An enzymatic method for microdetermination of aphidicolin: a promising anticancer drug

We have developed a method, based on the in vitro inhibition of purified human DNA polymerase alpha, the major enzyme of DNA replication, which allows the rapid and accurate determination of pmol amounts of aphidicolin, a promising anticancer drug. The efficacy of this simple method was verified by the determination of aphidicolin in the liver, spleen, blood and urine of mice treated parenterically with the drug. Given its sensitivity and the avoidance of radioactive tracers, this enzymatic method is suitable for the determination of the drug in body fluids and tissue biopsies from living humans. It allows the detection and quantitation of aphidicolin in the presence of inactive metabolite(s) with very similar chemical structure(s) such as those generated by liver microsomal oxidases. The technique will also be useful to monitor the purification of the drug from cultures of Cephalosporium aphidicola.     

草鱼出血病病毒对其它鱼的感染性研究

用草鱼出血病病鱼分离出的草鱼出血病病毒(Grass carp hemorrhage virus,GCHV)感染其它常见鱼并用ELISA方法检查感染鱼组织提取液,结果表明:青鱼、鲢鱼、布氏鳌条对GCHV抗体呈阳性反应;鲤鱼、鳙鱼、鲫鱼、团头鲂、泥鳅则呈阴性反应。综合感染鱼发病症状及死亡特征,初步认为:青鱼对GCHV是易感的,GCHV能在鲢鱼、布氏蟹条体内增值,但毒力较低,鳙鱼、鲫鱼、团头鲂、鲤鱼、泥鳅能抗GCHV感染。     

Silver Enhancement of Nickel-Diaminobenzidine as Applied to Single and Double Immunoperoxidase Staining

A reliable and practical method is proposed for increasing sensitivity and detection efficiency of immunocytochemical techniques, based on silver enhancement of the nickel-diaminobenzidine product of the peroxidase reaction. The procedure produces a strong signal at the site of the end product of the peroxidase reaction which is visible as black grains at the light microscopic level. The method has been used to detect peroxidase labeled probes in immunocytochemical tissue preparations and blotting assays and is ideal for the purposes of double staining and photographic documentation.     

Transfer of a dominant gene for powdery mildew resistance and DNA from Hordeum bulbosum into cultivated barley (H. vulgare)

Summary In an attempt to transfer traits of agronomic importance from H. bulbosum into H. vulgare we carried out crosses between four diploid barley cultivars and a tetraploid H. bulbosum. Eleven viable triploid F₁ plants were produced by means of embryo rescue techniques. Meiotic pairing between H. vulgare and H. bulbosum chromosomes was evidenced by the formation of trivalents at a mean frequency of 1.3 with a maximum of five per cell. The resulting triploid hybrids were backcrossed to diploid barley, and nine DC₁ plants were obtained. Three of the BC₁ plants exhibited H. bulbosum DNA or disease resistance. A species specific 611-bp DNA probe, pSc119.2, located in telomeres of the H. bulbosum genome, clearly detected five H. bulbosum DNA fragments of about 2.1, 2.4, 3.4, 4.0 and 4.8 kb in size present in one of the BC₁ plants (BC₁-5) in BamHI-digésted genomic Southern blots. Plant BC₁-5 also contained a heterozygous chromosomal interchange involving chromosomes 3 and 4 as identified by N-banding. One of the two translocated chromosomes had the H. bulbosum sequence in the telomeric region as detected using in situ hybridization with pSc119.2. Two other BC₁ plants (BC₁-1 and BC₁-2) were resistant to the powdery mildew isolates to which the barley cultivars were susceptible. Seventy-nine BC₂ plants from plant BC₁-2 segregated 32 mildew resistant to 47 susceptible, which fits a ratio of 11, indicating that the transferred resistance was conditioned by a single dominant gene. Reciprocal crosses showed a tendency towards gametoselection that was relative to the resistance. Mildew resistant plant BC₁-2 also had a 1-kb H. bulbosum DNA fragment identified with a ten-base random primer using polymerase chain reaction (PCR). Forty-three BC₁ plants, randomly sampled from the 79 BC₁ plants, also segregated 2320 for the presence versus absence of this 1-kb H. bulbosum DNA fragment, thereby fitting a 11 ratio and indicating that the PCR product originated from a single locus. The 1-kb DNA fragment and disease resistance were independently inherited as detected by PCR analysis of bulked DNA from 17 resistant and 17 susceptible plants as well as by trait segregation in the 43 individual plants. The progenies produced could serve as an important resistant source in plant breeding. This is the first conclusive report of the stable transfer of disease resistance and DNA from H. bulbosum to H. vulgare.     

