Analysis of Photosynthetic Activity at the Leaf and Canopy Levels from Reflectance Measurements: A Case Study

The photochemical reflectance index (PRI), based on reflectance signatures at 531 and 570 nm, and associated with xanthophyll pigment inter-conversion and related thylakoid energisation, was evaluated as an indicator of photosynthetic function in a Mediterranean holm oak (Quercus ilex L.) coppice. The chlorophyll fluorescence pulse-amplitude-modulation and the eddy correlation techniques were used to estimate the photosystem 2 photochemical efficiency of leaves and the CO₂ flux over the canopy, respectively. The reflectance and fluorescence techniques yielded identical estimates of the photosynthetic activity in leaves exposed to dark-light-dark cycles or to a variable irradiance in laboratory. However, there was no such correlation between photosynthetic performance and PRI when applied to a sun-exposed canopy in field conditions. Fluorescence profiles inside the canopy and especially a helpful use of multispectral reflectance imaging highlight the limitations of such method.     

Evoked Electrical Activity and Immunocytochemical Peculiarities of Cultured Excitatory and Inhibitory Neurons of the Rat Hippocampus

Experiments were carried out on cultured hippocampal neurons using a patch-clamp technique in the whole-cell configuration. We studied the characteristics of regular series of action potentials (APs), which were generated with a low frequency by inhibitory and excitatory interneurons after their direct stimulation with long-lasting (500 msec) current pulses. Nearly all parameters of the evoked impulse activity (except the frequency of generation and duration of APs) in excitatory and inhibitory neurons were significantly different. According to immunocytochemical analysis, Kv1.2- and Kv4.2-type potassium channels were expressed in the membrane of excitatory neurons (granular cells), and somatostatin was present in all these cells. As to inhibitory interneurons, only a part of such cells (large units) demonstrated immunopositivity with respect to somatostatin. In inhibitory neurons, only Kv1.2-type potassium channels were expressed. Therefore, mechanisms responsible for the ability of hippocampal interneurons to generate impulse activity under conditions of direct stimulation (in our experiments, regular low-frequency series of APs) in inhibitory and excitatory neurons are rather dissimilar. Neirofiziologiya/Neurophysiology, Vol. 37, No. 3, pp. 207–216, May–June, 2005.     

向日葵花盘水溶性多糖提取工艺及抗氧化研究

目的:研究了向日葵花盘中水溶性粗多糖的提取工艺及抗氧化性能.方法:采用单因素试验和L_9(3~4)正交试验设计,对多糖提取工艺进行优化,并采用Fenton体系和邻苯三酚自氧化法评价了该提取物的体外抗氧化能力.结果:优化工艺条件为:提取温度95℃、料液比1:20、提取时间4h,向日葵水溶性粗多糖得率为9.73%,其中温度是影响粗多糖提取的重要因素.结论:结果表明向日葵水溶性粗多糖有较好的抗氧化活性.     

春兰内生真菌的分离及其抑菌活性的初步研究

采用平板分离法从皖西大别山野生兰花的根、茎、叶中分离内生真菌32株,用琼脂块法对获取的菌株进行抑菌活性筛选,其中有4种兰花内生真菌对供试菌株有抑菌作用,占总分离菌株的12.50%,对抑菌活性较强的一株内生真菌进行形态学鉴定,结果表明它属于无孢类群。     

三种车前草的黄酮提取、纯化及其抗氧化活性分析

本研究采用响应面设计优化超声辅助提取车前总黄酮的最佳条件,然后用此条件提取大车前和平车前总黄酮,并探究大孔树脂纯化对三种车前草总黄酮抗氧化活性的影响。结果表明,在超声温度60℃、乙醇浓度70%的条件下,车前总黄酮最佳提取工艺参数为液料比20:1 m L/g、超声时间80 min、超声功率210 W,车前、大车前和平车前的总黄酮得率分别为5.04%、2.86%和1.22%。无论是纯化前还是纯化后,大车前总黄酮的还原力和对羟基自由基的清除作用最强,平车前最弱;车前总黄酮对DPPH自由基的清除作用最大,平车前最弱。纯化前后的还原力和对DPPH自由基、羟基自由基的清除作用都接近Vc的水平。     

抱茎蓼挥发油成分及其抗菌活性的研究

水蒸气蒸馏法从抱茎蓼全草中提取挥发油,用气相色谱-质谱联用技术对其挥发油组分进行分离和鉴定,运用气相色谱面积归一化法确定各组分的相对含量,并利用正构烷烃系列物质对各组分进行定性确定,从抱茎蓼全草的挥发油中检出41个组分,占全油的99.21%,鉴定出38个组分,其主要组分是石竹烯(16.98%)、3-己烯-1-醇(14.69%)、3-辛烯-3醇(8.89%)、a-里哪醇(7.13%)、β-环柠檬醛(6.36%)等。对抱茎蓼全草的挥发油做了抗菌试验,其挥发油对大肠埃希菌(ATCC25922株)、肠炎沙门菌(50040株)、金黄色葡萄球菌(ATCC25925株)有显著地抑制和灭活作用。     

库克诺你果汁提取物体外清除自由基及抗氧化活性研究

本文对诺你果汁多糖、乙醇溶出物和乙酸乙酯萃取物体外对超氧阴离子(O2·)、羟自由基(·OH)、DPPH和脂质过氧化(LPO)的抑制作用进行了研究。超氧阴离子(O2·)由邻苯三酚自氧化产生;羟自由基(·OH)由Fenton反应产生;利用Fe2 诱发卵黄脂蛋白产生丙二醛(MDA),TBA法测定。所有测定均为分光光度法。结果表明,与已知抗氧化剂L抗坏血酸相比,乙醇溶出物和乙酸乙酯萃取物均有明显的捕捉自由基和抗氧化能力,而多糖捕捉自由基和抗氧化能力很低,且对O2·没有抑制作用,反而会增加其生成速度。     

Bt菌株QCL-1中cry2Ac10基因的克隆、表达和活性研究

目的:从高毒力Bt菌株中克隆cry2Ac10基因,并研究其表达和杀虫活性。方法:以Bt菌株QCL-1质粒为模板,利用cry2特异性引物FY2A5和FY2A3进行PCR扩增,将目的片段克隆到表达载体pET-21b( ),构建T7启动子控制的大肠杆菌重组表达质粒pET21b-cry2Ac。经IPTG诱导后,SDS-PAGE检测基因表达情况,然后对表达产物进行生物活性测定。结果:从菌株QCL-1中克隆出目的基因,该基因的编码框由1 872个碱基组成,编码的蛋白质由623个氨基酸组成,与已报道的Cry2Ac氨基酸同源性为97.4%~99.7%。该基因(GenBank accession EF405952)已被国际Bt基因命名委员会正式命名为cry2Ac10。该基因在大肠杆菌BL21(DE3)中能够正常表达70kDa的蛋白,表达产物对棉铃虫、粘虫和粉纹夜蛾幼虫具有高毒力,同时对甜菜夜蛾幼虫生长有抑制作用,其中对棉铃虫和粘虫初孵幼虫的LC50分别为30.0μg/g和16.7μg/g。结论:成功克隆和表达了cry2Ac10基因,并明确了cry2Ac10蛋白的活性,为该基因的研究和应用奠定基础。