an early and continued increase in cytoplasmic content after estradiol injection. Thus, the marked increase in the intracytoplasmic content of K in the estradiol treated cells suggests that K, or the ratio of Na to K, may be directly or indirectly involved in growth stimulation.
Synthesis and degradation of tyrosinase in cultured melanoma cells
Authors: Saeki Hisaaki , Oikawa Atsushi 
Published: February 2005

AbstractThe tyrosinase (EC 1.14.18.1) activity of cultured B‐16 mouse melanoma cells (C2M) in the stationary phase depends greatly on whether the culture medium contains glucose or galactose. The activity in medium cotaining galactose was about ten times that in medium containing glucose at pH 7.2. This difference in tyrosinase activity was concluded to be due to a shift of balance between synthesis and degradation of the enzyme. Experiments were conducted with stationary phase cultures in the presence and absence of cycloheximide.The melanoma cells did not synthesize tyrosinase in medium containing glucose in the stationary phase. But when they were cultured under identical conditions, except that glucose was replaced by galactose, they continued to synthesize tyrosinase.The rate of synthesis in medium containing galactose at pH 6.3 was one third of that in the same medium at about pH 7, in which the increase in specific activity of tyrosinase per day was about 30 nmoles/mg cell protein per hr. The rate of degradation of the enzyme was practically the same in medium containing glucose as in medium containing galactose, and largely dependent on the pH of the culture medium. At pH 6.3 the half‐life was about one third of that at pH 7.2, where it was about 1.8 days.The degradation at acidic pH values was much reduced by ammonium salt and was strongly inhibited by the protease inhibitor, leupeptin.
Regulation of metastatic ovarian cell in serum‐free medium by epidermal growth factor and transferrin
Authors: Turner John T. , Wyche James H. 
Published: February 2005

AbstractA rat ovarian tumorous cell line (OV1N) has been isolated and established in tissue culture whose growth can be controlled by the addition of epidermal growth factor (EGF) and transferrin to serum‐free medium. EGF at 1 ng/ml (1.5 × 10−10M) stimulates growth about 300% in a six‐day incubation assay. A combination of 1 ng/ml EGF plus 1 μg/ml (1.25 × 10−8M) transferrin stimulates growth 1700% above controls in six days. EGF and transferrin at these concentrations completely replaced fetal calf serum (FCS), which maximally stimulates the cells at 2%. At maximal stimulation (either by FCS or EGF and transferrin) a doubling time of from 16–20 hours is obtained. The growth of OV1N cells was also studied in vivo and compared to another rat ovarian cell line, 31A‐F2. Cells from both cell lines were injected intrasplenically into normal, ovariectomized and hypophysectomized female Fischer 344 rats. Animal data have indicated that 31A‐F2 cells behave more like “normal” ovarian cells in that they grew only in ovariectomized hosts. OV1N cells, on the other hand, grew metastatically in all hosts and killed 36% of those individuals.The binding of 125I‐EGF was also studied in OV1N and 31A‐F2 cells. OV1N cells bound about eightfold more 125I‐EGF than did 31A‐F2 cells at 37°C. The dose of 125I‐EGF required to specifically saturate 31A‐F2 sites was 10 ng/ml (1.5 × 10−9M) or half‐maximally at 4 ng/ml (6 × 10−10M). Scatchard plots indicate that 31A‐F2 cells contain roughly fourfold less EGF‐specific sites than OV1N cells. Incubation of either OV1N or 31A‐F2 cells with a 100‐fold excess addition of various proteins plus a maximal or a half‐maximal addition of 125I‐EGF demonstrated that unlabeled EGF was most effective in reducing 125I‐EGF binding to both OV1N and 31A‐F2 cell sites. Insulin, ovarian growth factor, transferrin, or their combinations, had minimal, if any effect on 125I‐EGF binding.
Biosynthesis of erythrocyte membrane protein band 3 in DMSO‐induced friend erythroleukemia cells
Authors: Sabban Esther L. , Sabatini David D. , Marchesi Vincent T. , Adesnik Milton 
Published: February 2005

