bluuebunny/crossref_metadata_2025_split huggingface dataset:
Induction by vasoactive intestinal peptide of interferon α/β synthesis in glial cells but not in neurons
Authors: Chelbi‐Alix Mounira K. , Brouard Aline , Boissard Claudine , Pelaprat Didier , Rostene William , Thang Ming Nguy 
Published: February 2005

AbstractVasoactive intestinal peptide (VIP), a 28‐aminoacid peptide, plays a multifunctional neuromodulatory role in both peripheral and central nervous systems. We have recently reported that VIP induces interferon (IFN) α/β synthesis in human colon adenocarcinoma cell line HT‐29. It has been reported that VIP may counteract HIV‐induced neuronal cell death; therefore, we postulated that the action of VIP may be mediated by a cascade regulation, involving the production of some cytokines such as IFN. Here we demonstrate that primary cultures of rat mesencephalic neurons and glial cells respond differently to VIP. Thus VIP enhanced 2′5′ oligoadenylate (2′5′A) synthetase activity and inhibited vesicula stomatitis virus multiplication in glial cultures only. However, both cell cultures had functional adenylate cyclase coupled receptors for VIP. The increase in 2′5′A synthetase activity in glial cultures reached a maximum with 10−6M VIP and required cellular RNA and protein synthesis. Anti‐IFN α/β, but not anti‐IFN γ, antibodies abolished the induction of the antiviral and 2′5′A synthetase activities by VIP in rat glial‐enriched cultures, suggesting that these inductions were mediated through IFN α/β synthesis. Moreover, VIP or poly (i).poly (C12U) caused, in the glial cultures, the induction and secretion of an IFN of type α/β with a titer value of 16 and 32 units/ml respectively. In contrast, neither of these two substances was able to induce IFN synthesis in neurons, which were, however, sensitive to IFN α/β produced by VIP‐treated glial cells. IFN produced by VIP in glial cells may therefore play an important role in defending the brain against viruses. © 1994 Wiley‐Liss, Inc.
Age‐related changes in DNA synthesis stimulated by epinephrine and isoproterenol in primary cultured rat hepatocytes
Authors: Ishigami Akihito , Roth George S. 
Published: February 2005

AbstractWe examined epinephrine‐ and isoproterenol‐stimulated DNA synthesis in primary cultured hepatocytes from 6‐, 12‐, and 24‐month‐old rats. Epinephrine‐stimulated DNA synthesis in 6‐month‐old rat hepatocytes began after 20 h and reached a maximum at 50 h. Similarly, isoproterenol‐stimulated DNA synthesis in 6‐month‐old rat hepatocytes began after 10 h and reached a maximum at 45 h. In contrast, both epinephrine‐ and isoproterenol‐stimulated DNA synthesis in 12‐ and 24‐month‐old rat hepatocytes were reduced approximately 40–60% and 80%, respectively, as compared to that at 6 months. Both epinephrine‐ and isoproterenol‐stimulated DNA synthesis were strongly inhibited by the betaadrenergic antagonist, propranolol, but not by the alpha1‐adrenergic antagonist, prazosin, or the alpha2‐adrenergic antagonist, yohimbine. However, in the presence of EGF, epinephrine‐stimulated DNA synthesis activity was inhibited by prazosin but not by propranolol. These results indicate that stimulated DNA synthesis in rat hepatocytes declines with age and that there are two different pathways for epinephrine‐stimulated DNA synthesis in the presence or absence of EGF. © 1994 Wiley‐Liss, Inc.This article is a US Government work and, as such, is in the Public domain in the United States of America.
Thrombomodulin lacking the cytoplasmic domain efficiently internalizes thrombin via nonclathrin‐coated, pit‐mediated endocytosis
Authors: Conway Edward M. , Nowakowski Barbara , Steiner‐Mosonyi Marta 
Published: February 2005

