bluuebunny/crossref_metadata_2025_split huggingface dataset:
Glucose‐6‐Phosphate dehydrogenase activity in a hepatoma cell line: Preliminary evidence for negative genetic control
Authors: De Luca C. , Matheisz J. S. 
Published: February 2005

AbstractA line of cells, positive for glucose‐6‐phosphate dehydrogenase activity, has been separated from a negative parental stock derived from the H4‐II‐E‐C3 rat hepatoma line. Cytogenetic analyses showed specific marker chromosomes of the parent line were present in the variant. On the other hand, cells of the variant line contained three chromosomes less, on the average, than the total present in parent cells. Karyotypic analyses indicated the diminution in chromosome numbers to be in the subacrocentric group. The appearance of glucose‐6‐phosphate dehydrogenase associated with loss of chromosomes suggests this enzyme is suppressed or under negative control in the parental stock. The consistent loss of chromosomes of the subacrocentric group suggests that the locus bearing regulatory activity is in this specific group.
Regulation of translation in rabbit reticulocytes and mouse L‐cells; comparison of the effects of temperature
Authors: Craig Nessly 
Published: February 2005

AbstractVarious parameters of protein synthesis were analyzed in rabbit reticulocytes exposed to various temperatures for up to five hours. Between 10°C and 40°C total protein synthesis exhibited two different apparent activation energies (36 kcal/mole, 10–24°C; 22 kcal/mole, 24–40°C), as did protein elongation and release (35 kcal/mole, 10–25°C; 12 kcal/mole, 25–40°C). However, the level of polysomes remained essentially unchanged between 0°C and 42°C which implies that the activation energy for polypeptide initiation is quite similar to that for elongation and is also biphasic. This situation is different from that in cultured mouse L‐cells where the polysome level is dependent on temperatures. Nevertheless, reticulocytes and L‐cells appear to be similar in their temperature dependence of initiation and in their rate of elongation (5–6 amino acids/second at 36°C).
Arrest of 3T3 cells in G1 phase in suspension culture
Authors: Otsuka Haruki , Moskowitz Merwin 
Published: February 2005

Abstract3T3 cells do not grow in Methocel suspension culture, while other permanent cell lines do. The viability of 3T3 cells in suspension remains unchanged for at least three days with respect to plating efficiency, vital staining and resumption of normal growth when transferred into monolayer culture. When monolayer 3T3 cells in G1 phase are suspended they remain in G1 phase. Cells already in S phase which are suspended complete ongoing DNA synthesis and mitosis and then are arrested in the G1 phase. Progress through the cell cycle is reinitiated after suspended cells attach to a surface. When monolayer cells in late G1 phase (just before entering S phase) are put in suspension cultures they do not initiate DNA synthesis.
Growth of cultured cells from patients with Fanconi anemia
Authors: Elmore Eugene , Swift Michael 
Published: February 2005

AbstractFibroblast cultures derived from skin biopsies of patients with Fanconi anemia had doubling times (mean of five lines: 30.3 ± 0.2 hours) significantly longer than randomly selected normal controls (mean of nine lines: 22.9 ± 0.4 hours). Control cultures grew more slowly in the enriched media RPMI 1640 and McCoy's 5A than in MEM, while a culture from a patient with Fanconi anemia grew more slowly only in McCoy's 5A. Differences in growth characteristics between Fanconi anemia and normal cell cultures may be useful in analyzing the metabolic error determined by the Fanconi anemia gene.
The effect of pH on incorporation of galactose by a normal human cell line and cell lines from patients with defective galactose metabolism
Authors: Hill Helene Z. 
Published: February 2005

