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排序方式: 共有291条查询结果,搜索用时 46 毫秒
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MICHAEL J. HOOKER JOSEPH D. CLARK BOBBY T. BOND MICHAEL J. CHAMBERLAIN 《The Journal of wildlife management》2021,85(5):979-988
Habitat fragmentation and loss contribute to isolation of wildlife populations and increased extinction risks for various species, including many large carnivores. We studied a small and isolated population of American black bears (Ursus americanus) that is of conservation concern in central Georgia, USA (i.e., central Georgia bear population [CGBP]). Our goal was to evaluate the potential for demographic and genetic interchange from neighboring bear populations to the CGBP. To evaluate resource selection and movement potential, we used 35,487 global positioning system locations collected every 20 minutes from 2012 to 2014 from 33 male bears in the CGBP. We then developed a step selection function model based on conditional logistic regression. Male bears chose steps that avoided crops, roads, and human developments and were closer to forests and woody wetlands than expected based on availability. We used a geographic information system to simulate 300 bear movement paths from nearby bear populations in northern Florida, northern Georgia, and southern Georgia to estimate the potential for immigration to the CGBP. Only 4 simulated movement paths from the nearby populations intersected the CGBP. The creation of a hypothetical 1-km-wide corridor between the southern Georgia population and the CGBP produced only minor improvements in interchange. Our findings suggest that demographic connectivity between the CGBP and surrounding bear populations may be limited, and coupled with previous works showing genetic isolation in the CGBP, that creation of corridors may have only marginal effects on restoring gene flow, at least in the near term. Management actions such as translocation and the establishment of stepping stone populations may be needed to increase the genetic diversity and demographic stability of bears in the CGBP. © 2021 The Wildlife Society. 相似文献
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HH(Hedgehog)信号通路参与多种生物学过程,包括细胞分化、细胞增殖、细胞衰老、肿瘤的发生、肿瘤恶性转化以及肿瘤耐药,HH信号通路相关基因的异常表达或突变会在生物发生发展的不同阶段引起各种疾病的发生。而HH信号通路通过复杂的机制调控诸多信号通路,进一步影响生物体的功能。所以深入了解HH信号通路在各种遗传疾病、肿瘤发生发展以及化疗耐药发展过程中的作用,将有利于进一步发现和研究疾病治疗靶点。该文中,我们概述了HH信号通路,以及HH信号通路在癌症发生发展、发育以及衰老中的作用机制,可为针对HH信号通路的治疗方法研究提供理论依据。 相似文献
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MARY M. CONNER DAN L. BAKER MARGARET A. WILD JENNY G. POWERS MUHAMMAD D. HUSSAIN RICHARD L. DUNN TERRY M. NETT 《The Journal of wildlife management》2007,71(7):2346-2356
ABSTRACT Overabundant elk (Cervus elaphus) populations have become a significant problem in many areas of North America. This is particularly true for protected areas where high densities of elk can cause long-term ecological degradation. When lethal control is not acceptable in these environments, resource managers must often consider alternative methods for reducing the size of resident elk populations. A potential management alternative is controlling the fertility of female elk. A promising new approach to wildlife contraception involves the use of biodegradable implants containing the gonadotropin-releasing hormone (GnRH) agonist leuprolide. During fall 2002-spring 2004, we compared pregnancy rates, reproductive behavior, daily activity patterns, and body condition of 17 free-ranging female elk treated with a leuprolide formulation with 17 untreated females, in Rocky Mountain National Park, Colorado, USA. After treatment, the pregnancy rate of treated elk was 0%, whereas 79% of control elk became pregnant. The effects of treatment were reversed the subsequent year with the pregnancy rate of treated females 100% compared with 91% for controls. Reproductive behaviors were similar for treated and control elk during the breeding and postbreeding seasons; treated elk did not exhibit postrut reproductive behaviors. Moreover, we found no differences in daily activity patterns of experimental groups during the breeding or postbreeding seasons. Treated elk did not show improved body condition over pregnant females. Instead, treated females catabolized proportionately more body fat during winter after treatment and at a higher rate than pregnant control elk. However, this effect was reversed the next spring with no difference in body fat between treated and control elk. We conclude from this experiment that leuprolide, administered as a controlled release formulation, offers a safe and effective method of controlling fertility in free-ranging female elk. However, practical application is limited by treatment duration and the need to treat females before the breeding season. 相似文献
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【背景】胞外多糖(exopolysaccharide,EPS)是乳酸菌生长代谢过程中所产生的一种次级代谢产物,除了可以改善产品质构和品质外,其生理功能也是近年来研究人员追捧的热点。【目的】探究乳酸菌EPS的表征特性和分子结构,揭示其与EPS益生特性之间的联系。【方法】以产EPS的嗜热链球菌(Streptococcus thermophilus,S. thermophilus) MGB80-7为研究对象,利用苯酚-硫酸法测定菌株EPS产量。采用离子交换柱层析和凝胶分子筛层析对该菌株所产EPS进行分离纯化,结合凝胶色谱、红外光谱及高效液相色谱对EPS表型结构进行剖析。此外,为确定EPS表型特征对其抗氧化活性的影响,测定了EPS对超氧阴离子、羟自由基及DPPH自由基等的清除能力。【结果】S. thermophilus MGB80-7在M17培养基中EPS产量较高,为(268.25±5.36) mg/mL,分离纯化后共得到2种多糖组分,其中中性多糖(WPS-807)分子量为1.028×105 Da,主要由葡萄糖、半乳糖和甘露糖组成,并含有少量的鼠李糖和阿拉伯糖,酸性多糖(... 相似文献
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