[Show abstract][Hide abstract] ABSTRACT: Intracellular parasites manipulate host cell apoptosis in different ways either to increase their life span within infected cells or to spread infection. The present data provided information on the cellular changes taking place in spleen and peripheral blood during Plasmodium berghei-infection and indicated apoptosis mediated host immune response during infection. Our results suggested a significant change in cellular composition and absolute number of white blood cells in spleen and peripheral blood of P. berghei-infected Balb/c mice. Plasmodium berghei-infection was associated with marked increase in percentage of apoptotic mononuclear cells compared to polymorphonuclear white blood cells.
[Show abstract][Hide abstract] ABSTRACT: Present study was undertaken to purify and characterize thioredoxin reductase (TrxR) of Plasmodium berghei, a rodent malaria parasite. Plasmodium contains thioredoxin redox system that acts as efficient antioxidant system preventing damage caused by enhanced oxidative stress. Thioredoxin (Trx) functions as redox messenger in the parasite maintaining a reduced intracellular environment. Thioredoxin reductase (E.C.I.8.1.9) was analysed in rodent malaria parasite, Plasmodium berghei. Cell-free parasite showed TrxR specific activity of 0.128±0.10 U mg-1. Maximum TrxR activity was observed in cytosolic fraction of P. berghei. The parasite enzyme was purified by ammonium sulphate precipitation and Sephadex G-200. Its molecular weight was 22 kDa and the enzyme remained maximally active at pH 7.4 while the higher temperatures inactivated the enzyme. Km (Michaelis constant) and Vmax (Maximum velocity of enzyme) values for dithionitrobenzene (DTNB) substrate were 1.25 and 0.1 mM, respectively, l-chloro-2, 4-dinitro benzene (CDNB) uncompetitively inhibited the enzyme substrate reaction and the inhibition was concentration dependent. Ki (inhibition constant) for CDNB was found to be 1.25 mM for 0.01 mM CDNB and 1.3 mM for 0.1 mM CDNB.
[Show abstract][Hide abstract] ABSTRACT: Malaria parasites adapt to the oxidative stress during their erythrocytic stages with the help of vital thioredoxin redox system and glutathione redox system. Glutathione reductase and thioredoxin reductase are important enzymes of these redox systems that help parasites to maintain an adequate intracellular redox environment. In the present study, activities of glutathione reductase and thioredoxin reductase were investigated in normal and Plasmodium berghei-infected mice red blood cells and their fractions. Activities of glutathione reductase and thioredoxin reductase in P. berghei-infected host erythrocytes were found to be higher than those in normal host cells. These enzymes were mainly confined to the cytosolic part of cell-free P. berghei. Full characterization and understanding of these enzymes may promise advances in chemotherapy of malaria.
Preview · Article · Dec 2009 · The Korean Journal of Parasitology