ULTRASTRUCTURE OF THE DISCONNECTED PARS NERVOSA OF THE CRESTED NEWT (TRITURUS CRISTATUS CARNIFEX LAUR)

SUMMARY The morphological changes in the pars nervosa of the crested newt caused by transection of the hypothalamic floor just in front of the median eminence, were studied at various postoperative intervals. One to 2 days after the operation some dense bodies can be observed within the neurosecretory fibres. However, the most conspicuous changes are detectable after 4 to 7 days. Neurosecretory fibres, appear heavily electrondense as the elementary granules become more densely packed. The fibres often break into fragments and appear widely separated from one another, modifying the general pattern of the pars nervosa. Both ependymal cells and pituicytes are characterized by a strong macrophagic activity towards degenerating nerve fibres which often appear to be engulfed by them. Myelin-like formations containing vacuoles, empty vesicles and dense granules (1200–2000 A in diameter) can be observed among the nerve fibres. Pituicytes, generally rare in the normal animal, show an apparent increase in their num...