Effect of Schistosoma mansoni infection on physiological gastrointestinal transit and contractility.

The work aimed to study the effect of Schistosoma mansoni (S. mansoni) on gastrointestinal transit and contractility of the colonic muscles of two subgroups of experimental mice, infected by 50 & 200 cercaria/mouse respevtively, at 8th & 12th week postinfection (PI). In addition, the histopathologic changes in the colon, and the immunological changes of the host were studied at different durations. At 8th weeks PI, in both subgroups, gastrointestinal transit was statistically significant decreased, in concurrent with statistically significant increase in the colonic muscle contractility compared to the controls. The colon was inflamed as shown by mucosal inflammatory infiltrates, with large size and number of schistosomal granulomas. The serum antigen was absent, while the serum antibody was detectable at low titre. At 12th weeks PI, there was a more statistically significant decrease in gastro-intestinal transit, and increase in the colonic muscle contractility. The colon was still inflamed, but the granulomas were reduced in size and in number, with increase in the fibrocytes density. These alterations coincided with absence of serum antigen and increase in the antibody titre. All changes were more pronounced in the 2nd group of mice (200 ceraria/mouse) than the 1st one (50 cercaria/mouse). So, intestinal schistosomiasis is associated with great structural, functional and immunological changes, related to the time course and the infection intensity which may be involved in the pathogenesis and clinical manifestations of the disease.

Experimental trichinosis: parasitological, electrophysiological and biochemical studies.

Trichinosis is a parasitic infection affecting the gut and the muscles causing mild gastrointestinal symptoms followed by periorbital oedema, muscle pains, fever and eosinophilia. The infection evokes functional disturbances in physiological effector systems. Furthermore, several biochemical changes are associated with the infection. Therefore, this work was carried out to study the electrophysiological changes in intestine, striated and cardiac muscles by electromyography (EMG) and to assess the biochemical changes through measurement of serum cholinesterase and intestinal myeloperoxidase activity (MPO) in both light and heavy infected experimental animals by Trichinella spiralis (T. spiralis). Electrophysiological results showed increased contractility of the smooth muscle layers of the intestine only early in the infection, whereas both striated and cardiac muscles showed increase in the contractility with the progress of infection in both light and heavy infection. Significant myocardial dysfunction in the form of bradycardia, in addition to major histopathological changes in the heart occurred from the beginning of the infection and increased till the end of the study. Biochemical study showed gradual increase in serum cholinesterase, while, the intestinal MPO showed increase only in the early stage of the infection. It was noticed that all changes were more pronounced in the heavily infected group than the lightly infected one.