bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inhibition of cell‐cell adhesion and morphogenesis of Dictyostelium by carnitine
Authors: Siu Chi‐Hung , Brar Pretty , Fritz Irving B. 
Published: February 2005

AbstractCarnitine (γ‐trimethylammonium β‐hydroxy‐butyric acid) possesses the novel property of preventing cell aggregation elicited by clusterin or by fibrinogen (I.B. Fritz and K. Burdzy, J. Cell. Physiol., 140:18–28 [1989]). In investigations reported here, we show that carnitine also affects cell‐cell adhesion in Dicytostelium discoideum, a cellular slime mold whose cells interact in specific and complex manners during discrete stages of development. Two types of cell adhesion systems sequentially appear on the surface of developing Dictyostelium cells, involving the surface glycoprotein gp24 which mediates EDTA‐sensitive binding sites, and the surface glycoprotein gp80 which mediates the EDTA‐resistant binding sites. Addition of increasing concentrations of D(+)‐carnitine and L(‐)‐carnitine resulted in a progressive inhibition of both the EDTA‐sensitive binding sites and the EDTA‐resistant binding sites of Dictyostelium cells at different stages of development. In contrast, comparable or higher concentrations of choline, acetyl‐β‐methylcholine, or deoxycarnitine had no detectable effects on cell aggregation. Concentrations of carnitine required for 50% inhibition of EDTA‐resistant adhesion sites were found to be dependent upon levels of gp80 expressed by Dictyostelium, with greatest inhibition by carnitine of reassociation of cells containing the lowest levels of gp80. Removal of carnitine from cells by washing resulted in the rapid restoration of the ability of Dictyostelium to form aggregates and to resume normal development. We discuss possible mechanisms by which carnitine inhibits the aggregation of cells. © 1992 Wiley‐Liss, Inc.
Melanocyte stimulating hormone induces the differentiation of mouse epidermal melanocytes in serum‐free culture
Authors: Hirobe Tomohisa 
Published: February 2005

AbstractIn serum‐free primary culture of dissociated mouse epidermal cells, α‐melanocyte stimulating hormone (α‐MSH) and dibutyryl cyclic AMP (DBcAMP) induced the differentiation of melanocytes. Moreover, the proliferation of melanocytes was also induced in the dishes cultured with DBcAMP, but not with α‐MSH. In order to clarify the role of keratinocytes in melanocyte proliferation and differentiation, pure cultures of keratinocytes were established in serum‐free medium. Subconfluent primary keratinocytes were trypsinized and seeded into pure primary melanoblasts cultured with serum‐free medium that did not contain α‐MSH or DBcAMP. Melanoblasts were cultured with α‐MSH or DBcAMP in the presence or absence of keratinocytes. α‐MSH failed to induce melanocyte differentiation in the absence of keratinocytes. DBcAMP failed to induce melanocyte proliferation in the absence of keratinocytes, although it induced melanocyte differentiation even in the absence of keratinocytes. These results suggest that keratinocyte‐derived factors are required not only for the induction of melanocyte differentiation by α‐MSH but also for the induction of melanocyte proliferation by DBcAMP. © 1992 Wiley‐Liss, Inc.
Bethanechol inhibition of chicken intestinal brush border Na/H exchange: Role of protein kinase C and other calcium‐dependent processes
Authors: Musch Mark W. , Drabik‐Arvans Donna , Rao Mrinalini C. , Chang Eugene B. 
Published: February 2005

AbstractBethanechol, a muscarinic agonist, inhibits the initial rate of amiloride‐sensitive Na uptake by intact mucosa of avian small intestine as well as by isolated chicken villus enterocytes, an effect that is maximal at 90 seconds and reverses by 6 minutes. Bethanechol similarly decreases intracellular pH in isolated cells suspended in bicarbonate‐free buffer in a time course similar to inhibition of enterocyte Na uptake, suggesting inhibition of Na/H exchange. In brush border membrane vesicles rapidly prepared from cells stimulated with bethanechol, proton‐dependent 22Na uptake is transiently inhibited in a time course similar to inhibition of cell Na uptake. Bethanechol also stimulates transient translocation of protein kinase C from the cytosol to the particulate fraction, a portion of this activity translocating to the brush border membrane. To determine the calcium dependence of bethanechol's action, enterocytes were loaded with varying concentrations of the calcium buffering agent quin‐2. Inhibition of cell Na uptake by the calcium ionophore ionomycin could be completely reversed by quin‐2 buffering in a concentration‐dependent manner. In contrast, quin‐2 buffering had little or no effect on the inhibition of Na uptake caused by the protein kinase C activators phorbol esters and oleoylacetylglycerol. Bethanechol's inhibitory effects were partially, but not completely reversed by quin‐2 buffering. These data suggest that the effects of bethanechol on chicken villus enterocyte brush border Na/H exchange are mediated by calcium‐dependent process(es) as well as by protein kinase C. © 1992 Wiley‐Liss, Inc.
Competition between cell‐substratum interactions and cell‐cell interactions
Authors: Tung Pierre S. , Burdzy Krystyna , Wong Katherine , Fritz Irving B. 
Published: February 2005

