bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stimulation of DNA synthesis, cell multiplication, and ornithine decarboxylase in 3T3 cells by multiplication stimulating activity (MSA)
Authors: Nissley S. Peter , Passamani John , Short Patricia 
Published: February 2005

AbstractMultiplication stimulating activity (MSA) has been purified from the conditioned media of rat liver cells in culture by a modification of the procedure of Dulak and Temin. Purified MSA stimulates [3H] thymidine incorporation into DNA in subconfluent, serum starved 3T3 cells. Cell cycle analysis by the flow microfluorometer shows that the [3H] thymidine incorporation data reflects DNA synthesis. MSA also stimulates the multiplication of serum starved subconfluent 3T3 cells. MSA is approximately 10‐fold less active in 3T3 cells than in chick embryo fibroblasts in stimulating [3H] thymidine incorporation into DNA.MSA causes a 2–10‐fold increase in ornithine decarboxylase (ODC) activity in 3T3 cells and the dose response curve parallels the dose response curve for [3H] thymidine incorporation into DNA. The Km of ODC for ornithine is 0.12 mM. There is a 30% decrease in the activity of ornithine transaminase (OTA) during the time period in which MSA causes an increase in ODC activity. Insulin also stimulates [3H] thymidine incorporation into DNA, cell multiplication and ODC activity over the same concentration range as shown for MSA, however, the extent of stimulation by insulin is less than that observed following MSA addition.
Clonal lines of teratocarcinoma cells in vitro: Differentiation and cytogenetic characteristics
Authors: McBurney Michael W. 
Published: February 2005

AbstractClonal lines of embryonal carcinoma cells have been established in culture from four independently‐derived transplantable teratocarcinomas of mice: three from strain C3H and one from strain 129/Sv. Cells from all lines retain the capacity to differentiate into a variety of tissue types both in tumors formed following the injection of cells into syngeneic animals and in vitro under appropriate culture conditions. Analysis of their G‐banded chromosomes indicated that the four lines have near‐diploid but not absolutely normal karyo‐types. The same chromosomal abnormalities were often present in more than one line.Tetraploid embryonal carcinoma cells made by Colcemid or cytochalasin B treatment were also pluripotential in spite of chromosomal instability. Hybrid cells were readily obtained between diploid or tetraploid embryonal carcinoma cells and mouse 3T3 fibroblasts. Hybrid cells failed to differentiate and were contact inhibited like the 3T3 parent.
Effect of uncoupler on “Downhill” substrate efflux of Escherichia coli is dependent on (Mg2+,Ca2+)· adenosine triphosphatase
Authors: Rotman Boris 
Published: February 2005

AbstractPrevious studies have shown that mutations in the unc gene of Escherichia coli K12 cause defects in energy transduction as well as in a membrane‐bound (Mg2+,Ca2+)· adenosine triphosphatase.We studied the effect of this mutation on the “downhill” efflux of methyl‐β‐D‐galactopyranoside, a substrate of the mgl transport system. While unc+ and unc− isogenic strains of E. coli K12 did not show significant differences in substrate influx or efflux, a differential effect of an uncoupler, 2,4‐dinitrophenol was demonstrated. In contrast to the unc+, dinitrophenol failed to inhibit significantly the rate coefficient of efflux in the unc− strain.Analyses of spontaneous unc+ revertants of the unc− mutant provided additional evidence that a functional unc gene is necessary for dinitrophenol inhibition of efflux.Other uncouplers tested in the unc+ strain showed different effects on efflux. While arsenate, azide and carbonyl cyanide p‐trifluoromethoxyphenylhydrazone caused little or no effect, 2,4‐dibromophenol and pentachlorophenol increased efflux by a considerable factor.
Transport of nutrients by a thermophilic bacterium—reconstitution of vesicles from crystalline ATPase or solubilized alanine carrier
Authors: Kagawa Yasuo 
Published: February 2005

