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Biomedical subjects

T Yamawaki

Publications and source records attributed to T Yamawaki.

13 recordsLinked to original sources
PubMed1992

Cerebral microcirculatory changes during and following transient ventricular tachycardia in cats.

Although reduced cerebral perfusion is believed to be the cause of syncope due to cardiac arrhythmias, investigations on the cerebral microcirculation during cardiac arrhythmias have been rare. We therefore studied the effects of transient ventricular tachycardia on the local cerebral blood volume and blood flow. Experimental ventricular tachycardia was induced in cats by electrically stimulating the ventricle of the heart at a rate of 300/min for 1 min. Using our photoelectric method, the local cerebral blood volume, mean transit time of blood, and cerebral blood flow in the parieto-temporal region were measured during and for 3 h after ventricular tachycardia. Transient ventricular tachycardia of as short as 1 min caused cerebral ischemia with a blood flow reduction of approximately 30%. This was considered to be due to reduced blood pressure plus transient autonomic dysfunction, or dysautoregulation, during the ventricular tachycardia. Mild and transient reactive hyperemia occurred immediately after termination of the dysrhythmia, but continuous reductions of cerebral blood flow were observed thereafter for 3 h. This delayed hypoperfusion is attributable to either vasoconstriction of the large resistance vessels or changes in the hemorheological properties of the blood caused by cerebral ischemia. Ventricular tachycardia of the type reported has significant and long-lasting effects on the cerebral microcirculation.

Animals↗
PubMed1992

Alterations of charge barrier in the inner ear following immune reactions.

We investigated electron microscopically the changes of anionic sites of a charge barrier in the capillary basement membrane of the stria vascularis and endolymphatic sac following inner ear immune reactions. Hartley guinea pigs were immunized with bovine type II collagen, keyhole limpet hemocyanin, or horseradish peroxidase, with boosted and challenged antigens through the stylomastoid foramen. Animals were killed painlessly from several days up to 56 days after the antigen challenge. Polyethylenimine was used as a cationic tracer in order to observe the localization of anionic sites of the charge. In the animals immunized with bovine type II collagen or horseradish peroxidase, a significant decrease of anionic charge in the stria and the sac was found in the early stage of immunization. However, the keyhold limpet hemocyanin immunization group did not show any remarkable changes in the charge because of its lesser transfer into the inner ear due to of its high molecular weight and negative surface charge. A decrease of the charge under immunologic conditions may induce a hyperpermeability of vessels and a malabsorption of endolymph, and thus may cause endolymphatic hydrops.

Animals↗
PubMed1990

The mechanical filtration coefficient (Lp) of the cell membrane of cultured glioma cells (C6).

The mechanical filtration coefficient (Lp) of the membrane of cultured glioma cells was determined from the rate of swelling of the cells. The swelling was induced by exposing the cells to distilled water. Assuming that cells swell in a symmetrical manner, Lp was 2.2 x 10(-8) cm/s.mmHg, or 1.7 x 10(-4) microns/s.cmH2O when calculated from changes of the cell diameter.

Cell Membrane↗
PubMed1989

Effects of a selective inhibitor of cyclic AMP phosphodiesterase on the pial microcirculation in feline cerebral ischemia.

We evaluated the effects of cilostazol, a selective inhibitor of cyclic adenosine monophosphate phosphodiesterase, on the pial vessels of adult cats subjected to endothelial damage followed by middle cerebral artery occlusion. Six cats were treated with cilostazol and four with 30% N,N-dimethylformamide in 70% saline (solvent). The brain surface was irradiated with ultraviolet rays through a cranial window for 3 minutes to selectively damage the endothelium of the pial vessels in both groups. Beginning 32 minutes after termination of the irradiation, the middle cerebral artery was occluded for 30 minutes. Thirty minutes before occlusion, intravenous infusion of 30 micrograms/kg/min cilostazol or 0.1 ml/kg/min solvent was begun and continued until the end of the study. Before occlusion, the infusion of cilostazol induced a significant (p less than 0.05) dilatation while the infusion of solvent produced no significant changes in the diameter of the pial arteries. The pial veins of solvent-treated cats showed significant (p less than 0.05) constriction during occlusion, whereas cilostazol-treated cats exhibited only mild constriction of the pial veins. The formation of platelet thrombi after occlusion was significantly (p less than 0.05) inhibited in the pial veins of cilostazol-treated compared with solvent-treated cats. Similarly, the microcirculation of the pial veins was effectively restored after reopening of the middle cerebral artery in cilostazol-treated compared with solvent-treated cats. Our data suggest that cilostazol is an effective antithrombotic agent as well as a potent vasodilator acting on vascular smooth muscle.

Animals↗
PubMed1979

Resectability and functional reserve of the liver with obstructive jaundice in dogs.

Fifty-five dogs were used to evaluate the resectability of the liver with obstructive jaundice. Cholecystectomy and ligation of the distal common bile duct were used to produce obstructive jaundice. It was found that 40 per cent of the liver with obstructive jaundice was resectable with biliary decompression 2 weeks after ligation. At 1 week after induction of obstructive jaundice, 70 per cent hepatectomy with biliary decompression may be tolerated with careful postoperative management. From serum chemical studies it was found that if the serum albumin level was below 2.0 g/dl, 60 per cent of the dogs died after 40 per cent hepatectomy and all died after 70 per cent hepatectomy. From the standpoint of hepatic functional reserve 40 per cent hepatectomy is successful if the maximal removal rate of indocyanine green is above 0.14 mg/kg/min. Hepatic functional reserve is reliable for predicting the risk of hepatectomy, and it correlates well with the rate of hepatic regeneration after hepatectomy.

Animals↗
PubMed1978

Clinical significance of mitochondrial glutamic-oxaloacetic transaminase in serum of patients with liver disease.

Serum mitochondrial glutamic-oxaloacetic transaminase activity was determined in 83 patients with various liver diseases and 10 healthy adults. 1) The average of mitochondrial glutamic-oxaloacetic transaminase value was 1.2 mU in healthy adults, 8.3 mU in patients with acute hepatitis, 13.7 mU in patients with post-transfusion hepatitis, 5.0 mU in patients with persistent hepatitis, 4.5 mU in patients with chronic inactive hepatitis, 9.6 mU in patients with chronic active hepatitis, 5.6 mU in liver cirrhosis, and 295 mU in a patient with fulminant hepatitis. 2) While one patient with acute hepatitis showed the highest value in the group of 29 mU, one patient with fulminant hepatitis showed an extremely high value of 295 mU, revealing an obvious difference between them. 3) One patient with fresh myocardial infarction also showed an extremely high value of 110 mU.

Antibodies↗