bluuebunny/crossref_metadata_2025_split huggingface dataset:
Down‐regulation of statin, a nonproliferation‐specific nuclear protein, and up‐regulation of c‐myc after initiation of programmed cell death in mouse fibroblasts
Authors: Wang Eugenia , Pandey Siyaram 
Published: February 2005

AbstractDeprivation of growth factors has been shown to induce programmed cell death in many cell types, including mouse 3T3 fibroblasts. Programmed cell death (apoptosis) is an active process of self‐destruction which is thought to require the expression of unique genes. Recently, the expression of cell cycle genes such as c‐fos and c‐myc, and re‐entrance to cell cycle traverse, are thought to be necessary to induce programmed cell death. Previous work in this laboratory has shown that statin is a nonproliferation‐specific nuclear protein present in the nuclei of young quiescent or senescent human fibroblasts, as well as in growth‐arrested mouse 3T3 fibroblasts; we have reported that statin disappears rapidly after the blockage of growth arrest is removed and cells are allowed to resume cell cycle traverse. In this report we address the question of whether cells induced to enter the programmed cell death process also lose the expression of statin. We studied density‐arrested quiescent mouse 3T3 cells, which undergo rapid cell death by apoptosis upon serum deprivation. Our results suggest that c‐myc expression is induced, as previously reported in other systems of apoptotic death. Interestingly, we also find that statin indeed disappears after the induction of programmed cell death is initiated. These results further support the notion that when apoptosis is induced, cells behave as though released from replication arrest, and experience some part of the G1 phase of the cell cycle. The difference between this event and normal cell cycle traverse is that this experience of the G1 phase in the apoptotic process is an abortive one, with the end result of cell demise. © 1995 Wiley‐Liss, Inc.
Adrenocorticotropin‐resistant mutants of the Y1 adrenal cell line fail to express the adrenocorticotropin receptor
Authors: Schimmer Bernard P. , Kwan Wai King , Tsao Jennivine , Qiu Rong 
Published: February 2005

AbstractThis report examines the basis for adrenocorticotropin (ACTH) resistance in two mutant clones (Y6 and OS3) derived from the ACTH‐responsive Y1 mouse adrenocortical tumor cell line. These two mutants were originally characterized by their failure to respond to ACTH with increased adenylyl cyclase activity and as a consequence were resistant to the steroidogenic effects of the hormone. We now demonstrate that ACTH resistance in the Y6 and OS3 mutants results from the failure to express the gene encoding the ACTH receptor. Whereas parental Y1 cells express ACTH receptor transcripts at low levels and are stimulated by ACTH or 8‐bromo‐cAMP to increase the accumulation of ACTH receptor transcripts approximately twofold, the Y6 and OS3 mutants do not express receptor transcripts either in the presence or absence of 8‐bromo‐cAMP. The gene encoding the ACTH receptor appears to be present in the Y6 and OS3 mutants, as determined by Southern blot hybridization analysis. Moreover, in the Y6 mutant the ACTH receptor gene appears to be silenced by a modification that is reversed following the growth of the cells as tumors in mice. Clonal isolates of Y6 cells grown as tumors recover the ability to express ACTH receptor transcripts at low but detectable levels and acquire the ability to respond to ACTH with increased adenylyl cyclase activity. Finally, Y6 and OS3 cells transformed with a gene encoding the mouse β2‐adrenergic receptor respond to the β‐adrenergic agonist, isoproterenol, in a manner that is indistinguishable from the similarly transformed parent Y1 cell line. These latter results demonstrate the functional integrity of the adenylyl cyclase system in the ACTH‐resistant mutants and indicate that the failure to express ACTH receptor transcripts limits the responsiveness of these clones. © 1995 Wiley‐Liss, Inc.
Multiple second messenger pathways regulate IL‐β‐induced expression of PGHS‐2 mRNA in normal human skin fibroblasts
Authors: Warnock Lorna Jane , Hunninghake Gary W. 
Published: February 2005

