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Biomedical subjects

R Marcelle

Publications and source records attributed to R Marcelle.

At least 91 records · Page 5Linked to original sources
PubMedDate not supplied

Cholinergic mechanisms and bronchoconstriction in guinea-pigs.

Seventy-four guinea-pigs have been actively sensitized against ovalbumin. The effects of bilateral cervical vagotomy and of cholinergic efferent blockade on the bronchoconstriction induced by inhaled acetylcholine, histamine or antigen have been quantified. Animals were curarized then tested during controlled ventilation to ensure constant conditions throughout the whole experiment by suppressing the post-vagotomy apneusis. Bronchial sensitivity was estimated by calculating the bronchoconstrictor dose-threshold provoking respiratory asynchronism. Corresponding variation of total lung resistance and dynamic compliance were also measured as indices of bronchial reactivity. The data obtained in 27 guinea-pigs indicated that the vagi section produced no significant effect on the direct bronchial response to histamine (P greater than 0.5), to acetylcholine (P greater than 0.1) or to antigen (P greater than 0.5). In 47 guinea-pigs, atropine at doses 5 and 10 times higher than the acetylcholine blocking one did not alter the direct bronchial response to histamine (P greater than 0.5). Higher doses induced a progressive decrease in bronchial sensitivity to antigen (.05 greater than P greater than .01) which could be related to the repetitive administration of the antigen. According to the present results, peripheral cholinergic mechanisms play no significant role in guinea-pigs neither in histamine nor in anaphylactic bronchoconstriction. Curarization has no influence on resting bronchial tone.

Acetylcholine↗
PubMedDate not supplied

Identification of three-element windkessel model: comparison of time and frequency domain techniques.

The problem of the parameter identification of the three-element windkessel model is studied. Minimization by least-square technique--LSQ--in time domain and frequential techniques--FFT--are compared. Continuous pressure and flow curves were recorded in the proximal aorta of an open chest dog. Comparison shows very high correlations between the parameter estimations obtained by LSQ and FFT methods. However, systematic differences appear between the calculated values, but do not seem to endanger physiological interpretation of the results.

Animals↗