Rapid determination of plasmid-carrying yeast cells by using an imaging sensor system

A novel imaging sensor system for the determination of plasmid carrying yeast cells was developed. The sensor system consisted of an Silicon Intensifier Target (SIT) video camera, a fluorescent microscope, and a personal computer system equipped with an image memory board. This system was based on the fact that the membrane integrity of only plasmid-carrying cells is lost following cell growth in 5-fluoro-orotic acid (5-FOA) containing medium, and consequently these target cell can be stained with fluorescent probes and detected. In this study, plasmid-carrying cells were detected and their fraction determined in a mixture of both plasmid-carring and plasmid-free cells. A good correlation was observed between the values determined by this sensor system and the conventional method in the 30%-80% range, and one assay was possible within 4 h. This sensor system could be used for the monitoring of plasmid-carrying fraction in recombinant yeast cells during cultivation.     

水稻食叶类害虫等量损害系统与复合防治指标

稻纵卷叶螟Cnaphalocrocis.medinalis Guenèe中华稻蝗Oxya chinensis(Thunberg)稻苞虫Parnara guttatus (Bremer et Grey)是江苏地区水稻的主要食叶类害虫,取食水稻叶片,导致光合叶面积减少.剪叶模拟试验表明,水稻不同生育阶段叶面积损失率与产量损失率呈线性相关.其回归方程分蘖期、孕穗期、腊熟期分别为 D(I_t)=72.50759I_t^1.15906、D(I_t)=141.61737I_t^1.08002、D(I_t)=25.12434I_t^1.00569.在叶面积损失率相同的情况下,产量损失率孕穗期>分蘖期>腊熟期.试验通过三种害虫的各龄取食量,不同生育阶段水稻叶面积及为害与损失率之间的关系,建立了不同生育阶段的经济允许损害水平(EIL_t).并根据各种害虫的相对潜在取食量,计算了校正等量损害系数,为制订复合防治指标提供了依据.实践证明:以等量损害为单位的复合防治指标有较大的实用价值,生态效益、经济效益、社会效益明显.     

Circular dichroism detection in HPLC

A circular dichroism-based detection system presents several advantages in the HPLC analysis of chiral compounds because of the selective monitoring of optically active molecules. Its use allows reliable determination of enantiomeric excesses and elution order. To this end, the application of empirical, semiempirical, and nonempirical methods to get stereochemical information from the CD signal is reported. Furthermore, recording the CD spectra on line and evaluation of the dissymetry factor make the CD detection very powerful in characterizing the stereochemistry of chiral eluates.     

Response of cabbage head weight to simulated Lepidoptera defoliation

Studies were conducted to determine the effects of continuous constant amounts of artificial defoliation through the preheading and heading growth stages on head weight of cabbage. High levels of continuous artificial defoliation caused a reduction in head weight in all three years of the study, but the highest yield was always attained at some low level of preheading or heading defoliation. These results demonstrate that cabbage is tolerant to some levels of continuous defoliation before and after head formation. Results from this study are incorporated into a cost-benefit analysis to estimate an economic threshold.

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Résumé L'étude a porté sur le poids des pommes de choux (Brassica oleracea) soumis à différentes intensités de défoliations répétées avant et pendant la formation des pommes. Pendant les trois années de l'étude, huit intensités de défoliation continue ont réduit le poids des pommes, mais le poids le plus élevé a toujours été obtenu avec une faible défoliation avant et pendant la formation des pommes. Ceci montre que le chou tolère une certaine défoliation avant et pendant la formation des pommes. Les résultats de cette étude ont été utilisés dans une analyse coût-bénéfice pour estimer le seuil économique de défoliation.