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21.
Shelley M. ALEXANDER 《动物学报》2009,55(1)
We compared probability surfaces derived using one set of environmental variables in three Geographic Information Systems (GIS) -based approaches: logistic regression and Akaike's Information Criterion (AIC),Multiple Criteria Evaluation (MCE),and Bayesian Analysis (specifically Dempster-Shafer theory). We used lynx Lynx canadensis as our focal species,and developed our environment relationship model using track data collected in Banff National Park,Alberta,Canada,during winters from 1997 to 2000. The accuracy of the three spatial models were compared using a contingency table method. We determined the percentage of cases in which both presence and absence points were correctly classified (overall accuracy),the failure to predict a species where it occurred (omission error) and the prediction of presence where there was absence (commission error). Our overall accuracy showed the logistic regression approach was the most accurate (74.51% ). The multiple criteria evaluation was intermediate (39.22%),while the Dempster-Shafer (D-S) theory model was the poorest (29.90%). However,omission and commission error tell us a different story: logistic regression had the lowest commission error,while D-S theory produced the lowest omission error. Our results provide evidence that habitat modellers should evaluate all three error measures when ascribing confidence in their model. We suggest that for our study area at least,the logistic regression model is optimal. However,where sample size is small or the species is very rare,it may also be useful to explore and/or use a more ecologically cautious modelling approach (e.g. Dempster-Shafer) that would over-predict,protect more sites,and thereby minimize the risk of missing critical habitat in conservation plans. 相似文献
22.
Diffusion of low density lipoprotein-receptor complex on human fibroblasts 总被引:5,自引:7,他引:5 下载免费PDF全文
Diffusion of the complex consisting of low density lipoprotein (LDL) bound to its receptor on the surface of human fibroblasts has been measured with the help of an intensely fluorescent, biologically active LDL derivative, dioctadecylindocarbocyanine LDL (dil(3)-LDL). Fluorescence photobleaching recovering and direct video observations of the Brownian motion of individual LDL-receptor complexes yielded diffusion coefficients for the slow diffusion on cell surfaces and fast diffusion on membrane blebs, respectively. At 10 degrees C, less that 20 percent of the LDL-receptor complex was measurably diffusible either on normal human fibroblasts GM-3348 or on LDL-receptor- internalization-defective J.D. cells GM-2408A. At 21 degrees and 28 degrees C, the diffusion fractions of approximately 75 and 60 percent, respectively, on both cell lines. The lipid analog nitrobenzoxadiazolephosphatidylcholine (NBD-PC) diffused in the GM-2408A cell membrane at 1.5x10(-8) cm(2)/sec at 22 degrees C. On blebs induced in GM-2408A cell membranes, the dil(3)-LDL receptor complex diffusion coefficient increased to approximately 10(-9) cm(2)/s, thus approaching the maximum theoretical predictions for a large protein in the viscous lipid bilayer. Cytoskeletal staining of blebs with NBD- phallacidin, a fluorescent probe specific for F-actin, indicated that loss of the bulk of the F-actin cytoskeleton accompanied the release of the natural constraints on later diffusion observed on blebs. This work shows that the internalization defect of J.D. is not due to immobilization of the LDL-receptor complex since its diffusibility is sufficient to sustain even the internalization rates observed in the native fibroblasts. Nevertheless, as with many other cell membrane receptors, the diffusion coefficient of the LDL-receptor complex is at least two orders of magnitude slower on native membrane than the viscous limit approached on cell membrane blebs where it is released from lateral constraints. However, LDL-receptor diffusion may not limit LDL internalization in normal human fibroblasts. 相似文献
23.
Sequence, organization, and evolution of the A+T region of Drosophila melanogaster mitochondrial DNA 总被引:2,自引:0,他引:2
The long (4.6-kb) A+T region of Drosophila melanogaster mitochondrial DNA
has been cloned and sequenced. The A+T region is organized in two large
arrays of tandemly repeated DNA sequence elements, with nonrepetitive
intervening and flanking sequences comprising only 22% of its length. The
first repeat array consists of five repeats of 338-373 bp. The second
consists of four intact 464-bp repeats and a fifth partial repeat of 137
bp. Three DNA sequence elements are found to be highly conserved in D.
melanogaster and in several Drosophila species with short A+T regions.
