Biomedical subjects

Kayoko Segawa

Publications and source records attributed to Kayoko Segawa.

6 recordsLinked to original sources

PubMed2004

A forskolin derivative, colforsin daropate hydrochloride, inhibits the decrease in cortical renal blood flow induced by noradrenaline or angiotensin II in anesthetized rats.

A forskolin derivative, colforsin daropate hydrochloride (CDH), acts directly on adenylate cyclase to increase the intracellular cyclic adenosine monophosphate levels which produce a positive inotropic effect and a lower blood pressure. However, little is known about the effects of CDH on the renal function. We used laser Doppler flowmetry to measure the cortical renal blood flow (RBF) in male Wistar rats given a continuous intravenous infusion of CDH and evaluated the effects of CDH on the noradrenaline (NA) and angiotensin II (AngII) induced increases in blood pressure and reductions in RBF. Continuous intravenous administration of CDH at 0.25 microg/kg/min did not affect the mean arterial pressure (MAP), but increased heart rate and RBF. Continuous intravenous administration of CDH at high doses (0.5-0.75 microg/kg/min) decreased the MAP, with little effect on the RBF. The administration of exogenous NA (1.7 microg/kg) increased the MAP and decreased the RBF. However, a bolus injection of NA did not decrease the RBF during continuous intravenous administration of CDH, and CDH did not affect the NA-induced increase in MAP. The administration of exogenous AngII (100 ng/kg) increased MAP and decreased RBF and heart rate, but a bolus injection of AngII did not decrease RBF during continuous intravenous administration of CDH. These results suggest that CDH plays a protective role against the pressor effects and the decrease in RBF induced by NA or AngII.

Anesthesia↗

PubMed2004

The inhibition of aortic smooth muscle cell proliferation by the intravenous anesthetic ketamine.

Smooth muscle cell (SMC) proliferation has been recognized as central to the pathology of both major forms of vascular disease, atherosclerosis and hypertension. Recently, we reported that ketamine inhibits rat mesangial cell proliferation, suggesting that ketamine inhibits cell growth. Although the IV anesthetic ketamine has been widely used clinically, the exact effects of ketamine on vascular SMC proliferation have not been studied. In this study, we investigated the effects of ketamine on vascular SMC proliferation. Ketamine inhibited [(3)H]thymidine incorporation and decreased the number of SMCs in a concentration-dependent manner (10-200 microM); neither propofol nor fentanyl inhibited [(3)H]thymidine incorporation into human aortic SMCs. The protein kinase C (PKC) inhibitor GF109203x abolished the ketamine-induced inhibition of [(3)H]thymidine incorporation into SMC, but the inhibition was not affected by either the protein kinase A inhibitor H-89 or the protein kinase G inhibitor KT5823. A histological analysis demonstrated the inhibitory effect of ketamine on the intimal thickening of the balloon-injured rat aorta. Based on these results, ketamine inhibits SMCs at clinical concentrations via the PKC pathway. Our results indicate that ketamine might prevent the proliferation of SMCs clinically.

Anesthetics, Dissociative↗

PubMed2003

Effects of the intravenously administered anaesthetics ketamine, propofol, and thiamylal on the cortical renal blood flow in rats.

Intravenous anaesthetics such as ketamine, propofol, and thiamylal are widely used, although the direct effects of these anaesthetics on the renal blood flow (RBF) have not been well elucidated. In this study, we examined the effects of bolus and continuous administrations of ketamine, propofol, and thiamylal on cortical RBF and the effects of noradrenaline (NA) on RBF under continuous administration of these anaesthetics. We used laser Doppler flowmetry to measure the effects of bolus injection and continuous infusion of ketamine, propofol, and thiamylal on cortical RBF in male Wistar rats. We also examined the effects of the anaesthetics on mean arterial blood pressure (MAP) and heart rate (HR). Bolus injections of ketamine, propofol, or thiamylal (1-8 mg/kg each, n = 10) at clinically relevant concentrations did not affect MAP, HR, or RBF. Continuous administration of ketamine, propofol, or thiamylal (1-8 mg/kg/h each, n = 10) did not affect MAP, HR or RBF. Exogenous NA (2 microg/kg) caused an increase in MAP and a decrease in RBF and HR. In experiments with continuous infusions of propofol or thiamylal (1-8 mg/kg/h each, n = 10), similar results were observed without infusion of any anaesthetics. However, bolus injection of NA did not result in a decrease in RBF during continuous ketamine infusion (98.8 +/- 6.7% of control, n = 6, p < 0.05), while ketamine did not affect the NA-induced increase in MAP. In conclusion, bolus and continuous administrations of ketamine, propofol, and thiamylal did not affect the RBF. From our present findings, ketamine would be useful for maintaining the RBF.

