AN ULTRASTRUCTURAL, CYTOCHEMICAL AND FREEZE-FRACTURE STUDY OF THE SURFACE-STRUCTURES OF BRUGIA-MALAYI MICROFILARIAE

Ultrastructural analysis of the cuticle of Brugia malayi microfilariae indicated that it is composed of 2 regions: the inner one 15-20 nm th ick with a homogeneous aspect and the outer one, designated as epicuti cle, which is 15-20 nm thick. Three laminae separated by electron-luce nt regions were seen in the epicuticle. Labeling of the cuticle and ep icuticle of B. malayi and Wuchereria bancrofti microfilariae was obser ved when thin sections of Lowicryl-embedded parasites were incubated i n the presence of gold-labeled phospholipase-C. Replicas of freeze-fra ctured microfilariae showed the presence of 2 fracture planes in the e picuticle and no fracture plane in the inner region of the cuticle. Th e P face of the epicuticle outer fracture plane presented few particle s similar to intramembranous particles (IMPs). The epicuticle inner fr acture plane P and E faces presented large numbers of densely-packed s mall particles and many protuberances. Also, fracture faces of hypoder mal and muscle cell plasma membranes were analyzed. Faces P and E of f ractured membranes showed the presence of typical IMPs. P faces of bot h membranes showed larger amounts of particles than E faces. Fracture of muscle plasma membrane revealed a linear array of particles dispose d in parallel rows on its P face.