AbstractClusterin, a glycoprotein which elicits the aggregation of a wide variety of cells (Fritz, I.B., and Burdy, K.: J. Cell Physiol., 140:18–28, 1989), has been utilized to investigate some of the factors modulating the competition between cell‐substratum interactions and cell‐cell interactions. We compared the responses to clusterin by anchorage‐independent cells (erythrocytes) with those by anchoragedependent TM4 cells (a cell line derived from neonatal mouse testis cells). Cells were maintained in culture in the presence of various substrata chosen to enhance cell‐substratum interactions (laminin‐coated wells), or to diminish cell‐substratum interactions (agarose‐coated wells). Results obtained showed that the aggregation of erythrocytes elicited by clusterin was independent of the nature of the substratum. In contrast, clusterin addition resulted in aggregation of anchorage‐dependent TM4 cells only when TM4 cell‐substratum interactions were weak. Thus, clusterin did not aggregate TM4 cells plated upon a laminin substratum, but readily aggregated TM4 cells plated upon an agarose‐coated substratum, independent of the sequence of addition of cells and clusterin to the culture dish. We utilized YIGSR, a peptide which competes with laminin for laminin receptors, to determine the possible role of laminin receptors on TM4 cells in the competition between cell‐substratum interactions and cell‐cell interactions. The presence of YIGSR did not alter responses of erythrocytes to clusterin under all conditions examined. In contrast, the responses of TM4 cells to clusterin were greatly changed. YIGSR addition resulted in the inhibition of aggregation of TM4 cells otherwise elicited by clusterin. YIGSR also prevented attachment of TM4 cells to a laminin‐coated surface, but this was reversed by the presence of clusterin. We discuss the possible roles of clusterin and laminin in altering the balance in the competition between cell to cell interactions and cell to substratum interactions. © 1992 Wiley‐Liss, Inc.
Cytoskeletal elements are required for the formation and maturation of autophagic vacuoles
Authors: Aplin A. , Jasionowski T. , Tuttle D. L. , Lenk S. E. , Dunn W. A. 
Published: February 2005

AbstractWe evaluated the role of cytoskeletal elements in the degradation of endogenous proteins via autophgy using biochemical and morphological techniques. In the absence of exogenous amino acids, degradation of endogenous proteins was enhanced in cultured normal rat kidney cells. This enhanced degradative state was accompanied by a 4‐fold increase in the occurrence of autophagic vacuoles. In the presence of drugs that induce the depolymerization of microfilaments (cytochalasins B and D) or microtubules (nocodazole), protein degradation was not enhanced in nutrient‐deprived cells. Although these drugs had similar inhibitory effects on the protein degradation, their effect on autophagy differed. Cytochalasins B and D interfered with the formation of the autophagosome. In cells treated with these drugs, the fractional volume represented by autophagic vaculoes was not substantially increased despite nutrient depletion. On the contrary, nocodazole appeared to have no effect on the formation of autophagosomes. Instead, this drug suppressed the delivery of hydrolytic enzymes, thereby resulting in an accumulation of acidic autophagic vacuoles containing undegraded cellular components. © 1992 Wiley‐Liss, Inc.
Transforming growth factor‐β1 mediated alterations in ribonucleotide reductase gene expression in BALB/c 3T3 fibroblasts
Authors: Hurta Robert A. R. , Greenberg Arnold H. , Wright Jim A. 
Published: February 2005

