bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of lysophospholipids on signaling in the human Jurkat T cell line
Authors: Xu Yan , Casey Graham , Mills Gordon B. 
Published: February 2005

AbstractLysophospholipids have recently been demonstrated to induce activation and proliferation of fibroblasts and other cell lineages by interacting with high affinity cell surface receptors leading to specific intracellular signaling events. Platelet activation, likely at the site of injury or inflammation, results in increased production of lysophospholipids suggesting a possible source of lysophospholipids. We have recently demonstrated that high concentrations of lysophospholipids are present in ascites and plasma from ovarian cancer patients, suggesting that physiologically produced lysophospholipids could interact with cells present in these fluids, including lymphocytes, and alter their function. We demonstrate herein that lysophosphatidic acid (LPA), lysophosphatidylserine (LPS), and sphingosylphosphorylcholine (SPC) activate the Jurkat T cell line. Each of the lysophospholipids induced a transient increase in cytosolic free calcium ([Ca2+]i) in Jurkat cells. Increases in [Ca2+]i were cross‐desensitized by LPA, LPS and SPC, suggesting that the lysophospholipids share the same receptor(s) or that their downstream signaling pathways converge or interact. Lysophosphatidylgycerol (LPG), a competitive inhibitor of the putative LPA receptor, inhibited the calcium releasing activity of LPA, but not that of LPS and SPC, suggesting that these lysophospholipids interact with different receptors and that desensitization is due to interactions in downstream signaling pathways. The ability of the lysophospholipids to induce increases in [Ca2+]i was attenuated, but not completely blocked, by increases in [Ca2+]i induced by activation of the thrombin receptor. In contrast, increases in [Ca2+]i induced by the lysophospholipids and cross‐linking the CD3 component of the T cell receptor complex with the UCHT1 antibody did not undergo heterologous desensitization. Strikingly, LPA is sufficient to stimulate proliferation of Jurkat cells in serum‐free medium or in synergy with low concentrations of fetal bovine serum. In addition, LPA also increased the production of the T cell growth factor, interleukin 2 (IL‐2), by Jurkat cells treated with phorbol esters. LPS, in contrast, inhibited Jurkat proliferation while increasing IL‐2 production and SPC inhibited both processes. Thus, although all three lysophospholipids were sufficient to induce a transient increase in [Ca2+]i in Jurkat cells, they induced markedly different physiological consequences. © 1995 Wiley‐Liss, Inc.
P‐glycoprotein stability is affected by serum deprivation and high cell density in multidrug‐resistant cells
Authors: Muller Catherine , Laurent Guy , Ling Victor 
Published: February 2005

AbstractThe control of P‐glycoprotein (Pgp) expression in multidrug‐resistant cells (MDR) is complex and may be regulated at different levels. We have investigated Pgp stability in four different human and hamster MDR cell lines. Using a pulse‐chase procedure we show that Pgp half‐life is between 14 and 17 h in all these cell lines when they are growing exponentially. However, in the presence of a low level of serum, Pgp half‐life is increased four to sixfold. A similar effect is observed when the cell cultures are maintained in high cell density. The increased Pgp stability appears to be differently regulated as serum deprivation results in a general enhanced degradation of total cytoplasmic and membrane proteins. Moreover, the observed serum effect suggests the involvement of growth factors in the control of Pgp stability. These findings suggest that protein stability may be an important factor in the regulation of Pgp expression. © 1995 Wiley‐Liss, Inc.
Multiple pathways are involved in protection of MCF‐7 cells against death due to protein synthesis inhibition
Authors: Geier Avraham , Weiss Chana , Beery Rachel , Haimsohn Michal , Hemi Rina , Malik Zvi , Karasik Avraham 
Published: February 2005

