Yoshiyuki Masaoka

Strain differences in the induction of intestinal metaplasia by X-irradiation in rats

Strain differences in the susceptibility of rats to induction of intestinal metaplasia by X-irradiation were examined. The gastric regions of 5-week-old males of five inbred strains of rats (F344/NSlc, Copenhagen, Buffalo/NacJcl, and ACI/NHos) and three strains of randomly bred rats (HOS:Donryu, Slc:Wistar, Slc:SD) were irradiated with a total dose of 20 Gy X-ray given in two equal fractions at 3-day interrals. When examined after the rats were killed, 6 months after the last irradiation, the number of intestinal metaplastic crypts positive for alkaline phosphatase (ALP) was highest in the Donryu and lowest in the Copenhagen rats. Morphologically, the number of crypts with intestinal metaplasia in the glandular stomachs of Donryu, Wistar, SD, and Buffalo rats was higher than the number in ACI, F344, and Copenhagen rats. Intestinal metaplasia was more frequently observed in the pyloric than in the fundic glands. These results demonstrate that the induction of intestinal metaplasia by X-irradiation in rats is greatly influenced by the rat strain.

Inflammatory fibroid polyp of the ileum with the appearance of a borrmann type II lesion, caused by colostomy irrigation: Report of a case

Inflammatory fibroid polyps (IFPs) are rarely found in the gastrointestinal tract. The majority of IFPs are sessile-pedunculated or pedunculated polypoid lesions, whereas a polyp presenting like a Borrmann type II lesion is extremely unusual. This report describes the case of a 74-year-old man with a history of intussusception, in whom a preoperative diagnosis of a cecal tumor of the ileocecal valve was made. A laparotomy subsequently revealed a lesion similar to a Borrmann type II tumor located 15 cm above the ileocecal valve, but not at the valve. The lesion was diagnosed as an IFP which had been caused by repeated colostomy irrigation. The aim of the present report is to draw attention to this entity, which should be included in the differential diagnosis of intussusception and small bowel obstruction.

Inhibitory Effects of Crude Salts on the Induction and Development of Colonic Aberrant Crypt Foci in F-344 Rats Given Azoxymethane

The present study was designed to investigate the modifying effects of dietary exposure to NaCl and four kinds of crude salts on the induction and development of aberrant crypt foci in Fischer 344 rats. A total of 57 male rats were divided into five groups at six weeks of age, and all were given weekly injections of azoxymethane (15 mg/kg body wt sc) for three weeks. Group 1 was fed a normal diet throughout the experiment as control group. Groups 2, 3, 4, and 5 were fed diets containing 4.4% pure NaCl, 4.4% cooking salt, 4.4% rock salt, and 4.4% beach salt, respectively, from one week before the first azoxymethane dosing. The mean numbers of aberrant crypt foci and aberrant crypts per colon were significantly lower in Groups 3-5 than in Group 1 (p < 0.01). The present results suggest that the other mineral components (e.g., calcium and magnesium) of these crude salts, rather than pure NaCl, may be chemopreventive agents for colonic tumorigenesis.

Effects of Miso in Reducing Risk of Liver and Gastric Tumors in Experimental Animals

When intact male C3H or 252Cf neutron irradiated B6C3F1 mice were fed on a diet containing 10% miso for 13 months, the frequency and multiplicity of liver tumors were significantly reduced in both cases. In irradiated females only a tendency for a similar reduction was observed. B6C3F1 male mice i.p. injected once with diethylnitrosamine (DEN) at 15 days of age and exposed to neutrons at four weeks of age also demonstrated a significantly decreased multiplicity of liver tumors when given a diet supplemented with either 10% miso or 20ppm biochanin A (5,7-dihydroxy-4-methoxyisoflavone). In Sprague-Dawley (CD) rats treated with 100ppm N-methyl-N’ nitro-N-nitrosoguanidine (MNNG) for 16 weeks in their drinking water, the net incidence of gastric tumors per mg MNNG intake was reduced with a miso-supplemented diet. In addition, when six-week-old rats were given s.c. injections of azoxymethane (AOM, 15mg/kg body weight) once a week for three weeks, and fed on diets containing 5%, 10%, or 20% miso and 10ppm biochanin A from five weeks of age, the numbers of aberrant crypt foci four weeks after the first administration of AOM were decreased with increasing miso in a dose-dependent manner. The present results indicate that administration of a miso-supplemented diet may inhibit the development of liver and gastric tumors, as well as aberrant crypt foci, in experimental animals.