Comparison of the proportion method with mycobacteria growth indicator tube and E-test for susceptibility testing of Mycobacterium tuberculosis

The aim of this study was to investigate the correlation between proportion method with mycobacteria growth indicator tube (MGIT) and E-test for Mycobacterium tuberculosis. Forty clinical isolates were tested. MGIT and E-test with the first line antituberculous drugs correlated with the proportion method. Our results suggested that MGIT and E-test methods can be routinely used instead of the proportion method.     

A microdilution method for drug sensitivity testing of fish associated bacteria at 22°C

When applied to the psychrophilic and psychrotropic bacteria associated with diseases of fish, the disc-diffusion method generally fails to provide correct estimates of minimal inhibitory concentrations (MIC). A microdilution method using a medium containing agar (15 g/l) and 10 selected drugs has been developed. Serial four-fold dilutions of the drugs were performed in specially designed dilution plates, which were prepared and stored at −30° or −70°C. Although its reliability sometimes appeared to be influenced by the temperature at the time of testing, the temperature and duration of freezing and the nature of the drugs, the microtest provided results as accurate as other reference methods. In repeated experiments very rare major discrepancies were noted and minor variations of one dilution step were below 10%, except with tetracyclines and the sulphonamide-trimethoprim mixture. The advantages of the method and the optimum conditions for use in fish disease diagnosis are specified.     

Sequence analysis of phosphoserine-containing peptides. Modification for picomolar sensitivity

Sequencing of phosphoserine-containing peptides yields normally no identifiable PTH-derivatives at those positions where phosphoserine is located. Here a new method is described which allows identification of the position of phosphoserine by chemical modification just before sequence analysis. In a one-step microbatch reaction, phosphoserine present in the intact peptide can be transformed quantitatively into stable derivatives such as beta-methylaminoalanine (MAA), S-ethanolcysteine or S-ethylcysteine. These derivatives are detectable during microsequencing with less than 100 pmol peptide using an Applied Biosystems gas-phase sequencer equipped with an on-line PTH amino acid analyzer.     

蜜蜂褪黑素的测定方法

在脊椎动物中,褪黑素(5-甲氧基-N-乙酰色胺,MLT)是一种由松果体分泌的具有典型光周期信号作用的神经内分泌激素。近年在昆虫头部也发现了这种化学物质。该文简述了褪黑素常见测定方法,详细介绍了褪黑素的免疫测定方法RIA(radionimmunoassay),并使用该方法初步测定了中华蜜蜂ApisceranaFabricius工蜂头部褪黑素的含量,结果显示褪黑素含量与工蜂的社会分工相关。     

Mycothiol biosynthesis is essential for ethionamide susceptibility in Mycobacterium tuberculosis

Spontaneous mutants of Mycobacterium tuberculosis that were resistant to the anti-tuberculosis drugs ethionamide and isoniazid were isolated and found to map to mshA , a gene encoding the first enzyme involved in the biosynthesis of mycothiol, a major low-molecular-weight thiol in M. tuberculosis . Seven independent missense or frameshift mutations within mshA were identified and characterized. Precise null deletion mutations of the mshA gene were generated by specialized transduction in three different strains of M. tuberculosis . The mshA deletion mutants were defective in mycothiol biosynthesis, were only ethionamide-resistant and required catalase to grow. Biochemical studies suggested that the mechanism of ethionamide resistance in mshA mutants was likely due to a defect in ethionamide activation. In vivo , a mycothiol-deficient strain grew normally in immunodeficient mice, but was slightly defective for growth in immunocompetent mice. Mutations in mshA demonstrate the non-essentiality of mycothiol for growth in vitro and in vivo , and provide a novel mechanism of ethionamide resistance in M. tuberculosis.     

Modification of a microdialysis method for crystallization of proteins

Several variants of microdialysis cells have been developed for growing protein crystals suitable for X-ray analysis. The cells have simple construction and are made of easily available materials. Using these cells, over ten proteins have been crystallized, six of them in the form suitable for 3D-structure determination.