bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical stimulation of skeletal muscle cells mitigates glucocorticoid‐induced decreases in prostaglandin production and prostaglandin synthase activity
Authors: Chromiak Joseph A. , Vandenburgh Herman H. 
Published: February 2005

AbstractThe glucocorticoid dexamethasone (Dex) induces a decline in protein synthesis and protein content in tissue cultured, avlan skeletal muscle cells, and this atrophy is attenuated by repetitive mechanical stretch. Since the prostaglandin synthesis inhibitor indomethacin mitigated this stretch attenuation of muscle atrophy, the effects of Dex and mechanical stretch on prostaglandin production and prostaglandin H synthase (PGHS) activity were examined. In static cultures, 10−8 M Dex reduced PGF2α production 55–65% and PGE2 production 84–90% after 24–72 h of incubation. Repetitive 10% stretch‐relaxations of non‐Dex‐treated cultures increased PGF2α efflux 41% at 24 h and 276% at 72 h, and increased PGE2 production 51% at 24 h and 236% at 72 h. Mechanical stimulation of Dex‐treated cultures increased PGF2α production 162% after 24 h, returning PGF2α efflux to the level of non‐Dex‐treated cultures. At 72 h, stretch increased PGF2α efflux 65% in Dex‐treated cultures. Mechanical stimulation of Dex‐treated cultures also increased PGE2 production at 24 h, but not at 72 h. Dex reduced PGHS activity in the muscle cultures by 70% after 8–24 h of incubation, and mechanical stimulation of the Dex‐treated cultures increased PGHS activity by 98% after 24 h. Repetitive mechanical stimulation attenuates the catabolic effects of Dex on cultured skeletal muscle cells in part by mitigating the Dex‐induced declines in PGHS activity and prostaglandin production. © 1994 wiley‐Liss, Inc.
Uneven distribution of protein kinase C‐α and ‐β isozymes in human sarcomas and carcinomas
Authors: Cuadrado Antonio , Issing Wolfgang , Fleming Timothy P. , Molloy Christopher J. 
Published: February 2005

AbstractProtein kinase C (PKC) represents a family of structurally related Ser/Tre kinases which are involved in mitogenic signalling and may contribute to human neoplasia. To address this issue, the messenger RNA and protein levels of PKC isoenzymes α and β were analyzed in several human sarcoma‐ and carcinoma‐derived cell lines. Carcinomas contained low or undetectable levels of either PKC‐α or PKC‐β. Sarcomas exhibited similar or increased PKC expression compared to human diploid fibroblasts. Moreover, sarcoma cell lines expressing one PKC isoform did not contain detectable levels of the other. When PKC was depleted from the tumor cells, we observed that the PKC overexpressing sarcomas had reduced their malignant properties as determined by their ability to grow in semisolid medium. In addition, epidermal growth factor‐stimulated and erbB2‐transformed fibroblasts exhibited enhanced cell growth in the absence of PKC. We propose a model for the effect of PKC as a negative regulator of proliferation in epithelial cells and a growth promoter in fibroblasts. © 1994 wiley‐Liss, Inc.
Phenotypic modulation of keratins, vimentin, and α‐fetoprotein in cultured rat liver epithelial cells after chemical, oncogene, and spontaneous transformation
Authors: Bisgaard Hanne Cathrine , Ton Phuongnga T. , Nagy Peter , Thorgeirsson Snorri S. 
Published: February 2005