AbstractThe major integral membrane protein of red blood cells, the mouse equivalent of human band 3, was purified and used to raise a specific antiserum. The murine protein resembles its human counterpart in several of its properties, including susceptibility to digestion by chymotrypsin added to intact cells and an ability to bind to concanavalin A. The synthesis of 35S‐labeled band 3 was detected in Friend erythroleukemia cells treated with DMSO by immuneprecipitation followed by SDS gel electrophoresis and fluorography. Induction with DMSO led to a greater than tenfold increase in the synthesis of band 3 and maximal synthesis was reached 3 to 4 days after the beginning of induction.
Purification of human granulocytes by centrifugal elutriation and measurement of transmembrane potential
Authors: Jones G. S. , Van Dyke K. , Castranova V. 
Published: February 2005

AbstractViable cell samples containing 93% pure granulocytes were obtained from human blood using the techniques of dextran sedimentation followed by centrifugal elutriation. The resting transmembrane potential (Em) of human granulocytes was estimated using the fluorescent lipophilic cation, Di‐S‐C3(5), from the null point for potassium—i.e., the external K concentration at which there is no change in Em in response to valinomycin (a K ionophore). The Em of human granulocytes, as calculated from the Nernst potential for K at the null point, is approximately – 100 mV. Data indicate that this large transmembrane potential is due in part to the presence of an electrogenic Na‐K pump in human granulocytes which is stimulated by external potassium and inhibited by ouabain.
Protein synthesis and degradation in growth regulation in rat embryo fibroblasts: Role of fast‐turnover and slow‐turnover protein
Authors: Amenta J. S. , Sargus M. J. , Brocher S. C. 
Published: February 2005

AbstractCultured rat embryo fibroblasts, when stimulated to grow by the addition of fresh medium containing 10% serum, showed an increase in synthesis of slow‐turnover proteins while maintaining a uniform degradation rate for these proteins. Slow‐turnover proteins with a half‐life of 2.4 days accounted for approximately 95% of the cell protein, while the remaining protein could be described in terms of two fast‐turnover pools. When we labeled cells to limiting levels over a period of 4 days, the fast‐turnover pools became undetectable; with 2‐hour labeling periods, however, 25% of the label entered the fast‐turnover pools. Fibroblasts, stimulated to grow by fresh growth medium, showed proportionate and coordinate increases in synthesis of both fast‐turnover and slow‐turnover proteins during the growth period, both returning to baseline levels on reaching the new steady state. No changes could be detected in degradation of either pool during growth. Fibroblasts placed in a serum‐free medium showed a decrease in cellular protein and an increased degradation of slow‐turnover proteins, while degradation of fast‐turnover proteins remained unchanged. We conclude that the slow‐turnover protein pool forms the bulk of the cell proteins and turns over at a fairly constant rate. Growth stimulation is effected almost entirely by stimulation of protein synthesis in this pool, while decreasing cellular protein growth is a result of enhanced degradation within this pool.
Kirsten murine sarcoma virus transformed cell lines and a spontaneously transformed rat cell‐line produce transforming factors
Authors: Ozanne Brad , Fulton R. Jerrold , Kaplan Paul L. 
Published: February 2005

AbstractWe have examined culture fluids from a variety of Kirsten murine sarcoma virus (KiMSV) transformed rat and mouse cells for the presence of factors which induce normal Rat‐1 cells to assume the transformed phenotype. All KiMSV transformants produced transforming factor (TF). Revertants of KiMSV transformed rat or mouse cells failed to relase TF as did normal rat or mouse cells. Cells transformed by a temperature sensitive mutant of KiMSV produced TF at the permissive temperature but not at the nonpermissive temperature. Further, cells from a spontaneous transformant of Rat‐1 cells also produced TF. TF is a small polypeptide which competes for the epidermal growth factor receptor. Its effect upon normal cells is reversible and requires de novo RNA and protein synthesis. Cells treated with TF lose the actin fibers observed in normal fibroblasts, assume a transformed cell morphology, become anchorage independent for growth, grow in low concentrations of serum, grow to a high cell density, and have an increased rate of hexose uptake.
The use of 5‐bromodeoxyuridine and irradiation for the estimation of the myoblast and myocyte content of primary rat heart cell cultures
Authors: Masse M. J. O. , Harary Isaac 
Published: February 2005

