Impact of sublethal di‐n‐butyl phthalate on the aquaculture fish species Nile tilapia (Oreochromis niloticus): histopathology and oxidative stress assessment

Phthalates such as di‐n‐butyl phthalate (DBP) and their esters are widely used plasticizers, their ubiquitous presence in daily life, inevitably leads to their restricted use due to important environmental pollution and health impacts and endocrine disruption potential. The aim of this study was to examine the effects of a sublethal concentration of 10 mg L^?1 DBP on haematocrit (HCT) values, gills and liver histology, malondialdehyde (MDA, 2‐thiobarbituric acid‐TBA reactivity) and reduced glutathione (GSH) levels in gills and liver tissue as oxidative stress biomarkers in the aquaculture fish species Nile tilapia (Oreochromis niloticus) after 24 (DBP‐24) and 96 (DBP‐96) h exposure. No differences were found between per cent HCT values in the 24 h exposure groups (P > 0.05). Response of antioxidant defence systems in liver and gill tissues of the fish were dependent on exposure duration and changed to a higher extent during 96 h. MDA levels in liver tissue increased in DBP treated fish in comparison to the control fish. However, the differences between the exposure and control groups were not significant (P > 0.05). A statistically significant decrease (P > 0.05) was recorded in gill MDA levels in the DBP‐96 group when compared to the control and DBP‐24 groups. The liver GSH levels were unchanged in the DBP treated fish. However, GSH levels were significantly lower in the gill tissue of the DBP‐96 group. Exposure to DBP caused several degenerative changes in the histology of gill and liver tissue. Gills displayed hyperaemia, epithelial lifting, oedema, talengiectasia, epithelial hyperplasia and fusion of secondary lamellae, whereas in liver several circulatory anomalies (hyperaemia, blood congestion and sinosoid dilatation) and vacuolization of hepatocytes were observed. Histopathological results demonstrated that the gills were more affected than the liver perhaps due to their direct contact with DBP.     

三峡库区玉米地方品种产量性状的遗传潜势分析

从三峡库区征集到72份玉米地方品种并分别与改良兰卡斯特和改良瑞德血缘自交系进行测配，利用测交结果对玉米地方品种的遗传潜势进行分析。研究表明，单株粒重、穗长、穗行数、行粒数和百粒重在72份玉米地方品种间存在一定的遗传变异，决定品种间遗传变异的主导因子是加性效应。在72份玉米地方品种中通过选择有可能获得单株粒重和百粒重较高、果穗较长、穗行数和行粒数较多的品种，通过遗传改良获得长穗大粒、穗行数和行粒数多的材料或自交系的可能性也较大。     

两种塑料暖棚猪舍的应用效果观测

在青海省乌兰县舍外温度－6．30℃条件下，选用40头荣昌猪分作2组，每组20头，在自行设计的半开放－封闭式多用塑料暖棚猪舍与常用简易塑料暖棚猪舍内开展对比试验。结果表明，前者可显著提高舍内温度，降低舍内湿度，且育猪增重效果明显。     

Paratuberculosis with special reference to cattle. A review

Paratuberculosis is a chronic, granulomatous enteritis caused by Mycobacterium avium subspecies paratuberculosis affecting domestic and wild ruminants. The symptoms of clinical paratuberculosis are chronic diarrhoea and progressive weight loss while subclinically infected animals mainly have decreased production. The infection is widespread throughout the world and causes substantial financial losses for the farming industry. One of the major obstacles in the control of this disease, is the difficulty of identifying subclinically infected animals. This review gives a summary of several aspects of paratuberculosis including clinical importance, pathology, immunology and properties of the infectious agent. Special emphasis will be on the available diagnostic methods, their use and limitations.     

现场围隔及其在水域生态学研究中的应用

现场围隔通过围隔水体建立一个相对封闭的生态系,与周围水体没有交换。使用现场围隔始于20世纪60年代,经过几十年的发展,其结构和功能得到了不同程度的改进和完善,已成为研究水域生态的有效工具,主要用于污染生态学、养殖生态学方面的研究。现场围隔主体结构包括围隔幔、固定支架和围隔幔支架等,附属设备包括防雨罩、电动机、浮力装置和叶轮等,大型围隔容积>100m3,中型围隔容积10～100m3,小型围隔容积1～10m3。通过在目的水域现场开展围隔试验,从而模拟自然水域生态环境,能够大大缩小试验条件和自然环境的差异,使试验结果更加科学,针对性更加明显。现场围隔发展方向是多样化、实用化。     

Simultaneous Determination of Phorate and Oxyfluorfen in Well Water Samples with High Accuracy by GC-MS After Binary Dispersive Liquid-Liquid Microextraction

The potential risk of pesticides to cause harm to humans and other organisms even at trace levels calls for sensitive and accurate analytical techniques for their simultaneous qualitative and quantitative determinations. In this study, a sensitive binary dispersive liquid-liquid microextraction (B-DLLME) strategy was developed for the simultaneous determination of phorate and oxyfluorfen by gas chromatography mass spectrometry after extraction/preconcentration from aqueous solution. An experimental design was used to optimize parameters of the B-DLLME method to obtain maximum outcome. Under the optimum conditions of B-DLLME, the limit of detection (LOD) for phorate and oxyfluorfen were found to be 0.41 μg L^?1 and 0.54 μg L^?1, respectively. The detection limits correlate to about 37 and 73 folds enhancement in detection powers when compared to direct GC-MS determination of phorate and oxyfluorfen, respectively. In order to find out the applicability of developed method to real samples, recovery tests were performed for 20 μg L^?1 of phorate and oxyfluorfen spiked in well water samples. Percent recovery values were found to be 94.5% for phorate and 101.9% for oxyfluorfen.     

秸秆覆盖对冬小麦耗水特征及水分生产率的影响

2季冬小麦试验结果表明 ,秸秆覆盖具有减少土壤棵间无效蒸发的作用 ,冬小麦返青前 1 m土层贮水量在砂壤土条件下秸秆覆盖处理比无覆盖处理增加 2 %～ 2 5 .8% ,粘壤土条件下增加 2 %～ 1 4.5 %。返青前秸秆覆盖处理比无覆盖处理的日耗水量普遍小 ,返青后情况则相反。秸秆覆盖能够促进作物生长 ,与无覆盖相比 ,提高水分生产效率 4.6%～ 2 5 .2 %。     

微孔曝气增氧机的增氧能力试验

为探究微孔曝气增氧机对氧气的传递效果,从研究增氧能力出发,依据SC/T6009-1999增氧机增氧能力试验方法的标准检测程序,以直径为10m的标准室内水池作为试验平台,试验水温为20℃、气压为101.325kPa、初始溶氧浓度为0mg/L;试验用水为清水,将微孔曝气增氧机与射流式增氧机进行对比试验研究。研究结果表明,微孔曝气增氧机能有效增加水体底部溶解氧,与1.5kW射流式增氧机相比,射流式增氧机的增氧能力平均值为2.4kg/h,微孔曝气增氧机布管长度为20m时,增氧能力平均值为0.25kg/h,布管长度为42m时,增氧能力平均值为0.40kg/h,布管长度为98m时,增氧能力平均值为1.12kg/h,布管长度为200m时,增氧能力平均值为1.55kg/h,所以在目前试验布管密度条件下,增氧能力可以超过射流式增氧机。在进气口压力相同的情况下,微孔曝气增氧机增氧速度随着布管长度增加而增加。