Assessment of the effects of the carbamazepine on the endogenous endocrine system of Daphnia magna.

In the present study, the endocrine activity of the antiepileptic pharmaceutical carbamazepine (CBZ) in the crustacean Daphnia magna was assessed. To assess the hormonal activity of the drug, we exposed maternal daphnids and embryos to environmental relevant concentrations of CBZ (ranging from 10 to 200 µg/L) and to mixtures of CBZ with fenoxycarb (FEN; 1 µg/L). Chronic exposure to CBZ significantly decreased the reproductive output and the number of molts of D. magna at 200 µg/L. This compound induced the production of male offspring (12 ± 1.7 %), in a non-concentration-dependent manner, acting as a weak juvenile hormone analog. Results showed that this substance, at tested concentrations, did not antagonize the juvenoid action of FEN. Further, CBZ has shown to be toxic to daphnid embryos through maternal exposure interfering with their normal gastrulation and organogenesis stages but not producing direct embryo toxicity. These findings suggest that CBZ could act as an endocrine disruptor in D. magna as it decreases the reproductive output, interferes with sex determination, and causes development abnormality in offspring. Therefore, CBZ could directly affect the population sustainability.

Chitin synthase A: a novel epidermal development regulation gene in the larvae of Bombyx mori.

Chitin synthase is the key regulatory enzyme for chitin synthesis and excretion in insects, as well as a specific target of insecticides. The chitin synthase A gene (BmChsA) cloned from Bombyx mori, the model species of lepidopteran, is an epidermis-specific expressed gene during the molting stage. Knockdown BmChsA gene in 3rd instar larvae increased the number of non-molting and abnormal molting larvae. Exposure to nikkomycin Z, a chitin synthase inhibitor downregulated the expression of BmChsA and decreased the amount of epidermis chitin during the molting process. The thickness of the new epidermis and its dense structure varied greatly. The exogenous hormones significantly upregulated the expression of BmChsA with low levels of endogenous MH and high levels of endogenous JH immediately after molting. With low levels of endogenous hormones during the mulberry intake process, BmChsA was rarely upregulated by exogenous hormones. With high levels of endogenous MH and low levels of endogenous JH during the molting stage, we did not detect the upregulation of BmChsA by exogenous hormones. The expression of BmChsA was regulated by endocrine hormones, which directly affected the chitin synthesis-dependent epidermal regeneration and molting process.

Effects of a premolt calcium and low-energy molt program on laying hen performance, egg quality, and economics.

The objectives of this study were to evaluate and compare the effects of production, physiology, egg quality, and economics of laying hens housed in a cage system when offered a calcium premolt treatment and low-energy molt diets versus a traditional feed withdrawal (FW) treatment during and after molt. In total, 981 Hy-Line W-36 laying hens (85 wk of age) housed 3 per cage were used. Six treatments were compared in a 2 × 3 factorial design with 2 calcium premolt treatments (fine and coarse) and 3 molt diets (FW, soybean hulls, and wheat middlings). The coarse Ca was a 50:50 mix of fine (0.14-mm mean diameter) and coarse (2.27-mm mean diameter) CaCO(3), whereas the fine Ca was an all-fine CaCO(3). Both diets were formulated to contain 4.6% Ca, such that only the particle size of the CaCO(3) differed. Production parameters in experiment 1 included egg production, egg weight and mass, specific gravity, Haugh units, egg components, feed consumption and utilization, and BW. Physiological parameters in experiment 2 included ovary and oviduct weights, femur- and humerus-ash percentages, heterophil to lymphocyte ratios, plasma Ca and inorganic P concentrations, and alkaline phosphatase activity. Data were analyzed by ANOVA and P < 0.05 was significant. The fine-Ca premolt treatment was more effective than the coarse-Ca treatment at decreasing egg production during molt and increasing it postmolt, regardless of the molt diet. The FW molt diet resulted in the greatest decrease in production, but the soybean hulls diet resulted in lower production and ovary and oviduct weights during molt compared with those of the wheat middlings molt diet. Therefore, a fine-Ca premolt treatment and a low-energy molt diet, particularly soybean hulls, can be useful alternatives to a FW molt.

Assessment of species specificity of moulting accelerating compounds in Lepidoptera: comparison of activity between Bombyx mori and Spodoptera littoralis by in vitro reporter and in vivo toxicity assays.

BACKGROUND: Dibenzoylhydrazine analogues have been developed successfully as a new group of insect growth regulators, called ecdysone agonists or moulting accelerating compounds. A notable feature is their high activity against lepidopteran insects, raising the question as to whether species-specific analogues can be isolated. In this study, the specificity of ecdysone agonists was addressed through a comparative analysis in two important lepidopterans, the silkworm Bombyx mori L. and the cotton leafworm Spodoptera littoralis (Boisd.). RESULTS: When collections of non-steroidal ecdysone agonists containing different mother structures (dibenzoylhydrazine, acylaminoketone, tetrahydroquinoline) were tested, in vitro reporter assays showed minor differences using cell lines derived from both species. However, when compounds with high ecdysone agonist activity were examined in toxicity assays, larvicidal activity differed considerably. Of note was the identification of three dibenzoylhydrazine analogues with > 100-fold higher activity against Bombyx than against Spodoptera larvae. CONCLUSION: The present study demonstrated that species-specific ecdysone-agonist-based insecticides can be developed, but their species specificity is not based on differences in the activation of the ecdysone receptor but rather on unidentified in vivo parameters such as permeability of the cuticle, uptake/excretion by the gut or metabolic detoxification.