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Biomedical subjects

M R Harrison

Publications and source records attributed to M R Harrison.

At least 343 records · Page 19Linked to original sources
PubMed1984

Kaolin-induced congenital hydrocephalus in utero in fetal lambs and rhesus monkeys.

A model of congenital hydrocephalus in utero in fetal lambs and rhesus monkeys has been produced by the intracisternal injection of kaolin. Initial attempts to produce hydrocephalus using silicone oil were unrewarding. Hydrocephalus had developed by 2 weeks post-injection and could be followed by ultrasonography. The pathological findings were similar to those reported using kaolin in other species. Ventriculoamniotic shunting, when successful, was capable of partially reversing the deleterious effects of hydrocephalus. The major drawback of the present model is that hydrocephalus is produced during the second rather than the first trimester of pregnancy. However, kaolin produces mainly an obstructive hydrocephalus without other associated brain or systemic anomalies.

Animals↗
PubMed1983

Correction of congenital hydronephrosis in utero III. Early mid-trimester ureteral obstruction produces renal dysplasia.

Is the renal dysplasia (RD) commonly seen in babies with urinary tract obstruction a developmental consequence of the obstruction or is it an associated embryologic malformation? We produced complete unilateral ureteral obstruction in six 58- to 66-day old lamb fetuses by clipping a silastic ring on the ureter. Three fetuses survived to term. All obstructed kidneys were not only grossly hydronephrotic but dysplastic by histologic criteria; ie, parenchymal disorganization, primitive epithelial structures, and marked fibrosis. The contralateral unobstructed control kidneys were normal. The changes were similar to those seen in the human neonate with obstruction and RD, suggesting that in this model RD was caused by obstruction to the flow of urine early in fetal development.

Animals↗
PubMed1983

Intestinal plication in the treatment of atresia.

Twelve infants with jejunal atresia were managed by plication of the dilated proximal bowel and end-to-oblique anastomosis. The technique is simple and very effective in preventing functional obstruction of the dilated bowel, and it preserves the mucosal absorptive surface. It is easier to perform and seems to allow earlier return of function than resection or tapering of the dilated jejunum.

Gastrointestinal Motility↗
PubMed1983

Loop colon rectovaginoplasty for high cloacal anomaly.

We describe a simple technique for simultaneous reconstruction of all three perineal openings, including a functional vagina, in a case of high cloacal anomaly. End-to-end stapled colo-vaginal anastomosis allows creation of both vagina and rectum from one loop of bowel.

Anus, Imperforate↗
PubMed1983

Correction of congenital hydronephrosis in utero. I. The model: fetal urethral obstruction produces hydronephrosis and pulmonary hypoplasia in fetal lambs.

In an attempt to simulate congenital hydronephrosis secondary to urethral obstruction, we evaluated the consequences of obstructing the urethra in fetal lambs by several techniques. When the urethra was ligated before 108 days gestation, the bladder decompressed through the urachus and the upper-urinary tract developed normally. Ligation of both the urethra and urachus produced gross bilateral hydronephrosis, hydroureter, and megacystis, as well as severe pulmonary hypoplasia, and was associated with a high perinatal mortality. Intermittent urethral obstruction produced with a balloon constrictor or by diverting urine externally and pressure-limited obstruction produced with a Pudenz valve both proved unsatisfactory for producing congenital hydronephrosis. Finally, ligation of the urachus and progressive gradual obstruction of the urethra with an ameroid constrictor produced hydronephrosis and pulmonary hypoplasia. This model simulates urethral obstruction in the human fetus and produces a clinical and pathologic picture similar to that seen in infants born with congenital hydronephrosis.

Animals↗
PubMed1983

Correction of congenital hydrocephalus in utero I. The model: intracisternal kaolin produces hydrocephalus in fetal lambs and rhesus monkeys.

