bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stimulation of 86Rb+ and 32Pi movements in 3T3 cells by prostaglandins and phorbol esters
Authors: Moroney J. , Smith A. , Tomei L. D. , Wenner C. E. 
Published: February 2005

AbstractThe potent tumor promoter tetradecanoyl phorbol acetate (TPA) induces early changes in ion movements analogous to those induced by prostaglandins E1 and F2α. Among the earliest changes induced by TPA is a significant increase in 32Pi incorporation within 15 minutes incubation of TPA (10−8−10−6 M) with post‐confluent Swiss 3T3 mouse embryonic fibroblasts. Similarly, the active phorbol ester homolog 4‐;β‐;OH phorbol didecanoate but not the inactive stereoisomeric 4‐β‐OH phorbol didecanoate stimulated 32Pi incorporation. Also, TPA at the above concentrations stimulated 86Rb+ influx shortly after administration. Both fluxes were ouabain‐sensitive in accord with the idea that an early effect of TPA is to alter (Na+ + K+)−ATPase activity. Further, prostaglandin E1 (10−7−10−6 M) and prostaglandin F2α (3 × 10−9−10−7 M) caused a similar stimulation of 86Rb+ and 32Pi uptake. The finding that water‐soluble prostaglandin F2α also exhibited stimulatory effects indicated that those hormone‐induced responses are not mediated by solvent interactions. The similar responses of phorbol esters and prostaglandin derivatives suggests that phorbol esters and prostaglandin derivatives may act at common membrane sitesThe finding that stimulatory effects were observed at discrete times in the logarithmic phase of growth suggests that the activation of membrane receptors may be cell‐cycle dependent.
Enhancement of the synthesis of specific cellular polypeptides in a temperature‐sensitive chinese hamster cell line (K12) Defective for entry into S Phase
Authors: Melero Jose A. , Fincham V. 
Published: February 2005

AbstractTemperature‐sensitive Chinese hamster cells (K12) have been shown to be defective for the initiation of new rounds of DNA replication when incubated at the restrictive temperature (40.5°). By temperature shift experiments with synchronous cultures, we have marked out the step at which the mutation is expressed as the four hours preceding the initiation of DNa synthesis. The block imposed by the mutation has been shown to be irreversible. In order to approach the biochemical characterization of the temperature‐sensitive function in K12 cells, we have analyzed the cellular proteins synthesized under permissive (35°) and restrictive temperatures. The synthesis of three polypeptides is markedly enhanced when K12 cells are incubated at 40.5°. One of them (band B) has turned out to be a useful biochemical marker of the expression of K12 mutation since its synthesis is not affected in other ts‐mutants or in hybrids in which K12 mutation is complemented. In addition, the alteration in band B synthesis is irreversible and occurs during the same stage of the cell cycle at which the mutated function is expressed.
Constancy of the shift‐up point in two temperature‐sensitive mammalian cell lines that arrest in G1
Authors: Ashihara T. , Chang S. D. , Baserga R. 
Published: February 2005

AbstractTwo cell cycle‐specific temperature sensitive (ts) mutants of mammalian cell lines, AF8 and K12, are known to arrest in G1 when shifted to the non‐permissive temperature. We have determined the entry into S of both AF8 and K12 cells in five different growth conditions, namely: (1) quiescent sparse cultures stimulated to proliferate by serum; (2) quiescent dense cultures stimulated by serum; (3) quiescent sparse cultures stimulated by trypsinization and replating; (4) quiescent, dense cultures stimulated by trypsinization and replating; and (5) mitotic cells collected by mitotic detachment. In addition, for each cell line and for each different growth condition, we have determined the shift‐up time, i.e., the time at which a shift‐up to the nonpermissive temperature no longer prevents the entry of cells into S. In no case did K12 or AF8 enter S at the nonpermissive temperature. At the permissive temperature, the average time of entry into S varied in different growth conditions, and so did the shift‐up time. However, in both cell lines, the distance of the average shift‐up time from the average time of entry into S was remarkably constant, regardless of the growth conditions, i.e., 1.8 hours in K12 and 8.6 hours in AF8.
Relation between structure of bacterial lipopolysaccharide and the stimulation of B lymphocytes into colony formation
Authors: Sredni B. , Rozenszajn L. A. 
Published: February 2005

