Neural stem cell phenotype of tanycyte-like ependymal cells in the circumventricular organs and central canal of adult mouse brain.

Tanycyte is a subtype of ependymal cells which extend long radial processes to brain parenchyma. The present study showed that tanycyte-like ependymal cells in the organum vasculosum of the lamina terminalis, subfornical organ and central canal (CC) expressed neural stem cell (NSC) marker nestin, glial fibrillar acidic protein and sex determining region Y. Proliferation of these tanycyte-like ependymal cells was promoted by continuous intracerebroventricular infusion of fibroblast growth factor-2 and epidermal growth factor. Tanycytes-like ependymal cells in the CC are able to form self-renewing neurospheres and give rise mostly to new astrocytes and oligodendrocytes. Collagenase-induced small medullary hemorrhage increased proliferation of tanycyte-like ependymal cells in the CC. These results demonstrate that these tanycyte-like ependymal cells of the adult mouse brain are NSCs and suggest that they serve as a source for providing new neuronal lineage cells upon brain damage in the medulla oblongata.

Fine structural cytology of the rat subfornical organ during ontogenesis.

The main developmental events in the subfornical organ take place between 17 fetal days (fd) and 5 days post natum (dpn) at which time it possesses most of its mature fine structural characteristics. The surface regional characteristics of ependymal cells differentiate primarily during this time as well, while the ependymal cellular fine structure, shape and relationship with neurons and the vascularity are well established prior to birth. Undifferentiated neurons contain glycogen prior to 19 fd and then differentiate by developing processes and organelles characteristic of neurons. By 5 dpn, the various types of neurons found in the mature subfornical organ are all present, except for giant vacuolated cells. Synapses containing only electron-lucent vesicles are first present at 20 fd, those containing additional electron-dense vesicles at 3 dpn. Microglial cells are first identifiable at 17 fd, and the first protoplasmic astrocytes are recognizable at 21 fd, while fibrous astrocytes are not detectable prior to 7 dpn. By 5 dpn, the cytological elements of the subfornical organ are all in place, and further developmental changes leading to adult fine structural characteristics by 30 dpn are essentially quantitative in nature.

Increased number of angiotensin II receptors in the subfornical organ of spontaneously hypertensive rats.

Angiotensin II receptors were studied in the brain of spontaneously hypertensive rats (SHR) and their normotensive controls, Wistar-Kyoto rats (WKY) by quantitative autoradiographic methods coupled to computerized microdensitometry and comparison with 125I-standards, after incubation of brain sections with 125I-Sar1-angiotensin II. Binding sites for angiotensin II were highly localized in the subfornical organ. The number of binding sites was higher in the subfornical organ of young (4-week-old) and adult (14-week-old) SHR when compared with WKY rats (young rats: 735 +/- 91 and 444 +/- 85 fmol/mg protein, SHR and WKY, respectively; adult rats: 1390 +/- 64 and 848 +/- 136 fmol/mg protein, SHR and WKY, respectively). Our results suggest that subfornical organ angiotensin II receptors are involved in genetic hypertension in the rat. An increased number of subfornical organ angiotensin II receptors substantiates the idea of an overactive central angiotensin II system in spontaneous hypertension.

Acetylcholinesterase activity during the ontogenesis of the subfornical organ of the rat.

From 16 to 18 days of fetal life (fl) the subfornical organ (SFO) of the rat shows diffuse acetylcholinesterase (AChE) activity. From 21 fl its definitive pattern begins to be organized and is achieved at 30 days of postnatal life (pl). This pattern is characterized by a homogeneous AChE activity in the rostral region, a ring-like distribution in the anterior medial region and a hoof-like distribution in the posterior medial region. The caudal region shows intense, uniform activity. From the rostral region two tracts emerge, ventral and dorsal, that extend to different diencephalo-telencephalic areas. From the SFO caudal region another tract emerges that extends to posterior areas.

[Comparison of the intraspecific growth of the endocranial organs (hypophyseal lobes, pineal gland, SFO) in the white Wistar rat. Rattus norvegicus (Berkenhout), with their interspecific growth in the rodents]. / Comparison de la croissance intraspécifique des organes endocraniens (lobes hypophysaires, glande pinéale, OSF) du rat blanc Wistar Rattus Norvegicus (Berkenhout) avec leur croissance interspécifique chez les rongeurs

The intraspecific growth of various endocranian organs (hypophysis, pineal gland and SFO) in the Rat compared to a group of Rodents shows that their allometry coefficient/somatic weight is : close to isometry for the anterior and intermediate lobes of the hypophysis which is suitable for endocrine glands; lower and close to that found for the relation brain weight/somatic weight for the nervous lobe in the Rat and in Rodents; and extremely low (0,33) for the SFO in the Rat, which is comparable to that found in Rodents (0,44). The allometry coefficient found for the pineal gland is not comparable to that found in Rodents (1,25). Many facts (important intra and interspecific variations, existence of species or individuals deprived of pineal gland) seem to indicate that this gland is not related to an essential somatic function.

Development of the subfornical organ and area postrema of the male albino mouse. Karyometric effect of neonatal and prepuberal castration.

We have studied the karyometric development of the nuclei of the ependymal cells and neurons of the subfornical organ and the area postrema in the male albino mouse from the 5th to the 190th postnatal day. We have found similar patterns of development in both although the area postrema showed more significant postnatal oscillations than those of the subfornical organ, suggesting a more intimate chronological relationship to gonadal development. We have furthermore analyzed the development in two experimental groups: in the one animals were castrated at birth, in the other, castration was made on the 20th postnatal day. We have found that neonatal castration produced a significant decrease of nuclear sizes; this was more evident in the subfornical organ than in the area postrema in earlier stages of development while the response was similar in both at peripuberal ages. The response to prepuberal castration was similar in both organs.