We examined copper localization in the locus ceruleus and cerebellum of rat brain by Timm's sulfide-silver staining, as modified by Danscher. Dense silver particles revealing copper localization were observed in sections of the locus ceruleus and cerebellum after pre-treatment with trichloroacetic acid. In the locus ceruleus, copper appeared to be distributed to neuropil rather than glial or neuronal cell bodies, and at the ultrastructural level copper was mainly localized on synaptic membranes of afferent terminals in contact with somatic spines or dendrites of locus ceruleus neurons, whereas copper was distributed to mitochondria in the granular layers of cerebellum and fine, sparse silver particles were observed throughout ependymal cells and epithelial cells of blood vessels. The specific localization of copper to afferent terminals in the locus ceruleus was confirmed by X-ray microanalysis, which showed a significant level of copper, but not zinc, in synaptic membranes. These results suggest a distinct role of copper depending on its regional distribution. Copper or copper protein may be involved in neurotransmission in the locus ceruleus but in mitochondrial activity in the cerebellum.

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Identification and distribution of the precursors of amine-storage organelles in rat megakaryocytes during cell maturation were studied, using the uranaffin reaction for adenine nucleotide. The precursors of the amine-storage organelles appeared as 200-300 nm vesicles having an uranaffin electron dense granule, whereas they appeared as empty vesicles by conventional glutaraldehyde-OsO4 fixation. X-ray probe microanalysis confirmed the existence of U and P in the uranaffin reaction positive vesicles. The precursors appeared in the immature megakaryocytes, especially at the trans(mature) face of the Golgi apparatus, and rapidly increased in number in the maturing cells. The size of the uranaffin granules in the precursor organelles increased gradually during cell maturation and became almost equivalent to the dense body of blood platelets in the final stage of cell maturation.

This report describes the distribution and localization of thrombomodulin (TM) in the rat eye by light and electron microscopic immunocytochemistry. In addition to the endothelium of the entire vasculature, TM was found on the non-vascular structures lining the cavities of the posterior and anterior chambers and the limbus. TM was localized on the basal, lateral, and apical plasma membranes of the inner and outer ciliary epithelium, and the posterior iris epithelium in which there was no polarized expression of TM. In the anterior chamber, TM was localized on the luminal surface of the corneal endothelium, but was negative on the anterior border layer of the iris, which is composed of a discontinuous layer of fibroblasts and collagen fibers. Thus, TM was present at sites of cell-to-cell contact. TM was also present on the endothelia of the trabecular meshwork and the Schlemm's canal in the limbus. TM was localized not only on the luminal plasma membrane, but also on the cytoplasmic giant vacuoles in the endothelial cells of the Schlemm's canal. These findings extend the importance of anticoagulant mechanisms to the systems of secretion, circulation, and drainage of the aqueous humor.