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Soon after ovulation, the newly formed corpus luteum (CL) starts secreting progesterone (P(4)), necessary for implantation. The CL, an ovarian transient endocrine organ, undergoes growth and regression throughout its life span. The objective of this study was to evaluate if caspase-3 mediates cell death in the equine cyclic luteal structures and relate it to luteal endocrine function. Blood and luteal tissue were collected during the breeding season after slaughter from 38 randomly assigned cycling mares. Luteal tissues were classified as corpora haemorrhagica (CH; n = 7); mid luteal phase corpora lutea (Mid-CL; n = 17); late or regressing corpora lutea (Late-CL; n = 9) and corpora albicans (CA; n = 5). Plasma P(4) concentration, determined by radioimmunoassay, showed a significant increase from CH to Mid-CL (p < 0.001), followed by a decrease to Late-CL (p < 0.001) and CA (p < 0.001). Caspase-3 processing and poly (ADP) ribose polymerase (PARP) degradation were assessed by western blotting. Active caspase-3 was twofold increased in Mid-CL, Late-CL and CA as compared with CH (p < 0.05). Immunocytochemistry also showed a significant increase in caspase-3 expression in large luteal cells in all structures when compared with CH (p < 0.05). Consistently, the endogenous caspase-3 substrate, PARP, was markedly degraded from CH to CA (p < 0.05). In fact, the ratio of full-length to degraded PARP showed a significant decrease from CH to Mid-CL, Late-CL and CA (p < 0.05). Finally, the decrease in P(4) from Mid- to Late-CL coincided with no further increases in apoptosis. In conclusion, these results suggest that the effector caspase-3 of apoptosis, might play an important role during luteal tissue involution in the mare, even though its relationship with P(4) remains to be elucidated.  相似文献   
85.
双峰乡是中国“毛竹之乡”——宜丰县的毛竹重点产区.在对毛竹林的经营中,双峰乡通过全面规划、分类改造,改革机制、多种管理方式经营,建设样板、典型带动推广,以及基地建设与竹材深加工开发相结合等一系列措施,使这个“双料”的毛竹之乡真正发挥了资源优势,实现了毛竹丰产高效,促进了地方经济发展.调查总结了其成功的竹林经营管理经验,还介绍了向全县推广的措施方法.  相似文献   
86.
Off-axis electron holography in the transmission electron microscope was used to correlate the physical and magnetic microstructure of magnetite nanocrystals in magnetotactic bacteria. The magnetite crystals were all single magnetic domains, and the magnetization directions of small superparamagnetic crystals were constrained by magnetic interactions with larger crystals in the chains. Shape anisotropy was found to dominate magnetocrystalline anisotropy in elongated crystals. A coercive field between 300 and 450 oersted was determined for one chain.  相似文献   
87.
OBJECTIVE: To assess the effect of breed of cattle on the transmission rates of and innate resistance to Babesia bovis and B bigemina parasites transmitted by Boophilus microplus ticks. DESIGN: Groups of 56 purebred B indicus and 52 B indicus cross B taurus (50%, F1 generation) steers were placed in a paddock seeded with and also naturally infested with B microplus which were the progeny of females ticks fed on B taurus cattle specifically infected with a virulent isolate of B bovis. The cattle were placed in the infested paddock 50 days after seeding had started. PROCEDURE: Cattle were inspected from horseback daily for 50 days. Clinically ill cattle were brought to yards and assessed by monitoring fever, depression of packed-cell volume, parasitaemia and severity of clinical signs. Any animals that met preset criteria were treated for babesiosis. Blood samples were collected from all cattle on day 28, 35 and 42 after exposure and antibodies to Babesia spp and packed cell volume measured. RESULTS: All steers, except for one crossbred, seroconverted to B bovis and B bigemina by day 35 and 75% of the crossbred steers showed a maximum depression in packed cell volume of more than 15% due to infection with Babesia spp compared with only 36% of the B indicus group. Ten of the 52 crossbreds and 1 of the 56 B indicus steers showed severe clinical signs. Two of the crossbreds required treatment of which one died 2 weeks after initial treatment. CONCLUSIONS: Pure-bred B indicus cattle have a high degree of resistance to babesiosis, but crossbred cattle are sufficiently susceptible to warrant the use of preventive measures such as vaccination. Transmission rates of B bovis and B bigemina to B indicus and crossbred cattle previously unexposed to B microplus were the same.  相似文献   
88.
Gibberellins have been shown to be involved in such important processes as seed germination, flowering, maturation and tuberization in potato. Parents fromSolanum tuberosum Groups Andigena and Tuberosum were found to produce progeny containing dark green, rosette dwarf individuals which could be completely restored to normal appearance by exogenous GA3. Test crosses indicated that this phenomenon can be explained by the action of a single locus, the dwarfing characteristic being conferred by the nulliplex condition. The gene symbol “ga1” is proposed. Group Andigena dwarfs demonstrated much greater tuberization compared to their normal full sibs or dwarfs restored to normal phenotype by exogenous GA3. The possibility that such gibberellin mutants may be involved in the long day adaptation of Gp. Tuberosum is discussed. This character may also be a useful tool for investigating various aspects of the gibberellin status of the potato.  相似文献   
89.
Diploid wild potato species, classified as 1EBN (Endosperm Balance Number), do not cross with tetraploid or diploid forms ofS. tuberosum Gp. Tuberosum. The crossing of 2n pollen producing 1EBN clones as well as chromosome-doubled 1EBN clones with Gp. Tuberosum haploids was initiated to overcome this hybridization barrier. The screening of eleven 1EBN species,S. brachistotrichum, S. bulbocastanum, S. cardiophyllum, S. chancayense, S. commersonii, S. etuberosum, S. fernandezianum, S. jamesii, S. mochicense, S. pinnatisectum andS. trifidum, resulted in the identification of 2n pollen producers in eight of the species examined. Direct hybridization with Gp. Tuberosum haploids utilizing the above-mentioned crossing scheme was successful withS. chancayense andS. commersonii. The hybrids obtained, however, were male and female sterile. Abnormal microsporogenesis in the hybrids was postulated to be the result of an interaction between Gp. Tuberosum cytoplasm and nuclear genes contributed by the 1EBN male parent. Analyses of the growth of 1EBN species’ pollen tubes in the stigma/style of Gp. Tuberosum haploids were also conducted. Interspecific incompatibilities were observed with the most severe forms found with the use of species in the Series Etuberosa. The use of the Endosperm Balance Number theory can aid in designing crosses which overcome barriers to successful endosperm development. Sterilities in the hybrids obtained as well as interspecific incompatibilities will also need to be addressed, however, before 1EBN species germplasm can be successfully utilized for the improvement of the cultivated potato.  相似文献   
90.
Magnetic collapse in transition metal ions is predicted from first-principles computations at pressures reached in the Earth's lower mantle and core. Magnetic collapse would lead to marked changes in geophysically important properties, such as elasticity and conductivity, and also to different geochemical behavior, such as element partitioning, than estimated by extrapolating low-pressure data, and thus change the understanding of Earth's structure and evolution. Magnetic collapse results from band widening rather than from changes in crystal field splitting under pressure. Seismic anomalies in the outer core and the lowermost mantle may be due to magnetic collapse of ferrous iron, dissolved in iron liquid in the outer core, and in solution in magnesiowustite in the lowermost mantle.  相似文献   
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