AbstractA strain of aerobic thermophilic bacteria was selected in order to purify highly stable membrane proteins and to reconstitute proteoliposomes capable of transporting nutrients from them. These proteins responsible for the transport could be divided into (1) proteins which supply energy to the transporting system, and (2) specific nutrient carriers driven by the energy. The former included a stable ATPase (TF1) and a lipoprotein (TF0) which rendered TF1 sensitive to energy transfer inhibitors. The complex of TF0 and TF1 could transport protons into reconstituted proteoliposomes upon hydrolysis of ATP. And one of the latter reported in this paper was alanine carrier protein which was driven by proton movement.TF1 was the first crystallized ATPase in biomembranes, and was reconstituted from its five different polypeptides, two of which were necessary for ATPase activity and four of which, for proton translocation. Purification of alanine carrier and reconstitution of proteoliposomes capable of alanine accumulation were also demonstrated.
The application of rapid kinetic techniques to the transport of thymidine and 3‐O‐methylglucose into mammalian cells in suspension culture
Authors: Wohlhueter Robert M. , Marz Richard , Graff Jon C. , Plagemann Peter G. W. 
Published: February 2005

AbstractTechniques are described by which the transport of nutrients into mammalian cells in suspension can be measured at intervals of 1.5 seconds. By application of these techniques, the existence of a saturable (Km = 85 μM), non‐concentrative, transport system for thymidine was demonstrated in Novikoff rat hepatoma cells depleted of ATP. At concentrations of thymidine less than the Km, this system operated at velocities sufficient to nearly completely equilibrate intra‐ and extra‐cellular thymidine pools within 8 seconds. In phosphorylating cells, the transport system operated with similar rapidity, so that intracellular phosphorylation was rate‐limiting for the incorporation of thymidine into nucleotides. Uptake of 3‐O‐methylglucose occurred at comparable velocities, attaining 90% of equilibrium between internal and external pools within 25 seconds. Uptake of cytosine by simple diffusion was 100 times slower.
Glucose transport and metabolism in cultured cells of nervous tissue
Authors: Passonneau Janet V. 
Published: February 2005

AbstractThe effect of the concentration of glucose in the medium on the intracellular concentrations of metabolites in C‐6 astrocytoma cells and C‐1300 neuroblastoma cells in culture has been investigated. The intracellular concentrations of glucose, glycogen, glucose 6‐P and UDP‐glucose were measured at intervals after feeding the cells. A rapid increase in glucose and glucose 6‐P levels occurred when fresh medium containing 5.5 mM glucose was applied to the cells, followed by slower increases in UDP‐glucose and glycogen. When the medium glucose was increased ten‐fold, the intracellular concentration of glucose was increased, but the levels of glucose 6‐P, UDP‐glucose and glycogen were not altered, nor were the rates of accumulation. The addition of insulin to the medium resulted in an increase of intracellular glucose, glucose 6‐P and glycogen. The transport of glucose into the cells is not the rate‐limiting step of the regulation of metabolite levels in the cells.
Transport changes associated with growth control and malignant transformation
Authors: Weber Michael J. , Hale Arthur H. , Yau Tom M. , Buckman Trent , Johnson Marcia , Brady Terrance M. , Larossa Denise D. 
Published: February 2005

AbstractWe can distinguish two classes of membrane transport changes in cultured cells: (a) growth‐rate contingent changes are those which occur in coordination with the onset of density‐dependent inhibition of growth; (b) transformation‐specific changes are those which occur when cells become transformed, and which can be detected even when normal and transformed cells are growing at the same rate. Growth‐rate contingent changes include the density‐dependent changes in phosphate, nucleoside, glucose, amino acid, and potassium transport. Only one transformation‐specific transport change has been found in Rous‐transformed chicken embryo fibroblasts: an increased rate of hexose transport. The variations in potassium transport are associated with variations in the number of ouabain binding sites in the membrane. The molecular basis for changes in the rate of hexose transport is unknown, although gross changes in membrane bilayer composition and “fluidity” seem not to be involved. In analyzing the regulation of hexose transport activity, we find that decreased cAMP may play a role in the transformation‐specific increase in hexose transport, but that fibrinolytic activity is not necessary.
Genetic alteration in the (Na+ + K+ ATPase transport system expressed in human lymphoblasts and their isolated plasma membranes
Authors: Lever Julia E. 
Published: February 2005

