bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of calcium in growth inhibition induced by a novel cell surface sialoglycopeptide
Authors: Betz Natalie A. , Westhoff Brenda A. , Johnson Terry C. 
Published: February 2005

AbstractOur laboratory has purified an 18 kDa cell surface sialoglycopeptide growth inhibitor (CeReS‐18) from intact bovine cerebral cortex cells. Evidence presented here demonstrates that sensitivity to CeReS‐18‐induced growth inhibition in BALB‐c 3T3 cells is influenced by calcium, such that a decrease in the calcium concentration in the growth medium results in an increase in sensitivity to CeReS‐18. Calcium did not alter CeReS‐18 binding to its cell surface receptor and CeReS‐18 does not bind calcium directly. Addition of calcium, but not magnesium, to CeReS‐18‐inhibited 3T3 cells resuts in reentry into the cell cycle. A greater than 3‐hour exposure to increased calcium is required for escape from CeReS‐18‐induced growth inhibition. The calcium ionophore ionomycin could partially mimic the effect of increasing extracellular calcium, but thapsigargin was ineffective in inducing escape from growth inhibition. Increasing extracellular calcium 10‐fold resulted in an approximately 7‐fold increase in total cell‐associated 45Ca+2, while free intracellular calcium only increased approximately 30%. However, addition of CeReS‐18 did not affect total cell‐associated calcium or the increase in total cell‐associated calcium observed with an increase in extracellular calcium. Serum addition induced mobilization of intracellular calcium and influx across the plasma membrane in 3T3 cells, and pretreatment of 3T3 cells with CeReS‐18 appeared to inhibit these calcium mobilization events. These results suggest that a calcium‐sensitive step exists in the recovery from CeReS‐18‐induced growth inhibition. CeReS‐18 may inhibit cell proliferation through a novel mechanism involving altering the intracellular calcium mobilization/regulation necessary for cell cycle progression. © 1995 Wiley‐Liss, Inc.
Effect of herparin on bovine epithelial lens cell proliferation induced by heparin affin regulatory peptide
Authors: Delbé J. , Vacherot F. , Laaroubi K. , Barritault D. , Courty J. 
Published: February 2005

AbstractHARP (heparin affin regultory peptide) is an 18 kDa heparin binding protein, also known as HB‐GAM or pleiotrophin (PTN) which has been primarily isolated from brain and uterus, and displays neurite outgrowth, angiogenic and mitogenic activities. Previously, we have expressed the human cDNA encoding human HARP in NIH 3T3 cells. Purified recombinant HARP displayed mitogenic activity for endothelial cells. Its NH2‐terminal sequence indicates that the HARP molecule possesses a three amino acid extension from the signal peptide more than the NH2‐terminal described. For HB‐GAM or PTN, these three amino acids may be essential for the stability and the mitogenic activity of this growth factor. In an attempt to further study the mode of action of this growth factor, we have investigated the mitogenic effect of HARP on various cell types. In contrast to FGF‐2, HARP failed to induce stimulation of DNA synthesis on a CCL39 cell line. However, we found that in quiescent bovine epithelial lens (BEL) cells, the stimulation of DNA synthesis induced by HARP is dose‐dependent (EC50: 2.5 ng/ml) and maximal stimulation is as potent as that induced by FGF‐2 (EC50: 25 pg/ml). Interestingly, when BEL cells were allowed to quiesce in the presence of serum, the stimulation induced by HARP is considerably less potent. In this highly responsive cell system, heparin could potentiate the mitogenic activity of HARP at very low doses (0.1‐1 m̈g/ml) and inhibit this activity at concentrations of 10 m̈g/ml. In contrast to its protective effect on FGF‐1 and ‐2, heparin was unable to preserve HARP from tryptic and chymotryptic degradations. © 1995 Wiley‐Liss, Inc.
Apoptosis during HL‐60 cell differentiation is closely related to a G0/G1 cell cycle arrest
Authors: Terui Yasuhito , Furukawa Yusuke , Kikuchi Jiro , Saito Masaki 
Published: February 2005

