[Long-term prediction of age-specific mortality with a multivariate autoregressive model].
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Asia↗
Biomedical subjects
T Oba
Publications and source records attributed to T Oba.
Gold ion inhibits silver ion induced contracture and activates ryanodine receptors in skeletal muscle.
Effects of Au3+ on Ag(+)-induced contractures and Ca2+ release channel activity in the sarcoplasmic reticulum were studied in frog skeletal muscles. Single fibres spontaneously produced phasic and tonic contractures upon addition of 5-20 microM Ag+ or more than 50 microM Au3+. Simultaneous application of 5 microM Ag+ and 20 microM Au3+ inhibited contractures induced by Ag+. Au3+ applied immediately after development of Ag(+)-induced contractures shortened the duration of the phasic contracture and markedly decreased the subsequent tonic contracture. Pretreatment of fibres with Au3+ inhibited the Ag(+)-induced phasic contracture. Ca2+ release channels incorporated into planar lipid bilayers were activated in response to Au3+ at 20 to 200 microM. A close relationship was observed between Ca2+ release channel open probability and amplitude of the Au(3+)-induced tonic contracture. Channel activity was inhibited by 5 microM ruthenium red. We conclude that extracellular Au3+ at low concentrations modifies the interaction of Ag+ with voltage sensors in the transverse tubules to inhibit the Ag(+)-induced contracture and, if it enters the cell, Au3+ may directly activate the sarcoplasmic reticulum Ca2+ release channel to partially contribute to the tonic contracture.
Animals↗
A novel phasic contraction induced by dithiothreitol in frog skeletal muscle.
1. Dithiothreitol (DTT), at 50-100 mM, induced a phasic reversible contraction of frog skeletal muscle. 2. Exposure of single fibers to nifedipine (20 microM), an L-type Ca2+ antagonist, blocked the twitch and tetanus tensions but never affected the DTT-induced contraction. 3. DTT also produced a phasic contraction in fibers where voltage sensors were inactivated in the presence of high K+ concentration (190 mM). 4. A fiber was mechanically skinned after observation of DTT-induced contraction. The skinned fiber contracted in response to a DTT concentration similar to that required to produce contraction in intact fibers before skinning. 5. In skinned fibers, DTT, at 100 or 200 mM, inhibited the accumulation of Ca2+ by SR, but not Ca2+ ATPase activity. 6. These results suggest that a high concentration of DTT triggers Ca2+ efflux from the SR through action on the Ca2+ release channel and/or closely associated proteins, such as triadin and FK-506 binding protein.
Animals↗
H2O2 modulates twitch tension and increases Po of Ca2+ release channel in frog skeletal muscle.
The effect of H2O2 was examined to elucidate the basis of muscle injury after exercise. Exposure of single fibers to 1.5-6 mM H2O2 led to twitch potentiation followed by a marked decrease. Then, fibers contracted spontaneously. BAY K 8644 augmented twitch potentiation and slowed the decay of twitches. In 5 mM dithiothreitol (DTT), twitch potentiation and spontaneous contraction were not observed on H2O2 addition. Cytoplasmic application of 1.5-3 mM H2O2 to heavy sarcoplasmic reticulum (SR) vesicles incorporated into planar lipid bilayers increased the open probability of Ca2+ release channels, an effect reversed by DTT. We investigated oxidation of sulfhydryl groups on proteins in SR membrane by H2O2 with N-(7-dimethylamino-4-methyl-3-coumarinyl)maleimide. Pretreatment of light and heavy SR membranes with 1.5 mM H2O2 exponentially increased fluorescence intensity. The time constant of the intensity increase was increased markedly only in heavy SR in solution containing 50 microM cytoplasmic Ca2+, so Ca2+ release was associated with protein oxidation by H2O2. Thus extracellular H2O2 probably acts by oxidizing sulfhydryls of proteins at two distinct sites: the dihydropyridine receptors, oxidation of which elicits potentiation and subsequent inhibition of twitches, and Ca2+ release channels, whose oxidation elicits spontaneous contraction, resulting in muscle dysfunction.
Animals↗
Modulation of frog skeletal muscle Ca2+ release channel gating by anion channel blockers.
