一起兔球虫和大肠杆菌混合感染的诊治

1 发病情况 泰安市某种兔场饲养肉兔约500只,2002年5月,在1月龄的父母代兔群中突然爆发疾病。该病的潜伏期为6～9天,发病率61％。病兔消瘦,精神沉郁,食欲降低,少数拉灰色稀粪,体重下降。到5月中旬,共死亡67只,死亡率达13％。全群服用土霉素和四环素后,不见效果,兔只连续死亡。2 临床症状 病兔食欲不振或废绝,腹围增大,肝区有压痛,贫血,黄疸,被毛脆而易脱落,尿频或常做排尿姿势,眼、鼻分泌物增多,唾液分泌增多,口腔周围被毛潮     

利用CRISPR/Cas9系统构建的转基因家蚕对核型多角体病毒的抑制

CRISPR/Cas9介导的基因编辑已经被证明可以通过破坏病原体的基因来有效地抑制感染。西南大学的DONG Z等学者最近构建了表达CRISPR/Cas9的家蚕转基因系和以家蚕核型多角体病毒(BmNPV)为目标的sgRNA,以调节家蚕早期基因的表达。通过G,代杂交获得4个转基因杂交系:Cas9(-)/sgRNA(-),Cas9(C)/sgRNA(-),Cas9(-)/sgRNA(C)和Cas9(C)/sgRNA(C)。研究证明了Cas9(C)/sgRNA(C)转基因系有效地编辑了家蚕核型多角体病毒(BmNPV)基因组的目标位点,并在BmNPV感染后观察到大片段缺失。研究者进一步对Cas9(C)/sgRNA(C)转基因系的抗病毒分析表明,半致死剂量(LD_(50))比正常接种包涵体后的值高出1 000倍。作者分析了Cas9(C)/sgRNA(C)转基因杂交系的经济性状和脱靶效率,与正常水平无显著差异。作者的研究表明CRISPR/Cas9介导的基因编辑可以更有效地靶向家蚕核型多角体病毒(BmNPV)基因组,并可作为一种昆虫抗病毒的方法。     

家蚕组蛋白甲基转移酶BmAsh2对蚕蛹的性别决定至关重要

性别决定是一个分级管理的过程,包括昆虫在内的不同生物具有高度的多样性。在鳞翅目昆虫家蚕中,由W染色体衍生的FempiRNA被鉴定为主要的性别决定因子,它揭示了一个独特的piRNA介导的性别决定途径。然而,家蚕性别决定的综合机制目前尚不清楚。中国科学院昆虫发展与进化生物学研究中心的LI Z等研究发现蚕蛹蛋白BmSiwi是决定家蚕性别的关键,而不是BmAgo3。CRISPR/Cas9介导的BmSiwi的敲除导致发育中性别阻滞和部分雌性性别逆转,而BmAgo3耗竭只影响卵子发生。研究者鉴定了3种组蛋白甲基转移酶(HMTs),它们在BmSiwi突变蛾中显著下调。其中一种HMT是BmAsh2,引起了piRNAs和转座因子(TEs)的失调,支持了它在piRNA信号通路中的作用。更重要的是,研究发现BmAsh2突变导致了性别发育阻滞和部分雌性对雄性的性别逆转,以及性别决定基因Bmdsx和BmMasc的失调。其他两种HMT是BmSETD2和BmEggless,它们的突变并不影响piRNA介导的性别决定。组织学分析和免疫沉淀结果支持BmAsh2和BmSiwi蛋白之间的功能相互作用。试验数据首次提供了证据,证明组蛋白甲基转移酶(HMT)BmAsh2在piRNA介导的蚕蛹性别决定中起关键作用。     

Seasonal and photoperiodic regulation of secretion of hormones associated with reproduction in Magang goose ganders