AbstractThe cell cycle‐associated differences in the susceptibility to apoptosis were examined in HL‐60 cells before and after differentiation with phorbol 12, 13‐dibutyrate (PDBu). HL‐60 cells in various phases of the cell cycle were separated by the counterflow centrifugal elutriation and the susceptibility to apoptosis was measured by the morphological examination and by DNA fragmentation assay. Undifferentiated HL‐60 cells in S phase showed a significantly higher susceptibility to apoptosis than those in G0/G1 or G2/M phase either in the absence or presence of apoptosis‐inducing reagents such as A23187, actinomycin D (Act D), and cycloheximide (CHX). In contrast, PDBu‐treated HL‐60 cells preferentially underwent apoptosis in G0/G1 phase. When untreated HL‐60 cells enriched for G0/G1 phase were recultured in a complete medium, the percentage of apoptotic cells increased after 6‐12 h in correlation with the increase in S‐phase cells. When the same experiment was performed with PBDu‐treated cells, spontaneous increase of apoptotic cells was observed while almost all cells remained in G0/G1 phase. Northern blot analysis revealed that undifferentiated cells expressed the same amounts of bcl‐2 mRNA in each cell cycle phase, whereas G0/G1‐predominant reduction of bcl‐2 mRNA was noted in PDBu‐treated cells. There was no difference in the amounts of CD11b mRNA between G0/G1 fraction and S + G2/M fraction of differentiated HL‐60 cells. BCL‐2 overexpression could almost completely abrogate the G0/G1‐predominant induction of apoptosis in differentiated HL‐60 cells. These results suggest that G0/G1 cell cycle arrest and down‐regulation of bcl‐2 mRNA in G0/G1 phase might be associated with apoptosis in differentiated HL‐60 cells whereas the weakness of chromatin structure in S phase might be related to apoptosis in undifferentiated HL‐60 cells. © 1995 Wiley‐Liss, Inc.
Evidence for a pertussis toxin sensitive calcium entry pathway in thyroid FRTL‐5 cells
Authors: Törnquist Kid , Ekokoski Elina 
Published: February 2005

AbstractReceptor‐mediated calcium entry was investigated in Fura 2 loaded FRTL‐5 cells. The purinergic agonist ATP activated the release of sequestered calcium and the entry of extracellular calcium. Downregulation of protein kinase C (PKC) substantially enhanced the ATP‐evoked calcium entry. Pretreatment of the cells with pertussis toxin (Ptx) decreased the ATP‐evoked calcium entry by 56% and the release of sequestered calcium by 34%. In PKC‐downregulated cells, the effect of Ptx treatment on the ATP‐evoked increase in [Ca2+]iwas 73% and 44%, respectively. Phorbol myristic acetate (PMA) decreased the ATP‐evoked calcium entry to the same extent as Ptx. In Ptx‐treated cells, the ATP‐evoked influx of 45Ca2+ was attenuated. Stimulation of the cells with P2p‐purinergic agonist GTP evoked no entry of calcium, although GTP released the same amount of sequestered calcium as did ATP. PKC downregulation or pretreatment with Ptx had no effects on the GTP‐evoked responses, whereas PMA decreased the GTP‐evoked release of calcium. We conclude that the ATP‐activated rapid calcium entry pathway is a second messenger‐operated calcium channel. © 1995 Wiley‐Liss, Inc.
Role of protein kinase cα in the induction of carcinoembryonic antigen by transforming growth factor β
Authors: Chakrabarty Subhas , Huang Shuang 
Published: February 2005