AbstractThrombomodulin (TM) is a transmembrane vascular endothelial cell receptor that is a cofactor in a major physiologically relevant natural anticoagulant system. We recently developed a cell model to examine one mechanism of regulation of TM cell surface expression and visually demonstrated that the receptor undergoes internalization predominantly via noncoated pits (Conway et al., 1992, J. Cell. Phys., 151:604–612). We have extended these studies to examine the role of the cytoplasmic domain of TM by deleting this region and expressing the truncated version of the molecule in COS cells (COS.Cyto.Del cells). Electron microscopy demonstrated internalization of gold‐labeled anti‐TM antibody or thrombin in a time‐ and temperature‐dependent manner, similar to that seen with the wild‐type transfected cells (COS.TM‐CR). Endocytosis was characterized by initial surface clustering of gold particles, followed by aggregation into noncoated pits, early endosome formation, and, finally, entry into multivesicular bodies and lysosomes. There was a notable absence of gold particles in clathrin‐coated pits and vesicles. The kinetics of binding and internalization of 125I‐labeled ligand in COS.Cyto.Del cells was compared with that of COS.TM‐CR cells and was not significantly different. These studies provide ultrastructural and quantitative data to indicate that TM efficiently undergoes endocytosis via nonclathrin‐coated pits when the receptor is lacking the cytoplasmic domain. This finding suggests that there may be alternative regions of the molecule that mediate those signals necessary for internalization. © 1993 Wiley‐Liss, Inc.
Regulation of in vitro glia‐induced microvessel morphogenesis by urokinase
Authors: Laterra John , Indurti Ravi R. , Goldstein Gary W. 
Published: February 2005

AbstractPlasminogen activators (PAs) regulate a variety of processes involved in tissue morphogenesis and differentiation. We used a coculture system in which microvascular endothelial cells are induced by glial cells to form capillary‐like structures in order to examine the role of urokinase‐type PA (uPA) during microvessel morphogenesis within the central nervous system (CNS). Endotheliaderived uPA activity decreased sevenfold within glial‐endothelial cocultures when capillary‐like structures were formed. Incubation of cocultures with concentrations of phorbol 12‐myristate 13‐acetate (0.1 and 1.0 nM) that induced endothelial uPA activity (45–210%) inhibited endothelial differentiation (25–70%). Furthermore, incubation of cocultures with proteolytically active low molecular weight uPA (5–500 IU/ml) inhibited endothelial differentiation (37–75%), whereas the amino terminal cell‐binding fragment of uPA had minimal effect. Inhibition of plasminogen activation in cocultures with the serine protease/plasmin inhibitors aprotinin and soybean trypsin inhibitor increased glia‐induced capillary‐like structure formation (96–98%). These findings establish a paracrine/autocrine function for urokinase and its inhibitors in regulating endothelial responses to perivascular glia and provide insight into mechanisms of microvascular reactions to CNS pathology. © 1994 Wiley‐Liss, Inc.
Culture of a prostatic cell line in basement membrane gels results in an enhancement of malignant properties and constitutive alterations in gene expression
Authors: Freeman Michael R. , Bagli Darius J. , Lamb Carolyn C. , Guthrie Paul D. , Uchida Toshi , Slavin Richard E. , Chung Leland W. K. 
Published: February 2005

AbstractInteraction of a transformed rat prostate epithelial cell (NbMC‐2) with basement membrane gels (Matrigel) has been evaluated using a long‐term matrix culture system. NbMC‐2 cells, and single‐cell clonal derivatives, formed spheroidal multicellular structures (aggregates) on Matrigel surfaces and were weakly invasive or noninvasive during a 1 week period. During subsequent 2–4 week periods, invasive cells originating from the aggregates and exhibiting a fusiform morphology became evident and increased in number in the matrix cultures. This biphasic pattern of behavior did not occur on laminin, type I or type IV collagen, or fibronectin substrates, but it did occur on Matrigel in serum‐free medium. Characterization of sublines enriched in fusiform cells indicated that they maintained their distinct morphology with continuous culture. Further, they exhibited significantly greater invasive potential, saturation density, and random motility (chemokinesis) than the parent cell line. Steady‐state levels of fibronectin mRNA were highly elevated in the tusiform variants, demonstrating a constitutive alteration in patterns of gene expression coinciding with the altered morphology. These results indicate that clonal NbMC‐2 cells differentiate at a reproducible frequency into a more aggressive cell type in response to culture in the basement membrane–‐like matrix. The altered phenotypic properties appear to be stable since they can be inherited by daughter cells and because they are evident in the absence or matrix. These observations suggest a cell‐specific mechanism for promotion of malignant growth by matrix‐mediated induction of novel cell properties. © 1994 Wiley‐Liss, Inc.
Transition metal chelator TPEN counteracts phorbol ester–induced actin cytoskeletal disruption in C6 rat glioma cells without inhibiting activation or translocation of protein kinase C
Authors: Hedberg Karen K. , Birrell G. Bruce , Mobley Philip L. , Griffith O. Hayes 
Published: February 2005

