Showing papers by "Montreal Children's Hospital published in 1997"

Insulin expression in human thymus is modulated by INS VNTR alleles at the IDDM2 locus

Abstract: Type 1 diabetes or insulin-dependent diabetes mellitus (IDDM) is due to autoimmune destruction of pancreatic beta-cells. Genetic susceptibility to IDDM is encoded by several loci, one of which (IDDM2) maps to a variable number of tandem repeats (VNTR) minisatellite, upstream of the insulin gene (INS). The short class I VNTR alleles (26-63 repeats) predispose to IDDM, while class III alleles (140-210 repeats) have a dominant protective effect. We have reported that, in human adult and fetal pancreas in vivo, class III alleles are associated with marginally lower INS mRNA levels than class I, suggesting transcriptional effects of the VNTR. These may be related to type 1 diabetes pathogenesis, as insulin is the only known beta-cell specific IDDM autoantigen. In search of a more plausible mechanism for the dominant effect of class III alleles, we analysed expression of insulin in human fetal thymus, a critical site for tolerance induction to self proteins. Insulin was detected in all thymus tissues examined and class III VNTR alleles were associated with 2- to 3-fold higher INS mRNA levels than class I. We therefore propose higher levels of thymic INS expression, facilitating immune tolerance induction, as a mechanism for the dominant protective effect of class III alleles.

High-fat feeding alters both basal and stress-induced hypothalamic-pituitary-adrenal activity in the rat

Abstract: High-fat feeding induces insulin resistance and increases the risk for the development of diabetes and coronary artery disease. Glucocorticoids exacerbate this hyperinsulinemic state, rendering an ...

Pex/PEX tissue distribution and evidence for a deletion in the 3' region of the Pex gene in X-linked hypophosphatemic mice.

Abstract: PEX, a phosphate-regulating gene with homology to endopeptidases on the X chromosome, was recently identified as the candidate gene for X-linked hypophosphatemia. In the present study, we cloned mouse and human Pex/PEX cDNAs encoding part of the 5' untranslated region, the protein coding region, and the entire 3' untranslated region, determined the tissue distribution of Pex/PEX mRNA, and characterized the Pex mutation in the murine Hyp homologue of the human disease. Using the reverse transcriptase/polymerase chain reaction (RT/PCR) and ribonuclease protection assays, we found that Pex/PEX mRNA is expressed predominantly in human fetal and adult mouse calvaria and long bone. With RNA from Hyp mouse bone, an RT/PCR product was generated with 5' but not 3' Pex primer pairs and a protected Pex mRNA fragment was detected with 5' but not 3' Pex riboprobes by ribonuclease protection assay. Analysis of the RT/PCR product derived from Hyp bone RNA revealed an aberrant Pex transcript with retention of intron sequence downstream from nucleotide 1302 of the Pex cDNA. Pex mRNA was not detected on Northern blots of poly (A)+ RNA from Hyp bone, while a low-abundance Pex transcript of approximately 7 kb was apparent in normal bone. Southern analysis of genomic DNA from Hyp mice revealed the absence of hybridizing bands with cDNA probes from the 3' region of the Pex cDNA. We conclude that Pex/PEX is a low-abundance transcript that is expressed predominantly in bone of mice and humans and that a large deletion in the 3' region of the Pex gene is present in the murine Hyp homologue of X-linked hypophosphatemia.

Insulin VNTR allele-specific effect in type 1 diabetes depends on identity of untransmitted paternal allele

Abstract: The IDDM2 type 1 diabetes susceptibility locus was mapped to and identified as allelic variation at the insulin gene (INS) VNTR regulatory polymorphism. In Caucasians, INS VNTR alleles divide into two discrete size classes. Class I alleles (26 to 63 repeats) predispose in a recessive way to type 1 diabetes, while class III alleles (140 to more than 200 repeats) are dominantly protective. The protective effect may be explained by higher levels of class III VNTR-associated INS mRNA in thymus such that elevated levels of preproinsulin protein enhance immune tolerance to preproinsulin, a key autoantigen in type 1 diabetes pathogenesis. The mode of action of IDDM2 is complicated, however, by parent-of-origin effects and possible allelic heterogeneity within the two defined allele classes. We have now analysed transmission of specific VNTR alleles in 1,316 families and demonstrate that a particular class I allele does not predispose to disease when paternally inherited, suggestive of polymorphic imprinting. But this paternal effect is observed only when the father's untransmitted allele is a class III. This allelic interaction is reminiscent of epigenetic phenomena observed in plants (for example, paramutation; ref. 17) and in yeast (for example, trans-inactivation; ref. 18). If untransmitted chromosomes can have functional effects on the biological properties of transmitted chromosomes, the implications for human genetics and disease are potentially considerable.

