The aerobic metabolism of 14C-sugars and 14CO2 by the daughter sporocysts of Microphallus similis (Jäg.) and Microphallus pygmaeus (Levinsen) (Digenea: Microphallidae)

Workshop no. 2. Parasitic infection and host nutrition

Even if we do not always acknowledge the fact, nutrition is a fundamental aspect of symbiosis and parasitism. (1) The significance of nutrition often forms a basic feature in schemos of classification of the various associations between living organisms (see Read, 1908; Whitfield, 1979). (2) The growth and reproduction of different parasites appear to Vary in response to the nutrition of the host (see Mettrick & Podesta, 1974; Nesheim, Crompton, Arnold & Barnard, 1977; 1978; Parshad, Crompton & Nesheim, 1980). (3) The course of a parasitic infection may also vary in response to the nutritional status of the host and perhaps such variations are the result of the affocts of nutrition on the host's immune response (Chandra & Nowberne, 1977; Chandra, 1980). (4) Finally, parasitic disease is well known to be much more scrious in undernourished hosts (see Chandra & Newberne, 1977); when man's the deprived host, the impact of infections and parasitic disease on young children is Particularly severe and distressing (Latliam, 1975).

The ultrastructure of the tegument of the daughter sporocyst of Microphallus similis (Jäg., 1900) (Digenea: Microphallidae)

In the fully formed daughter sporocyst of Microphallus similis (Jäg.) the tegument is divided into a wide, outer cellular epithelium and a narrow, inner electron-dense anucleated microvillous syncytium. The narrow subtegument consists of circular and longitudinal muscle, nervous, synthesizing and germinal cells. It is suggested that during development of the tegument, an undifferentiated nucleated syncytium becomes divided by the formation of membranes between the nuclei and between the narrow, inner electron-dense microvillous and the outer cellular regions. The outer nucleated region of the tegument is homologous to the nucleated investing syncytium which surrounds redial and cercarial embryos and which is shed later in development. The retention of the nucleated region in some daughter sporocysts is, therefore, an example of paedogenesis.

Some problems associated with radiolabeling surface antigens on helminth parasites: a brief review

Recent developments in technology have facilitated substantial advances in the characterization of surface antigens from a wide variety of both normal and neoplastic cells. However, the immunochemistry of parasites has lagged behind. Efforts to apply conventional radiolabeling methods to helminths have not always been successful. Experimental work with Schistosoma mansoni is reviewed to illustrate common problems encountered in surface labeling studies. These findings should provide insight for the future investigation of other helminth species.

Aerobic glucose metabolism in the digestive gland of Littorina saxatilis rudis (Maton) and in the daughter sporocysts of Microphallus similis (Jäg.)

Experiments, some in vitro and some in vivo, with glucose-U-14C, acetate-U-14C, succinate-1,4-14C, pyruvate-U-14C and citrate-1,5-14C indicate that the digestive gland of Littorina saxatilis rudis and the daughter sporocysts of Microphallus similis aerobically catabolise glucose via an EMP pathway, a TCA cycle, phosphoenolpyruvate carboxylation and malate decarboxylation. The host and parasite have similar transamination and synthetic reactions and alanine as a major carbohydrate excretory product. Oxidative metabolism appears to be less efficient in the parasite than in the host.