AbstractLipopolysaccharide (LPS) was analyzed in order to determine which component, lipid A or polysaccharide (PS), is able to stimulate B lymphocytes from ICR lymph nodes and spleen cells from nude (nu/nu) mice into forming colonies in soft agar culture. Lipid A, obtained by acid hydrolysis of LPS and solubilized by complex‐formation with bovine serum albumin, was found to be the active moiety of LPS capable of stimulating colony growth of lymphoid cells in soft agar culture. The PS portion exhibited no significant activity at the concentrations used. Glycolipids from mutant strains of S. minnesota which contain the intact lipid moiety but are deficient in PS content, were as potent as S. abortus equi LPS in stimulating B cells into colony growth. Alkaline hydrolysis of LPS which cleaves ester‐linked fatty acids, substantially decreased the number of lymphocyte colonies formed. This indicates that the intact lipid moiety is required for stimulating lymphocytes into colony formation. The synthetic glycolipid, N‐palmitoyl‐D‐glucosamine (NPG), whose structure is similar to some components of lipid A, was also able to induce B lymphocyte colony development. In summary, our data point to lipid A as the active moiety of the endotoxin which induces B lymphocytes to grow and develop into colonies in the 2‐layer soft agar culture system.
Studies on the association of the Epstein‐Barr virus genome and human chromosomes
Authors: Glaser Ronald , Nonoyama Meihan , Hampar Berge , Croce Carlo M. 
Published: February 2005

AbstractWe have used human‐mouse somatic cell hybrid cells to study the association between the EBV genome and the cellular genome. Attempts were made to identify a specific human chromosome(s) with which the EBV genome is associated. Our data suggest that at least in the mouse fibroblast/Burkitt lymphoma hybrid combination studied, the EBV genome is not associated with any specific human chromosome.
Diffusible factor(s) controlling density inhibition of 3T3 cell growth: A new approach
Authors: Harel L. , Jullien M. , De Monti M. 
Published: February 2005

AbstractIn 3T3 Swiss mouse fibroblasts, incorporation of phosphate into cells and phosphorylation of small organic compounds were increased by shaking dense cultures. This response was not obtained with SV40 transformed Swiss 3T3 cells (SV‐3T3).It appeared likely that these results could be accounted for by an inhibitor released from 3T3 cells but not from SV‐3T3 cells.Our new method of co‐incubation of sparse and dense cultures allowed us to demonstrate inhibition of growth and phosphate metabolism in sparse 3T3 cultures which were shaken in the presence of dense cultures. The inhibition was much less when the cultures were co‐cultivated but not shaken.The inhibition of phosphate incorporation in acid‐soluble and acid‐insoluble fractions of sparse cultures was observed as early as 20 minutes of co‐incubation in the presence of dense cultures, so this inhibition is not the result of depletion of growth factors in the medium.Our experiments suggest that an inhibitor(s) was released from dense cultures of 3T3 cells.
Epstein‐barr virus in somatic cell hybrids between mouse cells and human nasopharyngeal carcinoma cells
Authors: Steplewski Zenon , Koprowski Hilary , Andersson‐Anvret Maria , Klein George 
Published: February 2005

AbstractSomatic cell hybrids between mouse cells and cells derived directly from NPC biopsies were produced in order to study the association of the Epstein‐Barr virus (EBV) genome and the expression of Epstein‐Barr nuclear antigen (EBNA) with the human chromosome(s). All attempts to correlate the presence of EBV‐DNA and the expression of EBNA with the presence of a particular human chromosome(s) showed that the segregation of EBV‐DNA or of EBNA and human chromosomes was dysconcordant. The data, therefore, suggest that in the hybrids studied the presence of EBA‐DNA is not determined by the presence of a specific human chromosome.
Effects of albumin on the phagocytosis of polysterene spherules by rabbit polymorphonuclear leucocytes
Authors: Beukers Harm , Deierkauf Frans A. , Blom Cornelis P. , Deierkauf Martha , Riemersma Jelle C. 
Published: February 2005

AbstractPolystyrene latex spherules are rapidly phagocytized by polymorphonuclear leucocytes. Surface modifications of the latex spherules can lead to an inhibition of phagocytosis, and the purpose of this study was to analyse in particular inhibition by bovine and human serum albumin. It can be shown that albumin is bound much more strongly by the PSL particle surface than by the cell surface. Furthermore, a correlation was established between the extent to which the particle surface is covered and the extent of phagocytosis inhibition. In the binding of albumin to the particle surface ionic as well as hydrophobic interactions play a role. As a result, the particle acquires a negatively charged hydrophilic coating which effectively diminishes the number of effective cell‐particle collisions leading to engulfment.
Expression of transformation in cell hybrids. II. Nonsuppression of the transformed phenotype in hybrids between a chemically transformed and nontransformed derivatives of Balb/3T3
Authors: Jha Krishna K. , Cacciapuoti Janice , Ozer Harvey L. 
Published: February 2005

