脂筏极化参与活性氧介导的白杄花粉管顶端生长

质膜上存在一种富含甾醇物质的液相有序膜脂微区，被称作脂筏 (lipid rafts或lipid microdomains)。这种小的膜微区可以通过在质膜上的侧向移动，聚集形成较大的片状结构，而与微区相关联的蛋白可以通过脂筏的这种聚合作用而凝聚分布于特定的亚细胞结构上。脂筏区域在真菌和动物质膜上具极性分布，并参与细胞的极性形态建成和运动。最近，通过生物化学研究证实，脂筏也存在于植物细胞，然而迄今为止，脂筏与植物细胞极性生长相关联的直接功能证据尚未见报道。 NADPH氧化酶 (NOX，在植物中又称为 Rboh) 产生的活性氧 (Reactive oxygen species, ROS) 可能是调控植物细胞（包括花粉管、根毛和墨角藻合子等）极性生长的通用信号机制。花粉管作为研究细胞极性控制的一种理想模式系统，已被许多信号转导调控研究所采用。在本研究中，我们使用一种能螯合甾醇类物质的多烯类抗生素filipin破坏脂筏结构，以探讨脂筏极化对ROS介导的白杄花粉管极性生长的作用。 我们首次在白杄 (Picea meyeri) 花粉管上应用一种全新的苯乙烯基染料di-4-ANEPPDHQ，成功地在活体细胞上观察到脂筏在花粉管生长顶端的极性分布模式。通过脂筏和甾醇在质膜上的相似定位清楚表明：在花粉管极性生长过程中，存在富含甾醇类物质的质膜微区在花粉管生长顶端的极化现象。 氮蓝四唑（NBT）的还原和二氯二氢荧光素（H2DCF）的氧化均显示，在活跃生长的花粉管顶端区域存在一个以顶端为基底的陡峭ROS梯度，从而进一步验证了ROS在细胞极性生长过程中的信号作用。此外，我们还发现在生长花粉管的亚顶端位置有另一类性质的活性氧组分存在，该ROS组分与线粒体的能量代谢相关。研究结果首次揭示，在快速生长的花粉管中同时存在两类性质不同的ROS组分。 ROS是一种寿命很短而且容易扩散的分子，NADPH氧化酶产生的ROS信号在细胞伸长位点的准确定位是调控极性生长的必要条件。免疫共定位实验显示，NOX成簇极化分布于花粉管的生长顶端。使用filipin进行甾醇的螯合会破坏膜的异质性，干扰NOX簇在生长顶端的定位，减少了顶端的ROS形成，消弱了胞质Ca2+ 浓度梯度，进而抑制了花粉管的顶端生长。 在纯化质膜的基础上，我们使用Triton去垢剂处理结合Optiprep密度梯度离心，分离纯化了抗去垢剂抽提的质膜微区 (Detergent-resistant microdomains, DRMs)。通过免疫印迹分析证实，NADPH氧化酶部分地存在于DRMs中。非变性胶活性实验证明，该酶需要脂筏定位来保持酶活性。因此我们认为，在正常的细胞极性生长中，脂筏招募并运载NADPH氧化酶到花粉管的生长顶端，并为NOX及其活性亚基的有效互作提供了适宜的微环境，由此保证了NOX蛋白产生ROS的较高酶活性，进而维持花粉管的极性顶端生长。 总之，甾醇螯合对白杄花粉管生长影响的研究，为脂筏极化在花粉管极性生长中的作用提供了证据。基于以上生物化学和细胞生物学的结果，我们针对花粉管中富含甾醇的脂筏微区和NOX功能之间的联系，提出了一种假说模式：(1) 植物细胞质膜上的脂筏为信号分子ROS在特定位点的聚集提供了物理载体；(2) 脂筏的完整性和甾醇依赖性对NOX的定位和活性是必要的，并为花粉管细胞极性产生和维持所必需。上述研究结果表明，脂筏在花粉管顶端的极化，以及作为关键生长因子的NOX在质膜脂筏中的定位，对花粉管的高度极性生长具有重要作用。

Effect of dietary carbohydrate-to-lipid ratios on growth and feed utilization in Chinese longsnout catfish (Leiocassis longirostris Gunther)

An 8-week growth trial was carried out in a semi-recirculation system at 26 +/- 0.5 degrees C to investigate the optimal dietary carbohydrate-to-lipid (CHO:L) ratio for carnivorous Chinese longsnout catfish (Leiocassis longirostris Gunther). Triplicate tanks of fish were assigned to each of five isocaloric and isonitrogenous diets with different carbohydrate-to-lipid ratios (0.75, 1.48, 1.98, 2.99 and 5.07). The results showed that a higher specific growth rate (SGR) and feed rate (FR) were observed in the fish fed diet ratios of 1.98 CHO:L (P < 0.05). Overloading dietary carbohydrate (5.07 CHO:L ratio) caused skeletal malformations. Apparent digestibility of dry matter (ADC(d)) significantly increased with dietary CHO:L ratio (P < 0.05), while significantly higher apparent digestibility of protein (ADC(p)) and apparent digestibility of energy (ACD(e)) was observed only in the 1.98 CHO:L group (P < 0.05). Whole body contents of dry matter, lipid and energy significantly increased as the CHO:L ratio decreased (P < 0.05). The hepatosomatic index (HSI) was highest at 1.98 CHO:L ratio (P < 0.05). Highest dietary CHO:L ratio resulted in lower liver glycogen, liver lipid, plasma glucose and plasma triacylglycerol (P < 0.05), whereas there was no significant difference in plasma total cholesterol (P > 0.05). High dietary CHO:L ratio caused pathological changes in fish morphology and liver histology. Based on maximum growth, the optimal carbohydrate-to-lipid ratio was 1.98 for Chinese longsnout catfish.

