The ontogenetical development of the subcommissural organ (SCO) was investigated in chick embryos collected daily from the 1st to the 21st day in incubation. Some duck embryos, and adult chickens and ducks were also studied. Immunocytochemistry using an anti-Reissner's fiber (RF) serum as the primary antibody was the principal method used. In the chick embryos the events occurring at different days of incubation were: day 3 morphologically undifferentiated cells in the dorsal diencephalon displayed immunoreactive material (IRM); days 4 to 6 immunoreactive cells proliferated, formed a multilayered structure and developed processes which traversed the growing posterior commissure and ended at the brain surface; day 7 blood vessels penetrated the SCO, scarce hypendymal cells appeared, the first signs of ventricular release of IRM were noticed, appearance of IRM bound to cells of the floor of the Sylvius aqueduct; day 7 to 10 the number of apical granules and amount of extracellular IRM increased progressively; day 11 RF was observed along the Sylvian aqueduct, day 12 RF was present in the lumbar spinal cord; day 13 IRM on the aqueductal floor disappeared; days 10 to 21 hypendymal cells proliferated, developed processes and migrated dorsally, ependymal processes elongated and their endings covered the external limiting membrane. In adult specimens the ependymal cells lacked basal processes and the external membrane was contacted by hypendymal cells. the duck SCO appears to follow a similar pattern of development.
Abstract. Adenomas of the pars intermedia from 19 horses and normal pituitary glands from seven horses were evaluated histologically and immunocytochemically for adrenocorticotropic hormone (ACTH), a-melanocyte-stimulating hormone (a-MSH), &endorphin (@-END), proopiomelanocortin (POMC), prolactin, neuron specific enolase, and glial fibrillary acidic protein (GFAP). The 26 horses ranged in age from 7 to 31 years. Histologically, all adenomas had a uniform pattern characterized by cords of large columnar cells forming palisades and pseudoacini separated by a delicate fibrovascular stroma. Immunostaining of adenomas derived from the pars intermedia was similar to that of non-neoplastic equine pars intermedia. An immunocytochemical evaluation revealed a diffuse, strong cytoplasmic reaction for POMC, a moderate to strong reaction for a-MSH and (3-END, a weak reaction for ACTH, and negative immunostaining for prolactin, GFAP, and neuron specific enolase in the adenomas. The unique clinicopathologic syndrome that develops in horses with pituitary adenomas appears to be the result of an over-production of POMC-derived peptides in addition to space-occupying effects resulting in dysfunction of the hypothalamus and neurohypophysis.
The subcommissural organ (SCO)-Reissner's fiber (RF) complex of rats suffering from postnatal hydrocephalus was investigated immunocytochemically (peroxidase-antiperoxidase technique) by use of an anti-serum against bovine RF. Hydrocephalus was induced by injecting kaolin into the cisterna magna or by intracerebral infection with Borna disease virus. The kaolin-injected, hydrocephalic male rats were divided into two groups: (1) possessing an open communication between the fourth ventricle and the central canal of the spinal cord; (2) enduring an obliteration of this communication. In the latter group of rats the dilation of the ventricular cavities was far greater than in the former group. The Borna disease virus-infected female rats developed a severe hydrocephalus although in these animals all ventricular cavities and the central canal were in fully open communication. All rats belonging to the above-mentioned three groups displayed essentially the same alterations of their SCO-RF complex: (i) A reduction in the size of SCO and in the height of the ependymal secretory cells. (ii) A progressive disappearance of the immunoreactive hypendymal cells. (iii) The amount of AFRU-immunoreactive secretory material located in the rough endoplasmic reticulum was reduced. (iv) In contrast, the amount, location and immunoreactivity of the apical secretory granules did not undergo variations in comparison to sham-operated rats. (v) In the area of the SCO the layer of pre-RF material was thin or missing and a RF was not formed, and thus the central canal was also free of such secretory products. (vi) Clusters of AFRU-immunoreactive material were found attached to the wall of the Sylvian aqueduct.(ABSTRACT TRUNCATED AT 250 WORDS)
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