Enzymes of PEP-succinate pathway in Setaria cervi and effect of anthelmintic drugs.

Localization of different enzymes of PEP-succinate pathway has been done in Setaria cervi, a bovine filarial worm. Succinate dehydrogenase and fumarate reductase were localized in mitochondria rich particulate fraction while all other enzymes were cytosolic. The in vitro effect of certain antifilarial/anthelmintic agents on these enzymes was also investigated. Sumarmin, at low concentration, could cause a marked inhibition of most of the enzymes of this pathway. Centperazine, an antifilarial drug being developed by CDRI showed significant inhibitory action on pyruvate kinase, lactate dehydrogenase, fumarase and succinate dehydrogenase while CDRI compound 72/70 showed significant inhibition of PEP-carboxykinase activity. Diethylcarbamazine and levamisole, however, were found to be more or less ineffective at lower concentrations against all the enzymes of this pathway.

Diethylcarbamazine: inhibitory effect on acetylcholinesterase of Dirofilaria immitis and Brugia pahangi.

Anti-acetylcholinesterase activity of diethylcarbamazine (DEC) was studied. Acethylcholinesterase (AchE) of adult worms of Dirofilaria immitis, those of the 4th-stage larvae, early 5th-stage larvae and adults worms of Brugia pahangi, and that of hamster brain tissue were all inhibited by DEC. Michaelis constant (Km) of D. immitis and B. pahangi adult worm AchE were 1.47 x 10(-4) and 1.81 x 10(-4) M respectively. DEC was a competitive inhibitor of the filarial AchE. Inhibition constant (Ki) for AchE of D. immitis and B. pahangi adult worms were 2.56 x 10(-4) and 6.39 x 10(-4) M, respectively. DEC is a less potent anticholinesterase inhibitor, because Ki of DEC is 10(4) times higher than that of eserine, a potent anti-cholinesterase agent.

Filarial enzymes by the horizontal starch-gel electrophoresis technique.

In preliminary studies, on adult filarial parasites, difference in the electrophoretic pattern of glucosephosphate isomerase (GPI) of B. malayi, B. pahangi and the rat filarial worm, B. booliati, was demonstrated. There also appears to be a difference in the GPI and lactate dehydrogenase isoenzyme patterns of B. malayi (subperiodic) from different animal hosts. These observations suggest that the zymogram technique may yet prove to be a sensitive taxonomic tool for use in the characterisation of filarial helminths. At present, the contention is that the subperiodic form of B. malayi exists as a zoonoses (possibly also with B. pahangi), which is drawn from findings backed by procedures that cannot easily differentiate between closely-related species and subspecies. Thus enzyme electrophoresis could complement the parasitological methods currently used, and contribute in enhancing the validity of this contention. More work, and on a larger scale to include the microfilariae and infective larvae, would be required.