AbstractPreviously we have shown that IGF‐1 protected MCF‐7 cells against death induced by the protein synthesis inhibitor cycloheximide (CHX). In the present study we investigated the ability of protein kinase C activator 12‐0‐tetradecanoyl‐phorbol‐13‐acetate (TPA), the protein kinase A activator 8‐bromoadenosine 3′5′‐cyclic monophosphate (Br‐cAMP), and the enzyme inhibitor aurintricarboxylic acid (ATA) to protect MCF‐7 cells against death, due to a continuous presence of CHX. Cell death was evaluated after 48 h of incubation by several techniques (trypan blue staining, release of lactic dehydrogenase, cellular ATP content, transmission electron microscopy, and DNA fragmentation). Apoptosis which terminates in necrosis, characterized this mode of cell death. TPA and ATA at optimal concentrations of 40 ng/ml and 100 μg/ml, respectively, reduced cell death to the control level (without CHX), while Br‐cAMP at an optimal concentration of 650 μg/ml reduced cell death only partially. IGF‐1, TPA, and ATA, which stimulated protein synthesis in the control MCF‐7 cells, had no effect on protein synthesis in the CHX‐treated cells, indicating that the survival effect is not due to new protein synthesis. The protein kinase C inhibitor staurosporine blocked the survival effect of TPA and IGF‐1 in a dose‐dependent manner, however did not affect the survival effect of ATA. The tyrosine kinase inhibitor genistein blocked the survival effect of IGF‐1, but not that of TPA and ATA. Our results provide evidence for several distinctive pathways, the activation of which protects MCF‐7 cells against death, due to protein synthesis inhibition. © 1995 Wiley‐Liss, Inc.
Specific binding of leukemia inhibitory factor to murine myoblasts in culture
Authors: Bower J. , Vakakis N. , Nicola N. A. , Austin L. 
Published: February 2005

AbstractLeukemia inhibitory factor (LIF) is a member of the cytokine family of growth factors. It has been shown to exert a variety of actions on a diverse range of cell types, including neuronal, bone, and hemopoietic cells (Hilton, 1992, Trends Biochem. Sci., 17:72–76). In many of these cell types, studies have indicated the presence of specific receptors for LIF (Godard et al., 1982, J. Biol. Chem., 267:3214–3222; Hilton et al., 1988, Proc. Natl. Acad. Sci. USA, 85:5971–5975; Hilton and Nicola, 1992, J. Biol. Chem., 267:10238–10247.). The mechanism by which these receptors act is believed to involve tyrosine phosphorylation and the signal transducing receptor component gp130. We have previously shown that LIF is capable of inducing both human and murine myoblasts to proliferate in culture (Austin et al., 1992, J. Neurol. Sci., 112:185–191). We now report that LIF binds specifically to receptors on the surface of myoblasts, with an equilibrium dissociation constant of 400 pM and the number of receptors per cell varies with cell density. Binding competition studies showed that LIF binding to these receptor sites was not competed for by a number of other growth factors which stimulate myoblast proliferation including basic fibroblast growth factor (bFGF), transforming growth factor‐α (TGFα), insulin‐like growth factor 1 (IGF‐1), and interleukin‐6 (IL‐6). There was a time and concentration‐dependent down‐regulation of receptor numbers following preincubation of myoblasts with LIF. The processing of these receptors subsequent to binding, involves as a first step, internalization and degradation by the myoblast. LIF appeared to stimulate myoblast proliferation rather than cell survival. © 1995 Wiley‐Liss, Inc.
Regulation of multidrug resistance gene mdr1b/mdr1 expression in isolated mouse uterine epithelial cells
Authors: Kuo M. Tien , Julian Joanne , Husain Farah , Song Renduo , Carson Daniel D. 
Published: February 2005

