Yoshimasa Kurata

Acute and subchronic toxicity and genotoxicity of SE5-OH, an equol-rich product produced by Lactococcus garvieae.

The consumption of soy-based products is associated with a number of health benefits and much of these benefits are proposed to be due to the soy isoflavones daidzein, genistein, glycitein, their glycosides, and equol, an isoflavone naturally produced from daidzein. Equol is a naturally bacterially-derived metabolite of daidzein and is produced by bacteria in the gut of those humans capable of hosting the particular organism. To allow all humans to enjoy the health benefits of equol, a new functional food ingredient has been developed that relies on bacterial conversion of daidzein to equol under strictly controlled conditions. This new food substance, termed SE5-OH, has been studied extensively for its acute and subchronic toxicity in Sprague-Dawley rats, as well as for its potential genotoxicity. The oral LD(50) is >4,000 mg/kg. In a 91-day, subchronic study, the no-observed-adverse-effect-level (NOAEL) was 2,000 mg/kg/day, the highest dose tested. SE5-OH was negative in Salmonella typhimurium tester strains TA98, TA100, TA1535 and TA1537 and in Escherichia coli tester strain WP2uvrA with and without metabolic activation. SE5-OH was negative for chromosome aberrations in Chinese hamster lung cells up to 3,000 microg/ml with and without metabolic activation and did not induce increases in micronucleated polychromatic erythrocytes taken from Sprague-Dawley rats administered (via gavage) up to 4,000 mg/kg SE5-OH twice daily for two consecutive days.

Effect of Di(2-Ethylhexyl) Phthalate (DEHP) on Genital Organs from Juvenile Common Marmosets: I. Morphological and Biochemical Investigation in 65-Week Toxicity Study

Recent studies demonstrated that preadolescent male rats are more sensitive to testicular damage from exposure to DEHP than adults. Male and female marmosets were treated daily with 0, 100, 500, or 2500 mg/kg DEHP by oral gavage for 65 wk from weaning (3 mo of age) to sexual maturity (18 mo). No treatment-related changes were observed in male organ weights, and no microscopic changes were found in male gonads or secondary sex organs. Sperm head counts, zinc levels, glutathione levels, and testicular enzyme activities were comparable between groups. Electron microscopic examination revealed no treatment-related abnormalities in Leydig, Sertoli, or spermatogenic cells. Histochemical examination of the testis after 3β-hydroxysteroid dehydrogenase (3β-HSD) staining did not reveal any alterations in steroid synthesis in the Leydig cells. Thus, although marmoset monkeys were treated with 2500 mg/kg DEHP, throughout the pre- and periadolescent period, no histological changes were noted in the testes. For females, increased ovarian and uterine weights and elevated blood estradiol level were observed in higher dosage groups, 500 and 2500 mg/kg. These increased weights were associated with the presence of large corpus luteum, a common finding in older female marmosets. Although an effect on the female ovary cannot be completely ruled out, no abnormal histological changes were observed in the ovaries or uteri in comparison to controls. No increases in hepatic peroxisomal enzyme activities were noted in treated groups; isolated hepatic enzyme activities (P-450 contents, testosterone 6β-hydroxylase, and lauric acid ω-1ω-hydroxylase activities) were increased in males and/or females of either the mid- or high-dose groups, but no consistent dose-related trend was observed.

The effects of a vitamin D-deficient diet on chronic cadmium exposure in rats.

Itai-itai disease (IID) of humans is one of the most severe forms of chronic cadmium (Cd) intoxication. Itai-itai disease occurs mainly in post-menopausal women and is characterized by osteoporosis with osteomalacia, renal tubular disorder, and renal anemia. Some researchers insist the major cause of IID is not Cd, but rather malnutrition, especially hypovitaminosis D. We administrated a low concentration of Cd chloride intravenously to ovariectomized female rats that were fed a vitamin D–deficient diet or a normal diet for fifty weeks. The vitamin D–deficient diet decreased serum concentration of vitamin D, but it did not affect the metabolism of the kidney or bone. Cadmium treatment alone induced a decrease in serum concentration of vitamin D, as well as renal dysfunction, renal anemia, and abnormal bone metabolism. Osteoporosis with osteomalacia, tubular nephropathy, fibrous osteodystrophy, and bone marrow hyperplasia occurred following Cd treatment. In rats treated with Cd and administered a vitamin D–deficient diet, the toxic effects of Cd on kidney, bone, and hematopoiesis were enhanced in comparison to rats treated with Cd and a normal diet. The present experiment demonstrated that hypovitaminosis D did not evoke morphologic features of IID in humans but did enhance Cd-induced toxicity in the rat model of this disease.

