bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulation of c‐myc and c‐Ha‐ras oncogene expression by cell shape
Authors: Farrell Robert E. , Greene James J. 
Published: February 2005

AbstractThe influence of cell shape on the expression of proto‐oncogenes was examined in normal and malignant human cells that varied in their sensitivities to contact‐inhibition of proliferation. Cells were constrained into varying degrees of roundness by plating onto culture surfaces coated with different concentrations of poly(2‐hydroxyethyl methacrylate) (poly[HEMA]) and assayed for proliferation capacity and levels of c‐myc, c‐ras, c‐fos, and c‐fes mRNAs. Proliferation of contact‐inhibited normal CUA‐1 fibroblasts and the variant HT‐IFNr cells was highly coupled to cell shape. As these cells became more rounded, a critical degree of roundess was reached at which proliferation ceased. In contrast, proliferation of non‐contact‐inhibited maligant HT‐1080 cells was independent of cell shape. Northern analysis revealed that expression of c‐myc and c‐ras was highly sensitive to cell shape in the normal CUA‐1 cells but not in the malignant HT‐1080 or variant HT‐IFNr cells. Levels of c‐myc and c‐ras mRNAs declined to nearly undetectable levels in CUA‐1 cells at degrees of roundness that correlated with loss of proliferative ability. Expression of c‐fos and c‐fes oncogenes were independent of cell shape in all cells tested. Quantification of transcription rates by the nuclear run‐off assay showed that shape modulation of c‐myc and c‐ras oncogene expression occurred at the transcriptional level. These data suggest that changes in cell shape can modulate expression of certain oncogenes and that these changes correlate with the cell's ability to proliferate. Moreover, inability to regulate c‐myc and c‐ras oncogene expression is associated with loss of shape‐dependent growth controls and contact inhibition but that loss of this regulation alone is not sufficient to release cells from contact‐inhibited controls. © 1992 Wiley‐Liss, Inc.
Similar, but not identical, modulation of expression of extracellular matrix components during in vitro and in vivo aging of human skin fibroblasts
Authors: Takeda Koji , Gosiewska Anna , Peterkofsky Beverly 
Published: February 2005

AbstractRegulation of the synthesis of procollagen and other extracellular matrix components was examined in human skin fibroblasts obtained from donors of various ages, from fetal to 80 years old (in vivo aged), and in fetal fibroblasts at varying passage levels (in vitro aged). Growth rates and saturation densities of fibroblasts decreased with increasing age of the donor and after passage 20 of fetal fibroblasts. The rates of collagen and proteoglycan synthesis also decreased during both types of aging to about 10–25% of the rate in early passage fetal fibroblasts, whereas the synthesis of total noncollagenous proteins was not greatly affected. Decreased collagen synthesis in both types of aging was correlated with lower steady‐state levels of mRNAs for the two subunits of type I procollagen mRNA, although their regulation was not coordinate. Type III collagen mRNA levels also declined in both types of aging. The concentration of fibronectin mRNA also decreased during in vitro aging but more rapidly than the collagen mRNAs, whereas in fibroblasts from 51–80‐year‐old donors, it was similar to or higher than in early passage fetal fibroblasts. This study suggests that the decreased synthesis of procollagen and proteoglycans in in vivo aged fibroblasts represents changes that are responsible for intrinsic degenerative changes that occur in human skin during aging. Furthermore, although in vitro and in vivo aging were similar in many respects, they were not equivalent, as evidenced by the differences in regulation of fibronectin expression. © 1992 Wiley‐Liss, Inc.
Regulation of Cu,Zn‐superoxide dismutase in bovine pulmonary artery endothelial cells
Authors: Kong Xue‐Jun , Fanburg Barry L. 
Published: February 2005

