bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contribution of glucose and gluconeogenic substrates to insulin‐stimulated glycogen synthesis in cultured fetal hepatocytes
Authors: Plas C. , Forest N. , Pringault E. , Menuelle P. 
Published: February 2005

AbstractThe influence of medium composition on basal and insulin‐stimulated glycogenesis was studied in cultured 17‐day‐old rat fetal hepatocytes, which contain no glycogen at the time of transplantation. Continuous‐labeling 14C‐glucose experiments were used to determine both glycogen content and glycogen labeling. The specific activity of glucose units in the newly formed glycogen (a) was compared to that of the medium glucose (b): the ratio a/b expresses the contribution of medium glucose to glycogen formation. In standard medium (5.5 mM glucose), this ratio averaged 0.60. Variations of glucose concentration in the medium from 1 to 40 mM were accompanied by a progressive increase in both glycogen content and the ratio a/b (up to 0.80). Supplementation of standard medium with fructose, galactose, glycerol, or lactate‐pyruvate decreased the hepatocyte glucose uptake from the medium. Galactose (1 to 5 mM) or lactate‐pyruvate (5 mM) enhanced the glycogen content whereas glycerol or fructose (1 to 5 mM) had no effect. The ratio a/b, not modified by glycerol or lactate‐pyruvate, was decreased to 0.45 by fructose (5 mM). Galactose at concentrations as low as 1 to 2 mM brought the ratio down to 0.30, indicating that it is a superior precursor of glycogen as compared to glucose. When the hepatocytes were grown in the presence of 10 nM insulin, the glycogen content was constantly higher than in the absence of the hormone (2‐fold stimulation). Also the amplitude of the glycogenic effect of insulin was similar whatever the modifications of the medium, whereas ratio a/b and glucose uptake were hardly increased by insulin. Thus several substrates can contribute to glycogen formation (especially galactose) in cultured fetal hepatocytes and the essential effect of insulin is a stimulation of the final step of the glycogenosynthetic pathway.
Putrescine dependent growth of mycoplasma infected mammalian cells
Authors: Kamatani Naoyuki , Willis Erik H. , McGarrity Gerard J. , Carson Dennis A. 
Published: February 2005

AbstractThe aliphatic diamine putrescine, a metabolic precursor of the polyamines spermidine and spermine, markedly stimulated the growth of a murine lymphoblastoid cell line (R 1.1) infected with Mycoplasma orale, under conditions of arginine limitation. The diamine acted by suppressing the growth of the mycoplasma, which use arginine as a major energy source, and thereby prevented the depletion of arginine from the medium. The antimycoplasmal effects of putrescine occurred at concentrations that were neither stimulatory nor toxic to uninfected cells.
Virus replication in infected epithelial cells is coupled to cell shape‐responsive metabolic controls
Authors: Ben‐Ze'ev Avri 
Published: February 2005

AbstractThe cell shape of monkey epithelial cells was varied from flat to spheroidal by gradually reducing the substrate adhesiveness with poly (HEMA) films of increasing thickness. The decrease in cell spreading is accompanied by a dramatic response in cellular macromolecular metabolism in the nucleus. Within 14 to 16 hr, DNA and RNA syntheses are inhibited by more than 95%, while the level of protein synthesis is reduced by only twofold after 24 hr in spheroidal‐suspension culture. When epithelial cells, spread to various degrees, are infected with SV40 or herpes virus a parallel inhibition of virus replication and cellular macromolecular metabolism occurs. However, VSV can proliferate in the metabolically active cytoplasm of epithelial cells in which nuclear activity is inhibited owing to alterations in cell shape. The results suggest that the metabolic restrictions imposed on epithelial cells, owing to changes in cell spreading, are a dominant phenomenon that cannot be overcome by virus infection. Rather, virus replication, which is dependent on the cellular metabolic machinery, is inhibited in parallel with the inhibition of cellular macromolecular metabolism.
The growth requirements of BHK‐21 cells in serum‐free culture
Authors: Bradshaw Gary L , Sato Gordon H. , McClure Don B. , Dubes George R. 
Published: February 2005

