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  • Articles  (41)
  • calcium  (41)
  • Springer  (41)
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  • 2010-2014
  • 1985-1989  (41)
  • 1955-1959
  • 1935-1939
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  • Articles  (41)
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  • Springer  (41)
  • American Institute of Physics
  • American Meteorological Society
  • American Society of Hematology
  • Cell Press
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  • 2010-2014
  • 1985-1989  (41)
  • 1955-1959
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  • 1
    Electronic Resource
    Electronic Resource
    Dystrophin and the integrity of the sarcolemma in Duchenne muscular dystrophy (1989)
    Springer
    Cellular and molecular life sciences 45 (1989), S. 175-177 
    Details
    ISSN: 1420-9071
    Keywords: Dystrophin ; calcium ; skeletal muscle ; muscular dystrophy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary It is suggested that in Duchenne muscular dystrophy the absence of dystrophin, which is probably a cytoskeletal protein underlying the sarcolemma, causes changes in stretch-activated cation channels rather than direct mechanical tearing of the surface membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01954866
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  • 2
    Electronic Resource
    Electronic Resource
    Cerebrovascular autoregulation is resistant to calcium channel blockade with nimodipine (1989)
    Springer
    Cellular and molecular life sciences 45 (1989), S. 305-306 
    Details
    ISSN: 1420-9071
    Keywords: Baboon ; 133xenon ; cerebral blood flow ; cerebrovascular resistance ; autoregulation ; nimodipine ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In normal baboons cerebrovascular resistance changed along with blood pressure to maintain blood flow constant. This ‘autoregulation’ was not significantly altered in animals treated with a dose of the calcium channel blocker nimodipine causing selective cerebral vasodilation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01951818
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  • 3
    Electronic Resource
    Electronic Resource
    Morphological evidence for calcium storage in the chromatoid body of rat spermatids (1989)
    Springer
    Cellular and molecular life sciences 45 (1989), S. 377-378 
    Details
    ISSN: 1420-9071
    Keywords: Chromatoid body ; spermatids ; calcium ; microtubules ; morphology ; pyroantimonate ; rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Morphological evidence for probable Ca2+ storage in the vesicular elements of the rat spermatid chromatoid body is documented using the K-pyroantimonate method, combined with EDTA chelation. Some vesicles are related to the microtubules associated with the chromatoid body. A possible involvement of Ca2+ in the intracellular movement and/or structural integrity of the chromatoid body is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01957484
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  • 4
    Electronic Resource
    Electronic Resource
    Involvement of a Ca2+-calmodulin interaction in the yeast-mycelial (Y-M) transition of Candida albicans (1989)
    Springer
    Mycopathologia 108 (1989), S. 47-54 
    Details
    ISSN: 1573-0832
    Keywords: Candida albicans ; dimorphism ; yeast-mycelium transition ; calcium ; calmodulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A yeast-mycelium (Y-M) transition of Candida albicans (3153A) was induced by 1.5 mM CaCl2 · 2H2O in defined liquid medium, pH 7, at 25 °C. Germ tube formation was detected after approximately 8 h and peaks of maximum germination occurred at approximately 20 h in all experimental treatments. Non-toxic concentrations of the calmodulin inhibitor R24571 almost completely suppressed germ tube formation whereas trifluoperazine (TFP) and the Ca2+ ionophore A23187 were only about half as effective. Further Ca2+ addition failed to reverse the inhibitory effect of R24571 and induced only about 10% of the cells inhibited by TFP or A23187 to germinate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00436783
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  • 5
    Electronic Resource
    Electronic Resource
    Calcium movements during each heart beat (1989)
    Springer
    Molecular and cellular biochemistry 89 (1989), S. 103-108 
    Details
    ISSN: 1573-4919
    Keywords: heart ; relaxation ; calcium ; sodium-calcium exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Transsarcolemmal calcium movements are closely related to force generation in the heart. It is important to understand the transport pathways that control these movements of calcium across the sarcolemmal membrane. In the normal, beating heart, sodium-calcium exchange appears to be an important mechanism for the extrusion of calcium from the cell. The kinetics of this exchange are dependent upon the characteristics of the cell action potential. Calcium efflux via sodium-calcium exchange may be sufficient to balance calcium entry through calcium channels during the action potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220760
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  • 6
    Electronic Resource
    Electronic Resource
    Sodium-calcium exchange in mammalian heart: current-voltage relation and intracellular calcium concentration (1989)
    Springer
    Molecular and cellular biochemistry 89 (1989), S. 97-102 
    Details
    ISSN: 1573-4919
    Keywords: calcium ; sodium ; fura-2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Membrane currents and changes in intracellular calcium ion concentration ([Ca2+]i) have been recorded that can be attributed to the operation of an electrogenic, voltage-dependent sodium-calcium (Na-Ca) exchanger in mammalian heart cells. Single guinea-pig ventricular myocytes under voltage clamp were perfused internally with the fluorescent Ca2+-indicator, fura-2, and changes in [Ca2+]i and membrane current that resulted from Na-Ca exchange were isolated through the use of various organic channel blockers (verapamil, TTX), impermeant ions (Cs+, Ni2+), and inhibitors of sarcoplasmic reticulum (ryanodine). The I-V relation of Na-Ca exchange was obtained from the Ni2+-sensitive current elicited by ramp repolarization from +90 mV to −80 mV. Ramps were sufficiently rapid that little change in [Ca2+]i occured during the ramp. The (constant) [Ca2+]i during the ramp was varied over the range 100 nM to 1000 nM by varying the amplitude and duration of a pre-pulse to the ramp. The reversal potential of the Ni2+-sensitive ramp current varied linearly with 1n([Ca2+])i. The I-V relations at different [Ca2+]i over the range −60 mV to +140 mV were in reasonable accord with the predictions of a simple, simultaneous scheme of Na-Ca exchange, on the basis that only [Ca2+]i had changed. The relationship between [Ca2+]i and current at a constant membrane voltage was also in accord with this scheme. We suggest that Ca2+-fluxes through the exchanger during the cardiac action potential can be understood quantitatively by considering the binding of Ca2+ to the exchanger during the [Ca2+]i-transient and the effects of membrane voltage on the exchanger.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220759
