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Biomedical subjects

I Elmadfa

Publications and source records attributed to I Elmadfa.

At least 55 records · Page 3Linked to original sources
PubMed1997

Antioxidant status in patients on chronic hemodialysis therapy: impact of parenteral selenium supplementation.

Reactive oxygen species may be involved in a broad pattern of tissue injury in patients on regular hemodialysis therapy and, in fact, increasing evidence suggests that the antioxidative system is compromized in these patients. One factor contributing to this reduction of antioxidative capacity is selenium deficiency. The present investigation was undertaken to further define the extent and type of impairment of the oxygen radical scavenger system in chronic hemodialysis patients and to evaluate the impact of selenium supplementation. Twelve non-wasted patients (6 male, 6 female, mean age of 58 years) on chronic hemodialysis for a minimum of 5 months (mean 46 months) were supplemented intravenously with 400 mg selenium (as sodium selenite) thrice weekly after each hemodialysis session over 8 weeks. Blood samples were taken before the start, at intervals of 2 weeks during, and 4 weeks after termination of supplementation. Concentrations were evaluated of selenium and alpha-tocopherol in plasma and erythrocytes, of retinol and ascorbic acid in plasma, of glutathione and the activities of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and, catalase (CAT) in erythrocytes. Lipid peroxidation endproducts were measured as malondialdehyde (MDA) in plasma. In patients on hemodialysis multiple alterations of the antioxidative system were present and the concentrations of selenium in plasma, of glutathione and the activity of GSH-Px in erythrocytes were profoundly decreased (p < 0.001). Selenium supplementation improved the selenium status of the patients, as indicated by an increase in selenium concentrations in plasma and erythrocytes and erythrocyte GSH-Px activity. Improvement in antioxidative capacity was further documented by an increase in alpha-tocopherol in erythrocytes. Plasma MDA showed a transient decrease after 6 weeks and increased activities of SOD and CAT were dampened. No effect was seen on plasma concentrations of ascorbic acid, a-tocopherol and retinol. We conclude that patients on chronic hemodialysis therapy manifest a profound depression in antioxidative potential and a selenium deficiency. Selenium supplementation improves the oxygen radical scavenger system and increases selenium concentrations in plasma and erythrocytes and the activity of selenium dependent glutathione peroxidase. Thus, selenium should also be considered for micronutrient supplementation in patients on chronic hemodialysis therapy.

Adult↗
PubMed1995

[Reducing lipid peroxidation of stored frozen trout fillet by supplementing feed with vitamin E].

Rainbow trouts were fed a complete diet with 12 mg vitamin K3 and supplemented with 20, 200 or 2,000 mg all-rac-alpha-tocopheryl-acetate/kg for 18 weeks. The ratio of the vitamin E-supplementation was 1:10:100. Fillets were minced and stored at -18 degrees C. Concentrations of alpha-tocopherol and phylloquinone and parameters of lipid peroxidation were measured after 4, 6, and 8 months of storage. The effects of alpha-tocopherol incorporated into fillets on storage stability were assessed by measuring free fatty acids, peroxides, malondialdehyde and lipofuscin. Mean alpha-tocopherol-concentrations in fillets were 1.4, 2.7 and 16.3 mg/100 g, respectively representing ratios of 1:2:12. The increase in alpha-tocopherol concentration resulted in a significant improvement of storage stability. The phylloquinone concentration in fillet was reduced in treatments with > or = 200 mg vitamin E/kg; however, this did not affect the prothrombin time. No peroxides were detectable at any time. The concentrations of malondialdehyde significantly decreased with increasing supplementation of vitamin E. Lipofuscin concentrations were higher with low than with high vitamin E supplementation. The dose-related inhibition of lipid peroxidation became apparent in decreased concentrations of free fatty acids in the crude fat. These results confirm the effectiveness of alpha-tocopherol as antioxidant in fish flesh. In this study the incorporation of alpha-tocopherol from dietary supplementation improved the long-term storage quality of trout fillets due to the effective inhibition of the lipid peroxidation. A measurable improvement of the storage stability was achieved with a supplementation of 200 mg vitamin E/kg feed.

Animal Feed↗
PubMed1995

Metabolic effect of sodium selenite: insulin-like inhibition of glucagon-stimulated glycogenolysis in the isolated perfused rat liver.

