bluuebunny/crossref_metadata_2025_split huggingface dataset:
1,25‐dihydroxycholecalciferol‐induced differentiation of myelomonocytic leukemic cells unresponsive to colony stimulating factors and phorbol esters
Authors: Bettens Florence , Schlick Erich , Farrar William , Ruscetti Francis 
Published: February 2005

AbstractThe murine myelomonocytic leukemia cell line WEHI‐3B D +, which differentiates in response to granulocyte colony stimulating factor (G‐CSF), can also be induced to differentiate into monocyte‐macrophages by phorbol myristate acetate (PMA) treatment, whereas the WEHI‐3B D− subline, which is unresponsive to G‐CSF and PMA, can be induced to differentiate to granulocytes as well as monocytes by, 1, 25‐dihydroxycholecalciferol [1, 25‐(OH)2 D3], the biologically active metabolite of vitamin D3. A newly developed variant of the WEHI‐3B D+ line, named WEHI‐3B D + G, which was responsive to G‐CSF but not to PMA, was also differentiated to granulocytes by 1,25‐(OH)2 D3. Although vitamin D3 has been reported to induce macrophage differentiation in responsive tumor cells, this is the first demonstration that 1,25‐(OH)2 D3 can induce granulocyte differentiation. In both differentiation pathways, cessation of. cellular proliferation accompanies changes in morphologic and cytochemical properties of the cells. This suggests that leukemic cell lines unresponsive to differentiation agents acting at the cell surface retain their ability to differentiate in response to agents that do not act via the plasma membrane such as 1,25‐(OH)2 D3, which has cytosolic/nuclear receptors. Vitamin D3 could act through different cellular pathways inducing differentiation or by bypassing only the first step of a common differentiation cascade used by agents with cell surface receptors such as CSF. These results suggest that low doses of 1,25‐(OH)2 D3 may be useful in combination with hemopoietic growth factors (CSFs) as therapeutic agent to induce leukemic cell differentiation in vivo.
Signal transduction in human monocytes: Relationship between superoxide production and the level of kinase C in the membrane
Authors: Costa‐Casnellie Maria R. , Segel George B. , Lichtman Marshall A. 
Published: February 2005

AbstractActivation of monocytes and neutrophils results in an increased production of superoxide, an important cytotoxic compound. The previous finding that two agents that induce superoxide production cause opposite translocation of kinase C (Costa‐Casnellie et al. [1985] Biochem. Biophys. Res. Commun., 133:1139–1144). led us to study the role of kinase C in superoxide production. In monocytes induction of superoxide production by 13‐tetradecanoate phor‐bol acetate requires translocation of kinase C from the cytosol to the membrane. Superoxide production is also induced by concanavalin A, but this induction is accompanied by a shift of kinase C from the membrane to the cytosol. Superoxide production by concanavalin A is greatly augmented by cytochalasin B. During activation by Con A and cytochalasin B the membrane kinase C is translocated to the cytosol in a manner similar to that observed in the presence of Con A alone. Under these conditions approximately 5–10% of kinase C remains associated with the membrane. Thus, induction of superoxide production by concanavalin A is independent of the levels of kinase C tightly bound to the membrane. We also show evidence that the concanavalin A‐induced release of kinase C from the membrane is not due to an increase in levels of intracellular calcium or increased phosphoinositide turnover. In summary, these data indicate that concanavalin A and phorbol ester‐induced superoxide production by human monocytes occurs by distinct pathways and that superoxide production is not closely correlated with specific levels of membrane‐associated kinase C activity.
Contradistinctive growth responses of cultured rat intestinal epithelial cells to epidermal growth factor depending on cell population density
Authors: Blay Jonathan , Brown Kenneth D. 
Published: February 2005

AbstractThe growth response of cultured rat intestinal epithelial (RIE‐1) cells to epidermal growth factor (EGF) depends on the cell population density. EGF stimulated the proliferation of RIE‐1 cells in dense cultures, but inhibited the proliferation of cells growing at low population densities. In contrast, insulin enhanced RIE‐1 cell growth irrespective of the population density. The tumour promoter 12‐0‐tetradecanoylphorbol 13‐acetate (TPA), like EGF, inhibited the proliferation of low‐density RIE‐1 cells, but differed from EGF in that it did not stimulate the growth of dense cultures.
Studies on the metabolism of retinol‐binding protein by primary hepatocytes from retinol‐deficient rats
Authors: Dixon Joseph L. , Goodman DeWitt S. 
Published: February 2005

