bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative studies of glucose‐fed and glucose‐starved hamster cell cultures: Responses in galactose metabolism
Authors: Christopher C. William , Colby Wendy W. , Ullrey Donna , Kalckar Herman M. 
Published: February 2005

AbstractThe metabolic flow of trace amounts of D‐[14C]‐galactose was followed in cultures of transformed and untransformed hamster cells over a period ranging from five minutes to two hours. The results of chromatographic and enzymatic analyses of the soluble pools are described. Non‐glycolytic cells (previously deprived of sugar for periods of up to 24 hours) convert D‐galactose to galactose‐1‐phosphate and uridine diphosphoglucuronic acid in 10 to 20 minutes. In the same short assay time, glycolytic cells which have been maintained for 24 hours in media containing glucose or galactose convert D‐galactose to uridine diphosphogalactose and uridine diphosphoglucose (ratio 1.4:1). Longterm deprivation of sugar also results in 3‐ to 4‐fold increases in the uptake of galactose. In addition, the incorporation of galactose label into chloroform‐methanol soluble material appears to be influenced by the culture conditions of the untransformed cells while incorporation in the transformed cells appears unaffected. When cycloheximide is included in the maintenance medium for extended periods, the non‐glycolytic cells also show increases in galactose uptake rates but the glucose‐fed, glycolytic cells lose uptake ability. UDPhexose is the main galactose metabolic peak in the soluble pools of the cycloheximide‐treated, glycolytic and the cycloheximide‐treated, non‐glycolytic cells. The results of these experiments suggest that uptake of galactose and its subsequent metabolism are under separate control.
Characterization of the cell cycle of cultured human diploid cells: Effects of aging and hydrocortisone
Authors: Grove Gary L. , Cristofalo Vincent J. 
Published: February 2005

AbstractAge‐related changes in the cytokinetics of human diploid cells in vitro have been compared in normal cultures and in cultures in which lifespan has been prolonged by the addition of hydrocortisone to the medium. For both cultures, with advancing age the fraction of cells in the actively proliferating pool decreased and the intercellular variation in cell cycle times increased. The average cell cycle time was prolonged during aging due almost entirely to changes in the duration of G1. The duration of S remained constant, while a small delay in G2 was observed in late passage cells near the end of their lifespan. Although the same pattern of change in proliferative parameters occurred in both control and hydrocortisone‐treated cultures, the changes were somewhat delayed in the presence of the steroid. The results are interpreted in terms of several cell cycle models and suggest that the events controlling cell proliferation are sensitive to hydrocortisone modulation during the G1 and possibly the G2 periods.
Surface membrane differentiation of hemopoietic cells as observed by radioactive labeling
Authors: Fehlmann M. , Lafleur L. , Marceau N. 
Published: February 2005

AbstractBone marrow cells from normal rats were separated by velocity sedimentation into three distinct populations corresponding to granulocytes, lymphocytes and reticulocytes. Cells from each population were surface labelled via the lactoperoxidase radioiodination or the tritiated borohydride reduction. Distinct labeling patterns were observed on SDS‐PAGE for each cell population. Separation of bone marrow cells from anemic rats injected with TAB vaccine led to four populations corresponding to successive stages of erythroid cell maturation. Labelled protein patterns were not in this case as different from one population to the other, except for one species which increased in intensity with the degree of maturation. The tritiated glycoprotein profiles show a shift from high to low molecular weight species during the process of maturation.
Coordinate regulation of protein synthesis and messenger RNA content during growth arrest of suspension Chinese hamster ovary cells
Authors: Levis Robert , McReynolds Larry , Penman Sheldon 
Published: February 2005

AbstractWe have found Chinese Hamster Ovary cells, cultured in suspension, are subject to growth control by serum. When suspended in medium containing 0.5% serum the cells become reversibly arrested in the beginning of the G1 phase of the cell cycle and can be maintained in this viable, nonproliferating state for several days.This system was used to examine the regulation of protein synthesis with growth rate. In particular, the experiments addressed the question whether mRNA content is the principal controlling factor determining the rate of protein synthesis. The rate of leucine incorporation in resting cells in low serum is 2‐ to 2.5‐fold lower than that of cells growing in 10% serum. The steady‐state number of cytoplasmic poly A (+) RNA molecules shows a proportional decrease, consistent with it being a determining factor controlling the rate of protein synthesis. Furthermore, the rate of production of poly A (+) and poly A (−) RNA appears to be regulated coordinately.Regulation of the rate of initiation of translation would result in fewer ribosomes bound per active message and/or a lower proportion of total mRNA's being active. Our measurements indicate that the fraction of cytoplasmic poly A (+) mRNA in polyribosomes and the relative degree of loading of each active poly A(+) mRNA with ribosomes is the same in resting and growing cells. Thus these cells resemble 3T6 and translational control does not appear to be an important part of the change in protein synthetic rate with the state of growth.
Chloride‐Stimulated sulfate efflux in Ehrlich ascites tumor cells: Evidence for 1:1 coupling
Authors: Villereal Mitchel L. , Levinson Charles 
Published: February 2005

