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J Sakurai

Publications and source records attributed to J Sakurai.

At least 127 records · Page 7Linked to original sources
PubMed1985

Role of one tryptophan residue in the lethal activity of Clostridium perfringens epsilon toxin.

The lethal activity of Clostridium perfringens epsilon toxin was inactivated by N-bromosuccinimide and N-chlorosuccinimide. Amino acid analysis of N-bromosuccinimide-treated prototoxin indicated that the one tryptophan residue present in the protein was abolished, and methionine and tyrosine reduced markedly. N-chloro-succinimide-treated prototoxin lost completely both tryptophan and methionine residues. The toxin was not inactivated by chloramine T, but all of methionine residues present in the protein was found to be oxidized by the agent. The data suggest that the one tryptophan residue present in the toxin is important for the lethal activity.

Amino Acids↗
PubMed1985

In vivo studies on DNA repair and turnover with age.

Since the capacity for DNA repair relative to other cellular processes should be an important parameter of mutagenesis, carcinogenesis, and also aging, this capacity should preferably be studied in intact animals. Thus, we developed autoradiographic techniques for measuring DNA repair directly in vivo. By these methods unscheduled DNA synthesis (UDS) was detected quantitatively as silver grains on epithelial cells of mouse skin after treatment with chemical carcinogens or UV irradiation, and on cerebral ganglion cells of aquarium fish after treatment with various chemical carcinogens. Several interesting findings so far obtained are presented. Possible age-related change in the UDS response was examined by the skin technique with mice of 2 and 18 months old. Similar dose-dependent induction of UDS was observed in mice of both ages after treatment with 4-hydroxyaminoquinoline 1-oxide; their levels of UDS at each dose were not significantly different. The dose-response curves for young and aged animals after UV irradiation showed similar increases to a plateau at low doses, but their responses to high doses were very different: in aged mice the UDS level decreased markedly with increase in the dose, whereas in young mice it remained at the same level. This suggests that in aged animals, high doses of UV irradiation cause deterioration of DNA repair systems, and that aged animals cannot repair extensive DNA damage efficiently. It is generally thought that DNA has a stable structure and a much slower turnover than other cellular components. Although the effect of DNA repair on DNA turnover may be insignificant, accumulation of repaired DNA in cells should result in detectable DNA turnover. Therefore, we investigated DNA turnover in postmitotic ganglion cells of rat retina. However, careful autoradiographic studies on pairs of eyes showed no detectable DNA turnover up to nearly their median life span (2 years). This result suggests that the DNA of post-mitotic cells, which are not replaced throughout the life span of the animal, is very stable and is possibly protected in some special way.

Aging↗
PubMed1985

Effect of Clostridium perfringens alpha toxin on the isolated rat vas deferens.

Alpha toxin produced by Clostridium perfringens potentiated norepinephrine-evoked contraction in the isolated rat vas deferens, but itself caused no contraction within 60 min. The potentiating activity was dependent on the dose of the toxin and was quantitatively related to the phospholipase C activity of the toxin preparation.

Animals↗
PubMed1985

Tryptophan content of Clostridium perfringens epsilon toxin.

The tryptophan content of Clostridium perfringens epsilon toxin was investigated. When the tryptophan content was determined by amino acid analysis after the hydrolysis of epsilon prototoxin with methanesulfonic acid containing 3-(2-aminoethyl)indole and by the spectrophotometric method with N-bromosuccinimide, the number of tryptophan residues was calculated at 1/mol of the protein. Cleavage of the prototoxin or the toxin with N-bromosuccinimide in the presence of urea gave two new fragments on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. There was only a tyrosine residue as the new N-terminal amino acid after the cleavage of the prototoxin or the toxin with N-bromosuccinimide. The data showed that epsilon prototoxin or epsilon toxin contained only one tryptophan residue.

Amino Acids↗
PubMed1985

[Uranium, thorium and potassium contents and radioactive equilibrium states of the uranium and thorium series nuclides in phosphate rocks and phosphate fertilizers].

Uranium, thorium and potassium contents and radioactive equilibrium states of the uranium and thorium series nuclides have been studied for 2 phosphate rocks and 7 phosphate fertilizers. Uranium contents were found to be rather high (39-117 ppm) except for phosphate rock from Kola. The uranium series nuclides were found to be in various equilibration states, which can be grouped into following three categories. Almost in the equilibrium state, 238U approximately 230Th greater than 210Pb greater than 226Ra and 238U greater than 230Th greater than 210Pb greater than 226Ra. Thorium contents were found to be, in general, low and appreciable disequilibrium of the thorium series nuclides was not observed except one sample. Potassium contents were also very low (less than 0.3% K2O) except for complex fertilizers. Based on the present data, discussions were made for the radiation exposure due to phosphate fertilizers.

Alpha Particles↗
PubMed1985

Effect of Clostridium perfringens alpha toxin on the cardiovascular system of rats.

Clostridium perfringens alpha toxin decreased heart rate, then elevated blood pressure, and finally caused some changes of electrocardiogram readings. The toxin decreased peripheral blood flow before blood pressure started to increase and the blood flow continued to decrease, without any affect on electrocardiogram readings, until the maximal pressure rise caused by the toxin. The toxin caused a rise in blood pressure in a dose-dependent manner. On the other hand, anti-alpha toxin antiserum inhibited both phospholipase C activity and pressor activity. When the toxin was pretreated with cysteine, calcium disodium ethylenediamine tetraacetate and calcium trisodium ethylenetriamine pentaacetate, pressor activity decreased, as well as phospholipase C activity. The results indicate that alpha toxin possesses pressor activity as well as phospholipase C activity.

Animals↗
PubMed1984

Effect of Clostridium perfringens beta toxin on blood pressure of rats.

Guanethidine treatment or adrenal medullectomy significantly inhibited the elevation in blood pressure induced by Clostridium perfringens beta toxin, and the combination of the two drastically reduced the pressure rise, to less than 19% of that in control rats. When rats were pretreated with tetrodotoxin or hexamethonium, the toxin-evoked rise was significantly inhibited. Elevation in blood pressure induced by the toxin in spinal rats tended to be less than that in control rats. When investigated by a microscopical technique, arteriolar constriction in the mesenteric vasculature was observed after the blood pressure elevation induced by the toxin reached a maximum. Blood flow in the skin decreased with an increase in blood pressure following intravenous injection of the toxin. It is concluded that beta toxin acts on the autonomic nervous system and produces arterial constriction.

Adrenal Medulla↗
PubMed1983

Effect of Clostridium perfringens epsilon toxin on the cardiovascular system of rats.

Pressor activity was demonstrated by the intravenous injection of purified epsilon toxin of Clostridium perfringens type D but not by that of epsilon prototoxin. The activity was completely abolished by C. perfringens type B or D antiserum, but not by type A, C, or E antiserum. The rise in blood pressure caused by the toxin was accompanied by a decrease in the blood flow in skin without any change of heart rate and electrocardiogram readings. These results indicate that epsilon toxin possesses pressor activity as well as lethal and dermonecrotic activities.

Animals↗