AbstractIncorporation of radioactive galactose into TCA‐insoluble material of galactosemic fibroblasts is more sensitive to low pH than is the incorporation by normal human fibroblasts. This study was undertaken to determine (1) whether there was any pH which could correct or counteract the galactosemic defect relative to galactose incorporation, and (2) whether the low pH effect was specific for galactose metabolism or whether general cellular metabolism in galactosemic cells was more sensitive to low pH than that in normal cells.The pH dependencies of incorporation of radioactive galactose and glucose into cellular macromolecules were investigated in galactosemic and normal cells. Normal cells have a biphasic curve with respect to galactose incorporation with peaks at pH 7.0 and 8.5. Galactosemic cells have only the high pH peak. The maximum incorporation by galactosemic cells was never more than about 30% that seen by normal cells under the conditions of these experiments. Thus manipulation of the pH alone cannot correct the galactosemic defect.The rate of incorporation of radioactive galactose was studied in normal, galactosemic and galactokinase deficient cells, at pH 7.2 and at pH 6.3. At pH 7.2, galactosemic cells incorporate galactose at a linear rate which is 30 to 40% that of normal cells while incorporation by kinase‐deficient cells is between 5 and 10% of normal. At pH 6.3, the incorporation is also linear. However, galactosemic cells now exhibit the same rate as kinase‐deficient cells in which the low level of incorporation is unaffected by pH.These results suggest that incorporation of galactose by galactosemic cells at low pH is not due to metabolic death of the cells, but may be due to the inhibition of some specific step or steps along a metabolic route of galactose metabolism other than the Leloir pathway.
Human lymphocyte potassium content during the initiation of phytohemagglutinin‐induced mitogenesis
Authors: Segel George B. , Lichtman Marshall A. , Hollander Marsha M. , Gordon Bruce R. , Klemperer Martin R. 
Published: February 2005

AbstractThe K+ content of human lymphocytes has been examined during the initial 24 hours after exposure of cells to phytohemagglutinin (PHA). We have reconfirmed that lymphocyte K+ exchanges rapidly for extracellular counterions during preparative washing if cells are exposed to PHA. By using a technique to measure cation content which does not require removal of cells from their culture medium, we have shown that K+ does not change for 24 hours following PHA treatment. Previous reports have demonstrated that an enhanced uptake of K+ occurs in lymphocytes treated with PHA. This increased uptake may be a compensatory change for an increased exodus, explaining the failure of K+ to change following lectin treatment.
Induction by short‐chain fatty acids of alkaline phosphatase activity in cultured mammalian cells
Authors: Koyama Hideki , Ono Tetsuo 
Published: February 2005

AbstractShort‐chain fatty acids, such as propionic, n‐butyric, n‐valeric, isovaleric, n‐caproic, and n‐caprylic acids, induce alkaline phosphatase activity in cultured mammalian cells. Long‐chain fatty acids have no similar effects. With B‐6 cells (mouse × Chinese hamster cell hybrids), n‐butyrate at 2 to 5 mM exhibits the greatest activity. Induction begins exponentially about 24 hours after addition of the fatty acid and continues over 48 hours. Studies on the inducing activity‐structure relationship revealed the necessity of a carboxyl and an ethyl or longer alkyl group.n‐Butyrate shows a marked synergistic action of induction when added along with other types of inducers: adenosine 3′:5′‐cyclic monophosphate (cAMP) or 5‐bromodeoxyuridine (BrdU). Treatment of other cell lines with either n‐butyrate, cAMP, or BrdU revealed a cell‐type specific response pattern of alkaline phosphatase. The biological significance of this effect of short‐chain fatty acids is discussed.This study was presented in part at the 45th Annual Meeting of the Japanese Biochemical Society, Tokyo, October, 1972. After submission of this manuscript, the authors noticed a similar study on alkaline phosphatase induction by n‐butyrate, reported by M. J. Griffin et al. ('74) in Arch. Biochem. Biophys., 164: 619–623.
SV40 transformation of mouse brain cells: Critical role of gene A in maintenance of the transformed phenotype
Authors: Anderson Jeffrey L. , Martin Robert G. 
Published: February 2005

AbstractBrain cells derived from the NIH Swiss mouse strain have been established in tissue culture. Astrocytic neuroglial cells, identified by morphology and staining properties, predominate. The brain cell culture was successfully transformed with SV40 wild type virus and with a representative early (A239) and late (C219) mutant. When subjected to growth analysis the A239 transformant displayed selective loss of six characteristics of the transformed phenotype at the restrictive temperature (40.5°C): doubling time, saturation density, ability to grow in low serum, efficiency of growth on plastic and on normal brain cell layers, and cloning in soft agar. Temperature shift experiments demonstrated the reversibility of the differences in saturation density. T‐antigen was expressed at both temperatures. Alteration in uptake of 2‐deoxyglucose was not a characteristic of the transformed phenotype. The cell lines may be of utility in brain culture work and in studies on the mechanism of SV40 transformation.
Triiodothyronine effects on some electrogenic properties of frog sartorius
Authors: Grossie J. 
Published: February 2005

