Systemic antibodies to Clostridium botulinum type C: do they protect horses from grass sickness (dysautonomia)?

The aetiology of equine grass sickness (EGS) is still unknown. There is increasing evidence that toxicoinfection with Clostridium botulinum type C is involved. Epidemiological evidence shows that resistance to EGS can occur in older horses and those that have been on a particular pasture for longer or have been in prior contact with the disease. This resistance may be in the form of an immune response to the aetiological agent. Levels of systemic antibodies to the surface antigens of C. botulinum type C (using the closely related and safe C. novyi type A as a phenotypic marker) and to the botulinum type C neurotoxin (BoNT/C) were investigated in horses with and without EGS. Horses with grass sickness were found to have significantly lower levels of systemic IgG to both surface antigens and BoNT/C. Horses with low levels of systemic immunity to these antigens may be more susceptible to developing EGS. There were no significant differences in antibody levels between the different categories of EGS, suggesting systemic immunity to C. botulinum type C does not play a significant role in influencing the severity of the disease. However, horses that had been in contact with EGS or that were grazing land where it had occurred frequently in the past had significantly higher antibody levels to these antigens. These horses may have been exposed to subclinical doses of C. botulinum type C and BoNT/C, resulting in the production of a protective immune response against the putative aetiological agent. This finding is of potential significance for the prospect of prevention of EGS by vaccination against C. botulinum type C.     

采用卵子-胚胎移植技术分析研究家畜受精和早期发育

为了阐明家畜受精及早期发育或者输卵管内未受精卵的变化过程,记述了4种卵-胚胎移植方面的研究：①将来自发情黄体期的猪卵母细胞移植到授精动物的输卵管内,可获得受精结果,但将卵移植到已经交配的猪输卵管内会导致多精受精。②把第7~8 d的猪孵化囊胚移植到同期处理的受体内,可以观察到胚胎成功发育到19~23 d。证明失去滋养外胚层的扩张囊胚可以承受移植的物理操作并保持发育能力,而且未交配受体的黄体寿命可以在第7 d和第8 d支持移植胚胎发育。③取2~6 mm直径发育卵泡的牛卵母细胞经体外成熟可以在授精小母牛的输卵管内正常受精,表明其具有受精和胚胎发育能力。④将马的卵母细胞移植到猪的输卵管内,卵母细胞到达子宫的时间仅需46~48 h,在此过程中没有发现未受精马卵的退化现象,暗示了输卵管中存在维持卵子生理机能的因子。综上所述,卵移植是研究家畜早期发育的有效分析技术。     

Systemic RNAi in C. elegans requires the putative transmembrane protein SID-1

Double-stranded RNA-mediated gene interference (RNAi) in Caenorhabditis elegans systemically inhibits gene expression throughout the organism. To investigate how gene-specific silencing information is transmitted between cells, we constructed a strain that permits visualization of systemic RNAi. We used this strain to identify systemic RNA interference-deficient (sid) loci required to spread gene-silencing information between tissues but not to initiate or maintain an RNAi response. One of these loci, sid-1, encodes a conserved protein with predicted transmembrane domains. SID-1 is expressed in cells sensitive to RNAi, is localized to the cell periphery, and is required cell-autonomously for systemic RNAi.     

Evaluation of potato varieties and selections for resistance to bacterial soft rot

Potato varieties and selections were evaluated for resistance to bacterial soft rot caused byErwinia carotovora subsp. carotovora and Erwinia carotovora subsp. atroseptica in mist chamber. A randomized complete block design with a single treatment and 3 replications was used in this study. Potato lines were inoculated with bacterial suspension (10 tubers / line) using the puncture inoculation method and incubated for 4 days in a mist chamber at 21 C and 100 % relative humidity in the dark. Although there were differences in incidence of soft rot and in amount of weight reduction, most of the potato lines were susceptible to tuber soft rot. Mean incidence (%) of soft rot ranged from 10 to 100%. Mean reduction of tuber weight (%) ranged from 0.13 to 16.43 %. Among the varieties and selections tested, AF 522-5 was the most resistant to tuber weight loss, while AF 1424-7 was most susceptible. There were also significant differences between years, and a variety by year interaction. Testing over a period of years is recommended. A significant correlation coefficient of soft rot incidence (%) and reduction of tuber weight (%) was obtained (r=0.65; P=0.05), indicating that incidence was a fair measure of soft rot potential. However, the greater variability in results for incidence make weight loss a better measure of soft rot reaction. There was a significant difference among varieties in the reduction of tuber weight when potato lines were inoculated either 1 month or 2 months after harvest, but the interaction of time by year prohibits a conclusion as to which time gives a better test reaction. Late maturing varieties had slightly less weight loss than earlier maturing varieties.     

Clinical signs, histopathology and genetics of experimental transmission of BSE and natural scrapie to sheep and goats

This paper compares the dinical signs, histopathology, detection of PrPSc protein and PrP genetics of the transmission of BSE to sheep and goats, with the effects of the transmission of natural scrapie from a brain homogenate from a single sheep. After intracerebral and oral inoculations there were similarities in the clinical signs due to the two sources of infection, but there were differences in pathology at the end stage of disease and in the genotypes of the sheep which succumbed to the challenges. The incubation period of BSE was associated with the sheep PrP codon 171 genotype, but the natural scrapie source, despite inducing disease only in known susceptible genotypes, showed no clear association with PrP genotype.