Myosin: Formation and maintenance of thick filaments

Skeletal muscle consists of bundles of myofibers containing millions of myofibrils, each of which is formed of longitudinally aligned sarcomere structures. Sarcomeres are the minimum contractile unit, which mainly consists of four components: Z‐bands, thin filaments, thick filaments, and connectin/titin. The size and shape of the sarcomere component is strictly controlled. Surprisingly, skeletal muscle cells not only synthesize a series of myofibrillar proteins but also regulate the assembly of those proteins into the sarcomere structures. However, authentic sarcomere structures cannot be reconstituted by combining purified myofibrillar proteins in vitro, therefore there must be an elaborate mechanism ensuring the correct formation of myofibril structure in skeletal muscle cells. This review discusses the role of myosin, a main component of the thick filament, in thick filament formation and the dynamics of myosin in skeletal muscle cells. Changes in the number of myofibrils in myofibers can cause muscle hypertrophy or atrophy. Therefore, it is important to understand the fundamental mechanisms by which myofibers control myofibril formation at the molecular level to develop approaches that effectively enhance muscle growth in animals.     

上蔟环境对制丝原料茧质影响的探讨

通过对不同优良蚕品种在不同的上蔟环境中吐丝面结成的蚕茧性状的调查，发现在合理的环境中上蔟时，茧形大，上茧率高，缩皱细，茧丝的强力大，伸度适当，净度成绩好。而在其他环境中上蔟，都不同程度地对茧丝品质有影响，特别是多湿环境上蔟时对茧质性关的影响最大。因此上蔟环境的合理控制是生产优质原料茧的有效途径。     

巴西蚕丝生产和贸易的分析

以巴西茧丝生产和贸易的统计及相关资料为依据，简要分析了巴西蚕丝生产条件，经营规模，技术体系，蚕茧和生丝的供求关系及其出口市场。巴西蚕丝业是以出口创汇为目的的市场导向型产业．巴西蚕丝业的发展主要取决于世界茧丝绸市场的需求。     

快速评茧仪的试验研究

以８０９８单片机处理机为核心组成的快速评茧仪,在设定温度条件下,能连续自动测量并显示出茧壳质量变化和相应的含水率,完成茧壳称重和分级显示。试验表明,评茧仪能够满足快速、准确评茧分级的要求。评茧仪也可用作其他物料收购、烘干及贮藏过程中含水率的快速检测。     

Evaluation of a technique to obtain development-stage-synchronised earthworms (Eisenia fetida )

 The aim of this experiment was to investigate whether Eisenia fetida hatchlings of different ages, kept initially without food, could be used to obtain worms of a comparable development stage (measured as growth) with similar maturation properties (measured as clitellum development). Seven groups of hatchlings, each differing in age by 7 days (range: 0–42 days) were collected as follows. Cocoons were kept in water in multicell containers and individuals that hatched during a 24-h period were placed on moist vermiculite with no food, at weekly intervals. The longest period that hatchlings were fasted was 42 days, after which food was added and growth monitored for 50 days. No differences in weight gain between the different batches were observed. Analysis of the growth curves and attainment of sexual maturity (clitellum development) indicated no effect of age or stage of development at the onset of feeding. It was concluded that this technique allows the production of cohorts of E. fetida, synchronised with respect to development stage, for use in toxicological and biological investigations that require control of factors such as development stage, age and size, and in particular for use in toxicological experiments complying with OECD regulatory procedures. Received: 16 June 1997     

Effect of coffee residues on growth and reproduction of Hyperiodrilus africanus (Oligochaeta, Eudrilidae) in Ivory Coast

Hyperiodrilus africanus (Beddard) is a 12-cm to 16-cm-long earthworm, which is widely distributed in West and Central Africa. It lives in the upper 10–20 cm of the soil, and feeds on a mixture of soil and above-ground litter. Cocoons obtained in the laboratory hatched on average 17 days after deposition and produced two juveniles on average. Paired individuals fed soil amended with 2% coffee residues grew significantly (P<0.05) faster than those in the control soil. Daily individual weight increments were respectively 6.1 mg worm^–1 day^–1 and 1.0 mg worm^–1 day^–1 in supplemented and control soil. The generation time was short, and cocoon production reached 9.6 month^–1 (i.e. 115 cocoons adult^–1 year^–1). When H. africanus collected from the field were raised in the laboratory, they grew slowly, laid fewer cocoons and mortality was high. Demographic parameters indicated an improvement when H. africanus were raised in batches rather than individually. Mating enhanced cocoon production although parthenogenesis was possible. Received: 4 April 1997     

家蚕茧质性状基因型—环境互作效应的研究

对 3个非减数分裂孤雌生殖蚕品种的 3个茧质性状数据进行了方差分析 ,并建立起一个包括微环境效应在内的基因型—环境互作生物统计模型 ,对该模型的参数作最大似然估计认为 :在家蚕的全茧量、茧层量和茧层率3个茧质性状中 ,除独立的基因型和环境效应外 ,基因型与环境的互作效应也是影响家蚕茧质性状的表现型的重要因素 ,而且这种互作效应有时要大于独立的基因型效应 ,即在茧质性状的表现型中基因型与微环境的交互作用非常重要。     

Growth and cocoon production of Drawidia nepalensis (Oligochaeta)

Summary The biology of the vermicomposting species, Drawidia nepalensis Mich. is poorly understood. We therefore studied the growth of this species at 25°C in urine-free cow and horse manure. The rate of maturation and cocoon production were studied under conditions of favourable moisture and nutrition over a period of 240 days. The results showed that D. nepalensis grew relatively slowly in comparison to other vermicomposting species, and that copulation was not a prerequisite for the production of viable cocoons, indicating that D. nepalensis may be parthenogenetic. A faster growth rate, and the production of more cocoons in cow compared with horse manure indicate that cow manure is a preferred source of food for D. nepalensis.     

高压静电场处理家蚕卵对蚕茧产量和质量的影响

通过实验室试验和生产中试,探讨了高压静电场处理家蚕卵对幼虫生命力、蚕茧产量及茧丝质量的影响。实验室试验结果表明,采用的2个加速电压处理组及4个无加速电压处理组对蚕的孵化和生命力均无不良影响,t检验结果显示全茧量、茧层量、蛹体重等指标比对照区均有显著提高,但处理对雌蚕茧层率影响不显著,而雄蚕的茧层率则多数有明显增加。生产中试结果表明,利用最佳处理条件处理蚕卵,张种产茧量比对照平均提高10.86%,茧层量提高15.45%,茧层率和茧层生产效率分别提高5.00%和12.72%,茧丝长和解舒丝长分别增加72.24、76.09 m,解舒率、上车率也均有所提高,光折降低,茧丝纤度略有增加,对茧丝洁净无明显影响。     

性别效应对家蚕茧质性状QTL定位的影响

家蚕茧质性状的性别效应十分明显。分别以性别效应调整前和调整后的家蚕全茧量、茧层量、茧层率和蛹体质量等数量性状值为基础,对性别效应调整前后的茧质性状作数量性状基因座(QTL)定位比较分析,以探讨性别效应对家蚕QTL定位的影响。结果显示,检测出的控制各性状的上位性位点数、QTL总数以及效应显著的QTL数等,都表现为调整前比调整后要多,有效QTL在连锁群上的分布也表现一定的差异。此结果说明由于性别效应的影响可能会导致检测出控制家蚕茧质性状的上位性位点数和QTL总数的增加及其分布的不同,从而引起QTL分析结果的偏差。