bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of extracellular Na and K in lymphocyte activation
Authors: Deutsch C. , Price M. 
Published: February 2005

AbstractThe transmembrane electrical potential has been measured across human peripheral blood lymphocytes under culture conditions using equilibrium distributions of the lipophilic cation 3H‐tetraphenylphosphonium (TPP). The TPP equilibrates to a steady‐state level that gives calculated voltages of −80 mV for unstirnulated lymphocytes. This value of Ihe potential is constant during the first few hours of succinyl concanavalin A stimulation. When the transmembrane electrical potential is lowered by isotonic replacement of Na with K, this neither by itself stimulates proliferation nor does it inhibit mitogen‐stimulated proliferation. Lymphocytes with similar membrane potentials, such as those incubated in normal‐Na MEM and low‐Na‐mannitol MEM, exhibit drastically different pro‐liferative responses to mitogen stimulation (Deutsch et al., 1981). These results show that isotonic replacement of K for Na prevents low Na inhibition of DNA synthesis and that at least during the first 2.5 hours of lymphocyte activation transmembrane electrical potential per se does not play a significant role in the activation process.
Migration inhibitory action of bacterial lipopolysaccharide on progenitor cells of monocyte/macrophage lineage growing in culture in the presence of colony‐stimulating factor (CSF‐1)
Authors: Ishii Y. , Shinoda M. , Shikita M. 
Published: February 2005

AbstractAddition of lipopolysaccharide (LPS) to the culture of mouse myeloid stem cells (CFUc) increased the incidence of compact colonies and decreased that of dispersed ones in the presence of colony‐stimulating factor (CSF‐1) which had not such an effect by itself even in high concentrations. Although colony morphology was thus changed, nearly all colonies were composed of monocytes. The incidence of compact colonies increased with the increase of LPS concentration but plateaued at about 50%. Bone marrow cells of LPS‐tolerant mice responded to LPS in vitro to a slightly decreased extent. The activity of LPS was decreased by alkaline or acid hydrolysis of the LPS molecule and inhibited by polymixin B, but not by indomethacin, α‐L‐fucose, nor by α‐methyl‐D‐mannoside. Other immunopotentiating substances, such as OK‐432, Lentinan, and Levamisole, had no effect on the colony morphology. Both muramyl dipeptide and poly(I)poly(C) were also ineffective. Furthermore, the action of LPS was not abolished by the use of heat‐inactivated serum in the culture. LPS was no longer stimulative for the induction of lysosomal enzymes in the CSF‐stimulated culture, although it greatly enhanced the enzyme induction in the unstimulated culture. These results indicate that the cells of monocyte/macrophage lineage develop the capacity for migration before they become responsive to LPS, and that the LPS‐responding monocytic cells can proliferate even in a state of confluence induced by LPS.
Temporal behavior of abrin in the intoxication of chinese hamster cells (line CHO)
Authors: Tsuzuki Junji , Wu Henry C. 
Published: February 2005

AbstractAbrin, a potent cytotoxin, was utilized as a probe to elucidate the mechanism by which external proteins are delivered to the cytoplasm of mammalian cells. Abrin bound rapidly to the surface receptors of the Chinese hamster cells (line CHO) and appeared to be internalized immediately without any significant lag. The maximum level of abrin internalization was achieved within eight minutes, based on both biochemical and electron microscopic autoradiographic studies with [125|] abrin. About 10% of the silver grains of internalized [125|] abrin were associated with vesicular structures, irrespective of the incubation time. Inhibition of protein synthesis began 30 minutes postincubation, and this latent period was not dependent on extracellular toxin concentration. SDS‐polyacrylamide gel electrophoresis of the internalized [125|] abrin indicated that internalized abrin molecules remained intact even after two hours of incubation.
A survey of intracellular Na+ and K+ of various normal, transformed, and tumor cells
Authors: Moyer Mary Pat , Mover Rex C. , Waite Marilynn R. F. 
Published: February 2005

AbstractIntracellular concentrations of Na+ and K+ of various normal, transformed, and tumor cell cultures were analyzed by atomic absorption spectrophotometry. In all of the cultures analyzed there were markedly different concentrations in the transformed and tumor cells when compared to their normal counterparts. Although increased Na+ was often observed, there were no definitive correlations between absolute ion concentrations, or Na+:K+ ratios, and cell transformation.
Dissociation of hemoglobin accumulation and commitment during murine erythroleukemia cell differentiation by treatment with imidazole
Authors: Gusella James F. , Tsiftsoglou Asterios S. , Volloch Vladimir , Weil Susan C. , Neumann Jeffrey , Housman David E. 
Published: February 2005

