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Biomedical subjects

M Kanno

Publications and source records attributed to M Kanno.

At least 307 records · Page 17Linked to original sources
PubMed1984

Influences of extracellular calcium ions, verapamil, and calcium antagonistic cations on the positive inotropic effects mediated by alpha- and beta-adrenoceptors in the left atria of rats.

Inotropic responses produced by stimulation of alpha-adrenoceptors were compared with those by isoproterenol in the left atria of rats. The negative frequency-force relationship was abolished or attenuated by isoproterenol, but not counteracted by phenylephrine in the presence of sotalol. The positive inotropic effect of phenylephrine was uniquely modulated by reduction in extracellular Ca2+ concentration. Verapamil at 10(-8) M (at which it produces no negative intropic action) depressed only the effect of phenylephrine. Pretreatment with Ca2+-antagonistic cations in low concentrations depressed the effect of phenylephrine without influencing that of isoproterenol.

Animals↗
PubMed1984

Delayed afterdepolarisations and triggered activity in canine Purkinje fibres treated with neuraminidase.

We investigated the electrophysiological alterations induced by the removal of sialic acid from the sarcolemma in canine Purkinje fibres. About 70% of total sialic acid content of Purkinje fibres was removed by 120 min of exposure to neuraminidase (1 U X ml-1). The treatment with neuraminidase did not change any of the action potential characteristics at normal Ca2+ concentration (2.7 mmol X litre-1). However, action potential duration and maximum upstroke velocity of phase zero of the action potential were reduced to a greater degree in neuraminidase-treated Purkinje fibres than in non-treated controls at high Ca2+ concentration (8.1 mmol X litre-1). At high Ca2+ concentration, delayed afterdepolarisations were induced in five out of nine neuraminidase-treated Purkinje fibres and triggered activity was observed in two, when driven in trains of 20 stimuli of different cycle length (1000 to 180 ms). No discernible delayed afterdepolarisations were observed in nine non-treated control Purkinje fibres. In addition, the amplitude of delayed afterdepolarisations induced by ouabain (0.2 mumol X litre-1) in neuraminidase-treated Purkinje fibres was larger than non-treated controls. These findings suggest that sialic acid residues of glycocalyx function as a kind of barrier to Ca2+ influx.

Action Potentials↗
PubMed1984

Suppression of lysophosphatidylcholine-induced abnormal automaticity by verapamil in canine Purkinje fibers.

Effects of verapamil on electrophysiological alterations induced by lysophosphatidylcholine (LPC), a toxic membrane-derived phospholipid potentially responsible for ischemia-induced arrhythmias, were evaluated in canine Purkinje fibers. LPC (10-160 microM) induced concentration-dependent decreases in resting membrane potential, action potential amplitude and maximum upstroke velocity of phase O. The depolarization was not associated with the reduction of the potassium equilibrium potential, which was calculated from the intracellular potassium ion activities measured by ion-selective electrodes. A graded increase in LPC concentration invariably induced abnormal automaticity arising from depolarized membrane potentials. Although verapamil did not prevent LPC-induced changes in action potential characteristics, it suppressed the appearance of rapid spontaneous activity at reduced membrane potential. These results suggest that verapamil may modify the dysrhythmias induced by LPC in ischemic myocardium.

Action Potentials↗
PubMed1984

Slow responses mediated by alpha-adrenoceptors in the cardiac muscles of the monkey (Macaca fuscata).

The effects of phenylephrine on force of contraction and on slow action potentials were studied in the cardiac muscles of the Japanese monkey (Macaca fuscata). 1) The concentration-response curves for the positive inotropic effect of phenylephrine in the left atria and right ventricular papillary muscles were shifted to the right by either prazosin (10(-7) M) or propranolol (10(-6) M), and were further shifted in the presence of both prazosin and propranolol. 2) Phenylephrine (10(-5) M) restored the tension development in the left atria and right ventricular papillary muscles which were depolarized and rendered inexcitable by elevating K+ concentration to 22 mM. The restored contractions with phenylephrine were abolished or diminished by either prazosin (10(-6) M), phenylephrine (10(-5) M) restored action potentials in 4 of 6 K+-depolarized right ventricular muscle preparations; the restored action potentials were abolished or diminished by prazosin (10(-6) M). These results indicate that alpha-adrenoceptors as well as beta-adrenoceptors are involved in inducing slow responses in the monkey heart.

Action Potentials↗
PubMed1984

Effects of verapamil on electrophysiological disturbances induced by lysophosphatidylcholine in isolated rabbit hearts.

