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排序方式: 共有225条查询结果,搜索用时 15 毫秒
141.
142.
F Castro-Sousa M Paranhos-Silva I Sherlock M S Paix?o L C Pontes-de-Carvalho W L dos-Santos 《Memórias do Instituto Oswaldo Cruz》2001,96(7):997-999
In this study, the ability of maxadilan and Lutzomyia longipalpis salivary gland lysate to enhance the infection of CBA mice by Leishmania major and of BALB/c mice by L. braziliensis was tested. No difference was observed between sizes of lesion in CBA mice infected with L. major and treated or not with salivary gland lysate or maxadilan, although they were injected in concentrations that induced cutaneous vasodilation. Although parasites were more frequently observed in foot pads and spleens of animals treated with maxadilan than in the animals treated with salivary gland lysate or saline, the differences were small and not statistically significant. The lesions in BALB/c mice infected with L. braziliensis and treated with maxadilan were slightly larger than in animals that received Leishmania alone. Such differences disappeared 14 weeks after infection, and were statistically significant only in one of two experiments. 相似文献
143.
SO2 污染油菜对桃蚜的影响 总被引:1,自引:0,他引:1
SO_2污染油菜对桃蚜的影响龚佩瑜,吴坤君,李秀珍(中国科学院动物研究所北京100080)SO2是我国大气污染的主要成分,它是一种对生物影响很大的污染物。so。曾被用作熏蒸剂来防治害虫,但只有在浓度很高时才有效。更多的观察表明,so:污染有利于蚜虫的?.. 相似文献
144.
The diagnosis of primary cancer of the liver was reviewed in 75 patients. A definitive diagnosis was made during life in 63% and in a further 20% this condition was suspected though histological confirmation was obtained only at necropsy. The most common presenting complaints were abdominal pain and weight loss and the most frequent findings hepatomegaly and ascites. Less than one-half of the patients were jaundiced and when present it was usually mild. An arterial bruit was heard over the liver in 25% of the patients. A sudden and unexplained deterioration in a patient known to have cirrhosis or haemochromatosis should raise the possibility of a primary hepatic tumour; this occurred in 24% of our patients.Alpha-fetoprotein was found in the serum of 11 out of 18 cases. The presence of a mass in the liver was frequently confirmed by liver scan, portal venography, or hepatic arteriography, but these showed no features diagnostic of a primary tumour. Liver scan also proved useful in localizing the lesion for biopsy purposes. Definitive diagnosis is dependent on the histological demonstration of the features of the tumour. This can frequently be achieved by percutaneous needle biopsy, which was positive in 38 out of 57 patients. Wedge biopsies were positive in a further nine patients. 相似文献
145.
146.
R W Chapman G Williams G Bydder R Dick S Sherlock L Kreel 《BMJ (Clinical research ed.)》1980,280(6212):440-442
Dual-energy computed tomography (CT) was used to estimate hepatic iron concentration in eight patients with primary haemochromatosis with varying degrees of iron overload. The values corresponded closely with these derived from chemical analysis of liver tissue obtained by biopsy (correlation coefficient 0.993). Dual-energy CT therefore seems to provide an accurate and non-invasive alternative to liver biopsy as a means of measuring liver iron concentration in patients with primary haemochromatosis and possibly other iron overload states. 相似文献
147.
Prevalence of Giardia spp. in beaver and muskrat populations in northeastern states and Minnesota: detection of intestinal trophozoites at necropsy provides greater sensitivity than detection of cysts in fecal samples. 总被引:2,自引:0,他引:2 下载免费PDF全文
S L Erlandsen L A Sherlock W J Bemrick H Ghobrial W Jakubowski 《Applied microbiology》1990,56(1):31-36
Surveys of the prevalence of the intestinal protozoan Giardia spp. in animal populations have relied almost exclusively on the detection of cysts in fecal samples. We have determined the prevalence of Giardia spp. in beaver and muskrat populations in four northeastern states and Minnesota by using both the detection of trophozoites in mucosal scrapings from live-trapped animals at necropsy and the detection of cysts in fecal samples collected from kill-trapped animals. In muskrats the prevalence of Giardia infection was 36.6% by cyst detection in fecal samples (n = 790) from kill-trapped animals and 95.9% in live-trapped muskrats when the intestinal contents were analyzed for the presence of trophozoites (n = 219). Similarly, in beavers, Giardia infection was 9.2% by cyst detection in fecal samples (n = 662) from kill-trapped beavers and 13.7% in live-trapped animals examined for the presence of intestinal trophozoites (n = 302). The detection of trophozoites in mucosal scrapings from live-trapped animals consistently yielded a significantly higher prevalence for both muskrats and beavers than did the method based on detection of cysts in the fecal samples. The prevalence of Giardia infection in juvenile and adult live-trapped muskrats was similar (92.5 and 94.4%, respectively), but the prevalence in juvenile live-trapped beavers (23.2%) was significantly greater than that seen in the adult animals (12.6%). No difference in Giardia prevalence on the basis of sex was seen in either animal species. Regional variation, often statistically significant, was seen in the prevalence of Giardia in beavers in the northeastern states and Minnesota, but was not detected for muskrats. 相似文献
148.
