Reed A Dimmitt

University of Alabama at Birmingham, Birmingham, Alabama, United States

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Publications (36)174.63 Total impact

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    ABSTRACT: The adrenocorticotropic hormone (ACTH) receptor, known as the melanocortin-2 receptor (MC2R), plays an important role in regulating and maintaining adrenocortical function. MC2R is a subtype of the melanocortin receptor family and has unique characteristic among MCRs. Endogenous adrenocorticotropic hormone (ACTH) is the only endogenous agonist for MC2R while the melanocortin peptides α,β and γ melanocyte-stimulating hormone (γ-MSH) and ACTH are full agonists for all other melanocortin receptors. In this study, we examined the molecular basis of MC2R responsible for ligand selectivity using ACTH analogues and MC2R mutagenesis. Our results indicate that substitution of Phe(7) with DPhe(7) or DNal(2')(7) in ACTH1-24 caused a significant decreased in ligand binding affinity and potency. Substitution of Phe(7) with DNal(2')(7) in ACTH1-24 did not switch ligand from agonist to antagonist at MC2R which is observed in MC3R and MC4R. Substitution of Phe(7) with DPhe(7) in ACTH1-17 resulted in the loss of ligand binding and activity. Molecular analysis of the MC2R indicates that only mutation of MC2R TM3 resulted in decrease in DPhe-ACTH binding affinity and potency. Our results suggest that Phe7 in ACTH play an important role in ligand selectivity and the TM3 of the MC2R is crucial for ACTH selectivity and potency. Copyright © 2015, The American Society for Biochemistry and Molecular Biology.
    Journal of Biological Chemistry 01/2015; 290(12). DOI:10.1074/jbc.M114.596122 · 4.60 Impact Factor
  • Yingkui Yang, Min Chen, Reed Allen Dimmitt, Carroll M Harmon
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    ABSTRACT: The melanocortin-4 receptor (MC4R) plays a key role in the regulation of food intake and body weight. Previous studies indicate that alpha-MSH binds to MC4R and activates three signal pathways: cAMP, calcium and MAPK pathway, whereas MC4R synthetic agonist THIQ can only activates cAMP pathway. The molecular basis of the MC4R responsible for different ligand mediated signaling is unknown. We hypothesize that different MC4R agonists can stabilize different MC4R conformation and result in ligand-mediated signal transduction. In this study, we examined the effect of the MC4R conformation change on different agonists mediated cAMP signaling pathway by cross-linking two transmembrane helices (TM3 and TM6). We generated and tested 11 single and 8 double mutations which are located in the end of TM3 and beginning of the TM6 in MC4R. Our results indicate that 1) Single or double mutations of the MC4R did not significantly alter cAMP production induced by NDP-MSH compared to that of MC4R wild type except single mutation 243H. The mutation 243H significantly decreased cAMP production mediated by NDP-MSH or THIQ due to low receptor expression at the cell surface; 2) the mutation 247H significantly decreased THIQ mediated cAMP production but not NDP-MSH. 3) the receptor cAMP signaling pathway activation by THIQ is blocked in the presence of Zn++ at the double mutation I150+242H but activation by NDP-MSH is not, suggesting that the activated conformation of MC4R mediated by NDP-MSH and THIQ is different. This study provides insight into the molecular basis of MC4R responsible for different agonists mediated receptor signaling.
