Aideen M. Moore

Modulation of disease severity in cystic fibrosis transmembrane conductance regulator deficient mice by a secondary genetic factor

Mice that have been made deficient for the cystic fibrosis transmembrane conductance regulator (Cftr) usually die of intestinal obstruction. We have created Cftr-deficient mice and demonstrate prolonged survival among backcross and intercross progeny with different inbred strains, suggesting that modulation of disease severity is genetically determined. A genome scan showed that the major modifier locus maps near the centromere of mouse chromosome 7. Electrophysiological studies on mice with prolonged survival show that the partial rectification of Cl− and Na+ ion transport abnormalities can be explained in part by up-regulation of a calcium-activated Cl− conductance. Identification of modifier genes in our Cftr m1HSC/Cftr m1HSC mice should provide important insight into the heterogeneous disease presentation observed among CF patients.

Correlation of sonographic findings and outcome in necrotizing enterocolitis

BackgroundThere is little in the literature regarding the use of gray-scale and Doppler sonography of the bowel in necrotizing enterocolitis (NEC) and how findings depicted by this modality might assist in predicting outcome and influence management.ObjectiveTo correlate sonographic findings with outcome in NEC.Materials and methodsThis was a retrospective analysis of clinical and abdominal ultrasonography (AUS) findings in NEC from January 2003 to December 2005. AUS findings were evaluated for portal venous gas, free gas, peritoneal fluid, bowel wall thickness, echogenicity, perfusion and intramural gas. Patients were categorized into two groups, according to their outcome.ResultsA total of 40 infants were identified who had AUS for NEC prior to any surgical intervention. Group A comprised 18 neonates treated medically and recovered fully, and group B comprised 22 neonates who required surgery or died. Free gas (six patients) and focal fluid collections (three patients) were only found in group B. Increased bowel wall echogenicity, absent bowel perfusion, portal venous gas, bowel wall thinning, bowel wall thickening, free fluid with echoes and intramural gas were seen in both groups, but more frequently in group B. Anechoic free fluid was seen more frequently in group A. Increased bowel perfusion was seen equally in both groups.ConclusionAn adverse outcome was associated with the sonographic findings of free gas, focal fluid collections or three or more of the following: increased bowel wall echogenicity, absent bowel perfusion, portal venous gas, bowel wall thinning, bowel wall thickening, free fluid with echoes and intramural gas. Sonographic findings are useful in predicting outcome and therefore might help guide management.

The role of peritoneal drains in treatment of perforated necrotizing enterocolitis: Recommendations from recent experience

BACKGROUND/PURPOSE Intraperitoneal drains have been used in the treatment of perforated necrotizing enterocolitis (NEC), especially in infants less than 1,000 g, yet their role is still debated. The authors wished to examine their more recent experience in the treatment of NEC to make recommendations for operative management. METHODS The authors reviewed the records of all infants seen between 1989 and 1995 who had clinical and radiological evidence of NEC at the Hospital for Sick Children, Toronto, Ontario. One hundred sixty-seven infants were treated for NEC and 73 (44%) infants required surgical intervention. RESULTS Forty-five patients had perforated NEC; 23 were treated initially by peritoneal drainage and 22 by primary laparotomy. The 23 newborns who had peritoneal drainage were of significantly lower birth weight, and 19 (83%) of these infants required subsequent laparotomy for worsening disease. The overall mortality rate for perforated NEC was 36%. CONCLUSION Insertion of a peritoneal drain is still useful in resuscitating small critically ill infants with NEC; however, the majority of these infants will also require laparotomy.

Placental Pathology in Neonatal Stroke

OBJECTIVE: Neonatal stroke is increasingly recognized, and risk factors have been identified. The placenta has been implicated as a potential contributor to neonatal stroke; however, pathology has not been previously described. This case series systematically evaluates prenatal, maternal, and neonatal risk factors and describes placental pathology in 12 cases of neonatal stroke. PATIENTS AND METHODS: We reviewed the Canadian Pediatric Ischemic Stroke Registry from 1992 to 2006, which consists of 186 neonatal stroke patients. Twelve patients with symptomatic cerebral arterial ischemic stroke or sinovenous thrombosis had their placenta available for pathologic examination. Clinical presentation; maternal, prenatal, and neonatal risk factors for stroke; and patient outcome were collected retrospectively from patient charts. Gross and microscopic placental pathology was described and classified into 4 pathologic categories. RESULTS: Of 12 patients studied, 10 patients were male, 5 patients had arterial ischemic stroke, and 7 patients had sinovenous thrombosis. Maternal risk factors were identified in 5 cases, prenatal risk factors in 10 cases, and neonatal risk factors in 10 cases. Placental lesions were present in 10 cases and were classified as thromboinflammatory process in 6 cases, sudden catastrophic event in 5 cases, decreased placental reserve in 3 cases, and stressful intrauterine environment in 2 cases. CONCLUSIONS: This study reviews detailed placental pathology in a selected cohort of patients presenting near the time of delivery and correlates this with clinical presentation, outcome, and risk factors for neonatal stroke. Our results suggest that multiple risk factors are involved in neonatal stroke, and placental pathology may be a contributing factor. The implications of specific placental lesions remain to be determined with larger, case-controlled studies.

