Biomedical subjects

P K H Tam

Publications and source records attributed to P K H Tam.

At least 19 recordsLinked to original sources

PubMed2006

Inhibition of tumor growth and metastasis in vitro and in vivo by targeting macrophage migration inhibitory factor in human neuroblastoma.

Macrophage migration inhibitory factor (MIF) has been defined as a novel oncogene. Our previous results have shown that MIF may contribute to the progression of neuroblastoma by (a) inducing N-Myc expression and (b) upregulating the expression of angiogenic factors. The aim of this study was to test whether tumor growth could be inhibited by reduction of endogenous MIF expression in neuroblastoma and clarify the molecular mechanisms underlying MIF reduction on the control of neuroblastoma growth. We established human neuroblastoma cell lines stably expressing antisense MIF (AS-MIF) cDNA. These stable transfectants were characterized by cell proliferation, gene expression profile, tumorigenicity and metastasis in vitro and in vivo. Decreased MIF expression was observed after transfection with AS-MIF in neuroblastoma cells and downregulation of MIF expression significantly correlated with decreased expression of N-Myc, Ras, c-Met and TrkB at protein level. Affymetrix microarray analysis revealed that expression of IL-8 and c-met was inhibited and neuroblastoma-favorable genes such as EPHB6 and BLU were upregulated in MIF reduced cells. Neuroblastoma cell growth exhibited a nearly 80% reduction in AS-MIF transfectants in vitro. Furthermore, mice in which tumors formed after subcutaneous injection of AS-MIF transfectants showed a 90% reduction in tumor growth compared to control. Metastasis in mice was also suppressed dramatically. Our data demonstrate that targeting MIF expression is a promising therapeutic strategy in human neuroblastoma therapy, and also identifies the MIF target genes for further study.

Animals↗

PubMed2006

A simple and secure method to fix laparoscopic trocars in children.

We introduce a simple method of fixing trocars to the abdominal wall in children. Before anchoring the trocar, a piece of Tegaderm polyurethrane adhesive (3M Healthcare, St. Paul, Minnesota) is attached to the trocar. A silk stitch is anchored to neighboring skin, and then transfixed over the shaft of the trocar through the adhesive. Both inward and outward movement of the trocar can be restrained. This method is simple, fast, secure, and can be applied to trocars of any size.

Abdominal Wall↗

PubMed2005

Prospective randomized single-center, single-blind comparison of laparoscopic vs open repair of pediatric inguinal hernia.

BACKGROUND: The repair of indirect inguinal hernia (IH) is one of the most common pediatric surgical procedures, and open surgery (OS) is the standard treatment. The aim of this study was to determine whether the recently developed laparoscopic repair (LR) of IH is superior to OS. METHODS: Between February 2003 and February 2004, we randomly assigned 97 consecutive IH patients at our institution into OS and LR groups. Fourteen patients were excluded from the study for various reasons, leaving study population of 83 patients. After operation, multiple dressings were placed to blind observers to the operation type. Two pain scales, the children and Infants Postoperative Pain were used to assess postoperative pain. Acetaminophen (15 mg/kg/dose every 6 h) was given at a fixed pain score. Analgesic doses were compared. Parents also provided assessments of their children's recovery and wound appearance. RESULTS: The amount of acetaminophen taken by the OS group (n = 42) was 1.05 +/- 1.248 doses per patient, whereas the amount taken by the LR group (n = 41) was 0.54 +/- 0.84 dose per patient (p = 0.032; 95% confidence interval 0.45-0.976). Laparoscopy detected 11 more bilateral hernias (p = 0.006). Although the operative times did not differ significantly for bilateral hernias (39.08 +/- 13.37 min vs 34.0 +/- 11.31 min, p = 0.623), it did differ for unilateral hernias (18.38 +/- 5.71 vs 23.25 +/- 6.26 min, p = 0.001). Five contralateral hernias were detected in the OS group on follow-up, but none were found in the LR group (p = 0.026). The scores given by parents for recovery and wound appearance were higher in the LR group (p = 0.05). CONCLUSIONS: As compared with IH patients who undergo open surgery, those who have a laparoscopic repair suffer less pain, and their recovery and wound cosmesis are more satisfactory. With LR, contralateral hernias can be detected and repaired in a single operative procedure. This procedure takes slightly longer for unilateral than for bilateral hernias.

Child, Preschool↗

PubMed2005

Meconium peritonitis: prenatal diagnosis, postnatal management and outcome.

