Biomedical subjects

C J Nader

Publications and source records attributed to C J Nader.

6 recordsLinked to original sources

PubMed1982

Adaptive effects of dietary ethanol in the pig: changes in plasma high-density lipoproteins and fecal steroid excretion and mutagenicity.

Six young mature male pigs were maintained on a high fat, low fiber "Western" type diet. Substitution of ethanol for sucrose raised plasma total cholesterol, an increase that was solely due to a rise in high-density lipoproteins. Plasma triacylglycerols and apo-B concentrations were unchanged and although apo-A1 rose with ethanol, this was not statistically significant. Ethanol did not alter total fecal steroids but both bile acids and the ratio of bile acids/neutral sterols were increased. In fecal extracts from these animals, mutagenic activity in the Ames bacterial test was also raised. The data are discussed in relation to the relationships between dietary ethanol and coronary heart disease and colorectal cancer.

Animals↗

PubMed1981

Mutagen production during pan-broiling compared with microwave irradiation of beef.

Segments of beef were cooked either by broiling on a hot plate or by irradiation at 2450 MHz in a microwave oven. Extracts of surface layers of the cooked meat were tested for mutagenic activity using Salmonella typhimurium TA98 and TA100 with and without S-9 liver microsomal preparation. The broiled beef extracts with S-9 activation exhibited marked frame-shift mutagenicity, which increased with cooking time. No such activity was detected with beef cooked by microwave irradiation, with exposures ranging from normal to 3 times the normal cooking period.

Animals↗

PubMed1980

Induction of DNA repair by some selenium compounds.

Selenium compounds were found to induce DNA repair synthesis as a measure of DNA damage in both the isolated rat liver cell system and by Ames' Salmonella assay. In liver cells, DNA repair measured by uptake of [3H]thymidine was found to be greater with sodium selenite and selenate than with selenomethionine. In the bacterial culture system, selenomethionine inhibited the repair-deficient variant more than the selenite and selenate. These in vitro test systems have been used to indicate that selenium has a DNA-damaging potential.

Animals↗

PubMed1976

The effect of molybdenum on the conversion of sulphate to sulphide and microbial-protein-sulphur in the rumen of sheep.

1. [35S]sulphate was used to measure the apparent turnover of sulphate, sulphide and microbial-protein-S in the rumen contents of four sheep that were intraruminally infused with 10 g sodium sulphate/d alone, or together with 126 mg sodium molybdate (50 mg molybdenum). 2. Infusion of molybdate increased the concentration of sulphate in rumen fluid from 2.2 to 7.2 mug S/ml and decreased the rate of reduction of sulphate to sulphide by 50%. Although the rate of sulphide production was slower, the concentration of sulphide in the rumen is suggested to explain these changes. 3. In animals that were not infused with molybdate, only one-third of the S (3.0 g/d) that passed through the sulphate pool in rumen fluid was converted to sulphide, decreasing to one-sixth when molybdate was infused. 4. The turnover of S amino acids in microbial protein was not significantly affected by molybdate. Only 52-57% of the S amino acid content of microbial protein was synthesized de novo by way of the sulphide pool.

Amino Acids, Sulfur↗

PubMed1970

Metabolic fate of cysteine and methionine in rumen digesta.

Estimates were obtained of the extent to which cysteine and methionine were incorporated into the protein of the microbes of rumen digesta without prior degradation and resynthesis. By using the amino acids labeled with both (35)S and (14)C, it was observed that a large proportion of the (35)S appeared in the sulfide pool and of the (14)C appeared in volatile fatty acids. By isolating the appropriate amino acid, obtaining the (14)C to (35)S ratio, and comparing this with the ratio in the added amino acid, the degree of direct incorporation was calculated. For cysteine it was estimated that at most 1% and for methionine, at most 11% of the amino acid in the free pool was incorporated unchanged into microbial protein. As a consequence of these findings, it is considered that the method for measuring microbial protein synthesis in rumen digesta based upon incorporation of (35)S from the free sulfide pool is not seriously affected by direct utilization of sulfur amino acids arising from dietary sources.

Animals↗

PubMed1968

Method for measuring microbial growth in rumen content.

Radioactive sodium sulfide was used to label the sulfide pool of rumen contents in vitro. Microbial protein synthesis was calculated from the size and rate of dilution of label in the sulfide pool, and from the radioactivity incorporated into protein together with a conversion factor specifying the nitrogen-sulfur ratio determined for microbial protein. The microbial cell yield, calculated on the basis of the adenosine triphosphate (ATP) available from fermentation, was 13 to 14 g (dry weight) per mole of ATP, which is in good agreement with the values obtained for pure cultures of bacteria. Calculation of microbial protein yield per kilogram of ration agreed fairly well with previous estimates for similar rations.

Animals↗