These include a 300-bp DNA sequence element that overlaps the DNA
replication origin and two thymidylate stretches identified on opposite DNA
strands. We conclude that the length heterogeneity observed in the A+T
regulatory region in mitochondrial DNAs from the genus Drosophila results
from the expansion (and contraction) of the number of repeated DNA sequence
elements. We also propose that the 300-bp conserved DNA sequence element,
in conjunction with another primary sequence determinant, perhaps the
adjacent thymidylate stretch, functions in the regulation of mitochondrial
DNA replication.
相似文献
24.
INTRODUCTIONAsearlyasin1948wehavefr8CtionatedisolatednucleifromnormalandtumorcellsbyextractionwithiMNaCIanddilutealkali[1].Thenuclearresiduewasthenstudiedmorethoroughly[2,3].Lateron,sillillarproteinousnuclearresidueswereisolatedbyotherworkers[46]andasstud… 相似文献
25.
Unlike all other social spiders, the social huntsman spider, Delena cancerides, has been reported to rapidly respond to non-nestmates with lethal aggression, similar to the behavior of some eusocial insects.
We tested for the presence of nestmate recognition in D. cancerides under laboratory conditions by introducing 105 unrelated alien conspecifics into foreign colonies and comparing their behavior
to 60 control spiders removed and returned to their natal colony. Spiders demonstrated nestmate recognition by investigating
alien spiders far more than nestmates and by resting closer to nestmates than to aliens. Serious attacks or deaths occurred
in 23% of all trials; however, aggression was not directed significantly more toward aliens than to nestmates. Most notably,
aggression was largely mediated by the adult females (resident or alien), who were most likely to attack or kill other subadult
or mature individuals. Young individuals (resident or alien) were largely immune from serious aggression. Spiders recently
collected from the field tended to be more aggressive than spiders born and raised in the laboratory, possibly due to blurring
of recognition cues related to laboratory husbandry. Our findings support the prediction that nestmate recognition should
evolve when there is a benefit to discriminating against non-kin, as in this social spider system where foraging individuals
may enter a foreign colony and the colony retreat is a limited resource. 相似文献
26.
27.
JENLS CHAURMW 《Cell research》1990,1(2):173-180
Retinal ganglion cells in the rat were studied using the heavy metal intensified cytochrome oxidase and horseradish peroxidase histochemical methods.The results show that a population of large retinal ganglion cells was consistently observed with the cytochrome oxidase staining method in retinas of normal rats or rats which received unilateral thalamotomy at birth.These cytochrome oxidase rich ganglion cells appeared to have large somata,3-6 primary dendrites and extensive dendritic arbors,and are comparable to ganglion cells labeled by the wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP).However,the morphological details of some of the cells revealed by the cytochrome oxidase staining method are frequently better than those shown by the HRP histochemical method.These results suggest that the mitochondrial enzyme cytochrome oxidase can be used as a simple but reliable marker for identifying and studying a population of retinal genglion cells with high metabolic rate in the rat. 相似文献
28.
Pollution of aquatic ecosystems often results in adverse environmental disturbances, including physiological and/ or histomorphological changes in fish. The health of Clarias gariepinus sampled from two polluted water bodies, Orlando Dam and a pond in the Klipspruit wetland catchment, Soweto, was investigated in 2015–2016. Limited fish health-related data is available for this highly impacted freshwater ecosystem. Fish were collected between April 2015 and February 2016. A necropsy and a histological assessment were done on various target organs of each fish. Water and sediment samples were analysed for selected organic and inorganic compounds. Macroscopic assessment revealed abnormally shaped urogenital papillae, morphological alterations of the gonads, as well as discoloration of liver tissue. These observations were supported by microscopic evidence of hepatic histological alterations in fish from Orlando Dam, as well as the presence of both female and male gonadal tissue (intersex) in 13.6% and 50% of fish from the wetland pond and the Orlando Dam, respectively. Water analyses showed high levels of faecal coliform bacteria and metal concentrations and sediment analyses showed detectable levels of potential endocrine disrupting chemicals. 相似文献
29.
