bluuebunny/crossref_metadata_2025_split huggingface dataset:
A reduction in energy‐dependent amino acid transport by microtubular inhibitors in ehrlich ascites tumor cells
Authors: Fyfe Mary Jo , Loftfield Sharon , Goldman I. David 
Published: February 2005

AbstractVincristine, other periwinkle alkaloids, and colchicine partially inhibit the energy dependent transport of α‐aminoisobutyric acid in Ehrlich ascites tumor cells. The properties of this phenomenon were characterized in detail for vincristine. Maximum depression of the steady‐state intracellular α‐aminoisobutyric acid level was achieved with a vincristine concentration of > 0.5 m̈M. The inhibitory effect of vincristine increases as the extracellular α‐aminoisobutyric acid concentration is increased reaching a maximum, however, of only ∼25% at a level of 5 mM, leaving a large gradient for α‐aminoisobutyric acid across the cell membrane. Vincristine produced an asymmetrical effect on the bidirectional fluxes decreasing the initial uptake rate, while increasing the efflux of α‐aminoisobutyric acid. Inhibition of net α‐aminoisobutyric acid transport by vincristine was partially reversible (∼40%). Colchicine (50 m̈M) reduced the steady‐state α‐aminoisobutyric acid level by 30%, an effect that was not reversible. Inhibition by vinleurosine and vinrosidine was comparable to that of vincristine. Addition of glucose to the medium resulted in a small, but significant, decrease in the inhibitory effects of both vincristine and colchicine.The data indicate that these agents inhibit a small component of the uphill transport of α‐aminoisobutyric acid in Ehrlich ascites tumor cells. The inhibitory effect of vincristine cannot be attributed to an increase in the passive permeability of the cell membrane to this agent. Rather, the data along with other studies from this laboratory suggest that vincristine reduces the energy‐dependent transport of α‐aminoisobutyric acid by either inhibiting cellular energy metabolism or by inhibiting the coupling of energy‐metabolism to the transport of this amino acid and raises the possibility that cellular microtubules play a role in these processes.
Cell Attachment to cllagen: The requirement for energy
Authors: Klebe Robert J. 
Published: February 2005

AbstractIt has previously been demonstrated that cell attachment to collagen depends on the presence of a serum‐derived cell attachment factor. Two steps in the cell attachment process have been defined. First, the cell attachment factor can bind to collagen in the absence of divalent cations. Secondly, either Ca++ or Mg++ are required for cells to attach to the collagen‐cell attachment factor complex. A third requirement for cell attachment to collagen is demonstrated here; namely, cellular metabolic energy.A simple method for the assay of ATP in tissue culture cells is presented.
Effect of pharmacological agents on human keratinocyte mitosis in vitro. II. Inhibition by catecholamines
Authors: Harper Robert A. , Flaxman B. Allen 
Published: February 2005

AbstractCatecholamines produce mitotic inhibition in primary cell cultures of human keratinocytes probably via a block in the G2 part of the cell cycle. Epinephrine produced significant mitotic inhibition (49%) at a concentration as low as 4.5 × 10−10 M, while its analog, isoproterenol, produced 47% inhibition at 1 × 10−10 M. Norepinephrine elicited a 49% inhibitory response at 1 × 10−8 M. One other catecholamine, dopamine, caused a 53% decrease in mitosis at 1 × 10−6 M. Other structurally related amines to exhibit mitotic inhibition were phenylephrine, 58% at 1 × 10−7 M; octopamine, 47% at 1 × 10−5 M; and tyramine, 52% at 1 × 10−4 M. Serotonin showed no mitotic inhibition at 1 × 10−4 M.Various alpha and beta adrenergic blocking agents were added to the cell system. The alpha blocking agent, phentolamine, had no effect on mitosis. When added in conjunction with epinephrine or norepinephrine, no reduction of the catecholamine‐induced mitotic inhibition was observed. The beta blocking agent, propranolol, by itself showed slight mitotic inhibition at 1 × 10−6 M. When added along with epinephrine or norepinephrine, propranolol reduced the catecholamine‐induced mitotic inhibition approximately 65%. In addition, propranolol blocked mitotic inhibition caused by phenylephrine, an alpha adrenergic agent. However, another beta blocking agent, dichloroisoproterenol, showed strong mitotic inhibition (53%) when added alone to the cultures at a concentration of 1 × 10−8 M. The effect was reduced to zero in the presence of propranolol. These data suggest that while beta receptors may be involved in the catecholamine‐induced mitotic inhibition of human keratinocytes in vitro, the nature of the receptor‐molecule interaction may be complex.
The effects of a glucocorticoid on the cell surface of RLC‐GAI cells
Authors: Berliner Judith A. , Gerschenson Lazaro E. 
Published: February 2005

