bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nature of enhanced mitochondrial oxidative metabolism by a calf blood extract
Authors: Kuninaka Termichi , Senga Yoshinori , Senga Hirobumi , Weiner Murray 
Published: February 2005

AbstractThe effect of calf blood extract (Solcoseryl, SS) on mitochondrial oxidative function in various states was studied polarographically in vitro. (1) Mitochondrial respiration in all 4 conventional study states (Estabrook, 1967) was enhanced by the addition of SS, including states 1 and 2 (endogenous substrates only). (2) The effect of SS on mitochondrial oxygen consumption was concentration dependent, while ADP/O ratio remained constant. The effect of added respiratory substrates varied with the particular substrate at optimally active concentrations. With suboptimal substrate levels, ADP/O ratios were concentration dependent, in contrast to the SS effect. Under oligomycin ATPase inhibition, SS was no longer active, in contrast to DNP, which remained active. (3) In states 3 (added ADP) and 4 (ADP exhausted), oxygen consumption and oxidative phosphorylation were enhanced by SS in the presence or absence of citrate, glutamate, pyruvate, lactate, or ascorbate. However, in the presence of succinate, SS had no effect. (4) ADP/O ratio was decreased by SS in the presence of added substrate, suggesting that SS activation of H+‐ATPase enhances ATP hydrolysis as well as oxidative phosphorylation and ATP synthesis. (5) The enhancing effect of SS on mitochondrial function is due to hydrophilic components of SS. The lipidic components obtained by Folch fraction of SS have no effect. It is concluded that the effects of SS respiratory substrates and uncouplers on mitochondrial function are essentially different. SS enhances both ATP synthesis and oxygen consumption by mitochondria.
Differential effects of interferon gamma and alpha on in vitro model of angiogenesis
Authors: Maheshwari R. K. , Srikantan V. , Bhartiya D. , Kleinman H. K. , Grant D. S. 
Published: February 2005

AbstractThe formation of blood vessels in vivo (angiogenesis) is an important process and is usually initiated in response to injury, tumor growth, or normal tissue development. We have studied the effect of human interferon (IFN) alpha (α) and gamma (γ) on the capillary‐like network formation in an in vitro model of angiogenesis using human umbilical vein endothelial cells (HUVEC). When HUVEC cells are plated on Matrigel (reconstituted basement membrane matrix enriched in laminin), a network of capillary like structures (endotubes) rapidly forms. IFN‐α enhanced the tube formation in a dose‐dependent manner, whereas IFN‐γ significantly inhibited the tube formation. In addition, both the enhancement and inhibition of angiogenesis by IFN‐α and γ was found to be greater if the cells were pretreated with IFN for 12 hr before plating on the Matrigel. These results suggest that IFN may play an important role in several vascular processes including early stages of wound healing, recanalization of thrombi, tumor growth, metastasis, normal growth, and development.
Glutamine is a powerful effector of heat shock protein expression in Drosophila Kc cells
Authors: Sanders Marilyn M. , Kon Christine 
Published: February 2005

AbstractWe have investigated the effects of extracellular anions on the regulation of expression of the heat shock response in DrosophilaKc cells incubated in defined balanced salt solutions. Widely varying chloride concentrations had no effect on normal or heat shock protein (hsp) expression. Increasing glutamate concentrations from zero to 15 mM increased hsp expression more than 100‐fold while affecting expression of non‐heat‐shock proteins minimally. Glutamine was 20–100‐fold more potent than glutamate in supporting hsp expression, while other amino acids were less effective or supported no detectable hsp synthesis in heat shock. Inhibition of glutamine synthetase with methionine‐sulfoximine resulted in very low hsp expression with glutamate and normal high level expression with glutamine, confirming the importance of glutamine. The absence of glucose and treatment with 2‐deoxyglucose did not change the requirement for adequate glutamine for hsp expression. Cells heat shocked under conditions which gave very low hsp expression resumed growth when returned to normal medium as well as cells which expressed normal levels of hsps. Measurements of free amino acid levels in cells heat shocked in the presence and absence of glutamine showed a correlation between glutamine levels and amount of hsp expression. We conclude that a physiological process regulated by glutamine or a glutamine metabolite is important for normal hsp expression in heat shock conditions in Drosophila.
Voltage‐dependent calcium channels regulate GH4 pituitary cell proliferation at two stages of the cell cycle
Authors: Ramsdell John S. 
Published: February 2005

