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41.
W A Priester D G Goodman G H Theilen 《Journal of the American Veterinary Medical Association》1977,170(8):823-826
An aged Boxer dog had 9 distinct primary tumors: chemodectoma, osteosarcoma, bronchiolo-alveolar adenocarcinoma, interstitial cell tumor, seminoma, basal cell tumor, fibropapilloma, adrenal cortical adenoma, and pancreatic adenoma. From this report, as well as from other studies, it is clear that Boxers have special susceptibilities to a variety of tumors. Analysis of clinical data on canine tumors indicated that the risk of Boxers for multiple tumors is only slightly higher than all tumors, indicating little or no specific predisposition for multiple tumors. In Boxers, however, certain tumor types occurred more frequently as multiple primary tumors than would be expected by chance. 相似文献
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The endemic species richness on Madagascar, relative to landmass area, is unparalleled in the world. Many organisms on the island have restricted geographical ranges. A comprehensive hypothesis explaining the evolution of this microendemism has yet to be developed. Using an analysis of watersheds in the context of Quaternary climatic shifts, we provide a new mechanistic model to explain the process of explosive speciation on the island. River catchments with sources at relatively low elevations were zones of isolation and hence led to the speciation of locally endemic taxa, whereas those at higher elevations were zones of retreat and dispersion and hence contain proportionately lower levels of microendemism. These results provide a framework for biogeographic and phylogeographic studies, as well as a basis for prioritizing conservation actions of the remaining natural forest habitats on the island. 相似文献
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喀斯特地区烟田土壤有效态微量元素的空间变异特征——以贵州省毕节地区为例 总被引:1,自引:0,他引:1
以典型的喀斯特地区——贵州省毕节地区为研究区域,采用地统计学和地理信息系统(GIS)相结合的方法,对烟田土壤中有效态微量元素Cu、Zn、Fe、Mn、B和Mo含量的空间变异特征进行研究。结果表明,烟田土壤中各微量元素的变异系数在45.75%~82.45%,均属于中等变异。半方差函数分析表明,烟田土壤微量元素中Cu、Zn、Fe的最适模型是线性模型,而Mn、B和Mo的最适模型为指数模型;各微量元素的块基比〔C0/(C0+C)〕均在25%~75%,表现为中等空间相关性,其空间变异受结构性因素(土壤母质、地形地貌、气候)和随机性因素(施肥、耕作措施、工业污染等)的共同影响。烟田土壤微量元素的空间分布表明,除有效铁含量分布呈现连续空间分布特点外,其他几种微量元素的空间分布并未呈现明显的分布规律。 相似文献
44.
有机氮部分替代无机氮对香料烟产量、产值及品质的影响 总被引:2,自引:0,他引:2
为了提高香料烟的产量、产值和品质,采用田间小区试验研究了有机氮部分替代无机氮(取代比例分别为0、25%、50%)对香料烟产值及品质的影响。结果表明,有机氮取代部分无机氮对烤烟的产量、产值、上等烟比例和化学成分协调程度及矿质营养元素含量有很大的影响。其中,产量、产值和上等烟比例以有机氮取代50%无机氮处理最高,分别达到2 212.00kg/hm2、53 362.00元/hm2和70.22%。有机氮部分取代无机氮对香料烟叶片中化学成分、矿质元素的影响比较复杂,不同部位叶片以及不同化学成分的响应不同,但总体表现为有机氮取代无机氮改善了烤烟化学成分的协调程度,促进了有益矿质元素的积累。总之,对浙江省绍兴香料烟烟区来说,在施氮水平为105kg/hm2情况下,有机氮取代50%的无机氮时香料烟的经济产量、产值和烟叶品质较好。 相似文献
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The current technology to sort X and Y chromosome bearing sperm population requires individual identification and selection of spermatozoa in a modified high-speed flow cytometer. For farm animal species, the technology is capable of producing sexed sperm at greater than 90% purity. However, only in the bovine, the technology has reached a developmental level that allows its commercial application. Meanwhile, the demand for female calves has grown rapidly, which encourages the demand for sex-sorted semen from high genetic value bulls. The success of the technology will depend mainly on the fertilizing capacity of the sorted spermatozoa, as this is the most affecting and economically relevant factor. To date, fertility is still variable and is quite dependant on post-sort processing. New processing techniques are under investigation and will likely be able to improve the fertility rates after AI with sex-sorted semen. It is of great importance to select the right bulls and to test the sorted samples on a routine basis. In addition to the demand for sex-sorted semen by the cattle industry, there is also a significant demand expressed by pig farmers. However, it is still unknown if the use of sex-sorted semen through commercial pig AI will be economically feasible. For the pig, the combination of in vitro fertilization with sexed semen and non-surgical embryo transfer is an alternative that merits further scientific attention. Recent developments in ovine AI and ET will make it very likely that commercial sheep industry will adopt the sexing technology in their breeding concepts. 相似文献