Antigen competition: antigens compete for a cell occurring with limited frequency

Experimentally altered ability of transferred spleen cells to generate hemolytic plaque-forming cells provided evidence that antigens compete for a type of multipotential cell that contributes to the formation of immunologically competent units. De'ay of exposure of transferred spleen cells to antigen provided results which suggest that different types of cells interact to form competent, antigen-reactive units even in the absence of antigen.     

Long-term changes in the sea-age at maturity and seasonal time of return of salmon, Salmo salar L., to Scottish rivers

Abstract Using catch data, changes in salmon, Salmo salar L., sea-age and seasonal return time were compared between several Scottish east coast rivers over the last 150–200 years. Parallel long-term trends were found, suggesting common influences affecting salmon at sea. Long-term associations with marine environmental factors were investigated by literature review and comparisons with an index of Icelandic sea-ice abundance. Apparent associations were shown to exist since about 1900, although the cause was not demonstrated. However, over a longer timescale, the same associations were not apparent. Unique gradual marine changes since 1900 may have resulted in perceptible associations with salmon data which may otherwise be imperceptible when short-term marine environmental variability is greater than long-term variability. Marine factors must affect salmon, but the complexity of the marine environment and controls on age at maturity and time of return mean that a retrospective analysis cannot be expected to identify the causal factors.     

Influence of dietary protein and energy on growth,food consumption and food conversion efficiency in Penaeus merguiensis de Man

The requirement of juvenile Penaeus merguiensis for dietary protein and energy was assessed in growth trials performed in indoor recirculation systems using rations based on freeze-dried Mytilus edulis meal. From the results of these experiments evidence was obtained to indicate that the rate of food consumption in this prawn is related to the energy content of the diet. The implications of this are that the protein level required to support maximum growth and optimum protein conversion efficiency are also energy dependent. Optimum protein levels were estimated in the range 34.0–42.0% for diets of energy content 2.9–4.4 kcal/g. A possible scheme relating food consumption, energy production and growth in P. merguiensis is presented.     

8种杀螨剂对苹果树红蜘蛛田间防效评价

对8种不同作用机理杀螨剂防治苹果树红蜘蛛的效果进行了田间试验。结果表明：三唑锡、炔螨特、哒螨灵、阿维菌素、唑螨酯、螺螨酯、双甲脒、甲氰菊酯均是防治苹果树红蜘蛛的有效药剂,以螺螨酯的总体防效最好。     

甘肃省农作物秸秆资源现状及利用潜力研究

[目的]厘清甘肃省农作物秸秆资源现状,可为减少农业面源污染,促进全省秸秆综合利用和农业可持续发展提供数据支撑。[方法]本文基于统计数据和农户调研数据,综述了全省主要农作物秸秆资源产生量、利用现状、秸秆资源量评估的主要影响因素及利用模式建议。分析了秸秆资源量变化趋势(2007-2017年);[结果]2017年甘肃省农作物秸秆理论资源量为1040.03万吨,可收集量923.62万吨,小麦、玉米、大豆三类农作物秸秆占总量的87.33%,利用量为829.79万吨,综合利用率达89.84%,资源化利用方式以饲料化为主,肥料化为辅。秸秆主要利用方式包括秸－饲－肥饲料化利用、 秸－菌－肥基料化利用、秸－沼－肥燃料化利用、秸－炭－肥原料化利用。[结论]以循环农业的角度出发,秸秆炭化还田作为一种重要的秸秆利用方式之一,具有培肥地力、固氮减排、间接增产增收等积极效用,可作为现有基础下秸秆资源化利用的一条重要的可行性新途径,对于资源短缺、环境污染和农业可持续发展具有重要意义。     

芦荟饮料褐变的控制研究

研究了芦荟凝胶在制汁过程及芦荟饮料在加工过程中温度和时间等因数对芦荟饮料色泽的影响。结果表明,搅汁时间10min,杀菌温度85℃,杀菌时间25min是有效控制芦荟饮料褐变的最佳工艺参数。     

优质黑猪育种30年工作体会

品种是影响养猪生产中的最重要因素,猪育种是一项复杂且系统的工程,文章从育种素材筛选、育种方案设计、育种方法选择、品种审定以及扩群产业化推广等方面进行详细的阐述,并结合育种经验提出相应猪育种建议。     

Preparation and evaluation of antigens used in serological tests for caprine syncytial retrovirus antibody in sheep and goat sera

Methods used to prepare antigens from caprine syncytial retrovirus (CSR) for use in the agarose gel immunodiffusion test (AGID) or an indirect enzyme-linked immunosorbent assay (ELISA) are described. Caprine and ovine sera were tested for antibody to CSR using the AGID test and ELISA incorporating a caprine system (CSR antigen and rabbit anti-goat IgG) or an ovine system (maedi-visna virus antigen and rabbit anti-sheep IgG). Good correlation was achieved in the results of the 3 tests when sera were devoid of antibody or were strongly positive. Variations in the results on weakly positive sera were considered to be more a matter of interpretation than due to basic differences in the reagents employed.