Cysticercus fasciolaris: Fine surface structural changes in the tegument following in vitro low doses of the antihelminthic drug, oltipraz

Abstract

Cysticercus fasciolaris is the larval form of the adult cat tapeworm, Hydatigera taeniaeformis (Taenia taeniaeformis). It is of increasing interest because of the considerable pathological conditions produced in a rat or mouse host in which it is normally found. The larvae encapsulate and develop on the liver of rats and mice and as a result of this infection, a serious cancer- like growth may develop (Noble and Noble, 1974). The surface tegument of cestodes 1ike that of schistosomes is a highly active layer in which many processes occur (Smyth 1969, 1966). It is a metabolically active syncytial, protoplasmic layer formed by cytoplasmic extensions from tegumental cells lying in the subtegumental zone. The tegument has two major components, namely the distal cytoplasmic zone (surface syncytium) and the perinuclear cytoplasmic zone (cytoplasm in the region of tegumental cells). Under the light microscope the surface of the distal cytoplasmic zone appears as a fringe of fine hair-like processes (Smyth, 1969; Jones et al., 1977a, 1977b Lumsden and Specian, 1980). At the electron microscope level, the distal surface is revealed as spine-like processes which morphologically resemble the brush border of many vertebrate and invertebrate cells and have been referred to as microtriches, microvilli, or tegumental projections (Smyth, 1969 Shivers et al., 1986). The tegument functions to: (1 mediate the absorption of nutrients by the worm from the host environment, (2) protect the integrity of the worm against the alien environment of its host, and (3) bear the immunologicaL mechanisms whereby the parasite is able to resist inactivation by antibodies produced against the invader by its host (Lumsden and Specian, 1980) . Though oltipraz has received less attention than the antihelminthic drug, praziquantel, recent clinical and biological tolerance studies have shown that patients administered the drug have shown a high proportion of egg reduction. The mechanism of action of oltipraz is unclear but there are indications that it might inhibit the parasite’s glutathione levels (Cerf et al. 1982; Bella et al., 1983; Lapierre et al. 1983; Rey et al., 1984; Kardaman et al.,1985; Bieder and Jumeau, 1985), The effects of radioactively labeled praziquantel has been reported in experimental cysticercosis (Anrews et al., 1980). However, the effects of oltipraz on the tegument of cestodes has received little attention. Thus, the objective of this preliminary study is to show the in vitro effects of oltipraz on the tegument of c. fasciolaris in relation to dose and time using scanning electron microscopy.