Animal models in clinical disease

Hypersecretion of mucus is a feature of several clinical diseases and in some is associated with mucous gland hypertrophy and goblet cell increase. In a variety of species these changes have been produced by irritants, by infection, or by administration of drugs. While the end result may appear the same, differences emerge in the type and amount of glycoprotein secreted and in the amount retained within the cell. Organ culture can be used to ascertain functional activity. The use of animal models has not only established that these environmental changes cause hypertrophy but indicated some of the intracellular events associated with their development. When new types of granules appear within a cell, they appear first at the apex: a flow chart is offered of the way of which individual cells change and hence the population. The nature of glycoprotein elaborated by a secretory cell can change within hours. A Clara or serous cell can develop into a mucus-secreting or goblet cell. The pattern of reversibility is emerging.