AbstractPrevious studies showed that transforming growth factor b̃ (TGFb̃1) regulates the expression of carcinoembryonic antigen (CEA) and CEA‐cross‐reactive glycoproteins (CEA‐GLYs) in human colon carcinoma cells through a signal‐transducing pathway associated with protein kinase C (PKC) (Chakrabarty, J. Cell. Physiol., 1992, 152 494–499). In this study we determined the role of the PKCα isoform in the regulation of CEA and CEA‐GLYs expression by TGFb̃1. Expression of PKCα antisense RNA, through transfection experiments with an antisense PKCα expression vector, resulted in down‐modulation of PKCα RNA and protein expression. TGFb̃1 was unable to stimulate the expression and secretion of CEA in cells in which the expression of PKCα protein was substantially reduced. The ability of TGFb̃1 to stimulate the expression of the 95‐ and 55‐KDa CEA‐GLYs, however, was not affected. We therefore conclude that TGFb̃1 regulates the secretion and expression of CEA through a signal‐transducing pathway associated with PKCα. TGFb̃1 may also regulate the expression of CEA‐GLYs through signal‐transducing pathways associated with other PKC isoforms. © 1995 Wiley‐Liss, Inc.
Esterification of 12(s)‐hydroxy‐5,8,10,14‐eicosatetraenoic acid into the phospholipids of human peripheral blood mononuclear cells: Inhibition of the proliferative response
Authors: Joulain Catherine , Meskini Nadia , Anker Genevieve , Lagarde Michel , Prigent Annie‐France 
Published: February 2005

Abstract12‐hydroxy‐eicosatetraenoic acid (12‐HETE), the lipoxygenase metabolite of arachidonic acid produced by activated platelets, has been shown to accumulate in peripheral blood mononuclear cells (PBMC) of elderly people. 12‐HETE being antimitogenic for lymphocytes, its accumulation in blood cells might be involved in the well‐known decline in immune function which accompanies aging. Because HETEs have been shown to be rapidly metabolized and/or incorporated into cellular lipids in a variety of cell types, we have investigated the uptake, metabolism, and intracellular distribution of exogenous 12‐HETE by human PBMC. [3H]‐12‐HETE was dose and time dependently incorporated by PBMC and also metabolized to more polar products. These polar metabolites were mainly released extracellularly and only marginally esterfied in phospholipids. Although [3H]‐12‐HETE radiolabel was preferentially associated with phosphatidylcholine, especially, a substantial amount of radiolabel was also found associated with phosphatidylinositol (20‐50% of the labeled phospholipids). The stability of 12‐HETE in the phospholipid pool was comparable to that reported for most other cell types, with 50% of the initial radiolabel being still present after 18 hr. Upon exposure to mitogenic activation, 12‐HETE‐labeled PBMC released unmodified 12‐HETE from phosphatidylinositol. In addition, 12‐HETE dose dependently inhibited the proliferative response of PBMC to Con A stimulation. These results suggest that 12‐HETE esterification in phospholipids might lead to the generation of unusual lipid second messengers with impaired capacity to transduce activation signals, thus decreasing lymphocyte function. © 1995 Wiley‐Liss, Inc.
Phenotypically and karyotypically distinct Madin‐Darby canine kidney cell clones respond differently to alkaline stress
Authors: Wünsch S. , Gekle M. , Kersting U. , Schuricht B. , Oberleithner H. 
Published: February 2005

