bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calcium effects on epidermal growth factor receptor‐mediated endocytosis in normal and SV40‐transformed human fibroblasts
Authors: Tupper Joseph T. , Bodine Peter V. 
Published: February 2005

AbstractLowering of extracellular Ca2+ levels will reversibly arrest the growth of human fibroblasts (WI38). Simian virus40(SV40)‐transformed WI38 cells do not exhibit this Ca2+‐dependent arrest. One possibility for this difference in Ca2+ requirement is that extracellular or surface membrane‐bound Ca2+ may be required for growth factor receptor‐mediated endocytosis and this Ca2+ requirement may differ in normal versus transformed cells. In this study we have evaluated the role of Ca2+ in the binding, internalization, and degradation of epidermal growth factor (EGF) in the WI38 and SV40 WI38 cell. The binding of [125I]EGF to the cell surface is not significantly altered by lowering of Ca2+ to 10−5‐M levels in either the normal or transformed cell. At this Ca2+ level, growth of the normal cell is inhibited. The subsequent internalization of EGF is reduced nearly threefold in the normal cell but not in the transformed cell following Ca2+ deprivation. Degradation of the EGF‐receptor complex is also sensitive to Ca2+. A twofold reduction in the rate of release of acid‐soluble 125I occurs in the normal but not the transformed cell under conditions of lowered medium Ca2+. In contrast, 2‐chloro‐10‐3‐aminopropyl phenothiazine (CP), an inhibitor of the Ca2+‐dependent regulator protein calmodulin, causes an inhibition of [125I]EGF internalization and degradation in both the normal and transformed WI38 cell, and a marked inhibition of [125I]EGF binding to the cell surface receptor of the transformed cell but not the normal cell.
Analysis of morphology and receptor metabolism in clonal variant A431 cells with differing growth responses to epidermal growth factor
Authors: Lifshitz Aliza , Lazar Cheri S. , Buss Janice E. , Gill Gordon N. 
Published: February 2005

AbstractHuman epidermoid carcinoma A431 cell clones have been obtained whose growth is inhibited, stimulated, or unaffected by epidermal growth factor (EGF). In clones exhibiting each type of growth response, EGF induced similar morphologic changes consisting of aggregation of cells into dense clusters with baring of large areas of the culture dish. The similarity of the clones' morphologic responses, despite their differing growth responses, indicates that the effects of EGF on morphology are distinct from effects on growth. Cells whose growth was inhibited by EGF contained high numbers of EGF receptors, whereas the concentration of EGF receptors was reduced in cells whose growth was stimulated or unaffected by EGF. There were, however, no consistent differences in EGF receptor concentrations between stimulated or null clones. Cells that exhibited each type of growth response displayed similar rates of EGF binding to receptors, rates of internalization of EGF, and rates and extent of EGF‐induced receptor down‐regulation. Changes in EGF‐stimulated tyrosine‐specific protein kinase activity paralleled changes in EGF receptors, both between clones and upon down‐regulation. These studies indicate that a reduction in the concentration of EGF receptors in A431 cells allows escape from the growth inhibitory effects of EGF, but suggest that the pattern of growth response depends on biochemical events subsequent to EGF‐receptor metabolism and activation of tyrosine‐specific protein kinase.
Inhibition of chemotactic factor‐induced neutrophil responsiveness by arachidonic acid
Authors: Naccache P. H. , Molski T. F. P. , Volpi M. , Mackin W. M. , Becker E. L. , Sha'Afi R. I. 
Published: February 2005

AbstractArachidonic acid when added simultaneously with the chemotactic peptide formyl‐methionyl‐leucyl‐phenylalanine (f‐Met‐Leu‐Phe) inhibits the ability of the latter to initiate several but not all of its effects on rabbit peritoneal neutrophils. Stimulated neutrophil aggregation, calcium uptake, and increases in the steady state level of exchangeable calcium are all inhibited by 1–10 μM arachidonic acid. The binding of f‐Met‐Leu‐Phe and the parameters of intracellular calcium redistribution (calcium efflux and changes in the steady state level of exchangeable calcium in the absence of extracellular calcium) and of stimulated sodium uptake are, on the other hand, unaffected by the same concentrations of arachidonic acid. Arachidic acid, the saturated analog of arachidonic acid, was found not to inhibit f‐Met‐Leu‐Phe‐stimulated aggregation and calcium uptake. Arachidonic acid, therefore, in addition to its well‐described agonist properties, also possesses antagonist activities toward rabbit neutrophils. These results add a new level of complexity to the study of the role of arachidonic acid in cell activation.
A voltage‐clamp study of the effects of colchicine on the squid giant axon
Authors: Chang D. C. 
Published: February 2005

