Quantitative effects of field water deficits on N2(C2H2) fixation in selected legumes grown in the Indian desert

Summary The nitrogenase activity of irrigated and rainfed plants of mung bean, cluster bean and moth bean was studied throughout the growth period in order to estimate the reduction in the potential nitrogen fixation (C₂H₂ reduction) rate due to field water deficits. Nitrogenase activity followed a similar trend in all crops and was dependent on both plant ontogeny and soil moisture levels. The loss of activity due to water deficits varied from 13% to 100% at different growth stages and was related to the plant water potential. The specific activity was directly correlated with the plant water potential under both the treatments. The average loss of nitrogen fixation rate during the season did not differ markedly among crops. There was an accumulation of ureides in the nodules with increasing field moisture stress in mung bean and moth bean while no such effect was found in cluster bean. The significance of these results is discussed in the N-economy of these legumes grown in the drought-prone areas of the Indian desert.     

Differentiation between bioavailable and total hazard potential of sediment-induced DNA fragmentation as measured by the comet assay with Zebrafish embryos

Goals, Scope and Background  While water quality strongly improved over decades in the Rhine River, sediments still reflect elapsed contaminations of organic pollutants and heavy metals. In comparing genotoxic effects induced by both sediment extracts and whole sediments, a ratio of bioavailable toxicity and total extractable toxicity is obtained. Since contaminated sites whose contaminants are toxic and as well bioavailable present an elevated risk to the ecosystem, such ratios may be used as a warning signal to identify sites of primary concern. Methods  Accordingly, two different exposure scenarios were compared to reveal the genotoxic potential of 18 sediment samples derived from 9 sample sites along the River Rhine. For assessment of effects on genome integrity, DNA fragmentation was measured using the comet assay with primary cells isolated from zebrafish embryos previously exposed to either organic sediment extracts or freeze-dried sediments at sublethal concentrations. Additionally, chemical data were used to determine responsible pollutants and correlate them with biological effects. Results  Whereas 17 out of 18 sediment extracts caused significant DNA damage to the embryo cells, only 4 native sediments showed a genotoxic potential. Thus, under field-like exposure conditions, a major part of potentially genotoxic compounds seem to remain particle-bound and ineffective, as shown for whole sediment exposure. Conversely, the organic extracts seem to contain enriched concentrations even of hardly soluble substances. Hence, organic extracts may be used as a screening tool to address potentially polluted sites, even though the relevance of these results for the field situation may be questionable. Investigations on native sediments determined few sites with bioavailable and therefore ecologically most relevant genotoxic sediment compounds. Discussion  However, these results may underestimate the total hazard potential of sample sites with hardly bioavailable substances. Chemical data revealed a variety of anthropogenic pollutants, ranging from PAHs to heavy metals. Nevertheless, chemical data on the measured priority pollutants did not fully explain the pollution pattern of the bioassays but clearly determined substances of concern (e.g., HCB, heavy metals) in particular sample sites. Conclusions  There is a striking advantage in assessing the genotoxicity by means of different exposure scenarios that focus on either bioavailable or extractable fractions, as the combination of the results allows obtaining information on specific properties of the genotoxicants and their bioavailability. An additional correlation with chemical data should be required to identify priority pollutants, as long as the responsible contaminant is known a priori. As many studies revealed inherent failures of such a correlation, an effect-driven analysis of pollutants is recommended as a promising tool to identify even non-priority pollutants by means of their ecotoxicological effectiveness.     

抗猪瘟兔化弱毒单克隆抗体杂交瘤细胞株的建立

用猪瘟兔化弱毒（ＳＦＶ—Ｃ）牛睾丸细胞培养上清液，经ＰＥＧ—２００００沉淀和蔗糖密度梯度离心提纯制备ＳＦＶ—Ｃ抗原，腹腔免疫Ｂａｌｂ／ｃ小鼠，取抗体阳性的免疫小鼠脾细胞，在５０％（Ｗ／Ｖ）ＰＥＧ—４０００作用下，与ＳＰ２／０－Ａｇ１４小鼠骨髓瘤细胞进行融合，产生杂交瘤细胞。用间接ＥＬＩＳＡ法筛选阳性杂交瘤细胞株。通过有限稀释进行３次克隆，获得了２株分泌抗ＳＦＶ—Ｃ的单克隆抗体杂交瘤细胞株，并对其染色体形态和数目进行分析鉴定。     