AbstractAt 21 °C in vitro, 0.2 and 2.0 m̈M of triiodothyronine (T3) produced an increase in resting membrane potential (RMP) of Rana pipiens sartorius when the pH of the external solution was 7.4. The RMP was increased by 2.0 m̈M T3 in the presence of 10−4 and 10−3 M ouabain but not in 10−3 M of 2, 4 dinitrophenol. Small increases in RMP were observed with 2.0 m̈M T3 in solutions with low external Na. At pH 7.1 0.2 m̈M T3 produced a small transient increase in RMP. Membrane resistance (Rm) was found to decline gradually during exposure to 0.2 m̈M at a pH of 7.4. Treatment with 2.0 m̈M T3 at pH 7.4 was accompanied by a transient reduction in Rm. Similar transient changes in Rm were produced by 0.2 and 2.0 m̈M T3 at pH of 7.1. T3 also reduced membrane resistance in isotonic K2SO4 and tris‐buffered Mn (20 mM) solutions indicating that T3 increases potassium permeability. Direct action potentials were studied at pH 7.1. Overshoot, amplitude and rate of rise of the action potential underwent a gradual decrease in the presence of 0.2 m̈M T3 while thresholds remained unchanged. Thresholds were increased during exposure to 2.0 m̈M T3 whereas overshoot, amplitude and rate of rise underwent transient decreases followed by a return toward control levels.
Purine and phosphoribosylpyrophosphate synthesis in differentiating murine virus‐induced erythroleukemic cells in vitro
Authors: Reem Gabrielle H. , Friend Charlotte 
Published: February 2005

AbstractPhosphoribosylpyrophosphate synthetase activity was determined in Friend virus‐inducted erythroleukemic cells in culture, stimulated to differentiate in the presence of dimethylsulfoxide. The activity of phosphoribosylpyrophosphate synthetase did not decrease in cells which had acquired the specialized function of hemoglobin synthesis, nor was the phosphoribosylpyrophosphate content of untreated erythroleukemic cells significantly different from that of cultures exposed to dimethylsulfoxide for 96 hours.However, the rate of the early steps of de novo purine biosynthesis as measured by the incorporation of [1‐14C] glycine and [1‐14C] formate into formyglycinamide ribonucleotide, was significantly lower in differentiating cell cultures. The addition of glutamine or ammonia increased glycine incorporation of control cultures, but failed to do so in treated cultures. In the course of the normal development of erythrocytes in vivo, phosphoribosylpyrophosphate synthetase activity is preserved, while the capacity to synthesize purines de novo is lost, as is the activity of the phosphoribosyl‐l‐amine synthesizing enzymes. Our present study suggests that the rate of de novo purine biosynthesis in this erythroleukemic cell line is not limited by the availability of phosphoribosylpyrophosphate, but rather by a decrease in the phosphoribosyl‐l‐amine synthesizing enzymes. These findings provide further evidence that during dimethyl‐sulfoxide‐stimulated erythroid maturation, the same regulatory mechanisms are operative as in normal cellular development, and that ammonia‐dependent purine biosynthesis is subject to the same regulatory mechanisms as is glutamine‐dependent biosynthesis.
Wasting of 18 S ribosomal RNA by human myeloma cells cultured in adenosine
Authors: Bynum John W. , Volkin Elliot 
Published: February 2005

AbstractWhen human myeloma cells are pulsed for one hour with 3H‐uridine and chased for six hours in fresh medium containing unlabeled uridine, the processing of 45 S rRNA precursor into the stable 28 S and 18 S rRNA components can be followed. However, when the cells are chased in exogenous adenosine instead of uridine, the accumulation of 18 S rRNA is selectively inhibited. Cells pulsed with 3H‐adenosine and chased in the absence of exogenous nucleosides exhibit normal rRNA precursor processing, while cells pulsed simultaneously with 3H‐uridine and 3H‐adenosine and chased with uridine and adenosine are deficient in labeled 18 S rRNA. Consequently, the inhibition of 18 S rRNA accumulation by adenosine is not an artifact of labeling nor is it relieved by an equal molar concentration of uridine. The wasting of 18 S rRNA in human myeloma cells is similar to that reported to occur in normal lymphocytes during the quiescent state.
Stimulation of ornithine decarboxylase activity in chick fibroblasts by non‐suppressible insulin‐like activity (NSILA), insulin and serum
Authors: Haselbacher Gisela K. , Humbel René E. 
Published: February 2005

