Chronic exposure of the skin to sunlight causes damage to the underlying connective tissue with a loss of elasticity and firmness. Silicon (Si) was suggested to have an important function in the formation and maintenance of connective tissue. Choline-stabilized orthosilicic acid ("ch-OSA") is a bioavailable form of silicon which was found to increase the hydroxyproline concentration in the dermis of animals. The effect of ch-OSA on skin, nails and hair was investigated in a randomized, double blind, placebo-controlled study. Fifty women with photodamaged facial skin were administered orally during 20 weeks, 10 mg Si/day in the form of ch-OSA pellets (n=25) or a placebo (n=25). Noninvasive methods were used to evaluate skin microrelief (forearm), hydration (forearm) and mechanical anisotropy (forehead). Volunteers evaluated on a virtual analog scale (VAS, "none=0, severe=3") brittleness of hair and nails. The serum Si concentration was significantly higher after a 20-week supplementation in subjects with ch-OSA compared to the placebo group. Skin roughness parameters increased in the placebo group (Rt:+8%; Rm: +11%; Rz: +6%) but decreased in the ch-OSA group (Rt: -16%; Rm: -19%; Rz: -8%). The change in roughness from baseline was significantly different between ch-OSA and placebo groups for Rt and Rm. The difference in longitudinal and lateral shear propagation time increased after 20 weeks in the placebo group but decreased in the ch-OSA group suggesting improvement in isotropy of the skin. VAS scores for nail and hair brittleness were significantly lower after 20 weeks in the ch-OSA group compared to baseline scores. Oral intake of ch-OSA during the 20 weeks results in a significant positive effect on skin surface and skin mechanical properties, and on brittleness of hair and nails.
In the present study, we investigated whether the length of light/dark cycle could influence the pre-adult developmental time and adult life span in Drosophila melanogaster. Flies were reared to adulthood and maintained as adults under both 24-h (light/dark 12:12 h) and 48-h (light/dark 24:24 h) cycles. The flies reared during pre-adult stages at the 48-h light/dark cycle had significantly prolonged developmental time compared to those in flies reared at normal 24-h cycle. Irrespective of the duration of pre-adult light/dark period, the males maintained as adults at prolonged 48-h cycle had a 13-16% longer mean adult life span than those maintained at normal 24-h cycle (P<0.001 in all cases). In females reared under normal 24-h cycle such differences were lower but also significant (P=0.03); no significant difference in life span was found in females reared under prolonged 48-h cycle. The results are interpreted to demonstrate that pre-adult developmental time and adult life span in Drosophila melanogaster are both influenced by the length of light/dark cycle.
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