AbstractTransforming growth factor‐β1 (TGF‐β1) stimulated DNA synthesis (3‐fold) in BALBc/3T3 fibroblasts following 24 hours of growth factor exposure. Since ribonucleotide reductase is important for the coordination of DNA synthesis and cell proliferation, we investigated the hypothesis that cells like BALB/c 3T3, which are TGF‐β1 responsive, would exhibit modifications in expression of the gene for ribonucleotide reductase following growth factor treatment. We observed 2.6, 4.1, and 4.8‐fold increases in ribonucleotide reductase activity following TGF‐β1 exposure for 6, 12, and 24 hours, respectively. Increased ribonucleotide reductase R2 gene expression (3, 3.7, and 4.5‐fold) and R1 gene expression (2, 2.5, and 2.6‐fold) were observed following 6, 12, and 24 hours of TGF‐β1 treatment, respectively. Western blots indicated 2.2, 3.1, and 4.1‐fold increases in protein R2 levels at 6, 12, and 24 hours exposure to TGF‐β1, whereas 2.6 and 3.3‐fold elevations in R1 protein levels were observed at 12 and 24 hours postTGF‐β1 exposure. These TGF‐β1 mediated modifications in ribonucleotide reductase gene expression occurred, in part, prior to any detectable changes in the rate of DNA synthesis, demonstrating alterations in the normal regulation of ribonucleotide reductase. Furthermore, these alterations could be markedly reduced by prolonged pretreatment with 12‐0‐tetradecanoylphorbol‐13‐acetate (R2 gene expression increased by only 1.3, 1.5 and 2.3‐fold after 6, 12, and 24 hours of TGF‐β1 treatment, respectively), suggesting a role for a protein kinase C pathway in the TGF‐β1 regulated changes in ribonucleotide reductase gene expression. These results indicate for the first time that TGF‐β1 can regulate the expression of the two genes for ribonucleotide reductase in BALB/c 3T3 fibroblasts, and suggest that regulation of these genes plays an important role in critical events involved in growth factor modulation of normal and transformed cell proliferation. © 1992 Wiley‐Liss, Inc.
Independent regulation of prostaglandin production and the stress response in human fibroblasts
Authors: Salzman J. , Bowman P. D. 
Published: February 2005

AbstractThe stress, or heat shock response of eukaryotic cells is characterized by dramatic changes in the metabolism of responding cells, most notably the increased synthesis of a group of proteins known as heat shock proteins. In this study, we examined the relationship of prostaglandin synthesis/release to the stress response. Stress protein synthesis was induced with sodium arsenite, and prostaglandin E2 and prostacyclin (measured as 6‐keto PGF1α) levels were determined by enzyme immunoassay. The stress response was monitored by the incorporation of [35S]methionine and separation of protein by one‐dimensional sodium dodecyl sulfate‐polyacrylamide gel electrophoresis. Prostaglandin synthesis and the stress response were both induced by sodium arsenite. However, aspirin, a cyclooxygenase inhibitor, inhibited arsenite‐induced prostaglandin synthesis but did not inhibit stress protein synthesis. Conversely, the calcium ionophore A23187 also stimulated prostaglandin synthesis, but did not induce the stress response. The results of this study indicate that sodium arsenite, a stress response inducer, stimulates prostaglandin production, but this appears to be a correlative rather than causative occurrence in the stress response. Determination of the cytotoxicity of arsenite indicated a high correlation of stimulation of prostaglandin release with cytotoxicity. © 1992 Wiley‐Liss, Inc.
Reversible G1 arrest of a human lung epithelial cell line by staurosporine
Authors: Lin Yuan , Chrest Francis J. , Gabrielson Edward W. 
Published: February 2005

AbstractStaurosporine, a microbial‐derived protein kinase inhibitor, reversibly blocked non‐synchronized, replicating cultures of the human lung epithelial cell line EKVX in the G1 phase of cell cycle and inhibited DNA synthesis and cell replication. The mechanism of this cell‐cycle arrest in EKVX cells by staurosporine was likely due to inhibition of protein kinase C (PKC) because: (1) dose‐dependent inhibition of DNA synthesis occurred at levels of staurosporine that inhibit phosphorylation of PKC substrate, (2) inhibition of DNA synthesis was also seen after treatment with another PKC inhibitor H7, but not by the chemically similar HA1004, which has a relative inhibitory specificity for cAMP‐dependent protein kinase, and (3) the DNA synthesis was not inhibited by specific tyrosine kinase inhibitors Genistein and Lavendustin A at concentrations that inhibit tyrosine kinase activity. Removal of staurosporine from cell culture media resulted in a rebound in PKC activity and synchronized DNA synthesis in EKVX cultures. The reversibility of the inhibition was noted even after 5 days of treatment with staurosporine, and DNA synthesis remained synchronized for at least two rounds of cell replication after removal of staurosporine. Flow cytometric analysis confirmed that more than 90% of the cell population was blocked in the G1 phase after cells were treated with staurosporine for 24 h. Agents such as staurosporine may be useful for synchronizing cell populations to study cell‐cycle specific biochemical events important for the regulation of cell replication in the EKVX cell line. © 1992 Wiley‐Liss, Inc.
Human umbilical vein endothelial cells submitted to hypoxia‐reoxygenation in vitro: Implication of free radicals, xanthine oxidase, and energy deficiency
Authors: Michiels Carine , Arnould Thierry , Houbion Andrée , Remacle José 
Published: February 2005