AbstractHybrid clones derived from a nitrosocarbaryl‐transformed Balb/3T3 cell line, Clone H, and a nontransformed cell line TH02 resemble the transformed parent in the clone morphology, higher saturation density, colony formation in medium with reduced serum concentration, growth in agarose and ability to form clones on Balb/3T3 monolayer. Results are discussed in the framework of genetic models which permit or require dominant mutations for the expression of transformed phenotype.
Inhibition of growth in vitro by glucocorticoids in mouse embryonic facial mesenchyme cells
Authors: Salomon David S. , Pratt Robert M. 
Published: February 2005

AbstractThe growth of primary embryonic facial mesenchyme cells established from cleft palate sensitive A/J and resistant C57BL/6J (C57) mice is inhibited by glucocorticoid treatment. A reduction in cell number in both A/J and C57 culture is accompanied by a significant decrease in [3H] thymidine incorporation into both acid soluble and insoluble material. No significant changes in total cellular protein or [14C] leucine incorporation were observed in either cell type. A greater reduction in [3H] thymidine incorporation occurs in cells undergoing exponential growth following steroid exposure than in cells approaching stationary growth. In both A/J and C57 cultures the reduction in cell number exhibits a dose‐dependent response to dexamethasone; is specific for glucocorticoids; and is dependent upon the concentration of serum in which the cells are maintained. A/J cells show a greater sensitivity to the inhibitory effect of dexamethasone on cell number and thymidine incorporation than comparably treated C57 cells. Specific, high affinity, saturable cytoplasmic receptors for [3H] dexamethasone are present in the maxillary cytosols from which the primary cultures were established. These receptors exhibit binding specificity for glucocorticoids, and have properties which are similar to glucocorticoid receptors identified in other systems. In both cell types, a correlation exists between the degree of growth inhibition or reduction of [3H] thymidine incorporation and the level of glucocorticoid receptors. These results provide evidence for a receptor‐mediated set of responses to glucocorticoids in these cells.
Physiological quiescence in plasma‐derived serum: Influence of platelet‐derived growth factor on cell growth in culture
Authors: Ross Russell , Nist Cynthia , Kariya Beverly , Rivest Mary Jane , Raines Elaine , Callis Jim 
Published: February 2005

AbstractA platelet‐derived growth factor can be shown to be the principal stimulant of DNA synthesis in whole blood serum for those cells that require serum for maintenance and growth in culture. Cell free plasma‐derived serum lacks such platelet‐derived material. 3T3 cells and primate arterial smooth muscle cells can be maintained in a quiescent state in culture for as long as six weeks in plasma‐derived serum. Such cells can grow logarithmically after exposure to 5% whole blood serum or as little as 100 ng/ml of partially purified platelet factor. The cell cycle of smooth muscle cells has been studied in the quiescent (5% plasma‐derived serum) and growing state (5% whole blood serum or 5% plasma‐derived serum plus platelet factor). The generation time of smooth muscle cells is 16 to 18 hours as shown by autoradiographic frequency of labelled mitoses. The generation time is the same for cells in the growth fraction in either 5% whole blood serum or 5% plasma‐derived serum. Thus, platelet factor acts by recruiting cells into the growth fraction rather than effecting a change in the duration of the cell cycle. Flow microfluorimetry studies on cells growing logarithmically in 5% whole blood serum give the following phase durations:G1 = 5.6 hours; S = 7.6 hours; and G2 + M = 3.8 hours.Based on these studies the argument is presented that cells cultured in 5% plasma‐derived serum provide a more physiological base for the study of quiescence than do cells in low concentrations of whole blood serum or confluent, density inhibited cells at high (5% or greater) concentrations of whole blood serum. Furthermore, 5% plasma‐derived serum represents an appropriate state to examine the perturbation of quiescent cells.
Lymphocyte response to phytohemagglutinin: Intracellular volume and intracellular [K+]
Authors: Holian A. , Deutsch C. J. , Holian S. K. , Daniele R. P. , Wilson D. F. 
Published: February 2005