AbstractThe effect of imidazole on DMSO‐induced murine erythroleukemia (MEL) cell differentiation has been examined. While imidazole does inhibit heme, globin mRNA, and hemoglobin accumulation in DMSO‐induced MEL cells, it does not affect the commitment of MEL cells to the specific limitation of proliferative capacity associated with the in vitro differentiation program. Furthermore, imidazole treatment does not affect DMSO‐induced changes in cell volume, in the relative proportion of nuclear protein IP25, and in the specific activity of the enzyme cytidine deaminase. A clonal analysis in the presence of imidazole indicated that the drug prevents heme accumulation even in MEL cells already committed to terminal differentiation. These observations suggest that imidazole effectively dissociates two aspects of the erythroid differentiation program of MEL cells: globin gene expression and commitment to loss of proliferative capacity.
Kinetics of chick embryo cell types in culture
Authors: La Rocca Paul J. , Rafferty Keen A. 
Published: February 2005

AbstractThe growth kinetics and population doubling limits of chick embryonic fibroblasts, chondroblasts, and retinal pigment cells were compared. Chondroblasts were found to have a cumulative population doubling level (37 ± 3 PDL) similar (p = 0.05) to that of control fibroblasts (42 ± 2 PDL), in individual and pooled clones. While both cell types have similar doubling potential, the proportion of tritium‐labeled nuclei decreases, and differs significantly as doubling level increases. This age‐associated decline is due to an extension in the population doubling time. Direct cell‐cycle analysis shows this increase to occur in the G1 phase. Furthermore, cartilage colonies maintain their phenotypic expression (metachromasia) throughout their lifespan under conditions of subcloning at sparse density.When fibroblasts derived from 15 day chick embryos are compared with fibroblasts from 10 day embryos (41 ± 2 PDL) there is no significant difference (p = 0.05) in cumulative PDL or percent labeled nuclei, indicating that fibroblasts of different embryonic age have similar potential. The addition of hydrocortisone and insulin to the medium significantly shortens (25 ± 2 PDL) the lifespan of 10 day chick fibroblasts. Kinetics of retinal pigment cells show a population doubling potential (29 ± 1 PDL) different from fibroblasts and chondroblasts, suggesting that different cell types may not have similar limits on doubling potential when first determined in embryogenesis. Hydrocortisone and insulin have no effect on the growth kinetics or lifespan of retinal pigment cells in culture.
Platelet‐derived growth factor is a chemoattractant for vascular smooth muscle cells
Authors: Grotendorst G. R. , Chang T. , Seppä H. E. J. , Kleinman H. K. , Martin G. R. 
Published: February 2005

AbstractIn previous experiments (Grotendorst et al, 1981), we showed that platelet‐derived growth factor promotes the migration of smooth muscle cells in vitro. Using a “checkerboard” analysis, we now establish that platelet‐derived growth factor (PDGF) acts as a true chemoattractant for cultured aortic smooth muscle cells. Other growth factors such as epidermal growth factor, fibroblast growth factor, and insulin are not chemoattractants. The chemotactic response occurs before the initiation of DNA synthesis and is not affected by inhibition of DNA synthesis. Chemotaxis occurs at levels of PDGF lower than required for mitogenesis. RNA and protein synthesis are required for the chemotactic response. As found previously in bacteria and leucocytes, we find that methylation reactions are required for the chemotactic response. The possibility is discussed that PDGF acts in vivo at sites of vascular injury to attract smooth muscle cells from the medial layer to the luminal surface, and is involved in the early stages of the formation of atherosclerotic plaques.
An early mitosis‐determining event in regenerating rat liver and its possible mediation by prostaglandins or thromboxane
Authors: Rixon R. H. , Whitfield J. F. 
Published: February 2005