AbstractA factor isolated from human serum (nonsuppressible insulin‐like activity, NSILA) stimulates multiplication of serum‐starved chick embryo fibroblasts and stimulates activity of ornithine decarboxylase (ODC). Physiological doses of NSILA (200 m̈ U/ml) and pharmacological doses of insulin (200 m U/ml) stimulate ODC 4–5‐fold, 10% fetal calf serum about 18‐fold. Combined addition of NSILA and insulin does not result in higher activities, suggesting a common mechanism of action. The increase in cell number obtained with NSILA, insulin or serum parallels the degree of ODC stimulation. Treatment of cells with pronase also stimulates ODC activity.A sharp increase in ODC activity occurs between 2.5 and 5.0 hours after addition of the growth factors with a peak at 4.0–4.5 hours (“activation period”). As cells leave G1 phase, ODC activity decreases rapidly. To achieve maximal activity of ODC, the growth factors have to be present during the entire “activation period.” The potential to reactivate ODC decreases as cells pass through S phase.Results obtained using cycloheximide suggest that ODC is translated only in the second half of the “activation period.” Data on effects of dbcAMP and dbcGMP on ODC activation by serum are discussed.
Effect of serum on the growth of balb 3T3 A31 mouse fibroblasts and an SV40‐transformed derivative
Authors: Bartholomew James C. , Yokota Hisao , Ross Priscilla 
Published: February 2005

AbstractThe effect of serum on the growth properties of non‐transformed Balb 3T3 A31 and SV40‐transformed Balb 3T3 A31 was studied. The concentration of serum in the growth medium of non‐transformed cells had little effect on the initial population doubling time, but did regulate the cell density at which the population became quiescent in G1. The doubling time of transformed cells, however, was increased significantly as the concentration of serum was decreased below 4%. This effect on the growth of transformed cells was seen at serum concentrations so low that non‐transformed cells did not complete one population doubling. Flow microfluorometric analysis of these populations indicated that the primary effect of different serum concentrations on the non‐transformed cells was to modulate the average residence time in G1; whereas, all the cell cycle phases of the transformed cells were affected by serum. At saturation densities, the non‐transformed cells became quiescent in G1, but the transformed cells still traversed the cell cycle and their saturation density appeared to be a balance between cell production and cell death occurring primarily in the G1 phase of the cell cycle.
Separation of megakaryocytes from rat bone marrow cells using velocity sedimentation in an isokinetic gradient of ficoll in tissue culture medium
Authors: Pretlow Thomas G. , Stinson Anthony J. 
Published: February 2005

AbstractA technique for the purification of rat megakaryocytes is described. Velocity sedimentation in a previously described isokinetic gradient of Ficoll (polysucrose) in tissue culture medium was more effective than isopycnic sedimentation for the purification of megakaryocytes and resulted in preparations of megakaryocytes which contained 2.4 ± 0.8% (range 1.85–3.60%) megakaryocytes. Megakaryocytes exhibited a broad range of density between 1.06 and 1.15 gm/ml. The inaccuracy which is inherent in the use of velocity sedimentation without isopycnic sedimentation as a means of particle size analysis is discussed.
Increased PRPP synthetase activity in cultured rat hepatoma cells containing mutations in the hypoxanthine‐guanine phosphoribosyltransferase gene
Authors: Graf L. H. , McRoberts J. A. , Harrison T. M. , Martin D. W. 
Published: February 2005

AbstractNine independently derived clones of mutagenized rat hepatoma cells selected for resistance to 6‐mercaptopurine (6‐MP) or 6‐thioguanine (6‐ThioG) have been isolated. Each has severely reduced catalytic activity of hypoxanthine‐guanine phosphoribosyltransferase (HPRT) and seven of them possess significantly increased activities of phosphoribosylpyrophosphate (PRPP) synthetase. The degrees of elevations of PRPP synthetase activities do not correlate with the degrees of deficiencies of HPRT activities.The cells from one of these clones, 1020/12, possess 40% of the normal HPRT catalytic activity and overproduce purines. We have extensively examined the cells from this clone. Immunotitration studies of 1020/12 cells indicate that there is a mutation in the structural gene for HPRT. Although they possess increased specific catalytic activities of the enzyme, PRPP synthetase, the catalytic parameters, heat stability, and isoelectric pH of PRPP synthetase from 1020/12 cells are indistinguishable from those of the enzyme from wild‐type cells.The cause of purine overproduction by 1020/12 cells appears to be the elevated PRPP synthetase activity, rather than a PRPP “sparing” effect stemming from reduced HPRT activity. Support for this idea is provided by the observation that the complete loss of HPRT activity in a clone derived from 1020/12 cells does not further enhance the levels of PRPP synthetase or purine overproduction.We propose that the elevated levels of PRPP synthetase activity in these HPRT deficient cells result from a mutational event in the structural gene for HPRT, and that this causes the disruption of a previously undescribed regulatory function of this gene on the expression of the PRPP synthetase gene.
Density‐dependent regulation of proliferation rate in cultured, androgen‐responsive, tumour cells
Authors: Robinson Jeffery H. , Smith James A. 
Published: February 2005

