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  • Articles  (428)
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  • Column liquid chromatography  (344)
  • calcium  (84)
  • Springer  (428)
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  • 1
    Electronic Resource
    Electronic Resource
    Divalent cation binding to ceruloplasmin (1996)
    Springer
    BioMetals 9 (1996), S. 66-72 
    Details
    ISSN: 1572-8773
    Keywords: calcium ; ceruloplasmin ; prothrombin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Binding of calcium to human and sheep ceruloplasniin was investigated by metal substitution with manganese and competitive displacement of bound manganese by calcium monitored by electron paramagnetic resonance spectroscopy. The K d for calcium was found to be 1.4mm. Magnesium also bound to ceruloplasmin, with K d = 0.3 and 0.7 mm for the human and sheep protein, respectively. The thermal stability of ceruloplasmin, as studied by differential scanning calorimetry, was affected by calcium but not by magnesium. A considerable increase of the T m value, from 73.8 to 83.1°C, was observed for sheep ceruloplasmin in the presence of calcium. The T m value of the human protein was only slightly altered by calcium (from 85.1 to 87°C). The interaction of ceruloplasmin with the chromatographic material used for its isolation, Sepharose 4B derivatized with chloroethylamine, was weakened by calcium. This allowed us to set up a novel purification scheme that made it possible to efficiently isolate ceruloplasmin and prothrombin from plasma with the same single-step chromatography.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00188092
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  • 2
    Electronic Resource
    Electronic Resource
    Calcium-binding proteins and development (1998)
    Springer
    BioMetals 11 (1998), S. 359-372 
    Details
    ISSN: 1572-8773
    Keywords: calcium ; EGF-domains ; cadherins ; integrins ; calmodulin ; cytoskeleton ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The known roles for calcium-binding proteins in developmental signaling pathways are reviewed. Current information on the calcium-binding characteristics of three classes of cell-surface developmental signaling proteins (EGF-domain proteins, cadherins and integrins) is presented together with an overview of the intra-cellular pathways downstream of these surface receptors. The developmental roles delineated to date for the universal intracellular calcium sensor, calmodulin, and its targets, and for calcium-binding regulators of the cytoskeleton are also reviewed.© Kluwer Academic Publishers
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009201824806
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  • 3
    Electronic Resource
    Electronic Resource
    Cation-dependent uptake of zinc in human fibroblasts (1996)
    Springer
    BioMetals 9 (1996), S. 29-37 
    Details
    ISSN: 1572-8773
    Keywords: calcium ; fibroblasts ; potassium ; transport ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The influence of K+ and Ca2+ on Zn2+ transport into cultured human fibroblasts was investigated. Zn2+ uptake was markedly reduced in the presence of both valinomycin and nigericin (electrogenic and electroneutral K + ionophores, respectively), and by reduction in the transmembrane K+ gradient produced by replacement of extracellular K+ with Na+, suggesting that Zn2+ may be driven by a Zn2+/K+ counter-transport system. To test the counter-transport hypothesis, we used 86Rb as an analog of K + for efflux studies. The rate of Rb+ efflux was 3760 times that of Zn2+ uptake, thus the component of K+ involved in the Zn2+ counter-transport system was only a small proportion of the total K+ efflux. In investigating the effect of Ca2+ on Zn2+ uptake, we identified two components: (1) a basal Zn2+ uptake pathway, independent of hormonal or growth factors which does not require extracellular Ca2+ and (2) a Ca2+-dependent mechanism. The absence of Ca2+ decreased Zn2+ uptake, while increasing extracellular C+a2+ stimulated Zn2+ uptake. The effect was mediated by Ca2+ influx as the ionophores A23187 and ionomycin also stimulated Zn2+ uptake. We could not ascribe the Ca2+ effect to known Ca2+ influx pathways. We conclude that Zn2+ uptake occurs by a K+-dependent process, possibly by Zn2+/K+ counter-transport and that a component of this is also Ca2+-dependent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00188087
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  • 4
    Electronic Resource
    Electronic Resource
    Mechanism of metal ion biosorption by fungal biomass (1996)
    Springer
    BioMetals 9 (1996), S. 21-28 
    Details
    ISSN: 1572-8773
    Keywords: biosorption ; decontamination ; cadmium ; calcium ; magnesium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Alkali extracted mycelial biomass from Aspergillus niger, referred to as Biosorb, was found to sequester metal ions (Cd2+, Cu2+, Zn2+, Ni2+ and Co2+) efficiently both from dilute and concentrated solutions upto 10% of its weight (w/w). Sequestration of metal ions from a mixture was also efficient but with attendant antagonisms. The kinetics of metal binding by Biosorb indicated that it is a rapid process and about 70–80% of the metal is removed from solution in 5 min followed by a slower rate. The mechanism of metal binding is shown to be due to exchange of calcium and magnesium ions of the Biosorb during which equimolar concentrations of both the ions were released into the medium. Following this an efficient procedure for the regeneration and reuse of Biosorb was standardized by washing the biosorbent with calcium and magnesium solution (0.1 m). Biosorbents prepared from Neurospora, Fusarium and Penicillium also exhibited similar mechanisms for metal ion binding, though they had a lower metal binding capacity when compared with Biosorb. Chemical modification of carboxylic acid functional groups of the Biosorb resulted in loss of 90% of metal binding capacity which could not be restored even on regeneration. The significance of this finding on the metal sequestration mechanisms of microbial biosorbents is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00188086
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  • 5
    Electronic Resource
    Electronic Resource
    Cadmium replaces calcium in the cell wall ofUlva lactuca (1996)
    Springer
    BioMetals 9 (1996), S. 241-244 
    Details
    ISSN: 1572-8773
    Keywords: cadmium ; calcium ; cell wall ; Ulva lactuca
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Electron microscopy, in conjunction with X-ray microanalysis, was used to investigate the effects of exposure to cadmium on the elemental composition of the macroalgaUlva lactuca. The cell wall was the only region of the cell to show any marked change in chemical composition as a result of exposure to cadmium, with less calcium evident in cadmium-treated thallus compared with untreated thalli. The cell wall ofU. lactuca is a complex structure made up of polysaccharides consisting of many-branched chains composed mostly of rhamnose and galactose subunits. Some of the hydroxyl groups on the subunits are substituted by sulphate groups. Borate is associated with the rhamnose subunits, which contain no sulphate groups, and calcium binds to borate, cross-linking the rhamnose groups. The borate-calcium complex adds rigidity to the cell wall; the replacement of calcium by cadmium will, therefore, influence the rigidity of the thallus. The ecological significance of this work is discussed with respect to the ability of the alga to withstand grazing or emersion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00817922
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  • 6
    Electronic Resource
    Electronic Resource
    The Displacement of Sr from Organic Chelates by Hydroxide, Carbonate, and Calcium in Concentrated Electrolytes (1998)
    Springer
    Journal of solution chemistry 27 (1998), S. 435-454 
    Details
    ISSN: 1572-8927
    Keywords: EDTA ; HEDTA ; NTA ; IDA ; solubility ; strontium ; calcium ; waste processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effects of calcium, hydroxide, and carbonate on the displacement of Sr from four organic chelates: ethylenedinitrilotetraacetic acid (EDTA), N-(2-hydroxyethyl)ethylenedinitrilotriacetic acid (HEDTA) nitrilotriacetic acid (NTA), and iminidiacetic acid (IDA) was studied in solutions with high base and carbonate concentration. Comparison of solutions with and without added chelators allowed the speciation changes in solution to be directly determined. Increases in both carbonate and calcium concentration were effective in displacing Sr from the chelators even under high carbonate concentration. Increases in hydroxide were ineffective in removal of Sr from the chelators, even at base concentrations as high as 6M. Under certain specific conditions, most notably when both CaCO3(s) and SrCO3(s) are present in solution, chemical equilibrium constraints result in cancelation of activity coefficient changes for aqueous Sr and Ca organic chelate complexes. Under such conditions the predicted ratios of chelated Ca and Sr become independent of the ionic media and predictive relations using known equilibrium constants give very good representations of the experimental data. These results indicate that manipulation of metal ion displacement reactions during chemical processing of Sr–chelate solutions can result in the displacement of Sr from organic chelators. The implications of such strategies in processing high level waste supernatants stored at Department of Energy (DOE) sites is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022652621788
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  • 7
    Electronic Resource
    Electronic Resource
    The role of calcium in apoptosis (1998)
    Springer
    BioMetals 11 (1998), S. 375-382 
    Details
    ISSN: 1572-8773
    Keywords: apoptosis ; programmed cell death (PCD) ; calcium ; DAP-Kinase ; calcineurin ; ALG-2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract In this chapter various aspects of apoptosis or programmed cell death (PCD) influenced by calcium as a mediator of signal transduction have been reviewed. Attention has been focused on recently described calcium-binding proteins such as ALG-2 or on a new calcium/calmodulin-dependent kinase, the death asso-ciated protein kinase or DAP-kinase. Both play a central role in apoptotic processes. Calcineurin, which normally is involved in the regulation of T-cell proliferation, is reported to interact with the apoptosis protec-tion protein bcl-2. Its possible involvement in the decision process whether T-cell activation leads to prolif-eration or apoptosis is discussed.© Kluwer Academic Publishers
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009226316146
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  • 8
    Electronic Resource
    Electronic Resource
    Annexins (1998)
    Springer
    BioMetals 11 (1998), S. 399-404 
    Details
    ISSN: 1572-8773
    Keywords: calcium ; membrane ; phospholipids ; annexin ; exocytosis ; anticoagulation ; ion channel ; secretion ; cytoskeleton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The annexins are a family of proteins that bind anionic phospholipid surfaces in a Ca 2+ -dependent manner (general reviews include Raynal & Pollard 1994, Swairjo & Seaton 1994, Seaton 1996, Mollenhauer, 1997). Due to this functional property, individual annexins have been discovered independently by numerous labo-ratories with diverse experimental goals. Ca 2+ characteristically causes the annexins to shift from a soluble to membrane associated state. This shift is believed to be the mechanism that underlies annexin cellular function.© Kluwer Academic Publishers
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009205925714
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  • 9
    Electronic Resource
    Electronic Resource
    Nuclear calcium: a key regulator of gene expression (1998)
    Springer
    BioMetals 11 (1998), S. 345-358 
    Details
    ISSN: 1572-8773
    Keywords: calcium ; CREB ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Through the evolution of multicellular organisms, calcium has emerged as the preferred ion for intracel-lular signalling. It now occupies a pivotal role in many cell types and nowhere is it more important than in neurons, where it mediates both the relaying and long-term storage of information. The latter is a process that enables learning and memory to be formed and requires the activation of gene expression by calcium signals. Evidence from a number of diverse organisms shows that transcription mediated by the transcrip-tion factor CREB is critical for learning and memory. Here we review the features of CREB activation by calcium signals in mammalian cells. In contrast to other transcription factors, its regulation is dependent on an elevation of nuclear calcium concentration, potentially placing this spatially distinct pool of calcium as an important mediator of information storage.© Kluwer Academic Publishers
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009257909785
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  • 10
    Electronic Resource
    Electronic Resource
    Ca 2+ /Calmodulin-dependent protein kinase IV and calcium signaling (1998)
    Springer
    BioMetals 11 (1998), S. 331-343 
    Details
    ISSN: 1572-8773
    Keywords: Ca 2+ /calmodulin-dependent protein kinase IV ; calcium ; calmodulin ; CREB ; T lymphocyte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Ca 2+ /calmodulin dependent protein kinase IV (CaMKIV) is a multifunctional, serine-threonine protein kinase that is activated in the presence of increased intracellular calcium ( Ca 2+ ).CaMKIV is a potent medi-ator of Ca 2+ induced gene expression, primarily through its ability to phosphorylate and activate transcrip-tion factors such as CREB. CaMKIV-dependent activation of CREB is a key event in the expression of genes involved in the processes of T-cell activation and neuronal long term potentiation. The focus of this review is to describe the biochemical regulation of CaMKIV and examine how CaMKIV activates tran-scription in response to calcium in both cell and animal models.© Kluwer Academic Publishers
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009276932076
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  • 11
    Electronic Resource
    Electronic Resource
    Expression of hepatic calcium-binding protein regucalcin mRNA is elevated by refeeding of fasted rats: Involvement of glucose, insulin and calcium as stimulating factors (1995)
    Springer
    Molecular and cellular biochemistry 142 (1995), S. 35-41 
    Details
    ISSN: 1573-4919
    Keywords: regucalcin ; calcium-binding protein ; insulin ; calcium ; gene expression ; rat liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of refeeding on the expression of Ca2+-binding protein regucalcin mRNA in the liver of fasted rats was investigated. When rats were fasted overnight, the hepatic regucalcin mRNA level was reduced about 70% of that in feeding rats. Refeeding produced a remarkable elevation of hepatic regucalcin mRNA level (about 150–170% of fasted rats). Liver regucalcin concentration was appreciably increased by refeeding, although it was not altered by fasting. The oral administration of glucose (2 g/kg body weight) to fasted rats caused a significant increase in hepatic regucalcin mRNA level. Moreover, hepatic regucalcin mRNA level was clearly elevated by a single subcutaneous administration of insulin (10 and 100 U/kg) to fasted rats. The hormonal effect was not further enhanced by the simultaneous administration of calcium chloride (250 mg Ca/kg) to fasted rats, although calcium administration stimulated regucalcin mRNA expression in the liver. The present study suggests that the expression of hepatic regucalcin mRNA stimulated by refeeding is significantly involved in the action of insulin and/or calcium as stimulating factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00928911
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  • 12
    Electronic Resource
    Electronic Resource
    Na+−Ca2+ exchange and Ca2+ channel characteristics in bovine aorta and coronary artery smooth muscle sarcolemmal membranes (1995)
    Springer
    Molecular and cellular biochemistry 144 (1995), S. 61-66 
    Details
    ISSN: 1573-4919
    Keywords: calcium ; calcium channels ; smooth muscle ; sarcolemma ; coronary artery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Tension generation and Ca2+ flux in smooth muscle varies depending upon the diameter of a vessel and its location. The purpose of the present investigation was to determine if the biochemical characteristics of the Na+−Ca2+ exchanger and the Ca2+ channel differ in sarcolemmal membrane preparations isolated from a large conduit vessel (thoracic aorta) or from large and small coronary arteries. We also investigated the possibility of differences between sarcolemmal membranes isolated from coronary arteries dissected from the right and left ventricles. The purification of the sarcolemmal membranes was of a similar magnitude amongst the different groups. Contamination of the sarcolemmal membranes with other membranous organelles was negligible and similar amongst the groups. The Km and Vmax of Na+-dependent Ca2+ uptake in sarcolemmal vesicles was similar amongst the groups. Calcium channel characteristics were examined by measuring [3H]PN200-110 binding to sarcolemmal vesicles. The right coronary artery membranes from both large and small caliber vessels exhibited a higher Kd and the small right coronary artery sarcolemmal preparation had a lower maximal binding density for [3H] PN200-110. The results suggest that the right coronary artery, and in particular the small diameter right coronary artery, possesses altered Ca2+ channel characteristics in isolated sarcolemmal membranes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00926741
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  • 13
    Electronic Resource
    Electronic Resource
    The role of magnesium in regulating CCK-8-evoked secretory responses in the exocrine rat pancreas (1996)
    Springer
    Molecular and cellular biochemistry 154 (1996), S. 123-132 
    Details
    ISSN: 1573-4919
    Keywords: rat pancreas ; cholecystokinin-octapeptide ; magnesium ; calcium ; secretion ; cyclic AMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract This study investigates the effect of magnesium (Mg2+) on the secretory responses and the mobilization of calcium (Ca2+) and Mg2+ evoked by cholecystokinin-octapeptide (CCK-8) in the exocrine rat pancreas. In the isolated intact perfused pancreas CCK-8 (10−10 M) produced marked increases in juice flow and total protein output in zero and normal (1.1 mM) extracellular Mg2+ [Mg2+]o compared to a much reduced secretory response in elevated (5 mM and 10 mM) [Mg2+]o Similar effects of perturbation of [Mg2+]o on amylase secretion and 45Ca2+ uptake (influx) were obtained in isolated pancreatic segments. In pancreatic acinar cells loaded with the fluorescent bioprobe fura-2 acetomethylester (AM), CCK-8 evoked marked increases in cytosolic free Ca2+ concentration [Ca2+]i in zero and normal [Mg2+]o compared to a much reduced response in elevated [Mg2+]o Pretreatment of acinar cells with either dibutyryl cyclic AMP (DB2 cAMP) or forskolin had no effect on the CCK-8 induced changes in [Ca2+]i. In magfura-2-loaded acinar cells CCK-8 (10−8 M) stimulated an initial transient rise in intracellular free Mg2+ concentration [Mg2+]i followed by a more prolonged and sustained decrease. This response was abolished when sodium Na+ was replaced with N-methyl-D-glucamine (NMDG). Incubation of acinar cells with 10 mM Mg2+ resulted in an elevation in [Mg2+]i. Upon stimulation with CCK-8, [Mg2+]i. decreased only slightly compared with the response obtained in normal [Mg2+]o. CCK-8 caused a net efflux of Mg2+ in pancreatic segments; this effect was abolished when extracellular sodium [Na+]o was replaced with either NMDG or choline. The results indicate that Mg2+ can regulate CCK-8-evoked secretory responses in the exocrine pancreas possibly via Ca2+ mobilization. Moreover, the movement of Mg2+ in pancreatic acinar cells is dependent upon extracellular Na+.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00226780