Cloning, expression and chromosomal mapping of human lysosomal sialidase and characterization of mutations in sialidosis.

Abstract: Sialidase (neuraminidase, EC 3.2.1.18) catalyses the hydrolysis of terminal sialic acid residues of glyconjugates. Sialidase has been well studied in viruses and bacteria where it destroys the sialic acid-containing receptors at the surface of host cells1–3, and mobilizes bacterial nutrients4. In mammals, three types of sialidases, lysosomal, plasma membrane and cytosolic, have been described5,7. For lysosomal sialidase in humans, the primary genetic deficiency results in an autosomal recessive disease, sialidosis, associated with tissue accumulation and urinary excretion of sialylated oligosaccharides and glycolipids. Sialidosis includes two main clinical variants: late-onset, sialidosis type I, characterized by bilateral macular cherry-red spots and myoclonus8,9, and infantile-onset, sialidosis type II, characterized by skeletal dysplasia, mental retardation and hepatosplenomegaly10–12. We report the identification of human lysosomal sialidase cDNA, its cloning, sequencing and expression. Examination of six sialidosis patients revealed three mutations, one frameshift insertion and two missense. We mapped the lysosomal sialidase gene to human chromosome 6 (6p21.3), which is consistent with the previous chromosomal assignment of this gene in proximity to the HLA locus.

Human Phenylalanine Hydroxylase Mutations and Hyperphenylalaninemia Phenotypes: A Metanalysis of Genotype-Phenotype Correlations

Abstract: We analyzed correlations between mutant genotypes at the human phenylalanine hydroxylase locus (gene symbol PAH) and the corresponding hyperphenylalaninemia (HPA) phenotypes (notably, phenylketonuria [OMIM 261600]). We used reports, both published and in the PAH Mutation Analysis Consortium Database, on 365 patients harboring 73 different PAH mutations in 161 different genotypes. HPA phenotypes were classified as phenylketonuria (PKU), variant PKU, and non-PKU HPA. By analysis both of homoallelic mutant genotypes and of "functionally hemizygous" heteroallelic genotypes, we characterized the phenotypic effect of 48 of the 73 different, largely missense mutations. Among those with consistent in vivo expression, 24 caused PKU, 3 caused variant PKU, and 10 caused non-PKU HPA. However, 11 mutations were inconsistent in their effect: 9 appeared in two different phenotype classes, and 2 (I65T and Y414C) appeared in all three classes. Seven mutations were inconsistent in phenotypic effect when in vitro (unit-protein) expression was compared with the corresponding in vivo phenotype (an emergent property). We conclude that the majority of PAH mutations confer a consistent phenotype and that this is concordant with their effects, when known, predicted from in vitro expression analysis. However, significant inconsistencies, both between in vitro and in vivo phenotypes and between different individuals with similar PAH genotypes, reveal that the HPA-phenotype is more complex than that predicted by Mendelian inheritance of alleles at the PAH locus.

Apoptotic Cell Death in Mouse Models of GM2 Gangliosidosis and Observations on Human Tay-Sachs and Sandhoff Diseases

Abstract: Tay-Sachs and Sandhoff diseases are autosomal recessive neurodegenerative diseases resulting from the inability to catabolize GM2 ganglioside by beta-hexosaminidase A (Hex A) due to mutations of the alpha subunit (Tay-Sachs disease) or beta subunit (Sandhoff disease) of Hex A. Hex B (beta beta homodimer) is also defective in Sandhoff disease. We previously developed mouse models of both diseases and showed that Hexa-/- (Tay-Sachs) mice remain asymptomatic to at least 1 year of age while Hexb-/- (Sandhoff) mice succumb to a profound neurodegenerative disease by 4-6 months of age. Here we find that neuron death in Hexb-/- mice is associated with apoptosis occurring throughout the CNS, while Hexa-/- mice were minimally involved at the same age. Studies of autopsy samples of brain and spinal cord from human Tay-Sachs and Sandhoff diseases revealed apoptosis in both instances, in keeping with the severe expression of both diseases. We suggest that neuron death is caused by unscheduled apoptosis, implicating accumulated GM2 ganglioside or a derivative in triggering of the apoptotic cascade.

The Juvenile Arthritis Quality of Life Questionnaire--development of a new responsive index for juvenile rheumatoid arthritis and juvenile spondyloarthritides.

