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item Fleming, Michael

Submitted to: Invertebrate Reproduction and Development
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/25/1994
Publication Date: N/A
Citation: N/A

Interpretive Summary: Understanding complex physiological processes that determine growth and development of an organism is inherently difficult. The level of complexity increases markedly when the biological system of interest involves an internal parasite. To ameliorate some of these difficulties, laboratory cultivation techniques have been developed to grow these parasites outside the host. One such system for the swine intestinal roundworm, Ascaris suum, has been adapted to examine minute quantities of potentially biologically active hormones, ecdysteroids. Previous work indicated that early, short-term exposure to these hormones enhanced growth and development. The current research indicates that effect does not extend later into development or for prolonged periods of exposure. Hence, temporal targeting of potential ecdysteroid antagonists as part of an anthelminthic strategy clearly is indicated.

Technical Abstract: A stationary, multi-well bioassay for growth and development of Ascaris suum larvae has proven markedly sensitive for the study of endocrinological and pharmacological substances. These experiments were designed to assess physical factors of the cultivation procedure (larval density and type of flask) as well as the temporal sensitivity of the larvae to growth stimulants. Larvae at lower density (100/ml) did not grow as quickly as larvae at higher density (400/ml). Large stationary flasks, irrespective of cap type, were similar in larval growth patterns. Addition of 20-hydroxyecdysone (20-OH) after the third molt had occurred had little effect on subsequent short-term or long-term development of the larvae. Therefore, the enhancement of larval growth by 20-OH appears to be limited to a specific narrow window 72 hr before molting occurs and is unlikely to constitute a generalized systemic effect.