| الوصف: |
In the intestine of experimentally infected mink, the scoop-shaped forebody of Alaria mustelae grasps a single villus, holding it tightly against the holdfast organ. Some breakdown of villous tissue occurs there but not near the invaginated lappets. Adult worms apparently feed on this tissue but also probably ingest intact tissue directly. Histochemical staining revealed nonspecific esterases in the holdfast organ gland cells, forebody gland cells and ducts, forebody tegumentary cells, and ceca. From effects of the organophosphate inhibitor diethyl p-nitrophenyl phosphate (E600), nonspecific esterase activity in the ceca is due to A-esterases and in other areas to B-esterases. Using E600 with A. marcianae adults (experimentally infected dog), A and B types occur in the holdfast organ, A, B, and C types in the forebody gland cells and ducts, and only B in other areas. A comparison of the structure and function of the holdfast organ and lappets of A. mustelae and A. marcianae is presented. Three recent studies (Johnson et al., 1971; Bhatti and Johnson, 1971, 1972) have been made on the structure and function of the holdfast organ and lappets of the strigeoid trematode Alaria marcianae (La Rue, 1917). These studies have indicated the importance of the lappets in extracorporeal digestion, with a secondary role in attachment. The holdfast organ was implicated in extracorporeal digestion and also possibly in nutrient absorption. Attachment of adults to the host mucosa was accomplished primarily by the forebody rather than by the holdfast organ and lappets. The subject of the present study is the closely related species, A. mustelae Bosma, 1931. In this preliminary investigation, histological studies were made as well as histochemical staining for esterases. Additionally, further histochemical staining of esterases in A. marcianae adults was carried out. Histochemical staining has demonstrated nonspecific esterases in the holdfast organ gland cells and in gland cells associated with the lappets, if present, of all adult strigeoids studied (Lee, 1962; Erasmus and Ohman, 1963; Ohman, 1965, 1966a, b; Bogitsh, 1966; Reid and Harkema, 1970; Johnson et al., 1971; Bhatti and Johnson, 1972). In studies attempting to identify these enzymes further, Erasmus and Ohman (1963) in Cyathocotyle bushiensis and Received for publication 9 July 1973. * Supported in part by Graduate School Research Grant, University of South Dakota. Ohman (1965) in Diplostomum spathaceum reported a B esterase and an unclassified resistant type. Ohman (1966a) in Apatemon gracilis minor and Ohman (1966b) in Holostephanus luehei found a type resembling B esterases, and Bhatti and Johnson (1972) reported a C esterase in A. marcianae. MATERIALS AND METHODS Mesocercariae of A. mustelae and A. marcianae were from naturally infected leopard frogs, Rana pipiens (Steinhilber and Co., Oshkosh, Wisc.). Two 7-month-old female mink (ranch-reared) were each injected intraperitoneally with about 400 A. mustelae larvae and killed 23 and 28 days after infection. One dog was injected intraperitoneally with 2,400 A. marcianae larvae and killed 34 days after infection. Portions of the small intestine with attached adult worms were immediately removed and fixed in cold (4 C) fixatives. Fixation for histological studies was for 24 to 48 hr in Bouin's fixative, neutral phosphatebuffered 5% glutaraldehyde, or neutral phosphatebuffered formalin. Free and attached adults were dehydrated in ethanol, cleared in benzene, embedded in Tissuemat, sectioned at 10 /t, and stained with hematoxylin and eosin. Fixation for staining of esterases was for 16 hr in formol-calcium (Barka and Anderson, 1962), followed by rinsing for 24 hr in cold 0.1 M cacodylate buffer (pH 7.4) containing 0.2 M sucrose and storage in this solution at 4 C until used. Before sectioning, material was infiltrated with 10% gelatin (12 hr at 37 C) to prevent loss of sections from slides. Free and attached adults were sectioned at 8 A in an International Harris cryostat (-22 C) and mounted on slides. |
