Smooth Rings Research Articles

Maturation of contractile response of ductus arteriosus to oxygen and drugs.

Contractile responses of rings of ductus arteriosus from fetal and neonatal guinea pigs were studied in buffered Krebs-Henseleit solutions of various oxygen tensions. Oxygen-induced contraction of ductus arteriosus increased with gestational age, peaking at term and attenuating within 24 h after birth. Contractions of ductus in response to potassium were not different in term and preterm fetuses. Maximal contractile response of pre- and postductal aortic rings to oxygen was 8.3% of the maximal oxygen-induced contraction of ductal rings from the same fetuses. Pulmonary artery was quite insensitive to oxygen. Of 12 ductus exposed to bradykinin in the absence of oxygen seven contracted (maximal response was obtained with 15.0 ng/ml). Exposure of ductus to bradykinin in the absence of oxygen enhanced subsequent contractions of ductal smooth muscle rings to air. Atropine failed to inhibit the oxygen-induced contraction of ductus. These data suggest that acetylcholine is not essential for oxygen-induced contraction of the guinea pig ductus arteriosus.

Gastric acidity and acid therapy in allergy

T HIS investigation was conducted to test the validity of the claim that a connection exists between allergy and gastric hypoacidity, and to test the worth of acid therapy. The association of low acidity with various allergic conditions has been found by numerous workers: Ehrmann,l, 2 Urbach,3 Csillag,4 Barber and his coworkeq5 Duke,6 Criep and McElroy,7 Rowe,’ HursLg Knott and his coworkers,10 Criep and Wechsler.ll BrayL2~“3 has reported the gastric analyses of 200 asthmatic children, 80 per cent of whom were below normal in free acid. When HemingwayI subjected isolated smooth muscle rings to changes in hydrogen ion concentration, he found that there was an increasing reaction (constriction) as the alkalinity increased. In line with this, McConnell and his coworkers15 showed that experimental alkalosis of the blood stream increased the size of the histamine wheal, whereas acidosis markedly diminished its size. Benefit of varying magnititude has been attributed to the use of different forms of acid therapy in allergic cases by such men as Criep and McElroy,? Peshkin and Fineman,l’j Beckman,17 Scheer,l* and Barborka.lQ Tiefensee’O studied the acid-base balance of asthmatic individuals and found that there was a shift toward alkalosis during attacks ; acid therapy was distinctly beneficial. Brayl*s ‘I3 advocates the acid therapy highly, giving his patients large therapeutic doses of dilute hydrochloric acid over a period of several months, with striking benefits which continue even after medication has ceased. Bray had been prescribing the acid therapy for eighteen months at the time of his publication,12 and stated that the majority of patients treated had remained symptom free for a year.