bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulation of programmed death in erythroid progenitor cells by erythropoietin: Effects of calcium and of protein and RNA syntheses
Authors: Kelley Linda L , Koury Mark J. , Bondurant Maurice C. 
Published: February 2005

AbstractErythropoietin (EPO) retards DNA breakdown characteristic of programmed cell death (apoptosis) and promotes survival in erythroid progenitor cells. The mechanism by which EPO inhibits programmed death is unknown. In the well‐characterized model of glucocorticoid‐treated thymocytes, activation of a Ca2+/Mg2+‐sensitive endonuclease and new protein and RNA syntheses have been found necessary for apoptosis. We examined the effects of EPO on the free intracellular calcium ion concentration ([Ca2+]i), and the roles of Ca2+ and RNA and protein syntheses on DNA cleavage in erythroid progenitor cells. The murine model of erythroid differentiation using Friend leukemia virus‐infected proerythroblasts (FVA cells) was used. EPO did not affect the [Ca2+]i in FVA cells. Decreasing [Ca2+]i by extracellular Ca2+ chelation with EGTA facilitated DNA breakdown. Increasing [Ca2+]i with the calcium ionophore 4‐bromo‐A23187 increased DNA cleavage; however, DNA fragments generated by high [Ca2+]i were much larger than those seen in the absence of EPO or presence of EGTA. Increased [Ca2+]i also inhibited DNA breakdown to small oligonucleosomal fragments characteristic of cells cultured without EPO. However no concentration of ionophore protected the high molecular weight DNA as did EPO. Cycloheximide inhibited DNA breakdown in a dose dependent manner in cultures lacking EPO, but two other protein synthesis inhibitors, pactamycin and puromycin, did not prevent DNA breakdown. Inhibition of RNA synthesis with actinomycin D did not prevent DNA breakdown. Cells with morphological characteristics similar to those reported in other cells undergoing programmed death accumulated in EPO‐deprived cultures. These studies demonstrate that although DNA cleavage and morphological changes are common to apoptotic cells, the roles for Ca2+ and protein and RNA syntheses are not universal and suggest that apoptosis can be regulated by different biochemical mechanisms in different cell types. © 1992 Wiley‐Liss, Inc.
Cell density dependent effects of TGF‐β demonstrated by a plasminogen activator‐based assay for TGF‐β
Authors: Flaumenhaft Robert , Rifkin Daniel B. 
Published: February 2005

AbstractTransforming growth factor‐β1 (TGF‐β1) induces a decrease in plasminogen activator (PA) expression in confluent cultures of bovine aortic endothelial (BAE) cells. We describe an assay using the suppression of PA expression in confluent BAE cells by TGF‐β1 which detects concentrations of the growth factor ranging from 5 to 200 pg/ml and has an ED50 of 15–20 pg/ml. The assay can be performed in 96‐well plates and requires a minimum of 35 ul of solution per sample, thereby limiting the amount of reagents required and allowing many samples to be tested in a single assay. Here we demonstrate that the effect of TGF‐β1 on PA expression in BAE cells depends on the length of time the cells are exposed to the growth factor and the density at which the cells are plated. In cells plated at a high density (3.5 × 105 cells/cm2), both 4 h and 24 h exposures to TGF‐β1 suppress PA expression. However, with cells plated sparsely (3.5 × 104 cells/cm2), a 4 h exposure to TGF‐β1 increases PA expression 2‐fold, whereas a 24 h exposure results in an 85% inhibition of basal PA expression. The paradoxical stimulation of PA expression in cells at a sparse density upon 4 h exposure to TGF‐β1 occurs in a dose‐dependent manner with an ED50 of 15–20 pg/ml. This bifunctional response of PA production in cells exposed to TGF‐β1 may have implications with regard to the role of TGF‐β1 in angiogenesis. © 1992 Wiley‐Liss, Inc.
Regulation of albumin expression in fetal rat hepatocytes cultured under proliferative conditions: Role of epidermal growth factor and hormones
Authors: De Juan Carmen , Benito Manuel , Fabregat Isabel 
Published: February 2005

