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Biomedical subjects

M Kishi

Publications and source records attributed to M Kishi.

At least 181 records · Page 10Linked to original sources
PubMed1984

Mechanism of inotropic action by hypotonic solution in the frog atrial muscle.

The effects of hypotonic solution on the mechanical activities and action potential of the bullfrog atrium were investigated. Exposure of muscle to hypotonic solutions (70% of normal solution) produced initially a transient increase in twitch after which twitch declined below the control level. The response is independent of the kinds of salts withdrawn to make the medium hypotonic and of the presence of beta-blocker (5 X 10(-7) M propranolol). The resting potential and the plateau level of action potential were little changed initially. When the twitch declined, a small amount of depolarization and a shortening of action potential duration were observed; however, the plateau level of action potential was not reduced. The initial increase in twitch was not observed, and only the gradual decline of twitch remained in the caffeine containing hypotonic solution. The weight of muscle increased 10% in the hypotonic solution. The resting tension was also increased transiently and then declined to reach a maintained plateau with exposure to hypotonic solution. In the 0-Ca2+ or caffeine containing medium, the transient component of contracture was suppressed but the plateau tension remained. It is suggested that the initial transient increase of twitch by the perfusion of the hypotonic solution was induced by the Ca2+ released from the sarcoplasmic reticulum (SR), and the resultant decline of twitch resulted from the depletion of Ca2+ from the SR and/or from the shortening of action potential duration.

Action Potentials↗
PubMed1983

A study on the mechanism of twitch potentiation by hypertonic solution in the frog atrial muscle.

Hypertonic solutions were found to exhibit both positive and negative inotropic effects on the contraction of the isolated atrial myocardium of bullfrog. The optimum tonicity for twitch potentiation was about 1.5 T. The mechanism for the positive inotropic action was investigated. The possibility of involvement of an increase in calcium influx during each action potential was excluded, since both the overshoot and the plateau of action potential were strongly depressed by perfusion of hypertonic solution. The effect on the time course of twitch potentiation was similar to that of muscle shrinkage, regardless of the type solute (sucrose, NaCl or LiCl) used for elevating the tonicity, except that excess sodium showed an initial rapid inhibitory phase of contraction. A marked post-rest potentiation was observed even after "zero" calcium perfusion, provided that the tonicity of the bathing medium was elevated previously. Potassium contracture occurred during the prolonged hypertonic perfusion in "zero" calcium condition. In addition, caffeine contracture was strongly augmented in hypertonic solution. The results suggest that an elevation in both the [Ca2+]i and amount of calcium bound intracellularly may play an important role in the positive inotropic action.

Action Potentials↗
PubMed1983

Collagenase activity in human saliva.

Fairly high collagenase activity was initially demonstrated in human whole saliva, and the activity from patients with periodontal diseases was statistically higher than that from healthy subjects. Based on some characteristic properties, the collagenase in whole saliva appeared to be of tissue, rather than bacterial, origin.

Adolescent↗
PubMed1983

Paradoxical after-potentiation of the myocardial contractility by lanthanum.

Lanthanum of 0.1 to 0.2 mM caused a twitch inhibition and further showed a marked, long-lasting twitch potentiation during washout in both ventricular strips of bullfrog and atrial or papillary muscles of guinea-pig. It was found that the effect was more conspicuous in the frog heart. A similar potentiation was observed by applying gadolinium instead of lanthanum. The participation of endogeneous catecholamine release is unlikely since the positive inotropic effect was never affected by the presence of beta-adrenergic blocker. The potentiation was not accompanied by any increase in the action potential plateau, suggesting independence of the phenomenon on the calcium current. A marked elevation of the resting tension was produced during a long-term lanthanum perfusion, reflecting the increase in the intracellular calcium level. On the other hand, transient increase in the resting tension was frequently observed on returning to normal Ringer solution. The latter change seemed to result from a transient increase in the resting permeability to calcium ions. The negative or positive inotropic effect by increasing or lowering the external sodium concentration observed under the control condition was strongly depressed during the twitch potentiation. In addition, sodium-free contracture induced by solutions isotonically replaced with sucrose or potassium chloride was augmented both during lanthanum perfusion and during its washout. These results suggest the possibility that the elevation of the intracellular calcium level due to inhibition of Na-Ca exchange mechanism and/or increase in the calcium permeability is the principal cause for the twitch potentiation caused by lanthanum washout.

Action Potentials↗
PubMed1980

Cell surface proteins extracted with urea from AH-66 hepatoma ascites cells.

The cell surface structure of AH-66 hepatoma ascites cells was examined by extracting the intact AH-66 cells with urea and analyzing the extracted proteins. When AH-66 cells were suspended in 1 M urea, material composed of approximately 90% protein and 10% carbohydrate was released. The extracted proteins amounted to about 3% of the total cell proteins and were composed of approximately 30 species as analyzed by sodium dodecyl sulfate gel electrophoresis. The major bands had apparent molecular weights of 84,000 and 50,000--60,000 on the gel. In marked contrast to chick embryo fibroblasts, the extracted proteins contained no components stainable with periodic acid-Schiff reagent. Lactoperoxidase-catalyzed iodination of intact AH-66 cells showed that most of the urea-extractable proteins were located on the outer surface of the plasma membranes of AH-66 cells. It was also found that there are two integral proteins exposed on the outer surface of the plasma membranes of AH-66 cells; one is a major glycoprotein (with a molecular weight of 165,000) and the other is a periodate-Schiff-negative protein with a molecular weight of 130,000.

Amino Acids↗