Improved enzymic assay for cyanogens in fresh and processed cassava

The assay for cassava cyanogens developed at the Natural Resources Institute has been modified to overcome some of the problems encountered when the assay is applied to cassava products. Inclusion of 25% ethanol in the extraction medium increased the volume of recovered extract from heat-processed cassava products, eliminated the need for centrifugation and did not interfere with any aspect of the assay. Greater cyanohydrin recovery was noted and the calculation for cyanogen contents was changed to take into account the total extract volume. The separate assay of the three cyanogens (glucosides, cyanohydrins and free cyanide) was achieved by buffering aliquots of the extract followed by appropriate treatment. The importance of assaying for free cyanide (HCN) at pH 4 was demonstrated. Above this pH, cyanohydrin degradation also produces free cyanide, giving rise to misleading values. The efficiency of the extraction medium in recovering added linamarin and cyanohydrin from cassava foods was determined. Recoveries of cyanohydrin were improved using the ethanol/acid medium. The stability of the cyanogens in the ethanol/acid extraction medium was tested at ambient and refrigeration temperatures. Over a two-month period, refrigerated extracts showed acceptable variation as compared with normal variation within the assay (5%) for total and non-glycosidic cyanogens but the levels of free cyanide showed heavy losses (15–56% lost). Since the relative toxicities of the three cyanogens have yet to be ascertained, the relative amount of each cyanogen may be important when assessing the safety of cassava products.     

钙调素抑制剂——~3H-苄普地尔放射受体结合分析法的研究

以~3H-苄普地尔作为放射性配体,从牛脑中提取钙调素作为结合受体,采用平衡柱结合法.研究了~3H-苄普地尔与牛脑钙调素的结合特性,建立了~3H-苄普地尔放射受体结合分析法。~3H-苄普地尔仅在Ca~(2+)存在下才能与钙调素产生特异结合,结合具有饱和性和可逆性。Scatchard分析得K_D=2.52±0.44μmol/l,B_(max)=13.95±2.33nmol/mg蛋白,Hill分析得n_H=0.96±0.03。该方法的批内和批间变异系数均为10％,重现性较好。还介绍了使用本法于新设计合成的化合物的竞争性抑制试验初步结果。     

植物选择标记基因hpt在大肠杆菌中的融合表达、纯化及活性测定

为对hpt基因编码蛋白进行的安全性评价，建立一种简便、高效的体外微生物表达体系，以获得大量的HPT蛋白，将用于植物转化的hpt基因的全编码序列克隆到原核表达载体pGEX4T-3上，在E．coli BL21中进行诱导表达，所得融合蛋白主要以包涵体的形式存在，且与Glutathione Sephrose 4B纯化介质的结合率不高。后经优化诱导表达的各种条件，成功地获得了可溶性的融合蛋白，该蛋白具有明显的生物活性。经Glutathione Sephrose 4B亲和层析，所得蛋白纯度＞95％。动物实验显示，融合蛋白还具有良好的免疫原性，免疫家兔后可诱导产生高滴度的抗体(＞1：10000)。ELISA及Western blotting检测进一步证实了所获纯化蛋白及其抗体的特性。这为深入进行HPT蛋白的安全性评价打下了良好的基础。     

QUANTIFICATION OF YEAST FLOCCULATION

A sedimentation method based in the Helm's flocculation test was improved. In this method, all steps were standardised: initial cell concentration, agitation, sampling and determination of settled cells. The results obtained with the sedimentation test do not differ significantly (P = 0.05) from those obtained with the Stratford test; besides, the precision of the two methods do not differ significantly (P = 0.05). The results presented clearly demonstrated that the method improved in this work is rigorous for quantification of yeast flocculation and allows the differentiation of flocculation ability of the strains. The respective micro-flocculation tests were also compared; Stratford micro-flocculation test was selected as producing the most meaningful results.     

一种以面向对象及形式化技术为基础的严格的软件开发方法

随着软件开发规模的迅速扩大，目前流行的软件开发方法（包括当前的软件工程法）已难以满足开发实践的要求，实践要求在软件开发方法学上能有新的进展。鉴于此，本文在面向对象及开式化方法的基础上，系统地提出了一种严格的软件开发方法，力图使开发者的创造性及开发环境的自动化能力都得到充分发挥，使软件开发能适应形势的需要     

Screening survey of deoxynivalenol in beer from the European market by an enzyme-linked immunosorbent assay

Deoxynivalenol (DON) was analysed in 313 beer samples collected from the European retail market using a commercially available immunoassay kit (enzyme-linked immunosorbent assay, ELISA). The incidence rate was about 87%, while most samples (73%) had contamination levels lower than 20 ng ml^-1. The contamination ranged between 4.0 and 56.7 ng ml^-1, with an average of 13.5 ng ml^-1. A statistically significant correlation between alcohol levels and DON contamination was found, as well as a significant difference between bottom, top and spontaneous fermenting beers. Twenty-seven beer samples were compared using a second ELISA kit and a good correlation was obtained between the two kits (r = 0.93). Although when compared with gas chromatography-mass spectrometry the ELISA tended to overestimate the results, a good correlation (r = 0.94) between the two methods was observed. Monitoring of DON in beer is important considering that DON production is dependent on the weather and that it can contribute significantly to the tolerable daily intake of DON, especially for frequent beer consumers.     

应用免疫印迹法检测人基因工程干扰素中大肠杆菌残余成分

用大肠杆菌抽提物免疫家兔制备相应的抗血清,并用该血清建立免疫印迹法,检测基因工程干扰素中大肠杆菌残余成分。初步试验结果表明,该方法的灵敏度高于SDS-PAGE银染法。检测3批人α_1.型基因工程干扰素的结果表明,制品的纯度较好。     

A sandwich enzyme-linked immunosorbent assay for κ-carrageenan determination

High titre antisera to κ-carrageenan were produced by immunisation of rabbits and guinea pigs with K-carrageenan. These antisera, rabbit serum as a capture antibody and guinea pig serum as a detector antibody, were used in a sandwich enzyme-linked immunosorbent assay. The range of determination of K-carrageenan was from 16 to 256 ng ml^?1 in the assay. The antisera showed no cross-reactivity with six thickeners. The assay was developed for application to foods such as jelly and custard pudding and demonstrated many advantages including high sensitivity, technical simplicity and the minimal requirement for food sample preparation before assay.     

^51Cr释放法检测赖氨酸锗对NK细胞活性的作用

采用~(51)Cr释放法,以K_(562)瘤株为靶细胞,观察赖氨酸锗(Ge_(401))对正常人外周血NK细胞活性(NK-A)的作用。结果表明:Ge_(401)在50、100、200μg/ml三种浓度与效应细胞预处理18h后,NK-A(％)从对照组24.30分别提高为32.52(p<0.05),39.70(p<0.01),43.42(p<0.001),呈明显的剂量依赖性。同时,Ge_(401)在100、200μg/ml两种浓度时,对~(51)Cr标记的K_(562)靶细胞的~(51)Cr释放率无明显直接影响。提示Ge_(401)对K_(562)靶细胞无直接细胞毒作用,其促进NK-A的作用部位在于效应细胞。     

A method for the estimation of the culturing quality of dehydrated mycological media

A relatively simple technique called 'multiconidial inoculation method' was developed to evaluate the culturing quality of dehydrated culture media. Four commercial PDA media were compared for their ability to maintain both the vegetative and fruiting phase of growth of Aspergillus niger . The evaluation was carried out by metric and densitometric methods.