草莓伪温和黄边病毒抗血清制备及血清学检测技术研究

将提纯的草莓伪温和黄边病毒（ＳｔｒａｗｂｅｒｒｙｐｓｅｕｄｏｍｉｌｄｙｅｌｌｏｗｅｄｇｅｖｉｒｕｓＳＰＭＹＥＶ）作抗原免疫家兔，获得效价较高的抗血清，经ＳＤＳ－对流免疫电泳测其效价为１：１２８．四点疫吸附固定法检测ＳＰＭＹＥＶ效果甚理想，可检测到微量病素，提纯病毒浓度低至０．０５μｇ／ｍｌ仍有效果．酶联免疫吸附测定法检出灵敏度也相当高，当病毒浓度为０．１μｇ／ｍｌ时及病叶汁液稀释至１０２４倍时，仍呈阳性反应．免疫电镜技术检视，ＳＰＭＹＥＶ抗血清能清晰地”捕获”同源病毒，并且有装饰作用，抗血清以稀释为１：５００时“捕获”病毒粒子最多．     

基因枪转化甘蔗愈伤组织体系的优化

以生产上广泛应用的甘蔗商业品种新台糖16号的愈伤组织为受体材料,以含有GUS基因的植物表达载体pBI121为外源DNA,利用基因枪PDS 1000/He,设定不同的参数,将pBI121轰击新台糖16号愈伤组织.经GUS染色,结果发现在发射距离1/4in、可裂膜压力1100psi、轰击距离6cm时转化效率最高.     

己烯雌酚人工抗原的合成和酶免疫检测方法的建立

通过化学方法合成己烯雌酚单羧甲基醚,并通过核磁共振和质谱进行鉴定;分别用混合酸酐法和碳二亚胺法将其与牛血清白蛋白(BSA)和鸡卵清蛋白(OVA)偶联,合成己烯雌酚人工抗原,经紫外扫描、聚丙烯酰胺凝胶电泳和动物免疫试验证实人工抗原合成成功,并制备了抗己烯雌酚的特异性多克隆抗体,同时建立了己烯雌酚的酶免疫检测方法,这对动物性食品中己烯雌酚的残留检测有重要意义。     

荧光定糖法测定纤维素酶活力的条件研究

研究结果表明 ,荧光定糖法测定纤维素酶活力的反应最佳条件 :反应液浓度为46.7mg·g-1,反应时间为10min,反应温度为150℃。将荧光定糖法与滤纸酶活测定法相结合应用于纤维素酶蛋白组分及土壤纤维素酶活力的研究与测定。     

斑点免疫金检测鸡传染性支气管炎病毒的研究

通过胶体金标记提纯后的兔抗ＩＢＶＩｇＧ，建立了一种以微孔滤膜为固相载体，以红色胶体金为标记物，检测鸡传染性支气管炎病毒（ＩＢＶ）的斑点免疫金测定法（ＤＩＧＦＡ）。ＤＩＧＦＡ对ＩＢＶ的最小检出量为２０．３×１０￣（－８）ｇ，在１０份自然病例样品中检出８份。鸡胚培养法以育传３～５代，出现侏儒胚者为阳性，从上述样品中检出６份。对接种ＩＢＶ的鸡胚尿囊液，ＤＩＧＦＡ法检出率为１００％。实验结果表明，ＤＩＧＦＡ法对鸡传染性支气管炎的早期诊断具有简便、灵敏、快速、特异性强和重复性好等优点。     

4种中药多糖对猪脾淋巴细胞增殖的影响

为筛选免疫活性较好的中药多糖和研制新型猪用免疫增强剂,用MTT比色法比较了不同浓度的板蓝根多糖(IRPS)、牛膝多糖(ABPS)、山药多糖(CYPS)和黄芪多糖(APS)等4种中药多糖对猪脾脏淋巴细胞增殖的影响。结果表明,IRPS,ABPS,CYPS,APS均能显著刺激ConA或LPS诱导的猪脾淋巴细胞增殖(P<0.05),且4种多糖促进猪脾淋巴细胞增殖的作用与多糖浓度有关。