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Biomedical subjects

J F Gregory

Publications and source records attributed to J F Gregory.

At least 91 records · Page 5Linked to original sources
PubMed1982

Effects of dietary fiber on the bioavailability of folic acid monoglutamate.

Low bioavailability of folacin has been previously reported for a variety of foods of plant origin. This study was conducted to examine the possible role of various types of dietary fiber on the bioavailability of folic acid monoglutamate. Cellulose, pectin, lignin, sodium alginate and wheat bran were selected for their differing physical and chemical properties. In vitro binding studies by equilibrium dialysis showed no evidence of physical or chemical binding of folic acid under physiological conditions. In vivo effects were evaluated by a chick bioassay with graded levels of folic acid in semipurified diets containing the fiber materials at 3% (weight/weight). Total liver and plasma folacin concentration and chick growth were used as response indicators. Dose-response curves indicated that pectin, lignin and alginate significantly reduced chick growth at all levels of dietary folacin. Plasma and liver folacin dose-response curves were not significantly different for any of the fiber materials, which indicated that the growth impairment was not due to a fiber effect on folic acid absorption. These results suggest that added dietary fiber has little or no effect on the bioavailability of folic acid monoglutamate.

Alginates↗
PubMed1982

Denaturation of the folacin-binding protein in pasteurized milk products.

The folacin-binding characteristics and chromatographic properties of the folacin-binding protein (FBP) of commercial pasteurized skim milk and whey protein concentrate were compared with those of fresh raw cows' milk. Native state FBP recently has been shown to enhance the intestinal absorption of folacin, whereas the FBP of pasteurized milk is ineffective. Anion-exchange chromatography indicated no major electrostatic differences in the FBP of these products, although gel-filtration chromatography provided evidence of enhanced FBP aggregation in the pasteurized whey protein concentrate. Analysis of folic acid binding kinetics by using Scatchard and Hill plots indicated that pasteurization or subsequent processing induces alterations in binding cooperatively, its pH dependence, or both. These results suggest that partial denaturation during pasteurization alters the folacin-binding characteristics and extent of molecular interaction of FBP. These changes may be responsible for the reported differences between raw and pasteurized milk products in their ability to enhance folacin absorption. Further research is needed to clarify the biological significance of these findings with respect to potential differences in folacin bioavailability from breast milk, pasteurized cows' milk and infant formulas.

Animals↗
PubMed1982

Relative activity of the nonphosphorylated B-6 vitamers for Saccharomyces uvarum and Kloeckera brevis in vitamin B-6 microbiological assay.

Accuracy in the microbiological assay of vitamin B-6 is dependent, in part, on equivalent response to each form of the vitamin by the assay organism. Recently, Kloeckera brevis (ATCC 9774) has been suggested as an alternative to Saccharomyces uvarum (ATCC 9080) because of its reported equivalent response to pyridoxine (PN), pyridoxal (PL), and pyridoxamine (PM) in turbidimetric yeast growth assays. Evaluation of the merits of these yeasts in our laboratory yielded contrasting results. As widely reported, S. uvarum exhibited greater growth response with PN than with equivalent molar concentrations of PL or PM. K. brevis exhibited an even greater disparity. Pronounced concentration dependence was observed for the response differences among vitaminers with each organism. On the basis of the variable specificity of K. brevis, this organism is not preferable to S. uvarum for the microbiological determination of total vitamin B-6.

Biological Assay↗
PubMed1982

High performance liquid chromatographic quantitation of aflatoxin metabolites in animal tissues.

A previously reported reverse phase high performance liquid chromatographic (HPLC) procedure was modified to permit the determination of the parent aflatoxins and various free and conjugated metabolites in animal tissues. The modified procedure was based on HPLC analysis of duplicate portions of a sample extract which had been prepared with and without treatment with trifluoroacetic acid (TFA). TFA catalyzes the conversion of aflatoxins G1, B1, M1, and Q1 to the fluorescent derivatives G2a, B2a, M2a, and Q2a. Aflatoxicol, which exhibited a sharp fluorescent peak in its native state, eluted as a tailing peak with weaker fluorescence following TFA treatment. Acid hydrolysis of the aqueous phase of tissue samples permitted the analysis of water-soluble conjugated forms of the various aflatoxins. Analysis of fluorescence spectra of manually collected HPLC fractions qualitatively supported the accuracy of the method. Representative data on the distribution of aflatoxins in turkey liver following ingestion of an experimentally contaminated ration are presented.