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  • 14
    Electronic Resource
    Electronic Resource
    Enhancement of nuclear Ca2+-ATPase activity in regenerating rat liver: involvement of nuclear DNA increase (1995)
    Springer
    Molecular and cellular biochemistry 146 (1995), S. 179-186 
    Details
    ISSN: 1573-4919
    Keywords: Ca2+-ATPase ; calcium ; nuclear DNA ; DNA fragmentation ; regucalcin ; regenerating rat liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The alteration of calcium content, Ca2+-ATPase activity, DNA content and DNA fragmentation in the nuclei of regenerating rat liver was investigated. Liver was surgically removed about 70% of that of sham-operated rats. the reduced liver weight by partial hepatectomy was completely restored at 3 days after the surgery. Regenerating liver significantly increased Ca2+-ATPase activity and DNA content in the nuclei between 1 and 5 days after hepatectomy. The nuclear calcium content was clearly increased from 2 days after hepatectomy. The increase of Ca2+-ATPase activity in regenerating liver was clearly inhibited by the presence of trifluoperazine (10 μM), staurosporine (2.5 μM) and dibucaine (10 μM), which are inhibitors of calmodulin and protein kinase, in the enzyme reaction mixture. However, the nuclear enzyme activity in normal rat liver was not significantly altered by these inhibitors. Meanwhile, the increase of nuclear DNA content in regenerating liver was completely blocked by the administration of trifluoperazine (2.5 mg/100 g body weight), suggesting an involvement of calmodulin. Now, the nuclear DNA fragmentation was significantly decreased in regenerating liver, suggesting that this decrease is partly contributed to the increase in nuclear DNA content. The present study clearly demonstrates that regenerating liver enhances nuclear Ca2+-ATPase activity and induces a corresponding elevation of nuclear calcium content. This Ca2+-signaling system may be involved in the regulation of nuclear DNA functions in regenerating rat liver.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00944611
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  • 15
    Electronic Resource
    Electronic Resource
    Characterization of regucalcin effect on proteolytic activity in rat liver cytosol: relation to cysteinyl-proteases (1995)
    Springer
    Molecular and cellular biochemistry 148 (1995), S. 67-72 
    Details
    ISSN: 1573-4919
    Keywords: regucalcin ; calcium ; protease ; calpain ; rat liver cytosol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The increasing effect of regucalcin, isolated from rat liver cytosol, on neutral proteolytic activity in the hepatic cytosol was characterized. The proteolytic activity was markedly elevated by the addition of regucalcin (0.1–0.5 μM) in the absence of Ca2+. This increase was not significantly altered by the presence of diisopropylfluorophsophate (DPF;2.5 mM)—although DFP caused a significant decrease in the proteolytic activity. Regucalcin (0.25 μM) additively enhanced the dithiothreitol (DTT; 1.0 mM)—increased proteolytic activity, while the regucalcin or DTT effect was completely abolished by NEM (5 mM), indicating that regucalcin may act on the SH group in proteases. Also, regucalcin (0.25 μM) enhanced the effect of Ca2+ (10 μM) increasing liver proteolytic activity, suggesting that regucalcin does not influence on the active sites for Ca2+ in proteases. Moreover, the proteolytic activity of regucalcin (0.25 μM) was significantly decreased by the presence of calpastatin (24 μg/ml), an inhibitor of Ca2+-activated neutral protease (calpain). Now, regucalcin (0.25 μM) increased about 7-fold the activity ofm-calpain isolated from rabbit skeletal muscle. These observations demonstrate that regucalcin directly activates cysteinyl-proteases. Regucalcin may have a role as a potent proteolytic activator in the cytoplasm of liver cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00929504
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  • 16
    Electronic Resource
    Electronic Resource
    Towards the molecular basis for the regulation of mitochondrial dehydrogenases by calcium ions (1995)
    Springer
    Molecular and cellular biochemistry 149-150 (1995), S. 203-212 
    Details
    ISSN: 1573-4919
    Keywords: calcium ; mitochondria ; FAD-glycerol 3-phosphate dehydrogenase ; pyruvate dehydrogenase ; oxoglutarate dehydrogenase ; isocitrate dehydrogenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In mammalian cells, increases in calcium concentration cause increases in oxidative phosphorylation. This effect is mediated by the activation of four mitochondrial dehydrogenases by calcium ions; FAD-glycerol 3-phosphate dehydrogenase, pyruvate dehydrogenase, NAD-isocitrate dehydrogenase and oxoglutarate dehydrogenase. FAD-glycerol 3-phosphate dehydrogenase, being located on the outer surface of the inner mitochondrial membrane, is exposed to fluctuations in cytoplasmic calcium concentration. The other three enzymes are located within the mitochondrial matrix. While the kinetic properties of all of these enzymes are well characterised, the molecular basis for their regulation by calcium is not. This review uses information derived from calcium binding studies, analysis of conserved calcium binding motifs and comparison of amino acid sequences from calcium sensitive and non-sensitive enzymes to discuss how the recent cloning of several subunits from the four dehydrogenases enhances our understanding of the ways in which these enzymes bind calcium. FAD-glycerol 3-phosphate dehydrogenase binds calcium ions through a domain which is part of the polypeptide chain of the enzyme. In contrast, it is possible that the calcium sensitivity of the other dehydrogenases may involve separate calcium binding subunits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01076578
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  • 17
    Electronic Resource
    Electronic Resource
    Free radical induced respiratory muscle dysfunction (1998)
    Springer
    Molecular and cellular biochemistry 179 (1998), S. 99-110 
    Details
    ISSN: 1573-4919
    Keywords: diaphragm ; oxygen-derived free radicals ; respiratory muscle fatigue ; nitric oxide ; sarcoplasmic reticulum ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract It is now recognized that respiratory muscle fatigue contributes to the development of respiratory failure in some patients with lung disease. This observation has prompted an examination into the mechanisms of development of muscle fatigue, with the understanding that an elucidation of these processes may lead to new therapeutic approaches to the treatment of these patients. A series of recent studies examining this issue have, moreover, discovered that oxygen-derived free radicals generated during strenuous contraction may modulate respiratory muscle contractile function and contribute to the development of muscle fatigue. The data supporting this concept include: (a) direct (e.g. EPR, ESR studies) and indirect (evidence of lipid peroxidation, protein carbonyl formation, glutathione oxidation) evidence that there is heightened free radical production in contracting muscle, (b) evidence that pharmacologic depletion of muscle antioxidant stores increases degree of muscle fatigue present after a period of exercise, and (c) evidence that administration of agents that act as free radical scavengers retard the development muscle fatigue. Free radicals may produce these changes in muscle force generating capacity by interacting with and altering the function of a number of intracellular-biophysical processes (i.e. sarcolemmal action potential propagation, sarcoplasmic reticulum calcium handling, mitochondrial function, contractile protein interactions).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006859920875
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  • 18
    Electronic Resource
    Electronic Resource
    Taurine indirectly increases [Ca]i by inducing Ca2+ influx through the Na+-Ca2+ exchanger (1998)
    Springer
    Molecular and cellular biochemistry 188 (1998), S. 187-197 
    Details
    ISSN: 1573-4919
    Keywords: heart cells ; taurine ; β-alanine ; taurine-Na+ cotransport ; CBDMB ; Na+-Ca2+ exchanger ; calcium ; nucleus ; confocal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Recent studies in heart cells have shown taurine to induce a sustained increase of both intracellular Ca2+ and Na+. These results led us to believe that the increase in Na+ by taurine could be due to Na+ entry through the taurine-Na+ cotransporter which in turn favours transarcolemmal Ca2+ influx through Na+-Ca2+ exchange. Therefore, we investigated the effect of β-alanine, a blocker of the taurine-Na+ cotransporter and low concentrations of CBDMB (a pyrazine derivative, 5-(N-4chlorobenzyl)-2′,4′-dimethylbenzamil), a Na+-Ca2+ exchanger blocker on taurine-induced [Ca]i increase in embryonic chick heart cells. Using Fura-2 Ca2+ imaging and Fluo-3 Ca2+ confocal microscopy techniques, taurine (20 mM) as expected, induced a sustained increase in [Ca]i at both the cytosolic and the nuclear levels. Preexposure to 500 μM of the blocker of the taurine-Na+ cotransporter, β-alanine, prevented the amino acid-induced increase of total [Ca]i. On the other hand, application of β-alanine did not reverse the action of taurine on total [Ca]i. However, low concentrations of the Na+-Ca2+ exchanger blocker, CBDMB, reversed the taurine-induced sustained increase of cytosolic and nuclear free calcium (in presence or absence of β-alanine). Thus, the effect of taurine on [Ca]i in heart cells appears to be due to Na+ entry through the taurine-Na+ cotransporter which in turn favours transarcolemmal Ca2+ influx through the Na+-Ca2+ exchanger.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006806925739
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    Dynamic regulation of intracellular calcium signals through calcium release channels (1999)
    Springer
    Molecular and cellular biochemistry 190 (1999), S. 185-190 
    Details
    ISSN: 1573-4919
    Keywords: calcium ; calcium wave ; calcium oscillation ; inositol 1,4,5-trisphosphate receptor ; ryanodine receptor ; excitation-concentration coupling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract After the seminal work of Ebashi and coworkers which established the essential role of the intracellular Ca2+ concentration ([Ca2+]i) in the regulation of skeletal muscle contraction, we have witnessed an explosive elongation of the list of cell functions that are controlled by the [Ca2+]i. In numerous instances, release of intracellular Ca2+ stores plays important roles in Ca2+ signalling which displays significant variation in spatio-temporal pattern. There are two families of Ca2+ release channels, ryanodine receptors and inositol 1,4,5-trisphosphate (IP3) receptors. These Ca2+ release channels are structurally and functionally similar. In particular, the activity of both types of channels is regulated by the [Ca2+]i. The [Ca2+]i dependence of the Ca2+ release channel activity provides both types of channels with properties of a Ca2+ signal amplifier. This function of the ryanodine receptor is important in striated muscle excitation-contraction coupling, whereas that of the IP3 receptor seems to be the basis of the generation of Ca2+ waves. Thus the wide variety of Ca2+ signalling patterns seem to be critically dependent on the [Ca2+]i dependence of the Ca2+ release channels.
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    URL: http://dx.doi.org/10.1023/A:1006951317052
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    Thermodynamic analyses of calcium binding to troponin C, calmodulin and parvalbumins by using microcalorimetry (1999)
    Springer
    Molecular and cellular biochemistry 190 (1999), S. 39-45 
    Details
    ISSN: 1573-4919
    Keywords: microcalorimetry ; calcium ; troponin C ; calmodulin ; parvalbumin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Results of microcalorimetric titrations of calcium-binding proteins with calcium or magnesium have been reviewed and evaluated. Results were analyzed mostly in terms of heat capacity changes, which is most closely related to the structural changes of the molecule on metal binding. Two high-affinity sites of rabbit skeletal troponin C are distinguishable in terms of their affinity to calcium and associated enthalpy changes. Heat capacity changes on calcium binding to one of the two high-affinity sites is negative and is in the range ascribed to the ligand binding. In contrast, that to the other of the high-affinity sites is large and positive, indicating that a substantial area of hydrophobic groups become exposed to the solvent. In frog skeletal troponin C, the anomalous positive heat capacity changes occur in one of the low-affinity calcium-specific sites, so that this may be involved in the regulation of contraction. Unlike skeletal troponin C, both of the two high-affinity sites of cardiac troponin C show negative heat capacity changes. In calmodulin, heat capacity changes are positive but small, indicating that calcium binding may induce clustering of the hydrophobic residues on the surface of the molecule. In parvalbumins, heat capacity changes are negative, characteristic of most ligand binding.
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    URL: http://dx.doi.org/10.1023/A:1006943426370
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    Interaction of heavy metal toxicants with brain constitutive nitric oxide synthase (1995)
    Springer
    Molecular and cellular biochemistry 149-150 (1995), S. 263-265 
    Details
    ISSN: 1573-4919
    Keywords: NO synthase ; toxic metals ; signal transduction ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract This study was designed to evaluate thein vitro effects of transition heavy metal cations on activity of constitutive isoform of nitric oxide synthase (cNOS) in rat brain. NOS activity was determined in the cytosolic fractions of rat cerebral hemispheres by conversion of3H-L-arginine to3H-L-citrulline. Different concentrations of mercury (Hg2+), nickel (Ni2+), manganese (Mn2+), zinc (Zn2+), cadmium (Cd2+), lead (Pb2+) and calcium (Ca2+) were tested on NOS activity. While all the cations caused inhibition, there were differences in the apparent inhibition constants (Ki) among the cations. With the exception of calcium ion no other cation required preincubation with the enzyme preparation. These results indicate that while calcium ion modulate cNOS activity at regulatory site(s), inhibitory influence of toxic heavy metal cations may be exerted on the catalytic site(s) either by direct binding to it or by interfering with the electron transfer during catalysis.
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    URL: http://dx.doi.org/10.1007/BF01076586
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    Regional alterations in calcium homeostasis in the primate brain following chronic aluminium exposure (1997)
    Springer
    Molecular and cellular biochemistry 168 (1997), S. 95-100 
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    ISSN: 1573-4919
    Keywords: aluminium ; calcium ; brain ; neurodegenerative disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The present study investigates the possible effects of chronic aluminium exposure on the various aspects of calcium homeostasis in the primate central nervous system. Aluminium administration caused a marked decline in the activity of Ca2+ ATPase in the monkey brain. The total calcium content was also significantly raised following aluminium exposure. Concomittant to the increase in the calcium content, the levels of lipid peroxidation were also augmented in the aluminium treated animals, thereby further accentuating the aluminium induced neuronal damage. In addition, aluminium had an inhibitory effect on the depolarization induced 45Ca2+ uptake via the voltage operated channels. The results presented herein, indicate that the toxic effects of aluminium could be mediated through modifications in the intracellular calcium homeostasis with resultant altered neuronal function.
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    URL: http://dx.doi.org/10.1023/A:1006891125762
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    Alterations in inotropy, nitric oxide and cyclic GMP synthesis, protein phosphorylation and ADP-ribosylation in the endotoxin-treated rat myocardium and cardiomyocytes (1996)
    Springer
    Molecular and cellular biochemistry 163-164 (1996), S. 305-318 
    Details
    ISSN: 1573-4919
    Keywords: nitric oxide ; endotoxin ; cardiomyocytes ; guanosine 3′, 5′-cyclic monophosphate ; calcium ; ADP-ribosylation ; phosphorylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract To evaluate the effects of the in vivo endotoxin treatment of the rat on (1) the contractile responses in the subsequently isolated papillary muscle to adrenergic and cholinergic agonists and (2) the biochemical parameters (cyclic GMP, nitric oxide synthesis, protein phosphorylation and ADP-ribosyslation) in the subsequently isolated cardiomyocytes. Following the in vivo endotoxin treatment (4 mg/kg i.p., 18 h), contractile responses to increasing amounts of isoprenaline or to increasing amounts of oxotremorine in the presence of a fixed amount of isoprenaline were determined in isolated papillary strips. Activities of nitric oxide synthase, guanylyl cyclase, as well as phosphorylation of phospholamban and troponin-inhibitory subunit, and pertussis toxin-catalyzed and endogenous ADP-ribosylations were determined in the intact cardiomyocytes and subcellular fractions. The increase in the force of contraction by isoprenaline was reduced, while its inhibition by oxotremorine was greater in the endotoxin-treated papillary strips. The activities of both nitric oxide synthase, primarily of the inducible form of the enzyme, and cytosolic guanylyl cyclase were higher while the phosphorylations of both phospholamban and troponin-inhibitory subunit were of lesser magnitude in the cardiomyocytes following the in vivo endotoxin treatment. Pertussis toxin-catalyzed ADP-ribosylation of the 41 kDa polypeptide, which is the alpha subunit of Gi, was also decreased. The results of the present study support the postulate that alterations in both the cyclic AMP and cyclic GMP signalling cascade contribute to the myocardial dysfunction caused by endotoxin and cytokines.
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    URL: http://dx.doi.org/10.1007/BF00408671
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    Modulation of cytosolic and nuclear Ca2+ and Na+ transport by taurine in heart cells (1997)
    Springer
    Molecular and cellular biochemistry 170 (1997), S. 1-8 
    Details
    ISSN: 1573-4919
    Keywords: taurine ; heart cells ; calcium ; sodium ; confocal microscopy ; nucleus ; fluo-3 ; sodium green ; Ca2+ overload
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of taurine on the different types of ionic currents appears to depend on [Ca]o and [Ca]i and may also vary accordingly to tissue or cell type studied. Using microfluorometry and Ca2+ imaging techniques, short-term exposure (5–10 min) of single heart cells to taurine was found to increase total intracellular free Ca2+ in a concentration-dependent manner. However, long-term exposure of heart myocytes to taurine was found to decrease both nuclear and cytosolic Ca2+ without significantly changing either nuclear or cytosolic Na+ levels, as measured by 3-dimensional Ca2+ and Na+ confocal imaging techniques. Long- term exposure to taurine was found to prevent cytosolic and nuclear increases of Ca2+ induced by permanent depolarization of heart cells with high [K]o. This preventive effect of taurine on nuclear Ca2+ overload was associated with an increase of both cytosolic and nuclear free Na+. Thus, the effect of long-term exposure to taurine on intranuclear Ca2+ overload in heart cells seems to be mediated via stimulation of sarcolemmal and nuclear Ca2+ outflow through the Na+-Ca2+ exchanger.