AbstractSeveral lines of evidence have indicated that rat liver epithelial (RLE) cell lines may be related to a dormant stem cell compartment in the liver in vivo. We have demonstrated that keratin 14 (K14) is expressed together with vimentin in undifferentiated RLE cells. However, upon spontaneous transformation and differentiation to hepatoblast‐like progeny the expression of these intermediate filaments (IF) is abrogated, while expression of another set of genes, among others keratin 18 (K18) and α‐fetoprotein (AFP), is induced (Bisgaard et al., 1994, J. Cell. Physiol., in press). To better understand the mechanisms underlying IF expression during transformation and differentiation of RLE cells we examined the expression and regulation of IFs in clonal cell lines of chemically, oncogene, and spontaneously transformed RLE cells and their resulting tumors. These clonal lines provided a wide variety of tumor phenotypes including trabecular, solid and tubular adeno‐carcinomas, undifferentiated carcinomas, and spindle cell carcinomas. Northern blot analysis of the cell lines confirmed the differential expression of IF mRNAs. While keratin 8 (K8) was expressed at similar steady‐state levels in all cell lines, K14 and vimentin but not K18 were expressed in the majority of cell lines chemically transformed with aflatoxin B1 or by transduction of oncogenes. In contrast, cell lines transformed spontaneously by prolonged passage in vitro expressed K18, while K14 and vimentin were absent. The keratin expression pattern in vitro was retained in the majority of the resulting tumors. However, the keratins expressed in vitro did not accurately predict the tumor phenotype in vivo. In particular, in tumors typed morphologically as adenocarcinomas, the keratin pair typically expressed in chemically transformed tumor cells was K8/K14, whereas K8/K18 was expressed in the tumors derived from spontaneously transformed cell lines. Finally we showed by nuclear run‐on and in vitro translation analyses that the expression of K14, K18, and vimentin in transformed RLE cell lines was regulated at the transcriptional level, whereas that of K8 appeared to be posttranslational. These findings suggest that events controlling the differential expression of IF genes are involved in the processes leading to transformation and differentiation of the RLE cell lines. We conclude that the transformed RLE cell lines provide a valuable model to further examine the regulatory mechanisms involved in hepatic differentiation of undifferentiated “progenitor‐like” RLE cells. © 1994 wiley‐Liss, Inc.
NIH 3T3 cells transfected with a yeast H+‐ATPase have altered sensitivity to insulin, insulin growth factor‐I, and platelet‐derived growth factor‐AA
Authors: Peterson Eric P. , Martinez Gloria M. , Martinez‐Zaguilan Raul , Perona Rosario , Gillies Robert J. 
Published: February 2005

AbstractThe role of intracellular pH (pHin) in the regulation of cell growth in both normal and transformed cells is a topic of considerable controversy. In an effort to study this relationship NIH 3T3 cells were stably transfected with the gene for the yeast H+‐ATPase, constitutively elevating their pHin. The resulting cell line, RN1a, has a transformed phenotype: The cells are serum independent for growth, clone in soft agar, and form tumors in nude mice. In the present study, we further characterize this system in order to understand how transfection with this proton pump leads to serum‐independent growth, using defined media to investigate the effects of specific growth factors on the transfected and parental NIH 3T3 cells. While both cell lines show similar growth increases in response to platelet‐derived growth factor (PDGF)‐BB and epidermal growth factor (EGF), they respond differently to insulin, insulin‐like growth factor‐I (IGF‐I) and PDGF‐AA. RN1a cells exhibit increased growth at nanomolar concentrations of insulin but the parental cells had only a relatively minor response to insulin at 10 μM. Both cell lines showed some response to IGF‐I in the nanomolar range but the response of RN1a cells was much larger. Differences in insulin and IGF‐I receptor number alone could not explain these results. The two cell lines also respond differently to PDGF‐AA. RN1a cells are relatively insensitive to stimulation by PDGF‐AA and express fewer PDGF α receptors as shown by Northern blots and receptor‐binding studies. We propose a unifying hypothesis in which the H+‐ATPase activates a downstream element in the PDGF‐AA signal transduction pathway that complements insulin and IGF‐I signals, while leading to downregulation of the PDGF α receptor. © 1994 wiley‐Liss, Inc.
Tenascin induction in tenascin nonproducing carcinoma cell lines in vivo and by TGF‐β1 in vitro
Authors: Sakai Takao , Kawakatsu Hisaaki , Ohta Masatsugu , Saito Masaki 
Published: February 2005

