Differential Mitochondrial Genome Expression of Four Hylid Frog Species under Low-Temperature Stress and Its Relationship with Amphibian Temperature Adaptation.

Extreme weather poses huge challenges for animals that must adapt to wide variations in environmental temperature and, in many cases, it can lead to the local extirpation of populations or even the extinction of an entire species. Previous studies have found that one element of amphibian adaptation to environmental stress involves changes in mitochondrial gene expression at low temperatures. However, to date, comparative studies of gene expression in organisms living at extreme temperatures have focused mainly on nuclear genes. This study sequenced the complete mitochondrial genomes of five Asian hylid frog species: Dryophytes japonicus, D. immaculata, Hyla annectans, H. chinensis and H. zhaopingensis. It compared the phylogenetic relationships within the Hylidae family and explored the association between mitochondrial gene expression and evolutionary adaptations to cold stress. The present results showed that in D. immaculata, transcript levels of 12 out of 13 mitochondria genes were significantly reduced under cold exposure (p < 0.05); hence, we put forward the conjecture that D. immaculata adapts by entering a hibernation state at low temperature. In H. annectans, the transcripts of 10 genes (ND1, ND2, ND3, ND4, ND4L, ND5, ND6, COX1, COX2 and ATP8) were significantly reduced in response to cold exposure, and five mitochondrial genes in H. chinensis (ND1, ND2, ND3, ND4L and ATP6) also showed significantly reduced expression and transcript levels under cold conditions. By contrast, transcript levels of ND2 and ATP6 in H. zhaopingensis were significantly increased at low temperatures, possibly related to the narrow distribution of this species primarily at low latitudes. Indeed, H. zhaopingensis has little ability to adapt to low temperature (4 °C), or maybe to enter into hibernation, and it shows metabolic disorder in the cold. The present study demonstrates that the regulatory trend of mitochondrial gene expression in amphibians is correlated with their ability to adapt to variable climates in extreme environments. These results can predict which species are more likely to undergo extirpation or extinction with climate change and, thereby, provide new ideas for the study of species extinction in highly variable winter climates.

Nine Mitochondrial Genomes of Phasmatodea with Two Novel Mitochondrial Gene Rearrangements and Phylogeny.

The classification of stick and leaf insects (Order Phasmatodea) is flawed at various taxonomic ranks due to a lack of robust phylogenetic relationships and convergent morphological characteristics. In this study, we sequenced nine new mitogenomes that ranged from 15,011 bp to 17,761 bp in length. In the mitogenome of Carausis sp., we found a translocation of trnR and trnA, which can be explained by the tandem duplication/random loss (TDRL) model. In the Stheneboea repudiosa Brunner von Wattenwyl, 1907, a novel mitochondrial structure of 12S rRNA-CR1-trnI-CR2-trnQ-trnM was found for the first time in Phasmatodea. Due to the low homology of CR1 and CR2, we hypothesized that trnI was inverted through recombination and then translocated into the middle of the control region. Control region repeats were frequently detected in the newly sequenced mitogenomes. To explore phylogenetic relationships in Phasmatodea, mtPCGs from 56 Phasmatodean species (composed of 9 stick insects from this study, 31 GenBank data, and 16 data derived from transcriptome splicing) were used for Bayesian inference (BI), and maximum likelihood (ML) analyses. Both analyses supported the monophyly of Lonchodinae and Necrosciinae, but Lonchodidae was polyphyletic. Phasmatidae was monophyletic, and Clitumninae was paraphyletic. Phyllidae was located at the base of Neophasmatodea and formed a sister group with the remaining Neophasmatodea. Bacillidae and Pseudophasmatidae were recovered as a sister group. Heteroptergidae was monophyletic, and the Heteropteryginae sister to the clade (Obriminae + Dataminae) was supported by BI analysis and ML analysis.

Calculation of Thallium's toxicity coefficient in the evaluation of potential ecological risk index: A case study.

As a common pollutive metal element, Tl is very biotoxic. The potential ecological risk index (RI) proposed by Håkanson is one of the commonest methods for evaluation of ecological risk of a metal in sedimentary environment of a water body. According to the calculation principle proposed by Håkanson, the toxicity coefficient of Tl was calculated, and determined as 10 in this paper. In addition, the environmental risk of Tl in the surface sediment of the Beijing-Hangzhou Grand Canal (Zaozhuang Section) was evaluated by RI method, enrichment factor method, etc. The South-to-North Water Diversion Project which benefits four billion people is the largest inter-basin water transfer project in China. The Zaozhuang Section is a significant water conveyance line of this project. We found that the Tl concentrations were 0.46-0.70 µg g-1 with the mean value of 0.61 µg g-1 and were higher than the local background value. The highest contents of Tl occurred in the middle of Zaozhuang section and Tai'erzhuang District, but the enrichment degree of it was much higher in the entrance of Nansihu Lake. The grain size and Al oxides/hydroxides were main factors which controlled the distribution of Tl. Analysis of enrichment factors indicated that Tl in sediments possessed obvious source of human activities which were mainly from combustion of fossil fuels such as coal and mining of mineral resources. As a whole, however, the research region has low Tl content, so Tl has a small probability of environmental pollution.

[Protective effect of oxymatrine on chronic heart failure and ADMA metabolism pathway in isoproterenol-induced chronic heart failure in rats].

OBJECTIVE: To investigate the protective effects of oxymatrine on chronic heart failure induced by isoproterenol (ISO) and to observe its effects on ADMA metabolism pathway in ISO-induced chronic heart failure in rats. METHOD: Male Sprague-Dawley rats were given oxymatrine (100,50 mg kg-1) orally for 14 days. Heart failure was induced in rats by subcutaneous injection of isoproterenol (5 mg kg-1 d-1 ) at the 8th day for 1 week. Serum parameters, haemodynamic parameters, Heart weight, and histopathological variables were analysed. Expression of protein levels were measured by Western blot. RESULT: Oxymatrine (100,50 mg kg-1) significantly attenuated serum content of cTn I, improved left ventricle systolic and diastolic function and left ventricular remodeling, reduced the ISO-induced myocardial pathological changes compared with ISO group. In addition, oxymatrine (100,50 mg kg-1) significantly reduced serum level of ADMA (P <0. 01), normalize the reduced dimethylarginine dimethylaminohydrolase 2 (DDAH2) expression (P <0. 01) , but had no effect on the isoproterenol-induced upregulated protein arginine methyltransferases 1 expression. CONCLUSION: Oxymatrine could ameliorate the experimental ventricular remodeling in ISO-induced chronic heart failure in rats and the mechanism involved in reducing serum content of ADMA and increased DDAH2 expression.