AbstractThe kinetics of Cl−‐SO4−2 exchange in Ehrlich ascites tumor cells was investigated in an attempt to determine the stoichiometry of this process.When tumor cells, equilibrated in Cl−‐free, 25 mM SO4−2 medium are placed in SO4−2‐free, 25 mM Cl− medium, both the net amount and rate of Cl− uptake far exceeds SO4−2 loss. Addition of the anion transport inhibitor SITS (4‐acetamido‐4′‐isothiocyano‐stilbene‐2,2′‐disulfonic acid) greatly reduces sulfate efflux (97%), but has no measurable effect on chloride uptake. Addition of furosemide, a Cl− transport inhibitor, reduces chloride uptake 94% but is without effect on sulfate efflux. These findings suggest that a chloride permeability pathway exists distinct from that utilized by SO4−2.SITS, when added to furosemide treated cells, further reduces chloride uptake as well as inhibiting sulfate efflux, and under these experimental conditions, a linear relationship exists between SITS‐sensitive, net chloride uptake and sulfate loss. The slope of this line is 1.05 (correlation coefficient = 0.996) which suggests the stoichiometry of Cl−‐SO4−2 exchange is 1:1. Assuming a 1:1 stoichiometry, measurement of the initial chloride influx and initial sulfate efflux indicate that 92% of net chloride uptake is independent of sulfate efflux.Taken altogether, these results support the contention that the tumor cell possesses a permeability pathway which facilitates the exchange of one sulfate for one chloride. Under conditions where anion transport is not inhibited, this coupling is obscured by a second and quantitatively more important pathway for chloride uptake. This pathway is SITS‐insensitive, although partially inhibited by furosemide.
Variations in prolactin and growth hormone production during cellular growth in clonal strains of rat pituitary cells
Authors: Haug Egil , Tjernshaugen Hans , Gautvik Kaare M. 
Published: February 2005

AbstractA permanent, clonal strain of rat pituitary tumor cells (GH3‐cells) spontaneously synthesizes and secretes prolactin (rPRL) and growth hormone (rGH) into the culture medium. The rates of hormone production (μg extracellular hormone/mg cell protein/24 hours) and synthesis (vida infra) as well as the rate of [3H]thymidine incorporation into DNA (DNA synthesis) have been studied.During logarithmic growth rPRL and rGH production increased to 160 and 250% of the value at day 2 after plating, while during the plateau phase of cell growth hormone production decreased to initial values. The fluctuations in rPRL production could be fully explained by variations in the rate of rPRL synthesis: [3H]leucine incorporated into rPRL as measured with immunoprecipitation and polyacryl‐amide gel electrophoresis. Also the rates of synthesis and production of rGH showed parallel changes during exponential and plateau phase of growth, but this hormone was probably degraded intracellularly. The relative reduction in the rate of synthesis of rPRL and rGH during the plateau phase of growth corresponded closely to the fall in the rate of DNA synthesis. The reduction in rPRL synthesis could not be explained through an inhibition by extra‐cellular rPRL accumulation or by cell to cell interaction occurring in dense cultures.The intracellular concentrations of both hormones were unaltered during logarithmic growth, but rose to 500% for rPRL and 200% for rGH during the plateau phase.In spite of the marked variations in basal rPRL and rGH production, the GH3 cultures of different ages were equally able to increase rPRL and decrease rGH production in response to thyrotropin releasing hormone (3 X 10−7 M) and 17β‐estradiol (10−8 M).
The effect of medium pH on rate of growth, neurite formation and acetylcholinesterase activity in mouse neuroblastoma cells in culture
Authors: Bear Mark P. , Schneider F. Howard 
Published: February 2005