AbstractPhorbol ester–induced reorganization of the actin cytoskeleton was investigated in C6 rat glioma cells. Observations by fluorescence microscopy and photoelectron microscopy indicated that pretreatment with the transition metal chelator N,N,N',N'‐tetrakis(2‐pyridylmethyl)ethylenediamine (TPEN) for 1–2 h at 50 μM reduced the sensitivity of the actin cytoskeleton to disruption by the subsequent addition of 200 nM phorbol myristate acetate (PMA). The protective effect of TPEN was eliminated by adding back Zn2+ prior to PMA addition, implicating chelation of metal ions as the mechanism of action of TPEN. C6 cells exposed to PMA experience potent activation of protein kinase C (PKC) and substantial redistribution of the kinase from a soluble to a particulate cellular fraction (translocation). TPEN pretreatment did not block PKC translocation in PMA‐exposed cells. By two‐dimensional gel analysis, TPEN also did not reduce, but rather slightly increased, the PMA‐stimulated phosphorylation of the acidic 80 kDa endogenous PKC substrate, as well as two other proteins at 18 kDa and 50 kDa. In contrast, TPEN significantly suppressed phosphorylation of a 20 kDa protein, both in cells treated with TPEN only and in TPEN‐pretreated PMA‐exposed cells. The results indicate that the ability of TPEN to protect against PKC‐mediated actin cytoskeletal disruption is not due to either a block of PKC translocation or to general inhibition of PKC activity. Rather, the action of TPEN is more selective and probably involves chelation of Zn2+ at a critical Zn2+ ‐dependent phosphorylation step downstream from the initial tumor promoter–‐induced effects on PKC. © 1994 Wiley‐Liss, Inc.
Dissociation of PDGF receptor tyrosine kinase activity from PDGF‐mediated inhibition of gap junctional communication
Authors: Pelletier Diane B. , Boynton Alton L. 
Published: February 2005

AbstractGap junction‐mediated intercellular communication (GJC) may play an important role in cell proliferation and transformation since GJC is inhibited by growth factors, oncogenes, tumor promoters, and carcinogens. We have studied inhibition of GJC by platelet‐derived growth factor‐BB (PDGF) in the mouse fibroblast cell line C3H/10T1/2 and have sought to determine whether PDGF‐induced inhibition of GJC is mediated by the PDGF receptor tyrosine kinase (RTK). PDGF‐mediated inhibition of GJC was rapid and transient, with maximal inhibition occurring 40 min after PDGF addition and GJC returning to control levels after 70 min. The effect of PDGF on GJC was concentration‐dependent, with maximal inhibition of 90% or greater occurring at 10 ng/ml PDGF. Stimulation of RTK activity, as determined by antiphosphotyrosine immunoblot analysis of PDGF receptor and the receptor substrates phospholipase C‐γl (PLC‐γl) and guanosine triphosphatase activating protein (GAP), was also concentration‐dependent. Inhibition of GJC required a greater concentration of PDGF than did stimulation of RTK activity. The tyrosine kinase inhibitor genistein blocked PDGF‐induced RTK activity, as measured by PDGF receptor, PLC‐γl, and GAP tyrosine phosphorylation, in a concentration‐dependent manner but did not affect PDGF‐mediated inhibition of GJC. Genistein alone had no effect on GJC or PDGF receptor expression. PDGF treatment in the presence or absence of genistein resulted in phosphorylation of the connexin 43 protein on nontyrosine residues. These results suggest that inhibition of GJC by ligand‐activated PDGF receptor is dissociable from the RTK activity responsible for PDGF, PLC‐γl, and GAP phosphorylation. © 1994 Wiley‐Liss, Inc.
Modulation of thrombospondin expression during differentiation of embryonal carcinoma cells
Authors: Liska Deann J. , Hawkins Richard , Wikstrom Kristina , Bornstein Paul 
Published: February 2005

AbstractThe thrombospondins (TSPs) are a family of extracellular glycoproteins that display distinct patterns of temporal and spatial expression during development. In this study, we investigated the expression of two of the TSPs–TPS1 and TSP2– during the course of differentiation of embryonal carcinoma cells in vitro. We report that both TSP1 and TSP2 mRNA and protein synthesis are induced during the differentiation of P19EC cells into neurons, glial cells, and fibroblasts. Immunofluorescence studies indicate that TSP1 displays a fibrillar pattern of staining, characteristic of an extracellular matrix protein, in differentiated P19EC cells. In contrast, TSP2 is cell‐associated and is present on differentiated P19EC cells and on primary neurons and glial cells obtained from a 17‐day embyronic mouse cerebral cortex. Interestingly, although both TSP1 and TSP2 are more prevalent in areas of differentiated cells, they display distinct patterns of deposition. These observations suggest that TSP1 and TSP2 may function differently during neurogenesis. The response of TSP1 and TSP2 to differentiation of P19EC cells indicates that this cell system will serve as a valuable model for the study of TSP expression and function during neurogenesis. © 1994 Wiley‐Liss, Inc.
Regulation of Na+/glucose cotransporter (SGLT1) mRNA in LLC‐PK1 cells
Authors: Yet Shaw‐Fang , Kong Cheng‐Te , Peng Hua , Lever Julia E. 
Published: February 2005

