Inactivation of the Glucose-Dependent Insulinotropic Polypeptide Receptor Improves Outcomes following Experimental Myocardial Infarction

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The large-scale evolution by generating new genes from gene duplication; similarity and difference between monoploid and diploid organisms

On the basis of the concept of biological activity, the large-scale evolution by generating new genes from gene duplication is theoretically compared between the monoploid organism and the diploid organism. The comparison is carried out not only for the process of generating one new gene but also for the process of generating two or more kinds of new genes from successive gene duplication. This comparison reveals the following difference in evolutionary pattern between the monoploids and diploids. The monoploid organism is more suitable to generate one or two new genes step by step but its successive gene duplication is obliged to generate smaller sizes of genes by the severer lowering of biological activity or self-reproducing rate. This is consistent with the evolutionary pattern of prokaryotes having steadily developed chemical syntheses, O₂-releasing photosynthesis and O₂-respiration in the respective lineages. On the other hand, the diploid organism with the plural number of homologous chromosome pairs has a chance to get together many kinds of new genes by the hybridization of variants having experienced different origins of gene duplication. Although this strategy of hybridization avoids the severe lowering of biological activity, it takes the longer time to establish the homozygotes of the more kinds of new genes. During this long period, furthermore different types of variants are accumulated in the population, and their successive hybridization sometimes yields various styles of new organisms. This evolutionary pattern explains the explosive divergence of body plans that has occasionally occurred in the diploid organisms, because the cell differentiation is a representative character exhibited by many kinds of genes and its evolution to the higher hierarchy constructs body plans.     

The Deep Phylogeny of Land Plants Inferred from a Full Analysis of Nucleotide Base Changes in Terms of Mutation and Selection

The occurrence frequencies of nucleotide bases are biased to those of T and A bases even at third codon positions for conserved amino acid residues with fourfold degeneracy in the chloroplasts of land plants. Regarding this bias as the result of selection, the base changes at these positions are fully analyzed theoretically in terms of mutation and selection. Although the degree of bias is considerably different depending on the lineages of land plants, the theoretical curves considering the influence of selection in the respective lineages provide a reasonable set of evolutionary distances for the relative base change probabilities estimated empirically from base changes enumerated in the comparison of rbcL genes. By using the fossil records of earliest seed plants in the Late Devonian and of uniaperturate and triaperturate pollen types in the early stage of the Cretaceous as calibration points, the divergence of Marchantiidae and a common ancestor of other land plants is estimated to have occurred 509 Mya, together with the estimation of a mutation rate of 1.45 × 10^–9 year^–1 per site. The other bryophytes such as Bryopsida, Anthocerotopsida, and Jungermanniidae are sister groups to tracheophytes, the divergence of bryophytes and tracheophytes being estimated to have occurred 483 Mya. The evolutionary distance of Gnetopsida from Coniferopsida and Magnoliophyta is concluded to be decisively longer than the distance between Coniferopsida and Magnoliophyta, i.e., the former divergence corresponds to 286 Mya and the latter to 211 Mya.     

不同尺度下停歇点湿地对迁徙水鸟的影响研究综述

停歇点湿地是迁徙水鸟重要的能量补给地,在水鸟每年的往返迁徙过程中具有十分重要的生态意义。近年来随着全球变化和人类活动增加,迁飞路线上的停歇点湿地正发生剧烈变化。各个停歇点湿地的生境变化及周围环境不仅是影响水鸟栖息地适宜性的重要因素,还改变了各路线上迁徙水鸟的种群大小和群落多样性。分析不同尺度下停歇点湿地影响迁徙水鸟种群变化的主要生态因子和环境因素,不仅有助于理解各停歇点景观变化的生态效应,也可为迁徙水鸟种群保护提供理论支持。首先分析了在栖息地斑块尺度上停歇点湿地内的水、食物、栖息地格局和人类干扰等生态要素对水鸟觅食和栖息活动的影响;其次,分析了景观尺度上湿地周围的气候变化、土地利用和外来生物等环境条件在各停歇点对水鸟栖息地质量的改变;最后,基于多尺度条件下湿地影响因素的耦合效应,分析了当前湿地生境与水鸟种群关系研究中存在的主要问题,并总结了对湿地和水鸟保护的启示。     

Discrimination between adaptive and neutral amino acid substitutions in vertebrate hemoglobins

Summary A discriminant analysis on the basis of the physicochemical properties of amino acid residues is developed to investigate the accumulation pattern of amino acid substitutions in a family of proteins. The application of this analysis to vertebrate hemoglobins reveals the following new results. (1) The major components of teleost fish and amphibian hemoglobins showing the Root effect are sharply discriminated from mammalian hemoglobins in several regions of the and chains, whereas shark, minor components of teleost fish and amphibian, reptile, and bird hemoglobins showing no Root effect exhibit a gradual change to mammalian hemoglobin in a straightforward way. This result suggests at least two lines of molecular evolution in vertebrate hemoglobins. (2) The nonadult hemoglobin chains are allocated to the latter line, i.e., tadpole, , and chains are similar to shark and trout I chains, and and chains are similar to some of the reptile chains. (3) In any case, most of the amino acid residues causing the discrimination are located near the sites that carry the amino acid residues conserved well throughout all classes of vertebrates, suggesting that modifications adapting to the respective living conditions or respiratory organs have taken place effectively near the amino acid residues essential for the manifestation of cooperative oxygen binding. (4) The amino acid residues at other sites are changed from one to another species even within the same class, showing a constant substitution rate as a whole. These amino acid substitutions may be nearly neutral, being under a weak functional constraint. The number of sites allowing such neutral substitutions is rather small, less than one-half of all the sites in the adult hemoglobins of bird and mammal, whereas it amounts to two-thirds in teleost fish hemoglobins.     