OBJECTIVES: Prenatal ultrasonography (USS) is a routine screening test for fetal abnormalities. Its accuracy for detecting meconium peritonitis (MP), which may carry high mortality, is important for prenatal counseling. The aim of this study was to assess the accuracy of prenatal USS for diagnosing MP and predicting patient outcomes. METHODS: The prenatal and postnatal medical records of all patients referred to our institutions with confirmed MP were reviewed, with emphasis on prenatal USS findings, results of postnatal investigations, operative findings, outcomes, and possible causes of MP. RESULTS: From January 2000 to November 2004, seven fetuses were confirmed to have MP at birth. Three MP patients (3/7, 43%) were diagnosed prenatally because of USS showing ascites and calcification/dilated or hyperechoic bowel loops. One (1/7, 14.3%) suspected cystic MP was confirmed by prenatal MRI. In the other three cases, USS showed only ascites. All patients had postnatal contrast CT scans. Two patients' CT scans showed persistent intestinal perforation not visible with prenatal USS, and required emergency operations. All patients survived and prospered, and were sweat test negative. CONCLUSIONS: Prenatal USS allows suspected MP babies to be transferred to a tertiary centre for delivery and appropriate management. In this way, the chances of survival of these babies can be excellent if they are not associated with cystic fibrosis (CF). Prenatal MRI can improve the low diagnostic yield of prenatal USS for MP. Postnatal contrast CT scan is required to define persistent intestinal perforation invisible with prenatal USS.

Female↗

PubMed2005

Up-regulation of macrophage migration inhibitory factor in infants with acute neonatal necrotizing enterocolitis.

AIMS: To investigate the role of macrophage migration inhibitory factor (MIF) and its downstream cytokine cascade in necrotizing enterocolitis (NEC). METHODS AND RESULTS: The expression of MIF mRNA and protein in NEC guts was assayed by in situ hybridization and immunohistochemistry, respectively. Concentrations of MIF, interleukin (IL)-6 and IL-8 in the serum and in the supernatant of macrophage cultures were examined by ELISA. Increased expression of MIF mRNA and protein was observed in the NEC guts, mainly in the infiltrating macrophages in the mucosa and submucosal layers. Up-regulation of MIF was associated with the accumulation of macrophages and T cells. In addition, serum levels of MIF, IL-6 and IL-8 in NEC patients during the acute stage of the disease were significantly increased. The expression of MIF decreased both locally and systemically after the disease was resolved. MIF was also found to increase the secretion of IL-6 and IL-8 by macrophages isolated from healthy individuals in vitro in NEC. CONCLUSIONS: MIF acts by stimulating macrophage production of IL-6 and IL-8. This further aggravates the inflammatory process by increasing the infiltration of neutrophils and activating inflammatory cells. The results of this study suggest that MIF plays an important role in the pathogenesis of NEC and may serve as a target for therapeutic intervention in NEC.

Acute Disease↗

PubMed2004

Post-operative magnetic resonance evaluation of children after laparoscopic anorectoplasty for imperforate anus.

BACKGROUND AND AIMS: Laparoscopic anorectoplasty (LAR) is a relatively new procedure in the treatment of imperforate anus. Using magnetic resonance imaging (MRI), we evaluated the anatomical features of the anorectal region of children treated with LAR and compared this with conventional posterior sagittal anorectoplasty (PSARP). The findings were correlated with functional outcome. PATIENT/METHODS: A retrospective review of ten children with the high/intermediate types of imperforate anus underwent LAR between May 2000 and December 2002. MRI of the pelvis was performed post-operatively and a semi-quantitative score was used to assess the degree of sphincter symmetry, peri-rectal fibrosis, and the position of the pull-through rectum. The defecation status of these patients was also recorded. Eight historical patients who had undergone PSARP served as a control group. RESULTS/FINDINGS: When compared with PSARP patients, a significantly lower proportion of LAR patients had sphincter asymmetry (40 vs. 100%, p < 0.05) and peri-rectal fibrosis (40 vs. 87.5%, p < 0.05). The positioning of the rectum was, however, central for both groups (90 vs. 87.5%). No statistical correlation was found between defecation status and the degree of sphincter asymmetry or peri-rectal fibrosis. INTERPRETATION/CONCLUSION: LAR allows more optimal anatomical reconstruction for patients with the high/intermediate types of imperforate anus. However, additional factors that are not correctable by surgery, such as intrinsic innervation deficiency, also influence the clinical outcome.