Selenium, an essential trace element, has been shown to decrease plasma glucose concentrations of diabetic rats. To study the short-term effects of selenium on hepatic carbohydrate metabolism, isolated perfused livers of fed Sprague-Dawley rats were continuously infused with sodium selenite for 90 minutes. This resulted in an immediate elevation of selenium in the effluent perfusate (3.3 +/- 0.1, 16.1 +/- 0.4, 30.3 +/- 1.6, and 118.9 +/- 0.8 mumol/L at infusion of 10, 50, 100, and 500 mumol/L sodium selenite, respectively). Basal hepatic glucose production decreased in a dose-dependent manner within 60 minutes of low-dose sodium selenite infusion (10: 0.60 +/- 0.20, 50: 0.21 +/- 0.40, and 100 mumol/L: 0.21 +/- 0.09 mumol.min-1.g-1 liver; P < .05 vs. zero time), while it was transiently increased by 500 mumol/L sodium selenite (1.11 +/- 0.18 mumol.min-1.g-1 liver; P < .05). Glucagon-stimulated glycogenolysis was suppressed by 50% (P < .05) at 1.8 nmol/L insulin and by 90% (P < .001) at 10 mumol/L sodium selenite. That selenium concentration did not affect glutathione peroxidase activities in liver and perfusate erythrocytes within 60 minutes. Toxic effects of high-dose selenite (500 mumol/L), but not of low-dose selenite (10 mumol/L) infusion, were indicated by increased hepatic glucose (P < .05), lactate (P < .01), and lactate dehydrogenase (P < .001) release as well as histologically by degeneration and necrosis of periportal hepatocytes. In conclusion, low-dose selenite exerts a potent insulinlike effect on hepatic glycogenolysis in vitro by counteracting glucagon action, whereas high-dose selenite may severely impair liver function.

Animals↗
PubMed1995

Rapid HPLC assay for the assessment of vitamin K1, A, E and beta-carotene status in children (7-19 years).

The method presented allows the determination of plasma concentrations of the fat soluble vitamins K1, A, E and beta-carotene. After the extraction of the plasma, the only clean-up step required consisted of washing the hexane-layer with a methanol/water mixture. The RP-HPLC system contained a zinc-filled reduction post-column and after chromatographic separation the vitamin K was detected by fluorescence. Only 0.5-1 ml plasma was required for this procedure. 2',3'-Dihydrophylloquinone was added as an internal standard. For phylloquinone the limit of detection was estimated at 0.09 nmol/l (0.04 ng/ml). Investigating a plasma pool with a mean concentration of 0.75 nmol phylloquinone/l plasma, the all-over coefficient of variation was 5.6% for within-day (n = 11) and 7.1% from day to day (n = 8). The rate of recovery was found to be in the range of 92-104% (the same pool as for the precision test was used, and the added amounts were 0.13, 0.5, 2.0 ng phylloquinone). From an aliquot of hexane-extract, the vitamins A, E and beta-carotene were separated by RP-HPLC. The concentrations of vitamins A, E and beta-carotene were measured on the UV and visible detector respectively. Coefficients of variation for all vitamins were < 10%. In a group of 7 to 19 year-old healthy children (n = 298), the concentrations of vitamins A, E, K1 and beta-carotene ranged from 0.34-2.10 mumol/l, 12.0-80.8 mumol/l, 0.09-2.22 nmol/l and 0.23-3.92 mumol/l respectively, and the medians were 1.02 mumol/l, 21.3 mumol/l, 0.49 nmol/l and 0.56 mumol/l respectively.

Adolescent↗
PubMed1994

Polychlorinated biphenyl congeners in foxes in Germany from 1983 to 1991.

Red foxes served as a biological indicator for the temporal development of environmental contamination with polychlorinated biphenyls (PCB). The concentration of PCB congeners nos. 28, 49, 52, 101, 138, 153, and 180 were analyzed in the body fat of 80 foxes (Canis vulpes) from Germany. The samples were from animals that had been submitted for examination in 1983, 1987, and 1991. Throughout this time period, a reduction was seen in the concentration of the highly chlorinated biphenyls 138, 153, and 180, whereas the concentration of the low-chlorinated congeners PCB nos. 28, 49, and 52 increased. No change in contamination with congener 101 was observed. These results show a trend toward reduction of environmental contamination with highly-chlorinated biphenyls since 1983, while contamination with low-chlorinated congeners is apparently increasing. An interesting observation is the disproportionately higher amount of 2,2',3,4,4',5,5'-hepatachlorobiphenyl (PCB 180) over that of 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153) in body-fat samples from all foxes analyzed. This phenomenon was also observed in 10 dogs examined as controls. Based on evidence from other authors of experimental toxicological studies on beagles, it appears that the fox possesses a similar cytochrome P-450 isoenzyme that can degrade 2,4,5-trichloro-substituted aromatic compounds. As a consequence, in canines, PCB 180 which is additionally meta-chloro substituted is accumulated to a greater degree than is PCB 153.

