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Biomedical subjects

R Kato

Publications and source records attributed to R Kato.

At least 685 records · Page 38Linked to original sources
PubMed1979

The apparent loss of cytochrome P-450 associated with metabolic activation of carbon tetrachloride.

Carbon monoxide inhibited the carbon tetrachloride-induced NADPH oxidation rate. The addition of methylviologen to the incubation mixture under the atmosphere of nitrogen resulted in the enhancement of the reductase activity of microsomes for carbon tetrachloride, as determined by chloroform formation. The addition of methylviologen also enhanced the carbon tetrachloride-induced loss of cytochrome P-450, while the apparent content of cytochrome b5 and the activity of NADPH-cytochrome c reductase remained unchanged. Under a strong inhibition of lipid peroxidation by addition of EDTA, carbon tetrachloride induced a clear loss of cytochrome P-450 to the extent similar to that seen in the absence of EDTA. These results indicate that cytochrome P-450 is directly degraded in association with the reductive metabolism of carbon tetrachloride by cytochrome P-450.

Animals↗
PubMed1979

Preparation of concanavalin A-ricin A-chain conjugate and its biologic activity against various cultured cells.

For the development of therapeutic agents that possess tissue-specific carriers, a method was devised to synthesize an artificial protein hybrid conjugate containing a moiety which binds to a cell membrane receptor and an active fragment of a toxic protein. By the introduction of an activated sulfhydryl group into concanavalin A (Con A), a conjugate of Con A and the ricin A-chain cross-linked with a disulfide linkage was synthesized. The purified conjugate was studied with regard to its inhibitory activity against protein synthesis in cell-free and cultured cell systems. The Con A-rich A-chain conjugate retained about one-third the inhibitory activity of ricin in a cell-free protein synthesis system. It also was highly toxic to cultured normal cells. These results indicate that the conjugate is a structural and functional analog of ricin and that the original membrane-binding chain (B-chain of ricin) could be replaced by Con A. Transformed cells were insensitive to this conjugate and required a longer preincubation time. The sensitivity of the normal cells was reduced in the presence of local anesthetics.

Animals↗
PubMed1977

Dopamine receptor blocking activity of sulpiride in the central nervous system.

Effects of sulpiride on the central nervous system were studied in catalepsy induction (I) and antagonism to gnawing behaviour (II) induced by apomorphine and methamphetamine in normal rats, and in antagonism to rotational behaviour (III) induced by apomorphine and methamphetamine in rats with substantia nigra unilaterally lesioned chronically by microinjection of 6-hydroxydopamine. Sulpiride was administered orally and intraventricularly, and the effects of sulpiride were compared to those of haloperidol and chlorpromazine administered through the same routes. In oral administration, sulpiride was almost inactive in (I), and was several hundreds to a thousand times less potent than haloperidol in (II) and (III), while chlorpromazine was 20 to 150 times stronger than sulpiride. In intraventricular administration, sulpiride was almost equipotent to haloperidol in (I), and was equally effective to or 2 to 3 times more effective than halopridol in (III), although several times less in all respects. These findings suggest that sulpiride is essentially a potent inhibitory substance on dopamine receptors in the central nervous system and the rather weak central effects of peripherally given sulpiride are due to poor penetration through the blood brain barrier.

Administration, Oral↗
PubMed1977

Species differences in metabolism of tiaramide hydrochloride, a new anti-inflammatory agent.

1. Urinary excretion of the radioactivity in 24 h after oral administration of [14C]tiaramide hydrochloride was 67% of the dose in mice, 59% in rats, 41% in dogs and 74% in monkeys. 2. The serum half-lives of tiaramide after intravenous administration were approximately 0-2 h in mice, 0-8 h in rats and 0-5 h in dogs. 3. Marked species variations were noted in the composition of metabolites in the serum and urinary radioactivity. The major metabolites found were 1-[(5-chloro-2-oxo-3(2H)-benzothiazolyl)acetyl]-piperazine (DETR) and 4-[(5-chloro-2-oxo-3(2H)-benzothiazolyl)acetyl]-1-piperazineacetic acid (TRAA) in mice, TRAA and 4-[(5-chloro-2-oxo-3(2H)-benzothiazolyl)acetyl]-1-piperazineethanol 1-oxide (TRNO) in rats, TRNO and tiaramide-O-glucuronide (TR-O-Glu) in dogs, and TRAA and TR-O-Glu in monkeys. 4. The binding of tiaramide to plasma protein of the various species of animals and human was about 24-34% and the extent of the binding of tiaramide to human plasma protein was independent of drug concentration within the range of 1-100 micron.