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    URL: http://dx.doi.org/10.1023/A:1006879918371
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    Hormonal stimulation, mitochondrial Ca2+ accumulation, and the control of the mitochondrial permeability transition in intact hepatocytes (1997)
    Springer
    Molecular and cellular biochemistry 174 (1997), S. 173-179 
    Details
    ISSN: 1573-4919
    Keywords: mitochondria ; calcium ; permeability transition ; vasopressin ; glucagon ; thapsigargin ; protein kineses and phosphatases ; rat hepatocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Ca2+ functions as an intracellular signal to transfer hormonal messages to different cellular compartments, including mitochondria, where it activates intramitochondrial Ca2+-dependent enzymes. However, excessive mitochondrial Ca2+ uptake can promote the mitochondrial permeability transition (MPT), a process known to be associated with cell injury. The factors controlling mitochondrial Ca2+ uptake and release in intact cells are poorly understood. In this paper, we investigate mitochondrial Ca2+ accumulation in intact hepatocytes in response to the elevation of cytosolic Ca2+ levels ([Ca2+]c) induced either by a hormonal stimulus (vasopressin), or by thapsigargin, an inhibitor of the endoplasmic reticulum Ca2+ pump. After stimulation, cells were rapidly permeabilized for the determination of the mitochondrial Ca2+ content (Ca2+_m) and to analyze the susceptibility of the mitochondria to undergo the MPT. Despite very similar levels of [Ca2+]c elevation, vasopressin and thapsigargin had markedly different effects on mitochondrial Ca2+ accumulation. Vasopressin caused a rapid (〈 90 sec), but modest (〈 2 fold) increase in Ca2+m that was not further increased during prolonged incubations, despite a sustained [Ca2+]c elevation. By contrast, thapsigargin induced a net Ca2+ accumulation in mitochondria that continued for up to 30 min and reached Ca2+_m levels 10–20 fold over basal. Accumulation of mitochondrial Ca2+ was accompanied by a markedly increased susceptibility to undergo the MPT. Both mitochondrial Ca2+ accumulation and MPT activation were modulated by treatment of the cells with inhibitors of protein kineses and phosphatases. The results indicate that net mitochondrial Ca2+ uptake in response to hormonal stimulation is regulated by processes that depend on protein kinase activation. These controls are inoperative when the cytosol is flooded by Ca2+ through artificial means, enabling mitochondria to function as a Ca2+ sink under these conditions. (Mol Cell Biochem 174: 173–179, 1997)
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    URL: http://dx.doi.org/10.1023/A:1006831703155
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    Dietary and physiological studies to investigate the relationship between calcium and magnesium signalling in the mammalian myocardium (1997)
    Springer
    Molecular and cellular biochemistry 176 (1997), S. 127-134 
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    ISSN: 1573-4919
    Keywords: heart ; calcium ; magnesium ; contractility ; dietary ; L-type calcium current
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract This study employs both dietary and physiological studies to investigate the relationship between calcium (Ca2+) and magnesium (Mg2+) signalling in the mammalian myocardium. Rats maintained on a low Mg2+ diet (LMD; 39 mg Kg-1 Mg2+ in food) consumed less food and grew more slowly than control rats fed on a control Mg2+ diet (CMD; 500 mg Kg-1 Mg2+ in food). The Mg2+ contents of the heart and plasma were 85 ± 3% and 34 ± 6.5%, respectively relative to the control group. In contrast, Ca2+ contents in the heart and plasma were 177 ± 5% and 95 ± 3%. The levels of potassium (K+) was raised in the plasma (129 ± 16%) and slightly decreased in the heart (88 ± 6%) compared to CMD. Similarly, sodium (Na+) contents were slightly higher in the heart and lowered in the plasma of low Mg2+ diet rats compared to control Mg2+ diet rat. Perfusion of the isolated Langendorff's rat heart with a physiological salt solution containing low concentrations (0-0.6 mM) of extracellular magnesium [Mg2+]0 resulted in a small transient increase in the amplitude of contraction compared to control [Mg2+]0 (1.2 mM). In contrast, elevated [Mg2+]0 (2-7.2 mM) caused a marked and progressive decrease in contractile force compared to control. In isolated ventricular myocytes the L-type Ca2+ current (ICa,L was significantly (p 〈 0.001) attenuated in cells dialysed with 7.1 mM Mg2+ compared to cells dialysed with 2.9 µM Mg2+. The results indicate that hypomagnesemia is associated with decrease levels of Mg2+ and elevated levels of Ca2+ in the heart and moreover, internal Mg2+ is able to modulate the Ca2+ current through the L-type Ca2+ channel which in turn may be involved with the regulation of contractile force in the heart.
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    URL: http://dx.doi.org/10.1023/A:1006839315221
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    Inhibitory effect of regucalcin on Ca2+/calmodulin-dependent cyclic AMP phosphodiesterase activity in rat kidney cytosol (1997)
    Springer
    Molecular and cellular biochemistry 177 (1997), S. 209-214 
    Details
    ISSN: 1573-4919
    Keywords: regucalcin ; calmodulin ; calcium ; cyclic AMP phosphodiesterase ; rat kidney cytosol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of regucalcin, a novel Ca2+-binding protein, on Ca2+/ calmodulin-dependent cyclic adenosine monophosphate (AMP) phosphodiesterase activity in the cytosol of rat renal cortex was investigated. Regucalcin with physiologic concentration (10-7 M) in rat kidney had no effect on cyclic AMP phosphodiesterase activity in the absence of CaCl2 and calmodulin. However, the activatory effect of both CaCl2 (10 µM) and calmodulin (20 U/ml) on cyclic AMP phosphodiesterase was markedly inhibited by the addition of regucalcin (10-8 to 10-6 M) in the enzyme reaction mixture. The inhibitory effect of regucalcin on the enzyme activity was also seen in the presence of CaCl2 (5-50 µM) or calmodulin (5-50 U/ml) with increasing concentrations. The presence of trifluoperazine (10 µM), an antagonist of calmodulin, caused a partial inhibition of Ca2+ /calmodulin-dependent cyclic AMP phosphodiesterase activity. This inhibition was further enhanced by the addition of regucalcin (10-7 M). The inhibitory effect of regucalcin (10-7 M) was not seen in the presence of 20 µM trifluoperazine. Moreover, the activatory effect of calmodulin (20 U/ml) on cyclic AMP phosphodiesterase was not entirely seen, when calmodulin was added 10 min after incubation in the presence of CaCl2 (10 µM) and regucalcin (10-7 M). The present results demonstrates that regucalcin has an inhibitory effect on Ca2+ /calmodulin-dependent cyclic AMP phosphodiesterase activation in the cytosol of rat renal cortex.
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    URL: http://dx.doi.org/10.1023/A:1006829926590
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    Metabolic disturbances in diabetic cardiomyopathy (1998)
    Springer
    Molecular and cellular biochemistry 180 (1998), S. 53-57 
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    ISSN: 1573-4919
    Keywords: diabetes ; cardiomyopathy ; lipids ; lipoprotein lipase ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract It has been established that diabetes results in a cardiomyopathy, and increasing evidence suggests that an altered substrate supply and utilization by cardiac myocytes could be the primary injury in the pathogenesis of this specific heart muscle disease. For example, in diabetes, glucose utilization is insignificant, and energy production is shifted almost exclusively towards β-oxidation of free fatty acids (FFA). FFA's are supplied to cardiac cells from two sources: lipolysis of endogenous cardiac triglyceride (TG) stores, or from exogenous sources in the blood (as free acid bound to albumin or as TG in lipoproteins). The approximate contribution of FFA from exogenous or endogenous sources towards β-oxidation in the diabetic heart is unknown. In an insulin-deficient state, adipose tissue lipolysis is enhanced, resulting in an elevated circulating FFA. In addition, hydrolysis of the augmented myocardial TG stores could also lead to high tissue FFA. Whatever the source of FFA, their increased utilization may have deleterious effects on myocardial function and includes the abnormally high oxygen requirement during FFA metabolism, the intracellular accumulation of potentially toxic intermediates of FFA, a FFA-induced inhibition of glucose oxidation, and severe morphological changes. Therapies that target these metabolic aberrations in the heart during the early stages of diabetes could potentially delay or impede the progression of more permanent sequelae that could ensue from otherwise uncontrolled derangements in cardiac metabolism.
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    URL: http://dx.doi.org/10.1023/A:1006882805197
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    Exercise-induced muscle injury: A calpain hypothesis (1998)
    Springer
    Molecular and cellular biochemistry 179 (1998), S. 135-145 
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    ISSN: 1573-4919
    Keywords: calcium ; non-lysosomal proteases ; muscle damage ; neutrophils ; muscle regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract It is well established that periods of increased contractile activity result in significant changes in muscle structure and function. Such morphological changes as sarcomeric Z-line disruption and sarcoplasmic reticulum vacuolization are characteristic of exercise-induced muscle injury. While the precise mechanism(s) underlying the perturbations to muscle following exercise remains to be elucidated, it is clear that disturbances in Ca2+ homeostasis and changes in the rate of protein degradation occur. The resulting elevation in intracellular [Ca2+] activates the non-lysosomal cysteine protease, calpain. Because calpain cleaves a variety of protein substrates including cytoskeletal and myofibrillar proteins, calpain-mediated degradation is thought to contribute to the changes in muscle structure and function that occur immediately following exercise. In addition, calpain activation may trigger the adaptation response to muscle injury. The purpose of this paper is to: (i) review the chemistry of the calpain-calpastatin system; (ii) provide evidence for the involvement of the non-lysosomal, calcium-activated neutral protease (calpain) in the response of skeletal muscle protein breakdown to exercise (calpain hypothesis); and (iii) describe the possible involvement of calpain in the inflammatory and regeneration response to exercise.
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    URL: http://dx.doi.org/10.1023/A:1006816123601
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    Endothelin-1 and insulin activate the steady-state voltage dependent R-type Ca2+ channel in aortic smooth muscle cells via a pertussis toxin and cholera toxin sensitive G-protein (1998)
    Springer
    Molecular and cellular biochemistry 183 (1998), S. 39-47 
    Details
    ISSN: 1573-4919
    Keywords: aortic cells ; steady state R-type Ca2+ channel ; ET-1 ; insulin ; calcium ; G-protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In single rabbit aortic smooth muscle cells, and at a concentration known to induce a maximum sustained increase of intracellular Ca2+ via activation of the steady-state voltage dependent R-type Ca2+ channels, endothelin-1 (10-7 M) and insulin (80 μU/ml) were found to induce a sustained increase in cytosolic free Ca2+ ([Ca]i) levels that was significantly attenuated by pre-treatment with either pertussis toxin (PTX), cholera toxin (CTX) or removal of extracellular Ca2+. However, both PTX and CTX failed to inhibit the sustained depolarization-evoked sustained Ca2+ influx and [Ca]i elevation via activation of the R-type Ca2+ channels. Moreover, ET-1 and insulin-evoked sustained increases in Ca2+ influx were not attenuated by the selective PKC inhibitor, bisindolylmaleimide (BIS), or the specific L-type Ca2+ channel blocker, nifedipine, but were completely reversed by the R-type Ca2+ channel blocker, (-) PN 200-110 (isradipine). These data suggest that both insulin and ET-1 activate the nifedipine-insensitive but isradipine-sensitive steady state voltage dependent R-type Ca2+ channels present on rabbit VSMCs and these channels are directly coupled to PTX and CTX sensitive G protein(s).
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    URL: http://dx.doi.org/10.1023/A:1006887714302
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    Hyperosmolality-induced abnormal patterns of calcium mobilization in smooth muscle cells from non-diabetic and diabetic rats (1998)
    Springer
    Molecular and cellular biochemistry 183 (1998), S. 79-85 
    Details
    ISSN: 1573-4919
    Keywords: hyperosmolality ; hyperglycemia ; calcium ; smooth muscle cells ; diabetes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Hyperglycemia and/or hyperosmolality may disturb calcium homeostasis in vascular smooth muscle cells (SMCs), leading to altered vascular contractility in diabetes. To test this hypothesis, the KCl induced increases in [Ca2+]i in primarily cultured vascular SMCs exposed to different concentrations of glucose were examined. With glucose concentration in solutions kept at 5.5 mM, KCl induced a fast increase in [Ca2+]i which then slowly declined (type 1 response) in 83% of SMCs from non-diabetic rats. In 9% of non-diabetic SMCs KCl induced a slow increase in [Ca2+]i (type 2 response). Interestingly, under the same culture conditions KCl induced type 1 and type 2 responses in 47 and 35% of SMCs from diabetic rats. When SMCs from non-diabetic or diabetic rats were cultured in 36 mM glucose, KCl induced a fast increase in [Ca2+]i which, however, maintained at a high level (type 3 response). The sustained level of [Ca2+]i in the presence of KCl was significantly higher in cells cultured with 36 mM glucose than that in non-diabetic cells cultured with 5.5 mM glucose. Furthermore, the hyperglycemia-induced alterations in calcium mobilization were similarly observed in cells cultured in high concentration of mannitol (30.5 mM) or L-glucose, indicating that hyperosmolality was mainly responsible for the abnormal calcium mobilization in diabetic SMCs.
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    Calcitonin gene-related peptide receptor independently stimulates 3′,5′-cyclic adenosine monophosphate and Ca2+ signaling pathways (1999)
    Springer
    Molecular and cellular biochemistry 197 (1999), S. 179-185 
    Details
    ISSN: 1573-4919
    Keywords: CGRP-1 receptor ; HEK-293 cells ; calcium ; cholera toxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Calcitonin gene-related peptide (CGRP) is a neuropeptide with diverse biological properties including potent vasodilating activity. Recently, we reported the cloning of complementary DNAs (cDNAs) encoding the human and porcine CGRP receptors which share significant amino acid sequence homology with the human calcitonin receptor, a member of the recently described novel subfamily of G-protein-coupled 7TM receptors. Activation of this family of receptors has been shown to result in an increase in intracellular cAMP accumulation and calcium release. In this study, we demonstrate that HEK-293 cells expressing recombinant CGRP receptors (HEK-293HR or PR) respond to CGRP with increased intracellular calcium release (EC50 = 1.6 nM) in addition to the activation of adenylyl cyclase (EC50 = 1.4 nM). The effect of CGRP on adenylyl cyclase activation and calcium release was inhibited by CGRP (8-37), a CGRP receptor antagonist. Both effects were mediated by cholera toxin-sensitive G-proteins, but these two signal transduction pathways were independent of each other. While cholera toxin pretreatment of HEK-293PR cells resulted in permanent activation of adenylyl cyclase, the same pretreatment resulted in an inhibition of CGRP-mediated [Ca2+]i release. Pertussis toxin was without effect on CGRP-mediated responses. In addition, CGRP-mediated calcium release appears to be due to release from a thapsigargin-sensitive intracellular calcium pool. These results show that the recombinant human as well as porcine CGRP receptor can independently increase both cAMP production and intracellular calcium release when stably expressed in the HEK-293 cell line.
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    Mechanical effects of ET-1 in cardiomyocytes isolated from normal and heart-failed rabbits (1996)
    Springer
    Molecular and cellular biochemistry 157 (1996), S. 149-155 
    Details
    ISSN: 1573-4919
    Keywords: endothelin-1 ; ventricular cardiomyocytes ; contraction ; calcium ; heart failure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Endothelin (ET-1) is found at elevated concentrations in the plasma of patients with heart failure and in animal models of cardiomyopathy. The peptide is a potent positive inotropic agent, the effects of which are mediated by increases in cytosolic Ca2+ in cardiomyocytes. The object of this study was to investigate at the cellular level, the actions of ET-1 on contractile function and on Ca2+ currents in heart-failed ventricular myocardium. Male New Zealand White rabbits (8 wks) were treated with twice weekly injections of epirubicin (4 mg/kg/wk, n=7) or with saline (n=7) for 6 wks, followed by a washout period of 2 wks. Ventricular cardiomyocytes were isolated from rabbit hearts using Langendorff perfusion with collagenase; contractile function was examined using a video microscopy method, and L-type Ca2+ currents were recorded using a whole-cell patch-clamp technique. ET-1 produced a concentration-dependent increase in contractile response (% increase from basal value) to a maximum at 1 nM ET-1 of 69 ± 11% (mean ± S.D.) in control cardiomyocytes and 33 ± 6% in heart-failed cells. However, there was no significant change in the EC50 obtained with ET-1 for healthy (0.31 ± 0.1 nM) and for failed cardiomyocytes (0.24 ± 0.1 nM). The effects of ET-1 on L-type Ca2+ channels were similar with a peak amplitude at 1 nM ET-1 of −3.26 ± 0.8 ⋬ in control cardiomyocytes and −3.32 ± 0.9 nA in heart-failed cells. The attenuation of the contractile response to ET-1 in heart-failed cells may reflect a desensitization of ET receptors as a consequence of elevated circulating levels of ET and was not reflected by alteration of transmembrane Ca2+ conductance. It is probable, therefore, that multiple signalling pathways are involved in the actions of ET on ventricular myocardium.
