SCANNING CRYO-ELECTRON MICROSCOPY OF RAT LUNG AT COLD EXPOSURE
The aim of research is to investigate important structures in vivo of mucociliary conveyor of respiratory and airway parts of the lung of intact rats against general cooling by the method of scanning cryoelectron microscopy without fixation and dehydration. The rats (male) in an amount of 40 pieces were exposed to general cooling during 14 days for 3 hours per day at the temperature of -15ºC. Frozen in liquid nitrogen tracheal samples were placed on a freezing Pelzer table (-30ºC) of the consoles Deben Coolstage of scanning electron microscope Hitachi S-3400. The study was conducted at low vacuum (80Pa) using backscattered electrons detector (BSECOMP). It was found out that the epithelial lining of the trachea of rats is covered with a liquid layer consisting of viscous gel and aqueous phases masking ciliary epithelial cells. Mucous secretion of the bronchi is presented by single plates with mucus cellular elements. On the alveolar surface in the monolayer of surfactant there were discovered globular clusters of lattice surfactant. With total cooling on the surface of epithelial layer the amount of bronchial secretions increases, the structure of the mucociliary apparatus changes and tracheal mucosa surface becomes wavy and there are sometimes marked accumulations of mucus. In the epithelial lining there are identified areas with the predominance of ciliated epithelium goblet cells lacking microvilli. The secretory activity of goblet cells and type 2 alveolocytes of respiratory department is accompanied by an increased release of secretion causing a disturbance of mucociliary transport.