Assessing population-level variation in the mitochondrial genome of <Emphasis Type="Italic">Euphausia superba</Emphasis> using 454 next-generation sequencing

The Antarctic krill (Euphausia superba Dana 1852) is widely distributed throughout the Southern Ocean, where it provides a key link between primary producers and upper trophic levels and supports a major commercial fishery. Despite its ecological and commercial importance, genetic population structure of the Antarctic krill remains poorly described. In an attempt to illuminate genetic markers for future population and phylogenetic analysis, five E. superba mitogenomes, from samples collected west of the Antarctic Peninsula, were sequenced using new 454 next-generation sequencing techniques. The sequences, of lengths between 13,310 and 13,326 base pairs, were then analyzed in the context of two previously-published near-complete sequences. Sequences revealed relatively well-conserved partial mitochondrial genomes which included complete sequences for 11 of 13 protein-coding genes, 16 of 23 tRNAs, and the large ribosomal subunit. Partial sequences were also recovered for cox1 and the small ribosomal subunit. Sequence analysis suggested that the cox2, nad5, and nad6 genes would be the best candidates for future population genetics analyses, due to their high number of variable sites. Future work to reveal the noncoding control region remains.     

Melatonin: neuritogenesis and neuroprotective effects in crustacean x-organ cells

Melatonin has both neuritogenic and neuroprotective effects in mammalian cell lines such as neuroblastoma cells. The mechanisms of action include receptor-coupled processes, direct binding and modulation of calmodulin and protein kinase C, and direct scavenging of free radicals. While melatonin is produced in invertebrates and has influences on their physiology and behavior, little is known about its mechanisms of action. We studied the influence of melatonin on neuritogenesis in well-differentiated, extensively-arborized crustacean x-organ neurosecretory neurons. Melatonin significantly increased neurite area in the first 24 h of culture. The more physiological concentrations, 1 nM and 1 pM, increased area at 48 h also, whereas the pharmacological 1 μM concentration appeared to have desensitizing effects by this time. Luzindole, a vertebrate melatonin receptor antagonist, had surprising and significant agonist-like effects in these invertebrate cells. Melatonin receptors have not yet been studied in invertebrates. However, the presence of membrane-bound receptors in this population of crustacean neurons is indicated by this study. Melatonin also has significant neuroprotective effects, reversing the inhibition of neuritogenesis by 200 and 500 μM hydrogen peroxide. Because this is at least in part a direct action not requiring a receptor, melatonin's protection from oxidative stress is not surprisingly phylogenetically-conserved.     

Endothelial protection from reperfusion injury by ischemic preconditioning and diazoxide involves a SOD-like anti-O2- mechanism.

Cardiac ischemia/reperfusion leads to coronary endothelial dysfunction, mediated by superoxide anion (O2-), but not hydroxyl radical (*OH). Ischemic preconditioning and mitochondrial ATP-dependent potassium channel opener (diazoxide) protect endothelium in the mechanism involving attenuation of O2- burst at reperfusion. We hypothesize that the endothelial protection involves upregulation of myocardial anty-O2- defense. Langendorff-perfused guinea-pig hearts were subjected to global ischemia/reperfusion (IR) or were preconditioned prior to IR with three cycles of ischemia/reperfusion (IPC) or infusion/washout of 0.5 microM diazoxide. Coronary flow responses to acetylcholine were measures of endothelium-dependent vascular function. Myocardial outflow of O2- and of *OH during reperfusion and myocardial activities of superoxide dismutase (SOD) and catalase were measured. IR impaired acetylcholine response and augmented cardiac O2- and *OH outflow. IPC, diazoxide, and SOD (150 IU/ml) attenuated O2- outflow, increased *OH outflow and protected endothelium. There were no differences in Cu/Zn-SOD, Mn-SOD and catalase activities between sham-perfused and IR hearts and only catalase activity was increased in the IPC hearts. We speculate that: (i) IPC and diazoxide endothelial protection involves activation of some SOD-like anti-O2- mechanism resulting in attenuation of O2- burst and increase in *OH burst, (ii) improved SOD activity might have not been detected because it was confined to a small, although functionally important, enzyme fraction, like that bound to the endothelial glycocalyx.     

