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71.
72.
鸭基因组研究现状和未来展望 总被引:4,自引:1,他引:4
作为禽流感病毒、乙肝病毒的自然贮存库和重要的农业经济动物,鸭在分子生物学(如宿主与病原物互作机制)和分子遗传学(如生长和屠体性状主效基因的克隆)领域的重要地位逐渐为人们所认可.近年来,鸭的基因组学研究取得了一些进展:①构建了鸭的遗传和细胞遗传图谱,并在此基础上定位了鸭生长、屠体和肉质性状的QTLs;②开展了鸡和鸭的比较基因定位研究;③建立了鸭的全基因组BAC文库;④克隆了约3 000条鸭的ESTs序列;⑤利用微卫星标记估计了鸭的遗传多样性.但与其它模式生物(如鸡、猪)相比较,鸭的基因组学研究仍处于起始阶段.随着分子生物学技术,特别是全基因组序列测定技术的发展,高密度的鸭遗传图谱、高分辨率的鸭和鸡以及其它脊椎动物的比较遗传图谱将会被构建,甚至是鸭全基因组序列的测定.这些基因组信息的获得将为大规模的鸭品种资源评定、重要经济性状分子机理的剖析进而改良其生产性能(如提高产蛋量和内质性能、增加对禽流感等疾病的抗性)奠定基础. 相似文献
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CrispinP. Spencer DVM Norman Ackerman DVM JamesK. Burt DVM 《Veterinary radiology & ultrasound》1981,22(6):262-266
Selected structures seen on right and left lateral thoracic radiographs of 12 dogs were evaluated for differences in position, size, and shape. The size and position of the cardiac silhouette were different when thoracic radiographs made in left and right lateral recumbency were compared. These changes were, however, considered insignificant. The position of the right cranial lobe bronchus relative to the left varied in right lateral recumbency and left lateral recumbency. The right cranial lung lobe was better aerated when dogs were positioned in left lateral recumbency.
Lesions seen in the caudal portion of the left cranial lung lobe or the right middle lobe were masked when the affected lobe was dependent, and enhanced when the affected lung lobe was non-dependent. It is believed that this difference occurred due to compression of the dependent lung with greater aeration of the non-dependent lung. 相似文献
Lesions seen in the caudal portion of the left cranial lung lobe or the right middle lobe were masked when the affected lobe was dependent, and enhanced when the affected lung lobe was non-dependent. It is believed that this difference occurred due to compression of the dependent lung with greater aeration of the non-dependent lung. 相似文献
75.
Abstract. Nitrate losses from a small catchment of mixed land use in south Devon, England, are described. The temporal pattern of leaching is dominated by major losses through the winter months when both streamflow and nitrate concentration are large. Storm runoff is generated mainly by subsurface stormflow, and nitrate losses are particularly important at such times. The spatial pattern of nitrate loss from the catchment is controlled both by land use and by topography. 相似文献
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Fish live in complex volumetric habitats, and as such, face a challenging environment through which to navigate. This problem might be simplified if fish could monitor their depth and determine their position within the water column. One possible cue that they could use to ascertain their vertical position is hydrostatic pressure, which varies linearly with depth. Until recently it was assumed that fish were incapable of using hydrostatic pressure to measure depth as they do not possess a mechanism to sense absolute pressure. However, in a recent article by G. Taylor et al., we describe a novel mechanism whereby fish could determine their depth by using the rate in change of pressure mediated by changes in swim‐bladder volume, together with their vertical speed. This mechanism requires fish to be able to sense changes in pressure using their swim‐bladder. Here, we examine fish sensitivity towards hydrostatic pressure by reviewing the literature from behavioural and physiological experiments. This research suggests that fish are acutely sensitive to the magnitude and sign of hydrostatic pressure changes, via changes in the volume of the swim‐bladder. We argue that fish have the necessary physiological measurements to sense the rate in change of pressure, meaning they are able to use the mechanism proposed by Taylor et al. to determine their vertical location. This has profound implications for the study of navigation through volumes, by providing a reliable global cue that fish can use to determine their depth. 相似文献
78.
Watermelon mosaic virus has caused losses in cucurbits in the last 8 years in the Gascoyne River district of Western Australia. Neither insecticides nor oil sprays have reduced the incidence of this disease. In three trials, plants mulched with reflective (aluminium) polythene were less infected (by 21%, 30% and 72%) than were those given a control treatment; yield increases of watermelons ranged from 77% to 270%. Black polythene mulch also reduced the incidence of virus and increased yield, but to a lesser degree. In all experiments the disease incidence rose more slowly in the mulch plots: this effect contributed greatly to the observed increase in yield. 相似文献
79.
Francisca C. Velkers Simon J. Blokhuis Edwin J. B. Veldhuis Kroeze Sara A. Burt 《The Veterinary quarterly》2017,37(1):182-194
Wild migratory birds are associated with global avian influenza virus (AIV) spread. Although direct contact with wild birds and contaminated fomites is unlikely in modern non-free range poultry farms applying biosecurity measures, AIV outbreaks still occur. This suggests involvement of other intermediate factors for virus transmission between wild birds and poultry. This review describes current evidence of the potential role of rodents in AIV transmission from wild birds to poultry and between poultry houses. Rodents can be abundant around poultry houses, share their habitat with waterfowl and can readily enter poultry houses. Survival of AIV from waterfowl in poultry house surroundings and on the coat of rodents suggests that rodents are likely to act as mechanical vector. AIVs can replicate in rodents without adaptation, resulting in high viral titres in lungs and nasal turbinates, virus presence in nasal washes and saliva, and transmission to naïve contact animals. Therefore, active AIV shedding by infected rodents may play a role in transmission to poultry. Further field and experimental studies are needed to provide evidence for a role of rodents in AIV epidemiology. Making poultry houses rodent-proof and the immediate surroundings unattractive for rodents are recommended as preventive measures against possible AIV introduction. 相似文献
80.