Development of type I cells of the rabbit subclavian glomera (aortic bodies): A light, fluorescence and electron microscopic study

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Abstract
The embryogenesis of the subclavian glomera (aortic bodies) is controversial. Past investigators have attributed the development of the Type I cells to mesodermal and/or neural elements. Based on the results of the present light microscopic, fluorescence histochemical and electron microscopic study of rabbit aortic bodies from 16 days of gestation (term: 31 days) to four days postpartum, it appears that the Type I glomus cells are derived from cells of neural crest origin. The subclavian glomus anlage is associated with cells of vagal origin throughout its development. Evidence of Type I cell development from pre-existing mesodermal condensations is not observed. Type I cells exhibit formaldehyde-induced-fluorescence by the twentieth day of gestation. Dense-cored cytoplasmic vesicles are apparent by the sixteenth day of gestation. The number of cytoplasmic vesicles increases steadily, but the greatest increase of vesicles is observed between the twenty-eighth day of gestation and birth. Primitive Type I glomus cells exhibit abundant polysomes and rough endoplasmic reticulum indicative of synthetic activity. Nerve terminals are apparent adjacent to Type I cells by the twentieth day of gestation, but synaptogenesis does not occur until sometime between the twenty-fourth and twentyeighth days of gestation. Abundant vascularity, characteristic of chemosensory glomera, is not achieved until the twenty-eighth day of gestation.