Effect of vitamin E (Tri E®) on antioxidant enzymes and DNA damage in rats following eight weeks exercise

<p>Abstract</p> <p>Background</p> <p>Exercise is beneficial to health, but during exercise the body generates reactive oxygen species (ROS) which are known to result in oxidative stress. The present study analysed the effects of vitamin E (Tri E^®) on antioxidant enzymes; superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (Cat) activity and DNA damage in rats undergoing eight weeks exercise.</p> <p>Methods</p> <p>Twenty four <it>Sprague-Dawley </it>rats (weighing 320-370 gm) were divided into four groups; a control group of sedentary rats which were given a normal diet, second group of sedentary rats with oral supplementation of 30 mg/kg/d of Tri E^®, third group comprised of exercised rats on a normal diet, and the fourth group of exercised rats with oral supplementation of 30 mg/kg/d of Tri E^®. The exercising rats were trained on a treadmill for 30 minutes per day for 8 weeks. Blood samples were taken before and after 8 weeks of the study to determine SOD, GPx, Cat activities and DNA damage.</p> <p>Results</p> <p>SOD activity decreased significantly in all the groups compared to baseline, however both exercised groups showed significant reduction in SOD activity as compared to the sedentary groups. Sedentary control groups showed significantly higher GPx and Cat activity compared to baseline and exercised groups. The supplemented groups, both exercised and non exercised groups, showed significant decrease in Cat activity as compared to their control groups with normal diet. DNA damage was significantly higher in exercising rats as compared to sedentary control. However in exercising groups, the DNA damage in supplemented group is significantly lower as compared to the non-supplemented group.</p> <p>Conclusions</p> <p>In conclusion, antioxidant enzymes activity were generally reduced in rats supplemented with Tri E^®probably due to its synergistic anti-oxidative defence, as evidenced by the decrease in DNA damage in Tri E^®supplemented exercise group.</p

Climate sensitive size-dependent survival in tropical trees

Survival rates of large trees determine forest biomass dynamics. Survival rates of small trees have been linked to mechanisms that maintain biodiversity across tropical forests. How species survival rates change with size offers insight into the links between biodiversity and ecosystem function across tropical forests. We tested patterns of size-dependent tree survival across the tropics using data from 1,781 species and over 2 million individuals to assess whether tropical forests can be characterized by size-dependent life-history survival strategies. We found that species were classifiable into four ‘survival modes’ that explain life-history variation that shapes carbon cycling and the relative abundance within forests. Frequently collected functional traits, such as wood density, leaf mass per area and seed mass, were not generally predictive of the survival modes of species. Mean annual temperature and cumulative water deficit predicted the proportion of biomass of survival modes, indicating important links between evolutionary strategies, climate and carbon cycling. The application of survival modes in demographic simulations predicted biomass change across forest sites. Our results reveal globally identifiable size-dependent survival strategies that differ across diverse systems in a consistent way. The abundance of survival modes and interaction with climate ultimately determine forest structure, carbon storage in biomass and future forest trajectories

Latitudinal patterns in stabilizing density dependence of forest communities

Numerous studies have shown reduced performance in plants that are surrounded by neighbours of the same species1,2, a phenomenon known as conspecific negative density dependence (CNDD)3. A long-held ecological hypothesis posits that CNDD is more pronounced in tropical than in temperate forests4,5, which increases community stabilization, species coexistence and the diversity of local tree species6,7. Previous analyses supporting such a latitudinal gradient in CNDD8,9 have suffered from methodological limitations related to the use of static data10,11,12. Here we present a comprehensive assessment of latitudinal CNDD patterns using dynamic mortality data to estimate species-site-specific CNDD across 23 sites. Averaged across species, we found that stabilizing CNDD was present at all except one site, but that average stabilizing CNDD was not stronger toward the tropics. However, in tropical tree communities, rare and intermediate abundant species experienced stronger stabilizing CNDD than did common species. This pattern was absent in temperate forests, which suggests that CNDD influences species abundances more strongly in tropical forests than it does in temperate ones13. We also found that interspecific variation in CNDD, which might attenuate its stabilizing effect on species diversity14,15, was high but not significantly different across latitudes. Although the consequences of these patterns for latitudinal diversity gradients are difficult to evaluate, we speculate that a more effective regulation of population abundances could translate into greater stabilization of tropical tree communities and thus contribute to the high local diversity of tropical forests