AbstractThe effect of phytohemagglutinin (PHA) on lymphocytes was examined with respect to free intracellular water volume and intracellular [K+]. At a cell concentration of 30 × 106 lymphocytes/ml in modified Hank's Buffered Salt Solution (HBSS) in the presence of 10% human AB serum, addition of PHA at 3 mg/ml resulted in a 24–27% decrease in free intracellular water space within 30 to 60 minutes and a return to control level after three hours. A larger change in intracellular water (44%) was observed under similar conditions in the absence of serum. The absolute intracellular K+ content did not change after PHA addition, but the cell water volume decrease arising from PHA addition resulted in a 29% increase in intracellular [K+] at 60 minutes. The decrease in lymphocyte water volume induced by PHA was also observed for concanavalin A which stimulates lymphocyte proliferation, but not for wheat germ lectin, an agglutinating agent which is not mitogenic. Thus, volume regulation may be closely associated with the mitogenicity of these compounds.
Superoxide dismutase specific activities in cultured human diploid cells of various donor ages
Authors: Duncan Michael R. , Dell'orco Robert T. , Kirk K. D. 
Published: February 2005

AbstractIt has been postulated that superoxide dismutase (SOD) protects cells from free radical‐induced damage. In these experiments SOD specific activity was measured as established human diploid cell lines from various donor ages progressed through their in vitro lifespans. Significant elevations in activity occurred during the in vitro lifespans of cells from fetal and newborn donors, but no change in activity was detected during the lifespan of cells from an adult donor. In addition, a direct relationship between enzyme activity and donor age was detected with the following relative activities: adult > newborn > fetal. The possible relationship between these findings and the free radical theory of aging is discussed.
Selective suppression of the transcription of ribosomal genes in mouse‐human hybrid cells
Authors: Perry R. P. , Kelley D. E. , Schibler U. , Huebner K. , Croce C. M. 
Published: February 2005

AbstractMouse‐human hybrid cells that preferentially segregate either mouse or human chromosomes were analyzed for their relative content of mouse and human rRNA genes and for their capacity to transcribe these genes. A distinctive Hind III restriction fragment containing 28S rRNA sequences was used to distinguish between mouse and human rDNA and a set of distinctive loop structures in the 45S pre‐rRNA was used to distinguish between mouse and human gene transcripts. Our results indicate that the genes of only one species are transcriptionally active in these hybrid cells, even though both sets of genes are present.
Intracellular proteolysis in rat cardiac and skeletal muscle cells in culture
Authors: Mayorek Nina , Pinson Arie , Mayer Michael 
Published: February 2005

AbstractTreatment of adult rats with dexamethasone resulted in an increase in cardiac muscle weight but a decrease in skeletal muscle weight. The different response of skeletal and cardiac muscles to the glucocorticoid was also reflected by a dexamethasone‐induced enhancement of myofibrillar protease activity in the gastrocnemius muscle and an inhibition of a similar proteolytic activity in the heart. Newborn rats also exhibit the same, tissue‐specific response to the glucocorticoid hormone. Consequently, the difference between cardiac and skeletal muscle responsiveness to conditions of wasting was investigated in culture. Average rates of degradation of intracellular proteins were determined in cultured cells derived from rat skeletal and cardiac muscle by following the release of radioactivity from cells prelabelled with 14C‐phenylalanine. The release of label into the TCA soluble medium as measured during 12 hours of incubation, conformed to a first‐order reaction and both cell types were found to degrade intracellular proteins at a similar rate. After 12 hours of incubation in a complete Ham F‐10 medium supplemented with serum approximately 18% of total cellular protein was degraded. Incubation in a minimal medium or serum‐deprivation enhanced the average rate of proteolysis to a value of 29% degradation at 12 hours indicating that intracellular proteolysis in these cells is responding to nutritional deprivation by increased activity. However, addition of glucose (22.2 nM) or dexamethasone (10−6M) to the incubation medium failed to affect the rate of net protein degradation. Under no experimental condition could a difference be found between the proteolytic response of skeletal muscle cells to that of cardiac muscle cells and both cell types displayed similar changes in rates of protein degradation under various nutritional and hormonal conditions in culture. Thus, protein sparing in the heart of intact animals under catabolic conditions which enhance protein loss in skeletal muscle can probably not be ascribed to intrinsic differences in the direct response of cellular proteases to the tested hormones and nutrients. Rather, an extracellular factor(s) is apparently required for induction of the differential response of these tissues in the intact animal to protein wasting conditions. Alternatively, cells in culture might have lost the property of differential degradative response which operates in vivo.
Abnormal regulation of de novo purine synthesis and purine salvage in a cultured mouse T‐cell lymphoma mutant partially deficient in adenylosuccinate synthetase
Authors: Ullman B. , Clift S. M. , Cohen A. , Gudas L. J. , Levinson B. B. , Wormsted M. A. , Martin D. W. 
Published: February 2005