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  • 7
    Electronic Resource
    Electronic Resource
    Appraisal of the physiological relevance of two hypotheses for the mechanism of calcium release from the mammalian cardiac sarcoplasmic reticulum: calcium-induced release versus charge-coupled release (1989)
    Springer
    Molecular and cellular biochemistry 89 (1989), S. 135-140 
    Details
    ISSN: 1573-4919
    Keywords: calcium ; heart ; sarcoplasmic reticulum ; excitation-contraction coupling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Recent studies correlating the calcium current with, respectively, the clamp-imposed voltage and the calcium current in intact isolated mammalian cardiac myocytes are reviewed. The major findings are the following: [1] With the exception of one group, all investigators agree that a calcium transient is never observed in the absence of a calcium current. In addition, there is a good correlation between voltage dependence of the calcium current and that of the calcium transient, although this correlation may vary among the cardiac tissues from different animal species. [2] Repolarization clamp pulses from highly positive potentials produce a ‘tail current’ which is associated with a ‘tail calcium transient’. [3] The calcium transient is inhibited when the calcium current is blocked by calcium deprivation or substitution, or by the addition of calcium current antagonists, despite the fact that sarcoplasmic reticulum still contains calcium that can be released by caffeine (with inhibition of this release by ryanodine). These three findings are strongly in favor of a calcium-induced release of calcium and against the hypothesis of charge-movement-coupled release of calcium from the sarcoplasmic reticulum. [4] The only finding that would be more in favor of the latter hypothesis (although till reconciliable with the former) is that repolarization occurring before the rapid rise of calcium transient is complete curtails the calcium transient. Thus, the possibility that charge movement might somehow regulate calcium-induced release of calcium cannot be excluded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220765
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  • 8
    Electronic Resource
    Electronic Resource
    The effect of acidosis on excitation-contraction coupling in isolated ferret heart muscle (1989)
    Springer
    Molecular and cellular biochemistry 89 (1989), S. 169-173 
    Details
    ISSN: 1573-4919
    Keywords: pH ; calcium ; heart muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The contractile response to acidosis is the final product of a number of different changes in the excitation-contraction coupling pathway: (i) Cai increases and subsequently decreases during acidosis; (ii) the action potential becomes longer; (iii) the sensitivity of the contractile proteins to Ca2+ decreases. The increase of Cai and the lengthening of the action potential may help to maintain contractile function, although this advantage may be offset if spontaneous Ca2− release from the s.r. occurs, secondary to the increase of Cai. The recovery of force shown in figure 1 occurs at a time when the calcium transient is decreasing, and therefore represents an increasing sensitivity of the contractile proteins to Cai, probably due to a recovery of intracellular pH(6), although it is also possible that a disappearance of spontaneous Ca2+ releases from the s.r. may be contributing [2].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220771
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  • 9
    Electronic Resource
    Electronic Resource
    The contribution of mitochondrial calcium ion exchange to relaxation of tension in cardiac muscle (1989)
    Springer
    Molecular and cellular biochemistry 89 (1989), S. 127-133 
    Details
    ISSN: 1573-4919
    Keywords: mitochondria ; sarcoplasmic reticulum ; calcium ; myocytes ; caffeine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The possible contribution of mitochondrial Ca2+ accumulation and release to contractile phenomena has been investigated. Two intracellular fractions of Ca2+ sequestration can be identified in cardiac myocytes, one ascribed to mitochondria. Two modes of Ca2+ transport exist within the mitochondrial fraction, one dependent upon mitochondrial respiration and the other upon extramitochondrial [Na+]. Experiments with trabeculae show that under appropriate conditions, the rate of relaxation and the amount of tension developed is dependent on these two modes of Ca2+ transport. A model is presented quantifying the contribution of the mitochondria to relaxation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220764
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  • 10
    Electronic Resource
    Electronic Resource
    The control of calcium influx by cytoplasmic calcium in mammalian heart muscle (1989)
    Springer
    Molecular and cellular biochemistry 89 (1989), S. 109-113 
    Details
    ISSN: 1573-4919
    Keywords: heart muscle ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The role of Ca2+ in the initiation and maintenance of contraction has been extensively studies. Many of these studies have focused on how Ca2+ influx and efflux affect cytoplasmic Ca2+ (Cai) and, therefore, contraction in cardiac muscle. However, it has recently become apparent that Cai itself may play a major role in the control of Ca2+ influx and efflux from cardiac muscle. Here we review current ideas on the mechanisms underlying Ca2+ homeostasis in cardiac muscle, with specific attention to how Cai may control Ca2+ influx, both under normal and pathological conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220761
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  • 11
    Electronic Resource
    Electronic Resource
    Redistribution of subcellular calcium in rat liver on administration of vanadate (1989)
    Springer
    Molecular and cellular biochemistry 90 (1989), S. 155-164 
    Details
    ISSN: 1573-4919
    Keywords: polyvanadate ; mitochondria ; calcium ; pyruvate dehydrogenase ; receptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary Mitochondria isolated from the livers of rats administered with sodium meta-, ortho-, or polyvanadate, but not vanadyl sulphate, exhibited enhanced Ca2+ — stimulated respiration and uptake of calcium. These effects were shown also by mitochondria isolated from livers perfused with polyvanadate. The concentration of acid-soluble calcium decreased significantly in the mitochondrial fraction on vanadate treatment, while that in the cytosol showed a corresponding increase. Phenoxybenzamine, an antagonist to a-adrenergic receptors, effectively inhibited vanadate-induced Ca2+ mobilization, but surgical sympathectomy was without effect. This is the first demonstration of vanadate mimicking α-adrenergic agonists in vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00221215
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  • 12
    Electronic Resource
    Electronic Resource
    ATP inhibits onset of exocytosis in permeabilised mast cells (1989)
    Springer
    Bioscience reports 9 (1989), S. 99-109 
    Details
    ISSN: 1573-4935
