Biomedical subjects
Publications and source records attributed to N Wilson.
Two children presented with congestive heart failure in the neonatal period due to malformations of the vein of Galen. Transtorcular coil embolisation produced rapid relief of heart failure. Post-mortem examination showed occlusion of the malformation in one child. The other child is clinically normal at seven months.
We have previously shown that testicular fluid contains factors that can inhibit luteinizing hormone (LH)-stimulated androgen production by Leydig cells, and others have reported the presence of immunoreactive vasopressin (iAVP) in the testes as well as in vitro inhibition by vasopressin of Leydig cell-androgen production. In the current report, we have used an established radioimmunoassay (RIA) to measure the concentration of iAVP in testicular fluid and have related changes in iAVP concentration to disruption of the seminiferous tubules. Spermatogenesis was disrupted in adult rats by surgically establishing bilateral cryptorchidism. The concentration of iAVP decreased progressively from 349 +/- 52 to 61 +/- 5 pg/ml during 4 wk. When cryptorchidism was unilaterally established, the concentration of iAVP in fluid from that testis decreased to 116 +/- 19 pg/ml while the concentration of iAVP in the contralateral scrotal testis remained unaffected. Unilateral ligation of the ductuli efferentes also caused an equivalent unilateral decrease in iAVP to 110 +/- 15 pg/ml. The osmotic pressure of the testicular fluid was not altered by disruption of gametogenesis, and the extracellular "albumin space" was not increased. Therefore, the decrease in concentration of iAVP was probably not due to dilution with increased amounts of interstitial fluid. We conclude that the disruption of spermatogenesis is associated with a decrease in the concentration of iAVP in testicular fluid and suggest that AVP or a similar peptide may be involved in the intratesticular mechanisms associated with increased production of androgen by Leydig cells after disruption of spermatogenesis.
Captopril was used in 20 infants aged less than 1 year with heart failure secondary to defects with predominantly a left to right shunt that was poorly controlled with digoxin and diuretics. Total daily dose of captopril ranged from 0.88 to 2.5 mg/kg (mean 1.3 mg/kg) in three divided doses. Improvement in the control of heart failure was seen mainly as an increase in the rate of weight gain from a mean of 48 g/week before treatment to 102 g/week on treatment and a decrease in the mean respiratory rate from 68 breaths/minute to 60 breaths/minute. Side effects were seen in four patients--two with asymptomatic mild hypotension, one with renal insufficiency which improved with a reduction in dose, and one with severe oliguria progressing to renal failure. Significant changes in plasma electrolyte concentration did not occur except in the infant who developed acute renal failure.
Three patients developed protein-losing enteropathy caused by intra-atrial obstruction of the systemic venous return after Mustard's operation. The enteropathy resolved in one case after reoperation and in the others after balloon dilatation of the stenosed caval pathways. Protein-losing enteropathy may occur as a complication of Mustard's operation. Balloon dilatation of the obstructed baffle is an effective alternative to reoperation.
Percutaneous balloon dilatation of a Waterston anastomosis was performed in a child who had had four shunt operations. Initially, the procedure was apparently successful, but pulmonary oedema developed and he died 12 hours after the procedure. Balloon dilatation of a Waterston anastomosis is technically possible and may prove to be an alternative to reoperation in certain patients. But further experience with the technique is necessary to determine the optimum size of the inflated balloon, and to avoid the risk of producing an excessive increase in pulmonary blood supply.
Intracardiac and great artery blood flow velocities were recorded by pulsed and continuous wave Doppler ultrasound in 18 children aged between eight months and four years (mean 25 months) who had undergone anatomical correction of transposition of the great arteries in the first month of life. Postoperative peak flow velocities across the mitral valve and in the ascending aorta were not significantly different from those in an age matched control population, but tricuspid flow velocities were higher than normal. Aortic regurgitation was detected in only one of the eighteen patients, a markedly lower frequency than that reported after two stage anatomical correction. Peak velocities in the pulmonary artery were higher than normal, and in most cases there was some degree of stenosis of the pulmonary artery at the site of anastomosis.
