Morphology and changes in Clara cells in the foetal bronchioles of Swiss mice.

In this work we have studied the morphology and evolution of Clara cells in the bronchiolar mucosa of lungs from 63 Swiss mice foetuses that were classified into three groups according to age (14, 16 and 18 days). A control group composed of 21 15-day-old Swiss mice was also studied. The most salient feature of the Clara cells observed was the occurrence of two types of secretory granules and a large smooth endoplasmic reticulum. On the other hand, the Clara cells of the control group had a single secretory granule. Clara cells thus seem to take part in bronchiolar metabolism, as they were quite abundant in the early foetal groups and diminished as birth approached. This cell decrease was confirmed by the control group (15-day-old mice), the bronchioles of which contained scant cells and numerous ciliated cells.