In the fetus with congenital hydrocephalus, obstruction to the flow of cerebrospinal fluid (CSF) results in ventricular dilation and neurologic impairment. Decompression of the obstructed ventricles before birth may ameliorate the damage and allow normal development to proceed. Although appealing, this pathophysiologic rationale has not been adequately tested because a satisfactory fetal model has not been available. We have developed a model of obstructive hydrocephalus in the fetal lamb and rhesus monkey by injecting kaolin into the cisterna magna through the posterior atlanto-occipital membrane early in the last trimester. Preliminary studies injecting silicone oil were unsuccessful. The development of fetal ventriculomegaly was followed using prenatal ultrasonography. Massive hydrocephalus developed in six sheep, three liveborn at term and three stillborn after premature vaginal delivery, and in 2 fetal rhesus monkeys. All treated animals had external signs of hydrocephalus with marked cranial enlargement. Neuropathologic examinations demonstrated fibrosis of the leptomeninges and subarachnoid spaces around the fourth ventricle. Dilation of the lateral and third ventricles resulted, with attenuation of the cerebral white matter. On histologic examination, the grey matter was relatively well preserved, while the white matter was severely attenuated. This model mimics the clinical and pathologic picture seen in human infants and should allow us to study the pathophysiology of congenital obstructive hydrocephalus and the efficacy and feasibility of its correction in utero.

Animals↗
PubMed1983

Experimental pulmonary hypoplasia due to oligohydramnios and its reversal by relieving thoracic compression.

To investigate the role of thoracic compression in the etiology of pulmonary hypoplasia associated with oligohydramnios, we shunted amniotic fluid into the maternal abdominal cavity at 25-days gestation in one group of fetal rabbits and occluded the bladder outlet in another. Bladder-neck obstruction produced severe bilateral hydronephrosis. Both procedures produced oligohydramnios (amniotic fluid volume reduced, p less than .001) at reexploration on day 28. At term (day 31) newborns undergoing these procedures had significantly decreased lung weights (p less than .01). Lung histology was not affected. To determine whether decompression of the thorax would prevent pulmonary hypoplasia, another group of fetuses had their bladders occluded and underwent one of two procedures to relieve thoracic compression. In one group, amniotic fluid volume was restored by a constant infusion of normal saline. In the other, opening the abdomen and allowing viscera to herniate avoided thoracic compression from a diaphragm elevated by a dilated urinary tract and ascites. Liveborn obstructed rabbits undergoing either procedure had increased lung weight-to-body weight ratios compared to those in newborns undergoing only the obstructive procedure (p less than 0.05). These experiments suggest that mechanical restriction to lung growth plays a role in the development of pulmonary hypoplasia associated with oligohydramnios, and that pulmonary hypoplasia may be partially reversible by procedures which reduce thoracic compression.

Amniotic Fluid↗
PubMed1983

Congenital diaphragmatic hernia diagnosed prenatally by ultrasound.

Seven infants born at our institution between July 1979 and June 1982 had congenital diaphragmatic hernia (CDH). Four cases of CDH were correctly identified by fetal ultrasonography. Diagnosis relied upon the demonstration of abdominal organs within the thorax. During this period, no false positive diagnoses of CDH were made. Significant associated sonographic features included polyhydramnios, mediastinal displacement, and distorted upper abdominal anatomy.

False Negative Reactions↗
PubMed1983

Ultrasonographic evaluation of fetal paranephric pseudocysts.

Ultrasonographic evaluation of the fetus with urinary tract obstruction requires not only precise delineation of the level of obstruction but also differentiation from other nonobstructive renal entities. The authors evaluated five fetuses in which large unilocular paraspinous fluid collections were seen at ultrasonography. While these masses simulated the appearance of large hydronephrotic sacs, they actually represented paranephric pseudocysts. In four of the five cases in which a paranephric pseudocyst was seen the ipsilateral kidney was nonfunctioning.

Diagnosis, Differential↗
PubMed1983

Visual display units.

The suggestion that cataracts or other organic damage can result from exposure to radiation from visual display units (VDUs) is not supported by the best currently available epidemiological and experimental evidence. Eyestrain is common among VDU operators but is usually due to factors in the office environment, rather than defects in vision. Visual screening tests for operators should be simple, and tests for extraocular muscle balance and colour vision are not recommended.

Cataract↗
PubMed1982

Fetal treatment 1982.

Explore the source record for details and available documents.

Congenital Abnormalities↗
PubMed1982

In utero treatment of urinary tract obstruction.

A male fetus (one of twins) was noted to have ascites at 17 menstrual weeks and during the following 13 weeks developed a dilated and hypertrophied bladder, hydroureters, and hydronephrosis. Placement of an indwelling suprapubic catheter in utero allowed drainage of urine from the fetal bladder and further in utero development. The infant was born vaginally at 34 weeks and had "prune belly" syndrome but had normal pulmonary and renal function.

Catheters, Indwelling↗