Publications by authors named "David N Finegold"

40 Publications

Global hypermethylation of intestinal epithelial cells is a hallmark feature of neonatal surgical necrotizing enterocolitis.

Clin Epigenetics 2020 12 11;12(1):190. Epub 2020 Dec 11.

Departments of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, 204 Craft Avenue, Pittsburgh, PA, 15213, USA.

Background: Necrotizing enterocolitis (NEC) remains one of the overall leading causes of death in premature infants, and the pathogenesis is unpredictable and not well characterized. The aim of our study was to determine the molecular phenotype of NEC via transcriptomic and epithelial cell-specific epigenomic analysis, with a specific focus on DNA methylation.

Methods: Using laser capture microdissection, epithelial cell-specific methylation signatures were characterized by whole-genome bisulfite sequencing of ileal and colonic samples at the time of surgery for NEC and after NEC had healed at reanastomosis (n = 40). RNA sequencing was also performed to determine the transcriptomic profile of these samples, and a comparison was made to the methylome data.

Results: We found that surgical NEC has a considerable impact on the epigenome by broadly increasing DNA methylation levels, although these effects are less pronounced in genomic regions associated with the regulation of gene expression. Furthermore, NEC-related DNA methylation signatures were influenced by tissue of origin, with significant differences being noted between colon and ileum. We also identified numerous transcriptional changes in NEC and clear associations between gene expression and DNA methylation.

Conclusions: We have defined the intestinal epigenomic and transcriptomic signatures during surgical NEC, which will advance our understanding of disease pathogenesis and may enable the development of novel precision medicine approaches for NEC prediction, diagnosis and phenotyping.
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http://dx.doi.org/10.1186/s13148-020-00983-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7730811PMC
December 2020

Problem-solving, Adherence to Lifestyle Goals, and Weight Loss Among Individuals Participating in a Weight Loss Study.

Int J Behav Med 2020 Jul 17. Epub 2020 Jul 17.

School of Nursing, University of Pittsburgh, Pittsburgh, PA, USA.

Background: The role of problem-solving is not well understood in behavioral weight loss interventions. In a 12-month behavioral weight loss study, we examined whether problem-solving changed over time and the relationships between problem-solving and changes in adherence to calorie, fat, and physical activity (PA) goals and percent weight change.

Methods: One of the 24 intervention sessions (15th) was devoted to problem-solving. Participants received individualized calorie and fat goals and were given a 150 min/week moderate-to-vigorous PA goal. Adherence to calorie/fat goals and PA goals was calculated at 1, 6, and 12 months using self-reported food intake in a mobile-based weight loss app and accelerometer data, respectively. Weight was measured via a digital scale at baseline, and 6 and 12 months. A general linear model was used to compare problem-solving across time points; post hoc linear mixed modeling was used to examine the relationships between problem-solving and changes in adherence to lifestyle goals and percent weight change.

Results: The sample (N = 150) was mostly female (90.7%), white (80.70%), with a mean age of 51.1 ± 10.2 years, and a mean body mass index of 34.1 + 4.6 kg/m. The mean total score of problem-solving at baseline was 81.2 ± 12.3. Problem-solving total and subscale scores did not significantly change over time. Baseline problem-solving was not significantly associated with changes in adherence to lifestyle goals and percent weight change (P > 0.05).

Conclusion: A behavioral weight loss study did not impact problem-solving, and problem-solving may not influence lifestyle adherence and weight changes. Future work needs to examine problem-solving in larger and more diverse samples.
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http://dx.doi.org/10.1007/s12529-020-09922-4DOI Listing
July 2020

Rare variants and biological pathways identified in treatment-refractory depression.

J Neurosci Res 2020 07 3;98(7):1322-1334. Epub 2020 Mar 3.

Center for Fetal Medicine, Magee-Womens Research Institute, Pittsburgh, PA, USA.

Individuals diagnosed with major depressive disorder not responding to at least two adequate treatments are defined as treatment-refractory major depressive disorder (TR-MDD). Some TR-MDD patients have altered metabolic phenotypes that may be pharmacologically reversed. The characterization of these phenotypes and their underlying etiologies is paramount, particularly their genetic components. In this study, TR-MDD patients (n = 124) were recruited and metabolites were quantified in their cerebrospinal fluid (CSF) and peripheral blood. Three sub-categories of deficiencies were examined, namely 5-methyltetrahydrofolte (in CSF; n = 13), tetrahydrobiopterin (in CSF; n = 11), and abnormal acylcarnitine profiles (in peripheral blood; n = 8). Whole exome sequencing was performed on genomic DNA from the entire TR-MDD cohort and exonic variant allele frequencies for cases were compared to a control cohort (1:5 matching on ancestry). Low frequency, damaging alleles were identified and used for in silico pathway analyses. Three association signals for TR-MDD approached genome-wide significance on chromosomes 22, 7, and 3. Three risk-associated variants from a prior depression study were replicated. Relevant biological pathways were identified that contained an enrichment of rare, damaging variants in central nervous system (CNS)-specific pathways, including neurotransmitter receptors, potassium channels, and synapse transmission. Some TR-MDD patients had rare variants in genes that were previously associated with other psychiatric disorders, psychiatric endophenotypes, CNS structural defects, and CNS-related cellular and molecular functions. Exome analysis of metabolically phenotyped TR-MDD patients has identified potentially functional gene pathways and low frequency, deleterious gene variants for further investigation. Further studies in larger cohorts of biochemically phenotyped TR-MDD patients are desirable to extend and confirm these findings.
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http://dx.doi.org/10.1002/jnr.24609DOI Listing
July 2020

Rare variants and biological pathways identified in treatment-refractory depression.

J Neurosci Res 2020 07 3;98(7):1322-1334. Epub 2020 Mar 3.

Center for Fetal Medicine, Magee-Womens Research Institute, Pittsburgh, PA, USA.

