Specific Staining of Egg-Shell Material in Trematodes and Cestodes

The material which forms the egg-shell in trematodes is an orthodihydroxyphenol-protein complex (Stephenson, 1947) which originates in the cells of the so-called vitellaria (Dawes, 1946). It has been found that both malachite and methyl green in aqueous solution have a marked and specific affinity for this material after formolsaline fixation. The same was found to be true for the egg-shell material in pseudophyllidean cestodes. These stains thus provide the helminthologist with a simple method by means of which the process of egg-shell formation in these groups may be worked out.     

Susceptibility of neuroactive peptides to aminopeptidase digestion is related to molecular size.

Peptide fragments derived from the NH₂-terminus of corticotropin were found to exhibit widely differing degrees of stability to degradation by aminopeptidase M. Corticotropin itself was 135 times more stable than its NH₂-terminal pentapeptide, and similar differences in stability were observed with peptides derived from the B-chain of bovine insulin. Enkephalin linked covalently to the A-chain of bovine insulin was at least 100 times more stable than the pentapeptide. The results demonstrate that the molecular size of a peptide is one factor that determines its NH₂-terminal stability.