Density-dependent processes in the life history of fishes: evidence from laboratory populations of zebrafish Danio rerio

Population regulation is fundamental to the long-term persistence of populations and their responses to harvesting, habitat modification, and exposure to toxic chemicals. In fish and other organisms with complex life histories, regulation may involve density dependence in different life-stages and vital rates. We studied density dependence in body growth and mortality through the life-cycle of laboratory populations of zebrafish Danio rerio. When feed input was held constant at population-level (leading to resource limitation), body growth was strongly density-dependent in the late juvenile and adult phases of the life-cycle. Density dependence in mortality was strong during the early juvenile phase but declined thereafter and virtually ceased prior to maturation. Provision of feed in proportion to individual requirements (easing resource limitation) removed density dependence in growth and substantially reduced density dependence in mortality, thus indicating that 'bottom-up' effects act on growth as well as mortality, but most strongly on growth. Both growth and mortality played an important role in population regulation, with density-dependent growth having the greater impact on population biomass while mortality had the greatest impact on numbers. We demonstrate a clear ontogenic pattern of change in density-dependent processes within populations of a very small (maximum length 5 mm) fish, maintained in constant homogeneous laboratory conditions. The patterns are consistent with those distilled from studies on wild fish populations, indicating the presence of broad ontogenic patterns in density-dependent processes that are invariant to maximum body size and hold in homogeneous laboratory, as well as complex natural environments.     

Noradrenergic control of gene expression and long-term neuronal adaptation evoked by learned vocalizations in songbirds

Norepinephrine (NE) is thought to play important roles in the consolidation and retrieval of long-term memories, but its role in the processing and memorization of complex acoustic signals used for vocal communication has yet to be determined. We have used a combination of gene expression analysis, electrophysiological recordings and pharmacological manipulations in zebra finches to examine the role of noradrenergic transmission in the brain's response to birdsong, a learned vocal behavior that shares important features with human speech. We show that noradrenergic transmission is required for both the expression of activity-dependent genes and the long-term maintenance of stimulus-specific electrophysiological adaptation that are induced in central auditory neurons by stimulation with birdsong. Specifically, we show that the caudomedial nidopallium (NCM), an area directly involved in the auditory processing and memorization of birdsong, receives strong noradrenergic innervation. Song-responsive neurons in this area express α-adrenergic receptors and are in close proximity to noradrenergic terminals. We further show that local α-adrenergic antagonism interferes with song-induced gene expression, without affecting spontaneous or evoked electrophysiological activity, thus dissociating the molecular and electrophysiological responses to song. Moreover, α-adrenergic antagonism disrupts the maintenance but not the acquisition of the adapted physiological state. We suggest that the noradrenergic system regulates long-term changes in song-responsive neurons by modulating the gene expression response that is associated with the electrophysiological activation triggered by song. We also suggest that this mechanism may be an important contributor to long-term auditory memories of learned vocalizations.     

Association of telomere instability with senescence of porcine cells

Telomeres are essential for the maintenance of genomic stability, and telomere dysfunction leads to cellular senescence, carcinogenesis, aging, and age-related diseases in humans. Pigs have become increasingly important large animal models for preclinical tests and study of human diseases, and also may provide xeno-transplantation sources. Thus far, Southern blot analysis has been used to estimate average telomere lengths in pigs. Telomere quantitative fluorescence in situ hybridization (Q-FISH), however, can reveal status of individual telomeres in fewer cells, in addition to quantifying relative telomere lengths, and has been commonly used for study of telomere function of mouse and human cells. We attempted to investigate telomere characteristics of porcine cells using telomere Q-FISH method. The average telomere lengths in porcine cells measured by Q-FISH correlated with those of quantitative real-time PCR method (qPCR) or telomere restriction fragments (TRFs) by Southern blot analysis. Unexpectedly, we found that porcine cells exhibited high incidence of telomere doublets revealed by Q-FISH method, coincided with increased frequency of cellular senescence. Also, telomeres shortened during subculture of various porcine primary cell types. Interestingly, the high frequency of porcine telomere doublets and telomere loss was associated with telomere dysfunction-induced foci (TIFs). The incidence of TIFs, telomere doublets and telomere loss increased with telomere shortening and cellular senescence during subculture. Q-FISH method using telomere PNA probe is particularly useful for characterization of porcine telomeres. Porcine cells exhibit high frequency of telomere instability and are susceptible to telomere damage and replicative senescence.     