AbstractThe effects of colchicine applied inside a squid giant axon were studied using voltage‐clamp and internal perfusion techniques. It was found that colchicine selectively and reversibly suppresses the sodium conductance during excitation. The possible involvement of the microtubular structure in the functioning of the excitable channel is discussed.
Comparative energy metabolism in cultured heart muscle and hela cells
Authors: Stanisz Jolanta , Wice Burton M. , Kennell David E. 
Published: February 2005

AbstractThe yields of energy from oxidation of fatty acids, glucose, and glutamine were compared in cultures of chick embryo heart muscle (heart) and HeLa cells. Aerobic energy production, as measured by oxygen utilization, was comparable in the two cell types. In media containing dialyzed sera, the rates of incorporation of fatty acids directly into lipids were similar in both cells and accounted for > 97% of fatty acid metabolism in HeLa cells. However, in heart cells only 45% ended in lipid, 42% in protein, and 13% was released as CO2; the latter two products probably reflect the oxidation of fatty acids to acetyl‐coenzyme A (‐CoA) and its subsequent metabolism in the citrate cycle. Increased serum concentration in the medium did not affect fatty acid metabolism in HeLa cultures, but resulted in greater oxidation by heart cells (> 100 times that by HeLa cells).The metabolisms of both glucose and glutamine were similar in heart and HeLa cells with ⩾ 60% of glucose carbon ending as medium lactate and only 3–5% converted to acetyl‐CoA. About 25% of glutamine carbon ended as CO2 and increased utilizations with increasing serum concentrations was accountable in both cells by increased lactate from glucose and glutamate from glutamine. CO2 production (and energy) from glutamine was independent of glutamine concentration within a tenfold range of physiological concentrations.The yields of energy have been calculated. In 10% dialyzed calf serum, oxidation of glutamine carbon provided about half of the total energy in heart cells, glucose about 35–45%, with most coming from glycolysis; oxidation of fatty acid carbon provided only 5–10%. That > 90% of the aerobic energy comes from glutamine in both cells can account for the comparable rates of oxygen utilization. HeLa cells derived little or no energy from fatty acids.
Hybrids between irradiated and unirradiated mammalian cells: Survival and chromosome segregation
Authors: Zelesco Paula A. , Graves Jennifer A. Marshall 
Published: February 2005

AbstractWe have studied the effect of X or γ irradiation, of one parent of a cell hybrid, on hybrid viability and chromosome segregation. The hybrid types studied were mouse‐Chinese hamster (which spontaneously lose a few hamster chromosomes) and Chinese hamster‐human (which spontaneously lose most of the human complement). Preirradiation of the segregated and retained cell parent resulted in highly asymmetric hybrid survival curves; survival was greatly reduced when the retained parent was irradiated, especially for hamster‐human fusions. Preirradiation of the parents of mouse‐hamster hybrids modified both the direction and the extent of chromosome segregation, but no consistent effect on elimination was observed for hamster‐human hybrids, and reversal of the direction of loss was never observed. These results are more consistent with the hypothesis that chromosome segregation from hybrids results from an intracellular chromosome selection, than with the hypothesis that cellular selection acts on randomly generated chromosome variants.
Isolation and characterization of a Chinese hamster ovary cell mutant which accumulates UDP glucuronic acid and requires uridine for growth
Authors: Patterson David , Vannais Diane B. , Laas William 
Published: February 2005

