Effects of crustacean hyperglycemic hormones from Carcinus maenas and Orconectes limosus on blood and muscle glucose and glycogen concentration of Chasmagnathus granulata

The effects of purified crustacean hyperglycemic hormones (CHH) from Carcinus maenas or Orconectes limosus, and of eyestalk extract of Chasmagnathus granulata on the blood and muscle glucose and glycogen concentration of Chasmagnathus granulata were investigated. Different groups of animals (at least 7 animals per group) were injected with CHH from either C. maenas or O. limosus CHH dissolved in saline (16 pmol/animal) or crude eyestalk extract of C. granulata (1 eyestalk equivalent/animal). All injections had a volume of 10 microliters. Blood and muscle glucose and glycogen concentrations were determined immediately before the injections and after 30, 60 and 120 min. CHH administration from both species, as well as eyestalk extract, resulted in marked hyperglycemia. However, their effects were different. CHH from C. maenas also caused a decrease in the glycogen concentration of blood (from 89.8 +/- 4.3 to 76.6 +/- 3.1 mg/100 ml) and muscle (from 7.9 +/- 0.8 to 4.0 +/- 0.7 mg/g) and glucose concentration of muscle (from 2.4 +/- 0.3 to 1.2 +/- 0.2 mg/g). CHH from O. limosus caused an increase of glycogen concentration of muscle (from 4.9 +/- 1.1 to 9.0 +/- 1.1 mg/g). The injection of eyestalk extract resulted also in a decrease of hemolymph glycogen (from 157.7 +/- 20.6 to 30.2 +/- 7.7 mg/100 ml). Therefore, C. granulata may have different receptors for CHH in its different tissues, and/or in the same tissue, which act through different metabolic pathways to achieve the same final result, i.e., hyperglycemia

The hemolymph of chasmagnathus granulata dana,1851 (Decapoda - grapsidae) as a target tissue ofthe crustacean hyperglycemic hormone

The effect of crustacean hyperglycemic hormone (CHH) was investigated on the hemolymph of Chasmagnathus granulata, a meso-supralitoral crab from southern Brazil. Serum glucose increased significantly (P®0.05) after incubation of total hemolymph in the presence of the eyestalk extract of a member of the same species. Also glucose uptake from blood serum, not affected by eyestalk extract (P¼0.05) was observed after incubation of total hemolymph in the presence of glucose.The results that the hemolymph may be a target tissue of CHH and that this hormone may act by mobilizing carbohydrate reserves possibly from hematocytes.

Effects of azadirachtin in Rhodnius prolixus: data and hypotheses

The effects of azadirachtin A, a tetranortriterpenoid from the neem tree Azadirachta indica J., on both development and interaction between Trypanosoma cruzi, the causative agent of Chagas' disease, and its vector Rhodnius prolixus were studied. Given through a blood meal, a dose-rsponse relationship of azadirachtin was established using antifeedant effect and ecdysis inhibition as effective parameters. A singlo dose of azadirachtin A was able to block the onset of mitosis in the epidermis and ecdysteroid titers in the hemnolymph, determined by radioimmuneassay, were too low for an induction of ecadysis. The survival of T. cruzi was also studied in R. prolixus treated with the drug. If the trypomastigotes were fed in presence of azadirachtin A the number of parasites drastically decreased. If the drug was applied after infection of the bug with T. cruzi, the parasite was still abolished from the gut. If the insect was pretreated with azadirachtin A before infection the same observation was obtained. A single dose of azadirachtin A was enough for a permanent resistance of the insect host against its reinfection with T. cruzi and for blocking the ecdysis for a long time. The effects of azadirachtin A on the hormonal balance of the host and growth inhibition of the parasite will be discussed on the basis of the present results.

Effects of proallatotoxins (precocenes) on the development and reproduction of Rhodnius prolixus: some data

Proallatotoxins, and particularly preconcenes, are exceptionally promising models for studying Rhodnius prolixus physiology and for comparison with other natural compounds with anti-hormonal activities. Effects of preconcenes on feeding, development and reproduction of R. prolixus are being detailed. The precocenes reveal significant effects on feeding, moulting cycle (inducing precocious metamorphosis and ecdysial stasis), and reproduction of these insect. The mechanism of action of proallatotoxins was discussed based on the corpus allatum cytotoxic effect and on the ecdysteroid biosynthesis in prothoracic glands and ovaries. Further studies of these compounds on R. prolixus are need and will hopefully reveal other unesplored points regarding the action of the proallatotoxins on insects.