桑椹菌核病研究进展

桑椹菌核病是由3种子囊菌真菌引起的相似症状病害的统称,为果桑生产中的毁灭性真菌病害,严重制约果桑产业的发展。这3种病原菌同为死体营养型病原菌,其侵染手段多样,侵染机制复杂。由于3种病原菌在人工培养上存在不同程度的困难(桑实杯盘菌和肉阜状杯盘菌难培养,核地杖菌在人工培养基上不能完成生活史),在一定程度上限制了病原菌的研究。本文综述了桑椹菌核病的侵染循环、病原菌、病害流行、病原菌与寄主互作等方面的研究进展,并对未来的研究进行了展望,以期对桑椹菌核病的深入研究提供参考。     

Mode of action of the anilino-pyrimidine fungicide pyrimethanil. 2. Effects on enzyme secretion in Botrytis cinerea

The effect of pyrimethanil on the levels of cell wall degrading enzymes secreted by Botrytis cinerea Pers. was investigated in diseased plant tissues and in liquid B. cinerea cultures. Total proteinase activity isolated from infected carrot slices which were treated with 5.0 μM pyrimethanil was decreased by 76%, 3 d after inoculation. Polygalacturonase, cellulase, proteinase and laccase activities were all decreased in the medium of three day-old cultures grown in the presence of pyrimethanil. The pyrimethanil concentrations resulting in 50% reduction in total enzyme activities (IC₅₀) were approximately 0.25 μM for polygalacturonase, cellulase and proteinase, and approximately 1.0 μM for laccase. No significant growth inhibition was observed at these pyrimethanil concentrations. Pyrimethanil did not inhibit the enzymes directly, nor did it inhibit the synthesis of cytosolic proteins. Therefore, it was proposed that the fungicide inhibits protein secretion at a post-translational stage in the secretory pathway. Large differences were found in the effects of pyrimethanil on the growth of B. cinerea in liquid cultures and on agar plates, depending on the composition of the medium. In liquid media containing cellulose and protein as carbon and nitrogen sources, growth inhibition occurred at 5.0 μM pyrimethanil, whilst no growth inhibition was observed with 50 μM pyrimethanil in malt extract. Similarly, growth occurred on potato/dextrose agar (PDA) at 0.5 μM pyrimethanil, but no growth was seen at this concentration on agars containing cellulose and protein. Thus it appears that pyrimethanil is most active in media where the fungus has to utilise extracellular enzymes to mobilise the nutrients it requires for growth.     

Accumulation of Sapogenin Conjugates and Histological Changes in the Liver and Kidneys of Lambs Suffering from Alveld,a Hepatogenous Photosensitization Disease of Sheep Grazing Narthecium ossifragum

Sixteen lambs exhibiting hepatogenous photosensitization (alveld) after grazing pasture containing Narthecium ossifragum and seven nonphotosensitized lambs grazing the same pastures were studied. All the alveld-affected lambs revealed liver damage dominated by single cell necrosis, portal fibroplasia and bile duct proliferation. Crystalloid clefts were demonstrated in the bile ducts of two and in the hepatocytes and Kupffer cells of nine photosensitized lambs. Plasma bilirubin concentration was severely increased in ten of the cases of alveld whereas the activity of aspartate aminotransferase was moderately to severely increased in seven cases. The activity of glutamate dehydrogenase was moderately elevated in one of the photosensitized lambs. The main histopathological findings in the kidneys from the alveld-affected lambs were dilated tubules, often with eosinophilic material in the tubular lumina. Regenerative changes were seen in a large proportion of the renal sections. Elevated plasma concentrations of urea and creatinine, and the renal histopathological changes, suggested that the photosensitized lambs had been through a phase of renal injury. Analysis of the free and conjugated sapogenin content in liver tissue and bile was performed by gas chromatography–mass spectrometry. There were significantly higher concentrations of conjugated episapogenins in both the liver and bile in the alveld-affected lambs than in the nonphotosensitized lambs.     

Neutrophil Phagocytosis Following Inoculation of Salmonella choleraesuis into Swine

Neutrophils are an important mediator of host defence, especially in early stages of infection. A major function of neutrophils is the uptake and killing of invading microbes. Little is known about the effect of neutrophil activity on the pathogenesis and development of the carrier state in swine following infection with Salmonella choleraesuis. A human whole-blood microassay using flow cytometry was modified to measure the effect of S. choleraesuis infection in vivo on the rate of ingestion, or rate of uptake, of homologous bacteria by porcine neutrophils. Pigs were inoculated intranasally with 5–8×10⁸ CFU S. choleraesuis and blood was collected in heparinized tubes at –5, 0, 1, 2, 3 and 4 days post inoculation (PI). Heat-killed S. choleraesuis were labelled with fluorescein isothiocyanate and incubated for various times with diluted whole blood. Red blood cells were lysed, external non-phagocytized bacteria were quenched with a commercially available lysing solution, and fluorescence from internalized bacteria labelled with fluorescein isothiocyanate was detected by flow cytometry. The rate of uptake by neutrophils did not increase until 2 days PI and then remained elevated to 4 days PI. The minimal uptake of S. choleraesuis early after exposure to these organisms may provide an opportunity for the pathogen to colonize and/or replicate to levels that facilitate establishment of a carrier state or clinical infection in swine.     