    Keywords: mast cells ; exocytosis ; G-protein ; GE ; calcium ; ATP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract ATP is not required for exocytosis from permeabilised mast cells, and therefore there is no direct role for protein phosphorylation in the late stages of the activation pathway. We have measured the timecourse of exocytosis from permeabilised cells triggered to release hexosaminidase following addition of Ca2+ to cells equilibrated for 2 min with GTP-γ-S. If ATP is included at the time of permeabilisation, then exocytosis commences after a delay, the duration of which depends on the square root of the product [Ca2+][GTP-γ-S], and which may extend to beyond 3 min. When ATP is excluded then the maximal rate of exocytosis is established within 3 secs of completing the effector combination. These results suggest that the achievement of a new steady-state, induced by Ca2+ and GTP-γ-S, and required for exocytosis is inhibited by ATP. From this we conclude that dephosphorylation of an unknown regulator protein may comprise a step in the exocytotic pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01117516
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  • 13
    Electronic Resource
    Electronic Resource
    A comparison of bradykinin, angiotensin II and muscarinic stimulation of cultured bovine adrenal chromaffin cells (1989)
    Springer
    Bioscience reports 9 (1989), S. 243-252 
    Details
    ISSN: 1573-4935
    Keywords: secretion ; exocytosis ; chromaffin cell ; calcium ; bradykinin ; angiotensin II, muscarinic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Bradykinin, angiotensin II and a mascarnic agonist, acetyl-B-methacholine (methacholine) were all found to elict catecholamine release from cultured bovine adrenal chromaffin cells. Bradykinin was the most potent of these secretagogues and methacholine the weakest, with angiotenin II intermediate in efficacy. All three secretagogues were much less effective than nicotinic stimulation. The three secretagogues all produced a rise in cytoplasmic free calcium concentration ([Ca2+]i), measured with the fluorescent indicator fura2, which was partially independent of external calcium. In the case of bradykinin the full rise in ([Ca2+]i) may involve a component of calcium entry in addition to release of calcium from an internal store. Secretion was also found to be partially independent of external calcium. The different efficacies of the three secretagogues in elicting secretion were correlated with the rise in ([Ca2+]i) produced. The differeing efficacies of the three secretagogues may be due to the extent of release of calcium from an intracellular store which itself is less effective in eliciting secretion than a rise in [Ca2+]i following calcium entry due to nicotine. Bradykinin also stimulates calcium entry, and this may increase the efficacy of the initial rise in [Ca2+]i. Treatment with pertussis toxin resulted in an enhancement of secretion in response to all of the secretagogues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01116001
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  • 14
    Electronic Resource
    Electronic Resource
    A nonselective cation channel activated by membrane deformation in oocytes of the ascidianBoltenia villosa (1989)
    Springer
    The journal of membrane biology 107 (1989), S. 179-188 
    Details
    ISSN: 1432-1424
    Keywords: stretch-activated channel ; calcium ; oocyte ; development ; patch clamp ; tunicate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Cell-attached patch clamp recordings from unfertilized oocytes of the ascidianBoltenia villosa reveal an ion channel which is activated by mechanical deformation of the membrane. These channels are seen when suction is applied to the patch pipette, but not in the absence of suction or during voltage steps. The estimated density of these stretch-activated channels is about 1.5/μm2, a figure equal to or greater than the density of known voltage-dependent channels in the oocyte. Ion substitution experiments done with combined whole-cell and attached patch recording, so absolute potentials are known, indicate that the channel passes Na+, Ca2+ and K+, but not Cl−. The channel has at least two open and two closed states, with the rate constant that leaves the longer-lived closed state being the primary site of stretch sensitivity. External Ca2+ concentration affects channel kinetics: at low calcium levels, long openings predominate, whereas at high calcium virtually all openings are to the short-lived open state. In multiple channel patches, the response to a step change in suction is highly phasic, with channel open probability decreasing over several hundred milliseconds to a nonzero steady-state level after an initial rapid increase. This channel may play a role in the physiological response of cells of the early embryo to the membrane strains associated with morphogenetic events.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01871723
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  • 15
    Electronic Resource
    Electronic Resource
    Role of calcium and calmodulin in the regulation of the rabbit ileal brush-border membrane Na+/H+ antiporter (1989)
    Springer
    The journal of membrane biology 108 (1989), S. 207-215 
    Details
    ISSN: 1432-1424
    Keywords: calcium ; calmodulin ; absorption ; ileum ; brush-border vesicle ; phosphorylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary In rabbit ileum, Ca2+/calmodulin (CaM) appears to be involved in physiologically inhibiting the linked NaCl absorptive process, since inhibitors of Ca2+/CaM stimulate linked Na+ and Cl− absorption. The role of Ca2+/CaM-dependent phosphorylation in regulation of the brush-border Na+/H+ antiporter, which is believed to be part of the neutral linked NaCl absorptive process, was studied using purified brush-border membrane vesicles, which contain both the Na+/H+ antiporter and Ca2+/CaM-dependent protein kinase(s) and its phosphoprotein substrates. Rabbit ileal villus cell brush-border membrane vesicles were prepared by Mg precipitation and depleted of ATP. Using a freezethaw technique, the ATP-depleted vesicles were loaded with Ca2+, CaM, ATP and an ATP-regenerating system consisting of creatine kinase and creatine phosphate. The combination of Ca2+/CaM and ATP inhibited Na+/H+ exchange by 45±13%. This effect was specific since Ca2+/CaM and ATP did not alter diffusive Na+ uptake, Na+-dependent glucose entry, or Na+ or glucose equilibrium volumes. The inhibition of the Na+/H+ exchanger by Ca2+/CaM/ATP was due to an effect on theV max and not on theK m for Na+. In the presence of CaM and ATP, Ca2+ caused a concentration-dependent inhibition of Na+ uptake, with an effect 50% of maximum occurring at 120nm. This Ca2+ concentration dependence was similar to the Ca2+ concentration dependence of Ca2+/CaM-dependent phosphorylation of specific proteins in the vesicles. The Ca2+/CaM/ATP-inhibition of Na+/H+ exchange was reversed by W13, a Ca2+/CaM antagonist, but not by a hydrophobic control, W12, or by H-7, a protein kinase C antagonist. we conclude that Ca2+, acting through CaM, regulates ileal brush-border Na+/H+ exchange, and that this may be involved in the regulation of neutral linked NaCl absorption.