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    URL: http://dx.doi.org/10.1007/BF00227893
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    Early after-depolarisations induced by noradrenaline may be initiated by calcium released from sarcoplasmic reticulum (1996)
    Springer
    Molecular and cellular biochemistry 163-164 (1996), S. 125-130 
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    ISSN: 1573-4919
    Keywords: cardiac myocytes ; early after depolarisations ; delayed after depolarisations ; calcium ; sarcoplasmic reticulum ; noradrenaline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract We investigated the effect of 10−8 M noradrenaline (NA) on [Ca2+], and electrical activity of single myocytes of guinea-pig ventricular myocardium loaded with Indo 1-AM. Membrane potential was recorded by means of the patch electrode and patch amplifier set to the current clamp mode. Cells were stimulated at a rate of 30/min by 3 ms pulses of the current injected through the recording electrode. Superfusion of NA resulted in slight shortening of action potentials (APs), increase in rate of rise and amplitude of the respective Ca2+ transients, and appearance of secondary Ca2+ transients of two kinds: 1. appearing before repolarisation of AP and decay of the preceding Ca2+ transient were completed and 2. appearing between the APs. We named them early after-transients (EAT) and delayed after-transients (DAT), respectively. Without any additional intervention EATS caused some prolongation of APs duration and DATs resulted in subthreshold delayed after-depolarisations (DADS). When sarcolemmal K+ conductance was decreased by tetraethylammonium (TEA) in the patch electrode or 20 μM BaCl2 in the Tyrode solution, EATs initiated early after depolarizations (EADs) and DATs initiated suprathreshold DADs triggering full-sized APs. Superfusion of 30.0 mM Na+ (replaced with LiCl) resulted in reduction of AP duration by -70% and appearance of DATs. Also, the frequent multiple oscillations of Ca 2+ concentration were often observed. Neither DATs nor the oscillations had any affect on electrical activity of the cells. Their electrogenicity could not be increased by TEA or 20.0 μM Ba2+. EATs and DATs and their respective EADs and DADs could not be initiated by NA or low Na+ superfusion in the cells pretreated with 2 × 10−7 M thapsigargin, a selective blocker of Ca2+-ATPase of sarcoplasmic reticulum (SR). We conclude that in contrast to the current hypothesis, EADs can be initiated by Ca2+ released early in the cardiac cycle from the overloaded SR, and that electrogenicity of both types of Ca2+ oscillations critically depends on the sarcolemmal K+ conductance.
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    Mimosa pudica apyrase requires polysaccharide and Ca2+ for the activity (1998)
    Springer
    Molecular and cellular biochemistry 187 (1998), S. 47-55 
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    ISSN: 1573-4919
    Keywords: Mimosa pudica ; apyrase ; arabinogalactan ; calcium ; circular dichroism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Mimosa pudica Linn leaves with pulvini contain unique isoforms (I and II) of apyrase enzyme (EC 3.6.1.5). The activity of isoform I depends on divalent cation Mn2+. This isoform is associated noncovalently with the polysaccharide, containing mainly of galactose and arabinose sugars. The apparent molecular mass of these 2 isoforms are 36 and 34 Kd respectively. The association of the polysaccharide with the isoform I has been found to be Ca2+ dependent which is endogenously present in this isoform. Removal of Ca2+ and polysaccharide from the enzyme (isoform I) leads to an inactivation. The enzyme activity can be restored when both Ca2+ and endogenous polysaccharide fraction were added at an optimal molar ratio of Ca2+:protein of 7:1. The endogenous polysaccharide can be replaced by the standard arabinogalactan. No other sugar or polysaccharide except the arabinogalactan can restore the apyrase activity. Calcium mediates a conformational change in the protein which helps in association of polysaccharide as evidenced from fluorometric and far UV-CD studies to restore the enzymic activity. Neither any interaction of the polysaccharide with the protein is detected in absence of Ca2+ nor the enzyme activity could be recovered under such condition.
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    Targets of oxidative stress in cardiovascular system (1998)
    Springer
    Molecular and cellular biochemistry 187 (1998), S. 1-10 
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    ISSN: 1573-4919
    Keywords: oxidant ; cardiovascular system ; signal transduction ; calcium ; mitogen activated protein kinases ; nuclear transcription factors ; tyrosine kinase ; protein kinase C ; superoxide ; hydrogen peroxide ; ischemia-reperfusion ; atherosclerosis ; phospholipases ; apoptosis ; antioxidant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Although oxidants such as superoxide (O2.-) and hydrogen peroxide (H2O2) play a role in host-mediated destruction of foreign pathogens yet excessive generation of oxidants may lead to a variety of pathological complications in the cardiovascular system. An important mechanism by which oxidants cause dysfunction of the cardiovascular system appears to be due to the increase in intracellular free Ca2+ concentration. Oxidants cause cellular Ca2+ mobilization by modulating activities of a variety of regulators such as Na+/H+ and Na+/Ca2+ exchangers, Na+/K+ ATPase and Ca2+ ATPase and Ca2+ channels that are associated with Ca2+ transport in the plasma membrane and the sarco(endo)plasmic reticular membrane of myocardial cells. Recent research have suggested that the increase in Ca2+ level by oxidants plays a pivotal role in indicing several protein kinases such as protein kinase C, tyrosine kinase and mitogen activated protein kinases. Oxindant-mediated alteration of different signal transduction systems and their interations eventually regulate a variety of pathological conditoins such as atherosclerosis, apoptosis and necrosis in the myocardium
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    The use of confocal microscopy in the investigation of cell structure and function in the heart, vascular endothelium and smooth muscle cells (1997)
    Springer
    Molecular and cellular biochemistry 172 (1997), S. 171-194 
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    ISSN: 1573-4919
    Keywords: heart ; vascular endothelium ; vascular smooth muscle ; confocal microscopy ; pH ; calcium ; sodium ; voltage probe ; heart ; endothelin-1 ; Angiotensin II ; PAF ; nucleus ; mitochondria ; SR ; cardiomyopathy ; cells interaction ; R-type Ca2+ channel ; excitation-contraction coupling ; dystrophic mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In recent years, fluorescence microscopy imaging has become an important tool for studying cell structure and function. This non invasive technique permits characterization, localisation and qualitative quantification of free ions, messengers, pH, voltage and a pleiad of other molecules constituting living cells. In this paper, we present results using various commercially available fluorescent probes as well as some developed in our laboratory and discuss the advantages and limitations of these probes in confocal microscopy studies of the cardiovascular system.
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    Cyclosporin A binding in mitochondrial cyclophilin inhibits the permeability transition pore and protects hearts from ischaemia/reperfusion injury (1997)
    Springer
    Molecular and cellular biochemistry 174 (1997), S. 167-172 
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    ISSN: 1573-4919
    Keywords: cyclosporin A ; mitochondrial permeability transition ; reperfusion injury ; cyclophilin ; oxidative stress ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract When loaded with high (pathological) levels of Ca2+, mitochondria become swollen and uncoupled as the result of a large non-specific increase in membrane permeability. This process, known as the mitochondrial permeability transition (MPT), is exacerbated by oxidative stress and adenine nucleotide depletion. These conditions match those that a heart experiences during reperfusion following a period of ischaemia. The MPT is caused by the opening of a non-specific pore that can be prevented by sub-micromolar concentrations of cyclosporin A (CsA). A variety of conditions that increase the sensitivity of pore opening to [Ca2+], such as thiol modification, oxidative stress, increased matrix volume and chaotropic agents, all enhance the binding of matrix cyclophilin (CyP) to the inner mitochondrial membrane in a CsA-sensitive manner. In contrast, ADP, membrane potential and low pH decrease the sensitivity of pore opening to [Ca2+] without affecting CyP binding. We present a model of pore opening involving CyP binding to a membrane target protein followed by Ca2+-dependent triggering of a conformational change to induce channel opening. Using the ischaemic/reperfused rat heart we have shown that the mitochondrial pore does not open during ischaemia, but does do so during reperfusion. Recovery of heart during reperfusion is improved in the presence of 0.2 µM CsA, suggesting that the MPT may be critical in the transition from reversible to irreversible reperfusion injury. (Mol Cell Biochem 174: 167–172, 1997)
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    Streptozotocin-induced diabetes increases (Ca2+-Mg2+)-ATPase activity in hepatic plasma membranes of rats: Involvement of protein kinase C (1998)
    Springer
    Molecular and cellular biochemistry 178 (1998), S. 311-316 
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    ISSN: 1573-4919
    Keywords: diabetes ; Ca2+-Mg2+-ATPase ; calcium ; liver plasma membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The alteration in calcium transport in the liver of rats with streptozocin(STZ)-diabetic state was investigated. STZ (6 mg/100 g body weight) was subcutaneously administered in rats, and 1 or 2 weeks later they were sacrificed by bleeding. STZ administration caused a remarkable elevation of serum glucose concentration. Liver calcium content was significantly increased by STZ administration. Hepatic plasma membrane (Ca2+-Mg2+)-ATPase activity was markedly elevated by STZ administration. This increase was completely abolished by the presence of staurosporine (10-7-10-5 M), an inhibitor of protein kinase C, in the enzyme reaction mixture, suggesting an involvement of protein kinase C signalling. Moreover, the STZ-induced increase in liver plasma membrane (Ca2+-Mg2+)-ATPase activity was significantly raised by the presence of okadaic acid (10-5 and 10-4 M). Meanwhile, the STZ-increased (Ca2+-Mg2+)-ATPase activity was not appreciably altered by the presence of anti-regucalcin IgG in the reaction mixture, indicating that the activatory protein regucalcin does not participate in the elevation of the enzyme activity. The present study demonstrates that STZ-induced diabetes causes the increase in hepatic plasma membrane (Ca2+-Mg2+)-ATPase activity of rats.
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    Role of cellular energetics in ischemia-reperfusion and ischemic preconditioning of myocardium (1998)
    Springer
    Molecular and cellular biochemistry 184 (1998), S. 393-400 
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    ISSN: 1573-4919
    Keywords: ATP synthase ; phosphorylation potential ; cytosolic pH ; reperfusion damage ; calcium ; free radicals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract A short period of ischemia followed by reperfusion produces a state of affairs in which the cells' potential for surviving longer ischemia is enhanced. This is called ischemic preconditioning. The effects of preconditioning are also related to the reperfusion damage which ensues upon tissue oxygenation. The role of the cellular energy state in reperfusion damage remains an enigma, although ischemic preconditioning is known to trigger mechanisms which contribute to the prevention of unnecessary ATP waste. In some species up to 80% of ATP hydrolysis in ischemia can be attributed to mitochondrial F1-F0-ATPase (ATP synthase), and a role for its inhibitor protein (IF1) in ATP preservation has been proposed. Although originally regarded as limited to large animals with a slow heart beat, inhibition by IF1 is probably a universal phenomenon. Coincidentally with ATPase inhibition, the decline in cellular ATP slows down, but even so the difference in ATP concentration between preconditioned and non-conditioned hearts is still small at the final stages of a long ischemia, when the beneficial effect of preconditioning is observable, although the energy state during reperfusion remains low in hearts which do not recover.
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    Alteration in calcium content and Ca2+-ATPase activity in the liver nuclei of rats orally administered carbon tetrachloride (1998)
    Springer
    Molecular and cellular biochemistry 185 (1998), S. 153-159 
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    ISSN: 1573-4919
    Keywords: calcium ; Ca2+-ATPase ; DNA fragmentation ; liver nuclei ; liver injury ; carbon tetrachloride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The alteration in calcium transport in the liver nuclei of rats orally administered carbon tetrachloride (CCl4) was investigated. Rats received a single oral administration of CCl4(5, 10, and 25%, 1.0ml/100 g body weight), and 5, 24 and 48 h later the animals were sacrificed. The administration of CCl4 (25%) caused a remarkable elevetion of calcium content in the liver tissues and the nuclei of rats. Liver nuclear Ca2+-ATPase activity was markedly decreased by CCl4 (25%) administration. The presence of dibutyryl cyclic AMP(10-4 and 10-3 M) or inositol 1,4,5-trisphosphate (10-6 and 10-5 M) in the enzyme reaction mixture caused a significant decrease in Ca2+-ATPase activity in the liver nuclei obtained from normal rat, while the enzyme activity was significantly increased by calmodulin (1.0 and 2.0 μg/ml). These signaling factor's effects were completely impaired in the liver nuclei obtained from CCl4 (25%)-administered rats. DNA fragmentation in the liver nuclei obtained from CCl4 -administered rats was significantly decreased by the presence of EGTA (2 mM) in the reaction mixture, suggesting that the endogenous calcium activates nuclear DNA fragmentation. The present study demonstrates that calcium transport system in the liver nuclei is impaired by liver injury with CCl4 administration in rats.
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    Effects of peroxide on contractility of coronary artery rings of different sizes (1999)
    Springer
    Molecular and cellular biochemistry 194 (1999), S. 159-164 
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    ISSN: 1573-4919
    Keywords: free radicals ; ischemia-reperfusion ; sarcoplasmic reticulum ; Ca2+-Mg2+-ATPase ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Reactive oxygen species (ROS, free radicals) produced during cardiac ischemia and reperfusion can damage the contractile functions of arteries. The sarcoplasmic reticulum (SR) Ca2+ pump in coronary artery smooth muscle is very sensitive to ROS. Here we show that contractions of de-endothelialized rings from porcine left coronary artery produced by the hormone Angiotensin II and by the SR Ca2+ pump inhibitors cyclopiazonic acid and thapsigargin correlate negatively with the tissue weight. In contrast, the contractions due to membrane depolarization by high KCl correlate positively. Peroxide also produces a small contraction which correlates negatively with the tissue weight. When artery rings are treated with peroxide and washed, their ability to contract with Angiotensin II, cyclopiazonic acid and thapsigargin decreases. Thus, the SR Ca2+ pump may play a more important role in the contractility of the smaller segments of the coronary artery than in the larger segments. These results are consistent with the hypothesis that ROS which damage the SR Ca2+ pump affect the contractile function of the distal segments more adversely than of the proximal segments.
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    Inhibition of calcium ATPase by phencyclidine in rat brain (1999)
    Springer
    Molecular and cellular biochemistry 194 (1999), S. 173-177 
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    ISSN: 1573-4919
    Keywords: calcium ; ATPase ; central nervous system ; phencyclidine ; inhibition ; in vitro ; in vivo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Phencyclidine (PCP) is a potent psychotomimetic drug of abuse and has profound effect on the functioning of the central nervous system (CNS). Many of the CNS functions are known to be mediated by calcium (Ca2+). In the present study we have investigated the effects of PCP on Ca2+ ATPase activity in rat brain both in vitro and in vivo. For in vitro studies, synaptic membrane fractions prepared from normal rat brain were incubated with PCP at different concentrations (25-100 μM) before the addition of substrate. For n vivo studies, rats were treated with a single moderate dose of PCP (10 mg/kg, IP) and animals were sacrificed at 1,2, 6 and 12 h after treatment. Ca2+ ATPase activity in synaptic membrane fractions was assayed by estimation of inorganic phosphate. PCP inhibited the Ca2+ ATPase in vitro in a concentration dependent manner with significant effect at 50 and 100 μM. A significant time-dependent reduction of the Ca2+ ATPase activity was evident in vivo. As early as 2 h after the treatment of rats with PCP the ATPase activity was significantly reduced. The reduction of Ca2+ ATPase observed even at 12 h after treatment suggesting a prolonged presence of the drug in the brain tissue. Further, kinetic studies in vitro indicated PCP to be a competitive inhibitor of Ca2+ ATPase with respect to the substrate, ATP. The present findings indicate that PCP inhibits synaptic membrane Ca2+ ATPase thus altering cellular Ca2+ homeostasis in CNS which may partially explain the pharmacological effects of the drug and/or its neurotoxicity.
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    Thrombin releases calcium from internal stores of ultraviolet C-treated V79 fibroblasts independent of phosphatidymositol bisphosphate hydrolysis: Role of oxidative stress (1999)
    Springer
    Molecular and cellular biochemistry 196 (1999), S. 23-30 
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    ISSN: 1573-4919
    Keywords: ultraviolet radiation ; oxidative stress ; calcium ; phospholipase A2 ; thrombin ; V79 fibroblast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract V79 fibroblasts were treated with ultraviolet (UV) C radiation alone as well as in conjunction with chronic oxidative stress. The effects of these treatments on calcium signaling were observed at 30 min post-irradiation. In the absence of extracellular calcium, thrombin released calcium from internal stores of UVC-irradiated V79 fibroblasts even after exposure to neomycin. In neomycin-treated control and chronic oxidative stress cells, no calcium release by thrombin was observed after chelation of external calcium. Calcium release by thrombin from internal stores of UV-irradiated and neomycin-treated cells was completely abolished by pretreatment with N-acetyl cysteine and dexamethasone. Cellular total soluble thiol content which is a good indicator of cellular reduced glutathione (GSH) level was significantly elevated 30 min after ultraviolet radiation, indicating an adaptive response after oxidative stress. Chronic oxidative stress alone resulted in a much smaller increase in GSH but chronic oxidative stress in conjunction with UVC produced a very prominent elevation in GSH levels. Our data suggest that thrombin can cause calcium release from internal stores of ultraviolet-irradiated fibroblasts which is independent of phosphatidylinositol bisphosphate hydrolysis and is directly related to the level of oxidative stress. Involvement of phopholipase A2 and a role for its products as possible mediators of calcium release from intracellular stores, is strongly indicated.
