Bronchomotor tone in protein-energy malnutrition

The study examined the reactivity of the tracheobronchial tree of rats maintained on low protein and tryptophan-deficient diets. It was found that: (1) Rats maintained on 5 percent protein or triptophan-deficient diets showed little or no weight gain. A 15 percent protein diet was adequate for normal growth of female rats, but not of male rats. (2) Airways of malnourished rats showed significant bronchoconstriction when treated to an acetylcholine (AcCH) concentration of 10 to the 11 power M. The treshold concentration of AcCh for normal rats was 10 to the -5 M. Airways of malnourished rats were also more sensitive to cold. (3) Rehabilitation of the malnourished rats attenuated the response to AcCh. Recovery, however, was not complete. (4) Prior application of phentolamine and atropine markedly reduced the sensitivity of the airways of malnourished rats to AcCh. The results seem to indicate that O-adrenoceptors and the vagus nerve may be involved in the observed increased reactivity of airways of malnourished rats.(AU)

Direct determination of luminal diameter changes in intrapulmonary airways

A method is decribed 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 O-adrenoreceptor blockade; (iv) at 35 degrees C rhythmic waves (frequency 6--20/min) were observed; these waves travelled from the periphery in a cranial direction. (AU)