We conducted a randomized placebo-controlled double-blind study in 20 healthy young female students (skin type II + III, body mass index 18-22) in order to evaluate the efficacy of 10 weeks of moderate dose (30 mg/d) beta-carotene (BC) on plasma and skin beta-carotene levels during 12 days of time and intensity controlled sunlight exposure at sea level (30 degrees latitude, Red Sea, Eilath, Israel). After 12 days of controlled sun exposure (total UV dose of about 10.000J/cm2), plasma beta-carotene decreased in the placebo (p < 0.01) and beta-carotene group (not significant). In addition cutaneous beta-carotene decreased significantly in both groups. Plasma alpha-tocopherol decreased significantly (p < 0.01) during exposure time in both groups. In the supplemented group, however, the decrease of a-tocopherol was significantly greater (p < 0.01) than in the placebo group. We conclude that sunlight influences the beta-carotene and alpha-tocopherol content of blood and tissues.
A rat model was used to investigate whether high oral doses of vitamin A lead to fetal malformations and to what extent retinyl esters (RES) are transferred from the mother to the fetuses. Retinol and RES concentrations in plasma behave similarly in rats and humans. When high concentrations of vitamin A are administered, plasma retinol concentrations remain relatively constant, whereas plasma RES increased in parallel with the dose. To achieve an elevation from approximately 150 to > 1525 nmol x L(-1) in the experimental group before mating, female Ibm: RORO (spf) rats were fed a maintenance diet enriched with 15.2 x 10(3) retinol equivalents (RE) x kg(-1) at the start and increased stepwise to 52.5 x 10(3) for a total of 8 mo. A parallel subgroup was maintained to measure progress in experimental rats without interference by blood taking. Rats of the control group received the basal diet analyzed to contain 4.5 x 10(3) RE x kg(-1). Before mating the mean body weights of experimental and control rats were not significantly different. All-trans, 13-cis, 4-oxo-all-trans and 5,6-epoxy-all-trans retinoic acid (RA) concentrations were determined in maternal and fetal plasma. With high vitamin A intake, 4-oxo- and 5,6-epoxy RA concentrations were significantly higher in the fetuses than in their mothers. Although these high intakes of vitamin A by the rat dams resulted in high maternal and fetal plasma concentrations of vitamin A and its metabolites, fetal malformations were not observed. This may be due to the fact that circulating RES are not teratogenic and that after crossing the placental barrier, they are stored mainly in fetal liver.
The distribution of complex carbohydrate structures during the embryonic development of the rat palate was analysed by examining lectin-binding patterns in serial paraffin and cryostat sections. With few exceptions, the binding patterns showed a general increase in lectin receptors in the more developed stages of palatogenesis. High mannose oligosaccharides were especially amplified during development. Terminal fucose molecules were not expressed. In contrast, terminal sialic acid molecules were ubiquitously distributed in epithelial and mesenchymal tissues. Non-sialylated terminal N-acetylglucosamine was specifically restricted to evolving bone matrix. Before palatal fusion, quantitative but not qualitative differences were detected between oral, nasal, and medial-edge epithelial surfaces. The only exception was LCA, which specifically marked epithelial cells at the tip of palatal shelves. A very selective affinity for Jacalin was demonstrated in the oral epithelium of the palate after day 16, suggesting the presence of sialylated terminal galactose-(beta-1,3)-N-acetylgalactosamine. PNA specifically marked the basal lamina of the oral side of palatal processes. The binding patterns of DBA, GSL IA, SBA, and VVA indicated that the epithelium of the tongue is characterized by terminal alpha- and beta-galactose residues, whereas palatine cells possess only molecules with beta-anomery. During palatogenesis, glycosaminoglycans patterns were significantly modified. Our data suggest that alteration of complex carbohydrate structures may play a central role in modulating cell-cell and cell-matrix interactions. The significance of these findings, however, remains to be elucidated.
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