Effects of niflumic acid and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) on frog skeletal muscle ryanodine receptors have been studied by incorporating sarcoplasmic reticulum vesicles into planar lipid bilayers. Niflumic acid increased the mean open probability (Po) at 10 microM and decreased Po at 100 microM with no change in open time constants, unitary conductance, and reversal potential. The Po was augmented by DIDS at 5-200 microM without affecting either unitary conductance or reversal potential. DIDS induced a new third open time constant, probably contributing to a long-lived open state. Channels modified by niflumic acid or DIDS still responded to Ca2+ release channel modulators. These results provide evidence that niflumic acid and DIDS modify the gating mechanism of ryanodine receptors without affecting binding sites to the modulators and the physical pathway of the conducting pore. p-Chloromercuriphenyl sulfonic acid (pCMPS) transiently increased the Po. The channel modified by DIDS responded to pCMPS, whereas that by ryanodine did not. The long open state of the channel induced by DIDS is produced by a quite different mechanism(s) from that by ryanodine. Contrary to cardiac ryanodine receptors, Po of skeletal muscle channels was independent of voltage after DIDS modification.
4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
Possible involvement of Ca(2+)-induced Ca2+ release mechanism in Ag(+)-induced contracture in frog skeletal muscle.
To determine if an Ag(+)-induced contracture is associated with the Ca(2+)-induced Ca2+ release mechanism in the sarcoplasmic reticulum, effects of Ca(2+)-induced Ca2+ release modulators on the Ag(+)-induced contracture were studied with single fibers of frog toe skeletal muscle. The fiber treated with 1 mM caffeine contracted significantly much more than controls without caffeine at Ag+ concentrations below 1 microM. Procaine shifted the Ag+ concentration-tension curve to the right, dose-dependently. When 10 mM procaine was applied to contracting fibers not treated with caffeine, the duration of 5 microM Ag(+)-induced contracture was shortened with a little decrease in tension amplitude, that was different from the effect of procaine on caffeine contracture. In caffeine solution, 0.5 microM Ag+ caused a long-lasting contracture with sometimes two peaks. 2 mM procaine led to disappearance of such two peaks, resulting in shortening of the contracture. K+ contracture was potentiated by 1 mM caffeine only at lower concentrations of K+, and inhibited by 10 mM procaine. These results suggest that the Ag(+)-induced contracture is composed of two components: Ca(2+)-induced Ca2+ release-dependent and -independent. 5 microM Ag(+)-induced contracture slowly relaxed with a wavy tension pattern to the resting level when 0.05 mM dithiothreitol was applied around peak of the tension. This relaxation was accelerated by procaine application. These findings may be explained by attributing a portion of Ag(+)-induced contracture to the effect of Ca2+ released through the Ca(2+)-induced Ca2+ release mechanism in the sarcoplasmic reticulum.
Animals↗
DNase I interaction on muscle Z-line.
The effect of deoxyribonuclease I on muscle Z-line structures was re-examined. Under conditions of deoxyribonuclease I activation (presence of the divalent cation Ca2+ and Mg2+), a deoxyribonuclease I preparation did not affect Z-line structure if phenylmethylsulfonylfluoride, an inhibitor of serine proteases, was also present. In the absence of protease inhibitor, both Z-lines and M-lines were digested, even in the presence of EDTA and EGTA as inhibitors of deoxyribonuclease I. These electron microscopic observations were consistent with the following results from sodium dodecyl sulphate gel electrophoresis: when the protease was inhibited but deoxyribonuclease I was activated, myofibrillar proteins remained essentially intact. However, degradation of proteins in both rabbit psoas and chicken pectoralis myofibrils was observed in the presence of deoxyribonuclease I inhibitors when the protease inhibitor was absent. Our data strongly suggest that the interaction of deoxyribonuclease I with Z-line proteins previously reported is most likely due to contamination of the deoxyribonuclease I fraction by the serine-type proteases.
Animals↗
Protein substrates and heat shock reduce the DNA-binding ability of Escherichia coli Lon protease.
Interaction between the fusion protein MBP-Lon, formed by maltose-binding protein and Lon protease, and the plasmid pBR322 was studied to clarify the DNA-binding behavior of the Lon protease. Since the MBP-Lon fusion protein that was bound to the plasmid was strongly adsorbed by amylose resin, complex formation and dissociation were determined by quantifying the unadsorbed plasmid using agarose gel electrophoresis. The autolysis of MBP-Lon fusion protein was suppressed when the protein was bound to the plasmid. The plasmid was completely dissociated from MBP-Lon fusion protein by the addition of the protein substrates of Lon protease (i.e. alpha-casein and denatured bovine serum albumin). In addition, at high temperatures, MBP-Lon fusion protein lost its plasmid-binding ability, although it fully retained ATP-dependent protease activity. These results suggest that Lon protease loses DNA-binding ability when cells are exposed to abnormal conditions and the amount of damaged proteins increases. On the other hand, DNA probably plays an important role in controlling the Lon protease activity in cells under normal conditions by entrapping the enzyme.
ATP-Binding Cassette Transporters↗
Overproduction and purification of Lon protease from Escherichia coli using a maltose-binding protein fusion system.