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    URL: http://dx.doi.org/10.1007/BF01871735
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  • 16
    Electronic Resource
    Electronic Resource
    Ca2+-activated K+ channels from cultured renal medullary thick ascending limb cells: Effects of pH (1989)
    Springer
    The journal of membrane biology 110 (1989), S. 49-55 
    Details
    ISSN: 1432-1424
    Keywords: loop of Henle ; potassium secretion ; channels ; acid/base balance ; thick ascending limb ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Ca2+-activated K+ channels were studied in cultured medullary thick ascending limb cells (MTAL) using the patch-clamp technique. The purpose was to determine the effect of acidic pH on channel properties in excised patches of apical cell membrane. At pH 7.4, increasing Ca2+ on the intracellular side or applying positive voltages increases channel open probability. Reducing pH to 5.8 on the intracellular face of the channel decreases channel open probability at each voltage and Ca2+ concentration. Channel mean open times display two distributions and mean closed times display three distributions. Increasing Ca2+ or applying depolarizing voltages lengthens each of the mean open times and shortens each of the closed times. Lowering pH to 5.8 decreases the mean open times and increases mean closed times at each Ca2+ and voltage with the greatest effect on the mean closed times. In contrast, both single-channel conductance and channel kinetics are unaffected when pH is reduced to 5.8 on the extracellular face of the membrane. We conclude that protons interfere with Ca2+ binding to the gate of Ca2+-activated K+ channels reducing the probability of channel opening.
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    URL: http://dx.doi.org/10.1007/BF01870992
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  • 17
    Electronic Resource
    Electronic Resource
    Ca2+ and cAMP activate K+ channels in the basolateral membrane of crypt cells isolated from rabbit distal colon (1989)
    Springer
    The journal of membrane biology 110 (1989), S. 19-28 
    Details
    ISSN: 1432-1424
    Keywords: colon ; ion transport ; ion channel ; cyclic nucleotides ; calcium ; potassium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Using patch-clamp techniques, we have studied Ca2+-activated K+ channels in the basolateral membrane of freshly isolated epithelial cells from rabbit distal colon. Epithelial cell clusters were obtained from distal colon by gentle mechanical disruption of isolated crypts. Gigaohm seals were obtained on the basolateral surface of the cell clusters. At the resting potential (approximately −45 mV), with NaCl Ringer's bathing the cell, the predominant channels had a conductance of 131±25 pS. Channel activity depended on voltage as depolarization of the membrane increased the open probability. In excised inside-out patches, channels were found to be selective for K+ over Na+. Channel activity correlated directly with bath Ca2+ concentration in the excised patches. Channel currents were blocked by 5mm TEA+ and 1mm Ba2+. In cell-attached patches, after addition of the Ca2+ ionophore A23187, which increases intracellular Ca2+, open probability was markedly increased. Channel activity was also regulated by cAMP as addition of 1mm dibutyryl-cAMP in the bath solution in cell-attached patches increased channel open probability over 20-fold. Channels that had been activated by cAMP were further activated by Ca2+. We conclude that the basolateral membrane of epithelial cells from descending colon contains a class of potassium channels, which are regulated by intracellular Ca2+ and cAMP.
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    URL: http://dx.doi.org/10.1007/BF01870989
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  • 18
    Electronic Resource
    Electronic Resource
    c-src Locus determines increased rate of Na+, K+-cotransport and increased calcium content in (SHR×WKY)F2 hybrid erythrocytes (1989)
    Springer
    Bulletin of experimental biology and medicine 108 (1989), S. 1634-1636 
    Details
    ISSN: 1573-8221
    Keywords: c-src locus ; calcium ; Na+, K+-cotransport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00839709
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  • 19
    Electronic Resource
    Electronic Resource
    Ca2+ interaction with phospholipid bilayers studied by multifrequency phase fluorometry (1989)
    Springer
    Bioscience reports 9 (1989), S. 497-502 
    Details
    ISSN: 1573-4935
    Keywords: calcium ; phosphatidate ; DPH ; phase fluorometry ; distributional analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Calcium interaction with phospholipid membranes containing phosphatidic acid is studied by multifrequency phase fluorometry, using DPH as fluorescent molecule. DPH decay is analysed by a continuous distribution of lifetimes. The results suggest an increase of membrane heterogeneity at low calcium concentrations, without changes in the polarity of the environment surrounding the probe.
