[Electron microscopy studies of innervation of nasal mucosa glands in humans]

Cystic fibrosis: ultrastructural changes of nasal mucosa

Cystic fibrosis (CF) is an inherited multisystemic disorder that results in a generalized dysfunction of exocrine glands. Besides chronic obstructive pulmonary diseases, chronic sinusitis, nasal polyposis and hypertrophy of the inferior turbinates with nasal airway obstruction are typical signs. Tissue samples of the inferior turbinates and nasal polyps were taken during nasal surgery from 21 children, ranging from 3 to 16 years of age. Light- and electron microscopical examination were carried out. Furthermore, specimens of nasal mucosa of patients without chronic inflammation as controls and specimens of duodenal mucosa of patients with CF were investigated. Under a thick layer of respiratory epithelium with a high proportion of goblet cells, the seromucous glands display abnormal morphological structures with wide mucous cells and cystic dilatation. The glandular cells show inhomogeneous glandular droplets in the supranuclear cell portion. The nucleus contains dispersed chromatin as a sign of increased activity and the structures of the Golgi apparatus are clearly detectable. Apart from investigations concerning nasal polyps in CF, studies on the different morphological changes of nasal mucosa at the electron microscopic level are rare. This histological study focuses on various morphological changes of nasal glands at the ultrastructural level in correlation with typical symptoms in CF. In addition, a comparison with electron microscopic findings of CF-enteropathies is proposed. These findings could help to bring information concerning new morphological aspects in the pathophysiology of patients with CF.

Ultrastructural detection of nitric oxide in human nasal mucosa

OBJECTIVE

Nasal vasculature and seromucous glands are exposed to complex mechanisms influenced by external as well as internal stimuli. In addition to classic and peptidergic neurotransmitters, nitric oxide (NO) was increasingly found to be important in the control of various physiologic functions. NO modulates nasal immunology, influences macrophage activity, and has antiviral and bacteriostatic properties. The aim of this study was to show the localization of nitric oxide synthases (NOS) I and III in the normal human nasal mucosa by using immunoelectron microscopical techniques.

STUDY DESIGN

Specimens of noninflammed inferior turbinates from 35 patients who underwent nasal surgery were fixed in phosphate-buffered glutaraldehyde. After dehydration, incubation in unicryl and polymerization, ultrathin sections were cut. Primary antibodies against NOS I and III were applied and the immunocomplexes were visualized by an immunocytochemical staining-technique using gold-labeled antibodies. Immunostained structures were photodocumented using a transmission electron microscope.

RESULTS

NOS-immunoreactive nerve fibers were mainly co-located in parasympathetic nerves in the adventitia of arterial vessels and in periglandular axons. Electron microscopy showed that NOS-positive axons were in close contact with acinus cells. A strong NOS III-immunoreactivity was found in endothelial cells of capillaries near the glands as well as in arterial vessels. Furthermore, immunoreaction products were deposited throughout the cytoplasm of fibroblasts.

CONCLUSION

Nitric oxide in nerve fibers, seromucous glands, and endothelial cells of capillaries and arterial vessels suggest that NO takes part in the regulation of physiologic processes of the human nasal mucosa. NOS was co-localized in parasympathetic nerves and plays a role in the neurotransmission and neuromodulation of the vascular tone and glandular secretion. Arteries showed a distinctly developed nitrergic innervation and endothelial accumulation. The NO production in axons of the adventitia and in the endothelium of arteries demonstrated that these vessels are influenced by a dual NO system. NO could mainly act on these structures with vasodilatatory effects. Finally, NO would be able to influence the functions of perivascular fibroblasts.

[Neural control of the respiratory nasal mucosa]

Respiratory nasal mucosa fulfils the function of pretreating the inspired air. The periodic nasal cycle and pathologic functional disturbances of the endonasal tissue influence the nasal passages. The secretion of the seromucous glands and extravasation from the blood vessels are essential for mucocilliary transport. These physiological mechanisms are partially controlled by neural regulation. Besides classic neurotransmitter neuropeptides such as VIP, CGRP, SP and NPY, nitric oxide also shares this role. A network of sensory, sympathetic and parasympathetic nerve fibres protects the respiratory mucous membranes from external and internal irritation. In addition, blood vessels and glands are influenced by endothelial and humoral factors. For the different types of rhinitis, sensory neuropeptides and inflammatory mediators take part in the pathomechanisms and can lead to a so called neurogenic inflammation of the nasal mucosa.