Fluid shear-induced mechanical signaling in MC3T3-E1 osteoblasts requires cytoskeleton-integrin interactions

Mechanical stimulation of bone induces new bone formation invivo and increases the metabolic activity and gene expression ofosteoblasts in culture. We investigated the role of the actin cytoskeleton and actin-membrane interactions in the transmission ofmechanical signals leading to altered gene expression in cultured MC3T3-E1 osteoblasts. Application of fluid shear to osteoblasts causedreorganization of actin filaments into contractile stress fibers andinvolved recruitment of₁-integrins and -actinin tofocal adhesions. Fluid shear also increased expression of two proteinslinked to mechanotransduction in vivo, cyclooxygenase-2 (COX-2) and theearly response gene product c-fos. Inhibition of actin stress fiberdevelopment by treatment of cells with cytochalasin D, by expression ofa dominant negative form of the small GTPase Rho, or by microinjectioninto cells of a proteolytic fragment of -actinin that inhibits-actinin-mediated anchoring of actin filaments to integrins at theplasma membrane each blocked fluid-shear-induced gene expression inosteoblasts. We conclude that fluid shear-induced mechanical signalingin osteoblasts leads to increased expression of COX-2 and c-Fos througha mechanism that involves reorganization of the actin cytoskeleton.Thus Rho-mediated stress fiber formation and the -actinin-dependentanchorage of stress fibers to integrins in focal adhesions may promotefluid shear-induced metabolic changes in bone cells.

     

miRNA Genes of an Invasive Vector Mosquito,Aedes albopictus

Aedes albopictus, a vector of Dengue and Chikungunya viruses, is a robust invasive species in both tropical and temperate environments. MicroRNAs (miRNAs) regulate gene expression and biological processes including embryonic development, innate immunity and infection. While a number of miRNAs have been discovered in some mosquitoes, no comprehensive effort has been made to characterize them from different developmental stages from a single species. Systematic analysis of miRNAs in Ae. albopictus will improve our understanding of its basic biology and inform novel strategies to prevent virus transmission. Between 10–14 million Illumina sequencing reads per sample were obtained from embryos, larvae, pupae, adult males, sugar-fed and blood-fed adult females. A total of 119 miRNA genes represented by 215 miRNA or miRNA star (miRNA*) sequences were identified, 15 of which are novel. Eleven, two, and two of the newly-discovered miRNA genes appear specific to Aedes, Culicinae, and Culicidae, respectively. A number of miRNAs accumulate predominantly in one or two developmental stages and the large number that showed differences in abundance following a blood meal likely are important in blood-induced mosquito biology. Gene Ontology (GO) analysis of the targets of all Ae. albopictus miRNAs provides a useful starting point for the study of their functions in mosquitoes. This study is the first systematic analysis of miRNAs based on deep-sequencing of small RNA samples of all developmental stages of a mosquito species. A number of miRNAs are related to specific physiological states, most notably, pre- and post-blood feeding. The distribution of lineage-specific miRNAs is consistent with mosquito phylogeny and the presence of a number of Aedes-specific miRNAs likely reflects the divergence between the Aedes and Culex genera.     

Spatio-Temporal Variation in Vegetation Biomass and Its Relationships with Climate Factors in the Xilingol Grasslands,Northern China

Knowledge about grassland biomass and its dynamics is critical for studying regional carbon cycles and for the sustainable use of grassland resources. In this study, we investigated the spatio-temporal variation of biomass in the Xilingol grasslands of northern China. Field-based biomass samples and MODIS time series data sets were used to establish two empirical models based on the relationship of the normalized difference vegetation index (NDVI) with above-ground biomass (AGB) as well as that of AGB with below-ground biomass (BGB). We further explored the climatic controls of these variations. Our results showed that the biomass averaged 99.01 Tg (1 Tg=10¹² g) over a total area of 19.6×10⁴ km² and fluctuated with no significant trend from 2001 to 2012. The mean biomass density was 505.4 g/m², with 62.6 g/m² in AGB and 442.8 g/m² in BGB, which generally decreased from northeast to southwest and exhibited a large spatial heterogeneity. The year-to-year AGB pattern was generally consistent with the inter-annual variation in the growing season precipitation (GSP), showing a robust positive correlation (R²=0.82, P<0.001), but an opposite coupled pattern was observed with the growing season temperature (GST) (R²=0.61, P=0.003). Climatic factors also affected the spatial distribution of AGB, which increased progressively with the GSP gradient (R²=0.76, P<0.0001) but decreased with an increasing GST (R²=0.70, P<0.0001). An improved moisture index that combined the effects of GST and GSP explained more variation in AGB than did precipitation alone (R²=0.81, P<0.0001). The relationship between AGB and GSP could be fit by a power function. This increasing slope of the GSP–AGB relationships along the GSP gradient may be partly explained by the GST–GSP spatial pattern in Xilingol. Our findings suggest that the relationships between climatic factors and AGB may be scale-dependent and that multi-scale studies and sufficient long-term field data are needed to examine the relationships between AGB and climatic factors.