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Biomedical subjects

N Kuwabara

Publications and source records attributed to N Kuwabara.

At least 91 records · Page 5Linked to original sources
PubMed1982

Long-term study on the effect of caffeine in Wistar rats.

Wistar rats of both sexes were given synthetic caffeine in their drinking water for 78 weeks. Three hundred Wistar rats were divided into three groups of 50 males and 50 females each. Group 1 was given normal tap water without caffeine as a control. Group 2 was given 0.1% caffeine solution and group 3 was given 0.2% caffeine solution for 78 weeks. All the animals were killed after 104 experimental weeks. Various tumors were found in both experimental and control groups, but their incidences were not higher in the experimental groups. Thus, there was no evidence that caffeine was carcinogenic to Wistar rats when given continuously in the drinking water for 78 weeks.

Animals↗
PubMed1981

Experimental colonic cancer in a dog.

Experimental colonic carcinoma in a dog was induced by anal insertion of an N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) suppository (each cone containing 50 mg of ENNG) for 17 months. The dog was autopsied 20 months after the initiation insertion of the suppository. Grossly, the colonic wall from the anus of the 10-cm oral side of the colon was thickened, and there was an infiltrating tumor with shallow depressions in the rough mucosa. The lymph node around this portion were enlarged, and white spots were found in the liver and redness in the lungs. Histological examination of the colon revealed a variety of pathologic features, e.g., undifferentiated carcinoma, squamous cell carcinoma and malignant melanoma in the region adjacent to the anus. Well and moderately differentiated adenocarcinomas involving the proper muscle layer were found in a region oral to these tumors and were accompanied by marked invasion of the blood vessels and lymphatic permeation. There were metastases to the liver, lungs and lymph nodes which corresponded to the gross findings, and also metastases to renal glomeruli. A well differentiated adenocarcinoma and signet ring cell carcinoma were evident in the gastric mucosa. This experimental model should be useful for studies related to colonic carcinoma in humans.

Adenocarcinoma↗
PubMed1981

Experimental model of infantile obstructive cholangiopathy using 1,4-phenylenediisothiocyanate.

Inflammatory processes on the hepato-biliary system may play an important role in the pathogenesis of infantile obstructive cholangiopathy (including biliary atresia, neonatal hepatitis and bile duct dilatation). A model of the disease was produced in rats using 1,4-phenylenediisothiocyanate (P.D.T.) P.D.T. was given to five groups of rats of different developmental stages from the fetal stage. Changes in the hepato-biliary system due to P.D.T. were compared histo-pathologically in 97 rats. Three groups of rats given P.D.T. after birth showed characteristic dilatation of the extrahepatic bile ducts with inflammation. One group of rats given P.D.T. during the fetal period showed thickening and fibrosis of the wall of the extrahepatic bile ducts without dilatation. The last group of rats given P.D.T. during the fetal period and again at thirty days postnatally showed stenosis or almost atresia of the ductal lumen due to severe fibrosis and thickening of the extrahepatic bile ducts. This experimental model suggests that the difference in developmental stages of the pathogenic processes may play an important role in the production of different pathogenic features of infantile obstructive cholangiopathy.

Animals↗
PubMed1981

A study on carcinogenesis induced by degraded carrageenan arising from squamous metaplasia of the rat colorectum.

We have undertaken studies on carcinogenesis arising from precancerous lesions, such as squamous metaplasia and ulcerative lesions of the rat colorectum, after termination of degraded carrageenan administration. Rates of tumor incidence in groups that were given a 10% diet of degraded carrageenan for 2, 6 and 9 months were 5 rats out of 39 (12.8%), 8 out of 42 (19.0%) and 17 out of 42 (40.5%), respectively. The colorectal squamous metaplasia persisted in all rats and progressed irreversibly. Degraded carrageenan was deposited not only in the colorectal propria mucosa, but also in the other reticuloendothelial organs. These results show that, even with short-term degraded carrageenan administration, degraded carrageenan is carcinogenic to the colorectum of the rat after a prolonged period.

