Fat body in some genera of leaf-cutting ants (Hymenoptera: Formicidae). Proteins, lipids and polysaccharides detection

The comparative histochemical analysis of the fat body of workers belonging to the basal species Cyphomyrmex rimosus and Mycetarotes parallelus and to derived species Acromyrmex disciger and Atta laevigata revealed that this tissue is constituted mainly by cells denominated trophocytes and oenocytes. The trophocytes of all species studied here were characterized mainly by the proteins and lipids synthesis and storage, being the derived species the ones who have presented higher quantity of lipids in the trophocytes when compared to the trophocytes of basal species. In workers M. parallelus and A. laevigata, besides proteins and lipids, there has being observed the presence of polysaccharides, however, in C. rimosus and A. disciger these elements were detected in lower quantities. The histochemical studies of the oenocytes of basal and derived species revealed significant presence of proteins as well as lipids in these cells. In the oenocytes of derived species A. disciger and A. laevigata a higher quantity of lipidic inclusions has being observed, when compared to the basal species.     

The use of fluorinated additives in fire retardance of polymers

Polytetrafluoroethylene (PTFE) is shown to improve fire retardance characteristics of brominated compounds/antimony trioxide systems added to polymers burning with or without dripping, as for example high-impact polystyrene or acrylonitrilebutadiene-styrene terpolymer, respectively. The action of PTFE seems to be the reduction of intrinsic flammability of the material as shown by parallel improvement of Underwriters Laboratories (UL94) tests and oxygen index parameters. A mechanistic interpretation is tentatively proposed which takes into account the very high effectiveness of PTFE.