不同利用方式下草地土壤微生物及土壤呼吸特性

通过对呼伦贝尔羊草(Leymus chinensis)草甸草原土壤呼吸特性及土壤微生物的测定,研究了3种不同利用方式(围封、放牧和刈割)对天然草地土壤呼吸特性及土壤微生物的影响,为草甸草原土壤呼吸研究提供基础理论依据。结果表明:不同利用方式下土壤呼吸速率、土壤微生物量碳含量与土壤酶活性(除脲酶)均表现为草地围封比放牧和刈割呼吸速率高(含量高、活性强);土壤微生物量氮含量、脲酶活性和微生物数量表现为草地放牧和刈割比围封的含量高(活性强、数量多);土壤微生物量碳、氮含量、土壤酶活性(除脲酶)和土壤微生物数量均以表层(0～10cm)最高(活性最强、数量最多),随着土层深度增加而降低(活性下降、数量减少)。土壤呼吸速率与微生物量碳、土壤酶活性(除过氧化氢酶)成正相关,与微生物量氮、过氧化氢酶和微生物数量成负相关,其中只与微生物量氮相关性显著,而其余之间均不显著。     

Detection of disease-specific PrP in the distal ileum of cattle exposed orally to the agent of bovine spongiform encephalopathy

The immunohistochemical localisation of the disease-specific protein, PrP(Sc), was examined in the distal ileum of cattle up to 40 months after they had been exposed orally to the agent of bovine spongiform encephalopathy (BSE), in the intestines and mesenteric lymph nodes of an additional group of cattle, killed six months after a similar exposure, and in the distal ileum of naturally occurring clinical cases of BSE. PrP(Sc) was detected, mainly in macrophages, in a small proportion of the follicles of Peyer's patches in the distal ileum of the experimentally exposed cattle throughout much of the course of the disease. The observations are in agreement with the infectivity data derived from mouse bioassays of the distal ileum. At the later stages of the disease, the proportion of immunostained follicles increased as the total number of follicles decreased with age. In the additional experimental group of cattle, PrP(Sc) was confined to the Peyer's patches in the distal ileum. No immunostaining was detected in the lymphoid tissue of the distal ileum of naturally occurring clinical cases of BSE. In some of the clinically affected experimentally induced and naturally occurring cases of BSE there was sparse immunostaining of the neurons of the distal ileal myenteric plexus.     

Evaluation of the effects of controlled autolysis on the immunodetection of PrP(Sc) by immunoblotting and immunohistochemistry from natural cases of scrapie and BSE

Seventeen clinically suspect scrapie sheep, and twelve suspected BSE-affected cattle were confirmed using routine histopathological examination by the detection of characteristic spongiform change in the medulla brain region taken at the level of the obex. Three sheep and four cows acquired as controls showed no spongiform change. Five aliquots of brain tissue from each of four brain regions were taken (cerebellum, medulla, frontal cerebral cortex and occipital cerebral cortex) from each of the 36 animals. One aliquot was frozen at -70 degrees C, the others were subjected to one of four autolysis regimes at 3 or 7 days at 25 degrees C or 37 degrees C. All samples were tested by Western immunoblotting for detection of PrP(Sc) using the Prionics - Check test (Prionics AG, Zurich, Switzerland). Further samples of medulla from 15 suspect scrapie cases, 10 healthy sheep, 13 suspect BSE cows and 5 healthy cows, were taken adjacent to the obex, and subjected to autolysis at 37 degrees C for 6, 12, 24 and 48 hours before being fixed in 10 per cent formal saline and subsequently examined by a routine immunohistochemical technique for detection of PrP(Sc) protein. The abnormal protein could not be detected in any of the control animals by either technique. PrP(Sc) could be detected by Western immunoblotting in at least one brain area from all the positive animals after autolysis for 7 days at 37 degrees C. The protein could be detected by immunohistochemistry in all cases which were positive by histopathological examination using all autolysis conditions. From the results of this study it is concluded that autolysis does not significantly compromise the diagnosis of scrapie or BSE by either of these diagnostic methods.     

原生质体融合技术改良植病生防木霉菌株

以产孢量大，对苯菌灵有抗性，对潮霉素B敏感的哈茨木霉菌株T9和产孢量少，对潮霉素B有抗性，对苯菌灵敏感的康宁木霉菌株Tk7a为亲本，进行原生质体融合，筛选获得抗最高浓度杀菌剂的融合子。所有融合子的产孢量均比亲本菌株Tk7a大。融合子按照菌落形态的不同分成4组，大部分融合子的几丁质酶、葡聚糖酶和内切葡聚糖酶的活性比亲本菌株高。融合子对棉花猝倒病菌和小麦全蚀病菌的寄生能力基本等同于亲本菌株；融合子对小麦全蚀病的防效比亲本菌株稍好，其刺激麦苗根部生长的能力与亲本菌株相差不大。两个融合子根际竞争能力比亲本菌株T9强，和亲本菌株Tk7a相当。     

BOOK REVIEWS

Book reviewed in this article:
Guide to the Dissection of Domestic Ruminants . RE Habel
Biology and Medicine of Rabbits and Rodents . JE Harkness and JF Wagner     

Porcine pleuropneumonia in Australian pigs due to Actinobacillus pleuropneumoniae serovar 5

Book reviewed in this article: Guide to the Dissection of Domestic Ruminants . RE Habel Biology and Medicine of Rabbits and Rodents . JE Harkness and JF Wagner     

Giardia infection in budgerigars

Budgerigars ( Melopsittacus undulatus ) from two different breeding colonies were found to have Giardia infection. Light microscopy, scanning electron microscopy and in-vitro and in-vivo studies confirmed the species was G psittaci . Chicks were clinically affected and showed signs of retarded growth, dehydration and diarrhoea. The faeces of adult birds treated with metronidazole in drinking water were negative for Giardia 5 days after treatment. Megabacteria were also found in adult birds but were not treated. This study extends the known host range for Giardia in Australia to include budgerigars.