Connection Input Mapping and 3D Reconstruction of the Brainstem and Spinal Cord Projections to the CSF-Contacting Nucleus.

Objective: To investigate whether the CSF-contacting nucleus receives brainstem and spinal cord projections and to understand the functional significance of these connections. Methods: The retrograde tracer cholera toxin B subunit (CB) was injected into the CSF-contacting nucleus in Sprague-Dawley rats according the previously reported stereotaxic coordinates. After 7-10 days, these rats were perfused and their brainstem and spinal cord were sliced (thickness, 40 µm) using a freezing microtome. All the sections were subjected to CB immunofluorescence staining. The distribution of CB-positive neuron in different brainstem and spinal cord areas was observed under fluorescence microscope. Results: The retrograde labeled CB-positive neurons were found in the midbrain, pons, medulla oblongata, and spinal cord. Four functional areas including one hundred and twelve sub-regions have projections to the CSF-contacting nucleus. However, the density of CB-positive neuron distribution ranged from sparse to dense. Conclusion: Based on the connectivity patterns of the CSF-contacting nucleus receives anatomical inputs from the brainstem and spinal cord, we preliminarily conclude and summarize that the CSF-contacting nucleus participates in pain, visceral activity, sleep and arousal, emotion, and drug addiction. The present study firstly illustrates the broad projections of the CSF-contacting nucleus from the brainstem and spinal cord, which implies the complicated functions of the nucleus especially for the unique roles of coordination in neural and body fluids regulation.

Calcitonin-like immunoreactivity in the subcommissural organ-Reissner's fiber complex of some freshwater and marine teleosts.

The subcommissural organ (SCO) is a highly specialised circumventricular ependymal organ covering and penetrating the posterior commissure. The secretory products of the SCO condense to form Reissner's fiber (RF). Because of its extensive secretory activity and the chemical properties of its secretion, the organ functions as similar to the neurosecretory cells. Teleosts comprised of more than 20,000 extant species that show great diversity in terms of the form, habit and habitat. Affinity of calcitonin antibodies for the SCO-RF complex was used as a histochemical tool to study the morphology of some freshwater and seawater teleosts and its potential correlate to their osmotic environment. While intense to moderate calcitonin-like immunoreactivity was seen in the cells of the SCO of majority of the freshwater species viz., common carp, catfish, eel and perch; the SCO of goldfish revealed limited immunoreactivity. Like the SCO, the RF in all species was also immunostained with antibodies against calcitonin. It appeared as a single, continuous fiber that ran from SCO into the third ventricle and extended through the aqueduct, fourth ventricle and central canal of the spinal cord. In contrast to that in the freshwater fishes, the SCO-RF complex in majority of the seawater fishes, showed no calcitonin-like immunoreactivity. The data presented in this study described the comparative histomorphology of the SCO-RF complex and suggest a possibility that the calcitonin-like immunoreactivity in the SCO-RF complex might be a feature correlated to the osmotic environment of the fish.

Radial secretory glia conserved in the postnatal vertebrate brain: a study in the rat.

Secretory glial cells in the roof of the last diencephalic prosomer, ependymocytes and hypendymocytes, form the subcommissural organ. The cells of this complex were labelled immunocytochemically, using an antiserum against their specific secretory products. The study aims at the characterization of this cell type in the rat as an anatomical model situation. Radially oriented secretory glial cells remain after birth behind the posterior commissure in the mesencephalic aqueduct. At about postnatal day 10, the cell bodies descend into the conventional ependyma and at postnatal day 25 they assume a compact, rounded appearance. The secretory product they release is involved in the formation of Reissner's fiber. This differentiation in phenotype is not accompanied by a change of the intermediate filament expression. In the adult rat these cells had been labelled immunopositive for cytokeratins 8 and 18 as well as vimentin but not for glial fibrillary acidic protein. DiI-marking from the third ventricle and from the dorsal surface of the brain shows that the basal processes of ependymocytes and hypendymocytes project to the external and internal glial limiting membrane, respectively, through the commissural fiber bundles. Also the subependymal located hypendymocytes have apical processes with contacts to the cerebrospinal fluid. When this secretory cell population is studied with respect to cyto-architectonical changes during ontogeny the results lead to a new understanding of the subcommissural cells. They are not specialized ependymal cells in a regionally restricted and secondary differentiated ependymal area, but rather descendants of an ontogenetically ancient, specific type of radial glia. Characteristic features for all subcommissural cells are that they: (1) appear very early during ontogeny, (2) are derived from a radial oriented glial cell type, (3) carry at least one kinocilium, (4) possess an original intermediate filament pattern, (5) release a secretory product.

Neuropathology and immunohistochemistry of the brain-stem in neonates with congenital hydrocephalus: comparative studies between aqueductal stenosis and Arnold-Chiari malformation.

Neuropathological and immunohistochemical studies were done on the brain-stem of neonates who had congenital hydrocephalus with aqueductal stenosis or Arnold-Chiari malformation (ACM). The infants with aqueductal stenosis showed heterogeneity in their clinicopathological findings while the infants with ACM were relatively similar in neuropathological findings. There were prominent astrogliosis, decreased immunoreactivity with antisera to tyrosine hydroxylase and myelin basic protein in the periaqueductal area, and an increased reactivity with antiserum to substance P in the tegmentum of most patients with aqueductal stenosis and other malformations. In ACM, there was little gliosis in the tegmentum and periaqueductal area and minimal immunoreactivity of tyrosine hydroxylase, myelin basic protein and substance P. In both groups of cases, the cells in the periaqueductal region differ in neurotransmitter/neuromodulator immunoreactivity and degree of myelination reflecting a difference possibly in their maldevelopment.