الفهرس 
MATERIALS AND METHODSOnly 14 pages are availabe for public view
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Abstract
Environmental tobacco smoke (ETS) is one of the most common indoor pollutants to which many children are exposed. Cigarette smoke is formed of a complex mixture of chemical compounds, that have the potential to induce tissue damage. The effect of postnatal exposure to cigarette smoke on the histological structure of tracheal epithelium has received little attention. Aim of the work: The aim of this workis to study the structure of tracheal epithelium of albino rat at different age groups and to investigate the histological changes of this epithelium following postnatal exposure to cigarette smoke. Methods: Experimental animals were exposed daily to sidestream cigarette smoke since the day of birth (10 cigarettes a day, 6 days a week) for 2 weeks, 4 weeks, 8 weeks or 12 weeks. The trachea was dissected out and the middle part was selected. Paraffin sections were prepared and stained with H&E, AB/PAS and AF/AB stains. Ultrathin sections were prepared for electron microscopic study. Results: The neonatal tracheal epithelium was formed mainly of columnar cells. Few cells had few short cilia. By age, the epithelium became higher, the cilia became higher and more numerous, and pseudostratification appearerd more evident. The electron microscope revealed the fine structure of seven cell types in 12 week old rats. After exposure to cigarette smoke, the tracheal epithelium showed flattening, atrophy, ulceration, polyp formation with epithelial invaginations inbetween, preneoplastic variants, basal cell hyperplasia, dysplasia and squamous metaplasia. Moreover, degenerated and apoptotic cells were observed. Various ciliary abnormalities including: ciliary loss, swollen cilia, intracytopolasmic cilia, disoriented cilia, degenerated cilia loss of basal bodies and defective ciliogenesis were seen. Increased number of globule leucocytes was also detected. The trachea of exposed animals revealed progressive increase in the number of mucous secreting cells with a marked shift from neutral (PAS+ve) towards acidic (AB +ve) mucins; mainly the carboxylated type. Conclusions: Exposure to ETS results in many histopathological changes in the tracheal epithelium and marked increase in the number of globule leucocytes which may have a possible role in the induction and exacerbation of bronchial asthma and increased suscebtibility to respirtory infection. In addition, children exposed to ETS are at a higher risk of developing precancerous tracheal lesions.