Animals↗
PubMed1977

Reduction of tertiary amine N-oxides by rat liver mitochondria.

Reduction of tertiary amine N-oxides by the mitochondrial fraction of rat liver was investigated. NADPH was required as a cofactor. The rate of reaction was faster with the NADPH-generating system than with NADPH. Isocitrate in the NADPH-generating system revealed the maximum stimulation. A little less activity was observed when NADH was used as a cofactor instead of NADPH. The reductase activity was markedly inhibited under aerobic conditions. The rates of mitochondrial tertiary amine N-oxide reduction expressed in nanomoles per milligram of protein per minute were: N,N-dimethylaniline N-oxide, 4.3; tiaramide N-oxide, 0.47; and imipramine N-oxide, 0.14. The activity for N,N-dimethylaniline N-oxide was comparable to the microsomal activity, but the activity for imipramine N-oxide was much less than that in microsomes. Isocitrate and alpha-ketoglutarate were found to stimulate mitochondrial tertiary amine N-oxide reduction more efficiently than other Krebs cycle intermediates. Oxalacetate, on the other hand, was the least effective intermediate. ATP together with NADPH and NADP stimulated the reaction efficiently, probably due to the energy-dependent intramitochondrial transhydrogenation. Antimycin, rotenone and cyanide had little or no effect on isocitrate-dependent N-oxide reduction, whereas an inhibitory effect was observed on succinate-supported N-oxide reductase. N-oxide reductase activity in mitochondria was partially suppressed under an atmosphere of carbon monoxide, althouth no increase of the activity was observed by phenobarbital pretreatment, nor inhibition by 2,4-dichloro-6-phenylphenoxyethylamine. Experiments with digitonin-treated mitochondria demonstrated that mitochondrial N-oxide reductase was bound to mitochondrial inner membrane or its matrix.

Adenosine Triphosphate↗
PubMed1977

Protection against varicella in family contacts by immediate inoculation with live varicella vaccine.

A live varicella vaccine (Oka strain) was given to susceptible household contacts of varicella to test the protective efficacy of the vaccination. Twenty-six contacts of 21 families were vaccinated, usually within three days after onset of the index cases. None of the vaccinated children developed clinical symptoms of varicella. Eighteen of 24 sera obtained before vaccination were found to be seronegative by complement fixation and neutralization tests. Seroconversion was observed in all of the 18. On the other hand, all of 19 unvaccinated contacts in the 15 families, who served as controls, showed typical manifestations of varicella from 10 to 33 days after onset of the index varicella cases. In three families, where only one sibling contact received vaccine and the other was an unvaccinated control, none of the vaccinated children showed any clinical symptoms while unvaccinated controls exhibited typical varicella symptoms 10 to 14 days after the onset of the index cases. These results indicate that varicella is prevented in household contacts by vaccination within three days following exposure.

Antibody Formation↗
PubMed1977

[Clinical experience with sustained release cephalexin (X-6437) (author's transl)].

Oral sustained release cephalexin (S-6437) was administered to 24 pediatric patients. Daily dose used was 18 approximately 60 mg/kg, which was divided into two doses and given after breakfast and dinner. The following are the results of the study. Out of 24 patients, 6 showed very good response, 10 good response, 6 fair, 1 poor and 1 unknown, Ratio of effectiveness was 69.6%. Two patients were reluctant to receive the drug and, therefore, they took other drugs. The other 22 patients, however, were easily given. No remarkable side effects due to S-6437 were found. From the above results, it was recognized that S-6437 has good effectiveness and safety, and it is convenient to give to children because the frequency of the drug administration is only twice a day.

Administration, Oral↗