禽致病性大肠杆菌luxS和rbsC双基因缺失株的构建及其生物特性分析

禽致病性大肠杆菌(APEC)能引起家禽严重的呼吸系统和全身性疾病,由于APEC耐药菌株的不断出现迫使新型抗菌方式的研发迫在眉睫.本研究旨在评价APEC的luxS和rbsC双缺失的突变株作为减毒疫苗候选株的潜力,通过在APEC分离株DE17的单基因缺失株DE17ΔluxS的基础上,利用Red重组系统构建双基因缺失株DE1...     

Generation of a uniform thymic malignant lymphoma model with C57BL/6J p53 gene deficient mice

Lymphoma is the third most common cancer diagnosed in children, and T-cell lymphoma has the worst prognosis based on clinical observations. To date, a lymphoma model with uniform penetrance has not yet been developed. In this study, we generated a p53 deficient mouse model by targeting embryonic stem cells derived from a C57BL/6J mouse strain. Homozygous p53 deficient mice exhibited a higher rate of spontaneous tumorigenesis, with a high spontaneous occurrence rate (93.3%) of malignant lymphoma. Because tumor models with high phenotypic consistency are currently needed, we generated a lymphoma model by a single intraperitoneal injection of 37.5 or 75 mg/kg N-methyl-N-nitrosourea to p53 deficient mice. Lymphoma and retinal degeneration occurred in 100% of p53^+/− mice administered with higher concentrations of N-methyl-N-nitrosourea, a much greater response than those of previously reported models. The main anatomic sites of lymphoma were the thymus, spleen, bone marrow, and lymph nodes. Both induced and spontaneous lymphomas in the thymus and spleen stained positive for CD3 antigen, and flow cytometry detected positive CD4 and/or CD8 cells. Based on our observations and previous data, we hypothesize that mice with a B6 background are prone to lymphomagenesis.     

12种杀虫剂对日本通草蛉不同虫态的毒力及安全性评价

为明确常见杀虫剂对日本通草蛉各虫态的影响,在室内分别采用浸渍法和喷雾法测定了12种(8类)杀虫剂对日本通草蛉卵、幼虫、蛹和成虫的毒性,并评价了杀虫剂对日本通草蛉的毒性风险。结果表明,高效氯氰菊酯对日本通草蛉为极高风险,毒死蜱、吡虫啉、烯啶虫胺和阿维菌素为高风险,溴氰虫酰胺、啶虫脒和氯虫苯甲酰胺为中等风险,噻嗪酮、吡蚜酮、螺虫乙酯和甲氧虫酰肼为低风险;与其他虫态相比,12种杀虫剂对日本通草蛉蛹的毒性均为最低。在害虫生物防治及综合治理中应尽量选用对日本通草蛉毒性低的杀虫剂,以起到保护天敌的作用。     

昆虫病原线虫JLSY 003的鉴定及其生物学特性测定

经28S rDNA和ITS序列分析,从吉林省松原市土样中分离到的昆虫病原线虫JLSY 003为Oscheius myriophila品系.本研究以大蜡螟末龄幼虫为寄主,测定该线虫的生物学特性.结果表明,JLSY 003浓度为80IJs/larva时具有较高的侵染力,致死中时间LT50为15.409 h,侵染24、48h...     

基于ResNet-50深度卷积网络的果树病害智能诊断模型研究

[目的/意义]果树病害危及农业生产安全,运用人工智能技术帮助果农及时准确地识别果树病害对保障农业安全生产具有重要意义.[方法/过程]采用10 000张果树叶片病斑图像数据集,通过旋转、污化、增噪、切割等图像增强手段,提高样本图像的多样性;使用ResNet-50深度卷积网络模型,进行机器学习,获得果树病害识别模型,并基于...     

