"养鸡生产中沙门氏菌病的预防与控制策略"专栏(八)利用饲料添加剂"多重阻断法"预防禽沙门氏菌

用于控制家禽沙门氏菌的"多重阻断"(multi-hurdle)型饲料添加剂新概念具有广阔的应用前景.此类添加剂是由有机酸、中链脂肪酸(MCFA)、丁酸盐和甘露二糖组成的混合物,可显著降低盲肠中的肠炎沙门氏菌(S.Enteritidis).该方法的原理是将对沙门氏菌在肉鸡肠道增殖、黏附或侵袭具有控制或阻断作用的添加剂复合在一起同时使用.     

Genetic control of surface curvature

Although curvature of biological surfaces has been considered from mathematical and biophysical perspectives, its molecular and developmental basis is unclear. We have studied the cin mutant of Antirrhinum, which has crinkly rather than flat leaves. Leaves of cin display excess growth in marginal regions, resulting in a gradual introduction of negative curvature during development. This reflects a change in the shape and the progression of a cell-cycle arrest front moving from the leaf tip toward the base. CIN encodes a TCP protein and is expressed downstream of the arrest front. We propose that CIN promotes zero curvature (flatness) by making cells more sensitive to an arrest signal, particularly in marginal regions.     

Soil and water degradation processes in burned areas: Lessons learned from a nested approach

Forest fires produce a major impact on soil, water and vegetation. Despite the amount of research published on this subject, there are two major problems that hamper the fully understanding of on and off-site impacts of forest fires. They include methodological problems steaming from the uniqueness of burned soil properties, easily erodible, by the fast degradation they undergo over a short period of time immediately after fire and by the meaning of the impacts at different scales.     

猪舍环境温湿度对育成猪的生理及生产指标的影响

试验采用美国DSI公司生产的动物生理参数无线遥测系统与猪舍环境参数及动物行为自动检测系统研究了长白猪在夏季湿热环境下的行为生理反应。结果表明猪舍高温将导致猪的体温升高、心率加快,猪的生产性能降低等热应激反应,高温高湿环境下猪的热应激反应更为严重,高温时环境湿度增大10%,相当于环境温度升高1℃对猪的影响。环境温度对猪的体温和心率影响极显著;环境湿度对猪的体温影响显著,对心率有影响但不显著     

Influence of paddy rice terraces on soil erosion of a small watershed in a hilly area of Northern Vietnam

Soil erosion is the main cause of soil degradation in northern Vietnam. In this study, soil erosion was measured in 2 m² field plots, a 19.1-ha sub-watershed, and a 248.9-ha main watershed in Tam Quan commune, Tam Duong district, northern Vietnam during 2 years, i.e., 2004–2005. The main watershed includes lowland paddy fields, and is representative for watersheds in the northern Vietnamese landscape. Soil erosion was measured for eight events, at all the three scales to increase our understanding of erosional processes and to assess the effects of paddy fields within the main watershed. The results show that total discharge and sediment yield in both sub-watershed and main watershed were much lower than those in the field plots. Total discharge per unit area in the main watershed was higher than in the sub-watershed, because during the growing season, the paddies are filled with water and any rainfall on them therefore becomes runoff. Sediment yield in the main watershed fluctuated, depending on the soil erosion contribution from many sub-watersheds. Annual rainfalls in 2004 and 2005 were 1,172 and 1,560 mm, respectively, resulting in corresponding total discharges of 54 and 332 mm and total soil losses of 163 and 1,722 kg ha^?1 year^?1. High runoff volumes occurred in July, August, and September, but April, June, the last 10 days of September and October, were the susceptible periods for soil erosion in the study area because of low plant cover and many agricultural activities during these periods.     

Experimental therapy of human glioma by means of a genetically engineered virus mutant.

Malignant gliomas are the most common malignant brain tumors and are almost always fatal. A thymidine kinase-negative mutant of herpes simplex virus-1 (dlsptk) that is attenuated for neurovirulence was tested as a possible treatment for gliomas. In cell culture, dlsptk killed two long-term human glioma lines and three short-term human glioma cell populations. In nude mice with implanted subcutaneous and subrenal U87 human gliomas, intraneoplastic inoculation of dlsptk caused growth inhibition. In nude mice with intracranial U87 gliomas, intraneoplastic inoculation of dlsptk prolonged survival. Genetically engineered viruses such as dlsptk merit further evaluation as novel antineoplastic agents.