Abstract: Objective. To develop a disease specific measure of quality of life for application in children with juvenile rheumatoid arthritis and juvenile spondyloarthritides - the Juvenile Arthritis Quality of Life Questionnaire (JAQQ). Methods. Patients and their parents were interviewed by a trained interviewer using a questionnaire focusing on physical function, psychosocial function, and general symptoms to determine the most appropriate items to include in the JAQQ. Respondents volunteered items and scored them for frequency of occurrence and importance. Items so generated were scored by a panel of experts for potential responsiveness and categorized into dimensions. Item number was reduced using this scoring system. The product was then pretested to confirm its construct validity and responsiveness. Thereafter, it was distributed to clinical experts to establish face and content validity. Results. 91 patients. mean age 10.35 years (range 1.25-18.0), mean disease duration 3.99 years, and their parents were included in the interview process. 220 items generated were ultimately reduced to 85. Pretesting this version of the instrument in a further 30 patients showed it to have construct validity and responsiveness and led to a further reduction in items to 74. distributed in 4 dimensions: gross motor function (17 items), fine motor function (16 items), psychosocial function (22 items), and general symptoms (19 items). Face and content validity were established in 20 clinicians. Scaling was by 7 point Likert scale to enhance responsiveness. English and French versions were developed. Conclusion. The JAQQ measures physical and psychosocial function and an array of general symptoms. Preliminary data suggest it is valid and responsive and thus might have potential in clinical trials.

Comprehensive assessment of childhood Attention-Deficit Hyperactivity Disorder in the context of a multisite, multimodal clinical trial:

Abstract: As the largest randomized clinical trial conducted by the National Institute of Mental Health, the Multimodal Treatment Study of Children with ADHD (MTA) will yield data on a diverse sample of 576 7.0- to 9.9-year-old children with attention-deficit hyperactivity disorder (ADHD), Combined type, regarding the relative and combined effectiveness of psychosocial and pharmacologic interventions. After delineating key challenges posed by such a multi-site investigation, we describe the MTA's multiple-gating procedures for recruitment, screening, and diagnosis of a diverse sample. We then discuss the cross-domain assessment battery for tracking the sample before, during, and after 14 months of active intervention. Throughout, we emphasize the guiding principles that shaped pertinent decision making. Highlighted are issues of psychometric adequacy; dimensional vs. categorical measurement; multi-method, multi-agent, and multi-domain coverage; plotting of individual trajectories of development and change; responde...

Congenital hyperthyroidism caused by a solitary toxic adenoma harboring a novel somatic mutation (serine281-->isoleucine) in the extracellular domain of the thyrotropin receptor.

Abstract: Activating somatic mutations in the thyrotropin (TSH) receptor have been identified as a cause of hyperfunctioning thyroid adenomas, and germline mutations have been found in familial nonautoimmune hyperthyroidism and sporadic congenital hyperthyroidism. All mutations reported to date have been located in the transmembrane domain. We now report an example of an activating mutation in the extracellular, TSH-binding domain, found in a male infant with congenital hyperthyroidism due to a toxic adenoma. The pregnancy was remarkable for fetal tachycardia. Scintigraphic studies demonstrated a large nodule in the right lobe, and a hemithyroidectomy was performed at the age of 2 yr. Direct sequencing of the TSH receptor gene revealed a mutation in one allele resulting in a substitution of serine281 by isoleucine (Ser281--> Ile) in the extracellular domain. The mutation was restricted to the adenomatous tissue. Expression of the Ser281--> Ile mutation in vitro revealed an increase in basal cAMP levels. Affinity for TSH was increased by the mutation. These findings demonstrate that activating mutations can also occur in the extracellular domain of the TSH receptor, and support a model in which the extracellular domain serves to restrain receptor function in the absence of TSH or antibody-induced conformational changes.

Familial neurofibromatosis 1 microdeletions: cosegregation with distinct facial phenotype and early onset of cutaneous neurofibromata.

Abstract: A notable subset of the recent literature on the disorder neurofibromatosis type 1 (NF1) describes patients with NF1, facial anomalies, and other unusual findings. We describe a molecular re-evaluation of two such families reported previously by Kaplan and Rosenblatt [1985], who suggested that their NF1 manifestations, facial phenotype, and other findings could result from a disorder distinct from NF1. Submicroscopic deletions involving the NF1 gene were identified in both families by fluorescent in situ hybridization and analysis of somatic cell hybrids. Affected subjects of the first family were heterozygous for a microdeletion of approximately 2 Mb, which included the entire NF1 gene and flanking contiguous sequences. The family was remarkable for cosegregation of the NF1 microdeletion with facial abnormalities and a pattern of early onset of cutaneous neurofibromata upon transmission from an affected mother to her three affected children. The propositus of the second family carried a deletion that at the least involved NF1 exon 2 through intron 27, which is ≥ 200 kilobases in length. Because all persons in the family were deceased, the size of the deletion could not be determined precisely. Facial anomalies were observed in the propositus and his NF1-affected mother and sister. The data from these families support our hypothesis, which was initially based solely on sporadic deletion cases, that deletion of the entire NF1 gene, or in conjunction with deletion of unknown contiguous genes, causes the facial anomalies and early onset of neurofibromata observed in this subset of NF1 patients. In addition, other features observed in the persons in these families suggest that some NF1 microdeletion patients may be at increased risk for connective tissue abnormalities and/or neoplasms. Am. J. Med. Genet. 73:197–204, 1997. © 1997 Wiley-Liss, Inc.