AbstractSustained production of plasma proteins, notably albumin, is a reliable indicator of the differentiated state of hepatocytes. In this work, we have developed a fetal hepatocyte culture system where studying the regulation of albumin expression in proliferating liver cells. Our results show that under proliferative conditions (i.e., in the presence of EGF) fetal hepatocytes maintain albumin production above control quiescent non‐treated cells. Glucagon and noradrenaline have no effect on the proliferation induced by EGF in cultured fetal hepatocytes; however, they act synergistically with this growth factor, increasing intracellular albumin levels. The maximum response is obtained by treatment of cells with EGF and noradrenaline. The stimulatory noradrenergic effect is mimicked by agents that increase cyclic AMP levels (forskolin plus IBMX). However, vasopressin or phorbol esters have no effect on albumin production, neither alone nor in combination with EGF. Dexamethasone, which does not alter the proliferative induction of EGF, increases albumin content. This effect is independent of the proliferative status of the cells and is not enhanced by glucagon, noradrenaline, or cyclic AMP increasing agents. The hormonal changes observed in albumin production partially correlate with changes in mRNA levels. This is the first time that cyclic AMP increasing agents are shown to act synergistically with EGF, increasing the expression of this liver specific gene. © 1992 Wiley‐Liss, Inc.
The proto‐oncogene C‐myc is involved in cell differentiation as well as cell proliferation: Studies on growth plate chondrocytes in situ
Authors: Farquharson Colin , Hesketh John E. , Loveridge Nigel 
Published: February 2005

AbstractA combination of immunocytochemistry and microdensitometry has been used to localize and quantify the expression of the proto‐oncogene c‐myc within chondrocytes of the proximal growth plates of rat and chick long bones. Although the c‐myc protein was localized in all chondrocytes of the growth plate of both species the most intense staining was restricted to the proliferating and differentiating chondrocytes. These were identified by their ability to synthesize DNA (bromodeoxyuridine positive) and the presence of alkaline phosphatase activity, respectively. Species differences did exist with the c‐myc concentration of the chick proliferating and differentiating chondrocytes being higher (128% and 240%, respectively) than the respective chondrocytes of the rat. The higher c‐myc concentration in the chick proliferating chondrocytes paralleled the differences in the bromodeoxyuridine labelling index between the two species. In the rat, the concentration of c‐myc protein present in the differentiating chondrocytes was 74% higher than in the respective proliferating chondrocytes, while in the chick it was 146% higher. The data not only provides further evidence for a role of the c‐myc protein in cell proliferation but also suggests involvement of this protein in chondrocyte differentiation and/or hypertrophy. © 1992 Wiley‐Liss, Inc.
Induction of fibronectin gene expression by transforming growth factor beta‐1 is attenuated in bronchial epithelial cells by ADP‐ribosyltransferase inhibitors
Authors: Beckmann Joe D. , Illig Mary , Romberger Debra , Rennard Stephen I. 
Published: February 2005

AbstractTransforming growth factor‐β (TGF‐β) exerts several effects on cultured airway epithelial cells including inhibition of proliferation and stimulation of fibronectin gene expression. ADP‐ribosylation is one potential regulatory mechanism of gene expression by TGF‐β. We tested this possibility by exposing cultured bovine bronchial epithelial cells to the chemical inhibitor of ADP‐ribosyl transferase enzymes, 3‐aminobenzamide (3‐AB) and, for comparison, 3‐aminobenzoic acid (3‐ABA), which is structurally similar to 3‐AB but which does not inhibit ADP‐ribosyl transferases. Exponential cell growth rate (1.2 doublings/day) or cellular morphology observed by phase contrast microscopy were not affected by 3 mM 3‐AB or 3‐ABA. Neither compound antagonized inhibition of cell division or induction of squamous morphology by TGF‐β1. In contrast, the sixfold stimulation of fibronectin production by exposure of cells to 30 pM TGF‐β1 for 48 h was reduced by 50% in the presence of 3 mM 3‐AB, whereas 3 mM 3‐ABA had no effect. The antagonistic effect was augmented by administration of 3‐AB 24 h prior to induction by TGF‐β1. Northern blot hybridization analyses demonstrated that 3‐AB, but not 3‐ABA, attenuated the induction of fibronectin mRNA by TGF‐β1 by up to 50%. These observations may implicate a role of cellular ADP‐ribosylation in the regulation of some gene expression by TGF‐β. © 1992 Wiley‐Liss, Inc.
Modulation of growth factor responsiveness of murine mammary carcinoma cells by cell matrix interactions: Correlation of cell proliferation and spreading
Authors: Elliott Bruce , Östman Arne , Westermark Bengt , Rubin Kristofer 
Published: February 2005

