仿脑组织体模研究进展

仿脑组织体模是指可以有效模拟人脑组织形状、性质的等效材料组织或数字模型,可以在实验中代表人脑组织的某些生理特性从而达到特定的研究目标,根据其物理形态,通常可分为固体、液体、数字体模3类。仿脑组织体模具有安全经济,配置简单并且可重复使用的优势,被广泛应用于脑部疾病诊断、系统安全性评估等研究。本文就仿脑组织体模的分类、物理特性和脑科学研究应用3方面进行论述,在阐述当前仿脑组织体模与真实脑组织存在一定性质差异的同时也说明其在替代真实脑组织实验上有良好的应用前景。     

拟南芥ACOL8基因在乙烯合成与响应中的功能分析

植物激素乙烯在多种生理生化过程中发挥重要作用,但其在特定组织器官中的合成机制尚不完全清楚。拟南芥中存在12个功能未知的ACC氧化酶类似蛋白（ACO-like homolog,ACOL）,运用基因定点编辑技术构建了ACOL8的功能丧失型突变体,发现该基因的突变削弱了经典的乙烯“三重反应”。与野生型相比,突变体黄化幼苗下胚轴及主根的长度显著增加,这与突变体对外源ACC的敏感性下降现象一致。同时还发现ACOL8基因的表达受乙烯信号的正反馈调控,EIN3过表达增强其表达水平,而etr1-3的突变则产生相反效应。再者,在正常条件下,ACOL8基因的突变并未影响拟南芥的生长;但在盐胁迫条件下,突变体的根冠比显著下降,这说明该基因参与植物的盐胁迫响应。综上,这些结果说明ACOL8可能具有ACC氧化酶的功能,参与乙烯的合成与响应。     

The application of reproductive technology to endangered species breeding programmes

Captive breeding plays an increasingly important role in species conservation, but special problems are encountered in achieving the ideal of a demographically stable but genetically diverse population. Breeding programmes involving co-operation among a number of centres are now being developed which will overcome some of these difficulties by identifying individual animals, genetic lineages or age cohorts from which to breed. Application of techniques such as artificial insemination, embryo transfer and semen collection and storage, as well as the monitoring of reproductive status will contribute to the success of such programmes. The usefulness of these procedures for various population problems is discussed and criteria for their appropriate implementation within breeding programmes is outlined.     

Non‐target habitat exploitation by Trichogramma brassicae (Hym. Trichogrammatidae): what are the risks for endemic butterflies?

Abstract 1 Trichogramma brassicae Bezdenko is inundatively released against the European corn borer in Switzerland. Because parasitoids dispersing from the release fields might pose a threat to native butterflies, the searching efficiency of T. brassicae was investigated in nontarget habitats. 2 In field studies, T. brassicae was released at rates of 120 000 females/ha. Parasitism of sentinel Ephestia kuehniella egg clusters was 1.6–3.6% in meadows and 2.0–4.0% in flower strips. The respective figures were 57.6–66.7% and 19.2–46.9% in maize, significantly higher than the parasitism rates in the nontarget habitats. Experiments carried out in small field cages confirmed these results: Again, significantly higher parasitism rates were found in maize compared to meadows and flower strips, and also compared to hedgerows (in sleeve cages). 3 To elucidate potential factors underlying the low searching efficiency in nontarget habitats, the behaviour of individual T. brassicae females was investigated on four meadow plants comparatively to maize and a filter paper control. Mean (±SE) walking speed on maize was 2.2 ± 0.2 mm/s, similar to three of the plants tested and filter paper but significantly higher than on Trifolium pratense (0.85 mm/s). A higher turning rate was found on T. pratense, Viola wittrockiana and Plantago lanceolata, in contrast to the longer leaved maize and Alopecurus pratensis. The number of wasps leaving the plant within the observation period differed significantly between plant species, and was twice as high for T. pratense (and the filter paper control) compared to the other plant species. 4 In a choice experiment carried out in a climate cabinet with all five host plant species in cages, we obtained the highest parasitism rates on maize and the lowest parasitism on T. pratense, thus confirming the behavioural observations. 5 In conclusion, there is evidence for a decreased searching efficiency on plants in nontarget habitats compared to maize. However, the data explain only part of the differences found between parasitism in maize compared to nontarget habitats. Other factors, such as the structural complexity of a habitat, may also play a role. We conclude that the risk for butterfly populations in the tested nontarget habitat due to mass released T. brassicae is low.     

Submitochondrial particles asin vitro biosensors of heavy metal toxicity

The effects on mitochondrial respiratory parameters of heavy metals, such as Cu, Ni, Pb, Cd, Zn, Ag, Hg, were recorded by using thein vitro response of submitochondrial particles (SMP) from beef heart mitochondria.The toxicity of these elements was estimated by determining their effects on the energy-coupled reverse electron transfer (RET), which is induced by ATP and succinate at first site level of the respiratory chain in SMP.The RET rate was easily monitored by recording spectrophotometrically at 340 nm the production of NADH, arising from the reduction of exogenous NAD⁺ by RET.The toxicity values were expressed as the toxicant molar concentration which decreases the rate of reduction of NAD⁺ to an extent of 50 percent (EC50). The toxicity increased in the following order: Ni²⁺2+2+< Cd²⁺2+2++.The SMP data were compared with the toxicity values obtained from a variety of biological systems currently used for toxicity testing. The results obtained demonstrate that the SMP test generally provides a good estimate of metal toxicity for several fish and invertebrate species. This is demonstrated by the statistical parameters obtained in the regression analysis. The broadened 95% confidence intervals and, in particular, the poor correlations obtained for some aquatic organisms can be ascribed to the more complex metabolic interactions and competing toxic pathways in aquatic organisms, when compared to SMP.     

