STUDY OF THE NERVE-ENDINGS IN THE HUMAN T HYROID PARAFOLLICULAR CELLS

We studied nerve endings in the parafollicular cells of thyroid glands in necropsy examinations of 50 young males with no know thyroid disor der. The Jabonero and Maillet techniques, ultrastructural and morpholo gy study were performed together with a statistical analysis of nerve endings. Optic microscope visualized pre terminal and exceptionally te rminal nerve endings located near parafollicular cells. Swellings of t he axons without Schwann's cell sheath were identified close to the pa r follicular cells with electronic microscopy, these swellings had an ellipsoidal or spherical shape and laid close to the cellular membrane (30 nm). Three types of synaptic-like resides were found in these ner ve endings. a) Abundant clear vesicles, generally spherical in shape ( aver age diameter 50.40 +/- 5.91 nm); b) A few large granural al vesic les with an electron-dense core (average diameter 105.49 +/- 9.98 nm); and c) Several small granular vesicles with an electron-dens core (av erage diameter 55.09 +/- 6.56 nm). Emphasis should be given to the fin ding of nerve endings (cholinergic-like, adrenergic-like and peptiderg ic-like nerve endings) in the parafollicular cells. We discuss their p ossible function.