AbstractThe isolation and characterization of a new pyrimidine requiring mutant of Chinese hamster ovary cells (CHO‐KI, pro) is described. This mutant (P192) shows an absolute requirement for uridine for growth but is fully capable of pyrimidine nucleotide synthesis. P192 cells accumulate exceedingly large amounts of a compound identified by a variety of chromatographic, chemical, and labelling criteria as UDP glucuronic acid (UDPglcUA). This compound comprises approximately 60% of the acid‐soluble nucleotides of P192 cells. Possible genetic mechanisms leading to the phenotype of P192 are examined, and the role of UDPglcUA in cellular metabolism is discussed.
Mitogenic effect of prostaglandin E1 in Swiss 3T3 cells: Role of cyclic AMP
Authors: Rozengurt Enrique , Collins Mary K. L. , Keehan Margaret 
Published: February 2005

AbstractAddition of prostaglandin E1 (PGE1) to quiescent cultures of Swiss 3T3 cells rapidly elevates the intracellular levels of cAMP and increases the activity of adenylate cyclase in particulate fractions of these cells. In the presence of insulin, PGE1 stimulates the reinitiation of DNA synthesis. Both effects (increase in cellular cAMP and stimulation of DNA synthesis) are markedly potentiated by 1‐methyl‐3‐isobutyl xanthine (IBMX) or by 4‐(3‐butoxy‐4 methoxy benzyl)‐2‐imidazolidine (Ro 20–1724), both of which are potent inhibitors of cyclic nucleotide phosphodiesterase activity. In the presence of 50 μM IBMX, PGE1 caused a dose‐dependent increase in cAMP levels and in [3H]thymidine incorporation into acid‐insoluble material at concentrations (5–50 ng/ml) that are orders of magnitude lower than those used in previous studies (50 μg/ml) to demonstrate growth‐inhibitory effects. Thus, the inhibitory effects produced by adding high concentrations of PGE1 on the initiation of DNA synthesis in Swiss 3T3 cells are not mediated by cAMP and should be regarded as nonspecific. In contrast, the mitogenic activity of PGE1 parallels its ability to increase the intracellular levels of cAMP. The findings support the propostion that a sustained increase in the level of this cyclic nucleotide acts as a mitogenic signal for confluent and quiescent Swiss 3T3 cells.
Change in water proton relaxation time during erythrocyte maturation
Authors: Cameron I. L. , Dung H. C. , Hunter K. E. , Hazlewood C. F. 
Published: February 2005

AbstractErythrocyte populations from newborn and mature mice were characterized according to: size; ultrastructural features; water content; concentration of intraerythrocyte elements including Na, Cl, K, P, S, Mg, and Fe; and the spin‐lattice (T1) and spin‐spin relaxation times of water protons as measured by nuclear magnetic resonance (NMR) spectroscopy. A significant increase in the T2 time from 142 ± 3 msec to 184 ± 3 msec occurred during erythrocyte maturation. This change in T2 time was correlated with a change from a polyribosome‐rich hemoglobin‐poor cell type to a polyribosome‐absent hemoglobin‐rich cell type. The change in T2 time could also be correlated to a significantly higher K and P concentration in the mature erythrocytes. The change in T2 time was not correlated to a change in cellular water content or to the concentration of any of the other elements measured by electron probe X‐ray microanalysis. If the NMR relaxation times of water molecules truly reflect their average motional freedom, then the findings suggest that greater water ordering interaction occurs in the ribosome containing immature erythrocyte.
Properties of a cell growth inhibitor produced by mouse embryo fibroblasts
Authors: Wells Valerie , Mallucci Livio 
Published: February 2005

AbstractSecondary mouse embryo fibroblasts produce a growth inhibitor with the character of a thermolabile, nondialysable protein. The inhibitor was harvested from conditioned medium, and following G‐75 Sephadex fractionation it was isolated in one peak which consisted of two fractions eluting at approximately two thirds of the bed volume of the column where approximately 80 percent of the original activity was recovered with an increase in specific activity of about tenfold. Polyacrylamide gradient gel electrophoresis of fractions from L‐[35S] methionine‐labelled conditioned medium showed that the two fractions with growth inhibitory activity contained some 4–5 bands and shared the two major components. Cell cycle studies showed that the growth inhibitory effect was exerted after addition during early and late G1 and during S phase, and morphological studies showed that where growth was inhibited the morphological expression of the cells was altered.
Optimal conditions for proliferation of bone marrow‐derived mouse macrophages in culture: The roles of CSF‐1, serum, Ca2+, and adherence
Authors: Hume David A. , Gordon Siamon 
Published: February 2005