AbstractA serum‐free medium for serial culture of baby hamster kidney cell line 21 (BHK‐21) as container‐adherent cells was developed. The medium is a 1:1 (v/v) mixture of Dulbecco's modified Eagle's medium and Ham's F‐12 medium supplemented with fibroblast growth factor, fibronectin, insulin, oleic acid (preincubated with fatty‐acid‐free bovine serum albumin as carrier), and transferrin. The fibronectin was required for cell adherence, the other factors for optimal cell multiplication. When cell input was greater than about 1,900 cells/cm2, this serum‐free medium supported cell multiplication at a rate approximately equal to the rate in medium with 10% serum. At lower cell input, growth in the serum‐free medium was poor unless it was supplemented with serum‐free medium which had been conditioned by BHK‐21 cells. The conditioned medium contained a factor(s) which enabled or stimulated cell multiplication.
[125I]EGF binding ability is stable throughout the replicative life‐span of WI‐38 cells
Authors: Phillips Paul D. , Kuhnle Ellen , Cristofalo Vincent J. 
Published: February 2005

AbstractUsing a serum‐free medium supplemented with hormones and growth factors, which included epidermal growth factor (EGF), we investigated the binding and processing‐degradation of [125I]EGF in WI‐38 cells of various in vitro ages. The binding and processing‐degradation systems of these cells remained esentially unchanged throughout their lifespan. The number of specific [125I]EGF binding sites per cell increased as the cultures senesced, thought the number of specific binding sites per μm2(surface area) remained constant. The kinetics of ligand degradation as well as the qualitative and quantitative nature of the degradation products also remained essentially unchanged throughout the life‐span. The only consistent alteration in any of the binding parameters measured was the slight decrease in the apparent kd of the ligand‐receptor complex, independent of temperature. Quantitation of EGF‐stimulated DNA synthesis revealed a decrease in the percentage of cells incorporating [3H]thymidine ([3H]TdR) during a 30‐h exposure from 45% in young cells to 0.25% in senescent cells, although [125I]EGF binding or processing‐degradation did not differ significantly in yong and old cells. Thus, EGF binding does not decrease in senescence.
Rearrangement of Con A and WGA receptors on murine mastocytoma cell membranes: Relationship to cell cycle
Authors: Lustig Shlomo , Pluznik Dov H. 
Published: February 2005

AbstractIncubation of interphase murine mastocytoma cells with fluorescein‐labeled wheat germ agglutinin (FITC‐WGA) or with rhodamine‐labeled concanavalin A (Rh‐Con A) shows binding of the lectins to all the cells in a ring form distribution. Treatment of the cells with trypsin before addition of FITC‐WGA, or with colchicine before addition of Rh‐Con A, promoted rearrangement of the lectin binding sites into cap formation in 27–29% of the cells. Trypsin had no effect on cap formation by Rh‐Con A, and colchicine had no effect on cap formation by FITC‐WGA. When the same cells were pretreated consecutively with trypsin and colchicine followed by incubation with FITC‐WGA and Rh‐Con A, no increase in the percentage of cells bearing caps was observed. Moreover, the same cells showed co‐capping with both lectins. Experiments with synchronous cultures of mastocytoma cells have indicated that capping induced by either lectin is maximal in the G2 phase and minimal in the G1 and S phases of the cell cycle. At the G2 phase 60% of the cells show cap formation either after trypsin‐WGA treatment or after colchicine‐Con A treatment. These data indicate that rearrangement of membrane receptors for Con‐A and WGA in murine mastocytoma cells can occur only at certain phases of the cell cycle.
Glucocorticoid hormone renders rat glioma cells dependent on high concentrations of external Ca2+ for growth
Authors: Ribeiro Solange M. F. , Armelin Hugo A. 
Published: February 2005

AbstractC6 rat glioma cells, like other tumor cells, grow optimally in Ca2+‐ or Mg2+‐ depleted 5% serum medium. However, the glucocorticoid hormone hydrocortisone renders these cells dependent on high concentrations of external Ca2+ for growth. Upon Ca2+ deprivation (30–80 μM Ca2+ medium) hydrocortisone‐treated C6 cells undergo reversible cell‐cycle arrest at G0/G1 phase. This effect is specific for glucocorticoid hormones and occurs at physiological concentrations.Growth restimulation of Ca2+‐deprived, hydrocortisone‐treated C6 cells by bovine pituitary growth factors or serum growth factors only takes place if the external Ca2+ concentration is increased. On the other hand, C6 cell growth requirement for external Mg2+ was not increased by the glucocorticoid hormone treatment. A minimum of 80 μM of external Mg2+ is required to keep cells adhered and spread in Ca2+‐depleted (30 μM) 5% serum medium; in high Ca2+ concentration (1.8 mM), Mg2+ is not required for adhesion or spreading. Thus, the hormone hydrocortisone renders the cell cycle of C6 glioma cells controllable by the levels of external Ca2+, a minimal external Mg2+ being necessary to warrant normal adhesion.
Insulin‐cholera toxin binding unit conjugate: A hybrid molecule with insulin biological activity and cholera toxin binding specificity
Authors: Roth Richard A. , Maddux Betty 
Published: February 2005

