Growth and cuticular synthesis in Ascaris suum larvae during development from third to fourth stage in vitro.

Growth, molting and cuticular protein synthesis were determined during the development of Ascaris suum grown in vitro from the third (L3) to the fourth (L4) larval stage. The larvae remained highly viable (90%) and 70% reached the L4 by 7 days in culture (DIC). Analysis of growth and development indicated that ecdysis was asynchronous. The synthesis of noncuticular and cuticular proteins was monitored using 35S-methionine as a metabolic label. Synthesis of noncuticular, cuticular and collagenous cuticular proteins increased in a constant manner, reaching maximal values at about 6 DIC. Synthesis of noncollagenous cuticular proteins (cuticlin) remained relatively constant during most of the culture period, but increased from 6 to 7 DIC. The increase in cuticlin synthesis and the corresponding decrease in cuticular collagen synthesis noted at 7 DIC might represent the synthesis of the outer portions of the adult cuticle in preparation for the fourth molt. The results of this study suggest that this in vitro development system for A. suum, while not suitable to study events regulating the precise timing of molting and cuticular synthesis, might be useful for the analysis of potential growth regulators.