排序方式: 共有34条查询结果,搜索用时 15 毫秒
1.
Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms 总被引:15,自引:0,他引:15
Orr JC Fabry VJ Aumont O Bopp L Doney SC Feely RA Gnanadesikan A Gruber N Ishida A Joos F Key RM Lindsay K Maier-Reimer E Matear R Monfray P Mouchet A Najjar RG Plattner GK Rodgers KB Sabine CL Sarmiento JL Schlitzer R Slater RD Totterdell IJ Weirig MF Yamanaka Y Yool A 《Nature》2005,437(7059):681-686
Today's surface ocean is saturated with respect to calcium carbonate, but increasing atmospheric carbon dioxide concentrations are reducing ocean pH and carbonate ion concentrations, and thus the level of calcium carbonate saturation. Experimental evidence suggests that if these trends continue, key marine organisms--such as corals and some plankton--will have difficulty maintaining their external calcium carbonate skeletons. Here we use 13 models of the ocean-carbon cycle to assess calcium carbonate saturation under the IS92a 'business-as-usual' scenario for future emissions of anthropogenic carbon dioxide. In our projections, Southern Ocean surface waters will begin to become undersaturated with respect to aragonite, a metastable form of calcium carbonate, by the year 2050. By 2100, this undersaturation could extend throughout the entire Southern Ocean and into the subarctic Pacific Ocean. When live pteropods were exposed to our predicted level of undersaturation during a two-day shipboard experiment, their aragonite shells showed notable dissolution. Our findings indicate that conditions detrimental to high-latitude ecosystems could develop within decades, not centuries as suggested previously. 相似文献
2.
Epithelial-cell-intrinsic IKK-beta expression regulates intestinal immune homeostasis 总被引:1,自引:0,他引:1
Zaph C Troy AE Taylor BC Berman-Booty LD Guild KJ Du Y Yost EA Gruber AD May MJ Greten FR Eckmann L Karin M Artis D 《Nature》2007,446(7135):552-556
Intestinal epithelial cells (IECs) provide a primary physical barrier against commensal and pathogenic microorganisms in the gastrointestinal (GI) tract, but the influence of IECs on the development and regulation of immunity to infection is unknown. Here we show that IEC-intrinsic IkappaB kinase (IKK)-beta-dependent gene expression is a critical regulator of responses of dendritic cells and CD4+ T cells in the GI tract. Mice with an IEC-specific deletion of IKK-beta show a reduced expression of the epithelial-cell-restricted cytokine thymic stromal lymphopoietin in the intestine and, after infection with the gut-dwelling parasite Trichuris, fail to develop a pathogen-specific CD4+ T helper type 2 (T(H)2) response and are unable to eradicate infection. Further, these animals show exacerbated production of dendritic-cell-derived interleukin-12/23p40 and tumour necrosis factor-alpha, increased levels of CD4+ T-cell-derived interferon-gamma and interleukin-17, and develop severe intestinal inflammation. Blockade of proinflammatory cytokines during Trichuris infection ablates the requirement for IKK-beta in IECs to promote CD4+ T(H)2 cell-dependent immunity, identifying an essential function for IECs in tissue-specific conditioning of dendritic cells and limiting type 1 cytokine production in the GI tract. These results indicate that the balance of IKK-beta-dependent gene expression in the intestinal epithelium is crucial in intestinal immune homeostasis by promoting mucosal immunity and limiting chronic inflammation. 相似文献
3.
High-latitude controls of thermocline nutrients and low latitude biological productivity 总被引:3,自引:0,他引:3
The ocean's biological pump strips nutrients out of the surface waters and exports them into the thermocline and deep waters. If there were no return path of nutrients from deep waters, the biological pump would eventually deplete the surface waters and thermocline of nutrients; surface biological productivity would plummet. Here we make use of the combined distributions of silicic acid and nitrate to trace the main nutrient return path from deep waters by upwelling in the Southern Ocean and subsequent entrainment into subantarctic mode water. We show that the subantarctic mode water, which spreads throughout the entire Southern Hemisphere and North Atlantic Ocean, is the main source of nutrients for the thermocline. We also find that an additional return path exists in the northwest corner of the Pacific Ocean, where enhanced vertical mixing, perhaps driven by tides, brings abyssal nutrients to the surface and supplies them to the thermocline of the North Pacific. Our analysis has important implications for our understanding of large-scale controls on the nature and magnitude of low-latitude biological productivity and its sensitivity to climate change. 相似文献
4.
M. K. Bijsterbosch Anneke M. Duursma J. M. W. Bouma M. Gruber 《Cellular and molecular life sciences : CMLS》1981,37(4):381-382
Summary The plasma volume of 43 male Wistar rats, weighing between 140 and 350 g, was determined. A close linear relationship between plasma volume and body weight was found: plasma volume (ml)=0.0291×body weight (g)+2.54.Acknowledgment. The excellent assistance of Mr J.S. Bouwer in animal experiments is gratefully acknowledged. 相似文献
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6.
