George M. Maxwell

The effect of dopamine upon oxidative metabolism of brown fat adipocytes

The effect of dopamine upon the oxygen consumption (QO2) of brown fat adipocytes was measured by polarography. The results showed a marked stimulation of QO2 by dopamine, similar to that induced by noradrenaline. The dopamine response could be blocked by haloperidol, butaclamol, propranolol and by high concentrations of tolazoline. These results suggest a role for dopamine in energy release from brown fat.

The cardiovascular effects of terbutaline

Abstract Terbutaline is claimed to be a nearly specific beta-2-adrenergic agonist. The cardiovascular effects were studied in anaesthetised intact dogs. The drug produced vasodilatation, but also considerable positive cardiac inotropism and chronotropism. The separation of beta-receptors into subtypes may be somewhat artificial.

THE ‘BATTERED-CHILD’ SYNDROME IN SOUTH AUSTRALIA

A study has been made of 26 children with the ‘battered baby’ syndrome, 8 of whom died. There was a high incidence of irregular unions among the parents and some evidence of other anti‐social behaviour. It is recommended that all such cases should be reported to a central authority, and that model legislation be considered for the protection of these patients, and of the reporting physicians.

The effect of Na3EDTA-induced hypocalcemia upon the general and coronary hemodynamics of the intact animal

Abstract The action of Na 3 EDTA-induced hypocalcemia upon the intact animal is reported. Respiratory exchange is stimulated, cardiac output is maintained, but there is a decrease in the pressures in the greater and lesser circuits. Coronary blood flow increases modestly, although coronary vascular resistance decreases. There is an increase in the cardiac usage of oxygen and carbon dioxide.

Indomethacin therapy of patent ductus in preterm infants controlled by plasma levels

Abstract Indomethacin was given by suppository to 18 neonates for the treatment of patent ductus arteriosus. The plasma levels of the drug were measured by high pressure liquid chromatography. Permanent closure of the ductus was achieved in 12 of 21 treatments and took up to 48 h. Successful treatment was strongly associated with a plasma indomethacin level >0.5 μg/ml in the 8 h after a dose. Decreased urinary output was more likely at the same level, but was also found with substantially lower figures. It is suggested that indomethacin therapy for patent ductus should be rationalized by measurement of the plasma level.

The effect of acute hypercalcemia upon the heart of the intact dog

Abstract This study demonstrates that the effect of acute hypercalcemia in the intact animal is to decrease heart rate and increase systemic pressure. The former is a baroceptor response, mediated by the vagus; the latter is perhaps due to release of catecholamines. There was. contrary to a previous report, 2 no evidence of increase in heart rate or coronary blood flow, nor any change in myocardial metabolism.

Urinary catecholamine levels in the newborn infant

The urinary concentrations of dopamine, noradrenaline and adrenaline were measured by a radioenzymatic method in 212 full-term and premature newborns. The ranges, means and standard deviations from birth to 4 days + are presented. The excretion of dopamine was ten times that of noradrenaline or adrenaline. The absolute concentrations of each catecholamine were reduced as birth weight decreased. The values were increased in babies with fetal distress. Any changes found in hypoglycaemic or jaundiced infants were attributable to prematurity. Very high levels were found in a few infants given tolazoline. We speculate that the role of dopamine production and excretion in the newborn has been underestimated. Dopamine may have an important role to play in the homeostatic mechanisms of the newborn.

A STUDY OF GROWTH IN CONGENITAL HEART DISEASE WITH A NOTE ON THE EFFECT OF SURGERY

Failure of growth in congenital heart disease is an accepted finding (Taussig, 1947), and among the many factors which have been adduced to explain this failure are: respiratory infections (Mehrizi and Drash, 1962), haemodynamic difficulties, and parental size (Umansky and Hauck, 1962).

The Action of Dopamine upon Brown Adipose Tissue

ABSTRACT: We increased the mass of interscapular brown adipose tissue in rats by dietary manipulation (“cafeteria” feeding), cold exposure, or by both. The animals were then used to determine the temperature response of the interscapular brown adipose tissue to dopamine or norepinephrine. These results, and the increase in blood glycerol values, were very similar for either catecholamine. These findings suggest that dopamine may have a role in releasing energy from brown adipose tissue similar to that of norepinephrine in the newborn infant.

The effect of thujaplicin (4-isopropyl tropolone) upon the general and cardiac haemodynamics and metabolism of the intact dog

Abstract Thujaplicin (4-isopropyl tropolone) interferes with catecholamine synthesis and destruction in vitro; the effects of the drug were studied in vivo, with reference to the general and coronary haemodynamics and metabolism of intact dogs. The drug caused a prolonged increase in cardiac output (Fick or dye-curve), vascular pressures, and cardiac work; vascular resistances were reduced. Coronary flow (N2O Fick) increased, as did cardiac oxygen consumption and carbon dioxide production. Cardiac efficiency was maintained. The drug increased blood glucose values, but had no effect upon non-esterified fatty acid levels. These results suggest a catecholamine-effect, probably brought about by inhibition of catechol-O-methyl transferase.