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    URL: http://dx.doi.org/10.1007/BF01117053
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  • 20
    Electronic Resource
    Electronic Resource
    Calcium absorption in man: Some dosing recommendations (1989)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 17 (1989), S. 631-644 
    Details
    ISSN: 1573-8744
    Keywords: calcium ; absorption ; efficiency ; dosing ; regimens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The absorption of calcium involves a saturable (active) and a nonsaturable (passive) component. The work of several investigators indicates that an inverse relationship exists between calcium intake and absorption efficiency. Human calcium absorption data from the literature were analyzed using a model which included both an active and a passive absorption component. Simulations were provided to illustrate the suitability of this model, and another previously reported model, to fit the data and to estimate the absorption efficiency of calcium when using different dosing regimens. Comparisons of the values predicted in this study with some literature values are provided and some assumptions and potential limitations associated with the use of this method are discussed. The division of the daily dose into equal increments taken at equally spaced intervals over the course of the day is recommended as a useful procedure for increasing the absorption efficiency and efficacy of calcium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01062122
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  • 21
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    The Role of Calcium Ions and Bile Salts on the Pancreatic Lipase-Catalyzed Hydrolysis of Triglyceride Emulsions Stabilized with Lecithin (1989)
    Springer
    Pharmaceutical research 6 (1989), S. 449-457 
    Details
    ISSN: 1573-904X
    Keywords: pancreatic lipase ; lipase ; lipolysis ; triglycerides ; kinetics ; mechanism ; calcium ; bile salts ; lecithin ; emulsions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Lecithin-stabilized triglyceride emulsions are subject to hydrolysis by pancreatic lipase. The time profiles of these reactions are characterized by a lag-phase and a zero-order phase. Lag phases are more pronounced with long-chain triglycerides. Ca2+ is effective in reducing the lag-phase and activating lipase. Kinetic analysis of the reactions suggests that, like previous findings by others, taurodeoxycholate (TDC) micellar solutions combine with the lipase–colipase complex to form another catalytically active enzyme form. This enzyme form exhibits reduced activity in the absence of Ca2+. In the presence of Ca2+ the mixed micelle–lipase complex becomes more active and opens a new pathway for lipolysis. It is suggested that this enzyme form can bind more easily to interfaces with different physicochemical properties. Under these conditions, Ca2+ activates the lipolysis of short-, medium-, and long-chain triglycerides by a similar mechanism. Maximum activities were measured in the presence of approximately 6 mM TDC and 30 mM Ca2+. The experimental conditions approximate the physiological conditions in the gastrointestinal tract since all of the factors studied here have been reported to be necessary for in vivo lipolysis and/or absorption of triglycerides. A mechanistic model for lipolysis in the presence of Ca2+ and the bile salt TDC is proposed which accounts for most of the experimental observations in a quantitative manner.
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    URL: http://dx.doi.org/10.1023/A:1015956104500
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    Autoradiographic study of human epidermocytes cultured in a low calcium medium (1989)
    Springer
    Bulletin of experimental biology and medicine 107 (1989), S. 574-577 
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    ISSN: 1573-8221
    Keywords: epidermocytes ; calcium ; multiplication ; autoradiographic investigation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1007/BF00842411
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    Cellular mechanisms of transient contraction of coronary arterial smooth muscles in hypoxia: Role of intracellular Ca++ (1989)
    Springer
    Bulletin of experimental biology and medicine 107 (1989), S. 3-6 
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    ISSN: 1573-8221
    Keywords: hypoxia ; coronary spasm ; calcium ; sarcoplasmic reticulum ; inositol-1,4,5-triphosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1007/BF00837042
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    Calcium-induced fusion of didodecylphosphate vesicles: The lamellar to hexagonal II (HII) phase transition (1987)
    Springer
    The journal of membrane biology 95 (1987), S. 255-263 
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    ISSN: 1432-1424
    Keywords: didodecylphosphate ; calcium ; membrane fusion ; lamellar phase ; hexagonal phase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Electron microscopic techniques have been employed to investigate the ability of didodecylphosphate vesicles (diameter approx. 900 Å) to fuse in the presence of Ca2+. As revealed by negative staining, Ca2+ induces extensive fusion and large vesicles with diameters up to 7000 Å are formed. In a processsecondary to fusion, the fused vesicles display a tendency to flatten and are subsequently transformed into extended tubular structures. Freeze-fracture electron microscopy, in conjunction with31P NMR and selected area electron diffraction measurements indicate that the tubes are packed in a hexagonal (HII) array and that the amphiphiles are converted from the lamellar to the hexagonal HII phase. The relationship between membrane fusion and the lamellar-to-hexagonal phase transition is discussed in terms of formation and abundance of transiently stable inverted micellar intermediates at contact regions between two interacting membranes. A model for the conversion of the (vesicular) lamellar into the (tubular) hexagonal HII phase is presented, taking into account the molecular shape of the amphiphile. The relevance of using simple synthetic amphiphiles as models for phospholipid bilayers and complex biomembrane behavior is briefly discussed.
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    URL: http://dx.doi.org/10.1007/BF01869487
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    Calcium transport affinity, ion competition and cholera toxin effects on cytosolic Ca concentration (1987)
    Springer
    The journal of membrane biology 96 (1987), S. 243-249 
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    ISSN: 1432-1424
    Keywords: cholera toxin ; ionophore ; calcium ; brush-border membrane vesicles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The physiological relevance of an apparent ionophore activity of cholera toxin towards Ca2+ has been examined in several different systems designed to measure affinity, specificity, rates of ion transfer, and effects on intracellular ion concentrations. Half-maximal transfer rates across porcine jejunal brush-border vesicles were obtained at a concentration of 0.20 μM Ca2+. When examined in the presence of competing ions the transfer process was blocked by very low concentrations of La3+ or Cd2+. Sr2+, Ba2+ and Mg2+ were relatively inefficient competitors for Ca2+ transport mediated by cholera toxin. The relative affinities observed would be compatible with a selectivity for Ca2+ transfer at physiological ion concentrations, as well as an inhibition of this ionophore activity by recognized antagonists of cholera toxin such as lanthanum ions. Entry rates of Ca2+ into brush-border vesicles exposed to cholera toxin were large enough to accelerate the collapse of a Ca2+ gradient generated by endogenous Ca, Mg-ATPase activity. The treatment of isolated jejunal enterocytes with cholera toxin caused a significant elevation in cytosolic Ca2+ concentrations as measured by Quin-2 fluorescence. This effect was specifically prevented by prior exposure of the cholera toxin to excess ganglioside GM1. We conclude that cholera toxin has many of the properties required for promoting transmembranes Ca2+ movement in membrane vesicles and appears to be an effective Ca2+ ionophore in isolated mammalian cells.
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    Biological effects of lithium: Experimental analysis in plant cytokinesis (1987)
    Springer
    Cellular and molecular life sciences 43 (1987), S. 1025-1027 
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    ISSN: 1420-9071
    Keywords: Plant cytokinesis ; lithium ; caffeine ; calcium ; magnesium ; sodium and potassium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The biological effects of lithium ions have been studied, using plant cytokinesis in onion root meristems as the experimental model. Lithium induces binucleate cells by inhibiting cell plate formation. Moreover, lithium and caffeine have additive effects on the induction of binucleate cells. Na+, K+, Ca++ and Mg++ antagonize lithium-induced inhibition of cytokinesis.