Animals↗
PubMed1981

Functional cooperation of the dnaE and dnaN gene products in Escherichia coli.

A system was designed to isolate second-site intergenic suppressors of a thermosensitive mutation of the dnaE gene of Escherichia coli. The dnaE gene codes for the alpha subunit of DNA polymerase III [McHenry, C. S. & Crow, W. (1979) J. Biol. Chem. 254, 1748-1753]. One such suppressor, named sueA77, was finely mapped and found to be located at 82 min on the E. coli chromosome, between dnaA and recF, and within the dnaN gene [Sakakibara, Y. & Mizukami, T. (1980) Mol. Gen. Genet. 178, 541-553]. The dnaN gene codes for the beta subunit of DNA polymerase III holoenzyme [Burgers, P. M. J., Kornberg, A. & Sakakibara, Y. (1981) Proc. Natl. Acad. Sci. USA 78, 5391-5395]. The sueA77 mutation was trans-dominant over its wild-type allele, and it suppressed different thermosensitive mutations of dnaE with different maximal permissive temperature. These properties were interpreted as providing genetic evidence for interaction of the dnaE and dnaN gene products in E. coli.

Bacteriophage lambda↗
PubMed1980

A histopathological study of the liver in paraquat poisoning--an analysis of fourteen autopsy cases with emphasis on bile duct injury.

Fourteen autopsy cases of paraquat poisoning were studied. Seven of the eight patients who died within 4 days after the ingestion of paraquat showed hepatocytic injury, and three of them revealed bile duct injury. Hepatocytic injury was similar to that of carbon tetrachloride intoxication. Bile duct injury consisted of epithelial changes of the bile ductules and bile ducts. Cholestasis in the bile ducts was produced by the injury. The affected bile ductules and ducts had hydropic and necrotic epithelium, associated with the infiltration of neutrophils and histiocytes in the intraductal and periductal tissues. The severity of bile duct injury increased gradually from the bile ductules to the septal bile ducts. The extrahepatic biliary tract showed the same injury as the septal bile ducts in one case. It is considered that bile duct injury was produced by a direct corrosive effect of paraquat. Five of the six patients who survived more than 8 days revealed intrahepatic cholestasis, the pathogenesis of which was not clearly understood.

Adult↗
PubMed1977

Carcinogenic activity of 2-(2-furyl)-3-(5-nitro-2-furyl)-acrylamide, a food additive, in mice and rats.

The carcinogenicity of a food additive, 2-(2-furyl)-3-(5-nitro-2-furyl)acrylamide (AF-2), was studied in Wistar rats and CDF1 mice. The rats developed mammary tumors; the first appearing 9 months after the start of the experiment. In mice fed AF-2 diet, squamous cell carcinoma of the forestomach was observed in the 11th month. Some mice had metastases in the liver, spleen, lymph nodes and peritoneal cavity.

Adenocarcinoma↗
PubMed1976

Spontaneous ovarian tumors in domestic carp (Cyprinus carpio): light and electron microscopy.

Massive abdominal enlargement was discovered in 8 adult carp (Cyprinus carpio) 4-6 years old, living in breeding ponds of carp fisheries in northern Japan. The abdominal enlargements rapidly progressed and the affected fish died within a few months. At necropsy, single or multiple tumors up to 20 cm in diameter were found in the abdominal cavities. Ovarian tissue identified within the tumor capsule in 4 fish supported the impression, based on gross anatomic features, that the neoplasm arose in the ovaries. Histologically, the tumors were composed mainly of various types of mesenchymal cells. In one sample, striated muscle was identified by electron microscopy; in another, squamous cell nests were intermixed with mesenchymal elements. Although some tumors had areas of cellular pleomorphism suggesting a malignant character, no evidence of invasion or metastasis was found. These neoplasms were classified tentatively as dysontogenetic tumors of the ovary, possibly teratoid in nature.

Animals↗