Individuals diagnosed with major depressive disorder not responding to at least two adequate treatments are defined as treatment-refractory major depressive disorder (TR-MDD). Some TR-MDD patients have altered metabolic phenotypes that may be pharmacologically reversed. The characterization of these phenotypes and their underlying etiologies is paramount, particularly their genetic components. In this study, TR-MDD patients (n = 124) were recruited and metabolites were quantified in their cerebrospinal fluid (CSF) and peripheral blood. Three sub-categories of deficiencies were examined, namely 5-methyltetrahydrofolte (in CSF; n = 13), tetrahydrobiopterin (in CSF; n = 11), and abnormal acylcarnitine profiles (in peripheral blood; n = 8). Whole exome sequencing was performed on genomic DNA from the entire TR-MDD cohort and exonic variant allele frequencies for cases were compared to a control cohort (1:5 matching on ancestry). Low frequency, damaging alleles were identified and used for in silico pathway analyses. Three association signals for TR-MDD approached genome-wide significance on chromosomes 22, 7, and 3. Three risk-associated variants from a prior depression study were replicated. Relevant biological pathways were identified that contained an enrichment of rare, damaging variants in central nervous system (CNS)-specific pathways, including neurotransmitter receptors, potassium channels, and synapse transmission. Some TR-MDD patients had rare variants in genes that were previously associated with other psychiatric disorders, psychiatric endophenotypes, CNS structural defects, and CNS-related cellular and molecular functions. Exome analysis of metabolically phenotyped TR-MDD patients has identified potentially functional gene pathways and low frequency, deleterious gene variants for further investigation. Further studies in larger cohorts of biochemically phenotyped TR-MDD patients are desirable to extend and confirm these findings.
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http://dx.doi.org/10.1002/jnr.24609DOI Listing
July 2020

Genetic association and differential expression of PITX2 with acute appendicitis.

Hum Genet 2019 Jan 3;138(1):37-47. Epub 2018 Nov 3.

Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA.

Appendicitis affects 9% of Americans and is the most common diagnosis requiring hospitalization of both children and adults. We performed a genome-wide association study of self-reported appendectomy with 18,773 affected adults and 114,907 unaffected adults of European American ancestry. A significant association with appendectomy was observed at 4q25 near the gene PITX2 (rs2129979, p value = 8.82 × 10) and was replicated in an independent sample of Caucasians (59 affected, 607 unaffected; p value = 0.005). Meta-analysis of the associated variant across our two cohorts and cohorts from Iceland and the Netherlands (in which this association had previously been reported) showed strong cumulative evidence of association (OR = 1.12; 95% CI 1.09-1.14; p value = 1.81 × 10) and some evidence for effect heterogeneity (p value = 0.03). Eight other loci were identified at suggestive significance in the discovery GWAS. Associations were followed up by measuring gene expression across resected appendices with varying levels of inflammation (N = 75). We measured expression of 27 genes based on physical proximity to the GWAS signals, evidence of being targeted by eQTLs near the signals according to RegulomeDB (score = 1), or both. Four of the 27 genes (including PITX2) showed significant evidence (p values < 0.0033) of differential expression across categories of appendix inflammation. An additional ten genes showed nominal evidence (p value < 0.05) of differential expression, which, together with the significant genes, is more than expected by chance (p value = 6.6 × 10). PITX2 impacts morphological development of intestinal tissue, promotes an anti-oxidant response, and its expression correlates with levels of intestinal bacteria and colonic inflammation. Further studies of the role of PITX2 in appendicitis are warranted.
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http://dx.doi.org/10.1007/s00439-018-1956-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6514078PMC
January 2019

The transcriptome of the opossum kidney OK proximal tubule cell line.

Am J Physiol Renal Physiol 2017 09 14;313(3):F585-F595. Epub 2017 Jun 14.

Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania;

The OK cell line derived from the kidney of a female opossum has proven to be a useful model in which to investigate the unique regulation of ion transport and membrane trafficking mechanisms in the proximal tubule (PT). Sequence data and comparison of the transcriptome of this cell line to eutherian mammal PTs would further broaden the utility of this culture model. However, the genomic sequence for is not available and although a draft genome sequence for the opossum (sequenced in 2012 by the Broad Institute) exists, transcripts sequenced from both species show significant divergence. The sequence is not highly annotated, and the majority of transcripts are predicted rather than experimentally validated. Using deep RNA sequencing of the OK cell line, we characterized its transcriptome via de novo transcriptome assembly and alignment to the genome. The quality of the de novo assembled transcriptome was assessed by the extent of homology to sequences in nucleotide and protein databases. Gene expression levels in the OK cell line, from both the de novo transcriptome and genes aligned to the genome, were compared with publicly available rat kidney nephron segment expression data. Our studies demonstrate the expression in OK cells of numerous PT-specific ion transporters and other key proteins relevant for rodent and human PT function. Additionally, the sequence and expression data reported here provide an important resource for genetic manipulation and other studies on PT cell function using these cells.
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http://dx.doi.org/10.1152/ajprenal.00228.2017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5625107PMC
September 2017

The transcriptome of the opossum kidney OK proximal tubule cell line.

Am J Physiol Renal Physiol 2017 09 14;313(3):F585-F595. Epub 2017 Jun 14.

Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania;

The OK cell line derived from the kidney of a female opossum has proven to be a useful model in which to investigate the unique regulation of ion transport and membrane trafficking mechanisms in the proximal tubule (PT). Sequence data and comparison of the transcriptome of this cell line to eutherian mammal PTs would further broaden the utility of this culture model. However, the genomic sequence for is not available and although a draft genome sequence for the opossum (sequenced in 2012 by the Broad Institute) exists, transcripts sequenced from both species show significant divergence. The sequence is not highly annotated, and the majority of transcripts are predicted rather than experimentally validated. Using deep RNA sequencing of the OK cell line, we characterized its transcriptome via de novo transcriptome assembly and alignment to the genome. The quality of the de novo assembled transcriptome was assessed by the extent of homology to sequences in nucleotide and protein databases. Gene expression levels in the OK cell line, from both the de novo transcriptome and genes aligned to the genome, were compared with publicly available rat kidney nephron segment expression data. Our studies demonstrate the expression in OK cells of numerous PT-specific ion transporters and other key proteins relevant for rodent and human PT function. Additionally, the sequence and expression data reported here provide an important resource for genetic manipulation and other studies on PT cell function using these cells.
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http://dx.doi.org/10.1152/ajprenal.00228.2017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5625107PMC
September 2017

Evaluation of disease burden and response to treatment in adults with type 1 Gaucher disease using a validated disease severity scoring system (DS3).

