Richard S. Yamamoto

Long-Term Effect of Benzene in C57BL/6N Mice

Weaning male C57BL/6N mice received repeated subcutaneous injections of benzene in corn oil for 54 weeks. These mice and surviving controls were killed 104 weeks after the first injection. There was no evidence of carcinogenic activity in benzene-injected mice. A high incidence of amyloidosis developed in mice of all treated and untreated groups. Butyinitrosourea, used as a positive control, induced lymphomas or leukemias (in most exposed mice) and intestinal tumors in a few.

Chronic Administration of Hydroxylamine and Derivatives in Mice

Summary Long-term administration of hydroxylamine, methoxyamine, or hydroxyurea to Swiss-Webster mice did not cause tumor formation. Hydroxylamine inhibited spontaneous formation of mammary tumors in female C3H mice. The principal toxic effects of hydroxylamine were anemia, splenomegaly and bone formation in the spleen. The authors appreciate the assistance of Mr. Gerome McDowell and Miss J. Zuefle in various phases of the experiments.

Effect of Vitamin B12-Deficiency in Colon Carcinogenesis

Summary The effect of vitamin B12 deficiency on intestinal carcinogenesis with azoxymethane was studied in male F344 rats. Upon weekly injection of 0.2 mmol/kg body wt of azoxymethane, most of the rats on vitamin B12-deficient diet failed to produce small intestinal or colon tumors, whereas, all of the rats on vitamin B12-deficient diet supplemented with 100 μg/kg vitamin B12 developed adenoma or adenocarcinoma of duodenum or colon. The vitamin B12-adequate diet was more effective in producing colon tumors in F344 rats than mixed commercial diet. It appears that vitamin B12 is necessary for intestinal carcinogenesis with azoxymethane.

An inverse linear correlation between uterine and ovarian levels of ornithine decarboxylase and S-adenosylmethionine decarboxylase in the rat.

Abstract The activities of the enzymes ornithine decarboxylase and S-adenosylmethionine decarboxylase at 9:00 AM were determined in the uterus and ovary of rats as a function of the estrous cycle. The uterine levels of both enzymes were highest at proestrus and lowest at estrus. On the other hand, the ovarian levels of both enzymes were highest at estrus and lowest at proestrus. Plotting the logarithms of each of the enzyme levels in the ovary versus the corresponding logarithm of the same enzyme observed in the uterus showed a linear correlation with a negative slope both during the estrous cycle and during proestrus alone. The changes in the activities of both enzymes in the uterus could be directly correlated with the growth of this organ observed during the estrous cycle.

Effect of carbon tetrachloride injury on plasma and liver vitamin B12 levels.

Summary (1) Administration of carbon tetrachloride increased the serum level of vit. B12 of rats fed a casein diet. No similar increase was observed in rats previously offered a low vit. B12 diet. (2) Administration of carbon tetrachloride likewise increased the urinary excretion of parenterally administered vit. B12 or of absorbed vit. B12 following oral administration. (3) Physiological significances of these findings are discussed.

EFFECT OF EXPERIMENTAL ALLERGIC ENCEPHALOMYELITIS ON GUINEA PIG PLASMA LIPID FRACTIONS.

Summary Significant elevations of plasma free fatty acid (FFA) concentrations have been observed in guinea pigs with experimental allergic encephalomyelitis (EAE). FFA values correlated well with disease index. Increased values were observed prior to marked clinical signs of disease and preceded development of visible lipemia. Those animals with lipemia had the highest FFA concentrations observed. Significant increases in other plasma lipid fractions were noted in guinea pigs fasted from one to ten days but these were smaller in all fractions than increases noted in encephalomyelitic guinea pigs, except for plasma cholesterol. Normal FFA concentration and no visible lipemia were noted in guinea pigs with severe aspermatogenesis. Two possible hypotheses are proposed which might relate these increased lipid fractions to the neurological damage noted in this encephalitis rather than to delayed hypersensitivity.

Absorption and Tissue Concentrations of Vitamin B12 in Obese Rats

Summary Rats made obese by feeding high fat diet had more Vit. B12 in the liver and higher plasma Vit. B12 levels than control lean rats receiving same concentration of Vit. B12 in low fat diet. The obese rats absorbed more of orally administered radioactive Vit. B12 than the controls. The increased absorption in obese rats, however, was not directly due to high percentage of fat in the diet and would therefore be accounted for by obesity. The possible involvement of this vitamin in lipid metabolism as based on these findings has been discussed.