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Oxidative Challenge (oxidative + challenge)

Distribution by Scientific Domains

Life Sciences	60%
Medical Sciences	40%

Selected Abstracts

Antioxidant and inflammatory responses of healthy horses and horses affected by recurrent airway obstruction to inhaled ozone

EQUINE VETERINARY JOURNAL, Issue 3 2005
C. M. DEATON
Summary Reasons for performing study: Inhaled ozone can induce oxidative injury and airway inflammation. Horses affected by recurrent airway obstruction (RAO) have a decreased pulmonary antioxidant capacity, which may render them more susceptible to oxidative challenge. It is currently unknown whether RAO-affected horses are more susceptible to oxidative stress than those unaffected by RAO. Objectives: To determine whether ozone exposure induces greater oxidative stress and airway inflammation in RAO-affected horses in remission than in healthy horses. Methods: Seven healthy control horses and 7 RAO-affected horses were exposed to 0.8 ppm ozone for 2 h at rest. Results: At baseline, bronchoalveolar lavage fluid (BALF) ascorbic acid concentrations were lower in RAO-affected horses than healthy controls. Ozone appeared to preferentially oxidise glutathione rather than ascorbic acid 6 h after exposure. Individual healthy and RAO-affected horses demonstrated oxidation of BALF glutathione after ozone exposure. Overall, RAO-affected horses did not demonstrate increased oxidative stress following ozone exposure, compared with healthy horses. Ozone did not induce significant airway inflammation in either group. Conclusions: RAO-affected horses in remission are not more sensitive to ozone despite a decreased pulmonary antioxidant capacity. Sensitivity to ozone appears to be independent of initial pulmonary antioxidant status. Potential relevance: Horses with high susceptibility to oxidative stress may benefit from antioxidant supplementation. [source]

RpoS involvement and requirement for exogenous nutrient for osmotically induced cross protection in Vibrio vulnificus

FEMS MICROBIOLOGY ECOLOGY, Issue 3 2005
Thomas M. Rosche
Abstract Vibrio vulnificus is an opportunistic human pathogen which is the causative agent of food-borne disease and wound infections. V. vulnificus is able to adapt to a variety of potentially stressful environmental changes, such as osmotic, nutrient, and temperature variations in estuarine environments, as well as oxidative, osmotic, and acidity differences following infection of a human host. After exposure to sub-lethal levels of a particular environmental stress, many bacteria become resistant to unrelated stresses, a phenomenon termed cross protection. In this study, we examined the ability of osmotic shock to cross protect V. vulnificus to high temperature as well as oxidative stress. Log phase cells of V. vulnificus strain C7184o were cross protected by prior osmotic shock to both heat and oxidative challenge, but only when exogenous nutrient was present during the osmotic upshift. Further, and unlike other bacteria, nutrient starvation alone did not result in cross protection against either stress. When small amounts of nutrient were present during osmotic shock, cross protection to an otherwise lethal heat challenge developed extremely rapidly, with significant protection seen within 10 min. Cross protection to oxidative stress was slower to develop, requiring several hours. Although stationary phase alone conferred some cross protection to heat and oxidative stress, the alternate sigma factor RpoS was required for complete cross protection of log phase cells to oxidative stress but not for resistance to heat challenge. Together these findings suggest that the cross protective response in V. vulnificus is complex and appears to involve multiple mechanisms. [source]

The oxidation handicap hypothesis and the carotenoid allocation trade-off

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2008
C. ALONSO-ALVAREZ
Abstract The oxidation handicap hypothesis proposes that testosterone mediates the trade-off between the expression of secondary sexual traits and the fight against free radicals. Coloured traits controlled by testosterone can be produced by carotenoid pigments (yellow,orange,red traits), but carotenoids also help to quench free radicals. Recently, it has been shown that testosterone increases the amount of circulating carotenoids in birds. Here, a testosterone-mediated trade-off in the carotenoid allocation between colour expression and the fight against oxidative stress is proposed. Male red-legged partridges were treated with testosterone, anti-androgens or manipulated as controls. Testosterone-treated males maintained the highest circulating carotenoid levels, but showed the palest red traits and no evidence of oxidative damage. Increased levels of a key intracellular antioxidant (i.e. glutathione) indicated that an oxidative challenge was in fact induced but controlled. The trade-off was apparently solved by reducing redness, allowing increased carotenoid availability, which could have contributed to buffer oxidative stress. [source]

Concentration-dependent effect of (,) epicatechin in hypertensive patients

PHYTOTHERAPY RESEARCH, Issue 10 2010
Navneet Kumar
Abstract Non-vitamin polyphenolic compounds are ubiquitous in food plants and therefore potentially present in human plasma in a diet-dependent concentration. The aim of this study was to evaluate the concentration-dependent effect of (,) epicatechin, a polyphenol present in green tea with antioxidant activity, on various biomarkers of oxidative stress. The current study examined the in vitro concentration-dependent (10,4,M to 10,7,M) effects of (,) epicatechin on biomarkers of oxidative stress viz. malondialdehyde (MDA), reduced glutathione (GSH), membrane sulfhydryl (-SH) group and protein carbonyl content in hypertensive patients and normal ones. This effect seems to be due to ability of (,) epicatechin to reduce MDA and protein carbonyl content while increase in GSH and membrane -SH group in hypertensive patients. It can be concluded that (-) epicatechin exerts an antioxidant action inside the cell, responsible for the observed modulation of cellular response to oxidative challenges. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Carotenoids in evolutionary ecology: re-evaluating the antioxidant role

BIOESSAYS, Issue 10 2009
Lorenzo Pérez-Rodríguez
Abstract The antioxidant role of carotenoids in the living organism was proposed as a possible basis for the honesty of carotenoid-based signals. However, recent studies have questioned the relevance of carotenoids as powerful antioxidants in vivo. Current evidence does not seem to support the "antioxidant role" hypothesis, but it does not allow us to reject it either. This paper proposes some steps to solve this controversy, such as taking a dynamic approach to antioxidant responses, designing protocols that expose individuals to oxidative challenges, analyzing tissues other than blood, and obtaining measures of antioxidant capacity and oxidative damage simultaneously. However, it should be considered that, irrespective of their antioxidant potential, carotenoids might still give information on oxidative stress levels if they are particularly sensitive to free radicals. Finally, lumping together the immunostimulatory and antioxidant roles of carotenoids should be avoided as these functions are not necessarily associated. [source]