AbstractCell division, neurite formation and acetylcholinesterase activity were examined in a clone (NBA2) of mouse neuroblastoma cells maintained for up to 120 hours in medium with pH values between 6.6 and 8.0. Growth rate decreased as pH was reduced from 7.8 to 6.6. Generation time at pH 7.4 was 25 hours, while the rate of cell division was negligible at pH 6.6. The total number of cells at stationary phase was less at the lower pH values. Neurite formation was enhanced markedly as the pH was reduced from 7.4 to 6.6. Acetylcholinesterase activity was 5‐ to 8‐fold greater in cells exposed to medium at pH 6.6 than in cells maintained in medium at pH 7.4. The reduction in the rate of cell division and increases in neurite formation and acetylcholinesterase activity at pH 6.6 were reversible upon exposure of the cells to pH 7.4 medium. Cell viability was greater than 90% at all medium pH values over a period of 120 hours. Uncloned T‐59 mouse neuroblastoma cells were affected similarly by changes in pH. These results show that manipulation of the environmental pH can reversibly alter growth, neurite formation, and acetylcholinesterase activity of mouse neuroblastoma cells in culture.
Erythroid colony formation in cultures of human marrow: Effect of leukocyte conditioned medium
Authors: Aye M. T. 
Published: February 2005

AbstractA method, based on the differing capacities of cells to adhere to a column of polyester fibres, has been described for separating human bone marrow cells into a nonadherent and an adherent fraction. The effect of this cell separation procedure on colony formation by erythroid progenitor cells was investigated. In contrast to the unseparated population, it was found that erythropoietin‐dependent erythroid colony formation by nonadherent cells could be considerably enhanced by the addition of leukocyte conditioned medium to the cultures. Similar erythroid enhancing activity was also detected in a partially purified preparation of granulocytic colony stimulating activity obtained from human embryo kidney culture supernatants.Erythroid colony formation in the absence of added erythropoietin, by non‐adherent bone marrow cells from patients with polycythemia rubra vera, were also enhanced by the addition of LCM to the cultures. This finding suggests that the enhancing factor in LCM may not be dependent on the presence of erythropoietin in the cultures for its activity.While the cellular mechanisms by which leukocyte conditioned medium enhances eyrthroid growth remain to be determined, the data presented provides strong evidence for the view that the plating efficiency of erythroid progenitor cells is determined not only be the concentration of erythropoietin, but also by the presence of leukocyte conditioned medium in the cultures.
Hormonal control of hyaluronic acid production in fibroblasts and its relation to nucleic acid and protein synthesis
Authors: Moscatelli David , Rubin Harry 
Published: February 2005

AbstractWhole serum and elevated pH previously had been found to stimulate both cell multiplication and hyaluronic acid production by chick embryo fibroblasts in culture. In a study to determine whether cell multiplication and hyaluronic acid production both respond to a single well‐defined substance, insulin was found to stimulate, and cortisol to inhibit both processes coordinately. It appears, therefore, that multiplication and differentiated function in fibroblasts respond to a common underlying regulatory signal.Inhibition of ribosomal RNA synthesis by actinomycin D does not prevent serum stimulation of hyaluronic acid production, but inhibition of total RNA synthesis does. If total RNA synthesis is inhibited only after the hyaluronic acid production has reached a new high level, it continues at that level for the next five hours. The stimulatory treatment causes an increase in the activity of the enzyme hyaluronate synthetase. Inhibition of protein synthesis prevents any increase in hyaluronic acid production, and reduces the basal level of production.Reduction of the availability of Mg2+ in the medium coordinately inhibits DNA synthesis and hyaluronic acid production. The results are discussed in the light of a model for coordinate control of growth and metabolism based on the availability of Mg2+.
The effect of 2‐deoxyglucose on guinea pig polymorphonuclear leukocyte phagocytosis
Authors: Boxer Laurence A. , Baehner Robert L. , Davis Jacqueline 
Published: February 2005