Jessica AB van Nies Celina Alves Audrey LS Radix-Bloemen Cécile Gaujoux-Viala Tom WJ Huizinga Johanna MW Hazes Elisabeth Brouwer Bruno Fautrel Annette HM van der Helm-van Mil 《Arthritis research & therapy》2015,17(1)
IntroductionMorning stiffness is assessed daily in the diagnostic process of arthralgia and arthritis, but large-scale studies on the discriminative ability are absent. This study explored the diagnostic value of morning stiffness in 5,202 arthralgia and arthritis patients and the prognostic value in early rheumatoid arthritis (RA).MethodsIn arthralgia patients referred to the Early Arthritis Recognition Clinics (EARC) of Leiden (n = 807) and Groningen (n = 481) or included in the Rotterdam Early Arthritis Cohort (REACH) study (n = 353), the associations (cross-sectional analyses) between morning stiffness and presence of arthritis at physical examination were studied. In early arthritis patients, included in the Leiden Early Arthritis Clinic (EAC) (n = 2,748) and Evaluation et Suivi de POlyarthrites Indifférenciées Récentes (ESPOIR) (n = 813), associations with fulfilling the 2010-RA criteria after one year were assessed. In 2010-RA patients included in the EAC (n = 1,140) and ESPOIR (n = 677), association with the long-term outcomes of disease-modifying antirheumatic drug (DMARD)-free sustained remission and radiological progression were determined. Morning stiffness was defined as a duration ≥60 minutes; sensitivity analyses were performed for other definitions.ResultsIn arthralgia, morning stiffness (≥60 minutes) associated with the presence of arthritis; Leiden EARC odds ratio (OR) 1.49 (95% CI 1.001 to 2.20), Groningen EARC OR 2.21 (1.33 to 3.69) and REACH OR 1.55 (0.97 to 2.47) but the areas under the receiver operating characteristic curve (AUCs) were low (0.52, 0.57, 0.54). In early arthritis, morning stiffness was associated with 2010-RA independent of other predictors (Leiden EAC OR 1.72 (95% CI 1.31 to 2.25, AUC 0.68), ESPOIR OR 1.68 (1.03 to 2.74, AUC 0.64)). Duration of ≥30 minutes provided optimal discrimination for RA in early arthritis. Morning stiffness was not associated with radiological progression or DMARD-free sustained remission.ConclusionsMorning stiffness in arthralgia and early arthritis is associated with arthritis and RA respectively. This supports the incorporation of morning stiffness in the diagnostic process.
Electronic supplementary material
The online version of this article (doi:10.1186/s13075-015-0616-3) contains supplementary material, which is available to authorized users. 相似文献30.
Larval feeding experience influences adult predator acceptance of chemically defended prey 总被引:1,自引:0,他引:1
Generalist predatory paper wasps, Polistes dominulus, experience plant secondary defensive compounds as developing larvae through their herbivorous lepidopteran caterpillar prey and as adults through attacking caterpillars while foraging. We evaluated the role that larval and early adult experience with unpalatable prey plays in subsequent foraging choices by adult wasps. For periods of two or four weeks, caged wasps were raised exclusively on caterpillars of either unpalatable Buckeye, Junonia coenia, that sequester substantial levels of iridoid glycosides (IG) or on Painted Lady, Vanessa cardui, that contain very low levels of IG. Wasps were then allowed to forage on both caterpillar species simultaneously. Patterns of prey capture differed significantly based on previous prey experience. Regardless of previous feeding experience, adult wasps overwhelmingly preferred to take Vanessa. Yet Junonia-experienced wasps continued to attack and take back to the nest over 50% more Junonia than did Vanessa-experienced wasps. The longer the wasps' larval experience with Junonia, the more likely they were to capture Junonia caterpillars. However, the life stage at which the wasps experienced Junonia was also influential as young adult experience with the unpalatable prey was more of a deterrent than was experience strictly as larvae for Junonia-experienced wasps. The results demonstrate that, in these predators, previous experience with deterrent chemicals during their larval development alters patterns of prey acceptability to the adult insects. 相似文献