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951.
952.
Oxygen-dependent transcriptional regulator Hap1p limits glucose uptake by repressing the expression of the major glucose transporter gene RAG1 in Kluyveromyces lactis 下载免费PDF全文
Bao WG Guiard B Fang ZA Donnini C Gervais M Passos FM Ferrero I Fukuhara H Bolotin-Fukuhara M 《Eukaryotic cell》2008,7(11):1895-1905
953.
954.
Chuva de Sousa Lopes SM Hayashi K Shovlin TC Mifsud W Surani MA McLaren A 《PLoS genetics》2008,4(2):e30
In the early epiblast of female mice, one of the two X chromosomes is randomly inactivated by a Xist-dependent mechanism, involving the recruitment of Ezh2-Eed and the subsequent trimethylation of histone 3 on lysine 27 (H3K27me3). We demonstrate that this random inactivation process applies also to the primordial germ cell (PGC) precursors, located in the proximal region of the epiblast. PGC specification occurs at about embryonic day (E)7.5, in the extraembryonic mesoderm, after which the germ cells enter the endoderm of the invaginating hindgut. As they migrate towards the site of the future gonads, the XX PGCs gradually lose the H3K27me3 accumulation on the silent X chromosome. However, using a GFP transgene inserted into the X chromosome, we observed that the XX gonadal environment (independently of the gender) is important for the substantial reactivation of the inactive X chromosome between E11.5 and E13.5, but is not required for X-chromosome reactivation during the derivation of pluripotent embryonic germ cells. We describe in detail one of the key events during female PGC development, the epigenetic reprogramming of the X chromosome, and demonstrate the role of the XX somatic genital ridge in this process. 相似文献
955.
Dunlin Calidris alpina is one of the most abundant shorebirds using coastal habitats in the East Atlantic migratory flyway, that links arctic breeding locations (Greenland to Siberia) with wintering grounds (West Europe to West Africa). Differential migration and winter segregation between populations have been indicated by morphometrics and ringing recoveries. Here, we analyse the potential of genetic markers (mitochondrial DNA – mtDNA) to validate and enhance such findings. We compared mtDNA haplotypes frequencies at different wintering sites (from north-west Europe to West Africa). All birds from West Africa had western (European) haplotypes, while the eastern (Siberian) haplotypes were only present in European winter samples, reaching higher frequencies further north in Europe. Compilation of published results from migrating birds also confirmed these differences, with the sole presence of European haplotypes in Iberia and West Africa and increasingly higher frequencies of Siberian haplotypes from south-west to north-west Europe. Comparison with published haplotype frequencies of breeding populations shows that birds from Greenland, Iceland, and North Europe were predominant in wintering grounds in West Africa, while populations wintering in West Europe originated from more eastern breeding grounds (e.g. North Russia). These results show that genetic markers can be used to enhance the integrative monitoring of wintering and breeding populations, by providing biogeographical evidence that validate the winter segregation of breeding populations. 相似文献
956.
The physiological response of Crypthecodinium cohnii batch cultivations and docosahexaenoic acid (DHA) production to n-dodecane additions were studied. Different n-dodecane concentrations [0, 0.5, 1, 2.5, 5, 10 and 20% (v/v)] were added to preliminary shake flask cultivations. The n-dodecane fraction that gave best results in terms of biomass and DHA production was 0.5% (v/v). The n-dodecane fractions of 2.5, 5, 10 and 20% (v/v) to C. cohnii preliminary shake flask cultures inhibited the microalgal growth and DHA production, although a high proportion of cells with intact cytoplasmic membrane was present in the end of these fermentations. After the addition of a pulse of n-dodecane (0.5% v/v) to C. cohnii exponential growing cells in a bioreactor, glucose uptake volumetric rate increased 2.5-fold, while biomass production volumetric rate increased 2.8-fold. The specific growth rate was increased 1.5-fold. The DHA % in biomass, DHA % of TFA and DHA concentration also increased (54, 22 and 58%, respectively), after the n-dodecane addition. At this n-dodecane fraction (0.5% v/v), multi-parameter flow cytometry demonstrated that C. cohnii cell membrane integrity was not affected. The results demonstrated that the addition of 0.5% of n-dodecane (v/v) to C. cohnii fermentations can be an easy and cheap way for enhancing the biomass and DHA production, avoiding the use of high speed rates (resulting in important power agitation costs) that affects the microalga proliferation and increases the bioprocess costs. A new strategy to improve the DHA production from this microalga in two-phase large-scale bioreactors is now in progress. 相似文献
957.
