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11.
Abstract HISTORY: A similar episodic neurological disorder occurred in new born lambs on two unrelated properties involving disparate breeds of sheep. Because of the number of lambs born, cross-breeding and the fact it occurred in some mating groups and not others, a dominant mode of inheritance was, initially and separately, suspected in each case. The sires of affected lambs were apparently normal. Whereas one was New Zealand Romney, the other was a composite breed with East Friesian genetics, but both rams originated from the same source property. To investigate the pathogenesis of the disorder these two rams were acquired and mated with unrelated sheep, under experimental conditions in a more controlled environment. CLINICAL FINDINGS: A proportion of lambs born to both sires exhibited a similar neurological disorder. Some lambs were noted to be abnormal at birth, both on home properties and in the experimental flock. They tended to adopt a head and neck extended posture and were slow to get to their feet and suckle when they then became more or less normal. When forced to move, they and other more robust lambs elicited an asymmetric gait, base-wide extensor hypertonia (hypometria) of thoracic limbs and flexor hypertonia (hypermetria) of pelvic limbs. In some there was nystagmus. After several metres of asymmetric ataxic gait they would fall to one side, sometimes adopting a sitting position. Recovery usually occurred in one to several minutes. As lambs aged, it became more difficult to elicit the episodes of dysfunction and by 6 months of age they appeared normal. DIAGNOSIS: The disorder was diagnosed as a dominant familial episodic cerebellovestibular ataxia inherited as a dominant trait, with incomplete penetration of observed clinical signs and variable expressivity. CLINICAL RELEVANCE: A proportion of affected lambs are likely to die in the neonatal period so the specific nature of the disorder may go unrecognised. Because of incomplete penetrance and varying expressivity, many of the lambs carrying this mutation will survive without showing clinical signs and may enter breeding flocks, where the disorder may be perpetuated and contribute to neonatal deaths. 相似文献
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José LM Gonçalves Clayton A Alvares José HT Rocha Carolina B Brandani Rodrigo Hakamada 《Southern Forests》2017,79(3):169-183
Most eucalypt plantations are managed in short rotations (6–8 years) and are established in regions with water and nutritional stresses of varying degrees. The mean annual increment in these regions ranges from 20 to 45 m3 ha?1 y?1 depending on the level of environmental stress. Improving natural resource use efficiency by breeding and matching genotypes to sites and using appropriate site management practices is a key challenge to sustain or increase productivity. Climate change is emerging as a driving force behind many of the current issues facing natural resources, and is likely to intensify the water constraint. The Intergovernmental Panel on Climate Change has predicted significant increases in surface air temperatures and decreases in rainfall (with more erratic rainfall patterns) over the tropics and subtropics, affecting drier regions in particular. To be truly sustainable, forest management practices must be environmentally friendly, prevent or reduce land degradation, improve biodiversity and increase resilience to climate variation and change. The main efforts should address the problems of water scarcity, low soil fertility and reduced biodiversity. Forest growers should take into account the inherent risks of different forest management systems on the regional water availability and consider reducing forest productivity in order to maintain both ecological and social equilibrium. The design and implementation of management techniques should be adapted to the specific production and protection objectives, which depend on the regional and local edaphoclimatic circumstances, water resources management, protection against soil erosion, diseases, pests, bushfires, strong winds and alien species. This paper addresses the basic requirements for integrating genetic and silvicultural strategies to minimise the water constraints in eucalypt plantations and surrounding water and native vegetation resources. We show several examples of effective forest management actions on the scale of forest stand and watershed in use in Brazil. 相似文献
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烟草黑胫病菌厚垣孢子和菌丝体在土壤中的存活状态 总被引：12，自引：0，他引：12
将实验条件下制备、提取的黑胫病菌厚垣孢子、菌丝体悬浮液定量加入含水量分别为４０％和７０％的灭菌土壤中,分别于４℃、２５℃和室温下保存,定期检测。结果表明：厚垣孢子在各处理土壤中至少可存活８个月,主要以细胞壁加厚、原生质浓缩的休眠状态存活,而菌丝体只能单独在土壤中存活２个月。在土壤中存活３个月内的厚垣孢子可用选择性培养基直接检测,３个月需用诱捕的方法才能检测出来。温度对厚垣孢子、菌丝体的存活影响明显 相似文献
14.
