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关键词： AHP, after-spike hyperpolarization   B   1–4   , identifiable Müller cells of Bulbar region   CC, contralaterally and caudally projecting interneuron   DC, dorsal cell   DA, dopamine   EC, edge cell   eCC, excitatory CC interneuron   EIN, excitatory interneuron   EPSP, excitatory postsynaptic potential   F-I, frequency versus current relationship   GABA, gamma-aminobutyric acid   GI, giant interneuron   HRP, horseradish peroxidase   5-HT, 5-hydroxytryptamine   I   1–2   , identifiable Müller cells of the Isthmic region   iCC, inhibitory CC interneuron   IIN, inhibitory interneuron   IPSP, inhibitory postsynaptic potential   LIN, lateral interneuron   M   1–3   , identifiable Müller cells of the Mesencephalon   MN, motoneuron   Mth, Mauthner cell   NMDA,   N   -methyl-   d   -aspartate   PSP, postsynaptic potential   RRN, rhombencephalic reticular nucleus   VR, ventral root  

摘要： Among the advantages offered by the lamprey brainstem and spinal cord for studies of the structure and function of the nervous system is the unique identifiability of several pairs of reticulospinal neurons in the brainstem. These neurons have been exploited in investigations of the patterns of sensory input to these cells and the patterns of their outputs to spinal neurons, but no doubt these cells could be used much more effectively in exploring their roles in descending control of the spinal cord. The variability of cell positions of neurons in the spinal cord has precluded the recognition of unique spinal neurons. However, classes of nerve cells can be readily defined and characterized within the lamprey spinal cord and this has led to progress in understanding the cellular and synaptic mechanisms of locomotor activity. In addition, both the identifiable reticulospinal cells and the various spinal nerve cell classes and their known synaptic interactions have been used to demonstrate the degree and specificity of regeneration within the lamprey nervous system. The lack of uniquely identifiable cells within the lamprey spinal cord has hampered progress in these areas, especially in gaining a full understanding of the locomotor network and how neuromodulation of the network is accomplished. (C) 2001 Elsevier Science Ltd. All rights reserved.

关键词： 线粒体DNA多态性   动物保护生物学   进化显著单位   管理单位  

摘要： 本文从两个方面论述了mtDNA在动物保护生物学中的应用 :一是对物种进行遗传多样性的检测与管理 ,二是进行与种群统计学数据相关的遗传分析。前者与保护的长期效益 (如进化 )密切相关 ,而后者则主要用于指导短期管理措施的制定。同时 ,本文重点论述了mtDNA在进化显著单位 (ESUs)和管理单位 (MUs)的认定方面的作用。认定ESUs的目的是隔离管理遗传多样性 ,它是一系列系统进化史独特的种群 ,这种独特性同时表现在mtD NA和核DNA上 ;MUs是种群统计意义上的生殖隔离单位 ,具有独特的等位基因频率 ,与系统发生结构和遗传分歧水平无关。ESUs与MUs都是保护生物学中保护与管理的重要基本单位。

关键词： 锌   生物学功能   动物生产   作用   必需微量元素   饲料添加剂   毒性  

摘要： 锌是动物体必需微量元素之一,现代科学研究证明,在已确认的15种动物必需微量元素中,锌的功能最多、作用最广,锌与动物体内多种酶的活性有关,许多蛋白质、核酸、粘多糖等物质的组成成分中,都有锌的存在;动物体如果锌含量不足,可致动物代谢紊乱、平衡失调,从而影响动物生长发育,降低经济价值,阻碍畜牧业发展.

关键词： VERTEBRATE evolution   HOMOLOGY (Biology)   CHORDATA  

摘要： Recent advances in molecular biology and microanatomy have supported homologies of body parts between vertebrates and extant invertebrate chordates, thus providing insights into the body plan of the proximate ancestor of the vertebrates. For example, this ancestor probably had a relatively complex brain and a precursor of definitive neural crest. Additional insights into early vertebrate evolution have come from recent discoveries of Lower Cambrian soft body fossils of Haikouichthys and Myllokunmingia (almost certainly vertebrates, possibly related to modern lampreys) and Yunnanozoon and Haikouella (evidently stem-group vertebrates), The earliest vertebrates had an unequivocally marine origin, probably evolved mineralised pharyngeal denticles before the dermal skeleton, and evidently utilised elastic recoil of the visceral arch skeleton for suction feeding. Moreover, the new data emphasise that the advent of definitive neural crest was supremely important for the evolutionary origin of the vertebrates. (C) 2001 John Wiley & Sons, Inc.