AbstractThe purpose of these studies was to examine the effects of a synthetic glucocorticoid, dexamethasone sodium phosphate, on the cell surface of an epithelial cell line, RLCGAI, and to investigate the mechanism of these effects. Within hours after addition of dexamethasone sodium phosphate to the cultures, the cells begin to spread going from a more bipolar to a more epithelioid form; this change is maximal by 24 hours. In the spread cells the density of surface microvilli, as visualized in the scanning electron microscope, is considerably reduced. The changes in cell surface and shape elicited by the glucocorticoid are blocked by actinomycin D but not by hydroxyurea. Cell spreading is probably related to the configuration of cell microfilaments since these are increased in numbers in the presence of the hormone and spreading is inhibited by cytochalasin B. An important role of microfilaments in the general mechanism of action of glucocorticoids is suggested.
The effect of Lanthanum on electrophoretic mobility and passive cation movements of the ehrlich ascites tumor cell
Authors: Smith Thomas C. 
Published: February 2005

AbstractWe have investigated the effects of La+3 binding to the surface of Ehrlich ascites tumor cells on cell electrophoretic mobility and passive movements of Na+ and K+. Incubation of tumor cells in La+3‐containing media results in a La+3 concentration‐dependent decrease in net surface charge negativity. At [La+3] greater than 0.5 mM, the net surface charge becomes positive with maximum positivity occurring at [La+3] = 0.9 mM. The effects of La+3 binding on passive Na+ and K+ movements were investigated by following 22Na and K+ losses from ouabain‐inhibited cells. Neither low (0.02) nor high (1.0 mM) [La+3] had any effect on the K+ efflux rate coefficient. 22Na losses from control and La+3‐treated cells were consistent with washouts from two cellular compartments. Low [La+3] (0.02 mM) was without effect on Na+ loss from the cells. However, higher [La+3] (1.0 mM) resulted in a 48% inhibition of Na+ loss from the more slowly exchanging compartment. These results are not consistent with simple electrostatic interactions exerting a major influence on the passive movements of Na+ and K+. It is suggested that La+3 interacts with sites specific for Na+, perhaps involved in a carrier‐mediated exchange system.
Rapid breakdown of diphosphoinositide and triphosphoinositide in erythrocyte membranes
Authors: Garrett N. E. , Burriss Garrett R. J. , Talwalkar R. T. , Lester Robert L. 
Published: February 2005

AbstractIncubation of rabbit erythrocytes with 32Pi resulted in labeling of membrane diphosphoinositide, triphosphoinositide, and phosphatidic acid. Hypotonic lysis at 37°C resulted in an extremely rapid breakdown of the labeled polyphosphoinositides. This breakdown could be retarded by lysis in the presence of EDTA and by lowering the temperature to 0° thus allowing preparation of membranes with minimum breakdown of the labeled lipids. Rapid breakdown of di‐ and triphosphoinositide in isolated membranes could be initiated by Ca++ or to a lesser extent by Mg++ and prevented by detergents and by heating to 75°C. Assay of radiolabeled lipid was carried out by a method which bypassed prior lipid extraction and which enabled sequential sampling of reactions at 10‐second intervals. This method was more convenient than standard procedures and gave yields of di‐ and triphosphoinositide equivalent to that obtained by the method of Folch.
Selection of chinese hamster somatic cell mutants after irradiation of BUdR‐Labelled cells
Authors: Thirion Jean‐Paul , Labrecque Romain , Vu Thuy‐Phung 
Published: February 2005

AbstractThe selection of somatic cell mutants after irradiation of BUdR‐labelled cells is improved with the use of a mercury lamp combined with a plastic sheet which filters the unwanted wave lengths below 303 nm. New somatic cell mutants defective for galactose metabolism or auxotrophe for fetal calf serum were thus isolated.
Control of normal differentiation of myeloid leukemic cells. X. Glucose utilization, cellular ATP and associated membrane changes in D+ and D− cells
Authors: Vlodavsky Israel , Fibach Eitan , Sachs Leo 
Published: February 2005

