高温季节控温诱导池养鳗鲡性腺发育的研究

在高温季节(6～9月),采用人工控温的方法,通过注射外源激素hCG和CPE,对日本鳗鲡进行了催熟试验.结果表明,在人工控制温度(18±2℃)条件下,雌性和雄性日本鳗鲡均可达到性成熟,诱导成熟率分别为73.33%和67.77%,而常温条件下(25～32℃)的诱导成熟率分别为0和33.33%.同时对控温条件下诱导成熟的部分雌性鳗鲡进行了催产,其排卵率为70%,受精率为32%,均接近或达到了低温季节相应的指标(平均分别为62.1%和3.2%).对胚胎发育过程也进行了观察,受精卵能正常发育,在22和2℃下,分别经过39 h 15 min和3 h 9 min孵化出膜.试验证明,在高温季节采用人工控温的方法诱导日本鳗鲡性成熟是可能的.     

高GC含量的鳜鱼rRNA基因家族的克隆

动物rRNA基因是一种GC含量较高、结构复杂的重复序列。该研究结合亲缘生物法生物信息学技术,经反复摸索后选用LA PCR法即LA PCR Taq酶结合GC缓冲液来扩增鳜鱼复杂的rRNA基因重复序列,经测序鉴定最终克隆了鳜鱼的3个rRNA基因及其2个间隔序列。分析了鳜鱼与相关动物的rRNA基因序列的同源性和进化关系。探索了克隆复杂DNA序列时引物设计的特别规则、反应体系的改进、DNA聚合酶的选用、循环参数的调整等措施。     

SSB蛋白的高效表达及其与ssDNA的相互作用

大肠杆菌单链结合蛋白SSB在DNA复制、重组和修复中起着重要作用。为研究单链结合蛋白SSB的体外生物功能构建了融合蛋白SSB的表达载体并使其高效表达及易于纯化。ssb基因片段是以E.coli K-12基因组为模板经PCR扩增获得,并通过基因的体外拼接成功构建了表达载体pQE30-ssb。重组菌株M15/ pQE30-ssb经过IPTG的诱导表达了蛋白SSB。收集菌体细胞、超声波破碎后离心取上清进行SDS-PAGE分析,结果表明有一与预期分子量（20.6 kD）相应的诱导表达条带出现,其表达量约占全细胞蛋白的30％且以可溶形式存在。利用固定化金属离子（Ni2+）配体亲和层析柱纯化融合蛋白SSB,其纯度达到90％。通过凝胶层析和等离子共振技术对SSB的生物功能进行了系统研究分析。结果表明,SSB蛋白以四聚体形式与单链DNA分子结合,其亲和力常数（KD）为4.79×10-7 M。     

Mapping a high oleic acid mutation in winter oilseed rape (Brassica napus L.)

Two winter oilseed rape mutant lines, 7488 and 19661, with a high oleic (HO) acid content in the seed oil were characterized phenotypically. In both mutant lines the HO trait was monogenically inherited. Segregation analysis in an F₂ population derived from a cross between 7488 and 19661 showed the two mutations to be allelic. From a comparison of seed, leaf and root fatty acid composition it was concluded that fad2, the endoplasmic oleic acid desaturase, is affected by the mutation. In a bulked segregant analysis three AFLP markers linked to this mutation were detected and localized on the genetic map of Brassica napus. The markers mapped near the locus of one copy of the fad2 gene in the rapeseed genome. Received: 16 February 2000 / Accepted: 28 March 2000     

A review of rhizosphere carbon flow modelling

Rhizosphere processes play a key role in nutrient cycling in terrestrial ecosystems. Plant rhizodeposits supply low-molecular weight carbon substrates to the soil microbial community, resulting in elevated levels of activity surrounding the root. Mechanistic compartmental models that aim to model carbon flux through the rhizosphere have been reviewed and areas of future research necessary to better calibrate model parameters have been identified. Incorporating the effect of variation in bacterial biomass physiology on carbon flux presents a considerable challenge to experimentalists and modellers alike due to the difficulties associated with differentiating dead from dormant cells. A number of molecular techniques that may help to distinguish between metabolic states of bacterial cells are presented. The calibration of growth, death and maintenance parameters in rhizosphere models is also discussed. A simple model of rhizosphere carbon flow has been constructed and a sensitivity analysis was carried out on the model to highlight which parameters were most influential when simulating carbon flux. It was observed that the parameters that most heavily influenced long-term carbon compartmentalisation in the rhizosphere were exudation rate and biomass yield. It was concluded that future efforts to simulate carbon flow in the rhizosphere should aim to increase ecological realism in model structure. This revised version was published online in June 2006 with corrections to the Cover Date.     

