bluuebunny/crossref_metadata_2025_split huggingface dataset:
Age related induction of platelet‐derived growth factor A‐chain mRNA in normal human fibroblasts
Authors: Karlsson Christina , Paulsson Ylva 
Published: February 2005

AbstractWe have previously found that stimulation of normal neonatal fibroblasts with PDGF or EGF leads to a transient induction of PDGF A‐chain mRNA and the synthesis of PDGF‐AA proteins. This finding may imply the existence of an autocrine feedback mechanism to amplify the mitogenic signal under certain conditions. We have now studied the PDGF‐BB mediated PDGF A‐chain induction in a set of fibroblasts from young and old donors to clarify if the levels of induction are correlated to the donor age and the replicative capacity of the cells. The PDGF A‐chain induction was found to be reduced in cells from old donors compared with cells from embryonic and neonatal donors. The different cell strains were also characterized further with respect to PDGF receptor expression and PDGF binding properties. PDGF β‐receptors were found to be enhanced in old donor cells strains, whereas the PDGF α‐receptors showed more variability in expression between the strains. The PDGF A‐chain mRNA induction was also decreased or absent in late passage human fibroblasts (senescent cells) when compared with early passage cells. These data suggest that the PDGF A‐chain mRNA induction is regulated by an age related mechanism in human fibroblasts. © 1994 Wiley‐Liss, Inc.
Effects of fibronectin on actin organization and respiratory burst activity in neutrophils, monocytes, and macrophages
Authors: Yang Kuender D. , Augustine Nancy H. , Shaio Men‐Fang , Bohnsack John F. , Hill Harry R. 
Published: February 2005

AbstractPrevious studies have shown that fibronectin (Fn) enhances phagocytosis and killing of antibody‐coated bacteria by neutrophils and macrophages. In an attempt to understand the mechanism of this enhancement, we have investigated the effects of Fn on phagocytosis‐related actin organization as well as respiratory burst activity in neutrophils, monocytes and culture‐derived macrophages. Employing an NBD‐phallacidin flow cytometric analysis of filamentous actin formation, we found that Fn promotes rapid actin polymerization within 30 seconds in neutrophils, monocytes, and macrophages, but not lymphocytes. Enhancement of actin polymerization by Fn was concentration‐dependent and mediated by a pertussis toxin‐ but not cholera toxin‐ sensitive G protein. Inhibition of protein kinase C by sphingosine (20 μM), calcium influx by verapamil (0.1 mM), or intracellular calcium mobilization by 8‐(N, N‐diethyl‐amino) octyl‐3,4,5‐trimethoxybenzoate HCI (TMB‐8; 0.1 mM) did not block Fn‐enhanced actin polymerization in phagocytes. Incubation of neutrophils and macrophages on microtiter plates precoated with Fn suppressed superoxide (O2−) production induced by IgG‐ and IgA‐ opsonized group B streptococci. In contrast, Fn significantly enhanced IgA‐ and IgG‐mediated O2− production by freshly isolated monocytes. These data suggest that Fn enhances phagocytosis, presumably through G protein‐coupled cytoskeleton reorganization and augments O2− production by circulating monocytes. In contrast, it appears to suppress O2− production by the active phagocytic cells, neutrophils and macrophages. This may result in enhanced phagocytosis and intracellular killing of microorganisms without damaging interstitial tissues. © 1994 Wiley‐Liss, Inc.
Up‐regulation of aFGF expression in quiescent cells is related to cell survival
Authors: Renaud F. , Oliver L. , Desset S. , Tassin J. , Romquin N. , Courtois Y. , Laurent M. 
Published: February 2005

AbstractExogenously administrated acidic FGF modulates the proliferation of several cell types, controls cell differentiation, and promotes cell survival. Most cells that are sensitive to exogenous aFGF are also capable of expressing it at very low levels. Thus in order to establish the role of endogenous aFGF as a mitogenic, differentiation, or survival factor, we studied the regulation of aFGF expression by evaluating the level of mRNA by PCR amplification and the concentration of protein by Enzyme Immuno Assay (EIA). In the lens, the amount of aFGF transcripts in nondividing cells of the central epithelium and in the differentiated fiber cells located at the periphery of the lens is similar, suggesting that endogenous aFGF is not involved with lens differentiation. In cultures, depending on the growth conditions, the endogenous aFGF expressed by Bovine Epithelial Lens (BEL) cells is sub ect to modulation. Cells arrested either by contact inhibition or by serum deprivation express more aFGF transcripts and protein than in exponentially growing cells, implying that endogenous aFGF has no mitogenic role under these conditions. In serum‐deprived cells, the addition of specific aFGF antisense primers inhibits endogenous aFGF express on and leads to the death of these cells. These results associated with the higher expression of aFGF in nondividing BEL cells, suggesting that, contrary to exogenous aFGF, endogenous aFGF is not a mitogenic factor but a survival factor.
Mitosis and cytokinesis in subconfluent endothelial cells exposed to increasing levels of shear stress
Authors: Wechezak Arlene R. , Viggers Robert F. , Coan Daniel E. , Sauvage Lester R. 
Published: February 2005