AbstractTo evaluate the regulation of endothelial cell Cu,Zn‐SOD, we have exposed bovine pulmonary artery endothelial cells in culture to hyperoxia and hypoxia, second messengers or related agonists, hormones, free radical generating systems, endotoxin, and cytokines and have measured Cu,Zn‐SOD protein of these cells by an ELISA developed in our laboratory. Control preconfluent and confluent cells in room air contained 196 ± 18 ng Cu,Zn‐SOD/106 cells. A23187 (0.33 μM), for skolin (10 μM), isobutylmethylxanthine (0.1 mM), dexamethasone (1 μM), triiodothyronine (1 μM) and retinoic acid (1 μM) failed to alter this level of Cu,Zn‐SOD. Exposure to anoxia and hyperoxia both elevated the level −1.5–2.0‐fold over 20% oxygen‐exposed controls at 48–72 hr. Similarly, exposures to glucose oxidase (0.0075 units/ml), menadione (12.5 μM), xanthine‐xanthine oxidase (10 μM, 0.03 units/ml) and H2O2 (0.0005%) increased the level up to two–threefold over controls at 24–48 hr. Lipopolysaccharide, TGFβ1, TNFα, and II‐1 also increased levels of cellular Cu,Zn‐SOD, but only in proliferating cells. II‐2, II‐4, interferon‐γ, and GM‐CSF had no effect on Cu,Zn‐SOD. All treatments that elevated SOD resulted in inhibition of cellular growth, but decreased growth of cells at confluence alone was not associated with increased Cu,Zn‐SOD. We propose from these studies that Cu,Zn‐SOD of endothelial cells is not under conventional second messenger or hormonal regulation, but that up‐regulation of the enzyme is associated with (and perhaps stimulated by) free‐radical or oxidant production that also may be influenced by availability of certain cytokines under replicating conditions. © 1992 Wiley‐Liss, Inc.
Inhibition of apoptosis in human tumour cells by okadaic acid
Authors: Song Qizhong , Baxter Glenn D. , Kovacs Eva M. , Findik Duygu , Lavin Martin F. 
Published: February 2005

AbstractGamma‐radiation, tetrandrine, bistratene A, and cisplatin were all found to induce pronounced morphological changes characteristic of apoptosis and extensive DNA fragmentation in the human BM13674 cell line 8 h after treatment. Apoptosis induced in BM13674 cells by these diverse agents was markedly inhibited by 1 μM okadaic acid, a tumour promoter that inhibits protein phosphatases 1 and 2A. This compound also inhibited the appearance of apoptosis in fresh human leukaemia cells that had been exposed to gamma‐radiation. The inhibition of apoptosis was confirmed using fluorescence microscopy and DNA gel electrophoresis. Dephosphorylation of a limited number of proteins was shown to be associated with apoptosis and okadaic acid prevented these dephosphorylations. Previous studies on the BM13674 cell line showed that an inhibitor of protein synthesis failed to prevent apoptosis in these cells. The present data provides further support that posttranslational modification of proteins, in particular, phosphorylation/dephosphorylation status, plays an important role in inhibition/activation of programmed cell death in different human cells after exposure to several cytotoxic agents. © 1992 Wiley‐Liss, Inc.
Transforming growth factor‐β1 (TGF‐β1) up‐regulation of collagen type II in primary cultures of rabbit articular chondrocytes (RAC) involves increased mRNA levels without affecting mRNA stability and procollagen processing
Authors: Galéra Philippe , Vivien Denis , Pronost Stéphane , Bonaventure Jacky , Rédini Françoise , Loyau Gérard , Pujol Jean‐Pierre 
Published: February 2005

AbstractThe effect of transforming growth factor‐β1 (TGF‐β1) on collagen biosynthesis was investigated in confluent primary monolayer cultures of rabbit articular chondrocytes (RAC). Exposure to TGF‐β (0.1, 1, and 10 ng/ml) in serum‐free medium caused a dose‐ and time‐dependent stimulation of collagen biosynthesis associated with an increase of steady‐state levels of procollagen type II mRNA. Elevation of the mRNA steady‐state did not result from a stabilization of the transcript, as shown by measure of the mRNA half‐life. Electrophoresis (SDS‐PAGE) showed that TGF‐β stimulates the synthesis of most collagen isotypes, including type II, without qualitative change in their distribution. Moreover, pulse‐chase experiments revealed that TGF‐β did not affect the processing rate of type II procollagen.TGF‐β slightly stimulated the production of prostaglandin E2 (PGE2), which could in turn exert an inhibition on collagen synthesis. However, addition of indomethacin to block prostaglandin synthesis did not further enhance the TGF‐β‐induced stimulation of collagen production, suggesting that this mediator was not implicated in the effect. Moreover, TGF‐β increased steady‐state levels of procollagen type II, I, and III mRNAs even in the presence of indomethacin. Despite these increased mRNA levels, only the production of type II collagen was significantly augmented, suggesting that type I procollagen mRNA was not fully translated. In addition, the TGF‐β‐induced stimulation of collagen synthesis was observed whenever ascorbic acid is added or not in the culture medium. In conclusion, TGF‐β, which is present in great amount in bone and cartilage, can increase the collagen production of cultured RAC and might therefore play a role in the early events of cartilage repair, such as those observed in osteoarthritis. © 1992 Wiley‐Liss, Inc.
Differential effects of SPARC and cationic SPARC peptides on DNA synthesis by endothelial cells and fibroblasts
Authors: Funk Sarah E. , Sage E. Helene 
Published: February 2005

