青霉素钠对萼花臂尾轮虫适合度的促进作用及其与藻密度的关系

以萼花臂尾轮虫（Brachionus calyciflorus）为受试动物,在1.0×10⁶（较低）、2.0×10⁶（中等）和4.0×10⁶个细胞/mL （较高）的斜生栅藻（Scenedesmus obliquus）密度下,研究了不同浓度（0、200、400、600、800和1000 μg/L）的青霉素钠对轮虫各生命表统计学参数的影响。结果表明,与各藻密度下的对照组相比,当藻密度为2.0×10⁶个细胞/mL时,200-1000 μg/L的青霉素钠处理组中轮虫的生命期望和世代时间分别延长了40.67%-70.67%和34.04%-50.23%（P<0.05）,净生殖率和内禀增长率分别提高了204.35%-358.70%和36.26%-62.09%（P<0.05）;藻密度的降低或升高均显著降低青霉素钠对轮虫存活、生殖和种群增长的促进幅度。1.0×10⁶ 个细胞/mL的斜生栅藻密度下,400 μg/L的青霉素钠处理组中轮虫的生命期望延长了21%（P<0.05）,200-400μg/L的青霉素钠处理组中轮虫的世代时间延长了23.15%-33.13%（P<0.05）,200-600和1000 μg/L的青霉素钠处理组中轮虫的净生殖率分别升高了40%-81.05%和41.05%（P<0.05）;但4.0×10⁶个细胞/mL的斜生栅藻密度下,各青霉素钠处理组中轮虫的所有生命表统计学参数均与对照组之间无显著性差异（P>0.05）。藻密度对轮虫的生命期望、净生殖率、内禀增长率和后代混交率均具有显著性影响（P<0.01）,青霉素钠浓度对轮虫的世代时间、净生殖率和内禀增长率均具有显著性影响（P<0.05）,藻密度和青霉素钠浓度的交互作用对轮虫的生命期望、净生殖率和内禀增长率也具有显著性影响（P<0.05）。在实验设置的青霉素钠浓度范围内,1.0×10⁶个细胞/mL藻密度下轮虫的生命期望、世代时间和净生殖率与青霉素钠浓度之间均具有显著的剂量-效应关系（P<0.05）;2.0×10⁶个细胞/mL藻密度下,轮虫的生命期望、世代时间和内禀增长率与青霉素钠浓度之间均具有显著的剂量-效应关系（P<0.05）。本研究结果提示,环境相关浓度的青霉素钠不会对萼花臂尾轮虫的存活、生殖和种群增长产生显著性影响。     

液体培养条件下细菌浓度两种测定方法比较

液体培养细菌后,分别测定培养液、培养液沉淀 无菌盐水的吸光度,结果存在明显差异。采用稀释平板法和显微计数法测定了培养液中细菌数量,并推导出嗜水气单胞菌活菌数与吸光度的关系为logI0/I=6.848×10-25·C。     

高CO2浓度下豆科4种乔木幼苗的生理生化反应

本文对４种豆科乔木幼苗在高ＣＯ２浓度（５５０×１０－６±５０×１０－６）和在对照ＣＯ２浓度（约为３５０×１０－６）下生长的幼苗的一些生理生化指标进行了比较研究。初步结果显示：高ＣＯ２浓度能缩短幼苗子叶的存活时间。高ＣＯ２环境下生长的４种幼苗叶片中的可溶性蛋白、可溶性糖、纤维素、Ｎ、Ｐ、Ｋ、Ｍｇ的含量（均为全量）较对照ＣＯ２环境下生长的幼苗的相应值低,而淀粉含量则较高。其中以全氮、可溶性糖差异较显著。以单位鲜重表示的幼苗叶片叶绿素（Ｃｈｌ）和类胡萝卜素（Ｃａｒ）含量降低。高ＣＯ２浓度下生长的４种幼苗（３０天龄）叶片中硝酸还原酶活性比对照ＣＯ２浓度下生长的幼苗的值低。高ＣＯ２浓度下生长的４种幼苗叶片的平均蒸腾速率有不同程度的降低,而气孔阻力升高。幼苗对高ＣＯ２环境的反应与种的生态特性有关。喜光的大叶合欢幼苗对高ＣＯ２环境的反应较大,喜光而具一定耐荫性的猴耳环幼苗次之,而耐荫的光叶红豆和茸荚红豆幼苗则较小     