Anal Canal↗

PubMed2004

Laparoscopic flip-flap hernioplasty: an innovative technique for pediatric hernia surgery.

BACKGROUND: Laparoscopic hernia repair is especially advantageous for bilateral or recurrent diseases in children because it avoids vas injury. However, it is more technically demanding, and the recurrent rate has been higher than with the open method. The authors developed a method of laparoscopic hernia repair that is easy and secure. METHODS: The hernia opening was repaired with a peritoneal flip-flap anchored with a single tension-free intracorporeal suture. The vas and testicular vessel were completely untouched. The valve mechanism of the flip-flap helped to avoid scrotal collection and prevent hernia recurrence. RESULTS: In 32 patients ages 1 month to 17 years 43 repairs were performed. The early result was promising, and no recurrence was noticed in a median follow-up period of 4 months. CONCLUSIONS: Laparoscopic flip-flap hernioplasty is easy to perform and has a number of theoretical advantages, although the long-term result still needs to be evaluated.

Adolescent↗

PubMed2004

Technical refinements in laparoscopic repair of childhood inguinal hernias.

BACKGROUND: This study aimed to evaluate the laparoscopic repair of childhood hernias and to identify technical refinements for improvements. METHODS: The records of 49 boys and 13 girls who underwent laparoscopic hernia repair in the authors' institution between July 2002 and July 2003 were reviewed. Their mean age was 4.5 years (range, 3 months to 15 years). No hernia opening was found in two patients, whereas 17 bilateral hernias (28%, 17/60) were found laparoscopically. Two bilateral hernias were diagnosed preoperatively. Four patients had the operation for recurrent hernias after open procedures. RESULTS: Over a mean follow-up period of 7.5 months (range, 3-15 months), there was one recurrence (1%, 1/79), but no other complication. With saline injection administered extraperitoneally, laparoscopic hernia repair can be performed safely for boys. Use of the "needle" sign avoided damage to the testicular vessel and vas. Placement of the needle medial to a prominent inferior epigastric artery and the presence of a "complete ring" sign prevented recurrence. The use of reusable 3-mm ports and round polypropylene stitches lowered the cost of the operation and improved the cosmesis for the patients. For recurrent hernias after open repair, the laparoscopic method was as simple as fresh hernia repair. CONCLUSIONS: Laparoscopic hernia repair allows detection and repair of contralateral hernias during the same operation. With refinements in technique, the procedure can be safely performed for boys, with the added advantages of lower costs, fewer recurrences, and improved cosmesis.

Adolescent↗

PubMed2004

Embryonic development of the ganglion plexuses and the concentric layer structure of human gut: a topographical study.

In this study, we performed a detailed topographical study on the development of ganglion plexuses and the smooth muscle layers of human embryonic and fetal gut. Neuron and glia differentiation was investigated with anti-PGP9.5 and anti-S100 antibodies respectively. The differentiation of smooth muscle and interstitial cells of Cajal (ICC) was studied with anti-smooth muscle alpha-actin and anti-C-Kit antibodies respectively. By week 7, rostro-caudal neural crest cell (NCC) colonization of the gut was complete, and NCCs have differentiated into neurons and glia. At the foregut, neurons and glia were aggregated into ganglion plexus in the myenteric region, and the longitudinal and circular muscle layers have started to differentiate; however, neurons and glia were not found in the submucosa. At the hindgut, neurons and glia were dispersed within the mesenchyme. Myenteric plexus, longitudinal and circular muscle layers formed along the entire gut by week 9. Scattered and individual neurons and glia, and small ganglion plexuses were detected in the foregut and midgut submucosa by week 12. Ganglion plexus was not seen in the hindgut submucosa until week 14. Muscularis mucosae was formed at the foregut and midgut by week 12 but was only discernible at the hindgut 2 weeks later. As the gut wall developed, ganglion plexus increased in size with more neurons and glia, and the formation of intra-plexus nerve fascicle. ICCs were localized in the ganglion plexus as early as week 7. ICCs were initially dispersed in the plexus and were preferentially localized at the periphery of the plexus by week 20. The specification of the annular layers of human embryonic and fetal gut follows a strict spatio-temporal pattern in a rostro-caudal and centripetal manner suggesting that interaction between (1) homotypic and/or heterotypic cells; and (2) cells and the extracellular matrix is critical for the embryonic development of the gut mesenchyme and the enteric nervous system.

Actins↗

PubMed2004

Esophageal atresia and achalasialike esophageal dysmotility.