A suspected inherited form of rickets was diagnosed in Corriedale sheep on a commercial sheep farm in Marlborough. Affected lambs were normal at birth but showed a reduced growth rate and a range of skeletal abnormalities, including both varus and valgus deformities and a characteristic dip in the shoulder region. Up to 20 affected lambs had been born on the property over the last two seasons. Skeletal lesions in affected lambs included swollen costochondral junctions, moderate to marked thickening of physes in long bones, and collapse of weakened subchondral bone, particularly in the proximal humerus. These lesions, together with the microscopic changes, strongly suggested a diagnosis of rickets. Affected lambs were hypocalcaemic and hypophosphataemic, consistent with a deficiency of vitamin D. Vitamin D assays revealed significantly higher 1,25(OH) vitamin D concentrations in affected lambs than in controls, suggesting a defect in the vitamin D receptor as the likely mechanism. DNA testing revealed that 4/10 Corriedale rams used during the previous season had sired affected lambs. Studies aimed at confirming the genetic nature of the disease and the mechanism are continuing at Massey University. 相似文献
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BALB/c mice are widely used in genetic, tumour and immunological studies. However, the mice demonstrate a lower reproduction rate, low fertility and small litters, because of their highly genetic homozygoisty. Based on in vitro fertilization (IVF), a routine technique for biomedical studies, it is worth to evaluate the effects to BALB/c mice on IVF efficiency. In order to test the genetic factor affecting the IVF efficiency of BALB/c, four reciprocal IVF tests of BALB/cByJ and FVB/NCrl mice were performed. The results showed that the average fertility of IVF sponsored by FVB/NCrl spermatozoa was 69.6%, but only 12.1% was obtained from BALB/cByJ strain. Effect of glucose contained in the culture medium to the IVF efficiency of BALB/cByJ was also evaluated. The results showed that the fertility of BALB/cByJ spermatozoa incubated with 0, 2.7, 5.5, 11.1 and 22.2 mm of glucose in the TYH medium were 6.8, 9.9, 13.9, 32.7 and 22.2%, respectively. It is showed that IVF efficiency of BALB/cByJ spermatozoa could be improved depending on the concentration of glucose in the IVF medium. According to the results, it is beleived that lower IVF of BALB/cByJ mice might be due to the genetic defect in spermatozoa and increasing glucose in the IVF medium which significantly affect the IVF efficiency of BALB/cByl via activating the spermatozoa. 相似文献
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The aim of this study was to generate a transgenic mouse that ubiquitously expressed enhanced green fluorescent protein (EGFP) under the control of the murine phosphoglycerate kinase 1 promoter by allotransplantation of transgenic mouse ovaries. The EGFP transgenic mice expressed green fluorescence in many organs, and the fluorescence was detected as early as the embryonic stage. Ovaries from the EGFP transgenic mice were allotransplanted into recipients and these mice were mated with normal male mice. Histological sections of EGFP‐allotransplanted ovaries from the recipient mice showed the well development and formation at follicles and corpora lutea. The green fluorescence was clearly detectable at the allotransplanted section of the ovaries, which had fused with the normal ovary. The average size of the first litter from these mice was 6.8 ± 1.2 pups per recipient, and 17.8% of the pups expressed EGFP. These results demonstrated that allotransplantation of transgenic ovaries can restore a normal reproductive lifespan and can be used to generate a ubiquitously expressing EGFP animal model. 相似文献
18.
SJ Uhm MK Gupta ZC Das JH Kim C Park T Kim HT Lee 《Reproduction in domestic animals》2009,44(1):106-115
Retrovirus-mediated exogenous gene transfection of somatic cells is an efficient method to produce transgenic embryos by somatic cell nuclear transfer (SCNT). This study evaluated whether efficiency of transgenic embryos production, by SCNT using fibroblast cells transfected by retrovirus vector, is influenced by the introduced transgene and whether recloning could further improve its efficiency. Transgenic cloned embryos were produced by SCNT of porcine foetal fibroblast cells transfected by either LNβ-Z or LNβ-enhanced green fluorescent protein (EGFP) retrovirus vector and evaluated for their developmental ability in vitro . Blastomeres from four-cell stage porcine embryos, produced by SCNT of foetal fibroblast cells transfected with LNβ-EGFP retroviral vector, were subsequently recloned into enucleated metaphase II oocytes and evaluated for changes in chromatin configuration, in vitro embryo development and gene expression. Analysis of results showed that cleavage and blastocyst rates of porcine SCNT embryos, using LacZ (53.6 ± 6.4%; 12.0 ± 5.7%) or EGFP (57.5 ± 6.3%; 10.1 ± 4.1%) transfected fibroblasts, did not differ (p > 0.05) from those of non-transfected controls (60.9 ± 8.2%; 12.3 ± 4.0%). Recloning of blastomeres did not further improve the in vitro development rate. Interestingly, the nuclei of blastomere underwent slower remodelling process than somatic cell nuclei. Both cloned and recloned embryos showed 100% transgene expression and there were no evidence of mosaicism. In conclusion, our data shows that the efficiency of transgenic cloned embryos production by SCNT of somatic cells transfected with replication-defective retrovirus vector is not influenced by the transgene introduction into donor cells and recloning of four-cell stage blastomere could not further improve its efficiency. 相似文献