Influence of a detergent on the catfish olfactory mucosa

The olfactory mucosa of the catfish (Ictulurus punctatus) has been briefly exposed to various concentrations of the non-ionic detergent Triton X-100. At high concentrations (1–4%) the upper layer of cells constituting the sensory and non-sensory areas of the lamellae is extensively damaged and new receptor cells do not appear in significant number before 2 months after treatment. Respiratory cells regenerate first followed by sustentacular and olfactory receptors. The regenerative process is very similar to that described previously after prolonged contact between the mucosa and ZnSO₄. Low detergent concentrations 0.03 – 0.1% affect only the sensory area. Olfactory and sustentacular microvilli and cilia, are immediately severed by the chemical. Regeneration occurs within the next 4 days. The cellular membranes appear also to be affected. From anatomical, electrophysiological and biochemical studies both in vivo and in vitro, it can be hypothesized that receptors involved in the transduction process are solubilized by the detergent but reappear at a level corresponding to 50–60% of their original activity within 2 h.Proteins, having an amino acid binding effectiveness correlated to the amino acid electrophysiological activities measured in vivo, can be isolated from the solubilized material. Further studies will be necessary to confirm that some of these molecules are involved in the olfactory transduction mechanism.     

Frequency of mast cells in the olfactory mucosa of rhesus monkeys

During studies of the olfactory mucosa and its response to the different levels of circulating sex hormones, considerable numbers of mast cells have been observed in its epithelia and subepithelial regions. The number of these cells in the olfactory mucosa of male monkeys differs greatly from that found in females. The frequency of these cells in the olfactory mucosa of females fluctuates significantly during the menstrual cycle. These fluctations stimultaneously correspond to the well known changes in olfactory sensitivity: around ovulation, when the olfactory sensitivity for certain odorants is high, the number of mast cells in the olfactory mucosa also increases.     

Cell dynamics in the olfactory mucosa

By means of ultrastructural and autoradiographic observations from the olfactory mucosa of frog, it has been shown that olfactory receptor neurons as well as supporting cells are continuously replaced during the adult life of the animal. The severing of the olfactory nerve in adult frogs results in rapid degeneration of all mature olfactory neurons. An increased mitotic activity of the basal cells accompanies the degeneration of the mature neurons and precedes the regeneration of new neurons. The capability of these newly formed neurons to re-establish their connections in the olfactory bulb has been ascertained and the modalities of the process will be dealt with in a further report.     

Target cells for methylsulphonyl-2,6-dichlorobenzene in the olfactory mucosa in mice

Previously we reported that methylsulphonyl-2,6-dichlorobenzene, 2, 6-(diCl-MeSO(2)-B), was irreversibly bound to the olfactory mucosa of mice and induced necrosis of the Bowman's glands with subsequent neuroepithelial degeneration and detachment. In this study, autoradiography and histopathology were used to determine tissue-localization and toxicity of 2,6-(diCl-MeSO(2)-B) in the olfactory mucosa of control mice and animals pretreated with cytochrome P450 (CYP) and glutathione (GSH) modulators. The Bowman's glands of the olfactory mucosa were the major target sites of non-extractable binding of 2,6-(diCl-(14)C-MeSO(2)-B), whereas the olfactory neuroepithelium and nerve bundles showed only background levels of silver grains. Metyrapone pretreatment slightly decreased binding in the Bowman's glands and markedly decreased toxicity in the olfactory mucosa after 2,6-(diCl-MeSO(2)-B) administration. These results support that a CYP-mediated activation of 2, 6-(diCl-MeSO(2)-B) takes place in the Bowman's glands giving rise to toxic reactive intermediates. In mice pretreated with the GSH-depleting agent phorone, a marked increase of irreversible binding of 2,6-(diCl-(14)C-MeSO(2)-B) in the Bowman's glands was observed. Tape-section autoradiograms also revealed a significant increase of uptake of radioactivity in the olfactory bulb. As determined by histopathology, GSH-depletion increased both the extent and severity of the lesion in the mucosa. These results imply that 2,6-(diCl-MeSO(2)-B)-reactive intermediates are conjugated with GSH. The amount of irreversible binding and toxicity in the olfactory mucosa seems to be associated with the level of 2, 6-(diCl-MeSO(2)-B)-reactive intermediates.     

