bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reduced permeability in CHO cells as a mechanism of resistance to colchicine
Authors: Ling Victor , Thompson Larry H. 
Published: February 2005

AbstractColchicine resistant (CHR) lines of stable phenotype have been isolated from cultured Chinese hamster (CHO) cells. Successive single‐step selections for increasing resistance were performed by isolating resistant colonies at each step. Two complementary assays involving [3H] colchicine uptake by whole cells and binding of [3H] colchicine by cytoplasmic extracts were developed to test for altered permeability and altered intracellular target protein, respectively. All clones isolated appeared to have decreased permeability to the drug while their colchicine‐binding ability was not reduced. The amount of reduction in colchicine uptake correlated strongly with cellular resistance. The CHR lines were also cross resistant to other drugs such as actinomycin D, vinblastine and Colcemid; furthermore, the degree of cross resistance was positively correlated with the degree of colchicine resistance. The non‐ionic detergent Tween 80 potentiated the cytotoxic action of colchicine on mutant cells as well as its rate of uptake into whole cells.
Establishment of a clonal strain of hepatoma cells which maintain in culture the five enzymes of the urea cycle
Authors: Richardson U. Ingrid , Snodgrass Philip J. , Nuzum C. Thomas , Tashjian Armen H. 
Published: February 2005

AbstractA clonal strain of epithelial cells has been established from the transplantable Morris hepatoma 7800 and is designated 7800C1. The cells grow with a population doubling time of about three days in serum‐supplemented synthetic medium. Cells of the 7800C1 strain have maintained measurable activities of all the enzymes of the urea cycle during 17 months in continuous culture. The activity of argininosuccinate lyase is approximately that found in normal rat liver, while argininosuccinate synthetase, carbamoyl phosphate synthetase, arginase and ornithine carbamoyl transferase activities are, respectively, 40%, 28%, 6%. and 1% of normal values. Treatment of 7800C1 cells with glucagon, dibutyryl 3′,5′‐cyclic adenosine monophosphate or hydrocortisone did not increase the activity of any of the five enzymes.
Effect of cAMP on nucleoside metabolism. I. Effect on thymidine transport and incorporation in monkey cells (CV‐1)
Authors: Roller Barbra , Hirai Kanji , Defendi Vittorio 
Published: February 2005

AbstractThe effect of cAMP on a monkey kidney cell line (CV‐1) noninfected and infected by SV40 was studied. No effect was found on either growth rate or cell morphology when concentrations up to 1 mM of 3′5′ cAMP were used. However, cAMP was found to increase the incorporation of 3H‐thymidine into both cellular and viral DNA without a net increase in DNA synthesis. This increased incorporation was found to be related to an enhanced uptake of thymidine into the nucleotide pool which is reflected in an increase of phosphorylated nucleotides. This, coupled with a lack of effect of cAMP on endogenous deoxyribonucleotide production, produces an increased specific activity of the deoxyribonucleotide triphosphates, with a resultant increase in specific activity of DNA.
Concanavalin A‐induced alterations in sodium and potassium content of Ehrlich ascites tumor cells
Authors: Aull Felice , Nachbar Martin S. 
Published: February 2005

AbstractNet fluxes of sodium and potassium were studied in Ehrlich mouse ascites tumor cells during contact with the agglutinating protein, concanavalin A. This lectin altered cation transport markedly at concentrations of 20–105 μg/ml (6–47 μg/mg cell protein). Whereas control cells extruded sodium and maintained or accumulated potassium against electrochemical gradients, in the presence of concanavalin A there was rapid net sodium entry and potassium loss. After 10–20 minutes in concanavalin A, sodium extrusion began and potassium loss diminished but these events were prevented by ouabain. The alterations in cation content induced by concanavalin A are unlikely to be the result only of agglutination since soybean agglutinin caused much smaller changes although it agglutinated the cells equally well.
Pyrimidine excretion by cultured fibroblasts: Effect of mutational deficiency in pyrimidine salvage enzymes
Authors: Chan Teh‐Sheng , Meuth Mark , Green Howard 
Published: February 2005

AbstractIn cultured fibroblasts, a mutation resulting in deficiency of a pyrimidine salvage enzyme leads to excretion of related pyrimidines. For example, absence of thymidine kinase led to loss of thymidine and deoxyuridine, and absence of deoxycytidine kinase to loss of deoxyuridine. Both wild type and mutant cells excreted uracil; if established lines are representative in this respect, a fully adequate salvage system for uracil does not seem to be present in the fibroblast.
Serum and insulin initiation of DNA synthesis in mammary gland epithelium in vitro
Authors: Hsueh H. W. , Stockdale Frank E. 
Published: February 2005