    Biochemistry 10/2014; DOI:10.1021/bi500856x · 3.19 Impact Factor
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    ABSTRACT: Background:The goal was to identify cytokines associated with necrotizing enterocolitis (NEC). Based on our earlier reports of decreased tissue expression of transforming growth factor (TGF)-β, we hypothesized that infants with NEC also have low blood TGF-β levels. We further hypothesized that because fetal inflammation increases the risk of NEC, infants who develop NEC have elevated blood cytokine levels in early neonatal period.Methods:Data on 104 extremely low birth weight (ELBW) infants with NEC and 893 without NEC from 17 centers were analyzed. Clinical information was correlated with blood cytokine levels on postnatal day 1 (D1), D3, D7, D14, and D21.Results:Male gender, non-Caucasian/non-African-American ethnicity, sepsis, lower blood TGF-β and interleukin (IL)-2, and higher IL-8 levels were associated with NEC. The NEC group had lower TGF-β levels than controls since D1. The diagnosis of NEC was associated with elevated IL-1β, IL-6, IL-8, IL-10, monocyte chemoattractant protein-1/CC-motif ligand (CCL)-2, macrophage inflammatory protein-1β/CCL3, and C-reactive protein.Conclusions:Clinical characteristics, such as gender and ethnicity, and low blood TGF-β levels are associated with higher risk of NEC. Infants who developed NEC did not start with high blood levels of inflammatory cytokines, but these rose mainly after the onset of NEC.Pediatric Research (2014); doi:10.1038/pr.2014.48.
    Pediatric Research 04/2014; DOI:10.1038/pr.2014.48 · 2.84 Impact Factor
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    ABSTRACT: Baclofen, a GABA(B) receptor agonist, has been shown to reduce the episodes of gastroesophageal reflux (GER) by reducing the incidence of transient lower esophageal sphincter relaxations. Although baclofen has been shown to reduce reflux symptoms in adults, data in pediatric patients is limited. The aim of the study was to evaluate the efficacy of baclofen in children with refractory GER. Medical charts of patients 1-18 years of age treated with baclofen for persistent GER symptoms were reviewed retrospectively. Short-term (at first clinic visit) and long-term (12 months) clinical responses were assessed. 53 patients were included in the final analysis. The mean duration of illness was 1.5 years and the mean age was 6.1 years. All patients were on either once (53%) or twice daily (47%) doses of proton pump inhibitors (PPIs) at the time of initiation of baclofen. Thirty-five (66%) patients experienced a significant reduction in clinical symptoms at their first follow-up visit. In the remaining 18 patients, however, baclofen was stopped due either to no response (n = 15) or adverse events (n = 3). 27 patients continued treatment and were assessed for long-term response. Of those, 22 (81%) had a sustained response to baclofen at 12 months while 5 (19%) lost response. We recognized no clinical characteristic differences between those with and without a response to baclofen at either time point. Baclofen can be used as supplemental therapy to PPIs in children with refractory GER; however, prospective trials are needed to further validate our results and assess safety.
    Journal of pediatric gastroenterology and nutrition 07/2013; DOI:10.1097/MPG.0b013e3182a2747b · 2.87 Impact Factor
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    ABSTRACT: BACKGROUND/PURPOSE: To examine whether as initial surgical intervention for necrotizing enterocolitis, primary peritoneal drainage as compared to primary laparotomy is associated with increased mortality or intestinal failure. METHODS: Retrospective observational study of 240 infants with surgical necrotizing enterocolitis. RESULTS: There was no difference concerning the composite outcome of mortality before discharge or survival with intestinal failure after adjusting for known covariates (Odds Ratio 1.73, 95% CI 0.88, 3.40). More surviving infants in the peritoneal drainage with subsequent salvage or secondary laparotomy had intestinal failure compared to those who received a peritoneal drain without subsequent laparotomy and survived (12% vs. 14% vs. 1%, p=0.015). CONCLUSIONS: There is no difference between peritoneal drainage and laparotomy in infants with surgical necrotizing enterocolitis concerning the combined outcome of mortality or survival with intestinal failure. There is increased intestinal failure in surviving infants treated with peritoneal drain with either subsequent salvage or secondary laparotomy compared to peritoneal drainage alone.