The arterial baroreceptors are known to influence the release of vasopressin, but the quantitative relationship between baroreceptor stimulation and plasma vasopressin concentration has not been defined. These experiments examine the effect of stepwise changes in carotid sinus pressure (40-160 mmHg) on the plasma concentration of vasopressin in chloralose-urethan anesthetized rabbits. Plasma vasopressin concentration (9.2 +/- 1.2 pg/ml, n = 27) did not change in response to changes in carotid sinus pressure when the aortic depressor nerves were intact. These results were unaltered by bilateral cervical vagotomy. However, after aortic depressor nerve section, decreases in carotid sinus pressure were associated with increases in plasma vasopressin concentration. There appeared to be a greater redundancy in the baroreceptor control of plasma vasopressin than in the baroreceptor control of arterial pressure or heart rate. The results provided no evidence that receptors with vagal afferents have a tonic influence on the baroreceptor control of vasopressin release in the anesthetized rabbit.
Four children and one spontaneously aborted fetus from 2 separate families have a similar pattern of malformation secondary to duplication of distal 15q. In both families, the abnormal chromosomes were derived from balanced reciprocal translocations carried by the mothers. Clinical features common to the 4 liveborn children include appropriate birth weight, length, and head circumference for gestational age; similar craniofacial anomalies, including sloping forehead, bulbous nose, prominent nasal bridge and septum, midline crease in the lower lip, and micrognathia; arachnodactyly; joint contractures involving hands and feet; cardiac defects; and genital anomalies. The 2 infants with duplication 15q22.1----qter and deletion 13q32.3----qter died in the immediate neonatal period. The abortus, who shared the same chromosome constitution, had an omphalocele and a cephalic defect in neural tube closure. The 2 children with duplication 15q22----qter and deletion 11q25----qter survived but have severe psychomotor retardation and postnatal onset growth deficiency, at 48 and 30 months, respectively. The findings in these 5 cases plus review of the literature permit further delineation of a recognizable pattern of malformation secondary to duplication of distal 15q.
Changes in levels of plasma immunoreactive atrial natriuretic peptide (IR-ANP) were measured in response to administration of isoproterenol in the anesthetized, vagotomized rabbit. A dose-dependent increase in plasma IR-ANP was seen in response to 10 min isoproterenol infusions between 0.1 and 10.0 micrograms/kg/min. The time course of these responses showed the maximum levels of IR-ANP to be attained 10 min after the cessation of infusion. In rabbits in which plasma vasopressin (AVP) levels were also measured, the maximum levels of AVP were attained during the infusion period. There was no correlation between levels of AVP and IR-ANP suggesting that AVP released into the plasma did not affect directly the release of IR-ANP. The changes in IR-ANP in response to isoproterenol were significantly reduced in rabbits which had been administered the beta-1-adrenoceptor blocking agent, atenolol. In six rabbits in which the vagi remained intact, the increases in IR-ANP were reduced and became significant only with 10 micrograms/kg/min isoproterenol infusion. The results demonstrate that isoproterenol infusion increases the level of plasma IR-ANP in the anesthetized rabbit and suggest that this is through an effect on the heart rather than on peripheral vessels.
The hypothesis tested was that transducers of different types and shapes would produce different peak and mean ascending aortic (AAo) velocities. Additionally, we sought to determine if mean and peak velocity recorded from the descending aorta (DAo) were similar to velocities in the AAo. Twenty-eight consecutive individuals who had normal hearts were studied. AAo velocities were measured with four transducers including a nonimaging device that transmitted Doppler at right angles to the transducer handle, a 30-degree angled continuous wave transducer, an imaging transducer that transmitted Doppler in line with the transducer handle, and a second imaging transducer that sectored at 25 degrees to the transducer handle. DAo was studied with a standard in-line imaging transducer. Results showed that mean and peak AAo velocities recorded by transducers that transmitted off the axis of the transducer handle were similar, but the transducer that imaged along the transducer handle axis produced significantly lower peak and mean velocities. The problem that caused lower velocity for the on-axis transducer was inability to image the area immediately posterior to the sternum to permit alignment in the azimuthal dimension. The continuous wave transducer provided a wide spectral dispersion. Mean DAo velocity was similar to mean AAo velocity, but variability was large.