Scanning electron microscopy of the channel catfish olfactory lamellae

The olfactory lamellae of the channel catfish (Ictalurus punctatus) are composed of sensory and indifferent (non-sensory) epithelia organized into two distinct regions on both surfaces of each lamella. The smaller sensory region located adjacent to the midline raphe has fewer cilia per unit surface area than the indifferent epithelium and contains the olfactory neurons whose ciliated dendritic terminals occur at the epithelial surface. The indifferent epithelium, comprising the greater surface area of the olfactory lamella, is covered with a dense mat of non-sensory cilia. Fractured carbon dioxide critical point dried lamellar tissue revealed the underlying cellular structure. The lamellae are composed of two layers of epithelium enclosing a thin stromal layer. Olfactory receptors were observed in the fractured tissue only within the sensory epithelium.     

Regulatory factors in the vertebrate olfactory mucosa

Access to and clearance of ligands from binding sites on olfactorycilia are regulated by a complex interplay of molecular, physicaland cellular factors. Nasal/olfactory glands secrete mucus thatcontains many proteins, among them odorant-binding proteins(OBP) that may solubilize lipophilic odorants in the aqueousmucous phase and subsequently transport them to receptor sites.The rate of transport of the ligand–OBP complex or unboundodorant is a function of the diffusion coefficient that, underphysiological conditions, is determined largely by the molecularsize of the complex or unbound odorant, the viscosity of mucusand the tortuosity factor. The binding constants must favorassociation of the ligand with the binding protein, dissociationof the complex and possible reassociation of the ligand withthe odorant receptor. Neural regulation of secretion determinesthe properties of the olfactory mucus that affect ligand accessand clearance, including viscosity, water content and depth.Extrinsic autonomic (adrenergic, cholinergic) and peptidergic(substance P/CGRP, VIP) neurons innervate olfactory glands andregulate both secretory granule release and electrolyte/waterbalance. Extrinsic peptidergic (substance (P/CGRP, VIP) neuronsterminate near the epithelial surface in close apposition tosustentacular cells and olfactory receptor neurons. The substanceP/CGRP fibers, in addition to functioning as sensory fibers,appear to regulate secretion from sustentacular cells througha secretomotor reflex and to neuromodulate the sensitivity ofolfactory receptor neurons to odorant stimulation. The actionof regulatory factors in the olfactory mucosa is an emergingtopic of research focused on molecular, physical and cellularfactors that affect sensory transduction.     

Bilateral projection of the olfactory mucosa in the frog

Bulbar potentials wer bilaterally recorded in the frog following electrical stimulation of one olfactory nerve bundle. The general features of the contralateral evoked response were very similar to those of ipsilateral ones. The contralateral response was shown to be produced in situ, not being electronically transmitted from the bulb on the stimulated side. Its response disappeared after section of the olfactory interbulbar adhesion but was not affected by sectioning through either the anterior or the habenular commissure. It was concluded that messages from the neuroreceptors belonging to either the ventral or the dorsal olfactory mucosa on one side, reach both olfactory bulbs.     

Drug-induced protoporphyria in the olfactory mucosa of the hamster

Administration of 3,5-diethoxycarbonyl-4-ethyl-1,4-dihydro-2,6-dimethylpyridine (4-ethyl-DDC) to hamsters resulted in a marked loss of cytochrome P-450-dependent reactions (peroxidase, 7-ethoxycoumarin O-deethylase, and 7-ethoxyresorufin O-deethylase) in both liver and olfactory epithelium within 2 hr. This inactivation of cytochrome P-450 was accompanied by inhibition of ferrochelatase (FK), stimulation of 5-aminolevulinate synthase (ALA-S), and accumulation of protoporphyrin both in the liver and to a lesser degree, in the olfactory epithelium. These results suggest that the mechanism of induction of protoporphyria in nasal tissues is similar to that occurring in the liver, namely, suicidal metabolism of 4-ethyl DDC by cytochrome P-450 resulting in formation of N-ethylprotoporphyrin, a potent inhibitor of FK. The consequent depletion of heme leads to stimulation of ALA-S and, thus, porphyrin accumulation. Investigation of the dose-response to 4-ethyl DDC demonstrated that, in liver, maximal inhibition of FK and accumulation of protoporphyrin occurred at a dose of 50 mg/kg while ALA-S activity continued to increase up to a dose of 100 mg/kg. This is compatible with an additional effect of the drug on ALA-S involving induction of cytochrome P-450 and, thus, further depletion of heme. In the olfactory epithelium, stimulation of ALA-S was significantly less marked, suggesting that this secondary effect does not operate in nasal tissue. This is consistent with reports that olfactory cytochrome P-450s are noninducible.     

