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The fidelity of the regenerative response in the adult newt, Notophthalmus viridescens, was examined following repeated amputations at the level of the distal one-third of humerus. Three to four months following amputation, all regenerates were scored for gross morphology, reamputated, and stained with methylene blue for skeletal elements. The occurrence of abnormal regeneration with respect both to gross morphology and to skeletal structure was found to increase directly with the number of times the limb stumps were required to initiate dedifferentiation and repair. The initial amputation-regeneration process produced structurally normal replacement limbs in 91% of the cases examined. Reamputations of 4-digit regenerates (3--4 months after the previous transection) resulted in structurally abnormal regenerates in 28% of the cases following two amputations; 50% of the cases following three amputations; 65% of the cases following four amputations; and 81% of the cases following five amputations. The relationships between repeated dedifferentiation, proliferation, and redifferentiation and normal limb development are discussed.

Leucine aminopeptidase (LAP) activity has been measured in extracts of eggs, miracidia, cercariae and adult worms of Schistosoma mansoni. Activity measured at pH 7.2 using L-leu-7-amino-4-trifluoro-methylcoumarin as substrate is 6- to 17-fold greater in eggs than in other life stages. LAP activity is also high in soluble egg antigen preparations and in hatching fluid. The release of LAP from eggs parallels hatching, and inhibitors of LAP also inhibit hatching. The possible role of LAP in the hatching process of S. mansoni eggs is discussed.