AbstractVery little is known about the specific regulation of PGHS‐2 mRNA compared with PGHS‐1 mRNA. Using normal human fibroblasts, we show that at baseline there is constitutive expression of PGHS‐1 mRNA and barely detectable amounts of PGHS‐2 mRNA. There was a marked increase in PGHS‐2 mRNA transcription following exposure to IL‐β. Maximal expression of PGHS‐2 mRNA occurred with concentrations of IL‐β ≥ 1 ng/ml at 3 hours after stimulation. Downregulation of protein kinase C (PKC) activity by pretreating fibroblast cultures with PMA inhibited IL‐1–induced PGHS‐2 mRNA expression without affecting the constitutive expression of PGHS‐1 mRNA. The addition of various PKC inhibitors also blocked the IL‐β induction of PGHS‐2 mRNA but did not alter PGHS‐1 mRNA expression; inhibitors of protein kinase A (PKA) or tyrosine kinase (TK) had only a limited effect on IL‐β‐induced PGHS‐2 mRNA expression. These findings show that IL‐β increases PGHS‐2 mRNA, at least in part, via activation of PKC. Activation of PKA or TK appears to have a more limited role in this process. © 1995 Wiley‐Liss, Inc.
Shear stress modulates endothelial cell morphology and F‐actin organization through the regulation of focal adhesion‐associated proteins
Authors: Girard Peggy R. , Nerem Robert M. 
Published: February 2005

AbstractFlow‐related shear stress has been shown to modulate endothelial cell structure and function including F‐actin microfilament organization. Focal adhesion‐associated proteins such as vinculin, talin, and specific integrins may play a role in the modulation of these cytoskeletal and morphological changes. Double‐label immunofluorescence studies indicated that, in static culture, α5β1 fibronectin receptors (α5β1 FNRs) and αvβ3 vitronectin receptors (αvβ3 VNRs) were found predominantly in the peripheral regions of bovine aortic endothelial cells (BAECs) corresponding to the localization of vinculin, talin, and actin microfilament terminations. In response to shear stress, concomitant with cell elongation and the appearance of stress fibers aligned with the direction of flow, there was a prominent localization of vinculin and αvβ3 VNRs as the “upstream” end of the cells. Stress fiber terminations were clearly evident at these concentrations of focal adhesion‐associated proteins. These data suggest that the upstream concentration of these proteins may direct shear stress‐induced stress fiber formation and may function in the alignment of the fibers in the direction of flow. Levels of surface αvβ3 VNRs were found to decrease in response to flow, possibly reflecting the decrease in numbers of “downstream” receptors. Unlike the arrangement of vinculin and αvβ3 VNRs observed following exposure to flow, talin and α5β1 FNRs, in addition to being localized at the upstream end of the cell, were also evenly distributed throughout the rest of the cell. Surface levels of α5β1 FNRs increased in response to shear stress, perhaps providing an increased adherence of BAECs to the extracellular matrix through these receptors. These data suggest that focal adhesion‐associated proteins play specific roles in the response of BAECs to shear stress. © 1995 Wiley‐Liss, Inc.
Thermotolerant cells possess an enhanced capacity to repair heat‐induced alterations to centrosome structure and function
Authors: Vidair Charles A. , Doxsey Stephen J. , Dewey William C. 
Published: February 2005

AbstractTo study the mechanism of thermotolerance, the adaptive response by which cells become transiently resistant to killing by heat shock, we have focused on the centrosome, an organelle whose disorganization is closely correlated with thermal killing in Chinese hamster ovary (CHO) cells. Centrosome structure was studied by use of antisera directed against pericentrin, a 220 Kd protein of the pericentriolar material (PCM). Centrosome function was measured in intact cells by performing microtubule regrowth following exposure to the drug nocodazole. Immediately following heating at 45°C for 4–18 min, centrosomal staining by antipericentrin decreased. Thereafter, staining gradually recovered, although abnormal configurations of staining appeared in heated cultures 10–20 h later. In contrast, abnormal patterns of staining rarely developed in thermotolerant cultures. Centriole number was not perturbed by heat, indicating that the heat effect was specific for the PCM. Heat also caused an immediate reduction in the number of microtubules nucleated by the PCM. As for staining by antipericentrin, microtubule nucleation recovered during 3–20 h at 37°C after heating. The immediate, heat‐induced decrease in antipericentrin staining or microtubule nucleation was similar in thermotolerant and nontolerant cells. In contrast, the inhibition for both endpoints recovered to control levels much more quickly in thermotolerant cells than in nontolerant cells. Furthermore, new protein synthesis was not required for the recovery of microtubule nucleation. These data show that thermotolerant cells have an enhanced capacity to repair thermal damage to centrosome structure and function, and suggest that a faster rate of recovery prevents disorganization of the PCM that is observed in nontolerant cells several hours after heating. © 1995 Wiley‐Liss, Inc.
Histone H4 proximal promoter mediates a complex transcriptional response during differentiation of 3T3L1 adipocytes
Authors: Ramsey‐Ewing Anna L. , Bortell Rita , Stein Gary S. , Stein Janet L. 
Published: February 2005