    Journal of Pediatric Surgery 03/2013; 48(3):568-572. DOI:10.1016/j.jpedsurg.2012.11.028 · 1.31 Impact Factor
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    ABSTRACT: The melanocortin-5 receptor (MC5R) is a subtype receptor of the melanocortin receptor (MCR) family, which is expressed centrally, as well as in a variety of peripheral tissues. MC5R has been implicated in many different physiological fields such as lipid metabolism and exocrine function. However, the specific molecular determinants of MC5R responsible for ligand binding and receptor signaling are currently unknown. The aim of this study is to determine the molecular basis of human MC5R (hMC5R) responsible for ligand binding and receptor signaling. Twenty-four single mutations of hMC5R were created and tested. Our results indicate that (1) substituting charged amino acid residue E92 in transmembrane domain 2 (TM2), aspartic acid 115 (D115) and D119 in TM3, and histidine (H) 257 in TM6 with alanine dramatically reduced NDP-α-MSH binding affinity and receptor signaling and (2) substituting aromatic amino acids phenylalanine (F) 195 in TM5, F254 in TM6, and H276 in TM7 with alanine also significantly decreased NDP-α-MSH binding and receptor activity. Combining pharmacological results and computer modeling, our results suggest that D115 and D119 in TM3, F195 in TM5, and F254 in TM6 may form a binding pocket for NDP-α-MSH binding. Our results provide important information about the structural aspects of hMC5R responsible for ligand binding and receptor signaling.
    Biochemistry 02/2013; 52(10). DOI:10.1021/bi3013593 · 3.19 Impact Factor
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    ABSTRACT: BACKGROUND AND AIMS: Cryptosporidiosis is usually a self-limiting illness in healthy patients. However, it can cause severe life threatening complications in immunocompromised patients. The effect of cryptosporidial infection on inflammatory bowel disease (IBD) has not been well studied and available literature is largely restricted to adult case reports. The purpose of this study is to describe the clinical characteristics of cryptosporidial infection in children with IBD. METHODS: Stool studies from children with IBD presenting with presumed relapse during the period 2005-2011 were reviewed retrospectively. Cryptosporidial infection was diagnosed by stool enzyme immunoassay. An age matched control group of IBD patients without cryptosporidial infection was used for comparison. RESULTS: Medical records of 170 IBD patients were reviewed and a total of 149 presumed relapses were identified. Cryptosporidial infection was found in seven of the 39 patients with positive stool studies (four ulcerative colitis/three Crohn's disease) presenting with relapse. The median age was 13years (range: 3-17) and five patients were female. The median duration of the IBD was 18months (range 2-48months). All but one patient had stable disease prior to acquiring infection. Five patients required hospitalization due to significant dehydration. Three of the five patients treated with nitazoxanide had significant clinical improvement in 3days. All patients had complete resolution of symptoms by three weeks and no infection related complications were noted. In comparison to patients with cryptosporidial infection, the control group required an increased need for escalation of therapy (71% vs. 0.0%, p=001) and higher re-hospitalization rates (24% Vs.0.0%, p=0.54) within 6months following indexed relapse. CONCLUSION: In IBD patients, cryptosporidiosis can cause significant illness leading to increased need for hospitalization. In the absence of appropriate stool studies, cryptosporidiosis can be misdiagnosed as disease relapse and lead to inappropriate therapy. Nitazoxanide appears to be effective along with supportive therapy.
    Journal of Crohn s and Colitis 02/2013; DOI:10.1016/j.crohns.2013.01.015 · 3.56 Impact Factor
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    ABSTRACT: Crohn's disease (CD) is a chronic granulomatous disease of unknown etiology that affects primarily the gastrointestinal system but can be associated with extraintestinal manifestations. Latent pulmonary involvement in children with CD has been described, but symptomatic pulmonary disease has rarely been reported in children. In this review, we report two pediatric cases, one with pleural effusion at the time of CD diagnosis and the other with bilateral cavitary lesions in a previously diagnosed CD patient. We review the current literature and summarize the diagnosis and management of pulmonary involvement in CD. Awareness of these pulmonary complications of CD in children may lead to more prompt diagnosis, guide appropriate therapy, and decrease morbidity.