AbstractAn in vitro flow apparatus in combination with cultured endothelium was used to determine the effects of fluid‐generated shear stress on cells undergoing mitosis and cytokinesis. Cell responses were recorded by time‐lapse video microscopy under phase contrast or Hoffman modulation contrast optics. Completion of cell division in mitotic cells was dependent upon both the initial presence of intercellular attachments and the magnitude of fluid wall shear stress. In nonisolated populations, 95.3%, 69.5%, and 57.1% of the cells completed cell division as opposed to 66.6%, 20.4%, and 11.9% in the isolated cell groups at 2.8, 14.1, and 33 dynes/cm2, respectively. Prestressing cells for 14 h prior to monitoring failed to increase retention of isolated mitotic cells. The presence of neighboring cells facilitated replication by providing an anchoring attachment or a luminal surface for completion of division. Cell detachment most commonly occurred at the onset of cytokinesis when substrate contact areas were minimal and focal contacts were absent. A comparison between no flow controls and shear stress specimens indicated no significant differences in transit times for mitosis and cytokinesis. Thus, subconfluent endothelial cells may be more susceptible to detachment during cell division due to increases in shear stress, the absence of intercellular attachments, and reduced cell‐substrate contacts. © 1994 wiley‐Liss, Inc.
Growth regulation of human glioblastoma t98g cells by insulin‐like growth factor‐1 and its receptor
Authors: Ambrose Diane , Resnicoff Mariana , Coppola Domenico , Sell Christian , Miura Masahiko , Jameson Steve , Baserga Renato , Rubin Raphael 
Published: February 2005

AbstractThe interaction of insulin‐like growth factors (IGFs) with the IGF‐1 receptor is an important step in the control of cell proliferation and development. In particular, IGF‐1 and IGF‐2 are key regulators of central nervous system development, and may modulate the growth of glial tumors. We have investigated the growth factor regulation of the human glioblastoma cell line T98G. These cells growth arrested in serum‐free medium at 34°C, despite their secretion of substantial amounts of bioactive IGF‐1. To be stimulated to divide, growth‐arrested cells required the addition of platelet‐derived growth factor (PDGF) or its equivalent, 1% serum. Cell proliferation in serum‐free medium could also be obtained by shifting the cells to a temperature of 39.6°C. Treatment of growth‐arrested cells with PDGF or temperature shift was accompanied by a transient increase in the expression of the mRNA for the IGF‐1 receptor. Transfection with a plasmid constitutively expressing the full cDNA for the human IGF‐1 receptor allowed autonomous growth in serum‐free medium at 34°C. By contrast, growth induction by growth factors or temperature shift was abrogated by transfection of the cells with a plasmid expressing a 300 bp segment of mRNA antisense to the IGF‐1 receptor mRNA. Cloning in soft agar was also inhibited by expression of antisense IGF‐1 receptor mRNA. These results demonstrate that the IGF‐1 receptor is strictly required for the growth of T98G glioblastoma cells. Moreover, the autocrine interaction of IGF‐1 with its receptor regulates both autonomous and anchorage‐independent growth of these cells. © 1994 wiley‐Liss, Inc.
Synthesis of and response to 1,25 dihydroxycholecalciferol by subpopulations of murine epidermal keratinocytes: Existence of a paracrine system for 1,25 dihydroxycholecalciferol
Authors: Rizk‐Rabin Marthe , Zineb Rougui , Zhor Bouizar , Michele Garabedian , Jana Pavlovitch 
Published: February 2005