AbstractThe mammalian uterine epithelium (UE) undergoes drastic physiological and morphological changes during pregnancy. Steady‐state levels of murine mdr1b mRNA, transcribed from a multidrug resistance gene encoding a membrane protein which functions as a transporter of lipophilic cytotoxic agents, are low in nonpregnant, cycling UE, but drastically increase (about 1,500‐ to 2,000‐fold) at day 8 of gestation. At day 16 of gestation, levels of mdr1b mRNA are 2,500‐ to 3,000‐fold higher than those in the cycling UE cells. Levels of mdr1b mRNA were elevated to levels comparable to those observed during pregnancy, in the UE of ovariectomized mice following 5–8 days of estrogen and progesterone administration. Withdrawal of these hormones resulted in a drastic reduction of mdr1b mRNA within 36 hr. These results suggested that steroid hormones alone can account for increased mdr1b mRNA expression and do not require the presence of other placenta/embryo‐derived factors. Moreover, the hormonal effect on uterine mdr1b mRNA biosynthesis during pregnancy apparently is a delayed phenomenon. Nuclear run‐on assays demonstrated that the rate of mdr1b transcription in UE cells prepared from 15‐day pregnant mice (d‐15 UE cells) was about two‐ to three‐fold higher than that in nonpregnant UE cells. This increased transcription rate alone cannot account for mdr1b mRNA accumulation during pregnancy. mdr1b mRNA expression was investigated in primary cultures of d‐15 UE cells. mdr1b mRNA levels decayed by 50% within 3‐4 hr of culture and reached a steady‐state 0.5‐2% of initial levels by 24 hr. The rate of mdr1b mRNA decay in primary d‐15 UE cells was decreased by treatment with α‐amanitin or cycloheximide, suggesting that the decay pathway requires both transcription and de novo protein synthesis. Our results suggest that multiple mechanisms are involved in the maintenance of the high levels of mdr1b mRNA in pregnant UE cells. Furthermore, these data suggest that increased mRNA stability may contribute to the accumulation of mdr1b transcript during pregnancy. © 1995 Wiley‐Liss, Inc.
Hepatocyte growth factor is involved in formation of osteoclast‐like cells mediated by clonal stromal cells (MC3T3‐G2/PA6)
Authors: Sato Takuya , Hakeda Yoshiyuki , Yamaguchi Yuji , Mano Hiroshi , Tezuka Ken‐Ichi , Matsumoto Kunio , Nakamura Toshikazu , Mori Yoshihisa , Yoshizawa Kenji , Sumitani Koji , Kodama Hiroaki , Kumegawa Masayoshi 
Published: February 2005

AbstractOsteoclast formation from hemopoietic precursors has been shown to require the support of stromal cells in bone tissue. In this study, we demonstrated that hepatocyte growth factor (HGF) is one of the stromal cell‐derived molecules responsible for osteoclast‐like cell formation. For our experimens, we used a coculture system for osteoclastic cell formation and activation in which hemopoietic blast cells are cocultured with calvaria‐derived stromal MC3T3‐G2/PA6 (PA6) cells on dentine slices in the presence of 1, 25‐dihydroxyvitamin D3 [1,25(OH)2D3]. Addition of anti‐HGF neutralizing IgG to the cocultures inhibited the formation of osteoclastic cells and their dentine‐recorbing activity. We detected a single 6.0‐kb transcript for HGF in PA6 cells, and also recognized immunoreactive Mr. 81,000 and 88,000 forms of HGF in conditioned medium (CM) from PA6 cell cultures, the level of which reached 6 ng/ml. Both the CM and HGF stimulated the proliferation of blast cells synergistically with granulocyte‐macrophage colony‐stimulating factor, resulting in an increased number of osteoclast precursors that respond to 1,25(OH)2D3 that are tartrate‐resistant acid phosphatase‐positive multinucleate cells in stromal cell‐free blast cell cultures in plastic wells. The effect of the CM was diminished by the addition of anti‐HGF IgG. However, neither the CM nor HGF stimulated the formation of osteoclastic cells and pits on dentine slices in the absence of PA6 cells. These results suggest that although HGF cannot completely replace stromal cells, it is one of the paracrine mediators produced by stromal cells that act on proliferation of osteoclastic cell precursors. © 1995 Wiley‐Liss, Inc.
Transforming growth factor‐β1 modulates adenylyl cyclase signaling elements and epidermal growth factor signaling in cardiomyocytes
Authors: Nair Bipin G. , Yu Yiming , Rashed Hani M. , Sun Hui , Patel Tarun B. 
Published: February 2005

