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Biomedical subjects

M Arita

Publications and source records attributed to M Arita.

At least 361 records · Page 20Linked to original sources
PubMed1982

Electrophysiological and inotropic effects of Coenzyme Q10 on guinea pig ventricular muscle depolarized by potassium under hypoxia.

The electrophysiological and inotropic effects of Coenzyme Q10 (CoQ10) on isoproterenol or barium-induced slow responses in ventricular papillary muscle, depolarized by high K+ concentration (21.6 mM) under hypoxia (PO2 = 40 mmHg), were studied with microelectrode techniques. For the isoproterenol-induced slow response, application of CoQ10 (50 micrograms/ml), which was emulsified with the aid of a special solvent, increased the maximum rate of rise of action potentials (Vmax), an indicator of the slow inward current, by about 40%, with no consistent effect on the action potential duration and developed tension. Application of the solvent alone produced a significant decrease in both Vmax and developed tension. However, in these solvent-pretreated preparations, CoQ10 produced a significant (by about 50%) recovery in both Vmax and developed tension. The action potential duration was not changed by either the solvent alone or the application of CoQ10. The developed tension of the slow response consisted of early and late components. CoQ10 produced significantly more recovery in the late component than in the early one, suggesting that the recovery effect was due to increased slow inward Ca2+ current. CoQ10 did not reverse any parameter in the slow response induced by BaCl2 (0.2 mM). The results suggest that CoQ10 has significant but limited reversing effects on the hypoxia-induced deterioration of the slow response, and that the recovery is presumably due to increased availability of slow channels via increased production of ATP.

Action Potentials↗
PubMed1982

Isotachophoretic analyses of metabolites of cardiac and skeletal muscles in four species.

We studied ATP and concentrations of other metabolites in cardiac and skeletal muscles from different species (frog, hamster, guinea-pig, and dog), using analytical capillary isotachophoresis. The method had several advantages for quantitative analysis of tissue metabolites: short separation time, high sensitivity, high resolution, and good reproducibility. It was also possible to detect a number of compounds simultaneously, including ATP, ADP, AMP, cyclic AMP, creatine phosphate (CP), inosine monophosphate, NAD, NADH, glucose-6-phosphate, pyruvate, and inorganic phosphate. Generally, the concentrations of high-energy phosphates (ATP and CP) in the cardiac muscle were significantly lower than those in the skeletal muscle, in all species tested, except for hamster where the concentration of CP in the skeletal muscle was comparable to that in the cardiac muscle. In mammals, ATP and CP concentrations were comparable in the atrium and ventricle while the concentration in the frog ventricle was significantly higher than that in the atrium. The data obtained by this isotachophoretic analysis were comparable to the data reported by the use of other conventional analytical methods. The significance and reliability of isotachophoresis in the determination of the various metabolites in the cardiac muscle were discussed.

Adenine Nucleotides↗
PubMed1982

Surface layer ATP-related contraction in isolated, superfused canine ventricular papillary muscle: an isotachophoretic analysis.

The relationship among contractile tension, ATP content and concentration was examined in isolated, superfused ventricular papillary muscle under normoxic (Po2 not equal to 300 mmHg) and hypoxic (Po2 not equal to 100 mmHg) conditions, using capillary isotachophoresis. The muscle preparations were exposed to each condition for 30 min, and the contractile tension was recorded with a strain gauge. Immediately after the recordings, the preparations were homogenized and the metabolites (ATP, ADP, AMP, creatine phosphate, inosine monophosphate, NAD, NADH, glucose-6-phosphate, pyruvate, and inorganic phosphate) were extracted in 50% methanol-1.25 mM EDTA solution at -20 degrees C for 4 days. The supernatant of the extract was used for the isotachophoretic analysis. Hypoxia markedly depressed ATP content and concentration in the tissue. Under conditions of normoxia, but not hypoxia, the developed tension positively correlated with the ATP content and concentration. Under normoxic conditions, the tension tended to be proportional to the estimated surface area of the preparation, while in hypoxia it tended to be inversely proportional thereto. The ATP concentration appeared to be inversely proportional to the muscle weight, thereby suggesting that the outer layer of the preparation contains more ATP than the inner. In fact, an isotachophoretic analysis of the tissue revealed significantly higher ATP concentrations in the outer layer. Our findings indicate that there is a central anoxic core in the isolated canine papillary muscle superfused with oxygenated Tyrode solution and that surface layer ATP probably plays a pivotal role in the initiation of contraction.

Adenosine Triphosphate↗
PubMed1982

Antigen-induced acceleration of automaticity in electrically depolarized ventricular myocardium of sensitized guinea pigs.

