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Biomedical subjects

J G Bieri

Publications and source records attributed to J G Bieri.

At least 19 recordsLinked to original sources
PubMed1992

Plasma carotenoid response to chronic intake of selected foods and beta-carotene supplements in men.

We determined serial changes in four major plasma carotenoid fractions (alpha-carotene, beta-carotene, lutein/zeaxanthin, and lycopene) in 30 men consuming defined daily doses of carotenoids from foods (broccoli, carrots, or tomato juice) or from purified beta-carotene in capsules (12 or 30 mg) for 6 wk while fed a controlled diet. Compared with baseline, beta-carotene increased in the 30- and 12-mg-capsule and carrot groups whereas alpha-carotene increased in the carrot group and lutein increased in the broccoli group. Lower lutein concentrations in recipients of beta-carotene capsules suggested an interaction between these two carotenoids. Lycopene declined in all groups except the tomato-juice group. Total carotenoid concentration changes only reflected the large increases in beta-carotene concentrations and not the smaller changes observed in other individual carotenoids. Overall, purified beta-carotene produced a greater plasma response than did similar quantities of carotenoids from foods sources. However, some foods increased plasma concentrations of certain carotenoids.

Adult↗
PubMed1979

Simultaneous determination of alpha-tocopherol and retinol in plasma or red cells by high pressure liquid chromatography.

This paper describes a rapid, microprocedure for the simultaneous determination of alpha-tocopherol (vitamin E) and retinol (vitamin A) in plasma, and of alpha-tocopherol alone in red cells since cells do not contain retinol. A total lipid extract from 0.1 ml plasma or 0.125 ml red cells and containing internal standards of alpha-tocopheryl acetate and retinyl acetates is injected onto a high pressure liquid chromatography with a reverse phase column developed with methanol-water. An ultraviolet detector with 280-nm filter is used. The chromatogram is complete in 8 min and the alpha-tocopherol and retinol are quantitated by the peak height ratio method. Comparison of results with both plasma and red cells gave excellent agreement with conventional methods for these vitamins. The procedure should be particularly useful for clinical studies and nutrition surveys.

Chromatography, High Pressure Liquid↗
PubMed1979

AIN-76 diet.

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Animal Nutritional Physiological Phenomena↗
PubMed1979

Structural and biochemical changes in vitamin A--deficient rat retinas.

The levels of rhodopsin and opsin were investigated in relation to the maintenance of retinal structure in retinas of vitamin A--deficient rats in low levels of cyclic illumination (1.5 to 2 foot-candles). Rhodopsin levels decreased in the deficient retinas to approximately 20% of control at 9 weeks, and this level was retained through 39 weeks on the deficient diet. Opsin levels decreased at a slower rate but reached about 20% of control levels at 32 weeks. Despite the decrease in rhodopsin levels, obvious deterioration of disc structure was not observed until 16 weeks of deficiency, when opsin levels had already decreased to 60% to 70% of control. The structural disruption of photoreceptor outer segments was localized initially in discs of the distal third. Rod cell degeneration preceded cone cell degeneration in vitamin A--deficient retinas. Most of the rods and cones persisted in the posterior retina at 23 weeks on the deficient diet; however, by 40 weeks, only 11% of the rod nuclei remained. In contrast, about 63% of the cone nuclei were present at 40 weeks of deficiency. The photoreceptor cells were affected by the deficiency to a greater extent in the inferior hemisphere than in the superior hemisphere of the eye.

Animals↗
PubMed1979

Vitamin E deficiency and the retina: photoreceptor and pigment epithelial changes.

To investigate the role of normal vitamin E levels and the interrelationships between vitamin E and A in maintaining the visual cells of the retina, weanling female Sprague-Dawley rats were fed vitamin E-free diets differing tenfold in their vitamin A content (0.8 and 8.0 mg of retinol per kilogram of diet). Rats on vitamin E-free diets with the higher vitamin A level exhibited marked disruption of photoreceptor outer segment membranes and a fivefold increase in the number of lipofuscin granules in the pigment epithelial cells which ingest these membranes. Rats on vitamin E-free diets with the lower vitamin A level showed the same retinal damages plus significant loss of photoreceptor cells compared to age-matched rats on control diets. Rods and cones were involved equally, and their pattern of loss was not like that found in vitamin A deficiency. Normal levels of vitamin E probably protect photoreceptor membranes from oxidative damage and retard the accumulation of their remnants and other products of lipid breakdown in the pigment epithelium. The vitamin A status of rats has a significant influence on the extent of damage induced by vitamin E deficiency.

