[Ultrastructural changes of the tegument on Diphyllobothrium erinacei and Hymenolepis nana treated with paromomycin sulfate in vitro].

The effects of paromomycin sulfate on Diphyllobothrium erinacei and Hymenolepis nana in vitro were examined morphologically with a scanning and a transmission electron microscope. D. erinacei was incubated for 3 and 6 hours at 37 degrees C in a culture medium, 0.85% physiological saline solution, containing 0.5% paromomycin sulfate. H. nana was incubated in the same medium for 3 hours only. The concentration of paromomycin sulfate was set basing on the results which Kitamoto (1968) reported as the concentration level in feces after administrations of this drug in a clinical survey. The effect of the drug on the surface structure in both worms appeared markedly in the neck region. Mechanisms of breakdown on the tegument were supposed as follows. First, microtriches were disconnected from the tegumental surface and many vesicles were formed in the cytoplasm of the tegument. Finally, the tegument layer was excoriated to exposed the basal lamina. In 6 hours incubation, this surface of the worm suffered more damage than that in 3 hours. The damage of the basal lamina as in the case of D. latum expelled from a man by paromomycin (Y. Tongu et al.), however, could not be observed in the present study in vitro. It suggests that the destruction of basal lamina usually observed with the expelled worms from clinically treated human might be due to the combined effect of digestive enzymes secreted from host and the mechanical impact of intestinal peristalsis. Some of the vesicles in the tegument may originate from mitochondria because the fine structure of cristae were occasionally observed remaining in the vesicles.