摘要:

AbstractCatecholamines, acting via the alpha‐1 adrenergic receptor, have been demonstrated to influence adult rat hepatocyte DNA synthesis in primary culture and in vivo during liver regeneration following partial hepatectomy (PHX). Earlier investigations have suggested that the alpha‐1 effect on DNA synthesis is significant only during the first day following PHX. We examined receptor binding at several early and late time points after surgery, and we observed a significant loss of specific [3H]‐prazosin binding to cells isolated from rat livers 48 and 72 hr after PHX. In contrast, the ability of norepinephrine to stimulate inositol phosphate production in isolated cells prelabeled with [3H]‐myo‐inositol was transiently reduced between 8 and 16 hr, when alpha‐1 binding capacity was virtually unchanged. This uncoupling of phosphoinositide turnover from binding was preceded by a drop in hepatic membranerasp21 content, as assayed by liquid competition radioimmunoassay. The loss of immunoreactive p21 from membranes was significant by 2 hr after PHX. These findings suggest a role for alpha‐1 receptors andrasprotein in the early events of liver

ISSN:0021-9541    

DOI:10.1002/jcp.1041400202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractIn chick embryo fibroblasts (CEFs), a partial substitution of extracellular Na+with other cations or carbohydrates decreased the intracellular Na+content without altering the K+level. Concomitantly, a significant decrease in the serum‐dependent rate of protein synthesis occurred. This phenomenon appeared to be quickly reversible upon reconstitution of the correct extracellular Na+concentration in the culture medium. The presence of a transcriptional inhibitor such as actinomycin D during the treatment did not inhibit the reversibility of the phenomenon. The presence in the culture medium of K+in such excess as to dissipate the membrane potential did not alter the observed relationship between the protein synthesis rate and the internal Na+content. Analysis of the amino acid pool indicated that the observed inhibition of the rate of protein synthesis in CEFs incubated in low Na+medium was not caused by an unbalanced availability of intracellular amino acids. In addition, intracellular pH, as estimated by the measurement of the equilibrium distribution of benzoic acid, did not show any significant alteration in cells incubated in the presence of bicarbonate buffer and in low extracellular Na+. Moreover, the relationship between the rate of protein synthesis and the internal Na+content was still observed in CEFs cultured in bicarbonate‐containing media, but at lower or higher than physiological pH. Analysis by two‐dimensional polyacrylamide gel electrophoresis (2D‐PAGE) of the proteins synthesized by CEFs cultured at a reduced extracellular Na+concentration showed that specific alterations of gene expression o

ISSN:0021-9541    

DOI:10.1002/jcp.1041400203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe effect of inhibitors of RNA synthesis on 1,25(OH)2vitamin D3‐induced monocytic differentiation was studied in a well‐differentiating clone AB 47 of HL 60 cells. The concentrations of these inhibitors were chosen to permit the maintenance of cell viability for at least 48 hours, and resulted in 40‐60% inhibition of total cellular RNA synthesis. No impairment of 1,25(OH)2vitamin D3‐induced monocytic differentiation was observed with all inhibitors tested, and the presence of cordycepin actually enhanced differentiation. The phenotypic evidence of monocytic differentiation correlated with the increased levels of mRNA for c‐fos and c‐fms measured by hybridization to appropriate nick‐translated cDNA probes. In contrast, nuclear run‐on experiments showed the expected inhibition of transcription of these genes by the compounds used. The data suggest that interference by external agents with transcription of genes essential for a differentiation program brings into play compensatory mechanisms which permit the program to continue. Thus, differentiation appears to have a high priority among various competing intracellular pathways in 1,25(OH)2vitamin D3‐treated HL 60 cells. Stabilization of messenger RNA levels evident in this study may therefore represent a general cellular mechanism for the correction of unwanted effects of xenobi

