The role of basal cells in attachment of columnar cells to the basal lamina of the trachea.
ABSTRACT The mechanism by which basal cells play a role in attachment of airway epithelium to the basal lamina has not been determined. Our hypothesis is that basal cells form a structural bridge between columnar cells and the basal lamina via hemidesmosomes, the cytoskeleton, and desmosomes. To evaluate this hypothesis, we determined the percentage of the columnar cell surface area associated with attachment to the basal lamina and the basal cell in tracheal epithelia of different heights. Tracheas from mice, hamsters, rats, bonnet monkeys, cats, and sheep were prepared for electron microscopy by standard techniques. The height of the epithelia ranged from 8.6 microns in the hamster to 56.8 microns in the sheep. The number of basal cells/100 microns ranged from 3.4 in the hamster to 21.4 in the sheep. The percentage of the basal lamina covered by basal cells increased from 32.6 in the hamster to 94.7 in the sheep. In the shorter epithelia of the hamster, 32% of the columnar cell attachment to the basal lamina was indirect through basal cells, and in the taller epithelia of the sheep, 92% of the columnar cell attachment was by this means. Conversely, the percentage of columnar cell surface in contact with the basal lamina decreased from 67.4% in the hamster to 5.3% in the sheep. These data demonstrate that basal cells play a role in attachment of columnar epithelium to the basal lamina by presenting a surface area for cell-to-cell attachment, thus acting as a bridge between columnar cells and the basal lamina.
- Laboratory Investigation 08/1974; 31(1):68-74. · 3.96 Impact Factor
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ABSTRACT: Of the eight categories of epithelial cells identified in pulmonary conducting airways, four are found in the trachea of adult primates: basal, mucous goblet, intermediate, and ciliated cells. While their ultrastructure is well characterized, little is understood about their origin or differentiation. This study describes the pattern of differentiation of the tracheal luminal epithelium in a species of nonhuman primate, the rhesus monkey, Macaca mulatta. Tracheas of 57 fetal and postnatal rhesus were fixed with glutaraldehyde/paraformaldehyde: ten at 29-54 days gestational age (GA), ten at 59-80 days GA (pseudoglandular stage), sixteen at 82-130 days GA (canalicular stage), ten at 141-168 days GA (saccular stage), eight at 1-134 days postnatal, and three adults (2 yr 11 months to 11 yr 11 months). Slices taken proximal to the carina were processed for electron microscopy by a selective embedding procedure. In the youngest fetuses, essentially one population of cells lined the tracheal epithelial surface. These cells were columnar in shape with a central nucleus, few organelles, and large amounts of cytoplasmic glycogen. At 46 days GA, ciliated cells were observed on the membranous side of the trachea. Some nonciliated cells had concentrations of organelles in the most apical portion of their cytoplasm. At 59 days GA, membrane-bound cored granules were intermixed with organelles in the apices of some glycogen-filled cells. They were observed first on the cartilaginous side. Between 59 and 100 days GA, a large number of cell forms which appeared to be transitional between ciliated, secretory, basal, and undifferentiated cells were present. These included ciliated cells with electron-lucent inclusions resembling mucous granules. Mucous secretory cells were more numerous and had more granules and less glycogen in older fetuses. By 105 days GA, few of the secretory cells had significant amounts of glycogen and the cytoplasm was condensed. Secretory granules were very abundant in some cells and minimal in others. The Golgi apparatus was prominent. In animals 120 days GA and older, small mucous granule cells and basal cells resembling these cells in adults were present. By 134 days postnatal age, the epithelium resembled that in adults. We conclude that most of the differentiation of tracheal epithelium in the rhesus monkey occurs prior to birth; the cells differentiate in the following sequences: ciliated, mucous goblet, small mucous granule, basal; and basal and small mucous granule cells do not play a role in ciliated and mucous cell formation in the fetus.American Journal of Anatomy 02/1986; 175(1):59-71.
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ABSTRACT: The purpose of the present study was to identify the proliferative cell types in the nonciliated cell population of the upper airways and determine the capacity of each to act as progenitor cells. Sprague-Dawley rats (30 days old) were exposed to 20 ppm NO2 for 24 hours to stimulate cell division, given injected tritiated thymidine (3H-TdR), sacrificed 1 hour and 1, 3, 5, and 7 days later, and prepared for light- and electron-microscopic autoradiography. One hour after injection of 3H-TdR, the mean labeling index (LI) was 1.6% in control animals and 5.2% in exposed animals. Mean grain counts per cell decreased from 15.6 at 1 hour after 3H-TdR to 6.9 on the third day, indicating that the labeled cell population had divided. Labeled cells in the control and exposed cell populations were identified with electron microscopy. At 1 hour after injection of 3H-TdR, basal cells and nonciliated columnar cells were labeled. However, only nonciliated columnar cells were stimulated to divide by NO2. The labeled nonciliated columnar cell population was made up of serous, "intermediate" and goblet cells. Each of these cell types was stimulated to divide to the same degree. After cell division (1-7 days) labeled cells of all types were observed with labeled ciliated cells appearing on the third day. It was concluded that the basal cell is not a primary progenitor cell. The primary progenitor cell for epithelium in the upper airway is the total columnar secretory cell population (serous, "intermediate," and goblet cells).American Journal Of Pathology 05/1986; 123(1):126-33. · 4.52 Impact Factor