AbstractSPARC (secreted protein, acidic and rich in cysteine), also known as osteonectin, is an extracellular Ca+2‐glycoprotein that inhibits the incorporation of [3H]‐and delays the onset of S‐phase in synchronized cultures of bovine aortic endothelial (BAE) cells. This effect appears not to be dependent on the functional properties of SPARC associated with changes in cell shape or inhibition of cell spreading. In this study we investigate the conditions under which cell cycle modulation occurs in different types of cells. Human umbilical vein endothelial cells, a transformed fetal BAE cell line, and bovine capillary endothelial cells exhibited a sensitivity to SPARC and a cationic peptide from a non‐Ca+2‐region of SPARC (peptide 2.1, 0.2—0.8 mM) similar to that observed in BAE cells. In contrast, human foreskin fibroblasts and fetal bovine ligament fibroblasts exhibited an increase in the incorporation of [3H]‐in the presence of 25 μM—0.2 mM peptide 2.1; inhibition was observed at concentrations in excess of 0.4 mM. This biphasic modulation could be further localized to a sequence of 10 amino acids comprising the N‐terminal half of peptide 2.1. A synthetic peptide from another cationic region of SPARC (peptide 2.3) increased [3H]‐incorporation by BAE cells and fibroblasts in a dose‐dependent manner. In endothelial cells, a stimulation of 50% was observed at a concentration of 0.01 mM; fibroblasts required ∼ 100‐fold more peptide 2.3 for levels of stimulation comparable to those obtained in endothelial cells. The observation that SPARC and unique SPARC peptides can differentially influence the growth of fibroblasts and endothelial cells in a concentration‐dependent manner suggests that SPARC might regulate proliferation of specific cells during wound repair and remodeling. © 1993 Wiley‐Liss, Inc.
Role of the plasma membrane in signal transduction in human polymorphonuclear leukocytes
Authors: DelBuono Brian J. , Simons Elizabeth R. 
Published: February 2005

AbstractTo more closely examine the role of the cell surface in transmembrane signal transduction in human neutrophils, sealed right‐side‐membrane vesicles free of organellar membrane components were used as models of the plasma membrane. These vesicles, incubated with a fluorescent analogue of the chemotactic peptide fMLP, bound this ligand similarly in extent and kinetics to intact neutrophils. Vesicles responded to this stimulation with a slow increase in internal [Ca++] which was inhibited by EGTA but not by verapamil; the cytosolic Ca++ transient seen in intact cells within 10 sec of stimulation was absent in vesicles. The vesicles also maintained a transmembrane potential (ψ) and were depolarized by the K+ ionophore valinomycin. However, unlike intact cells which hyperpolarized and then depolarized in response to fMLP, the vesicles demonstrated only a sustained hyperpolarization. Vesicles also differed from intact cells by not producing superoxide (O2−) in response to fMLP. Finally, fMLP caused dramatic alterations in membrane vesicle lipid metabolism: at early time points (within 5–10 sec), there was a transient production of diacylglycerol (DAG) concomitant with inositol lipid breakdown, with no apparent hydrolysis of non‐inositol phospholipids. For up to 5 min after stimulation, there was no increase in the levels of phosphatidic acid or of inositol lipids. Thus, a significant portion of the signalling pathway in neutrophils is located at the cell surface or in the plasma membrane and functions independently of intracellular components. Furthermore, the plasma membrane is intimately involved in events occurring during both the early (DAG generation) and late (slow, prolonged rise in [Ca++]) phases of cellular response. In contrast, several of the responses to fMLP (the Ca++ transient, depolarization, generation of O2−, recycling of lipid metabolites) involve signalling machinery not constitutively resident on the neutrophil surface. © 1993 Wiley‐Liss, Inc.
Internalization of basic fibroblast growth factor (bFGF) in cultured endothelial cells: Role of the low affinity heparin‐like bFGF receptors
Authors: Rusnati Marco , Urbinati Chiara , Presta Marco 
Published: February 2005