Does Ribavirin Impact on the Hospital Course of Children With Respiratory Syncytial Virus (RSV) Infection? An Analysis Using the Pediatric Investigators Collaborative Network on Infections in Canada (PICNIC) RSV Database

Abstract: Objectives. To determine the relationship between receipt of aerosolized ribavirin and the hospital course of high-risk infants and children with respiratory syncytial virus (RSV) lower respiratory infection (LRI). Methods. The 1993–1994 Pediatric Investigators Collaborative Network on Infections in Canada (PICNIC) RSV database consists of prospectively enrolled children with acute RSV LRI, admitted to nine Canadian pediatric tertiary care centers. After excluding cases with compromised immunity and/or nosocomial infection, subsets with any congenital heart disease (CHD), chronic lung disease (CLD), age ≤6 weeks (INFANT), gestation ≤36 weeks (PREM), or severe disease within 48 hours of admission as shown by an oxygen saturation ≤90% or an FiO2 requirement of >.35 (EARLY HYPOXIA) were studied in two ways. First, each risk group subset was analyzed separately to assess the association between ribavirin receipt and measures of disease severity including duration of intensive care, mechanical ventilation, hy- poxia and RSV-attributable hospital stay. Secondly, ribavirin was added as an independent variable to a previously described multiple regression model for RSV-attributable length of hospital stay and two mutually exclusive subsets were analyzed: 1) previously healthy patients with ≥1 of: INFANT, PREM, or EARLY HY- POXIA; 2) patients with CHD and/or CLD. Results. Between January 1993 and June 1994, 1425 community-acquired hospitalized cases of RSV LRI were entered into the RSV database. Among these 750 (52.6%) fit into one or more of the defined subsets including 97 CHD, 134 CLD, 213 INFANT, 211 PREM, and 463 EARLY HYPOXIA. The proportion ventilated in each group was 20.6%, 20.9%, 15.5%, 15.2%, and 13.3%, respectively. Across the subsets ribavirin use ranged from 36% to 57% of ventilated patients and 6% to 39% of nonventilated patients. For nonventilated patients in each subset the median RSV-attributable hospital length of stay (RSV-LOS) was 2 to 3 days longer for ribavirin recipients and the duration of hypoxia was significantly increased. Duration of intensive care unit (ICU) stay was also increased for all ribavirin-treated subgroups except those with CHD. In contrast, for ventilated patients, ribavirin therapy was not significantly associated with any of the outcome measures regardless of risk group. In the multiple regression model, ribavirin was significantly associated with a prolonged RSV-LOS both for children with CHD and/or CLD as well as for those whose only risk factors included INFANT, PREM, and/or EARLY HY- POXIA. Conclusions. These data raise further doubts about the clinical effectiveness of ribavirin in infants and children with risk factors for severe disease. Selection bias, with ribavirin used for sicker children, may have influenced outcome. Nevertheless the long durations of hospitalization, ICU, ventilation, and oxygen supplementation in nonventilated ribavirin recipients stress the need for further randomized trials to assess its efficacy. ribavirin, respiratory syncytial virus, pneumonia, bronchiolitis.

Exercise ability in survivors of severe bronchopulmonary dysplasia.