Orphanet J Rare Dis 2015 May 22;10:64. Epub 2015 May 22.

Mount Sinai Hospital, 600 University Avenue, Toronto, ON, M5G 1X5, Canada.

Background: GD1-DS3 is an integrated assessment of type 1 Gaucher disease (GD1) burden based on bone, hematologic and visceral domains. We investigated this disease severity scoring system (DS3) methodology for initial assessment, long-term follow-up and evaluation of treatment responses.

Methods: We enrolled 133 treated adult GD1 patients. Baseline DS3 scores were calculated near the initial treatment date and patients stratified by severity as marked (DS3 6.00-19.00), moderate (DS3 3.00-5.99), mild (DS3 < 3.00). Follow-up scores were calculated annually. Minimal clinically important improvement (MCII), is defined as ΔDS3 of -3.1.

Results:

Patient Characteristics: N370S was the most common allele (118 patients had at least one), 52 were N370S/N370S (48/52 were Ashkenazi Jews), N370S/L444P was the most common genotype among non-Jews. Median age of treatment: 45 years; median follow-up: 14 years. Baseline DS3 scores: Patients with marked disease (N = 58; median 7.84) were least likely to be N370S homozygous (19 %) and most likely to have had splenectomy (53 %), early age at diagnosis (median 18 years) and major pre-treatment bone pathology (76 %). Among patients with moderate disease (N = 53; median 4.33), 49 % were N370S/N370S, 15.1 % had splenectomy and 17 % had major bone disease. Median age at diagnosis: 32 years. No patient with mild disease (N = 22; median 2.4) had splenectomy or major skeletal disease. Median age at diagnosis: 40 years. 68 % were N370S homozygous. Response to treatment: Health-state transitions occurred primarily during the early treatment years. At Year 5, among 48 evaluable patients with marked baseline disease, eight were unchanged in severity status whereas 40 had MCII of varying degrees with 11 scored as mild. Among 42 evaluable moderate patients, none worsened, 16 remained moderate and 26 improved to mild. Among 16 evaluable mild patients, 14 remained so and 2 had DS3 scores in the low moderate range.

Conclusions: DS3 is effective for assessing disease burden in GD1 and for monitoring response. ERT was associated with MCII in DS3 scores in patients with high severity. Nevertheless, despite better DS3 scores with treatment, GD1 patients especially those with splenectomy and pre-treatment bone pathology, continued to have bone complications.
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http://dx.doi.org/10.1186/s13023-015-0280-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4471923PMC
May 2015

Lymphedema prevention and early intervention: a worthy goal.

Oncology (Williston Park) 2012 Mar;26(3):249, 254, 256

Department of Surgery, University of Pittsburgh, and Lymphedema Program, UPMC-Magee Comprehensive Breast Cancer Program, Pittsburgh, Pennsylvania, USA.

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March 2012

Connexin 47 mutations increase risk for secondary lymphedema following breast cancer treatment.

Clin Cancer Res 2012 Apr 20;18(8):2382-90. Epub 2012 Feb 20.

Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA.

Purpose: Secondary lymphedema is a frequent complication of breast cancer associated with surgery, chemotherapy, or radiation following breast cancer treatment. The potential contribution of genetic susceptibility to risk of developing secondary lymphedema following surgical trauma, radiation, and other tissue insults has not been studied.

Experimental Design: To determine whether women with breast cancer and secondary lymphedema had mutations in candidate lymphedema genes, we undertook a case-control study of 188 women diagnosed with breast cancer recruited from the University of Pittsburgh Breast Cancer Program (http://www.upmccancercenter.com/breast/index.cfm) between 2000 and 2010. Candidate lymphedema genes, GJC2 (encoding connexin 47 [Cx47]), FOXC2, HGF, MET, and FLT4 (encoding VEGFR3), were sequenced for mutation. Bioinformatics analysis and in vitro functional assays were used to confirm significance of novel mutations.

Results: Cx47 mutations were identified in individuals having secondary lymphedema following breast cancer treatment but not in breast cancer controls or normal women without breast cancer. These novel mutations are dysfunctional as assessed through in vitro assays and bioinformatics analysis and provide evidence that altered gap junction function leads to lymphedema.

Conclusions: Our findings challenge the view that secondary lymphedema is solely due to mechanical trauma and support the hypothesis that genetic susceptibility is an important risk factor for secondary lymphedema. A priori recognition of genetic risk (i) raises the potential for early detection and intervention for a high-risk group and (ii) allows the possibility of altering surgical approach and/or chemo- and radiation therapy, or direct medical treatment of secondary lymphedema with novel connexin-modifying drugs.
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http://dx.doi.org/10.1158/1078-0432.CCR-11-2303DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3625665PMC
April 2012

Infant with unusual food reactions.

Acta Paediatr 2011 Oct;100(10):1289, 1394-5

University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.

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http://dx.doi.org/10.1111/j.1651-2227.2011.02316.xDOI Listing
October 2011

Sudden death in medium chain acyl-coenzyme a dehydrogenase deficiency (MCADD) despite newborn screening.

Mol Genet Metab 2010 Sep 9;101(1):33-9. Epub 2010 Jun 9.

Division of Genetics, Children's Hospital Boston, Boston, MA 02115, USA.

Introduction: Medium chain acyl-CoA dehydrogenase deficiency (MCADD) is the most frequent of the fatty acid oxidation disorders (FAOD), a group caused by defects in the mitochondrial B-oxidation of fatty acids. Fatty acid oxidation is critical in supplying energy during periods when glucose is limited or when energy needs are increased beyond the availability of glucose. In MCADD, this energy shortage can result in acute metabolic episodes or sudden death. The prevention of sudden death from MCADD served as the primary impetus to expand newborn screening. However, we have experienced sudden death in four children with MCADD despite their detection by newborn screening. The purpose of this report is to alert others to the danger of sudden death in MCADD even when it is detected by newborn screening, to identify the clinical symptoms that precede sudden death, and to examine the relationship between the newborn screening result and the risk for sudden death.

Methods: We describe these children and their metabolic findings with emphasis on their newborn screening octanoylcarnitine (C8) level, the primary marker for newborn detection of MCADD. We also performed a literature search of cases of sudden death in MCADD in which the clinical status preceding death is described.