AbstractA method is described for the analysis of [3H]‐thymidine incorporation in microtitre cultures of bone marrow‐derived mouse macrophage responding to macrophage colony‐stimulating factor (CSF‐1). [3H]‐thymidine incorporation depends on cell density, culture medium, and the concentration of CSF‐1 and serum, but is independent of Ca2+. Bone marrow‐derived macrophages are strongly adherent, but adherence can be dissociated from [3H]‐thymidine incorporation.
Serum stimulates na entry and the Na‐K pump in quiescent cultures of epithelial cells (MDCK)
Authors: Reznik Vivian M. , Villela Javier , Mendoza Stanley A. 
Published: February 2005

AbstractThe growth of an epithelial canine kidney line (MDCK) was reversibly arrested by gradually lowering the serum concentration in the medium over a 3‐day period. The cells were demonstrably quiescent by autoradiography after an additional 24 hours in serum‐free media. Addition of fresh serum produced DNA synthesis after an 18‐hour lag period. The quiescent cells then grew to confluency retaining their transport capacities as seen by the formation of “domes”. This system allows for measurement of monovalent ion fluxes and its relationship to growth regulation. The addition of fresh serum to quiescent MDCK cells increased the uptake of 86Rb, a measure of Na‐K pump activity. This stimulation was mediated by increased uptake of Na into the cells. Serum‐stimulated DNA synthesis was blocked by the addition of ouabain in concentrations that inhibit the Na‐K pump. Serum appears to stimulate growth in epithelial cells by increasing the amount of intracellular Na available to the Na‐K pump. Monovalent ion transport may play a role in the regulation of epithelial cell proliferation.
Glycerol transport and phosphorylation by rat hepatocytes
Authors: Li Chien‐Chung , Lin E. C. C. 
Published: February 2005

AbstractThe entry of glycerol into isolated rat hepatocytes appears to be catalyzed by a specific carrier. At a physiological concentration of 0.1 mM, glycerol utilization is rate limited by the permeation step. Intracellular glycerol is trapped by an excess of glycerol kinase, which has a higher apparent affinity for the substrate than that of the membrane carrier. The entry of glycerol into the hepatocytes is highly sensitive to inhibition by monoacetin and cytochalasin B, but not by DL‐1,2‐propanediol, erythritol, D‐glucose, D‐galactose, D‐mannose, or D‐fructose.
Autocrine and paracrine growth stimulation of cells derived from human skin
Authors: Gilchrest Barbara A. , Karassik Rita L. , Wilkins Leon M. , Vrabel Michael A. , Maciag Thomas 
Published: February 2005

AbstractA sensitive serum‐free culture system was used to demonstrate that cells derived from normal human skin release soluble mediators which can modulate keratinocyte, melanocyte, and fibroblast growth in vitro. In M199 supplemented with epidermal growth factor, hydrocortisone, insulin, transferrin, triidothyronine, bovine serum albumin, and an extract of bovine hypothalamus, keratinocytes underwent approximately three to five cumulative population doublings (CPD) over a 7‐day period. Addition of 20% keratinocyte‐conditioned medium more than doubled keratinocyte growth and increased fibroblast growth 25–40% above controls. Dermal fibroblasts maintained in the same serum‐free hormone‐supplemented medium (SFHSM) alone underwent approximately 4.5–5.5 CPD over a 7‐day period; 20% fibroblast‐conditioned medium increased fibroblast growth 50–80% and increased keratinocyte growth 30–50%. Melanocytes maintained in the same SFHSM underwent approximately 1 CPD over a 14‐day period and 2 CPD if the medium was supplemented with 2% fetal bovine serum (FBS). Addition of 20% melanocyte‐conditioned medium more than doubled melanocyte growth in either SFHSM or in medium containing 2% FBS, but decreased both keratinocyte and fibroblast growth up to 30–60%. None of the conditioned media altered cellular morphology. These data provide the first demonstration of mutual growth modulation by cell types normally contiguous in vivo and expand existing evidence for autocrine and paracrine growth regulation by normal human cells.
Regulation and drug insensitivity of f‐actin association with adhesion areas of transformed cells
Authors: Carley William W. , Lipsky Mary G. , Webb Watt W. 
Published: February 2005