Animals↗
PubMed1977

Rat liver alpha-tocopherol binding protein.

1. The properties of rat liver cytoplasmic alpha-tocopherol binding protein have been studied. 2. The binding protein sedimented in the 3 S region of sucrose density gradients, and gel filtration indicated an approximate molecular weight of 30 500. 3. Of the tissues examined by the present assay, binding was detectable only in the liver. 4. Optimal binding was achieved by incubation at 26 degrees C for 4 h and was independent of pH between 7.4 and 9.0. 5. Pronase completely abolished binding. The binding protein was, however, almost completely resistant to trypsin, and unaffected by RNAase, DNAase, triacylglycerol lipase, and phospholipase C. 6. A variety of tocopherol analogues and other lipid-soluble compounds were tested for their ability to compete for binding. Only alpha-tocopherol and to a lesser extent alpha-tocotrienol and gamma-tocopherol exhibited competition. alpha-Tocopherol acetate, alpha-tocopherol quinone and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid had no effect on binding. 7. Tocopherol binding was reversible, and the tocopherol was not metabolized during incubation.

Animals↗
PubMed1977

Factors affecting the exchange of tocopherol between red blood cells and plasma.

The purpose of this study was to clarify factors that affect the equilibrium distribution of alpha-tocopherol between red blood cells and plasma. Plasma labeled with 14C-alpha-tocopherol was incubated with red cells for 4 to 6 hr and the distribution of the tocopherol determined in the two compartments (red blood cell (RBC: plasma ratio). Use of heparin as anticoagulant gave a higher RBC: plasma ratio than acid citrate dextrose. The RBC:plasma ratio was affected by the hematocrit of the incubation mixture, higher ratios being obtained with lower hematocrits. The ratio was not related to the plasma concentration of alpha-toxopherol, indicating that the red cell was not saturated up to four times normal plasma levels. Of possible clinical significance was the finding that the RBC: plasma ratio was related to the total lipid concentration of plasma. Red cell content of alpha-tocopherol decreased as plasma lipids increased, until at three times normal plasma lipid concentration the red cells had one-third or less of their normal concentration of alpha-tocopherol. The implications of this observation on the relationship between plasma and tissue aplha-tocopherol are discussed.

Animals↗
PubMed1977

Potassium requirement of the growing rat.

On the basis of maximum weight gain in weanling male rats fed a semipurified diet for 21 days, the requirement for potassium was found to be 0.23% of the diet. This compares with the NRC requirement of 0.18%. The higher requirement is believed to be due to the greater rate of growth, 6.6 to 7.0 g/day, compared with that obtained in older studies on which the NRC estimate was based. The higher potassium level also improved efficiency of food utilization.

Age Factors↗
PubMed1977

The occurrence and effects of human vitamin E deficiency. A study in patients with cystic fibrosis.

