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Biomedical subjects

R Kawai

Publications and source records attributed to R Kawai.

At least 91 records · Page 5Linked to original sources

MR imaging of dural arteriovenous malformations with ocular signs.

Four patients with dural arteriovenous malformation (AVMs) draining into the cavernous sinus, who presented ophthalmic manifestations, were studied by magnetic resonance (MR) imaging. In all patients signal decrease in the involved cavernous sinus was demonstrated in coronal spin-echo (SE) imaging. It is attributable to rapid venous flow in the sinus, and this "high velocity signal loss" is a fairly pathognomonic finding in this condition. We stress the validity of MR imaging in the primary diagnosis of dural AVMs with ophthalmic symptoms.

Arteriovenous Malformations↗

Metabolic fate of indeloxazine hydrochloride: alpha-glucoside formation in rats.

1. After oral administration of indeloxazine hydrochloride ((+/-)-2-[(inden-7-yloxy)methyl]morpholine hydrochloride) to rats, two conjugates, which were labile to alpha-glucosidase hydrolysis but refractory to beta-glucosidase, were isolated from the urine. 2. Mass spectral and n.m.r. analyses confirmed that these conjugates were alpha-D-glucopyranosides of M-2 (trans-4-(2-morpholinylmethoxy)-1,2-indandiol) and M-3 (trans-6-[[(1,2-dihydroxy-4-indanyl)oxy]-methyl]-3-morpholinone). 3. These are probably the first examples of foreign compounds conjugated with glucose in the alpha-configuration.

Animals↗

Cerebral peak time mapping uniformity of the value of peak time.

By studying patients with clinically suspected cerebrovascular occlusive disease using dynamic CT technique, we have shown that contrast peak attenuation of the whole normal cerebral tissue was uniformly reached at the same time within a given individual. On the other hand, the delay of peak time was shown to correlate with some vascular occlusive mechanism. The main implications of delayed contrast peak time can be summarized as follows: Reduced regional blood flow due to stenosis or occlusion of main vessel without tissue damage. Delayed contrast arrival time due to occlusion of main vessel, but with sufficient circulation. Tissue organically injured by cerebrovascular occlusion.

Cerebral Arterial Diseases↗

Disposition and metabolism of indeloxazine hydrochloride, a cerebral activator, in rats.

1. The disposition and metabolism of indeloxazine hydrochloride ((+/-)-2-[(inden-7-yloxy)methyl]morpholine hydrochloride) were studied in male Sprague-Dawley rats. 2. After oral administration of 14C-indeloxazine hydrochloride, the plasma concentration of total radioactivity reached a maximum at 15 min and declined with an apparent half-life of 2.2 h in the first 6 h period and declined more slowly thereafter. Unchanged drug in the plasma represented 13.5%, 5.9% and 0.4% of the total radioactivity at 15 min, 1 h and 6 h respectively after administration and levels decayed with a half-life of 0.9 h. 3. After oral and i.v. administration of the labelled compound, the urinary and faecal excretion of radioactivity in 72 h were 61-65% and 31-36% of the dose, respectively. Biliary excretion in bile duct-cannulated animals amounted to 49% of the dose in 72 h. 4. Seven metabolites have been isolated from the plasma or urine and characterized by i.r., n.m.r. and mass spectrometry. They were derived through dihydrodiol formation in the indene ring, hydroxylation of the indene ring and N-acetylation, oxidation and oxidative degradation of the morpholine ring. Some metabolites were excreted as their glucuronic acid or glucose conjugates. The major metabolite appeared to the trans-indandiol analogue of indeloxazine. 5. Possible metabolic pathways of degradation of the morpholine ring are discussed.

Animals↗

Radiation necrosis of the brain and radiation-induced cerebrovasculopathy.

Thirteen patients with radiation necrosis and 6 patients with occlusive radiation-induced cerebrovasculopathy were reviewed. Computed tomography (CT) demonstrated low attenuation with a mass effect and irregular contrast enhancement in the radiation necrosis. The mass effect and the contrast enhancement decreased gradually. Angiography showed an avascular mass, generalized narrowing of the ipsilateral arteries and slow blood circulation in 3 cases. Radiation-induced vasculopathy appeared as localized stenosis and irregular walls of the arteries within the irradiated area. In cases with radiation vasculopathy accompanied by sufficient collateral blood flow brain damage was rarely demonstrated by CT. In patients with radiation-induced vasculopathy the lesion was not associated with signs of radiation necrosis.

Adult↗

Age associated alteration of lidocaine metabolism is position selective.

Patterns of associated alterations in N-deethylation, 3-hydroxylation, and aromatic methylhydroxylation of a single substrate, lidocaine in liver microsomes from 0.7 - 28 months old Fischer 344 rats were examined. These three patterns were all different from one another. In addition to this position selectiveness, a clear sex difference was observed in the pattern of alteration in N-deethylation. These results are consistent with the hypothesis that age associated alterations in drug metabolism are caused by age associated alterations in relative abundance of multiple species of cytochrome P-450.

Aging↗

Simultaneous quantitation of lidocaine and its four metabolites by high-performance liquid chromatography: application to studies on in vitro and in vivo metabolism of lidocaine in rats.

A convenient and sensitive high-performance liquid chromatographic assay for the simultaneous quantitation of lidocaine and its four metabolites has been developed. The samples containing lidocaine and its metabolites were eluted from a microparticulate octadecylsilane column using a mobile phase of 0.1 M phosphate buffer (pH 3.0) containing 10% acetonitrile. This method was applied to studies on in vitro metabolism and in vivo pharmacokinetics of lidocaine in rats. Kinetic studies of in vitro microsomal metabolism of lidocaine indicated that the apparent Km and Vmax for aromatic hydroxylation were smaller than those for N-deethylation. Lineweaver-Burk plots of the N-deethylation of lidocaine and those of its two primary metabolites indicated that at least two isozymes are taking part in these reactions. In in vivo lidocaine pharmacokinetics, the area under the blood concentration-time curve for the monodeethylated product, omega-ethylamino-2,6-dimethylacetanilide (1), varied considerably depending on the route of administration.

Animals↗