Acute Hypoxemia Does Not Increase the Oxidative Stress in Resting and Contracting Muscle in Humans

In healthy humans sustaining static handgrip at 60% of maximal voluntary contraction (MVC) until exhaustion, we measured the venous blood concentration of reduced ascorbic acid (RAA) and thiobarbituric acid reactive substances (TBARS), respectively, used as markers of the post-exercise oxidative stress and lipid peroxidation. Measurements were conducted in normoxemia, then during a 30-min period of hypoxemia (PaO 2 =56 mmHg) produced by inhalation of an hypoxic gas mixture. Compared to normoxemia, hypoxemia did not significantly modify the resting concentrations of TBARS and RAA, and did not affect the consumption of ascorbic acid after 60% MVC but suppressed the post-exercise TBARS increase. We conclude that acute hypoxemia does not modify the production of oxygen free radicals after strenuous static efforts and even seems to attenuate the lipid peroxidation.     

Ubiquinol and a Coenzyme Q Reducing System Protect Platelet Mitochondrial Function of Transfusional Buffy Coats from Oxidative Stress

The conditions under which Coenzyme Q (CoQ) may protect platelet mitochondrial function of transfusional buffy coats from aging and from induced oxidative stress were investigated. The Pasteur effect, i.e. the enhancement of lactate production after inhibition of mitochondrial respiratory chain, was exploited as a marker of mitochondrial function as it allows to calculate the ratio of mitochondrial ATP to glycolytic ATP. Reduced CoQ 10 improves platelet mitochondrial function of transfusional buffy coats and protects the cells from induced oxidative stress. Oxidized CoQ is usually less effective, despite the presence, shown for the first time in this study, of quinone reductase activities in the platelet plasma membranes. The addition of a CoQ reducing system to platelets is effective in enhancing the protection of platelet mitochondrial function from the oxidative stress. The results support on one hand a possibility of protection of mitochondrial function in aging by exogenous CoQ intake, on the other a possible application in protection of transfusional buffy coats from storage conditions and oxidative deterioration.     

Acclimation responses to temperature vary with vertical stratification: implications for vulnerability of soil‐dwelling species to extreme temperature events

The occurrence of summer heat waves is predicted to increase in amplitude and frequency in the near future, but the consequences of such extreme events are largely unknown, especially for belowground organisms. Soil organisms usually exhibit strong vertical stratification, resulting in more frequent exposure to extreme temperatures for surface‐dwelling species than for soil‐dwelling species. Therefore soil‐dwelling species are expected to have poor acclimation responses to cope with temperature changes. We used five species of surface‐dwelling and four species of soil‐dwelling Collembola that habituate different depths in the soil. We tested for differences in tolerance to extreme temperatures after acclimation to warm and cold conditions. We also tested for differences in acclimation of the underlying physiology by looking at changes in membrane lipid composition. Chill coma recovery time, heat knockdown time and fatty acid profiles were determined after 1 week of acclimation to either 5 or 20 °C. Our results showed that surface‐dwelling Collembola better maintained increased heat tolerance across acclimation temperatures, but no such response was found for cold tolerance. Concordantly, four of the five surface‐dwelling Collembola showed up to fourfold changes in relative abundance of fatty acids after 1 week of acclimation, whereas none of the soil‐dwelling species showed a significant adjustment in fatty acid composition. Strong physiological responses to temperature fluctuations may have become redundant in soil‐dwelling species due to the relative thermal stability of their subterranean habitat. Based on the results of the four species studied, we expect that unless soil‐dwelling species can temporarily retreat to avoid extreme temperatures, the predicted increase in heat waves under climatic change renders these soil‐dwelling species more vulnerable to extinction than species with better physiological capabilities. Being able to act under a larger thermal range is probably costly and could reduce maximum performance at the optimal temperature.     

