Summary The anatomical basis of gas exchange impairment in the anaesthetised horse was studied by computerised tomography (CT; three Shetland ponies) and morphological analysis (one pony and three horses). By means of CT, densities were seen in dependent lung regions early during anaesthesia, both with spontaneous breathing and with mechanical ventilation. The densities remained for some time where they had initially been created when the animal was turned from dorsal to sternal recumbency. Deep insufflation of the lungs reduced the dense area. Gas exchange was impaired roughly in proportion to the dense area. On histological analysis, the densities were atelectatic and congested with blood. Gravimetry showed no more extravascular water per unit lung tissue in the atelectatic than in the ‘normal’ regions, and the blood content was increased only slightly. It is concluded that the horse develops atelectasis in dependent lung regions early during anaesthesia in dorsal recumbency, and that atelectasis is the most likely explanation for the large shunt and impaired arterial oxygenation regularly seen during anaesthesia.

Following intranasal instillation of vesicular stomatitis virus (VSV) in mice there was an extensive infection of the olfactory epithelium in contrast to a minimal involvement of the respiratory epithelium. Sendai virus (SV), on the other hand, caused an extensive infection of the respiratory epithelium and only minimal infection of the olfactory mucous membrane. VSV budded from basolateral surfaces of supporting cells and olfactory neurons, but not from their apical surfaces or the ciliated bulbous endings of the olfactory neuron dendrites. This asymmetric release of VSV favoured neuroinvasion. The virus spread along the olfactory nerves to the glomeruli in the olfactory bulbs after which it propagated transneuronally into the rest of the brain. SV budded only from the apical surface of respiratory epithelial cells, was released into the air passages, and there were no signs of invasion into the olfactory bulbs. Inoculation of the olfactory mucous membrane is a useful procedure for studies on selectivity of attack on peripheral neurons by viruses and on mechanisms of virus invasion of the nervous system in vivo.

Sections from the nasal cavity of 12-day-old Swiss albino mice (NMRI strain) were subjected to lectin histochemistry. A panel of biotinylated lectins (Con A, WGA, s-WGA, PNA, SBA, DBA and UEA I) and a horseradish peroxidase-conjugated lectin (GSA II) showed marked differences in binding to the respiratory and the neuroepithelial cells. SBA (affinity for galactose and N-acetylgalactosamine), PNA (galactose) and WGA (sialic acids and N-acetylglucosamine) labelled the receptor neurons in the olfactory and vomeronasal epithelium. DBA (N-acetylgalactosamine) labelled a subgroup of about 5% of the olfactory receptor neurons, but most neurons in the vomeronasal organ. UEA I (fucose) and s-WGA (N-acetylglucosamine) intensely labelled the entire nerve cell population in the vomeronasal organ, but in the olfactory epithelium the labelling with these lectins was stratified. In the respiratory epithelium the ciliated cells were labelled with WGA and s-WGA, while the secretory cells bound most of the lectins. Thus different sugars are exposed on the surface of the different types of epithelia in the nasal cavity, providing a basis for selectivity in microbial attacks on these areas.

In order to induce a non-lethal infection restricted to central aminergic neurons projecting to the olfactory bulbs a series of temperature sensitive (ts) and G-protein monoclonal antibody escape mutants of vesicular stomatitis virus (VSV) were instilled into the nasal cavity of mice. In three-week (wk)-old NMRI mice four monoclonal antibody escape mutants caused an extensive infection of the olfactory epithelium and, like a wild type strain, a lethal brain infection after spread along olfactory pathways. Three ts mutant strains showed an attenuated pathogenic potential. Strain G31 caused a lethal infection with a somewhat prolonged course while the strain G11 failed to invade the nervous system. Strain G41 showed minimal invasion of central nervous system in three-wk-old mice and caused a lethal infection in newborn and one-wk-old mice. In contrast, two-wk-old mice survived infection with this mutant, which spread along olfactory pathways and rather selectively affected aminergic reticular core neurons in the diagonal band, the locus ceruleus and the raphe nuclei in the brainstem. Thus, an age-dependent virus infection of the olfactory pathways can cause restricted lesions in the brain providing a model for studies of virus-induced changes in aminergic neurotransmission.

The incidence of nasal adenocarcinoma is greatly increased in wood dust exposed furniture workers. The background is discussed and histological and cytological examinations are performed in 45 workers. The histological findings are compared with different kinds of cytological methods, May-Grünwald-Giemsa and Papanicolau. It was a significant increase in cuboidal cell metaplasia revealed by histology and Papanicolau stained cytology. MGG, on the other hand, revealed significantly raised occurrence of goblet cell hyperplasia. These findings are discussed in relation to a morphogenetical model which could explain some features in the development of premalignant changes which could precede nasal adenocarcinomas.