Aflatoxins↗
PubMed1981

Effects of selected polysaccharides on the bioavailability of pyridoxine in rats and chicks.

The effects of cellulose, pectin and bran on the bioavailability of pyridoxine (PN) were examined using rat and chick bioassay methods. Dose-response curves for growth, feed consumption, feed efficiency and either lever pyridoxal 5'-phosphate (PLP) or erythrocyte aspartate aminotransferase (Asp-AT) activity and PLP stimulation in vitro were compared among animals fed experimental diets varying in dietary fiber source and suboptimal levels. of PN. In rats, the observed stimulation of growth and feed efficiency by pectin, as compared to cellulose, at suboptimal PN levels was attributed to increased synthesis of vitamin B-6 intestinal microflora. Diets containing pectin markedly increased the fecal vitamin B-6 content. No difference in liver PLP was detected among rats fed various diets. In chicks, 5% dietary pectin resulted in increased feed consumption, but also diarrhea and depressed growth. Asp-AT activities at the lower level of dietary PN showed a significant (P greater than 0.05) but modest stimulating effect of pectin on the apparent bioavailability of PN. Bran resulted in a 17% bioavailability decrease of PN as indicated by growth and feed consumption data in the chick. However, no difference in Asp-AT activity or in vitro PLP stimulation was detected in comparison of responses from bran-fed chicks with the standard responses. These results suggest that the polysaccharides tested did not have important deleterious effects on the bioavailability of pyridoxine.

Animals↗
PubMed1981

High performance liquid chromatographic determination of aflatoxins in animal tissues and products.

A method was developed for the determination of aflatoxins, M1, B1, G1, B2, and G2 in animal tissues, meat, eggs, and dairy products by high performance liquid chromatography (HPLC). Previous extraction procedures were modified to optimize the precision and recovery of the method. HPLC is performed isocratically with a 5 micrometer microparticulate octadecylsilica column and fluorometric detection. The analysis is based on treatment of the purified sample extract or standard with trifluoroacetic acid (TFA) to catalyze the hydration of aflatoxins M1, B1, and G1 to the highly fluorescent M2a, B2a, and G2a derivatives. Analysis by HPLC with and without TFA treatment of the extract provides quantitative and qualitative data. The recovery of added aflatoxins and the precision of the recovery depend on the type of sample; mean coefficient of variation for all recovery values was 19.7 +/- 11.0% for the analysis of liver, ground beef, dairy products, and eggs. The method was sensitive, with a detection limit of 0.05 + 0.10 ng/g for each aflatoxin. This procedure provides an alternative to existing thin layer chromatographic methods for determining aflatoxins in animal tissues and products

Aflatoxins↗
PubMed1980

Effects of epsilon-pyridoxyllysine bound to dietary protein on the vitamin B-6 status of rats.

The nutritional properties of protein bound epsilon-pyridoxyllysine residues in a phosphopyridoxyl bovine serum albumin (PP-BSA) preparation were examined by rat bioassay employing various levels of PP-BSA and pyridoxine (PN) fortification in the diets. Previous studies have shown that vitamin B-6 aldehydes can reductively bind to food proteins as epsilon-pyridoxyllysine complexes during processing and storage. The bound pyridoxyllysine was found to possess 50% molar vitamin B-6 activity, as indicated by slope ratios for rat growth, feed efficiency and liver pyridoxal 5'-phosphate concentration. The response curves indicated that high dosages of epsilon-pyridoxyllysine would fully satisfy the vitamin B-6 requirement. Direct antivitamin B-6 activity of epsilon-pyridoxyllysine was observed in diets containing low levels of PP-BSA. Classical rat acrodynia symptoms, depression of erythrocyte aspartate aminotransferase (AspAT) activity and elevation of in vitro coenzyme stimulation of AspAT were observed to be inversely related to PP-BSA concentration in the diet. The antivitamin B-6 effects were readily prevented by the presence of added 0.5--1.0 micrograms pyridoxing/g diet. In contrast to the previous study, the presence of PP-BSA in the diet did not inhibit the utilization of added PN. This difference was postulated to be due to a difference in vitamin B-6 concentration of the basal diets. The results of this study indicate that protein bound epsilon-pyridoxyllysine is nutritionally significant, presumably by its participation in the normal metabolism of vitamin B-6. The metabolic implications are discussed.

