Presence of calmodulin and NADPH-diaphorase activity but not of neuronal nitric oxide synthase in the subcommissural organ of the Mongolian gerbil.

The subcommissural organ (SCO) and the ventricular ependyma of the third ventricle of the Mongolian gerbil (Meriones unguiculatus) exhibit a highly positive histochemical reaction to NADPH-diaphorase and a considerable immunocytochemical expression of calmodulin. The SCO, however, does not display an immunocytochemical response to the neuronal isoform of nitric oxide synthase (NOS) whereas it was demonstrated in the ventricular ependyma. Since the NADPH-diaphorase, which detects all isoforms of NOS, was clearly positive at the level of the SCO, the obtained results suggest that the SCO of the Mongolian gerbil produces nitric oxide but contains a NOS whose antigenic specificity differs from that of the neuronal isoform of this enzyme.

Differential immunocytochemical staining for glial fibrillary acidic (GFA) protein, S-100 protein and glutamine synthetase in the rat subcommissural organ, nonspecialized ventricular ependyma and adjacent neuropil.

Antibodies raised against glial fibrillary acidic protein (GFA), S-100 protein (S100) and glutamine synthetase (GS) are currently used as glial markers. The distribution of GFA, S100 and GS in the ependyma of the rat subcommissural organ (SCO), as well as in the adjacent nonspecialized ventricular ependyma and neuropil of the periaqueductal grey matter, was studied by use of the immunocytochemical peroxidase-antiperoxidase technique. In the neuropil, GFA, S100 and GS were found in glial elements, i.e., in fibrous (GFA, S100) and protoplasmic astrocytes (S100, GS). The presence of S100 in the majority of the ventricular ependymal cells and tanycytes, and the presence of GFA in a limited number of ventricular ependymal cells and tanycytes confirm the glial nature of these cells. The absence of S100, GFA and GS from the ependymocytes of the SCO, which are considered to be modified ependymal cells, suggests either a non-astrocytic lineage of these cells or an extreme specialization of the SCO-cells as glycoprotein-synthesizing and secreting elements, a process that may have led to the disappearance of the glial markers.

Angiotensin-converting enzyme in discrete areas of the rat forebrain and pituitary gland.

With the use of a sensitive radioisotopic method we have examined the activity of the angiotensin-converting enzyme (ACE, E.C. 3.4.15.1) in specific nuclei of the rat forebrain and in the anterior, intermediate and posterior lobes of the pituitary gland of the rat. We reported that ACE activity is heterogeneously distributed in the rat forebrain, with a 200-fold difference between the lowest and the highest values. Highest enzyme activities were found in the subfornical organ and in the posterior lobe of the pituitary gland. High ACE activity was also detected in the intermediate and anterior lobes of the pituitary gland, the caudate nucleus, and the medial habenular nucleus. Substantial activity also existed in the globus pallidus, the median eminence, the supraoptic and paraventricular nuclei, the lateral habenular nucleus and the organon vasculosum laminae terminalis. Our results demonstrate that one of the components of the renin-angiotensin system, the angiotensin-converting enzyme, is highly localized to a few discrete brain structures and the pituitary gland. These findings suggest that angiotensin II could be formed locally in some of these structures, supporting previous immunohistochemical data.

Immunohistochemical localization of catechol-O-methyltransferase in circumventricular organs of the rat: potential variations in the blood-brain barrier to native catechols.

Catechol-O-methyltransferase (COMT) was localized in the organum vasculosum of the lamina terminals, subfornical organ, subcommissural organ and area postrema of rat brain using an indirect immunofluorescence technique. COMT immunofluorescence was apparent in neuroglia within the organum vasculosum and was most intense in the ependyma between this structure and the optic recess of the third ventricle. In both the subfornical organ and the area postrema, COMT was localized in a neuroglial network, but was noticeably absent in the ependymal layer. COMT immunofluorescence in the ependyma of the subcommissural organ was continuous with the more intense immunofluorescence of the cuboidal ependyma of the third ventricle. Each of the circumventricular organs studied, with the exception of the subcommissural organ, lies outside the blood-brain barrier. However, the unique pattern of COMT immunofluorescence in the area postrema and the subfornical organ suggests that these two structures, of all circumventricular organs, are most likely to permit the entry of peripherally circulating catechols to the cerebrospinal fluid.

[Histophysiologic characteristics of the subcommissural organ during isolated suppression of the functional activity of the zona glomerulosa of the adrenal gland]. / Gistofiziologicheskaia kharakteristika subkommural'nogo organa mozga v usloviiakh izolirovannogo podavleniia funktsional'noi aktivnosti klubochkovoi zony nadpochechnika.

The effect of prolonged administration of heparin on the histophysiological characteristics of the subcomissural organ (SCO) of the brain and adrenal glomerular zone (AGZ) was studied in 30 male rats. It was established that heparin inhibits the functional activity of AGZ adrenocorticocytes. This is associated with the lowered content of 3-beta-ol-steroid dehydrogenase, RNA, total protein, and a decrease in the zone width (by 50%). Ependimocytes of brain SCO show an abruptly reduced activity of glutamate dehydrogenase, NAD-dependent alpha-glycerophosphate dehydrogenase, lactate dehydrogenase acid phosphatase, which is evidence of their secretory function inhibition. The changes indicate the presence of the functional relationship between the ependimocytes of brain SCO and AGZ adrenocorticocytes as well as to the participation of brain SCO in AGZ function control.