Lon protease, which plays a major role in degradation of abnormal proteins in Escherichia coli, was overproduced and efficiently purified using the maltose-binding protein (MBP) fusion vector. The MBP-Lon fusion protein was expressed in a soluble form in E. coli and purified to homogeneity by amylose resin in a single step. Lon protease was split from MBP by cleaving a fusion point between MBP and Lon with factor Xa and purified by amylose resin and subsequent gel filtration. In this simple method, Lon protease was purified to homogeneity. Purified MBP-Lon fusion protein and Lon protease showed similar breakdown activities with a peptide (succinyl-L-phenylalanyl-L-leucyl-phenylalanyl-beta-D-methoxynaphthyl amide) and protein (alpha-casein) in the presence of ATP. Therefore, the gene-fusion approach described in this study is useful for the production of functional Lon protease. MBP-Lon fusion protein, which both binds to the amylose resin and has ATP-dependent protease activity, should be especially valuable for its application in the degradation of abnormal proteins by immobilized enzymes.
2-Naphthylamine↗
[[An application of spectral analytic method (MEM) to the time series of frequency of deaths by cause of death: the case of total deaths]].
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Cause of Death↗
Involvement of thiols in the induction of inward current induced by silver in frog skeletal muscle membrane.
Exposure of voltage-clamped frog skeletal muscle fibres to silver caused a maintained inward current which could be carried by Ca2+, Mg2+ or Na+. Inorganic Ca2+ channel blockers and dithiothreitol (SH reducing agent) diminished this current, but a Na+ channel blocker did not. Thus, silver activates the Ca2+ channel by acting on SH groups in a Ca2+ channel protein.
Animals↗
Gold ion induces contraction in frog skeletal muscle fibers.
In Ringer solution, gold ions (Au3+) at concentrations more than 50 microM produced a phasic and subsequent tonic contraction spontaneously in single toe muscle fiber of frog. When 1.8 mM Ca2+ in Ringer solution was replaced by 3 mM Mg2+, tonic contraction was no longer provoked in response to Au3+. Only phasic contraction was potentiated by 10 mM perchlorate (an L-type Ca2+ channel activator) irrespective of external Ca2+, and both phasic and tonic contractions were blocked by 10 microM nifedipine (an L-type Ca2+ channel blocker). Upon application of 5 mM dithiothreitol to the contracting fiber, the Au(3+)-induced tension disappeared rapidly. The fiber pretreated with 0.05% H2O2 for 10 min did not respond to Au3+ with visible contraction. Treatment of H2O2-paralyzed fibers with dithiothreitol (to reduce oxidized sulfhydryl groups) fully restored the Au(3+)-induced contraction. These results suggest that the phasic contraction induced by Au3+ probably is mediated through sulfhydryl groups in the L-type Ca2+ channel (dihydropyridine receptor) on the transverse tubular membrane. Sustained contraction was produced by Ca2+ application to Au(3+)-treated fibers in Mg(2+)-Ringer solution, and Au3+ caused membrane depolarization in a dose-dependent manner. These effects of Au3+ may explain tonic contraction development.
Animals↗
Sulfhydryl oxidation induces calcium release from fragmented sarcoplasmic reticulum even in the presence of glutathione.
Alcian blue and plumbagin induced transient Ca2+ release from fragmented sarcoplasmic reticulum. Dithiothreitol (DTT) and glutathione (GSH) partially blocked Ca2+ release induced by these oxidizing compounds. Pretreatment of alcian blue and plumbagin with DTT or GSH for more than 1 min was required to abolish the ability of the oxidizing compounds to release Ca2+. Mg2+ and ruthenium red completely blocked alcian blue-and plumbagin-induced Ca2+ release. These results suggest that oxidation of sulfhydryls on Ca2+ release channels induces Ca2+ release even in the presence of GSH in situ.
Animals↗
Muscle contraction and inward current induced by silver and effect of Ca2+ channel blockers.
Single fibers from toe or anterior tibialis muscle contracted transiently and then tonically in the presence of 1.8 mM Ca2+ on addition of 10 microM Ag+. Exposure of fibers to Cd2+ completely inhibited tonic contraction and modified phasic contraction to some extent. Nifedipine at 10 microM initially potentiated and then completely inhibited twitch tension; subsequently, fibers no longer contracted phasically in response to 20 microM Ag+, whereas slight tonic contraction still occurred. Fibers with membrane potential clamped at -90 mV produced maintained inward current on application of Ag+. Simultaneous administration of 1 mM Cd2+ and 10 microM Ag+ to fibers voltage clamped with the double mannitol gap technique almost completely blocked the inward current. Removal of Cd2+ elicited a rapid and large inward current. Ag(+)-induced inward current was inhibited when 1 mM Cd2+ was applied to fibers during development of the inward current. In fibers paralyzed with 10 microM nifedipine, the inward current induced by 10 microM Ag+ was partially inhibited. These results suggest that phasic contraction induced by Ag+ is controlled by L-type Ca2+ channels (probably voltage sensors) located in the T-tubular membrane, whereas tonic contraction involves Ca2+ channels sensitive and/or insensitive to dihydropyridine in the surface and T-tubular membranes.
