Date of Award

5-1-1982

Degree Type

Thesis

University or Center

Atlanta University (AU)

Degree Name

M.S.

Department

Biology

First Advisor

Gordon J. Leitch

Abstract

Axenically cultured Entamoeba histolytica trophozoites of the pathogenic strain HM-1 were harvested in phosphate buffered saline (PBS). The cells were disrupted with ultrasonic energy, centrifuged, and the supernatant fluid tested for enterotoxic activity in the i[n vivo rabbit ileum loop .and-the rat proximal colon loop. This HM-1 extract, equivalent to 106 trophozoites/ml, had no effect on intestinal absorption in either animal model, but secretion resulted in both preparations when indomethacin (0.1 mg/kg) was administered subcutaneously to reduce cytoprotection. In the rat colon a lower dose of indomethacin was ineffective in allowing the ameba preparation to cause frank secretion, while higher doses, 1 and 10 mg/kg, directly inhibited this secretory response. In the absence of indomethacin, a preparation equivalent to 107 trophozoites/ml reduced colonic absorption without producing secretion, while a preparation of 107 trophozoites/ml of the non-pathogenic E_. histolytica-like Laredo strain was ineffective even in the presence of 0.1 mg/kg indomethacin. The HM-1 enterotoxic activity was heat labile. Prior exposure of the loop lumen to fetuin (100 wg/ml) blocked the secretory response to subsequent enterotoxin exposure in indotnethacin-treated animals. Fetuin inhibition of secretion could not be reversed by inoculating the loop with fresh trophozoite extract at hourly intervals for 4 hours.

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Biology Commons

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