A 14-year-old boy presented with regurgitation, malnutrition, and chronic lung insufficiency with a history of successful repair of esophageal atresia and tracheoesophageal fistula in the newborn period. Barium swallow and manometry results showed achalasia. Hellar operation with antireflux procedure resulted in complete symptomatic relief. Histology and immunohistochemistry including PGP9.5, MAP5, cKit, and nNOS of myotomy specimen showed intact innervation. Although esophageal dysmotility after esophageal atresia repair usually is caused by gastroesophageal reflux and incoordination of peristalsis, the possibility of achalasia should also be considered, because a casual relationship between esophageal atresia and achalasia may exist.

Adolescent↗

PubMed2004

Depletion of intestinal resident macrophages prevents ischaemia reperfusion injury in gut.

BACKGROUND AND AIMS: The cellular and molecular events involved in ischaemia reperfusion (IR) injury are complex and not fully understood. Previous studies have implicated polymorphonuclear neutrophils (PMN) as major inflammatory cells in IR injury. However, anti-PMN antiserum treatment offers only limited protection, indicating that other inflammatory cells are involved. We have therefore investigated the contribution of resident macrophages in IR injury using an IR gut injury model. METHODS: DA rats were divided into sham operation and IR groups. The superior mesenteric artery was clamped for 30, 45, or 60 minutes (ischaemia) followed by 60 minutes of reperfusion. IR injuries were evaluated by histological staining. Expression of early growth response factor 1 (Egr-1), myeloperoxidase (MPO), and proinflammatory cytokines was analysed by immunohistochemistry, reverse transcription-polymerase chain reaction, and western blotting analysis. The specific role of macrophages in IR gut injury was also evaluated in resident macrophage depleted rats. RESULTS: Mucosal sloughing and villi destruction were seen in 45/60 minute and 60/60 minute IR guts. PMN infiltration at the damaged mucosal area was undetectable in 45/60 minute and 60/60 minute IR guts. PMN were localised around the capillaries at the base of the crypts in 60/60 minute IR gut. Obvious PMN infiltration was only observed in damaged villi after three hours of reperfusion. Elevated nuclear Egr-1 immunostaining was localised in resident macrophages at the damaged villi before histological appearance of mucosal damage. Furthermore, resident macrophages at the damaged site expressed MPO. Protein levels of the proinflammatory cytokines RANTES and MCP-1 were increased in IR gut. Depletion of resident macrophages by dichloromethylene bisphosphonate significantly reduced mucosal damage in rat guts after IR. CONCLUSION: Our findings indicate that resident macrophages play a role in early mucosal damage in IR gut injury. Therefore, macrophages should be treated as a prime target for therapeutic intervention for IR damage.

Animals↗

PubMed2004

Dendritic cells: sentinels against pathogens.

Dendritic cells (DCs) are the most potent antigen-presenting cells, and are regarded as "natural adjuvants" for the induction of primary T or T-dependent immunity. DCs in the peripheral sites capture and process antigens. Encounter of exogenous or endogenous stimuli mature the function of DCs, and they thus acquire T-cell stimulatory capacity and distinct chemotactic behavior which enables them to migrate to lymphoid tissue. In the secondary lymphoid organs, they present antigens to T- and B-cells and stimulate their proliferation. Dendritic cells are also involved in tolerance induction, in particular, to self antigens. DCs also play a key role in the transmission of many pathogens, and therefore may become targets for designing new therapies. DCs have been manipulated in vitro and in vivo for cancer immunotherapy. In this article, we provide a concise overview of DC biology and its current and future role in clinical settings.

Animals↗

PubMed2003

Pathogenesis of neonatal necrotizing enterocolitis: a study of the role of intraluminal pressure, age and bacterial concentration.