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    Effect of anti-regucalcin antibody on neutral phosphatase activity in rat liver cytosol: Involvement of endogenous regucalcin (1999)
    Springer
    Molecular and cellular biochemistry 197 (1999), S. 25-29 
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    ISSN: 1573-4919
    Keywords: regucalcin ; anti-regucalcin antibody ; protein phosphatase ; calcium ; rat liver cytosol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of anti-regucalcin monoclonal antibody on neutral phoshatase activity in rat liver cytosol was investigated. Phosphotyrosine, phosphoserine, and phosphothreonine were used as the substrate toward phosphatase asssy. Liver cytosolic phosphatase activity with three phosphoaminoacids was significantly increased in the presence of anti-regucalcin antibody (100 and 200 ng/ml) in the enzyme reaction mixture with calcium chloride (0.1 mM) or EGTA (1.0 mM). The effect of anti-regucalcin antibody was completely abolished in the presence of exogenous regucalcin (1.0 μM), indicating the involvement of endogenous regucalcin. The anti-regucalcin anti body- increased phosphatase activity was not significantly altered in the presence of trifluoperazine (20 μM), an antagonist of calmodulin, or akadaic acid (10 μM), an inhibitor of protein phosphatase, although these inihibitors caused a slight decrease in liver cytosolic phosphatase activity. The effect of endogenous regucalcin might be not related to calmodulin, and it was insensitive to okadaic acid. The present findings suggest that endogenous regucalcin is involved in the regulation of protein phasphatase in rat liver cytoplasm.
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    Calcium- and ADP-Magnesium-induced respiratory uncoupling in isolated cardiac mitochondria: Influence of cycolsporin A (1999)
    Springer
    Molecular and cellular biochemistry 202 (1999), S. 73-84 
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    ISSN: 1573-4919
    Keywords: isolated cardiac mitochondria ; cyclosporin A ; calcium ; magnesium ; oxidative phosphorylation ; high energy phosphate production ; Krebs cycle intermediates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract This study was designed to determine the effect of calcium and ADP-Mg on the oxidative phosphorylation in isolated cardiac mitochondria. The influence of cyclosporin A was also evaluated. The mitochondria were extracted from rat ventricles. Their oxidative phosphorylations were determined in two respiration media with different free Ca2+ concentrations. Respiration was determined with palmitoylcarnitine and either ADP- or ADP-Mg. With elevated free Ca2+concentrations and ADP-Mg, the transition state III to state IV respiration did not occurred. The ADP:O ratio was reduced. The phenomenon was not observed in the other experimental conditions (low free Ca2+ concentration with either ADP- or ADP-Mg or elevated free Ca2+ concentration with ADP-). Uncoupling was allied with a constant AMP production, which maintained an elevated ADP level in the respiration medium and prevented the return to state IV respiration. It was also observed in a respiration medium devoid of free Ca2+ when the mitochondria were pre-loaded with Ca2+. Uncoupling was inhibited by cyclosporin A. Furthermore, the Krebs cycle intermediates released from14C-palmitoylcarnitine oxidation revealed that succinate was increased by elevated free Ca2+ and ADP-Mg. Succinate is a FAD-linked substrate with low respiration efficiency. Its accumulation could account for the decreased ADP:O ratio. The Ca2+- and ADP-Mg-induced uncoupling might be partly responsible for the mechanical abnormalities observed during low-flow ischemia. (Mol Cell Biochem 000: 000-000, 1999)
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    The effect of immunization with porins on gut pathophysiological response in rats infected with salmonella typhimurium (1999)
    Springer
    Molecular and cellular biochemistry 201 (1999), S. 169-181 
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    ISSN: 1573-4919
    Keywords: Salmonella typhimurium ; diarrhoea ; porins ; calcium ; protein kinase C ; free radicals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Attachment of Salmonella typhimurium to epithelial surfaces elicit significant alterations in different cell signalling events which lead to the development of disease. The present investigation was conducted to evaluate the effect of immunization of rats with porins, on gut physiologic markers following challenge with S. typhimurium. Male albino Wistar rats were immunized with purified porins and challenged by intragastric infection with S. typhimurium. Electrolyte transport, levels of different second messengers and inflammatory mediators were studied. A net absorption of transepithelial fluxes of Na+ and Cl- in immunized-challenged group and secretion in infected group was found. Ca2+ and 3-O-methyl-D-glucose fluxes did not show any change. Significant increase in the levels of [Ca+]i, cAMP, membrane form of protein kinase C, prostaglandins, NADPH oxidase, Glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, total oxygen free radicals, reactive nitrogen intermediates, citrulline and lipid peroxidation was found in the infected group. However, in the immunized-challenged group, the values of all the parameters were found to be almost the same as that of control as well as immunized groups. Na+, K+-ATPase and calmodulin levels were unaltered in all the groups of animals. The results of this study thus suggest that immunization of rats with purified Salmonella porins followed by subsequent challenge with the organism might be helpful for the prevention of multiple physiologic derangements in isolated ideal cells.
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    Calcium-induced aggregation of neuroendocrine protein 7B2in vitro and its modulation by ATP (1995)
    Springer
    Molecular and cellular biochemistry 151 (1995), S. 39-47 
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    ISSN: 1573-4919
    Keywords: 7B2 ; calcium ; protein aggregation ; secretogranins ; protein sorting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract To study the behavior of the neuroendocrine polypeptide 7B2 in the presence of calcium, various fragments of this molecule were produced inEscherichia coli as fusion proteins to glutathione S-transferase (GST). Addition of millimolar concentrations of Ca2+ to purified preparations of hybrid molecules carrying the N-terminal segment of 7B2 induced precipitation in a manner dependent on protein and cation concentrations. This precipitation occurred at pH 7.5 but not at pH 5.2. It was augmented by 4 and 8 mM ATP, and reduced by 12 and 24 mM ATP. ADP had a similar but weaker effect. Calcium failed to cause precipitation of GST alone or of GST fused to the C-terminal peptide 7B2156–186. However, when the latter protein was mixed with a GST protein carrying a short fragment of the N-terminal region of 7B2, both proteins were precipitated by calcium. Except for the pH dependence, the behavior of 7B2 fusion proteins in the presence of calcium and adenosine nucleotides are reminiscent of those exhibited by chromogranins and secretogranins, which, like 7B2, are acidic proteins found in the secretory granules of a variety of neuroendocrine cells. As suggested for other granins, this property may underlie the segregation of 7B2 fragments into secretory granules.
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    Suppressed expression of calcium-binding protein regucalcin mRNA in the renal cortex of rats with chemically induced kidney damage (1995)
    Springer
    Molecular and cellular biochemistry 151 (1995), S. 55-60 
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    ISSN: 1573-4919
    Keywords: regucalcin ; calcium ; gene expression ; kidney damage ; rat kidney cortex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The alteration of Ca2+-binding protein regucalcin mRNA expression in the kidney cortex of rats administered cisplatin and cephaloridine, which can induce kidney damage, was investigated. Cisplatin (0.25, 0.5 and 1.0 mg/100 g body weight) or cephaloridine (25, 50 and 100 mg/100 g) was intraperitoneally administered in rats, and 1, 2 and 3 days later they were sacrificed. The alteration in serum findings after the administration of cisplatin (1.0 mg/100 g) or cephaloridine (50 and 100 mg/100 g) demonstrated chemically induced kidney damage; blood urea nitrogen (BUN) concentration increased markedly and serum inorganic phosphorus or calcium concentration decreased significantly. Moreover, the administration of cisplatin (1.0 mg/100 g) or cephaloridine (100 mg/100 g) caused a remarkable increase of calcium content in the kidney cortex of rats, indicating kidney damage. The expression of regucalcin mRNA in the kidney cortex was markedly reduced by the administration of cisplatin or cephaloridine in rats, when the mRNA levels were analyzed by Northern blotting using rat liver regucalcin cDNA (0.9 kb). The mRNA decreases were seen with the used lowest dose of cisplatin or cephaloridine. The present study clearly demonstrates that the mRNA expression of Ca2+-binding protein regucalcin in the kidney cortex of rats is decreased by chemically induced kidney damage.
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    Energy metabolism response to calcium activation in isolated rat hearts during development and regression of T3-induced hypertrophy (1995)
    Springer
    Molecular and cellular biochemistry 151 (1995), S. 99-106 
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    ISSN: 1573-4919
    Keywords: hyperthyroid heart ; high energy phosphates ; oxidative metabolism ; cardiac work ; calcium ; 31P-NMR spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of calcium activation on energy production was investigated in isolated perfused hearts from rats treated with triiodothyronine (T3) during 15 days (0.2 mg/kg/day) and in hearts of rats allowed to recover after T3-treatment during 15 days. Changes in phosphorylated compound concentrations were followed in the isolated hearts perfused with a glucose-pyruvate medium by 31P-NMR spectroscopy, when the external calcium concentration was increased from 0.5–1, 1.5 and 2 mM. As expected, T3-treatment resulted in the hypertrophy of the heart (50% increase in HW/BW) that was nearly reversible 15 days after discontinuation of the treatment. When compared to controls, creatine, phosphocreatine (PCr) and glycogen contents were lower (58, 24 and 17% decrease respectively) in the hypertrophied hearts and higher (10, 14 and 18% respectively) after regression of hypertrophy. Intracellular pH, ATP, inorganic phosphate concentrations and the phosphorylation potential were not altered under T3-treatment and after regression of hypertrophy, while calculated free ADP concentration was lower in hypertrophied hearts (control: 40±2 μM, T3-treatment: 21±1 μM, regression: 37±1 μM). Increasing the calcium concentration induced a similar increase in left ventricular developed pressure in the three groups of hearts, with inorganic phosphate concentration increasing with cardiac work. The PCr concentration slightly decreased while the ATP concentration did not change. In spite of different initial PCr concentrations, the evolutions of PCr and Pi concentrations for each stepwise increase in external calcium were similar in the three groups. It is concluded that, in spite of the well-known decrease in efficiency induced by the drug, the mechanisms of PCr (ATP) production ramain able to respond to an acute moderate increase in energy demand provoked by a physiological stimulus. This adaptation also persists after the treatment when the energy metabolism balance is apparently improved.
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    Properties of the sarcoplasmic reticulum Ca2+-pump in coronary artery skinned smooth muscle (1995)
    Springer
    Molecular and cellular biochemistry 151 (1995), S. 149-155 
    Details
    ISSN: 1573-4919
    Keywords: SERCA2 ; ATPase ; calcium ; transport ; vascular
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Pig coronary artery cultured smooth muscle cells were skinned using saponin. In the presence of an ATP-regenerating system and oxalate, the skinned cells showed an ATP-dependent azide insensitive Ca2+-uptake which increased linearly with time for 〉1 h. The Ca2+-uptake occurred with Km values of 0.20±0.03 μM for Ca2+ and 400±34 μM for MgATP2−. Thapsigargin and cyclopiazonic acid inhibited this uptake with IC50 values of 0.13±0.02 and 0.56±0.04 μM, respectively. These properties of SR Ca2+-pump are similar to those reported for membrane fractions isolated from fresh smooth muscle of coronary artery and other arteries. However, optimum pH of the uptake in the skinned cells (6.2) was lower than that reported previously using isolated membranes (6.4–6.8).
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    Implication of the nucleus in excitation contraction coupling of heart cells (1996)
    Springer
    Molecular and cellular biochemistry 154 (1996), S. 113-121 
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    ISSN: 1573-4919
    Keywords: heart cells ; nucleus ; calcium ; R-type channel ; excitation-contraction coupling ; pacemaker activity ; Fura-2 ; Fluo-3 ; confocal microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In the present study, Fluo-3 Ca2+ measurement and confocal microscopy techniques were used in order to localize cytosolic [ ]c and nuclear [ ]n free Ca2+ distribution in resting and spontaneously contracting single heart cells from 10-day-old chick embryos. In resting single cells, the concentration of Ca2+ in the cytoplasm was lower than that in the nucleus. Increasing cytosolic free Ca2+ from 100–1600 nM gradually increased [Ca2+]n with a maximum capacity near 1200 nM. Results from Fura-2 microfluorometry and Fluo-3 confocal microscopy suggest a potential cross talk between the increase of cytosolic free Ca2+ and the uptake and release of Ca2+ by the nucleus during spontaneous contraction of single myocytes. Calcium waves in spontaneously contracting cells were found to spread from one cell to the next with the nucleus acting as a fluorescent beacon in which Ca2+ levels remained elevated for several milliseconds even after cytosolic Ca2+ had returned to near basal values. These results strongly suggest that the nucleus plays a negative and positive feedback role in controlling cytosolic free Ca2+ concentration during excitation-contraction coupling in heart cells.
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    Role of hydroxyl radical in the oxidant H2O2-mediated Ca2+ release from pulmonary smooth muscle mitochondria (1996)
    Springer
    Molecular and cellular biochemistry 159 (1996), S. 95-103 
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    ISSN: 1573-4919
    Keywords: hydroxyl radical ; oxidant ; hydrogen peroxide ; smooth muscle tissue ; mitochondria ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract We sought to investigate the mechanism(s) by which the oxidant H2O2 stimulates Ca2+ release from mitochondria of bovine pulmonary vascular smooth muscle tissue and to test the hypothesis that hydroxyl radical is involved in this phenomenon. Treatment of the smooth muscle tissue with 1 mM H2O2 dramatically stimulated hydroxyl radical generation as measured by methane (CH4) production by GLC using dimethylsulfoxide (DMSO) as the substrate. Pretreatment of the mitochondria with the hydroxyl radical scavanger dimethylthiourea (DMTU) prevented the increase in CH4 production caused by H2O2. In the absence of EGTA, H2O2 caused stimulation of Ca2+ release from mitochondria occurred with a lag time of about 4 min. Addition of EGTA to Ca2+ loaded mitochondria resulted an immediate loss of Ca2+ and that has been found to be augmented by H2O2. The release of Ca2+ by H2O2 did not appear to occur with concommitant increase in sucrose entry into, K+ release from, and swelling of mitochondria when the Ca2+ cycling was prevented by EGTA. These observations suggested that H2O2-mediated Ca2+ release from bovine pulmonary vascular smooth muscle tissue mitochondria occurred (i) through the involvement of hydroxyl radical; (ii) via specific pathway(s); and (iii) did not appear to happen primarily via nonspecific ‘pore’ formation.
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    Inhibitory effect of calcium-binding protein regucalcin on ribonucleic acid synthesis in isolated rat liver nuclei (1997)
    Springer
    Molecular and cellular biochemistry 173 (1997), S. 169-175 
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    ISSN: 1573-4919
    Keywords: regucalcin ; calcium-binding protein ; calcium ; nuclear RNA synthesis ; regenerating ratliver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of regucalcin, a Ca2+-bindingf protein isolated from rat livercytosol, on ribonucleic acid (RNA) synthesis in the nuclei of normal ratliver and of regenerating rat liver was investigated. The liver weight at 1day after partial hepatectomy was increased about 50% of that ofsham-operated (control) rats. Calcium chloride (1.0-20 µM Ca2+ asfinal concentration) was added into the reaction mixture of nuclear RNAsynthesis. RNA synthesis was established by incorporation of [3H]-uridine5'-triphosphate (UTP) into the nuclear RNA. Addition of Ca2+ (5 and 10µM) caused a significant increase of RNA synthesis in the nuclei fromcontrol rat liver. Such effect of Ca2+ was potentiated in the nuclei ofregenerating liver; nuclear RNA synthesis was increased about 2 fold by the1.0 and 2.5 µM Ca2+ addition. The stimulatory effect of Ca2+ wassignificantly inhibited by the presence of a-amanitin (10-8 M), an inhibitorof RNA polymerase II. The presence of regucalcin (0.25 and 0.5 µM)significantly inhibited RNA synthesis in the nuclei from control rat liverand from regenerating rat liver. The inhibitory effect of regucalcin wasremarkable in the presence of EGTA (0.5 mM), and it was weakened by theaddition of Ca2+ (5 µM). Such regucalcin effect was not seen in thepresence of a-amanitin. The presence of anti-regucalcin IgG in the reactionmixture significantly increased RNA synthesis in the nuclei from control ratliver, indicating that the endogenous regucalcin may be involved in nuclearRNA synthesis. The present resuits demonstrate that regucalcin can inhibitnuclear RNA synthesis in rat liver. Regucalcin may have an inhibitory rolein the regulation of liver nuclear RNA synthesis.