关键词： microbial biomass   nematodes   New Zealand   organic matter   sustainability  

摘要： Information on the influence of duration of cultivation on soil organic matter (SOM) dynamics is needed by researchers, policy makers and farmers for assessment of global ramifications of carbon (C) sequestration and agricultural sustainability. This paper examines the changes in microbial biomass carbon (MBC) and nitrogen (MBN), metabolic quotient (qCO(2)). microfaunal populations, and C and N mineralisation to assess the effect of cultivation on SOM dynamics. Cultivation. for up to 34 years, of soils previously under permanent ryegrass (Lolium perenne L.) and clover (Trifolium sp.) pastures, resulted in a 30-60% decline in concentration of soil organic C and N, and had a significant influence on soil biological parameters in two New Zealand (Eutric Gleysol, Kairanga silty clay loam and Gleyic Luvisol, Marton silt loam) soil types. Cultivated soils had consistently fewer MBC and MBN contents, and higher qCO(2) than their counterparts in permanent pastures. Changes in the soil microfauna following cultivation were consistent with changes in microbial biomass. Both the amount and proportion of mineralisable N were also reduced with cultivation. In the pasture soils C mineralisation rates (under laboratory conditions) were twice those (ca. 15 mg (CO2-C) kg(-1) soil) in the 5-20 year cultivated soils (ca, 7 mg (CO2-C) kg(-1) soil), and were reduced to one-half (ca. 3.5 mg (CO2-C) kg(-1) soil) in the 34-year cultivated soil. Over 112 days, the soils lost approximately 2.4-5.0% of their total C, and 1.4-5.0% of total N was mineralised. The percentage C loss also differed with oil type, with Marton silt loam (260 g kg(-1), clay) soil losing one and half times as much percentage C as Kairanga silty clay loam (420 g kg(-1), clay) soil. Despite greater C mineralisation in soil from pasture, more C and N were conserved in it than in the cultivated soils. As annual C inputs in cultivated soils are smaller than the C decomposition. this would result in a negative soil C balance

关键词： 淡水生态系统   浓集   分布   大瓶螺   石螺   锶90   生物学特性   放射生态学  

摘要： 本文报道了两种淡水腹足类动物对90 Sr的浓集与分布的过程 ,大瓶螺 (Am pullariagigasSpix) 4h开始便迅速浓集90 Sr并转至螺体各个部位 ,小个体各器官组织对90 Sr的浓集系数大于大个体 ,刚孵化的幼螺在 1 5min内便对90 Sr有浓集作用 ,并随时间的延长而增加。石螺 (Bellarnyapurificata)对90 Sr于 4h开始有吸收浓集作用 ,但其浓集系数低于大瓶螺 ,在各自积累高峰期大瓶螺的贝壳对90 Sr的浓集系数为石螺的 1 4倍。两种母螺的卵和子螺的90 Sr比活度均高于同时间两种螺贝壳的比活度 ,说明90

关键词： Food products   Methods of analysis   Microbiology   Micro-organisms   Specimen preparation   Testing   Verification   Volumes  

