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Biomedical subjects

H Okayasu

Publications and source records attributed to H Okayasu.

28 records · Page 2Linked to original sources
PubMed1983

Xenon-enhanced CT CBF measurements in cerebral AVM's before and after excision. Contribution to pathogenesis and treatment.

Unlike neurological deficits resulting from intracranial hemorrhage in patients with cerebral arteriovenous malformation (AVM), which have well defined etiology, the pathogenesis and treatment of progressive and/or fluctuating non-hemorrhagic neurological and psychological deficits require clarification. Values for local cerebral blood flow (LCBF) and local partition coefficients (L lambda) were measured by the method using stable xenon (Xe)-computerized tomography (CT-CBF) scanning, and were compared to 133Xe inhalation values using external probes in 16 patients with cerebral AVM's. Values were measured by both methods before and after total excision of AVM's in five cases. Neurological and mental status assessments were compared with LCBF results. Clinical improvement was most evident after total excision of AVM's. Other procedures, such as clipping of vessels, partial excision, and ventriculoperitoneal shunting for hydrocephalus, were associated with frequent complications. Embolization carried risks of cerebral infarction and was not efficacious unless combined with excision. Medical treatment resulted in poor or unsuccessful seizure control, with neurological deterioration despite anticonvulsant therapy. Compared with age-matched normal individuals, LCBF values in patients with AVM's were significantly reduced, particularly adjacent to the AVM's. Mean L lambda values for gray and white matter were normal. After excision, LCBF values in gray and white matter increased significantly up to normal. Due to overestimation of CBF by shunt flow with the 133Xe method of measurement, no correlation was found with results of the CT-CBF method before AVM excision, but significant correlation of the two methods resulted after excision. If accurate LCBF values are obtained by high resolution, direct measurement of tracer clearance from brain tissue, progressive and/or fluctuating neuropsychological deficits correlate with the degree of cerebral steal.

Adolescent↗
PubMed1982

Long-term prognosis in ischemic cerebrovascular disease in relation to cerebral blood flow and metabolism.

The correlation between long-term prognosis and cerebral hemodynamics and oxygen consumption was investigated in 46 patients with ischemic supratentorial cerebrovascular disease. Cerebral blood flow (CBF) and cerebral oxygen consumption (CMRO2) were measured by the N2O method 1-6 months (mean 68 days) after disease onset. No significant correlation was observed among CBF, CMRO2 and activities of daily living at the time of measurement. The patients' physical condition was reevaluated by the questionnaire method 2 years or more (mean 53 months) later. The CBF values in patients who were independent after completion of the follow-up period significantly exceeded those of patients dying during the period (P less than 0.05). No correlation was observed in CMRO2. The relationship among CBF, CMRO2 and changes in physical condition during the period was evaluated. Mean CBF values in patients with better prognosis exceeded those of patients with poor prognosis. Notably, CBF values in the "improved" group significantly exceeded those in the "unchanged" or "died" group (P less than 0.05, P less than 0.01). CMRO2 was not significantly correlated with changes of physical condition. These results emphasize the importance of total CBF for long-term prognosis and indicate that flow values, rather than metabolic indices, obtained in the chronic stage can usefully predict the long-term prognosis.

Aged↗
PubMed1982

Video camera method for simultaneous measurement of blood flow velocity and pial vessel diameter.

A new method for the simultaneous measurement of blood flow velocity and pial vessel diameter is described. The system consists basically of a high-sensitivity vidicon camera, camera control, width analyzer, video densitometer, TV monitor, desktop computer, and multi-pen recorder. The pial vessels are visualized through a cranial window at 25-200x magnification on the TV monitor. The diameter of three target vessels can be recorded simultaneously on the recorder by adjustment of controllable video signal gates using the width analyzer. At the same time, the optical densities of two targets at points upstream and downstream of the pial vessel are measured continuously with video densitometers, and their outputs are recorded on the polygraph and analyzed by the computer. The time difference in the two peaks of time--concentration curves, produced very 2-3 s at the highest frequency by the injection of a small amount of saline through the lingual artery, is measured on-line using the computer. The flow velocity in the vessel is calculated from the time difference and the distance between the two targets. The system was shown to be stable, reliable, and rapid in response. This method may provide a useful tool for research in the field of blood circulation in the brain or any other organ.

Animals↗
PubMed1982

Effect of nimodipine, a calcium antagonist, on cerebral vasospasm after subarachnoid hemorrhage in cats.