Abstract: There is limited information concerning the exercise performance of long-term survivors of bronchopulmonary dysplasia (BPD), and much of what is available pertains to those with relatively mild disease. The present study was undertaken to describe exercise responses in patients with a history of severe BPD, defined as those patients with a clinical and radiographic diagnosis of BPD who required supplemental oxygen at least until they were 44 wk postconceptual age and who were discharged home on oxygen. Fifteen children with a history of severe BPD were matched for gestational age with 15 children who had previously had respiratory distress syndrome but who did not develop BPD (Prem). These Prem control children were subsequently compared with 13 healthy control children born at term (Control) who were of similar postnatal age. Participants underwent pulmonary function testing, progressive exercise testing on a cycle ergometer, and a steady-state exercise test with cardiac output determined by CO2-rebreathing. Despite the patients with BPD having a lower FEV1 than those in the Prem group, who had lower values than the Control group (BPD, 64 +/- 21%; Prem, 85 +/- 11%; Control, 95 +/- 8%), the exercise capacity did not differ between the BPD and the Prem and between the Prem and the Control groups (BPD, 84 +/- 15%; Prem, 81 +/- 17%; Control, 91 +/- 12%). However, the BPD patients used a greater percentage of their ventilatory reserve (VEmax/40 FEV1: BPD, 93 +/- 20%; Prem, 67 +/- 12%; Control, 59 +/- 13%). Of the four patients with BPD who had significant oxygen desaturation with exercise, three had the lowest values for FEV1. Cardiac output was appropriate for oxygen consumption in most patients.

Activity levels and the relationship to lung function and nutritional status in children with cystic fibrosis.

Abstract: Cystic fibrosis is characterized by chronic obstructive lung disease and malnutrition. Previous studies have shown that nutritional status and lung function are limiting factors for exercise capacity. A reduced exercise capacity may in turn diminish activity levels. We evaluated whether the total time spent somewhat active (e.g., walking) or active (e.g., biking), as reported by the Habitual Activity Estimation Scale, was related to lung function, as evaluated by forced expiratory volume in one second (%predicted FEV1), and nutritional status, measured as body mass percentile, in 36 children with cystic fibrosis, aged 6 to 16 years. The Habitual Activity Estimation Scale questionnaires were completed by the parents for children younger than 12 years of age and by both the parent and the child, independently, for those 12 years and older. Patients had a body mass percentile of 99 +/- 15.2% and % predicted FEV1 of 85.7 +/- 20, with no differences between boys (15/36) and girls (21/36). Boys spent 8.1 hours and girls spent 7.5 hours (P > 0.1) being at least somewhat active. These values are similar to those reported for healthy boys and girls. In patients with significant lung disease (%predicted FEV1, 0.1). Activity level reported by patients 12 years of age and older was on average 24.1% higher (P < 0.05) than that reported by their parents, but the two reportings were related (r = 0.758; P = 0.004). These results suggest that activity level may be restricted by nutritional status in those patients with significant air flow limitation. We suggest that improving the nutritional status of cystic fibrosis patients may prevent decreases in activity levels and quality of life of these affected children.

Are there injury-prone children? A critical review of the literature

Abstract: Results: A critical review of the literature suggests that aggression is a consistent risk factor for general injuries but not for pedestrian injuries, hyperactivity is inconsistently associated with all types of injuries, and both a general measure of behaviour problems and a measure of unsafe behaviour were found to be significantly related to pedestrian injuries. A look at the pedestrian injury literature suggests that child risk factors make a consistent but minor contribution to injuries in comparison with environmental and social risk factors. Conclusions: We need to address the environmental and social risk factors by educating parents about the roles of home stressors, poor supervision, and high-risk exposure in child injuries and by adding our voice to the efforts to bring into effect engineering and legislative interventions. (Can J Psychiatry 1997;42:602‐610)

NIMH collaborative multimodal treatment study of children with ADHD (MTA): Design, methodology, and protocol evolution:

Abstract: The steering committee of the collaborative six-site Multimodal Treatment Study of Children with Attention-Deficit/Hyperactivity Disorder (the MTA) had to develop a common protocol consistent with public health goals and with scientific and clinical state of the art. With the aid of statistical, educational, and public health consultation, the steering committee balanced the stated objectives of the RFA against budgetary, clinical, ethical, and logistical practicalities. Two primary questions will be addressed: (1) What is the relative long-term effectiveness of excellent medication vs. excellent behavioral treatment vs. the combination? (2) What is the relative long-term effective ness of each of these state-of-the art intense treatments vs. routine community care? In a parallel-group design, 576 children (96 at each site) age 7-9 in grades 1-4 are thoroughly assessed in multiple domains from multiple informants and randomized to 4 treatment conditions: a medication-alone strategy, a psychosocial-treatme...