AbstractInhibitors of prostaglandin and thromboxane production such as mefenamic acid, hydrocortisone, and dexamethasone prevented a large proportion of the parenchymal cells of rat liver, proliferatively activated by a two‐thirds partial hepatectomy, from entering mitosis without preventing them from initiating or completing DNA synthesis. This specific mitosis‐inhibiting action was maximum when the drugs were present during the first few hours after partial hepatectomy. In contrast, indomethacin, another inhibitor of prostaglandin and thromboxane production, maximally inhibited both DNA synthetic and mitotic activities when present during the same early period of prereplicative development, which showed that it had an action not shared by the other inhibitors. Arachidonic acid completely reversed the hydrocortisone‐ or dexamethasone‐induced inhibition of mitotic activity, but it did so only when it was injected between 2 and 3 hours after partial hepatectomy and glucocorticoid injection. Arachidonate's reversal of the hydro‐cortisone‐induced inhibition did not occur in the presence of mefenamic acid. These observations indicate that there is an early, prostaglandin‐ or thromboxane‐mediated, prereplicative process in proliferatively activated hepatocytes which determines their later entry into mitosis and which is separate from the early events leading to DNA synthesis.
A clonal analysis of the differentiation of 3T3‐L1 preadipose cells: Role of insulin
Authors: Steinberg Marcia M. , Brownstein Barbara L. 
Published: February 2005

AbstractCells of the established preadipose line, 3T3‐L1, appear to be undifferentiated fibroblasts during exponential growth. When cells become quiescent, a small percentage of them accumulate triglyceride and become morphologically indistinguishable from mature adipocytes. When insulin is added to quiescent cultures, up to 50% of the cells differentiate into adipocytes. The distribution of lipid‐containing cells which appear in clusters of varying sizes was analyzed to determine whether commitment to differentiation occurred after quiescence or during exponential growth and whether insulin was required as an inducer of commitment. The spatial arrangement of 3T3‐L1 cells at quiescence on some culture dishes was destroyed by replating. This resulted in random distribution of these cells. The distribution of adipocytes among replated and nonreplated cells in these experiments was compared to a computer generated random distribution of differentiated among undifferentiated cells. Dispersal of cells at confluence resulted in a distribution of fat among nonfat cells not significantly different from the computer generated random distribution. In undisturbed cultures, the distribution of fat cells is not random and is consistent with a commitment event in single cells at any cell division during exponential growth followed by divisions of both committed and uncommitted cells. Since insulin affected the number of mature adipocytes only when added after cessation of exponential growth, insulin is not the inducer of commitment but merely enhances lipid production in previously committed cells.
Factors involved in supporting the growth and steroidogenic functions of bovine adrenal cortical cells maintained on extracellular matrix and exposed to a serum‐free medium
Authors: Ill C. R. , Gospodarowicz D. 
Published: February 2005

AbstractBovine adrenal cortex cells maintained on extracellular matrix (ECM)‐coated dishes will proliferate actively when serum is replaced by HDL (25 μg protein/ml), insulin (10 ng/ml), and FGF (100 ng/ml). The cells have an absolute requirement for HDL in order to survive and grow. The omission of insulin, FGF, or both results in a slower growth rate and lower final cell density of the cultures. A requirement for transferrin (1 μg/ml) becomes apparent only when cells have been grown for at least four generations in the absence of serum.Early passage (P1–P3) bovine adrenal cortex cells cultured in serum‐free medium responded to ACTH (10−8M) with increased 11‐deoxycortisol production; this effect was not observed in later passage cells (P7–P15). The cells' ability to utilize LDL‐derived cholesterol and to respond to db cAMP (1mM) by increased steroid release was preserved in cells cultured for over 60 generations in the serum‐free medium. HDL, although also able to increase steroid production in early‐passage cultures exposed to ACTH or to ACTH and dibutyryl cyclic AMP (db cAMP), was 10 fold less potent than LDL. It did not support steroidogenesis in cultures not exposed to these trophic agents.The life span of bovine adrenal cortex cells grown in the serum‐free medium on fibronectin (FN)‐ versus ECM‐coated dishes was compared. Cells seeded in serum‐containing medium and grown in serum‐free medium had a life span of 34 versus 60 generations when maintained on fibronectin‐ or ECM‐coated dishes, respectively. Cells seeded in the complete absence of serum in the serum‐free medium on ECM‐ or fibronectin‐coated dishes could be passaged for 26 or 13 generations, respectively. While FGF was an absolute requirement for cells cultured on fibronectin‐coated dishes, it was not required when cells were maintained on ECM. These observations demonstrate the influence of the ECM not only in promoting cell growth and differentiation but also on the life span of cultured cells.
Formyl peptide stimulation of superoxide anion release from lung macrophages: Sodium and potassium involvement
Authors: Holian Andrij , Daniele Ronald P. 
Published: February 2005