The Role of the Lipid Bilayer in Tau Aggregation

Tau is a microtubule associated protein whose aggregation is implicated in a number of neurodegenerative diseases. We investigate the mechanism by which anionic lipid vesicles induce aggregation of tau in vitro using K18, a fragment of tau corresponding to the four repeats of the microtubule binding domain. Our results show that aggregation occurs when the amount of K18 bound to the lipid bilayer exceeds a critical surface density. The ratio of protein/lipid at the critical aggregation concentration is pH-dependent, as is the binding affinity. At low pH, where the protein binds with high affinity, the critical surface density is independent both of total lipid concentration as well as the fraction of anionic lipid present in the bilayer. Furthermore, the aggregates consist of both protein and vesicles and bind the β-sheet specific dye, Thioflavin T, in the manner characteristic of pathological aggregates. Our results suggest that the lipid bilayer facilitates protein-protein interactions both by screening charges on the protein and by increasing the local protein concentration, resulting in rapid aggregation. Because anionic lipids are abundant in cellular membranes, these findings contribute to understanding tau-lipid bilayer interactions that may be relevant to disease pathology.     

Trypanosoma evansi: Pharmacological evidence of a nicotinic acetylcholine receptor

The role of calcium and its relevance have been deeply revised with respect to trypanosomatids, as the mechanism by which calcium enters trypanosomes was, until now, not well understood. There is evidence supporting the presence of a nAChR in another member of the trypanosomatidae family, Trypanosoma cruzi, these receptors being one entry path to calcium ions. The aims of this work were to determine if there was a nicotinic acetylcholine receptor (nAChR) in Trypanosoma evansi, and to subsequently perform a partial pharmacological characterization of this receptor.After being loaded with FURA-2AM, individual cells of T. evansi, were exposed to cholinergic compounds, and the cells displayed a dose-dependent response to carbachol. This observation indicated that a cholinergic receptor may be present in T. evansi. Although a dose-dependent response to muscarine could not be demonstrated, nicotine could promote an incremental dose-dependent response. The relative potency of this specific agonist of nAChR is in agreement with previous reports. The estimated affinity values were a K_d1 value of 29.6 ± 5.72 nM and a K_d2 value of 315.9 ± 26.6 nM, which is similar to the K_d value reported for the α4 nicotinic receptor. The Hill coefficients were determined to be an n₁ of 1.2 ± 0.3 and an n₂ of 4.2 ± 1.3. Finally, our calculations indicated that there are about 1020 receptors in each T. evansi parasite, which is approximately 15-fold lower than the number reported in Torpedo californica electric cells. These results suggest the presence of a nAChR in T. evansi, which is able to bind nicotinic ligands and induce calcium signals.     

氮、磷对缺刻缘绿藻生长、总脂及花生四烯酸积累的影响

本文以缺刻缘绿藻(Parietochloris incisa)为实验材料,研究了其在四种不同氮、磷浓度下的生长、总脂(TL)及花生四烯酸(AA)含量的变化,分析测定了低氮和低磷浓度下脂肪酸的组成。结果表明:在BG-11培养基基础上,氮浓度的改变对缺刻缘绿藻的生物量影响不明显,不同氮浓度下的最终生物量均在2.1 g.L-1左右。在低氮浓度下TL和AA达到最大,分别为33.37%(%干重)和36.63%(%总脂肪酸,TFA),其中AA占藻体干重的11.56%。不同磷浓度对缺刻缘绿藻的生长有显著影响,最终生物量在0.90～2.07 g.L-1之间。TL在8～20 mg.L-1的磷浓度范围内没有明显变化,为28%左右。TL与氮、磷浓度呈显著负相关关系,且低氮有利于AA的积累。     