AbstractWe have investigated the promoter element(s) required by the cell cycle regulated FO108 human histone H4 gene for control of gene expression during adipocyte proliferation and differentiation. Stable 3T3L1 cell lines were established that express fusion genes in which the histone H4 promoter is joined to chloramphenicol acetyltransferase (cat) as a reporter gene. Expression of the H4CAT fusion genes was monitored in proliferating and confluent 3T3L1 preadipocytes and in differentiating 3T3L1 adipocytes. The results indicate that the H4 cell cycle element (CCE), which mediates S phase‐specific stimulation of H4 gene transcription, is not required for transcriptional regulation during differentiation. Instead, a minimal H4 promoter (nucleotides −46 to −11) is sufficient to mediate the complex transcriptional response of H4 gene expression observed during the process of adipocyte differentiation of 3T3L1 cells. In addition, the data suggest that down‐regulation of histone gene expression during cellular differentiation may be mediated by passive inactivation of the promoter due to loss of positive regulatory factor(s). © 1995 Wiley‐Liss, Inc.
Identification of insulin‐like growth factor binding proteins from cultured human epidermal keratinocytes
Authors: Murashita Mari M. , Russo Vincenzo C. , Edmondson Stephanie R. , Wraight Christopher J. , Werther George A. 
Published: February 2005

AbstractThe role and mechanisms of action of insulin‐like growth factors (IGFs) in skin remain unclear. Epidermal keratinocytes possess IGF‐I receptors and are responsive to IGF‐I, which is primarily derived from underlying dermal fibroblasts. IGF binding proteins (IGFBPs), also synthesized by fibroblasts, may be involved in paracrine targeting of IGF‐I to its receptors. We therefore examined whether human keratinocytes synthesize IGFBPs and their mRNAs. Following culture in complete medium (containing bovine pituitary extract and epidermal growth factor) Western ligand blotting (WLB) of cell conditioned medium revealed a major band of 32 kD, a less abundant IGFBP of 24 kD at all passages, and a 37–42 kD IGFBP which increased in abundance in late passage. Immunoprecipitation followed by WLB confirmed that the predominant 32 kD band was IGFBP‐2. Radioimmunoassay of IGFBP‐1, ‐3, and ‐6 revealed detectable levels of IGFBP‐3 and significant levels of IGFBP‐6, but not IGFBP‐1. Northern analysis following culture in complete medium revealed that at early passage IGFBP‐1, ‐2, ‐4, and ‐6 mRNAs were detectable. IGFBP‐3 and ‐5 mRNAs were not detectable. Following culture in growth factor‐free medium a 37–42 kD band, consistent with IGFBP‐3, was predominant and a 24 kD band consistent with IGFBP‐4 was also present. These data demonstrate the expression of a distinct pattern of IGFBPs by cultured human keratinocytes dependent on culture conditions. Keratinocyte‐derived IGFBPs are likely to play a role in the transport and targeting of IGF‐I from dermally derived fibroblasts to the epidermis. © 1995 Wiley‐Liss, Inc.
Ascorbic acid stimulates barrier function of cultured endothelial cell monolayer
Authors: Utoguchi Naoki , Ikeda Kenji , Saeki Kazuhiko , Oka Naomi , Mizuguchi Hiroyuki , Kubo Kazuyosi , Nakagawa Shinsaku , Mayumi Tadanori 
Published: February 2005

AbstractThe macromolecular permeability of cultured bovine aortic, bovine venous, and human umbilical vein endothelial cell monolayers was decreased significantly in culture medium containing L‐ascorbic acid (Asc Acid; 0.01–0.1 mM) and L‐ascorbic acid 2‐phosphate (Asc 2‐P). Dithiothreitol, which shows reducing activity equivalent to that of Asc Acid, did not affect endothelial permeability. Asc Acid induced a sixfold increase in collagen synthesis by the endothelial cells. The coexistence of L‐azetidine 2‐carboxylic acid, an inhibitor of collagen synthesis, attenuated the effect of Asc 2‐P in a dose‐dependent manner. Another collagen synthesis inhibitor, ethyl‐3,4‐dihydroxybenzoate, also inhibited collagen synthesis and increased endothelial permeability. The decrease in permeability of the endothelial monolayer was dependent on a reduction of the permeability coefficient of the endothelial monolayer. These findings indicate that endothelial barrier function is stimulated by Asc Acid via an increase in collagen synthesis. © 1995 Wiley‐Liss, Inc.
Matrix protein synthesis by glomerular mesangial cells in culture: Effects of transforming growth factor β (TGFβ) and platelet‐derived growth factor (PDGF) on fibronectin and collagen type IV mRNA
Authors: Hänsch Gertrud Maria , Wagner Christof , Bürger Antje , Dong Wenjie , Staehler G. , Stoeck Michael 
Published: February 2005

