title: Direct determination of luminal diameter changes in intrapulmonary airways.
abstract: A method is described for the direct measurement of changes in luminal diameter at all levels of the airway. Using this method it was found that (i) abrupt bronchiolar collapse occurred in the preterminal and terminal bronchioles once the luminal diameter was reduced to a critical level: (ii) decreased temperatures resulted in airway narrowing which was reversed by increasing the temperature to above 25 degrees C; as a rule, airway narrowing followed a cranial to caudal direction, and higher concentration of a drug being required to close the peripheral airways; (iii) bronchodilators except Carbuterol had no effect on resting bronchial tone or on acetylcholine-induced constriction in the absence of alpha-adrenoceptor blockade; (iv) at 35 degrees C rhythmic waves (frequency 6--20/min) were observed; these waves travelled from the periphery in a cranial direction.
mesh_terms: D000200:Action Potentials; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D001980:Bronchi / Q000033:anatomy & histology / Q000502:physiology*; D005260:Female; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009129:Muscle Tonus / Q000187:drug effects*; D009130:Muscle, Smooth / Q000502:physiology*; D051381:Rats; D012701:Serotonin / Q000494:pharmacology; D013696:Temperature
chemical_list: D000318:Adrenergic beta-Agonists; D012701:Serotonin