AbstractIschemia‐reperfusion is observed in various diseases such as myocardium infarct. Different theories have been proposed to explain the reperfusion injury, among them that the free radical generation plays a crucial role. To study the mechanisms of the reperfusion injury, a hypoxia (H)‐reoxygenation (R) model upon human umbilical vein endothelial cells in culture was developed in order to mimic the in vivo situation. Different parameters were quantified and compared under H or H/R, and we found that oxygen readmission led to damage amplification after a short hypoxia period. To estimate the importance of various causes of toxicity, the effects of various protective molecules were compared. Different antioxidant molecules, iron‐chelating agent, xanthine oxidase inhibitors, and energy‐supplying molecules were very efficient protectors. Synergy could also be observed between the antioxidants and the energy‐supplying molecules or the xanthine oxidase inhibitors. The toxic effect of O2·(−) could be lowered by the presence of SOD or glutathione peroxidase in the culture medium, whereas glutathione peroxidase was the most efficient enzyme when injected into the cells. The production of O2·(−) and of H2O2 by endothelial cells was directly estimated to be, respectively, of 0.17 and 0.035 μmol/min/mg prot during the R period. O2·(−) production was completely inhibited when allopurinol was added during H and R. In addition, a xanthine oxidase activity of 21.5 10−6 U/mg prot could be observed by a direct assay in cells after H but not in control cells, thus confirming the previous conclusions of xanthine oxidase as a potent source of free radicals in these conditions. Thanks to the use of cultured human endothelial cells, a clear picture was obtained of the overall process leading to cell degenerescence during the reoxygenation process. We particularly could stress the importance of the low energetic state of these cells, which is a critical factor acting synergistically with the oxidant molecules to injure the cells. These results also open new possibilities for the development of new therapeutics for ischemia. © 1992 Wiley‐Liss, Inc.
Differential modulation of vascular cell integrin and extracellular matrix expression in vitro by TGF‐β1 correlates with reciprocal effects on cell migration+
Authors: Basson Craig Todd , Kocher Olivier , Basson Marc D. , Asis Antonio , Madri Joseph A. 
Published: February 2005

AbstractIn vitro, BAEC and BASMC migratory phenotypes are known to be reciprocally modulated by both soluble factors and extracellular matrix proteins. In addition, integrin matrix receptors mediate endothelial and smooth muscle cell attachment and migration. To further elucidate these phenomena, we studied the effects of TGF‐β1 on intergin expression by vascular BASMC and BAEC in tissue culture. TGF‐β1 upregulated mRNA levels and surface pools of BASMC β3 integrin classes without modulating β1 integrin mRNA levels or expression of β1 integrin organization. In contrast to its effect on BASMC, TGF‐β1 increased BAFC mRNA levels and surface expression of β1 and β3 integrins without altering their organization. Conversely, extracellular matrix components (fibronectin, laminin, and fibrinogen) organized cell surface integrins in both BASMC and BAEC without affecting the size of their cell surface pools. These data are consistent with the hypothesis that SMC and EC behavior in neointimal lesions may modulated in part, through a coordination of soluble factor and extracellular matrix protein regulation of integrin surface expression and organization. © 1992 Wiley‐Liss, Inc.
Regulation of cell proliferation: Late down‐regulation of c‐myb preceding myelo‐monocytic cell differentiation
Authors: Yen Andrew , Samuel Varman , Forbes Mary 
Published: February 2005

