Giardia lamblia: Identification of peroxisomal-like proteins.

The protozoan parasite Giardia lamblia has traditionally been reported as lacking peroxisomes, organelles involved in fatty acid metabolism and detoxification of reactive oxygen species. We here report the finding with transmission electron microscopy of an oxidase activity in cytoplasmic vesicles of trophozoites and cysts of G. lamblia. These vesicles were positive to 3,3'-diaminobenzidine and to cerium chloride staining. In addition, using bioinformatic tools, two peroxisomal proteins were identified in the G. lamblia proteome: acyl-CoA synthetase long chain family member 4 (ACSL-4) and peroxin-4 (PEX-4). With confocal and immunoelectron microscopy using polyclonal antibodies both proteins were identified in cytoplasmic vesicles of trophozoites. Altogether, our results suggest for the first time the presence of peroxisomal-like proteins in the cytoplasm of G. lamblia.

Histopathologic analysis of hamster hepatocytes submitted to experimental infection with Leishmania donovani.

Hepatocytes from different vertebrates are used increasingly as models of environmentally driven cell structure plasticity and for the investigation of ultrastructural pathological patterns induced by cell injury. The present study was carried out to assess the morphological changes in hamster hepatocytes subjected to chronic infection by amastigote forms of Leishmania donovani. Liver fragments were processed for routine light and transmission electron microscopy. For cytochemical visualization of peroxisomes, liver slices were incubated in alkaline 3,3'-diaminobenzidine (DAB) medium at pH 10.0. The results showed that the presence of Leishmania donovani induced distinct ultrastructural changes in the liver acinus (zone 2). The significant pathological changes in hepatocytes consisted of disruption of the endomembrane system and alterations of both the peroxisomal compartment and the distribution of hepatic glycogen. Particularly, hepatic peroxisomes exhibited different shapes and sizes, with modifications of the peroxisomal matrix, including absence of the catalase reaction. These observations suggest an adaptive response of hepatocytes, with cytological reorganization after parasitic infection. The presence of DAB-negative peroxisomes could be morphological evidence of a metabolic disturbance of this organelle. The parasitic infection, through deregulation of the cytokene network, is probably responsible for those structural alterations, since similar changes have been observed in vivo and in vitro.