AbstractThe porcine kidney epithelial cell line LLC‐PK1 expresses a sodium‐coupled glucose cotransporter (SGLT1) together with other differentiation markers of renal proximal tubule such as trehalase and γ‐glutamyltranspeptidase. Expression is regulated by cell density and exogenous differentiation inducers such as hexamethylene bisacetamide (HMBA). Northern blot and PCR analysis of clonal cell populations indicated SGLT1 mRNA was not detectable in subconfluent cultures, but 2.2 and 3.9 kb SGLT1 mRNA species appeared after cell confluence, accompanying expression of the transport activity. SGLT1 mRNA levels were significantly increased after treatment of confluent cultures with HMBA, paralleling increases in the transport activity and immunodetectable 75 kD cotransporter subunit. SGLT1 mRNA was also increased after treatment of cultures with the cyclic AMP phosphodiesterase inhibitor 3‐isobutyl‐1‐methylxanthine (IBMX), an inducer of Na+/glucose cotransport activity. The 3.9 kb SGLT1 transcript showed the largest increase after either HMBA or IBMX treatment. HMBA treatment also resulted in increased mRNA levels of two other differentiation markers–trehalase and γ‐glutamyltranspeptidase. By contrast, trehalase and γ‐glutamyltranspeptidase mRNA levels were not increased by IBMX. Regulation of Na+/glucose symporter expression by either cell density, cyclic AMP elevation, or differentiation inducer treatment occurs, at least in part, at the level of SGLT1 mRNA and can be dissociated from regulation of other differentiation markers. © 1994 Wiley‐Liss, Inc.
Ligation of CD3 triggers transmembrane proximity between LFA‐1 and cortical microfilaments in a cytotoxic T cell clone derived from tumor infiltrating lymphocytes: A quantitative resonance energy transfer microscopy study
Authors: Poo Haryoung , Fox Bernard A. , Petty Howard R. 
Published: February 2005

AbstractWe have explored the transmembrane associations of leukocyte function associated antigen‐1 (LFA‐1) in response to T cell receptor ligation using resonance energy transfer (r.e.t.) microscopy to detect receptor to microfilament proximity. R.e.t. was detected using both imaging and photon counting techniques. T cells were labeled with fluorescein‐conjugated F(ab')2 fragments of an anti—LFA‐1 monoclonal antibody. Cells were incubated at 37°C on unmodified glass surfaces and surfaces coated with anti‐CD3 or anti—H‐9 antibodies. Microfilaments of fixed cells were labeled with rhodamine‐phalloidin. R.e.t. was not affected on unmodified (blank) or irrelevant antibody‐treated (H‐9) surfaces. However, both fluorescence images and photon count rates were significantly enhanced when cells bound to anti‐CD3‐coated surfaces. This enhancement was not due to a general effect of T cell activation on transmembrane cytoskeletal proximity since CD45‐phalloidin r.e.t. was not affected by CD3 ligation. These experiments provide direct physical evidence that ligation of the CD3 complex specifically increases the proximity of LFA‐1 and microfilaments, which may be relevant to T cell mediated adherence reactions. © 1994 wiley‐Liss, Inc.
Growth modulation and proteoglycan turnover in cultured mesangial cells
Authors: Wang Aimin , Fan Mei‐Ying , Templeton Douglas M. 
Published: February 2005