To evaluate the qualitative and quantitative changes in Doppler velocities in the normal fetus and newborn, 61 echo Doppler studies were performed in 18 neonates, nine of whom were also studied as fetuses. Four studies were inadequate in fetuses (one pulmonary artery, two mitral, and one tricuspid) and some post natal studies were inadequate due to inability to separate atrioventricular valve E and A velocity component waveforms (one tricuspid, three mitral). Heart rates for fetuses and newborns more than 24 hours of age and less than 24 hours of age were similar. Pulmonary artery diastolic velocities consistent with patent ductus arteriosus were present in 11 of 12 examinations at less than 6 hours of age, in 5 of 13 examined at 6 to 24 hours of age, and in 2 of 27 examined after 24 hours of age. Pulmonary artery times to peak velocity were similar in fetuses, m = 46, SD = 3 msec, and in neonates less than 6 hours of age, m = 51, SD = 13 msec, but lengthened significantly, p less than 0.05, at 6 to 24 hours (m = 69, SD = 14 msec). These changes are probably due to the dramatic changes in pulmonary vascular pressure that occur after birth. Data from 6 to 24 hours and greater than 24 hours (m = 78, SD = 13 msec) were similar. Significant differences existed for transmitral valve E/A ratios, which increased from m = 0.85 in utero to m = 1.17 (p less than 0.05) after birth, with no significant change thereafter.(ABSTRACT TRUNCATED AT 250 WORDS)
A baby presented in cardiac failure with cyanosis on the first day of life. Investigations demonstrated severe pulmonary valve stenosis and duct-dependent coarctation of the aorta. This combination is impossible to explain using recognised embryological theories.
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Two new cases of persistent fifth aortic arch are described, one with a distal connexion to the pulmonary circulation and the other to the systemic circulation. The previously reported cases are reviewed and the advantages conferred clinically by persistence of this structure are noted.
Operative balloon dilatation of the aortic valve was performed in seven neonates with critical stenosis of the aortic valve. The procedure was followed by the development of severe aortic regurgitation in four patients. Necropsy was performed in three and revealed partial detachment of the right coronary cusp of the aortic valve. Damage to the valve leaflet caused by balloon dilatation was probably the result of using a balloon with a diameter that was too large in relation to the aortic valve ring diameter and of shearing forces created in the aortic wall by the contracting ventricle. The diameter of the inflated balloon should not be larger than the diameter of the aortic valve ring.
In six infants with pulmonary atresia and intact ventricular septum operative balloon dilatation was used to achieve continuity between the right ventricle and the main pulmonary artery as the initial procedure. Two of the six subsequently needed an aortico pulmonary shunt. All six are alive and well.
Infusions of norepinephrine led to a significant sevenfold increase in plasma immunoreactive atrial natriuretic peptide, while infusions of acetylcholine caused no significant change in the level of the peptide. Efferent stimulation of the right vagus nerve or right inferior cervical ganglion in anesthetized, vagotomized rabbits produced no significant changes in the immunoreactive atrial natriuretic peptide. The findings suggest that the mechanism by which norepinephrine releases immunoreactive atrial natriuretic peptide is not the result of a direct action on the cardiac myocytes.
Immunoreactive atrial natriuretic peptide (iANP) levels in plasma of edematous rats with an experimental nephrotic syndrome produced by the injection of puromycin aminonucleoside (PAN) were not different from those in untreated rats. To test the ability of nephrotic rats to secrete iANP in response to a volume stress, the rats were subjected to 20% expansion of their estimated blood volumes using blood from donor rats. PAN-treated rats had very small natriuretic and diuretic responses compared with untreated rats; however, there was no difference in the secretory response of iANP, which increased approximately threefold in each group. There were highly significant correlations between changes in plasma iANP and changes in right atrial pressure in both normal and nephrotic rats. Nephrotic rats that were infused with synthetic ANP showed only a very small natriuretic and diuretic response compared with normal rats, and no change in glomerular filtration rate. The hypotensive response was still present, however. Urine concentration in nephrotic rats was much lower than in controls and was not increased by exogenous arginine vasopressin. It is concluded that the absence of a normal natriuretic and diuretic response to hypervolemia in PAN-treated rats is not caused by a failure to secrete ANP but might be a result of an intrarenal defect that makes their kidneys unresponsive.