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    Second messenger role of magnesium in pancreatic acinar cells of the rat (1995)
    Springer
    Molecular and cellular biochemistry 149-150 (1995), S. 175-182 
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    ISSN: 1573-4919
    Keywords: rat pancreas ; cholecystokinin ; magnesium ; calcium ; acetylcholine ; amylase secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Application of either acetylcholine (ACh, 10−5 M) or cholecystokininoctapeptide (CCK-8, 10−8 M) to the isolated rat pancreas elicited large increases in amylase secretion, radiolabelled45Ca2+ influx and cytosolic free calcium [Ca2+]i levels in zero and normal (1.1 mM) extracellular magnesium [Mg2+]o. Elevated [Mg2+]o significantly (p〈0.001) reduced the secretagogueevoked secretory responses and Ca2+ mobilisation. Stimulation of pancreatic segments with either ACh (10−5 and 10−6 M) or CCK-8 (10−8 and 10−10 M) resulted in marked elevation in Mg2+ concentration in effluent samples (net efflux). On removal of either ACh or CCK-8, Mg2+ concentration returned to resting level. In pancreatic acinar cells loaded the flourescent dye magfura, ACh and CCK-8 evoked marked reduction in cytosolic free Mg2+ concentration [Mg2+]i compared to the resting value of 0.82±0.03 mM (n=50) in normal medium in the absence of secretagogues. In elevated [Mg2+]o (10 mM) medium, [Mg2+]i rises to 0.98±0.04 mM (n=6). Addition of CCK-8 led to only a small reduction in [Mg2+ i in elevated [Mg2+]o. In Mg2+ loaded pancreatic acinar cells, Mg2+ is released in a time dependent manner and this efflux of Mg2+ was sensitive to sodium, extracellular amiloride (1 mM), dinitrophenol (10 mM) and lidocaine (1 mM). The results indicate that Mg2+ is acting as an intracellular messenger to regulate the mobilisation of Ca2+ which in turn mediates enzyme secretion.
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    Regulation of Ca2+ homeostasis by glucose metabolism in rat brain (1997)
    Springer
    Molecular and cellular biochemistry 176 (1997), S. 317-326 
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    ISSN: 1573-4919
    Keywords: calcium ; metabolism ; glucose ; hypoxia ; rat brain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In a previous communication we reported that glucose deprivation from KHRB medium resulted in a marked stimulation of Ca2+ uptake by brain tissue, suggesting a relationship between glucose and Ca2+ homeostasis in brain tissue [17]. Experiments were carried out to investigate the significance of glucose in Ca2+ transport in brain cells. The replacement of glucose with either D-methylglucoside or 2-deoxyglucose, non-metabolizable analogues of glucose, resulted in stimulation of Ca2+ uptake just as by glucose deprivation. These data show that glucose metabolism rather than glucose transfer was necessary to stimulate Ca2+ uptake in brain tissue. Inhibition of glucose metabolism with either NaF, NaCN, or iodoacetate resulted in stimulation of Ca2+ uptake similar to that produced by glucose deprivation. These results lend further support for the concept that glucose metabolism is essential for Ca2+ homeostasis in brain. Anoxia promotes glucose metabolism through glycolytic pathway to keep up with the demand for ATP by cellular processes (the Pasteur effect). Incubation of brain slices under nitrogen gas did not alter Ca2+ uptake by brain tissue, as did glucose deprivation and the inhibitors of glucose metabolism. We conclude that glucose metabolism resulting in the synthesis of ATP is essential for Ca2+ homeostasis in brain. Verapamil and nifedipine which block voltage-gated Ca2+ channels, did not alter Ca2+ uptake stimulated by glucose deprivation, indicating that glucose deprivation-enhanced Ca2+ uptake was not mediated by Ca2+ channels. Tetrodotoxin which specifically blocks Na+ channels, abolished Ca2+ uptake enhanced by glucose deprivation, but had no effect on Ca2+ uptake in presence of glucose (controls). These results suggest that stimulation of Ca2+ uptake by glucose deprivation may be related to Na+ transfer via Na-Ca exchange in brain.
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    Characterization of phospholipase A1, A2, C activity in Ureaplasma urealyticum membranes (1999)
    Springer
    Molecular and cellular biochemistry 201 (1999), S. 159-167 
    Details
    ISSN: 1573-4919
    Keywords: phospholipases A1, A2 and C ; Ureaplasma urealyticum ; calcium ; plasma membrane ; phospholipids ; pH ; detergents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The presence of endogenous phospholipase A (PL-A) activity of U. urealyticum hydrolyzing the acyl ester bond and phospholipase C (PL-C) activity hydrolyzing the phosphodiester bond is primarily localized in the membranes of ureaplasmas. Characterization of the membrane PL-A and PL-C activity in exponential growing cells of serovars 3, 4, and 8 was investigated. The pH optimum was about 8.5-9 for phospholipase A1 (PL-A1) in the three serovars. A more acidic pH optimum of 6 was observed for phospholipase A2 (PL-A2) enzymes in serovars 3 and 4. However, a very significant stimulation of PL-A2 activity in serovar 8 occurred around pH 7. The specific activity of PL-A2 was always 50-100 fold higher than PL-A1 activity in the pH range studied. Ca2+ ions only slightly stimulated PL-A1 activity in all 3 serovars. PL-A2 activity was stimulated about 6-fold from 0.5-0.8 mM Ca2+ ion concentrations for serovar 3 and 12-fold for serovar 8. Only lower concentrations (0.2-0.4 mM) of calcium stimulated PL-A2 activity in serovar 4. EDTA inhibition corresponded to Ca2+ stimulation for PL-A2 activity for serovars 3 and 8. A general stimulation of PL-A2 activity by diethyl ether was evident but the degree of stimulation varied with the serovar. Sodium deoxycholate enhanced PL-A activity of serovars 4 and 3, but partially inhibited that of serovar 8. PL-A activity in the three serovars were not significantly affected by p-hydroxymercuribenzoate, a marker of -SH groups in the enzyme. All 3 serovars were inactivated by heat. A broad pH optimum for PL-C activity was evident around 7-8. Diethyl ether enhanced PL-C activity of serovar 8. Sodium deoxycholate and heat were inhibitory to PL-C activity. The results demonstrate that the major characteristics of ureaplasma membrane bound PL-A and PL-C are basically similar to those of other mollicutes and bacteria. However, the major differences in the specific characteristics of specially PL-A1 and PL-A2 suggest that the ureaplasma phospholipases are unique enzymes different from the phospholipases of bacteria. Both the PL-A and PL-C enzymes function over the broad range at which ureaplasma can grow, pH 5-9 essential for survival. The ureaplasma PL-As are also markedly different from one serovar to another. This variation in specific activity could contribute significantly to differences in virulence among serovars in specific host milieus. There is significant variation from acidic pH of the vagina and alveolar surface of the lung to a more neutral pH of the endometrium and placenta. There are marked differences in calcium concentrations under specific circumstances in various host tissues. Thus the differences in specific activity among the phospholipases of the serovars of U. urealyticum may be of physiological importance in interactions with host tissues and pathogenesis of disease.
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    The structure and interactions of Ca2+-ATPase (1995)
    Springer
    Bioscience reports 15 (1995), S. 263-281 
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    ISSN: 1573-4935
    Keywords: ATPase ; calcium ; structure ; X-ray crystallography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Electron crystallographic studies on membrane crystals of Ca2+-ATPase reveal different patterns of ATPase-ATPase interactions depending on enzyme conformation. Physiologically relevant changes in Ca2+ concentration and membrane potential affect these interactions. Ca2+ induced difference FTIR spectra of Ca2+-ATPase triggered by photolysis of caged Ca2+ are consistent with changes in secondary structure and carboxylate groups upon Ca2+ binding; the changes are reversed during ATP hydrolysis suggesting that a phosphorylated enzyme form of low Ca2+ affinity is the dominant intermediate during Ca2+ transport. A two-channel model of Ca2+ translocation is proposed involving the membrane-spanning helices M2–M5 and M4, M5, M6 and M8 respectively, with separate but interacting Ca2+ binding sites.
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    The mechanism of coupling chemical and physical reactions by the calcium ATPase of sarcoplasmic reticulum and other coupled vectorial systems (1995)
    Springer
    Bioscience reports 15 (1995), S. 283-287 
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    ISSN: 1573-4935
    Keywords: ATPase ; calcium ; transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The coupling of the chemical reaction of ATP hydrolysis to the transport of calcium from the cytoplasm into the lumen of sarcoplasmic reticulum vesicles can be defined by a set of rules that define alternating changes in the specificities of the enzyme for catalysis of chemical and physical reactions.
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    Fluorometric study on conformational changes in the catalytic cycle of sarcoplasmic reticulum Ca2+-ATPase (1995)
    Springer
    Bioscience reports 15 (1995), S. 317-326 
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    ISSN: 1573-4935
    Keywords: ATPase ; calcium ; conformational change ; EDANS ; fluorescence ; sarcoplasmic reticulum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Changes in the fluoresence ofN-acetyl-N′-(5-sulfo-1-naphthyl)ethylenediamine (EDANS), being attached to Cys-674 of sarcoplasmic reticulum Ca2+-ATPase without affecting the catalytic activity, as well as changes in the intrinsic tryptophan fluorescence were followed throughout the catalytic cycle by the steady-state measurements and the stopped-flow spectrofluorometry. EDANS-fluorescence changes reflect conformational changes near the ATP binding site in the cytoplasmic domain, while tryptophan-fluorescence changes most probably reflect conformational changes in or near the transmembrane domain in which the Ca2+ binding sites are located. Formation of the phosphoenzyme intermediates (EP) was also followed by the continuous flow-rapid quenching method. The kinetic analysis of EDANS-fluorescence changes andEP formation revealed that, when ATP is added to the calcium-activated enzyme, conformational changes in the ATP binding site occur in three successive reaction steps; conformational change in the calcium enzyme substrate complex, formation of ADP-sensitiveEP, and transition of ADP-sensitiveEP to ADP-insensitiveEP. In contrast, the ATP-induced tryptophan-fluorescence changes occur only in the latter two steps. Thus, we conclude that conformational changes in the ATP binding site in the cytoplasmic domain are transmitted to the Ca2+-binding sites in the transmembrane domain in these latter two steps.
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    Ca2+ binding and translocation by the sarcoplasmic reticulum ATPase: Functional and structural considerations (1995)
    Springer
    Bioscience reports 15 (1995), S. 327-339 
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    ISSN: 1573-4935
    Keywords: ATPase ; calcium ; sarcoplasmic reticulum ; translocation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Three experimental systems are described including sarcoplasmic reticulum (SR) vesicles, reconstituted proteoliposomes, and recombinant protein obtained by gene transfer and expression in foreign cells. It is shown that the Ca2+ ATPase of sarcoplasmic reticulum (SR) includes an extramembranous globular head which is connected through a stalk to a membrane bound region. Cooperative binding of two calcium ions occurs sequentially, within a channel formed by four clustered helices within the membrane bound region. Destabilization of the helical cluster is produced following enzyme phosphorylation by ATP at the catalytic site in the extramembranous region. The affinity and orientation of the Ca2+ binding site are thereby changed, permitting vectorial dissociation of bound Ca2+ against a concentration gradient. A long range linkage between phosphorylation and Ca2+ binding sites is provided by an intervening peptide segment that retains high homology in cation transport ATPases, and whose function is highly sensitive to mutational perturbations.
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    Use of thapsigargin to study Ca2+ homeostasis in cardiac cells (1995)
    Springer
    Bioscience reports 15 (1995), S. 341-349 
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    ISSN: 1573-4935
    Keywords: ATPase ; calcium ; sarcoplasmic reticulum ; thapsigargin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Several reports have documented that thapsigargin is a potent inhibitor of the SR Ca2+ ATPase isolated from cardiac or skeletal muscle. We have characterized the specificity of this agent in intact rat cardiac myocytes using cells maintained in the whole cell voltage clamp configuration. We have shown that thapsigargin decreases the magnitude of the Ca2+ transient and the twitch by about 80% while it slows the decay rate for these responses. These changes were not accompanied by any alterations in sarcolemmal currents or in the trigger Ca2+ generated by the inward calcium current. Taken together these results reveal that the action of thapsigargin is restricted to the SR Ca2+ ATPase in intact cardiac myocytes. Furthermore, it is demonstrated unambiguously that SR intracellular Ca2+ stores are an absolute requirement for the development of contractile tension in rat heart myocytes. It is shown that thapsigargin is a valuable probe to examine the importance of SR pools of Ca2+ and the role of the Ca2+ ATPase in intact myocytes as well as in genetically altered heart cells.
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    How do Ca2+ ions pass through the sarcoplasmic reticulum membrane (1995)
    Springer
    Bioscience reports 15 (1995), S. 377-385 
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    ISSN: 1573-4935
    Keywords: ATPase ; calcium ; sarcoplasmic reticulum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract We propose an overview of the mechanism of Ca2+ transport through the sarcoplasmic reticulum membrane via the Ca2+-ATPase. We describe cytoplasmic calcium binding, calcium occlusion in the membrane and lumenal calcium dissociation. A channel-like structure is discussed and related to structural data on the membranous domain of the Ca2+-ATPase.
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    Reactive Oxygen and Nitrogen Species Regulate Mitochondrial Ca2+ Homeostasis and Respiration (1997)
    Springer
    Bioscience reports 17 (1997), S. 53-66 
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    ISSN: 1573-4935
    Keywords: Superoxide ; nitrogen monoxide ; NO, peroxynitrite ; calcium ; membrane potential ; cytochrome oxidase ; apoptosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The reduction of molecular oxygen to water provides most of the biologically useful energy. However, oxygen reduction is a mixed blessing because incompletely reduced oxygen species such as superoxide or peroxides are quite reactive and can, when out of control, cause damage. In mitochondria, where most of the oxygen utilized by eukaryotic cells is reduced, the dichotomy of oxygen shows itself best. Thus, reactive oxygen is a threat to them, as is evident from oxidative damage to mitochondrial lipids, proteins, and nucleic acids. Reactive oxygen, in the form of peroxides, also serves useful functions in mitochondria. This is exemplified by the control of mitochondrial and cellular calcium homeostasis, whose understanding has improved greatly during the last few years. An exciting new aspect is the discovery that nitric oxide and congeners have an enormous impact on mitochondria. Physiological concentrations of nitrogen monoxide (NO) at physiological cellular oxygen pressure inhibit cytochrome oxidase and thereby respiration. A transient inhibition of cytochrome oxidase by NO appears to be used in at least some forms of cell signalling. Peroxynitrite, the product of the reaction between superoxide and NO, can stimulate the specific calcium release pathway from mitochondria by oxidizing some vicinal thiols in mitochondria. There is evidence mounting that mitochondrial calcium handling and its modulation by reactive oxygen and nitrogen species is important for necrotic and apoptotic cell death.
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    Heterologous expression of sarcoplasmic reticulum Ca2+-ATPase (1996)
    Springer
    Bioscience reports 16 (1996), S. 107-113 
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    ISSN: 1573-4935
    Keywords: ATPase ; calcium ; expression systems ; sarcoplasmic reticulum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract In recent years, expression of rabbit sarcoplasmic reticulum (SR) Ca2+-ATPase in heterologous systems has been a widely used strategy to study altered enzymes generated by site-directed mutagenesis. Various eukaryotic expression systems have been tested, all of them yielding comparable amounts of recombinant protein. However, the relatively low yield of recombinant protein obtained so far suggests that novel purification techniques will be required to allow further characterization of this enzyme based on direct ligand-binding measurements.
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    Catalytic and structural modifications of sarcoplasmic reticulum and plasma membrane (Ca2+ + Mg2+)ATPases induced by organic solutes that accumulate in living systems (1996)
    Springer
    Bioscience reports 16 (1996), S. 115-127 
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    ISSN: 1573-4935
    Keywords: ATPase ; calcium ; magnesium ; plasma membrane ; polyols ; organic solutes ; sarcoplasmic raticulum ; urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Organic solutes such as urea, methylamines, polyols and amino acid can accumulate in the cytoplasm of cells to compensate for hyperosmotic conditions in the external medium. Whereas urea is considered to be typical of solutes that destabilize structure and function of proteins, methylamines, polyols and some amino acids appear to have the opposite effect, and can also compensate for the perturbing effects of urea. These effects have been extensively analyzed for a variety of proteins in terms of global changes in enzyme structure and acceleration or inhibition of overall reaction rates. Here the influence of these solutes on sarcoplasmic reticulum and plasma membrane (Ca2+ + Mg2+)ATPases is reviewed. The focus is on the changes induced by “perturbing” and “stabilizing” solutes at specific steps of the catalytic cycles of these enzymes, which can run forward (leading to ATP hydrolysis) and backward (leading to ATP synthesis). Structural changes promoted by osmolytes are correlated with functional changes, especially those that are related to energy coupling.
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    Synthesis of caprolactamates of group II metals (1995)
    Springer
    Russian chemical bulletin 44 (1995), S. 2179-2182 
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    ISSN: 1573-9171
    Keywords: ɛ-caprolactam ; caprolactamates of magnesium ; calcium ; strontium, and barium ; anionic polymerization of lactams
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Caproiactamates of alkaline-earth metals and magnesium of the general formula $${\text{M[}}{\text{O}}]_2 $$ , where M = Mg, Ca, Sr, and Ba, were synthesized from alkoxides, hydrides, and organometallic compounds of these metals and ɛ-caprolactam. The catalytic activities of caprolactamates obtained under conditions of anionic polymerization of ɛ-caprolactam were compared. It was demonstrated that the purest caprolactamates and, hence, the most effective catalysts of anionic polymerization of lactams can be obtained from organometallic and hydride compounds of these metals. The reactivities of alkoxides of the alkaline-earth metals and magnesium increase in metallation reactions of ɛ-caprolactam in the order Mg 〈 Ca 〈 Sr 〈 Ba.