AbstractF‐actin aggregates have been found near the substrate attachments in a variety of transformed cells (Carley et al., 1981). Interference reflection microscopy shows that these aggregates are present in central close adhesion areas in Rous sarcoma virus (RSV)‐transformed rat kidney cells. If these transformed cells are incubated with N6, O2‐dibutyryl 3′:5′‐cyclic monophosphoric acid (db‐cAMP), adenosine (5′‐monophosphoric acid (5′‐cAMP) or adenosine, the F‐actin aggregates and their associated close adhesion areas disappear, and the cells flatten out. Treatment of untransformed cells with db‐cAMP spreads their local adhesion plaques and thickens microfilament bundles. Furthermore, f‐action aggregates are substantially more resistant to cytochalasin B and the Ca2+ ionophore A23187 than microfilament bundles in untrasformed cells. These differences between F‐acttin complexes in untransformed and in RSV‐transformed cells, with respect to morphology and sensitivities to db‐cAMP and cytoskeleton‐disrupting drugs, define properties of the change in F‐actin regulation and association with the plasma membrane due to transformation.
Immunofluorescent visualization of specifically bound thrombin reveals cellular heterogeneity in number and density of preclustered receptors
Authors: Carney Darrell H. 
Published: February 2005

AbstractThrombin binding to formaldehyde‐fixed mouse embryo (ME) cells was visualized by indirect immunofluorescence as a dot‐like pattern with dots of approximately 500 nm diameter located over the entire cell surface. Experiments comparing the binding of 125I‐thrombin and dot appearance on parallel cultures indicate that the immunofluorescent pattern is specific for thrombin‐binding to high‐affinity receptors. Similar patterns were observed on cells fixed in ethanol or glutaraldehyde prior to thrombin binding and on cells maintained at 4°C. These patterns were also observed in a number of established cell lines. Thus, thrombin receptors may be clustered prior to thrombin binding on all cells with these receptors. Comparing the amount of 125I‐thrombin bound to CHO cells with the number of fluorescent dots per cell indicated that each dot represents a cluster of over 1000 receptors. On ME cells, the number of thrombin receptor clusters per cell ranged from fewer than 50 to over 5,000. Based on previous studies, this indicates that on ME cells each cluster contains an average of approximately 200 thrombin binding sites with some cells having few, if any, receptors and others having more than a million receptors per cell.
Rat esophageal and epidermal keratinocytes: Intrinsic differences in culture and derivation of continuous lines
Authors: Heimann Ruth , Rice Robert H. 
Published: February 2005

AbstractSerially cultivated with 3T3 feeder layer support as colonies of stratified squamous epithelium, rat epidermal and esophageal epithelial cells were readily distinguishable by three critera. First, the epidermal colonies, exhibiting extensive piling up of squarnes in the centers, were more stratified than esophageal colonies. Second, in sparse culture 70 to 90% of the esophageal cells but as few as 1 to 5% of the epidermal cells were competent in cross‐linked envelope formation upon treatment with the ionophore X537A. After reaching confluence, up to 90% of the cells of both types formed envelopes upon ionophore treatment. Third, epidermal cells in suspension culture reached maximal levels of spontaneously cross‐linked envelopes in 1 day or less, while esophageal cells required about 4 days in suspension to reach maximal levels. A reproducible finding with both cell types was that initial colony‐forming efficiencies of less than 1% increased to about 40% upon serial passage with consequent derivation of continuous lines. Sparse cultures of esophageal cells with high colony‐forming ability retained a high degree of envelope competence (70 to 90%), indicating these two properties are not mutually exclusive. The derived lines exhibited reduced dependence upon feeder layer support at clonal density, but in suspension culture the cells did not grow and lost colony‐forming ability with a half‐time of several hours. We conclude that cells from these keratinized rat epithelia exhibit intrinsic differences in culture and become continuous lines expressing characteristic regulation of envelope competence and loss of germinative capability in suspension.