Climate change and the risks associated with delayed breeding in a tropical wild bird population

There is growing evidence of changes in the timing of important ecological events, such as flowering in plants and reproduction in animals, in response to climate change, with implications for population decline and biodiversity loss. Recent work has shown that the timing of breeding in wild birds is changing in response to climate change partly because individuals are remarkably flexible in their timing of breeding. Despite this work, our understanding of these processes in wild populations remains very limited and biased towards species from temperate regions. Here, we report the response to changing climate in a tropical wild bird population using a long-term dataset on a formerly critically endangered island endemic, the Mauritius kestrel. We show that the frequency of spring rainfall affects the timing of breeding, with birds breeding later in wetter springs. Delays in breeding have consequences in terms of reduced reproductive success as birds get exposed to risks associated with adverse climatic conditions later on in the breeding season, which reduce nesting success. These results, combined with the fact that frequency of spring rainfall has increased by about 60 per cent in our study area since 1962, imply that climate change is exposing birds to the stochastic risks of late reproduction by causing them to start breeding relatively late in the season.     

Multiple targets of miR-302 and miR-372 promote reprogramming of human fibroblasts to induced pluripotent stem cells

The embryonic stem cell-specific cell cycle-regulating (ESCC) family of microRNAs (miRNAs) enhances reprogramming of mouse embryonic fibroblasts to induced pluripotent stem cells. Here we show that the human ESCC miRNA orthologs hsa-miR-302b and hsa-miR-372 promote human somatic cell reprogramming. Furthermore, these miRNAs repress multiple target genes, with downregulation of individual targets only partially recapitulating the total miRNA effects. These targets regulate various cellular processes, including cell cycle, epithelial-mesenchymal transition (EMT), epigenetic regulation and vesicular transport. ESCC miRNAs have a known role in regulating the unique embryonic stem cell cycle. We show that they also increase the kinetics of mesenchymal-epithelial transition during reprogramming and block TGFβ-induced EMT of human epithelial cells. These results demonstrate that the ESCC miRNAs promote dedifferentiation by acting on multiple downstream pathways. We propose that individual miRNAs generally act through numerous pathways that synergize to regulate and enforce cell fate decisions.     

Early dysregulation of the mitochondrial proteome in a mouse model of Alzheimer's disease

Mitochondrial structural and functional alterations appear to play to an important role in the pathogenesis of Alzheimer's disease (AD). In the present study, we used a quantitative comparative proteomic profiling approach to analyze changes in the mitochondrial proteome in AD. A triple transgenic mouse model of AD (3xTg-AD) which harbors mutations in three human transgenes, APP(Swe), PS1(M146V) and Tau(P301L), was used in these experiments. Quantitative differences in the mitochondrial proteome between the cerebral cortices of 6-month-old male 3xTg-AD and non-transgenic mice were determined by using two-dimensional difference gel electrophoresis (2D-DIGE) and tandem mass spectrometry. We identified 23 different proteins whose expression levels differed significantly between triple transgenic and non-transgenic mitochondria. Both down-regulated and up-regulated mitochondrial proteins were observed in transgenic AD cortices. Proteins which were dysregulated in 3xTg-AD cortices functioned in a wide variety of metabolic pathways, including the citric acid cycle, oxidative phosphorylation, pyruvate metabolism, glycolysis, oxidative stress, fatty acid oxidation, ketone body metabolism, ion transport, apoptosis, and mitochondrial protein synthesis. These alterations in the mitochondrial proteome of the cerebral cortices of triple transgenic AD mice occurred before the development of significant amyloid plaque and neurofibrillary tangles, indicating that mitochondrial dysregulation is an early event in AD.     