AbstractThese experiments demonstrate that serum, like insulin, can initiate DNA synthesis in mouse mammary gland epithelium, resulting in a three‐ to four‐fold increase in the rate of DNA synthesis and number of cells synthesizing DNA. Both serum and insulin also increase the tritiated thymidine counts in the acid soluble material of these cells, suggesting that each alters thymidine transport. When combined at any concentration, these agents produce an additive effect on DNA synthesis, number of cells synthesizing DNA and thymidine transport. The factor(s) in serum responsible for these effects is associated with high molecular weight material. These experiments suggest that DNA synthesis and thymidine transport are affected independently by serum and insulin in mammary gland epithelium.
Erythroid colony formation in cultures of mouse and human bone marrow: Analysis of the requirement for erythropoietin by gel filtration and affinity chromatography on agarose‐concanavalin A
Authors: Iscove N. N. , Sieber F. , Winterhalter K. H. 
Published: February 2005

AbstractAssay of red cell progenitors by colony formation in culture is expected to allow study of early events in erythroid differentiation in animal models and in man. In this communication, a simplification of the culture method for mouse bone marrow cells originally reported by Stephenson et al. ('71) is described. In the modified procedure, plasma clot is replaced by methyl cellulose, and scoring of erythroid colonies is done directly in the plates without staining. With additional modification the system proved applicable to the culture of erythroid colonies from human bone marrow as well. The development of both mouse and human erythroid colonies was dependent on “erythroid colony stimulating activity” (E‐CSA) supplied by extracts of anemic sheep plasma, or by extracts of urine from anemic patients. Over a certain range, the number of colonies was a function of dose of E‐CSA.In addition to E‐CSA, these extracts also possessed erythropoietin activity as measured in plethoric mice. The possible chemical equivalence of urinary E‐CSA and erythropoietin was suggested by their similar behavior on both gel filtration and affinity chromatography on agarose‐concanavalin A. The finding further suggests that the culture method might prove useful for the bioassay of erythropoietin.Granulocyte colony stimulating activity (G‐CSA) was also present in the urine extracts, as detected in cultures of mouse bone marrow. Virtually all of this activity was bound on agarose‐con A, whereas only a small fraction of E‐CSA was retained on this material. Agarose‐con A may thus be useful for the purification of erythropoietin.
Calcium transport in isolated bone cells II. Calcium transport studies
Authors: Dziak Rosemary , Brand John S. 
Published: February 2005

AbstractCalcium transport was studied in bone cells isolated from fetal rat calvaria. 45Ca uptake experiments revealed an active component of calcium exchange. Calcium uptake was inhibited by iodoacetamide, DNP, CCCP and oligomycin and appeared to be dependent on medium phosphate concentration. Initial influx values exhibited saturation kinetics from 0.6 mM to 1.5 mM extracellular calcium.Efflux of 45Ca from loaded cells increased in the presence of iodoacetamide, DNP and CCCP. Incubation of the cells af 4° C inhibited both influx and efflux of calcium.Parathyroid hormone had no consistent effect on calcium uptake although characteristic increases in cyclic AMP levels were seen with the hormone. Calcitonin appeared to cause a transient increase in calcium uptake.
Some biological characteristics of a pituitary growth factor (CGF) for cultured lapine articular chondrocytes
Authors: Malemud Charles J. , Sokoloff Leon 
Published: February 2005

AbstractA recently described pituitary chondrocyte growth factor (CGF) is a contaminant of several related glycoprotein hormones (TSH, LH and HCG). Chondrocytes were cultured from rabbits two to three months old. Bovine TSH (NIH) 69.5 μg/ml, used as the source of CGF, reduced the generation time from 16 to 10 hours through a virtual effacement of the G1 period. Incorporation of 3H‐thymidine declined rapidly after 48 hours from maximal values (control 300 cpm/μg DNA; CGF, 679). Total DNA accumulated thereafter until 116 hours when the figures were 36 and 98 μg/flask, respectively. Little growth response occurred in spinner cultures. CGF lowered plating efficiency from 4.5 to 2.3%. The stimulatory effect diminished when CGF was removed from the medium. The treated cells were smaller and contained less protein and RNA than controls. They synthesized smaller quantitites of sulfated mucopolysaccharides (chondroitin sulfates 4,6 and doubly sulfated chondroitin as well as some dermatan sulfate) but hyaluronate production was not diminished.
Formation of eosinophilic‐like granulocytic colonies by mouse bone marrow cells in vitro
Authors: Metcalf D. , Parker J. , Chester H. M. , Kincade P. W. 
Published: February 2005