AbstractStudies presented in this report were designed to investigate the effects of transforming growth factor‐b̃1 (TGF‐b̃1) on epidermal growth factor (EGF)‐ mediated stimulation of cAMP accumulation in cardiac myocytes and elucidate the mechanism(s) involved in this modulation. TGF‐b̃1 (20 pM) treatment of cardiac myocytes, in a time‐dependent manner, decreased the ability of EGF (100 nM) to increase cAMP accumulation. Significant attenuation of EGF‐elicited cAMP accumulation was observed 2 h after exposure to TGF‐b̃1 and 18 h after addition of TGF‐b̃1, the ability of EGF to increase cAMP accumulation was completely obliterated. TGF‐β1 neither decreased immunoprecipitable EGF receptors in membranes from cardiomyocytes nor altered the specific binding of [125I] EGF to cardiomyocyte membranes. However, TGF‐b̃1 decreased the ability of EGF to phosphorylate membrane proteins on tyrosine residues. TGF‐b̃1 treatment of cardiomyocytes also decreased the ability of forskolin to augment cAMP accumulation in intact cells and stimulate adenylyl cyclase activity. Similarly, in membranes of TGF‐b̃1‐treated cells, neither isoproterenol nor EGF stimulated adenylyl cyclase activity. Interestingly, as assessed by the ability of A1F4− to stimulate adenylyl cyclase, TGF‐b̃1 did not alter the coupling between Gs and catalytic subunits. Likewise, TGF‐b̃1 did not alter the functional activity of the inhibitory regulatory element of the system, Gi. Western analysis of cellular proteins revealed that TGF‐b̃1 did not alter the amounts of Gsα, Giα2, and Giα3. We conclude that TGF‐b̃1 attenuates EGF‐elicited cAMP accumulation in cardiomyocytes, in part, by decreasing the EGF receptor kinase function and that TGF‐b̃1‐mediated alterations in the activity of adenylyl cyclase catalytic subunit also contribute toward the regulation of adenylyl cyclase by various agonists. © 1995 Wiley‐Liss, Inc.
Repression of the Id2 (inhibitor of differentiation) gene promoter during exit from the cell cycle
Authors: Biggs Joseph R. , Zhang Yong , Murphy Elizabeth V. 
Published: February 2005

AbstractThe Id2 gene is one of several “Id‐like” genes which encode helix‐loop‐helix proteins which dimerize with basic helix‐loop‐helix proteins and inhibit binding to the DNA enhancer element known as an E box. By repressing the DNA binding activity of basic helix‐loop‐helix proteins, Id proteins inhibit transcription of tissue‐specific genes in myoblasts, hematopoietic precursor cells, and other types of undifferentiated cells. Serum starvation results in the disappearance of Id gene transcripts in most types of cultured cells, and often induces differentiation of these cells. In order to gain some insight into this process, we have analyzed Id2 promoter function in the glioma cell line U87Y. We have isolated 300 base pairs of Id2 promoter sequence which is sufficient to repress the activity of a reporter gene in serum‐starved U87Y cells, but induces the activity of the reporter gene when the cells are stimulated with fresh serum. Two regions within this 300 base pair sequence contain repressor elements; deletion of either region results in increased promoter activity. Both repressor regions serve as binding sites for a protein in extracts from serum‐starved U87Y cells but not in serum‐stimulated cells. © 1995 Wiley‐Liss, Inc.
Preferential induction of apoptosis in mouse CD4+CD8+αβTCRIoCD3εIo thymocytes by zinc
Authors: Telford William G. , Fraker Pamela J. 
Published: February 2005