AbstractThe polypeptide hormone insulin and the binding unit of cholera toxin (CTB) were coupled via a disulfide bond. This hybrid molecule had 1/30 the ability of native insulin to bind to the insulin receptor and 1/30 the biological activity of native insulin in H35 rat hepatoma cells and rat adipocytes. Thus, in these two cell types that are very sensitive to insulin, the biological activity of the hybrid molecule was as predicted on the basis of the ability of the molecule to interact with the insulin receptor. In contrast, in HTC rat hepatoma cells and rat thymocytes, two poorly responsive cell types, the insulin‐CTB conjugate had 1/3 the biological activity of native insulin, a value 10 times greater than its insulin receptor binding potency. This increased activity of the conjugate did not appear to be due to cholera toxin in the preparation, since a control of uncoupled CTB had no biological activity. Furthermore, native cholera toxin increased intracellular levels of cAMP by 20‐fold, whereas the conjugate had no effect on cAMP levels. The CTB moiety did, however, contribute to the biological activity of the conjugate, since the activity of the hybrid molecule, like cholera toxin, was inhibited by gangliosides, whereas the activity of native insulin was not. Finally, the binding to thymocytes of insulin‐CTB conjugate, but not insulin, was inhibited by gangliosides. Thus, a hybrid hormone molecule has been constructed which has insulin‐like biological activity with the receptor specificity of cholera toxin in poorly responsive cells.
Glucagon regulation of amino acid transport in hepatocytes: Effect of cell enucleation
Authors: Crettaz Marco , Ronald Kahn C. , Fehlmann Max 
Published: February 2005

AbstractGlucagon and cAMP analogs stimulate amino acid transport in freshly isolated hepatocytes by inducing the synthesis of new transport proteins. The role of the cell nucleus in the glucagon regulation of amino acid transport has been studied in rat hepatocytes enucleated by centrifugation through a discontinuous Ficoll gradient in the presence of cytochalasin B. Enucleated hepatocytes take up alpha‐aminoisobutyric acid (AIB) through a Na+‐dependent transport component with kinetic properties similar to those found in intact hepatocytes. Cytoplasts prepared from glucagon‐stimulated cells retain the increase AIB transport induced by the hormone in the intact cells. The direct addition of glucagon to cytoplasts has no effect on AIB transport, in spite of the fact that the cytoplasts exhibit a higher capacity to bind glucagon than their nucleated counterparts. These data indicate that the nucleus is required for the glucagon stimulation of amino acid transport in isolated hepatocytes.
Consequences of parental exposure to epidermal growth factor for progeny cell division
Authors: Heath John K. 
Published: February 2005

AbstractThe consequences of parental exposure to epidermal growth factor (EGF), for progeny cell cycle times was investigated. Slowly dividing mouse 3T3 fibroblasts were exposed to EGF for 8 hr, the EGF was withdrawn, and the cell cycle times of parental and progeny cells were measured by time‐lapse video microscopy. It was observed that exposure to EGF induced a round of cell division following a lag phase of approximately 8 hr. The progeny of these cells exhibited accelerated cell cycle times compared to cells that had not been exposed to EGF. Parental cell division time was significantly correlated with progeny cell cycle time. Sibling progeny cell cycle times were also significantly correlated. EGF can therefore apparently exert an effect on the cell cycle times of more than one generation of cells.
Hemopoiesis in spleen and bone marrow cultures
Authors: Keller Gordon M. , Johnson Gregory R. , Phillips Robert A. 
Published: February 2005

AbstractLong‐term cultures established from spleen cells were compared to those established from bone marrow cells for their ability to maintain hemopoiesis as measured by the presence of hemopoietic progenitor cells (in vitro CFU) and multipotent stem cells (CFU‐S). The frequency of both in vitro CFU and CFU‐S increased dramatically during the first 2 weeks in the spleen cultures. Following this early peak of activity, the number of progenitors and stem cells declined to undetectable levels by week 6 of culture. During this short phase of hemopoiesis, large amounts of GM‐CSF could be detected in the supernatant of the spleen cultures. In contrast, bone marrow cultures did not share this early peak of hemopoiesis; however, they maintained activity for much longer periods of time than did the spleen cultures. When spleen stem cells were seeded onto functional bone marrow adherent cells, spleen‐derived in vitro CFU were maintained well beyond week 6 of culture. Spleen cultures established from athymic nu/nu mice showed a greatly reduced ability to support hemopoiesis while those from S1/S1d mice maintained GM‐CFU as well as cultures from normal mice.
Changes in water proton relaxation times and in nuclear to cytoplasmic element gradients during meiotic maturation of Xenopus oocytes
Authors: Cameron I. L. , Labadie D. R. L. , Hunter K. E. , Hazlewood C. F. 
Published: February 2005