AbstractWe examined the role of the monovalent cations Na+ and K+ in the events encompassing the release of O by alveolar macrophages after stimulation with formyl methionyl phenylalanine (FMP). This was accomplished by determining the effect of changing the extracellular [Na+] and/or [K+] on FMP‐stimulated O production; and measuring 22Na+ 42K+ and 86Rb+ influx and efflux and intracellular [K+] for control and FMP‐stimulated alveolar macrophages. Stimulated O production was relatively insensitive to changes in extracellular K+ or Na+ concentrations until the [Na+] was decreased below 35 mM. At 4 mM [Na+], the rate of O production remained at 75% of the maximal rate observed at physiological concentrations of [Na+]. Both influx and efflux of 22Na+ were stimulated above control rates by FMP. The increased rates of fluxes lasted for a few minutes suggesting a transient increase in membrane permeability to Na+. Ouabain partially inhibited 22Na+ efflux but had no effect on O release. The influx of 86Rb+ and 42K+ was not altered by the addition of FMP but was virtually abolished in the presence of 10 μM ouabain or 1 mM quinine. In the presence of extracellular calcium, FMP‐stimulated a prolonged (> 20 minutes) increase in 86Rb+ or 42K+ efflux which was inhibitable by 1 mM quinine. In the absence of extracellular calcium, FMP stimulation of K+ efflux was greatly diminished and was not affected by quinine, although quinine still inhibited O production under these conditions. It was also observed that there was a loss of intracellular K+ when cells were stimulated by FMP in the presence of Ca+2, but not in the absence of Ca+2. Taken together, these results suggest a minimal direct role, if any, for K+ in the events that lead to FMP‐stimulated O release by alveolar macrophages.
Genetic evidence that a phorbol ester tumor promoter stimulates ornithine decarboxylase activity by a pathway that is independent of cyclic AMP‐dependent protein kinases in CHO cells
Authors: Lichti Ulrike , Gottesman Michael M. 
Published: February 2005

AbstractOrnithine decarboxylase (ODC) inductions by cholera toxin and by the phorbol ester tumor promoter, TPA, were compared in wild‐type Chinese hamster ovary (CHO) cells and in mutant cells having altered cyclic AMP‐dependent protein kinase activity. The aim of these studies was to determine whether cyclic AMP‐dependent protein kinase is involved in these inductions. The time course and the magnitude of ODC inductions by either 100 ng/ml cholera toxin or 100 ng/ml TPA were similar in wild‐type cells with a maximum at 3–4 hours after treatment and a return to unstimulated levels by 8 hours. Induction of ODC by cholera toxin was suppressed more than 80% in the four protein kinase mutants studied (10215, 10248, 10260, and 10265), strongly implicating a cyclic AMP‐dependent kinase step in the mechanism of induction. Similar results were found with the cyclic AMP analog 8‐Br‐cyclic AMP and the phosphodiesterase inhibitor, methyl‐isobutylxan‐thine. The induction of ODC by TPA, on the other hand, was only partially inhibited (approximately 50%) in three of four mutants. Lower ODC activity in two mutants stimulated by cholera toxin or TPA whose kinetics were studied in more detail could not be ascribed to a reduced affinity (Km) of ornithine for the enzyme, but appeared to be due to reduced catalytic activity (Vmax) in the extracts. These results suggest that the induction of ODC by TPA proceeds by a mechanism which is only partially dependent on an intact cyclic AMP‐dependent protein kinase activity.
A stochastic model of self‐renewal and commitment to differentiation of the primitive hemopoietic stem cells in culture
Authors: Nakahata Tatsutoshi , Gross Alan J. , Ogawa Makio 
Published: February 2005