Adipose Tissue↗
PubMed1993

Influence of a single parenteral application of a 10% fish oil emulsion on plasma fatty acid pattern and the function of thrombocytes in young adult men.

50 ml of a 10% fish oil emulsion (41% omega-3 fatty acids of total fatty acids) were infused for 1 h into the arm vein of young, healthy, male volunteers. The fatty acid composition of the plasma, aggregation of the blood platelets as well as the thromboxane synthesis, were measured before the beginning of infusion, 20, 60, 120, 360 and 1,440 min after the start of the fat infusion. In the first 60 min, the fatty acid composition of the plasma changed in correspondence with the supplied fatty acid pattern. At the end of the investigation it was again within the normal range. As a result of fat application thromboxane synthesis was reduced and the aggregation of the platelets was inhibited but it was normalized by the 1,440-min value. Fish oil emulsions might be beneficial for parenterally fed patients with a high risk of thrombosis. Therefore the performance of further investigations using a varying dosage and multiple application can be recommended.

Adult↗
PubMed1992

Development of vitamin-E-status of premature infants after intravenous application of all-rac-alpha-tocopheryl acetate.

A low vitamin-E-status was found in premature infants with birth weight less than or equal to 1,500 g. In this study the plasma vitamin-E-concentration of premature infants was analysed 2-3 h postpartal. During a total parenteral nutrition including fat emulsions the children received 4.5 mg all-rac-alpha-tocopherol acetate/kg/d (approximately 3 mg rrr alpha-tocopherol equivalents/kg/d) intravenously for 5 days. On the same days control-infants received the same fat emulsions without supplemented vitamin E. Serum alpha-tocopherol-levels were analysed on day 1, 3, 7 and 14 by HPLC. Initially the serum vitamin E level was 0.33 mg alpha-tocopherol/dl. Following the intravenous administration there was a significant increase in serum free alpha-tocopherol level. 7 days after end of supplementation the alpha-tocopherol concentration in serum reached 1,000 mg/dl serum. The highest level analysed after tocopheryl acetate supplementation was 2.45 mg alpha-tocopherol/dl. The choosen dose of 4.5 mg all-rac-alpha-tocopheryl acetate/kg body weight/day and this form of application were suitable to achieve normal serum alpha-tocopherol concentrations in premature infants without any complications.

Female↗
PubMed1991

[In vitro studies of the effect of different mixture proportions of omega-3 and omega-6 fatty acids on thrombocyte aggregation and thromboxane synthesis in human thrombocytes].

In order to estimate the influence of the tested fatty acids on platelet aggregation, synthesis of prostaglandin E and thromboxane B in vitro, platelet rich plasma (PRP) was incubated with the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), with linoleic acid as representative of the omega-6 fatty acids, as well as with mixtures of EPA and DHA and all fatty acids, resp., with and without addition of alpha-tocopherol. For the determinations, platelets were prepared from blood of young adult male volunteers (age 26.6 +/- 8 years). Platelet aggregation and synthesis of thromboxane were measured after 30 and 60 min of incubation. Smoking habits were not regarded. The incubation of platelets with DHA and EPA itself, as well as the mixture of fatty acids dominated by omega-3 fatty acids (omega-3/omega-6 = 15/1) caused a significant decrease (p less than 0.05) of collagen-induced platelet aggregation. Tocopherol, linoleic acid, and the linoleic-acid-rich mixtures (omega-3/omega-6 = 1/4) caused only a slight inhibition of platelet aggregation. No uniform influence of omega-3 fatty acids could be observed that showed their influence on synthesis of thromboxane to be of importance for the promotion of platelet aggregation. EPA and the mixture of EPA and DHA did decrease thromboxane synthesis significantly (p less than 0.05). On the other hand, single incubation with DHA as well as with linoleic acid rich mixtures caused a statistically not significant increase of rate of the synthesis, which did not increase the aggregation. This observation indicates the formation of less effective TXA3. An influence of tocopherol could also not be observed.

Adult↗