Discovery of insect anti-juvenile hormones in plants.?2U

Two simple chromenes with anti-JH activity have been isolated and identified from the bedding plant Ageratum houstoianum. By contact and fumigation these compounds induce precocious metamorphosis and sterilization in several hemipteran species of insects. Certain holometabolous species are sterilized, forced into diapause, or both. Each of these biological actions is equivalent to removal of the corpora allata, which produce the JH's, and is reversible by treatment with exogenous JH. Thus, the action of these compounds is to stop the production or depress the titer of the JH's. To our knowledge, this is the first discovery of anti-JH, and we hope it will guide the way to the emergence of a fourth generation of safe and insect-specific pesticides.     

Amino acid and energy interrelationships in growing beef steers: II. Effects of energy intake and metabolizable lysine supply on growth

We conducted three experiments to determine the optimal metabolizable Lys:net energy ratio for growth of beef calves. The single basal diet fed contained corn (56.1%), soybean hulls (18%), cottonseed hulls (15%), animal fat (4.25%), and corn gluten meal (5.6%). In Exp. 1, 54 steers were individually fed the basal diet at 1.5, 2.25, and 3.0 times NEm requirement; rations were top-dressed with 3.4 g of rumen-stable (RS) Met and either 0, 2, 4, 6, 8, or 12 g of RS-Lys daily. An additional 18 steers were fed the same three levels of energy and supplemented with 125 g of blood meal per steer. In Exp. 2, 68 crossbred steers were subjected to the same experimental protocol, with the exception that only the two highest levels of energy were used. Of these steers, 48 were fed individually and received the RS-Lys treatments; the remaining 20 steers received 125 g of blood meal per steer. No interaction (P > .10) was detected between level of supplemental Lys and energy intake in Exp. 1 or 2. Supplementation with RS-Lys improved (P < .01) ADG in Exp. 1, but it had no effect (P > .10) on growth in Exp. 2. The Lys requirement estimates were 44.3 and 51.3 g/d, corresponding to maximal growth rates of 1.21 and 1.64 kg/d for the 2.25 and 3.0 times maintenance treatments, respectively. Comparing the growth rates of steers fed supplemental Lys with those of steers fed blood meal in Exp. 1 and 2 revealed an ADG advantage (P < .03) with blood meal supplementation. To confirm the blood meal response, Exp. 3 used 75 crossbred steers fed the basal diet at 3.0 times NEm requirement plus either 3.4 g RS-Met, 3.4 g RS-Met and 12 g RS-Lys, or 125 g of blood meal per steer. Blood meal supplementation improved (P < .01) growth of steers over those fed supplemental Met or Met plus Lys. Although a distinct relationship between amino acid requirements and energy supply may exist, Lys and Met were not first-limiting in these experiments, or selective supplementation with undegradable protein may have provided some factor that enhanced performance beyond that detected with Lys and Met alone.     

Histometric study of meat products. A literature review

In the present paper, the literature on the development of methods for histometric monitoring the quality of meats is reviewed. The value of specific techniques, statistical interpretation of results and the practicability of automation of histometric analysis are examined more closely. It is concluded from the study of the literature that histometric examination of meats allows an objective assessment of volume percentages of tissue components. When a distinct difference in contrast between various tissues is achieved by specific staining methods, developments in the field of image analysis systems will allow automation of the quantitative histological examination of meats.     

多壁碳纳米管湿敏传感器的研究

传感器的基底为Al板电化学氧化成Al2O3绝缘层模板,上面真空溅射了叉指金电极,在电极之间旋涂微量多壁碳纳米管的水悬浊液,干燥后作为敏感膜.室温下测试传感器暴露在不同湿度的电阻变化,发现吸附了H2O后传感器的导电能力降低,且下降的幅度与被测湿度有良好的梯度关系.同时该多壁碳纳米管再经缩合剂EDC修饰后旋涂于电极上形成的敏感膜对湿度呈指数级变化.对它们的湿敏响应的机理进行了一些初步的探讨.     

基于WebGIS的城市供水管网系统的设计与实现

介绍了基于WebGIS的城市供水管网信息系统的体系结构、功能组成以及供水管网建模技术.城市供水管网系统主要包括管网建模、查询统计、爆管事故分析、运行状态监控、漏损分析、系统维护等六个方面.城市供水管网建模是进行城市供水系统规划、设计、分析与优化调度的重要支撑技术,充分发挥WebGIS的分布式与可视化地理空间信息分析的优势,结合城市供水管网的管理需求,将WebGIS技术应用到城市供水管网的建模中.该系统可为城市供水部门的高效管理提供决策依据.     

Radiation down-regulates replication origin activity throughout the S phase in mammalian cells

An asynchronous culture of mammalian cells responds acutely to ionizing radiation by inhibiting the overall rate of DNA replication by approximately 50% for a period of several hours, presumably to allow time to repair DNA damage. At low and moderate doses, this S phase damage-sensing (SDS) pathway appears to function primarily at the level of individual origins of replication, with only a modest inhibition of chain elongation per se. We have shown previously that the majority of the inhibition observed in an asynchronous culture can be accounted for by late G1cells that were within 2-3 h of entering the S period at the time of irradiation and which then fail to do so. A much smaller effect was observed on the overall rate of replication in cells that had already entered the S phase. This raised the question whether origins of replication that are activated within S phase per se are inhibited in response to ionizing radiation. Here we have used a two-dimensional gel replicon mapping strategy to show that cells with an intact SDS pathway completely down-regulate initiation in both early- and late-firing rDNA origins in human cells. We also show that initiation in mid- or late-firing rDNA origins is not inhibited in cells from patients with ataxia telangiectasia, confirming the suggestion that these individuals lack the SDS pathway.