AbstractCalcium is an intracellular signal implicated in the regulation of cell proliferation. We have examined the growth regulatory role of voltage‐dependent calcium channels (VDCC) in a rat pituitary cell line (GH4C1) that expresses two well‐characterized VDCC subtypes (L and T) and is growth‐inhibited by several agents known to enhance calcium entry. Thyrotropin‐releasing hormone (TRH), tetrade‐canoylphorbol acetate (TPA), and epidermal growth factor (EGF), each known to enhance calcium entry in GH4 cells, decrease GH4 cell number and incorporation of [3H]‐thymidine. The growth inhibitory action of these agents is cytostatic with a predominant effect to block G1 cells from entering S‐phase. We next examined the growth regulatory action of pharmacologic agents that interact directly and specifically with type L VDCC. Activation of type L VDCC with the dihydropyridine BAY K8644 inhibits GH4 proliferation as measured by cell number and [3H]‐thymidine incorporation. This action of BAY K8644 is enhanced by a submaximal K+‐maintained depolarization, and the growth inhibitory action of these agents is also cytostatic as evident by the block of G1 cells from entering S‐phase. Nimodipine, an antagonist specific for type L VDCC blocks (IC50 = 30 nM) BAY K8644‐inhibited cell proliferation by substantially reducing the S‐phase block. Taken together these findings indicate that calcium entry through type L VDCC inhibits GH4 cell proliferation by blocking entry into S‐phase. By contrast, nimodipine caused only a small reversal of the TRH‐induced S‐phase block, suggesting that TRH inhibits proliferation by a mechanism that differs at least in part from L‐channel activation. Unexpectedly, nimodipine, given alone, caused a substantial inhibition of GH4 cell proliferation. This action of nimodipine was cytostatic, yet differed from calcium channel activators in that the percentage of S‐phase cells was unchanged whereas G2‐M‐phase cells increased with a parallel decrease in G1‐phase cells. Similar effects were also observed with other classes of calcium channel blockers. Taken together these results indicate that calcium entry through VDCC regulates GH4 cell proliferation differently cepending on the stage of the cell cycle. In G1‐phase cells, sustained entry of calcium through type L VDCC blocks entry into S‐phase. In G2‐M‐phase cells entry of calcium promotes progression through mitosis.
Regulation of glucose transport as well as glucose transporter and immediate early gene expression in 3T3‐L1 preadipocytes by 8‐bromo‐cAMP
Authors: Cornelius Peter , Marlowe Melissa , Call Kenneth , Pekala Phillip H. 
Published: February 2005

AbstractIn the present study we have examined the ability of 8‐bromoadenosine cyclic 3′, 5′‐phosphate (8‐bromo‐cAMP; the membrane permeant analog of cAMP which can activate protein kinase A) to mimic hormone action and stimulate glucose transport and glucose transporter (GLUT‐1) gene expression as well as the expression of several growth‐related protooncogenes in quiescent 3T3‐L1 fibroblasts. 8‐Bromo‐cAMP induced a rapid and prolonged increase in the rate of hexose transport. Early activation of hexose transport (within 30 min) was associated with increased plasma membrane immunoreactive glucose transporters, which corresponded to a doubling in the number of D‐glucose‐displaceable, plasma membrane cytochalasin B binding sites. The time course for 8‐bromo‐cAMP‐induced hexose transport preceded the accumulation of GLUT‐1 mRNA, which peaked between 4 and 8 h after exposure to the agent, and subsequently declined to approach basal (control) levels. Expression of the immediate‐early genes c‐fos and jun‐B was induced by 8‐bromo‐cAMP on a rapid, but sustained time course, whereas induction of c‐jun expression was delayed. Alterations in specific mRNAs following exposure to 8‐bromo‐cAMP were due to increased gene transcription (as judged by nuclear transcription run‐on assays), although with respect to GLUT‐1, an increase in mRNA stability was also observed. Treatment of the cells with forskolin resulted in the induction of GLUT‐1 expression as well as expression of the immediate early genes. Exposure of quiescent 3T3‐L1 fibroblasts to 8‐bromo‐cAMP resulted in a substantial increase in rates of total protein and RNA synthesis, but had little effect on DNA synthesis. The results demonstrate that 8‐bromo‐cAMP initiated a G0/G1 transition, but did not permit progression into S‐phase. The results further suggest that increased cytosolic cAMP results in the stimulation of glucose transport by three distinct mechanisms to include translocation of pre‐existing transporters, increased transcription of the GLUT‐1 gene and increased stability of GLUT‐1 mRNA.
Regulation of motility in bovine brain endothelial cells
Authors: Rosen Eliot M. , Jaken Susan , Carley William , Luckett Peter M. , Setter Eva , Bhargava Madhu , Goldberg Itzhak D. 
Published: February 2005