Lysophosphoglycerides such as lysophosphotidylcholine (LPC) have been shown to accumulate in ischemic myocardium and may be important in the genesis of arrhythmias. In this study effects of verapamil on electrophysiological and biochemical derangements induced by LPC were evaluated in Langendorff-perfused rabbit hearts. LPC perfusion (10 microM) produced conduction disturbances and enhanced spontaneous firing concomitantly with increasing potassium and creatine phosphokinase contents in the coronary effluents. Although pretreatment with verapamil (2 microM) did not show any significant effects on the conduction delay and biochemical changes, it suppressed the occurrence of rapid spontaneous firing during LPC perfusion. These results suggest that relatively low concentration of LPC can induce electrophysiological and biochemical derangements comparable to those observed during myocardial ischemia and that verapamil may modify the dysrhythmias induced by LPC.

Animals↗
PubMed1983

Effects of histamine on mechanical performance and biochemical and electrical activity in the heart of monkeys (Macaca fuscata).

The properties of the cardiac effects of histamine on the isolated heart muscles of the Japanese monkey (Macaca fuscata) were investigated. Histamine had a concentration-dependent positive inotropic effect on left atria and papillary muscles and a positive chronotropic effect on right atria. Histamine increased the levels of cyclic AMP and shortened the duration of the action potential in Purkinje fibers, measures of its biochemical and electrophysiological effects. All of these effects of histamine were blocked by 10(-5) M cimetidine. These results indicate that histamine H2-receptors mediate the cardiac effects of histamine on the monkey heart. Histamine (10(-5) M) also restored the action potentials and contractility of K+-depolarized preparations. These effects were inhibited by verapamil (10(-6)-10(-5) M) but not by TTX (10(-5) M), suggesting that, in the monkey heart, histamine may act by increasing the slow inward current.

Action Potentials↗
PubMed1983

Electrophysiological effects of diltiazem, nifedipine and Ni2+ on the subepicardial muscle cells of canine heart under the condition of combined hypoxia, hyperkalemia and acidosis.

Using microelectrode techniques, we examined the effects of the slow channel blockers diltiazem, nifedipine and Ni2+ on the tissue deterioration induced by a modified superfusion solution imitating some of the metabolic changes in acute myocardial ischemia (pO2 = 4.0--5.1 kPa, [K+] = 8 mmol/l, pH = 6.80) in the isolated right ventricular subepicardial muscles of canine heart. Resting membrane potential (RMP), action potential amplitude (APA), action potential duration and maximum upstroke velocity of action potential (V max) were reduced, and conduction time was prolonged during superfusion with the modified solution. In the presence of diltiazem (6.7 mumol/l), nifedipine (2.9 mumol/l) and Ni2+ (1.0 mmol/l), the degree of the reductions of APA and V max, and of the prolongation of conduction time induced by the modified solution was significantly reduced. However, none of the three slow channel blockers affected the change in RMP. These results suggest that decreasing calcium influx reduces the deteriorating effect of the modified solution on the sodium channels, and this action can partly explain the reduction of ischemia-induced conduction delay by slow channel blockers.

Acidosis↗
PubMed1983

Effects of an antiulcer drug, sucralfate (a basic aluminum salt of sulfated disaccharide), on experimental gastric lesions and gastric secretion in rats.

The effects of oral sucralfate, a basic aluminum salt of sulfated disaccharide, on various experimental gastric lesions and on gastric secretion were studied in rats. Sucralfate at 300 mg/kg potently inhibited the development of Shay ulcers and indomethacin- and aspirin-induced erosions. The drug at 1000 mg/kg also potently inhibited histamine-induced erosions. Water-immersion stress-induced erosions were inhibited with 1000 mg/kg of the drug, but the degree of inhibition was weaker than that seen in other types of erosion formation. Sucralfate at 1000 mg/kg given twice daily for 14 days significantly accelerated the spontaneous healing of acetic acid-induced ulcers. Sucralfate at over 300 mg/kg tended to increase the volume of gastric juice but had an insignificant effect on acid and pepsin output of pylorus-ligated rats. As a whole, the effects of sucralfate on experimental gastric lesions appear to be much more potent than Maalox, propantheline bromide, and cimetidine. The mechanism of action of sucralfate remains to be determined.

Acetates↗
PubMed1983

New intraoral x-ray fluorographic imaging for dentistry.

A new dental x-ray fluorographic unit has been developed. This unit is composed of small intraoral x-ray tube, a compact x-ray image intensifier, and a high-resolution TV system. The purposes for developing this equipment were to (1) directly observe the tooth during endodontic procedures and (2) reduce x-ray exposure to the patient and the dentist. The radiation exposure can be reduced to about 1/600 the exposure used with conventional dental film. In clinical trials, a satisfactory fluorographic dental image for endodontic treatment was obtained with this new device.