The pathogenesis of neonatal necrotizing enterocolitis (NEC) is unknown. Intestinal dilatation and preferred occurrence of NEC at sites of bacterial overgrowth (colon and ileum) are common findings. The study attempted to produce NEC with increasing intraluminal pressures and bacterial concentrations in two different aged groups of rats. First, 10-cm terminal ileum segments were isolated with intact vascular pedicles in 1-and 3-month-old rats, and a dose of 10(11) E. coli in 1 ml was injected into each segment. Intraluminal pressure was sustained for 1 h at 150, 100, 50 and 0 cmH(2)0, respectively, in four experimental groups ( n=6). The isolated loop was then returned to the abdominal cavity and assessed grossly for NEC after 24 h. Histological examination was performed by a pathologist (KWC) who was blinded to the procedures. Second, the procedure was repeated with doses of 10(8), 10(5) and 0 bacteria/ml ( n=6) at intraluminal pressure of 100 cmH(2)0 in 1-month-old rats. Third, in another experimental group, oxygenation of the pedicled loop was assessed by oximetry as the intraluminal pressure increased and the findings were correlated with aortic blood pressure. The blood pressures (mean+/-SD) for 3- and 1-month-old rats were 110+/-6 and 72+/-4 mmHg, respectively. Hypoxia (<50% oxygen saturation) of the bowel was detected when the intraluminal pressure exceeded the mean blood pressure. The relative incidences of NEC in the bowel with intraluminal pressure above and below mean blood pressure were 100% (6/6) vs. 4% (1/24; P<0.05) in 3-month-old rats, and 100% (12/12) vs. 11% (2/18; P<0.05) in 1-month-old rats. There was no occurrence of NEC in bowel injected with 10(5) E. coli/ml and less at 100 cm intraluminal pressure. Increased intraluminal pressure results in bowel hypoxia and in the presence of adequate bacterial concentration predisposes to the development of NEC. Young age is associated with a lower threshold for increased intraluminal pressure leading to NEC.

Age Factors↗

PubMed2003

Earlier appearance and higher incidence of the rectoanal relaxation reflex in patients with imperforate anus repaired with laparoscopically assisted anorectoplasty.

BACKGROUND: This study aimed to evaluate clinically and manometrically the anorectal function of patients with imperforate anus after repair with laparoscopically assisted anorectoplasty (LAR), as compared with the function of patients after undergoing the conventional method, posterior sagittal anorectoplasty (PSARP). METHODS: The defecation status and anorectal manometry of patients with high or intermediate type imperforate anus repaired with LAR ( n = 9) and age-matched patients repaired with PSARP ( n = 13) were assessed and compared during the first year of postoperative follow-up evaluation. The defecation status was classified by the frequency of bowel openings (<1, 1-4, and >5 times per day). Manometric assessment was performed by an open-tip hydraulic capillary infusion system. The presence of the rectoanal relaxation reflex was determined, and the resting sphincteric pressure and resting rectal pressure were measured. RESULTS: Seven of nine LAR patients had an "acceptable" frequency of one to four bowel openings per day, in contrast to 7 of 13 PSARP patients. The difference in the presentation of daily stooling is not significant ( p > 0.05). A positive RAR was detected in 88.9% (8/9) of the LAR patients, and in only 30.8% (4/13) of the PSARP patients ( p < 0.01). The presence of a rectoanal relaxation reflex also significantly correlated with an acceptable frequency of bowel opening (1-4 times per day) in both LAR and PSARP patients ( p < 0.05). Moreover, a rectoanal relaxation reflex was detected significantly earlier in LAR than in PSARP patients (4.9 +/- 1.2 vs 10.1 +/- 2.5 months; postoperatively p < 0.0001). Both the LAR and PSARP patients had a similar resting sphincteric pressure (21.5 +/- 4.7 vs 25.4 +/- 6.2 cm H2O; p > 0.05). By contrast, the resting rectal pressure was significantly lower in LAR than in PSARP patients (7.7 +/- 1.5 vs 11.5 +/- 1.3 cmH(2)O; p < 0.05). CONCLUSIONS: In the early postoperative stage, patients repaired with LAR had more favorable findings in anorectal manometry than patients repaired with PSARP. Long-term follow-up studies to confirm a superior defecation continence achieved with LAR are warranted.

Abnormalities, Multiple↗

PubMed2003

Endoscopic balloon dilatation of esophageal strictures in infants and children: 17 years' experience and a literature review.

PURPOSE: Whereas endoscopic balloon dilatation (EBD) of benign esophageal strictures is an established mode of therapy in adults, this has not been accepted universally in the pediatric population. The aim of this study is to report the safety, efficacy, and long-term results of EBD for children in the authors' center. METHODS: Between 1986 and 2002, a total of 77 children (median age, 1.8 years; range, 2 months to 20 years) were treated by EBD for various causes: 2 had achalasia, and 75 had esophageal strictures (postesophageal atresia repair, 63; reflux esophagitis, 7; postfundoplication, 2; caustic injury, 3). Dilatations were performed using flexible endoscopy and fluoroscopic screening under general anesthesia. RESULTS: A total of 260 dilatations were carried out with the mean number of EBD per patient being 3.4 (range, 1 to 19). A mean period of 5 months (maximum, 28 months) for each patient was required. Four complications of esophageal perforations (1.5%) were observed, but only one required surgical repair because of persistent leakage. The remaining patients have undergone long-term follow-up (median follow-up, 6.6 years), and all are asymptomatic. CONCLUSIONS: This large series has shown that EBD can provide a safe and effective mean of relieving esophageal strictures with good long-term results.

