Ultrastructural Evaluation of Thyroid Parafollicular Cells of Pigs with Naturally Occurring Atrophic Rhinitis

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Abstract
The thyroid parafollicular cells of 4-month-old control pigs and pigs with naturally occurring atrophic rhinitis were evaluated ultrastructurally. Significant difference was not observed in populations of parafollicular cells between the 2 groups of pigs. Parafollicular cells occurred in actively synthesizing and storage phases of the secretory cycle in both groups. Actively synthesizing cells had a well-developed endoplasmic reticulum, aggregated ribosomes, and prominent Golgi apparatuses with prosecretory granules. The cytoplasm of parafollicular cells in the storage phase was packed with electron-dense secretory granules. The Golgi apparatus and ergastoplasm were less prominent. There was no evidence to suggest that an interference in the synthesis or release of thyrocalcitonin by parafollicular cells was of criologic importance in the pathogenesis of atrophic rhinitis.