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61.
A method is reported that enables selective suppression of absorption of radioactive strontium from ingested food material, permitting calcium to remain available to the body. Studies were carried out by measuring blood levels and bone uptake of Sr89 and Ca45 at different time intervals after orogastric intubation of rats. The addition of sodium alginate, derived from brown marine algae, to the radioactive isotopes increased the overall physiological discrimination against strontium by amounts up to 60% after 24 hours. This discrimination was further increased by feeding sodium alginate mixed with standard diet in the proportions of 20:80 and 30:70. The observed ratio was reduced by administration of sodium alginate from 0.25 to 0.09.Determination of the limiting dosage in rats is restricted to the amounts which rats will consume. In the event of an inadvertent release of radioactive strontium, human subjects probably could increase their intake of alginate at will, permitting a greater effectiveness of sodium alginate than could be obtained in experimental animals. 相似文献
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Sebastian Jäger Stefanie Leuchtenberger Anne Martin Eva Czirr Johanna Wesselowski Marco Dieckmann Elaine Waldron Carsten Korth Edward H. Koo Michael Heneka Sascha Weggen Claus U. Pietrzik 《Journal of neurochemistry》2009,111(6):1369-1382
The Swedish mutation within the amyloid precursor protein (APP) causes early‐onset Alzheimer’s disease due to increased cleavage of APP by BACE1. While β‐secretase shedding of Swedish APP (APPswe) largely results from an activity localized in the late secretory pathway, cleavage of wild‐type APP occurs mainly in endocytic compartments. However, we show that liberation of Aβ from APPswe is still dependent on functional internalization from the cell surface. Inspite the unchanged overall β‐secretase cleaved soluble APP released from APPswe secretion, mutations of the APPswe internalization motif strongly reduced C99 levels and substantially decreased Aβ secretion. We point out that α‐secretase activity‐mediated conversion of C99 to C83 is the main cause of this Aβ reduction. Furthermore, we demonstrate that α‐secretase cleavage of C99 even contributes to the reduction of Aβ secretion of internalization deficient wild‐type APP. Therefore, inhibition of α‐secretase cleavage increased Aβ secretion through diminished conversion of C99 to C83 in APP695, APP695swe or C99 expressing cells. 相似文献
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Understanding the effects of trophic status and dissolved organic carbon concentration (DOC) on lake carbon cycling is essential
for accurate ecosystem carbon models. Using isotopically labelled substrates we assessed spatial and temporal variability
in bacterial respiration (BR) and algal primary production (PP) in two trophically, morphometrically and hydrologically different
basins in Loch Lomond, a large temperate lake in Scotland. GIS modelling was used to construct a whole lake balance for bacterial
production/respiration and PP, and from this the proportion of heterotrophy fuelled by allochthonous carbon was estimated.
We tested the hypotheses that trophic status and DOC concentration affect the balance between PP and BR and examined which
is the more significant driving factor. Additionally we estimated the percentage of BR that is fuelled by terrestrial carbon.
PP varied seasonally and showed inter-basin homogeneity. BR was greatest in the mesotrophic south basin in autumn, which corresponded
to measured peak DOC input, though over an annual cycle no relationship was observed between BR and DOC concentration. The
PP:BR ratio was 0.37 ± 0.30 and 0.3 ± 0.45 in the north and south basins, respectively, assuming a bacterial growth efficiency
of 0.1. We have found that allochthonous carbon potentially supports a substantial quantity of pelagic production, even during
periods of high photosynthesis. Less productive systems are thought to be dominated by heterotrophic processes. However, we
have found that the mesotrophic basin of a large lake to be as heterotrophic as its neighbouring oligotrophic basin, an observation
that has implications for our understanding of modelling of the role of lakes in linking the terrestrial-atmospheric carbon
cycle. 相似文献
67.
Metagenomic biomarker discovery and explanation 总被引:19,自引:0,他引:19
Segata N Izard J Waldron L Gevers D Miropolsky L Garrett WS Huttenhower C 《Genome biology》2011,12(6):R60
This study describes and validates a new method for metagenomic biomarker discovery by way of class comparison, tests of biological
consistency and effect size estimation. This addresses the challenge of finding organisms, genes, or pathways that consistently
explain the differences between two or more microbial communities, which is a central problem to the study of metagenomics.
We extensively validate our method on several microbiomes and a convenient online interface for the method is provided at
. 相似文献
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The results presented here demonstrate that protein kinase D (PKD) and PKCeta transiently coexpressed in COS-7 cells form complexes that can be immunoprecipitated from cell lysates using specific antisera to PKD or PKCeta. The presence of PKCeta in PKD immune complexes was initially detected by in vitro kinase assays which reveal the presence of an 80-kDa phosphorylated band in addition to the 110-kDa band corresponding to autophosphorylated PKD. The association between PKD and PKCeta was further verified by Western blot analysis and peptide phosphorylation assays that exploited the distinct substrate specificity between PKCs and PKD. By the same criteria, PKD formed complexes only very weakly with PKCepsilon, and did not bind PKCzeta. When PKCeta was coexpressed with PKD mutants containing either complete or partial deletions of the PH domain, both PKCeta immunoreactivity and PKC activity in PKD immunoprecipitates were sharply reduced. In contrast, deletion of an amino-terminal portion of the molecule, either cysteine-rich region, or the entire cysteine-rich domain did not interfere with the association of PKD with PKCeta. Furthermore, a glutathione S-transferase-PKDPH fusion protein bound preferentially to PKCeta. These results indicate that the PKD PH domain can discriminate between closely related structures of a single enzyme family, e.g. novel PKCs epsilon and eta, thereby revealing a previously undetected degree of specificity among protein-protein interactions mediated by PH domains. 相似文献
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