    Journal of Crohn s and Colitis 06/2012; DOI:10.1016/j.crohns.2012.05.007 · 3.56 Impact Factor
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    ABSTRACT: P-glycoprotein (P-gp), the functional product of the multidrug resistance gene (MDR), is a transmembrane protein that extrudes substrates from the intracellular environment. P-gp is expressed on the apical surface of epithelial cells and on cells from the hematopoietic lineage. Human MDR polymorphisms have been associated with the increased risk of inflammatory bowel disease, and FVB/N animals deficient in mdr1a expression develop spontaneous colitis. Previous studies using adult bone marrow chimeras indicated that colitis development in this animal model was contingent on P-gp deficiency in radiation-resistant epithelial cells; however, the use of adult animals may mask the role of hematopoietic immune cells in colitis initiation, due to preexisting epithelial abnormalities. To assess the importance of P-gp expression in intestinal epithelial and hematopoietic-derived cells on colitis induction in FVB.mdr1a(-/-) animals, we developed a neonatal model of bone marrow reconstitution. FVB/N and FVB.mdr1a(-/-) adult and neonatal animals were lethally irradiated and reconstituted with bone marrow from FVB/N or FVB.mdr1a(-/-) donors. Animals were observed for 20 weeks. Adult FVB/N animals deficient in P-gp expression in hematopoietically derived immune cells developed colitis similar to adult animals deficient in P-gp expression in radiation-resistant epithelial/stromal cells. Neonatal animals deficient in P-gp expression in hematopoietically derived immune cells developed a more histologically significant colitis than those deficient in P-gp expression in epithelial tissue. The use of a neonatal model of bone marrow reconstitution has revealed a critical role for P-gp expression in hematopoietically derived immune cells in colitis development in the FVB.mdr1a(-/-) model.
    Journal of pediatric gastroenterology and nutrition 06/2011; 53(6):666-73. DOI:10.1097/MPG.0b013e31822860f1 · 2.87 Impact Factor
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    ABSTRACT: The programmed, stepwise acquisition of immunocompetence that marks the development of the fetal immune response proceeds during a period when both T cell receptor and immunoglobulin (Ig) repertoires exhibit reduced junctional diversity due to physiologic terminal deoxynucleotidyl transferase (TdT) insufficiency. To test the effect of N addition on humoral responses, we transplanted bone marrow from TdT-deficient (TdT−/−) and wild-type (TdT+/+) BALB/c mice into recombination activation gene 1-deficient BALB/c hosts. Mice transplanted with TdT−/− cells exhibited diminished humoral responses to the T-independent antigens α-1-dextran and (2,4,6-trinitrophenyl) hapten conjugated to AminoEthylCarboxymethyl-FICOLL, to the T-dependent antigens NP19CGG and hen egg lysozyme, and to Enterobacter cloacae, a commensal bacteria that can become an opportunistic pathogen in immature and immunocompromised hosts. An exception to this pattern of reduction was the T-independent anti-phosphorylcholine response to Streptococcus pneumoniae, which is normally dominated by the N-deficient T15 idiotype. Most of the humoral immune responses in the recipients of TdT−/− bone marrow were impaired, yet population of the blood with B and T cells occurred more rapidly. To further test the effect of N-deficiency on B cell and T cell population growth, transplanted TdT-sufficient and -deficient BALB/c IgMa and congenic TdT-sufficient CB17 IgMb bone marrow were placed in competition. TdT−/− cells demonstrated an advantage in populating the bone marrow, the spleen, and the peritoneal cavity. TdT deficiency, which characterizes fetal lymphocytes, thus appears to facilitate filling both central and peripheral lymphoid compartments, but at the cost of altered responses to a broad set of antigens. Electronic supplementary material The online version of this article (doi:10.1007/s00251-011-0543-7) contains supplementary material, which is available to authorized users.