Alterations in the membrane potentials during anaphylactic reactions were studied in ventricular muscle obtained from actively sensitized guinea pigs. The preparation was depolarized by constant current in a sucrose gap chamber to induce repetitive automatic action potential discharges (RAD) from the reduced membrane potentials (-60 to 0 mV). Application of specific antigen (human gamma-globulin, 6.8 X 10(-8) mol/L) markedly accelerated the firing frequency of the RAD. Overshoot and maximum rate of rise (Vmax) of the RAD increased during the initial 3 to 6 min of the antigenic challenge. The acceleration phase was followed by a long period of severe depression with marked reduction in the firing frequency of the RAD. These changes could be mimicked by an application of histamine (6.3 X 10(-7) mol/L) but were abolished in the presence of metiamide, a histamine H2-receptor antagonist (1 X 10(-5) mol/L). These findings indicate that an anaphylactic reaction transiently enhances the automaticity in electrotonically depolarized ventricular muscle, probably via the action of released histamine. Initial enhancement and later depression of the ectopic automaticity may be significant in the genesis of arrhythmias which occur during anaphylactic shock.

Action Potentials↗
PubMed1981

Microbial Transformation of beta-Ionone and beta-Methylionone.

Aspergillus niger JTS 191 was selected from many microorganisms tested as capable of converting ionones to other compounds having aromas. The individual transformation products from beta-ionone were isolated and identified by comparison with synthetically derived compounds. The major products were (R)-4-hydroxy-beta-ionone and (S)-2-hydroxy-beta-ionone. 2-Oxo-, 4-oxo-, 3,4-dehydro-, 2,3-dehydro-4-oxo-, 3,4-dehydro-2-oxo-, (S)-2-acetoxy-, (R)-4-acetoxy-, and 5,6-epoxy-beta-ionone and 4-(2,3,6-trimethylphenyl)-but-3-en-2-one were also identified. Analogous transformation products of beta-methylionone also were identified. Based on gas-liquid chromatographic analysis during the fermentation, we propose two main oxidative pathways of beta-ionone. The results of this study suggest that these transformations of beta-ionones may be useful as tobacco-flavoring compounds.

Journal Article↗
PubMed1981

Complete heart block in mumps myocarditis.

A patient with mumps myocarditis is reported. The onset of mumps was typical, with fever and parotid swelling followed by raised virus antibody titres. Atrioventricular block occurred and persisted despite steroid treatment for two weeks. He had an Adams-Stokes attack. A permanent pacemaker was implanted and, thereafter, the patient remained dependent upon it. The published material on conduction disturbance in mumps myocarditis is reviewed.

Adult↗
PubMed1981

Chirally selective synthesis of sugar moiety of nucleosides by chemicoenzymatic approach: L- and D-riboses, showdomycin, and cordycepin.

The symmetric dimethyl esters derived from furan and dimethyl acetylenedicarboxylate was efficiently hydrolysed with pig liver esterase to yield half esters with high optical purity. Following chemical transformations afforded precursors with L-configuration, and chirality transfer through ester exchange was achieved to afford precursors with D-configuration of the sugar moiety of nucleosides. Thus, an efficient approach to L- and D-riboses, showdomycin, and cordycepin (3'-deoxy-adenosine) has been demonstrated.U

Animals↗
PubMed1980

[Molecular study in polyacrylamide gel of polypeptides of several strains of rabies virus].

Comparative study of structural polypeptides of five rabies virus strains (serotype 1) and one serotype IV, demonstrates difference in molecular weight of the envelope polypeptides M1 and G of all strains. There is little difference between the structural polypeptides N, M2 and probably L. Some purified strains have been treated by trypsine to localize the position of polypeptides. There was no difference between the four major polypeptides of complete and defective virus. Pasteur strain cultivated on different cells shows very little difference in molecular weight of the four major polypeptides.

Electrophoresis, Polyacrylamide Gel↗
PubMed1980

Virion polypeptides of poxviruses.

Structural polypeptides from a number of poxviruses were analysed by SDS-polyacrylamide gel electrophoresis. The patterns obtained with orthopoxviruses were generally quite similar to one another, but variola, monkeypox, cowpox and vaccinia viruses could be distinquished by their profiles in the molecular weight (mol. wt.) region around 30,000 to 40,000; some additional variation was found amongst cowpox and vaccinia strains. Whitepox virus was shown to have structural polypeptides indistinguishable from those of variola virus. The structural polypeptides of poxviruses belonging to other genera were different from those of the orthopoxvirus, except those of mol. wt. about 122,000 and 97,000, which were common to all viruses irrespective of genus. A polypeptide of mol. wt. about 25,000 was also observed in all cases, though its position varied slightly with the individual virus.

Chymotrypsin↗
PubMed1980

The effect of angiotensin II antagonist, Sar1-Ile8-angiotensin II, on furosemide-induced increase in plasma noradrenaline, renin activity and aldosterone in unanesthetized dogs.