AbstractThe epidermis is both a target tissue for and a source of 1,25 dihydroxycholecal‐ciferol. The present study determines which of the epidermal cell populations synthesizes 1,25 dihydroxycholecalciferol and which responds to this hormone. Epidermal keratinocytes from new born rat epidermis were separated by unit gravity sedimentation into poorly differentiated cells, slow‐cycling more differentiated cells, actively proliferating cells, and terminally differentiating subpopulations. The keratinocyte populations were characterized by cell size analysis, cell morphology, and DNA and RNA contents (acridine orange flow cytometry). 1,25(OH)2D3 synthesis was studied by measuring the conversion of [3H] 25(OH)D3 to [3H] 1,25(OH)2D3. The purified product was tested for its ability to compete with synthetic [3H] 1,25(OH)2D3 for binding to chick intestinal cytosol. The responses of the keratinocyte subpopulations to exogeneous 1,25(OH)2D3 were evaluated by the increase in 25(OH)D3‐24 hydroxylase activity. Furthermore the expression of 1,25(OH)2D3 receptors (VDR) was examined in these cell populations. The results show that only the least differentiated cells produced 1,25(OH)2D3. In contrast, immunocytochemical detection of VDR, the VDR mRNA, and a 25(OH)D3‐24 hydroxylase response to 1,25(OH)2D3 were mainly found in the more differentiated cells. Thus, the ability of epidermis to synthesize 1,25(OH)2D3 and be simultaneously sensitive to it depends on the state of cell differentiation. This suggests that the mammalian epidermis contains a paracrine system in which the more differentiated keratinocytes are sensitive to the 1,25(OH)2D3 produced locally by neighboring immature ones. © 1994 wiley‐Liss, Inc.
Release of potassium, lipids, and proteins from nonionic detergent treated chicken red blood cells
Authors: Kellermayer Miklós , Ludáany Andrea , Miseta Attila , Kǒszegi Tamás , Berta Gábor , Bogner Péter , Hazlewood Carlton F. , Cameron Ivan L. , Wheatley Denys N. 
Published: February 2005

AbstractThe plasma membrane of erythrocytes, as of other cells, is thought to act as the barrier responsible for maintaining intracellular gradients of most ions and small molecular species between the cell and its environment. Controlled application of the nonionic detergent Brij 58 effectively opened the erythrocyte plasma membrane, as judged by electron microscopy and lipid mobilization, but the cytoplasm maintained much of its integrity for about 30 min. Release of K+ correlated well with release of protein into the surrounding medium. The results demonstrate that permeabilization of the erythrocyte plasma membrane does not result in an instantaneous equilibration of small ions, such as K+, between the cell and its environment. A comparison was made between erythrocytes treated with Brij 58 and Triton X‐100. The lipid and protein solubilizing actions of Triton X‐100 were not as easily separable in time as those of Brij 58. The results of treatment of the erythrocytes with different types of nonionic detergents suggest that the membranolytic and cytoplasmic protein destabilizing actions of nonionic detergents correspond with their hydrophilic‐lipophilic balance numbers (HLB values). © 1994 wiley‐Liss, Inc.
Modulation of the Na–;H antiport by insulin: Interplay between protein kinase C, tyrosine kinase, and protein phosphatases
Authors: Incerpi S. , Baldini P. , Bellucci V. , Zannetti A. , Luly P. 
Published: February 2005

AbstractThe insulin modulation of Na‐H antiport in rat hepatocytes was studied using the fluorescent, pH‐sensitive intracellular probe, 2′,7′ bis (carboxyethyl)‐5(6)‐carboxyfluorescein (BCECF). Our data show that insulin stimulates the NaH antiport. The dose‐response of insulin effect shows a behavior typical of other insulin responses: a maximum in the physiological range (1 nM) and smaller effects at higher and lower hormone concentrations. The time‐course of activation is very fast at high hormone concentrations and slow, but reaching a higher value, for the physiological concentrations (0.26± 0.05 and 0.18 ± 0.022 pH units for 1 nM and 1 μM insulin respectively). The use of phorbol, 12‐myristate, 13‐acetate (PMA), a potent activator of protein kinase C and its inhibitor staurosporine, and the inhibitor of tyrosine kinase erbstatin analog, suggests that both protein kinase C and tyrosine kinase could be involved in the mechanism leading to NaH antiport activation by insulin. We suggest that the activation of the antiport involves the two pathways depending on the hormone concentration. In particular, protein kinase C would mediate the effects of high hormone concentrations, acting as a growth factor, since staurosporine fully inhibited insulin 1 μM, but only partially 1 nM effects, and tyrosine kinase would mediate the effect of insulin 1 nM and only partially 1 μM. Okadaic acid 1 μM, a potent inhibitor of protein phosphatases, mimicked the hormone effects on the antiport and abolished the different time‐course due to hormone concentration, suggesting a role of kinases and phosphatases in the signal transduction. The effect of all activators was abolished by amiloride analog, 5‐(N‐ethyl‐N‐isopropyl) amiloride (EIPA), confirming the specificity of these effects. © 1994 wiley‐Liss, Inc.
Nitric oxide decreases in vitro phagocytosis of photoreceptor outer segments by bovine retinal pigmented epithelial cells
Authors: Becquet F. , Courtois Y. , Goureau O. 
Published: February 2005