The ecosystem approach to environmental assessment: moving from theory to practice

The ecosystem approach to environmental management is viewed by many as being fundamental to the development of appropriate management strategies. While this approach represents a major advance in the way researchers view environmental assessment, the approach in itself does not provide practical information as to what questions to ask and what tools to use in assessing and managing ecosystems. Similarly, the concept of ecosystem health, as it is usually defined, has little practical value for ecosystem managers. We suggest the next stage in environmental assessment will be the development of specific frameworks designed to assess individual ecosystems. Of primary importance is the need to consider the basic structure and function of the ecosystem itself. Such consideration, together with explicit identification of anthropogenic stresses particular to the system, serves to identify those components most at risk and those issues most deserving of attention. Researchers should explore critical linkages between environmental stressors and their observable, measurable and predictable effects on ecological parameters and use this understanding to develop a management strategy that incorporates appropriate ecological indicators. The importance of these considerations will be illustrated using examples from the Northern River Basins Study.     

Utility of field-based artificial streams for assessing effluent effects on riverine ecosystems

Experimentation using field-based artificial streams provides a promising, complimentary approach to biomonitoring assessments because artificial streams provide control over relevant environmental variables and true replication of treatments. We have used large and small artificial stream systems, based in the field, to examine the effect of treated bleached kraft pulp mill effluent (BKME) on the benthos of three large rivers in western Canada. Under natural regimes of temperature, water chemistry, and insolation, these artificial streams provide current velocities and substrata to food chains or food webs that are representative of those in the study river. With these tools we have shown that BKME stimulated mayfly growth in the Thompson River above that which could be accounted for by fertilization of their algal food supply. In contrast, moulting frequency was inhibited at high BKME concentrations. Results from artificial streams also indicate that increased algal biomass and abundances of benthic communities downstream of BKME outfalls were induced by nutrient enrichment from the effluent. BKME treatments did not change diatom species richness in the Fraser River, or diatom species diversity in either the Athabasca or Fraser Rivers. Artificial streams provide a means of understanding the mechanisms of stressor effects over a continuum ranging from single stressor effects on specific taxa to the effects of multiple stressors on communities and ecosystems. Because riverside deployment provides environmental realism within a replicated experimental design, this approach can (i) address questions that cannot be examined using laboratory tests or field observations, (ii) improve our mechanistic understanding of stressor effects on riverine ecosystems, and (iii) can contribute directly to the development, parameterization, and testing of models for predicting ecosystem-level responses.     

Environmental biotechnology in India: prospects and case studies

The emergence and acceptance of the concept of sustainable development warrants that the scope of environmental biotechnology be enlarged to address issues like environmental monitoring, restoration of environmental quality, resource/residue/waste-recovery/utilization/treatment, and substitution of the non-renewable resource base with renewable resources. This paper delineates the current and prospective applications in these sub-areas of environmental biotechnology, and documents case studies on environmental monitoring (enteric viruses), restoration of environmental quality (oil spill remediation), resource recovery (hydrocarbon recovery from oily sludges, biosurfactants from distillery spentwash, desulphurization of coal & sour gases), and substitution of non-renewable resources with renewables (conversion of lignocellulisics into value added chemicals).The author is with the National Environmental Engineering Research Institute, Nagpur: 440 020, India     

Environmental risk assessment of releases of transgenic plants containing virus-derived inserts

Sequences derived from the genomes of plant viruses are being used to provide virus resistance in transgenic crop plants. Although the environmental hazards associated with the release of such plants have been discussed widely, it has not been possible to reach generally acceptable conclusions about their safety. A case-by-case approach to the risk assessment of real examples is recommended as a means of building up confidence and of indicating areas of uncertainty. A logical framework for risk assessment is suggested, a key feature of which is identification of the viruses in the release environment that may infect the transgenic plants. Each of these is considered in relation to each of the three main classes of hazard (transcapsidation, recombination and synergism), and the risk associated with each event is analysed.     

Natural Occurrence ofChondrostereum purpureumin Relation to Its Use as a Biological Control Agent in Canadian Forests

The incidence of natural fructification ofChondrostereum purpureumwas estimated quantitatively on southern Vancouver Island during two winter seasons in randomly located 1000-m²plots and compared with potential added fructification that might occur as a result of using the fungus to control stump-sprouting of hardwood weeds in young forest stands. Fructification was surveyed in forests as well as in urban or agricultural areas by estimating the surface areas of woody substrates covered with basidiocarps. In addition to random plots, estimates were made also in locations where the fungus would be expected to occur (woodpiles, silvicultural thinnings, and killed trees). Basidiocarps were found throughout the area in various types of forest cover as well as in urban or agricultural situations. The amount of added fructification through the use of the fungus as a biological control agent was determined from inoculated plots as well as from calculated stump-surface areas developed from published stand-density data. Added fructification was multiplied by a factor representing the maximum biological control frequency in order to compare added fructification with natural fructification values. From the various calculations, it was determined that the added fructification ofC. purpureumis of the same order of magnitude as naturally occurring levels or even lower. In addition, there is a distinct geographical separation between predominantly forestry and predominantly settled areas where fruit and ornamental trees are cultivated. Accordingly, it was concluded that using the fungus as a biological control agent in forestry is not likely to pose a significant threat to fruit growing and commercial forests.