Morphological studies of marginal nuclei in chicken spinal cord.

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Marginal nuclei (MN) consist of 3 subnuclei, major (Mj), minor (Mn) and ventral (V) marginal nuclei. We observed light and electron microscopically marginal nuclei. Mn were segmentally located in the lateral column. Mj consisted of the white matter and projected parts and the adjoining white matter parts overlaped partly in distribution. Neurons in Mn and Mj were medium in mean size and in V were large. Appearance of Nissle substances correlated with the size of neurons. Small-sized neurons included a few small clusters of nissle substance separated from one another. Cytoplasm of medium-sized neurons included plenty of rER and free ribosomes that consist of Nissle substance but the Nissle substance did not form cluster or block. In large-sized neurons Nissle substance had the form of large blocks separated from one another.Presynaptic boutons on their somata and dendrites of marginal nuclei neurons were divided according to the shape of synaptic vesicles. There were 4 types of presynap … More tic boutons, S type characterized by clear and spherical vesicles, SG type characterized by clear and spherical vesicles plus granular vesicles, SF type characterized by clear and spherical vesicles plus clear and flattened vesicles, and SFG type characterized by the above mentioned 3 types of vesicles. S type occurred most frequently. There were not significant differences in the frequency of these type of presynaptic boutons among the subnuclei.Based on the morphology, we suggested that Mn and Mj may be the same functional significance but different from V.The white matter and projected parts of Mj may be the same functional significance.Astrocytes in MN had pecliar structures. Mj and V included a large amount of glycogen containing astrocytes. These glycogen containing astrocytes ranged in structure from glycogen body cells to fibrous astrocytes. Astorocytes with a few processes and markedly dilated cisterns of rER distributed in Mn and Mj. Although Mn appeared to be gray matter, astrocytes in Mn were fibrous type.Axons of MN neurons in the lumbosacral intumescence terminated in the rostral various levels below the cervical intumescence and axons of MN neurons in the cervical one terminated in the various caudal levels above the lumbosacral one Less