ISSN:
1432-0878
Keywords:
Crested newt
;
Pars nervosa
;
Electron microscopy
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary In the crested newt, the ultrastructural organization of the pars nervosa is analogous to that already known in non-mammal tetrapods. An orderly array of ependymal cells makes up the inner limiting layer while less abundant pituicytes are irregularly distributed within this organ. “Light” and “dark” pituicytes can be distinguished on the basis of the relative density of the cytoplasmic matrix and the distribution of the cell organelles. Both the ependymal cells and pituicytes are rich in dense bodies and possess extensive processes which ramify among the nerve fibers, often reaching the pericapillary space which they can line for long distances. The main components of the pars nervosa are nerve fibers and nerve terminals (type A), containing electron dense granules 1200–2000 Å in diameter together with clear vesicles averaging 250–400 Å. These fibers are likely to correspond to the aldehyde fuchsin positive neurosecretory fibers revealed by light microscopy. Differences in the granule size within the fibers and terminals lead to further recognition of two subgroups (A1 and A2). Other fibers and terminals (type B) containing clear vesicles and granular vesicles 600 to 1000 Å in diameter, possibly of aminergic type, are also encountered. These fibers are rare and can be seen only in the portion of the pars nervosa near the pars intermedia of the adenohypophysis. Lastly, fibers and terminals containing only clear vesicles ranging from 250 to 400 Å (type C) are occasionally found. Nerve endings are often formed by type A fibers on the perivascular space and on the perivascular processes of the ependymal cells and pituicytes. In agreement with recent findings available in the literature, the occurrence of synaptoid contacts between these terminals and both pituicytes and ependymal cells may confirm the active role of these cells in transport and release of neurosecretion.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00307172
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