AbstractThe presence of nitric oxide synthase (NOS) in the retina, the constitutive isoform in photoreceptor outer segments and the inducible form in retinal pigmented epithelial (RPE) cells, has been demonstrated, but the role of the free radical NO produced, remains unknown. We have investigated the effect of NO on the process of rod outer segment (ROS) phagocytosis. Using an in vitro assay for phagocytosis in primary cultures of bovine RPE cells, we demonstrate that NO released by SIN‐1 (3‐morpholinosydnonimine) in the culture medium inhibits the phagocytosis of ROS. Furthermore, endogenous NO, produced by RPE cells cotreated with lipopolysaccharide (LPS) and interferon‐γ (IFN‐γ), is also able to decrease RPE cell phagocytic activity. This effect depends upon the continuous presence of NO during the assay and is abolished by the scavenging of NO by hemoglobin or by the inhibition of NO synthase activity by L‐arginine analog, NG‐monomethyl‐L‐arginine. Pretreatment of ROS with SIN‐1 failed to impair subsequent phagocytosis, demonstrating that NO directly affects the RPE cells ability to phagocytose ROS. The inhibitory effect of NO is cGMP independent, since 8‐bromo‐cGMP does not modify this process. This decrease of ROS phagocytosis by RPE cells caused by NO may occur as a result of retinal inflammation, and could lead to photoreceptor degeneration. © 1994 wiley‐Liss, Inc.
Enhancement of differentiation induction of mouse myelomonocytic leukemic cells by extracellular ATP
Authors: Yamaguchi Masahiro , Hirayoshi Kazunori , Okuma Minoru , Nagata Kazuhiro 
Published: February 2005

AbstractWe examined the effect of ATP on the terminal differentiation of mouse myelomonocytic leukemic M1 cells to macrophages. Although ATP alone did not induce M1 cell differentiation, addition of ATP with the differentiation inducer, interleukin 6 (IL‐6), enhanced the induction of differentiation by IL‐6 about twofold. Comparison among several adenine nucleotides revealed that the order of effectiveness on differentiation enhancement was ATP > ADP > AMP ≥ adenosine. Using reactive blue 2, a P2 receptor antagonist, we confirmed that the effect of ATP on the stimulation of differentiation was mediated through the P2 purinergic receptor. Examination of cytosolic [Ca2+] elevation by ATP and comparison of potency of differentiation enhancement among several ATP analogs demonstrated that the effect of differentiation enhancement was mediated through P2y purinergic receptors expressed on M1 cell surface. Within 3 h of exposure, ATP alone slightly increased the expression of differentiation‐related immediate early response genes, c‐myc and JunB, and ATP also enhanced the IL‐6–induced expression of these genes. Induction of JunB expression by ATP analogs correlated with their potency of differentiation enhancement, which suggested that induction of JunB by ATP is one of signaling pathways involved in the exertion of its differentiation‐enhancing effect. © 1994 wiley‐Liss, Inc.
Calmodulin concentrated at the osteoclast ruffled border modulates acid secretion
Authors: Radding Wilson , Williams John P. , Hardy Robert W. , McDonald Jay M. , Whitaker Charles H. , Turbat‐Herrera Elba A. , Blair Harry C. 
Published: February 2005

AbstractOsteoclasts mediate acid dissolution of bone for maintenance of serum [Ca2+] and for replacement of old bone in terrestrial vertebrates. Recent findings point to the importance of intracellular signals, particularly Ca2+, in osteoclast regulation. However, acid degradation of bone mineral subjects the osteoclast to uniquely high extracellular [Ca2+]. We hypothesized that this high calcium environment would affect calcium signalling mechanisms, and studied the calcium binding regulatory protein, calmodulin, in the osteoclast. Avian osteoclast bone resorption was inhibited 30% at 1 μM and 90% at 7 μM by the calmodulin antagonist trifluoperazine. Osteoclast bone attachment was not affected by 10 μM trifluoperazine. Quantitative immunofluorescence using fluorescein‐labelled calmodulin monoclonal antibody showed a severalfold increase of calmodulin concentration in bone attached relative to plastic attached osteoclasts. Western blots confirmed this, showing two to threefold increased osteoclast calmodulin per milligram of cell protein in 3‐day bone‐attached vs. nonattached cells. Scanning confocal microscopy showed calmodulin polarization to areas of bone attachment. Electron micrographs with 9nm colloidal gold labelling showed calmodulin in the acid secreting ruffled membrane. ATP‐dependent acid transport in osteoclast membrane vesicles was inhibited by the calmodulin antagonist calmidazolium. This effect was reversed by addition of excess calmodulin, showing that the inhibition is specific. Vesicle acid transport inhibition reflects an approximately fourfold shift in the apparent Km for ATP of vesicular acid transport in the presence of the calmodulin antagonist. We conclude that calmodulin concentration and distribution is modified by bone attachment, and that osteoclastic acid secretion is calmodulin regulated. © 1994 Wiley‐Liss, Inc.
Expression of cytochrome P450 in rat pleural mesothelial cells in secondary cultures
Authors: Buard Annie , Renier Annie , Jaurand Marie‐Claude , Bignon Jean , Laurent Philippe , Beaune Philippe H. 
Published: February 2005

