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Quarterly Journal of Microscopical Science, Vol s3-96, 57-71, Copyright © 1955 by Company of Biologists
1 Department of Anatomy, Harvard Medical School, Boston 15, Mass., U.S.A.
The properties of the amoebocytes and intestinal epithelium of Venus mercenaria were studied by a variety of cytochemical procedures designed to demonstrate proteins, enzymes, carbohydrates, and lipids.
The cytoplasm of the amoebocytes contains specific granules which are constantly present and which are interpreted as being atypical mitochondria. Identification of their mitochondrial nature rests on their staining with Janus green B, their positive reaction for phospholipid by Baker's test, and the presence of dehydrogenase activity. Unlike typical mitochondria, the specific granules are eosinophil. Protein-bound carbonyl groups and disulphide and sulphydryl groups are present in both the specific granules and the cytoplasm. The sulphydryl groups may in part be associated with the presence of dehydrogenase, lipase, and serum cholinesterase. Amoebocytes also ontain glycogen and a material that is resistant to diastase and positive to the periodic acid / Schiff test; this material may be a neutral polysaccharide, unsaturated lipid, or mucoprotein.
Cytoplasmic structures which are inconstantly present in amoebocytes include sudanophil droplets, neutral red vacuoles, metachromatic granules, and granules of an excretory pigment resembling ceroid. The sudanophil droplets may be stored neutral fat or lipid associated with the Golgi apparatus. The neutral red vacuoles are not preformed inclusions, but form as the dye accumulates within the cells. Metachromatic granules, which are confined solely to the intestinal amoebocytes, consist of phagocytosed intestinal mucus liberated from goblet cells.
The histochemical reactions of the columnar intestinal epithelium suggest that these cells may be active in the digestion and absorption of nutrients, since eosinophil granules, lipid droplets, alkaline phosphatase, lipase, and serum cholinesterase are present in them.
Masses of a ceroid-like excretory pigment and goblet cells containing mucus are present between the columnar intestinal epithelial cells. The pigment contains phospholipid and apparently arises as an oxidized end-product of lipid metabolism.