AbstractScatter factor (SF) is a fibroblast‐derived cytokine which stimulates motility of epithelial and vascular endothelial cells. We used a quantitative assay based on migration of cells from microcarrier beads to flat surfaces to study the regulation of motility in bovine brain endothelial cells (BBEC). Peptide growth factors (EGF, ECGF, basic FGF) did not stimulate migration. Tumor promoting phorbol esters (PMA, PDD) markedly stimulated migration, while inactive phorbol esters (4a‐PDD, phorbol‐13,20‐diacetate) did not affect migration. Both SF‐ and PMA‐stimulated migration were inhibited by (1) TGF‐beta; (2) protein kinase inhibitors (e.g., staurosporine, K‐252a); (3) activators of the adenylate cyclase signaling pathway (e.g., dibutyryl cyclic AMP, theophylline); (4) cycloheximide; and (5) anti‐cytoskeleton agents (e.g., cytochalasin B, colcemid). However, PMA and SF pathways were distinguishable: (1) PMA induced additional migration at saturating SF concentrations; (2) the onset of migration‐stimulation was immediate for PMA and delayed for SF; and (3) down‐modulation of protein kinase C (PKC) ablated PMA but not SF responsiveness. Assessment of PKC by (3H)‐phorbol ester (PDBu) binding and by immunoblot showed (1) scatter factor does not cause significant redistribution or down‐modulation of PDBu binding or alpha‐PKC; and (2) PDBu mediates redistribution and down‐modulation of both binding and alpha‐PKC. These findings suggest two pathways for BBEC motility: a PKC‐dependent pathway and an SF‐stimulated/PKC‐independent pathway.
Effect of transforming growth factor beta‐1 on ovine satellite cell proliferation and fusion
Authors: Hathaway Marcia R. , Hembree Joan R. , Pampusch Mary S. , Dayton William R. 
Published: February 2005

AbstractWe have evaluated the effect of transforming growth factor beta‐1 (TGF beta‐1) on proliferation and fusion of cultured ovine satellite cells isolated from 5‐month‐old wether lambs. The isolation and culture protocols were validated by clonal analysis of the original cell preparation and assessment of proliferation and fusion of control cultures. Approximately 85% of the original cells isolated were myogenic as assessed by clonal analysis. The ovine cells doubled approximately every 18 hours during their exponential growth period and achieved a maximum percent fusion of 39.5% after 144 hours in culture. TGF beta‐1 inhibited fusion of these cells in a dose‐dependent manner with half‐maximal inhibition occurring at.08 ng/ml. Maximal inhibition (95% suppression) occurred between.1 and.5 ng/ml. TGF Beta‐1 (.05–3.0 ng/ml) did not inhibit proliferation of cultured ovine satellite cells in serum‐containing medium or in serum‐free defined medium. In contrast, TGF beta‐1 did significantly suppress serum‐stimulated proliferation of either porcine or bovine satellite cells that were isolated by using a procedure identical to that used to isolate the ovine satellite cells. Thus, proliferation of ovine satellite cells appears to respond differently to TGF beta‐1 than does proliferation of either porcine or bovine satellite cells.
Multiple signal transduction pathways lead to extracellular ATP‐stimulated mitogenesis in mammalian cells: II. A pathway involving arachidonic acid release, prostaglandin synthesis, and cyclic AMP accumulation
Authors: Huang Ning‐Na , Wang Ding‐Ji , Gonzalez Fernando , Heppel Leon A. 
Published: February 2005