Do systemic corticosteroids effectively treat obstructive sleep apnea secondary to adenotonsillar hypertrophy

Abstract: To determine if pediatric obstructive sleep apnea syndrome (OSAS) caused by adenotonsillar hypertrophy (ATH) could be treated by a short course of systemic corticosteroids, we conducted an open-label pilot study in which standardized assessments of symptomatology, OSAS severity, and adenotonsillar size were performed before and after a 5-day course of oral prednisone, 1.1+/-0.1 (+/-SE) mg/kg per day. Outcome measures included symptom severity, adenotonsillar size, and polysomnographic measures of OSAS. Selection criteria included age from 1 to 12 years, ATH, symptomatology suggesting OSAS, an apnea/hypopnea index (AHI) > or = 3/hour, and intent to perform adenotonsillectomy. Only one of nine children showed enough improvement to avoid adenotonsillectomy. Symptomatology did not improve after corticosteroid treatment but did after removal of tonsils and adenoids. Polysomnographic indices of OSAS severity did not improve after corticosteroid treatment. After corticosteroids, tonsillar size decreased in only two patients, adenoidal size was only marginally reduced, and the size of the nasopharyngeal airway was not significantly increased. These results suggest that a short course of prednisone is ineffective in treating pediatric OSAS caused by ATH.

Evaluation of the newborn’s blood gas status

Abstract: Blood gas measurements and complementary, noninvasive monitoring techniques provide the clinician with information essential to patient assessment, therapeutic decision making, and prognostication. Blood gas measurements are as important for ill newborns as for other critically ill patients, but rapidly changing physiology, difficult access to arterial and mixed venous sampling sites, and small blood volumes present unique challenges. This paper discusses considerations for interpretation of blood gases in the newborn period. Blood gas measurements and noninvasive estimations provide important information about oxygenation. The general goals of oxygen therapy in the neonate are to maintain adequate arterial PaO2 and SaO2, and to minimize cardiac work and the work of breathing. Pulse oximetry and transcutaneous oxygen monitoring are extraordinarily useful techniques of estimating and noninvasively monitoring the neonate's oxygenation, but each method has limitations. Arterial blood gas determinations of pCO2 provide the most accurate determinations of the adequacy of alveolar ventilation, but capillary, transcutaneous, and end-tidal techniques are also useful. An approach to and examples of acid-base disorders are presented. Three hemoglobin variants relevant to the newborn are considered: fetal hemoglobin, carboxyhemoglobin, and methemoglobin. Blood gases obtained in the immediate perinatal period can help assess perinatal asphyxia, but particular attention must be paid to the sampling site, the time of life, and the possible and proven diagnoses.

Aberrant imprinting of the insulin-like growth factor II receptor gene in Wilms' tumor

Abstract: Wilms’ tumor (WT) is an embryonal renal malignancy,which overexpresses insulin-like growth factor II (IGF-II), a fetal mitogen. Relaxation of parental imprintingof IGF2, the gene encoding IGF-II, is found in Wilms’tumors, suggesting an important role for IGF2 dosagein tumorigenesis. The IGF2R gene encodes a non-mitogenic receptor which targets IGF-II to thelysosomes for degradation and, therefore, inhibits themitogenic function of IGF-II. The human IGF2R isimprinted in a proportion of normal individuals. To testthe hypothesis that IGF2R imprinting predisposes toWilms’ tumor through the e•ect of decreased IGF2Rdosage on IGF-II inactivation, we examined IGF2Rimprinting in Wilms’ tumors. Two transcribed CArepeat polymorphisms were used to distinguish the twoalleles in the RT–PCR product. We observed that in 7/16 of Wilms’ tumor patients, the paternal IGF2R wasmarkedly but not completely repressed in both tumorand normal kidney. In one additional case, IGF2R waslikewise imprinted in the tumor but not in the normalkidney. A similar imprinting was observed in fetaltissues and placenta prior to 20 weeks fetal age but notin term placenta or postnatal blood cells, indicatingabnormal persistence of a fetal pattern in the kidneys ofWilms’ patients. Genetic analysis showed association ofthe imprinting with a cis-acting locus. The highfrequency of aberrant persistence of IGF2R imprintingin the kidneys of Wilms’ tumor patients, which may bean embryonic feature, suggests that it is a predisposingfactor in tumorigenesis. This is in accordance withevidence that IGF2R is a tumour suppressor in othertypes of malignancies.Keywords: imprinting; Wilms’ tumor; insulin-likegrowth factor II; receptor; gene dosageIntroductionWilms’ tumor is a childhood kidney cancer derivedfrom metanephric blastemal cells. It is usuallydiagnosed in the first 5 years of life. At the time ofresection, these tumors express IGF2 at levelscharacteristic of fetal tissues, which are much higherthan those found in the surrounding normal kidney(Reeve et al., 1985; Scott et al., 1985). This over-expression may, at least in part, be related todisruption of the parental genomic imprinting of theIGF2 gene.The term parental imprinting refers to the differ-ential behavior of the two copies of a gene dependingon the sex of the parent from which each wastransmitted. IGF2, one of the few mammalian genesknown to be imprinted, is normally expressedexclusively from the paternal copy in the mouse(DeChiara et al., 1991) and human (Giannoukakis etal., 1993). Interestingly Igf2r, the murine gene encodingone of the two receptors to which IGF-II binds, is alsoimprinted, but with exclusive maternal expression(Barlow et al., 1991). Thus IGF2 is reversiblyinactivated upon passage from the maternal germline,while Igf2r is inactivated upon passage from thepaternal one.The presence, in opposite parental sexes, of thisunusual property in two genetically unlinked butfunctionally coupled genes may be related to opposinge•ects of Igf2 and Igf2r expression on fetal growth(Haig and Graham, 1991). It is known that themitogenic actions of IGF-II are transmitted by thetype I IGF receptor (Kiess et al., 1987; Ellis et al.,1996), which binds both IGF-I and IGF-II and acts asa ligand-activated tyrosine kinase. By contrast, IGF2Rencodes a 280 kDa membrane receptor with no knownintracellular transduction mechanism, involved in thetargeting of lysosomal enzymes to the lysosomes(reviewed by Polychronakos, 1989). In addition to itsmannose 6-phosphate binding site through which itrecognizes the unique glycosylation pattern of lysoso-mal enzymes, this receptor has a high-a†nity specificIGF-II binding site, involved in the targeting of IGF-IIfor rapid lysosomal degradation (Oka et al., 1985; Elliset al., 1996). This may explain the lower mitogenicpotency of IGF-II in most biologic systems, although itbinds to the type I receptor with a†nity equal to thatof IGF-I (Germain-Lee et al., 1992). It may also berelated to a tumor suppressor function of IGF2R (DeSouza et al., 1995a,b; Hankins et al., 1996).It is not known whether the postnatal persistence ofthe high fetal levels of IGF2 expression is of etiologicsignificance in Wilms’ tumor, or merely a marker of itsembryonal nature. In favor of a causative role is therecent discovery of three completely independentmolecular pathologies, all with the potential toincrease IGF2 expression, and all occurring with highfrequency in Wilms’ tumors: (1) Paternal disomy of11p15.5, that would result in expression of IGF2 fromtwo instead of one gene copy, is sometimes seen inWilms’ tumors (Slater and Mannens, 1992) and theBeckwith-Wiedemann syndrome (Henry et al., 1991), acondition that predisposes to Wilms’ tumors. (2) Two-thirds of Wilms’ tumors maintaining heterozygosity atthe IGF2 locus show relaxation of imprinting (Rainieret al., 1993; Ogawa et al., 1993a), allowing expression