AbstractWe have shown (Presta et al., Cell Regul., 2:719–726, 1991) that a long‐lasting interaction of basic fibroblast growth factor (bFGF) with endothelial GM 7373 cells is required to induce cell proliferation. In the present work, we have investigated the interaction of 125I‐bFGF with GM 7373 cells, its pathway of internalization, and its intracellular fate under the same experimental conditions previously utilized to assess the mitogenic activity of the growth factor. Cell cultures were incubated with 10 ng/ml 125I‐bFGF for 2 h at 4°C. Then, cells were shifted to 37°C without changing the medium. A rapid down‐regulation of high affinity sites, paralleled by a rapid internalization of 125I‐bFGF, was observed during the first 1–2 h at 37°C. After 6–8 h, also low affinity sites down‐regulate. This was paralleled by a continuous internalization of 125I‐bFGF and by a slow disappearance of the growth factor from the culture medium. This suggests that GM 7373 cells activate, when exposed to bFGF for a long period of time, a late internalization pathway mediated by low affinity sites. This hypothesis was supported by the following experimental evidence: 1) soluble heparin inhibited the prolonged internalization of 125I‐bFGF and its binding to low affinity sites with the same potency; 2) treatment of GM 7373 cells with heparinase, which removes most of the low affinity sites, also inhibited the prolonged internalization of 125I‐bFGF internalized via low affinity sites was partially protected from lysosomal degradation. This was the case also when 125I‐bFGF was internalized in the presence of soluble heparin, suggesting that the complexes bFGF—surface glycosaminoglycan and bFGF—soluble heparin are maintained during the internalization of the growth factor. Moreover, the capacity of soluble heparin to inhibit the mitogenic activity of bFGF also when added to cell cultures several hours after the growth factor indicates that the requirement for a prolonged interaction of bFGF with GM 7373 cells in order to induce cell proliferation might be related to the late internalization of the growth factor via low affinity sites. © 1993 Wiley‐Liss, Inc.
Induction of glucose regulated proteins during growth of a murine tumor
Authors: Cai Jie‐Wei , Henderson Barbara W. , Shen Jun‐Wen , Subjeck John R. 
Published: February 2005

AbstractChronic anoxia, glucose starvation, low pH, and numerous other conditions induce the glucose‐regulated system of stress proteins (GRPs), whose principal members are observed at 78, 94, and 170 kDa. These stresses may be expected to occur during growth in untreated tumors. To examine the possibility that GRPs are correspondingly induced, we have examined the protein profiles of small (<0.1 g), intermediate (0.2–0.8 g), and large (>1.8 g) radiation‐induced fibrosarcoma (RIF) tumors grown on C3H mice. One and two‐dimensional gel electrophoresis indicate that the principal GRPs at 78 and 94 are coordinately and substantially increased in large tumor masses, relative to the small, and may be partially increased in the intermediate tumors. Necrotic material removed from large tumors exhibited an identical pattern of GRP induction with no visible indication of protein degradation and also contained a significant fraction of viable cells. Western blot analysis using rabbit antisera raised against the 78 and 170 kDa GRPs also demonstrated the enhanced accumulation of these proteins in the large tumors. The antibody against the 170 kDa GRP was also capable of detecting the induction of this stress protein in large tumors by indirect immunofluorescence analysis. Northern blot studies using a probe for the GRP 78 gene also showed an increase in GRP 78 message in large tumors as well as in RIF cells exposed to anoxic stress in vitro. Two‐dimensional gel electrophoresis indicated that the major heat shock proteins at 70 and 90 kDa were not increased in the larger tumors, and the amount of the 90 kDa species was reduced. Finally, the quantity of vimentin and its degradation products is significantly diminished in large tumors and in anoxic cells. This study demonstrates that RIF tumor cells undergo a glucose regulated stress response in situ during tumor growth. © 1993 Wiley‐Liss, Inc.
Kinetics of 125I‐PDGF binding and down‐regulation of PDGF receptor in arterial smooth muscle cells derived from patients with moyamoya disease
Authors: Aoyagi Masaru , Fukai Naomi , Matsushima Yoshiharu , Yamamoto Mari , Yamamoto Kiyotaka 
Published: February 2005

