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H Komai

Publications and source records attributed to H Komai.

10 recordsLinked to original sources
PubMed1991

Contribution of the known subcellular effects of anesthetics to their negative inotropic effect in intact myocardium.

The results of these studies suggest that halothane, in addition to its effect of reducing the trans-sarcolemmal Ca2+ influx, has a direct effect on the function of the sarcoplasmic reticulum by making the organelle leaky to Ca2+ and reducing the amount of Ca2+ stored. Isoflurane, on the other hand, does not appear to make the sarcoplasmic reticulum leaky to Ca2+. In fact, our observations suggest that isoflurane makes the sarcoplasmic reticulum less leaky to Ca2+. Halothane may enhance the reduction in the myofibrillar response to activator Ca2+ when the muscle fiber length is shortened. Thiopental appears to reduce the trans-sarcolemmal Ca2+ influx without reducing the amount of Ca2+ stored in the sarcoplasmic reticulum.

Anesthetics↗
PubMed1991

Harmful effects of inotropic agents on myocardial protection.

Using an isolated working rat heart model, the pretreatment effects of positive inotropic agents on ischemia-reperfusion injury were investigated. The experiment consisted of (1) working control perfusion; (2) working perfusion with isoproterenol (I), milrinone (M), a combination of these drugs (I + M) and dibutyl-cyclic adenosine monophosphate (DB) followed by ischemic arrest for 33 minutes at 37 degrees C or 150 minutes at 20 degrees C and Langendorff reperfusion; and (3) working perfusion. Under conditions of normothermic ischemia, percent recoveries of postischemic cardiac output (mean +/- standard error of the mean) in the I, M, I + M, and DB groups were 37.8% +/- 12.7%, 61.3% +/- 3.1%, 0%, and 53.1% +/- 5.2%, respectively. Under conditions of hypothermic ischemia, the percent recoveries in I + M and DB groups were 10.9% +/- 7.9% and 29.8% +/- 9.5%; they were all significantly lower than that in the control group. The addition of diltiazem or ryanodine at several concentrations and lowering of the Ca2+ concentration in the St. Thomas' cardioplegic solution did not prevent I + M-induced injury. Our data suggest that pretreatment by I + M aggravated ischemia-reperfusion injury, and adjustments in Ca2+ concentration were not sufficient to prevent that injury.

Animals↗
PubMed1991

Effects of thiopental and halothane on spontaneous contractile activity induced in isolated ventricular muscles of the rabbit.

To see if the known properties of thiopental of reducing Ca2+ and K+ fluxes across the myocardial sarcolemma account for its arrhythmogenic action, we have evaluated the effect of the anesthetic on spontaneous contractile activity induced in isolated rabbit papillary muscles. Thiopental (20 mg/l) prolonged the duration of sustained automaticity induced by stimulation at 1-2 Hz in the presence of 1 mumol/l isoproterenol. Thiopental (10, 20 mg/l) shortened the delay before the onset of Ba(2+)-induced automaticity, which involves a decrease in a K+ current. The minimum concentration of Ba2+ required to induce automaticity was lowered by thiopental. Whether spontaneous activities were induced by high frequency stimulation in the presence of isoproterenol or by Ba2+, thiopental lowered the frequency of spontaneous beats. Thus, thiopental appears to have both arrhythmogenic and antiarrhythmic actions, and the former may be unmasked when catecholamines counteract the latter by increasing Ca2+ influx. Like thiopental, halothane (1.0%) decreased the frequency and force of Ba(2+)-induced automatic beats but, unlike thiopental, prolonged the delay before the onset of Ba(2+)-induced automaticity, indicating that halothane acts as a purely antiarrhythmic agent in this type of automaticity.

Animals↗
PubMed1991

[The effects of calcium concentration of reperfusion solution upon myocardial protection].

The effects of several calcium concentrations in reperfusion solution were studied. Experimental time course was as followed: 20 min working perfusion, 3 min cardioplegic infusion with St. Thomas cardioplegic solution (STS) followed by global ischemia for 30 min at 37.5 degrees C, 15 min early Langendorff reperfusion with reperfusion solution and 5 min late reperfusion with Krebs Henseleit bicarbonate buffer [( Calcium] = 2.5 mM), followed by 20 min working perfusion. Percent recoveries of aortic flow at the Ca concentration of 0, 0.1, 0.6, 1.2, 1.8, 2.5 mM were 0, 14 +/- 1, 43 +/- 4, 64 +/- 3, 55 +/- 2, 59 +/- 1 (%), respectively. Our data indicated that reperfusion solution with less than 1.2 mM calcium reduced the protective properties of STS.

