SECRETION OF TRYPSIN IN THE OESOPHAGUS OFNEREIS VIRENSSARS (POLYCHAETA: ERRANTIA). A BIOCHEMICAL AND HISTOLOGICAL STUDY

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Abstract
1. The sites of production of a specific digestive enzyme, trypsin, were examined in the digestive tract of the polychaete Nereis virens. Additional histochemical and ultrastructural observations were also made. 2. Homogenates of pharynx, oesophagus with caeca and anterior intestine were incubated with N-CBZ-diglycyl-arginyl-4-methoxy-β-naphthylamide at pH 8.2. Reaction product was coupled with Fast Blue B at pH 5.3 and analysed spectrophotometrically at 530 nm. Only extracts of oesophagus with caeca exhibited high tryptic activity, and the reaction was inhibited in the presence of phenylmethyl-sulfonylfluoride and N-α-p-tosyl-L-lysine-chloromethyl ketone. 3. Two types of glandular cells were distinguished in the anterior oesophagus and proximal part of the caeca after histological and histochemical stainings. Mucous glands were present. Serous glands demonstrated a granular secretion which stained histochemically like that of vertebrate pancreatic exocrine cells and showed a cyclic activity parallel with the digestive cycle of the annelid. 4. The ultrastructural aspects of the serous glandular cells were examined and compared with the glandular cells of the pharynx of another polychaete, Eulalia viridis, and with vertebrate pancreatic exocrine cells.

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