Animals↗
Ag(+)-induced inward current on frog skeletal muscle.
Ag+ caused an inward current on voltage-clamped skeletal muscle. The current was carried by Ca2+, Mg2+, and Na+, and was blocked by Cd2+ or Ni2+ but not by nifedipine or D600. Channel gating is supposed to be modified by Ag+.
Animals↗
Silver-induced frog skeletal muscle contraction and its modulation by calcium antagonists nifedipine and felodipine and calcium agonist Bay K 8644.
1. Ag+ induces one phase of a transient contracture in frog skeletal muscle (0.3-10 microM) and potentiates twitch tension when the fiber is given continuous stimulation. 2. The potentiation of fiber contraction by Ag+ is similar to the effect of Ca2+ antagonists nifedipine and felodipine. 3. Bay K 8644 (100 nM) potentiates and accelerates Ag(+)-induced tension development and the inactivation occurs more rapidly than in the control (Ag+ alone). 4. Two factors can be considered to be essential for the induction of Ag+ contracture: (1) a certain number of Ag+ ions must bind to free SH groups of the voltage sensor; and (2) the binding must occur within a limited time to raise the mechanical threshold to induce contracture. 5. All results suggest that Ag+ binding to crucial SH groups on the Ca2+ channel may be responsible for the activation of muscle contraction, potentiation, and the inhibition of excitation-contraction coupling in skeletal muscle.
3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
Modulation of the Ca2+ channel voltage sensor and excitation-contraction coupling by silver.
Ag+ (0.5-10 microM) is known to produce a transient contraction of intact frog skeletal muscle fibers followed by complete inhibition of excitation-contraction (E-C) coupling. We have carried out physiological and biochemical experiments to investigate the basis of this effect. Dihydropyridine (DHP) Ca2+ channel blockers, which inhibit the voltage sensor of the Ca2+ channel, completely inhibit Ag+ contractions. Removal of extracellular Ca2+, or blockade of Ca2+ entry with cadmium, does not inhibit Ag+ contractions. Activation of the Ca2+ channel's voltage sensor with the Ca2+ channel agonists Bay K 8644 or with perchlorate, potentiates the Ag(+)-induced contraction. Ag+ binds to the partially purified rabbit skeletal muscle Ca2+ channel and inhibits DHP binding (IC50 = 1.1 microM) and sulfhydryl (SH) reactivity (IC50 = 0.11 microM) over the concentration range where it inhibits E-C coupling. Oxidation of free SH groups by H2O2 or their reaction with DTNB prevents Ag+ contractions, while DTT reduction of oxidized SH groups restores Ag+ contractions. These results suggest that Ag+ binds to critical SH groups on the DHP receptor Ca2+ channel, resulting in modification of the channel's voltage sensor and the failure of E-C coupling.
Animals↗
Partial inhibition of skeletal muscle contraction by dantrolene sodium and its modification with perchlorate and Bay K 8644.
The effects of dantrolene sodium (DAN) on the dihydropyridine receptor (DHPR) of the transverse (T) tubule voltage sensor (Ca2+ channel) was studied with single fibers from bullfrog toe muscle. Perchlorate (ClO4-), which acts selectively on the DHPR, overcame DAN-induced inhibition of twitch tension. Bay K 8644, a DHPR agonist, slowed the rate of twitch inhibition by DAN. DAN inhibited twitch tension to a greater extent in Ca(2+)-free solution than in Ringer solution or solution containing Zn2+, whereas twitch inhibition by DAN was less in caffeine-containing solution than in the control. The effects of DAN on Zn(2+)- and caffeine-treated fibers and on fibers in Ca(2+)-free solution suggest that DAN must act near the voltage sensor of the T tubule. However, differences in net twitch inhibition by DAN between control fibers and fibers potentiated by ClO4- or Bay K 8644 suggest that DAN does not bind to the same site as these potentiating agents do. The role of myoplasmic Ca2+ in DAN-induced inhibition of twitch and the effects of DAN on the mechanical threshold and membrane potential in skeletal muscle are discussed.
3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