Results: The newborn screening C8 levels in our four cases were markedly elevated, ranging from 8.4 to 24.8micromol/L (cut off<0.8micromol/L). Only two of the children were homozygous for the common c.985A>G MCAD mutation; the other two were heterozygous for this mutation. Similarly, among the eight reported cases which included MCAD genotypes, five were homozygous for the c.985A>G mutation, while two were heterozygous and one was homozygous for a splice site mutation. Vomiting 12-24h before sudden death was present in all four of our cases, and the review of reported cases of sudden death in MCADD disclosed vomiting as a frequent symptom.

Conclusion: We suggest that in MCADD (1) a newborn screening C8 level of 6micromol/L or greater represents particular risk of sudden death; (2) that MCAD genotypes other than homozygosity for the c.985A>G mutation are also associated with sudden death; (3) that vomiting is a frequent symptom preceding sudden death; and (4) social support and medical follow-up of these families are crucial in reducing the occurrence of sudden death.
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http://dx.doi.org/10.1016/j.ymgme.2010.05.007DOI Listing
September 2010

GJC2 missense mutations cause human lymphedema.

Am J Hum Genet 2010 Jun 27;86(6):943-8. Epub 2010 May 27.

Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15261, USA.

Lymphedema is the clinical manifestation of defects in lymphatic structure or function. Mutations identified in genes regulating lymphatic development result in inherited lymphedema. No mutations have yet been identified in genes mediating lymphatic function that result in inherited lymphedema. Survey microarray studies comparing lymphatic and blood endothelial cells identified expression of several connexins in lymphatic endothelial cells. Additionally, gap junctions are implicated in maintaining lymphatic flow. By sequencing GJA1, GJA4, and GJC2 in a group of families with dominantly inherited lymphedema, we identified six probands with unique missense mutations in GJC2 (encoding connexin [Cx] 47). Two larger families cosegregate lymphedema and GJC2 mutation (LOD score = 6.5). We hypothesize that missense mutations in GJC2 alter gap junction function and disrupt lymphatic flow. Until now, GJC2 mutations were only thought to cause dysmyelination, with primary expression of Cx47 limited to the central nervous system. The identification of GJC2 mutations as a cause of primary lymphedema raises the possibility of novel gap-junction-modifying agents as potential therapy for some forms of lymphedema.
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http://dx.doi.org/10.1016/j.ajhg.2010.04.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3032064PMC
June 2010

Effects of flutamide therapy on craniofacial growth and development in a model of craniosynostosis.

J Craniofac Surg 2010 May;21(3):711-8

Department of Surgery, Division of Plastic and Reconstructive Surgery, University of Pittsburgh, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania 15201, USA.

Research has implicated the faulty regulation of transforming growth factor beta signaling as one mechanism for premature calvaria suture fusion. Androgens have been shown to increase the expression and activity of the transforming growth factor beta, resulting in increased osteoblast proliferation and differentiation and possibly premature suture fusion. The present study was designed to test the hypothesis that flutamide, an androgen receptor-blocking agent, would "rescue" a coronal suture destined to fuse and improve craniofacial growth in a familial rabbit model of craniosynostosis. Thirty rabbits with delayed-onset, coronal suture synostosis were examined via longitudinal cephalometry. The rabbits were divided into 4 groups: (1) sham surgical controls (n = 10), (2) bovine serum albumin (500 ng) protein controls (n = 6), (3) flutamide diluent controls (n = 6), and (4) flutamide (15 mg dissolved in ethanol) experimental group (n = 8). At 10 days of age, radiopaque amalgam markers were implanted in all rabbits on either side of the coronal suture to monitor sutural growth. At 25 days of age, the bovine serum albumin, ethanol, and flutamide were combined with a slow-resorbing collagen vehicle and injected subperiosteally above the coronal suture into the respective groups. Although results revealed a slight but significant increase in coronal suture marker separation in flutamide-treated rabbits compared with controls at 42 days of age, few significant differences were noted for craniofacial growth and intracranial volume among groups. Results suggest that androgen receptor-blocking using flutamide may only provide a transient rescue to suture fusion in this model. Further research is needed to investigate the effects of hormones on suture development and maintenance.
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http://dx.doi.org/10.1097/SCS.0b013e3181d80a36DOI Listing
May 2010

Evidence supporting a role for the calcium-sensing receptor in Alzheimer disease.

Am J Med Genet B Neuropsychiatr Genet 2009 Jul;150B(5):703-9

Department of Health Promotion and Development, University of Pittsburgh, Pennsylvania, USA.

The calcium-sensing receptor (CASR) is a G-protein coupled, transmembrane receptor that responds to changes in Ca(2+) levels. We hypothesized that the CASR could have a role in Alzheimer disease (AD) given expression of the CASR in brain, knowledge that calcium dysregulation promotes susceptibility to neuronal cell damage, the important role that the CASR plays in calcium regulation, and the fact that systemic calcium homeostasis and G-protein signal transduction are altered in AD patients. To investigate the association of CASR variation in AD susceptibility, we genotyped a polymorphic dinucleotide repeat marker within intron 4, one SNP within the promoter region and three non-synonymous SNPs within exon 7 of the CASR gene and tested for association analysis, using a well-characterized cohort of AD cases (n = 692) and controls (n = 435). The dinucleotide repeat polymorphism was significantly associated with AD status (OR = 1.62; 95% CI: 1.27-2.07, P = 0.00037, Bonferroni corrected P = 0.0011) and the three non-synonymous SNP haplotype was boarderline associated with AD status (P = 0.032, Bonferroni corrected P = 0.096). Stratifying by APOE4 allele carrier status revealed that the significant association was only in non-APOE4 carriers (OR of 1.90; 95% CI: 1.37-2.62, P = 0.0001). We also investigated whether apoE or beta amyloid could activate the calcium-sensing receptor. The receptor activation assays revealed that apoE as well as beta amyloid activated the CASR and that the level of activation appeared to be isoform dependent for apoE. These data support our hypothesis that the CASR has a role in AD susceptibility, particularly in individuals without an APOE4 allele.
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http://dx.doi.org/10.1002/ajmg.b.30896DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3062902PMC
July 2009

Candidate gene analysis in primary lymphedema.