    Immunogenetics 06/2011; 63(9):599-609. DOI:10.1007/s00251-011-0543-7 · 2.49 Impact Factor
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    ABSTRACT: Therapy with broad-spectrum antibiotics is a common practice for premature infants. This treatment can reduce the biodiversity of the fecal microbiota and may be a factor in the cause of necrotizing enterocolitis. In contrast, probiotic treatment of premature infants reduces the incidence of necrotizing enterocolitis. We hypothesized that 1 mechanism for these observations is the influence of bacteria on postnatal development of the mucosal immune system. Expression of immune molecules and microbial sensors was investigated in the postnatal mouse gastrointestinal tract by real-time polymerase chain reaction. Subsequently, 2-week-old specific pathogen-free and microbial-reduced (MR; antibiotic treated) mice were compared for immune molecule and microbial sensor expression, mesenteric lymph node T-cell numbers and activation, intestinal barrier function/permeability, systemic lymphocyte numbers, and T-cell phenotype commitment. Toll-like receptor 2, 4, and 5 expression was highest in 2-week-old specific pathogen-free mice, and this expression was decreased in MR mice. There was no difference in intestinal tight-junctional function, as evaluated by fluorescein isothiocyanate-dextran uptake, but MR mice had increased bacterial translocation across the intestinal epithelial barrier. MR mice had significantly fewer splenic B cells and mesenteric lymph node CD4+ T cells, but there were normal numbers of splenic T cells. These systemic T cells from MR mice produced more interleukin-4 and less interferon-gamma and IL-17, indicative of maintenance of the fetal, T-helper cell type 2 phenotype. The present study shows that intestinal commensal microbiota have an influence on early postnatal immune development. Determining specific bacteria and/or bacterial ligands critical for this development could provide insight into the mechanisms by which broad-spectrum antibiotics and/or probiotic therapy influence the development of the mucosal immune system and mucosal-related diseases.
    Journal of pediatric gastroenterology and nutrition 09/2010; 51(3):262-73. DOI:10.1097/MPG.0b013e3181e1a114 · 2.87 Impact Factor
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    ABSTRACT: Premature neonates are predisposed to necrotizing enterocolitis (NEC), an idiopathic, inflammatory bowel necrosis. We investigated whether NEC occurs in the preterm intestine due to incomplete noninflammatory differentiation of intestinal macrophages, which increases the risk of a severe mucosal inflammatory response to bacterial products. We compared inflammatory properties of human/murine fetal, neonatal, and adult intestinal macrophages. To investigate gut-specific macrophage differentiation, we next treated monocyte-derived macrophages with conditioned media from explanted human fetal and adult intestinal tissues. Transforming growth factor-β (TGF-β) expression and bioactivity were measured in fetal/adult intestine and in NEC. Finally, we used wild-type and transgenic mice to investigate the effects of deficient TGF-β signaling on NEC-like inflammatory mucosal injury. Intestinal macrophages in the human preterm intestine (fetus/premature neonate), but not in full-term neonates and adults, expressed inflammatory cytokines. Macrophage cytokine production was suppressed in the developing intestine by TGF-β, particularly the TGF-β(2) isoform. NEC was associated with decreased tissue expression of TGF-β(2) and decreased TGF-β bioactivity. In mice, disruption of TGF-β signaling worsened NEC-like inflammatory mucosal injury, whereas enteral supplementation with recombinant TGF-β(2) was protective. Intestinal macrophages progressively acquire a noninflammatory profile during gestational development. TGF-β, particularly the TGF-β(2) isoform, suppresses macrophage inflammatory responses in the developing intestine and protects against inflammatory mucosal injury. Enterally administered TGF-β(2) protected mice from experimental NEC-like injury.
    Gastroenterology 09/2010; 140(1):242-53. DOI:10.1053/j.gastro.2010.09.043 · 13.93 Impact Factor
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    ABSTRACT: Premature infants receiving probiotics have a decreased incidence of necrotizing enterocolitis. This may be mediated by intestinal bacterial signaling via toll-like receptors (TLRs) 2 and 4 maintaining intestinal homeostasis. We hypothesized that TLRs 2 and 4 are protective against ischemia-reperfusion (I/R) intestinal injury. Two-week-old C57BL/6 wild-type (WT), B6.TLR2(-/-), B6.TLR4(-/-), B6.TLR2(-/-)4(-/-), and microbially reduced (antibiotic-treated) mice (MR) underwent 60 minutes of superior mesenteric artery occlusion (I) followed by 90 minutes of reperfusion (R). Small intestine was harvested for analysis of microscopic injury, apoptosis, and inflammatory gene expression using quantitative polymerase chain reaction. After I/R, the median histologic injury scores of the B6.TLR4(-/-), B6.TLR2(-/-)4(-/-), and MR pups were higher than the WT or B6.TLR2(-/-) pups that corresponded with greater apoptosis based on terminal deoxynucleotidyl transferase-mediated dUTP-FITC nick-end labeling and activated caspase-3 immunostaining. B6.TLR4(-/-), B6.TLR2(-/-)4(-/-), and MR also had elevated tissue innate immunity-associated chemokine and cytokine expression. Neonatal mice deficient in TLR4, either alone or also deficient in TLR2, as well as those lacking a normal commensal intestinal microbiome are more susceptible to an I/R model of intestinal injury. These results may provide a mechanism for commensal bacterial-mediated protection, which may help to direct further studies to elucidate the mechanism of probiotic protection.