AbstractGlucose utilization, energy metabolism and associated membrane changes, have been studied in D+ myeloid leukemic cells that can be induced to undergo cell differentiation to mature granulocytes by incubation with the appropriate conditioned medium (CM) and in D− myeloid leukemic cells that cannot be induced to differentiate to mature cells. Before incubation with CM, glycolysis and the glycolytic production of ATP were lower and the activity of the pentose cycle was higher in D+ than in D− cells. ATP depletion induced a higher degree of agglutination by concanavalin A in D− than in D+ cells, indicating a difference in their surface membrane. There were no detectable differences in the transport of glucose and the synthesis of sterols and fatty acids. After incubation with CM, the D+ cells, like normal granulocytes, showed a higher glycolysis, produced their ATP more through glycolysis than oxidative phosphorylation, became less dependent on the exogenous supply of glucose and oxygen and had a lower rate of sterol and fatty acid synthesis. The differentiating D+ cells also showed a change in their surface membrane resulting in an increased agglutinability without a change in ATP content and a stimulation of the pentose cycle by concanavalin A. These properties, which were not acquired by D− cells, were found before most of the D+ cells had differentiated to mature granulocytes. The data indicate, that the block in the ability of the D− cells to differentiate and the acquisition of the metabolic properties of normal granulocytes by differentiating D+ cells, were associated with differences in the organization of the cell surface membrane.
Polynucleotide aggregates enhance the transport of protein at the surface of cultured mammalian cells
Authors: Ryser H. J.‐P. , Termini T. E. , Barnes P. R. 
Published: February 2005

AbstractIt was known that polycationic polymers enhance the entry of macromolecules into cells. We now show that polynucleotides may have similar effects, when used as large aggregates. Poly(1‐vinylcytosine):polyinosinic acid, an inducer of interferon production in human cells, can cause at 40 μg/ml a 75‐fold enhancement of albumin uptake by sarcoma cells in culture. Most of this activity (85%) is related to the presence of aggregates retained by 0.65 μ millipore membranes. The prior finding that enhancers of albumin transport have increasing effects with increasing molecular sizes may thus extend to complexes of supramolecular sizes.
The interaction of chloride with the sulfate transport system of ehrlich ascites tumor cells
Authors: Levinson Charles 
Published: February 2005

AbstractThe effect of Cl− on SO4−2 efflux was studied in both Cl−‐containing and Cl−‐free ascites tumor cells loaded with 35SO4−2 to test the hypothesis that Cl−‐SO4−2 exchange is mediated by the same mechanism responsible for SO4−2‐self exchange.The addition of Cl−‐free, 35SO4−2 loaded cells to a SO4−2‐free, Cl− medium results in: (1) SO4−2 efflux that is dependent on the extracellular Cl− concentration (Km = 4.85 mM; ke = 0.048 min−1 at 50 mM Cl−) and (2) net Cl−‐uptake that exceeds SO4−2 loss. Both SITS (4‐acetamido‐4′‐isothiocyanostilbene‐2,2′‐disulfonate) and ANS (1‐anilino‐8‐napthalene sulfonate) inhibit SO4−2 efflux but are without effect on Cl− uptake.The addition of Cl−‐containing, 35SO4−2 loaded cells to a SO4−2‐free, C1− medium results in: (1) a slight gain in cellular Cl− and (2) k efor SO4−2 efflux identical to that for Cl−‐free cells.The results are compatible with the suggestion that: (1) Cl− interacts with a membrane component responsible for transmembrane SO4−2 movement; (2) Cl− interaction stimulates the rate of unidirectional SO4−2 efflux from cells initially free of Cl− as well as the rate of SO4−2 turnover in cells maintained in the steady state with respect to Cl− and SO4−2; and (3) in the case of cells initially free of Cl−, the Cl−‐SO4−2 pathway represents only a small fraction of the total unidirectional Cl−‐influx the remainder being compatible with the electroneutral accumulation of NaCl and KCl.
Nucleotidase activity in regenerating liver and in clonal strains of hepatoma and pituitary cells in culture
Authors: Tjernshaugen Hans , Gautvik Kaare M. 
Published: February 2005