AbstractWe have previously shown that extracellular ATP acts as a mitogen via protein kinase C (PKC)‐dependent and independent pathways (Wang, D., Huang, N., Gonzalez, F.A., and Heppel, L.A. Multiple signal transduction pathways lead to extracellular ATP‐stimulated mitogenesis in mammalian cells. I. Involvement of protein kinase C‐dependent and independent pathways in the mitogenic response of mammalian cells to extracellular ATP. J. Cell. Physiol., 1991). The present aim was to determine if metabolism of arachidonic acid, resulting in prostaglandin E2 (PGE2) synthesis and elevation of cAMP levels, plays a role in mitogenesis mediated by extracellular ATP. Addition of ATP caused a marked enhancement of cyclic AMP accumulation in 3T3, 3T6, and A431 cells. Aminophylline, an antagonist of the adenosine A2 receptor, had no effect on the accumulation of cyclic AMP elicited by ATP, while it inhibited the action of adenosine. The accumulation of cyclic AMP was concentration dependent, which corresponds to the stimulation of DNA synthesis by ATP. The maximal accumulation was achieved after 45 min, with an initial delay period of about 15 min. That the activation of arachidonic acid metabolism contributed to cyclic AMP accumulation and mitogenesis stimulated by ATP in 3T3, 3T6, and A431 cells was supported by the following observations: (a) extracellular ATP stimulated the release of [3H]arachidonic acid and PGE2 into the medium; (b) inhibition of arachidonic acid release by inhibitors of phospholipase A2 blocked PGE2 production, cyclic AMP accumulation, and DNA synthesis activated by ATP, and this inhibition could be reversed by adding exogenous arachidonic acid; (c) cyclooxygenase inhibitors, such as indomethacin and aspirin, diminished the release of PGE2 and blocked cyclic AMP accumulation as well as [3H]thymidine incorporation in response to ATP; (d) PGE2 was able to restore [3H]thymidine incorporation when added together with ATP in the presence of cyclooxygenase inhibitors; (e) pertussis toxin inhibited ATP‐stimulated DNA synthesis in a time‐and dose‐dependent fashion as well as arachidonic acid release and PGE2 formation. Other evidence for involvement of a pertussis toxin‐sensitive G protein(s) in ATP‐stimulated DNA synthesis as well as in arachidonic acid release is presented. In A431 cells, the enhancement of arachidonic acid and cyclic AMP accumulation by ATP was partially blocked by PKC down‐regulation, implying that the activation of PKC may represent an additional pathway in ATP‐stimulated metabolism of arachidonic acid. In all of these studies, ADP and AMP‐PNP, but not adenosine, were as active as ATP. In summary, the data support a role for arachidonic acid metabolism in ATP‐dependent DNA synthesis in 3T3, 3T6, and A431 cells.
Phosphorylation of HSP27 during development and decay of thermotolerance in Chinese hamster cells
Authors: Landry Jacques , Chrétien Pierre , Laszlo Andrei , Lambert Herman 
Published: February 2005

AbstractThe small molecular weight heat shock protein HSP27 was recently shown to confer a stable thermoresistant phenotype when expressed constitutively in mammalian cells after structural gene transfection. These results suggested that HSP27 may also play an important role in the development of thermotolerance, the transient ability to survive otherwise lethal heat exposure after a mild heat shock. In Chinese hamster O23 cells increased thermoresistance is first detected at 2 h after a triggering treatment of 20 min at 44°C, attains a maximum at 5 hours, and decays thereafter with a half‐life of 10 h. We found that the development and decay of transient thermotolerance cannot be solely explained on the basis of changes in the cellular concentration of HSP27. The cellular HSP27 concentration is not increased appreciably at 2 h after heat shock and attains a maximum at 14 h. Similar results were obtained in the case of another heat shock protein, HSP70. HSP70 follows slightly faster kinetics of accumulation (peaks at 10 h) and decays much more rapidly (t1/2 = 4h) than HSP27 (t1/2 = 13h). HSP27 has 3 isoelectric variants A, B, and C of which B and C are phosphorylated. In cells maintained at normal temperature, HSP27A represents more than 90% of all HSP27. Shifting the cell culture temperature from 37 to 44°C induces the incorporation of 32P into the more acidic B and C forms, a process that occurs very rapidly since the reduction in the concentration of the A form and a corresponding increase in the level of B and C is detectable by immunoblot analysis within 2.5 min at 44°C. Analyses performed at various times during development and decay of transient thermo‐tolerance revealed a close relationship between the effect of heat shock on HSP27 phosphorylation and cell ability to survive. For example, fully thermotolerant cells (5 h post‐induction) are refractory to induction of HSP27 phosphorylation by a 20‐min heat shock. The induction of HSP27 phosphorylation was also studied in a family of clonal cell lines of O23 cells that are thermoresistant as a result of the constitutive expression of a transfected human HSP27 gene. In these thermore‐sistant cells, phosphorylation of the endogenous hamster HSP27 is induced to a level comparable to that found in the thermosensitive parental cells. However, phosphorylation of the exogencus human protein, which represents more than 80% of total HSP27 in these cells, was much less induced. Although different mechanisms are involved in the maintenance of a high level of unphosphorylated HSP27 in induced‐thermotolerant and thermoresistant transfectant O23 cells, our results suggest that the degree of HSP27 phosphorylation could be a determinant of the ability of cells to survive hyperthermia.
Histamine inhibits cell spreading and C3bi receptor clustering and diminishes hydrogen peroxide production by adherent human neutrophils
Authors: Francis Joseph W. , Todd Robert F. , Boxer Laurence A. , Petty Howard R. 
Published: February 2005