敌百虫对三疣梭子蟹幼体的急性毒性研究

试验结果表明,随着三疣梭子蟹幼体的发育,其半致死质量浓度以及安全质量浓度呈上升趋势。三疣梭子蟹Ⅰ期溞状幼体24 h LC50和48 h LC50分别为0.0095 mg/L和0.0082 mg/L,安全质量浓度为0.0018 mg/L;三疣梭子蟹Ⅱ期溞状幼体24 h LC50和48 h LC50分别为0.019 mg/L和0.010 mg/L,安全质量浓度为0.0038 mg/L;三疣梭子蟹Ⅳ期溞状幼体24 h LC50和48 h LC50分别为0.085 mg/L和0.047 mg/L,安全质量浓度为0.0043 mg/L;三疣梭子蟹大眼幼体24 h LC50和48 h LC50分别为0.085mg/L和0.050 mg/L,安全质量浓度为0.0052 mg/L。     

镉对海湾扇贝的急性毒性研究

利用水生生物毒性试验方法,分5个浓度进行镉对日照海域海湾扇贝的急性毒性实验,以期对日照海域海湾扇贝养殖提供理论依据。利用概率单位和浓度对数作线性回归,得出镉对海湾扇贝(Argopectenirradiams)在24、48、96h的半致死量LC50,其值分别为5.85、4.52和3.45mg/L。并计算出镉对海湾扇贝的安全质量浓度为0.0345mg/L。实验证明,Cd对海湾扇贝是剧毒性的毒物,海湾扇贝发育越往后期,它对Cd的耐受性就越大。     

聚维酮碘对海湾扇贝等贝类幼虫的毒性试验研究

测定了聚维酮碘(PVP—I)对虾夷扇贝、海湾扇贝、牡蛎的壳预期幼虫以及牡蛎的眼点期幼虫的24h半致死浓度分别为：32．5mg／L，31．7mg／L，44．4mg／L；安全浓度分别为：3．25mg／L，3．17mg／L，4．48mg／L，4．44mg／L。     

水温和盐度对大菱鲆稚鱼存活的影响

采用突然改变温度和盐度的方法,试验不同水温和盐度对大菱鲆稚鱼存活的影响。试验结果表明,水温为15.0~18.0℃、盐度为28~32,大菱鲆稚鱼存活率最高;用曲线回归的方法求出24 h内存活率与温度的关系式,其回归方程为y=-0.5506x2 18.4970x-53.13,依此得到大菱鲆稚鱼的高、低起始致死温度为26.54℃和7.06℃。依同样方法得到24h内存活率与盐度的回归方程为y=-0.4353x2 23.4226x-213.81,高、低起始致死盐度为37.76和16.05。经t检验显著相关(P<0.01)。     

Effects of dietary lipids on body composition and liver function in juvenile red drum, Sciaenops ocellatus

This study was conducted to evaluate the effects of different concentrations of dietary lipids on body composition and liver function in juvenile red drum, Sciaenops ocellatus. Diets were formulated to contain 40% crude protein from solvent-extracted menhaden fish meal and 0, 7, 14 or 21% lipid from menhaden fish oil. The basal diet, without supplemental fish oil, contained lipid at 0.4% of dry weight. The diets were fed to groups of 25 juvenile red drum initially averaging 7.3 ± 0.18 g fish^–1 in a recirculating culture system for 8 weeks and weight gain was recorded. After an additional 8 weeks, 16 fish from each treatment were sacrificed and the following measurements were recorded: hepatosomatic index (HSI), intraperitoneal fat (IPF) ratio, and liver -tocopherol, malondialdehyde (MDA) formation, and cytochrome P-4501A activity (measured as 7-ethoxyresorufin O-deethylase (EROD) activity). The activity of alanine and aspartate aminotransferases and concentrations of -tocopherol also were measured in plasma.Weight gain was significantly (p<0.05) affected by dietary lipid concentration, with values ranging from 361% of initial weight for fish fed the basal diet to 527% of initial weight for fish fed the diet containing 7% lipid. The HSI and IPF ratio values also were significantly affected by lipid with the lowest values recorded for fish fed the basal diet and the highest values observed in fish fed the diet containing 21% lipid. Increasing dietary lipid significantly increased oxidative stress as reflected in reduced -tocopherol in liver and plasma and increased MDA formation in the liver, although no overt pathological signs were observed. These findings suggest that lipid concentrations between 7 and 14%, when the diet contains 60 IU vitamin E kg^–1, are likely to limit oxidative stress and result in normal physiological responses of red drum.