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ELECTRON MICROSCOPIC OBSERVATION ON THE HYPOTHALAMO-HYPOPHYSEAL SYSTEM IN THE RAT II. ULTRAFINE STRUCTURE OF THE MEDIAN EMINENCE AND OF THE NERVE CELLS OF THE ARCUATE NUCLEUS

1967; Japan Endocrine Society; Volume: 14; Issue: 2 Linguagem: Inglês

10.1507/endocrj1954.14.158

2185-6370

Takashi Kobayashi, Takuro Kobayashi, Kōichi Yamamoto, Manabu Kaibara, Yuzuru Kameya,

Biochemical effects in animals

Ultrafine structure of the median eminence was examined with the electron microscope in adult female normal and castrated rats. In the internal layer of the median eminence there are many un-myelinated and a few myelinated nerve fibers. The un-myelinated nerve fibers contain in their axoplasma numerous granules and vesicles, the diameter of which varies from 40 to 340mμ. The diameter of vesicles with the largest population measures 60-80mμ. Electron dense granules show two peaks in their size distribution histogram, a major one at 100-140mμ and a minor one at 220-240mp. In the external layer, too, both in its middle portion and in its peripheral contact region, a number of nerve fibers containing granules and vesicles are found. Nerve fibers in this layer are exclusively un-myelinated. The granules and vesicles found in this layer are much more in number and distributed in a narrower size range than those in the internal layer. The largest population have the dense granules and the vesicles the diameter of which measure 120mμ-160mμ and 80-120mμ respectively. Small vesicles resembling synaptic vesicles are also abundantly found. Two weeks after castration, small vesicles in the internal layer are slightly decreased in number, while in the external layer small dense granules (less than 120mμ in diameter) and small vesicles (60, -120mμ) are markedly increased. The number of larger dense granules remained almost unchanged both in the internal and in the external layer. Furthermore, the fine structure of the cells of arcuate nucleus was studied in normal rats. Besides well developed endoplasmic reticula and Golgi apparatus, small electron dense granules measuring about 100mμ in diameter are not infrequently found in the cytoplasm, in particular, in the vicinity of the Golgi apparatus. Possible significance of the findings observed was discussed.