AbstractCultured rat pleural mesothelial cells (RPMC) isolated from male Sprague‐Dawley rats have been shown to metabolize polycylic aromatic hydrocarbons to more oxygenated metabolites. This capacity, which is maintained with passages, suggested the presence of monooxygenase enzymes. In order to clarify the enzymatic pathway, we investigated the expression of cytochromes P450 (CYP) in cultured RPMC by Western and Northern blot analyses. Cells were cultured in Ham's F10 medium supplemented with 10% fetal calf serum. The CYP expression was studied from passage 9 to 16 on different cell strains treated for 48 hours with P450 inducers. CYP1A1 apoprotein expression was very low in untreated cells, but was markedly induced after treatment with 1 μM 3‐methylcholanthrene or 22 μM β‐naphthoflavone. CYP1A1 mRNA was not detected in untreated cells and appeared after 3‐methylcholanthrene treatment. CYP2E1 apoprotein was constitutively expressed in cultured RPMC, and markedly increased by 170 mM ethanol, and 0.1 μM or 1 μM dexamethasone treatments. Unexpectedly, whereas the amount CYP2E1 mRNA was not modified by ethanol treatment, dexamethasone has a marked inductive effect on CYP2E1 mRNA level. The CYP expression pattern was found similar in RPMC issued from different rats, and not dependent on passage number. The CYP expression and the detection of NADPH‐P450 reductase, and of epoxide hydrolase, ascertained that RPMC contain the overall enzymatic pathway required for the biotransformation and activation of procarcinogen compounds, such as polycyclic aromatic hydrocarbons and nitrosamines. Both expression and regulation properties are maintained in long‐term cultures of RPMC. © 1994 Wiley‐Liss, Inc.
EGF modulates phosphoinositide levels in ovarian granulosa cells stimulated by luteinizing hormone
Authors: Hubbard C. J. 
Published: February 2005

AbstractHamster granulosa cells were exposed to epidermal growth factor (EGF) and luteinizing hormone (LH) to study cross‐talk between second messenger pathways involving tyrosine kinase, cAMP, and phosphoinositides. Granulosa cells from ovarian preovulatory follicles of PMSG‐primed hamsters were incubated with various additives in serum‐free medium. LH, but not EGF, stimulated inositol phosphate (IP) accumulation; however, when combined with LH, EGF inhibited IP accumulation in a manner that was concentration dependent for both LH and EGF. The inhibitory effects of EGF were significantly reduced by the tyrosine kinase inhibitor genistein and by pertussis toxin suggesting a role for tyrosine kinase and an inhibitory G‐protein (Gi) in this system. EGF stimulated an increase in cAMP, but it does not appear to modulate LH‐stimulated IP levels via cAMP. © 1994 Wiley‐Liss, Inc.
Platelet‐derived growth factor isoforms prevent cell death during starvation of AKR‐2B fibroblasts
Authors: Simm Andreas , Hoppe Viviane , Hoppe Jürgen , Gazit Aviv 
Published: February 2005

AbstractConfluent AKR‐2B fibroblasts rapidly desintegrate upon removal of serum until a final density of ∼50% of the initial value was reached after 12 h. This density remained unchanged for at least 48 h. Platelet‐derived growth factor (PDGF)‐BB stimulated more than 95% of these cells to divide. PDGF‐AB or ‐BB added immediately after serum removal caused complete survival of the cells, but did not stimulate cell division as demonstrated by two‐dimensional DNA flow cytometry. PDGF‐AA was less effective leading to ∼75% of the initial cell density. This effect could be augmented by the addition of ocadaic acid, a potent phosphatase inhibitor, suggesting that protein phosphorylation plays a role in this process. By using tyrphostin AG807 it was demonstrated that the signaling mechanism for survival requires receptor tyrosine autophosphorylation. © 1994 Wiley‐Liss, Inc.