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51.
The observation that a few species in ecological communities are exceptionally abundant, whereas most are rare, prompted the development of species abundance models. Nevertheless, despite the large literature on the commonness and rarity of species inspired by these pioneering studies, some widespread empirical patterns of species abundance resist easy explanation. Notable among these is the observation that in large assemblages there are more rare species than the log normal model predicts. Here we use a long-term (21-year) data set, from an estuarine fish community, to show how an ecological community can be separated into two components. Core species, which are persistent, abundant and biologically associated with estuarine habitats, are log normally distributed. Occasional species occur infrequently in the record, are typically low in abundance and have different habitat requirements; they follow a log series distribution. These distributions are overlaid, producing the negative skew that characterizes real data sets. 相似文献
52.
C. H. W. Horne R. S. Patrick R. N. M. Macsween A. R. Henderson 《Cellular and molecular life sciences : CMLS》1972,28(3):306-307
Résumé L'albumine intracellulaire a été démontrée dans le foie de rats par une technique d'immunofluorescence. Il y a une réduction significative du nombre des cellules fluorescentes dans les foies des animaux souffrant de cirrhose produite par le CCl4. 相似文献
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Phototransduction in the vertebrate retina is dependent in part on a cyclic GMP-activated ionic channel in the plasma membrane of rods and cones. But other vertebrate cells are also photosensitive. Cells of the chick pineal gland have a photosensitive circadian rhythm in melatonin secretion that persists in dissociated cell culture. Exposure to light causes inhibition of melatonin secretion, and entrainment of the intrinsic circadian oscillator. Chick pinealocytes express several 'retinal' proteins, including arrestin, transducin and a protein similar to the visual pigment rhodopsin. Pinealocytes of lower vertebrates display hyperpolarizing responses to brief pulses of light. Thus it is possible that some of the mechanisms of phototransduction are similar in retinal and pineal photoreceptors. We report here the first recordings of cyclic GMP-activated channels in an extraretinal photoreceptor. Application of GMP, but not cyclic AMP, to excised inside-out patches caused activation of a 15-25 pS cationic channel. These channels may be essential for phototransduction in the chick pineal gland. 相似文献
55.
Bacteriorhodopsin, a membrane protein with a relative molecular mass of 27,000, is a light driven pump which transports protons across the cell membrane of the halophilic organism Halobacterium salinarum. The chromophore retinal is covalently attached to the protein via a protonated Schiff base. Upon illumination, retinal is isomerized. The Schiff base then releases a proton to the extracellular medium, and is subsequently reprotonated from the cytoplasm. An atomic model for bacteriorhodopsin was first determined by Henderson et al, and has been confirmed and extended by work in a number of laboratories in the last few years. Here we present an atomic model for structural changes involved in the vectorial, light-driven transport of protons by bacteriorhodopsin. A 'switch' mechanism ensures the vectorial nature of pumping. First, retinal unbends, triggered by loss of the Schiff base proton, and second, a protein conformational change occurs. This conformational change, which we have determined by electron crystallography at atomic (3.2 A in-plane and 3.6 A vertical) resolution, is largely localized to helices F and G, and provides an 'opening' of the protein to protons on the cytoplasmic side of the membrane. 相似文献
56.
Laurie CC Laurie CA Rice K Doheny KF Zelnick LR McHugh CP Ling H Hetrick KN Pugh EW Amos C Wei Q Wang LE Lee JE Barnes KC Hansel NN Mathias R Daley D Beaty TH Scott AF Ruczinski I Scharpf RB Bierut LJ Hartz SM Landi MT Freedman ND Goldin LR Ginsburg D Li J Desch KC Strom SS Blot WJ Signorello LB Ingles SA Chanock SJ Berndt SI Le Marchand L Henderson BE Monroe KR Heit JA de Andrade M Armasu SM Regnier C Lowe WL Hayes MG Marazita ML Feingold E Murray JC Melbye M Feenstra B Kang JH Wiggs JL 《Nature genetics》2012,44(6):642-650
We detected clonal mosaicism for large chromosomal anomalies (duplications, deletions and uniparental disomy) using SNP microarray data from over 50,000 subjects recruited for genome-wide association studies. This detection method requires a relatively high frequency of cells with the same abnormal karyotype (>5-10%; presumably of clonal origin) in the presence of normal cells. The frequency of detectable clonal mosaicism in peripheral blood is low (<0.5%) from birth until 50 years of age, after which it rapidly rises to 2-3% in the elderly. Many of the mosaic anomalies are characteristic of those found in hematological cancers and identify common deleted regions with genes previously associated with these cancers. Although only 3% of subjects with detectable clonal mosaicism had any record of hematological cancer before DNA sampling, those without a previous diagnosis have an estimated tenfold higher risk of a subsequent hematological cancer (95% confidence interval = 6-18). 相似文献
57.
Kote-Jarai Z Olama AA Giles GG Severi G Schleutker J Weischer M Campa D Riboli E Key T Gronberg H Hunter DJ Kraft P Thun MJ Ingles S Chanock S Albanes D Hayes RB Neal DE Hamdy FC Donovan JL Pharoah P Schumacher F Henderson BE Stanford JL Ostrander EA Sorensen KD Dörk T Andriole G Dickinson JL Cybulski C Lubinski J Spurdle A Clements JA Chambers S Aitken J Gardiner RA Thibodeau SN Schaid D John EM Maier C Vogel W Cooney KA Park JY Cannon-Albright L Brenner H Habuchi T Zhang HW Lu YJ Kaneva R 《Nature genetics》2011,43(8):785-791
Prostate cancer (PrCa) is the most frequently diagnosed male cancer in developed countries. We conducted a multi-stage genome-wide association study for PrCa and previously reported the results of the first two stages, which identified 16 PrCa susceptibility loci. We report here the results of stage 3, in which we evaluated 1,536 SNPs in 4,574 individuals with prostate cancer (cases) and 4,164 controls. We followed up ten new association signals through genotyping in 51,311 samples in 30 studies from the Prostate Cancer Association Group to Investigate Cancer Associated Alterations in the Genome (PRACTICAL) consortium. In addition to replicating previously reported loci, we identified seven new prostate cancer susceptibility loci on chromosomes 2p11, 3q23, 3q26, 5p12, 6p21, 12q13 and Xq12 (P = 4.0 × 10(-8) to P = 2.7 × 10(-24)). We also identified a SNP in TERT more strongly associated with PrCa than that previously reported. More than 40 PrCa susceptibility loci, explaining ~25% of the familial risk in this disease, have now been identified. 相似文献
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59.
Haiman CA Patterson N Freedman ML Myers SR Pike MC Waliszewska A Neubauer J Tandon A Schirmer C McDonald GJ Greenway SC Stram DO Le Marchand L Kolonel LN Frasco M Wong D Pooler LC Ardlie K Oakley-Girvan I Whittemore AS Cooney KA John EM Ingles SA Altshuler D Henderson BE Reich D 《Nature genetics》2007,39(5):638-644
After the recent discovery that common genetic variation in 8q24 influences inherited risk of prostate cancer, we genotyped 2,973 SNPs in up to 7,518 men with and without prostate cancer from five populations. We identified seven risk variants, five of them previously undescribed, spanning 430 kb and each independently predicting risk for prostate cancer (P = 7.9 x 10(-19) for the strongest association, and P < 1.5 x 10(-4) for five of the variants, after controlling for each of the others). The variants define common genotypes that span a more than fivefold range of susceptibility to cancer in some populations. None of the prostate cancer risk variants aligns to a known gene or alters the coding sequence of an encoded protein. 相似文献
60.
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