Ultrastructural characterization of the accessory lobes of Lachi (Hofmann's nuclei) in the nerve cord of the chick. II. Scanning and transmission electron microscopy with observations on the glycogen body

Abstract

The ultrastructure of the accessory lobes of Lachi (Hofmann's nuclei) and that of the glycogen body were studied by transmission and scanning electron microscopy in 1-day-old chicks. Glycogen cells of the accessory lobes appeared like those of the glycogen body with nuclei of similar form which were flanked by organelles and by glycogen. The predominant cell type in each structure possessed glycogen-filled processes which were in contact with those of neighboring cells and with blood vessels throughout the tissue. The primary difference between the tissues is that the glycogen cells of the accessory lobes are associated with an extensive meshwork of nerve cells of the marginal nerve nuclei. Glycogen processes of accessory lobe cells appeared to intertwine with each other in such fashion as to completely envelop the multipolar nerve cells that are embedded in those structures. Axo-somatic and axo-dendritic synapses, as well as lamellar whorls were also noted in the vicinity of the perikarya of these nerve cells. The glycogen body and accessory lobes contained extensive extracellular spaces which when viewed by scanning electron microscopy appeared as sinusoid-like networks of channels between the glycogen cells and their processes. The close proximity of these glycogen-rich structures in the lumbosacral nerve cord and the morphological similarities shared by their cell types suggest that they have some specialized functional relationship within the avian nervous system. '

Ultrastructural characterization of the accessory lobes of Lachi in the lumbosacral spinal cord of the pigeon with special reference to intrinsic mechanoreceptors

“…However, glycogen cells issue two types of processes that are free of organelles: processes with dense material near the pial border of accessory lobe or glycogen body and in the lacunae of the accessory lobes and processes with light cytoplasm, which often form whorls wrapped around profiles of glycogen cells. Such whorls seem to be more typical of accessory lobe glycogen cells (De Gennaro and Benzo, 1978;Uehara et al, 1982;Schroeder and Murray, 1987; present investigation) than of glycogen body cells (Paul, 1973).…”

“…The large amount of synaptic contacts means that the neurons are under strong neural control. As shown previously (De Gennaro and Benzo, 1978;Schroeder and Murray, 1987), synaptic vesicles are typically round and clear, and synaptic densities are asymmetrical, with a prominent postsynaptic density. This points to a predominantly excitatory input (Peters et al, 1976).…”

The blood-brain barrier of the chick glycogen body (corpus gelatinosum) and its functional implications

“…However, the size of the glycogen body and its organ-like separation from the spinal cord seem to exclude this possibility. DeGennaro and Benzo (1978) observed local enlargements of the intercellular space between glycogen body cells by transmission and scanning electron microscopy. Our results confirm the existence of a wide cisternal system which communicates with the intercellular clefts.…”