Copper exposure effects on yeast mitochondrial proteome

Mitochondria play an important role on the entire cellular copper homeostatic mechanisms. Alteration of cellular copper levels may thus influence mitochondrial proteome and its investigation represents an important contribution to the general understanding of copper-related cellular effects. In these study we have performed an organelle targeted proteomic investigation focusing our attention on the effect of non-lethal 1mM copper concentration on Saccharomyces cerevisiae mitochondrial proteome. Functional copper effects on yeast mitochondrial proteome were evaluated by using both 2D electrophoresis (2-DE) and liquid chromatography coupled with tandem mass spectrometry. Proteomic data have been then analyzed by different unsupervised meta-analysis approaches that highlight the impairment of mitochondrial functions and the activation of oxidative stress response. Interestingly, our data have shown that stress response generated by 1mM copper treatment determines the activation of S. cerevisiae survival pathway. To investigate these findings we have treated yeast cells responsiveness to copper with hydrogen peroxide and observed a protective role of this metal. These results are suggestive of a copper role in the protection from oxidative stress possibly due to the activation of mechanisms involved in cellular survival and growth.     

Complex determinants in human immunodeficiency virus type 1 envelope gp120 mediate CXCR4-dependent infection of macrophages

Host cell range, or tropism, combined with coreceptor usage defines viral phenotypes as macrophage tropic using CCR5 (M-R5), T-cell-line tropic using CXCR4 (T-X4), or dually lymphocyte and macrophage tropic using CXCR4 alone or in combination with CCR5 (D-X4 or D-R5X4). Although envelope gp120 V3 is necessary and sufficient for M-R5 and T-X4 phenotypes, the clarity of V3 as a dominant phenotypic determinant diminishes in the case of dualtropic viruses. We evaluated D-X4 phenotype, pathogenesis, and emergence of D-X4 viruses in vivo and mapped genetic determinants in gp120 that mediate use of CXCR4 on macrophages ex vivo. Viral quasispecies with D-X4 phenotypes were associated significantly with advanced CD4+-T-cell attrition and commingled with M-R5 or T-X4 viruses in postmortem thymic tissue and peripheral blood. A D-X4 phenotype required complex discontinuous genetic determinants in gp120, including charged and uncharged amino acids in V3, the V5 hypervariable domain, and novel V1/V2 regions distinct from prototypic M-R5 or T-X4 viruses. The D-X4 phenotype was associated with efficient use of CXCR4 and CD4 for fusion and entry but unrelated to levels of virion-associated gp120, indicating that gp120 conformation contributes to cell-specific tropism. The D-X4 phenotype describes a complex and heterogeneous class of envelopes that accumulate multiple amino acid changes along an evolutionary continuum. Unique gp120 determinants required for the use of CXCR4 on macrophages, in contrast to cells of lymphocytic lineage, can provide targets for development of novel strategies to block emergence of X4 quasispecies of human immunodeficiency virus type 1.     

Molecular characterization of Clostridium perfringens isolates from humans with sporadic diarrhea: evidence for transcriptional regulation of the beta2-toxin-encoding gene

Clostridium perfringens type A food poisoning is caused by C. perfringens isolates carrying a chromosomal enterotoxin gene (cpe), while non-food-borne gastrointestinal (GI) diseases, such as antibiotic-associated diarrhea (AAD) and sporadic diarrhea (SD), are caused by C. perfringens plasmid cpe isolates. A recent study reported the association of beta2 toxin (CPB2) with human GI diseases, and particularly AAD/SD, by demonstrating that a large percentage of AAD/SD isolates, in contrast to a small percentage of food poisoning isolates, carry the beta2-toxin gene (cpb2). This putative relationship was further tested in the current study by characterizing 14 cpe+ C. perfringens fecal isolates associated with recent cases of human SD in England (referred to hereafter as SD isolates). These SD isolates were all classified as cpe+ type A, and 12 of the 14 cpe+ isolates carry their cpe gene on the plasmid and 2 carry it on the chromosome. Interestingly, cpb2 is present in only 12 plasmid cpe isolates; 11 isolates carry cpe and cpb2 on different plasmids, but cpe and cpb2 are located on the same plasmid in one isolate. C. perfringens enterotoxin is produced by all 14 cpe+ SD isolates. However, only 10 of the 12 cpe+/cpb2+ SD isolates produced CPB2, with significant variation in amounts. The levels of cpb2 mRNA in low- to high-CPB2-producing SD isolates differed to such an extent (30-fold) that this difference could be considered a major cause of the differential level of CPB2 production in vitro by SD isolates. Furthermore, no silent or atypical cpb2 was found in a CPB2 Western blot-negative isolate, 5422/94, suggesting that the lack of CPB2 production in 5422/94 was due to low expression of cpb2 mRNA. This received support from our observation that the recombinant plasmid carrying 5422/94 cpb2, which overexpressed cpb2 mRNA, restored CPB2 production in F4969 (a cpb2-negative isolate). Collectively, our present results suggest that CPB2 merits further study as an accessory toxin in C. perfringens-associated SD.     