AbstractThe pathogenesis of glomerular scarring is multifactional; recent evidence suggests that transforming growth factor β (TGFβ), a pleiotropic cicatricial mediator, may promote mesangial sclerosis by enhancing the production of extracellular matrix proteins. We studied the effect of TGFβ1 and TFGβ2 on collagen type IV and fibronectin (FN) synthesis in human glomerular mesangial cells in culture (GMC). Two hours after addition of TGFβ, an up to twofold increase in abundance of collagen type IV mRNA was found, which further increased up to fivefold within 24 h. Addition of cycloheximide did not inhibit the TGFβ effect, but caused by itself an up to twofold increase in the abundance of collagen type IV mRNA after 2 h. Together with collagen mRNA, the mRNA for FN and for platelet‐derived growth factor (PDGF) was also enhanced. PDGF was found to enhance abundance of the collagen type IV and fibronectin mRNA in GMC. A neutralizing antibody to PDGF or a PDGF‐antisense oligonucleotide partly inhibited the TGFβ‐induced increase of collagen type IV mRNA, suggesting that TGFβ can affect the collagen type IV synthesis not only directly but also indirectly via the synthesis of PDGF. © 1995 Wiley‐Liss, Inc.
Effects of the overexpression of the small heat shock protein, HSP27, on the sensitivity of human fibroblast cells exposed to oxidative stress
Authors: Arata Satoru , Hamaguchi Shino , Nose Kiyoshi 
Published: February 2005

AbstractThe role of the human small heat shock protein (HSP27) in oxidative stress was examined using stable transformants of an immortalized human fibroblast cell line (KMST‐6) isolated by transfection of HSP27 expression vectors. Several stable transformants that expressed high or low levels of HSP27 protein were obtained. Clones expressing high levels of HSP27 were more sensitive to growth inhibition by a low dose of hydrogen peroxide (0.1 mM) than those expressing low levels. Clones expressing high levels of HSP27 did not acquire obvious resistance to hyperthermy and cytotoxic agents, except for one (#13), in which resistance to cytotoxic agents was increased. The level of phosphorylated HSP27 in clones expressing high levels of this protein increased at 30 min and was sustained even 4 hours after exposing the cells to 0.1 mM of hydrogen peroxide. On the other hand, the levels in clones expressing low levels of HSP27 were reduced within 4 hours after exposure to hydrogen peroxide. Furthermore, overexpression of nonphosphorylatable mutant HSP27 did not affect sensitivity to oxidative stress. These results suggested that constitutively high expression of HSP27 in KMST‐6 cells make them susceptible to oxidative stress resulting in growth arrest, and this mechanism could involve the phosphorylation of HSP27. © 1995 Wiley‐Liss, Inc.
Immunochemical characterisation of megakaryocyte potentiator activity from mouse bone marrow
Authors: Banu Naheed , Williams Neil 
Published: February 2005

AbstractMegakaryocyte potentiator derived from mouse bone marrow has been shown to be immunologically similar to Interleukin‐6 (IL‐6). In this study the activity has been characterised by biochemical and immunochemical techniques. The activity is described as a O‐linked glycosylated molecule with an apparent MW of 15 Kd and pl of the range pH 5.9–6.35. The data show that mouse bone marrow potentiator activity is a variant of IL‐6 and with the potential to enhance megakaryocyte growth. © 1995 Wiley‐Liss, Inc.
Growth of mouse hepatocytes is stimulated by gastrin
Authors: Yao Chong Zheng , Bold Richard J. , Ishizuka Jin , Townsend Courtney M. , Thompson James C. 
Published: February 2005