AbstractA series of ouabain‐resistant human lymphoblastoid lines were shown to be genetically altered in the (Na+ + K+) ATPase transport system. The sensitivity to ouabain of Rb+ uptake in intact cells and (Na+ + K+)‐dependent ATP hydrolysis in purified plasma membrane vesicles was compared with measurement of ouabain binding to intact cells. Preliminary evidence for at least two categories of ouabain resistance was obtained.
The function and activity of certain membrane enzymes when localized on – and off – the membrane
Authors: Hochstadt Joy , Quinlan Dennis 
Published: February 2005

AbstractA group of enzymes known to be involved in group translocation‐type transport mechanisms for the uptake of a variety of nucleotide precursors are enzymatically active both in their natural membrane milieu and in aqueous solution. The activity in aqueous solution markedly differ, however, from the enzymatic activity when the enzyme is membrane localized. The adenine phosphoribosyltransferase (PRT) of E. coli (Hochstadt‐Ozer and Stadtman, 1971 a) is capable of carrying out an exchange reaction between the base moieties of adenine and AMP without requiring P‐ribose‐PP as an intermediate; the enzyme in aqueous solution requires P‐ribose‐PP, indicating a different reaction mechanism in the two environments. Like the adenine PRT of E. coli, the hypo‐xanthine PRT of Salmonella typhimurium (Jackman and Hochstadt, 1976) also carried out an exchange reaction on the membrane only and also is more sensitive to a number of inhibitors in aqueous solution relative to the sensitivity when embedded in the membrane. In addition, however, the hypoxanthine PRT, while restricted to hypoxanthine as a substrate in the membrane, also accepts guanine as substrate in its soluble form. The membrane capacities reflect the in situ capacities of the enzyme and the gain of guanine specificity was determined in a guanine PRT deletion strain (Jackman and Hochstadt, 1976). Finally, in mammalian cell lines purine nucleoside phosphorylase, which translocates the ribose moiety of inosine across the plasma membrane of mouse fibroblasts undergoes a 30‐fold increase in substrate turnover number upon liberation from the membrane. These data raise two important caveats with respect to study of membrane enzymes and transport. Firstly, an enzyme once solubilized and found to differ kinetically from substrate transport in situ cannot be excluded from participating in translocations in the membrane on the basis of its activity in aqueous solution. Secondly, an enzyme which “appears” largely soluble upon cell rupture cannot be assumed to be a cycloplasmic enzyme because the majority of the solubilized activity may represent only a small fraction of the enzyme molecules highly activated concomitant to their solubilization. In this latter case the ability to activate enzyme still residing on the membrane (e.g., with detergents) would be necessary in order to estimate total membrane associated activity after cell rupture.
G2 + M arrest of cultured mammalian cells after incorporation of tritium‐labeled nucleosides
Authors: Marz R. , Zylka J. M. , Plagemann P. G. W. , Erbe J. , Howard R. , Sheppard J. R. 
Published: February 2005

AbstractNovikoff rat hepatoma cells were propagated in suspension cultures containing 0.5 to 10 μC of 3H‐methyl‐thymidine, 3H‐5‐uridine, 3H‐G‐adenosine or 3H‐8‐adenine. The presence of the 3H‐labeled precursors caused an inhibition of cell replication which was due to a delay or arrest of the cells in G2 and M. The degree of inhibition was proportional to the amount of radioactivity incorporated into nucleic acids. Almost immediate and complete inhibition resulted from incubation with 10 μC 3H‐thymidine/ml. The presence of 0.5 μC 3H‐thymidine/ml caused a significant increase in the relative proportion of cells in G2 + M, even though the population doubling time of the culture appeared to be unaltered.
Phosphohydrolases on the cell surface of BHK cells: Loss during long term culture
Authors: Deppert W. , Walter G. 
Published: February 2005

AbstractLow passage BHK 21/13 cells contain two cell surface enzymes, a nucleotide pyrophosphatase and a monophosphoester hydrolase, which together hydrolyze exogenous UDP‐galactose to free galactose. During serial passage, BHK cells successively lose both enzymes. Concomitant with the loss of these enzymatic activities, changes in cell morphology, as well as in the serum requirement for the initiation of DNA synthesis, were observed. Clonal sublines of BHK cells were isolated, which differed qualitatively in their ability to hydrolyze UDP‐galactose. Clonal BHK sublines, which exhibited both enzymatic activities on their cell surface, resembled low passage BHK cells in morphology and serum requirement for the initiation of DNA synthesis. Sublines not containing these enzymes resembled BHK cells of high passage cultures. The ability of intact BHK cells to hydrolyze exogenous nucleotide sugars may serve as an indicator for the progression of BHK cells from a normal to a more transformed state.
Chromosome replication in somatic hybrids of mouse and temperature sensitive Chinese hamster cells
Authors: Marin G. , Labella T. 
Published: February 2005