AbstractStudies were conducted to explore the regulation of retinol‐binding protein (RBP) metabolism in cultured primary hepatocytes from retinol‐deficient rats. Newly isolated hepatocytes from retinol‐deficient rats contained elevated levels (3.4‐fold) of RBP, compared to hepatocytes from normal (retinol‐adequate) rats. Addition of retinol to retinol‐depleted hepatocytes stimulated RBP secretion by the cells in a concentration‐dependent manner. Maximal sitmulation of RBP secretion was seen with a retinol level of 0.3 μg/ml. The effect of retinol was quite rapid, and was evident by 20 minutes after addition of retinol to the medium. Stimulation of RBP secretion was only seen during the first few hours after retinol addition. The effect of retinol was specific for RBP; thus, retinol had no effect on the secretion rates of transthyretin or albumin. Addition of retinoic acid also stimulated RBP secretion by retinol‐deficient hepatocytes. Addition of dexamethasone to retinol‐deficient cells did not maintain the initial rate of RBP secretion. Dexamethasone also had no effect on the secretion of transthyretin or albumin by these cells. The effects of retinol and of dexamethasone seen here with retinol‐depleted cells differed dramatically from effects seen in other studies with normal (retinol‐adequate) hepatocytes. Thus, with normal cells, dexamethasone maintains RBP, TTR, and albumin production and secretion rates close to initial rates. Also in normal hepatocytes, with ample retinol available within the cell, addition of exogenous retinol does not appear to influence RBP secretion. In contrast, and as shown previously in intact rats, in retinol deficiency the availability of retinol specifically regulates the secretion of RBP by hepatocytes.
Induction of DNA synthesis in dog thyrocytes in primary culture: Synergistic effects of thyrotropin and cyclic AMP with epidermal growth factor and insulin
Authors: Roger Pierre P. , Servais Patricia , Dumont Jacques E. 
Published: February 2005

AbstractWe have investigated the growth effects of thyrotropin (TSH) (mimicked by forskolin and acting through cyclic AMP), epidermal growth factor (EGF), serum (10%) and insulin on quiescent dog thyroid epithelial cells in primary culture in a serum‐free defined medium. These cells were previously shown to retain the capacity to express major thyroid differentiation markers. In the presence of insulin and after a similar prepreplicative phase of 18 ± 2h, TSH, EGF, and serum promoted DNA synthesis in such quiescent cells only a minority of which had proliferated in vitro before stimulation. The combination of these factors induced more than 90% of the cells to enter S phase within 48 h and near exponetial proliferation. Analysis of the cell cycle parameters of the stimulated cells revealed that the G1 period duration was similar to the length of the prepreplicative phase of quiescent thyroid cells; this might indicate that they were in fact in an early G1 stage rather than in G0 prior to stimulation. TSH and EGF action depended on or was potentiated by insulin. Strikingly, nanomolar concentrations of insulin were sufficient to support stimulation of DNA synthesis by TSH, while micromolar concentrations of insulin were required for the action of EGF. This suggests that insulin supported the action of TSH by acting on its own high affinity receptors, whereas its effect on EGF action would be related to its somatomedinike effects at high supraphysiological concentrations. Insulin stimulated the progression in the prepreplicative phase initiated by TSH or forskolin. In addition, in some primary cultures TSH must act together with insulin to stimulate early events of the prereplicative phase. In the presence of insulin, EGF, and forskolin, an adenylate cylase activator, markedly synergized to induce DNA synthesis. Addition of forskolin 24 h after EGF or EGF 24 h after forskolin also resulted in amplification of the growth response but with a lag equal to the prepreplicative period observed with the single compound. This indicates that events induced by the second factor can no longer be integrated during the prereplicative phase set by the first factor. These finding demonstrate the importance of synergistic cooperation between hormones and growth factors for the induction of DNA synthesis in epithelial thyroid cells and support the proposal that essentially different mitogenic pathways‐cyclic AMP‐dependent or independent‐may coexist in one cell.
Binding sites for elastase on cultured human fibroblasts that do not mediate internalization
Authors: Campbell Corinne Horn , Cunningham Dennis D. 
Published: February 2005