Comparative study on the effect of dietary lipid level on growth and feed utilization for gibel carp (Carassius auratus gibelio) and Chinese longsnout catfish (Leiocassis longirostris Gunther)

An 8-week growth trial investigated the effect of dietary lipid level on growth performance of a carnivorous fish, Chinese longsnout catfish (Leiocassis longirostris Gunther) and an omnivorous fish, gibel carp (Carassius auratus gibelio). For each species, seven isonitrogenous semi-purified diets (455 g kg(-1) crude protein for Chinese longsnout catfish and 385 g kg(-1) crude protein for gibel carp) were formulated to contain 30, 60, 90, 120, 150, 180 or 210 g kg(-1) lipid. For Chinese longsnout catfish, feed intake (FI) decreased with increasing dietary lipid and there was no significant difference in feed intake from 90 to 210 g kg(-1) lipid. Specific growth rate (SGR) increased with dietary lipid level (P < 0.05) and the 150 and 180 g kg(-1) groups were the best. Feed conversion efficiency (FCE), protein retention efficiency (PRE) and energy retention efficiency (ERE) were higher at 180 g kg(-1) lipid. For gibel carp, FI decreased with increased dietary lipid and 180 and 210 g kg(-1) lipid groups showed lower values. SGR increased with dietary lipid level and the 150 and 180 g kg(-1) were the best. FCE was higher at 180 g kg(-1) lipid level. PRE increased with dietary lipid level and there was no significant difference in groups from 120 to 210 g kg(-1) dietary lipid. ERE increased with increasing dietary lipid level, and groups fed 120, 150 and 180 g kg(-1) lipid showed the highest values. In Chinese longsnout catfish, increase in dietary lipid level, resulted in increased carcass dry matter, crude protein, crude lipid and gross energy. In gibel carp, dry matter, crude protein, and crude lipid increased with dietary lipid level. Based on regression between SGR and dietary lipid, dietary lipid requirements for Chinese longsnout catfish and gibel carp were 142.6 and 140.5 g kg(-1), respectively.

RAFT调控的丙烯腈可控/活性自由基聚合研究

可逆加成裂解链转移(RAFT)聚合已经成为高分子合成的研究热点之一，这是因为它同时具有自由基聚合和活性聚合的优点，能够有效控制分子量和分子量分布，反应条件温和，可用于本体、溶液、悬浮、乳液等体系，单体范围广，能够合成嵌段、接枝、支化等复杂结构的聚合物。在已经报道的丙烯腈RAFT聚合研究中，所得聚合物具有较窄的分子量分布，分子量接近理论预测值，然而，最高值只达到5000左右。本论文的研究工作正是从这一个基本问题展开的。 1. 利用三硫代碳酸二苄基酯代替二硫代羧酸酯作为链转移剂，降低中间态自由基断裂反应的活化能，保证活性态与休眠态之间的平衡以一较快的交换速率进行，聚合结果表明，在文献报道的反应条件下，聚合速率有了明显的提高，同时聚合以一种可控的方式进行，所得聚合物分子量最高达8000，且分子量分布较窄。 2. 将二硫代苯甲酸异丙腈酯调控的丙烯腈聚合实验参数优化，提高反应温度降低缓聚，选择碳酸乙二酯作为溶剂减小链转移反应，导致中间态自由基断裂反应的效率大大提高，以一种可控/活性自由基聚合方式进行，首次合成了分子量高达32800、分子量分布指数小于1.3的聚丙烯腈。 3. 由于RAFT试剂很难制备和长期保存，当以二硫代物作为替代的调控试剂, 偶氮二异丁腈作为引发剂，可以在“原位”合成RAFT聚合所需的链转移剂，直接调控丙烯腈的自由基聚合，得到高分子量、分子量分布指数比较小的丙烯腈均聚物和共聚物。 4. 将不对称的双乙烯基单体作为支化剂引入到丙烯腈聚合体系中，同时采用RAFT技术来抑制交联反应，单体转化率增加至较高值而不形成凝胶，1H NMR和凝胶渗透色谱证明了合成的聚合物具有支化结构，并且聚合物的特性粘数低于相近分子量的线性聚合物的对应值。

LIPID MICRORESISTOR AS MIMICKING OLFACTORY SENSOR - THE RULE OF THE RESPONSE OF LIPIDS TO C-1-C-4 ALCOHOLS

Phosphatidylcholine (PC) and six other PC-similar lipids are coated on interdigital electrodes, IEs, as sensitive membranes. Eight alcohols (C-1-C-4) are tested in a flow system at room temperature. It is found that all responses are log(response)-log(concentration) linear relations. These results agree with Steven's law in psychophysics. Moreover, the thresholds of the sensors are coincident with human olfactory thresholds. The authors have analysed the data of the lipid hypothesis suggested by Kurihara et al. We have found that this hypothesis is also in agreement with Steven's law. Lipid microresistors are real mimicking olfactory sensors. A definition of an olfactory sensor is suggested.

A NOVEL ODOR SENSOR COATED WITH A LIPID-MEMBRANE

In this paper, an interdigital electrode lipid film odour sensor (ILOS) is designed, fabricated and tested. It is made from a microfabricated chemiresistor coated with a synthetic multibilayer film. Nine odorants in gas phase at room temperature have been detected using the odour sensor. For most of the odorants, the relation between the response of the ILOS and odorant concentration obeys Stevens' power law, and there is a good correlation between the minimum odorant concentrations that give rise to a change of the sensor's conductance and human olfactory thresholds.