Lymphat Res Biol 2008 ;6(2):69-76

Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, 130 Desoto Street, Pittsburgh, PA 15261, USA.

Background: Primary lymphedema, the accumulation of protein-rich fluid in the interstitial space, is the clinical manifestation of mutations involved in lymphatic development and function. Mutations in three genes, VEGFR3, FOXC2, and SOX18, cause primary lymphedema. However, mutations in these three genes only account for a fraction of primary lymphedema. To identify other genes mutated in primary lymphedema, we resequenced twenty-five biologically plausible candidate genes for lymphedema in a large collection of primary lymphedema families.

Methods And Results: Candidate genes were selected on the basis of gene expression in lymphatic endothelial cells, differential antigenic expression in lymphatics, and mouse studies of lymphatic development. The gene sequence was downloaded from GenBank and sequence primers designed to amplify 1 Kb of the 5' sequence, exons and flanking intron-exon boundaries, and 500 bp of the UTR of each gene. No common causative mutations were observed among the 25 genes screened. Single mutations were observed in elastin microfibril interfacer (EMILIN1), lymphocyte cytosolic protein 2 (LCP2), fatty acid binding protein 4 (FABP4), protein tyrosine kinase SYK (SYK), neuropilin-2 (NRP2), SpSRY-box 17 (SOX17), vascular cell adhesion molecule 1 (VCAM1), ROR orphan receptor C (RORC), and vascular endothelial growth factor B (VEGFB). Among these, the mutations in EMILIN1, RORC, LCP2, SYK, and VEGFB failed to segregate with lymphedema. The mutations in FABP4 (2), NRP2, SOX17, and VACM1 are consistent with being causative mutations, but occur in families too small to convincingly confirm cosegregation of mutation and phenotype.

Conclusion: We excluded mutation in 21 biological candidate genes as a common cause of primary lymphedema. Mutations in FABP4, NRP2, SOX17 and VCAM1 are consistent with causality and follow up of these four genes are warranted. The evidence for FABP4 harboring lymphedema mutations is discussed.
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http://dx.doi.org/10.1089/lrb.2007.1022DOI Listing
October 2008

HGF and MET mutations in primary and secondary lymphedema.

Lymphat Res Biol 2008 ;6(2):65-8

Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, 130 Desoto Street, Pittsburgh, PA 15261, USA.

Background: Lymphedema is the abnormal accumulation of protein-rich fluid in the interstitial space. Primary lymphedema is a rare genetic condition with both autosomal dominant and autosomal recessive modes of inheritance. Three genes, FLT4 (VEGFR3), FOXC2, and SOX18 cause varying forms of primary lymphedema. In industrialized countries, secondary lymphedema is usually associated with cancer therapy and/or trauma. Recent observations suggested that hepatocyte growth factor/high affinity hepatocyte growth factor receptor (HGF/MET) were new candidate lymphedema genes.

Methods And Results: The coding exons and flanking regions of HGF and MET were directly sequenced in 145 lymphedema probands, 59 unrelated women with secondary lymphedema following treatment for breast cancer, 21 individual patients with lymphedema and intestinal lymphangiectasia, and at least 159 unrelated ethnic matched control individuals. Mutations leading to truncation or missense changes in evolutionarily conserved residues of HGF and MET were identified. These mutations were not polymorphic in control individuals.

Conclusions: The identification of HGF/MET mutations in primary lymphedema, lymphedema/lymphangiectasia, and breast cancer-associated secondary lymphedema suggests that the HGF/MET pathway is causal or alters susceptibility for a broad range of lymphedema phenotypes. The HGF/MET pathway provides a new target for the prevention and/or treatment of lymphedema.
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http://dx.doi.org/10.1089/lrb.2008.1524DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4298750PMC
October 2008

Research perspectives in inherited lymphatic disease: an update.

Ann N Y Acad Sci 2008 ;1131:134-9

Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh PA 15261, USA.

Genetic studies of inherited lymphedema have provided the starting point for the molecular dissection of lymphatic development and disease. Here, we update the recent contribution of the study of inherited lymphedema and discuss the parallels between mouse models of lymphedema and inherited lymphedema. That the known mutations leading to lymphatic phenotypes explain fewer than half the cases of lymphedema means that the continued study of these disorders may reveal new pathways in lymphatic biology.
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http://dx.doi.org/10.1196/annals.1413.012DOI Listing
July 2008

Predicting scoliosis progression from skeletal maturity: a simplified classification during adolescence.

J Bone Joint Surg Am 2008 Mar;90(3):540-53

Department of Orthopaedics and Rehabilitation, University of Rochester, 601 Elmwood Avenue, Rochester, NY 14624, USA.

Background: Both the Tanner-Whitehouse-III RUS score, which is based on the radiographic appearance of the epiphyses of the distal part of the radius, the distal part of the ulna, and small bones of the hand, and the digital skeletal age skeletal maturity scoring system, which is based on just the metacarpals and phalanges, correlate highly with the curve acceleration phase in girls with idiopathic scoliosis. However, these systems require an atlas and access to the scoring system, making their use impractical in a busy clinical setting. We sought to develop a simplified system that would correlate highly with scoliosis behavior but that would also be rapid and reliable for clinical practice.

Methods: A simplified staging system involving the use of the Tanner-Whitehouse-III descriptors was developed. It was tested for intraobserver and interobserver reliability by six individuals on thirty skeletal age radiographs. The system was compared with the timing of the curve acceleration phase in a cohort of twenty-two girls with idiopathic scoliosis.

Results: The average intraobserver unweighted kappa value was 0.88, and the average weighted kappa value was 0.96. The percentage of exact matches between readings for each rater was 89%, and 100% of the differences were within one unit. The average interobserver unweighted kappa value was 0.71, and the average weighted kappa value was 0.89. The percentage of exact matches between two reviewers was 71%, and 97% of the interobserver differences were within one stage or matched. The agreement was highest between the most experienced raters. Interobserver reliability was not improved by the use of a classification-specific atlas. The correlation of the staging system with the curve acceleration phase was 0.91.