AbstractA method for killing dividing cells (Puck and Kao, '67) was adapted for the elimination of dividing heart muscle cells (myoblasts) in cultures. We have used this method to demonstrate their presence and to estimate their number as well as the number of nondividing heart muscle cells (myocytes) in the neo‐natal rat heart. Cells were cultivated in BUdR (5‐bromodeoxyuridine) 10−4 M for 3 days and then irradiated with long UV light. The selective elimination of dividing cells led to a loss of myosin Ca2+‐activated ATPase in the cultures. This indicates the presence of dividing cells which contain myosin. The percent of ATPase left after irradiation was 32% of the control in cultures derived from 1‐day postnatal rats and 48% in cultures from 4‐day postnatal rats. This reflects an in vivo shift of myoblasts to myocytes in the muscle cell population as the rat ages.
Insulin inhibition of protein degradation in cell monolayers
Authors: Ballard F. J. , Wong S. S. C. , Knowles S. E. , Partridge N. C. , Martin T. J. , Wood C. M. , Gunn J. M. 
Published: February 2005

AbstractProtein degradation has been measured in confluent monolayers of eleven lines of contact‐inhibited cells and ten transformed lines as the rate of release of trichloroacetic acid‐soluble radioactivity after prelabeling cell protein with [3H]leucine. Insulin, at concentrations from 10−12 M to 10−6 M, has been added at the beginning of the 4‐hour degradation period to detect selective effects of this hormone as an inhibitor of the inducible proteolysis occurring in serumfree medium. In addition insulin binding measurements have been performed on selected cell lines in an attempt to relate receptor properties to insulin action. Substantial effects of insulin are found in most cells with a selective inhibition at low insulin concentrations noted in several of the transformed lines. The difference in insulin sensitivity is not entirely definitive because temperature‐sensitive transformation mutants of NRK cells are not more sensitive to insulin at a temperature where they show the transformed phenotype. Although insulin receptors on different cell lines have similar binding properties, two of the hepatomas used, H35 and MH1C1, show inhibition of protein degradation at insulin concentrations where receptor occupancy is extremely low. Calvarial osteoblast‐like cells have a high rate of protein degradation which can be reduced by growth factors but not by insulin. The lack of an insulin response is a consequence of poor insulin binding to the cells. Insulin binds to the osteogenic sarcoma cells in substantial amounts. However, its normal action to inhibit the induced proteolysis is restricted because with these cells no increase of proteolysis occurs in serum‐free medium. Generally higher rates of protein degradation are observed in the contact‐inhibited lines than the transformed cells. We suggest that this difference may provide a selective growth advantage to transformed cells.
Electrolyte and non‐electrolyte distribution in the ehrlich ascites tumor cells during the cell cycle
Authors: Dupre A. M. , Hempling H. G. 
Published: February 2005

AbstractIn a previous study, evidence was presented for changes in the state of water and osmotically active solutes during the cell cycle. Total water was constant at 82% (w/w), while the fraction of water that was osmotically active decreased from a maximum during S to a minimum at mitosis. Total Na+, K+, and C1− in milliequivalents per liter of cell water remained constant. Therefore, electrolytes are sequestered in the osmotically inactive water. Evidence is now presented that Na+ exists primarily as one compartment, with a second, slower compartment appearing during S and disappearing during G2. Na+ is completely exchangeable during the entire cell cycle.The distribution of other penetrating solutes was also investigated. When placed in hyperosmotic ethylene glycol solutions, cells first shrink, then swell to their original volumes. 14C‐ethylene glycol distributes in 89% of cell water throughout the cell cycle. However, 14C‐urea distributes in anywhere from 86–100% of the cell water, depending on the stage in the cell cycle. Both solutes are at chemical equilibrium in water in which they are distributed, but they differ in their effects on cell volume. The final volume at which cells equilibrate in urea varies with the concentration of urea in the environment and with time into the cell cycle. Results suggest a loss of osmotically active particles or decreased osmotic activity of urea.
Studies on the control of plasminogen activator production by cultured human embryonic lung cells: Requirements for inhibition by corticosteroids
Authors: Rifkin Daniel B. , Crowe Ruth M. 
Published: February 2005