AbstractWe recently identified a murine hemopoietic stem cell colony which consists of undifferentiated (blast) cells and appears to be more primitive than CFU‐GEMM in the stem cell hierarchy. The progenitors for the colony which we termed “stem cell colony” possess an extensive self‐renewal capacity and the ability to generate many secondary multipotential hemopoietic colonies in culture. We replated a total of 68 stem cell colonies from cultures of murine spleen cells and analyzed the number of stem cell–and granulocyte(neutrophil)‐erythrocyte‐macrophage‐megakaryocyte (GEMM) colony‐forming cells in individual stem cell colonies. Of the 68 stem cell colonies, 35 contained progenitors (abbreviated as “S”‐cells) for stem cell colonies. The distributions of S‐cells and CFU‐GEMM in individual stem cell colonies were extremely heterogeneous. Neither the frequency distributions of S‐cells nor CFU‐GEMM in stem cell colonies could be fitted well by Poisson distribution. Rather, the frequency distribution of the s‐cells could be approximated by a geometric distribution and that of CFU‐GEMM by an exponential distribution, both of which are variates of the gamma distribution. Our observations are in agreement with those on the distributions of CFU‐S in individual spleen colonies and provided support for a stochastic model for stem cell self‐renewal and commitment in culture. Application of the theory of the branching process to the distribution of S‐cells revealed a distributional parameter “p” of 0.589 which is also in agreement with the earlier report on the p value for reproduction of CFU‐S.
Proliferative variability of endothelial clones derived from adult bovine aorta: Influence of fibroblast growth factor and smooth muscle cell extracellular matrix
Authors: Loncenecker J. P. , Kilty L. A. , Ridge J. A. , Miller D. C. , Johnson L. K. 
Published: February 2005

AbstractFour endothelial cell clones derived from adult bovine aorta were examined with respect to their proliferative characteristics In vitro. Three of these clones, derived in the absence of fibroblast growth factor (FGF), displayed variable basal proliferative rates. One of these non‐FGF derived clones grew at a maximal rate which could not be further enhanced with FGF. The other two clones grew at a suboptimal rate which was stimulated by low doses of FGF (10–50 ng/ml) and inhibited by higher doses (100–250 ng/ml). The fourth clone, derived in the presence of FGF, was stimulated by FGF in a dose‐dependent manner (10–250 ng/ml) and was not growth inhibited at high FGF concentrations (250–1,000 ng/ml). Growth of all four clones on extracellular matrix (ECM) derived from bovine aortic smooth muscle (BASM) cells was optimal in the absence of FGF. ECM‐coated dishes also significantly increased the sensitivity of all clones by at least fivefold to mitogenic stimulation by serum. The proliferative lifespans of the clones ranged between 60 and 120 generations with the most actively proliferating clones attaining the greatest lifespan. Continuous subculture of two of the endothelial clones in the presence of FGF or on ECM‐coated dishes did not induce a dependence of the cells on either factor for subsequent growth in its absence. The results indicate that aortic endothelial cells display considerable clonal variability in ther basal proliferative rate and in their response to FGF. This clonal variability is not observed when the cells are maintained on ECM‐coated dishes derived from vascular smooth muscle cells.
Age dependent production of a competence factor by human fibroblasts
Authors: Clemmons David R. 
Published: February 2005

AbstractSeveral cell types such as Balb/c 3T3 have been shown to require platelet‐derived growth factor (PDGF); however, strains of human fibroblasts from fetal donors have been shown to divide in medium containing plasma free of PDGF. Since human fibroblasts have been demonstrated to secrete other peptide growth factors such as somatomedin‐C, we have undertaken a study to determine if fibroblasts derived from fetal donors are capable of producing a mitogen(s) which will substitute for PDGF and support growth in plasma alone. Quiescent human fibroblasts from donors ages 12‐wk embryo, newborn, and 3‐yr‐old were exposed to serum‐free minimum essential medium (MEM) for 24 hr. The conditioned media collected from embryonic and newborn fibroblast donors were demonstrated to stimulate growth in the 3‐yr‐old cells with the addition of plasma alone, whereas conditioned medium from the 3‐yr‐old donor cells was without effect. The increases in growth and DNA synthesis were dependent upon concentration of media used. Conditioned medium derived from newborn fibroblasts also supported 3‐yr‐old cell growth but embryonic conditioned medium was more potent. The embryonic conditioned medium factor was heat and acid stable but destroyed by trypsin and excluded by a 5,000 (MW) molecular weight filter. The factor(s) had full competence factor activity since transient exposure to fibroblasts (3‐yr‐old donor) stimulated 78% nuclear labeling vs. 81% with continuous exposure. These results support the concept that there is an age‐dependent production of a competence factor by human fibroblasts which may partially account for their capacity to grow in medium devoid of PDGF and supplemented with plasma alone.