Temperature acclimation and learning in fish

Summary Control fish acclimated at 21°C learned to swim upright following the attachment of floats to their ventral surfaces, while fish acclimated at both 5°C and 33°C failed to learn the swimming skill. Fish previously acclimated at 5°C and then transferred to 21°C 48 h before the task, learnt the swimming skill better than the control fish, but fish acclimated at 33°C and transferred to 21°C failed to acquire the new skill. Acclimation temperature, therefore, significantly modifies the learning behaviour of fish.     

Transgenesis in fish

Gene transfer into fish embryo is being performed in several species (trout, salmon, carps, tilapia, medaka, goldfish, zebrafish, loach, catfish, etc.). In most cases, pronuclei are not visible and microinjection must be done into the cytoplasm of early embryos. Several million copies of the gene are generally injected. In medaka, transgenesis was attempted by injection of the foreign gene into the nucleus of oocyte. Several reports indicate that the injected DNA was rapidly replicated in the early phase of embryo development, regardless of the origin and the sequence of the foreign DNA. The survival of the injected embryos was reasonably good and a large number reached maturity. The proportion of transgenic animals ranged from 1 to 50% or more, according to species and to experimentators. The reasons for this discrepancy have not been elucidated. In all species, the transgenic animals were mosaic. The copy number of the foreign DNA was different in the various tissues of an animal and a proportion lower than 50% of F1 offsprings received the gene from their parents. This suggests that the foreign DNA was integrated into the fish genome at the two cells stage or later. An examination of the integrated DNA in different cell types of an animal revealed that integration occurred mainly during early development. The transgene was found essentially unrearranged in the fish genome of the founders and offsprings. The transgenes were therefore stably transmitted to progeny in a Mendelian fashion. Southern blot analysis revealed the presence of possible junction fragments and also of minor bands which may result from a rearrangement of the injected DNA. In all species, the integrated DNA appeared mainly as random end-to-end concatemers. In adult trout blood cells, a small proportion of the foreign DNA was maintained in the form of non-integrated concatemers, as judged by the existence of end fragments. The transgenes were generally only poorly expressed. The majority of the injected gene constructs contained essentially mammalian or higher vertebrates sequences. The comparison of the expression efficiency of these constructs in transfected fish and mammalian cells indicates that some of the mammalian DNA sequences are most efficiently understood by the fish cell machinery. Chloramphenicol acetyl transferase gene under the control of promoters from Rous sarcoma virus, and human cytomegalovirus, was expressed in several tissues of transgenic fish. Chicken -crystallin gene was expressed in several tissues of transgenic fish. Rainbow trout growth hormone cDNA driven by the Rous sarcoma virus promoter was expressed in transgenic carps leading to a faster growth of these animals. The antifreeze protein gene from flounder was expressed in transgenic salmon. These data indicate that transgenesis in fish is relatively easy but that fish gene sequences must be preferably used to obtain a good expression of the transgenes. Fish is a good biological model, specially for developmental studies and it is an increasing part of human food. For these reasons, transgenesis in fish is most likely to be more and more practised in the coming years.     

The karyotype and genome structure of the pirate perchAphredoderus sayanus (Aphredoderidae: Teleostei)

Summary The standard karyotype, genome size (DNA content), and genomic DNA base composition and distribution of the relict paracanthopterygian fish,Aphredoderus sayanus, were investigated. Several features of theA. sayanus genome appear to be derived rather than primitive conditions. These include a large number (at least 10 pairs) of bi-armed chromosomes, a low genome size, and high DNA asymmetry. This may indicate thatA. sayanus is not a typical paracanthopterygian fish in terms of its genome structure.     

陡帮缩界开采在露天矿中的应用研究

以最终帮坡角作为圈定开采境界的依据,介绍了一种基于矿床三维地质实体模型的储量计算方法.并通过境界圈定储量计算对这连河露天矿两种不同最终帮坡角的境界方案进行比较.     