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    URL: http://dx.doi.org/10.1007/BF01952228
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    Regulation of exocytosis in electrically permeabilized insulin-secreting cells. Evidence for Ca2+ dependent and independent secretion (1987)
    Springer
    Bioscience reports 7 (1987), S. 443-454 
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    ISSN: 1573-4935
    Keywords: calcium ; exocytosis ; insulin secretion ; permeabilized cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The regulation of insulin secretion from RINm5F cells exposed to high voltage discharge has been investigated. Electron microscopy revealed that the overall structure of the cells was preserved after permeabilization. In this preparation insulin release was stimulated by Ca2+ (EC50=2.4 μM). The stable GTP analogue GTPγS enhanced secretion both at intermediate (nano- to micromolar) and vanishingly low (〈10 pM) Ca2+ concentrations. At optimal Ca2+ (10 μM) the effect of GTPγS was greatly reduced. We investigated whether the secretory response to GTP analogues was mediated by any of three enzyme systems regulated by GTP-binding proteins, i.e. generation of cyclic AMP by adenylate cyclase, of diacylglycerol by phospholipase C and of arachidonic acid by phospholipase A2. The involvement of these messenger systems could be excluded as (i) cyclic AMP only had minor, Ca2+ dependent effects, (ii) phospholipase C was not activated in the absence of Ca2+ and insulin secretion due to the phorbol ester TPA displayed a different Ca2+ dependency, (iii) arachidonic acid did not elicit Ca2+ independent insulin secretion. These results, taken together with the finding that insulin secretion due to Ca2+ or TPA is attenuated by the inhibitory guanine nucleotide GDPβS, suggest the existence of a regulatory site in exocytosis which is sensitive to guanine nucleotides.
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    Calcium and diacylglycerol control of secretion (1987)
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    Bioscience reports 7 (1987), S. 355-367 
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    ISSN: 1573-4935
    Keywords: calcium ; diacylglycerol ; exocytosis ; secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Measurements of intracellular Ca2+ in adrenal medullary cells suggest that a transient rise in Ca2+ leads to a transient secretory response, the rise in Ca2+ being brought about by an influx through voltage-sensitive Ca channels which subsequently inactivate. The level of Ca2+ observed is much smaller than the Ca2+ needed to trigger secretion when introduced directly into the cell. The discrepancy is removed by the presence of diacylglycerot, which increases the sensitivity of the secretory process to Ca2+. The site of action of Ca2+ and diacylglycerol is probably protein kinase C, and tile different secretory responses to increases of Ca2+ and diacylglycerol can be modelled in terms of a preferential order of binding of these two substrates to the enzyme. ATP is needed for secretion: one role is possibly to confer stability to the secretory apparatus; another may involve phosphorylation of some key protein. The kinetics of secretion suggest that if Ca2+ regulates phosphorylation or dephosphorylation, then it is therate of change of phosphorylation that controls secretion rather than theextent of phosphorylation or dephosphorylation. Guanine nucleotide-binding proteins may play a role not only at the level of signal transduction coupling, but also at or near the site of exocytosis, and the mechanism by which some Botulinum toxins inhibit secretion may be associated with these proteins.
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    How calcium may cause exocytosis in sea urchin eggs (1987)
    Springer
    Bioscience reports 7 (1987), S. 383-397 
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    ISSN: 1573-4935
    Keywords: calcium ; eggs ; exocytosis ; sea urchin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The process of secretory granule-plasma membrane fusion can be studied in sea urchin eggs. Micromolar calcium concentrations are all that is required to bring about exocytosisin vitro. I discuss recent experiments with sea urchin eggs that concentrate on the biophysical aspects of granule-membrane fusion. The backbone of biological membranes is the lipid bilayer. Sea urchin egg membrane lipids have negatively charged head groups that give rise to an electrical potential at the bilayer-water interface. We have found that this surface potential can affect the calcium required for exocytosis. Effects on the surface potential may also explain why drugs like trifluoperazine and tetracaine inhibit exocytosis: they absorb to the bilayer and reduce the surface potential. The membrane lipids may also be crucial to the formation of the exocytotic pore through which the secretory granule contents are released. We have measured calcium-induced production of the lipid, diacylglycerol. This lipid can induce a phase transition that will promote fusion of apposed lipid bilayers. The process of exocytosis involves the secretory granule core as well as the lipids of the membrane. The osmotic properties of the granule contents lead to swelling of the granule during exocytosis. Swelling promotes the dispersal of the contents as they are extruded through the exocytotic pore. The movements of water and ions during exocytosis may also stabilize the transient fusion intermediate and consolidate the exocytotic pore as fusion occurs.
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    The molecular and biochemical basis of cystic fibrosis (1987)
    Springer
    Bioscience reports 7 (1987), S. 167-185 
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    ISSN: 1573-4935
    Keywords: cystic fibrosis ; exocrine ; autonomic ; cyclic AMP ; calcium ; chloride ; epithelial
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1007/BF01124787
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    Electrophysiological evidence suggests a defective Ca2+ control mechanism in a newParamecium mutant (1987)
    Springer
    The journal of membrane biology 98 (1987), S. 275-283 
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    ISSN: 1432-1424
    Keywords: Paramecium ; calcium ; cilia ; mutants ; Ca2+ pump ; Ca2+ buffering ; ion channels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary A new mutant ofParamecium tetraurelia, k-shyA, was characterized behaviorally and electrophysiologically. The mutant cell exhibited prolonged backward swimming episodes in response to depolarizing conditions. Electrophysiological comparison of k-shyA with wild type cells under voltage clamp revealed that the properties of three Ca2+-regulated currents were altered in the mutant. (i) The voltage-dependent Ca2+ current recovered from Ca2+-dependent inactivation two- to 10-fold more slowly than wild type. Ca2+ current amplitudes were also reduced in the mutant, but could be restored by EGTA injection. (ii) The decay of the Ca2+-dependent K+ tail current was slower in the mutant. (iii) The decay of the Ca2+-dependent Na+ tail current was also slower in the mutant. All other membrane properties studied, including the resting membrane potential and resistance and the voltage-sensitive K+ currents, were normal in k-shyA. Considered together, these observations are consistent with a defect in the ability of k-shyA to reduce the free intracellular Ca2+ concentration following stimulation. The possible targets of the genetic lesion and alternative explanations are discussed. The k-shy mutants may provide a useful tool for molecular and physiological analyses of the regulation of Ca2+ metabolism inParamecium.
