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S T Omaye

Publications and source records attributed to S T Omaye.

At least 55 records · Page 3Linked to original sources
PubMed1986

Alteration of guinea pig erythrocyte superoxide dismutase activity by dietary antioxidants.

An improved method for the measurement of superoxide dismutase (SOD) activity in guinea pig erythrocytes was developed. Alteration of guinea pig erythrocyte superoxide dismutase activity by the dietary antioxidants ascorbic acid and selenium was investigated. Erythrocyte SOD activity was directly related to the ascorbic acid intake of guinea pigs fed 0.05 ppm of selenium. Dietary levels of ascorbic acid were 0, 200 and 400 mg/kg). In guinea pigs fed 0.20 ppm of selenium, there was an increase in superoxide dismutase activity only in the group of animals fed the 400 mg ascorbic acid/kg of diet. Results suggest that substantial protection from deleterious O2-. can be provided by changes in dietary ascorbic acid.

Animals↗
PubMed1985

Comparative pharmacokinetics of vitamin A (retinol) in rats and hamsters.

The absorption and elimination of all-trans-retinol in the plasma of rats and hamsters were studied after an oral dose of 45 mg/kg body weight. The hamsters exhibited a higher pretreatment mean circulating retinol concentration than rats maintained on an identical diet. The increase in plasma retinol after a single oral dose was much greater in hamsters than rats. The area under the plasma concentration v. time curve was approximately 60% greater for rats than for hamsters. The elimination half-times for rats were much longer than for hamsters. Plasma retinol uptake and disappearance were consistent with a two-compartment open model with first-order absorption.

Administration, Oral↗
PubMed1985

Bioavailability of vitamin E in rats fed graded levels of pectin.

Dietary pectin at levels of 0, 3, 6 and 8% was fed ad libitum to rats for 8 wk to evaluate whether the bioavailability of vitamin E fed at 0.001% of the diet was affected by pectin. Rats fed 3% pectin were not different in any vitamin E parameters from those fed 0% pectin. By the end of the study body weights were significantly lower in the 6 and 8% pectin groups after adjusting for their nonsignificant trend of lower food intake. At wk 8, liver vitamin E levels were reduced in the 6 and 8% pectin group compared to values at the start of the study. Both groups had significantly higher red blood cell hemolysis compared to 0% pectin at 8 wk. Fecal fat excretion was not different among the diet groups, but weights of the small and large intestines were significantly increased in rats fed 6 or 8% pectin compared to those fed 0 or 3%. Our results show that 6 and 8 but not 3% dietary pectin decreased vitamin E availability in rats.

Animals↗
PubMed1984

Safety of megavitamin therapy.

Carbon compounds that are needed in small amounts in the diet because they are not made in the body of vertebrates are defined as vitamins. Excluded from this definition are vitamins D, K, and niacin which can be synthesized by the organism or, as in the case of vitamin K, by the host's intestinal bacteria. Lack of such vitamins can result in characteristic deficiency diseases. The therapeutic use of such compounds (megavitamin intake) is based on the spectacular effect of vitamins on deficiency diseases; however, evidence that the ingestion of large amounts of vitamins beyond the "Recommended Daily Allowances" (RDA) is beneficial is not within the basic concept of nutrition. Vitamins, like many substances, may be toxic when taken in large quantities, especially the fat-soluble vitamins, and the concept of "more is better" is a common misconception. Vitamin supplements can be suggested only in the unusual cases of patients having inadequate intake, disturbed absorption (genetic or otherwise), or increased tissue requirements. A well-balanced diet that includes a wide variety of foods from each of the four food groups is adequate for the supply of vitamins, as well as other nutrients, in healthy people. This paper will review some of the recent findings regarding vitamin toxicity and the mechanisms of toxicity.

Ascorbic Acid↗
PubMed1983

Use of antioxidants in the analysis of vitamins A and E in mammalian plasma by high performance liquid chromatography.

A simple, sensitive, quantitative method for the simultaneous assay of retinol, alpha-tocopherol and gamma-tocopherol in rat, guinea pig, monkey and human plasma was developed by using high performance liquid chromatography. It was found that antioxidant was required to stabilize the fat-soluble vitamins in the plasma of rats. The effect of several antioxidants on the recovery of fat-soluble vitamins was evaluated. Results showed that 0.125% butylated hydroxytoluene (BHT) in ethanol and 0.025% BHT in heptane yielded recoveries greater than 95% in 0.1 ml plasma.

Adult↗
PubMed1981

Influence of dietary thiamine on pulmonary, renal, and hepatic drug metabolism in the mouse.

The effect of dietary thiamine status on the in vitro metabolism of drugs in mouse lung, kidney, and liver was investigated. Administration of a diet deficient in thiamine resulted in a tendency toward an elevated hepatic and pulmonary microsomal content of cytochrome P-450 and elevated activities of aminopyrine demethylase and aniline hydroxylase compared to those in similar mice fed 5 or 20 mg of thiamine per kilogram of diet. There was also a tendency for renal drug metabolism to be inversely related to dietary thiamine status. The effect of dietary thiamine on the induction of drug metabolism by phenobarbital in hepatic and extrahepatic tissues was also studied. In general, there was little to no difference in the percent induction as a function of thiamine status. These studies suggest that dietary thiamine is an important determinate in drug metabolism, and the metabolism varies with different tissues.