AbstractThe proteolytic actions of elastases have been implicated in extracellular matrix damage, which is characteristic of a variety of pathological conditions including emphysema and rheumatoid arthritis. In order to elucidate the molecular events involved in elastase interaction with connective tissue cells, the present study was designed to investigate the association of elastase with human fibroblasts at 4°C. Elastase bound saturably to binding sites that were present on the surface of these cells. Analysis of cell‐bound elastase by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis revealed the presence of a high molecular weight complex (Mr 54,000) that was not formed with elastase whose catalytic site serine was derivatized with a diisopropylphosphate group. The complex did not represent elastase bound to either protease nexin or contaminating serum. The cellular component with which elastase formed a complex could not be detected in the cell culture medium. Unexpectedly, elastase that had been pre‐bound at 4°C was not internalized after cells were warmed to 37°C. The elastase binding site described in this report is therefore distinct from high affinity binding sites involved in receptor‐mediated endocytosis and intracellular degradation.
Characterization of beta‐adrenergic receptors throughout the replicative life span of IMR‐90 cells
Authors: Scarpace Philip J. 
Published: February 2005

AbstractBeta‐adrenergic receptor number and receptor affinity for isoproterenol were assessed at various in vitro ages of the human diploid fibroblast cell line IMR‐90. From population doubling level (PDL) 33 to 44, there was a positive correlation between beta‐adrenergic receptor density and PDL (r = 0.709). Beta‐adrenergic receptors, assessed by Scatchard analysis of [125I]‐iodocyano‐pindolol (ICYP) binding, increased from 15 fmol/mg protein at PDL 33 to 36 fmol/mg protein at PDL 44. In contrast, from PDL 44 to 59, there was a negative correlation between beta‐adrenergic receptor density and PDL (r = −0.768). Receptor density declined to 12 fmol/mg protein at PDL 59. When the density of beta‐adrenergic receptors was expressed as receptor per cell, the findings were similar. Receptor agonist affinity for isoproterenol was determined from Hill plots of [125I]‐ICYP competition with isoproterenol. There was no change in the dissociation constant for isoproterenol with in vitro age. In humans, serum norepinephrine concentrations increase with age. This increase in serum norepinephrine may be partially responsible for the decreased betaadrenergic receptor‐agonist affinity observed with age in human lymphocytes and rat heart and lung. Similar changes in receptor‐agonist affinity are observed in rat heart and human lymphocytes following exposure to betaagonists and are part of the desensitization process. The present findings are consistent with the hypothesis that the decreases in receptor agonist affinity in rat and man with age are secondary to increases in catecholamine concentrations.
The control of DNA synthesis in primary cultures of hepatocytes from adult and young rats: Interactions of extracellular matrix components, epidermal growth factor, and the cell cycle
Authors: Tomomura Akito , Sawada Norimasa , Sattler Gerald L. , Kleinman Hynda K. , Pitot Henry C. 
Published: February 2005

AbstractHepatocytes from adult and 4‐week‐old rats cultured on one of several extra‐cellular matrix components were stimulated to replicate by epidermal growth factor (EGF). DNA synthesis was increased at 44–48 hr in adult hepatocytes and at 24, 48, and 72 hr in hepatocytes from young rats when EGF was added 2 hr after explantation. When EGF was added at 24 hr, maximal DNA synthesis of adult hepatocytes was observed at 48 hr, whereas that of 4‐week‐old hepatocytes was seen at 48 and 72 hr. Ten ng EGF per ml was the optimal concentration for maximal DNA synthesis in both adult and young cells. DAN synthesis decreased with increasing cell density, but this effect was less in hepatocytes from young than in those from adults.When hepatocytes were cultured on substrata consisting of individual extracellular matrix components, neither the time that adult cells needed to respond to EGF nor the time from stimulation by EGF to the peak of maximal DNA synthesis was altered in either adult or young cells. The optimal EGF concentration for maximal DNA synthesis and the cell density control of replication were also not altered by the substrata used. Substrata made from each of the extracellular matrix components studied enhanced DNA synthesis of adult and young hepatocytes stimulated by EGF in the following decreasing order: fibronectin, type IV collagen, type I collagen, and laminin. In both adult and young hepatocytes the enhancement of DNA synthesis was greatest when cultured on fibronectin. Thus the initiation and magnitude of DNA synthesis in primary cultures of rat hepatocytes were altered both by the age of the donor and the substratum on which the cells were explanted.
Induction of major histocompatibility class I antigens by interferons in undifferentiated F9 cells
Authors: Wan Yu‐Jui Yvonne , Orrison Bonnie M. , Lieberman Ronald , Lazarovici Philip , Ozato Keiko 
Published: February 2005

