Biomedical subjects
C Morley
Publications and source records attributed to C Morley.
Factors that regulate extrarenal erythropoietin production.
Extrarenal sites are the major source of erythropoietin (Ep) production in fetuses and neonates. Afterwards, however, the kidneys are the major site. The most likely site of Ep production is the liver, although attempts to extract Ep from the liver have been, to date, unsuccessful. Extrarenal Ep production, as is the case for renal Ep production, is regulated primarily by the oxygen demand: supply. However, some differences have been identified in the response of extrarenal and renal sites of Ep production to several conditions. Two classes of conditions that selectively influence extrarenal Ep production are the subject of this paper. These are the following: 1) factors that cause reparable hepatic injury--including partial hepatectomy, CC14, and bile duct ligation, and 2) continuous perfusion of angiotensin II. The differences between the mechanism by which these two factors influence extrarenal Ep production will be explored and discussed.
Aetiological associations of intraventricular haemorrhage.
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Interaction of spontaneous respiration with artificial ventilation in preterm babies.
During a four-month period, all babies who received mechanical ventilation in the Neonatal Intensive Care Unit were studied to determine the effects of artificial ventilation on spontaneous respiratory activity. The babies were either totally apneic or ventilator inflation stimulated one of four distinct spontaneous respiratory patterns: synchronous breathing, Hering-Breuer reflex, augmented inspiration, or active expiration against ventilator inflation. The particular interaction evoked was dependent on the frequency of ventilation and the clinical condition of the baby. Only one pattern, active expiration against ventilator inflation, was consistently recorded before the development of pneumothorax. Preliminary evidence indicates that immediate paralysis of the baby as soon as that pattern is demonstrated may prevent the occurrence of pneumothoraces.
Sustained improvement in exercise tolerance following physiological cardiac pacing.
Fifty-three patients have received 'physiological' pacemakers, 37 with atrioventricular (AV) block having atrial synchronous units (VAT or VDD) implanted and the remaining 16 patients with both AV block and sick sinus syndrome having 'universal' (DDD) pacemakers. Effort tolerance was assessed by serial bicycle ergometry and in 16 patients direct comparisons between ventricular pacing and atrial synchronous pacing could be made acutely. Physiological pacemakers were found to increase maximum effort tolerance by 43% compared to pre-pacing values (P less than 0.01). The increase was sustained over a mean of 33 months post pacing. The atrial synchronous mode increased maximum effort tolerance by 34% acutely compared to ventricular inhibited pacing. Dual chambered 'physiological' pacemakers represent a significant therapeutic advance over standard ventricular inhibited pacemakers.
Physiological benefits of atrial synchrony in paced patients.
Over a five-year period, hemodynamic exercise capacity studies and a randomized controlled trial have been performed in a total of 50 patients. DVI vs. VVI pacing showed an increase in stroke work index (P less than 0.005) and a fall in left ventricular filling pressure (P less than 0.05) in 17 patients. VDD/DDD pacing vs. VVI showed an exercise capacity benefit in 44 patients (P less than 0.01) including 8 patients with sinus node disease and a lower peak heart rate (P less than 0.02). Maintenance of benefit was also shown of VDD/DDD pacing in the longer term (13 months) vs. acute (P - NS). The controlled trial VDD/DDD vs. VVI showed benefit in shortness of breath (P less than 0.01) and general well being (P less than 0.01). It is concluded that atrial synchronous ventricular pacing (VDD/DDD) is the mode of choice in suitable patients.
Physiological benefits of atrial synchrony in paced patients.
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Modern atrial and ventricular leads for permanent cardiac pacing.
Three hundred and fifteen transvenous pacing leads of various modern designs have been assessed over a period of three years. Of these, 103 were implanted in the atrium and 212 in the ventricle. Screw-in leads in the right atrial appendage and short tined leads in the ventricle have resulted in the virtual elimination of lead displacement, and a very low incidence of other lead related problems. In two lead systems it has been found advantageous to have both leads constructed of urethane.
Artificial surfactant and natural surfactant. Comparative study of the effects on premature rabbit lungs.
Premature newborn rabbits, delivered on day 27 of gestation, were treated with tracheal deposition of dry artificial surfactant containing dipalmitoyl phosphatidylcholine and unsaturated phosphatidylglycerol (7:3), or crude natural surfactant prepared by centrifugation of lung wash from adult rabbits. Before receiving surfactant, the animals were allowed to breathe for 7--27 min; they were then subjected to artificial ventilation under standardised conditions. In comparison with littermate controls, both groups of surfactant-treated animals showed statistically significant improvement in lung-compliance 30 and 60 min after onset of ventilation. However, necrosis of bronchiolar epithelium and hyaline membranes was present in nearly all animals, even in those treated with natural surfactant; this suggests that in order to prevent epithelial lesions, surfactant should be given as soon as possible and preferably at birth. Our findings confirm earlier observations that treatment with supplementary surfactant has a beneficial effect on lung mechanics in the premature neonate. The fact that this effect can be obtained not only with natural surfactant but also with dry artificial surfactant should increase the possibility of clinical application.
Proceedings: Case of hyperammonaemia due to ornithine transcarbamylase deficiency.
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Effects of androgenic steroids on erythropoiesis.
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Lethal short-bowel syndrome: more than a medical challenge.
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