AbstractThe effects of 2‐deoxyglucose (DOG), an inhibitor of glycolysis, on guinea pig polymorphonuclear leukocytes (PMN) obtained from peritoneal exudates was examined. ATP levels in PMN were reduced by 40% by one hour following an incubation with 2‐deoxyglucose. When complement (C3) coated 14C‐staphylococcus aureus, C3 coated lipopolysaccharide‐paraffin oil droplets (LPSPO), 14C‐pneumococcus opsonized with IgG, or albumin coated paraffin oil droplets opsonized with IgG were added to cell suspensions containing DOG, the phagocytizing rate was 1,310 ± 55 cpm/5 x 106 cells/15 minutes, 6 ± 2 μg paraffin oil (PO)/107 cells/minute, 2,250 ± 175 cpm/1 x 106 cells/20 minutes or 0.037 ± 0.01 mg PO/107 cells/minute compared to control values of 5,970 ± 275 cpm/5 x 106 cells/15 minutes, 35 ± μg PO/107 cells/15 minutes, 4,510 ± 200 cpm/1 x 106 cells/20 minutes and 0.067 ± 0.01 mg PO/107 cells/minute. In parallel studies the phagocytic index for latex was 0.74 ± 0.28 in DOG compared to control of 2.36 ± 1.13 and the phagocytic rate of albumin coated paraffin oil droplets was 0.029 ± 0.01 mg PO/107 PMN/minute in DOG compared to control of 0.048 mg PO/107 cells/minute. When ATP levels were maintained by the simultaneous addition of 5 mM glucose or pyruvate to media containing DOG, latex ingestion was improved to 1.15 ± 0.3 with glucose and 1.59 ± 0.64 with pyruvate and albumin coated particles to 0.045 ± 0.01 mg PO/107 PMN/minute with pyruvate. There was no improvement in the uptake of either the C3 dependent particles or IgG coated Pneumococci in media containing DOG and glucose and/or pyruvate. Following the removal of DOG from the extracellular medium and the addition of pyruvate or glucose, phagocytosis of C3 dependent LPS‐PO was restored to normal values. Neither the binding of C3 or IgG coated particles to the PMN nor the lateral movement of glycoprotein utilizing concanavalin A capping was affected by DOG. Thus, the presence of DOG in the PMN containing adequate amounts of ATP will selectively and reversibly inhibit those surface events required for phagocytosis of C3 and IgG bound particles but not latex particles or albumin particles which non‐specifically bind to PMN.
Characterization of a depolarizing dopamine response in a vertebrate neuronal somatic cell hybrid
Authors: Myers Paul R. , Livengood David R. , Shain William 
Published: February 2005

AbstractThe physiology and pharmacology of a depolarizing dopamine response was studied in the vertebrate neuronal somatic cell hybrid TCX11. The average resting membrane potential was −50 mV (S.D. = ±7) with a membrane resistance of 40.5 mOhms (S.D. = ±8) as determined from intracellular recordings. Depolarizing current pulses did not elicit an action potential. Cells displayed a linear current‐voltage relationship when artificially depolarized up to +30 mV. Iontophoretically applied dopamine elicited a depolarizing response with a conductance increase and a reversal potential of −15 mV (S.D. = ±4.7). Experiments altering medium ion concentrations demonstrated the conductance increase was to sodium and most likely potassium. The dopamine agonist ET495 (Piribedil) and the analogue epinine mimicked dopamine, while closely related biogenic amines, with the exception of noradrenaline, elicited no response. Apomorphine also elicited a depolarizing response but was much less efficacious than Piribedil. Noradrenaline was less potent than dopamine and appeared to act at the dopamine receptor. Methylation (3‐methoxytyramine) or absence of the 3‐hydroxy group (tyramine) of dopamine resulted in total loss of activity. The dopamine antagonists chlorpromazine, trifluoperazine, promazine, and bulbocapnine reversibly blocked the response to dopamine at medium concentrations less than 5 μM. The adrenergic antagonist phentolamine blocked the response while phenoxybenzamine only reduced the response at higher concentrations. The acetylcholine antagonists α‐bungarotoxin, hexamethonium, and scopolamine did not block the dopamine response. Both d‐tubocurarine and atropine acted as antagonists.Collectively, these results demonstrate the presence of a receptor on a cultured cell line that is specific for dopamine, mediates a depolarizing and conductance increase response to dopamine, and displays the pharmacology most closely associated with dopamine receptors.
In vitro activation of the in vivo colony‐forming units of the mouse yolk sac
Authors: Perah Gershon , Feldman Michael 
Published: February 2005