AbstractThe ability of actinomycin D to interfere with the dexametha‐sone‐mediated inhibition of plasminogen activator (PA) production by human‐embryonic lung (HuEL) cells has been examined. The enzyme produced by HuEL cells in the presence of both dexamethasone and actinomycin D appears to be the product of de novo protein synthesis, as determined by the dependence of PA production on active protein synthesis and the net increase in total PA during the course of an experiment. Inhibition of RNA synthesis must be continuous to maintain PA production in the presence of dexamethasone, since reinitiation of RNA synthesis causes an immediate loss of PA activity in the cells. Cordycepin and α‐amanitin also prevent dexamethasone‐mediated inhibition of PA in HuEL cells, indicating that the RNA whose synthesis must be prevented is of the mRNA class. These experiments imply that PA production in HuEL cells may be under translational as well as transciptional control.
Inhibition of calcium and glucose uptake by murine leukemia L5178Y cells treated with antiserum
Authors: Woodcock‐Mitchell Janet , Yang Tsu‐Ju (Thomas) 
Published: February 2005

AbstractStudies were performed to determine whether decreases in transport of calcium and glucose might be among the earliest changes triggered by the antigen‐antibody reactions occurring on the cell surface of murine leukemia L5178Y cells after treatment with rabbit antisera. After treatment with antisera, in the absence of complement, these cells exhibited a decreased uptake of 45Ca, 2‐deoxy[3H]glucose, and 3‐0‐methyl[3H]glucose. These changes occurred rapidly, within 2 minutes after the addition of antiserum, in contrast to the previously reported inhibitory effects of antiserum on DNA, RNA, and protein synthesis, which became demonstrable only after 4 to 8 hours. The kinetics of uptake of the radioactive substrates was biphasic, with a very rapid initial uptake followed by less rapid linear uptake. The precise mechanism of cell growth inhibition remains to be elucidated, but one of the initial effects of antiserum treatment may be a perturbation at the cell membrane such that transport of specific nutrients is decreased, resulting in the observed effects on macromolecular synthesis.
Effect of ouabain on growth regulation by serum components in Balb/C‐3T3 cells: Inhibition of entry into s phase by decreased protein synthesis
Authors: Frantz Christopher N. , Stiles Charles D. , Pledger W. J. , Scher Charles D. 
Published: February 2005

AbstractThe effect of inhibition of the cell membrane Na+‐K+ pump on the Balb/c‐3T3 cell growth cycle was studied. Inhibition of the Na+‐K+ pump resulted in a dose‐dependent reduction of intracellular K+ concentration ({K+}i). However, inhibition of protein synthesis in G0/G1 and of subsequent entry into S phase occurred only after {K+}i fell below a critical threshold (50–60 mmoles/liter). Thus, when the {K+}i falls below a critical threshold, protein synthesis is inhibited, preventing cells from entering the S phase.The platelet‐derived growth factor (PDGF) induces cells to become “competent” to traverse the cell cycle; the platelet‐poor plasma component of serum allows competent cells to progress through G0/G1 and enter S phase. Inhibition of the Na+‐K+ pump did not prevent the induction of competence by PDGF, but it did reversibly inhibit plasma‐mediated events in early G0/G1. Similarly, cycloheximide inhibited plasma‐mediated events but did not prevent PDGF‐induced competence. Thus, protein synthesis may not be required for induction of competence; alternatively, the induction of the competent state may occur in these cells after removal of PDGF and protein synthesis inhibitor. Protein synthesis is required for subsequent plasma‐mediated events in G0/G1.
Cyclic AMP surges during the dihydrotestosterone‐induced growth‐division cycle of rat seminal vesicle cells
Authors: Tsang B. K. , Whitfield J. F. , Rixon R. H. 
Published: February 2005