标准号: NF V08-100-2001

关键词： 分子生物学技术   动物营养学   应用   发展前景   植酸酶   基因工程   转基因技术  

摘要： (接上期)2.2植酸酶的基因工程　　植酸酶的研究已有近40年的历史，植酸酶作为一种单胃动物的饲料添加剂，其饲喂效果已在世界范围内得到广泛的确证，随着饲料工业的发展和分子生物学的兴起，从90年代开始的植酸酶的分子生物学研究，已成为世界性的研究热点之一。目前国内外研究的主要思路集中在通过基因工程这一手段解决饲用植酸酶的两个主要问题：一个是植酸酶在天然材料中表达水平太低，这造成植酸酶难以大量生产及生产成本过高的问题，通过基因工程技术，利用生物反应器则有望成百上千倍地提高它的表达量；另一个问题是天然植酸酶的一些酶学性质，如耐温性，pH适性、催化活性等不能完全适合饲料加工业和养殖业的要求，利用基因工程手段在分子水平上对植酸酶基因进行改造，从而提高其在饲料中使用的有效性。2.2.1在微生物中高效表达植酸酶基因　　目前，植酸酶基因表达的研究主要集中在来源于曲霉的植酸酶基因phyA和plyB上。Hartingsveldt等(1993)将来源于***3135的phyA基因导回原菌株，使phy基因的拷贝数增加到15个以上，从而使植酸酶的表达量提高到7600u/ml。Ehrlich等（1995）在***中表达来源于酵母的植酸酶基因和来源于***762的phyB基因，其结果也是使表达量分别提高到840u/ml和750u/ml，将植酸酶基因phyA置于来源于***的淀粉葡萄糖甘酶(AG)启动子之下，信号肽序列分别用AG信号肽的18个氨基酸序列、AG信号肽的24个氨基酸序列及植酸酶原来的信号肽序列3种构建，将植酸酶基因重组到***基因组中而获得植酸酶基因的阳性克隆子，在这3种构建中其植酸酶在重组菌株中的表达量分别达到了1.1,0.5,2.8×105u/ml，比原植酸酶产生菌株的表达量高约1000～3000倍左右。

关键词： 主题词：野生动物-动物学：微生物学  

关键词： 固硫型煤，普通煤，家兔，生物学指标  

摘要： 目的 探讨生活性燃煤造成室内二氧化硫污染对健康的潜在危害作用，比较生物固硫型煤与普通煤造成危害作用的差异。 方法 以家兔为实验对象，将36只健康雄性家兔随机分成3组，每组12只，分别喂养在燃烧生物固硫型煤、普通煤及不烧煤的空白对照环境中连续观察90天，每天监测三种室内环境中SO2、CO的浓度；实验前、实验中（45天）、实验后（90天）三次测定家兔的下列生物学指标：LYS含量、血清中SOD、GSH-PX、SA浓度以及外周血淋巴细胞的DNA损伤率（彗星试验），并在实验结束时作支气管和肺的病理切片观察。 结果 1.环境监测结果：普通煤组SO2 值在生火时平均浓度达到24.65 mg/m3，而固硫型煤组仅为3.60 mg/m3；SO2 24小时平均浓度普通煤组为13.04mg/m3，是固硫型煤组的4.86倍（2.68mg/m3），是空白对照组的31.95倍（0.41mg/m3），但CO水平普通煤组和固硫型煤组两组间无明显差异。2.生物学指标结果：普通煤组和固硫型煤组家兔的淋巴细胞DNA损伤率有随着时间和SO2浓度逐渐增加的趋势，实验45天后，普通煤组出现彗星细胞的家兔数较其他两组明显增加（P<0.05），实验90天后，彗星细胞阳性率普通煤组为10.36%，固硫型煤组为5.42%，空白对照组为1.73%，各组间的差异有显著性意义（P<0.01）, 并且彗星细胞阳性率同SO2浓度存在一定的剂量效应关系（R2=0.784，p<0.01）。病理切片发现普通煤组家兔支气管上皮细胞增生明显，且有一例发现支气管上皮重度鳞形化生伴不典型增生细胞。实验90天后与实验前的GSH-PX值的差值，普通煤>空白对照组>固硫型煤组,普通煤和固硫型煤组间的差别有显著性意义（P<0.05）；SOD、SA、LYS值随时间不断变化，但各组间的变化无显著性（p>0.05）。 结论 研究结果提示燃煤煤烟中的SO2能影响生物体内SOD、GSH-PX、SA等的浓度，特别是引起淋巴细胞DNA损伤的增加，结合支气管上皮增生伴鳞形化生表明燃煤煤烟具有致癌的可能性；证实燃烧生物固硫型煤具有明显降低室内SO2浓度的能力，故使用生物固硫型煤可减少燃煤煤烟对健康的危害，但燃煤煤烟中有害气体对机体的危害有待于深入研究。