AbstractProgressive stenosis or occlusion of bilateral internal carotid arteries by fibrocellular intimal thickening results in cerebral ischemia in moyamoya disease. We recently found that cultured smooth muscle cells (SMC) derived from arteries of patients with moyamoya disease responded poorly to serum mitogens, especially to platelet‐derived growth factor (PDGF). In the present study, we investigated further the binding and processing of 125I‐PDGF, as well as down‐regulation of the PDGF receptors in arterial SMC derived from patients with moyamoya disease. The specific binding sites of 125I‐PDGF were reduced significantly at both 4°C and 22°C on SMC from moyamoya disease compared with those from controls (4.78 vs. 11.92 × 104/cell at 4°C), though the apparen dissociation constant (Kd) were the same. Kinetics of 125I‐PDGF binding at 37°C in cells from moyamoya disease showed fewer binding sites (less than 1/3 of controls) and lower degradation per cell than in those from controls, though no difference was observed in either internalization or degradation of each receptor. When SMC were exposed to lower concentrations of nonlabeled PDGF at 37°C, the percentage of remaining binding sites on cells from moyamoya disease was significantly less than that from controls. This excess down‐regulation of PDGF receptor in SMC from moyamoya disease may be interpreted as insufficent recycling or a decreased intracellular pool of the PDGF receptor. These results are closely correlated with the diminished proliferation responses to PDGF in SMC from moyamoya disease and provide evidence that functional alterations in vascular cells are involved in the mechanism of development of intimal thickening in moyamoya disease. © 1993 Wiley‐Liss, Inc.
Timing of protooncogene expression varies in toxin‐induced liver regeneration
Authors: Schmiedeberg Phyllis , Biempica Luis , Czaja Mark J. 
Published: February 2005

AbstractHepatic expression of the protooncogenes c‐fos and c‐myc occurs within 2 h after partial hepatectomy, and these immediate early genes are thought to prime the hepatocytes for subsequent proliferation. To examine whether such gene activation occured in the setting of hepatocyte proliferation after toxic liver injury, protooncogene expression was examined during the regenerative response following liver injury from carbon tetrachloride (CCI4) or galactosamine (GaIN). The pattern of protooncogene expression after CCI4 mirrored that seen after partial hepatectomy, with rises in c‐fos and c‐myc mRNA content within 2 h, and then a rapid return to baseline levels. In contrast, early c‐fos and c‐myc expression did not occur after GaIN injury. Instead GaIN‐induced regeneration led to a delayed and prolonged c‐fos an c‐myc activation which peaked 24–48 h after injury. Increase in c‐jun, jun‐B, and jun‐D mRNA levels also occured in both models at times similar to the rises of c‐fos and c‐myc expression. Although the timing of DNA synthesis was identical after GaIN or CCI4 treatment the proliferative response after GaIN injury was significantly less than that of CCI4, and marked by the histologic appearance of oval cells. The coadministration of 2‐acetylaminofluorene, an inhibitor of differentiated hepatocyte proliferation, together with CCI4 altered the usual pattern of post‐CCI4 protooncogene expression to one resembling that seen after GaIN injury. Thus, the timing of protooncogene expression during liver regeneration may vary considerably. These variations may influence the nature of the proliferative response in terms of which cell types(s) proliferates, and the amount of regeneration that ensures. © 1993 Wiley‐Liss, Inc.
Increase in portal flow induces c‐myc expression in isolated perfused rat liver
Authors: Isomura Hiroshi , Sawada Norimasa , Nakajima Yasuo , Sakamoto Hirofumi , Ikeda Tatsuru , Kojima Takashi , Enomoto Katsuhiko , Mori Michio 
Published: February 2005

AbstractWe examined expression of the c‐myc oncogene in isolated perfused livers to elucidate the mechanisms involved in triggering the proliferation of hepatocytes after partial hepatectomy (PH). During perfusion with a 1:1 mixture of Dulbecco's modified Eagle's medium and the oxygen transport fluid FC‐43, rat livers were two‐thirds resected (PH), and further perfused for 1 1/2 hours at the physiological portal flow throughout the perfusion. Expression of c‐myc in the perfused livers with PH(+) was ten times higher than in those with PH(−). Furthermore, expression of c‐myc in the PH(−) livers perfused with a threefold volume of the physiological portal flow was 5–10 times higher than that in the livers perfused with the physiological portal flow. The perfusates that passed through the livers did not induce DNA synthesis of primary cultured hepatocytes. These results suggest that an increase in the portal flow volume may act as a trigger for hepatocyte proliferation after PH. © 1993 Wiley‐Liss, Inc.