AbstractHigh concentrations of zinc salts (500 m̈M and greater) are known to inhibit apoptosis in a variety of systems. However, closer examination of dose effects revealed that lower concentrations of zinc (80‐200 m̈M) could induce apoptosis in approximately 30‐40% of mouse thymocytes following 8 h incubation. The ability of zinc to cause thymocyte apoptosis was detected flow‐cytometrically by reductions in propidium iodide DNA fluorescence and forward scatter, both quantitative indicators of apoptotic death. Zinc induced both internucleosomal DNA fragmentation and morphological changes characteristic of apoptosis as determined by gel electrophoresis and electron microscopy, respectively. In addition, transcriptional and translational inhibitors prevented zinc‐induced apoptosis, indicating a requirement for de novo mRNA and protein synthesis, another characteristic of apoptotic death. Fluorescent immunophenotype‐specific apoptotic analysis indicated that zinc‐induced apoptosis occurred primarily in the less mature CD4+CD8+αb̃TCRIoCD3εIo thymocyte subset, with lower amounts of death occurring in the other subsets. This lineage specificity was shared with glucocorticoid‐induced apoptosis. Taken together, these results indicate that zinc induces true apopotitic death in mouse thymocytes and suggests a role for zinc in the regulation of apoptosis. © 1995 Wiley‐Liss, Inc.
Different regulatory pathways involved in ATP‐stimulated chloride secretion in rat epididymal epithelium
Authors: Chan H. C. , Zhou W. L. , Fu W. O. , Ko W. H. , Wong P. Y. D. 
Published: February 2005

AbstractThe regulatory pathways involved in the ATP‐stimulated CI− secretion across rat epididymal epithelium were investigated by the short‐circuit current (ISC) technique. Biphasic characteristic was observed in the ISC responded to ATP (0.01‐10 m̈M). Inhibitor of P1 receptor, 8‐phenyltheophylline (up to 100 m̈M), did not have any effect on both phases of the ATP‐stimulated ISC. The order of potency for stimulation of the two phases in ISC was ATP>ADP> AMP, adenosine, consistent with the presence of P2‐purinoceptors. CI− channel blocker, disulfonic acid stilbene (DIDS, 300 m̈M), only inhibited the first peak of the ATP‐stimulated ISC while diphenylamine‐dicarboxylic acid (DPC, 1 mM) reduced both, indicating the involvement of different conductance pathways. DIDS was found to have an inhibitory effect on Ca2+‐activated ISC (induced by ionomycin, 10 m̈M) but not cAMP‐activated ISC (induced by forskolin, 1 m̈M) which could only be blocked by DPC. Both peaks of the ATP‐activated ISC could be significantly inhibited by pretreatment with a Ca2+‐chelating agent, BAPTA‐AM (50 m̈M). An increase in cellular cAMP content upon stimulation of ATP was measured by radioimmunoassay. No significant increase in cAMP production was observed in cells stimulated with adenosine. The ATP‐induced cAMP increase was prevented by pretreatment with BAPTA‐AM (100 m̈M) indicating that cAMP production upon ATP stimulation was secondary to an increase in intracellular Ca2+ concentration. These results indicate that the ATP‐stimulated CI− secretion could be mediated by Ca2+ and cAMP‐dependent regulatory pathways giving rise to the biphasic nature of the ATP‐induced ISC. © 1995 Wiley‐Liss, Inc.
Developmental changes in phosphorylation of the transcription factor CREB in the embryonic murine palate
Authors: Weston Wayde M. , Greene Robert M. 
Published: February 2005

