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Biomedical subjects

K Kawada

Publications and source records attributed to K Kawada.

At least 91 records · Page 5Linked to original sources
PubMed1985

Fluorine-containing amino acids and their derivatives. 4. Synthesis and antibacterial activity of threo and erythro 1-fluorodehydroxylated chloramphenicol analogues.

Both threo and erythro 1-fluorodehydroxylated chloramphenicol analogues were synthesized and tested for antimicrobial activity. None showed antibacterial or antifungal activity, clearly demonstrating that substitution of the secondary hydroxyl group with fluorine abolishes the antibacterial activity of the parent compound, chloramphenicol. This finding sharply contrasts with that of previous workers, in which fluorination of the 3-hydroxyl group enhanced antibacterial activity against many chloramphenicol-resistant strains.

Chloramphenicol↗
PubMed1985

DNA strand scission by enzymatically reduced mitomycin C: evidence for participation of the hydroxyl radical in the DNA damage.

Phage DNA, as well as plasmid and mammalian DNA's, were exposed to a superoxide and hydroxyl radical-generating system containing NADPH-cytochrome P-450 reductase and mitomycin C, both with and without added Fe3+-ADP, in phosphate buffer at pH 7.5. The generation of superoxide (O2-.) and hydroxyl (.OH) radicals in the system was demonstrated by using ESR spectrometry with N-tert -butyl-alpha-phenylnitrone (PBN) as a spin trapping agent. Only the lambda DNA isolated after exposure to the O2-./.OH-generating system containing many lower molecular weight DNA fragments indicating DNA strand breaks. This breakage was completely inhibited by a .OH radical scavenger (sodium benzoate) and by catalase, but only slightly by superoxide dismutase. Thyroid and plasmid DNA's were both cleaved when exposed to the O2-./.OH-generating systems. It is suggested that the mechanism of DNA scission by mitomycin C described here closely resembles that induced by the anthracycline drugs.

Animals↗
PubMed1984

Carcinogenic activities of hydroxymethyl derivatives of 4-(dimethylamino)azobenzene in the liver of rats, mice, and hamsters.

The carcinogenic activity of 3'-hydroxymethyl-N,N-dimethyl-4-aminoazobenzene (3'-CH2OH-DAB) was studied in Sprague-Dawley rats of both sexes, male ddy mice, and male Syrian golden hamsters. The activity of 2'-CH2OH-DAB and 4'-CH2OH-DAB was studied in male Sprague-Dawley rats. Azo dyes were given in the diet at a concentration of 0.064% for 3 months followed by a stock diet for 1 month; animals were sacrificed 4 months after beginning of the experiment. Liver hyperplastic nodules developed in all 8 male rats (100%) and in all 10 female rats (100%) which received 3'-CH2OH-DAB and in 7 out of 12 male rats (58%) which received 2'-CH2OH-DAB. Hepatocellular carcinomas were produced in 1 out of 8 male rats (13%) and in 1 out of 10 female rats (10%) receiving 3'-CH2OH-DAB. No hepatic lesions were observed in rats receiving 4'-CH2OH-DAB and in mice and hamsters receiving 3'-CH2OH-DAB. These results indicate that a carcinogenic effect of 3'-CH2OH-DAB and 2'-CH2OH-DAB could be detected in rats.

Animals↗
PubMed1983

Normalized natural killer (NK) cell activity in long-term remission of acute leukaemia.

NK cell activity was studied in 28 cases of acute leukaemia in remission. It was found that patients in long-term remission for 5 years or more had normal NK cell activity but those in remission for less than 5 years had significantly lowered activity. This suggests that patients with acute leukaemia had not been constitutionally deficient in NK cell activity. Low activity was augmented but not fully restored by interferon pretreatment in vitro. Therefore, the low NK cell activity observed during remission is not solely attributable to inadequate secretion of interferon in the host. It is suggested that the production of NK cells in bone marrow is impaired, or the function of NK cells is suppressed, by the leukaemia itself or by chemotherapeutic agents. Increased consumption of NK cells is also a possibility.

Acute Disease↗
PubMed1982

Clinical results of cardiopulmonary bypass with selective cerebral perfusion for aneurysm of the ascending aorta and the aortic arch.

The purpose of this report is to describe our experience using cardiopulmonary bypass with selective cerebral perfusion in 10 patients whose aneurysms required cross-clamping the aorta and brachiocephalic vessels. Cerebral perfusion was carried out with individual roller pumps. Flow rate was 11.2 +/- 4.8 ml per kilogram of body weight per minute to the right axillary artery, 8.5 +/- 1.0 to the right common carotid artery, 7.0 +/- 2.0 to the left common carotid artery, and 3.9 to the left subclavian artery. All the patients came off bypass smoothly, and only 3 required small amounts of inotropic agents postoperatively. One patient with mycotic aneurysm died in the fourth postoperative week of massive bleeding due to disruption of the suture line. No cerebral complications were experienced. The operative results of this series suggest the usefulness of cardiopulmonary bypass with selective cerebral perfusion, and reasonably favorable outlook for patients with aneurysm involving the aortic arch and the ascending aorta.

Adult↗
PubMed1982

[Experimental studies on iron deficiency anemia in pregnant rat and its feto-maternal influence (author's transl)].

The purpose for this experiment is to know the influence on fetus of the iron deficient pregnant rat, fed with iron deficient diet. On day 21st of gestation in normal pregnant rat, RBC, Ht and non-hemin iron of maternal liver are significantly lower than those of non-pregnant, but in iron deficient pregnant, those indexes as well as Hb are slightly but further decreased. We studied ferrokinetics with 59Fe specific binding transferrin by 59Fe-NTAmethod. Plasma iron disappearance rate T (1/2) was 97 minutes in non-pregnant, 25 minutes in normal pregnant and 22 minutes in iron deficient pregnant rat. It is significantly faster in pregnant than non-pregnant rat, but there was little difference between normal and iron-deficient pregnant rat. The mean body weight of fetuses was 4.5g in iron deficient pregnancies against significantly higher 5.2g in normal pregnancies. Hb and non-hemin iron of fetal liver were significantly decreased in iron deficient group. These result suggest that maternal iron utilization must be maintained at minimum level, so that supply of iron to fetus can be kept at maximum level. When pregnant rat is fed with iron deficient diet, there are some adverse influences on fetus, especially of intrauterine fetal growth retardation.

Anemia, Hypochromic↗