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Biomedical subjects

T Okuda

Publications and source records attributed to T Okuda.

At least 613 records · Page 34Linked to original sources

III. New developments: 2. Virtual MR endoscopy in the central nervous system.

Recent advances in three-dimensional (3D) data acquisition and postprocessing technologies have been playing a important role in widening the potential applications of 3D display. The authors described new applications of a virtual endoscopic algorithm for 3D display of high resolution MR images: (a) intracranial intravascular virtual MR endoscopy using the 3D fast imaging with steady state precession (FISP) sequence, and (b) virtual MR endoscopy of the cerebrospinal fluid (CSF) spaces using the constructive interference in steady state (CISS) three-dimensional Fourier transform (3DFT) sequence. The virtual endoscopic images were displayed with use of a commercially available perspective volume-rendering algorithm. Our initial experience showed that virtual MR endoscopy can be performed to observe the intracranial arteries and CSF spaces from the viewpoints within themselves. Although the clinical use of the intracranial virtual MR endoscopy has not been established yet, the images obtained are very attractive and further investigations in this field will be expected.

Central Nervous System↗

Inhibition of herpes simplex virus infection by tannins and related compounds.

Several chemically defined plant extracts were investigated for their antiviral action on herpes simplex virus (HSV-1, HSV-2)-infected African green monkey kidney cells and human adenocarcinoma cells, using a plaque formation assay. Among them, the monomeric hydrolyzable tannins, oligomeric ellagitannins and condensed tannins, having galloyl groups or hexahydroxydiphenoyl groups, had the most potent anti-HSV activity. Their 50% effective doses (0.03-0.1 microgram/ml) were by two-three orders of magnitude lower than their 50% cytotoxic doses (greater than 10 micrograms/ml). On the other hand, gallic acid, neutral polysaccharides, chemically modified (N,N-dimethylaminoethyl-, carboxymethyl-, and sulfated-) glucans, sialic acid-rich glycoproteins, and uronic acid-rich pine cone polysaccharide showed little or no activity. Using radiolabeled virus particles, we demonstrated that the anti-HSV effect of the tannins is due to inhibition of virus adsorption to the cells.

Adsorption↗

FK778 controls acute rejection after rat liver allotransplantation showing positive interaction with FK506.

This study including prevention and rescue experiments was performed to examine the efficacy of FK778 and its interactions with FK506. In the prevention experiment, Brown-Norway rats transplanted with a 7 Lewis livers received day-course of FK778 or a combination of FK778 and FK506 treatment. For the rescue experiment, the recipients were additionally treated with FK778 from days 7 to 13. Blood chemistry and histopathological findings were used to examine the host and the graft condition. Donor-specific IgM was measured using enzyme-linked immunosorbent assays. The serum trough level of FK778 was examined by high-performance liquid chromatography. FK778 suppressed acute rejection in a dose-dependent manner. The optimal FK778 dosage was 20 mg/kg body weight (BW) d. FK778 treatment from days 7 to 13 rescued liver grafts from ongoing rejection. The combination of FK506 (0.125 mg/kg BW/d) and FK778 (20 mg/kg BW/d) maintained better graft condition than FK778 (20 mg/kg BW/d) monotherapy. In conclusion, FK778 prevents acute rejection in and rescues transplant recipients from ongoing rejection after rat liver transplantation. The optimal monotherapy dosage of FK778 was 20 mg/kg BW/d. Combination therapy with FK506 was more beneficial than FK778 monotherapy.

Alkynes↗

Ultrafast FLAIR imaging with single-shot echo-planar technique in evaluation of intracranial lesions.

We evaluated the detection of the brain lesions with single-shot echo-planar FLAIR imaging (EP-FLAIR) relative to fast spin-echo FLAIR imaging (fast-FLAIR). In 30 patients with variety of intracranial lesions, a prospective comparison of EP-FLAIR and fast-FLAIR was performed. Data acquisition time per image was 0.1 s with EP-FLAIR. Quantitative and qualitative criteria as well as lesion detectability were evaluated. EP-FLAIR provided almost same tissue contrast and CSF suppression as fast-FLAIR did. In the quantitative analysis, contrast and contrast-to-noise ratio (C/N) of EP-FLAIR were comparable to those of fast-FLAIR, and there was no significant difference between them. The increased magnetic susceptibility effect was useful in screening for subtle hemorrhage. However, EP-FLAIR was degraded by susceptibility artifacts at the skull base and posterior to the frontal sinuses. Motion artifacts were not encountered owing to the very short imaging time, and EP-FLAIR was particularly useful in screening for the lesions in uncoorporative patients.

