Short neuropeptide F in integrated insect physiology

The short neuropeptide F(sNPF)family of peptides is a multifunctional group of neurohormones involved in the regulation of various physiological processes in insects.They have been found in a broad spectrum of species,but the number of isoforms in the precursor molecule varies from one to four.The receptor for sNPF(sNPFR),which belongs to the G protein-coupled receptor family,has been characterized in various insect orders and was shown to be an ortholog of the mammalian prolactin-releasing peptide receptor(PrPR).The sNPF signaling pathway interacts with other neurohormones such as insulin-like peptides,SIFamide,and pigment-dispersing factors(PDFs)to regulate various processes.The main physiological function of sNPF seems to be involved in the regulation of feeding,but the observed effects are species-specific.sNPF is also connected with the regulation of foraging behavior and the olfactory system.The influence of sNPF on feeding and thus energy metabolism may also indirectly affect other vital processes,such as reproduction and development.In addition,these neurohormones are involved in the regulation of locomotor activity and circadian rhythm in insects.This review summarizes the current state of knowledge about the sNPF system in insects.

The long-term immunological effects of alloferon and its analogues in the mealworm Tenebrio mofitor

The subject of this article is a search for the long-term immunological effects of alloferon and 3 structural analogues of alloferon, which were earlier characterized by the highest pro-apoptotic activity in Tenebrio molitor. The differences in the actions of these peptides on immune response were observed. Alloferon increased nodulation and significantly phenoloxidase activity in the hemolymph of experimentally infected T. molitor. However, [Phe（p-NH2）^1 ]- and [Phe（p-OMe） ^1 ]-alloferon strongly inhibited cellular and humoral defense of the mealworm against Staphylococcus aureus infection. One day after injection of these peptides, the specific biochemical and morphological hallmarks of apoptosis in bacteria-challenged hemocytes were visible; in contrast, 3 days after peptides injection in all hemocytes, caspase activation was not observed. However, these new, circulating hemocytes differed from the control and the peptide-untreated bacteria-challenged hemocytes. They had an increased adhesion that led to a separation of viable, anucleated fragments of hemocytes that retain the ability to adhere and to form long filopodia. The peptide-induced separation ofhemocyte fragments may resemble the formation ofplatelets in mammals and perhaps play a role in sealing wounds in insects. The results of in vivo studies may suggest a long half-life of studied peptides in the hemolymph of mealworm. Moreover, we showed the importance of the N-terminal histidine residues at position one of the alloferon molecule for its immunological properties in insects. The results obtained here show that alloferon plays pleiotropic functions in insects.

Cardioactive properties of Solanaceae plant extracts and pure glycoalkaloids on Zophobas atratus

Glycoalkaloids, the biologically active secondary metabolites produced by Solanaceae plants, are natural defenses against animals, insects and fungi. In this paper, the effects of glycoalkaloids present in extracts of Solanaceae plants （potato, tomato and black nightshade） or pure commercial glycoalkaloids on the coleopteran Zophobas atratus E were evaluated by in vitro and in vivo bioassays using heart experimental models. Each tested extract induced a dose-dependent cardioinhibitory effect. The perfusion of Zophobas atratus semi-isolated heart using the highest potato and tomato extract concentration （1 mmol/L） caused irreversible cardiac arrests, while extract from black nightshade pro- duced fast but reversible arrests. Pure commercial glycoalkaloids caused similar but less evident effects compared with extracts. Our results showed that the bioactivity of tested compounds depended on their structure and suggested the existence of synergistic interac- tions when combinations of the main glycoalkaloids of potato and black nightshade were used for trials. Surprisingly, injection of tomato and potato extracts in 1-day-old pupae of Zophobas atratus induced reversible positive chronotropic effects and decreased the duration of the both phases （anterograde and retrograde） of the heart contractile activity. Furthermore, these extracts affected the amplitude of the heart contractions.