Humans↗
PubMed1983

Cell cycle-dependent expression of antigen-binding and I-J-bearing molecules on suppressor T cell hybridomas.

The I-J and antigen-binding chains with constant region determinant (Ct) that compose an antigen-specific suppressor T cell factor were found on the surface of suppressor T cell hybridomas, serologically and morphologically demonstrated by a fluorescence-activated cell sorter (FACS) and immunoelectron microscopic analyses. Moreover, the surface expression of the I-J and Ct-bearing chains fluctuating with the same kinetics depended entirely upon the cell cycle. The maximum expression of these two chains was observed in the early stage of the M phase, and the minimum in the S phase. Similarly, the magnitude of the suppressor activity was maximal in the late stage of the M phase, and was minimal in the S phase. The results therefore demonstrated that there exists good correlation between the cell surface expression of the I-J and Ct-bearing chains and the magnitude of the suppressor activity produced. The antigen recognition units on suppressor T cell hybridomas have serologically and morphologically been characterized by using radiolabeled antigens or monoclonal antibodies against the I-J or Ct on the antigen-binding molecule. Cell-binding assay and radioautographic analysis demonstrated that the suppressor T cell hybridoma possesses the capacity to bind native antigen in an antigen-specific fashion as does the hybridoma-derived, antigen-specific suppressor factor composed of the I-J and the Ct-bearing chains, indicating that the recognition unit on the cell surface is composed of a structure similar to the factor.

Animals↗
PubMed1983

[Multiple brain tumors with von Recklinghausen's disease].

Thirty-three cases of von Recklinghausen's disease, nine of which had multiple brain tumors, were experienced in our clinic. In this report, these nine cases were reported and discussed, especially representative two cases in detail. Nine cases had various combinations of multiple brain tumors: bilateral acoustic neurinomas in two cases, multiple neurinomas in two cases, multiple meningiomas in one case and multiple neurinomas and meningiomas in two cases. In two cases, multiple brain tumors were totally extirpated at one stage, but both died within ten months. In three cases, partial extirpation of multiple brain tumors were performed at one stage, one died thirteen years after the operation and two are alive but dependent on their families. In recent two cases, two stage operations were performed, by which tumors were successfully removed totally. These postoperative courses were good. The other two cases were treated conservatively. One is alive and working, but has severe auditory disturbance. The other died after six years from onset. Autopsy was performed in this case, which revealed multiple neurinomas in the left 3rd and bilateral 5-12th cranial nerves and numerous meningiomas. In the review of the cases with more than three brain tumors in von Recklinghausen's disease were discussed.

Adult↗
PubMed1982

Effects of verapamil on conduction delay and potassium efflux induced by global ischemia in isolated rabbit hearts.

The effects of verapamil on the conduction delay and potassium efflux induced by global ischemia were evaluated in 40 isolated Langendorff-perfused rabbit hearts under constant ventricular pacing. Global ischemia of 7 min duration, which was produced by stopping the perfusion flow, prolonged the intramyocardial conduction time by 86.5 +/- 9.6% of the pre-ischemic values in 10 non-treated control hearts. Verapamil, when perfused in various concentrations (10-1000 ng/ml) in Tyrode solution for 15 min prior to the global ischemia, significantly and concentration-dependently reduced the ischemia-induced conduction delay. However, the increased potassium content of the coronary effluents collected during ischemia and 1 min after reperfusion, which was assumed to reflect the extracellularly accumulated potassium during ischemia, was not significantly reduced by verapamil. These results suggest that the favorable effect of verapamil on the ischemia-induced conduction delay is a direct action on the ischemic myocardial cells, being independent of its vasodilating action. It also seems unlikely to be mediated by reduction of extracellular potassium accumulation in the ischemic myocardium.

Animals↗
PubMed1982

Characterization of eight beta-lactamases of Gram-negative bacteria.

Eight kinds of beta-lactamases produced by gram-negative bacteria were characterized by the following properties: molecular weight, isoelectric point, pH optimum, molecular activity, immunochemical reactivity, and kinetic parameters with respect to twelve kinds of common beta-lactam antibiotics. These beta-lactamases included two types of penicillinases mediated by R plasmids and six kinds of species-specific cephalosporinases. To determine a reliable value of the kinetic parameter, Km, we introduced a continuous and acidimetric assay method of beta-lactamase activity with a pH stat.

Citrobacter↗