The effect of calcium on the production of ethylene and abscisic acid by fungus Fusarium culmorum and by wheat seedlings infected with that pathogen

Wheat seedlings infected and non-infected with Fusarium culmorum were grown on mediums with different content of calcium (0, 2, 4, 8 mM). It was found that the higher the content of calcium in the medium, the greater the amounts of ethylene produced in both non-infected and infected wheat seedlings, whereas the level of ABA in their tissues was decreased. Taking into consideration the fact that ethylene inhibits, whereas ABA stimulates the growth and development of Fusarium culmorum, it may be assumed that the production of ethylene increased under the influence of calcium and the decreased level of ABA in wheat seedlings causes the reduction growth and development of pathogen and as a result it lowers the degree of infection of wheat seedlings by this fungus. Thus, on the base of the obtained results it may be concluded that the inhibiting influence of calcium on injurying the wheat seedlings by Fusarium culmorum may be caused by the influence of this cation on the hormone balance in the plant.     

Crystal structure and functional characterization of selenocysteine-containing glutathione peroxidase 4 suggests an alternative mechanism of peroxide reduction

Glutathione peroxidases (GPX) are anti-oxidative enzymes that reduce organic and inorganic hydroperoxides to the corresponding alcohols at the expense of reduced glutathione. The human genome involves eight GPX genes and five of them encode for selenocysteine-containing enzymes. Among the human GPX-isoforms, GPX4 is unique since it is capable of reducing complex hydroperoxy ester lipids such as hydroperoxy phospholipids and hydroperoxy cholesterolesters. Using a number of genetically modified mouse strains the biological role of GPX4 has comprehensively characterized but the molecular enzymology is less well explored. This lack of knowledge is partly related to the fact that mammalian selenoproteins are not high-level expressed in conventional overexpression systems. To explore the structural and functional properties of human GPX4 we expressed this selenoprotein in a cysteine-auxotrophic E. coli strain using a semi-chemical expression strategy. The recombinant enzyme was purified in mg amounts from the bacterial lysate to electrophoretic homogeneity and characterized with respect to its protein-chemical and enzymatic properties. Its crystal structure was solved at 1.3?Å resolution and the X-ray data indicated a monomeric protein, which contains the catalytic selenium at the redox level of the seleninic acid. These data suggest an alternative reaction mechanism involving three different redox states (selenol, selenenic acid, seleninic acid) of the catalytically active selenocysteine.     

Physiological loading of the mandibular osteosynthesis: development of an improved mandibular load simulator]

Loading conditions physiologically approximating those acting on the normal masticatory system were incorporated into a new mandibular load simulator. Separate tension wires attached to each ramus of the mandible simulated the resultant force vectors of the masticatory musculature. The muscle insertion points were chosen in accordance with the anatomical situation, and the maximum in vivo forces acting on the joint. In a first application, the stability of a 2.4 mm LC-WDCP was compared with that of a 2.7 mm EDCP in plastic mandible models. It was found that under largely physiological loading, the 2.4 mm LC-EDCP exerted a stabilizing effect similar to that of a 2.7 mm EDCP. Although of smaller dimensions, the 2.4 mm LC-EDCP appears to enable an osteosynthesis of similar stability in the treatment of fractures of the mandibular angle.     

Increased ribonucleic Acid polymerase activity associated with chromatin from internodes of dwarf pea plants treated with gibberellic Acid

Gibberellic acid increases the level of RNA polymerase associated with chromatin isolated from expanding internodes of light-grown, dwarf pea plants (Pisum sativum L.), without a detectable increase in the amount of DNA template available.