AbstractWe isolated two cell clones from the wild‐type Madin‐Darby canine kidney cell line (MDCK) that resembles renal collecting duct epithelium. Morphology and karyotypes of the two cell clones were evaluated. The MDCK‐C7 cell clone morphologically resembles principal cells (polygonal cell shape, flat), while the MDCK‐C11 clone resembles intercalated cells (cuboidal cell shape, high). The diploid chromosome number of MDCK‐C7 cells is 83.1 ± 0.2 (n = 139); that for MDCK‐C11 cells is 78.8 ± 0.1 (n = 128). Culture of MDCK‐C7 cells in alkaline medium (pH 7.7) induced irreversible phenotypical and genotypical alterations. transformed MDCK‐C7F cells are characterized by two abnormal (biarmed) chromosomes. In contrast, MDCK‐C11 cells are not phenotypically altered by alkaline stress. In order to elucidate the role of intracellular pH (pHi) in the transformation process, we measured pHi under control conditions (pH 7.4). after 5 min exposure to alkaline stress (“acute experiment,” pH 7.7) and after incubation of the cells in alkaline medium for two weeks (“chronic experiment,” pH 7.7). Under control conditions, MDCK‐C7 cells maintained pHi at 7.14 ± 0.01 (n = 154) and MDCK‐C11 cells at 7.01 ± 0.01 (n = 147). Acute alkaline stress increased pHi of both cell types to similar steady‐state values. Under chronic alkaline stress, MDCK‐C7 cells were unable to maintain intracellular pH within normal limits exhibiting sustained alkalinization, whereas MDCK‐C11 cells could successfully regulate pHi. We conclude that wild‐type MDCK cells consist of two genetically distinct subpopulations with different morphology and function. Only the MDCK‐C7 clone that resembles the principle cell type of renal collecting duct can be transformed by alkaline stress while the MDCK‐C11 clone resists this treatment, due to efficient pHi control mechanisms. © 1995 Wiley‐Liss, Inc.
Proteoglycan biosynthesis is required in BC3H1 myogenic cells for modulation of vascular smooth muscle α‐actin gene expression in response to microenvironmental signals
Authors: Lee Sang Hoon , Yan Hua , Reeser Jonathan C. , Dillman John M. , Strauch Arthur R. 
Published: February 2005

AbstractInduction of vascular smooth muscle (VSM) α‐actin mRNA expression during cytodifferentiation of mouse BC3H1 myogenic cells coincides with the accumulation of cell surface‐ and extracellular matrix‐associated sulfated proteoglycans. Inhibition of proteoglycan biosynthesis in myogenic cells using an artificial b̃‐D‐xyloside glycosaminoglycan acceptor was accompained by a reduction in cell surface/extracellular matrix proteoglycans and VSM α‐actin mRNA expression while enhanciang the secretion of free chondroitin sulfate/dermatan sulfate and heparan sulfate glycosaminoglycans into the culture medium. Maximum inhibition of VSM α‐actin mRNA expression required that proteoglycan biosynthesis be blocked during the early phase of cytodifferentiation when myoblasts were fully confluent and quiescent. The inhibitory effect of b̃‐D‐xyloside on α‐actin mRNA expression resulted from attenuation at both the transcriptional and post‐transcriptional control points. Sustained proteoglycan biosynthesis was required for induction of VSM α‐actin mRNA in quiescent myoblasts in response to cytodifferentiation‐permissive, substrate‐associated macromolecules (SAM) or upon exposure to soluble serum factors capable of transiently stimulating VSM α‐actin gene transcription. The results suggested that efficient myoblast cytodifferentiation and modulation of VSM α‐actin mRNA levels depended on intact cell surface proteoglycans to convey signals generated as a consequence of cellular interaction with substrate components and serum factors. © 1995 Wiley‐Liss, Inc.
Swelling activates chloride current and increases internal calcium in nonpigmented epithelial cells from the rabbit ciliary body
Authors: Botchkin Lev M. , Matthews Gary 
Published: February 2005

AbstractMembrane current and [Ca]i in rabbit nonpigmented ciliary body epithelial cells (NPE cells) were monitored with combined patch‐clamp and fura‐2 measurements during cell swelling induced by anisosmotic conditions. In the presence of K‐channel blockers, cell swelling produced an increase in membrane current, accompanied by an increase in [Ca]i. Structural changes in the cell, associated with membrane deformation, may be the cause of the increase in [Ca]i during swelling. The conductance activated by swelling was permeable to CI: it was dependent on the CI concentration gradient across the cell membrane, and it was blocked by the CI‐channel blockers DIDS, SITS, NPPB, and DIOA. Although swelling increased both CI current and [Ca]i, there was no evidence that Ca was involved in the regulation of the CI conductance. Cell swelling activated the current even when [Ca]i was strongly buffered at an elevated level (500 nM) or at a low level (∼0) with internal Ca‐BAPTA/Cs‐BAPTA mixtures. In addition, CI conductance was unaffected when [Ca]i was increased with a Ca ionophore. There was also no evidence that cAMP participates in the regulation of the CI conductance: swelling activation of the current occurred in the presence of cAMP inhibitor (Rp‐cAMP‐S) and cAMP mimic (Sp‐cAMP‐S). The data suggest independent involvement of CI conductance and internal Ca in the regulation of cell volume in NPE cells. © 1995 Wiley‐Liss, Inc.
Modulation of the adhesion of hemopoietic progenitor cells to the rgd site of fibronectin by interleukin 3
Authors: Hardy Cheryl L. , Minguell José J. 
Published: February 2005