AbstractExperiments were performed to investigate the presence of colony‐forming units (CFU) in the mouse embryonic yolk sac during the developmental period in which the yolk sac is the sole hemopoietic organ. Injection of yolk sac cell suspensions from normal embryos into syngeneic, lethally irradiated adult recipients evoked a very low number of spleen colonies. However, prior cultivation of yolk sacs in vitro caused a dramatic increase in the spleen colony‐forming capacity–as high as 84‐fold–following 48 hours in culture. The yolk sac origin of the spleen colonies was confirmed by: (a) Chromosomal marker analysis; (b) dose‐response analysis; (c) demonstrating that the above colonies were not of endogenous origin induced by the mere injection of grafted cells. We conclude that the yolk sac contains many precursors of colony‐forming cells which though undetectable by immediate grafting apparently become activated in culture by an as yet unknown induction process.
The dissociation of the surface architecture described by enhanced lectin agglutinability and the transformed phenotype expressed as anchorage independence
Authors: Noonan Kenneth D. , Bouck Noël , di Mayorca Giampiero 
Published: February 2005

AbstractUsing a series of cold‐sensitive variants of chemically transformed BHK‐21 cells, revertants to the normal phenotype derived from a dimethylnitrosamine transformed clone of BHK‐21 as well as revertants to the normal phenotype derived from polyoma transformed BHK‐21 cells we have demonstrated that the surface phenotype described by enhanced agglutinability with Con A and WGA can be dissociated from the transformed phenotype described by anchorage independence (growth in semisolid medium). Specifically we have demonstrated that the surface characteristic of enhanced agglutinability may be found in a variety of cell lines which fail to display an ability to grow in agar. Our work clearly shows that the two phenotypes described are not concomitantly controlled and tends to suggest that the phenotype of enhanced lectin agglutinability may be dissociated from the transformed phenotype.
Penetration of mouse fibroblasts by 2′‐deoxyadenosine 5′‐phosphate and incorporation of the nucleotide into DNA
Authors: Plunkett William , Cohen Seymour S. 
Published: February 2005

AbstractThe metabolism of 2′‐deoxyadenosine 5′‐phosphate (dAMP) by exponentially growing mouse fibroblasts (L‐cells) in suspension culture has been studied. Cells incubated for four hours with 0.10 μmole [3H, 32P]dAMP/ml in medium containing 9.6 μmole 31Pi/ml incorporate both activities at nearly linear rates into acid‐soluble and acid‐insoluble fractions. The 3H/32P value increased about 30‐fold in each fraction during the incubation, indicating extensive dephosphorylation of dAMP. The DNA from treated cells was degraded enzymatically to 5′‐mono‐nucleotides, which were fractionated by ion‐exchange chromatography. 3H was associated exclusively with dAMP (53%) and dGMP (47%). 32P, associated with all deoxynucleotides, was at a 20‐fold higher specific activity in dAMP than in either dGMP or dCMP. The specific activity of [32P]dAMP incorporated into DNA in four hours was 24‐fold greater than that of 32Pi in the cellular pool. In experiments in which cells were incubated with 32Pi plus or minus 0.10 μmole dAMP/ml, the specific activity of dAMP was slightly less than that of dGMP or dCMP, which were equal. These results suggest that the higher specific activity of [32P]dAMP in the DNA of cells after incubation with doubly‐labeled dAMP was due to the intact penetration of some dAMP into the cells with its subsequent incorporation into DNA. Calculations, based on the amount of exogenously added [3H]thymidine incorporated into the cellular DNA in parallel cultures and the 32P of dAMP isolated from this DNA, suggest that 1% of the total dAMP residues incorporated during the 4‐hour incubation were derived directly from intact, exogenously added dAMP.
Cation specificity of propranolol‐induced changes in RBC membrane permeability: Comparative effects in human, dog and cat erythrocytes
Authors: Müller‐Soyano Aixa , Glader Bertil E. 
Published: February 2005

AbstractPropranolol, in the presence of calcium, causes marked K efflux from human red blood cells (high K, low Na). The studies reported here indicate this effect of propranolol is specific for K and does not represent a nonspecific permeability increase for intracellular cations to leave the cell. Amphotericin‐treated human RBC's (high Na, low K) and dog RBC's (high Na, low K) both gain K and increase in size when incubated in a K‐medium containing propranolol and calcium. No effect was noted when cat RBC's (high Na, low K) were similarly treated. Propranolol, independent of added calcium, also inhibited the normally increased Na efflux observed when dog RBC's are suspended in K‐medium. These species differences in response to propranolol thus may serve as a focus for elucidating the mechanism by which this drug alters normal membrane physiology. The unique drug effect on Na permeability of canine erythrocytes also may be a useful probe for the study of dog RBC volume regulation.