AbstractFully grown oocytes 1.2mm in diameter were removed from Xenopus laevis ovaries and were exposed to progesterone (2.5 μg/ml in Ringer's solution) to induce completion of the first maturation division or germinal vesicle breakdown (GVBD). This process required 5.5 ± 0.5 hr. Neither oocyte vo ume nor water content was observed to change throughout muturation. At selected times, the oocytes were quick frozen in liquid propane and cryosectioned. The sections were freeze‐dried, and analyzed for K, Na, Cl, P, S, and Mg in millimolar per kilogram dry weight content in the nucleus and the yolk‐free cytoplasm using electron probe X‐ray microanalysis. Unstimulated oocytes showed significant nuclear to yolk‐free cytoplasmic content gradients (N/C ratio) for the following elements: K (1.84), P (0.65), and S (1.56), but significant N/C content gradients were not found for Na and Mg. By 10 min after progesterone stimulation, a significant change in the N/C ratio of the following elements had occurred due to a rapid increase in nuclear content: K (2.29), Cl (2011). A significant N/C ratio for Mg (1.35) had developed by 10 min after progesterone stimulation and a significant N/C ratio for Na (2.07) had developed by 45 min. In addition the following elements showed significant content increases in both the nucleus and the yolk‐free cytoplasm from the time prior to progesterone stimulation to the time just prior to GVBD at 240 min: K, Na, Cl, P, S, and Mg. Nuclear magnetic reasonance measurements of the spin‐lattice relaxation time (T1) of water proton in oocytes showed a sinificant increase in the T1 time after progesterone exposure. The changes in N/C ratios of specific elements and in the physical parameter of water proton relaxation time suggest that progesterone is responsible for inducing changes in the physicochemical interactions between various macromolecules, specific elements, and water.
Comparative studies of collagen lattice contraction utilizing a normal and a transformed cell line
Authors: Buttle David J. , Ehrlich H. Paul 
Published: February 2005

AbstractDifferences between the behavior of cultured rat skin fibroblasts and that of a line of transformed rat sarcoma cells incorporated into a polymerized collagen lattice were examined. Fibroblast‐populated collagen lattices (FPCL) were manufactured. Within 24 to 48 hr after manufacture, both cell lines reduced lattice size by a process known as lattice contraction. Contraction occurred more rapidly in both cell lines when the media were supplemented with 25% serum rather than the usual concentration of 10% serum. Similar growth patterns were observed with transformed cells within collagen lattices and on plastic surfaces. Normal rat fibroblasts were found to contract lattices faster than transformed cells. At the end of a 2‐week period, the final contracted size of the transformed cell lattice was the same as that of normal cell lattices. The cellular density of transformed cells within the FPCL was eight times greater than that of FPCL made with normal rat cells. Normal rat fibroblasts elongated and flattened more, and organized the collagen matrix to a greater degree, than did transformed cells. In this instance, therefore, lattice contraction was shown to be linked more to the process of fibroblast elongation and collagen fiber organization than to cell number or density.
Cell growth and differentiation in vitro in mouse macrophages transformed by a tsA mutant of simian virus40. I. Cellular response in proliferative and phagocytic activities to the shift of temperature differs depending on the culture state in mouse bone marrow cells transformed by the tsA640 mutant of simian virus 40
Authors: Tanigawa Takahiko , Takayama Hisao , Takagi Atsushi , Kimura Genki 
Published: February 2005

