Chronically and acutely exercised rats: biomarkers of oxidative stress and endogenous antioxidants.

The responses to oxidative stress induced by chronic exercise (8-wk treadmill running) or acute exercise (treadmill running to exhaustion) were investigated in the brain, liver, heart, kidney, and muscles of rats. Various biomarkers of oxidative stress were measured, namely, lipid peroxidation [malondialdehyde (MDA)], protein oxidation (protein carbonyl levels and glutamine synthetase activity), oxidative DNA damage (8-hydroxy-2'-deoxyguanosine), and endogenous antioxidants (ascorbic acid, alpha-tocopherol, glutathione, ubiquinone, ubiquinol, and cysteine). The predominant changes are in MDA, ascorbic acid, glutathione, cysteine, and cystine. The mitochondrial fraction of brain and liver showed oxidative changes as assayed by MDA similar to those of the tissue homogenate. Our results show that the responses of the brain to oxidative stress by acute or chronic exercise are quite different from those in the liver, heart, fast muscle, and slow muscle; oxidative stress by acute or chronic exercise elicits different responses depending on the organ tissue type and its endogenous antioxidant levels.     

The hybrid-cluster protein ('prismane protein') from Escherichia coli. Characterization of the hybrid-cluster protein, redox properties of the [2Fe-2S] and [4Fe-2S-2O] clusters and identification of an associated NADH oxidoreductase containing FAD and [2Fe-2S].

Hybrid-cluster proteins ('prismane proteins') have previously been isolated and characterized from strictly anaerobic sulfate-reducing bacteria. These proteins contain two types of Fe/S clusters unique in biological systems: a [4Fe-4S] cubane cluster with spin-admixed S = 3/2 ground-state paramagnetism and a novel type of hybrid [4Fe-2S-2O] cluster, which can attain four redox states. Genomic sequencing reveals that genes encoding putative hybrid-cluster proteins are present in a range of bacterial and archaeal species. In this paper we describe the isolation and spectroscopic characterization of the hybrid-cluster protein from Escherichia coli. EPR spectroscopy shows the presence of a hybrid cluster in the E. coli protein with characteristics similar to those in the proteins of anaerobic sulfate reducers. EPR spectra of the reduced E. coli hybrid-cluster protein, however, give evidence for the presence of a [2Fe-2S] cluster instead of a [4Fe-4S] cluster. The hcp gene encoding the hybrid-cluster protein in E. coli and other facultative anaerobes occurs, in contrast with hcp genes in obligate anaerobic bacteria and archaea, in a small operon with a gene encoding a putative NADH oxidoreductase. This NADH oxidoreductase was also isolated and shown to contain FAD and a [2Fe-2S] cluster as cofactors. It catalysed the reduction of the hybrid-cluster protein with NADH as an electron donor. Midpoint potentials (25 degrees C, pH 7.5) for the Fe/S clusters in both proteins indicate that electrons derived from the oxidation of NADH (Em NADH/NAD+ couple: -320 mV) are transferred along the [2Fe-2S] cluster of the NADH oxidoreductase (Em = -220 mV) and the [2Fe-2S] cluster of the hybrid-cluster protein (Em = -35 mV) to the hybrid cluster (Em = -50, +85 and +365 mV for the three redox transitions). The physiological function of the hybrid-cluster protein has not yet been elucidated. The protein is only detected in the facultative anaerobes E. coli and Morganella morganii after cultivation under anaerobic conditions in the presence of nitrate or nitrite, suggesting a role in nitrate-and/or nitrite respiration.     

Strategies providing success in a variable habitat: II. Ecophysiology of photosynthesis of Cladophora glomerata

Cladophora glomerata (L.) Kütz. is the dominant filamentous algae of the river Ilm, Thuringia, Germany. For most of the year it can be found at open as well as at shaded sites. Photosynthetic acclimation of C. glomerata to different light intensities was detected by chlorophyll fluorescence measurements and pigment analysis. Cladophora glomerata from highlight sites showed decreased values of efficiency of open photosystem II (F_v/F_m) as compared with C. glomerata from low‐light sites. Winter populations revealed higher F_v/F_m values than summer populations. A light‐induced decrease in efficiency of the closed photosystem II was observed at increasing irradiance intensities. The decrease was higher in C. glomerata from shaded sites compared with plants from open sites. Differences in the photosynthetic electron transport rate of different populations of C. glomerata were shown by photosynthesis–irradiance curves. Summer populations from high‐light sites yielded higher maximum electron transport rates than plants from low‐light sites, whereas winter populations exhibited significantly decreased values compared with the summer populations. Results of the analysis of photosynthetic pigments corresponded with data from chlorophyll fluorescence measurements. In addition to these long‐term acclimation effects, C. glomerata expressed its ability to cope with rapid changes in the light environment by the de‐epoxidation of violaxanthin during exposure to high light intensities.     

Heat stress reduces the contribution of diazotrophs to coral holobiont nitrogen cycling

Efficient nutrient cycling in the coral-algal symbiosis requires constant but limited nitrogen availability. Coral-associated diazotrophs, i.e., prokaryotes capable of fixing dinitrogen, may thus support productivity in a stable coral-algal symbiosis but could contribute to its breakdown when overstimulated. However, the effects of environmental conditions on diazotroph communities and their interaction with other members of the coral holobiont remain poorly understood. Here we assessed the effects of heat stress on diazotroph diversity and their contribution to holobiont nutrient cycling in the reef-building coral Stylophora pistillata from the central Red Sea. In a stable symbiotic state, we found that nitrogen fixation by coral-associated diazotrophs constitutes a source of nitrogen to the algal symbionts. Heat stress caused an increase in nitrogen fixation concomitant with a change in diazotroph communities. Yet, this additional fixed nitrogen was not assimilated by the coral tissue or the algal symbionts. We conclude that although diazotrophs may support coral holobiont functioning under low nitrogen availability, altered nutrient cycling during heat stress abates the dependence of the coral host and its algal symbionts on diazotroph-derived nitrogen. Consequently, the role of nitrogen fixation in the coral holobiont is strongly dependent on its nutritional status and varies dynamically with environmental conditions.Subject terms: Microbial ecology, Climate-change ecology     

Viral Protein Synthesis in Bacteriophage φ29-Infected Bacillus subtilis

Twenty-three (14)C-labeled phage phi29-specific proteins in lysates of UV-irradiated Bacillus subtilis have been resolved by sodium dodecyl sulfate polyacrylamide gel electrophoresis and identified by autoradiography. Included in this group of proteins are the six major structural proteins of the virion. Analysis of the temporal sequence of viral protein synthesis indicates that three groups of proteins can be identified by time of appearance, beginning at 2 to 4, 4 to 6, or 8 to 10 min after infection, respectively. These proteins account for approximately 90% of the coding capacity of the phi29 genome.     

Development, preparation, and testing of VAQTA®, a highly purified hepatitis A vaccine

Manufacture of VAQTA^®, an inactivated hepatitis A vaccine, uses state-of-the-art technologies in cell culture and bioprocessing science, which have made it possible to routinely produce the vaccine at manufacturing scale. VAQTA^® consists of an attenuated strain of hepatitis A virus that is highly purified and formaldehyde-inactivated, then formulated with an aluminum hydroxide adjuvant. Process development and scale-up have resulted in a well-characterized vaccine manufacturing process with appropriate in-process controls to assure consistent performance, and a reproducible, well-defined product. Results are presented from a series of manufacturing demonstration lots to show consistency, as well as comparability to clinical lots prepared at an earlier stage in development.