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PubMed1986

Conducting sites in excitable membranes.

Electrical activity of conducting membranes is produced by transient changes in membrane conductance to Na and K ions. These time- and voltage-dependent conductance changes are controlled by intrinsic proteins that span the membrane and provide a pathway for ion movement. Several lines of evidence indicate that the membrane conducting sites are indeed largely or entirely protein structures. Proteolytic enzymes, when applied on unmyelinated axonal membrane such as the gar olfactory nerve or on eel electroplax, completely destroyed tetrodotoxin (TTX) binding. Treatment of the internal face of the giant axon of the squid with proteases resulted in the loss of the inactivation mechanism of the increased sodium conductance. The binding site of the TTX component in membrane isolated from eel electroplax, estimated by the method of irradiation inactivation, revealed MWs in the range of 230-240 kd. Moreover, this membrane component undergoes a cycle of phosphorylation-dephosphorylation that is affected by electrical activity and various neurotropic compounds and has also been shown to be a protein by the use of proteolytic enzymes. The membrane conducting sites through which ions are flowing are generally called "channels," and the activated "channels" are thought to form "pores" through which ions diffuse according to their electrochemical potential. The channel behaves as though it exists in open or closed permeability or "gating" states. The gating is generally assumed to be solely controlled by the voltage gradient across the membrane. Hence, the denominations of "gating proteins" are often attributed to the specific protein forming the membrane conducting sites. These proteins are intrinsic membrane proteins whose conformational changes, driven by the electric field in the membrane, are responsible for the ion fluxes generating the electrical activity in excitable cells. Electrical excitation of conducting cells involves transient permeability increases to Na+, K+, and Ca+ ions. In some specific cases, Cl-ions may also be involved. These ionic permeabilities are voltage-dependent and can be modified selectively and independently by a variety of compounds, thus leading to the idea that specific entities are spatially separated in the membrane and are acting independently. However, some data of patch-clamp analysis are best interpreted if one assumes that the activation of a specific entity may control the activation of another entity, thereby suggesting a kind of cooperation among some specific ionic sites.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

A developmentally regulated antigen associated with neural cell and process migration.

The distribution of an epitope recognized by the monoclonal antibody JONES has been studied immunohistochemically in the developing nervous system of the rat. In the present report, we survey selected regions of the fetal, postnatal, and adult rat nervous system to test the hypothesis that JONES binding is invariably associated with neural cell migration and axon growth in the developing rat. A series of selected developmental stages extending from embryonic day (E) 9 to adult were used in this investigation. The distribution of JONES binding was examined using indirect immunofluorescence, as well as the immunogold procedure. Particular attention was paid to regions where the positions and timing of cell and axon migrations have been well described for the rat. JONES immunoreactivity first appears at E11-12, when it is localized to the lamina terminalis, the telencephalic-diencephalic junction, the midbrain, and the rhombic lip regions of the cytologically undifferentiated neural tube. In all the regions studied, during embryonic and early postnatal life, the labeling is very intense in the ventricular zone and shows a radial array in the adjacent intermediate and marginal zones. The expression of JONES epitope correlates particularly with times of cell migration in the retina, superior colliculus, cerebellum, and telencephalon and in regions undergoing neurite extension, such as the developing optic tract, the white matter of the cerebellum, the dorsal roots, the trigeminal system, and olfactory nerve. JONES binding becomes progressively restricted in the postnatal period. In the adult brain, immunoreactivity is present only in the retina and cerebellum. In the retina, JONES labeling is present in the outer plexiform layer and optic fiber layer. The labeling in the optic fiber layer extends to the optic nerve head and stops abruptly outside the orbit. In the cerebellum, JONES shows a radially oriented pattern throughout the molecular layer and delineates the cell bodies in the Purkinje cell layer. The only non-neural regions that show JONES immunoreactivity are the adrenal medulla and the kidney glomeruli. We conclude that the antigens recognized by the JONES monoclonal antibody are associated with the migration of subsets of cells and axons within the developing rat nervous system and, consequently, may play a role in conveying selectivity to these processes.

Animals↗
PubMed1985

A panel of monoclonal antibodies to the rat olfactory epithelium.