AbstractMouse embryonal carcinoma F9 cells, upon treatment with interferons (IFNs), express major histocompatibility (MHC) Class I antigens, which are otherwise not expressed in these cells. Both IFN‐γ and IFN‐α/β increase the steady‐state level of Class I mRNA within 60 min of the treatment which leads to the subsequent surface expression of the H‐2Kb and H‐2Db antigens, suggesting that undifferentiated F9 cells express IFN receptors. IFNs induce Class I antigen expression in F9 cells in a highly selective manner: unlike retinoic acid treatment which also stimulates the antigen expression, IFNs induce neither morphological differentiation, increased binding of epidermal growth factor, nor reduction of expression of stage specific embryonic antigen. The effect of IFNs is reversible; removal of IFNs, even after prolonged exposures, results in a rapid loss of the Class I gene expression. Further, Class I mRNA induction is not inhibited by cycloheximide, suggesting possible independence from de novo protein synthesis. This Class I antigen induction in F9 cells is reminiscent of that observed in somite stage mouse embryos by IFN treatment and may offer a model system to study activation of MHC genes during development.
Species‐specific differences in the toxicity of rhodamine 123 toward cultured mammalian cells
Authors: Gupta Radhey S. , Dudani Anil K. 
Published: February 2005

AbstractThe toxicity of cationic fluorescent dye, rhodamine 123, towards a number of independently established cell lines from three different species, namely human, mouse, and Chinese hamster, has been examined. All of the cell lines from any one species that were examined were found to exhibit similar sensitivities towards rhodamine 123 and no appreciable differences were observed between the normal and transformed cell types. However, in comparison to the cells of human origin, mouse and Chinese hamster cell lines exhibited about 10‐fold and 70‐fold higher resistance, respectively, and these differences appeared to be species related. In contrast to rhodamine 123, no differences in relative toxicities for these cell lines were observed for the structurally related neutral dye, rhodamine B. Fluorescence studies with rhodamine 123 show that in comparison to mouse and Chinese hamster cells, the more sensitive human cells show much higher uptake/binding of the drug, and a good correlation was seen in these studies between the extent of dye uptake/binding and the relative sensitivities of cell lines to rhodamine 123. These results provide evidence that the observed species‐related differences in cellular toxicities are due to differences in the cellular uptake/binding of the dye.
Effect of essential amino acids on the phosphorylation of a 40S ribosomal protein and protein synthesis in Acanthamoeba castellanii
Authors: Jantzen Helga , Schulze Ingrid 
Published: February 2005

AbstractReversible and multiple phosphorylation of a 40S ribosomal protein is observed in a variety of eukaryotic cells. In the primitive eukaryote Acanthamoeba, one or three phosphorylated S3 derivatives are observed during growth phase in nondefined nutrient medium (ND cells) or in chemically defined nutrient medium (D cells), respectively. In both cases, stationary phase cells exhibit nonphosphorylated S3; however, transfer of these cells into the respective fresh nutrient media results in a transient accumulation of four phosphorylated S3 derivatives. Transfer of D cells into nutrient medium, deficient in all or any single essential amino acids, leads to reversible inhibition of S3 phosphorylation and growth arrest. The low level of phosphorylated S3 is not simply the consequence of growth arrest, since in cells where growth is arrested differently, the level of phosphorylated S3 can be high. In response to amino acid deficiency, a number of other changes can be observed. These include a 2–3‐fold decrease of total protein synthesis, 13 changes in the cellular protein pattern, and specific alterations in the ribosome absorbance profiles and in the distribution of poly‐A+ within subribosomal and ribosomal fractions. While the rate of total protein synthesis seems to be associated with the level of phosphorylated S3, the level of the synthesis of at least 10 of the particular proteins can be dissociated from the level of S3 phosphorylation.
Cytoplasmic maturation of the snRNAs
Authors: Zieve Gary W. 
Published: February 2005

