Passive stretch reduces calpain activity through nitric oxide pathway in unloaded soleus muscles

Unloading in spaceflight or long-term bed rest induces to pronounced atrophy of anti-gravity skeletal muscles. Passive stretch partially resists unloading-induced atrophy of skeletal muscle, but the mechanism remains elusive. The aims of this study were to investigate the hypotheses that stretch tension might increase protein level of neuronal nitric oxide synthase (nNOS) in unloaded skeletal muscle, and then nNOS-derived NO alleviated atrophy of skeletal muscle by inhibiting calpain activity. The tail-suspended rats were used to unload rat hindlimbs for 2 weeks, at the same time, left soleus muscle was stretched by applying a plaster cast to fix the ankle at 35° dorsiflexion. Stretch partially resisted atrophy and inhibited the decreased protein level and activity of nNOS in unloaded soleus muscles. Unloading increased frequency of calcium sparks and elevated intracellular resting and caffeine-induced Ca(2+) concentration ([Ca(2+)]i) in unloaded soleus muscle fibers. Stretch reduced frequency of calcium sparks and restored intracellular resting and caffeine-induced Ca(2+) concentration to control levels in unloaded soleus muscle fibers. The increased protein level and activity of calpain as well as the higher degradation of desmin induced by unloading were inhibited by stretch in soleus muscles. In conclusion, these results suggest that stretch can preserve the stability of sarcoplasmic reticulum Ca(2+) release channels which prevents the elevated [Ca(2+)]i by means of keeping nNOS activity, and then the enhanced protein level and activity of calpain return to control levels in unloaded soleus muscles. Therefore, stretch can resist in part atrophy of unloaded soleus muscles.     

Protective Effects of Salvianolic Acid B on Schwann Cells Apoptosis Induced by High Glucose

Diabetic peripheral neuropathy (DPN) is one of the most common and debilitating microvascular complications of diabetes, and there is no effective therapy for the prevention or treatment of DPN. Oxidative stress triggers several pathways of injury and may be the unifying factor of hyperglycemia. The aim of this study was to investigate protective effect of Salvianolic acid B (Sal B) on the high glucose (HG)-induced oxidative stress-induced mitochondrial pathway activation and Schwann cells (SCs) apoptosis in vitro. We found that Sal B inhibited the HG-induced oxidative stress by reducing ROS and 8-hydroxy-2-deoxy Guanosine (8-OHdG) production, and mitochondrial depolarization and apoptosis in SCs in a dose-dependent manner. Furthermore, Sal B down-regulated the HG-mediated Bax expression and AIF nuclear translocation and the release of cytochrome c, but up-regulated the HG-induced BcL-2 expression in SCs. In addition, Sal B attenuated the HG-induced activation of caspase 3 and 9 and minimized the cleavage of PARP in SCs. Our results indicated that Sal B antagonized the HG-induced oxidative stress, activation of the mitochondrial pathway and apoptosis in SCs.     

Distribution and Feeding Behavior of Omorgus suberosus (Coleoptera: Trogidae) in Lepidochelys olivacea Turtle Nests

Omorgus suberosus (Fabricius, 1775) has been identified as a potential predator of the eggs of the turtle Lepidochelys olivacea (Eschscholtz, 1829) on one of the main turtle nesting beaches in the world, La Escobilla in Oaxaca, Mexico. This study presents an analysis of the spatio–temporal distribution of the beetle on this beach (in areas of high and low density of L. olivacea nests over two arrival seasons) and an evaluation, under laboratory conditions, of the probability of damage to the turtle eggs by this beetle. O. suberosus adults and larvae exhibited an aggregated pattern at both turtle nest densities; however, aggregation was greater in areas of low nest density, where we found the highest proportion of damaged eggs. Also, there were fluctuations in the temporal distribution of the adult beetles following the arrival of the turtles on the beach. Under laboratory conditions, the beetles quickly damaged both dead eggs and a mixture of live and dead eggs, but were found to consume live eggs more slowly. This suggests that O. suberosus may be recycling organic material; however, its consumption of live eggs may be sufficient in some cases to interrupt the incubation period of the turtle. We intend to apply these results when making decisions regarding the L. olivacea nests on La Escobilla Beach, one of the most important sites for the conservation of this species.     