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    Na+/K+/Cl− cotransport in cultured vascular smooth muscle cells: Stimulation by angiotensin II and calcium ionophores, inhibition by cyclic AMP and calmodulin antagonists (1987)
    Springer
    The journal of membrane biology 99 (1987), S. 51-63 
    Details
    ISSN: 1432-1424
    Keywords: endothelial cells ; Na+/K+/Cl− cotransport ; cyclic AMP ; phenothiazines ; calcium ; angiotensin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The specific activity of the Na+/K+/Cl− cotransporter was assayed by measuring the initial rates of furosemide-inhibitable86Rb+ influx and efflux. The presence of all three ions in the external medium was essential for cotransport activity. In cultured smooth muscle cells furosemide and bumetanide inhibited influx by 50% at 5 and 0.2 μm, respectively. The dependence of furosemide-inhibitable86Rb+ influx on external Na+ and K+ was hyperbolic with apparentK m values of 46 and 4mm, respectively. The dependence on Cl− was sigmoidal. Assuming a stoichiometry of 1∶1∶2 for Na+/K+/Cl−, aK m of 78mm was obtained for Cl−. In quiescent smooth muscle cells cotransport activity was approximately equal to Na+ pump activity with each pathway accounting for 30% of total86Rb+ influx. Growing muscle cells had approximately 3 times higher cotransport activity than quiescent ones. Na+ pump activity was not significantly different in the gorwing and quiescent cultures. Angiotensin II (ANG) stimulated cotransport activity as did two calcium-transporting ionophores, A23187 and ionomycin. The removal of external Ca2+ prevented A23187, but not ANG, from stimulating the cotransporter. Calmodulin antagonists selectively inhibited86Rb+ influx via the cotransporter. Beta-adrenoreceptor stimulation with isoproterenol, like other treatments which increase cAMP, inhibited cotransport activity. Cultured porcine endothelial cells had 3 times higher cotransport activity than growing muscle cells. Calmodulin antagonists inhibited cotransport activity, but agents which increase cAMP or calcium had no effect on cotransport activity in the endothelial cells.
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    Effect of a calcium channel blocker on pituitary luteinizing hormone secretion in intact and castrated male and female rats (1987)
    Springer
    Bulletin of experimental biology and medicine 103 (1987), S. 400-402 
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    ISSN: 1573-8221
    Keywords: luteinizing hormone ; sex steroids ; calcium ; verapamil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1007/BF00840576
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    Genetic analysis of inheritance of rates of Na+, K+-cotransport, calcium concentration in erythrocytes, and blood pressure of F2 hybrids of spontaneously hypertensive and normotensive rats (1987)
    Springer
    Bulletin of experimental biology and medicine 103 (1987), S. 518-520 
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    ISSN: 1573-8221
    Keywords: calcium ; spontaneous hypertension ; orthovanadate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1007/BF00842486
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    Antioxidant-induced calcium transport in biological membranes (1987)
    Springer
    Bulletin of experimental biology and medicine 104 (1987), S. 1220-1223 
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    ISSN: 1573-8221
    Keywords: biological membranes ; antioxidant ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1007/BF00841997
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    The dual effector system for exocytosis in mast cells: Obligatory requirement for both Ca2+ and GTP (1987)
    Springer
    Bioscience reports 7 (1987), S. 369-381 
    Details
    ISSN: 1573-4935
    Keywords: stimulus-secretion coupling ; G-proteins ; mast cells ; calcium ; permeabilised cells ; streptolysin-O ; exocytosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The secretory process is a coordinated cellular response, initiated by occupation of surface receptors and comprising an ordered sequence of biochemical steps subject to multiple controls. Conceptually we can divide the sequence into two main sections comprising early, receptor-mediated events leading to generation of intracellular second messengers, and later events leading to membrane fusion and exocytosis. With the discovery that occupation of Ca2+ mobilising receptors leads to activation of polyphosphoinositide phosphodiesterase (PPI-pde) through the mediation of a G-protein (Gp), all the early events can be ascribed to the plasma membrane. Investigation of the exocytotic stage of secretion has been simplified by the use of permeabilised cells in which the composition of the cytosol can be precisely controlled. We have used streptolysin-O, a bacterial cytolysin which generates protein-sized pores in the plasma membrane, to investigate the exocytotic mechanism of rat mast cells. We find that in addition to the activation of PPI-dpe, GTP also acts in concert with Ca2+ at, or close to, the exocytotic site. Exocytosis can occur after substantial depletion of cytosol lactate dehydrogenase and 3-phosphoglycerate kinase indicating that soluble cytosol proteins are unlikely to play any role. There is no absolute requirement for ATP or phosphorylating nucleotide in exocytosis though when present the effective affinities of the two obligatory effectors (i.e. Ca2+ and GTP) are substantially enhanced.