    Journal of Pediatric Surgery 06/2010; 45(6):1246-55. DOI:10.1016/j.jpedsurg.2010.02.093 · 1.31 Impact Factor
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    ABSTRACT: To determine the independent impact of acute kidney injury (AKI) and renal replacement therapy (RRT) in infants and children who receive extracorporeal membrane oxygenation. Despite continued expertise/technological advancement, patients who receive extracorporeal membrane oxygenation have high mortality. AKI and RRT portend poor outcomes independent of comorbidities and illness severity in several critically ill populations. Retrospective cohort study. The primary variables explored are AKI (categorical complication code for serum creatinine > 1.5 mg/dL or International Statistical Classification of Diseases and Related Health Problems, Revision 9 for acute renal failure), and RRT (complication/Current Procedural Terminology code for dialysis or hemofiltration). Multiple variables previously associated with mortality in this population were controlled, using logistic stepwise regression. Decision tree modeling was performed to determine optimal variables and cut points to predict mortality. Critically ill neonates (0-30 days old) and children (> 30 days but < 18 yrs old) in the Extracorporeal Life Support Organization registry. None. Neonatal mortality was 2175 (27.4%) of 7941. Nonsurvivors experienced more AKI (413 [19%] of 2175 vs. 225 [3.9%] of 5766, p < .0001), and more received RRT (863 [39.7%] of 2175 vs. 923 [16.0%] of 5766, p < .0001) than survivors. Pediatric mortality was 816 (41.6%) of 1962. Pediatric nonsurvivors similarly experienced more AKI (264 [32.3%] of 816 vs. 138 [12.0%] of 1146, p < .0001) and RRT (487 [58.9%] of 816 vs. 353 [30.8%] of 1146, p < .0001) than survivors. After adjusting for confounding variables, the adjusted odds ratio for neonatal group was 3.2 (p < .0001) post AKI and 1.9 (p < .0001) given RRT. Similarly, the pediatric adjusted odds ratio for mortality was 1.7 (p < .001) post AKI and 2.5 (p < .0001) given RRT. AKI and RRT were essential in the neonatal and pediatric mortality decision trees. After adjusting for known predictors of mortality, AKI and RRT independently predict mortality in neonates and children, who receive extracorporeal membrane oxygenation. Ascertainment of AKI risk factors, testing novel therapies, and optimizing the timing/delivery of RRT may positively impact survival.
    Pediatric Critical Care Medicine 03/2010; 12(1):e1-6. DOI:10.1097/PCC.0b013e3181d8e348 · 2.33 Impact Factor
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    ABSTRACT: Necrotizingenterocolitis (NEC) is a major health concern for premature infants and its patho-genesis remains poorly understood. The current mouse NEC model has not well been characterized. In this study, we develop a simple mouse model of NEC and determine the role of several factors modulating human NEC (i.e., breast milk, birth weight, cesarean section and bacteria) on intestinal injury. In a first experiment, pups born naturally and dam fed for <12 hours were gavaged with adult commensal bacteria or E. Fecalis, and exposed to hypoxia-cold stress-formula feeding, and compared with controls without bacteria inoculation. 72-hour mortality was recorded, and small intestines were examined histologically. In a second experiment, we compared the incidence of NEC in mice dam fed for <12 hours to those dam fed for 12 to 24 hours or delivered by cesarean section prior to being submitted to the NEC protocol. In pups inoculated with 10(7) CFU of a standardized preparation of adult commensal bacteria or 10(5) CFU of E. Fecalis, the incidence of severe NEC (>grade 2) was 70% and 37% respectively vs 6% in the controls (no bacteria)(p<0.05). In pups dam fed for 12 to 24 hours, NEC incidence was 44(±12)% lower vs those dam fed less than 12 hours (p<0.05). We did not find any difference in the NEC incidence between naturally-born pups dam fed for less than 12 hours and these born by cesarean section. The incidence of severe NEC was higher in pups with low birth weight. we have simplified and characterized a neonatal mouse NEC model that shares several risk factors with human NEC. Now that transgenic mice are available, this model will be useful to study the role played by specific proteins in vivo in NEC development.