Cellular and Molecular Mechanisms of Renal Phosphate Transport

Abstract: (Pi) homeostasis and, as such, plays a key role in bone mineralization and growth. The bulk of filtered Pi is reabsorbed in the proximal tubule, with approximately 60% of the filtered load reclaimed in the proximal convoluted tubule and 15‐20% in the proximal straight tubule. In addition, a small but variable portion (,10%) of filtered Pi is reabsorbed in more distal segments of the nephron. The overall capacity of the kidney to reabsorb Pi can be estimated by measuring the maximum tubular capacity (Tm) for Pi per unit volume of glomerular filtrate (TmPi/GFR). In practice, this is achieved by measuring Pi and creatinine excretions and plasma concentrations during acute Pi infusions. (1) Considerable effort has been devoted to the study of Pi transport in the proximal tubule, the principal site of its reabsorption (for reviews, see Refs. 2‐8). A wide variety of experimental systems, from the intact animal to vesicular membrane preparations, have been used to characterize proximal tubular Pi transport systems and to elucidate mechanisms involved in their regulation. These issues are briefly reviewed in the context of recent advances in the cloning of cDNAs encoding renal-specific Na 1 -Pi cotransporters and the application of these new tools to study the role of Na 1 -Pi cotransporter genes in Mendelian disorders of renal Pi reabsorption. (9‐13)

Acoustic Characteristics of Naturally Occurring Cries of Infants with "Colic.".

Abstract: Although infantile colic has long been defined by a perceived excessive amount of crying, acoustic attributes of the cry sound may also contribute to perceptions that this early social behavior is excessive or problematic. From an original sample of 76 infants (38 infants referred to physicians for problematic crying, or "colic," and 38 pair-matched comparison infants), 48 infants who produced naturally occurring cry bouts both before and after an evening feeding were studied: 11 infants with Wessel's colic, 15 infants with non-Wessel's colic, and 22 comparison infants. Standard and vociferous cry segments were selected from up to 2 min of tape-recorded crying for spectrum analysis. Vociferous cry segments had a longer duration, a higher fundamental frequency, and a greater percentage of dysphonation than did standard segments. No differences between infant groups were found in cries before feeding. After feeding, infants who were problematic criers, independent of Wessel's criteria, showed a greater percentage of dysphonation in the vociferous cry segment than did comparison infants. This finding resulted from a decrease in dysphonation in the cries of comparison infants after feeding and an increase in those of infants with non-Wessel's colic. The dominant frequency also increased after feeding in the vociferous cries of infants with Wessel's colic, resulting in these infants having higher-pitched cries after feeding than infants in the other 2 groups. Results indicate that infants who are perceived to have problematic crying have objectively different acoustic features in their cry sounds that are particularly aversive, and that complaints about excessive crying cannot be accounted for simply on the basis of reporting bias in overly concerned or emotionally labile parents.