Secretory activity and histoenzymological characteristics in the subcommissural organ of hormone-injected ducks, Anas platyrhynchos.

Gonadotrophin and gonadal hormone injections performed on male ducks induce some changes in the activity of the subcommissural organ (SCO). Particularly LH, FSH and testosterone propionate injections are followed by a depletion of secretory material accompanied by increased activities of investigated dehydrogenases and acid phosphatase in SCO cells.

Effects of light and of testosterone derivatives or antiandrogens on the secretory content of the subcommissural organ of the quail, Coturnix coturnix japonica.

Photosensitivity of the quail subcommissural organ (SCO) is demonstrated. When the birds are submitted to continuous light the SCO cells appear depleted in secretory material and the enzyme activities investigated are of greater intensity. Such a diminished secretory content is observed in birds exposed to short daylength when they are injected with testosterone derivatives. Besides, injections of antiandrogenic compounds in continuously illuminated quails abolish the decrease of the secretory material induced by photostimulation. These results indicate that the SCO responsiveness to light appears to be mediated by some hormonal mechanism. Moreover it is more than a generalized metabolic effect: the response to antiandrogen injections suggests indeed that the SCO is a likely target organ for hormonal action.

The subcommissural organ of submammalian vertebrates: a histochemical study.

Since morphological data do not allow to draw conclusions concerning the phyletic evolution of the subcommissural organ (SCO), a "metabolic" criterion is considered. Histoenzymology permits a comparison of metabolic activity in the subcommissural organ and that found within the ependyma. During the course of phyletic evolution, one notes various changes. Indeed, in lower vertebrates, the SCO presents a greater degree of enzyme activity than the ependyma while in birds the ependyma demonstrates a more intense activity than the SCO. The results are also compared with those previously reported in reptiles and mammals. In all vertebrates, glucid catabolism seems predominent in this areas.

[Histochemical study of the subcommissural organ in chickens during development]. / Etude histochimique de l'organe sous-commissural du Poulet au cours du développement.

Some histochemical and particularly histoenzymological tests are performed on the subcommissural organ of chick embryos. A secretory activity appears about the 7th day. In 10 days old embryos and new hatched chicken the enzyme activities are of rather low intensity. Compared with the 10 days embryos, the newborn show some increase, but compared with the adult birds the activities remain weak. However the acid phosphatase activity is higher in the subcommissural organ than in the ependyma even in 10 days embryos.

Enzymatic organization of the subcommissural organ.

In the subcommissural organ (SCO) of the guinea pig, rat, golden hamster, and mouse the activity and distribution of enzymes related to the energy-supplying metabolism and of some marker enzymes of different cell organelles have been investigated by means of mostly modified histochemical methods. The results were compared with findings in the ciliated ependyma of the ventricular wall and with those in the ependyma of the choroid plexus of the third ventricle. In the ependymal part of the SCO only a moderate activity of hexokinase is observed in its specialized columnar cells whereas a high activity is present both in the ciliated ependyma and the choroid plexus. - The staining pattern of glucose-6-phosphatase is similar to that of hexokinase but this enzyme is found is the SCO only. - Likewise hexokinase, glycogen granules and enzymes related to glycogen metabolism (phosphoglucomutase, uridine-diphosphoglucose pyrophosphorylase, glycogen synthetase and phosphorylase) are regularly found most numerous and active in the nuclear and supra-nuclear area of the ependymal part. These enzymes are less active in both the other ependymal regions. - Uridine-diphosphoglucose dehydrogenase could not be demonstrated in the SCO. The NADP-linked enzymes of the pentose phosphate shunt, glucose-6-phosphate and 6-phosphogluconate dehydrogenase, show a moderate activity which decreases also from the nuclear towards the apical area of the ependymal cells of the SCO. Enzymes of the glycolytic pathway, such as glucosephosphate isomerase, fructose-6-phosphate kinase, fructose-I,6-diphosphate aldolase, glyceraldehyde-3-phosphate and lactate dehydrogenase, are highly active in the SCO and are located mainly in the supranuclear area, too. Fructose-1,6-diphosphatase could not be demonstrated thus indicating that in the SCO the pathway is most probably only glycolytic but not gluconeogenetic. Compared to the ependyma of the ventricular wall and of the choroid plexus, in the SCO the M type subunits of lactate dehydrogenase predominate. Glycolytic enzymes are also very active in the choroid plexus but less in the ciliated ependyma. Compared to the ciliated ependyma and especially to the ependyma of the choroid plexus, the activities of enzymes which are only present in mitochondria (NAD-linked isocitrate dehydrogenase, succinate dehydrogenase, NAD-linked malate dehydrogenase after preextraction, cytochrome oxidase, 3-hydroxybutyrate and glycerolphosphate and glutamate dehydrogenase) are relatively low. Mitochondria are accumulated near the superior pole of the nuclei as well as in the most apical part of the ependymal cells. - The staining pattern of NADP-linked isocitrate and malate dehydrogenase as well as of NADH dehydrogenase suggests that these enzymes are localized both in and out of mitochondria. The extramitochondrial activity of the first two enzymes might be localized in the cytosol. The extramitochondrial activity of NADH dehydrogenase might be localized in the endoplasmic reticulum...