Effect of a calcium antagonist, isopropyl-(2-methoxyethyl)-1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5- pyridinedicarboxylate (nimodipine) on the cerebral vasospasm after experimental subarachnoid hemorrhage (SAH) was studied in ten adult cats. The vasospasm was induced by injecting of 0.2-0.3 ml fresh autologous whole blood into the cisterna magna. Diameter of pial vessels was continuously measured by means of the vidicon camera system developed in our laboratory. Intravenous administration of nimodipine (0.1 mg/kg) 20-30 min after SAH resulted in a complete disappearance of the spasm with the reduction of blood pressure. The dilatory response was more marked in the smaller arteries (less than 100 microns) than in the larger ones (greater than or equal to 100 microns). Administration of smaller dose of nimodipine (0.01 mg/kg) also produced dilation of the pial vessels, although the effect was less remarkable in the smaller arteries. These data suggest that nimodipine might be useful in the treatment of the cerebral vasospasm after SAH. The mechanism underlying the action of nimodipine was discussed.

Animals↗
PubMed1980

Effects of nimodipine (Bay e 9736) on cerebral circulation in cats.

The response of feline pial arteries to i.v. administration of isopropyl-(2-methoxyethyl)-1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylate (nimodipine, Bay e 9736) was studied by means of the vidicon camera system developed in our laboratory. Pial arteries showed a dose-dependent dilation with a reduction of systemic arterial blood pressure in the dose range of 0.001 mg/kg to 0.1 mg/kg of nimodipine. The dilatory response was more marked in the smaller arteries (< 100 mu) than in the larger ones (greater than or equal to 100 mu).

Animals↗
PubMedDate not supplied

Stable xenon CT CBF measurements in prevalent cerebrovascular disorders (stroke).

Local cerebral blood flow (LCBF) and local tissue: blood partition coefficient (L lambda) values were measured for small volumes of gray or white matter by CT CBF. Single compartment analysis was used but fitted to infinity in normal volunteers aged between 20 to 100 years (N = 20). Hemispheric LCBF and L lambda values were compared to those of 61 age matched patients with transient ischemic attacks (TIAs, N = 10), reversible ischemic neurologic deficits (RINDS, N = 10), acute and chronic cerebral infarctions associated with emboli from atherosclerotic plaques or complete occlusion of internal carotid or middle cerebral arteries (n = 9) or of cardiac origin (N = 3), cerebral hemorrhage (N = 1), multi-infarct dementia (MID) (N = 11) and arteriovenous malformations (AVM) (N = 17). In normal aging, L lambda s were normal, but LCBF showed diffuse age-related declines. Symptomatic cerebrovascular disease was characterized by accentuation of age-related LCBF declines. TIAs with unilateral ICA occlusion showed bilateral reductions of LCBF more evident in ischemic hemispheres. TIAs due to fibrino-platelet emboli from ulcerated, non-occlusive ICA plaques were characterized by transient unilateral, localized LCBF reductions. All TIAs showed normal L lambda values. RINDS showed both LCBF and L lambda reductions. Larger embolic infarctions of ICA origin, whether acute or chronic, showed zones of zero flow with surrounding reductions of LCBF and L lambda values. Recent cerebral embolism of cardiac origin likewise exhibited zones of zero flow surrounded by reduced LCBF and L lambda values; but in chronic stages LCBF and L lambda values adjacent to zero flow zones were normal. MID was characterized by patchy reductions of LCBF and L lambda values throughout both hemispheres. Brain tissues surrounding AVM showed normal L lambda values but LCBF values were reduced due to steal.

Adult↗
PubMedDate not supplied

Cytotoxic activity of vitamins K1, K2 and K3 against human oral tumor cell lines.

Vitamin K1, K2 and K3 were compared for their cytotoxic activity, radical generation and O2- scavenging activity. Among these compounds, vitamin K3 showed the highest cytotoxic activity against human oral tumor cell lines (HSC-2, HSG), human promyelocytic leukemic cell line (HL-60) and human gingival fibroblast (HGF). Vitamin K3 induced internucleosomal DNA fragmentation in HL-60 cells, but not in HSC-2 or HSG cells. The cytotoxic activity of vitamins K2 and K1 was one and two orders lower, respectively, than K3. Vitamin K2, but not vitamin K3, showed tumor-specific cytotoxic action. ESR spectroscopy showed that only vitamin K3 produced radical(s) under alkaline condition and most potently enhanced the radical intensity of sodium ascorbate and scavenged O2- (generated by hypoxanthine-xanthine oxidase reaction system); vitamin K2 was much less active whereas vitamin K1 was inactive. These data suggest that the cytotoxic activity of vitamin K3 is generated by radical-mediated oxidation mechanism and that this vitamin has two opposing actions (that is, antioxidant and prooxidant), depending on the experimental conditions.

Carcinoma, Squamous Cell↗