Differentiation of human olfactory system-derived stem cells into dopaminergic neuron-like cells: A comparison between olfactory bulb and mucosa as two sources of stem cells

Cell transplantation has become a possible therapeutic approach in the treatment of neurodegenerative diseases of the nervous system by replacing lost cells. The current study aimed to make a comparison between the differentiation capacity of the olfactory bulb neural stem cells (OB-NSCs) and olfactory ectomesenchymal stem cells (OE-MSCs) into dopaminergic-like neurons under the inductive effect of transforming growth factor β (TGF-β). After culturing and treating with TGF-β, the differentiation capacities of both types of stem cells into dopaminergic neuron-like cells were evaluated. Quantitative real-time polymerase chain reaction analysis 3 weeks after induction demonstrated that the mRNA expression of the dopaminergic activity markers tyrosine hydroxylase (TH), dopamine transporter (DAT), paired box gene 2 (PAX2), and PAX5 in the neuron-like cells derived from OB-NSCs was significantly higher than those derived from OE-MSCs. These findings were further supported by the immunocytochemistry staining showing that the expression of the tyrosine hydroxylase, DAT, PAX2, and paired like homeodomain 3 seemed to be slightly higher in OB-NSCs compared with OE-MSCs. Despite the lower differentiation capacity of OE-MSCs, other considerations such as a noninvasive and easier harvesting process, faster proliferation attributes, longer life span, autologous transplantability, and also the easier and inexpensive cultural process of the OE-MSCs, cumulatively make these cells the more appropriate alternative in the case of autologous transplantation during the treatment process of neurodegenerative disorders like Parkinson's disease.     

Effects of electrical stimulation of the human olfactory mucosa

Electrical stimulation of the human olfactory mucosa was performed by means of an electrode attached to a rhinoscope . Stimulation of the nasal mucosa did not evoke smell sensations, but suppressed smell sensations of presented odorants. When electrical stimulation followed the exposure to an odorant within a certain interval, the stimulus recalled the already faded sensation of the preceding odorant. Electrical stimulation without prior natural stimulation produced unpleasant sensations in 3 patients with a history of temporal lobe seizures and olfactory auras , but not in patients with primary, generalized or focal epilepsy.     

Association of substance-P-immunoreactive nerves with the murine olfactory mucosa

Location and distribution of nerve fibers immunoreactive to substance P were studied in the mouse olfactory mucosa. A moderately dense plexus of fibers is present at the interface of the olfactory epithelium and the connective tissue of the lamina propria. In addition, many immunoreactive nerve fibers are noted in close association with Bowman's glands and blood vessels in the lamina propria. However, such fibers were not observed in olfactory epithelium proper nor in the fila olfactoria. Substance-P-immunoreactivity is almost totally abolished by treatment of animals with capsaicin, an agent known to deplete substance P from primary sensory neurons. It is suggested that the substance-P-immunoreactive fibers are of sensory origin, with their perikarya most likely located in the trigeminal ganglia. Functionally, they might influence local blood flow and/or the secretion of Bowman's glands.     

Electron microscopic observations of the olfactory mucosa of the mole

The olfactory mucosa of the mole has been studied with the electron microscope. Bipolar ciliated neurons, supporting and basal epithelial cells have been recognized and theirultrastructure described. Morphological differences of the various parts of the sensory neurons have been emphasized. The considerable number of organelles observed in supporting cells and the complexity of their free surface suggests a more active role for these cells than their name implies.