Animals↗
PubMed1981

Effect of ascorbic acid on copper and cholesterol in adult cynomolgus monkeys fed a diet marginal in copper.

The effects of prolonged consumption of high levels of dietary ascorbic acid on copper metabolism and cholesterol in adult monkeys fed a diet low or marginal in copper were investigated. Small reductions in serum copper and in serum ceruloplasmin levels were observed when high levels of ascorbic acid were fed. During the period of copper depletion there was a gradual but significant (p less than 0.001) increase in serum cholesterol. The level of ascorbic acid supplementation had no effect during this phase. When copper was added back to the diet, serum cholesterol levels leveled off or declined in the monkeys receiving the low (1 mg/day/kg body weight) dose of ascorbic acid. Cholesterol levels continued to increase in the group receiving the higher ascorbic acid supplement (25 mg/day/kg body weight). These data suggest that high levels of ascorbic acid supplementation may make dietary copper relatively unavailable for regulating cholesterol metabolism.

Animals↗
PubMed1981

Oxidation of 1-14C-ascorbic acid in the guinea pig: effect of the route of administration.

Twenty-four hours after the administration of (1-14C)-ascorbic acid to guinea pigs by oral, intraperitoneal or intracardiac routes, 14CO2 expired levels were 22.6 plus or minus 1.8, 17.6 plus or minus 1.4 and 14.4 plus or minus 0.6 percent, respectively, of the administered radioactive doses. Whole blood concentrations of ascorbic acid were 80.2 plus or minus 2 micrograms per ml and, in general they were inversely related to expired 14CO2 production, which in turn reflects the degree of ascorbic acid catabolism in ascorbic acid adequate animals. Regardless of the route of (1-14C)-ascorbic acid administration, there was a biphasic pattern of 14CO2 evolution; the first peak occurs at two hours and the second peak at five hours after administration of the doses. Thin layer chromatography analysis of (1-14C)-ascorbic acid verified the reagent's purity. In vitro isolated stomach content and intestinal content experiments illustrated that at least 1-2% of the expired 14CO2 might also result from enterohepatic circulation of the label.

Administration, Oral↗
PubMed1981

Depletion and repletion of ascorbic acid in the Rhesus monkey: relationship between ascorbic acid concentration in blood components with total body pool and liver concentration of ascorbic acid.

Eight female monkeys (Macaca mulatta) were fed an ascorbic acid-free diet for 7 weeks, followed by repletion with a supplementation of 10 mg ascorbic acid per kg of body weight for 3 weeks. Once each week the ascorbic acid contents of blood components and liver samples, obtained by closed needle biopsy, were determined as the 2,4-dinitrophenylhydrazine derivative. In selected animals the size of the total body pool ascorbic acid was determined by isotope dilution after administration (i.v.) of 14C-ascorbic acid. At no time were the monkeys frankly scorbutic. Values for r2 were less than 0.10 between plasma, whole blood, and erythrocyte ascorbic acid contents compared with the total body pool of ascorbic acid. Leukocyte ascorbic acid content was positively related to the total body pool of ascorbic acid (P less than 0.001, r2 = 0.923). Values for r2 were less than 0.15 when whole blood and (erythrocyte) ascorbic acid content were each compared with liver ascorbic acid levels; however, there was a tendency for plasma ascorbic acid levels to be directly related to liver ascorbic acid levels (P less than 0.05, r2 = 0.477), when plasma ascorbic acid was greater than 0.1 micrograms/ml. The relationship between liver ascorbic acid and leukocyte ascorbic acid levels was statistically significant (P less than 0.01, r2 = 0.683). The high correlation of leukocyte ascorbic acid levels with liver ascorbic levels and with the total body pool of ascorbic acid suggests that leukocyte ascorbic acid values best represent the vitamin C status of the female Rhesus monkeys.

Animals↗
PubMed1980

Effect of vitamin C on copper and iron metabolism in the guinea pig.

Although interaction of vitamin C, copper and iron have been studied in several species, little is known about these interactions in species which require the vitamin in the diet. Young male Hartley guinea pigs were fed a basal diet, or a basal diet and supplemented daily with vitamin C, p.o. Pharmacologic doses (25 mg per 100 g BW per day) of vitamin C resulted in two-to-three-fold decreases in liver copper, when compared with those receiving normal (0.5 mg per 100 g BW per day) intakes. Under conditions of vitamin C deficiency, serum copper and ceruloplasmin were elevated along with liver copper. Serum and hepatic iron levels, hepatic microsomal cytochrome P-450 and cytochrome b5, and blood heme parameters all appeared to be directly related to vitamin C intake, i.e. the iron and heme parameters increased as the vitamin dose increased. These data are consistent with the hypothesis that interaction between vitamin C, copper and iron influence normal heme formation through the oxidation/reduction of iron and/or by regulating iron absorption and availability at the gut level.

Animals↗