The role of vitamin E in human nutrition was studied by investigation of patients with cystic fibrosis (CF) and associated pancreatic insufficiency. Vitamin E status was assessed by measurement of the plasma concentration of the principal circulating isomer, alpha-tocopherol. Results of such determinations in 52 CF patients with pancreatogenic steatorrhea revealed that all were deficient in the vitamin. The extent of decreased plasma tocopherol varied markedly but correlated with indices of intestinal malabsorption, such as the serum carotene concentration and percentage of dietary fat absorbed. Supplementation with 5-10 times the recommended daily allowance of vitamin E in a water-miscible form increased the plasma alpha-tocopherol concentrations to normal in all 19 CF patients so evaluated. Studies on the effects of vitamin E deficiency focused on possible hematologic alterations. An improved technique was developed to measure erythrocyte hemolysis in vitro in the presence of hydrogen peroxide. While erythrocyte suspensions from control subjects demonstrated resistance to hemolysis during a 3-h incubation, all samples from tocopherol-deficient CF patients showed abnormal oxidant susceptibility, evidenced by greater than 5% hemoglobin release. The degree of peroxide-induced hemolysis was related to the plasma alpha-tocopherol concentration in an inverse, sigmoidal manner. The possibility of in vivo hemolysis was assessed by measuring the survival of (51)Cr-labeled erythrocytes in 19 vitamin-E deficient patients. A moderate but statistically significant decrease in the mean (51)Cr erythrocyte half-life value was found in this group. Measurement of erythrocyte survival before and after supplementation of 6 patients with vitamin E demonstrated that the shortened erythrocyte lifespan could be corrected to normal with this treatment. Other hematologic indices in deficient subjects, however, were normal and did not change upon supplementation with vitamin E. It is concluded that CF is invariably associated with vitamin E deficiency, provided that the patient in question has pancreatic achylia and is not taking supplementary doses of tocopherol. Concomitant hematologic effects consistent with mild hemolysis, but not anemia, occur and may be reversed with vitamin E therapy. Patients with CF should be given daily doses of a water-miscible form of vitamin E to correct the deficiency.

Adolescent↗
PubMed1976

Vitamin E.

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Animals↗
PubMed1976

Relative activity of alpha-tocopherol and gamma-tocopherol in preventing oxidative red cell hemolysis.

The purpose of this study was to compare the antioxidant activities of alpha-tocopherol and gamma-tocopherol in protecting the red cell membrane against lipid peroxidation. Tocopherols were incorporated into the red cell membrane by incubating cells with solutions of the tocopherols in bovine albumin. The cells were then washed and subjected to the dialuric acid hemolysis test. Analysis of variance of the response curves revealed that gamma-tocopherol had 38% of the activity of alpha-tocopherol. No evidence was found for an interaction between the two tocopherols when present in the red cell membranes simultaneously.

Animals↗
PubMed1975

Megavitamin E supplementation in man.

To assess possible toxic and/or beneficial effects of vitamin E supplementation, a group of 28 adults voluntarily ingesting 100 to 800 IU/day of tocopherol for an average of 3 years were evaluated in this study. Half of the subjects claimed a feeling of improved health or well being, but no specific beneficial effects were noted consistently; the other half indicated no change in health status after beginning vitamin E supplements. No gross evidence of toxicity was apparent on reviewing past medical histories with the subjects. Plasma alpha-tocopherol was found to be elevated significantly in the group from 650 micrograms/100 ml (control mean) to 1,340 micrograms/100 ml; however, 25% of the values were within 2 SD of the control mean. Plasma alpha-tocopherol levels did not correlate with total daily dose but did relate to plasma triglyceride and cholesterol concentrations. Total plasma carotenoids were also significantly increased along with vitamin A levels; the former did not correlate with plasma vitamin E, whereas the latter showed a significant correlation. Laboratory screening for toxic side effects of vitamin E supplementation by performance of 20 standard clinical blood tests failed to reveal any disturbance in liver, kidney, muscle, thyroid gland, erythrocytes, leukocytes, coagulation parameters, or blood glucose. It is concluded that megavitamin E supplements in this group produced no apparent toxic side effects and that subjective claims for beneficial effects were highly variable.

Adult↗
PubMed1975

Tocopherols and polyunsaturated fatty acids in human tissues.

Five tissues from three adults who died suddenly and three adult cancer victims were analyzed for alpha- and gamma-tocopherols and fatty acids. When compared with two reports in 1949 and 1958, the three presumably normal subjects had alpha-tocopherol concentrations in liver, muscle and adipose tissue in about the same range as earlier, but heart was twice as high and lung was three times higher than earlier. The content of gamma-tocopherol in all tissues was considerably higher than in 1949 or 1958. Tissues from cancer patients were no lower in alpha-tocopherol than tissues from normal subjects. Adipose tissue from three of the six subjects contained linoleic acid exceeding 15 per cent of total fatty acids. Tocopherols in these subjects, expressed on a tissue weight or tissue lipid basis, were not remarkable. The molar ratio of polyunsaturated fatty acids to alpha-tocopherol in heart and lung was calculated and its possible use in evaluating vitamin E status is discussed.

Adipose Tissue↗
PubMed1975

Vitamin E.

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Adult↗