AbstractTenascin, a novel six‐armed extracellular‐matrix glycoprotein, is expressed in a temporally and spatially restricted pattern during carcinogenesis in association with stromal‐epithelial interactions. In this study, we have tested the hypothesis that tenascin expression depends upon the change of the cellular environment from in vitro to in vivo. The distribution and alterations in the expression of tenascin were compared between in vitro and in vivo studies in a variety of human epithelial‐ and nonepithelial‐derived cell lines. When cell lines were transplanted into nude mice, all xenografts induced host‐mouse‐stroma‐derived tenascin. Four carcinoma‐derived cell lines and all sarcoma‐derived lines, which secreted tenascin in vitro, were found to produce human tenascin after transplantation. Furthermore, three carcinoma‐derived cell lines, A431, HEp‐2, and MCF7, which did not synthesize tenascin in vitro, did synthesize human tenascin after transplantation. These tenascin nonproducing carcinoma cell lines did not express tenascin mRNA in vitro. The addition of TGF‐β1 to the culture medium induced the synthesis and secretion of tenascin, but TGF‐β2 and bFGF were less effective. TGF‐β1 also induced other extracellular‐matrix components, fibronectin and laminin. TGF‐β1 did not induce tenascin in tenascin nonproducing carcinoma cell lines, such as WiDr and A549, in which human tenascin was not induced after transplantation. We have established an in vitro system in which tenascin is induced by the diffusible factor TGF‐β1. This system could shed light on the mechanism of induction of human tenascin observed in vivo in tenascin nonproducing carcinoma cell lines. © 1994 wiley‐Liss, Inc.
IL‐3 and ribavirin induce high level expression of megakaryocytic markers and messages during long‐term treatment of a megakaryocytic leukemia cell line
Authors: Majumdar Alokes , Kerby Stephen , Mullikin Brian , Seidman Michael M. , Stenberg Paula E. , Beckstead Jay H. , Cooney David A. 
Published: February 2005

AbstractMegakaryocyte differentiation is a lengthy process with cells moving through a continuum delineated by the sequential expression of specific gene products. The limited number of primary cells available from marrow for analysis has brought attention to some leukemic cell lines which show enhanced megakaryocyte marker expression following incubation with inducing agents, the most common of which is phorbol myristate acetate (PMA). We developed an alternative induction protocol for the megakaryocytic leukemic cell line CMK, which involved incubation of the cells with IL‐3 and the nucleoside analog, ribavirin, for 1–2 weeks. This treatment was neither toxic nor cytostatic and yielded increased levels of the surface glycoproteins GPIIb/IIIA and GPIb‐IX. Levels of some megakaryocytic messages (GPIIIa, GPIX) showed a marked rise by 12 days of incubation in the inducer combination. This was due to a synergistic interaction between IL‐3 and ribavirin which influenced both transcriptional and posttranscriptional events. Light and electron microscopy demonstrated the presence of large polyploid cells, with morphological features similar to those of megakaryocytes, in the induced cultures. Analysis of the heterogeneity of response in the cell population to the induction regimen after several days of treatment suggested that cells which failed to display surface markers had been stimulated by the inducers but did not have sufficient time to complete expression of that marker. The results were consistent with the view that the cells in the starting population were distributed along a temporal expression pathway, and those which were first to express the earliest marker would also lead in the expression of a later marker. The order of expression was the same as that during normal megakaryocyte development. © 1994 Wiley‐Liss, Inc.
Differential expression of thrombospondin, collagen, and thyroglobulin by thyroid‐stimulating hormone and tumor‐promoting phorbol ester in cultured porcine thyroid cells
Authors: Bellon Georges , Chaqour Brahim , Wegrowski Janusz , Borel Jacques‐Paul , Antonicelli Frank , Claisse Didier , Haye Bernard 
Published: February 2005