AbstractExpression of the c‐myb nuclear oncogene during the cell proliferation and differentiation of HL‐60 human promyelocytic leukemia cells was characterized and compared to the expression of c‐fos, another nuclear oncogene with transcriptional regulatory activity. During progression through the cell cycle, the amount of c‐myb protein increased. The increase was commensurate with total cell size, thus preserving the relative abundance of c‐myb protein present at the onset of the cell cycle. In HL‐60 cells, the induced metabolic cascade leading to terminal myeloid or monocytic differentiation segregates into two steps occuring over two division cycles. Expression of c‐myb did not diverge from the control until late in this metabolic cascade when it declined prior to onset of terminal differentiation. This course of expression was similar for both the retinoic acid induced myloid or the 1,25‐dihydroxy vitamin D2 induced monocytic terminal differentiation of the cells. Bromodeoxyuridine, which induces proliferative arrest but not phenotypic differentiation of these cells, induced the same course of c‐myb expression as the inducers of terminal differentiation. The same course of c‐myb expression with growth arrest induced by these three different means is consistent with a potential proliferation regulatory role for c‐myb in late but not early events leading to terminal differentiation. The dynamics of c‐myb expression during this process were qualitatively, out not quantitatively, similar to the course of c‐fos expression. Thus, taken with previous results, then amongst the nuclear oncogenes or tumor suppressor genes, c‐myc, RB, c‐fos, and c‐myb, only c‐myc and RB expression exhibit early regulation during induced HL‐60 cell differentiation. © 1992 Wiley‐Liss, Inc.
Norepinephrine stimulates the direct breakdown of phosphatidyl inositol in rat tail artery
Authors: Labelle Edward F. , Gu Hong , Trajkovic Snezana 
Published: February 2005

AbstractWhen segments of rat tail artery were labeled with [3H]inositol and then stimulated with norepinephrine (NE), the inositol phosphates produced were primarily IP and IP2, together with a small but significant amount of Ins(1,4,5)P3 and a very small amount of Ins(1,3,4,5)P4. It has been unclear in many studies whether or not the relatively large levels of IP and IP2 produced in [3H]inositol‐labeled tissue represent indirect products of phosphatidyl inositol(4,5)bis phosphate breakdown (through Ins(1,4,5)P3) or direct products of phosphatidyl inositol 4 monophosphate and phosphatidyl inositol breakdown. In order to answer this question tail artery segments were prelabeled with [3H]inositol and then permeabilized with β escin and stimulated with norepinephrine and GTPγS, so that increases in IP, IP2, and Ins(1,4,5)P3 were still observed. If these permeable segments were stimulated with agonist in the presence of compounds known to inhibit Ins(1,4,5)P3 5‐phosphatase, such as glucose 6P, (2,3)diphosphoglycerate, or Ins(1,4,5)P3, the levels of labeled Ins(1,4,5)P3 and labeled IP2 were increased, while the level of stimulated labeled IP was unchanged. This indicated that some of the IP2 and IP formed in these cells was produced from PIP2 but that some of these compounds might be formed from PIP or PI. When the isomers of inositol monophosphate, Ins 1P and Ins 4P, were separated by HPLC, it was shown that after prelabeled tail artery was stimulated by norepinephrine for periods of 1–2 min, the predominant isomer formed was Ins 4P, indicating either PIP2 or PIP as the source. However, after 5–20 min stimulation, both Ins 1P and Ins 4P were formed in equal amounts, suggesting that during sustained stimulation of smooth muscle PI itself was broken down directly. Therefore it appears that within 1–2 min of norepinephrine addition to vascular smooth muscle the bulk of the IP and IP2 produced are derived from PIP2 via IP3, while after 20 min of norepinephrine treatment much of the IP comes directly from PI. This suggests that the regulation of PLC in this tissue is more complicated than has been previously believed. © 1992 Wiley‐Liss, Inc.
Growth on type I collagen promotes expression of the osteoblastic phenotype in human osteosarcoma MG‐63 cells
Authors: Andrianarivo Aurelie G. , Robinson John A. , Mann Kenneth G. , Tracy Russell P. 
Published: February 2005

AbstractUsing MG‐63 cells as a model system capable of partial osteoblastic differentiation, we have examined the effect of growth on extracellular matrix. MG‐63 cell matrix and purified type I collagen induced a morphological change characterized by long cytoplasmic processes reminiscent of those seen in osteocytes. Concurrent biochemical changes involving bone marker proteins included increased specific activity of cell‐associated alkaline phosphatase and increased secretion of osteonectin (up to 2.5‐fold for each protein); all changes occurred without alterations in the growth kinetics of the MG‐63 cells. The increase in alkaline phosphatase activity was maximal on days 6–8 following seeding; increased osteonectin secretion was most prominent immediately following seeding; all changes decreased as cells reached confluence. Growing cells on type I collagen resulted in an increased induction of alkaline phosphatase activity by 1,25 (OH)2D3 (with little change in the 1,25 (OH)2D3 induction of osteonectin and osteocalcin secretion), and increased TGF‐β induction of alkaline phosphatase activity as well (both TGF‐β1 and TGF‐β2). Both the 1,25 (OH)2D3 and TGF‐β effects appeared to be synergistic with growth on type I collagen. These studies support the hypothesis that bone extracellular matrix may play an important role in osteoblastic differentiation and phenotypic expression.