元宝山露天矿矿床地质模型的构建及其可视化研究

本文紧紧围绕露天矿地质模型的建立及其显示这一主题,将矿床地质模型分为地质界面模型和矿床实体模型。用加权趋势面法对地质界面进行估值,生成地质界面的插值曲面;用边界多边形及断层对地质界面进行裁剪,形成地质界面的裁剪曲面;以地质界面的裁剪曲面和地表面的三角剖分面按空间组合成矿床实体模型。以元宝山露天煤矿为倒,实现了矿床模型的三维可视化。     

仿尺蠖步态的爬杆机器人的动态仿真研究

以仿尺蠖步态的爬杆机器人为研究对象,对其机械结构及行进步态进行了分析,并进一步利用ADAMS软件建立了该仿生机器人的虚拟样机,对该仿生机器人进行了动态模拟仿真实验。研究了在爬杆过程中仿生机器人头部与尾部的速度及位移随时间的变化关系,以及该仿生机器人对变直径工作杆的适应能力,同时分析了不同摩擦材料制成的自锁机构对机器人运动特性的影响。仿真结果表明：该仿生机器人对于直径在一定范围内变化的工作杆有着较好的适应能力,且自锁机构的静摩擦系数为影响该机器人运动特性的关键参数。     

具有环境适应能力的蛇形机器人仿生控制方法

基于生物学原理,本文构建了一种能够产生蛇形机器人多种仿生步态的多模态中枢模式发生器模型.该模型通过外部激励的引入,可以实现蛇形机器人运动形式的自由调整和转换,有助于提高蛇形机器人的环境适应能力.文中主要针对任意节数的多模态中枢模式发生器模型的稳定性进行了证明;分析了多模态中枢模式发生器模型参数对系统输出的影响;研究了蜿蜒运动中环境参数与蛇形机器人关节最优幅值的对应关系,从而确定了多模态中枢模式发生器幅值优化调整策略;并通过建立外部激励与模型参数之间的约束,使得蛇形机器人在多模态中枢模式发生器控制下具有三维运动能力以及相应的环境适应能力.最后,利用蛇形机器人平台验证了仿生控制方法的有效性以及与生物蛇步态的相似性.     

Endocrine and environmental aspects of sex differentiation in fish

This paper reviews the current knowledge concerning the endocrine and environmental regulations of both gonadal sex differentiation in gonochoristic and sex inversion in hermaphroditic fish. Within the central nervous system, gonadotropins seem to play a role in triggering sex inversion in hermaphroditic fish. In gonochorists, although potentially active around this period, the hypothalamo-pituitary axis is probably not involved in triggering sex differentiation. Although steroids and steroidogenic enzymes are probably not the initial triggers of sex differentiation, new data, including molecular approaches, have confirmed that they are key physiological steps in the regulation of this process. Environmental factors can strongly influence sex differentiation and sex inversion in gonochoristic and hermaphroditic fish, respectively. The most important environmental determinant of sex would appear to be temperature in the former species, and social factors in the latter. Interactions between environmental factors and genotype have been suggested for both gonochoristic and hermaphroditic fish.     

The role of muscle in determining growth and size in teleost fish

Summary Rapid growth to large size in fish results from a sustained recruitment of new fibres into their axial series of myomeres. Cessation of recruitment at a small fish size leads to slow growth and a small final size of the fish. Fibre growth dynamics of fishes evidently govern growth and size through fibres' surface area to length ratios, which control their nutrient assimilation rates.     

Prey localization by surface wave ray-tracing: Fish track bugs like oceanographers track storms

Summary Surface-feeding fish accurately determine direction and distance to the center of a concentric wave stimulus, even if only a single, short lasting wave train is presented^1,2. It has been suggested that one cue used by these fish to localize the wave center is the distance dependent frequency modulation of the initial part of a wave stimulus^3,4. Here we show how the distance information contained in the fractional frequency change of a capillary wave group can be decoded. We suggest that wave source localization in surface-feeding fish in part is based on a principal similar to that used by oceanographers to track storms by the frequency change of forerunners of swell.     

Protein synthesis and cyclic GMP content in rat cardiac muscle after swimming exercise

Summary Rats were exercised for 6 h by swimming. Phenylalanine incorporation into myocardial proteins was increased when 2 h had elapsed after the termination of exercise. Cyclic GMP concentration did not change during the experiment, which indicates that cyclic GMP does not act directly as a trigger of myocardial protein synthesis in volume overload.     