AbstractFormation of granulocytic and macrophage colonies in agar cultures of mouse marrow or spleen cells was stimulated by the addition of medium from pokeweed mitogen‐stimulated cultures of mouse spleen cells (PKW‐CM). Approximately 5% of the colonies developing were large, dispersed granulocytic colonies (DG‐colonies) composed of cells with eosinophilic cytoplasmic granules. The capacity to stimulate DG‐colonies was shown by media conditioned by PKW‐treated lymphoid and peritoneal cells but not by other cells or organ fragments.Velocity sedimentation studies indicated that cells generating DG‐colonies were separable from cells generating regular granulocytic or macrophage colonies. DG‐colonies did not survive if transfered to cultures containing other forms of CSF. The active colony stimulating factor in pokeweed mitogen‐conditioned medium which stimulates DG‐colony formation was antigenically distinct from the factor stimulating granulocytic and macrophage colony formation, was separable electrophoretically from the latter factor and on gel filtration had an apparent molecular weight of 50,000.Although the cells in DG‐colonies have not been established to be eosinophils, DG‐colonies represent an interesting new system for analysing further aspects of the control of growth and differentiation in hemopoietic populations.
Cell cycle dependent modulations of the surface membrane of normal and SV40 virus transformed 3T3 cells
Authors: Smets L. A. , De Ley L. 
Published: February 2005

AbstractAgglutinability with Concanavalin was studied as function of cell cycle transition in normal and SV40 virus transformed 3T3 cells. In synchronized cultures of normal cells, agglutinbility was high during mitosis and disappeared rapidly. Agglutinability of transformed cells remained high in G1 phase but diminished gradually upon entering S phase and reached minimum in G1 phase. Decreased agglutinability a the end of the cell cycle was also observed in synchronous SV3T3 cultures by a combined technique of haemadsorption and density gradient centrifugation. In normal 3T3 cells, similar variations in agglutin ability during interphase could not be observed.
The role of the electrogenic sodium pump in modulation of pacemaker discharge of Aplysia neurons
Authors: Willis James A. , Gaubatz Gary L. , Carpenter David O. 
Published: February 2005

AbstractThe discharge of Aplysia pacemaker neurons varies with temperature over the range 10 to 22°C. Three types of frequency‐temperature plots are found, with maximal discharge at lowest, intermediate or highest temperatures. In the presence of ouabain, however, all cells show maximal discharge at the highest temperature, suggesting that the steady state activity of an electrogenic sodium pump is an important determinant of membrane excitability. The average magnitude of pump current, as indicated by the applied current necessary to restore discharge to control values after ouabain application, was about 4 namps at 20°C but near zero at 10°C. These neurons may be excellent models of mammalian thermoreceotprs.
Growth control in primary fetal rat liver cells in culture
Authors: Paul Dieter , Walter Stephanie 
Published: February 2005

AbstractPrimary fetal rat liver cells cultured in medium deficient in, but not free of, arginine in the presence of dialyzed fetal calf serum grow until the final cell density is attained and cells become quiescent in the G0 phase of the cell cycle. When growing cells are transferred into arginine free medium, cells become reversibly arrested in G0. Fetal rat liver cells can be induced to synthesize DNA by addition of high levels of arginine to serum free medium. Low arginine levels in the culture medium do not induce cell growth unless serum is present. Serum stimulates arginine uptake in fetal rat liver cells suggesting that serum growth factor(s) act by increasing intracellular arginine levels high enough to initiate the growth cycle. Fractionation of fetal calf serum by gel filtration on G‐200 Sephadex yields a partially purified arginine uptake stimulating activity which is eluted from the column in the same fractions that contain fetal rat liver cell growth promoting activity. Insulin induces DNA synthesis in quiescent fetal rat liver cells. Glucagon reverses the stimulatory effects of insulin. N6,O2‐Dibutyryl adenosine 3′:5′‐cyclic monophosphoric acid (But2c‐AMP) (10−4 M) and theophilline (10−3 M) inhibit arginine uptake and the initiation of DNA synthesis by serum. The role of arginine in the control of DNA synthesis in fetal rat liver cells and the mechanism of action of serum growth factors are discussed.
Cell to substrate adhesion and spreading: Inhibition by cationic anesthetics
Authors: Rabinovitch Michel , Destefano Maryjo 
Published: February 2005