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    Oxidation of acetophenone in a high temperature open-tubular capillary column liquid chromatographic system (1995)
    Springer
    Chromatographia 40 (1995), S. 99-101 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; High temperature open-tubular columns ; Solvent make-up ; Acetophenone oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Acetophnone, a substance stable at room temperature, is readily oxidizes in a high temperature open tubular liquid chromatographic system by the residual oxygen in the mobile phase. The oxidation product is less UV absorptive and detection sensitivity decreases greatly. To prevent the oxidation, through degassing of the mobile phase is necessary.
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    URL: http://dx.doi.org/10.1007/BF02274615
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    The removal of endotoxins from protein solutions using column packings with aminated poly (γ-methyl L-glutamate) spheres (1995)
    Springer
    Chromatographia 40 (1995), S. 33-38 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Endotoxins ; Lipopolysaccharide ; Aminated poly(γ-methyl L-glutamate) ; Bovine serum albumin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method is described for the selective removal of endotoxins from various protein solutions using columns packed with aminated poly (γ-methyl L-glutamate) (PMLG-NH2) spheres. The PMLG-NH2 adsorbents showed a high adsorbing activity for endotoxins which had an ionic strength of μ=0.05–1.0 and pH 5.0–9.0. The endotoxin-adsorbing capacity per millitre of the wet adsorbent increased from 0.40 to 1.35 mg (E. coli O111: B4 LPS) at μ=0.2 and pH 7.0 while the aminogroup content of the adsorbent increased from 0.8 to 3.5 meq g−1. The PMLG-NH2-3.5 has an amino-group content of 3.5 meq g−1. This column packing selectively adsorbed endotoxins, without loss of the protein, from a γ-globulin or cytochromec solution which contained endotoxins at μ=0.05 and pH 7.0. On the other hand, when bovine serum albumin (BSA) was present in solution with endotoxins, both the endotoxins and the BSA were adsorbed by the column. The BSA-adsorbing activity increased with increasing amino-group content of the adsorbent. However, this undesirable adsorption was suppressed with increasing ionic strength of the buffer. As a result, when the packing which had an amino-group content of 1.5 meg g−1 was used in conditions of μ=0.2 and pH 7.0, the endotoxins were removed from a BSA-containing solution without affecting the recovery of the BSA.
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    URL: http://dx.doi.org/10.1007/BF02274604
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    Analysis of lignin degradation products by capillary electrophoresis (1995)
    Springer
    Chromatographia 40 (1995), S. 51-57 
    Details
    ISSN: 1612-1112
    Keywords: Column electrophoresis ; Column liquid chromatography ; Phenolic lignin degradation compounds ; Sugar degradation products ; Quantitative analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method for the quantitative analysis of phenolic lignin degradation products by capillary electrophoresis (CE) with on-column UV detection has been developed. The liquid biomass solutions contain low molecular hemicellulosic sugars and phenolic lignin degradation products with various degrees of polymerization. Special attention has been paid to the monomeric phenolic components of lignin degradation fragments, e.g. derivatives of phenolic acids, aldehydes, and alcohols. Uncoated fused silica capillaries and borate-phosphate buffer systems at moderate pH conditions were used in order to separate the compounds of interest. To provide validation of the method, the same samples were analyzed independently by HPLC using gradient elution on a RP-C18 column. As sugar degradation fragment, furan-2-carboxylic acid was detected.
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    URL: http://dx.doi.org/10.1007/BF02274608
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    Liquid chromatography of phenolic compounds in natural water using on-line trace enrichment (1995)
    Springer
    Chromatographia 40 (1995), S. 85-90 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Phenolic compounds ; Ion-pair solid phase extraction ; On-line trace enrichment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Two packing materials, C18 and PLRP-S, are studied for on-line trace enrichment of phenolic compounds in water. Various precolumns of different internal diameter are also tested and the addition of an ion-pair reagent to increase retention and thus, breakthrough volumes of phenolic compounds, is studied. Best results are obtained when a PLRP-S precolumn is coupled on-line with a C18 analytical column and DAD detector. Addition of TBA considerably increases breakthrough volumes. In contrast, when a C18 precolumn is used, breakthrough volumes are lower and it is impossible to determine TCP and PCP, under the experimental conditions used, because of interference of other nonpolar compounds in the samples. The performance of the system is evaluated with river and tap water and the preconcentration of 10 ml of sample in a PLRP-S precolumn involves a linear range between 1 μg 1−1 and 20 μl−1 and limits of determination between 0.5 μg l−1 and 1 μg l−1 are obtained.
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    URL: http://dx.doi.org/10.1007/BF02274612
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    Screening of water samples for polar organic micropollutants using on-column sample enrichment (1995)
    Springer
    Chromatographia 40 (1995), S. 631-637 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Trace analysis ; Pesticides in tap water ; Aromatic sulphonates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Methodology and instrumentation are described which allow chromatographic screening of water samples under substantially simplified conditions and at reduced cost. A single column is used to accomplish sample extraction, trace enrichment, and separation. The performance of such a system is demonstrated, and the results compared with conventionally used concepts.
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    URL: http://dx.doi.org/10.1007/BF02315129
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    Analysis of pyrithiones by reversed-phase high-performance liquid chromatography (1995)
    Springer
    Chromatographia 40 (1995), S. 669-673 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Transchelation ; Zinc pyrithione and related compounds ; Antidandruff formulations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An analytical procedure has been developed for the determination of zinc pyrithione in antidandruff formulations. Zinc pyrithione was converted into a stable copper complex and then analysed by reversed-phase HPLC. The proposed method allows the separation of the analyte from related pyrithiones and therefore is able to verify the compliance of cosmetic preparations with current legislation.
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    URL: http://dx.doi.org/10.1007/BF02315135
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    Marked differences between acetonitrile/water and methanol/water mobile phase systems on the thermodynamic behavior of benzodiazepines in reversed phase liquid chromatography (1995)
    Springer
    Chromatographia 41 (1995), S. 84-87 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Benzodiazepines ; Solvent effects ; ACN clusters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Two different methods were used to determine the separation factor α at different temperatures and the Gibbs-Helmholtz parameters (Δ(ΔH), Δ(ΔS)) of two adjacent benzodiazepines on a chromatogram were obtained from plots of lnα versus 1/T. We first studied each factor (fraction of water ϕ in the ACN/water mixture and column temperatureT), which controls the retention mechanism, and then we examined the simultaneous variation of all these factors. The changes in Δ(ΔH) and Δ(ΔS) in relation to a volume fraction of water ϕ in an ACN/water mixture were examined. In the ACN/water system, Δ(ΔH) was fairly constant in the acetonitrile region of ϕ≤0.52 and appears to be a roughly linear function of ϕ for ϕ≥0.52. In this system Δ(ΔS) is approximately a parabolic function of ϕ with an optimum at ϕ≅0.52. The retention mechanism of ten benzodiazepines was found to be significantly different in the methanol/water and ACN/water mixtures. The separation optimization of these ten benzodiazepines was then considered. A fraction of water of 0.43 in the ACN/water mixture and a column temperature of 44°C gave the most efficient separation conditions in the ACN/water mixture.
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    URL: http://dx.doi.org/10.1007/BF02274199
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    HPLC determination of urinary 2,4- and 2,6-toluendiamines as potential degradation products of polyurethane breast implants (1995)
    Springer
    Chromatographia 41 (1995), S. 661-664 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polyurethane degradation products ; 2,4- and 2,6-toluendiamine ; Urine analysis ; Breast implants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A reversed-phase HPLC method has been developed for the urinary determination of mutagenic 2,4- and 2,6-toluendiamines. These amines are degradation products of polyurethane, a material used to cover textured silicone breast implants. FMOC-Cl was used as fluorescent derivatising agent in order to obtain a limit of detection of 15 ng/ml in urine. Pre-treatment of urine samples was by liquid/liquid extraction and urine specimens of patients after surgury were analysed.
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    URL: http://dx.doi.org/10.1007/BF02267801
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    HPLC analysis of flavonoids and phenolic acids and aldehydes inEucalyptus spp. (1995)
    Springer
    Chromatographia 41 (1995), S. 657-660 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polyphenols ; Flavonoids ; Phenolic acids and aldehydes ; Eucalyptus spp.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Standards of the polyphenols occurring in wood, bark and leaf extracts ofEucalyptus spp. (i.e. flavonoids and phenolic acids and aldehydes) have been analyzed by HPLC using reversed phase columns, gradient elution and diode-array detection. The conditions used are reported.
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    URL: http://dx.doi.org/10.1007/BF02267800
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    Polymer encapsulated stationary phases with improved efficiency (1995)
    Springer
    Chromatographia 40 (1995), S. 657-661 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed phases ; Polyencapsulated silica ; Polyacrylates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary By copolymerization of silica modified with vinyl groups and acrylic acid esters in suspension highly efficient, polymeric-encapsulated stationary-phases can be prepared. The suspending liquid has to be selected such that the monomers are at least partially adsorbed on the surface and the polymer formed does not precipitate. Under these conditions stationary phases capable of speedy mass transfer can be prepared, where the reduced plate heights are between 2 and 3. The silica surface shielding is optimized so that basic and acidic solutes elute with symmetrical peak.
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    URL: http://dx.doi.org/10.1007/BF02315133
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    Determination of D- and L-amino acid residues in peptides with fluorescent chiral tagging reagents by high-performance liquid chromatography (1995)
    Springer
    Chromatographia 40 (1995), S. 645-651 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral resolution of amino acids ; Pre-column derivatization ; Fluorescent chiral tagging reagents ; Stereochemical purity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Derivatization of amino acid enantiomers with fluorescent chiral Edman-type reagents, 4-(3-isothiocyanatopyrrolidin-1-yl)-7-nitro-2,1,3-benzoxadiazole [R(−)- and S(+)-NBD-PyNCS] and 4-(3-isothiocyanatopyrrolidin-1-yl)-7-(N,N-dimethylaminosulfonyl)-2,1,3-benzoxadiazole [R(−)-and S(+)-DBD-PyNCS], yields corresponding diastereomers separable by reversed-phase HPLC on normal achiral columns. The resolved diastereomers were detected fluorometrically at 530 nm with excitation at 490 nm for the NBD-PyNCS derivatives and at 560 nm with excitation at 450 nm for those derived from DBD-PyNCS reagents. This HPLC-derivatization method was used for evaluation of stereochemical purity for some synthetic commercial peptides. The enantioanalysis was reliable down to 0.05% racemization of the amino acid residues and a quantity of 100 μg peptide sample was usually enough for the analysis. Two acid hydrolysis methods, i.e. the standard procedure with constant-boiling hydrochloric acid (HCl) and a rapid vapor-phase procedure with HCl-trifluoroacetic acid (TFA) mixture, were compared. The later was found to be unsuitable owing to increased racemization of the amino acid residues during the hydrolysis. Judging from the results obtained for proline and leucine residues, most of the tested peptides including biologically active peptides, such as neurotensin, [d-Ala2,d-Leu5]-enkepharin and morphine tolerance peptide, possessed stereochemical purities higher than 98%. Influence of structural features of the peptides on the racemization of the amino acid residues was found to be significant.
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    URL: http://dx.doi.org/10.1007/BF02315131
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    HPLC-continuous-flow fast atom bombardment mass spectrometry (HPLC-CFFAB) — a convenient method for the analysis of bile acids in bile and serum (1995)
    Springer
    Chromatographia 40 (1995), S. 674-679 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mass spectrometric detection ; Fast atom bombardment ionization ; Serum bile acid ; Rat bile
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In order to analyse bile acids in biological matrices, e.g. rat bile and human serum, high performance liquid chromatography (HPLC) was coupled to continuous-flow fast atom bombardment mass spectrometry (CFFAB-MS). A gradient elution system which had already proved to be well suited for the quantitative determination of conjugated bile acids in bile was modified to allow HPLC-CFFAB-MS-coupling. Due to the sensitivity of this coupling method it is possible to obtain more information about the biliary bile acid pattern and species-specific secondary bile acids. Furthermore, we were able to identify obviously unknown bile acid species in rat bile which most likely classify as mono-oxo and di-oxo-taurocholates (MW 513 Da, 511 Da) and mono-oxo-glycocholates (MW 463 Da). In the present study we show that using this system it is possible to determine both conjugated and unconjugated as well as sulfated bile acids, without time consuming group separation and derivatization, from rat bile and human serum. In addition, it is suggested that the method presented here should be considered for use in routine analysis.
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    URL: http://dx.doi.org/10.1007/BF02315136
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    Fluorescence enhancement of dansylamino acids by bovine serum albumin as mobile phase additive in microcolumn liquid chromatography (1995)
    Springer
    Chromatographia 40 (1995), S. 159-162 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fluorescence enhancement ; Bovine serum albumin ; Dansylamino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The effects of acetonitrile and bovine serum albumin (BSA) concentrations on the signal intensity and retention behavior of dansylamino acids have been examined by using γ-cyclodextrin-bonded silica gel as the stationary phase in microcolumn liquid chromatography. Fluorescence intensities of dansylamino acids were enhanced by BSA as a mobile phase additive, e.g., detection limits of dansyl derivatives of L-Ala and L-Phe were improved by a factor of 12–18.
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    URL: http://dx.doi.org/10.1007/BF02272165
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    A statistical study of the correlation between k′ or log k′ and log Pow for a group of benzene and naphthalene derivatives in micellar liquid chromatography using a C-18 column (1995)
    Springer
    Chromatographia 40 (1995), S. 185-192 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micellar liquid phases ; Octanol-water partition coefficient ; Benzene and naphthalene derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary It is shown that the logarithm of the capacity factor (log k′) for fifteen benzene and naphthalene derivatives in micellar liquid chromatography with forty nine different mobile phases generally correlates better with the logarithm of the octanol-water partition coefficient (log Pow) than the capacity factor (k′). Optimum conditions are established to obtain the best linear correlations of log k′-log Pow.
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    URL: http://dx.doi.org/10.1007/BF02272169
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    Improvement of selectivity of electrochemical detection for the determination of compounds with chloro aromatic rings (1995)
    Springer
    Chromatographia 40 (1995), S. 247-252 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Photolysis ; Electrochemical detection ; Drugs with chlorinated aromatic rings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Pharmaceuticals containing a thiazide ring or chlorinated aromatic ring were investigated with respect to enhanced selectivity in determination. Oxidative electrochemical detection coupled with HPLC was used to study the influence of the pH of the mobile phase under conditions of photolysis. To cover a pH range 3.9–12, the employment of a polymer column stable in alkaline media was necessary. The method offers the great advantage of derivatization without chemicals at low operating potentials, thereby providing high selectivity.
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    Separation of structural isomers using cyclodextrin-polymers coated on silica beads (1995)
    Springer
    Chromatographia 40 (1995), S. 296-302 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Structural isomer separation ; Cyclodextrin ; Polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Several β-cyclodextrin (CD)-bonded stationary phases for high performance liquid chromatography (HPLC) were prepared, based on silica beads coated with a poly(alkylamine), [poly(ethyleneimine)(PEI)]. In order to obtain stationary phases with a high content of CD and maximum accessibility of the CD cavity, the functionalization was carried out after the coating, using the mono-tosyl derivative of CD as the intermediate. The ability of these supports to separate ortho, meta and para isomers of some disubstituted benzene derivatives was examined. The contribution of the amino groups of the polymer and of the CD cavity to the separation process is discussed. The resolution is mainly based on the difference in the stability of the complexes of the various isomers with CD. The influence of the amount of CD on the height of the theoretical plate is also studied.
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    A potential application for large diameter pellicular supports in the reversed phase study of ultra high molecular mass polystyrenes (1995)
    Springer
    Chromatographia 40 (1995), S. 307-312 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed phase ; Polystyrene ; Pellicular ; Ultra high molecular mass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Ultra high molecular mass (〉 7 million dalton) polystyrenes are prone to degradation in size exclusion chromatography. In gradient elution reversed phase HPLC they do not elute visibly on small particle size porous supports. However, large diameter C18 pellicular particles were successfully employed for reversed phase study of ultra high molecular mass (15 million dalton) polystyrenes without polymer degradation during elution. Although retention for the lower molecular mass polystyrenes was lower than on small diameter porous particles, the medium high molecular mass polystyrenes (0.5–1 million dalton) showed similar retention. The addition of small diameter porous particles in small quantities, to the large diameter pellicular particles, increased the amount of retention of the low molecular mass polystyrenes without affecting the higher molecular mass polystyrenes.
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    High performance liquid chromatographic determination of methyl ethyl ketone in urine as its 3-methyl-2-benzothiazolinone hydrazone derivative (1995)
    Springer
    Chromatographia 40 (1995), S. 336-340 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Methyl ethyl ketone in urine ; Derivatization ; 3-Methyl-2-benzothiazolinone hydrazone ; Comparison with GC-MS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A HPLC method for the determination of methyl ethyl ketone (MEK) in urine after derivatization with 3-methyl-2-benzothiazolinone hydrazone is proposed. The calibration curve for the ketone was linear, ranging between 0.23–10 mg/L, with a detection limit of 0.025 mg/L. The results were compared to those obtained by GC-MS, coupled to the headspace technique. MEK derivatization and the derivative purification processes were verified with respect to the main variables such as reaction temperature, reagent concentration, probable interferences and enrichment phase. The method is simple and reliable and shows a good sensitivity.
