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1.
Methanol is a major volatile organic compound on Earth and serves as an important carbon and energy substrate for abundant methylotrophic microbes. Previous geochemical surveys coupled with predictive models suggest that the marine contributions are exceedingly large, rivaling terrestrial sources. Although well studied in terrestrial ecosystems, methanol sources are poorly understood in the marine environment and warrant further investigation. To this end, we adapted a Purge and Trap Gas Chromatography/Mass Spectrometry (P&T-GC/MS) method which allowed reliable measurements of methanol in seawater and marine phytoplankton cultures with a method detection limit of 120 nanomolar. All phytoplankton tested (cyanobacteria: Synechococcus spp. 8102 and 8103, Trichodesmium erythraeum, and Prochlorococcus marinus), and Eukarya (heterokont diatom: Phaeodactylum tricornutum, coccolithophore: Emiliania huxleyi, cryptophyte: Rhodomonas salina, and non-diatom heterokont: Nannochloropsis oculata) produced methanol, ranging from 0.8–13.7 micromolar in culture and methanol per total cellular carbon were measured in the ranges of 0.09–0.3%. Phytoplankton culture time-course measurements displayed a punctuated production pattern with maxima near early stationary phase. Stabile isotope labeled bicarbonate incorporation experiments confirmed that methanol was produced from phytoplankton biomass. Overall, our findings suggest that phytoplankton are a major source of methanol in the upper water column of the world’s oceans. 相似文献
2.
Athena Pentzos-Daponte 《Molecular & general genetics : MGG》1964,95(2):129-144
Ohne Zusammenfassung 相似文献
3.
Neele Schumacher D?rte Meyer Andre Mauermann Jan von der Heyde Janina Wolf Jeanette Schwarz Katharina Knittler Gillian Murphy Matthias Michalek Christoph Garbers J?rg W. Bartsch Songbo Guo Beate Schacher Peter Eickholz Athena Chalaris Stefan Rose-John Bj?rn Rabe 《The Journal of biological chemistry》2015,290(43):26059-26071
Generation of the soluble interleukin-6 receptor (sIL-6R) is a prerequisite for pathogenic IL-6 trans-signaling, which constitutes a distinct signaling pathway of the pleiotropic cytokine interleukin-6 (IL-6). Although in vitro experiments using ectopically overexpressed IL-6R and candidate proteases revealed major roles for the metalloproteinases ADAM10 and ADAM17 in IL-6R shedding, the identity of the protease(s) cleaving IL-6R in more physiological settings, or even in vivo, remains unknown. By taking advantage of specific pharmacological inhibitors and primary cells from ADAM-deficient mice we established that endogenous IL-6R of both human and murine origin is shed by ADAM17 in an induced manner, whereas constitutive release of endogenous IL-6R is largely mediated by ADAM10. Although circulating IL-6R levels are altered in various diseases, the origin of blood-borne IL-6R is still poorly understood. It has been shown previously that ADAM17 hypomorphic mice exhibit unaltered levels of serum sIL-6R. Here, by quantification of serum sIL-6R in protease-deficient mice as well as human patients we also excluded ADAM10, ADAM8, neutrophil elastase, cathepsin G, and proteinase 3 from contributing to circulating sIL-6R. Furthermore, we ruled out alternative splicing of the IL-6R mRNA as a potential source of circulating sIL-6R in the mouse. Instead, we found full-length IL-6R on circulating microvesicles, establishing microvesicle release as a novel mechanism for sIL-6R generation. 相似文献
4.
We investigated the expression of the secreted frizzled-related proteins (SFRPs) in keratoconus (KC) and control corneas. KC buttons (∼8 mm diameter) (n = 15) and whole control corneas (n = 7) were fixed in 10% formalin or 2% paraformaldehyde and subsequently paraffin embedded and sectioned. Sections for histopathology were stained with hematoxylin and eosin, or Periodic Acid Schiff’s reagent. A series of sections was also immunolabelled with SFRP 1 to 5 antibodies, visualised using immunofluorescence, and examined with a Zeiss LSM700 scanning laser confocal microscope. Semi-quantitative grading was used to compare SFRP immunostaining in KC and control corneas. Overall, KC corneas showed increased immunostaining for SFRP1 to 5, compared to controls. Corneal epithelium in all KC corneas displayed heterogeneous moderate to strong immunoreactivity for SFRP1 to 4, particularly in the basal epithelium adjacent to cone area. SFRP3 and 5 were localised to epithelial cell membranes in KC and control corneas, with increased SFRP3 cytoplasmic expression observed in KC. Strong stromal expression of SFRP5, including extracellular matrix, was seen in both KC and control corneas. In control corneas we observed differential expression of SFRP family proteins in the limbus compared to more central cornea. Taken together, our results support a role for SFRPs in maintaining a healthy cornea and in the pathogenesis of epithelial and anterior stromal disruption observed in KC. 相似文献
5.
Gecko phylogeography in the Western Indian Ocean region: the oldest clade of Ebenavia inunguis lives on the youngest island 下载免费PDF全文
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Replication stress often induces chromosome instability. In this study, we explore which factors in replication-compromised
cells promote abnormal chromosome ploidy. We expressed mutant forms of either polymerase α (Polα) or polymerase δ (Polδ) in
normal human fibroblasts to compromise DNA replication. Cells expressing the mutant Polα-protein failed to sustain mitotic
arrest and, when propagated progressively, down-regulated Mad2 and BubR1 and accumulated 4N-DNA from the 2N-DNA cells. Significantly,
a population of these cells became tetraploids. The Polα mutant expressing cells also exhibited elevated cellular senescence
markers, suggesting as a mechanism to limit proliferation of the tetraploids. Expression of the Polδ mutant also caused cells
to accumulate 4N-DNA. In contrast to the Polα mutant expressing cells, the Polδ mutant expressing cells expressed sufficient
levels of Mad2, BubR1, and cyclin B1 to sustain mitotic arrest, and these cells had normal chromosome ploidy. Together, these
results suggest that replication-compromised cells depend on the mitotic checkpoint to prevent mitotic slippage that could
result in tetraploidization. 相似文献
10.
C. Athena Aktipis Lee Cronk Rolando de Aguiar 《Human ecology: an interdisciplinary journal》2011,39(2):131-140
We use agent-based modeling to study osotua, a gift giving system used by the Maasai of East Africa. Osotua’s literal meaning is “umbilical cord,” but it is used metaphorically
to refer to a specific type of gift-giving relationship. Osotua relationships are characterized by respect, responsibility
and restraint. Osotua partners ask each other for help only if they are in need and provide help only when asked and only
if they are able. We hypothesize that under the ecologically volatile conditions in which Maasai pastoralists have traditionally
lived, such a system is particularly suited to risk pooling. Here we explore whether osotua increases the viability of herds
by comparing herd survivorship and stability under osotua rules to a) no exchange and b) probabilistic rules for requesting
and giving livestock. Results from this model suggest that this gift-giving system can dramatically increase herd longevity
through a limited pooling of risk. 相似文献