AbstractIn the present study, we have investigated the potential regulation of thyroglobulin (Tg) and extracellular matrix components synthesis by thyroid‐stimulating hormone (TSH) and tetradecanoyl phorbol‐13‐acetate (TPA) on thyroid cells. Porcine thyroid cells isolated by trypsin‐EGTA digestion of thyroid glands were maintained in serum containing medium on poly (L‐lysine)‐coated dishes. Cells differentiated into follicular or vesicular‐like structures were distinguished by their ability to organify Na[125l] and to respond to TSH stimulation. After an incubation of the cells with radiolabeled proline or methionine, two major proteins were identified, p450–480 and p290 (so named because of their molecular masses). Tg (p290) synthesis was demonstrated by the synthesis of [131l]‐labeled polypeptides with electrophoretic properties identical to those of authentic Tg molecules. P450–480 resolved to Mr 190,000 under reducing sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE) conditions. It was identified as thrombospondin by its reactivity with a monoclonal anti‐human thrombospondin and by peptide sequencing of some of its tryptic fragments that displayed identity to thrombospondin l. Collagen synthesis was demonstrated by the formation of radioactive hydroxyproline and by the synthesis of pepsin‐resistant polypeptides ranging from Mrs 120,000 to 200,000. When the cells were cultured in the presence of 100 nM TPA, the culture medium contents of thrombospondin and collagen were increased by 2.7 and 1.6‐fold, respectively, whereas Tg content was decreased by a factor 3.9. In contrast, the acute treatment of control cells with TPA induced a decrease in both Tg and collagen content by factors 3.0 and 1.5, respectively, and an increase in thrombospondin content by a factor 2.5. In the presence of 100 nM TPA, TSH (1 mU/ml) did not counteract the stimulating effect of TPA on extracellular matrix components synthesis. In contrast, when cells were cultured in the presence of TSH alone at concentrations higher than 0.1 mU/ml, collagen and thrombospondin in the medium were decreased by a factor 2.0 and 1.9, respectively, and TSH preferentially activated Tg synthesis. However, no acute response to TSH was observed in cells incubated for 2 days without effectors (control cells). On TSH differentiated cells, TPA decreased both collagen and Tg accumulation by factor 1.2 and 1.8, respectively, whereas it increased the one of thrombospondin by a factor 2. These results, together with the stimulating effect of TPA on TSH mediated cell proliferation, argue for a role of thrombospondin in cell adhesion and migration events within the thyroid epithelium. © 1994 Wiley‐Liss, Inc.
Ca2+‐conductances in cultured rat retinal pigment epithelial cells
Authors: Strauss Olaf , Wienrich Marion 
Published: February 2005

AbstractMembrane conductances for Ca2+ in cultured rat pigment epithelial cells were studied in the whole‐cell configuration of the patch‐clamp technique using barium (10 mM) as a charge carrier. Two types of voltage‐dependent and verapamiland diltiazem‐sensitive Ba2+ currents were observed. First, a nearly sustained current was activated by depolarization to potentials more positive than — 30mV and blocked by nifedipine (1 μM). This current was observed in cells of primary cultures less than 13 days old. Second, a transient nifedipine (1 μM) insensitive current was activated by depolarization to potentials more positive than — 55mV in cultures which were more than 13 days old. This current was not carried by sodium and blocked by 1 μM tetrodotoxin (TTX). In summary, cultured rat retinal pigment epithelial cells in younger primary cultures express Ba2+ currents indicating the presence of L‐type Ca2+ channels. In order primary cultures a low‐voltage activated channel was observed with properties different from T‐type calcium channels or TTX‐sensitive calcium conducting sodium channels. © 1994 Wiley‐Liss, Inc.
Transforming growth factor β1 inhibits interleukin‐1‐induced but enhances ionomycin‐induced interferon‐γ production in a t cell lymphoma: Comparison with the effects of rapamycin
Authors: Dumont Francis J. , Kastner Carolyn A. 
Published: February 2005