AbstractA nucleotidase of the combined 3′‐ and 5′‐type (nucleotide phosphohydrolase, E.C.3.1.3.31) was present in the cytosol of regenerating rat liver cells, and of rat hepatoma and pituitary cells in culture. The enzyme activity per milligram of cell protein was very similar in regenerating liver and in three of the different cell types. The hepatoma cell strain which showed the slowest growth rate had a three‐fold higher basal enzyme activity. After the first days of regenerative growth in rat liver and during early plateau phase of cell growth, there was a 50–120% increase in specific enzyme activity. In the hepatoma cells, the enzyme activities were also compared to the cellular content and synthesis of RNA and DNA. The increase in enzyme activity occurred concomitantly with a reduced incorporation of 3H‐thymidine into DNA. The possible physiological role of this nucleotidase in nucleic acid and nucleotide metabolism is discussed.
Cell surface control in Blepharisma intermedium (Protozoa ciliata). Blocking of gamone II‐induced homotypic pairing by different membrane interacting ligands
Authors: Ricci Nicola , Esposito Fulvio , Nobili Renzo , Revoltella Roberto 
Published: February 2005

AbstractPHA, Con‐A, or anti‐tubulin antibodies inhibit homotypic pair formation, in B. intermedium mating type‐I cells in the presence of suboptimal concentrations of gamone II. The inhibition is dependent on the dose of gamone added; the structural conformation and the relative concentration of the inhibitor; and the time of addition of the inhibitor. The block can be selectively prevented by competitive inhibitors of each ligand. The receptors for the inhibitors are distinctive and there is no cross‐reaction between the ligands. It is concluded that ligand binding and subsequent receptor‐ligand aggregation must induce a change within the cell‐surface membrane, which distorts the distribution and/or affects an optimal conformational aspect of a specific membrane‐receptor system for the gamone, a prerequisite for cell pair formation.
Selective isolation of reversible cold sensitive variants from chinese hamster ovary cell cultures
Authors: Ohlsson‐Wilhelm B. M. , Freed J. J. , Perry R. P. 
Published: February 2005

AbstractVariants of the Chinese hamster ovary cell line CHO‐K1 (ATCC CCL 61) which grow almost normally at 38.5°C but very poorly or not at all at 30°C were obtained after treatment with mutagens and application of an indirect selection procedure. Two kinds of variants were recovered. In the first of these, the cold sensitive phenotype is expressed completely only at low cell densities. At higher cell density, growth continues at the nonpermissive temperature, but at a reduced rate. In the second class, the cold sensitive phenotype is independent of cell density. Two members of the latter class were studied in detail. In both lines, after shift to the nonpermissive temperature, the rate of 3H‐thymidine incorporation declines markedly; the rates of 3H‐uridine and 3H‐phenylalanine uptake are less drastically reduced. Autoradiographs indicate that the decline in thymidine uptake at the nonpermissive temperature is due to an elongation of part of the cell cycle, so that a smaller proportion of the cells lie in the synthetic (S) phase of the cell cycle with a consequent reduction in the fraction of labeled cells. The uridine labeling patterns of the mutants appear to rule out a ribosomal lesion. Low temperature growth inhibition of both cell strains was reversible. In one of the cell lines, an apparent stretching of the cells at the low temperature produces substantial alterations in cell shape.
The partial replacement of the serum growth factor requirement of SV3T3 cells by lactalbumin hydrolyzate
Authors: Young Delano V. 
Published: February 2005

AbstractLactalbumin hydrolyzate (LH), a commercially prepared, enzymatic digest of a milk protein fraction, can partially replace the serum requirement of SV3T3 cells. In a low, but obligatory, background of calf serum (0.15% v/v), LH causes a large increase in the final cell density (5–10 x over the control) while modestly stimulating the actual growth rate. Lactalbumin hydrolyzate does not contain survival activity for SV3T3 cells and does not affect the growth of 3T3 cells.Since even prolonged exposure to pH 4 or 2 results in complete abolishment of the growth‐rate stimulatory capability without affecting the capacity to increase the final cell density, it is possible that the LH growth activity may consist of two dissociable components. All of LH growth activity is water soluble, autoclavable, and resists proteolytic treatment. On Sephadex G15 growth activity appears as a single peak at the void volume but on G25 it is retained beyond the void volume as a broad, skewed peak. The relevant molecular weight range lies between 1,500 and 4,000. The putative low pH resistant material is strongly adsorbed to Dowex 1 × 2 and can be displaced from the column by a reduction in the pH.A comparison of the properties of the LH factors with those of known growth promoting agents isolated from serum and various enzymatic digests indicates that these new factors do not correspond to any of these agents.
Stimulation by N6,O2′‐dibutyryl adenosine 3′,5′‐cyclic monophosphate of RNA and DNA synthesis and of cell proliferation of rat hepatocytes in primary tissue culture
Authors: Armato Ubaldo , Draghi Enrica , Andreis Paola G. , Meneghelli Virgilio 
Published: February 2005