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    Liquid chromatographic analysis of sulfornamides in foods (1995)
    Springer
    Chromatographia 40 (1995), S. 382-386 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sulfonamides in foodstuffs ; Honey ; Milk ; Eggs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A procedure for the simultaneous determination of several sulfonamides in different foods, such as honey, milk and eggs is proposed. The analysis is carried out using reversed phase liquid chromatography with spectrophotometric detection. Optimization of the mobile phase led to good separation and a short analysis time when an initial isocratic step with a 3∶97 acetonitrile: water mixture was used for 5 minutes, followed by a linear gradient up to a 40∶60 mixture over 15 min. The proposed method is suitable for routine quality control analysis to ensure the absence of sulfonamides in foods. Recovery studies yielded good results for all food samples because there were no interferences from the matrices.
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    Determination of aflatoxins in peanut meal by LC/MS with a particle beam interface (1995)
    Springer
    Chromatographia 40 (1995), S. 411-416 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Particle beam LC/MS interface ; Capillary columns for LC ; Mycotoxins ; Peanut meal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new method for the analysis of aflatoxins in food extracts, based on liquid chromatography/mass spectrometry interfacing, is presented. The chromatographic separation was performed with a reversed phase packed capillary column coupled with a modified particle beam interface capable of handling microliter per minute flow rates. This system allows higher overall sensitivity and easier operation procedures. The method has proved to be particularly suitable for the analysis of the toxins in very complex matrices. The specificity of electron impact ionization allowed positive identification of the aflatoxins with an excellent response linearity for accurate quantitation.
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    URL: http://dx.doi.org/10.1007/BF02269904
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    Retention parameters of some isomeric 2-benzoylbenzoic acids in reversed-phase ion-pair high performance thin-layer and column chromatography (1995)
    Springer
    Chromatographia 40 (1995), S. 453-457 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin-layer chromatography ; Reversed phase ; 2-benzoylbenzoic acids ; Anionic and cationic counter ions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The 2-benzoylbenzoic acid series was investigated by reversed-phase, high-performance, thin-layer and column chromatography using various alkylammonium salts and di(2-ethylhexyl)orthophosphoric acid as polar associating reagents. The effects of the individual substituents on retention were quantified by Δlog k′ and ΔRM values. The compounds investigated differing in molecular structure (hydrophilic and hydrophobic substituents) commonly occurring groups in drugs and biologically active substances provide information on molecular interaction in these ion-pair systems. The combined effects on retention of organic modifier and ion-pair reagent concentration were investigated.
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    URL: http://dx.doi.org/10.1007/BF02269912
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    Determination of D- and L-amino acids in biological samples by two-dimensional column liquid chromatography (1995)
    Springer
    Chromatographia 41 (1995), S. 6-14 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Two-dimensional separation ; D- and L-amino acids ; Enantioseperation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A two-dimensional, column liquid chromatographic system is used for the determination of the D- and L-enantiomers of amino acids in biological samples. Separation of the amino acids is first on ion-exchange column by gradient elution with a sodium citratesodium chloride buffer. Enantioseparation is by subsequent injection of 3 μl heart-cuts of the individual amino acids onto a second column with a chiral crown ether stationary phase. Finally, fluorescence detection is after post-column labelling of the amino acids using ano-phthalaldehyde-2-mercaptoethanol reagent solution. The high separation power and selectivity of the system allow processing of complex samples with hardly any additional treatment and the determination of small quantities of D-amino acids in the presence of excess L-form. Applicability of the system is illustrated by the determination of D- and L-aspartate, serine, glutamate and alanine in various complex biological samples, such as protein hydrolysates, urine and biotechnological and food samples. Data are given on detectability, repeatability and linearity.
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    Simultaneous determination of preservatives, sweeteners and antioxidants in foods by paired-ion liquid chromatography (1995)
    Springer
    Chromatographia 41 (1995), S. 43-50 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion pair LC ; Sweeteners, preservatives and antioxidants ; Food additive analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A paired-ion, reversed-phase high-performance liquid chromatographic method was developed for the simultaneous determination of sweeteners (dulcin, saccharin-Na and acesulfame-K), preservatives (sodium dehydroacetate, sorbic acid, salicyclic acid, benzoic acid, succinic acid, methyl-para-hydroxybenzoic acid, ethylpara-hydroxybenzoic acid, n-propyl-para-hydroxybenzoic acid, isopropyl-para-hydroxybenzoic acid, n-butyl-para-hydroxybenzoic acid, and isobutyl-para-hydroxybenzoic acid), and antioxidants (3-tertiary-butyl-4-hydroxyanisole and tertiary-butyl-hydroquinone). A mobile phase of acetonitrile-50 mM aqueous α-hydroxy-isobutyric acid solution (pH 4.5) (2.2 ∶ 3.4 or 2.4 ∶ 3.6, v/v) containing 2.5 mM hexadecyltrimethylammonium bromide and a C18 column with a flow rate at 1.0 mL/min and detection at 233 nm were used. This method was found to be very reproducible with detection limits ranged from 0.15 to 3.00 μg. The retention factor (k) of each additive could be affected by concentrations of hexadecyltrimethylammonium bromide and α-hydroxyisobutyric acid, and pH and ratio of mobile phase. The presence of additives in some food samples was determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02274194
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  • 91
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    Prediction of precision from signal and noise measurement in liquid chromatography: Mathematical relationship between integration domain and precision (1995)
    Springer
    Chromatographia 41 (1995), S. 75-83 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Limit of detection ; Precision ; Uncertainty prediction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The precision of integration over noisy instrumental output for quantitative analysis is studied. A probability theory is developed to predict the relative standard deviation (RSD) of integration results over an integration domain from one-point integation (peak height measurement) to entire area integration in HPLC. Common integration modes of horizontal zero line and oblique zero line are taken into account, but no peak overlap is assumed. The question of the analytical superiority of peak height measurement or integration for quantitation is answered. In the HPLC apparatus used, the minimum RSD of measurements is found in the integration domain of ca. ±0.5 σ for analytes [peaks are approximated by the Gaussian signal of width, σ (standard deviation)]. The RSD of integration measurements is also shown to depend on the stochastic properties of back-ground noise (uncorrelated noise and correlated 1/f type noise). The theoretical conclusion is verified by Monte Carlo simulation and HPLC experiments for some aromatic compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02274198
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  • 92
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    Ion-pair reversed-phase and low-molecular-weight aqueous gel permeation high-performance liquid chromatography methods for the determination of amoxicillin oligomersa (1995)
    Springer
    Chromatographia 41 (1995), S. 651-656 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-pair and GPC separations ; Amoxicillin oligomers ; β-Lactam ring polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Polymeric substances formed from concentrated sodium amoxicillin in an aqueous solution have been separated using two high-performance liquid chromatographic methods. We used a C18 reversed-phase column with tetrabutylammonium chloride as an ion-pairing agent with an acetonitrile gradient and a TSKgel G2500PWxl column with water as the solvent for gel permeation chromatography. The separated materials, ranging in size from the monomer to the tetramer, have been characterized by functional-group chemical analysis, while the identification of the piperazine-2,5-dione was done using a pure standard. A greater number of peaks which were also better defined were obtained using the ion-pair reversed-phase method, and open and closed beta-lactam ring polymer forms could be distinguished. Using the gel permeation method, only a few monomer, piperazine-2,5-dione, dimer, trimer and combined amoxicillin trimer and tetramer peaks were obtained with water, although those obtained were quite well defined. The data on the time-course of formation of the oligomers and the amoxicillin degradation product were virtually identical by both methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267799
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  • 93
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    Signal enhancement by on-column fluorimetric detection in gradient elution of dansyl amino acids in liquid chromatography (1995)
    Springer
    Chromatographia 41 (1995), S. 148-152 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; On-column fluorimetric detection ; Gradient elution ; Dansyl amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Fluorimetric detection in the presence of a stationary phase has been applied to gradient elution of dansyl amino acids in liquid chromatography. A 1.5 mm ID quartz tube packed with the same materials as the separation column was employed for the flow cell. Conventional-size columns were employed. The peak height of analytes increased with increasing retention owing to focusing and environmental effects of the stationary phase, leading to improvements in sensitivity, which was pronounced for analytes eluting late. The lower the gradient, the larger the improvement in sensitivity achieved. Detection limits were improved by a factor of up to 5.1 by fluorimetric detection using the packed flow cell, compared with those achieved using a common empty flow cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267946
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  • 94
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    A study of the behaviour of some new column materials in the chromatographic analysis of Cinchona alkaloids (1995)
    Springer
    Chromatographia 41 (1995), S. 153-160 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; LC-MS ; Cinchona alkaloids ; New column packing materials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A major problem in the HPLC analysis of alkaloids is the poor peak shape and consequently low resolution, due to the interactions of the basic alkaloids with the residual acidic silanol groups of most reversed phase materials. The performance of new packing materials specially designed for the separation of basic compounds has been studied using mobile phases without the special additives commonly applied in the analysis of alkaloids. Strongly basic Cinchona alkaloids were used as test compounds. Retention characteristics and selectivities of each material were studied, after mobile phase optimisation for the column. The influence of the major factors (nature and content of the organic modifier, pH value, salt concentration) affecting resolution was studied. The mobile phases were chosen so that they could be used in thermospray LC-MS. The addition of salts to the mobile phase improves separation but in general the modification of the mobile phase gave little change in selectivity. The performance of silicabased C18 material proved superior to the polymer materials tested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267947
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  • 95
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    Somatostatin analogs: angiogenesis inhibitors with novel mechanisms of action (1997)
    Springer
    Investigational new drugs 15 (1997), S. 77-86 
    Details
    ISSN: 1573-0646
    Keywords: somatostatin ; angiogenesis ; somatostatin receptors ; signal transduction ; xanthines ; calcium ; proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005774713202
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  • 96
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    Inhibition of Mitochondrial Permeability Transition by Low pH is Associated with Less Extensive Membrane Protein Thiol Oxidation (1999)
    Springer
    Bioscience reports 19 (1999), S. 525-533 
    Details
    ISSN: 1573-4935
    Keywords: Mitochondrial permeability transition ; acid pH ; protein sulfhydryl oxidation ; calcium ; reactive oxygen species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Ca2+ and inorganic phosphate-induced mitochondrial swelling and membrane protein thiol oxidation, which are associated with mitochondrial permeability transition, are inhibited by progressively decreasing the incubation medium pH between 7.2 and 6.0. Nevertheless, the detection of mitochondrial H2O2 production under these conditions is increased. Permeability transition induced by phenylarsine oxide, which promotes membrane protein thiol cross-linkage in a process independent of Ca2+ or reactive oxygen species, is also strongly inhibited in acidic incubation media. In addition, we observed that the decreased protein thiol reactivity with phenylarsine oxide or phenylarsine oxide-induced swelling at pH 6.0 is reversed by diethyl pyrocarbonate, in a hydroxylamine-sensitive manner. These results provide evidence that the inhibition of mitrochondrial permeability transition observed at lower incubation medium pH is mediated by a decrease in membrane protein thiol reactivity, related to the protonation of protein histidyl residues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020210827389
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  • 97
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    Signal transduction and motility ofDictyostelium (1995)
    Springer
    Bioscience reports 15 (1995), S. 445-462 
    Details
    ISSN: 1573-4935
    Keywords: Myosin II ; cyclic GMP ; calcium ; motility ; myosin heavy chain kinase ; myosin light chain kinase ; signal transduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract This review is concerned with the roles of cyclic GMP and Ca2+ ions in signal transduction for chemotaxis ofDictyostelium. These molecules are involved in signalling between the cell surface cyclic AMP receptors and cytoskeletal myosin II involved in chemotactic cell movement. Evidence is presented for uptake and/or eflux of Ca2+ being regulated by cyclic GMP. The link between Ca2+, cyclic GMP and chemotactic cell movement has been explored using “streamer F” mutants whose primary defect is in the structural gene for the cyclic GMP-specific phosphodiesterase. This mutation causes the mutants to produce an abnormally prolonged peak of cyclic GMP accumulation in response to stimulation with the chemoattractant cyclic AMP. The production and relay of cyclic AMP signals is normal in these mutants, but certain events associated with movement are (like the cyclic GMP response) abnormally prolonged in the mutants. These events include Ca2+ uptake, myosin II association with the cytoskeleton and regulation of both myosin heavy and light chain phosphorylation. These changes can be correlated with changes in the shape of the amoebae after chemotactic stimulation. Other mutants in which the accumulation of cyclic GMP in response to cyclic AMP stimulation was absent produced no myosin II responses. A model is described in which cyclic GMP (directly or indirectly via Ca2+) regulates accumulation of myosin II on the cytoskeleton by regulating phosphorylation of the myosin heavy and light chain kinases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01204348
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  • 98
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    Identification and phylogenetic classification of eleven putative P-type calcium transport ATPase genes in the yeastsSaccharomyces cerevisiae andSchizosaccharomyces pombe (1996)
    Springer
    Bioscience reports 16 (1996), S. 75-85 
    Details
    ISSN: 1573-4935
    Keywords: Yeast ; Ca++-ATPases ; phylogenetic tree ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Calcium is an essential second messenger in yeast metabolism and physiology. So far, only four genes coding for calcium translocating ATPases had been discovered in yeast. The recent completion of the yeastSaccharomyces cerevisiae genome allowed us to identify six new putative Ca++-ATPases encoding genes. Protein sequence homology analysis and phylogenetic classification of all putative Ca++-ATPase gene products from the yeastsSaccharomyces cerevisiae andSchizosacchraomyces pombe reveal three clusters of homologous proteins. Two of them comprises seven proteins which might belong to a new class of P-type ATPases of unknown subcellular location and of unknown physiological function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01206198
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  • 99
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    Parathyroid hormone co-stimulation of hepatocyte proliferation is sensitive to protein kinase A and calcium channel inhibitors (1996)
    Springer
    Bioscience reports 16 (1996), S. 343-350 
    Details
    ISSN: 1573-4935
    Keywords: dHGF ; hepatocyte ; protein kinase A ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Parathyroid hormone (PTH) mobilises calcium in the hepatocyte, an effect which is abolished by verapamil and staurosporine. In our study parathyroid hormone was shown to act additively to dHGF in inducing hepatocyte DNA synthesis. It is also shown that PTH induced the production of inositol 1,4,5 trisphosphate (IP3) andc-fos expression at early times in culture. Co-incubation of PTH and dHGF with ac-fos antisense oligodeoxynucleotide inhibited hepatocyte DNA synthesis, indicating that the additive effect of PTH is correlated with the induction ofc-fos. H-89, a PKA specific inhibitor, inhibited the PTH effect on IP3 production as well as the PTH effect on hepatocyte DNA synthesis. Verapamil and staurosporine also inhibited the PTH effect in dHGF-induced DNA synthesis. Therefore it is suggested that PKA mediated at a great extent the co-stimulatory effects of PTH on hepatocyte proliferation via IP3 production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01855017
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  • 100
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    Forest soil solutions: Acid/base chemistry and response to calcite treatment (1996)
    Springer
    Biogeochemistry 32 (1996), S. 195-220 
    Details
    ISSN: 1573-515X
    Keywords: acidification ; acid neutralizing capacity ; aluminum ; calcite ; calcium ; liming ; nitrogen cycling ; soil chemistry ; soil solutions ; spodosols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Soil solution chemistry was investigated at a forested watershed draining into Woods Lake. N.Y. as part of the Experimental Watershed Liming Study (EWLS). The objective of this study was to assess the response of soil water to watershed treatment of calcite (CaCO3). This material was applied in an effort to mitigate the effects of acidic atmospheric deposition. Soil solutions draining Oa and Bs horizons in reference subcatchments were characterized by low pH and acid neutralizing capacity (ANC) due to elevated concentrations of SO 4 2− , NO 3 − and organic anions relative to the sum of base cation (CB Ca2+, Mg2+, Na+, K+) concentrations. Seasonal and spatial variation of pH andANC in soil solutions appeared to belargely controlled by variations in the concentrations of dissolved organic acids which, in turn, were regulated by reactions of Al with soil organic matter. Nitrate was positively correlated and SO2+ was negatively correlated with Ca2+ and Al concentrations in reference soil solutions, indicating that changes in NO 3 − influences spatial and seasonal variations in Ca2+ and Al concentrations. On this basis, NO 3 − appears to be important in soil acidification and the dynamics of drainage water acidity. Comparison of our results with historical data for the site showed declines in concentrations of SO 4 2− , which are consistent with decreases in emissions of SO4, in the eastern U.S. and atmospheric deposition of SO 4 2− , to the Adirondack region. Mineral soil solutions have shown large increases in concentrations of NO 3 − . Declines in concentrations of CB and increases in concentrations of Al have occurred over the last ten years, suggesting depletion of soil pools of exchangeable basic cations and increased sensitivity to acidic deposition. Calcite (CaCO3) treatment of 6.89 Mg/ha resulted in a significant increase of Ca2+, ANC and pH in both Oa and Bs horizon soil solutions. Soil water response to CaCO3 addition was most evident during the first year after treatment, apparently due to macropore transport of particulate and dissolved CaCO3 However, increases in ANC and pH in the mineral soil waters were not sustained and appeared insufficient to result in substantial improvement in surface water quality over the 43 month study period.
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    URL: http://dx.doi.org/10.1007/BF02187139
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