AbstractHybrid clones were obtained between a mouse cell line (3TP) and a temperature‐sensitive Chinese hamster cell line (K12) unable to grow at 40° because of a ts defect apparently located at the G1/S transition. The great majority of hybrid clones grew at 40°, showing the ts defect to be “recessive.” Chromosome DNA replication was analyzed in some detail in three hybrid clones with balanced complements. Although the S period of these hybrids was longer than that of K12, DNA replication in mouse and hamster chromosomes started and ended synchronously. Upon prolonged culture, mouse chromosomes were lost as they are in hybrids involving a non ts Chinese hamster partner, in which case asynchronous chromosome replication appears to be the rule. It seems therefore that asynchronous replication is not the determining factor in chromosome loss from cell hybrids.
Production of 5‐hydroxyindoleacetic acid from serotonin by cultured endothelial cells
Authors: Small Roy , Macarak Edward , Fisher Aron B. 
Published: February 2005

AbstractEndothelial cells from bovine aorta and human umbilical vein and fibroblasts from human foreskin were cultured and subsequently evaluated for ability to metabolize serotonin (5‐HT) to 5‐hydroxyindoleacetic acid (5‐HIAA). Cells were incubated for three hours with 4 × 10−6 M [14C] 5‐HT creatinine sulfate. [14C] 5‐HIAA was separated from labeled 5‐HT by column chromatography and measured by scintillation counting. Production of 5‐HIAA by bovine aorta cells was 39.0 ± 7.5 (S.E.M., n = 6) nmoles per 109 cells per hour. Production of 5‐HIAA was markedly inhibited by the presence of 10−4 M iproniazid (an inhibitor of monoamine oxidase) or 10−4 M imipramine (an inhibitor of amine transport). 5‐HIAA was the only product of 5‐HT metabolism detected by thin layer chromatography. Production of 5‐HIAA by human umbilical vein endothelial cells was 5.4 ± 2.0 nmoles per 109 cells per hour (n = 5) and by human foreskin fibroblasts was 3.9 ± 1.4 nmoles per 109 cells per hour (n = 5). The results obtained during incubation in the presence and absence of inhibitors indicate that bovine aorta endothelial cells maintained in tissue culture are able to transport serotonin with subsequent production of 5‐HIAA. By contrast, human umbilical vein endothelial cells and fibroblasts exhibited relatively low rates of 5‐HT uptake and metabolism.
Development of spike potentials in skeletal muscle cells differentiated in vitro from chick embryo
Authors: Kano Masaakira , Yamamoto Mitsue 
Published: February 2005

AbstractThe development of spike potential mechanisms during cell differentiation was studied in chick myotubes formed in vitro from trypsin‐dissociated myoblasts. The spike potential and its rate of rise were measured in myotubes from 4–14 day old cultures. A depolarizing current pulse was delivered to evoke the spike potential after the steady membrane potential had been adjusted to a standard level of −80 mV in all cases. This gives the greatest maximum rate of rise of the spike potential and eliminates variation due to differences in the resting membrane potential of the myotubes. The size and maximum rate of rise of the spike potential increased significantly during the period examined. The spike potential was blocked by tetrodotoxin in almost all myotubes. These results suggest that during differentiation myotubes develop the ability to generate a spike potential due to an inward current carried by sodium ions.
Essential factors in the kinetic analysis of RNA synthesis in HeLa cells
Authors: Puckett Larry , Darnell James E. 
Published: February 2005

AbstractFurther evidence of mRNA in HeLa cells with a half‐life two hours or less is given. A kinetic model of RNA synthesis in HeLa cells is described in which equilibration of label occurs first into the acid soluble pool (evidence is given that this pool feeds RNA synthesis) and thence in nuclear and cytoplasmic molecules. The measured accumulation of label in nuclear and cytoplasmic poly(A) is examined with the model and parameters were found which are consistent with the quantitative transfer of nuclear poly(A) to the cytoplasm. The strengths and limitations of the model are discussed.
Cell cycle changes in transformed cells growing under serum‐free conditions
Authors: Bush H. , Shodell M. 
Published: February 2005