Four-week repeated inhalation study of HCFC 225ca and HCFC 225cb in the common marmoset

Four male and three female marmosets in each group were exposed to air only, 1000 ppm of HCFC 225ca or 5000 ppm of HCFC 225cb, for 6 h per day for 28 consecutive days. HCFC 225ca caused a slight reduction in body weight. HCFC 225cb occasionally caused somnolence during exposure and vomiting on the first day of exposure. Clinical chemistry findings included a mild reduction of triglyceride, cholesterol and phospholipid levels and increased GOT level in the HCFC 225ca exposure group. HCFC 225cb also caused a reduction of triglyceride levels in some animals. HCFC 225ca caused a slight increase of hepatic carnitine palmitoyltransferase (CPT) activity while HCFC 225cb slightly increased cyanide-insensitive palmitoyl CoA beta-oxidation (FAOS) activity. In the HCFC 225cb exposure group, an increase in cytochrome P-450 content was also observed. HCFC 225ca caused a fatty change in the hepatic cells. Increased incidence of lipid droplets in the hepatic cells and myelin-like bodies in hepatic cells, Kupffers cells and hepatic blood vessels were observed electron microscopically in the HCFC 225ca exposure group. A proliferation of smooth endoplasmic reticulum was observed in the HCFC 225cb exposure group. Decreased peroxisome volume density in the HCFC 225ca group, and increased volume density in the HCFC 225cb exposed females were seen. However, organ weight measurement and histopathological examination did not reveal hepatomegaly or hypertrophy with either substance. Although slight changes were noticed in peroxisome volume density and in some of the peroxisomal enzyme activities, the changes related to peroxisome proliferation with HCFC 225ca and 225cb were minimal in marmosets compared to those seen in rats. Histopathological examination and hormonal analysis did not reveal any abnormalities in the pancreas or testes.

Intravenous 1α, 25[OH]2 vitamin D3 (calcitriol) pulse therapy for bone lesions in a murine model of chronic cadmium toxicosis

The aim of the present study was to clarify the therapeutic effects of 1α, 25[OH]2 vitamin D3 (calcitriol) pulse injection on bone lesions induced in a rat model of chronic cadmium toxicosis. Ovariectomized (OVX) and control‐operated (sham‐OVX) rats were given repeated intravenous injections of 0.5 mg/kg/day CdCl2 for 70 weeks. The rats were then treated intravenously with 0.02 μg/kg/day calcitriol 3 days per week for 8 weeks. CdCl2 treatment induced increases in osteoid volumes of the femur cortex and trabecula. This change was accompanied by an increase in the volume of iron deposition at the mineralization front of the trabeculae and a reduction in mineral density. Abnormalities of bone metabolic parameters, which were increases in the blood calcium, inorganic phosphorous, bone‐specific alkaline phosphatase, parathyroid hormone (PTH) and osteocalcin levels, and in the urine deoxypyridinoline (D‐PYR) level, were also induced. Calcitriol treatment increased the blood calcium and inorganic phosphorous levels, and reduced the blood PTH level. Decreases in blood tartrate‐resistant acid phosphatase and urine d‐PYR levels were also induced indicating that bone resorption was suppressed. The findings indicated that the increased osteoid volume of the cortex and Fe‐deposition volume of the trabecula were improved. These effects or improvements were observed in the sham‐OVX rats but not in the OVX rats.

Chronic Cadmium Treatment Induces Tubular Nephropathy and Osteomalacic Osteopenia in Ovariectomized Cynomolgus Monkeys

In an attempt to establish a primate model of chronic cadmium toxicosis, we ovariectomized cynomolgus monkeys and treated them with CdCl2 by repeated intravenous injections for 13 to 15 months. The animals showed normocytic-normochromic anemia. The cadmium treatment resulted in increases of urinary enzyme activity indicative of renal tubular degeneration. Histopathology of the kidney revealed renal proximal tubular atrophy accompanied by interstitial fibrosis. Decreased bone mineral density was evident in the trabecular and cortical zones of the lumbar vertebra and femur, with osteoid accumulation around the trabeculae and Haversian canals. Iron deposition at the mineralization front and osteoclasts hyperplasia were indicative of impairment of bone mineralization and an increase of resorption. Blood inorganic phosphorus and 1α,25(OH)2 vitamin D3 levels decreased and urinary deoxypyridinoline level increased in cadmium-treated animals. The renal and bone lesions closely resemble those of itai-itai disease patients, the most severe case of cadmium toxicosis in terms of clinical chemistry and histopathology. Thus, ovariectomized monkeys chronically exposed to cadmium can serve as a primate itai-itai disease model, which is beneficial for developing novel therapeutic methods, investigating the mechanisms of the renal and bone lesions, and establishing more clearly defined criteria for diagnosing the disease.