Animals↗
PubMed1990

Direct effect of halothane and isoflurane on the function of the sarcoplasmic reticulum in intact rabbit atria.

The negative inotropic effect of halothane and isoflurane on potentiated-state contractions of isolated rabbit atria in a normal Ca2+ (2.5 mM) medium was compared with the force depression in low Ca2+ media without an anesthetic. When this comparison was made in the presence of 1 microM ryanodine so that the force of contraction was dependent only upon transsarcolemmal Ca2+ influx with no Ca2+ contribution from the sarcoplasmic reticulum (SR), the force of contraction was depressed equally by 0.6% halothane in a normal Ca2+ medium and by a 1.5 mM Ca2+ medium without the anesthetic. Similarly, 1.0% halothane or 1.5% isoflurane and a 1.0 mM Ca2+ medium were equally depressant as were 2.4% isoflurane and a 0.5 mM Ca2+ medium. In the absence of ryanodine, where the atrial contractile activity is largely dependent on Ca2+ released from the SR, 0.6% halothane in the normal Ca2+ medium depressed contractile force by 32%, whereas the force was depressed by only 16% in the 1.5 mM Ca2+ medium without the anesthetic. Similar results were obtained when the effects of 1.0% halothane and of 1.0 mM Ca2+ were compared. In contrast, the force of contraction measured in the absence of ryanodine was not at all inhibited by 1.5% isoflurane and minimally (11%) inhibited by 2.4% isoflurane. Consequently, the force depression by isoflurane was less than that found in the low Ca2+ media.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Negative inotropic effect of ketamine in rabbit ventricular muscle.

The effect of ketamine on myocardial contractile force was examined in rabbit papillary muscles in order to determine the underlying mechanism of action of the anesthetic. Ketamine HCl (20 and 40 mg/L) inhibited rested-state contractions that are dependent on the transsarcolemmal influx of Ca2+ for activation and reduced the upstroke velocity of the slow action potential, which reflects Ca2+ influx through the slow Ca2+ channel. On the other hand, ketamine had a relatively small effect on potentiated-state contractions and no effect on rapid cooling induced contractures, both of which are activated by the release of Ca2+ stored in the sarcoplasmic reticulum. These results suggest that ketamine inhibition of transsarcolemmal Ca2+ influx plays a major role in the negative inotropic action of the anesthetic.

Animals↗
PubMed1990

[Changes in lymphocyte subsets, neutrophil function and complement levels in patients with complications following open heart surgery].

In order to evaluate the immune response during and after open heart surgery, we have studied 34 patients who received open heart surgery under extracorporeal circulation. Age range of these patients were from 41 to 76 years. These patients were divided into three groups, depending upon existence of multiple organ failure (MOF), low output syndrome (LOS) and non-LOS and non-MOF diagnosed from our criteria. The following cytological and immunological study has been performed pre-operatively, immediately after and on 1, 2, 7 and 14th postoperative day; 1) the leukocyte differential cell count, 2) function test of neutrophils, 3) lymphocyte subpopulation and subsets, 4) serum level of complement fractions (C3, C4) and CH 50. By lymphocytes analysis, postoperative early reduction of OKT 3 (CD 3) and OKT 4 (CD 4) was observed in patients with poor prognosis. Patients with the postoperative high activity of NBT reduction test was developed into MOF. Complement activity (C3, C4, CH50) decreased during surgery and recovered to preoperative level in patients without LOS and MOF. However in MOF patients, these values showed lower level than that of patients without LOS and MOF. Our data suggested that lymphocytes and leukocytes tests were useful to evaluate the prognosis in open heart surgery.

Adult↗
PubMed1976

Targets of gazing and eye contact during interviews: effect on Japanese nonverbal behavior.

The gaze direction of both the subject and his interviewer were varied independently, such that either looked at the other's eyes or at the other's knees in a 2 X 2 design. A repeated measures design was used with nonverbal vehaviors of Japanese manes as dependent variables. When the interviewers gazed at the subjects' eyes, the response latencies of the subjects were shortened and their torso movements were reduced. Results from other studies of Japanese nonverbal behavior suggest that this pattern of response indicated greater subject invlovement in the interaction. The magnitude of these effects was unchanged whether the subject was reciprocating the interviewer's gaze and making eye contact or looking at the interviewer's knees. It was thus reasoned that effects produced by eye contact in other research may have resulted from subjects' knowledge that they were being gazed at and not from the unique properties of eye contact. When the subjects gazed at the interviewer's eyes, the hand self-manipulations of the subjects increased, reflecting the upsetting effects of monitoring the interviewer's face during interaction. The consequences of gazing at another's eyes thus appear to be different from having one's eyes gazed at by another.

Adult↗