The longevity of Aedes aegypti mosquitoes is determined by carbohydrate intake / [A longevidade de mosquitos Aedes aegypti é determinada pela ingestão de carboidrato]

Aedes aegypti is the vector of several viral diseases. The main way to control these diseases is to fight the vector. Thus, it is necessary to breed mosquitoes in the laboratory in order to develop strategies to control these insects. In laboratories, different carbohydrates are used for feeding mosquitoes. The aim of this study is to evaluate the longevity and the weight of Ae. aegypti fed with different carbohydrates diets. As methods, 120 mosquitoes were distributed in insectaries and each group received a different diet, based on honey, dextrose or maltodextrin. To assess the longevity, survival analysis was performed using the Long Rank test and chi square test. To assess the weight, the dead insects were frozen and weighed at the end of the experiment. As results it was observed that mosquitoes fed with the honey, maltodextrin and dextrose diet lived on average 33, 35 and 47 days respectively. When weight was assessed, mosquitoes fed with honey weighed 125 ± (35.3) µg, while those fed with dextrose and maltodextrin weighed 225 ± (35.3) µg and 275 ± (35.3) µg respectively. The results show that the intake of dextrose and maltodextrin by Ae. aegypti adults increases their survival and their weight.(AU)

O Aedes aegypti é vetor de várias doenças virais. A principal maneira de controlar essas doenças é combatendo o seu vetor. Nesse sentido, é necessário criar esses mosquitos em laboratório, visando desenvolver estratégias de controle. Nos laboratórios, diferentes carboidratos são utilizados na alimentação de mosquitos. O objetivo deste estudo é avaliar longevidade e peso de Ae. aegypti alimentados com diferentes fontes de carboidratos. Como método, distribuíram-se 120 mosquitos insetários. Cada grupo recebeu uma dieta diferente à base de mel, dextrose ou maltodextrina. Para avaliar a longevidade, a análise de sobrevida foi realizada pelo teste de Logrank e pelo teste de qui quadrado. Para avaliar o peso, os insetos mortos foram congelados e pesados ​​no final do experimento. Como resultado, observou-se que os mosquitos alimentados com a dieta à base de mel, maltodextrina e dextrose viveram em média 33, 35 e 47 dias, respectivamente. Com relação ao peso, os mosquitos alimentados com mel pesavam 125 ± (35,3)µg, enquanto os alimentados com dextrose e maltodextrina pesavam 225 ± (35,3)µg e 275 ± (35,3)µg, respectivamente. Os resultados mostram que a ingestão de dieta à base de dextrose e maltodextrina por Ae. aegypti adultos aumenta sua sobrevivência e seu peso.(AU)

Cloning and molecular characterization of the novel human melanin-concentrating hormone receptor MCH2.

Using a genomics-based approach for screening orphan G-protein-coupled receptors, we have identified and cloned a novel high-affinity, melanin-concentrating hormone (MCH) receptor. This receptor, named S643b, displays the greatest overall identity (32%) with the previously reported human SLC-1 receptor (MCH1) and to a lesser extent with the somatostatin receptor subtypes. The gene encoding the S643b receptor spans more than 23 kilobase pairs (kb) and was mapped, by radiation hybrid experiments, on chromosome 6q14.3-q15. Comparison of the S643b cDNA with human genomic sequence reveals that the 340-amino-acid receptor is encoded by five exons. Its tissue distribution, as determined by Northern blot and reverse transcription-polymerase chain reaction analysis, indicates that a 4-kb transcript is predominantly expressed in the brain. When expressed in Chinese hamster ovary (CHO) cells, the S643b receptor displays a strong, dose-dependent, transient elevation of intracellular calcium in response to MCH (EC(50) = 9.5 nM). During the present study, we isolated a splice variant, designated S643a, encoding for a receptor that was not activated by MCH in a cellular calcium mobilization assay. Comparative pharmacological studies using CHO cells stably expressing either SLC-1 or S643b receptors demonstrated that similar structural features of MCH are required to stimulate intracellular Ca(2+) mobilization at both receptors. The identification and localization of this new MCH receptor (MCH2) provides further insight into the physiological implication of MCH in modulating behavioral responses, including food intake.

Structure-activity relationship studies of melanin-concentrating hormone (MCH)-related peptide ligands at SLC-1, the human MCH receptor.

Melanin-concentrating hormone (MCH) is a cyclic nonadecapeptide involved in the regulation of feeding behavior, which acts through a G protein-coupled receptor (SLC-1) inhibiting adenylcyclase activity. In this study, 57 analogues of MCH were investigated on the recently cloned human MCH receptor stably expressed in HEK293 cells, on both the inhibition of forskolin-stimulated cAMP production and guanosine-5'-O-(3-[(35)S]thiotriphosphate ([(35)S]- GTPgammaS) binding. The dodecapeptide MCH-(6-17) (MCH ring between Cys(7) and Cys(16), with a single extra amino acid at the N terminus (Arg(6)) and at the C terminus (Trp(17))) was found to be the minimal sequence required for a full and potent agonistic response on cAMP formation and [(35)S]- GTPgammaS binding. We Ala-scanned this dodecapeptide and found that only 3 of 8 amino acids of the ring, namely Met(8), Arg(11), and Tyr(13), were essential to elicit full and potent responses in both tests. Deletions inside the ring led either to inactivity or to poor antagonists with potencies in the micromolar range. Cys(7) and Cys(16) were substituted by Asp and Lys or one of their analogues, in an attempt to replace the disulfide bridge by an amide bond. However, those modifications were deleterious for agonistic activity. In [(35)S]- GTPgammaS binding, these compounds behaved as weak antagonists (K(B) 1-4 microm). Finally, substitution in MCH-(6-17) of 6 out of 12 amino acids by non-natural residues and concomitant replacement of the disulfide bond by an amide bond led to three compounds with potent antagonistic properties (K(B) = 0.1-0.2 microm). Exploitation of these structure-activity relationships should open the way to the design of short and stable MCH peptide antagonists.