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Ultrastructure of the Pineal Body of the Domestic Chicken, with Special Reference to the Changes Induced by Altered Photoperiods

1968; Volume: 29; Issue: 3 Linguagem: Inglês

10.1679/aohc1950.29.271

0004-0681

Eiichi Fujie,

Mitochondrial Function and Pathology

The ultrastructure of the pineal body of the domestic chicken was studied with the electron microscope. Morphological changes of this organ due to exposure to long or short photoperiods for 9 weeks were examined and discussed in connexion with melatonin secretion and altered growth of the gonad.The parenchyma of the chicken pineal body consists of three cell types: the pinealocytes, main constituents of this organ probably derived from the neuron, the supporting cells, probably of ependymal origin, and the glial cells.The pinealocyte is shaped like a flask, having a small round head, a narrow neck and a large round body. Into the central cavity of the pineal lobule extends the head from which a cilium projects. The cilium expands considerably but contains no particular internal structure. Nine pairs of axial filaments radiate along the surface of the swollen cilium. In some cases myelin-like membranes are formed by superimposition of partially flattened cilia.The head and neck are filled with many longitudinally arranged microtubules but have no mitochondria. The neck is surrounded by a thickened plasma membrane resembling the terminal bar of the epithelium. The round cell body contains a nucleus, a supranuclear aggregate of mitochondria, rough endoplasmic reticulum, and Golgi apparatus. Small granules about 700Å in diameter, resembling the socalled cored synaptic vesicles, are thought to contain the pineal hormone, melatonin. They are contained in the cell body and processes, and considered to be produced in the Golgi apparatus.The pinealocytes of chickens reared in long photoperiods have a greater amount of cytoplasm which contains an increased number of small granules, lysosomes and lipid droplets. A few basal processes extend from the bottom of the cell body toward the periphery of the lobule. These processes often contain small granules and characteristic synaptic ribbons.The supporting cells intervene among the pinealocytes and make the littoral region of the central cavity. The cytoplasm is clear and contains dark granules of various sizes. Irregularly shaped microvilli extend from this cell surface into the central cavity. The glial cells often contain many filaments and are situated in the peripheral part of the lobule.The interlobular connective tissue separated by the basement membrane from the parenchyma contains blood capillaries with a fenestrated endothelium and unmyelinated nerve fibers. The latter is considered to be of the sympathetic system and contains many cored synaptic vesicles about 500Å in diameter. The cores of these synaptic vesicles decrease in number in the chickens reared in long photoperiods, but are numerous in those reared in short photoperiods.