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Biomedical subjects

R A MacMahon

Publications and source records attributed to R A MacMahon.

At least 19 recordsLinked to original sources
PubMed1997

Antenatal intestinal vascular accident with subsequent small bowel atresia: case report.

A woman was referred at 25 weeks' gestation with decreased fetal movements. Ultrasound revealed a large solid fetal abdominal mass and gross fetal ascites. Amniocentesis and viral titers were normal. On subsequent ultrasound examinations, the mass and ascites slowly disappeared, but a small bowel obstruction developed. Spontaneous labor occurred at 35 weeks and the child was born with a distended abdomen. At laparotomy there was type 3 jejunal atresia, indicating that the fetal mass and ascites were secondary to this antenatal small bowel ischemia.

Adult↗
PubMed1994

Acute appendicitis in children: when does ultrasound help?

Fifty-six patients with possible appendicitis were evaluated clinically and by ultrasound. Ultrasound examination visualized the appendix in 18 of the patients evaluated and showed another pathology in six others. It was useful when the clinical picture was not clear (25 patients) as it showed an inflamed appendix in 10 patients. This was of particular value when there was another critical illness making clinical evaluation difficult (three patients), and for the diagnosis of other unsuspected pathological conditions (six patients). It did not affect the line of management when the clinical picture was clear enough to diagnose or exclude acute appendicitis.

Acute Disease↗
PubMed1993

In utero repair of diaphragmatic hernia.

This report describes the first in utero repair of diaphragmatic hernia in Australia. The patient was a 32 year old woman with major infertility problems who was diagnosed at 15 weeks gestation as having an infant with diaphragmatic hernia. After extensive consideration and counselling the parents requested in utero repair. This was performed at 28 weeks gestation and was technically successful, but the infant was found to be dead after uterine closure. The mother has subsequently been delivered of normal twins at term by Caesarean section. In utero repair of diaphragmatic hernia requires a high degree of team work, is technically demanding and has major ethical implications. It should be restricted to nationally designated units.

Adult↗
PubMed1991

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.

Biopsy↗
PubMed1991

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.

Adolescent↗
PubMed1990

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.

Biliary Atresia↗
PubMed1990

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.

Amino Acids↗
PubMed1990

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.

Animals↗
PubMed1986

Changes in plasma amino acids in the developing chick.

We have sampled arterial blood from chicken embryos during development and measured the changes in plasma amino acids from mid-gestation to hatching. During gestation, several amino acids rise to a peak concentration at 16 days and fall prior to hatching. After hatching, most amino acids fall, although the plasma concentrations of aspartate, glutamate and taurine rise significantly.

Amino Acids↗
PubMed1981

Intravenous solutions in parenteral nutrition.

A review of the theoretical basis on which amino acid intravenous solutions are formulated leads to the conclusion that the first class protein model is not ideal for the very small premature infant. Comparison of the serum and urine amino acid levels in a controlled trial between intravenous feeding with "Vamin" and intragastric milk feeding, and further comparison of these values with the cord blood values of premature infants supports the conclusion that the first class protein model is not ideal. The balance studies also support the view that the urinary output of amino acids, as well as the serum levels, should be taken into account in determining the ideal amino acid input.

Amino Acids↗
PubMed1980

Results of the use of autotransplantation of the intraabdominal testis using microsurgical vascular anastomosis.

This study indicates that where facilities are available, the use of autotransplantation of the intraabdominal testis with microsurgical anastomosis to vessels of the groin is an acceptable, and possibly the best, alternative to orchidectomy for the intraabdominal testis. It is certainly justifiable in the case of the bilateral intraabdominal testis but in the case of the unilateral intraabdominal testis with a normally descended and apparently normal testis in the opposite hemiscrotum, the incresed incidence of neoplasia in intraabdominal testes should be taken into account in the decision on the method of treatment.

Adolescent↗
PubMed1980

Importance of early diagnosis and gonadectomy in 46, XY females.

Gonadal neoplasms developed in three 46, XY females aged 3 yr and 10 mo, 15 yr, and 19 yr. One patient died from metastatic neoplasia. Early diagnosis of 46, XY gonadal dysgenesis is essential, and should be considered in female infants and children with any features of Turner's syndrome, ambiguous genitalia, phallic hypertrophy, excessive height, large hands and feet, failure of development of secondary sexual characteristics, primary amenorrhea, abdominal mass, or unexplained hypertension. Any female with gonadal dysgenesis and a Y chromosome in her karyotype should have prophylactic gonadectomy as soon as possible. The absence of Sertoli cells in these patients, causing lack of androgen binding protein with deficient local concentration of androgens and consequent failure of maturation of spermatogonia, may lead to unregulated proliferation of germ cells, and hence explain the frequency of gonadal neoplasia in the 46, XY female.

Adolescent↗
PubMed1979

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.

Child, Preschool↗