Biogenetic studies in Mentha x piperita. 2. Stereoselectivity in the bioconversion of pulegone into menthone and isomenthone.

Mentha x piperita shoot tips and first leaf pairs were fed with aqueous solutions of different deuterium-labeled pulegone and various enantiomeric distributions. The essential oil was extracted by solid-phase microextraction and analyzed using enantioselective multidimensional gas chromatography/mass spectrometry. The genuine p-menthan-3-ones (-)-menthone and (+)-isomenthone as well as their labeled analogues were analyzed simultaneously. Both enantiomers of labeled pulegone were converted into the corresponding labeled p-menthan-3-ones by Mentha x piperita, indicating an unspecific reduction process. The generation of 4S- and 4R-configured p-menthan-3-ones differed in their stereoselectivities. Labeled (S)-pulegone was reduced by Mentha x piperita more rapidly rather than (R)-pulegone. From a comparison of labeled pulegone enantiomers the bioconversion preferrably led to 4S-configured diastereomers.     

Effect of dietary betaine on growth performance,antioxidant capacity and lipid metabolism in blunt snout bream fed a high-fat diet

An 8-week feeding experiment was conducted to determine the effect of dietary betaine levels on the growth performance, antioxidant capacity, and lipid metabolism in high-fat diet-fed blunt snout bream (Megalobrama amblycephala) with initial body weight 4.3 ± 0.1 g [mean ± SEM]. Five practical diets were formulated to contain normal-fat diet (NFD), high-fat diet (HFD), and high-fat diet with betaine addition (HFB) at difference levels (0.6, 1.2, 1.8%), respectively. The results showed that the highest final body weight (FBW), weight gain ratio (WGR), specific growth rate (SGR), condition factor (CF), and feed intake (FI) (P < 0.05) were obtained in fish fed 1.2% betaine supplementation, whereas feed conversion ratio (FCR) was significantly lower in the same group compared to others. Hepatosomatic index (HSI) and abdominal fat rate (AFR) were significantly high in fat group compared to the lowest in NDF and 1.2% betaine supplementation, while VSI and survival rate (SR) were not affected by dietary betaine supplementation. Significantly higher (P < 0.05), plasma total cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL), aspartate transaminase (AST), alanine transaminase (ALT), cortisol, and lower high-density lipoprotein (HDL) content were observed in HFD but were improved when supplemented with 1.2% betaine. In addition, increase in superoxide dismutase (SOD), catalase (CAT), and reduced glutathione (GSH) in 1.2% betaine inclusion could reverse the increasing malondialdehyde (MDA) level induced by HFD. Based on the second-order polynomial analysis, the optimum growth of blunt snout bream was observed in fish fed HFD supplemented with 1.2% betaine. HFD upregulated fatty acid synthase messenger RNA (mRNA) expression and downregulated carnitine palmitoyltransferase 1, peroxisome proliferator-activated receptor α, and microsomal triglyceride transfer protein mRNA expression; nevertheless, 1.2% betaine supplementation significantly reversed these HFD-induced effects, implying suppression of fatty acid synthesis, β-oxidation, and lipid transport. This present study indicated that inclusion of betaine (1.2%) can significantly improve growth performance and antioxidant defenses, as well as reduce fatty acid synthesis and enhance mitochondrial β-oxidation and lipid transportation in high-fat diet-fed blunt snout bream, thus effectively alleviating fat accumulation in the liver by changing lipid metabolism.     

Multiple Resistance in the Larger House Fly Musca domestica in Germany

Populations of the housefly Musca domestica isolated from farms in different German districts with strong resistance problems were compared to laboratory strains with varying resistance spectra. Resistance against pyrethroids, organophosphates and carbamates was tested using impregnated filter papers, and by topical application using a susceptible housefly strain (origin WHO) for comparison. The multi-resistant fly strains tested had a strong resistance against these insecticide groups, ranging from 37- to >10000-fold for organophosphates and 150- to >6600-fold for pyrethroids. The constituent enantiomer pairs of the α-cyano-pyrethroid cyfluthrin were tested, as was beta-cyfluthrin. With respect to multi-resistant fly strains, the isomers II and IV had the best activity, with LD₅₀ values of 0·012 and 0·014 μg per fly, respectively. In addition, different groups of insect growth regulators (juvenile hormone analogues, chitin synthesis inhibitors and one triazine derivative) were tested in a special larvicidal test. The chitin synthesis inhibitors were quite effective against multi-resistant M. domestica strains except for one strain with strong resistance against chitin synthesis inhibitors, developed after extensive treatments with benzoylphenylureas for several years. The fly strains tested were not resistant against cyromazine. Additionally, the insecticides were combined with the synergists piperonyl butoxide, tributylphosphorotrithioate (DEF) and Cibacron blue and tested against the fly strain with the strongest resistance spectrum (‘Grimm’) in comparison to the susceptible strain (‘WHO-N’). Piperonyl butoxide had the greatest effect on the efficacy of cyfluthrin followed by Cibacron blue and DEF. In a parallel investigation with susceptible and resistant house fly strains, different enzyme activities related with resistance mechanisms were tested, e.g. glutathione S-transferase (3·5-fold) and mixed-function oxidase (2·3-fold). Implications of these results for management of insecticide resistance in M. domestica are discussed.