Conclusions: The simplified skeletal maturity scoring system is reliable and correlates more strongly with the behavior of idiopathic scoliosis than the Risser sign or Greulich and Pyle skeletal ages do. The system has a modest learning curve but is easily used in a clinical setting and, in conjunction with curve type and magnitude, appears to be strongly prognostic of future scoliosis curve behavior.
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http://dx.doi.org/10.2106/JBJS.G.00004DOI Listing
March 2008

Progress in developing polymerized crystalline colloidal array sensors for point-of-care detection of myocardial ischemia.

Analyst 2008 Mar 18;133(3):385-90. Epub 2008 Jan 18.

Department of Chemistry, Univeristy of Pittsburgh, 219 Parkman Ave, Pittsburgh, PA 15260, USA.

The difficulty of rapid, definitive diagnosis of myocardial ischemia leads to unnecessary hospital admissions and treatment delays. Previously, decreased metal binding affinity in human serum was investigated as a marker for myocardial ischemia. Polymerized Crystalline Colloidal Array (PCCA) sensors for Ni2+ may be useful in developing a point-of-care test to determine metal binding affinity in plasma and to help rule out myocardial ischemia. PCCA sensors for Ni2+, with 5-amino-8-hydroxyquinoline as a chelating agent, were tested in aqueous solutions and diluted human plasma. The peak wavelength diffracted by the sensors was monitored by reflectance spectrometry and correlated with Ni2+ concentration. The PCCA sensors show a linear response to aqueous Ni2+ concentrations between 0.2 and 1.0 mmol L(-1), and can detect changes in free Ni2+ concentration of <60 micromol L(-1). The sensors respond at physiologic pH and can be reversibly dehydrated. The PCCA sensors developed here can report on free Ni2+ concentration in the presence of human plasma. These sensors can be used to detect a decrease in the Ni2+ affinity of plasma proteins, which may indicate recent myocardial ischemia. PCCA sensors offer a practical approach to rapid, point-of-care detection of a proposed biochemical signature of myocardial ischemia.
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http://dx.doi.org/10.1039/b712482aDOI Listing
March 2008

Tear glucose analysis for the noninvasive detection and monitoring of diabetes mellitus.

Ocul Surf 2007 Oct;5(4):280-93

Department of Chemistry, Chevron Science Center, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.

One approach to the noninvasive monitoring of blood glucose concentration is to monitor glucose concentrations in tear fluid. While several methods for sensing glucose in tear fluid have been proposed, controversy remains as to the precise concentrations of tear glucose in normal and diabetic subjects and as to whether tear fluid glucose concentrations correlate with blood glucose concentrations. This review covers the present understanding of the physiology of glucose transport in tears, the regulation of the aqueous tear fraction, and studies of tear glucose concentration over the last 80 years. The various tear collection methods employed greatly influence the measured tear glucose concentrations. Studies that involve mechanical irritation of the conjunctiva during sampling measure the highest tear glucose concentrations, while studies that avoid tear stimulation measure the lowest concentrations. Attempts to monitor tear glucose concentration in situ by using contact lens-based sensing devices are discussed, and new observations are presented of tear glucose concentration obtained by a method designed to avoid tear stimulation. These studies indicate the importance of the sampling method in determining tear glucose concentrations. On the basis of these results, we discuss the future of in vivo tear glucose sensing and outline the studies needed to resolve the remaining questions about the relationship between tear and blood glucose concentrations.
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http://dx.doi.org/10.1016/s1542-0124(12)70094-0DOI Listing
October 2007

Potential misdiagnosis of 3-methylcrotonyl-coenzyme A carboxylase deficiency associated with absent or trace urinary 3-methylcrotonylglycine.

Pediatrics 2007 Nov 1;120(5):e1335-40. Epub 2007 Oct 1.

Division of Medical Genetics, Department of Pediatrics, Children's Hospital of Pittsburgh, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA.

We report 2 patients with isolated 3-methylcrotonyl-coenzyme A carboxylase deficiency whose urine was devoid of, or contained only trace, 3-methylcrotonylglycine, the pathognomonic marker for this disorder. The first patient, a girl with trisomy 21, was detected through newborn screening with an elevated 5 carbon hydroxycarnitine species level, and the second patient came to clinical attention at the age of 5 months because of failure to thrive and developmental delay. Investigation of urinary organic acids revealed an elevated 3-hydroxyisovaleric acid level but no demonstrable 3-methylcrotonylglycine in both patients. Enzyme studies in cultured fibroblasts confirmed isolated 3-methylcrotonyl-coenzyme A carboxylase deficiency with residual activities of 5% to 7% and 12% of the median control value, respectively. Incorporation of 14C-isovaleric acid into intact fibroblasts was essentially normal, showing that the overall pathway was at least partially functional and potentially explaining the absence of 3-methylcrotonylglycine in urine. Mutation analysis of the MCCA and MCCB genes revealed that both patients were compound heterozygous for a missense mutation, MCCB-c.1015G-->A (p.V339M), and a second mutation that leads to undetectable MCCB messenger (poly A+) RNA. Absent or trace 3-methylcrotonylglycine levels in urine raises the potential for misdiagnosis in the clinical biochemical genetics laboratory based solely on urine organic acid analysis using combined gas chromatography-mass spectrometry.
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http://dx.doi.org/10.1542/peds.2007-0674DOI Listing
November 2007

Mass spectral determination of fasting tear glucose concentrations in nondiabetic volunteers.

Clin Chem 2007 Jul 10;53(7):1370-2. Epub 2007 May 10.

Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, USA.

Background: There is considerable disagreement regarding the concentration of glucose in tears and its relationship to the concentration in blood. Improved sampling and analysis methods may resolve these discrepancies and possibly provide a basis for in situ tear glucose sensors.

Methods: We used liquid chromatography (LC) with electrospray ionization mass spectrometry (ESI-MS) to determine glucose in 1-muL tear fluid samples obtained from 25 fasting study participants. Tear fluid was collected with microcapillaries and a slitlamp microscope.

Results: The median (range) of fasting tear glucose concentrations was 28 (7-161) micromol/L or 0.50 (0.13-2.90) mg/dL. The SD of tear glucose measurements for individuals varied linearly with the mean tear glucose concentration and was approximately half of the mean. We found no significant difference in tear glucose concentrations between contact lens users and nonusers (P = 0.715). We observed significant correlations between fasting blood and tear glucose concentrations (R = 0.50, P = 0.01).