AbstractIt was shown previously that mouse bone marrow cells transformed by simian virus 40 (SV40) show a reversible cell density‐dependent phenotypic transition between the nonmacrophage (rapidly growing) and the macrophage (stationary) states; cells in low‐density cultures are in the growing phase, express SV40 T antigen strongly as revealed by immunofluorescence, and lose typical macrophage properties such as immune phagocytosis; whereas cells in high‐density cultures are in the stationary (nongrowing) phase, express SV40 T antigen weakly, and recover their macrophage properties (Takayama, 1980). In the hope of clarifying the relationship between T antigen, cell growth, and macrophage‐specific cellular function, we examined the behavior at 33 and 39°C of mouse bone marrow cells transformed by an SV40 gene A mutant (tsA640) whose mutation renders the molecular weight of 90K (large) T antigen temperature sensitive. The results presented in this paper suggest that functional large T antigen is required for cells in the stationary phase to initiate multiplication when transferred at lower density and is not necessary for a majority of them to maintain the nongrowing state (viability) at both high and lower cell densities, whereas it is required for cells in the growing phase to keep multiplying without losing their viability. The results also suggest that the functional large T antigen does not play a direct role in maintaining the cells as either phagocytic or nonphagocytic. It is also suggested that the physiological or tsA mutation‐mediated arrest of growth may or may not be accompanied by induction and/or maintenance of cellular phagocytic activity depending on the culture state.
Glucocorticoid receptors and cortico‐sensitivity in a human clonal monocytic cell line, CM‐SM
Authors: Ranelletti F. O. , Starace G. , Piantelli M. , Lambertenghi‐Deliliers G. , Revoltella R. P. 
Published: February 2005

AbstractCM‐SM is a clonal line of human precursor mononuclear phagocytes inducible to macrophage differentiation in response to the tumor promoter phorbol ester 12‐O‐tetradecanoyl‐phorbol‐13‐acetate (TPA). Untreated CM‐SM cells contain single class, high‐affinity (KD = 4.0 × 10−9 M) glucocorticoid‐specific receptor sites (∼60,000 per cell), as measured by a whole cell assay, at 37°C, using [3H]triamcinolone acetonide (TA). Exposure of CM‐SM to dexamethasone (DEX) produced a progressive, dose‐ and time‐related series of changes in CM‐SM cell growth, saturation density, morphology, and functional properties, with half‐maximal effects at about 10−9 M for DEX. TA‐receptor sites rapidly decreased (about 70%) after DEX treatment, without any apparent change in steroid specificity and affinity. After 5 days in culture with a saturating concentration (3.6 × 10−8 M) of hormone, the cells reached a saturation density of about 9.0 × 106 viable cells/ml (about 4.0 × 106 viable cells/ml in the controls), while the modal volume of the resulting cell population was approximately 60%, as compared to the volume of untreated cells. DEX‐treated cells appeared less differentiated than controls, as assessed by combined morphologic, antigenic, and cytoenzymatic analyses. DEX almost completely inhibited TPA activation of the following macrophage functions: adherency to the culture plate, expression of lysosomal enzymes, Fc and C3 receptors, and stimulation of phagocytosis. After removal of DEX, the cells, within a few passages, returned to a state apparently identical to the untreated controls and could be induced to macrophage differentiation in response to TPA.
A multicomponent analysis of amino acid transport systems in human lymphocytes. 1. Kinetic parameters of the A and L systems and pathways of uptake of naturally occurring amino acids in blood lymphocytes
Authors: Segel George B. , Simon William , Lichtman Marshall A. 
Published: February 2005

AbstractWe have determined the kinetic parameters of natural and system‐specific synthetic amino acid transport by human blood lymphocytes, using a multi‐component computer analysis that separates carrier‐mediated uptake from diffusion. These studies were initiated in order to provide the basis for studies of human blood T and B lymphocytes and malignant lymphocytes. Methylaminoisobutyric acid (methyl‐AIB) and 2‐amino‐2‐carboxy‐bicyclo (2,2,1) heptane (BCH) uptakes into lymphocytes were measured as prototypes of A‐ and L‐system amino acid transport. The Michaelis constant for methyl‐AIB uptake was 540 μM; the maximal velocity of uptake was 28 μmol/L cell water/min, and the diffusion coefficient was .004 min−1. In contrast, the Michaelis constant for BCH uptake was 63 μM; the maximal velocity was 969 μmol/L cell water/min, and the diffusion coefficient was .141 min−1. The transport of the naturally occurring amino acids, alanine, proline, and leucine was defined by studies of: (1) competitive inhibition with the system‐specific synthetic amino acids, methyl‐AIB and BCH, (2) the effect of the transcellular sodium gradient on transport, and (3) evaluation of the time‐dependent increase of transport in amino acid‐deficient medium (adaptation). Alanine was transported principally (∼70%) by the ASC‐system, and leucine was transported principally (70%) by the L‐system in lymphocytes. The analysis of proline transport was more complex because of a large component of uptake by diffusion even at low amino acid concentrations. Taken together, the kinetics of sodium‐sensitive uptake and the results of competitive inhibition studies indicated that proline was transported by the A‐system (30%), the ASC system (30%), and also by the L‐system (15%).