BALB/c mice were immunized with dissected olfactory mucosa from young adult Sprague-Dawley-derived, CD, rats and antibody-secreting hybridomas were produced. Supernatants from hybridoma cultures were screened by immunocytochemical methods for their ability to react with specific cell populations in frozen sections of rat olfactory epithelium. Approximately 60 clones were identified that showed various degrees of specific staining. These have been classified on the basis of their particular staining specificities. One group of monoclonal antibodies, designated LUM, reacts with the luminal surface of the epithelium. Closer examination reveals these antibodies to react variously with the apical brush border of sustentacular cells, respiratory cilia, and the luminal membrane of respiratory cells. Another group of monoclonal antibodies reacts primarily with sustentacular cells, as is indicated by the SUS prefix. Some antibodies in this group also react with the membranes of respiratory cells and the cells comprising the acini of Bowman's glands. A larger group of antibodies reacts with olfactory neurons and/or their axons, as denoted by the NEU prefix. This group can be further subdivided by the criteria of whether both the olfactory nerve and vomeronasal nerve react with the same monoclonal antibody. A fourth group of monoclonal antibodies, designated GLA, reacts with Bowman's glands and in some instances with secretory cells present in the respiratory mucosa. Two clones, BCL, stain at the level of the basal cell layer just above the lamina propria. A number of other antibodies react with cells and structures of the epithelium that have not been previously described. One of this group, NIS-1, stains globular structures present in the mucosa of the neuroepithelium.

Animals↗
PubMed1989

Alternative pathways for drainage of cerebrospinal fluid in the canine brain.

Although the brain has no formal lymphatic system, a substantial quantity of cerebrospinal fluid (CSF) has nonetheless been shown to drain via cervical lymphatics. To pursue further the issue of alternative drainage pathways for CSF, we infused a solution of Ringer's lactate (RL) into the cisterna magna of the dog brain and monitored both the flow and concentration of total protein of cervical lymph. This maneuver promoted a nearly three-fold rise in intracranial pressure and was accompanied by a rise in cervical lymph flow and fall in its protein content. In addition, a profuse nasal discharge (11.4 ml/hr) developed with a moderately high protein content of the rhinorrhea fluid (1.8 g/dl), along with similar appearance times of Evans blue dye (instilled in the cisterna magna) in both cervical lymph and the rhinorrhea fluid (48-70 minutes after infusion). These findings suggest alternative drainage pathways for CSF besides the arachnoid villi (Pacchionian bodies) including connections with lymphatics in the neck and along the olfactory nerve, and around the cribiform plate to the nasal submucosa, and with proptosis, perhaps also through the aqueous humor-canal of Schlemm and nasolacrimal duct.

Animals↗
PubMed1989

[Ectopic meningioma of the ethmoid sinus: case report and a review of the literature].

A rare case of ectopic meningioma of the ethmoid sinus is reported. A 57 year-old male patient was admitted with complaints of anosmia and headache. Computed tomography revealed a relatively high-density mass in the bilateral ethmoid and sphenoid sinuses. The mass was markedly enhanced after intravenous administration of contrast medium. The cerebral angiography showed tumor stains fed by bilateral internal and external carotid arteries with right side dominance. The tumor in the ethmoidal sinus was removed by otolaryngologists at first and then the tumor in the sphenoid sinus was removed using sublabial transseptal sphenotomy. The histological examination resulted in a diagnosis of transitional meningioma with psammoma bodies. The tumor in this case is suspected to have originated from heterotopic meningocytes or meningocytes accompanying the perineural sheath of the olfactory nerve.

Cerebral Angiography↗
PubMed1988

Electrical activity of the toad telencephalon during tonic immobility (animal hypnosis).

During tonic immobility obtained in toads by restraining maneuvers there was an increased incidence of waves in the 8-12 c/s range grouped in spindles, in addition to an overall power increase detected by frequency analysis. There was also abolition of phasic movements, increased firing of anti-gravity muscles, and myosis. The electrographic recordings were characteristic of a state of behavioral alert in this species, supporting the hypothesis that a certain level of information processing may occur during tonic immobility, permitting the animal to detect the moment most appropriate for flight. These changes also occurred in animals with sectioned olfactory nerves, showing that they did not depend solely on ventilatory modifications.

Animals↗
PubMedDate not supplied

Brain anomalies found in 18 trisomy: CT scanning, morphologic and morphometric study.

Brain anomalies in 9 cases of cytogenetically proven 18 trisomy were reported. In addition to the various cerebral anomalies such as gyral or lobar abnormalities, hippocampal dysplasia, abnormal lateral geniculate body, agenesis or hypoplasia of the corpus callosum, absent or hypoplastic olfactory nerves, small optic tracts, and dysplasia of the inferior olivary nucleus, hypoplasia of the cerebellum and ventral pons was found in all cases. Cranial computed tomography was performed and revealed cerebellar and pontine hypoplasia with or without hypoplasia of the posterior cranial fossa as a characteristic finding in all 9 cases. A comparative morphometric study was done using age-matched controls. Macroscopically, the weight ratio of the cerebellum and brain stem to the whole brain was reduced compared with the controls. Microscopically, the thickness of the internal granular layer of the cerebellum was reduced especially at the convex area.

Brain↗