AbstractThe snRNAs are abundant and stable components of the interphase nucleus. Aqueous and non‐aqueous cell fractionation demonstrate that the snRNAs appear transiently in the cytoplasm shortly after transcription, before returning permanently to the interphase nucleus. In pulse label and chase experiments, the newly synthesized snRNA species appear in the cytoplasm after 1 min of labeling and then return to the interphase nucleus after approximately 15 min in the cytoplasm. In order to study the maturation and intracellular transport of these particles, a battery of metabolic inhibitors and alterations in cell culture conditions were investigated for their ability to interfere with the return of the newly synthesized snRNAs to the nucleus. A wide range of inhibitors of the cytoskeleton did not interfere with this process. Only the inhibition of protein synthesis and exposure of cells to medium of at least twice the normal tonicity block the return of the snRNAs to the nucleus. Immunofluorescent staining of cells exposed to hypertonic medium identifies discrete foci in the cytoplasm that stain with the Sm antiserum, directed against proteins associated with the snRNAs. Using a detergent extraction procedure that preserves the cytoskeleton, the newly synthesized snRNAs in the cytoplasm fractionate as soluble complexes. These data are consistent with the hypothesis that the snRNAs partition into the interphase nucleus because of a preferential solubility and the existence of specific binding sites.
Growth kinetics and differentiation in vitro of normal human uroepithelial cells on collagen gel substrates in defined medium
Authors: Reznikoff Catherine A. , Loretz Linda J. , Pesciotta Donna M. , Oberley Terry D. , Ignjatovic Melanie M. 
Published: February 2005

AbstractConditions have been described for the selective growth, serial cultivation, and postconfluent morphological differentiation in vitro of normal adult human uroepithelial cells (HUC) on collagen gel substrates in a serum‐free medium without the deliberate addition of undefined components and without a requirement for a polypeptide growth factor. The culture medium used (F12*) was the standard Ham's F12 medium (0.3 mM calcium) supplemented with 1 μg/ml hydrocortisone, 5 μg/ml transferrin, 10 μg/ml insulin, 0.1 mM nonessential amino acids, 2.0 mM L‐glutamine, 2.7 mg/ml D‐glucose, 10−4 M ethanolamine or 10−4 M phosphoethanolamine, and 5 × 10−8 M selenium. HUC grown in F12* on Type I collagen gel substrates had a generation time of 33 hours and could be serially passed 3–5 times during log phase of growth (20–25 population doublings) before spontaneously senescing. Transmission electron microscopy showed that cultures of HUC grown entirely in serumfree F12* on collagen gel substrates morphologically differentiate postconfluence to resemble in some respects the stratified uroepithelium in vivo, although neither a basal lamina nor an asymmetric unit membrane develop. The addition of epidermal growth factor (EGF) to the F12* did not improve either the growth rate or the lifespan in vitro of HUC. In contrast, the addition of fetal bovine serum (FBS) to F12* was mitogenic to HUC in a dose‐dependent manner in the concentration range 0.01–1.00% (4–400 μg/ml protein), but higher concentrations of FBS did not improve growth further. The generation time of HUC in 1% FBS‐F12* decreased to 21 hours, and the potential population doublings in vitro increased to 31–36. Small amounts (140 μg/ml) of bovine pituitary extract (BPE) were similarly mitogenic to HUC in F12*. Altering the calcium concentration in the standard Ham's F12 medium (0.3 mM), however, did not improve the growth of HUC in serum‐containing or serumfree medium. Higher calcium concentrations (0.30–0.90 mM) were neither mitogenic nor inhibitory to HUC growth, but resulted in decreasing viability of HUC in growing cultures, suggesting an accelerating rate of cellular differentiation. In contrast HUC in low calcium, serum‐free F12* (0.1 mM) failed to stratify and morphologically differentiate even in postconfluent cultures. This failure of HUC to differentiate in low calcium F12* medium did not confer a long‐term growth advantage. On the contrary, optimal long‐term growth of HUC serially passaged in F12* was obtained using a moderate calcium concentration (0.3 mM) which supported morphological differentiation and stratification of HUC in postconfluent cultures, showing that these two parameters are not mutually exclusive in this system and that there exists a delicate calcium‐regulated balance between growth of HUC in nonconfluent cultures and stratification and differentiation of HUC in postconfluent cultures.