Biomedical subjects

Justin Wu

Publications and source records attributed to Justin Wu.

6 recordsLinked to original sources

PubMed2006

Effects of neonatal maternal separation on neurochemical and sensory response to colonic distension in a rat model of irritable bowel syndrome.

Early life stress has been implicated as a risk factor for irritable bowel syndrome (IBS). We studied the effect of neonatal maternal separation on the visceromotor response and the expression of c-fos, 5-HT, and its receptors/transporters along the brain-gut axis in an animal model of IBS. Male neonatal Sprague-Dawley rats were randomly assigned to a 3-h daily maternal separation (MS) or nonhandling (NH) on postnatal days 2-21. Colorectal balloon distention (CRD) was performed for assessment of abdominal withdrawal reflex as a surrogate marker of visceral pain. Tissues from dorsal raphe nucleus in midbrain, lumbar-sacral cord, and distal colon were harvested for semiquantitative analysis of c-fos and 5-HT. The expression of 5-HT expression, 5-HT3 receptors, and 5-HT transporter were analyzed by RT-PCR. Pain threshold was significantly lower in MS than NH rats. The abdominal withdrawal reflex score in response to CRD in MS rats was significantly higher with distension pressures of 40, 60, and 80 mmHg. In MS rats, the number of c-fos-like immunoreactive nuclei at dorsal horn of lumbar-sacral spinal cord increased significantly after CRD. 5-HT content in the spinal cord of MS rats was significant higher. In the colon, both 5-HT-positive cell number and 5-HT content were comparable between MS and NH groups before CRD. Post-CRD only MS rats had significant increase in 5-HT content. Protein and mRNA expression levels of 5-HT3 receptors and 5-HT transporter were similar in MS and NH rats. Neonatal maternal separation stress predisposes rats to exaggerated neurochemical responses and visceral hyperalgesia in colon mimicking IBS.

Animals↗

PubMed2006

Association of intestinal granulomas with smoking, phenotype, and serology in Chinese patients with Crohn's disease.

INTRODUCTION: Crohn's disease (CD) is a heterogenous disease characterized by variable manifestations and outcomes, and increasing in incidence in China. Phenotypic classification has been proposed to assist in subtyping of disease. Non-caseating intestinal granulomas are a hallmark of CD, but whether intestinal granulomas help predict Chinese CD phenotypes or determine severity, is not known. AIMS: To determine the association between intestinal granulomas with CD phenotype, severity, risk factors, and serological markers. METHODS: This was a single-centre study of consecutive definite Chinese CD cases. Granulomas were diagnosed by an experienced GI pathologist. Correlation with the Vienna Classification and other parameters was performed. RESULTS: Eighty Chinese CD patients were recruited, 40 (50%) of whom had intestinal granulomas. Intestinal granulomas were independently associated with the stricturing behavior (OR: 4.71; 95% CI: 1.41-15.72), colonic location of disease (OR: 26.96; 95% CI: 2.68-271.14), but not with age of CD diagnosis. Current or previous smoking protected against the development of granulomas (OR: 0.16; 95% CI: 0.04-0.59). Granulomas were not associated with peri-anal involvement, extra-intestinal manifestations, anti-neutrophil cytoplasmic antibody or anti-Saccharomyces cerevisiae antibody serology, or severity of CD gauged by the requirement of major intestinal surgery or immunomodulating therapy. CONCLUSIONS: Intestinal granulomas in the setting of CD may be helpful in determining phenotypic subtypes of CD, but is unhelpful in predicting disease severity. Smoking impairs the formation of granulomas in CD.

Adult↗

PubMed2005

Refinement of multidomain protein structures by combination of solution small-angle X-ray scattering and NMR data.

Determination of the 3D structures of multidomain proteins by solution NMR methods presents a number of unique challenges related to their larger molecular size and the usual scarcity of constraints at the interdomain interface, often resulting in a decrease in structural accuracy. In this respect, experimental information from small-angle scattering of X-ray radiation in solution (SAXS) presents a suitable complement to the NMR data, as it provides an independent constraint on the overall molecular shape. A computational procedure is described that allows incorporation of such SAXS data into the mainstream high-resolution macromolecular structure refinement. The method is illustrated for a two-domain 177-amino-acid protein, gammaS crystallin, using an experimental SAXS data set fitted at resolutions from approximately 200 A to approximately 30 A. Inclusion of these data during structure refinement decreases the backbone coordinate root-mean-square difference between the derived model and the high-resolution crystal structure of a 54% homologous gammaB crystallin from 1.96 +/- 0.07 A to 1.31 +/- 0.04 A. Combining SAXS data with NMR restraints can be accomplished at a moderate computational expense and is expected to become useful for multidomain proteins, multimeric assemblies, and tight macromolecular complexes.

Computational Biology↗

PubMed2005

Engineering DNA topology with locked nucleosides: a structural study.

DNA dodecamers modified with nucleotide building blocks based on a bicyclo[3. 1.0]hexane system that effectively locks the ribose template into an RNA-like or North (N) conformation were analyzed by various biophysical techniques including high field nuclear magnetic resonance (NMR). Replacement of either one or both of the center thymidines in the Dickerson Drew dodecamer (CGCGAAT*T*CGCG) caused a progressive shift in the bending propensity of the double helix as shown by a newly developed rapid technique that compares the residual dipolar coupling (RDC) values of the modified duplexes with those previously determined for the native DNA.

Biophysics↗

PubMed2004

Normal colon transit time in healthy Chinese adults in Hong Kong.

BACKGROUND AND AIM: Colon transit study with radio-opaque markers is helpful in the evaluation of chronic constipation. Normal reference values, based on radio-opaque markers, have not been reported from Chinese adults in Hong Kong. METHODS: Fifty-one healthy Chinese (27 men, age 42 +/- 12 years) were enrolled through a newspaper advertisement. They were requested to fill in detailed dietary records and a gastrointestinal symptom questionnaire. Each subject swallowed, under supervision, a total of three Sitzmarks capsules, one capsule at the same time on each of day 1, 2 and 3. Abdominal films were taken on days 4 and 7, also at the same time of the day. Total and segmental transit times were calculated using Metcalf's method. RESULTS: The upper limit of normal total colonic transit time (CTT) was 62 h, while right, left and rectosigmoid CTT were 16 h, 31 h and 32 h, respectively. Women of age 18-35 years had a longer rectosigmoid and total CTT compared with their male counterparts (mean total CTT: 39 h vs 18 h, P = 0.05). The CTT appeared to be unaffected by the usual dietary components. CONCLUSION: A single normal reference value for CTT appeared to be applicable to Chinese adults in Hong Kong, irrespective of age, sex and dietary content. However, young Chinese women (age 18-35 years) appeared to have longer total and rectosigmoid CTT.

Adolescent↗

PubMed2002

Airway management of a patient with facial trauma.

Airway management in patients with facial trauma is usually challenging. In this case, we report the airway management of a patient who had multiple midface fractures and a two-inch tree limb implanted into his face.

Adolescent↗