No abstract

The distribution of radioactivity in association with sympathetic nerve terminals and intraneuronal organelles 30 min after the administration of tritiated norepinephrine (NE 3H) was studied by electron microscope radioautography with recently developed quantitative methods of analysis reported in the accompanying paper (Salpeter et al ., 1969) . Nerves from the pineal body and the adrenal capsule were examined . It was found that nerve terminals containing vesicles were heavily labeled . (These terminals were not necessarily in contact with some innervated structure .) There was no selective labeling of either the intraneuronal mitochondria or the relatively small population of large (1000 A) dense core granules . Small vesicles (--500 A), some of which have a dense internal granule, could not be analysed separately because they are closely packed and occupy -60% of the volume in terminals . Because of the extensive distribution of these small granular and agranular vesicles in the radioactive terminals, they remain the most likely site for norepinephrine binding . Yet although the vesicles were uniformly distributed within the nerve terminals, it appears that the radioactivity was not . There appeared to be a somewhat higher concentration of radioactivity at the periphery of the nerve terminals than in the center . The usefulness of the method of analysis used in this study for determining the location of bound H 3NE pools in the nerve is discussed .

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Immunocytochemistry using peroxidase antiperoxidase (PAP) techniques showed insulin-like immunoreactivity in the human retina, and in the mouse retina and optic nerve. The immunoreaction product was seen in the inner nuclear, ganglion cell, outer and inner plexiform layers of the retinas, and in glial cell bodies of the optic nerve. A similar staining pattern using antiserum to S-100 protein, a marker for glial elements, was also seen in these tissues. This demonstrates that insulin or insulin-like immunoreactivity appears to be limited to glial cells of the retina and optic nerve. Our study suggests that the presence of insulin or a similar peptide in retina and optic nerve may be important for their normal function and metabolism.