Animals↗
PubMed1980

Activity of pyridoxamine as a substrate for brain pyridoxal kinase.

The substrate activity of pyridoxamine (PM) for brain pyridoxal (PL) kinase was examined in view of a recent report which indicated that PM was a poor substrate for this enzyme. Bovine brain PL kinase was shown by liquid chromatography to catalyze the phosphorylation of PM (Km = 65 microM). The identity of the reaction product, pyridoxamine 5'-phosphate, was confirmed by is ability to act as a substrate for liver pyridoxine (pyridoxamine) 5'-phosphate oxidase. The results, which indicate that PM is a good substrate for brain PL kinase, are consistent with the proposed role of intracellular phosphorylation in the uptake of vitamin B-6 brain tissue.

Animals↗
PubMed1979

Determination of urinary 4-pyridoxic acid using high performance liquid chromatography.

A high performance liquid chromatographic method is presented for the determination of the vitamin B6 metabolite, 4-pyridoxic acid, in urine. Urine samples are treated with trichloroacetic acid to precipitate protein. An aliquot of the supernatant is chromatographed using 0.033 M phosphate buffer containing 5% (v/v) methanol (pH 2.2), a fluorometric detector and a commercial reverse phase octadecylsilica column. The high precision of the method and the absence of interfering compounds have been demonstrated. This method provides a rapid, sensitive, and quantitative technique for the measurement of urinary 4-pyridoxic acid for use in metabolic and nutritional studies.

Chromatography, High Pressure Liquid↗
PubMed1978

Vitamin B-6 activity for rats of epsilon-pyridoxyllysine bound to dietary protein.

The biological activity of protein bound epsilon-pyridoxyllysine residues in a phosphopyridoxyl-bovine serum albumin (PP-BSA) preparation was evaluated. Previous studies have demonstrated that pyridoxal phosphate may bind to food proteins as epsilon-pyridoxyllysine complexes during processing and storage. The present research, employing PP-BSA as a model, was initiated to determine the nutritional consequences of epsilon-pyridoxyllysine formation in foods. The concentration of epsilon-pyridoxyllysine residues in the PP-BSA was determined spectrophotometrically and chromatographically. Rat bioassay of the PP-BSA revealed that epsilon-pyridoxyllysine exhibited 60% activity relative to the molar potency of pyridoxine. These results suggest the partial release of bound vitamin B-6 possibly by in vivo enzymatic hydrolysis of epsilon-pyridoxyllysine. The presence of PP-BSA in a test diet containing 0.25 microgram added pyridoxine per g of diet inhibited the utilization of approximately half of the free pyridoxine by the rats. It is postulated that the observed inhibition resulted from an antivitamin B-6 effect of intact epsilon-pyridoxyllysine. This effect requires further investigation.

Animals↗
PubMed1975

Modified fluorometric determination of vitamin A in milk.

A modified fluorometric procedure for determination of vitamin A in milk was developed to provide rapid analysis of large numbers to samples.. Saponification and a single extraction in a reaction vessel without transfer provided simplicity and standardization. Time and temperature of saponification and time of extraction were studied. Fifteen replicates of four different milks gave standard deviations of .71, .82, 1.26, and .71 on samples with 29, 26, 38, and 26 mug retinol per 100 ml. Recovery of added vitamin A in six amounts in two experiments gave ranges of recovery of 96.0 to104.0 and 95.2 to 105.3% with average recoveries of 100.0 and 99.9%.

Animals↗