AbstractThe integrins are a class of adhesion molecules which have been implicated in the homing of hemopoietic stem cells and in their restriction within the bone marrow. Integrins function as mediators of cell‐extracellular matrix (ECM) interactions and also of cell‐cell interactions. They are unique membrane receptors which are capable of activation, change in affinity, and change in expression. Because of their broad potential for modulation we examined the effect of a cytokine growth factor which is present constitutively in the marrow, interleukin 3 (IL3), on integrin‐mediated adherence of hemopoietic progenitor cells to the matrix component fibronectin (FN). The multipotential murine cell line B6Sut and the committed granulocyte progenitor cell line FDCP‐1 were used. Both of these cell lines have been shown to bind to FN‐coated dishes and to dishes coated with the 120 kDa and 40 kDa chymotryptic fragments of FN. It was found that after a brief withdrawal of IL3 the cells lost 80% adherence to the 120 kDa FN fragment containing the RGD cell binding site. This loss of binding was not related to a loss of viability, appeared unrelated to the growth/survival activity of IL3, and was quickly reversible by readdition of the growth factor. Adhesion of these cells to the RGD site was likely mediated by α5b̃1 integrin which was identified in the cell membrane of both cell lines, but present in low copy number in B6Sut cells. Two antibodies against the external and internal domains of α5 and one antibody against b̃1 were used to study expression of the integrin. By flow cytometry the expression of α5 was found to decrease in both cell lines by 4 h in the absence of IL3. The relative mean fluorescence intensity for B6Sut cells decreased from 1.0 (control cells always in the presence of IL3) to 0.6 over 4 h, and for FDCP‐1 cells the decrement was from 1.0 to 0.8. The loss of RGD‐mediated adhesion in the absence of IL3 appeared to proceed through this decrement in expression of the integrin; a loss of affinity of the receptor for its substrate was not detected. The general modulation of integrin activity by growth factors is of great interest because of its potential negative impact on the endothelium in cytokine‐treated patients, and also because of its potential positive impact on engraftment during clinical bone marrow transplantation. © 1995 Wiley‐Liss, Inc.
Comparative studies between freshly isolated and spontaneously immortalized bovine granulosa cells: Protein secretion, steroid metabolism, and responsiveness to growth factors
Authors: Lerner Alejandro A. Colman , Salamone Daniel F. , Chiappe M. Eugenia , Barañao J. Lino 
Published: February 2005