Conclusions: Our tear fluid collection and analysis method enables reliable measurement of equilibrium, fasting tear glucose concentrations. These concentrations are lower than those previously reported for nondiabetic persons. Larger population studies are required to determine correlations between blood and tear glucose concentrations and to determine the utility of contact lens-based sensors for the monitoring of diabetes. Our methods are applicable for study of other tear fluid analytes and may prove useful for monitoring other disease states.
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http://dx.doi.org/10.1373/clinchem.2006.078543DOI Listing
July 2007

Maturity assessment and curve progression in girls with idiopathic scoliosis.

J Bone Joint Surg Am 2007 Jan;89(1):64-73

Shriners Hospitals for Children, 1645 West 8th Street, Erie, PA 16505, USA.

Background: Scoliosis progression during adolescence is closely related to patient maturity. Maturity has various indicators, including chronological age, height and weight changes, and skeletal and sexual maturation. It is not certain which of these indicators correlates most strongly with scoliosis progression. The purpose of the present study was to evaluate various maturity measurements and how they relate to scoliosis progression.

Methods: Physically immature girls with idiopathic scoliosis were evaluated every six months through their growth spurt with serial spinal radiographs; hand skeletal ages; Oxford pelvic scores; Risser sign determinations; height; weight; sexual staging; and serologic studies of the levels of selected growth factors, estradiol, bone-specific alkaline phosphatase, and osteocalcin. These measurements were then correlated with the curve-acceleration phase.

Results: The period and pattern of curve acceleration began during Risser stage 0 for all patients. Skeletal maturation scores derived with the use of the Tanner-Whitehouse-III RUS method, particularly those for the metacarpals and phalanges, were superior to all other indicators of maturity. Regression of the scores provided good estimates of maturity relative to the period of curve progression (Pearson r = 0.93). The initiation of this period occurred simultaneously with digital changes from Tanner-Whitehouse-III stage F to G. At this stage, curves also separated into rapid, moderate, and low-acceleration patterns, with specific curve types in the rapid and moderate-acceleration groups. The low-acceleration group was not confined to a specific curve type.

Conclusions: The curve-acceleration phase separates curves into various types of curve progression. The Tanner-Whitehouse-III RUS scores are highly correlated with timing relative to the curve-acceleration phase and provide better maturity determination and prognosis determination during adolescence than the other parameters tested. Accurate skeletal maturity determination should be used as the primary maturity measurement in girls with idiopathic scoliosis.
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http://dx.doi.org/10.2106/JBJS.F.00067DOI Listing
January 2007

Analysis of tear glucose concentration with electrospray ionization mass spectrometry.

J Am Soc Mass Spectrom 2007 Feb 2;18(2):332-6. Epub 2006 Nov 2.

Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.

We have developed a mass spectrometry-based method that allows one to accurately determine the glucose concentration of tear fluid. We used a 1 microL micro-capillary to collect tear fluid from the tear meniscus with minimal irritation of the eye. We analyzed the 1 muL volume of collected tear fluid with liquid-chromatography electrospray ionization mass spectrometry with the use of D-glucose-6,6-d2 as an internal standard. Repeated measurements and a recovery experiment on pooled, onion-induced tears showed that the analysis of the glucose in tears was precise (4% relative standard deviation) and provided 100% recovery. We found the tear glucose concentration of one fasting nondiabetic subject to be 13 to 51 microM while the onion-induced tear glucose concentration of a different nondiabetic subject to be 211 to 256 microM.
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http://dx.doi.org/10.1016/j.jasms.2006.10.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1975784PMC
February 2007

Correlates of the peak height velocity in girls with idiopathic scoliosis.

Spine (Phila Pa 1976) 2006 Sep;31(20):2289-95

Shriners Hospitals for Children, Erie, PA 16505, USA.

Study Design: Prospective longitudinal.

Objective: Determine correlates of the peak height velocity (PHV) in girls with idiopathic scoliosis.

Summary Of Background Data: Only identifiable retrospectively, the PHV is the most useful known maturity marker in idiopathic scoliosis. Clinically useful correlates are needed to make PHV timing helpful.

Methods: A total of 24 immature girls with idiopathic scoliosis were followed with serial heights, sexual staging, skeletal ages, spinal radiographs, insulin-like growth factor (IGF)-1, IGF binding protein-3, dehydroepiandrosterone sulfate, estradiol, bone-specific alkaline phosphatase, and osteocalcin levels. These markers were correlated to PHV timing.

Results: There were 14 girls who had identifiable growth peaks that averaged 10.5 +/- 1.8 cm/y at age 11.7 +/- 1 years. At the PHV, all girls were Risser 0 with open triradiate cartilages. On a skeletal age radiograph, digital uncapped phalangeal epiphyses were indicative of pre-PHV and fused epiphyses of post-PHV. Capped but unfused epiphyses were indeterminate. Tanner stage 1 for breast strongly indicates pre-PHV. Stage 3 for breast and pubic hair occurred at or after the PHV, and stage 4 always occurred after PHV. Higher IGF-1 and estradiol levels after PHV are potentially discriminatory.

Conclusions: The PHV occurs during Risser 0 with open triradiate cartilages. If triradiate cartilages are open, then Tanner stages, IGF-1, estradiol levels, and the appearance of the epiphyses on a skeletal age radiograph are useful in determining status before or after PHV.
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http://dx.doi.org/10.1097/01.brs.0000236844.41595.26DOI Listing
September 2006

Progress toward the development of a point-of-care photonic crystal ammonia sensor.

Anal Bioanal Chem 2006 Jun 5;385(4):678-85. Epub 2006 May 5.

Department of Chemistry, School of Medicine, Chevron Science Center, University of Pittsburgh, Pittsburgh, PA 15260, USA.