AbstractThe plasma membrane is the postulated site of action of anesthetics on nerve or muscle. The drugs may be useful in the analysis of membrane phenomena in other cells. We show here that cationic anesthetics and tranquilizers inhibit cell adhesion and spreading, metabolically dependent processes that involve membrane motility and changes in cell shape. Adhesion was measured by layering 51Cr labeled Sarcoma I (Sa I) cells on glass coverslips for 20 minutes at 34°C, rinsing and estimating the glass‐associated radioactivity. Spreading was evaluated microscopically. Both cell adhesion to untreated glass and the Mn2+ dependent adhesion to serum‐coated coverslips were inhibited by the drugs, in the following order of increasing activity: tetracaine, promethazine, cyclomethycaine, chlorpromazine and fluphenazine. Similar ranks of drug activity have been reported for nerve blocking, inhibition of cell fusion and inhibition of induced spreading of macrophages. Microscopic observations showed the drugs also inhibited Mn2+ induced spreading of Sa I. Drug treated cells were rounded, refractile, devoid of cell processes or ruffles visible by light microscopy. The effects of the drugs on adhesion and spreading were reversible upon washing of the cells. We postulate that the inhibition of adhesion and spreading are a consequence of the inhibition of cell surface motility by the anesthetics.
Immunological characterization of hypoxanthine‐guanine phosphoribosyl transferase mutants of mouse L cells: Evidence for mutations at different loci in the HGPRT gene
Authors: Wahl G. M. , Hughes S. H. , Capecchi M. R. 
Published: February 2005

AbstractA large collection (105) of mouse L cell mutants lacking hypoxanthine‐guanine phosphoribosyl transferase activity (HGPRT; E. C. 2.4.2.8) were analyzed for the presence of serologically cross reacting material (CRM). Antibody directed against highly purified mouse liver HGPRT was used for detecting CRM activity by two methods: (1) the standard precipitation‐inhibition assay; and (2) a radioimmune‐precipitation assay. The latter assay proved to have far greater sensitivity for the detection of altered forms of HGPRT. Approximately 40% of the HGPRT− cell lines contain CRM activity (i.e., were CRM+). This indicates that a minimum of 40% of the HGPRT− clones arose as a result of mutations in the HGPRT structural gene. The CRM+ cell lines were shown to contain different levels of CRM activity. Measurements of the heat sensitivity of CRM in the different HGPRT− cell lines showed a broad spectrum of CRM heat inactivation kinetics. These latter two observations provide strong evidence that the mutations giving rise to the HGPRT−CRM+ phenotype occurred at different sites in the HGPRT structural gene.
The role of sulfhydryl groups in cellular adhesiveness
Authors: George John V. , Rao K. Vasudeva 
Published: February 2005

AbstractAggregation of chick embryonic liver and kidney cells was completely abolished by a treatment with carboxypyridine disulfide which binds –SH groups. The effect could be reversed by a subsequent treatment with some thiols. Inhibition of RNA synthesis or respiratory metabolism did not prevent cell aggregation. Cell adhesion is discussed in the light of these observations.
Galactose and glucose metabolism in galactokinase deficient, galactose‐1‐P‐uridyl transferase deficient and normal human fibroblasts
Authors: Friedman Thomas B. , Yarkin Rhoda J. , Merril Carl R. 
Published: February 2005

AbstractDespite the genetic interruption of the Leloir pathway both galactosemic patients and galactosemic fibroblasts can convert galactose to CO2 and TCA precipitable products, although at less than the normal rate. These observations stimulated investigations into the identity of the alternative metabolic routes which allow for galactose metabolism in the absence of in vitro galactose‐1‐P‐uridyl transferase. Four lines of galactosemic cells, each without detectable gal‐transferase, produced 14CO2 from [1‐14C]‐galactose (0.094 μmoles in 20 cc of medium) at approximately 39% ± 16% the rate of transferase positive cells over a 48‐hour period. However, galactokinase deficient fibroblasts produced 14CO2 and TCA precipitable products from [1‐14C] ‐galactose or [U‐14C] ‐galactose at only 3% to 9% the rate of normal fibroblasts. Therefore it seems likely that galtransferase deficient fibroblasts must first synthesize galactose‐1‐P for further metabolism of galactose.
Sodium and calcium transport in cat red cells
Authors: Sha'afi R. I. , Naccache P. 
Published: February 2005