AbstractWe have examined the role of growth factors and extracellular matrix in the proliferation and cell adhesion of a murine mammary carcinoma, SP1, and a stable highly metastatic variant, SP1‐3M. On fibronectin, both cell types proliferated strongly in response to basic fibroblast growth factor (bFGF) and platelet‐derived growth factor BB (PDGF‐BB) after culture for 24 h and 72 h. In contrast, on collagen type I, SP1 cells proliferated only weakly to PDGF‐BB at either time, and SP1‐3M cells showed a response to PDGF‐BB only at 72 h. The proliferative response to bFGF was also consistently lower when the cells were cultured on collagen than on fibronectin. No significant proliferative responses were detected to epithelial growth factor (EGF), transforming growth factor‐β (TGF‐β), or estrogen on any substratum. The lack of responsiveness to PDGF‐BB of cells cultured on collagen type I was not due to differences in numbers or affinity of PDGF receptors. We therefore examined the adhesion and spreading properties of SP1 and SP1‐3M cells. Without exogenous growth factors, both cell lines adhered to fibronectin and laminin. SP1‐3M cells did not bind to collagen type I, whereas SP1 cells did. Attachment to all three substrata was inhibited by anti‐β1 integrin IgG, suggesting that the primary adhesion to these substrata is mediated by β1 integrins. SP1 and SP1‐3M cells showed similar integrin patterns following immunoprecipitation by anti‐β1 integrin IgG. bFGF stimulated increased adhesion and spreading of both SP1 and SP1‐3M cells to collagen type I within 24 h, whereas PDGF‐BB was less capable of this effect. Our results suggest that the proliferative response of SP1 and SP1‐3M cells to PDGF‐BB and bFGF is dependent on the extracellular matrix environment, and imply that modification of extracellular matrix and/or surface integrin receptors may regulate responsiveness to these growth factors in the SP1 tumor model. © 1992 Wiley‐Liss, Inc.
Effect of protein and steroidal osteotropic agents on differentiation and epidermal growth factor‐mediated growth of the CFK1 osseous cell line
Authors: Bernier Suzanne M. , Goltzman David 
Published: February 2005

AbstractThe effects of factors known to influence bone metabolism were examined using the osseous cell line CFK1. Parathyroid hormone (PTH) and dexamethasone (DEX) appeared to enhance the formation of cell foci of CFK1 cells in culture whereas retinoic acid (RA) caused a marked alteration in individual cell morphology. Bone morphogenetic protein (BMP‐2) and PTH increased alkaline phosphatase activity, however, this index of differentiation was suppressed by epidermal growth factor (EGF), DEX, and RA. BMP‐2 and EGF each stimulated DNA synthesis in a dose‐dependent manner and enhanced cell numbers, but, no synergistic response of EGF and BMP‐2 was observed. PTH and DEX failed to significantly alter cell number of EGF‐stimulated DNA synthesis or cell proliferation. Although RA treatment of CFK1 cells resulted in a reduction in cell number compared to control, pretreatment with RA enhanced EGF‐stimulated DNA synthesis and proliferative effects. At least part of this effect was by increasing the EGF receptor binding capacity of the cells. Furthermore, using cell cycle analysis, addition of EGF stimulated the progression of RA‐treated cells into the DNA synthesis (S) phase with a reduced lag time. EGF and BMP‐2, therefore, appear to exert a role in the expansion dynamics of the CFK1 population although BMP‐2 may also enhance differentiation. PTH and DEX may act primarily to modulate the differentiated function of the CFK1 cells. RA inhibited cell proliferation and may mediate differentiation towards a less established cell population with upregulation of EGF receptors. The CFK1 cell model may, therefore, provide insight into microenvironmental control of growth and differentiation of precursor osseous cells. © 1992 Wiley‐Liss, Inc.
UV induction of transforming growth factor alpha in melanoma cell lines is a posttranslational event
Authors: Chenevix‐Trench G. , Cullinan M. , Ellem K. A. O. , Hayward N. K. 
Published: February 2005