AbstractThe effects of DBcAMP in doses from 1.5 × 10−8 to 1.5 × 10−3 M on the compartmental apparent surface area (ASA) and (5‐3H)uridine radioactivity concentration (URC), (methyl‐3H)thymidine labelling index per 1 hour ([Me‐3H]Tdr LI/h) and per cent mitotic index (MI%) and colchicine metaphase index (CMI%) of young rat differentiated hepatocytes in primary tissue culture were investigated by morphometric and radioautographic methods. In these cells DBcAMP was found to elicit: (1) progressive increments in the ASA of nucleoli, karyoplasm and cytoplasm; (2) peak increases in nucleolar URC at 1.5 × 10−8 and 10−5 M, but a slight decrease at 1.5 × 10−3 M; (3) significant increments in karyoplasmic and total nuclear URC at all doses, except at 1.5 × 10−6 and 10−4 M, when such parameters remained at control levels; (4) steady and progressive increases in cytoplasmic and total cell URC values; (5) marked increments in (Me‐3H)Tdr LI/h, MI% and CMI% up to the dose of 1.5 × 10−4 M, but at 1.5 × 10−3 M these parameters were found to be either much less enhanced or to approach closely to control values.cAMP in doses from 1.5 × 10−8 to 10−4 M also markedly incremented the in vitro hepatocyte CMI%, while having a lesser stimulatory effect at 1.5 × 10−3 M.Finally of the various possible metabolites of DBcAMP administered at 1.5 × 10−8 M to liver cultures, N6‐ and O2′‐MBcAMP and, again, cAMP significantly increased the CMI% of cultured hepatocytes, whereas 5′‐AMP, adenosine and allantoin had no significant effect and Na‐butyrate slightly decreased it.The present observations strengthen the hypothesis that cAMP and its butyrated derivatives, by possibly amplifying the template activity of the liver chromatin, accelerate the flow of differentiated primary young rat hepatocytes into the various stages of the mitotic cell cycle.
Variation in melanosome numbers in cultured B‐16 melanoma cells
Authors: Doezema Philip , Slesinski Ronald S. 
Published: February 2005

AbstractMelanosomes from B‐16 mouse melanoma cells in culture were isolated by treatment of pigmented cells with 2% SDS, sonication, and heating at 100°C. The total number of melanosomes in cultures of B‐16 mouse melanoma cells increased exponentially during the rapid phase of sigmoid growth. The numbers of melanosomes per cell decreased during rapid phase of growth, and repigmentation was observed only when the cultures attained the stationary growth phase. BUdr at a minimum concentration of 0.5 μg/ml decreased both cell growth and numbers of melanosomes per cell, and completely inhibited repigmentation following a period of active growth. Cells cultured in 0.1 μg/ml BUdr grew at the same rate as untreated cells but contained fewer melanosomes/cell and lower total numbers of melanosomes during the late stages of the growth cycle.
Stimulation of WI‐38 cell cycle transit: Effect of serum concentration and cell density
Authors: Bartholomew James C. , Neff Nicola T. , Ross Priscilla A. 
Published: February 2005

AbstractFlow microfluorometry has been used to characterize the effects of serum concentration and cell density on the initiation of cell cycle transit of stationary phase (G0) human diploid fibroblasts (strain WI‐38). The concentration of serum used to stimulate these cultures had no effect on the time cells began appearing in S (the DNA synthetic period), nor on the synchrony with which they moved around the cell cycle. However, as the serum concentration increased, the fraction of the stationary phase population released from G0 increased. Cell density modulated the ability of serum to stimulate cell cycle traverse. For example, at a cell density of 1.81 × 104 cells/cm2, 78% of the population was sensitive to serum stimulation; whereas, when the density was increased to 7.25 × 104 cells/cm2, only 27% of the population could be stimulated. This effect of cell density on the serum response is not simply the result of changing the ratio of serum concentration to cell density, but appears to reflect a true modulation of the population's sensitivity to serum stimulation. These results are consistent with the interpretation that the primary action of serum is to determine the transition of cells from a non‐cycling G0 state to a cycling state and that cell density determines the proportion of the population capable of undergoing this transition.