Major axes of variation in tree demography across global forests

The future trajectory of global forests is closely intertwined with tree demography, and a major fundamental goal in ecology is to understand the key mechanisms governing spatio-temporal patterns in tree population dynamics. While previous research has made substantial progress in identifying the mechanisms individually, their relative importance among forests remains unclear mainly due to practical limitations. One approach to overcome these limitations is to group mechanisms according to their shared effects on the variability of tree vital rates and quantify patterns therein. We developed a conceptual and statistical framework (variance partitioning of Bayesian multilevel models) that attributes the variability in tree growth, mortality, and recruitment to variation in species, space, and time, and their interactions – categories we refer to as organising principles (OPs). We applied the framework to data from 21 forest plots covering more than 2.9 million trees of approximately 6500 species. We found that differences among species, the species OP, proved a major source of variability in tree vital rates, explaining 28–33% of demographic variance alone, and 14–17% in interaction with space, totalling 40–43%. Our results support the hypothesis that the range of vital rates is similar across global forests. However, the average variability among species declined with species richness, indicating that diverse forests featured smaller interspecific differences in vital rates. Moreover, decomposing the variance in vital rates into the proposed OPs showed the importance of unexplained variability, which includes individual variation, in tree demography. A focus on how demographic variance is organized in forests can facilitate the construction of more targeted models with clearer expectations of which covariates might drive a vital rate. This study therefore highlights the most promising avenues for future research, both in terms of understanding the relative contributions of groups of mechanisms to forest demography and diversity, and for improving projections of forest ecosystems

Comparative antioxidant and anti-inflammatory activity of different extracts of centella asiatica (L.) urban and its active compounds, asiaticoside and madecassoside.

The potential of Centella asiatica (CA) as an antioxidant and anti-inflammatory agent has been well described. However the extraction method which gives the best yield is debatable. In this study, we evaluated three different methods of extractions and compared the extracts in terms of antioxidant, anti-inflammatory activities as well as the contents of its bioactive compounds, asiaticoside and madecassoside. Centella asiatica was extracted using ethanol, methanol and aqueous extraction methods. The extracts were then measured for their phenolic contents using Folin-Ciocalteu reagent. Asiaticoside and madecassoside were determined using HPLC. Antioxidant activity was measured using the 2,2-diphenyl-1-picrylhydrazyl (DHPP) and ferric reducing antioxidant power (FRAP) assays. Anti-inflammatory activities were determined by the ability of the extracts to inhibit the inflammatory pathway enzyme, COX-1 and COX-2 as well as their ability to protect fibroblasts against 12-O-tetradecanoylphorbol-13-acetate (TPA) -induced production of prostaglandin E2 (PGE2). Results showed that the level of phenolic constituents, asiaticoside and madecassoside were highest in the ethanol, followed by methanol and then aqueous extracts (17.76 g/100g, 15.52 g/100g, 13.16 g/100g for phenolics, 42.86 mg/g, 36.37 mg/g, 2.82 mg/g for asiaticoside and 18.66 mg/g, 15.87 mg/g, 3.75 mg/g for madecassoside respectively. All extracts showed considerable antioxidant activity compared to the positive controls. The extracts, asiaticosside and madecassoside inhibited both COX-1 and COX-2 and suppressed the TPA-induced production of PGE2. The ethanol and methanol extracts were stronger COX inhibitors and more potent suppressor of PGE2 formation than aqueous extract. Thus although the aqueous extract showed higher antioxidant potential, in terms of anti-inflammatory activities, the hydrophobic solvents, ethanol and methanol, proved to be the better extraction method for Centella asiatica

Gamma-Tocotrienol Pretreatment Reduces DNA Damage in Lymphocytes of Normal Subjects and Patients with Down&apos;s Syndrome

Abstract The degeneration process associated with Down syndrome (DS) has been partly attributed to the excess hydrogen peroxide formation as a result of excess expression of SOD gene. The increased production of hydroxyl radicals result in damage to macromolecules including the DNA. In this study we evaluated the effect of gamma-tocotrienol (GTT), a subfamily of vitamin E, on DNA damage as measured by the single gel electrophoresis (otherwise known as the comet assay) in lymphocytes of normal and DS subjects. We also studied whether gamma-tocotrienol can reduce DNA damage when the DNA repair phase of the cell cycle is inhibited with caffeine. Blood samples were taken from 11 normal and 8 DS children aged 1-7 years old. The lymphocytes were harvested and then cultured in RPMI folate free medium for 72 h before treatment with 20 uM GTT or 5 mM caffeine. For the study on gamma-tocotrienol pretreatment on caffeine treated cells, the lymphocytes were incubated with GTT for 2 h before the addition of caffeine into the culture medium. Results showed that GTT significantly reduced basal DNA damage as well as when DNA repair was inhibited in lymphocytes taken from DS and normal subjects suggesting a potential role of GTT in the treatment and management of DS patients