This study examined the reproductive endocrine profile under natural and artificial photoperiods in Magang goose ganders. Group 1 ganders (n=8) served as non-treated controls and were exposed to natural photoperiod throughout the experiment from 13th January to 17th December 2004. Group 2 ganders (n=8) were exposed to 18 h long daily photoperiod for 60 days from 13 January till 15 March 2004 and again to 16 h photoperiod for 75 days till 10th October 2004, and the 11h short photoperiod in the remainder periods of the experiment. In control ganders, plasma LH concentrations were high in normal breeding seasons (August-March) and decreased to low levels in non-breeding season from April to July. Testosterone concentrations changed similarly to that of LH throughout the seasons. Seasonal pattern of PRL concentrations was opposite to those of LH and testosterone, with low values in breeding season and high values in non-breeding season. In artificial photoperiod treated ganders, increasing photoperiod increased PRL and decreased LH and testosterone concentrations, while decreasing photoperiod reversed these changes. There were no seasonal or photoperiod caused changes in plasma T3 concentrations in both control ganders and artificial photoperiod treated ganders. These results demonstrated that in Magang goose ganders that long photoperiod stimulates PRL secretion and decreases LH secretion, which terminates reproductive season in spring and early summer, and short photoperiod stimulates LH secretion and inhibits PRL secretion rendering ganders enter into reproductive season.     

Differences between primiparous and multiparous dairy cows in the inter-relationships between metabolic traits, milk yield and body condition score in the periparturient period

During the early postpartum period dairy cows mobilize fat and muscle to support lactation. This is associated with alterations in blood metabolite and hormone profiles which in turn influence milk yield and fertility. This study developed models to determine how metabolic traits, milk yield and body condition score were inter-related at different times in the periparturient period and to compare these relationships in primiparous (PP, n=188) and multiparous (MP, n=312) cows. Data from four previous studies which included information on blood metabolic parameters, parity, milk yield, body condition score and diet were collated into a single dataset. Coefficients of polynomial equations were calculated for each trait between -1 week pre-calving and week +7 postpartum using residual maximum likelihood modelling. The completed dataset was used in a multiple correlation model to determine how the best fit curves were related to each other over time. PP cows had higher concentrations of insulin-like growth factor-I and lower beta-hydroxybutyrate concentrations throughout, higher leptin concentrations pre-partum and both the peak in non-esterified fatty acids and the nadir in urea concentration occurred earlier after calving. These differences were associated with significantly lower milk production. Leptin concentrations fell at calving and were related to body condition score. Insulin was negatively correlated with yield in MP cows only. In MP cows the relationship between insulin-like growth factor-I and yield switched from negative to positive between weeks +4 and +7. Both beta-hydroxybutyrate and urea were positively related to yield in PP cows. In contrast, in MP cows beta-hydroxybutyrate was negatively correlated with yield and urea was strongly related to body condition score but not yield. These results suggest that there are differences in the control of tissue mobilization between PP and MP cows which may promote nutrient partitioning into growth as well as milk during the first lactation.     

Synovial fluid analysis and bacterial findings in arthritic joints of juvenile male camel (Camelus dromedarius) calves

Eighteen synovial fluid samples from 11 male dromedarian calves, 9-12 month old, were analysed cytologically and bacteriologically. Calves were lame and all joints were grossly swollen. The mean +/- SD of total nucleated cell count was 7970 +/- 5000 cells/microl (range 2800-20,000 cells/microl). Polymorphonuclear (PMN) leucocytes were the predominant cell type. The mean +/- SD of absolute and percentages of each cell type were as follows: PMN leucocytes 5518 +/- 3600 cells/microl and 68 +/- 19%, monocytes/macrophages 1600 +/- 1120 cells/microl and 26 +/- 17%, lymphocytes 830 +/- 140 cells/microl and 8 +/- 7%, and red blood cell 350 +/- 130 cells/microl. The mean +/- SD of total protein concentration was 3.5 +/- 1 g/dl (range 2.5-5 g/dl). The most commonly isolated bacteria were non-haemolytic streptococci spp., followed by Arcanobacterium pyogenes and Staphylococcus aureus. No bacterial growth was obtained in eight samples and non-revealed Mycoplasma spp.