斜带石斑鱼经葡萄糖灌喂后的代谢反应

糖类的主要生理功能是为动物机体提供能量,而且是比蛋白质和脂肪更为廉价的能源。相对于陆生恒温动物,鱼类尤其是肉食性鱼类对糖的利用能力低下,似乎先天性地具有糖尿病患者的某些生理特征。饲料中过高的糖水平会导致鱼类抗病力下降、生长速度减缓、死亡率增加等症状。鱼类解除葡萄糖负荷的能力有限从而表现     

播期对陇中黄土高原半干旱区马铃薯生长发育及产量的影响

在气候变化的背景下,为了探寻陇中黄土高原半干旱区马铃薯的适宜播种期,2010年在甘肃定西进行了马铃薯分期播种试验,并对不同播期条件下马铃薯生长发育及产量形成进行了分析.结果表明:随着播期的推迟,马铃薯全生育期缩短,株高出现明显变化,单株干物质最大积累速率提前;从不同播期来看,5月27日播种的植株高度、叶面积指数、单株干物质积累量和最大积累速率均最大,马铃薯块茎鲜重的增长过程呈“慢-快-慢”S型曲线;块茎鲜重最大积累速率出现的时间随播期的推迟而提前;产量数据的方差和多重比较分析结果表明,播期是影响产量的主要因素,其中5月27日播期的丰产性最好;对各播期不同生育期的气候条件进行比较表明,5月底或6月初是陇中黄土高原半干旱区马铃薯的适宜播种时间.     

天津于桥水库大型底栖动物群落结构及其水质生物学评价

于2010年5月-2011年5月按季度对于桥水库大型底栖动物进行了采样调查.结果表明:于桥水库底栖动物有51种,其中水生昆虫23种,占总数的45.1％;软体动物15种,占29.4％;寡毛类12种,占23.5％;其他类1种,占2.0％,优势种类为侧叶雕翅摇蚊(Glyptotendipes lobiferus)、中华圆田螺(Cipangopaludina cathayensis)、霍甫水丝蚓(Limnodrilus hoffmeisteri)、克拉泊水丝蚓(L.claparedeianus);底栖动物年均密度为159.58 ind·m-2,年均生物量为3.31 g·m-2;各季度底栖动物密度表现为春季＞冬季＞秋季＞夏季,生物量表现为冬季＞夏季＞春季＞秋季.利用Goodnight修正指数(GBI)、Shannon-Wiener多样性指数(H')、Margalef丰富度指数(d)、生物学污染指数(BPI)、科级生物指数(FBI)和综合生物污染指数(BI)对于桥水库的水质进行综合评价,结果显示,于桥水库水质整体处于轻-中污型(Ⅱ-Ⅲ),相比1999-2000年(Ⅲ)于桥水库水质污染状况有所好转.     

光质对东北次生林生态系统主要树种种子萌发的影响

以东北次生林生态系统5个主要树种（日本落叶松、黄檗、色木槭、水曲柳和红松）种子为对象,采取室内控制(5个主要树种)和野外模拟(红松和日本落叶松)相结合的方法,研究光质对种子萌发的影响.室内和实际林分下分别设置了4种不同光质类型处理（以黑暗为对照）和3个红光/远红光比值(R/FR)梯度.结果表明： 不同光质类型除对日本落叶松种子萌发的影响不显著外,对其他4个树种种子萌发影响均显著.其中,黄檗种子萌发率在白光下达到最高,色木槭、水曲柳和红松种子萌发率在红光-远红光-红光照射下达到最高.林分内试验结果与室内一致,红松种子萌发率随林内R/FR下降而明显下降,落叶松种子萌发则不受光质的影响.在自然林分条件下,R/FR随着光斑活动不断变化,色木槭、水曲柳和红松种子萌发格局可能是对森林光斑环境适应的结果.大粒种子萌发显著受光质的影响.     

蛋白质突变库高通量表达筛选方法的研究

人工进化方法被越来越多地应用于重组蛋白的表达筛选及其结构功能的研究,在适当的选择压力下,它可以有效地改善野生型蛋白固有的低表达和低稳定性等问题。本研究就如何进行快速、有效的蛋白质人工进化以提高重组蛋白表达量,进行了方法学探索,通过建立以绿色荧光蛋白为报告基因、结合流式细胞仪分选和96孔板等高通量筛选方法,成功地进行了一例高通量蛋白质点突变库重组表达株的筛选。     

滁州市家蝇对6种杀虫剂的抗药性调查

采用微量滴定法测定了滁州市家蝇对6种常见杀虫剂的抗药性。结果表明,滁州市的家蝇对毒死蜱、敌敌畏、高效氯氰菊酯、敌百虫、辛硫磷、溴氰菊酯6种常用杀虫剂都产生了很高的抗性,其LD50分别为1.1858、1.9505、0.9530、47.1834、1.2120、1.0053μg/只,相对抗性系数分别为49.62、139.32、207.17、263.59、390.97、1675.50。滁州应停止使用这些杀虫剂,加强对家蝇抗性对策的研究,延缓家蝇抗性的发展。