AbstractCell adherence plays a central role in many host defense mechanisms. Human peripheral blood neutrophils possess cell surface receptors that contribute to cell adherence or detachment. Receptors specific for the C3bi cleavage fragment of the third component of complement (CR3) promote adhesion, whereas histamine receptors promote detachment. In the present study, we tested the ability of histamine to down‐regulate the physiological effects of CR3 receptors. Histamine decreased the binding of 51Cr‐labeled neutrophils to complement‐coated surfaces (C3‐coated surfaces) in a dose‐dependent fashion. Scanning electron microscopic and optical microscopic observations of neutrophils on C3‐coated surfaces revealed polarized or spherical cell morphologies in the absence or presence of histamine, respectively. Histamine inhibited the ability of CR3 to cluster on plasma membranes of neutrophils adherent to C3‐coated surfaces as shown by fluorescence microscopy. In addition, histamine diminished but did not abolish the FMLP‐stimulated increase in plasma membrane CR3 expression as measured by fluorometry. Histamine did not inhibit the release of marker proteins from specific or gelatinase containing granules by neutrophils in suspension. Histamine also diminished the FMLP‐stimulated production of respiratory burst oxidants from cells in suspension or cells allowed to adhere to fibrinogen substrates. We suggest that histamine may modulate selective changes in neutrophil function by diminishing adherence and preventing changes in cell shape following cell activation.
Heparin augments osteoclast resorption‐stimulating activity in serum
Authors: Fuller K. , Chambers T. J. , Gallagher A. C. 
Published: February 2005

AbstractIncreased numbers of mast cells are commonly seen at sites of increased bone resorption and in osteoporosis. Long‐term administration of heparin, a major component of mast cell granules, causes osteoporosis. We therefore tested the effect of heparin on bone resorption by osteoclasts disaggregated from neonatal rat long bones. We found that, in the absence of serum, heparin was without effect on osteoclast function. However, in the presence of newborn calf serum, rat serum, or bovine platelet‐poor plasma‐derived serum, heparin, in the range 25–100 μg/ml, induced an increase in osteoclastic bone resorption. Heparin appeared to act through binding and enhancement of an osteoclast resorption‐stimulating activity (ORSA) present in serum. A number of known factors that show an affinity for heparin, including transforming growth factor‐p, platelet‐derived growth factor, insulin‐like growth factors I or II, acidic or basic fibroblast growth factors, fibfonectin, or laminin, could not substitute for ORSA, suggesting that the activity may represent a novel heparin‐binding factor. The ability of glycosaminoglycans (GACs) and related molecules to enhance resorption was dependent on the degree of sulfation and on their size: The high molecular weight GAG heparan sulfate and polysaccharides fucoidan or dextran sulfate showed a similar effect, while low molecular weight heparin, chondroitin‐2‐sulfate, chon‐droitin‐4‐sulfate, and chondroitin‐6‐sulfate were without effect. We propose that mast cells or heparin therapy increases bone resorption through augmentation of the activity of a factor invoked in the locd and systemic regulation of osteoclastic bone resorption.