Forest-stream linkages: effects of terrestrial invertebrate input and light on diet and growth of brown trout (Salmo trutta) in a boreal forest stream

Subsidies of energy and material from the riparian zone have large impacts on recipient stream habitats. Human-induced changes, such as deforestation, may profoundly affect these pathways. However, the strength of individual factors on stream ecosystems is poorly understood since the factors involved often interact in complex ways. We isolated two of these factors, manipulating the flux of terrestrial input and the intensity of light in a 2×2 factorial design, where we followed the growth and diet of two size-classes of brown trout (Salmo trutta) and the development of periphyton, grazer macroinvertebrates, terrestrial invertebrate inputs, and drift in twelve 20 m long enclosed stream reaches in a five-month-long experiment in a boreal coniferous forest stream. We found that light intensity, which was artificially increased 2.5 times above ambient levels, had an effect on grazer density, but no detectable effect on chlorophyll a biomass. We also found a seasonal effect on the amount of drift and that the reduction of terrestrial prey input, accomplished by covering enclosures with transparent plastic, had a negative impact on the amount of terrestrial invertebrates in the drift. Further, trout growth was strongly seasonal and followed the same pattern as drift biomass, and the reduction of terrestrial prey input had a negative effect on trout growth. Diet analysis was consistent with growth differences, showing that trout in open enclosures consumed relatively more terrestrial prey in summer than trout living in covered enclosures. We also predicted ontogenetic differences in the diet and growth of old and young trout, where we expected old fish to be more affected by the terrestrial prey reduction, but we found little evidence of ontogenetic differences. Overall, our results showed that reduced terrestrial prey inputs, as would be expected from forest harvesting, shaped differences in the growth and diet of the top predator, brown trout.     

Sequestration of G3BP coupled with efficient translation inhibits stress granules in Semliki Forest virus infection

Dynamic, mRNA-containing stress granules (SGs) form in the cytoplasm of cells under environmental stresses, including viral infection. Many viruses appear to employ mechanisms to disrupt the formation of SGs on their mRNAs, suggesting that they represent a cellular defense against infection. Here, we report that early in Semliki Forest virus infection, the C-terminal domain of the viral nonstructural protein 3 (nsP3) forms a complex with Ras-GAP SH3-domain–binding protein (G3BP) and sequesters it into viral RNA replication complexes in a manner that inhibits the formation of SGs on viral mRNAs. A viral mutant carrying a C-terminal truncation of nsP3 induces more persistent SGs and is attenuated for propagation in cell culture. Of importance, we also show that the efficient translation of viral mRNAs containing a translation enhancer sequence also contributes to the disassembly of SGs in infected cells. Furthermore, we show that the nsP3/G3BP interaction also blocks SGs induced by other stresses than virus infection. This is one of few described viral mechanisms for SG disruption and underlines the role of SGs in antiviral defense.     

逆转录套式PCR检测粪便样本中的SARS冠状病毒

为了观察SARS冠状病毒在SARS患者粪便中的存在规律,建立了检测SARS冠状病毒RNA的逆转录-聚合酶链反应(RT-PCR)方法,并应用该方法检测了241份SARS患者粪便样本。部分PCR产物应用测序技术进行验证。RT-PCR的灵敏度为10^-10稀释度的病毒原液(原液为10^8TCID50／ml)。241份粪便样本的总体检出率为24．1％(58／241),其中发病后的前10d和20d的检出率均为50．0％。随着发病时间的延长,阳性检出率呈下降趋势。应用RT-PCR从粪便中检测SARS冠状病毒是可行的,在发病50d以后仍有17．0％左右的阳性检出率,提示SARS恢复期患者具有排毒的可能性,给后续的卫生防疫措施提供了一定的参考数据。     

Caspase与神经系统疾病

近年来,细胞凋亡发生机制的研究已取得众多进展。研究表明,许多神经系统疾病与caspase家族有着密切联系。现将细胞凋亡的最新研究结果及其与神经系统疾病的关系,尤其是caspase家族在神经系统疾病中的主导地位作简单综述,希望由此了解神经元细胞凋亡的内在机制并达到治疗目的。     