ISSN:0021-9541    

DOI:10.1002/jcp.1041400204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractSecretion of urokinase‐type plasminogen activator (uPA) by RAW264.7 cells was stimulated by heparin in a dose‐ and time‐dependent manner. Secretion of uPA was not detected when cells were exposed to heparin at 4°C, indicating that heparin was not simply releasing receptor‐bound uPA. Furthermore, prior removal of membrane‐associated uPA did not influence heparin's ability to stimulate the release of uPA from the macrophage‐like line. Low molecular weight and weakly anticoagulant heparins stimulated uPA secretion but less effectively than other heparin fractions. The observed stimulation in macrophage uPA secretion by heparin is similar to that previously reported for polyanions recognized by the scavenger receptor including fucoidan, polyinosinic acid, dextran sulfate, and acetyl‐LDL (Falcone and Ferenc:J. Cell. Physiol. 135:387–396, 1988). Evidence that heparin's binding to RAW264.7 cells is mediated by the scavenger receptor is derived from experiments in which fucoidan blocked the specific binding of [3H]‐heparin to RAW264.7 cells. However, heparin partially inhibited the stimulation of cholesteryl [3H]‐oleate synthesis observed in these cells upon incubation with acetyl‐LDL and weakly inhibited cellular binding of125l‐acetyl‐LDL at 4°C. These data indicate that heparin's binding to RAW264.7 cells is mediated, only in part, by the scavenger receptor. Nonetheless, neither heparin nor fucoidan was able to stimulate the release of plasminogen activator activity from monocyte‐like U937 cells which are devoid o

ISSN:0021-9541    

DOI:10.1002/jcp.1041400205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe temperature‐sensitive (ts) Chinese hamster ovary (CHO) cell mutant tsH1 contains a thermolabile leucyl‐tRNA synthetase. Upon incubation at the nonpermissive temperature of 39.5°C, the enzyme became reversibly inhibited over a period of minutes, and the cells lost viability over a period of many hours. However, killing of tsH1 by acute heating at 45°C was identical to that of wild‐type (SC) cells. In addition, the heat‐induced inhibition of protein synthesis was similar for both cell types, as measuredafteracute heating at 45°C. Furthermore, both killing and inhibition of protein synthesis showed thermotolerance in both cell types. In contrast to the effects at 45°C, at 39.5°C, neither the inhibition of leucyltRNA synthetase activity nor the killing of tsH1 expressed thermotolerance. Also, treatment of tsH1 at 39.5°C did not induce thermotolerance to killing at 45°C. The inhibition of leucyl‐tRNA synthetase activity in tsH1 at 39.5°C was further distinguished from the 45°C‐induced inhibition of protein synthesis in SC cells by a much more rapid reversal of the inhibition of leucyl‐tRNA synthetase activity. Also, the rate of reversal of the inhibition of protein synthesis by 45°C in SC cells was decreased by increased heat dose. Such was not true for the 39.5°C inhibition of leucyl‐tRNA synthetase activity in tsH1. The data indicate that there exist two distinct types of thermal inhibition‐one slowly reversible type which was observedduringandafterheating at 45°C and both induced and expressed thermotolerance, and a second, rapidly reversible type, which was evident onlyduringheating of tsH1 at 39.5°C and neither induced

ISSN:0021-9541    

DOI:10.1002/jcp.1041400206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractWe examined the effects of transforming‐growth factor‐B (TGF‐B) on growth ([3H]‐thymidine uptake) and function (dehydroepiandrosterone sulfate [DHAS]and cortisol production) of human fetal zone adrenal cells. Results indicate that TGF‐B significantly inhibits, in a dose‐related manner, both basal and epidermal growth factor (EGF)‐stimulated cell growth: IC50= 0.1–;0.25 ng/ml. EGF is ineffective in overcoming the inhibitory effect of TGF‐B, suggesting a noncompetitive antagonism between the two factors. Also, the inhibitory effect of TGF‐B is additive to that of adrenocorticotropic hormone (ACTH). On the other hand, TGF‐B (1 ng/ml) does not significantly change basal or ACTH‐stimulated DHAS or cortisol secretion. We conclude that, unlike its effect on other steroid‐producing cells, TGF‐B inhibits growth of fetal zone cells and does not appear to have a significant inhibitor