Rapid intracellular alkalinization of Saccharomyces cerevisiae MATa cells in response to α-factor requires the CDC25 gene product

The α-factor mating pheromone induces a transient intracellular alkalinizatin of MATa cells within minutes after exposure to the pheromone, and is the earliest biochemical event that can be identified subsequent to the exposure. Dissipation of the pheromone induced pH gradient, using 2,4-dinotrophenol or sodium orthovanadate, does not inhibit the biological response of the yeast to the pheromone such as mating and ‘schmoo’ formation. These findings suggest that the pheromone mediated pH change per se is not a part of the transmembrane signalling but rather the consequence of a biochemical reaction triggered by the α-pheromone interaction with its receptor and may have a permissive effect on the pheromonal response. The cdc25^ts mutation causes MATa cells to become nonresponsive to α-factor subsequent to a shift to the restrictive temperature, suggesting that the CDC25 gene product participates in the pheromone response pathway.     

The Na+-specific interaction between the LysR-type regulator, NhaR, and the nhaA gene encoding the Na+/H+ antiporter of Escherichia coli.

We used partially purified NhaR and a highly purified His-tagged NhaR derivative to identify the cis-regulatory sequences of nhaA recognized by NhaR and to study the specific effect of Na+ on this interaction. Gel retardation assay with DNase I footprinting analysis showed that NhaR binds a region of nhaA which spans 92 bp and contains three copies of the conserved LysR-binding motif. Na+, up to 100 mM, had no effect on the binding of NhaR to nhaA. The dimethylsulfate methylation protection assay in vivo and in vitro, showed that bases G-92, G-60, G-29 and A-24 form direct contacts with NhaR; in the absence of added Na+ in vivo, these bases were protected but became exposed to methylation in a DeltanhaR strain; accordingly, these bases were protected in vitro by the purified His-tagged NhaR. 100 mM Na+, but not K+, removed the protection of G-60 conferred by His-tagged NhaR in vitro. Exposure of intact cells to 100 mM Na+, but not K+, exposed G-60. The maximal effect of Na+ in vitro was observed at 20 mM and was pH dependent, vanishing below pH 7.5. In contrast to G-60, G-92 was exposed to methylation by the ion only in vivo, suggesting a requirement for another factor existing only in vivo for this interaction. We suggest that NhaR is both sensor and transducer of the Na+ signal and that it regulates nhaA expression by undergoing a conformational change upon Na+ binding which modifies the NhaR-nhaA contact points.     

Trophic positioning and microphytobenthic carbon uptake of biofilm‐dwelling meiofauna in a temperate river

1. δ¹³C and δ¹⁵N stable isotope signatures combined with an in situ microphytobenthic ¹³C labelling experiment were performed on epilithic biofilms of a large temperate river (the Garonne, France) to infer the trophic positioning of biofilm‐dwelling meiofauna and their uptake of microphytobenthic carbon. 2. Chironomidae larvae and Chromadorina spp. nematodes rapidly incorporated freshly produced microphytobenthic carbon in contrast to Rhyacophilidae larvae and Naididae oligochaetes. Quantitatively, macrofaunal Chironomidae incorporated more microphytobenthic carbon per day than did meiofauna. Moreover, Chironomidae seemed more involved in the spatial export of microphytobenthic carbon than nematodes. 3. Rhyacophilidae larvae were predators feeding on large meiofauna (Naididae and Chironomidae) but not on nematodes. Naididae oligochaetes primarily gained their carbon from allochthonous and/or microbial‐loop recycled sources. 4. A rapid and significant loss of labelled microphytobenthic carbon was observed. Feeding activity of biofilm‐dwelling invertebrates seemed not to be primarily involved in this loss.