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The preliminary results of investigating the lateral nasal wall are presented. In this study only three strips of mucosa are analysed from histological point of view using serial sections. One strip corresponded to the plane of lateral osteotomy, the second crossed the middle of turbinates and the third corresponded to the vestibular area. The accurate number and distribution of vascular and glandular elements were determined by help of Visopan and micro-photographs.

An in vitro method was developed for the biochemical and autoradiographic demonstration of low muscarinic receptor densities in peripheral tissue. Histological criteria point clearly to the necessity for fixation to preserve tissue quality. [3H]l-Quinuclidinylbenzilate bound specifically to a homogeneous class of binding sites in 0.5% glutardialdehyde-fixed cryostat sections (10 microns) of rat nasal glands with high affinity (Kd = 0.47 +/- 0.06 nM) and with a receptor density (Bmax) of 41 +/- 1 fmol/mg protein. This binding was linearly dependent on the thickness of the sections. Kinetic experiments resulted in a Kd value of 0.19 nM. Binding was stereoselectively inhibited by benzetimide enantiomers. Autoradiograms, generated after incubation with 0.6 nM [3H]l-quinuclidinylbenzilate and dipping in nuclear K2 emulsion, showed specific labelling of the glandular acini and excretory ducts. These in vitro observations provide conclusive evidence for the presence of acetylcholine receptors in the nasal glands of the rat.

Rats are used extensively in inhalation toxicologic studies, but little information is available on the rat nasal mucociliary apparatus. The function of the rat nasal mucociliary apparatus was studied in vitro by video analysis, and its structure was examined by light and electron microscopy. Video analysis permitted determination of mucus flow rate and ciliary beat frequency without disrupting mucociliary function. In different regions of the nose, there was a characteristic mucus flow rate, flow pattern, and ciliary beat frequency, with minimal interanimal variation. Analysis of data pairs revealed no evidence of a correlation between mucus flow rate and ciliary beat frequency, ciliary length, density of the ciliated cell population, or the products of these factors. Mucus was seen to flow over certain nonciliated areas, and it is proposed that the mucus is pulled over these areas. Mucus flow characteristics indicated that the hypophase was less viscous than, and moved in the same direction as, the epiphase. The nasal mucus was present as a continuous layer over the respiratory epithelium, and had an osmiophilic surface film, which was found to be made up of 2 separate membranous components. On the basis of these studies, it was concluded that the rat nasal mucociliary apparatus represents a useful and readily accessible model for in vitro studies of nasal mucociliary function.

The low odor specificities of the olfactory receptors suggest that odor recognition depends on the simultaneous activity in an ensemble of receptor neurons. This ensemble could conceivably code quality without reference to the point of origin of each input on the receptor sheet. However, the nose-to-bulb projection appears sufficiently precise to provide the bulb with a topographical map of the receptor sheet although it is poorly delineated in the anteroposterior plane. (It is also known that the morphological changes that follow prolonged exposure to odors are more differentiated in the coronal than in the anteroposterior plane.) Furthermore, it is clear from work at both epithelial and bulbar levels that a spatiotemporal pattern of excitation is generated by odor stimulation of the receptor sheet and that this pattern differs for different odors. This evidence, then, supports the view that there is a spatial component to odor quality coding. This spatial pattern has two elements. One is imposed and depends (at least in part) on differences in the retentivity of different odorants by the mucous sheet, which has powerful sorptive properties. It effectiveness seems particularly weak for odorants with relatively long retention times. The second component is inherent and depends on the tendency of receptors with similar peak odor specificities to aggregate in the same region (or regions) of the epithelium. Different odors or groups of odors maximally excite different regions, which may overlap. The imposed component could not, in itself, provide an adequate mechanism for odor recognition, partly because many compounds have comparable or even identical mean retention times (e.g., enantiomeric isomers). The inherent component, on the other hand, possesses this potential. However, either or both forms of patterning may cooperate with a third nonspatial mechanism (based on differential responsiveness of receptors to different odors) in coding odor quality.

Animal studies frequently are used in assessing potential human health effects from exposure to inhaled toxicants. Such studies also are used to investigate sensitive subpopulations such as children. Among other factors that influence the degree to which animal models are predictive of human effects in the delivered dose of the toxicant to the various regions of the respiratory tract. Because the rat is an obligatory nose breather, an understanding of the rat nasal-pharyngeal airway geometry is needed to relate exposures to delivered doses. In this study, the growth and development of the rat nasal-pharyngeal airway was studied at one-week intervals in male Fischer-344 rats from one to five weeks. Casts of an adult (60 day) and an aging (441 day) rat were included for comparison. Replica casts of the nasal-pharyngeal airway were made by injecting silicone rubber through the trachea, and sections in anterior-posterior positions were made for morphometric study. A simple structure of the nasal-pharyngeal airway was found in the young rats. While the percentage of the airway composed of turbinates was similar at all ages, the surface area of the turbinates increased 7.7-fold between 7 and 60 days. Because of the simpler structure and smaller surface area in the young rat, extrathoracic clearance is probably less efficient, resulting in a higher delivered dose to the lung of a young rat than to that of an adult rat exposed to the same toxicant concentration.

Based on studies of the mucosa in foetuses, infants, children and adults, using whole-mount methods, the mucous-gland and goblet-cell density in the nose, rhinopharynx, pharynx, phypopharynx and trachea is described. Glandular density was highest in the nose, lowest in the trachea, where the glands are considerably larger than in the nose. The nasal, pharyngeal and hypopharyngeal glands contain more serious elements than do the tracheal ones. The goblet-cell density is greatest in the lateral wall and the roof of the rhinopharynx, smallest in the anterior part of the nose, In acute and chronic tracheal disease, and on constant exposure to dust, the goblet-cell density is increased.

Stimulation of preparations of rabbit olfactory epithelium with aqueous solutions containing the odorants linalool or inalyl isobutyrate, or both, initiates molecular changes that can be monitored by a specific decrease in absorbance at 267 nanometers. This change in absorbance appears to be associated with a change in macromolecular conformation which is initiated by formation of a complex involving the stimulant molecules.