PICNIC (Pediatric Investigators Collaborative Network on Infections in Canada) Study of the Role of Age and Respiratory Syncytial Virus Neutralizing Antibody on Respiratory Syncytial Virus Illness in Patients With Underlying Heart or Lung Disease

Abstract: Objective. To determine the effects of age and respiratory syncytial virus (RSV) antibody status on frequency and severity of RSV infections in children with underlying heart or lung disease. Design. Cohort study conducted during two consecutive RSV seasons. Setting. Ambulatory patients at eight Canadian pediatric tertiary care centers. Methods. Subjects under 3 years old with underlying heart disease who were digoxin-dependent or had not received corrective cardiac surgery or with underlying lung disease were enrolled. Demographic information and an acute sera for RSV neutralizing antibody was obtained on enrollment. Weekly telephone follow-up consisting of a respiratory illness questionnaire was followed with a home visit to obtain a nasopharyngeal aspirate when there was new onset of respiratory symptoms. The specimen was used to detect RSV antigen. RSV illnesses were grouped as upper or lower respiratory tract infection (LRI) based on clinical and radiographic findings. RSV hospitalizations were considered to be those RSV infections that resulted in hospitalization. Results. Of 427 enrolled subjects, 160 had underlying lung disease only, 253 had underlying heart disease only, and 14 had both. Eleven percent and 12% of lung and heart disease groups, respectively, had an RSV LRI. Three percent and 6% of lung and heart disease groups, respectively, were hospitalized with RSV infection. A significant decrease in frequency of RSV LRI and RSV hospitalization occurred with increasing age, with a major drop in those older than 1 year vs those younger than 1 year. Acute sera were available from 422 subjects. Geometric mean RSV antibody titers demonstrated a U-shaped distribution with increasing age. The trend to lower antibody concentrations in premature infants did not reach statistical significance. The frequency of RSV infection and RSV LRI was lower in patients with antibody at a titer more than 100, although the difference for RSV hospitalization was not statistically significant. These differences remained significant after age adjustment. Conclusion. Both age and RSV antibody status impact on RSV illness and LRI. Reduction in illness frequency with increasing age may lead to more informed targeting of those children most likely to benefit from RSV immune globulin prophylaxis. respiratory syncytial virus, cohort study, passive prophylaxis, neutralizing antibody.

An autosomal dominant form of familial persistent hyperinsulinemic hypoglycemia of infancy, not linked to the sulfonylurea receptor locus.

Abstract: Persistent hyperinsulinemic hypoglycemia of infancy (PHHI), a rare disorder due to defective negative feedback regulation of insulin secretion by low glucose levels, is often familial. Most cases are recessively inherited, and mutations of the sulfonylurea receptor gene (SUR) or the closely linked KIR6.2 gene have been found in several families. Both of these genes encode components of the potassium channels responsible for glucose-regulated insulin release. However, in some families recessive PHHI is not linked to the SUR-KIR6.2 locus, suggesting genetic heterogeneity. We report here a French Canadian kindred with hypoglycemia in five first cousins. All five patients had documented hypoglycemia, and all responded well to diazoxide. In two, inappropriately elevated insulin levels during hypoglycemia were documented. This familial clustering strongly suggests the existence of an autosomal dominant form of PHHI. By preliminary linkage analysis, we tested the possibility of a dominant negative SUR or KIR6.2 mutant. The insulin (INS) and glucokinase (GCK) genes were also tested as additional candidates. Microsatellite markers closely linked to each gene were used, and large negative Lod scores were obtained at the known recombination fractions between all three genes studied and the corresponding marker. We conclude that mutation of a gene other than SUR or KIR6.2 is responsible for the dominant PHHI in this family, and this gene cannot be INS or GCK. We propose that a genome-wide search for this gene is important for elucidating this rare disorder and, more importantly, for determining its potential impact on understanding noninsulin-dependent diabetes mellitus and on the effort to develop bioengineered beta-cells for transplantation.