462 research outputs found

    Bottom mixed layer oxygen dynamics in the Celtic Sea

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    The seasonally stratified continental shelf seas are highly productive, economically important environments which are under considerable pressure from human activity. Global dissolved oxygen concentrations have shown rapid reductions in response to anthropogenic forcing since at least the middle of the twentieth century. Oxygen consumption is at the same time linked to the cycling of atmospheric carbon, with oxygen being a proxy for carbon remineralisation and the release of CO2. In the seasonally stratified seas the bottom mixed layer (BML) is partially isolated from the atmosphere and is thus controlled by interplay between oxygen consumption processes, vertical and horizontal advection. Oxygen consumption rates can be both spatially and temporally dynamic, but these dynamics are often missed with incubation based techniques. Here we adopt a Bayesian approach to determining total BML oxygen consumption rates from a high resolution oxygen time-series. This incorporates both our knowledge and our uncertainty of the various processes which control the oxygen inventory. Total BML rates integrate both processes in the water column and at the sediment interface. These observations span the stratified period of the Celtic Sea and across both sandy and muddy sediment types. We show how horizontal advection, tidal forcing and vertical mixing together control the bottom mixed layer oxygen concentrations at various times over the stratified period. Our muddy-sand site shows cyclic spring-neap mediated changes in oxygen consumption driven by the frequent resuspension or ventilation of the seabed. We see evidence for prolonged periods of increased vertical mixing which provide the ventilation necessary to support the high rates of consumption observed

    Modifikasi Pati Ubi Jalar Putih untuk Mendapatkan Karakter Mirip Pati Kentang Melalui Metode Asetilasi.

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    Pati kentang memiliki karakteristik yang sesuai untuk diaplikasikan sebagai bahan industri pangan untuk produk ekstrusi, bakeri, pastri, sup, dan pangan instan. Pati kentang memiliki suhu gelatinisasi, konsistensi pasting, dan kejernihan yang tinggi serta rasa yang netral sehingga banyak dimanfaatkan di industri pangan. Namun, pati kentang sampai saat ini masih menjadi komoditas impor dengan harga yang relatif tinggi. Oleh karena itu, diperlukan alternatif pati lokal, misalnya pati ubi jalar yang dapat dimodifikasi agar memiliki karakter mirip pati kentang. Tujuan penelitian ini adalah memodifikasi pati ubi jalar putih sehingga memiliki karakteristik mirip dengan pati kentang komersial. Metode yang digunakan dalam penelitian ini adalah asetilasi. Asetilasi merupakan modifikasi kimia yang dilakukan dengan menambahkan asetat anhidrat dengan katalis basa. Pengembangan substitusi pati kentang diharapkan dapat menjadi solusi pengganti pati kentang impor yang harganya tinggi serta meningkatkan nilai ekonomis ubi jalar lokal. Obyek pati ubi jalar yang digunakan diperoleh dari Jogjakarta. Perangkat lunak pengolahan data yang digunakan dalam penelitian ini adalah Design Expert 11 dan Minitab 17. Penelitian dilakukan dalam tiga tahap. Tahap pertama adalah penentuan konsentrasi natrium asetat anhidrat yang digunakan. Tahap kedua adalah proses optimasi dengan metode permukaan respon central composite design. Sedangkan tahap ketiga adalah melakukan verifikasi menggunakan pegujian paired t-test dengan pati kentang komersial. Hasil penelitian menunjukkan respon daya kembang (0,839), kelarutan (0,353), dan kapasitas pengikatan air (0,185) pada pati ubi jalar asetilasi tidak berbeda nyata (p>0,05) pada uji paired t-test dengan pati kentang komersial. Pati asetilasi memiliki kadar air 10,22±0,4%, kadar abu 0,50±0,02%, kadar amilosa 41,48±0,7%, kadar amilopektin 53,53±0,8%, kadar pati 95,01±0,49%, derajat kecerahan 87,31±0,01, pH 5,2±0,00, kapasitas pengikatan air 90,10±0,44%, daya kembang 32,29±1,69g/g, dan kelarutan 5,06±0,16%. Analisis mikrografi menggambarkan terjadinya pengklusterangranula disebabkan subtitusi gugus hidrofilik pada pati asetilasi yang dapat meningkatkan terbantuknya ikatan hidrogen. Terdapat pita absorbsi pada 1735-1740 cm-1 (C=O stretching asetil), 1368 cm-1 (C-H asetil), dan 1234 cm-1 (C-O stretching asetil), serta penurunan intensitas peak 3000-3600 cm-1 sebagai bukti terjadinya asetilasi pada analisis ikatan antar atom.Analisis sifat pasting menunjukkan penurunan setback dan breakdown pati asetilasi yang mengimplikasikan kestabilan pasta yang lebih baik serta kecenderungan retrogradasi dan sineresis yang lebih rendah. Pengaplikasian pati modifikasi dalam pembuatan produk bakeri dan pangan ekstrusi disarankan sebagai pengganti pati kentang