AbstractPolyoma transformed hamster cells (PyBHK) and SV40 transformed mouse cells (SV3T3) were transferred in culture using crystalline trypsin followed by neutralisation with soybean trypsin inhibitor. Such cells were able to proliferate freely in defined medium without any serum supplement and without any intervening period of adaptation. However, growth rates were reduced under serum‐free conditions. Re‐establishment of rapid growth rates could be achieved by addition of serum, with the rate attained being proportional to the serum concentration. Irrespective of the prevailing rates of growth, percentages of cells synthesising DNA were the same. However, the rate at which DNA was being synthesised was found to change proportionately with the changes in overall growth rate.
Pentose utilizing variants of Novikoff hepatoma cells: Modification of growth and morphological properties
Authors: Hoffee Patricia , Jargiello Patricia , Zaner Linda , Martin Judith 
Published: February 2005

AbstractA series of variant lines that utilize multiple pentoses for growth in place of glucose have been isolated from an 8‐azaguanine resistant line of Novikoff hepatoma cells (N1S167). These variants utilize for growth ribose, xylose, arabinose, and/or deoxyribose. The variants growing on pentose containing medium (a) exhibit a density dependent cessation of growth, (b) have a morphology change to a more flattened cell type, (c) become binucleated in the presence of cytochalasin B, and (d) show an altered sensitivity to trypsin treatment.
Expression of liver and placental alkaline phosphatases in Chang liver cells
Authors: LudueñA Marilyn A. , Iverson G. Michael , Sussman Howard H. 
Published: February 2005

AbstractThis paper presents evidence that a protein characteristic of differentiated liver cells, liver alkaline phosphatase, is synthesized by the Chang liver cell line. Liver alkaline phosphatase was demonstrated by immumochemical assay, 32P‐labeling and polyacrylamide gel electrophoresis, immunofluorescence microscopy, and the fluorescence‐activated cell sorter. The synthesis of the liver enzyme by the Chang liver cells is interpreted to indicate fidelity of the Chang cells to their origin from human liver tissue. Chang liver cells also synthesize a phosphatase which is similar if not indentical to the placental alkaline phosphatase. Since a placental‐type alkaline phosphatase has been observed in a number of non‐trophoblastic cell lines and also in some neoplasms, it does not seem reliable as an index of the origins of the cell line. Because of the claims that Chang liver cells are actually HeLa cells, HeLa cells were studied in tandem with the Chang cells. The results showed that the HeLa cells do not make the liver type phosphatase. The data are discussed in relation to the question of HeLa cell contamination of the Chang cell line and the validity of criteria normally used to identify cell lines.
Effects of hormones and serum on glycogen metabolism in adult rat liver parenchymal cell primary cultures
Authors: Walker P. Roy , Grindle Marie J. 
Published: February 2005

AbstractParenchymal cells from adult rat liver, isolated by a collagenase perfusion technique, have been maintained in primary culture and a detailed study on carbohydrate metabolism carried out over the initial 48‐hour culture period. The glucose concentration of the medium exerts a major influence on glycogen accumulation by the cells. Insulin, particularly at high glucose concentrations, stimulates glycogen biosynthesis, whereas glucagon prevents glycogen accumulation. Dexamethasone was without effect on glycogen metabolism. Glucose appears to stimulate glycogen accumulation by activation of glycogen synthetase enzyme. However, there is a gradual loss of synthetase activity throughout the culture period. Similar decreases in activity were noted for pyruvate kinase, aldolase and hexokinase. Glucose, insulin and dexamethasone were unable to prevent these decreases in enzyme activity. Foetal bovine serum contains fructose and this hexose appears to be the factor in serum which is responsible for the activation of glycogen accumulation in the presence of physiological glucose concentrations. The lactic acid content of the serum may also stimulate glycogen accumulation. In general, there is a gradual loss of the pattern of carbohydrate metabolism typical of differentiated hepatocytes during the culture period.