Experimentally-derived haplotypes substantially increase the efficiency of linkage disequilibrium studies. 总被引:23,自引:0,他引:23
The study of complex genetic traits in humans is limited by the expense and difficulty of ascertaining populations of sufficient sample size to detect subtle genetic contributions to disease. Here we introduce an application of a somatic cell hybrid construction strategy called conversion that maximizes the genotypic information from each sampled individual. The approach permits direct observation of individual haplotypes, thereby eliminating the need for collecting and genotyping DNA from family members for haplotype-based analyses. We describe experimental data that validate the use of conversion as a whole-genome haplotyping tool and evaluate the theoretical efficiency of using conversion-derived haplotypes instead of conventional genotypes in the context of haplotype-frequency estimation. We show that, particularly when phenotyping is expensive, conversion-based haplotyping can be more efficient and cost-effective than standard genotyping. 相似文献
7.
Marthe-Susanna Wegner Nina Schömel Lisa Gruber Stephanie Beatrice Örtel Matti Aleksi Kjellberg Peter Mattjus Jennifer Kurz Sandra Trautmann Bing Peng Martin Wegner Manuel Kaulich Robert Ahrends Gerd Geisslinger Sabine Grösch 《Cellular and molecular life sciences : CMLS》2018,75(18):3393-3410
The UDP-glucose ceramide glucosyltransferase (UGCG) is a key enzyme in the synthesis of glycosylated sphingolipids, since this enzyme generates the precursor for all complex glycosphingolipids (GSL), the GlcCer. The UGCG has been associated with several cancer-related processes such as maintaining cancer stem cell properties or multidrug resistance induction. The precise mechanisms underlying these processes are unknown. Here, we investigated the molecular mechanisms occurring after UGCG overexpression in breast cancer cells. We observed alterations of several cellular properties such as morphological changes, which enhanced proliferation and doxorubicin resistance in UGCG overexpressing MCF-7 cells. These cellular effects seem to be mediated by an altered composition of glycosphingolipid-enriched microdomains (GEMs), especially an accumulation of globotriaosylceramide (Gb3) and glucosylceramide (GlcCer), which leads to an activation of Akt and ERK1/2. The induction of the Akt and ERK1/2 signaling pathway results in an increased gene expression of multidrug resistance protein 1 (MDR1) and anti-apoptotic genes and a decrease of pro-apoptotic gene expression. Inhibition of the protein kinase C (PKC) and phosphoinositide 3 kinase (PI3K) reduced MDR1 gene expression. This study discloses how changes in UGCG expression impact several cellular signaling pathways in breast cancer cells resulting in enhanced proliferation and multidrug resistance. 相似文献
8.
Pujana MA Han JD Starita LM Stevens KN Tewari M Ahn JS Rennert G Moreno V Kirchhoff T Gold B Assmann V Elshamy WM Rual JF Levine D Rozek LS Gelman RS Gunsalus KC Greenberg RA Sobhian B Bertin N Venkatesan K Ayivi-Guedehoussou N Solé X Hernández P Lázaro C Nathanson KL Weber BL Cusick ME Hill DE Offit K Livingston DM Gruber SB Parvin JD Vidal M 《Nature genetics》2007,39(11):1338-1349
Many cancer-associated genes remain to be identified to clarify the underlying molecular mechanisms of cancer susceptibility and progression. Better understanding is also required of how mutations in cancer genes affect their products in the context of complex cellular networks. Here we have used a network modeling strategy to identify genes potentially associated with higher risk of breast cancer. Starting with four known genes encoding tumor suppressors of breast cancer, we combined gene expression profiling with functional genomic and proteomic (or 'omic') data from various species to generate a network containing 118 genes linked by 866 potential functional associations. This network shows higher connectivity than expected by chance, suggesting that its components function in biologically related pathways. One of the components of the network is HMMR, encoding a centrosome subunit, for which we demonstrate previously unknown functional associations with the breast cancer-associated gene BRCA1. Two case-control studies of incident breast cancer indicate that the HMMR locus is associated with higher risk of breast cancer in humans. Our network modeling strategy should be useful for the discovery of additional cancer-associated genes. 相似文献
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Endogenous digitalis-like substance in plasma of volume-expanded dogs 总被引:16,自引:0,他引:16
10.
Zulässiger Schalldruck bei binauraler Reizung ohne überschwelliges interaurales Übersprechen (Katze)
Summary A report is given of the sound pressure levels which must not be exceeded in order to avoid suprathreshold interaural crosstalk during the stimulation of the cat auditory system by means of earphones. 相似文献