Malic dehydrogenase isoenzymatic pattern in lung-nematode parasite species.

The malic dehydrogenase (MDH) isoenzymatic pattern of Dictyocaulus viviparus, Protostrongylus rufescens, and Slovakian and Spanish isolates of D. filaria was studied. The MDH isoenzymatic pattern in both isolates of D. filaria was characterized by the presence of three phenotypes: (1) a single, slow anodic band; (2) a single, fast anodic band; and (3) a large spot matching its migration with bands 1 and 2. These three phenotypes may be explained as the existence of only one gene locus for the MDH in D. filaria. Allelic frequencies and the Hardy-Weinberg test were determined for Slovakian and Spanish isolates of D. filaria. This test indicated that the population was not in Hardy-Weinberg equilibrium. The MDH isoenzymatic pattern of D. viviparus displayed the same phenotypes 1 and 2 observed in D. filaria. Furthermore, the MDH isoenzymatic pattern of P. rufescens was characterized by the presence of two bands with anodic and cathodic migration. The isoenzyme with anodic migration appeared more intensively stained than did that with cathodic migration. This last isoenzyme was not observed when the samples had been stored for 1 month.