EFFICACY OF THE LARYNGEAL REFLEX DURING OXYGEN-NITROUS OXIDE SEDATION (RELATIVE ANALGESIA)

The efficacy of the laryngeal reflex during dental treatmentin two groups of children was tested using propyliodone 10ml.In 25 children not specially afraid of dental treatment therewas no aspiration of radiopaque dye into the larynx or chest.A similar group of 25 anxious children treated using oxygen-nitrousoxide sedation (relative analgesia) were examined in the sameway; there was no aspiration of radiopaque dye. ^*Present address: New Channg Cross Hospital, Fulham Palace Road,SW6.     

Red Cell Superoxide Dismutase Activity in the Newborn

Red cell superoxide dismutase activity was determined on cord blood samples. The normal range of activity in neonates, measured per gram of haemoglobin, was lower than that obtained for adults, with the mean value for neonates being approximately two-thirds of the adult level. When activity was measured on a per cell basis it was still lower than the adult level. Adult levels are reached at approximately three months postnatal age. No correlation was found between low superoxide dismutase activity and prematurity, low birthweight. Apgar, respiratory distress syndrome, or sex.     

Arrhythmias Caused by Platelet Activating Factor

Platelet Activating Factor and Arrhythmias. Introduction: Both ischemia and reperfusion are associated with ventricular arrhythmias. In both instances, neutrophils migrate into the ischemic zone, are activated by locally released factors, and hind to myocytes. The activated neutrophils liberate platelet activating factor (PAF). We have studied the arrhythmogenic actions of PAF on transmembrane potentials of isolated canine cardiac myocytes. Methods and Results: Cardiac myocytes were prepared from normal canine hearts by standard methods and studied in vitro by recording transmembrane potentials under control conditions and during exposure to graded doses of PAF, usually 0.25 to 1.25 μg (0.25 to 1.2 μM). Myocytes were superfused with Tyrode's solution (2.0 mL/min), paced at a cycle length of 1000 msec, and maintained at a temperature between 36° and 38°C. PAF caused a consistent and dose-dependent set of alterations in the transmembrane potential, including increased action potential duration, runs of early afterdepolarizations (EADs), and transient arrest of repolarization (PA). In addition, in some myocytes PAF caused intermittent small depolarizations both at the plateau voltage and resting potential. The effects of PAF were transient: only some residual action potential prolongation was noted after Tyrode's washout for 5 minutes. Effects of PAF were blocked in a dose-dependent manner by the PAF receptor antagonist, CV-6209. Both tetrodotoxin (1.2× 10^-6 M)and xylocaine (5 × 10^-5 M) antagonized the ability of PAF to cause EADs and PA. Conclusions: PAF consistently exerts arrhythmogenic effects on the membrane of ventricular myocytes. Since PAF is liberated by activated neutrophils and since activated neutrophils migrate into ischemic myocardium on reperfusion, we judge that PAF liberated by such neutrophils is an important arrhythmogenic factor for reperfusion arrhythmias. The same mechanism may be a cause of arrhythmias during the evolution of infarction.     

Imaging Yttrium-90 Synovectomy Studies

The method of planar imaging utilizing Bremsstrahlung radiation in patients treated with intraarticular Yttrium-90 for joint synovitis is described, illustrated and discussed.