    International Journal of Clinical and Experimental Medicine 01/2010; 3(4):293-302. · 1.42 Impact Factor
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    ABSTRACT: Purpose: Toll-like receptors (TLRs) mediate host-microbial interaction. Premature infants receiving probiotic therapy have a decreased incidence of NEC. The mechanism of this protection may be secondary to intestinal mucosal maturation through commensal bacterial signaling of TLRs 2 and 4. We hypothesized that TLRs 2 and 4 are protective against injury in an ischemia-reperfusion (IR) model in neonatal mice. Methods: Two week old C57BL/6 wild-type (WT), B6.TLR 2-/-, B6.TLR 4-/-, and B6.TLR 2-/-4-/-underwent laparotomy and superior mesenteric artery occlusion for 60 minutes followed by 90 minutes of reperfusion. Sections of the mid-jejunum were sent for staining with H&E, and masked comparisons were made between groups using a scoring system scaled from 0 (no injury) to 5 (transmural necrosis). Apoptosis was evaluated by staining with antibodies to activated caspase-3 and TUNEL. Additionally, RT-PCR normalized to 18s was performed for several cytokines and chemokines comparing baseline mock vs IR. Parametric and non-parametric analysis was used as indicated with significance being p<0.05 Results: Median histological injury scores were significantly greater for B6.TLR 4-/- and B6.TLR 2-/-4-/- compared to WT and B6.TLR 2-/- (median 3 versus 2, respectively). Subjectively, there was more apoptosis in the B6.TLR 4-/- and B6.TLR 2-/-4-/- compared to both WT and B6.TLR2-/-. RT-PCR revealed a decrease in MIP-2 at baseline between B6.TLR 2-/-4-/- and WT. No other significant differences were seen between groups at baseline. After IR, B6.TLR 2-/-4-/- had increased expression compared to WT of the inflammatory cytokines IL-1α, IL-2, IL-6, IL-10, IL-22, TNF-α, and TGF-β and chemokines MIP-2, KC, LIX, and CXCL15. B6.TLR 4-/- mice showed increased expression of IL-1α, IL-6, IL-10, IL-22 and LIX. Conclusions: Mice lacking TLR 4, alone or in conjunction with lacking TLR 2, have increased ischemia reperfusion induced intestinal damage as evidenced by higher injury scores and increased apoptosis. They also have a dysregulated inflammatory response which may further worsen damage. We speculate that these neonatal mice mirror premature human infants receiving antibiotics with a delay in establishing a normal commensal intestinal microbiome. Determining the specific ligands and signaling molecules in early mucosal development may provide insight to a future clinical trial of probiotic therapy to prevent NEC.