AbstractLow, mitogenic fluences of UVC (3.7–5.6 Jm−2) have previously been shown to cause increases of radioimmunoassayable transforming growth factor alpha (TGFα) in the medium and cells of cultures of melanocytes, melanoma lines, and HeLa cells (Ellem, K.A.O., Cullinan, M., Baumann, K.C., Dunstan, A.: Carcinogenesis 9:797–801, 1988). Here the cellular mechanism of this increase is explored by Northern blotting to detect any changes in TGFα mRNA levels, and the use of inhibitors of macromolecular synthesis to attempt to block the increase in TGFα protein. We were unable to detect any increase in TGFα mRNA levels attributable to UVC between 2 and 24 hours after irradiation. Inhibition of DNA synthesis (arabinosylcytosine, 10 μM), RNA synthesis (actinomycin D, 3 μg/ml; DRB 93 μM), or protein synthesis (cycloheximide, 10 μg/ml) failed to prevent the UVC induced increase in TGFα. We conclude that the UVC induction of TGFα is by a posttranslational mechanism. There was considerable discordance between the amount of TGFα protein and its mRNA in cultures of 15 different melanoma cell lines, which again emphasized that posttranscriptional mechanisms modulate the release of immunodetectable TGFα. We also found that the inhibitors themselves were capable of inducing an increase in TGFα in MM229 cultures. This suggests that the inhibitors and UV may effect the increase by a common mechanism, perhaps the activation of cell surface proteases as suggested for other stimuli (e.g., Pandiella, A., and Massagué, J.: Proc. Natl. Acad. Sci., USA 88:1726–1730, 1991) and that the response may be part of a global response to perturbation of DNA synthesis. © 1992 Wiley‐Liss, Inc.
Age‐related alterations in superoxide anion generation in mouse peritoneal macrophages studied by repeated stimulations and heat shock treatment
Authors: Lavie Lena , Weinreb Orly , Gershon David 
Published: February 2005

AbstractThe ability of thioglycollate‐elicited peritoneal macrophages (PM) from young and senescent mice to generate superoxide anions (O−2) under repeated stimulation or thermal stress was studied using either zymosan, opsonized zymosan (OZ), or phorbol myristate acetate (PMA). A diminished capacity to recover from repeated stimulation was found with aging. When stimulated for a second time 24 hours after the primary stimulation, PM from young animals generated 80% of the initial O−2 responses to either zymosan, or OZ. Under the same conditions, PM from senescent mice generated 62% of the initial O−2 produced in response to zymosan, and 45% in response to OZ. In both age groups the response to a second PMA stimulation comprised only 10% of the primary response. A considerably diminished capacity to generate O−2 was also demonstrated in PM from senescent mice after recovery from exposure to thermal stress. Exposure to 42.5°C for 20 minutes was found to be the threshold temperature for irreversible loss of activity in senescent PM, whereas at this temperature, PM from young animals recovered up to 70% of their O−2 generating activity. Since NADPH oxidase and superoxide dismutase activities were only mildly affected by the hyperthermia in all age groups, they could not account for the age‐related decline in the recovery from stress. Age‐related alterations in signal transduction or receptor alterations could possibly play a primary role in this decline. © 1992 Wiley‐Liss, Inc.
Signal transduction during liver regeneration: Role of insulin and vasopressin
Authors: Marino M. , Mangiantini M. T. , Spagnuolo S. , Luly P. , Leoni S. 
Published: February 2005

AbstractThe relationship between cell proliferation and inositol lipid turnover has been studied by comparing the steady state of inositol derivative metabolism in quiescent and regenerating rat hepatocytes isolated at 4 h (G1 phase of first cell cycle) and 24 h (onset of M phase) after partial hepatectomy. The effect of two hormones able to regulate hepatic regeneration, insulin and vasopressin, has been considered, and the results can be summarized as follows: (i) at 4 h after partial hepatectomy, the precursor incorporation into inositol polyphosphates and the particulate phospholipase C activity increase with respect to quiescent hepatocytes, whereas the content of I1,4,5P3 does not change, suggesting an increased turnover of this molecule in this step of cell cycle priming; (ii) 24 h after partial hepatectomy, the radioactivity linked to IP3 and IP4, as well as soluble and particulate phospholipase C activity, and IP3 content increase, suggesting the presence, at the onset of M phase, of second messenger accumulation; (iii) only 24 h after partial hepatectomy, the inositol derivative metabolism is affected by vasopressin; and (iv) insulin exerts a modulatory role on inositol polyphosphate production without involving membrane‐bound PLC activity or phosphoinositide hydrolysis. These data suggest that inositol‐derived signal molecules are associated with hepatic regneration; moreover, the metabolic pathway of such compounds seems to be regulated so that only specific inositol phosphates are present in each step of the cell cycle. © 1992 Wiley‐Liss, Inc.
Role of protein kinase C in transforming growth factor‐β1 induction of carcinoembryonic antigen in human colon carcinoma cells
Authors: Chakrabarty Subhas 
Published: February 2005