    Experience and Challenges from Clinical Trials with Malaria Vaccines in Africa.

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    Malaria vaccines are considered amongst the most important modalities for potential elimination of malaria disease and transmission. Research and development in this field has been an area of intense effort by many groups over the last few decades. Despite this, there is currently no licensed malaria vaccine. Researchers, clinical trialists and vaccine developers have been working on many approached to make malaria vaccine available.African research institutions have developed and demonstrated a great capacity to undertake clinical trials in accordance to the International Conference on Harmonization-Good Clinical Practice (ICH-GCP) standards in the last decade; particularly in the field of malaria vaccines and anti-malarial drugs. This capacity is a result of networking among African scientists in collaboration with other partners; this has traversed both clinical trials and malaria control programmes as part of the Global Malaria Action Plan (GMAP). GMAP outlined and support global strategies toward the elimination and eradication of malaria in many areas, translating in reduction in public health burden, especially for African children. In the sub-Saharan region the capacity to undertake more clinical trials remains small in comparison to the actual need.However, sustainability of the already developed capacity is essential and crucial for the evaluation of different interventions and diagnostic tools/strategies for other diseases like TB, HIV, neglected tropical diseases and non-communicable diseases. There is urgent need for innovative mechanisms for the sustainability and expansion of the capacity in clinical trials in sub-Saharan Africa as the catalyst for health improvement and maintained

    Enhanced In Vitro Refolding of Fibroblast Growth Factor 15 with the Assistance of SUMO Fusion Partner

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    Fibroblast growth factor 15 (Fgf15) is the mouse orthologue of human FGF19. Fgf15 is highly expressed in the ileum and functions as an endocrine signal to regulate liver function, including bile acid synthesis, hepatocyte proliferation and insulin sensitivity. In order to fully understand the function of Fgf15, methods are needed to produce pure Fgf15 protein in the prokaryotic system. However, when expressed in Escherichia coli (E. coli), the recombinant Fgf15 protein was insoluble and found only in inclusion bodies. In the current study, we report a method to produce recombinant Fgf15 protein in E. coli through the use of small ubiquitin-related modifier (SUMO) fusion tag. Even though the SUMO has been shown to strongly improve protein solubility and expression levels, our studies suggest that the SUMO does not improve Fgf15 protein solubility. Instead, proper refolding of Fgf15 protein was achieved when Fgf15 was expressed as a partner protein of the fusion tag SUMO, followed by in vitro dialysis refolding. After refolding, the N-terminal SUMO tag was cleaved from the recombinant Fgf15 fusion protein by ScUlp1 (Ubiquitin-Like Protein-Specific Protease 1 from S. cerevisiae). With or without the SUMO tag, the refolded Fgf15 protein was biologically active, as revealed by its ability to reduce hepatic Cyp7a1 mRNA levels in mice. In addition, recombinant Fgf15 protein suppressed Cyp7a1 mRNA levels in a dose-dependent manner. In summary, we have developed a successful method to express functional Fgf15 protein in prokaryotic cells

    A comprehensive 1000 Genomes-based genome-wide association meta-analysis of coronary artery disease

