Polymorphism of 14α-demethylase Gene (CYP51) in the Cereal Eyespot Fungi Tapesia acuformis and Tapesia yallundae

Cereal eyespot fungi Tapesia acuformis and Tapesia yallundae are closely related species which show different behaviours upon treatment with sterol 14-demethylase inhibitors (DMIs). T. acuformis is naturally resistant to DMIs belonging to the triazole family and susceptible to the imidazole ones, whilst T. yallundae is sensitive to both inhibitors. Cloning of the target enzyme gene, CYP51, from the two species revealed an important polymorphism between them. Further sequencing of CYP51 from sixteen T. acuformis and eleven T. yallundae strains with different phenotypes with regards to resistance to DMIs confirmed that at least eleven variations are species related. Among them, a conserved phenylalanine residue at position 180, found both in T. yallundae and in all known CYP51 proteins from filamentous fungi and yeast, was replaced in T. acuformis by a leucine. Therefore, a leucine at 180 could be possibly involved in natural resistance of T. acuformis to triazoles. Other mutations were observed in some resistant strains, sometimes simultaneously, but in contrast to what was reported for other filamentous fungi, where a mutation at the 136 position of the CYP51 gene product seemed to correlate with resistance to DMIs, we did not find a clear relationship between a given mutation and a particular phenotype. This result suggests that resistance to DMIs could have a polygenic nature in Tapesia. We took advantage of species-related variations to develop a PCR-based assay allowing rapid and easy discrimination between field strains of the two species.     

Brucellosis in Argentina

Brucellosis has been recognized in Argentina since the 19th century. Several studies demonstrated the presence of the disease in most of the domestic species. Actually, the estimate of prevalence is that between 10 and 13% of the farm animals are infected with bovine brucellosis with an individual rate of 4–5%. The annual economical losses have been estimated at US$ 60,000,000. The control of bovine brucellosis began in 1932 and successive resolutions have been issued since then. The current resolution indicates that B. abortus S19 is mandatory in female calves between 3 and 8 months of age. The vaccine strain B. abortus RB51 was provisionally approved but only for cattle older than 10 months of age. The brucellosis control program consists principally of test and slaughter. This methodology has been successful mainly in the dairy farms that have the incentive due to increased pricing because of obtaining a low prevalence of the disease. Brucellosis has been found in porcine, caprine, ovine and canine species. All Brucella species have been found in the country. Human brucellosis is an important disease and a national coordinated diagnostic net has been formed to better control the disease in man.     

Major outer membrane proteins of Brucella spp.: past,present and future

The major outer membrane proteins (OMPs) of Brucella spp. were initially identified in the early 1980s and characterised as potential immunogenic and protective antigens. They were classified according to their apparent molecular mass as 36–38 kDa OMPs or group 2 porin proteins and 31–34 and 25–27 kDa OMPs which belong to the group 3 proteins. The genes encoding the group 2 porin proteins were identified in the late 1980s and consist of two genes, omp2a and omp2b, which are closely linked in the Brucella genome, and which share a great degree of identity (>85%). In the 1990s, two genes were identified coding for the group 3 proteins and were named omp25 and omp31. The predicted amino acid sequences of omp25 and omp31 share 34% identity. The recent release of the genome sequence of B. melitensis 16 M has revealed the presence of five additional gene products homologous to Omp25 and Omp31. The use of recombinant protein technology and monoclonal antibodies (MAbs) has shown that the major OMPs appear to be of little relevance as antigens in smooth (S) B. abortus or B. melitensis infections i.e. low or no protective activity in the mouse model of infection and low or no immunogenicity during host infection. However, group 3 proteins, in particular Omp31, appear as immunodominant antigen in the course of rough (R) B. ovis infection in rams and as important protective antigen in the B. ovis mouse model of infection. The major OMP genes display diversity and specific markers have been identified for Brucella species, biovars, and strains, including the recent marine mammal Brucella isolates for which new species names have been proposed. Recently, Omp25 has been shown to be involved in virulence of B. melitensis, B. abortus and B. ovis. Mutants lacking Omp25 are indeed attenuated in animal models of infection, and moreover provide levels of protection similar or better than currently used attenuated vaccine strain B. melitensis Rev.1. Therefore, these mutant strains appear interesting vaccine candidates for the future. The other group 3 proteins identified in the genome merit also further investigation related to the development of new vaccines.     