Anesthetics, Intravenous↗

PubMed2003

A forskolin derivative, colforsin daropate hydrochloride, inhibits rat mesangial cell mitogenesis via the cyclic AMP pathway.

A forskolin derivative, colforsin daropate hydrochloride (CDH), has been introduced as an inotropic agent that acts directly on adenylate cyclase to increase intracellular cyclic AMP (cAMP) levels and ventricular contractility, resulting in positive inotropic activity. We investigated the effects of CDH on rat mesangial cell (MC) proliferation. CDH (10(-7)-10(-5) mol/l) inhibited [(3)H]thymidine incorporation into cultured rat MCs in a concentration-dependent manner. CDH (10(-7)-10(-5) mol/l) also decreased cell numbers in a similar manner, and stimulated cAMP accumulation in MCs in a concentration-dependent manner. A protein kinase A inhibitor, H-89, abolished the inhibitory effects of CDH on MC mitogenesis. These findings suggest that CDH would inhibit the proliferation of rat MCs via the cAMP pathway.

Animals↗

PubMed2002

Endotoxin removal by direct hemoperfusion with an adsorbent column using polymyxin B-immobilized fiber ameliorates systemic circulatory disturbance in patients with septic shock.

Direct hemoperfusion (DHP) with an adsorbent column using polymyxin B-immobilized fiber (PMX-F) has been shown to improve the state of shock in patients with septic shock. However, no evidence has been presented for a direct link between endotoxin removal by DHP with PMX-F and improvement in septic shock. We retrospectively analyzed clinical profiles of 24 patients with septic shock (16 patients, gram-negative; 8 patients, non-gram-negative septic shock) who underwent DHP with PMX-F. Patients with gram-negative septic shock were characterized by hyperdynamic circulation. DHP with PMX-F reduced blood endotoxin concentrations and ameliorated shock, with an improvement in hyperdynamic circulation in patients with gram-negative septic shock. Mean arterial pressure also was elevated after therapy in patients with non-gram-negative septic shock, but systemic hemodynamics were unaffected. Regardless of the causative microorganism, patients with endotoxemia (blood endotoxin level > 10 pg/mL) showed hyperdynamic shock, and DHP with PMX-F reduced blood endotoxin levels and ameliorated hyperdynamic circulation, whereas patients without endotoxemia showed features of shock without hyperdynamic circulation, and DHP with PMX-F ameliorated shock without affecting cardiac performance. In patients with gram-negative septic shock, blood endotoxin concentration correlated positively with cardiac output and negatively with systemic vascular resistance before DHP therapy. Reduction in blood endotoxin concentration by DHP therapy positively correlated with the reduction in cardiac output. Our findings indicate that the improvement in hyperdynamic circulation was related directly to endotoxin removal by the PMX-F column, and endotoxin has an important role in the development of hyperdynamic circulation in patients with gram-negative septic shock.

Adsorption↗

PubMed2002

Inhibitory effects of ethanol on rat mesangial cell proliferation via protein kinase C pathway.

A large body of evidence has shown that ethanol inhibits the cell growth and cell proliferation in a variety of cell types. However, it has not been studied whether ethanol inhibits the proliferation of mesangial cells (MC) in the kidney. We examined the effects of ethanol on cell proliferation in cultured rat MC. Treatment with ethanol (10-200 mM) for 48 hr inhibited [(3)H]thymidine incorporation into MC in a concentration-dependent manner. The same concentrations of ethanol also inhibited the increase in cell number of MC. GF109203X and chelerythrine chloride, inhibitors for protein kinase C, eliminated the inhibitory effects of ethanol; and protein kinase C activator, PMA, mimicked the effects of ethanol. In contrast, neither the protein kinase A inhibitor H-89 nor the protein kinase G inhibitor KT5823 had any effect. These findings suggest that ethanol has inhibitory effects on the proliferation of MC, probably via activation of the protein kinase C pathway.

Animals↗