Ultrastructure of Lamellar Bodies in Congenital Surfactant Deficiency

Congenital surfactant deficiency (CSD) is a newly identified neonatal lung disorder associated with a variety of molecular defects affecting surfactant synthesis and secretion in alveolar type II cells. The authors present ultrastructural findings of abnormal lamellar bodies in lung biopsies from 4 infants with CSD. All were term infants presenting shortly after birth with severe respiratory failure that was unresponsive to conventional therapy and all died within the first month of life. Lung biopsies were performed between 8 and 25 days of age. Biochemical and molecular studies in 2 unrelated male infants identified SP-B deficiency, one case with 121 ins 2 mutation and the second with a 209 + 4 A > G mutaion. Light microscopy in both cases showed features of alveolar proteinosis. Ultrastructurally, alveolar type II cells lacked mature lamellar bodies, and their cytoplasm contained numerous pleomorphic inclusions with membranous and vesicular structures not seen in normal type II cells. The other 2 infants were a pair of siblings in whom molecular studies identified mutations in ABCA3 transporter gene. Light microscopy showed features of acinar dysplasia and desquamative interstitial pneumonitis. TEM studies revealed absence of mature lamellar bodies in type II cells and instead showed a mixture of cytoplsamic electron-dense inclusions with concentric membranes and distinctive electron dense aggregates. The ultrastructual changes in alveolar type II cells correlated well with specific gene defect. In SP-B deficiency, the absence of mature lamellar bodies is consistent with the postulated role for this protein in the formation of lamellar bodies. The lack of mature lamellar bodies in the ABCA3 gene mutations is due to the dysfunction of this endogenous lipid transporter that targets surfactant lipid moieties to the lamellar bodies. The findings demonstrate the importance of TEM studies of lung biopsies from infants with CSD as it is a critical adjunct in the diagnosis of neonatal lung disease and in defining the underlying cellular defects.

The Effect of Graded Intake of Glycyl-l-Tyrosine on Phenylalanine and Tyrosine Metabolism in Parenterally Fed Neonates with an Estimation of Tyrosine Requirement

Although tyrosine is considered indispensable during the neonatal period, its poor solubility has limited its inclusion in parenteral amino acid solutions to less than 1% of total amino acids. Dipeptides of tyrosine are highly soluble, have been shown to be well used and safe in animal models and humans, and, therefore, may be used as an effective means of providing tyrosine in the parenterally fed neonate. The goal of the present study was to determine the tyrosine requirement of the parenterally fed neonate receiving graded intakes of glycyl-l-tyrosine as a source of tyrosine. Thirteen infants receiving adequate energy (340 ± 38 kJ·kg-1·d-1) and protein (2.4 ± 0.4 g·kg-1·d-1) were randomized to receive parenteral nutrition with one of five graded levels of glycyl-l-tyrosine. The mean requirement and safe level of intake were estimated using a 1-13C-phenylalanine tracer and linear regression cross-over analysis that identified a break point in the response of label appearance in breath CO2 (F13CO2) and phenylalanine oxidation to graded tyrosine intake. Based on the mean estimates of whole-body phenylalanine oxidation, the tyrosine mean requirement and safe level of intake were found to be 74 mg·kg-1·d-1 and 94 mg·kg-1·d-1, respectively. This represents 3.1 and 3.9% of total amino acids, respectively, considerably higher than levels found in present commercially available pediatric amino acid solutions. These data raise concern regarding the adequacy of aromatic amino acid intake in the parenterally fed neonate.

