Beneficial effects of alpha-lipoic acid and ascorbic acid on endothelium-dependent, nitric oxide-mediated vasodilation in diabetic patients: relation to parameters of oxidative stress.

The impairment of nitric oxide (NO)-mediated vasodilation in diabetes has been attributed to increased vascular oxidative stress. Lipoic acid has been shown to have substantial antioxidative properties. The aim of this study was to assess the effect of lipoic acid on NO-mediated vasodilation in diabetic patients in comparison with the well-recognized effect of ascorbic acid. Using venous occlusion plethysmography, we examined the effects of lipoic acid (0.2 mM) and ascorbic acid (1 and 10 mM) on forearm blood flow responses to acetylcholine, sodium nitroprusside and concomitant infusion of the NO-inhibitor, N(G)-monomethyl-L-arginine, in 39 diabetic patients and 11 control subjects. Plasma levels of antioxidants and parameters of lipid peroxidation were measured and correlated to endothelial function tests. Lipoic acid improved NO-mediated vasodilation in diabetic patients, but not in controls. NO-mediated vasodilation was improved by ascorbic acid at 10 mM, but not 1 mM. Improvements of endothelial function by ascorbic acid and lipoic acid were closely related. The beneficial effects of lipoic acid were positively related to plasma levels of malondialdehyde and inversely related to levels of ubiquinol-10. These findings support the concept that oxidative stress contributes to endothelial dysfunction and suggest a therapeutic potential of lipoic acid particularly in patients with imbalance between increased oxidative stress and depleted antioxidant defense.     

Multi-scale response of wetland bird assemblages to landscape patterns on a Neotropical island: when wetland type matters more than size

Wetlands Ecology and Management - Understanding wetland bird responses to landscape patterns is central for wetland management and bird conservation. This is particularly relevant on islands, where...     

Scatterhoarding of Manchurian walnut <Emphasis Type="Italic">Juglans mandshurica</Emphasis> by small mammals: response to seed familiarity and seed size

Dispersal patterns can be affected by seed familiarity and seed traits, including size, mass, and nutritional value, but these factors have not been intensively studied in the context of seed dispersal processes. Our aim was to study how small rodents respond to seed size and seed familiarity in their pattern of Manchurian walnut (Juglans mandshurica) seeds in two different habitats in temperate forests of northeast China. Our results demonstrated that Apodemus penisulae acts as the most important disperser for Manchurian walnut seeds. Inexperienced small rodents did not reject seeds of the Manchurian walnut and show similar seed removal rates as compared with experienced rodents. Both experienced and naïve rodents actively participated in seed scatterhoarding of Manchurian walnut seeds. Consecutive survey showed that seeds with large size/mass were removed faster than those with small size/mass, indicating a preference for large seeds. However, small seeds scatter-hoarded by small rodents were transported farther than large ones, failing to support the traditional optimization models for various tree species. Small seeds of Manchurian walnut in caches were less likely to be recovered than large ones and showed greater cache survival rates, indicating that small seeds would be more advantageous for regeneration than large seeds in small rodent-dominated forests.