AbstractCyclic AMP, via activation of cAMP‐dependent protein kinase (PKA) and subsequent protein phosphorylation, regulates a number of cellular and tissue responses that are critical to normal development of the mammalian palate. The present study examines the expression, distribution, and phosphorylation in the developing murine palate of a substrate for PKA known as the cAMP‐response element binding protein (CREB). This 43 × 103 Mr protein functions as a regulator of cAMP‐inducible gene expression. CREB is expressed constituitively throughout the palatal morphogenetic period and is ubiquitously distributed throughout palatal tissue. Immunofluorescent staining of palatal cells and tissues with an anti‐CREB antibody revealed CREB to be localized to cell nuclei. Western blot analysis of extracts of staged palatal shelves with an antibody specific for phospho‐ser 133‐CREB demonstrated a steady increase in CREB phosphorylation at this residue during palate development. These observations show a temporal correlation with expression levels of cAMP‐regulated genes in palate cells. The data indicate that CREB activity in the developing palate is most likely to be regulated at the level of protein phosphorylation as opposed to changes in levels of CREB protein expression. © 1995 Wiley‐Liss, Inc.
Effects of dexamethasone, heat shock, and serum responses on the inhibition of hsc70 synthesis by antisense RNA in NIH 3T3 cells
Authors: Li Ting , Hightower Lawrence E. 
Published: February 2005

AbstractA dexamethasone (Dex)‐inducible antisense RNA expression vector was constructed that contains the 5′‐untranslated region and one third of the coding sequence for the bovine hsc70 protein. This vector was used to transfect NIH 3T3 cells from which clonal cell lines expressing hsc70 antisense RNA were developed. Quantitative Northern blot analysis with strand‐specific probes was used to demonstrate the Dex‐inducible accumulation of hsc70 antisense RNA in proliferating cell cultures and the inhibition of hsc70 RNA levels. Surprisingly, antisense RNA was either much less effective in reducing the amounts of hsc70 RNA in Dex‐treated cultures than in untreated controls or cells compensated by producing more hsc70 RNA in response to increasing amounts of antisense RNA. Hsc70 protein synthesis did not decrease in either Dex‐treated or untreated cultures: it actually increased, again suggesting the activation of a compensatory response. In Dex‐treated cultures subjected to heat shock, hsc70 antisense RNA blocked the induction of hsp70, indicating that newly synthesized RNA was targeted effectively before it became translationally active. To test this hypothesis further, Dex‐treated cultures were made quiescent by serum deprivation and then restimulated with serum, which causes a burst of RNA and protein synthesis. Consistent with this hypothesis, increased synthesis of hsc70 was blocked in serum‐stimulated cultures expressing antisense RNA. © 1995 Wiley‐Liss, Inc.
Vasculotropin/Vascular endothelial growth factor is an autocrine growth factor for human retinal pigment epithelial cells cultued in vitro
Authors: Guerrin Marina , Moukadiri Hafida , Chollet Pascale , Moro Fraņoise , Dutt Kamla , Malecaze Fraņois , Plouët Jean 
Published: February 2005

AbstractVasculotropin (VAS), also called vascular endothelial growth factor (VEGF) or vascular permeability factor, is a secreted growth factor whose target cell specificity has been reported as restricted to vascular endothelium. Its effects are mediated by at least two distinct membrane‐spanning tyrosine kinase receptors, KDR and flt‐1, the expression of which also seems restricted to vascular endothelium. We describe here that cultured human retinal pigment epithelial (HRPE) cells express both KDR and flt‐1 receptors, bind VAS/VEGF on two high affinity sites (apparent Kd of 9 and 210 pM corresponding to 940 and 18,800 sites per cell) and proliferate or migrate upon recombinant VAS/VEGF addition. HRPE cells also express the mRNA corresponding to the 121 and 165 amino acid forms of VAS/VEGF. HRPE cells release in their own culture medium and store in their extracellular matrix self‐mitogenic and chemoattractant factors indistinguishable from 121 and 165 VAS/VEGF isoforms. The autocrine role of VAS/VEGF was confirmed by the inhibition of these bioactivities by neutralizing specific anti‐VAS/VEGF antibodies. © 1995 Wiley‐Liss, Inc.