We have developed an ammonia-sensitive material by coupling the Berthelot reaction to our polymerized crystalline colloidal array (PCCA) technology. The material consists of a periodic array of highly charged colloidal particles (110 nm diameter) embedded in a poly(hydroxyethyl acrylate) hydrogel. The particles have a lattice spacing such that they Bragg-diffract visible light. In the Berthelot reaction, ammonia, hypochlorite, and phenol react to produce the dye molecule indophenol blue in an aqueous solution. We use this reaction in our sensor by covalently attaching 3-aminophenol to the hydrogel backbone, which forms cross-links through the Berthelot mechanism. Ammonia reacts with hypochlorite, forming monochloramine, which then reacts with a pendant aminophenol to form a benzoquinone chlorimine. The benzoquinone chlorimine reacts with another pendant aminophenol to form a cross-link. The creation of new cross-links causes the hydrogel to shrink, which reduces the lattice spacing of the embedded colloidal array. This volume change results in a blue-shift in the diffracted light proportional to the concentration of NH3 in the sample. We demonstrate that the NH3 photonic crystal sensing material is capable of quantitative determination of concentrations in the physiological range (50-350 micromol NH3 L(-1)) in human blood serum.
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http://dx.doi.org/10.1007/s00216-006-0453-yDOI Listing
June 2006

Photonic crystal glucose-sensing material for noninvasive monitoring of glucose in tear fluid.

Clin Chem 2004 Dec 30;50(12):2353-60. Epub 2004 Sep 30.

Department of Chemistry, Chevron Science Center, Department of Pediatrics, University of Pittsburgh Medical School, University of Pittsburgh, Pittsburgh, PA 15260, USA.

Background: We recently developed a photonic crystal glucose-sensing material, which consists of a crystalline colloidal array embedded within a polymer network of a polyacrylamide-poly(ethylene glycol) hydrogel with pendent phenylboronic acid groups. The aim of the present work was to improve this approach for application to noninvasive or minimally invasive monitoring of glucose.

Methods: We used new boronic acid derivatives such as 4-amino-3-fluorophenylboronic acid and 4-carboxy-3-fluorophenylboronic acid as the molecular recognition elements to achieve sensing at physiologic pH values.

Results: The improved photonic glucose-sensing material sensed glucose in the range of the 100 mumol/L concentrations found in tear fluid. The detection limits were approximately 1 mumol/L in synthetic tear fluid. The visually evident diffraction color shifted across the entire visible spectral region from red to blue over the physiologically relevant tear-fluid glucose concentrations. This sensing material is selective for glucose over galactose, mannose, and fructose.

Conclusions: These new glucose sensors have properties appropriate for use in such glucose-sensing applications as ocular inserts or diagnostic contact lenses for patients with diabetes mellitus.
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http://dx.doi.org/10.1373/clinchem.2004.039701DOI Listing
December 2004

Results of growth trophic therapy in children with short bowel syndrome.

J Pediatr Surg 2004 Mar;39(3):335-9; discussion 335-9

Clinical Nutrition Department & Intestinal Care Center, Children's Hospital of Pittsburgh, Pittsburgh, PA 15213, USA.

Purpose: In addition to the structural, ultrastructural, and functional changes that occur after extensive enterectomy or in utero bowel loss that results in short bowel syndrome (SBS), a complex array of humoral responses take place that may also affect adaptation of the remaining small intestine as well as nutritional status or growth. These include alterations in the levels of circulating hormones and trophic substances such as growth hormone (GH) and insulinlike growth factors (IGF-1 and IGFBP-3). The purpose of this investigation is to report on the management/treatment of 3 children with SBS (>4 years in duration) and growth failure.

Methods: Serum measures of growth factors and the response to GH stimulation after an arginine insulin tolerance test (AITT) were determined. Weight and height z-scores as well as linear growth velocity were calculated annually pre- and postinitiation of medication therapy.

Results: Patient 1 (boy, 8.5 years old, midgut volvulus, 18-cm bowel) was found to be GH deficient, whereas patients 2 (girl, 12.5 years old, gastroschisis, 70-cm bowel) and 3 (boy, 9 years old, jejunal atresia, 21 cm bowel) were found to have limited GH responsiveness. Subsequently, treatment with GH (1) and growth releasing factor (GRF; 2 & 3) was prescribed. Z-scores for both weight and height improved over time. Positive linear growth velocity was observed from initiation of therapy (<0.5 cm/yr for all) to more than 3 years of treatment (mean 1, 4.7 cm/yr; 2, 8.7 cm/yr; 3, 5.0 cm/yr [age adjusted normals >4.5, >8.5, and >4.9 cm/yr, respectively]). All patients received a regular diet with oral supplements, whereas 2 received parenteral nutrition support for about 1 year.

Conclusions: In children with medically refractory SBS, it is not only important to offer trophic factors but also essential that sufficient nutrient substrate be provided to achieve adequate growth.
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http://dx.doi.org/10.1016/j.jpedsurg.2003.11.022DOI Listing
March 2004

A general photonic crystal sensing motif: creatinine in bodily fluids.

J Am Chem Soc 2004 Mar;126(9):2971-7

Department of Chemistry, University of Pittsburgh, Pennsylvania 15260, USA.

We developed a new sensing motif for the detection and quantification of creatinine, which is an important small molecule marker of renal dysfunction. This novel sensor motif is based on our intelligent polymerized crystalline colloidal array (IPCCA) materials, in which a three-dimensional crystalline colloidal array (CCA) of monodisperse, highly charged polystyrene latex particles are polymerized within lightly cross-linked polyacrylamide hydrogels. These composite hydrogels are photonic crystals in which the embedded CCA diffracts visible light and appears intensely colored. Volume phase transitions of the hydrogel cause changes in the CCA lattice spacings which change the diffracted wavelength of light. We functionalized the hydrogel with two coupled recognition modules, a creatinine deiminase (CD) enzyme and a 2-nitrophenol (2NPh) titrating group. Creatinine within the gel is rapidly hydrolyzed by the CD enzyme in a reaction which releases OH(-). This elevates the steady-state pH within the hydrogel as compared to the exterior solution. In response, the 2NPh is deprotonated. The increased solubility of the phenolate species as compared to that of the neutral phenols causes a hydrogel swelling which red-shifts the IPCCA diffraction. This photonic crystal IPCCA senses physiologically relevant creatinine levels, with a detection limit of 6 microM, at physiological pH and salinity. This sensor also determines physiological levels of creatinine in human blood serum samples. This sensing technology platform is quite general. It may be used to fabricate photonic crystal sensors for any species for which there exists an enzyme which catalyzes it to release H(+) or OH(-).
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http://dx.doi.org/10.1021/ja038187sDOI Listing
March 2004