灭虫精对西施舌幼贝的毒性试验

在静水条件下,进行灭虫精对西施舌幼贝的毒性试验,试验结果显示:灭虫精对西施舌幼贝24 h致死浓度LC100为400 ms／L,半数致死浓度LC100为250 mg/L,安全浓度为2．50mg／L;48h致死浓度为260 mg／L,半数致死浓度LC50为224ms／L,安全浓度为2．24mg／L。灭虫精用于西施舌人工育苗过程中桡足类等敌害生物防治,具有较强的可用性。根据试验结果,建议使用2 mg／L浓度的灭虫精进行防治,可达到显著效果。     

仔猪精氨酸的内源合成及其影响因素

由于精氨酸及其代谢产物具有广泛生物学作用,使得近年来研究者们在生理、生化和营养等方面对其作了大量的研究。母乳严重缺乏精氨酸,仔猪精氨酸内源合成对精氨酸的平衡起了重要作用,使得哺乳仔猪精氨酸的内源合成成为精氨酸营养的研究核心。通过对精氨酸内源合成路径和场所的了解,研究者们进一步研究了精氨酸内源合成的影响因素,主要有仔猪日龄、日粮中精氨酸的水平、乳酸盐和皮质醇的浓度等。本文就仔猪精氨酸内源合成的途径和场所、内源合成的量、影响因素以及精氨酸的需要量等进行了综述,重点阐述了精氨酸内源合成的影响因素。     

哺乳动物嵌合体制作及分析进展

嵌合体技术对研究哺乳动物早期胚胎的发育,探索细胞分化规律,掌握基因的表达调控规律,建立遗传疾病动物模型等具有重要意义。本文分别就近几年来嵌合体动物的制作方法及分析手段作一简要概述。     

体细胞计数及其在降低奶牛乳房炎发病率方面的应用

介绍奶牛体细胞计数的概念、特征、测量方法、体细胞值所受到的影响及其在乳制品行业的应用,尤其是在降低奶牛乳房炎发病方面,用体细胞值作为一种遗传性状进行选择以提高奶牛对乳房炎抗性的应用。     

反刍动物采食量测定方法的研究进展

在单位时间内反刍动物实际采食的饲草(料)数量称为反刍动物的采食量。据研究发现,反刍动物的采食过程是一个动态的过程,是由生物和非生物因素共同、相互的影响过程。准确地计算和测定反刍动物的采食量,是制定反刍动物的良好的营养方案的基础;是确定其补饲的重要依据。研究反刍动物的采食量对整个畜牧产业有重要的作用。本文对反刍动物在自由进食状态下的采食量的影响因素进行了阐述,并对其采食量的测定方法进行了深入的探讨和研究。     

胚胎干细胞的研究进展

胚胎干细胞来源于附植前胚胎的内细胞团或附植后胎儿的原始生殖细胞具有发育全能性的细胞。本文从它的研究概况、生物学特性、胚胎干细胞的分离培养与建系等方面做一概述。     

牛磺酸的生物学功能及其在蛋鸡生产中的研究应用

牛磺酸是一种具有广泛生物学功能的营养物质,它在畜牧业生产中的应用已引起人们的密切关注,成为当今研究的一个亮点。本文概述了牛磺酸的结构、性质、分布、合成代谢、生物学功能及其在蛋鸡生产中的研究应用进展,并指出了今后需解决的问题和发展前景。