Adolescent↗

Inhibitory effect of tannins on reverse transcriptase from RNA tumor virus.

Twenty-four tannins and related compounds were examined for inhibition against reverse transcriptase from RNA tumor virus. Hydrolyzable tannins showed a potent inhibitory effect comparable to nitidine, in the presence of polyadenylic acid-oligothymidylic acid as a template-primer. A lesser inhibitory activity was observed for the monomeric ellagitannins, gallotannins, and nitidine using polycytidylic acid-oligodeoxyguanylic acid as a template-primer, whereas the inhibitory activity of dimeric ellagitannins was almost as potent as that observed for these compounds in the polyadenylic acid-oligothymidylic acid directed reaction. Inhibition by tannins was reversed by the addition of either template-primer or enzyme, suggesting that the inhibition is due to the interaction of tannins with both of them.

Animals↗

Studies on the activities of tannins and related compounds, X. Effects of caffeetannins and related compounds on arachidonate metabolism in human polymorphonuclear leukocytes.

As part of a series of biological examinations of various tannins and related compounds, the present paper reports the effects of caffeetannins and related compounds isolated from medicinal plants on arachidonate metabolism in human peripheral polymorphonuclear leukocytes (PMN-L). The formation of leukotriene B4 (LTB4) induced by calcium ionophore A 23187 (A 23187) in human PMN-L was inhibited by 3,5-, 4,5-, and 3,4-di-O-caffeoylquinic acid, caffeoylmalic acid, caffeoyltartric acid, rosmarinic acid, and caffeic acid. Rosmarinic acid strongly inhibited the formation of 5-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE) and LTB4 (5-lipoxygenase products) at concentrations of 10(-5)-10(-3) M. On the other hand, the formation of prostaglandin E2 (PGE2) was enhanced in a concentration-dependent fashion by caffeic acid, caffeoylmalic acid, caffeoyltartaric acid, and 3,4-di-O-caffeoylquinic acid. On the basis of experimental results, it seems likely that caffeoyl derivatives could be developed as therapeutic drugs for treatment of allergic inflammation such as asthma.

Arachidonic Acid↗

Inhibitory effects of various flavonoids isolated from leaves of persimmon on angiotensin-converting enzyme activity.

The leaves of the persimmon Diospyros kaki, have been traditionally used for treatment of hypertensive diseases in Japan. We have studied the inhibitory effects of four flavonoids isolated from the leaves of the persimmon on angiotensin-converting enzyme activity. The four flavonoids astragalin [1], kaempferol-3-O-(2"-O-galloyl)-glucoside [2], isoquercitrin [3], and quercetin-3-O-(2"-O-galloyl)-glucoside [4] inhibited the angiotensin-converting enzyme activity in a dose-dependent fashion. Compounds 1-4 produced 67%, 53%, 33%, and 48% inhibition at a concentration of 300 micrograms/ml, respectively. The 50% inhibitory concentrations (IC50) of 1 and 2 for the angiotensin-converting enzyme were 180 micrograms/ml and 280 micrograms/ml, respectively. On the other hand, 2 and 4 were shown to have tannin activities, but 1 and 3 had no tannin activities. These results suggest that there is no relationship between the inhibition for angiotensin converting enzyme activity and the tannin activity for the four flavonoids.

Angiotensin-Converting Enzyme Inhibitors↗

Determination of (+)- and (-)-bromoisovalerylurea in sera of overdosed subjects.

Bromoisovalerylurea (bromisovalum) is a sedative-hypnotic given orally as a racemic mixture of optical isomers (i.e., (+)- and (-)-enantiomer) and frequently taken in overdose in order to commit suicide. Sera from 16 overdosed subjects were analyzed for each enantiomer by high-performance liquid chromatography on chiral stationary phases. The (+)-enantiomer concentration was lower than the (-)-enantiomer concentration in all specimens, that is, the ratio of the (+)-enantiomer to the total concentration ranged from about 50% to 0%. The ratio of the (+)-enantiomer was continuously decreasing in each subject. The data indicate that the drug in gastrointestinal tract was absorbed into blood nonstereoselectively and that the drug in blood was eliminated stereoselectively. The enantioselective determination of this drug will give useful information on absorption and elimination.

Bromisovalum↗