AbstractShort‐term cultures of androgen‐responsive Shionogi 115 (S115) cells exhibited density‐dependent regulation of proliferation rate in the presence or absence of testosterone. The average surface area per cell exposed to the growth medium was inversely proportional to population density. By contrast, long‐term cultures (serially passaged in testosterone‐containing medium for several months) did not exhibit density‐dependent regulation of proliferation rate when grown in testosterone‐containing medium. In this medium, cells became elongated and no longer exhibited any obvious decrease in exposed surface area with increasing density. Nevertheless, when subcultured into testosterone‐free medium, these cells reverted to an epithelial morphology and exhibited density‐dependent regulation of proliferation rate. These relationships suggested that the proliferation rate of cells decreased with density in proportion to the decrease in exposed surface area.Activity of the “A” neutral amino acid transport system decreased with density in proportion to the decrease in proliferation rate whereas activities of the “L” system and sugar transport system(s) did not. Treatment of cells with testosterone for 24 hours increased proliferation rate but did not change activity of the “A” system, indicating that activity of the “A” system changes with density but not with proliferation rate per se. It is suggested that a decrease in exposed surface area of cells produces the change in activity of the “A” system, possibly by changes in activity of the sodium pump.
Population density and regulation of cell division in 3T3 cells. I. Inorganic phosphate levels, uptake and release
Authors: Gray Peter N. , Cullum Malford E. , Griffin Martin J. 
Published: February 2005

AbstractTriggering mechanisms for initiating density dependent inhibition of cell division in 3T3 cell monolayers are activated approximately two to three population doublings prior to cessation of cell division at monolayer confluency. This activation occurs at a critical contact cell density of approximately 8 × 103 cells/cm2. During this period there are selective controls on transport and storage of required low molecular weight nutrients. A possible correlation between orthophosphate and rates of cell division has been investigated. We have demonstrated a relationship between cellular concentrations of orthophosphate and initiation of density dependent inhibition of cell division. Prior to critical intercellular contact, the [Pi] in 3T3 cells is 10 mM. During critical contact, this concentration is quickly reduced to approximately 2 mM and remains at this concentration to confluency. Similar alterations do not occur in Py 3T3 cells, which maintain a concentration of approximately 2 mM Pi regardless of cell density. After confluent 3T3 cells are released from inhibition of cell division the [Pi] must increase several‐fold before DNA synthesis commences. These are physiological changes in 3T3 cellular [Pi] as a function of cell density, and cannot be attributed to nutrient depletion, altered transport of Pi into the cell, increased [ATP], or increased [PPi] levels. The controlled modulation of [Pi] may regulate glycolysis and coordinate counter‐ion changes (Ca++) may regulate mitochondrial activity.
The effect of oxygen tension on the growth and metabolism of WI‐38 cells
Authors: Balin Arthur K. , Goodman David B. P. , Rasmussen Howard , Cristofalo Vincent J. 
Published: February 2005

AbstractThe effect of oxygen tension on cellular growth and metabolism was studied in actively growing WI‐38 cells [>90% labeled nuclei (LN)] grown under atmospheres containing 5% CO2 and various combinations of O2 and N2. Cells grown under a partial pressure of oxygen (P) of 7.8 ± 3.5 mm Hg had a significantly slower growth rate, lower saturation densities and higher rates of glucose consumption and lactate production than did cells grown under a P of 44 ± 7 mm Hg. There were no significant differences in saturation density or the rates of glucose consumption or lactate production between cells grown under P 26 ± 4 mm Hg, 44 ± 7 mm Hg, or 134 ± 11 mm Hg. Population doubling time was slightly prolonged at a P of 134 mm Hg compared to a P of 44 mm Hg. Cells grown under a P of 291 ± 25 mm Hg showed only 20–30% of the growth rate and 10–20% of the saturation density of cells grown under a P of 134 mm Hg. Despite this reduced growth, cells grown under a P of 291 mm Hg consumed four to six times as much glucose and produced four to six times as much lactate per cell as cells grown at a P of 134 mm Hg. Cells grown under a P of 560 ± 38 mm Hg attached but did not proliferate. This toxic effect of oxygen on cell proliferation was reversible and was not due to an effect of oxygen on the media.