Biomedical subjects
R A MacMahon
Publications and source records attributed to R A MacMahon.
Unilateral enlargement of the testis in childhood: does it need exploration?
Unilateral testicular enlargement in the pubertal boy is not an indication for exploration and biopsy, if the clinical features and investigations show no evidence of malignancy. In the prepubertal boy, unilateral testicular enlargement is not necessarily an indication for exploration if there are no clinical or investigational grounds for suspicion of neoplasia. Close follow-up is essential.
Detection of gonadal carcinoma in situ in childhood and implications for management.
Cells with the characteristic features of carcinoma in situ (CIS) were detected in histological sections of the gonads of three of seven children with clinical syndromes associated with a high risk of gonadal neoplasia. It is suggested that early detection of these cells may be useful in resolving problems of management, including gonadectomy and decisions about sex of rearing. Early detection of CIS cells may have a place in the management of the undescended testis.
Fatal air embolism following endoscopy of a hepatic portoenterostomy.
The case reported is that of a 10-year-old girl born with congenital biliary atresia who had undergone a Kasai procedure in the first year of life. She presented with ascending cholangitis, and investigations revealed a stricture of her portoenterostomy with an intrahepatic stone above the stricture. At laparotomy there were numerous adhesions and dilated varices, so the descending loop of the Kasai was exteriorized to enable a subsequent percutaneous endoscopic manipulation of the stone. During manipulation of the stricture via a pediatric endoscope in the jejunal loop the patient collapsed and died. Post mortem revealed a massive air embolism and varices of the jejunal loop.
Effect on the fetus of infusing a commercial amino acid preparation into a pregnant sheep.
The common clinical practice of intravenous feeding of the pregnant woman poses the question of the effect on the fetus of such infusions. We have used the sheep as a model to study the change in fetal amino acid levels after a maternal infusion of Synthamin 13. The maternal plasma aminogram largely reflects the amino acid pattern in the infusate. However, in the fetal circulation only the branched chain amino acids (leucine, isoleucine and valine), phenylalanine and alanine rose significantly after infusion. Only leucine and isoleucine were observed to spill into the fetal urine. The results suggest that the ovine placenta selectively modifies the amino acid profile presented to the fetus when the maternal plasma aminogram is distorted. However, the fetus is not totally protected from changes in phenylalanine, which in high concentrations, is detrimental to normal development.
Failure of IGF-1 to affect protein turnover in muscle from growth-retarded neonatal rats.
To investigate the response of the growth retarded neonatal rat to insulin-like growth factor-I (IGF-I) we have measured the effect of IGF-I on in vitro muscle protein synthesis and degradation rates in growth retarded and control neonatal rat pups. The growth retarded pups were growth retarded in utero by ligation of the uterine blood supply at day 17 of gestation. Basal levels of muscle protein synthesis in vitro were significantly lower in growth retarded pups compared with controls. Protein degradation rate were not different in muscles taken from the two groups. IGF-I stimulated protein synthesis in muscle from control pups by 12% and 15% at 20 ng/ml and 200ng/ml respectively. Net protein degradation was inhibited by 20% in the presence of 20ng/ml IGF-I. IGF-I had no effect on net protein synthesis or degradation in muscle from growth retarded pups. Neither Multiplication Stimulating Activity (at 20ng/ml or 200ng/ml) nor insulin (at 40ng/ml or 800ng/ml) was able to increase synthesis or decrease degradation of protein. Specific receptors for IGF-I are present on muscle membranes from both groups. Unlabelled IGF-I was more effective than MSA or insulin in competing with 125I-IGF-I for binding to the receptor. The relative affinities are consistent with type I IGF receptors. The affinity of these receptors for IGF-I was similar (Kd approximately 5nM) in both groups and the receptor concentration in both cases was approximately 250 fmol/mg protein. The refractility of tissue from growth retarded pups to IGF-I may be partially responsible for the lack of catch up growth in growth retarded neonates.
Germ cells and ova in dysgenetic gonads of a 46-XY female dizygotic twin.
The frequency of germ cell neoplasms in girls with 46-XY gonadal dysgenesis suggests that germ cells may persist in the dysgenetic gonads for many years. A phenotypic female infant with a karyotype of 46-XY in blood, skin, and gonads had a few ova in primordial follicles and numerous germ cells in her dysgenetic gonads at the age of 3 months. At 3 years and 10 months of age her gonads contained no primordial follicle and the only remaining germ cells were in a gonadoblastoma. We propose that germ cells are lost from dysgenetic gonads much more rapidly than from normal gonads, but that the rate of loss in patients with a karyotype of 46-XY may be less than the rate of loss in patients with a karyotype of 45-XO.
Total parenteral nutrition of premature infants. 1. Requirement for macronutrient elements.
Explore the source record for details and available documents.
Total parenteral nutrition of premature infants. 2. Requirement for micronutrient elements.
Explore the source record for details and available documents.
Glucose tolerance in very low birthweight infants.
Explore the source record for details and available documents.
Total parenteral nutrition in very low birthweight infants: a controlled trial.
Explore the source record for details and available documents.
Nitrogen balance studies during oral and complete intravenous feeding of small premature infants.
Explore the source record for details and available documents.
The use of microsurgery in the treatment of the undescended testis.
An experimental method of orchidopexy for high inguinal or abdominal testes, in the dog, using microsurgical anastomosis of the testicular vessels to vessels of the thigh or inferior epigastric vessels, is described. Experimental results suggest that this is a feasible method of treatment of such testes. A clinical trial of the method has commenced.
Balance studies of nine elements during complete intravenous feeding of small premature infants.
Explore the source record for details and available documents.
Congenital granular-cell myoblastoma.
The clinical and pathologic features of congenital granular-cell myoblastoma in five infant girls are reported. One lesion, treated expectantly, progressively decreased in size and after 3 yr and 9 mo could not be detected, while two lesions which were imcompletely excised did not recur. It is suggested that congenital granular-cell myoblastoma is caused by an intrauterine stimulus, and that this stimulus may possible be production of estrogen by the fetus. Congential granular-cell myoblastoma should be treated expectantly or by limited excision, and has an excellent prognosis.
Preliminary results of a clinical trial of intravenous feeding of premature infants of birth weight 1050g or less.
Explore the source record for details and available documents.