鳥類脳下垂体後葉の微細構造

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The structure of the pars nervosa of normal and dehydrated pigeons was studied by means of the light-and electron microscope. Ten adult pigeons (Columba livia domestica) of both sexes were divided into 2 groups: one group comprising 4 birds was kept under the standard diet conditions (control), while the other consisting of 6 birds was given a 0.5M NaCl solution as drinking water, for 5 days before sacrifice. For study with the light microscope, the pars nervosa was fixed in Bouin's solution, embedded in paraffin, sectioned at 10μ and stained by the paraldehyde-fuchsin method (Gomori, 1950). For the electron microscope study, the pars nervosa was fixed in Dalton's fixative (Dalton, 1955) with pH adjusted at 7.4, for 2 hours, dehydrated in graded series of ethanol, embedded in a mixture of n-butyl methacrylate and methyl methacrylate (8.5:1.5) and observed with the JEM-T6 electron microscope. In sections stained with paraldehyde-fuchsin, the pars nervosa of the control birds showed a dense accumulation of neurosecretory substance (Fig. 1), whereas that of the dehydrated birds was almost devoid of the substance (Fig. 2). Electron micrographs of the pars nervosa of the controls exhibited among glial cells many non-myelinated neurosecretory axons containing mitochondria, two kinds of synaptic vesicles and two kinds of neurosecretory granules; they also exhibited non-neurosecretory axons bearing mitochondria and synaptic vesicles but no neurosecretory granules (Fig. 3). The size distribution of these granules and vesicles is shown in Figure 4. Some of the processes of the glial cells ended near blood capillaries and were penetrated by neurosecretory axons (Fig. 5). This fact seems to suggest an intimate relationship between the glial cells and the neurosecretory axons. A neurosecretory axon penetrating into the nucleus of an oligodendrocyte was observed (Fig. 6). Some neurosecretory granules changing into lamella-like structure were also encountered (Fig. 7). In the pars nervosa of dehydrted pigeons, most of the electron-dense neurosecretory granules had disappeared, however synaptic vesicles and "empty" granules each with an electron-lucent center surrounded by an electron-dense membrane remained (Fig. 8). The diameter range of the granules and synaptic vesicles in dehydrated pigeons was the same as that in control pigeons (Fig. 4). However, both the neurosecretory granules and the synaptic vesicles were decreased in number in dehydrated birds. Moreover, "empty" granules with broken menbranes were occasionally obseved (Fig. 8, T). But neurosecretory granules located outside the cells, or those migrating into thick connective tissue spaces around capillary cavities have never been observed. Therefore, it seems likely that, at the time of release of the neurosecretory substance into the blood vascular system, the contents of neurosecretory granules become "liquefied".
社団法人日本動物学会の論文
1962-07-15

鳥類脳下垂体後葉の微細構造

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