AbstractTransforming growth factor β1 (TGF‐β1) is a multifunctional cytokine whose potent immunomodulatory activity is well documented. To explore the mechanisms of this activity we examined the effect of TGF‐β1 on the production of IFN‐γ measured at the mRNA and protein levels in the YAC‐1 cell lymphoma. In previous studies, this model proved useful to characterize the mode of action of the immunosuppressant rapamycin (RAP). Here, we found that when induced by IL‐1 or IL‐1 + PMA, the production of IFN‐γ is suppressed by both TGF‐β1 (ED50 = 1.9 pM) and RAP (ED50 = 0.2 nM). In contrast, when induced by the calcium ionophore ionomycin, in the absence or in the presence of PMA, this production is enhanced up to 10‐fold by TGF‐β (ED50 = 1.8 pM) and 1.5—3‐fold by RAP. Therefore, in YAC‐1 cells, TGF‐β1 exerts opposite effects on IFN‐γ production depending on the mode of activiation, and these effects parallel those of RAP. To further analyze the mode of action of TGF‐β1 in this system, we used okadaic acid (OA), an inhibitor of serine/threonine protein phosphatases. Treatment with OA rendered the expression of IFN‐γ mRNA induced by IL‐1 insensitive to TGF‐β1 or RAP, indicating that activation of a phosphatase may play a role in the suppressive effect of both agents. However, OA did not prevent the augmentation of ionomycin‐mediated induction of IFN‐β mRNA by either TGF‐β1 or RAP. Hence, the up‐regulation of IFN‐β production by TGF‐β1 and RAP may involve a different biochemical mechanism that that mediating their suppressive action. These observations also favor the hypothesis that the two agents act on the same regulatory pathways. This was further supported by the finding that TGF‐β1 and RAP modulate IFN‐γ production in an additive rather than synergistic fashion. However, their effects could be dissociated in mutants of YAC‐1 cells selected for resistance to the inhibition of IL‐1‐mediated IFN‐γ induction by RAP. Moreover, the IFN‐γ modulatory action of RAP in YAC‐1 cells was accompanied by an antiproliferative effect, whereas TGF‐β1 failed to alter the growth of these cells. Therefore, the immunomodulatory action of TGF‐β1 may result from the dis ruption of biochemical processes related to, although distinct from, those affected by RAP. © 1994 Wiley‐Liss, Inc.
Mechanism of cigarette smoke condensate induced adhesion of human monocytes to cultured endothelial cells
Authors: Kalra Vijay K. , Ying Yong , Deemer Kathleen , Coates Thomas D. , Natarajan Rama , Nadler Jerry L. 
Published: February 2005

AbstractCigarette smoking is ranked among the leading risk factors in the etiology of atherosclerotic vascular disease. The mechanisms, however, that link cigarette smoking to increased incidence of atherosclerosis are not understood. The adherence of circulating monocytes to the endothelium, migration into the subendothelium, and subsequent formation of foam cells are principal initial events in the development of atherosclerosis. We therefore determined whether cigarette smoke caused increased adherence of monocytes to endothelial cells and the cellular mechanism of this increased adherence. Cigrette smoke condensate (CSC), the particulate fraction of cigarette smoke derived from 2R1 standard research cigarettes, at a concentration of 25–30 μg/ml (average yield of CSC is 26.1 mg/cigarette), augmented (70–90%) basal adherence of human peripheral blood monocytes to a cultured monolayer of endothelial cells derived from bovine aorta (BAEC) and human umbilical vein (HUVEC). There was a concomitant increase in the expression of CD11b ligand on the surface of monocytes as determined by flow cytometry, utilizing FITC conjugated Mab MO‐1 (CD11b). However, nicotine (1–15 μg/ml) and cadmium sulfate (10 μg/ml), constituents of CSC, individually or in combination had no effect either on CD11b expression or adherence of monocytes to endothelial cells. Treatment of HUVEC with CSC for 60 min also resulted in an increased expression of ICAM‐1 and ELAM‐1 as determined by mean fluorescence intensity of ICAM‐1 and ELAM‐1 labeled cells in flow cytometric analysis. The CSC induced expression of CD11b in monocytes was optimal at 25–30 min and was inhibited by protein kinase C inhibitors, staurosporine and H‐7, and also by baicalein, a lipoxygenase inhibitor. Similarly, CSC induced ICAM‐1 and ELAM‐1 expression in HUVEC was inhibited by protein kinase C inhibitors. CSC stimulated the adherence of human monocytes but not the monocytic cell lines HL‐60, U937, and THP‐1 to endothelial cells. The CSC stimulated adherence of human monocytes was inhibited (80%) by MAb to CD11b and 50% by Mab to ICAM‐1 and ELAM‐1. These results suggest that cigarettee smoke particulate constituents activate protein kinase C, leading to increased surface expression of adhesive ligand CD11b on peripheral blood monocytes and counter receptor(s) ICAM‐1 and ELAM‐1 in endothelial cells. The expression of ligand and counter receptor leads to potentiated adherence of monocytes to endothelial cells, an initial event in the pathogenesis of cigarette smoke induced inflammatory response in the vessel wall. © 1994 Wiley‐Liss, Inc.