温度和CO2浓度升高对荒漠藻结皮光合作用的影响

2007年,对腾格里沙漠东南缘沙坡头地区1956年(51龄)和1981年(26龄)人工植被区及自然植被区的藻结皮净光合速率(P_n)变化,及其与结皮含水量(>100%、40%～60%和<20%)、大气CO₂浓度(360和700 mg·L^-1)和温度(13 ℃、24 ℃ 和28 ℃)的关系进行研究.结果表明：51龄、26龄人工植被区和自然植被区的藻结皮P_n分别为3.4、4.4和3.2 μmol·m^-2·s^-1,且51龄人工植被区藻结皮的P_n显著高于26龄人工植被区和自然植被区;藻结皮含水量对其P_n影响显著,且中等含水量(40%～60%)藻结皮的P_n显著高于低含水量(<20%)和高含水量(>100%);CO₂倍增(700 mg·L^-1)后,中等和高含水量藻结皮的P_n增加了1.8～3.3倍,而低含水量时,藻结皮的P_n变化不明显;高含水量和中等含水量处理时,24 ℃和28 ℃条件下藻结皮的P_n较13 ℃时提高27%～66%,而在低含水量时,不同温度的藻结皮P_n值无显著差异.     

Hormonal and ion regulatory response in three freshwater fish species following waterborne copper exposure

We evaluated effects of sublethal copper exposure in 3 different freshwater fish: rainbow trout (Oncorhynchus mykiss), common carp (Cyprinus carpio) and gibel carp (Carassius auratus gibelio). In a first experiment we exposed these fishes to an equally toxic Cu dose, a Cu level 10 times lower than their 96 h LC₅₀ value: 20, 65, and 150 µg/L Cu. In a second series we exposed them to the same Cu concentration (50 µg/L). Na⁺/K⁺-ATPase activity in gill tissue was disturbed differently in rainbow trout then in common and gibel carp. Rainbow trout showed a thorough disruption of plasma ion levels at the beginning of both exposures, whereas common carp and gibel carp displayed effects only after 3 days. Rainbow trout and common carp thyroid hormones experienced adverse effects in the beginning of the exposure. The involvement of prolactin in handling metal stress was reflected in changes of mRNA prolactin receptor concentrations in gill tissue, with an up regulation of this mRNA in rainbow trout and a down regulation in gibel carp, which was more pronounced in the latter. Overall, rainbow trout appeared more sensitive in the beginning of the exposure, however, when it overcame this first challenge, it handled copper exposure in a better manner then common and gibel carp as they showed more long term impacts of Cu exposure.     

塔玛亚历山大藻的生长研究

在室内条件下研究了温度、N和P、维生素、抗生素对有毒赤潮甲藻塔玛亚历山大藻(香港株Ⅱ)生长的影响。结果表明,塔玛亚历山大藻的最适生长温度为21—25℃,最适N、P浓度分别为882—1765μmol/L和18—72μmol/L。复合维生素B1、B6、B12的加入有利于塔玛亚历山大藻的生长,而50U/mL以上的抗生素(氨苄青霉素液体)则对其有明显的抑制作用。     

模糊线性回归模型在河流水体总氮浓度预测中的应用

以湘江熬洲断面为例,将该断面水体中总氮浓度及其有关影响因子用三角模糊数来表征.同时,结合己有的模糊线性回归模型成果,构造了带有三角模糊参数的水体中总氮浓度模糊线性回归预测模型.并应用所建模型预测该断面水体中2002-2005年总氮浓度,所得的预测值与已有的实测值之间的相对误差均小于20%,完全满足实际应用对误差的要求,预测合格率为100%,说明这种预测模型在预测河流水体总氮浓度变化中有一定的实用性,为今后开展河流水体中污染物浓度预测提供了新途径.