The ecto-ATPases of endoparasites and of blood cells and vessels

The cells of blood vessel walls and the external surface of all blood cells have an ecto-ATPase which hydrolyzes ATP to ADP and also ADP to AMP. This enzyme has also been called apyrase or ATP-diphosphohydrolase. The enzyme hydrolyzes a broad range of tri-and diphosphate nucleosides such as UTP and UDP, GTP and GDP in additon to the adenine nucleotides and because of that it has also been called a nucleoside triphosphate hydrolase. The possible physiological roles for this ecto-ATPase involve the control of vascular tone by modulation of the levels of ATP and ADP binding to purino-receptors of the vasculature, the modulation of thrombogenesis by controlling the extracellular level of ADP which is known to activate platelet aggregation, and the protection from cytolytic effects of extracellular ATP. An ATP-diphosphohydrolase activity has been characterized on the external surface of Schistosoma mansoni, a parasite that lives in the circulation of the human host, and on the outer surface of Entamoeba histolytica, a parasite that may enter the circulation of the host through ulceration in the intestinal mucosa. The endoparasite Toxoplasma gondii also exhibits a nucleoside triphosphate hydrolase of high activity, although in this case the ecto-localization is still not documented. We raise the possibility that the endoparasites have evolved in a way to possibly mimic some of the conditions on the surface of cells normally present in the host circulation, thus escaping hemostatic defense responses of the host which require extracellular ADP or ATP.

Leishmania mexicana amazonenesis: heterogeneity in 5-nucleotidase and peroxidase activities of mononuclear phagocytes during in vivo and in vitro infection

Um estudo sobre o grau de maturaçäo das células do Sistema Fagocítico Mononuclear foi realizado durante a infecçäo in vivo e in vitro com a Leishmania mexicana amazonensis. A caracterizaçäo da diferenciaçäo das células fagocíticas foi obtida com a localizaçäo ultraestrutural de dois marcadores enzimáticos bam conhecidos: a enzima 5'-Nucleotidase marcadora de membrana plasmática de células maduras e a enzima peroxidase, presente em grânulos, marcadora de células imaturas. A atividade da enzima 5'-Nucleotidase foi encontrada apenas em alguns macrófagos, presentes no foco inflamatório, em projeçöes da membrana plasmática e em algumas vesículas citoplasmáticas. Macrófagos peritoneais de camundongo apresentaram a mesma reatividade para este marcador. Contudo a análise da atividade peroxidásica demonstrou a predominância da presença de fagócitos mononucleares imaturos nas lesöes crônicas induzidas neste sistema por Leishmania mexicana amazonensis

Contenido proteico y actividades enzimáticas presentes en el veneno de la araña casera - Loxosceles laeta: II Parte / Protein content and enzymatic activities present in the poison of the house spider - Loxosceles laeta: Part II

Se ha investigado el contenido proteico y varias actividades enzimáticas en el veneno de la araña casera Loxosceles laeta. La cantidad de proteína encontrada en 3 de los 4 lotes de arañas en estudio fue de 38 ug por especímen. Asi mismo, se ha encontrado actividad de 5 nucleotidasa, fosfatasa ácida y alcalina, ADPasa y ATPasa, enzima cascinolítica y hialuronidasa. En cambio, no se ha registrado actividad de exonucleasa, endonucleasa, enzima semejante a trombina, enzima fibrinolítica, ni actividad esterásica