Rapid identification of female Culexmosquito species using Expert System in the South East Asian region

Rapid identification of mosquito (vector) species is critical for vector control and disease management. Pictorial keys of mosquito species are currently used for the identification of new mosquito species. However, this approach is not very effective. Here, we describe the use of an ID3 algorithm (part of artificial intelligence) for the rapid identification of the South East Asian female Culex mosquito species.

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Solution structure and backbone dynamics of Calsensin, an invertebrate neuronal calcium-binding protein

Calsensin is an EF-hand calcium-binding protein expressed by a subset of peripheral sensory neurons that fasciculate into a single tract in the leech central nervous system. Calsensin is a 9-kD protein with two EF-hand calcium-binding motifs. Using multidimensional NMR spectroscopy we have determined the solution structure and backbone dynamics of calcium-bound Calsensin. Calsensin consists of four helices forming a unicornate-type four-helix bundle. The residues in the third helix undergo slow conformational exchange indicating that the motion of this helix is associated with calciumbinding. The backbone dynamics of the protein as measured by (15)N relaxation rates and heteronuclear NOEs correlate well with the three-dimensional structure. Furthermore, comparison of the structure of Calsensin with other members of the EF-hand calcium-binding protein family provides insight into plausible mechanisms of calcium and target protein binding.     

Severe hypertriglyceridemia in human APOC1 transgenic mice is caused by apoC-I-induced inhibition of LPL

Studies in humans and mice have shown that increased expression of apolipoprotein C-I (apoC-I) results in combined hyperlipidemia with a more pronounced effect on triglycerides (TGs) compared with total cholesterol (TC). The aim of this study was to elucidate the main reason for this effect using human apoC-I-expressing (APOC1) mice. Moderate plasma human apoC-I levels (i.e., 4-fold higher than human levels) caused a 12-fold increase in TG, along with a 2-fold increase in TC, mainly confined to VLDL. Cross-breeding of APOC1 mice on an apoE-deficient background resulted in a marked 55-fold increase in TG, confirming that the apoC-I-induced hyperlipidemia cannot merely be attributed to blockade of apoE-recognizing hepatic lipoprotein receptors. The plasma half-life of [3H]TG-VLDL-mimicking particles was 2-fold increased in APOC1 mice, suggesting that apoC-I reduces the lipolytic conversion of VLDL. Although total postheparin plasma LPL activity was not lower in APOC1 mice compared with controls, apoC-I was able to dose-dependently inhibit the LPL-mediated lipolysis of [3H]TG-VLDL-mimicking particles in vitro with a 60% efficiency compared with the main endogenous LPL inhibitor apoC-III. Finally, purified apoC-I impaired the clearance of [3H]TG-VLDL-mimicking particles independent of apoE-mediated hepatic uptake in lactoferrin-treated mice. Therefore, we conclude that apoC-I is a potent inhibitor of LPL-mediated TG-lipolysis.