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51.
52.
Valle L Serena-Acedo T Liyanarachchi S Hampel H Comeras I Li Z Zeng Q Zhang HT Pennison MJ Sadim M Pasche B Tanner SM de la Chapelle A 《Science (New York, N.Y.)》2008,321(5894):1361-1365
Much of the genetic predisposition to colorectal cancer (CRC) in humans is unexplained. Studying a Caucasian-dominated population in the United States, we showed that germline allele-specific expression (ASE) of the gene encoding transforming growth factor-beta (TGF-beta) type I receptor, TGFBR1, is a quantitative trait that occurs in 10 to 20% of CRC patients and 1 to 3% of controls. ASE results in reduced expression of the gene, is dominantly inherited, segregates in families, and occurs in sporadic CRC cases. Although subtle, the reduction in constitutive TGFBR1 expression alters SMAD-mediated TGF-beta signaling. Two major TGFBR1 haplotypes are predominant among ASE cases, which suggests ancestral mutations, but causative germline changes have not been identified. Conservative estimates suggest that ASE confers a substantially increased risk of CRC (odds ratio, 8.7; 95% confidence interval, 2.6 to 29.1), but these estimates require confirmation and will probably show ethnic differences. 相似文献
53.
CX3CR1-mediated dendritic cell access to the intestinal lumen and bacterial clearance 总被引:3,自引:0,他引:3
Niess JH Brand S Gu X Landsman L Jung S McCormick BA Vyas JM Boes M Ploegh HL Fox JG Littman DR Reinecker HC 《Science (New York, N.Y.)》2005,307(5707):254-258
Dendritic cells (DCs) and macrophages are critical to innate and adaptive immunity to the intestinal bacterial microbiota. Here, we identify a myeloid-derived mucosal DC in mice, which populates the entire lamina propria of the small intestine. Lamina propria DCs were found to depend on the chemokine receptor CX3CR1 to form transepithelial dendrites, which enable the cells to directly sample luminal antigens. CX3CR1 was also found to control the clearance of entero-invasive pathogens by DCs. Thus, CX3CR1-dependent processes, which control host interactions of specialized DCs with commensal and pathogenic bacteria, may regulate immunological tolerance and inflammation. 相似文献
54.
Schiestl FP Peakall R Mant JG Ibarra F Schulz C Franke S Francke W 《Science (New York, N.Y.)》2003,302(5644):437-438
The "sexually deceptive" orchid Chiloglottis trapeziformis attracts males of its pollinator species, the thynnine wasp Neozeleboria cryptoides, by emitting a unique volatile compound, 2-ethyl-5-propylcyclohexan-1,3-dione, which is also produced by female wasps as a male-attracting sex pheromone. 相似文献
55.
Krause O Rieke GH Birkmann SM Le Floc'h E Gordon KD Egami E Bieging J Hughes JP Young ET Hinz JL Quanz SP Hines DC 《Science (New York, N.Y.)》2005,308(5728):1604-1606
Two images of Cassiopeia A obtained at 24 micrometers with the Spitzer Space Telescope over a 1-year time interval show moving structures outside the shell of the supernova remnant to a distance of more than 20 arc minutes. Individual features exhibit apparent motions of 10 to 20 arc seconds per year, independently confirmed by near-infrared observations. The observed tangential velocities are at roughly the speed of light. It is likely that the moving structures are infrared echoes, in which interstellar dust is heated by the explosion and by flares from the compact object near the center of the remnant. 相似文献
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Conditions, genesis and value of recultivated loess soils Physical, chemical, microbiological and micromorphological investigations have been executed on recultivated loess soils deposited between 1963 and 1968 and under agriculture since than. The main results are: 1. Dry deposited materials are often strongly compressed at 50-120 cm depth. Wet and dry deposited materials may be compressed at 30-50 cm by tillage. 2. The new soils show already a notable carbonate metabolism, loss of sodium and magnesium and a certain enrichment of humus and potassium. 3. Well recultivated soils are forming fertile Pararendzina soils, whereas the other ones are developing into difficult Pseudogley soils. 4. Land evaluation gives values of 60 to 80. However, fertility is not as high, and 10-15 should be subtracted from the values. 5. In compressed soils, melioration by deep loosening and drainage is the only method to evoid further degradation. It is, however not free from difficulties. 相似文献
60.
Regional Sediment Deficits in the Dutch Lowlands: Implications for Long-Term Land-Use Options (8 pp)
Michiel J. van der Meulen Ad J. F. van der Spek Ger de Lange Stephan H. L. L. Gruijters Serge F. van Gessel Buu-Long Nguyen Denise Maljers Jeroen Schokker Jan P. M. Mulder Rob A. A. van der Krogt 《Journal of Soils and Sediments》2007,7(1):9-16
Background, Aim and Scope
Coastal and river plains are the surfaces of depositional systems, to which sediment input is a parameter of key-importance.
Their habitation and economic development usually requires protection with dikes, quays, etc., which are effective in retaining
floods but have the side effect of retarding sedimentation in their hinterlands. The flood-protected Dutch lowlands (so-called
dike-ring areas) have been sediment-starved for up to about a millennium. In addition to this, peat decomposition and soil
compaction, brought about by land drainage, have caused significant land subsidence. Sediment deficiency, defined as the combined
effect of sediment-starvation and drainage-induced volume losses, has already been substantial in this area, and it is expected
to become urgent in view of the forecasted effects of climate change (sea-level rise, intensified precipitation and run-off).
We therefore explore this deficiency, compare it with natural (Holocene) and current human sediment inputs, and discuss it
in terms of long-term land-use options.
Materials and Methods:
We use available 3D geological models to define natural sediment inputs to our study area. Recent progress in large-scale
modelling of peat oxidation and compaction enables us to address volume loss associated with these processes. Human sediment
inputs are based on published minerals statistics. All results are given as first-order approximations.
Results:
The current sediment deficit in the diked lowlands of the Netherlands is estimated at 136 ± 67 million m3/a. About 85% of
this volume is the hypothetical amount of sediment required to keep up with sea-level rise, and 15% is the effect of land
drainage (peat decomposition and compaction). The average Holocene sediment input to our study area (based on a total of 145
km3) is ~14 million m3/a, and the maximum (millennium-averaged) input ~26 million m3/a. Historical sediment deficiency has
resulted in an unused sediment accommodation space of about 13.3 km3. Net human input of sediment material currently amounts
to ~23 million m3/a.
Discussion:
As sedimentary processes in the Dutch lowlands have been retarded, the depositional system's natural resilience to sea-level
rise is low, and all that is left to cope is human countermeasure. Preserving some sort of status quo with water management
solutions may reach its limits in the foreseeable future. The most viable long-term solutions therefore seem a combination
of allowing for more water in open country (anything from flood-buffer zones to open water) and raising lands that are to
be built up (enabling their lasting protection). As to the latter, doubling or tripling the use of filling sand in a planned
and sustained effort may resolve up to one half of the Dutch sediment deficiency problems in about a century.
Conclusions:
Conclusions, Recommendations and Perspectives. We conclude that sediment deficiency – past, present and future – challenges
the sustainable habitation of the Dutch lowlands. In order to explore possible solutions, we recommend the development of
long-term scenarios for the changing lowland physiography, that include the effects of Global Change, compensation measures,
costs and benefits, and the implications for long-term land-use options.
Recommendations and Perspectives:
- 相似文献