Characterization of the accessory layer of the cuticle of muscle larvae of Trichinella spiralis.

The accessory layer of the cuticle of infective larvae of Trichinella spiralis has been studied with electron microscopy using cytochemical techniques and chemical extractions. The accessory layer lacks negative charges and carbohydrates demonstrable in vivo. Staining with ruthenium red and tannic acid is interpreted as being consistent with their reactions with phospholipids. Freeze fractures demonstrate an external layer of granules that can be partially released by means of detergents (CTAB and SDS). The granules are considered to be proteins. Their removal makes the worms acid sensitive and prevents them from infecting mice. Extraction of whole worms with ethanol, acetone and methanol (via reaction with 2,2-DMP), or chloroform and methanol destroys an internal layer of filaments. Thin-layer chromatography of chloroform/methanol extracts showed principally ethanolamine phospholipids from the surface of the worms. A model is presented for the molecular organization of the accessory layer. Ethanolamine phospholipids are suggested to occur as tubular micelles. Proteins may attach to these by lipophilic moieties and perhaps by a cryptic sugar group (demonstrated by others) that may penetrate into the hydrophilic core of the lipid micelles.