The role of sampling effort,taxonomical resolution and abundance weight in multivariate comparison of stream dwelling caddisfly assemblages collected from riffle and pool habitats

We examined how the sample representativeness of a single assemblage and the separation of two assemblages can be improved by finding appropriate combinations of sampling effort, taxonomical resolution and abundance weight for stream dwelling caddisflies as model organisms. We found that these parameters strongly influenced the outcome of multivariate analyses both individually and when considered jointly. This is the first study to show that sample representativeness of an assemblage can decrease with increasing sampling effort. We assume that the turnover rate of the assemblage and the rarity of the species are responsible for this phenomenon. We found that the separation of two assemblages can be improved by increasing sampling effort and applying abundance data. Further, we observed that the effect of taxonomical resolution on the separation of ecological assemblages was highly context-dependent. Decreased taxonomical resolution, i.e. changing from species to genus or to family, did not decrease, or even more increased the separation of assemblages. In sum, this study demonstrates the importance of the careful selection of sampling, laboratory and data processing related factors (i.e. sampling effort, taxonomical resolution, abundance weight) in the multivariate comparison of assemblages.     

Irisin inhibits high glucose‐induced endothelial‐to‐mesenchymal transition and exerts a dose‐dependent bidirectional effect on diabetic cardiomyopathy

Emerging evidence indicates that irisin provides beneficial effects in diabetes. However, whether irisin influences the development of diabetic cardiomyopathy (DCM) remains unclear. Therefore, we investigated the potential role and mechanism of action of irisin in diabetes‐induced myocardial dysfunction in mice. Type 1 diabetes was induced in mice by injecting streptozotocin, and the diabetic mice were administered recombinant r‐irisin (low or high dose: 0.5 or 1.5 μg/g body weight/day, I.P.) or PBS for 16 weeks. Irisin treatment did not alter blood glucose levels in the diabetic mice. However, the results of echocardiographical and histopathological assays indicated that low‐dose irisin treatment alleviated cardiac fibrosis and left ventricular function in the diabetic mice, whereas high‐dose irisin failed to mitigate the ventricular function impairment and increased collagen deposition. The potential mechanism underlying the effect of low‐dose irisin involved irisin‐mediated inhibition of high glucose‐induced endothelial‐to‐mesenchymal transition (EndMT); conversely, high‐dose irisin treatment enhanced high glucose‐induced MMP expression by stimulating MAPK (p38 and ERK) signalling and cardiac fibroblast proliferation and migration. Low ‐ dose irisin alleviated DCM development by inhibiting high glucose‐induced EndMT. By contrast, high‐dose irisin disrupted normal MMP expression and induced cardiac fibroblast proliferation and migration, which results in excess collagen deposition. Thus, irisin can inhibit high glucose‐induced EndMT and exert a dose‐dependent bidirectional effect on DCM.     

Light and electron microscopic histochemical observations on cholinesterase-containing sympathetic nerve fibres in the pineal body of the rat

Synopsis Pineal glands of adult albino rats were examined histochemically using, first, formaldehyde-induced fluorescence to study monoamines and, second, copper thiocholine or copper ferrocyanide methods to study acetylcholinesterase and non-specific cholinesterase by light and electron microscopy. Cholinesterase was determined quantitatively by a constant pH titration assay.Fluorescent and acetylcholinesterase-positive nerve nets formed identical patterns. Nonspecific cholinesterase was observed only in nerve trunks outside the pineal. Bilateral removal of superior cervical ganglia resulted in complete disappearance of fluorescence and acetylcholinesterase from nerve fibres. Electron microscopically, acetylcholinesterase was found on sympathetic axons containing small granular vesicles. Quantitative cholinesterase determinations suggested that the pineal activity was mainly due to acetylcholinesterase. Comparison of the incubation times required for equal histochemical acetylcholinesterase reactions suggested that the activity of the sympathetic nerve fibres in the pineal is of the same order of magnitude as that in the nerve fibres of the iris.