The Stichosome and Its Secretion Granules in the Mature Muscle Larva of Trichinella spiralis

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Abstract
The stichosome of the mature muscle larva of T. spiralis consists of a single row of 45-55 stichocytes. Each stichocyte is .apprx. 25 .mu.m in diameter and possesses a single nucleus. A duct leads from each stichocyte to the lumen of the esophagus. The stichocyte cytoplasm contains mitochondria, structures resembling Golgi-complexes, rough endoplasmic reticulum, and usually 1 of 2 types of secretory granules. The .alpha.-granule measures .apprx. 800 nm in diameter, contains a prominent inclusion, and has a granular matrix. The .beta.-granule is .apprx. 600 nm in diameter and is homogenous in appearance. Both granule types are surrounded by a single membrane. Ten to thirteen stichocytes containing .alpha.-granules are confined to the posterior portion of the stichosome. After isopycnic centrifugation in sucrose gradient of large granule fractions obtained from cell-free homogenates, the .alpha.- and .beta.-granules show characteristic distribution patterns as revealed by the morphology of the fractions. The median equilibrium density of the .alpha.-granules is 1.245, while that of the .beta.-granules is 1.230. There is a correlation between the distribution of the granules and of antigens reacting with hyperimmune anti-Trichinella serum. At least 4 unique antigens can be attributed to each of the granule types. Fractions enriched in mitochondria do not contain specific antigens. Antigens from both types of secretory granules cross react totally with those present in the excretion-secretion products of living muscle larvae. Cytoimmunochemical data show that antigens are distributed in a patchy fashion throughout the stichocyte cytoplasm, consistent with the distribution of the secretory granules in the intact stichocyte.