Development of rapid and highly sensitive HSPA1A promoter-driven luciferase reporter system for assessing oxidative stress associated with low-dose photodynamic therapy

Photodynamic therapy (PDT) is a regulatory-approved modality for treating a variety of malignant tumors. It induces tumor tissue damage via photosensitizer-mediated oxidative cytotoxicity. The heat shock protein 70 (HSP70-1) is a stress protein encoded by the HSPA1A gene and is significantly induced by oxidative stress associated with PDT. The aim of this study was to identify the functional region of the HSPA1A promoter that responds to PDT-induced oxidative stress and uses the stress responsiveness of HSPA1A expression to establish a rapid and cost-effective photocytotoxic assessment bioassay to evaluate the photodynamic potential of photosensitizers. By constructing luciferase vectors with a variety of hspa1a promoter fractions and examining their relative luciferase activity, we demonstrated that the DNA sequence from −218 to +87 of the HSPA1A gene could be used as a functional promoter to detect the PDT-induced oxidative stress. The maximal relative luciferase activity level of HSPA1A (HSP70-1) induced by hypericin-PDT was nearly nine times that of the control. Our results suggest that the novel reporter gene assay using a functional region of the HSP70A1A promoter has significant advantages for the detection of photoactivity in terms of both speed and sensitivity, when compared with a cell viability test based on ATP quantification and ROS levels. Furthermore, phthalocyanine zinc and methylene blue both induced significantly elevated levels of relative luciferase activity in a dose-dependent manner.     

Caractérisation des peuplements de macroinvertébrés benthiques à l’aide de la carte auto-organisatrice (SOM)

Macrobenthic organisms are much used nowadays as bio-indicators for their ability to reflect different disturbances of aquatic ecosystems. However, they have never been used to assess the ecological status of the lagoons of Benin. The current study aims at revealing the ecological state of the lagoon of Porto-Novo through the study of changes in the settlement of benthic organisms collected in this lagoon. The sampling was carried out from July 2007 to June 2009 on a frequency of four seasons of collection per year. The self-organizing map (SOM) of Kohonen has been used for various patterns of distribution of collected organisms. A discriminant analysis (AFD) has allowed the identification of the parameters that govern the patterns observed in this environment. Four groups of macrobenthic communities emerged that were well predicted (75%). The distribution of benthic macro invertebrates of this lagoon is therefore zonal, seasonal and discriminated by variables of mineralization and sediment grain size. The difference in taxonomic richness corresponds to environmental conditions of stations appearing more or less stable and highlighting a gradient of the stress on organisms. Places with unstable conditions are affected by human activities due to their proximity to homes that are enriched in organic matter. These places are full of polluted-tolerant species such as the Gastropods Potamididae, Cirratulidae Polychaetes, Diptera Chironomidae and Oligochaeta. The macrobenthic fauna, which is well differentiated in the groups, is then subjected to human disturbance.     

An in vivo and in silico analysis of novel variation in TMBIM6 gene affecting cardiopulmonary traits of Indian goats

Transmembrane Bax Inhibitor Motif-containing 6 (TMBIM6) gene acts as calcium leak channel and negatively regulates autophagy and autophagosome formation. The TMBIM6 gene was amplified and searched for variation in three different goat populations (i.e. Black Bengal, Ganjam and Raighar) of Odisha state of the India. The result indicated two substitutions i.e. 55th position (C55T) and 95th position (C95A) in the amplified region of the gene resulting in change of amino acids (Leu > Phe and Thr > Asn). The identified SNPs were combined to form haplotypes and animals were grouped accordingly. Structural analysis showed minor changes (5%) in between mutant and wild TMBIM6 protein structures. However, any functional variation could not be identified with respect to the calcium ligand and open pore state. But an alteration of calcium binding site was found. The binding interaction of calcium with the TMBIM6 protein was hydrophobic in nature in closed state whereas hydrophilic in open pore stage. The stress releasing function was the result of calcium leakage controlled by amino acids coded by exon 4 and exon 5 regions of TMBIM6 gene. The effect of breed and haplotype on cardiopulmonary traits was studied. The data on cardiopulmonary traits of body i.e. rectal temperature, skin temperature, heart rate and respiration rate were recorded when ambient temperature usually remained the highest. The statistical analysis showed, significant difference in rectal temperature, skin temperature and respiration rate among these goat populations. The haplotypes (CC and TA) were found to have a significant (P < 0.05) effect on rectal temperature, skin temperature and respiration rate. However, any such significant effect could not be identified in recorded heart rate. The objective of the present study to identify the genetic variations in TMBIM6 gene having significant effect on cardiopulmonary traits which can be further uses as the molecular markers to improve heat tolerance mechanism in goats.