It is likely that this critical window of time will also apply to human exposures in the third trimester because the timing of cellular development, as well as conducting airway architecture/cellular composition, in the rhesus monkey lung closely recapitulates that in humans (Table 1) (Burri 1997; Plopper and Hyde 2008; Tarantal and Gargosky 1995).
Because the amount of site-specific paraffin sections was limited in these fetal lungs, we quantified only the abundance of mucosubstance in the airway epithelium of proximal (intrapulmonary generations 1-3) conducting airways, determined using stereologic assessment of lung structure (Hsia et al.
The recent discovery of profound remodeling in the distal conducting airways of young rhesus monkeys exposed since infancy to cyclic episodes of ozone and house dust mite aerosol (10) emphasizes the urgency of the situation.
Repeated episodes of exposure to ozone alters postnatal development of distal conducting airways in infant rhesus monkeys.
Conducting airways receive their blood supply from branches of bronchial arteries, while the terminal respiratory units receive blood from branches of the pulmonary arteries.
The walls of the conducting airways are mostly composed of epithelial lining, connective tissue elements, and a smooth muscle sleeve.
From the 144 embedded tissue blocks, 96 contained intrapulmonary conducting airways as well as lung parenchyma, and these were used for analysis by TEM.
The microscopic analyses of inhaled and deposited MMVF 10a in hamster lungs described here show that in the conducting airways almost all fibers were submersed in the aqueous lining layer, whereas in the alveoli only about one-third of the fibers were completely covered by lining layer material.
They cover the entire alveolar surface, or air sacs, of the lungs and the terminal conducting airways
which lead to the alveoli.
The size and number of holes in the packet's membrane, in conjunction with Aradigm's proprietary system to control breathing parameters, can be adjusted to target drugs to different areas of the lung -- the conducting airways
for certain types of respiratory therapy, or the alveoli (peripheral lung) for drugs where absorption into the systemic circulation is required for therapeutic effect.
There was little evidence of visible particle accumulation in the larger conducting airways
(generations 2-6), except in bronchial-associated lymphoid tissues and within peribronchial connective tissue.