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    Effect of calcium and F-actin on the rate of SH2 modification in skeletal myosin (1987)
    Springer
    Bioscience reports 7 (1987), S. 543-551 
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    ISSN: 1573-4935
    Keywords: calcium ; F-actin ; myosin ; SH2 region
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The rate constant of modification of a specific thiol group, SH2, with N-ethylmaleimide (NEM) has been used to estimate the conformational change in the local area containing SH2 (SH2 region) of skeletal myosin as a structural probe. The rate of Mg2+-ATP-induced SH2 modification of subfragment-1 (S-l) isozymes was regulated by Ca2+ in the pCa range below 6.4 and was not regulated in the pCa range above 6.4. No substantial difference between S-1 containing alkali light chain, A1, (S-1(A1)) and S-1 containing alkali light chain, A2, (S-1(A2)) was observed in the Ca2+-dependent rate of SH2 modification. Due to the presence of this Ca2+ regulation in myosin (absence in S-1 isozymes) in the pCa range above 6.4, absence of 5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB) light chain in S-1 isozymes, and high affinity of Ca2+ for DTNB light chain, this Ca2+ regulation in the pCa range above 6.4 is possibly related to the Ca2+ binding to DTNB light chain. F-Actin, which is entirely free from tropomyosin and troponin, enhanced the rate of Mg2+-ATP-induced SH2 modification of S-1 isozymes equally and of myosin, and reduced the Ca2+ sensitivity with an increase in F-actin concentration.
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    Action of cyclosporine on mitochondrial calcium fluxes (1987)
    Springer
    Journal of bioenergetics and biomembranes 19 (1987), S. 297-303 
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    ISSN: 1573-6881
    Keywords: Cyclosporine ; calcium ; mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Cyclosporine (Cys A) is a potent immunosuppressor used to reduce rejection in transplantation surgery. We studied its action upon mitochondrial functions: oxidative phosphorylation and Ca2+ movements through mitochondrial membrane. We show that Cys A exhibits an inhibitory effect upon mitochondrial respiration. This result is in good agreement with previous works and may be correlated with Cys A toxicity. The action of cyclosporine on calcium fluxes is more pronounced. Indeed it blocks mitochondrial calcium efflux and allows mitochondria to accumulate a large amount of calcium. If this effect occurs in the cell, it would induce a Ca2+ decrease in cytosol. This action might be correlated with the inhibitory effect of Cys A upon the mitogenic stimulation of T lymphocytes.
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    The mechanism of lead-induced mitochondrial Ca2+ efflux (1987)
    Springer
    Journal of bioenergetics and biomembranes 19 (1987), S. 285-295 
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    ISSN: 1573-6881
    Keywords: Mitochondria ; lead ; calcium ; NAD(P)H oxidation ; calcium transport ; mitochondrial calcium ; pyridine nucleotide oxidation ; kidney mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Addition of Pb2+ to rat kidney mitochondria is followed by induction of several reactions: inhibition of Ca2+ uptake, collapse of the transmembrane potential, oxidation of pyridine nucleotides, and a fast release of accumulated Ca2+. When the incubation media are supplemented with ruthenium red, the effect of Pb2+ on NAD(P)H oxidation, membrane ΔΨ, and Ca2+ release are not prevented if malate-glutamate are the oxidizing substrates; however, the latter two lead-induced reactions are prevented by ruthenium red if succinate is the electron donor. It is proposed that in mitochondria oxidizing NAD-dependent substrates, Pb2+ induces Ca2+ release by promoting NAD(P)H oxidation and a parallel drop in ΔΨ due to its binding to thiol groups, located in the cytosol side of the inner membrane. In addition, it is proposed that with succinate as substrate, the Ca2+-releasing effect of lead is due to the collapse of the transmembrane potential as a consequence of the uptake of Pb2+ through the calcium uniporter, since such effect is ruthenium red sensitive.
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    Inhibition of the Na+/Ca2+ antiport of heart mitochondria by diethylpyrocarbonate (1987)
    Springer
    Journal of bioenergetics and biomembranes 19 (1987), S. 515-524 
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    ISSN: 1573-6881
    Keywords: Mitochondria ; diethylpyrocarbonate ; heart ; inhibition ; sodium ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Diethylpyrocarbonate inhibits Na+/Ca2+ antiport activity in isolated heart mitochondria. The inhibition is time-dependent with maximum activity developed after 5 min at 25°C. The reaction of diethylpyrocarbonate with the mitochondrial membrane is biphasic with 25–30 nmol mg−1 reacting rapidly and an additional 30 nmol mg−1 taken up slowly over a 30-min incubation. Inhibition of mitochondrial Na+/Ca2+ antiport by diethylpyrocarbonate decreases theV max of the reaction, and the inhibition cannot be reversed by washing the mitochondria or addition of excess histidine. The inhibition occurs at levels of inhibitor that have little or no effect on Ca2+ uptake, Na+/H+ antiport, or succinate respiration. A portion of the Na+-dependent efflux of Ca2+ is insensitive to diethylpyrocarbonate and this component is abolished by diltiazem. The mechanism by which diethylpyrocarbonate inactivates Na+/Ca2+ antiport is still uncertain, but may involve the modification of an unprotonated histidine residue in the transporter.
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    Control of mitochondrial Ca2+ retention by ADP-stimulated glutamic dehydrogenase (1987)
    Springer
    Journal of bioenergetics and biomembranes 19 (1987), S. 571-580 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; calcium ; mitochondrial Ca2+ transport ; adenine nucleotides ; glutamic dehydrogenase ; kidney mitochondria ; ADP-stimulated glutamic dehydrogenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The protective effect of ADP on unspecific Ca2+ release and collapse of the transmembrane potential was analyzed in mitochondria from kidneys of rats. The presence of ADP in the incubation mixture prevents Ca2+ leakage and collapse of δω in sucrose-containing medium, but fails to do so in KCl medium. The effect of the adenine nucleotide in sucrose media correlates with an increase in the level of reduced pyridine nucleotides; the increase was due to a stimulatory effect on the activity of glutamic dehydrogenase. It also was observed that in KCl media, in the presence and in the absence of ADP the rate of NADH oxidation through the respiratory chain was higher than in sucrose; in this latter medium a high level of reduced pyridine nucleotides was found, in comparison to KCl media. It is proposed that the role of ADP is to increase glutamic dehydrogenase activity and in consequence to provoke a higher rate of formation of NADH which in turn controls Ca2+ release.
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