The Role of Parenteral Lipids in the Development of Advanced Intestinal Failure–Associated Liver Disease in Infants A Multiple-Variable Analysis

BACKGROUND Given the recent interest in the role of ω-6 lipids in the development of intestinal failure-associated liver disease (IFALD), the authors sought to examine the role of parenteral lipids in the development of a serum conjugated bilirubin >100 µmol/L (5.9 mg/dL; CB100) in infants. METHOD Between 2003 and 2004, data were collected prospectively on infants undergoing an abdominal surgical procedure. Univariate logistic regression models for the prediction of CB100 by 1 year postoperatively were developed. Predictors significant at the 0.2 level on univariate analysis were entered into a backward stepwise multiple variable logistic regression. RESULTS Of 152 infants who received parenteral nutrition (PN) postoperatively, 22 developed CB100. Predictors that met criteria for consideration in the multiple-variable model were age, weight, small bowel length, presence of a stoma, proportion of enteral feeds postoperatively, septic episodes, days of maximal PN amino acid (>2.5 g/kg/d), days of maximal lipid (>2.5 g/kg/d), and PN duration. The final model included septic episodes (odds ratio, 3.23; 95% confidence interval, 1.8-5.9) and days of lipid >2.5 g/kg/d (1.04; 1.003-1.06). At 60 days of maximal lipid, the odds of advanced IFALD were increased 10-fold. CONCLUSIONS This model suggests a key role of parenteral lipids and septic events in the development of CB100 from IFALD. These data may provide targets, such as careful line care, reduction in maximal lipid dose, or alternate lipids such as ω-3 fatty acids, to prevent CB100, an identified marker of subsequent liver failure from IFALD.

Cytokine levels in neonatal necrotizing enterocolitis and long-term growth and neurodevelopment.

Objective:  To investigate if circulating cytokines are related to growth and neurodevelopmental outcome following necrotizing enterocolitis (NEC).

Changes in gastric emptying in early postnatal life

OBJECTIVE To study the pattern of gastric emptying in very premature infants and to determine whether there are changes with postnatal age and the ability to tolerate feedings. METHODS Sequential ultrasound measurements of the gastric antral cross-sectional area were obtained in 32 infants (mean gestational age, 26 +/- 1 weeks) before and after feeding for 2 hours. Studies were carried out after initiation of feedings, when full feedings were received, and at 32 weeks. Infants classified as feeding intolerant (n = 9) were also studied when feedings were restarted. Gastric emptying was assessed by the time taken for antral cross-sectional area to reach maximal value and to decrease to half the maximal increment (half-antral clearance). RESULTS Delayed antral distention was observed at the time of the initial study in both feeding-tolerant (8 of 23) and feeding-intolerant (8 of 9) infants; however, there were significant differences in times for maximal antral distention (p < 0.002) and half-antral clearance (p < 0.006) between the feeding-tolerant and feeding-intolerant infants. By the time of full feedings, the feeding-intolerant infants showed immediate gastric emptying but still had a longer half-antral clearance time (p < 0.01). By 32 weeks, all infants had immediate antral distention and a more mature curvilinear pattern of gastric emptying. CONCLUSIONS Knowledge of these different patterns of gastric emptying in very premature infants may lead to the development of more rational feeding strategies.

Threonine requirement of parenterally fed postsurgical human neonates

BACKGROUND The threonine requirement of human neonates who receive parenteral nutrition (PN) has not been determined experimentally. OBJECTIVE The objective was to determine the parenteral threonine requirement for human neonates by using the minimally invasive indicator amino acid oxidation technique with L-[1-(13)C]phenylalanine as the indicator amino acid. DESIGN Nine postsurgical neonates were randomly assigned to 16 threonine intakes ranging from 10 to 100 mg . kg(-1) . d(-1). Breath and urine samples were collected at baseline and at plateau for (13)CO(2) and amino acid enrichment, respectively. The mean threonine requirement was determined by applying a 2-phase linear regression crossover analysis to the measured rates of (13)CO(2) release (F(13)CO(2)) and L-[1-(13)C]phenylalanine oxidation. RESULTS The mean threonine parenteral requirement determined by using phenylalanine oxidation was 37.6 mg . kg(-1) . d(-1) (upper and lower confidence limits, respectively: 29.9 and 45.2 mg . kg(-1) . d(-1)) and by using F(13)CO(2) oxidation was 32.8 mg . kg(-1) . d(-1) (upper and lower confidence limits, respectively: 29.7 and 35.9 mg . kg(-1) . d(-1)). Graded intakes of threonine had no effect on phenylalanine flux. CONCLUSION This is the first study to report on the threonine requirement for human neonates receiving PN. We found that the threonine requirement for postsurgical PN-fed neonates is 22-32% of the content of threonine that is presently found in commercial PN solutions (111-165 mg . kg(-1) . d(-1)).