Adolescent↗

PubMed2003

Deficient motor innervation of the sphincter mechanism in fetal rats with anorectal malformation: a quantitative study by fluorogold retrograde tracing.

BACKGROUND/PURPOSE: Deficiency of motoneuron innervation to the sphincter mechanism has been described in patients with anorectal malformation. Whether this event is primary or secondary remains unclear. METHODS: The authors quantified the motoneuron innervation of the sphincter mechanism by Fluorogold (FG) retrograde tracing experiment in fetal rats with anorectal malformation. Anorectal malformation was induced in rat fetuses by ethylenethiourea (ETU). Serial longitudinal sections encompassing the whole width of lumbosacral spinal cord were examined. The number of FG-labelled motoneurons were scored and compared between male fetuses with or without malformation in the ETU-fed group and normal controls. RESULTS: The number of FG-labelled motoneurons in the fetuses without defect, with imperforate anus (IA), with neural tube anomalies (NTA), with combined IA and NTA, and normal controls were determined to be (mean +/- SEM) 109.13 +/- 37.88, 55.05 +/- 25.85, 48.20 +/- 30.34, 54.43 +/- 28.55, and 135.22 +/- 28.78, respectively. FG-labelled motoneurons in the fetuses with IA, NTA, and combined IA and NTA are significantly fewer than that in fetuses without defects (P <.05) and in normal controls (P <.005). CONCLUSIONS: These findings suggest that defective motoneuron innervation to the sphincter mechanism is a primary anomaly that coexists with the alimentary tract anomaly in anorectal malformation during fetal development. The intrinsic neural deficiency is an important factor likely to contribute to poor postoperative anorectal function despite surgical correction of anorectal malformation.

Anal Canal↗

PubMed2003

Laparoscopic pancreatic resection of an insulinoma in a child.

Insulinoma is a rare neuroendocrine tumour infrequently reported in children. Operative excision is the treatment of choice, but requires a disproportionately large incision to remove a small and benign tumour located deep in the retroperitoneum. Laparoscopic resection of benign tumours of the pancreas has been increasingly reported in adults and seems to be ideal for pancreatic insulinomas. We present the case of pancreatic insulinoma in a 13-year-old boy treated by laparoscopic distal pancreatectomy.

Adolescent↗

PubMed2003

Association study of PHOX2B as a candidate gene for Hirschsprung's disease.

BACKGROUND: Hirschsprung's disease (HSCR) is a congenital disorder characterised by an absence of ganglion cells in the nerve plexuses of the lower digestive tract. Manifestation of the disease has been linked to mutations in genes that encode the crucial signals for the development of the enteric nervous system-the RET and EDNRB signalling pathways. The Phox2b gene is involved in neurogenesis and regulates Ret expression in mice, in which disruption of the Phox2b results in a HSCR-like phenotype. AIMS: To investigate the contribution of PHOX2B to the HSCR phenotype. METHODS: Using polymerase chain reaction amplification and direct sequencing, we screened PHOX2B coding regions and intron/exon boundaries for mutations and polymorphisms in 91 patients with HSCR and 71 ethnically matched controls. Seventy five HSCR patients with no RET mutations were independently considered. Haplotype and genotype frequencies were compared using the standard case control statistic. RESULTS: Sequence analysis revealed three new polymorphisms: two novel single nucleotide polymorphisms (A-->G(1364); A-->C(2607)) and a 15 base pair deletion (DEL(2609)). Statistically significant differences were found for A-->G(1364). Genotypes comprising allele G were underrepresented in patients (19% v 36%; chi(2)=9.30; p=0.0095 and 22% v 36%; chi(2)=7.38; p=0.024 for patients with no RET mutations). Pairwise linkage disequilibrium (LD) analysis revealed no LD between physically close polymorphisms indicating a hot spot for recombination in exon 3. CONCLUSION: The PHOX2B A-->G(1364) polymorphism is associated with HSCR. Whether it directly contributes to disease susceptibility or represents a marker for a locus in LD with PHOX2B needs further investigation. Our findings are in accordance with the involvement of PHOX2B in the signalling pathways governing the development of enteric neurones.

Base Sequence↗