AbstractTransforming growth factor‐β1 (TGF‐β1) regulates the expression of the carcinoembryonic antigen (CEA) gene family in the human colon carcinoma cell line Moser. The mechanisms through which it acts, however, are unknown. In this communication, several lines of evidence are presented to show that the induction of CEA expression and secretion (collectively called CEA responses) by TGF‐β1 is associated with protein kinase C (PKC) pathway of signal transduction. Treatment of intact cells with the PKC‐specific inhibitor calphostin C downmodulated cellular PKC phosphotransferase activity and blocked the induction of the CEA responses by TGF‐β1. Depletion of PKC by treatment of intact cells with phorbol ester also blocked the action of TGF‐β1. The induction of the CEA responses by TGF‐β1 was also blocked by the protein kinase inhibitor 1‐(isoquinolinesulfonyl)‐2‐methylpiperazine dihydrochloride (H‐7), which also inhibited cellular PKC activity. However, TGF‐β1 did induce the CEA responses in intact cells treated with the calmodulin antagonist N‐(6‐aminohexyl)‐5‐chloro‐1‐naphthalenesulfonamide hydrochloride (W‐7), the calmodulin‐dependent phosphodiesterase inhibitor calmidazolium, the diacylglycerol kinase inhibitor R59 022, and the G‐protein inhibitors cholera toxin and pertussis toxin. Treatment of intact cells with TGF‐β1 induced a rapid and transient increase in PKC phosphotransferase activity. TGF‐β1, however, was unable to induce PKC enzymatic activity in cells pretreated with calphostin C. Therefore, it is concluded that TGF‐β1 regulates the CEA responses through a signal transducing pathway associated with PKC. © 1992 Wiley‐Liss, Inc.
Transforming growth factor‐β1 rapidly induces Hsp70 and Hsp90 molecular chaperones in cultured chicken embryo cells
Authors: Takenaka Ivone M. , Hightower Lawrence E. 
Published: February 2005

AbstractIn this report we show that: (1) molecular chaperones in the heat shock protein (hsp) family are a new class of cellular proteins induced by Transforming Growth Factor‐β1 (TGFβ), a cytokine present in serum, (2) rapid induction of Hsc70 precedes a general increase in protein synthesis and may be a preparatory event, (3) TGFβ is a potent regulator of overall protein synthesis in chicken embryo cells (CEC), and (4) isoforms of Hsp90 with different biochemical properties exist, raising the possibility that they may have different functions. TGFβ can substitute for serum in stimulating synthesis of members of the Hsp90 and Hsp70 families of stress proteins, whereas other cytokines, including PDGF, FGF, and EGF, were not effective nor did they enhance the stimulatory effect of TGFβ on the hsp's. Analysis of the induction of hsp's using one‐and two‐dimensional polyacrylamide gel electrophoresis indicated that members of the Hsp70 family of molecular chaperones were induced rapidly by TGFβ, reaching maximum rates of accumulation by 5 hours of treatment. Total protein synthesis increased more slowly, undergoing an ∼twofold increase in 24 hours. Using a modified protocol for two‐dimensional gel electrophoresis, the Hsp90 protein family was separated into four isoelectric forms, two of which were phosphorylated (Hsp90‐2 and ‐4). These phosphorylated isoforms turned over faster than the unphosphorylated forms of Hsp90. All four isoforms were heat inducible, but only Hsp90‐2 and ‐3 were induced rapidly by TGFβ, again within 5 hours of treatment. The effects of serum on these protein families were similar to those of TGFβ, suggesting that this cytokine may be the serum component primarily responsible for up‐regulating members of the Hsp90 and Hsp70 families. We hypothesize that cells rapidly increase their chaperoning capacity for newly synthesized polypeptides in preparation for an increase in the rate of synthesis of proteins up‐regulated by TGFβ. © 1992 Wiley‐Liss, Inc.