朊病毒致病机理的研究进展

就细胞型朊蛋白PrP^c的分子生物学特性、朊蛋白的生理功能、致病性朊蛋白PrP^sc对免疫系统的影响、朊病毒的外周致病机理以及相关细胞因子、化学因子与朊病毒神经侵袭之间的关系、朊病毒从外周到中枢的转运机制、入侵门户、血液传播及朊病的其他病理标志和检测方法的研究做一综述。     

牛瑟氏泰勒虫病致病机理的研究进展

牛瑟氏泰勒虫病是由蜱传染的一种血液原虫病。近年来,随着养牛业的发展,牛瑟氏泰勒虫病的发生呈上升趋势,尤其是引进牛和改良牛的发病率和致死率均较高,给养牛业带来了巨大的经济损失。本文对近年来牛瑟氏泰勒虫病的病原体、流行病学、病理学和致病作用等与此病的致病机理相关的方面的研究进展作一总结,以便广大兽医工作者对此病有更加深入的认识。     

猪胸膜肺炎放线杆菌Apx毒素的分子生物学与致病机理

猪传染性胸膜肺炎是由胸膜肺炎放线杆菌(App)引起的猪的一种呼吸道传染病.到目前为止,APP已经被分离鉴定出了15种血清型(1～15).15种血清型的APP能产生属于RTX毒素家族的4种Apx毒素,分别为ApxⅠ、ApxⅡ、ApxⅢ和ApxⅣ.ApxⅠ操纵子包含有ApxⅠ C、A、B、D 4个基因;ApxⅠ毒素含有13个富含甘氨酸的重复区.ApxⅡ操纵子仅包括结构基因ApxⅡA和激活基因ApxⅡC,而无分泌基因;ApxⅡ蛋白含有8个甘氨酸的序列重复.ApxⅢ操纵子与ApxⅠ操纵子相同,具有一个完整的操纵子;ApxⅢ在N～末端有3个疏水区,在C末端部分有13个富含甘氨酸的区域.Apx毒素的致病机理为先由没有活性的前体蛋白转变为有活性的ApxA蛋白,再由有活性的ApxA蛋白侵害细胞.     

新城疫病毒糖蛋白致病作用的研究

本实验以分子生物学和现代免疫学方法,对新城疫病毒（ＮＤＶ）中国毒株Ｆ４８Ｅ９和ＬａＳｏｔａ等毒株的糖蛋白的致病作用进行了探讨。结果表明,ＮＤＶ Ｆ和ＨＮ蛋白为糖蛋白,强弱毒株之间Ｆ蛋白裂解位点的氨基酸序列有明显的不同,并决定了毒株的毒力,但ＮＤＶ的致病作用尚需ＨＮ、Ｆ蛋白的协同作用,单一的Ｆ或ＨＮ蛋白不能构成ＮＤＶ的致病作用。     

Streptococcus uberis: A Permanent Barrier to the Control of Bovine Mastitis?

The prevalence of bovine mastitis has been reduced over the past 25 years due to the implementation of a five-point control plan aimed at reducing exposure, duration and transmission of intramammary infections by bacteria. This has markedly reduced the incidence of bovine mastitis caused by bacteria which show a contagious route of transmission, but has had little effect on the incidence of mastitis due to bacteria which infect the gland from an environmental reservoir. Streptococcus uberis is one such bacterium which is responsible for a significant proportion of clinical mastitis worldwide.The inadequacies of the current methods of mastitis control have led to the search for additional measures, particularly vaccines to prevent intramammary infection by this bacterium. Such an approach requires detailed knowledge of the pathogenesis of intramammary infection. Our understanding of this area has grown in recent years but a lack of information still hampers disease control. Both live vaccines and, recently, crude sub-unit vaccines have shown promise against bovine mastitis due to S. uberis. Vaccines against mastitis must, however, be able to control infection without the participation of a marked inflammatory response. This review provides an overview of the recent advances which have been made in our understanding of host-pathogen interactions which promote infection and disease and highlights areas for strategic research aimed at controlling this bacterial infection.     

Streptococcus Suis: Past and Present

Staats, J.J., Feder, I., Okwumabua, O. and Chengappa, M.M., 1997. Streptococcus suis: past and present. Veterinary Research Communications, 21 (6), 381-407Steptococcus suis is a Gram-positive, facultatively anaerobic coccus that has been implicated as the cause of a wide range of clinical disease syndromes in swine and other domestic animals. In swine, the disease has spread worldwide but is more prevalent in countries with intensive swine management practices. The disease syndromes caused by S. suis in swine include arthritis, meningitis, pneumonia, septicaemia, endocarditis, polyserositis, abortions and abscesses. S. suis has also been implicated in disease in humans, especially among abattoir workers and swine and pork handlers. In humans, S. suis type 2 can cause meningitis, which may result in permanent hearing loss, septicaemia, endocarditis and death. The pathogenic mechanism of S. suis is not well defined. Several virulence factors have been identified, but their roles in pathogenesis and disease have not been well elucidated. Much work is in progress on characterization of virulence factors and mechanisms, with emphasis on the control of the disease. Because of the non-availability of suitable immunoprophylaxis, control of S. suis infection has depended mainly on the use of antimicrobials.