AbstractHepatocyte growth is regulated by various growth factors, including epidermal growth factor (EGF) and insulin. Recently, several additional peptide hormones have been shown to stimulate growth of hepatocyte only in the presence of EGF or insulin and are thus termed secondary mitogens. Gastrin regulates growth of normal and neoplastic gastrointestinal tissues, but the effect on growth of hepatocyte is unknown. We examined the effect of gastrin on growth of a normal mouse hepatocyte (NMH) line established in our laboratory. Effect of gastrin‐17 (G‐17) (10−8 to 10−6 M) on growth of NMH cells was examined in either the presence or absence of EGF in the culture medium. Growth of NMH cells was evaluated by incorporation of either bromodeoxyuridine (BrdU) or 3H‐thymidine and by counting cells. Presence of a cell‐surface receptor for G‐17 was determined by Scatchard analysis using 125I‐G‐17. In the presence of EGF, gastrin stimulated growth of NMH cells; in the absence of EGF, gastrin did not affect growth. The stimulatory effect of gastrin on NMH cells was blocked by JMV 320, a CCK‐B type receptor antagonist. NMH cells possess a single, high affinity binding site for gastrin (Kd = 1.2 nM); EGF increased the gastrin binding capacity compared to non‐treated cells (3.5 ± 0.4 vs. 2.2 ± 0.6 fmol/106 cells). G‐17 stimulated growth of NMH cells through a single high affinity receptor for G‐17 which pharmcologically appears to be the CCK‐B type only in the presence of EGF and thus can be considered a secondary mitogen. © 1995 Wiley‐Liss, Inc.
Isolation of nonsedimentable lipid‐protein particles from insect intestine
Authors: Desantis T. A. , Paliyath G. , Thompson J. E. , Downer R. G. H. 
Published: February 2005

AbstractNonsedimentable lipid‐protein particles have been isolated from intestinal tissue of the American cockroach, Periplaneta americana. Most of the particles were within the range 30–50 nm in diameter and appear to originate from larger structures. Lipid analysis of the particles showed them to be enriched in neutral lipid components relative to microsomal membranes. Specifically, there is a decline in the amounts of phosphatidylcholine and phosphatidylethanolamine in the nonsedimentable particles compared with the microsomal membranes. Also, in contrast to microsomal membranes, the particles have a higher content of phosphatidic acid along with 1,2‐ and 1,3‐diacyglycerols, free fatty acids and an unidentified lipid that co‐migrates with sterol ester, wax ester and hydrocarbon standards in thin layer chromatograms. The cytosol, separated from the particles by ultrafiltration, contained phosphatidic acid, free fatty acids and the unidentified lipid. By contrast, the composition of neutral lipids in the cytosol resembles that of the particles. SDS—PAGE analysis of microsomal membranes, the particles and particle free cytosol shows an enrichment of low molecular weight proteins in the particles and cytosol. The particles and cytosol appear to possess proteolytic activity that is distinguishable from that of corresponding microsomal membranes since the incubation of these components with BSA resulted in the formation of distinct polypeptides. Many characteristics of these particles resemble those of the deteriosomes that have been isolated from plant tissue. © 1995 Wiley‐Liss, Inc.
Cyclic‐AMP inhibits cell growth and negatively interacts with platelet membrane glycoprotein expression on the Dami human megakaryoblastic cell line
Authors: Vittet Daniel , Duperray Christophe , Chevillard Claude 
Published: February 2005

AbstractIntracellular signaling processes by which hematopoietic growth factors regulate megakaryocytopoiesis remain uncompletely understood. Cyclic AMP (cAMP) has been shown to be implicated in the regulation of growth and differentiation in various normal and malignant cell types. Since a few studies have suggested the possible involvement of the cAMP pathway as one of the intracellular mechanisms whereby megakaryocytopoiesis may be regulated, we investigated the functional effects of cAMP on the human megakaryoblastic Dami cell line. We observed that exposure of Dami cells to cAMP analogs or to agents elevating intracellular cAMP levels yielded dose‐dependent cell growth inhibition. Cell cycle progression analysis of cells predominantly synchronized at the G1/S boundary by prior treatment with hydroxyurea revealed that cAMP transiently accumulated cells in the G2/M phase, then slowing down cell cycle. On the other hand, immunofluorescence and Northern blot analysis of megakaryocytic differentiation marker expression showed that probes we have used significantly inhibited GPlb expression. Moreover, although these agents used alone did not affect GPllb/llla expression, they markedly reversed phorbol ester‐induced GPllb/llla expression increase. These inhibitory cAMP actions on glycoprotein expression were not the result of cell cycle perturbation since we observed that GPlb and GPllb/llla expression were not cell cycle dependent. All these data may then be consistent with a potential negative regulatory role of the cAMP intracellular signaling pathway during megakaryocytopoiesis. © 1995 Wiley‐Liss, Inc.