a-d, Muc5b+/+, Muc5b−/−, and Muc5ac−/− olfactory glands (a), nasopharynxes (b), tracheal glands (c), and bronchial surface epithelial cells (d) stained with AB-PAS or with anti-Muc5b (c,d bottom). Solid arrowheads, mucous cells. Open arrowheads, ciliated cells. e-i, Effects of mucin expression on growth, survival, MCC, and ciliary function. j-l, Microsphere movement, transport velocity, and transport index in primary tracheal epithelial cells in vitro. Scale bars, 20 μm (a, j), 10 μm (b-d). Error bars, sem. ‘*’ significant differences (p<0.05). Numbers in parentheses, ‘n’ mice.