ISSN:0021-9541    

DOI:10.1002/jcp.1041400207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractWe have characterized the induction of glucose‐regulated proteins (GRPs) inXenopus laevisA6 cells, a kidney epithelial cell line. Exposure of A6 cells to medium in which 2‐deoxyglucose replaced galactose resulted in enhanced synthesis of two proteins at 78 and 98 kd. The 78 kd protein was determined by two‐dimensional PAGE to consist of two isoelectric variants with pls of 5.3 and 5.2 whereas the 98 kd protein resolved into a single spot with a pl of 5.1. The 78 kd protein cross‐reacted with antiserum against chicken GRP78 (glucose‐regulated protein), suggesting that theXenopusprotein shares homology with a previously characterized GRP. This was supported by the finding that a rat GRP78 probe hybridized with a 2‐deoxyglucose‐inducible mRNA. Synthesis of the two proteins was also induced by tunicamycin, 2‐deoxygalactose, and dithiothreitol. However, the GRPs were not induced by glucosamine or calcium ionophore A23187 at concentrations and exposure periods that have previously been shown to elicit a GRP response in mammalian and avian cells. Enhanced synthesis of the two GRPs by 2‐deoxyglucose was transient, reaching maximal levels by 12‐24 h and decreasing to near control levels by 48 h. Removal of the stress at the point of peak synthesis resulted in decreased synthesis of both proteins within 6 h and a return to control levels within 24 h of recovery. These data suggest thatXenopuscells have a GRP response that is similar, but not identical, to that found

ISSN:0021-9541    

DOI:10.1002/jcp.1041400208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractTransforming growth factor‐β (TGF‐β) stimulates DNA synthesis in human foreskin fibroblasts after a prolonged lag period as compared with other growth factors. The mechanism of induction of DNA synthesis appears to be dependent on the synthesis and secretion of PDGF‐related proteins as antibodies which are specific for PDGF can block the TGF‐β‐induced DNA synthesis. Other growth factors such as PDGF, EGF, or FGF do not induce the synthesis of these PDGF‐related proteins. Additionally, TGF‐β treatment of human foreskin fibroblasts induces the expression of the PDGF A‐chain gene but not the B‐chain gene. This phenomenon appears to function in vivo, as subcutaneous injection of TGF‐β in rat skin induces the expression of the PDGF A‐chain gene. These data suggest that TGF‐β may stimulate the growth of fibroblastic cells via an autocrine produc

ISSN:0021-9541    

DOI:10.1002/jcp.1041400209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe 1246‐3A cell line is an insulin‐independent variant derived from the adipogenic cell line 1246. Data presented in this paper indicate that the 1246‐3A cell line releases in its culture medium two types of transforming growth factors, TGF‐α and TGF‐β‐like polypeptides, and a growth inhibitor. TGF‐α like polypeptide eluted from Biogel P60 column into two fractions with an apparent molecular weight of 50 kDa and 13 kDa. These high‐molecular‐weight TGF‐α‐like factors competed with125l‐EGF for binding to epidermal growth factor (EGF) receptors and were specifically immunoprecipitated by incubation with antirat TGF‐α antibody, not by incubation with anti‐EGF antibody. Both fractions promoted anchorage‐independent growth of normal rat kidney NRK cells in the absence of EGF and stimulated DNA synthesis in quiescent Balb/c‐3T3 cells in a fashion similar to EGF and synthetic TGF‐α. In addition to secreting TGF‐α‐like polypeptides, 1246‐3A cells produce TGF‐β. This polypeptide, eluted from Biogel P60 chromatography with an apparent molecular weight of 25 kDa, promoted anchorage‐independent growth of NRK cells in the presence of EGF and was growth inhibitory for Chinese hamster lung fibroblasts CCL 39 cells. Interestingly, another growth inhibitory activity was detected in Biogel P60 fractions and eluted with an apparent molecular weight of between 9.5‐11 kDa. This fraction was different from TGF‐β and TGF‐α as determined by specific radioreceptor competition assays. TGF‐α and TGF‐β‐like polypeptides could represent autocrine growth stimulators for the insulin‐independent 1246‐3A cells and act in synergy with insulin‐related factor (IRF) for

ISSN:0021-9541    

DOI:10.1002/jcp.1041400210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractIn cultured foreskin fibroblasts, bradykinin stimulates inositol phosphate generation, arachidonic acid release, and Na+/H+exchange, with doses of 1‐3 nM yielding half‐maximal stimulation. Binding of3H‐bradykinin to these cells demonstrates a single receptor site with a Kdof 2.0 nM and a Bmaxof 91 fmoles/mg protein. Bradykinin analogs of the B2 type inhibit this binding. GTP synergizes with bradykinin to stimulate phosphatidylinositol turnover in permeabilized fibroblasts and GTP‐γ‐S decreases the Bmaxof bradykinin binding to fibroblast membranes, indicating that a G‐protein couples the receptor to phospholipase C. Pretreatment of fibroblasts with either cholera or pertussis toxin enhances bradykinin stimulation of inositol phosphate

ISSN:0021-9541    

DOI:10.1002/jcp.1041400211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY