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Biomedical subjects

M Muneyuki

Publications and source records attributed to M Muneyuki.

At least 19 recordsLinked to original sources
PubMed2000

Ca(2+)-dependent inhibition of actin-activated myosin ATPase activity by S100C (S100A11), a novel member of the S100 protein family.

S100C (S100A11, calgizzarin) inhibits the actin-activated myosin Mg(2+)-ATPase activity of smooth muscle in a dose-dependent manner: its half-maximal effect occurs at a S100C/actin molar ratio of 0.05 and its maximal effect occurs at a ratio of 0.20. Furthermore, S100C was found to bind to actin with a stoichiometry of 1:6-7 in the presence of Ca(2+), with an affinity of 1 x 10(-6) M determined by cosedimentation assays. Other Ca(2+)-binding proteins such as S100A1, S100A2, S100B, and calmodulin did not inhibit actin-activated myosin Mg(2+)-ATPase activity. Calmodulin, S100A1, and S100B reversed the inhibitory effect of calponin in a Ca(2+)-dependent manner, S100A2 had no effect, and S100C had additional inhibitory effects. The results suggest that S100C might be involved in the regulation of actin-activated myosin Mg(2+)-ATPase activity through its Ca(2+)-dependent interaction with actin filaments.

Actins↗
PubMed1995

Vasodilatory effects of ketamine on pulmonary arteries in rats with chronic hypoxic pulmonary hypertension.

To study the effects of ketamine on structurally remodeled pulmonary arteries from rats with hypoxic pulmonary hypertension (PH) and the effects of ketamine on endothelium-dependent and -independent relaxation, rats were exposed to hypobaric hypoxia (air at 380 mm Hg for 10 days). We measured the responses to ketamine, acetylcholine, and sodium nitroprusside (SNP) in prostaglandin F2 alpha-precontracted ring segments from a left extrapulmonary artery (EPA, 1.4-1.6 mm in outside diameter [OD] and an intrapulmonary artery (IPA, 0.7-1.1 mm OD) obtained from control and PH rats. The effects of acetylcholine and SNP were decreased in EPA and IPA rings from PH rats compared with control rings. In contrast, ketamine produced a greater relaxation response in rings from PH rats at 3 x 10(-5) -3 x 10(-4) in the EPA and at 10(-4) -10(-3) M in the IPA compared to control rings. A nitric oxide synthase inhibitor, nitro-L-arginine (10(-4) M), inhibited the relaxation in response to acetylcholine in both control and PH rats. Pretreatment with ketamine (10(-4) M) had no effect on the relaxation response to any concentration of acetylcholine or SNP in either control or PH rats. We conclude that nitric-oxide-mediated relaxation, but not ketamine-induced relaxation, was impaired in structurally remodeled hypertensive pulmonary arteries. Ketamine had no effects on nitric oxide-mediated relaxation in either normal or PH rats.

Acetylcholine↗
PubMed1995

[Clinical evaluation of prophylactic nitroglycerin infusion during coronary artery bypass grafting].

We evaluated retrospectively the benefit of prophylactic nitroglycerin (TNG) infusions during elective coronary artery bypass grafting (CABG) in 73 patients. In all patients anesthesia was maintained with high dose fentanyl. Thirty-seven patients were infused TNG 0.3 microgram.kg-1.min-1 during surgery and 36 patients were not. The TNG-infused patients demonstrated lower perfusion pressure during cardiopulmonary bypass (CPB) and higher incidence of inotropic administrations than the uninfused patients. Serum myocardial creatine phosphokinase (CPK-MB) levels of TNG-infused patients were higher than those of TNG-uninfused patients on the first postoperative day. We speculate that inotropic administrations under low myocardial perfusion pressure at the time of weaning from CPB induces myocardial ischemia which in turn causes an increase in serum CPK-MB level. We conclude that prophylactic administration of TNG does not prevent perioperative ischemia during CABG.

Anesthesia, General↗
PubMed1993

Intrathecal injection of high-dose meglumine amidotrizoate with complete recovery.

Rarely we are faced with accidental spinal injection of potentially toxic substances. We present 2 cases in which amidetrizoate, water-soluble ionic contrast medium, was accidentally injected intrathecally. Our treatment consisted of vigorous hydration and barbiturate coma. This report suggests that for water-soluble ionic contrast media increasing cerebrospinal fluid circulation by vigorous hydration may be as effective as spinal lavage in diminishing toxicity.

Adult↗
PubMed1993

Whole body oxygen consumption after hypothermic cardiopulmonary bypass.

Whole body oxygen consumption and the substrate for energy production during the post-bypass period have not been clarified. We hypothesized that the substrate composition for energy production during post-bypass period might be different from that during pre-bypass period because of surgical diabetic state induced by hypothermic cardiopulmonary bypass (CPB). We measured whole body oxygen consumption, carbon dioxide production and respiratory quotient by the gas exchange method using the Datex Deltatrac before and after hypothermic cardiopulmonary bypass. We also measured oxygen consumption by Fick's principle. Whole body oxygen consumption (P < 0.001) and carbon dioxide production (P < 0.05) increased significantly above pre-CPB values after the termination of CPB. Respiratory quotient (P < 0.01) decreased significantly below pre-CPB values after the termination of CPB. We conclude that oxygen consumption increased significantly above pre-bypass values after the termination of hypothermic cardiopulmonary bypass at least under the fentanyl, diazepam, chlorpromazine anesthesia with continuous infusion of nitroglycerin and nicardipine. The changes in respiratory quotient suggest a relatively higher ratio of lipid metabolism for energy production during post-bypass period.

Journal Article↗
PubMed1993

Effect of nicardipine on pulmonary hypertension after repair of congenital heart defects in early postoperative period.

We examined the effect of nicardipine and hyperventilatin on pulmonary arterial pressure (PAP) in four patients with pulmonary hypertension in congenital heart defect especially in the early postoperative period. There was a significant positive correlation between the values of arterial carbon dioxide tension (PaCO2) and the ratio of mean PAP to mean systemic arterial pressure (Pp/Ps) in two patients whose Heath Edwards classification was Grade II; one of them also had 20% reduction of mean PAP by nicardipine without changing mean arterial pressure. In the remaining two patients showing no correlation between the values of PaCO2 and Pp/Ps, nicardipine did not reduce PAP. Although nicardipine reduced PAP without changing systemic arterial pressure in only one out of four patients, these results suggest that nicardipine may be a drug for control of PAP during weaning phase from the ventilator especially in patients whose PAP decreases under hyperventilation.

Journal Article↗
PubMed1993

Endocrine and hemodynamic changes during liver surgery in patients with compensated liver cirrhosis.

The purpose of this study was to determine hormonal levels in compensated liver cirrhotic patients under general anesthesia before and after liver surgery. We measured plasma norepinephrine, epinephrine, arginine vasopressin, and aldosterone levels and renin activity in non-cirrhotic and compensated cirrhotic patients undergoing liver resection after induction of anesthesia but before skin incision and after the end of operation but before discontinuation of nitrous oxide. We simultaneously measured hemodynamic variables. Plasma levels of norepinephrine (P < 0.001), epinephrine (P < 0.001), arginine vasopressin (P < 0.05), renin (P < 0.05) and aldosterone (P < 0.001) significantly increased after completion of surgery compared with those before incision in both groups. There was a significant positive correlation between plasma renin and aldosterone (r = 0.56, P < 0.01) levels in non-cirrhotics, but no correlation was observed in cirrhotics; and there was a significant positive correlation between plasma norepinephrine and arginine vasopressin (r = 0.45, P < 0.05) levels in non-cirrhotics, but no correlation in cirrhotics. Cardiac index and arterial pressure increased after the end of operation (P < 0.05). This increase after the operation was the same between cirrhotic and non-cirrhotic groups. There were no changes in heart rate, mean pulmonary arterial pressure, and pulmonary capillary wedge pressure after the end of operation. We conclude that hemodynamic and endocrinological changes were similar between compensated cirrhotic patients and non-cirrhotic patients during liver surgery. Endocrine changes might partly explain the hemodynamic changes during surgery.

Journal Article↗
PubMed1993

Decrease of ischaemia-reperfusion related lung oedema by continuous ventilation and allopurinol in rat perfusion lung model.

Using isolated perfusion rat lung model, we studied the effect of continuous ventilation without perfusion and allopurinol on the development of ischaemia-reperfusion lung injury. Ischaemia was induced by stopping the perfusion. Normothermic ischaemia for 90 min without ventilation caused significant lung oedema. Continuous ventilation during ischaemia with 21% O2 decreased lung oedema significantly after 60 min of reperfusion. The same protection could be achieved by 100% N2 ventilation during 90 min of ischaemia, suggesting that xanthine oxidase (XO) is unlikely to cause the ischaemia-reperfusion lung injury. On the other hand allopurinol, XO inhibitor, equally inhibited lung oedema after 90 min of ischaemia and 60 min of reperfusion. These results indicate that mechanical movement of alveoli provides successful preservation of ischaemic lung, and allopurinol has some protective effect other than XO inhibition.

Allopurinol↗
PubMed1991

[31P]MRS study of the protective effects of prostaglandin oligomers on forebrain ischemia in rats.

Two ester-type prostaglandin oligomeric compounds were synthesized, one from prostaglandin E1 (termed MR-356) and the other from prostaglandin B2 (termed OC-5186). Using in vivo [31P]MRS, the protective effects of these oligomers on forebrain ischemia (15 min) were evaluated in a rat model. Forebrain ischemia caused a decrease in intracellular high energy phosphates and intracellular pH (pHi) in the control and compounds-treated groups, but changes of these values in the OC-5186-treated group were significantly smaller than those in the control group. Moreover, the cerebral energy metabolism of the OC-5186-treated group returned to the preischemia level more rapidly than in the control group after forebrain ischemia. MR-356 had some effects, but the differences were not significant.

Adenosine Triphosphate↗
PubMed1991

Effects and arterial concentration of prostaglandin E1 during cardiopulmonary bypass.

The effects an infusion prostaglandin E1 (PGE1) on both haemodynamics and PGE1 arterial blood concentration during and after cardiopulmonary bypass (CPB) were studied in 15 patients (eight patients received PGE1 30 ng kg-1 min-1; seven served as controls and did not receive PGE1 administration). Mean arterial blood pressure and systemic vascular resistance were significantly lower in the PGE1 group than in the control group during CPB. There were no statistically significant differences between the two groups with regard to mean pulmonary-artery pressure, central venous pressure, and cardiac or perfusion index. The arterial blood concentration of PGE1 in the control group during CPB was about 50 pg ml-1. In the PGE1 group it increased rapidly after the beginning of CPB and reached a level of 1500 pg ml-1 at 60 min of CPB. After weaning off CPB, PGE1 concentration decreased rapidly to 70 pg ml-1 in spite of the continuous PGE1 infusion. It is concluded that the metabolism of PGE1 is strongly inhibited during CPB and the effects of PGE1 may be unexpectedly heightened. Therefore, the infusion rate of PGE1 during CPB should be 30 ng kg-1 min-1 or less in order to avoid severe hypotension.

Alprostadil↗
PubMed1990

Timing of injection and plasma concentration of lidocaine before endotracheal intubation.

The optimal time of intravenous lidocaine for attenuation of pressor responses to laryngoscopy and endotracheal intubation was evaluated in fifty adult patients and the correlation between plasma lidocaine level and its clinical effects were also studied. The plasma lidocaine levels were highest 0.5 min after administration of lidocaine 1.5 mg.kg(-1) intravenously. However, endotracheal intubation 0.5 min after lidocaine administration caused significant increase in mean arterial pressure (MAP) and heart rate (HR). Mean arterial pressure and HR increased with endotracheal intubation following 1, 2 and 3 min after lidocaine administration, but the magnitude of increase was not statistically significant. There were no significant differences in MAP changes among these three groups. It was concluded that the plasma lidocaine levels did not correlate with its suppressive effect on circulatory responses due to laryngoscopy and endotracheal intubation. Laryngoscopy and endotracheal intubation should be carried out at least 1 min after intravenous lidocaine administration.

Journal Article↗
PubMed1990

Effects of intravenous or endotracheal lidocaine on circulatory changes during recovery from general anesthesia.

Intravenous lidocaine (1.5 mg.kg(-1)) was not effective in attenuating the circulatory changes and the cough reflex induced by airway stimulation during recovery from general anesthesia, whereas endotracheal 4% lidocaine (3 ml) was effective. The arterial concentration of the intravenously administered-lidocaine peaked at a level of 9.52 +/- 0.81 microg.ml(-1) 0.5 min later. The arterial concentration of the endotracheally administered-lidocaine peaked at 1.44 +/- 0.13 microg.ml(-1) 15 min later. These findings indicate that the endotracheal administration of lidocaine may be superior to the intravenous administration for attenuating the circulatory changes and the cough reflex during recovery from general anesthesia, and that the arterial concentration of lidocaine did not correlate with the clinical efficacy for this purpose.

Journal Article↗
PubMed1990

Effect of combined infusion of nitroglycerin and nicardipine on femoral-to-radial arterial pressure gradient after cardiopulmonary bypass.

Nitrates and calcium channel blockers are frequently administered during cardiac surgery. We simultaneously measured femoral arterial pressure and radial arterial pressure to investigate whether nitrates, in conjunction with calcium channel blockers, would influence the central-to-peripheral arterial pressure gradient. Combined nitroglycerin and nicardipine infusion during cardiac surgery involving coronary artery bypass grafting or valve replacement resulted in a significant increase above baseline levels in the femoral-to-radial arterial pressure gradient at 60 min after cardiopulmonary bypass. In control patients there was no significant increase in the femoral-to-radial arterial pressure gradient at 60 min after completion of cardiopulmonary bypass. A subsequent study in patients given nitroglycerin and nicardipine identified that the difference in the systolic arterial pressure between femoral and radial arteries was observed 15, 60, and 120 min after completion of cardiopulmonary bypass. However, there was no difference in the mean arterial pressure between femoral and radial arteries throughout the same period. We conclude that combined infusion of nitroglycerin and nicardipine, a new calcium channel blocker, intensifies the magnitude and duration of the femoral-to-radial arterial pressure gradient after cardiopulmonary bypass.

Adult↗
PubMed1989

Effects of various catecholamines on high-energy phosphates of rat liver and brain during hemorrhagic shock measured by 31P-NMR spectroscopy.

The effects of dopamine, epinephrine and norepinephrine on energy metabolism as well as intracellular pH in rat liver and brain during hemorrhagic shock were examined by in vivo 31P-NMR spectroscopy. The hemorrhagic shock was induced by arterial bleeding to a mean arterial pressure (MAP) of 30-40 mmHg. Upon the induction of hemorrhagic shock, there was a dramatic fall in adenosine triphosphate (ATP) and a rise in inorganic phosphate (Pi) in the liver. The intracellular pH indicated severe acidosis. However, no change in these parameters was observed in the brain during hemorrhagic shock. After infusion of the above catechollamines following 10 min of hemorrhagic shock, MAP increased to 90-100% of its control value. Only dopamine improved hepatic energy metabolism, whereas brain energy metabolism was not affected by any of them. This suggests that dopamine protects liver function during hemorrhagic shock without affecting brain energy metabolism.

Journal Article↗