Protein synthesis and cyclic GMP content in rat cardiac muscle after swimming exercise

Rats were exercised for 6 h by swimming. Phenylalanine incorporation into myocardial proteins was increased when 2 h had elapsed after the termination of exercise. Cyclic GMP concentration did not change during the experiment, which indicates that cyclic GMP does not act directly as a trigger of myocardial protein synthesis in volume overload.     

Lake Tanganyika as an evolutionary reservoir of old lineages of East African cichlid fishes: Inferences from allozyme data

Genetic differences between 20 species of cichlid fish, representing all the 12 tribes proposed for the cichlid fish fauna of Lake Tanganyika, were studied by allozyme electrophoresis. Most species were genetically very differentiated from each other. Phylogenetic analysis based on the allozyme data indicated that at least seven old, ancestral lineages have contributed to the present cichlid fauna of the lake. Lake Tanganyika, the oldest of the rift-valley lakes, can be recognized as an evolutionary reservoir of major lineages of cichlids in East Africa.     

Transfer and isolation effects on the feeding behaviour of the angelfish,Pterophyllum scalare

The feeding behaviour of juvenile angelfish (Pterophyllum scalare) has been used as an indicator of their recovery following handling and transfer to a new environment, both with and without conspecifics. Isolated specimens fed less readily than group-housed fish, or those transferred to the test aquaria in groups of three or five, and continued to do so for at least ten days following isolation. Feeding rank-order frequently changed following isolation, suggesting that better foragers may not take the greatest risks in isolation.     

Dynamics of increase in muscle fibers in fishes in relation to size and growth

Summary Dynamics of increase of white myotomal muscle fibers of four species of freshwater teleosts (Salmo gairdneri, Pimephales notatus, Esox masquinongy andE. americanus vermiculatus) from three families (Salmonidae, Cyprinidae, Esocidae) representing a variety of maximum attainable sizes and growth rates, have been investigated. There are at least three major differences in these dynamics, and there appears to be an association between the ability of a fish species to attain large size (and grow fast) and its ability to recruit new fibers into this predominant tissue of the myotomal mass.     

Relationship between size of muscle fibres and body dimensions in a number of teleosts.

In a survey of 17 species of teleosts, a direct relationship was found between the diameter of muscle fibres and estimated volume of the fish. The results also suggested an inverse relationship between muscle fibre diameter and 'streamlinedness' of the fish (as measured by length:height ratio).     

The effect of chronic heat stress on cortisol levels in the antarctic fishPagothenia borchgrevinki

Radioimmunoassay was used to determine levels of the stress-inducible glucocorticoid, cortisol, circulating in the plasma of the extremely stenothermal Antarctic fishPagothenia borchgrevinki at rest and after heat stress. Fish sampled immediately after capture (–1.9°C) had low cortisol levels (10.4±1.4 ng ml^–1, mean±SEM) as did fish which were laboratory rested for 3 days. Sudden exposure to 5°C (48h) resulted in a peak cortisol value after 3 h (69.9±6.8 ng ml^–1) whereas exposure to 8°C (6h) resulted in a peak value after 1 h (73.5±8.0 ng ml^–1). At both temperatures levels remained significantly elevated (p<0.05) for the entire period of exposure. Increased temperature also resulted in a significant change in haemoglobin, haematocrit and mean cell haemoglobin concentration (MCHC) (p<0.05). Plasma lactate was significantly elevated only after exposure to 8°C (p<0.05). Plasma cortisol levels fromP. borchgrevinki are reported here for the first time and show this cryopelagic Antarctic species to have an unusual hormonal stress profile.     

基于LPC2387的车载数据采集系统设计

该文设计了一种基于LPC2387嵌入式微处理器的数据采集与控制系统方案,详细介绍了软件部分的设计与实现,描述了采集模块可配置的实现,GPRS丢包处理方法。目前该方案已经达到实用化的阶段,运行稳定,达到了预期的功能需求。     

Modeling of multi-inclusion composites with interfacial imperfections: Micromechanical and numerical simulations

A micromechanical approach based on a two-layer built-in model and a numerical simulation based on boundary element method are proposed to predict the effective properties of the multi-inclusion composite with imperfect interfaces. The spring model is introduced to simulate the interface imperfection. These two methods are compared with each other, and good agreement is achieved. The effects of interface spring stiffness, volume ratio and stiffness of inclusions on the micro- and macro-mechanical behaviors ...