In order to evaluate the role of the renin-angiotensin system and the sympathetic nervous system in the maintenance of blood pressure in the sodium-depleted state, the changes of plasma renin activity (PRA), plasma aldosterone concentration (PAC) and plasma noradrenaline (PNA) were examined in unanesthetized dogs after the administration of furosemide. Furthermore, the role of the renin-angiotensin system in the increased sympathetic nerve activity induced by furosemide was assessed by using Sar1-Ile8-angiotensin II, an angiotensin II antagonist. When a dose of 0.8 mg/kg of furosemide was injected intravenously, 3 times every 15 minutes, PRA and PNA were significantly increased with a concomitant increase in PAC. Sar1-Ile8-angiotensin II induced a significant increase in PAC and a slight increase in PRA, while no changes were found in PNA and the mean blood pressure. The increase in PNA induced by furosemide was inhibited dose-dependently by Sar1-Ile8-angiotensin II, through PRA and PAC were further increased. There results suggest that an administration of furosemide induced the increase in PNA and the increase in PNA by furosemide might by mediated by the renin-angiotensin system.

1-Sarcosine-8-Isoleucine Angiotensin II↗
PubMed1980

Effects of verapamil and its optical isomers on repetitive slow responses induced by electrical depolarization in canine ventricular myocardium.

The electrophysiological effects of verapamil (racemic compounds) and its optical (d- and 1-) isomers on canine ventricular myocardial fibers were investigated in current clamp conditions using single sucrose gap chamber and microelectrodes. The current-voltage (I-V) relationships were obtained in normal and low Na (12 mM)--low Ca (0.45 mM) solutions with and without the drugs. Verapamil and its optical isomers blocked repetitive action potential discharges (slow responses) induced by depolarizing DC-currents. However, l-isomer was more potent than d-isomer in suppressing these responses. The difference in the potency was attributed to their different actions on the steady state I-V relationships. Namely, l-isomer increased time independent membrane conductance to potassium ions (probably gk1), while d-isomer did not. This effect of l-isomer may favor the suppression of phase 4 depolarization and hence reduce the frequency of repetitive action potential discharges in depolarized ventricular muscle more effectively than d-isomer.

Action Potentials↗
PubMed1979

Electrophysiological actions of mexiletine (Kö1173) on canine Purkinje fibres and ventricular muscle.

1 The effects of mexiletine (Kö1173) were investigated in canine isolated cardiac Purkinje fibres and ventricular muscle with microelectrodes. Some Purkinje fibres were depolarized by mechanical stretch to induce spontaneous activity with slow upstroke velocity. The preparations were stimulated at rates of 1, 2, 3 and 4 Hz. The drug concentrations tested were 0.4, 2 and 10 mug/ml in Tyrode solution (KCl = 5.4 mM).2 The ;therapeutic' drug concentration (2 mug/ml) shortened action potential duration and effective refractory period of Purkinje fibres, the effect being pronounced at lower stimulation rates. In ventricular fibres, action potential duration changes were not consistent while the effective refractory period was prolonged.3 In depolarized Purkinje fibres showing automatic activity, the drug (0.4 or 2 mug/ml) depressed phase 4 depolarization and reduced the firing rate without changing maximum diastolic potential. However, when depolarized Purkinje fibres were electrically driven at a constant rate, the maximum diastolic potential became more negative with a concomitant decrease of pacemaker slope and increase of maximum rate of rise (V(max)) of action potentials.4 Moderate (2 mug/ml) to high (10 mug/ml) concentrations of the drug depressed V(max) in Purkinje fibres stimulated at 2 Hz by 12 and 42% respectively and depressed ;membrane responsiveness'. The decrease in V(max) depended upon the stimulation rate, being minimum at the lowest (1 Hz) and maximum at the highest (4 Hz) stimulation rate.5 The drug (2 mug/ml) improved V(max) of the earliest propagated premature action potentials by shifting the takeoff potential to more negative levels in both Purkinje and ventricular fibres.6 Membrane conductance in fibres mounted in a single sucrose gap chamber was increased by the drug (2 mug/ml) in both fibre types in normal and in Na(+)-deficient solutions. This increase was attributed to an increase in membrane K(+) permeability produced by the drug.7 All these effects are similar to those of lignocaine, diphenylhydantoin or aprindine, and can explain the antiarrhythmic action of mexiletine.

Animals↗
PubMed1978

Takayasu's disease in twin sisters. Possible genetic factors.

Takayasu's disease is well-known for its characteristic clinical features and its elusive etiology. Recently, we encountered twin Japanese sisters, both of whom were diagnosed as having Takayasu's disease. The parents, two sisters, and one brother are healthy. Family history revealed the parents are first cousins. Analyses of serveral blood types and HLA typing were performed on all members of the family, and it was confirmed that these twins are monozygotic. Moreover, HLA typing analyses revealed that one haplotype found in the father was passed only to these twins. The history of consanguinity of the parents, the occurrence in twins, and the results of HLA typing suggest a genetic factor in the etiology of Takayasu's disease.

Adolescent↗