Metaplasia Of Respiratory Epithelium Research Articles

Histologic Aspect of the Curved Vomerine Mucosa in Cleft Lip and Palate.

Background:Common surgical techniques aim to turn the entire vomerine mucosa with vomer flaps either to the oral side or to the nasal side. The latter approach is widely performed due to the similarity in color to the nasal mucosa. However, we lack a histologic description of the curved vomerine mucosa in cleft lip and palate malformations.Methods:We histologically examined an excess of curved vomerine mucosa in 8 patients using hematoxylin–eosin, periodic acid–Schiff, Elastin van Gieson, and Alcian blue stains. Tissue samples were obtained during surgery at 8 months of age.Results:Our histological analysis of the mucoperiosteum overlying the curved vomer revealed characteristics consistent with those of an oral mucosa or a squamous metaplasia of the nasal mucosa, as exhibited by a stratified squamous epithelium containing numerous seromucous glands. Some areas showed a palisaded arrangement of the basal cells compatible with metaplasia of respiratory epithelium, but no goblet cells or respiratory cilia were identified. Abundant fibrosis and rich vascularity were present.Conclusion:The vomer mucosa showed no specific signs of nasal mucosa. These findings should be considered in presurgical cleft orthopedics and palatal surgery for further refinement. Shifting the vomer mucosa according to a fixed physiologic belief should not overrule other important aspects of cleft repair such as primary healing and establishing optimal form and function of palatal roof and nasal floor.

A panel of antibodies for identifying squamous metaplasia in endobronchial biopsies from smokers

Toxic injury can induce squamous metaplasia of respiratory epithelium, which normally is pseudostratified. Terminally differentiated squamous epithelial cells have a flattened, elongated appearance. During differentiation, they have an intermediate phenotype that is difficult to identify and distinguish from tangentially cut columnar cells in tissue sections from endobronchial biopsies, whose small size makes orientation difficult. The aim of our study was to develop a panel of antibodies that could be employed to distinguish normal epithelium from metaplastic epithelium and would be suitable for use on endobronchial biopsies. Nasal polyp tissue and tonsil tissue, which have pseudostratified and squamous epithelia, respectively, were collected from surgical cases and embedded in glycol methacrylate resin. Cut sections were stained immunohistochemically with a panel of antibodies to cytokeratins (CK), whose expression varies with epithelial type and stage of differentiation, and involucrin, a marker of terminal squamous differentiation. Squamous epithelium stained positively for CK5/6, CK13 and involucrin. In the pseudostratified epithelium, basal cells exhibited weak staining for CK13 and strong staining for CK5/6, and columnar cells exhibited strong immunoreactivity for CK7, CK8 and CK18. Application of this panel to endobronchial biopsies from smokers enabled areas of squamous metaplasia to be distinguished from tangentially sectioned epithelium.

Isobutyraldehyde administered by inhalation (whole body exposure) for up to thirteen weeks or two years was a respiratory tract toxicant but was not carcinogenic in F344/N rats and B6C3F1 mice.

Isobutyraldehyde (a chemical structurally related to formaldehyde and used as a flavoring agent) was studied for toxicity and carcinogenicity by exposing male and female F344/N rats and B6C3F1 mice. Animals were exposed to isobutyraldehyde vapors 6 h per day, 5 days per week for up to 13 weeks or 2 years. In the 13-week studies, groups of 10 male and 10 female F344/N rats and B6C3F1 mice were exposed to concentrations of 0, 500, 1000, 2000, 4000, or 8000 ppm. Chemical-related body weight depression and deaths occurred in rats and mice exposed to 4000 and 8000 ppm. Necrosis of the epithelium accompanied with acute inflammatory reaction was observed in the nasal turbinate, larynx, and trachea of rats exposed to 8000 ppm. Exposure of rats to 4000 ppm resulted in metaplasia of the nasal respiratory epithelium, inflammation, degeneration of the olfactory epithelium, and osteodystrophy of the nasal turbinate bone. In the 13-week mouse study, exposure to 8000 ppm or 4000 ppm resulted in necrosis of the epithelium lining of the nasal turbinates. Osteodystrophy of the nasal turbinate bone and squamous metaplasia of the nasal respiratory epithelium were noted in mice exposed 4000 ppm. Degeneration of the olfactory epithelium was noted in males exposed 2000 ppm and in females exposed to 4000 ppm. In the 2-year studies, groups of 50 male and 50 male F344/N rats and B6C3F1 were exposed to concentrations isobutyraldehyde vapors of 0, 500, 1000, or 2000 ppm 6 h per day, 5 days per week. There were no differences in survival rates or mean body weights between exposed groups and control rats. Survival of male mice exposed to 2000 ppm and mean body weights of female mice exposed to 1000 or 2000 ppm were lower than those of the of the controls. No increase in neoplasm incidence was observed in rats and mice in the 2-year studies that could be attributed to isobutyraldehyde exposure. Chemical-related nonneoplastic lesions were limited to the nose of rats and mice. They included squamous metaplasia of the respiratory epithelium (rats), suppurative inflammation (rats), and olfactory epithelial degeneration (rats and mice) at 1000 and 2000 ppm.

High survial rate of hamsters given intratracheal instillations of benzo[a]pyrene and ferric oxide and kept on a high β-carotene diet

The study described in this paper was primarily conducted to identify the cell types involved in the formation, progression and regression of metaplastic changes in the respiratory tract epithelium of hamsters after intratracheal intubations with benzo[a]pyrene. Furthermore, the role of vitamin A and beta-carotene in these processes was studied. In the course of the study a remarkable effect of dietary beta-carotene on survival of hamsters became a subject of investigation. Hamsters were fed diets with various levels of vitamin A or beta-carotene and were treated intratracheally with a suspension of benzo[a]pyrene with ferric oxide in saline. The tumour response of the respiratory tract was very low (2.8%) and hyper- and metaplasia of respiratory epithelium were virtually absent. However, an interesting observation was an exceptionally low mortality of only 2% after 69 weeks in the group of hamsters fed a high beta-carotene diet (1% w/w), whereas in the other groups mortality after 69 weeks amounted to 25%. Although the exact cause of death of most of the hamsters could not be established, a 40% reduction of lipid peroxidation in the livers was found in the high beta-carotene group. Moreover, in this group the degree and incidence of nephrosis and of focal mineralization of kidneys and heart were lower than in the other groups. These favourable effects of the high beta-carotene diet may have contributed to the unusually high survival rate in hamsters fed this diet. Further studies are planned to verify and study this observation.

Repeated exposure to α-ethylacrolein vapour: Subacute toxicity study in rats

The subacute inhalation toxicity of α-ethylacrolein was examined in rats by repeated exposure of 4 groups of 10 males and 10 females each to α-ethylacrolein vapour at concentrations of 0, 2.0, 9.8 or 48.4 ppm, respectively, (6 h/day, 5 days/week) for a period of 13 weeks. The effects at 48.4 ppm were found to include growth retardation, focal alopecia, increased activity of glutamic-oxalacetic transaminase, glutamic-pyruvic transaminase and alkaline phosphatase in the blood serum, decreased concentrations of total proetin and albumin in the blood serum, increased relative weight of the heart, liver, adrenals and lungs, and histopathological changes in the respiratory tract mainly consisting of hyper- and metaplasia of respiratory epithelium and atrophy of the nasal olfactory epithelium. While at the 9.8 ppm level only a few relatively minor effects were noticed, viz. decreased concentrations of total protein and albumin in the blood serum and minimal hyper- and metaplasia of the tracheobronchial epithelium, no changes attributable to α-ethylacrolein were observed at the 2.0 ppm level.