Catherine C Beauheim Farrell Wymore Michael Nitzberg Zachariah K Zachariah Heng Jin JH Pate Skene Catherine A Ball Gavin Sherlock 《BMC bioinformatics》2007,8(1):338
Background
Biomedical ontologies are being widely used to annotate biological data in a computer-accessible, consistent and well-defined manner. However, due to their size and complexity, annotating data with appropriate terms from an ontology is often challenging for experts and non-experts alike, because there exist few tools that allow one to quickly find relevant ontology terms to easily populate a web form. 相似文献149.
Grace Avecilla Julie N. Chuong Fangfei Li Gavin Sherlock David Gresham Yoav Ram 《PLoS biology》2022,20(5)
The rate of adaptive evolution depends on the rate at which beneficial mutations are introduced into a population and the fitness effects of those mutations. The rate of beneficial mutations and their expected fitness effects is often difficult to empirically quantify. As these 2 parameters determine the pace of evolutionary change in a population, the dynamics of adaptive evolution may enable inference of their values. Copy number variants (CNVs) are a pervasive source of heritable variation that can facilitate rapid adaptive evolution. Previously, we developed a locus-specific fluorescent CNV reporter to quantify CNV dynamics in evolving populations maintained in nutrient-limiting conditions using chemostats. Here, we use CNV adaptation dynamics to estimate the rate at which beneficial CNVs are introduced through de novo mutation and their fitness effects using simulation-based likelihood–free inference approaches. We tested the suitability of 2 evolutionary models: a standard Wright–Fisher model and a chemostat model. We evaluated 2 likelihood-free inference algorithms: the well-established Approximate Bayesian Computation with Sequential Monte Carlo (ABC-SMC) algorithm, and the recently developed Neural Posterior Estimation (NPE) algorithm, which applies an artificial neural network to directly estimate the posterior distribution. By systematically evaluating the suitability of different inference methods and models, we show that NPE has several advantages over ABC-SMC and that a Wright–Fisher evolutionary model suffices in most cases. Using our validated inference framework, we estimate the CNV formation rate at the GAP1 locus in the yeast Saccharomyces cerevisiae to be 10−4.7 to 10−4 CNVs per cell division and a fitness coefficient of 0.04 to 0.1 per generation for GAP1 CNVs in glutamine-limited chemostats. We experimentally validated our inference-based estimates using 2 distinct experimental methods—barcode lineage tracking and pairwise fitness assays—which provide independent confirmation of the accuracy of our approach. Our results are consistent with a beneficial CNV supply rate that is 10-fold greater than the estimated rates of beneficial single-nucleotide mutations, explaining the outsized importance of CNVs in rapid adaptive evolution. More generally, our study demonstrates the utility of novel neural network–based likelihood–free inference methods for inferring the rates and effects of evolutionary processes from empirical data with possible applications ranging from tumor to viral evolution.This study shows that simulation-based inference of evolutionary dynamics using neural networks can yield parameter values for fitness and mutation rate that are difficult to determine experimentally, including those of copy number variants (CNVs) during experimental adaptive evolution of yeast. 相似文献
150.
Effects of afforestation on phosphorus dynamics and biological properties in a New Zealand grassland soil 总被引:7,自引:0,他引:7
Selected chemical, biochemical and biological properties of mineral soil (0–30 cm) were measured under a 19 year old forest
stand (mixture of Pinus ponderosa and Pinus nigra) and adjacent unimproved grassland at a site in South Island, New Zealand. The effects of afforestation on soil properties
were confined to the 0–10 cm layer, which reflected the distribution of fine roots (< 2 mm) in the soil profile. Concentrations
of organic C, total N and P and all organic forms of P were lower under the forest stand, while concentrations of inorganic
P were higher under forest compared with grassland, supporting the previously described suggestion that afforestation may
promote mineralisation of soil organic matter and organic P. On the other hand, microbial biomass C and P, soil respiration
and phosphatase enzyme activity were currently all lower and the metabolic quotient was higher in soil under forest compared
with grassland, which is inconsistent with increased mineralisation in the forest soil. Reduced biological fertility by afforestation
may be mainly attributed to changes in the quantity, quality and distribution of organic matter, and reduction in pH of the
forest soil compared with the grassland soil. We hypothesize that the lower levels of C, N and organic P found in soil under
forest are due to enhanced microbial and phosphatase activity during the earlier stages of forest development. Forest floor
material (L and F layer) contained large amounts of C, N and P, together with high levels of microbial and phosphatase enzyme
activity. Thus, the forest floor may be an important source of nutrients for plant growth and balance the apparent reduction
in C, N and P in mineral soil through mineralisation and plant uptake.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献