AbstractThe transport of radioactive sodium and calcium in high sodium low potassium cat red blood cells has been studied under various experimental conditions. In these cells, calcium uptake was found to increase by 25‐fold when cell volume was decreased from 1.0 normal to 0.55. Increasing cell volume from 1.0 to 1.1 normal was found to decrease calcium‐uptake by 30%. N‐ethylmaleimide, NEM, phloretin, colchicine, and vinblastine were found to inhibit Na‐uptake by these cells. Among these four agents, phloretin was the most potent inhibitor of Na‐influx. It appears that phloretin produces its effect through its interaction with the cell membrane and not with cell interior.
Variations in the cell‐free translating apparatus of cultured animal cells as a function of time during cell growth
Authors: Engelhardt Dean L. , Sarnoski Joseph 
Published: February 2005

AbstractVero M3 cells, a line derived from the kidney of an African Green Monkey, display certain alterations in their protein synthetic apparatus as a function of time during a growth cycle. (Growth cycle here refers to exponential growth of unsynchronized cells in culture and their subsequent passage into the stationary phase.) The capacity of cytoplasmic extracts of these cells to promote endogeneous mRNA‐mediated polypeptide synthesis or poly U‐mediated polyphenylalanine synthesis declines from the second day after the initiation of the growth cycle. The ribosome sedimentation profile indicates that after the second day of growth a decrease also occurs in the total amount of ribosomes per cell, and that a shift occurs from predominantly polyribosome structures to predominantly subunits and monoribosomes structures. The activity of the translation factor, elongation factor 1, also progressively decreases after the second day of growth. Furthermore, when crude factor preparations from cells in the second day of growth (Exponential phase) and from cells in the fifth day of growth (Stationary phase) are compared for leucyl‐tRNA synthetase and prolyl‐tRNA synthetase activities, it is found that the extracts from fifth‐day cells have significantly less activity. The activity of another enzyme, acid phosphatase, remains relatively unaffected as a function of time during the cell growth cycle. When HeLa S3 plating cells are grown under the same conditions, they do not display the same responses.
The effect of serum on the transport and phosphorylation of 2‐deoxyglucose by untransformed and transformed mouse 3T3 cells
Authors: Hassell John A. , Colby Clarence , Romano Antonio H. 
Published: February 2005

AbstractSerum starvation of growing and nongrowing (density‐inhibited) mouse 3T3 cells resulted in decreased phosphorylation of 2‐deoxy‐D‐glucose. while the time course of transport of this sugar remained unchanged. Serum starvation of SV40 transformed 3T3 cells (SV101) and spontaneously transformed 3T6 cells did not alter either the time course of transport, or phosphorylation of the sugar. Treatment of SV101 cells with 10−4 M dibutyryl adenosine cyclic 3′:5′ monophosphate and 10−3 M theophylline did not restore the capacity to regulate 2‐deoxy‐D‐glucose phosphorylation when these cells were serum deprived. We conclude that serum factors are involved in the modulation of phosphorylation of 2‐deoxy‐D‐glucose in 3T3 cells rather than its transport. This regulation is operative both in growing as well as nongrowing 3T3 cells. In contrast, transformed cells do not respond to this regulation of 2‐deoxy‐D‐glucose phosphorylation.
The role of cyclic AMP in myogenesis
Authors: Epstein Charles J. , De Asua Luis Jiminez , Rozengurt Enrique 
Published: February 2005

AbstractThe effect of exogenously administered cyclic AMP derivatives and of endogenously elevated cyclic AMP levels on the spontaneous fusion of skeletal muscle myoblasts has been investigated. Contrary to earlier reports, cAMP does not appear to have a direct inhibitory effect on the fusion of an established line (L8) of rat myoblasts. Similarly, cAMP did not block the fusion of primary chick myoblasts. However, fusion of the rat myoblasts was prevented when the cAMP induced inhibition of growth prevented the cells from reaching the “critical” cell density necessary for fusion.
Preparation and neutralization characteristics of an anti‐CSF antibody
Authors: Shadduck Richard K. , Metcalf Donald 
Published: February 2005

AbstractNine of ten rabbits immunized with a partially purified L‐cell CSF had demonstrable titers of anti‐CSF activity. In vitro the antibody was markedly inhibitory to both post‐endotoxin mouse sera and several mouse tissue extracts. CSF containing conditioned media prepared from a number of sources showed variable inhibition suggesting that murine CSF's may be characterized by marked antigenic differences. Human sources of CSF were also inhibited thus indicating a degree of cross‐reactivity between murine and human factors. These studies may provide the initial steps toward definition of the role of CSF in vivo.