AbstractThe isolation and characterization of a mutant murine T‐cell lymphoma (S49) with altered purine metabolism is described. This mutant, AU‐100, was isolated from a mutagenized populatio of S49 cells by virtue of its resistance to 0.1 mM 6‐azauridine in semisolid agarose. The AU‐100 cells are resistant to adenosine mediated cytotoxicity but are extraordinarily sensitive to killing by guanosine.High performance liquid chromatography of AU‐100 cells extracts has demonstrated that intracellular levels of GTP, IMP, and GMP are all elevated about 3‐fold over those levels found in wild type cells. The AU‐100 cells also contain an elevated intracellular level of pyrophosphoribosylphosphate (PPriboseP), which as in wild type cells is diminished by incubation of AU‐100 cells with adenosine. However AU‐100 cells synthesize purines de novo at a rate less than 35% of that found in wild type cells.In other growth rate experiments, the AU‐100 cell line was shown to be resistant to 6‐thioguanine and 6‐mercaptopurine. Levels of hypoxanthine‐guanine phosphoribosyltransferase (HGPRTase) measured in AU‐100 cell extracts, however, are 50‐66% greater than those levels of HGPRTase found in wild type cell extracts. Nevertheless this mutant S49 cell line cannot efficiently incorporate labeled hypoxanthine into nucleotides since the salvage enzyme HGPRTase is inhibited in vivo.The AU‐100 cell line was found to be 80% deficient in adenylosuccinate synthetase, but these cells are not auxotrophic for adenosine or other purines. The significant alterations in the control of purine de novo and salvage metabolism caused by the defect in adenylosuccinate synthetase are mediated by the resulting increased levels of guanosine necleotides.
Stimulation of hexose transport in cultured human skin fibroblasts by insulin
Authors: Germinario Ralph J. , Oliveira Maureen 
Published: February 2005

AbstractThe effect of insulin on hexose transport in cultured human skin fibroblasts.Studies were carried out on cultures of human skin fibroblasts to explore the effect of insulin on hexose transport in serum‐starved monolayers. Insulin (100 mU/ml) stimulated 2‐deoxy‐D‐glucose transport (30% above control values) after 30 minutes exposure time, the response being similar up to four hours exposure to insulin. In several experiments (n = 22) employing three cell strains, insulin (100 mU/ml) exposure led to variable stimulation of 2‐deoxy‐D‐glucose transport (an average of 37% above control values, with a range of 0 = 120%). The insulin‐induced stimulation of 2‐deoxy‐D‐glucose transport showed a dose dependency with increasing amounts of insulin, the response being maximal at an insulin concentration of 100 mU/ml. Kinetic analysis of 2‐deoxy‐D‐glucose transport showed that insulin addition resulted in a slight change in the transport Km (3.13 to 4.06 mM) and a 1.8‐fold increase in the transport Vmax (17.6 nanomoles/mg protein/min to 32.1 nanomoles/mg protein/min). Insulin also stimulated the transport of 3‐0‐methyl‐D‐glucose while the hexokinase activity of the cells was not affected. Further, this insulin‐induced stimulation of sugar transport was not blocked by cycloheximide. The results indicate that insulin stimulated the stereospecific carrier‐mediated of hexose transport in cultured human skin fibroblasts.
Stimulation of chondroitin sulfate synthesis by β‐D‐xyloside in chondrocytes of the proteoglycan deficient mutant nanomelia
Authors: Stearns K. , Goetinck P. F. 
Published: February 2005

AbstractThe potential of nanomelic chondrocytes to synthesize chondroitin sulfate was investigated by providing the mutant cells with p‐nitrophenyl‐β‐D‐xyloside, a compound which acts as an artificial acceptor for glycosaminoglycan synthesis. Under these conditions the synthesis of chondroitin sulfate in nanomelic and normal chondrocytes is comparable. The chondroitin sulfate synthesized by the mutant is indistinguishable in molecular size and composition from that synthesized by similarly treated normal chondrocytes.