Experimental transmission of abnormal prion protein (PrPsc) in the small intestinal epithelial cells of neonatal mice

Using an immunohistochemical method, we attempted to detect the transmission of abnormal prion protein (PrPsc) to the enterocytes of the small intestine of neonatal mice by oral exposure with sheep brain affected by scrapie. Five 1-day-old neonatal mice were exposed by oral inoculation to the homogenized brain of a scrapie-affected sheep. In the small intestine of all mice 1 hour after inoculation, immunoreactivity with antinormal prion protein (PrPc) antibody was seen in the cytoplasm of villus enterocytes. This finding suggests transmission of abnormal PrPsc into the cytoplasm of enterocytes. In control mice treated with normal sheep brain, no PrPc signal was seen in enterocytes of the small intestine. Immunopositivity for neurofilament protein and glial fibrillary acidic protein was seen in the cytoplasm of enterocytes of mice inoculated with scrapie and normal sheep brain. This suggests that the enterocytes of neonatal mice can absorb PrPsc and other macromolecular proteins of the sheep brain affected by scrapie and may be more important than previously thought as a pathway for PrPsc transmission in neonatal animals.     

Plasma disposition and renal clearance of sulphadimidine and its metabolites in laying hens

Plasma disposition of sulphadimidine (SDM) and its metabolites was studied in laying hens after 100 mg SDM kg-1 doses were administered as a single intravenous dose, a single oral dose and multiple oral doses once daily for five consecutive days. SDM was extensively metabolised by acetylation and hydroxylation. In plasma, the metabolite observed with the highest concentration was N4-acetylsulphadimidine (N4-SDM) followed by hydroxymethylsulphadimidine (CH2OH) and 5-hydroxysulphadimidine. Following intravenous administration a biphasic elimination (as seen for a capacity limited reaction) pattern for SDM and its metabolites was observed. Multiple (5x) SDM dosing revealed plasma SDM concentrations ranging between 7 and 108 micrograms ml-1; within 96 hours of termination of the multiple SDM dosing, the plasma SDM concentration was below 0.01 micrograms ml-1. The renal clearances of N4-SDM and the hydroxy metabolites were approximately 10 times greater than that of SDM. The SDM mass balance (faecal/urinary recovery) showed a loss of 56 per cent after intravenous dosage and of 67 per cent after a single oral dosage; the hydroxy metabolites accounted for the highest percentage in faeces/urine. Thus additional metabolic pathways must exist in laying hens.     

北京市设施蔬菜施肥状况及减施潜力分析

通过对北京市352 个设施蔬菜地块的施肥状况进行实地调研，查明设施蔬菜施肥现状及存在问题，估算肥料减施潜力。结果表明，北京市设施蔬菜养分投入量普遍超过推荐施肥量（养分超标率＞72%）。不同设施类型施肥量差异较大，其中日光温室每季蔬菜平均氮磷钾（N、P₂O₅ 和K₂O）投入总量分别为858 、409、572 kg · hm^-2，明显高于塑料大棚每季蔬菜平均氮磷钾投入总量593、317、438 kg · hm^-2。设施蔬菜养分主要来源于有机肥基施，对日光温室和塑料大棚养分投入总量的贡献分别为66% 和52%。不同蔬菜种类肥料减施潜力巨大，其中甘蓝、黄瓜和茄子总养分相对减施潜力分别为61%～62%、43%～48% 和18%～47%。日光温室和塑料大棚氮磷钾养分投入比例（N∶P₂O₅∶K₂O）分别为1∶0.47∶0.66和1∶0.53∶0.73，表明钾肥比例相对不足。建议加快设施蔬菜水肥一体化技术的推广应用，加强设施蔬菜施肥技术指导，尤其要降低日光温室的氮、磷肥投入量，避免过量施肥带来的资源浪费和环境污染。     

Evaluation in vitro of the antagonistic substances produced by Lactobacillus spp. isolated from chickens

To determine the inhibitory capacity of lactic acid bacteria due to the action of antagonistic substances, we tested 474 isolates of Lactobacillus from the crop and cecum of chickens against gram-positive and gram-negative indicator microorganisms by the spot-on-the-lawn and well-diffusion antagonism methods. Of the 474 isolates, 265 demonstrated antimicrobial activity against the indicator microorganisms. Isolates identified as L. reuteri, L. salivarius, or Lactobacillus spp. inhibited Enterococcus faecalis, E. faecium, Listeria monocytogenes, and Salmonella spp. but not L. casei, L. delbrueckii, L. fermentum, or L. helveticus by the well-diffusion simultaneous antagonism method under anaerobic incubation conditions. The antagonistic substances produced by some of the Lactobacillus isolates were inactivated after treatment by proteolytic enzymes, which suggested that the substances could be antimicrobial peptides or bacteriocins.     

Joint Parameters Estimation for CDMA Signals

In wireless communications,mobiles emit signals that arrive at a receiver with multiple paths,each with its own direction of arrival(DOA),path delay,fading,and Doppler shift frequency,which influence the quality of communication seriously.These parameters should be taken into account in array signal processing.Based on CDMA signal,a novel Space-Time approach is proposed to estimation the DOA,time delay,and the Doppler shift frequency.Because utilize special signal model about space-time-frequency of mobile communications.The proposed algorithm has simpler structure and high quality of division.The simulation results show the feasibility and effectiveness of the method.     

基于因次分析的盐田铺膜机动力参数研究

盐田铺膜机采用旋耕机逆转工作，一次完成切土，升土，抛土等工序，与一般旋耕机的工作方式不同，难以直接应用现有的研究结果分析其动力损耗，因此，根据土壤的特性，采用流体力学中分析流体状态的因次分析方法，由泊金汉π定理得出通用模型的准数方程并线性化，测出样机在预定工况下工作时各主要参灵敏，用最小二乘法估计各系数，并在实验值范围内分析各参数对动力损耗有无显著影响，对盐田铺膜机的改进及优化提供了基本参考依据。