AbstractA single subcutaneous injection of the active androgen DHT (5α‐androstan‐17β‐01‐3‐one or 5α‐dihydrotestosterone; 5 mg/Kg body weight) into rats 7 days after orchidectomy stimulated DNA synthesis in the seminal vesicle, which began between 30 and 35 hr after injection and peaked at 48 hr. Mitotic activity began between 35 and 45 hr after DHT injection and peaked around 55 hr. These proliferative responses appeared to be confined mainly to the epithelial cells of the seminal vesicles. The DHT injection did not rapidly (between 5 min and 2 hr) increase the cyclic AMP level, but it did result in two small later surges of the cyclic nucleotide; the first of which peaked between 18 and 28 hr, but well before the onset of DNA synthesis, and the second of which peaked between 48 and 60 hr, when both the DNA‐synthetic and mitotic activities were near or at their peak values.
Defective RNA polymerase II in the G1 specific temperature sensitive hamster cell mutant TsAF8
Authors: Shales Michael , Bergsagel John , Ingles C. James 
Published: February 2005

AbstractTsAF8 is a temperature‐sensitive (TS) mutant of BHK21 cells that arrests at nonpermissive temperatures in the mid‐G1 phase of the cell cycle. TsAmaR‐1 is a TS for growth mutant of CHO cells with a Ts‐ and α‐amanitin‐resistant (AmaR) RNA polymerase II activity. Hybrid TsAmaR‐1 x TsAF8 cell lines were constructed at permissive temperatures. Such hybrid cells did not grow at nonpermissive temperatures; the two TS mutations did not complement. Two different AmaR derivatives of TsAF8 were isolated. Each contained only AmaR polymerase II activity, indicating that this RNA polymerase II gene locus in TsAF8 is functionally hemizygous, as would be expected for a locus in which the recessive TsAF8 mutation had occurred. One of these AmaR isolates of TsAF8 had a partially reverted TS+ phenotype. Taken together these results suggest that the TS mutation in TsAF8 is in RNA polymerase II.
In vitro development of CFU‐E and BFU‐E in cultures of embryonic and post‐embryonic chicken hematopoietic cells
Authors: Samarut J. , Bouabdelli M. 
Published: February 2005

AbstractA culture method is proposed for the in vitro development of chicken erythrocytic progenitors. When grown with avian erythropoietin, Colony Forming Unit Erythrocytic (CFU‐E) and Burst Forming Unit‐Erythrocytic (BFU‐E) give rise respectively to erythrocytic colonies and bursts within 3 and 6 days. BFU‐E development is greatly enhanced by pokeweed‐mitogen‐spleen‐cell‐conditioned medium and requires higher erythropoietin concentrations than for CFU‐E. An antigen specific to immature red cells can be detected on CFU‐E but not on BFU‐E, showing that both progenitors represent distinct entities. BFU‐E and CFU‐E are found in embryonic marrow and yolk sac. In the young blastoderm BFU‐E becomes detectable at the primitive streak stage.
Biophysical properties of human astrocytic brain tumor cells in cell culture
Authors: Black Peter McL. , Kornblith Paul L. 
Published: February 2005

AbstractFor malignant cells cultured from a human astrocytoma, electrophysiological characteristics of the plasma membrane included specific resistivity of 446.82 ± 279.5 ohm·cm2, specific capacitance of 0.758 ± 0.52 microfarads/cm2, time constant 0.318± 0.10 msec. The resting membrane potential averaged‐14.07 ± 7.4 mV; the mean input resistance 8.1 ± 4.0 megohms. The average cell area was 1638 ± 585 ±2 for contactual and 1919 ± 989 ±2 for noncontactual cells. Changes in input resistance and resting membrane potential were observed with increasing time in culture, possibly reflecting cell cycling. There did not appear to be electrical coupling in this cell line.