环丁烷嘧啶二聚体累积与水稻UV—B敏感性的关系

利用单克隆抗体ELISA ,研究了UV_B对水稻DNA中环丁烷嘧啶二聚体 (CPD)的诱导形成及其光、暗修复 ,并对CPD累积与水稻UV_B敏感性的关系进行了分析。结果表明 ,我国南方的 5个水稻 (OryzasativaL .)品种经13.6kJ·m-2 ·d-1UV_B处理 15d后 ,在株高、生物量、光合作用等方面表现出明显的品种间差异。不同品种水稻的DNA中CPD累积比对照明显增加 ,且敏感品种CPD的累积比抗性品种显著提高。统计分析证实 ,CPD的累积与生物量的抑制呈显著正相关 (r2 =0 .6 2 2 )。UV_B诱导的水稻DNA中CPD的清除以光修复为主 ,不同品种CPD暗修复能力相似 ,而光修复能力存在明显差异。根据以上结果推测 ,不同水稻品种UV_B敏感性与CPD光修复能力的差异有关。     

高压静电场(HVEF)对柑桔青、绿霉病菌的抑制效果

用高压静电场(HVEF)对柑桔青霉菌 (P.italicum )和绿霉菌 (P.digitatum)分别进行了不同时间和方法的处理 ,以比较这些处理对病菌孢子在不同温度下萌发力和致病力的抑制效果。结果表明 ,HVEF处理后病菌孢子的萌发率、芽管长度和产孢量都显著地低于对照。而且处理时间越长 ,效果越明显。处理的孢子接种在柑桔果实上的感病率也显著低于对照 ,并能有效地抑制感病果实病斑的扩展。     

大棕蝠下丘听神经元频率调谐的方向敏感性

实验在8只大棕蝠(Eptesicusfuscus)上进行.选取了5个声源方位记录部位对侧80°(C-80°)、40°(C-40°)、0°和同侧40°(I-40°)、80°(I-80°).下丘听神经元的频率调谐曲线的形状有三种V型、封闭型和U型.以C-40°的频率调谐曲线为对照,声源方位改变时,多数神经元频率调谐曲线的形状和最佳频率不变.多数神经元在声源方位由记录部位对侧转向同侧时,频率调谐曲线的锐度(以QndB值为指标)由小变大;神经元在I-80°、I-40°的QndB值显著高于C-80°、C-40°、0°的QndB值.在所观察的47个神经元中,5个声源方位的最低阈值的平均值有显著差异,由高到低的分布为MTI-80°＞MTI-40°＞MT0°＞MTc-80°＞MTc-40°.我们推测,声源方位对神经元频率调谐特性影响的机制,可能是抑制性和兴奋性输入的比例不同而相互整合的结果.     

静电场对苜蓿愈伤组织抗寒能力的影响

用正负高压静电场 (HVEF)处理苜蓿叶片来源的愈伤组织后 ,在4℃下暗培养。我们发现静电场处理可不同程度地提高愈伤组织的淀粉酶 ,过氧化物酶 ,和超氧化物岐化酶的活性和可溶性蛋白的含量 ,促进愈伤组织对冷害的防御能力。在冷处理过程中 ,细胞膜中饱和脂肪酸 (棕榈梭和硬脂酸 )和不饱和脂肪梭含量先升高然后降低 ,而高压静电场处理组的不饱和脂肪酸 (油酸、亚油酸、α -亚麻酸、β-亚麻酸 )含量高于对照组 ,脂肪酸不饱和指数 (UIFA)也高于对照组 ,这说明静电场处理可促进愈伤组织细胞抗寒能力提高。此外 ,丙二醛 (MDA)含量在静电场处理组低于对照组的测定结果也验证了前面的结果。     

高速逆流色谱法分离纯化茶黄素

首次应用高速逆流色谱法分离纯化茶黄素单体成分,溶剂系统为乙酸乙酯－正己烷－甲醇－水（３：１：１：６）,优化了分离茶黄素的条件。同时与ＳｅｐｈａｄｅｘＬＨ－２０柱色谱法梯度洗脱对比,结果表明,高速逆流色谱法分离时间相对较短,可进行较大量的分离制备。高速逆流色谱法较之ＳｅｐｈａｄｅｘＬＨ－２０柱色谱法还有一个突出的优点,即无不可逆吸附污染及不会导致样品化学变性。