Jozala AF Lopes AM Mazzola PG Magalhães PO Vessoni Penna TC Pessoa A 《Enzyme and microbial technology》2008,42(2):107-112
Nisin is a natural additive for conservation of food, and can also be used as a therapeutic agent. Nisin inhibits the outgrowth of spores, the growth of a variety of Gram-positive and Gram-negative bacteria. In this paper we present a potentially scalable and cost-effective way to purify commercial and biosynthesized in bioreactor nisin, including simultaneously removal of impurities and contaminants, increasing nisin activity. Aqueous two-phase micellar systems (ATPMS) are considered promising for bioseparation and purification purposes. Triton X-114 was chosen as the as phase-forming surfactant because it is relatively mild to proteins and it also forms two coexisting phases within a convenient temperature range. Nisin activity was determined by the agar diffusion assay utilizing Lactobacillus sake as a sensitive indicator microorganism. Results indicated that nisin partitions preferentially to the micelle rich-phase, despite the surfactant concentration tested, and its antimicrobial activity increases. The successful implementation of this peptide partitioning, from a suspension containing other compounds, represents an important step towards developing a separation method for nisin, and more generally, for other biomolecules of interest. 相似文献
958.
De Melo LD Sant'Anna C Reis SA Lourenço D De Souza W Lopes UG Cunha-e-Silva NL 《Parasitology》2008,135(8):955-965
The actin cytoskeleton controls pivotal cellular processes such as motility and cytokinesis, as well as cell-cell and cell-substrate interactions. Assembly and spatial organization of actin filaments are dynamic events regulated by a large repertoire of actin-binding proteins. This report presents the first detailed characterization of the Trypanosoma cruzi actin (TcActin). Protein sequence analysis and homology modelling revealed that the overall structure of T. cruzi actin is conserved and that the majority of amino-acid changes are concentrated on the monomer surface. Immunofluorescence assays using specific polyclonal antibody against TcActin revealed numerous rounded and punctated structures spread all over the parasitic body. No pattern differences could be found between epimastigotes and trypomastigotes or amastigotes. Moreover, in detergent extracts, TcActin was localized only in the soluble fraction, indicating its presence in the G-actin form or in short filaments dissociated from the microtubule cytoskeleton. The trypanosomatid genome was prospected to identify actin-binding and actin-related conserved proteins. The main proteins responsible for actin nucleation and treadmilling in higher eukaryotes are conserved in T. cruzi. 相似文献
959.
Biflavones, a chalcone-flavone, and a tetraflavonoid with a new carbon skeleton were isolated from the leaves of Aristolochia ridicula. Their structures were determined by chemical derivatizations and spectrometric analyses. 相似文献
960.
Embryonic stem cells (ESCs) are apparently homogeneous self-renewing cells, but we observed heterogeneous expression of Stella in ESCs, which is a marker of pluripotency and germ cells. Here we show that, whereas Stella-positive ESCs were like the inner cell mass (ICM), Stella-negative cells were like the epiblast cells. These states were interchangeable, which reflects the metastability and plasticity of ESCs. The established equilibrium was skewed reversibly in the absence of signals from feeder cells, which caused a marked shift toward an epiblast-like state, while trichostatin A, an inhibitor of histone deactelylase, restored Stella-positive population. The two populations also showed different histone modifications and striking functional differences, as judged by their potential for differentiation. The Stella-negative ESCs were more like the postimplantation epiblast-derived stem cells (EpiSCs), albeit the stella locus was repressed by DNA methylation in the latter, which signifies a robust epigenetic boundary between ESCs and EpiSCs. 相似文献