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    Existing knowledge of genetic variants affecting risk of coronary artery disease (CAD) is largely based on genome-wide association studies (GWAS) analysis of common SNPs. Leveraging phased haplotypes from the 1000 Genomes Project, we report a GWAS meta-analysis of 185 thousand CAD cases and controls, interrogating 6.7 million common (MAF>0.05) as well as 2.7 million low frequency (0.005<MAF<0.05) variants. In addition to confirmation of most known CAD loci, we identified 10 novel loci, eight additive and two recessive, that contain candidate genes that newly implicate biological processes in vessel walls. We observed intra-locus allelic heterogeneity but little evidence of low frequency variants with larger effects and no evidence of synthetic association. Our analysis provides a comprehensive survey of the fine genetic architecture of CAD showing that genetic susceptibility to this common disease is largely determined by common SNPs of small effect siz

    Analysis of RNA Binding by the Dengue Virus NS5 RNA Capping Enzyme

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    Flaviviruses are small, capped positive sense RNA viruses that replicate in the cytoplasm of infected cells. Dengue virus and other related flaviviruses have evolved RNA capping enzymes to form the viral RNA cap structure that protects the viral genome and directs efficient viral polyprotein translation. The N-terminal domain of NS5 possesses the methyltransferase and guanylyltransferase activities necessary for forming mature RNA cap structures. The mechanism for flavivirus guanylyltransferase activity is currently unknown, and how the capping enzyme binds its diphosphorylated RNA substrate is important for deciphering how the flavivirus guanylyltransferase functions. In this report we examine how flavivirus NS5 N-terminal capping enzymes bind to the 5′ end of the viral RNA using a fluorescence polarization-based RNA binding assay. We observed that the KD for RNA binding is approximately 200 nM Dengue, Yellow Fever, and West Nile virus capping enzymes. Removal of one or both of the 5′ phosphates reduces binding affinity, indicating that the terminal phosphates contribute significantly to binding. RNA binding affinity is negatively affected by the presence of GTP or ATP and positively affected by S-adensyl methoninine (SAM). Structural superpositioning of the dengue virus capping enzyme with the Vaccinia virus VP39 protein bound to RNA suggests how the flavivirus capping enzyme may bind RNA, and mutagenesis analysis of residues in the putative RNA binding site demonstrate that several basic residues are critical for RNA binding. Several mutants show differential binding to 5′ di-, mono-, and un-phosphorylated RNAs. The mode of RNA binding appears similar to that found with other methyltransferase enzymes, and a discussion of diphosphorylated RNA binding is presented

    Choice of Bacterial Growth Medium Alters the Transcriptome and Phenotype of Salmonella enterica Serovar Typhimurium

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    The type of bacterial culture medium is an important consideration during design of any experimental protocol. The aim of this study was to understand the impact of medium choice on bacterial gene expression and physiology by comparing the transcriptome of Salmonella enterica SL1344 after growth in the widely used LB broth or the rationally designed MOPS minimal medium. Transcriptomics showed that after growth in MOPS minimal media, compared to LB, there was increased expression of 42 genes involved in amino acid synthesis and 23 genes coding for ABC transporters. Seven flagellar genes had decreased expression after growth in MOPS minimal medium and this correlated with a decreased motility. In both MOPS minimal medium and MEM expression of genes from SPI-2 was increased and the adhesion of S. Typhimurium to intestinal epithelial cells was higher compared to the levels after growth in LB. However, SL1344 invasion was not significantly altered by growth in either MOPs minimal media or MEM. Expression of SPI-2 was also measured using chromosomal GFP reporter fusions followed by flow cytometry which showed, for the first time, that the reduction in SPI-2 transcript after growth in different media related to a reduction in the proportion of the bacterial population expressing SPI-2. These data highlight the profound differences in the global transcriptome after in vitro growth in different media and show that choice of medium should be considered carefully during experimental design, particularly when virulence related phenotypes are being measured

    Protein Expression in the Nucleus Accumbens of Rats Exposed to Developmental Vitamin D Deficiency

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    Introduction: Developmental vitamin D (DVD) deficiency is a candidate risk factor for schizophrenia. Animal models have confirmed that DVD deficiency is associated with a range of altered genomic, proteomic, structural and behavioural outcomes in the rat. Because the nucleus accumbens has been implicated in neuropsychiatric disorders, in the current study we examined protein expression in this region in adult rats exposed to DVD deficienc
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