AbstractA bovine granulosa cell line (BGC‐1) has been obtained by spontaneous immortalization of primary cultures. BGC‐1 cells have retained some characteristics of primary cultures, such as the hormonal regulation of fibronectin biosynthesis. In the present study we have compaed BGC‐1 cells and primary cultures of bovine granulosa cells in terms of protein secretion, steroid metabolism, and mitogenic responses to growth factors. The pattern of protein secretion in BGC‐1 cells was qualitatively similar to that of primary cultures. The main differences were a higher proportion of fibronectin and the relative amounts of several other unidentified proteins. Progesterone levels in BGC‐1 cultures were undetectable. When BGC‐1 cells and primary cultures were incubated with [3H]‐pregnenolone, the former showed a lower conversion rate to progesterone. In contrast, the conversion rate of [3H]‐progesterone to 5α‐reduced metabolites was markedly increased in BGC‐1 cells. We also examined the effects of epidermal growth factor (EGF), insulin like growth factor‐1 (IGF‐I), and transforming growth factor‐b̃ (TGF‐b̃) on DNA synthesis under serum‐free conditions. Both primary cultures and BGC‐1 cells exhibited a stimulatory response to EGF and IGF‐I on [3H]‐thymidine incorporation. Neither BGC‐1 cells nor primary cultures showed a significant response to TGF‐b̃ when added alone. However, in the presence of a combination of EGF and IGF‐I, TGF‐b̃ displayed an inhibitory effect on primary cultures while it stimulated DNA synthesis in BGC‐1 cells even further. The addition of conditioned medium from BGC‐1 cells (BGC‐1‐CM) stimulated DNA synthesis on primary cultures to a greater extent than the addition of conditioned medium from primary cultures. These results suggest that BGC‐1 cells may be a useful model to study the regulation of granulosa cell function during the period previous to the preovulatory stage of follicular development. The differential responses of the immortalized cells to growth regulators may offer some clues on the mechanisms that control cell proliferation in normal tissues. © 1995 Wiley‐Liss, Inc.
Effect of hypoxia and reoxygenation on the formation and release of reactive oxygen species by porcine pulmonary artery endothelial cells
Authors: Yang Wenbo , Block Edward R. 
Published: February 2005

AbstractEndothelial cells are critical targets in both hypoxia‐and reoxygenation‐mediated lung injury. Reactive O2 species (ROS) have been implicated in the pathogenesis of hypoxic and reoxygenation lung injury, and xanthine dehydrogenase/oxidase (XDH/XO) is a major generator of the ROS. Porcine pulmonary artery endothelial cells (PAEC) have no detectable XDH/XO. This study was undertaken to examine (1) ROS production by hypoxic porcine PAEC and their mitochondria and (2) ROS production and injury in reoxygenated PAEC lacking XDH/XO activity. Intracellular H2O2 generation and extracellular H2O2 and O/2 release were measured after exposure to normoxia (room air‐5% CO2), hypoxia (0% O2 ‐95% N‐5% CO2), or hypoxia followed by normoxia or hyperoxia (95% O2‐5% CO2). Exposure to hypoxia results in significant reductions in intracellular H2 O2 formation and extracellular release of H2 O2 and O2 by PAEC and mitochondria. The reductions occur with as little as a 2 h exposure and progress with continued exposure. During reoxygenation, cytotoxicity was not observed, and the production of ROS by PAEC and their mitochondria never exceeded levels observed in normoxic cells. The absence of XDH/XO may prevent porcine PAEC from developing injury and increased ROS production during reoxygenation. © 1995 Wiley‐Liss, Inc.
Control of matrix synthesis in isolated bovine chondrocytes by extracellular and intracellular pH
Authors: Wilkins Robert J. , Hall Andrew C. 
Published: February 2005

AbstractThe effects of extracellular and intracellular pH on matrix synthesis by isolated bovine chondrocytes were studied using radioisotope incorporation (35SO4 and 3H proline) and fluorescence techniques. Matrix synthesis exhibited a bimodal relation with decreased extracellular pH; with slight reductions (7.4>pH>7.1), synthesis increased (by up to 50%), whereas in more acidic media (pH<7.1), synthesis was inhibited by up to 75% of control levels. The pHi was largely unchanged with extracellular acidity over the range producing stimulation of matrix synthesis but fell when exposed to the more acidic media shown to have an inhibitory action on matrix synthesis. The inhibition of matrix synthesis by lactic acid addition was unaffected by the lactic acid transporter α‐CHC, suggesting H+ transport by this pathway is small. Direct imposition of a sustained intracellular acidosis (pHi = 6.65) using ammonium prepulse with amiloride inhibited matrix synthesis by about 20%. These results show that matrix synthesis by chondrocytes was affected by extracellular pH, an action which could not be entirely explained by changes to pHi. © 1995 Wiley‐Liss, Inc.