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Obvious Source (obvious + source)

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Life Sciences50%

Selected Abstracts

Sources for sedimentary bacteriohopanepolyols as revealed by 16S rDNA stratigraphy

ENVIRONMENTAL MICROBIOLOGY, Issue 7 2008
Marco J. L. Coolen
Summary Bacteriohopanoids are widespread lipid biomarkers in the sedimentary record. Many aerobic and anaerobic bacteria are potential sources of these lipids which sometimes complicates the use of these biomarkers as proxies for ecological and environmental changes. Therefore, we applied preserved 16S ribosomal RNA genes to identify likely Holocene biological sources of bacteriohopanepolyols (BHPs) in the sulfidic sediments of the permanently stratified postglacial Ace Lake, Antarctica. A suite of intact BHPs were identified, which revealed a variety of structural forms whose composition differed through the sediment core reflecting changes in bacterial populations induced by large changes in lake salinity. Stable isotopic compositions of the hopanols formed from periodic acid-cleaved BHPs, showed that some were substantially depleted in 13C, indicative of their methanotrophic origin. Using sensitive molecular tools, we found that Type I and II methanotrophic bacteria (respectively Methylomonas and Methylocystis) were unique to the oldest lacustrine sediments (> 9400 years BP), but quantification of fossil DNA revealed that the Type I methanotrophs, including methanotrophs related to methanotrophic gill symbionts of deep-sea cold-seep mussels, were the main precursors of the 35-amino BHPs (i.e. aminopentol, -tetrol and -triols). After isolation of the lake ,3000 years ago, one Type I methanotroph of the ,methanotrophic gill symbionts cluster' remained the most obvious source of aminotetrol and -triol. We, furthermore, identified a Synechococcus phylotype related to pelagic freshwater strains in the oldest lacustrine sediments as a putative source of 2-methylbacteriohopanetetrol (2-Me BHT). This combined application of advanced geochemical and paleogenomical tools further refined our knowledge about Holocene biogeochemical processes in Ace Lake. [source]

Primary vesical actinomycosis: A case report and literature review

INTERNATIONAL JOURNAL OF UROLOGY, Issue 10 2007
Sabah Al-Kadhi
Abstract: Pelvic actinomycosis is a chronic granulomatous infection caused by the gram-positive anaerobic bacteria, Actinomyces Israelli. Vesical lesions, particularly without any obvious source of infection, are rare. We report a case of primary vesical actinomycosis which presented as a bladder mass, giving suspicion of malignancy. Repeated trans-urethral deep resections and histo-pathological examinations revealed the true nature of the mass, which was treated by medical means. A high index of suspicion of potentially benign bladder lesions, particularly in a younger age group of patients, is advocated, to prevent unnecessary major surgical procedures. [source]

Internal amplification controls have not been employed in fungal PCR hence potential false negative results

JOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2007
R.R.M. Paterson
Abstract Polymerase chain reaction (PCR) is subject to false negative results. Samples of fungi with the genes of interest (e.g. a disease or mycotoxin) may be categorized as negative and safe as a consequence. Fungi are eukaryotic organisms that are involved in many fields of human activity such as antibiotic, toxin and food production. Certain taxa are implicated in human, animal and plant diseases. However, fungi are difficult to identify and PCR techniques have been proposed increasingly for this purpose. Internal amplification controls (IACs) will ameliorate the situation and need to become mandatory. These are nucleic acids that posses a sequence which will provide a PCR product (i) using the same primers employed for the target gene, and (ii) that will not coincide on the gel with the product of the target gene. Only one group of workers employed an IAC, to respond to potential inhibition, which was reported in 1995 from this present assessment of numerous reports. Inhibitors in cultures need to be minimized, and secondary metabolites are an obvious source. The fields reviewed herein include medical mycology, mycotoxicology, environmental mycology and plant mycology. The conclusion is that previous reports are compromised because IACs have not been employed in fungal PCR; future research must include this control at an early stage. [source]

Estimating the Causal Effects of Media Coverage on Policy-Specific Knowledge

AMERICAN JOURNAL OF POLITICAL SCIENCE, Issue 1 2009
Jason Barabas
Policy facts are among the most relevant forms of knowledge in a democracy. Although the mass media seem like an obvious source of policy-specific information, past research in this area has been plagued by design and methodological problems that have hindered causal inferences. Moreover, few studies include measures of media content, preventing researchers from being able to say what it is about media coverage that influences learning. We advance the literature by employing a simple but underutilized approach for estimating the causal effects of news coverage. Drawing upon a unique collection of cross-sectional survey data, we make within-survey/within-subjects comparisons under conditions of high and low media coverage. We show how the volume, breadth, and prominence of news media coverage increase policy-specific knowledge above and beyond common demographic factors. [source]