AbstractProliferation of mesangial cells is a common feature of renal disease, and conditioned media from glomerular epithelial and endothelial cells have been found to contain heparin‐like molecules that suppress proliferation of rat mesangial cells (RMC). We have partially characterized the glycosaminoglycans that are labeled with 35SO42− by RMC in culture at early passage and examined their ability to inhibit mitogenic stimulation of the cells. Four chondroitin/dermatan sulfate proteoglycans (CS/DSPG) were identified, the largest and smallest of which (Kd of 0.04 and 0.26 on Superose 6) were retained in the cell layer while the other two (Kd = 0.17 and 0.22) were secreted into the medium. Heparan sulfate proteoglycans (HSPG) with Kd values of 0.09, 0.13, and 0.39 were minor components of the cell layer, while a single heparan sulfate (Kd = 0.17) was recovered from the medium. After 16 h of labeling in serum‐free medium, about 60% of macromolecular 35S was cell‐associated and 40% was in the medium. Cell‐associated label consisted of 7% CS/DSPG, 9% HSPG, and 84% free glycosaminoglycan chains (mostly CS/DS), whereas the medium contained 52% CS/DSPG, 17% HSPG, and approximately equal amounts of free HS and CS/DS chains. Bovine lung heparin (1 μg/ml) decreased by 45% the incorporation of [3H]‐thymidine into DNA after release of serum‐starved RMC from growth arrest. Heparin acted prior to the G1/S interface; arrest of the cells in early S phase with aphidicolin abrogated the heparin response. The endogenous HSPGs had a slight antimitogenic effect on the RMC, but heparan sulfate chains from both the medium and cell layer had a potent effect. On an equivalent mass basis, only the free glycosaminoglycan chains were more potent than heparin in this regard, decreasing thymidine incorporation by over 90% when present at 1 μg/ml. These results demonstrate that heparan sulfate glycosaminoglycans derived from mesangial proteoglycans are potential negative autocrine growth regulators. Proteoglycan metabolism releases these soluble heparan sulfate chains, determining the level of this activity. © 1994 wiley‐Liss, Inc.
Serum response elements mediate protein kinase C dependent transcriptional induction of early growth response gene‐1 by arginine vasopressin in rat mesangial cells
Authors: Rupprecht Harald D. , Sukhatme Vikas P. , Rupprecht Anneli P. , Sterzel R. Bernd , Coleman David L. 
Published: February 2005

AbstractArginine vasopressin (AVP) regulates glomerular hemodynamics, alters extracellular matrix production, and induces proliferation of glomerular mesangial cells (MCs). Therefore, AVP may play a role in glomerular sclerosis and the progression of chronic renal failure. To investigate changes in early gene expression which may link intracellular biochemical events with changes in MC phenotype following AVP stimulation, we studied expression of the Early growth response gene‐1 (Egr‐1). Nuclear run off assays demonstrate that AVP induces Egr‐1 at the tran‐scriptional level. Transcriptional induction was, like induction of mitogenesis, dependent upon activation of protein kinase C (PK C). Promoter deletion analysis revealed that the region critical for Egr‐1 inducibility by AVP contained several serum response element (SRE) consensus sequences. Sequential deletion of these SREs led to a drop in AVP‐stimulated promoter activity. AVP was also able to stimulate transcription from a construct containing an Egr‐1 SRE upstream of a heterologous promoter and this effect required activation of PK C. Electrophoretic mobility shift assays, using an Egr‐1 SRE as probe, demonstrate up to four protein‐SRE complexes of differing size that undergo modest quantitative changes following AVP stimulation. These data in MCs suggest that upstream SREs mediate transcriptional induction of Egr‐1 by AVP in a PK C‐dependent fashion and that changes in DNA‐protein interaction involving the SREs may be in part responsible for this effect. © 1994 wiley‐Liss, Inc.
Inhibition of the chondrocyte phenotype by retinoic acid involves upregulation of metalloprotease genes independent of TGF‐β
Authors: Ballock R. Tracy , Heydemann Ahlke , Wakefield Lalage M. , Flanders Kathleen C. , Roberts Anita B. , Sporn Michael B. 
Published: February 2005

AbstractRetinoic acid has been identified as a key morphogen governing pattern formation in the developing cartilaginous skeleton. Retinoids have also been implicated in the premature closure of the cartilage growth plate following vitamin A intoxication or administration of retinoids for dermatologic conditions. Previous studies of the mechanism of action of retinoids in non‐chondrogenic cells have concluded that retinoic acid is a negative regulator of AP‐1 responsive metalloprotease genes. We show that inhibition of expression of the cartilage phenotype by retinoic acid in epiphyseal chondrocytes is associated with positive regulation of AP‐1 responsive metalloprotease genes, as well as induction of gene expression for the two components of the transcription factor AP‐1, c‐fos and c‐jun. Despite the similar effects of TGF‐β1 on expression of cartilage matrix proteins and metalloproteases in this culture system, no appreciable changes in the expression of TGF‐β isoforms were evident in response to retinoic acid treatment. The present investigation demonstrates that regulation of AP‐1 responsive genes by retinoic acid can be either positive or negative, depending on the target cell type, and illuminates new mechanisms by which retinoic acid and other retinoids may exert control during development and growth of the limb. © 1994 wiley‐Liss, Inc. This article is a US Government work and, as such, is in the public domain in the United States of America.