The influence of body size, habitat and diet concentration on feeding of Laternula marilina Reeve

A Chinese duckbilled marine clam (Laternula marilina Reeve) was cultured in a simulated natural culture system for the preliminary determination of its physiological energetics. The results showed that both clearance rate (CR) and ingestion rate (IR) were related exponentially to body size (flesh dry weight, W) as described by the equations CR=0.49W^0.65, IR=0.96W^0.57. Body size had no effect on assimilation efficiency (AE) at water temperatures of 10°C, 16°C and 23°C, but within this range AE significantly increased with increasing water temperature. It was found that L. marilina performed in feeding behaviour far better when natural substrates conditions were provided. On a sand or silt substrate both CR and IR were two times higher than on an uncovered tank bottom. AE was also improved when sand (13.12% increase) or silt (14.19% increase) was provided. It is evident in our results that within the range of diet (as particulate organic matter, POM) concentration of 2.30±0.21 to 6.20±0.13 mg POM L^?1 the relationships between POM and CR and IR were exponential and as described by the equations CR=0.29 [POM]^0.75, IR=0.33 [POM]^1.34. In these experiments, the diet concentration threshold of pseudofaecal excretion was found to be 3.05 mg POM L^?1. There was no marked influence of diet concentration on AE, which was consistently about 60%.     

Uptake and clearance of exogenous estradiol-17β and testosterone during the early development of coho salmon (Oncorhynchus kisutch), including eggs,alevins and fry

The uptake and clearance of estradiol-17β (E₂) and testosterone (T) were examined during the initial stages of development of coho salmon (Oncorhynchus kisutch), including eyed-eggs, newly hatched alevins and first feeding fry. Radiolabeled steroids were administered through the water in tracer amounts with or without their nonradioactive form at 400 μg l⁻¹. Regardless of developmental stage, saturation levels were invariably attained earlier for T than for E₂, thus resulting in a higher incorporation of E₂. However, both steroids had similar clearance patterns. Uptake and clearance was clearly stage-dependent, being fastest in fry, intermediate in alevins and slowest in eggs. Furthermore, combined uptake and clearance patterns showed that exposure to steroid was also higher for E₂ than for T and stage-dependent, but always markedly highest in alevins. Subsequently, based on the observed elimination of the estrogen, a double immersion in E₂ at 400 μg 1⁻¹, administered 2 days apart to maximize exposure during the alevin stage, was assayed for its effect on sex reversal and found to induce the production of 100% females. We suggest that the yolk, which is present in substantial amounts during the initial stages of development in salmonids, can retain the exogenously administered liposoluble steroids, thus providing developing embryos with an extended supply of, and exposure to, these steroids well after the treatment is finished. Together, these findings help to explain the previously observed high effectiveness of sex steroids administered during early development in regulating gonadal differentiation in salmonids, the higher effectiveness of E₂ compared to T, and clarify the localization of the most sensitive period to the action of exogenous steroids at the alevin stage in the coho salmon.     

In vitro metabolism in Sprague-Dawley rat liver microsomes of forsythoside A in different compositions of Shuang-Huang-Lian

Shuang–Huang–Lian (SHL), a traditional Chinese formula containing Lonicerae japonicae flos (LJF), Scutellariae radix (SR) and Forsythiae fructus (FF), is commonly used to treat acute upper respiratory tract infection, acute bronchitis and light pneumonia. Forsythoside A is one of the main active ingredients in Forsythiae fructus, a key herb in SHL. In the present study, effects of different compositions in SHL on the in vitro metabolism in Sprague–Dawley rat liver microsomes of forsythoside A were investigated. The observations from Sprague–Dawley rat liver microsomes in the presence of β-NADPH or UDPGA that forsythoside A may be the substrates of CYP3A4, CYP2C9, CYP1A2, UGT1A6, UGT1A3, UGT1A1 and UGT1A9; Chlorogenic acid may be the substrates of CYP3A4, CYP2C9, CYP1A2, CYP2C19, UGT1A6, UGT1A3 and UGT1A1; Baicalin may be the substrates of CYP3A4, CYP2C19, CYP1A2, UGT1A9, UGT1A1 and UGT1A3; Baicalein may be the substrates of CYP3A4, CYP2E1 and UGT1A6. It was also found that the residue of forsythoside A in SHL, FF + LJF and FF + SR was greatly increased compared with that in FF in Sprague–Dawley rat liver microsomes in the presence of β-NADPH or UDPGA, which indicated that the metabolism of forsythoside A in SHL may be influenced by chlorogenic acid in LJF acting on the CYP3A4, CYP2C9, CYP1A2, UGT1A6, UGT1A3 and UGT1A1; baicalin in SR acting on the CYP3A4, CYP1A2, UGT1A9, UGT1A1 and UGT1A3; baicalein acting on the CYP3A4 and UGT1A6 respectively.     

采棉机六辊清杂机构的优化与试验研究

软摘锭采棉机的采收含杂量较高,为解决田间试验受季节因素影响较大的问题,自行研制了六辊清杂装置的试验台,并且在此基础上以结构参数优化、喂入量和刺钉端线速度为考虑因素,重点以含杂率为试验指标,得出其影响因素,对于棉花采收的初步清杂、提高棉花品级以及改善软摘锭采棉机的清杂效果具有重要意义。     

清热活血法对鸡肺热喘咳的疗效试验

为探讨用清热活血中草药对鸡肺热喘咳症的治疗效果，本试验先后两次分别对80日龄青年鸡和200日龄产蛋鸡（符合肺热喘咳症的患病鸡）进行对比治疗试验。青年鸡试验组治愈率和总有效率分别为75%和95%，治愈后不复发，药物对照组的治愈率和总有效率分别为50%和72%；蛋鸡试验组治愈率和总有效率分别为73%和93%，药物对照组的治愈率和总有效率分别为53%和80%。实验证明用清热活血中草药对鸡肺热喘咳症的治疗效果显著。     

四冲程内燃机气门间隙调整方法的探讨

主要介绍了气门间隙大小的变化及其对内燃机工作性能的影响,探讨了四冲程内燃机气门间隙调整的方法。     

高地隙植保机油门自动控制系统研制与试验

针对农业无人驾驶系统对高地隙植保机提出的油门自动控制需求,研制了以直流电机为动力源的油门自动控制系统,主要包括油门控制器、直流减速电机、电机驱动器、角度传感器、拉线轮等。油门控制器用以读取角度传感器的输出值,将其与CAN总线上的油门指令进行比较,将控制信号发送至电机驱动器以控制减速电机的正反转,从而带动拉线轮旋转至目标位置。研究根据高地隙植保机发动机油门动作原理,进行自动油门装置的总体结构设计,并对直流电机、角度传感器进行选型,加工制作零部件完成了自动油门装置的组装和调试。试验结果表明,所研制的油门自动控制系统在［0°,70°］范围内,角度相对误差不超过4%;发动机转速误差最大值发生在拉线轮转动角度为65°时,为19.8 r/min;发动机转速误差最小值发生在转动角度为50°时,为10 r/min;最小标准偏差和最大标准偏差发生50°和55°时,分别为3.03 r/min、6.33 r/min,相对标准偏差≤0.55%。本文研制的油门自动控制装置具备良好的控制稳定性和可靠性,能够满足农业无人驾驶系统对油门控制的基本要求。