Development of an immunoassay (ELISA) for the quantification of thiram in lettuce.

Two competitive immunoassays, a laboratory assay based on microwell plates and a field test based on the use of polystyrene tubes, have been developed for the quantification of thiram in lettuces. Concerning the laboratory assay, the calibration curve for thiram had a linear range of 11 to 90 ng/mL and a detection limit of 5 ng/mL. Precision of the assay presented coefficient of variation values <9% and the recovery of thiram from lettuce averaged 89% across the range of the immunoassay method using 30 min extraction with water/acetone (50:50, v/v). The tube-based method was developed in order that an extract of lettuce, containing thiram at the MRL (8 ppm), would be found on the linear part of the standard curve. The calibration curve for thiram has a linear range of 100 to 800 ng/mL (1.39 to 11.1 ppm in lettuce) and a detection limit of 40 ng/mL.

Optimization of glucosinolate separation by micellar electrokinetic capillary chromatography using a Doehlert's experimental design.

The aim of this study was to optimize by micellar electrokinetic chromatography the separation of four glucosinolates, i.e. sinigrin, glucobrassicin and methoxyglucobrassicin involved in Cruciferae resistance mechanisms and glucotropaeolin used as an internal standard. The separation borate buffer which contained sodium dodecyl sulphate, tetramethylammonium hydroxide and methanol was firstly optimized by using a three variable Doehlert experimental design. The optimum concentrations found enabled, for the first time, to obtain an acceptable resolution between the two indole glucosinolates, glucobrassicin and methoxyglucobrassicin. Modifications of the method such as a capillary pre-rinse with pure borate buffer and a step change in voltage during experiment were performed to improve the resolutions between glucosinolates and to reduce the analysis time. This method was validated by a statistical analysis and showed good linearity, repeatability and reproducibility.

Gavaserin and saltavalin, new peptide antibiotics produced by Bacillus polymyxa.

A strain of Bacillus polymyxa (BPl), isolated from cauliflower seeds, inhibited the growth of microbial phytopathogens. Growth of this strain in liquid medium containing lactose, ammonium sulfate, biotin, and amino acids, resulted in optimal inhibition in vitro. Two new antibacterial substances were isolated and purified from culture broth. Their molecular masses were, respectively, 911 and 903 daltons. The first compound was named gavaserin because it contained glutamic acid, alanine, valine, serine and 2,4-diaminobutyric acid, and octanoic acid. No fatty acid was detected in the second compound, which was named saltavalin because it contained serine, alanine, leucine, threonine, valine, and 2,4-diaminobutyric acid.

[Zinc in the human prostate]. / Le zinc dans la prostate humaine.

The quantities of zinc naturally present in prostatic epithelial cells determine the human prostate to be a zinc-rich gland. Since the growth of the prostate depends on androgenic steroid hormones, interrelationships between steroids and zinc were investigated. It appears now that zinc in hyperplastic prostates is bound to cytoplasmic citrate. Metabolic homeostasia in prostatic secretory cells may be insured by inhibition of cis-aconitase by free zinc and its binding to accumulating citrate. The yields of bound zinc are decreased by androgenic steroids (testosterone, 5 alpha-dihydrotestosterone, 5 alpha-androstane-3 alpha, 17 beta-diol) which increase in turn the levels of free zinc, the uptake and the reduction of testosterone and citrate accumulation. In dedifferentiated hormono-independent neoplastic cells, there is less reduction of testosterone and a drastic decrease in zinc levels due to the sole presence of a metallothionein for binding.

Effects of steroid androgens on the uptake and distribution of zinc in slices from human prostates.

Slices of human hyperplastic prostates were superfused with magnitude of [6 5Zn] Cl2 in the absence or in the presence of testosterone or 5 alpha - dihydrotestosterone or 5 alpha-androstane-3 alpha, 17 beta-diol. Uptake of magnitude of [6 5Zn] Cl2 was not significantly changed by steroid androgens but the binding of magnitude of [6 5Zn] to the citrate of prostatic cytosol was generally significantly decreased by the tested steroids. The 5 alpha-reduced androgens were more efficient that testosterone in decreasing bound zinc levels and increasing free zinc concentrations. Implications of these findings on the metabolism and differentiation of prostatic cells are discussed.

Identification of a low molecular weight ligand for zinc in the human hyperplastic prostate.

Gel filtration and high performance gel filtration showed the zinc of prostatic cytosol to be associated with a low molecular weight ligand. Absence of degradation of this ligand by proteolytic enzymes but its disappearance after action of the citrate lyase system led to the identification of the ligand with citrate. Involvement of zinc-citrate in prostatic zinc homeostasis is discussed.

[The track pheromone of the termite Schedorhinotermes lamanianus (Sjöstedt)]. / Sur la phéromone de piste du termite Schedorhinotermes lamanianus (Sjöstedt)

The trail pheromone of the African Termite Schedorhinotermes lamanianus has been investigated. It consists of two active components: an unsaturated fatty alcohol probably in C14 and a corresponding esterified fraction. The interconversion of the two by acetylation-saponification has been demonstrated. However, it is not yet known whether the ester occurs naturally as an acetate or not. A carbonyl derivative, biologically inactive, has also been isolated; its reduction with NaBH4 leads to an active alcohol of same Rf value as the preceding one.