    2009 American Academy of Pediatrics National Conference and Exhibition; 10/2009
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    ABSTRACT: Macrophages are first seen in the fetal intestine at 11-12 wk and rapidly increase in number during the 12- to 22-wk period of gestation. The development of macrophage populations in the fetal intestine precedes the appearance of lymphocytes and neutrophils and does not require the presence of dietary or microbial antigens. In this study, we investigated the role of chemerin, a recently discovered, relatively selective chemoattractant for macrophages, in the recruitment of macrophage precursors to the fetal intestine. Chemerin mRNA/protein expression was measured in jejunoileal tissue from 10- to 24-wk human fetuses, neonates operated for intestinal obstruction, and adults undergoing bariatric surgery. The expression of chemerin in intestinal epithelial cells (IECs) was confirmed by using cultured primary IECs and IEC-like cell lines in vitro. The regulatory mechanisms involved in chemerin expression were investigated by in silico and immunolocalization techniques. IECs in the fetal, but not mature, intestine express chemerin. Chemerin expression peaked in the fetal intestine at 20-24 wk and then decreased to original low levels by full term. During the 10- to 24-wk period, chemerin accounted for most of the macrophage chemotactic activity of cultured fetal IECs. The maturational changes in chemerin expression correlated with the expression of retinoic acid receptor-beta in the intestine. Chemerin is an important mediator of epithelial-macrophage cross talk in the fetal/premature, but not in the mature, intestine. Understanding the regulation of the gut macrophage pool is an important step in development of novel strategies to boost mucosal immunity in premature infants and other patient populations at risk of microbial translocation.
    AJP Gastrointestinal and Liver Physiology 06/2009; 297(1):G1-G10. DOI:10.1152/ajpgi.90730.2008 · 3.74 Impact Factor
  • Reed A. Dimmitt, Anna Seay, Robin G. Lorenz
    Gastroenterology 04/2008; 134(4). DOI:10.1016/S0016-5085(08)63046-2 · 13.93 Impact Factor
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    ABSTRACT: The ELR(+) chemokine CXCL15, which recruits neutrophils during pulmonary inflammation, is also known as lungkine due to its reported exclusive expression in the lung. We now report that CXCL15 mRNA and protein are also expressed in other mucosal and endocrine organs including the gastrointestinal and urogenital tracts and the adrenal gland. Our results indicate that CXCL15 is expressed throughout the gastrointestinal tract, with the exception of the cecum. Gastric CXCL15 protein expression is approximately 10-fold lower than pulmonary expression and primarily occurs in a specific lineage of gastric epithelial cells, the prezymogenic and zymogenic cell. Similar to the increased expression of CXCL15 during pulmonary inflammation, gastric inflammation induced by infection with Helicobacter felis caused an increase in gastric CXCL15 expression. However, colonic CXCL15 expression was not altered in two different models of colonic inflammation, the Helicobacter hepaticus T-cell transfer model and the mdr1a(-/-) model of colitis. These findings clearly demonstrate that CXCL15, previously reported to be the only lung-specific chemokine, is also highly expressed in other murine mucosal and endocrine organs. The functional role of CXCL15 in mucosal disease remains to be elucidated. This manuscript contains online supplemental material at (http://www.jhc.org). Please visit this article online to view these materials.
    Journal of Histochemistry and Cytochemistry 06/2007; 55(5):515-24. DOI:10.1369/jhc.6A7121.2007 · 2.40 Impact Factor
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    ABSTRACT: Subgaleal hematomas (SGHs) in neonates may result from trauma to the scalp sustained during delivery. In the majority of cases, these lesions will resolve on their own without serious or long-term consequences. The authors report on a case of SGH resulting in hypotension, anemia, coagulopathy, and eventually direct hyperbilirubinemia in a neonate. After several weeks of medical management failed to resolve the hyperbilirubinemia, surgical evacuation of the clot was undertaken and yielded favorable results. The direct bilirubinemia in this case was believed to be the result of an overload of iron to the hepatocytes. It is the authors' contention that the evacuation of the hematoma resulted in a reduction in the amount of iron being presented to the liver for metabolism and significantly contributed to this patient's recovery.
    Journal of Neurosurgery 03/2007; 106(2 Suppl):131-3. DOI:10.3171/ped.2007.106.2.131 · 3.23 Impact Factor

Publication Stats

908 Citations
174.63 Total Impact Points

Institutions

  • 2003–2015
    • University of Alabama at Birmingham
      • • Department of Pediatrics
      • • Department of Surgery
      • • Department of Microbiology
      Birmingham, Alabama, United States
  • 2000–2002
    • Stanford University
      • Department of Pediatrics
      Palo Alto, California, United States