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Biomedical subjects

W Wang

Publications and source records attributed to W Wang.

At least 73 records · Page 4Linked to original sources
PubMed2005

A comparison of maternal age, sex ratio and associated anomalies among numerically aneuploid, structurally aneuploid and euploid holoprosencephaly.

During the period January 1987-July 2003, 59 cases of perinatally detected holoprosencephaly (HPE) with cytogenetic results were identified among 97,306 deliveries at Mackay Memorial Hospital. Among these 59 cases with HPE, 25 had euploidy, 27 had numerical aneuploidy, and 7 had structural aneuploidy. In the euploid cases, the male:female sex ratio was 0.39:1, whereas in the aneuploid cases, the ratio was 1:1. The mean (+/-SD) maternal ages for numerical aneuploidy, structural aneuploidy, and euploidy were 33.0 +/- 5.1 years, 27.9 +/- 2.1 years, and 27.8 +/- 5.0 years, respectively. The frequencies of associated major structural anomalies other than craniofacial defects in the cases with numerical aneuploidy, structural aneuploidy, and euploidy were 85.7%, 0%, and 16%, respectively. The present study of HPE suggests that a female excess appears only in the euploid cases, and advanced maternal age and structural anomalies are more commonly associated with the numerically aneuploid cases than the structurally aneuploid and euploid cases.

Abnormalities, Multiple↗
PubMed2005

Anorexia and cachexia in prostaglandin EP1 and EP3 subtype receptor knockout mice bearing a tumor with high intrinsic PGE2 production and prostaglandin related cachexia.

Previous studies in our laboratory have suggested that prostaglandin (PG) E2 is involved in anorexia/cachexia development in MCG 101 tumor-bearing mice. However, the role of COX pathways in the pathogenesis of cancer anorexia/cachexia is not fully resolved. In the present study, we investigated the role of PGE receptors subtype EP1 and EP3 on the development of anorexia in MCG 101-bearing mice. Our results show that the absence of host EP1 or EP3 receptors did not alter the magnitude of anorexia in tumor-bearers. However, anorexia in tumor-bearing EP1 and EP3 knockouts was not improved by indomethacin treatment as observed in wild type tumor-bearers. By contrast, indomethacin improved body composition similar in EP1 and EP3 knockouts as well as in wild type tumor-bearing animals and tumor growth was retarded in EP1 and promoted in EP3 knock outs. Our results demonstrate that host EP1 and EP3 receptors are involved in the control of local tumor growth, which translates into anorexia, this being the main cause of metabolic adaptive alterations to explain weight loss in this model. Brain EP1 and EP3 subtype receptors do not seem to directly control anorexia, which leaves EP2 and EP4 as potential candidates.

Animal Feed↗
PubMed2005

One hundred years of orthopaedic education in Singapore.

The Department of Orthopaedic Surgery at the University of Malaya (in Singapore) was established in 1952. Prior to this, the teaching of Orthopaedic Surgery at the University was undertaken by the Department of Surgery under the Professor of Surgery and Professor of Clinical Surgery. From a course consisting of 15 weekly classes on fractures for 18 undergraduates in the late 1930s, and the clinical postings in orthopaedic surgery for over 40 students in 1952, the programme now encompasses an exposure to musculoskeletal diseases and trauma in all 5 years of the undergraduate course. Over this time, the spectrum of clinical conditions has also changed, and with it the emphasis on the conditions to be taught; from that dealing primarily with tuberculosis of bones and joints, poliomyelitis, and childhood deformity, to those resulting from degenerative disorders, sports injuries, industrial and motor vehicle accidents, and cancer. The students are now taught orthopaedic surgery in all the major public hospitals. Local postgraduate training programmes for orthopaedic surgery started in the 1980s. From 1993, a more structured training and assessment programme was introduced for basic and advanced training in surgery and orthopaedics. Advanced trainees rotate through the various teaching hospitals to expose them to a wider range of orthopaedic problems as well as teachers. The postgraduate training programme is now well established, and Singapore is accredited by the Royal College of Surgeons of Edinburgh as an orthopaedic training centre for higher surgical training.

Education, Medical↗
PubMed2004

O2 microsensors for minimally invasive tissue monitoring.

Tissue oxygenation is a key factor ensuring normal tissue functions and viability. Continuous real-time monitoring of the partial pressure of oxygen, pO(2), in tissues gives insight into the dynamic fluctuations of O(2) supplies to tissues by blood circulation. Small oxygen sensors enable investigations of the spatial variation of pO(2) in tissues at different locations in relation to local microvessels. In this paper, pO(2) measurement using microelectrodes and biocompatible sensorsv is discussed and recent progress of their application in human skin is reviewed. Emphasis is given to working principles of a number of existing oxygen sensors and their potential application in vivo and in tissue engineering. Results on spatial and temporal variations of the pO(2) in human skin introduced by localized ischaemia-reperfusion are presented when the surface of the skin is covered by an oxygen-free paraffin oil layer and the range of the tissue pO(2) is deduced to be between 0 and 60 mmHg. In the study, pO(2) increases from 8.0 +/- 3.2 mmHg (n = 6) at the surface of the skin to 35.2 +/- 8.0 mmHg (n = 9) at a depth just above the subpapillary plexus. Temporal decay in pO(2) following tissue compression and rise in pO(2) following pressure release can be described using mono-exponential functions. The time constant for the exponential decay, tau = 8.44 +/- 1.53 s (n = 7) is consistently greater than that for the exponential rises, tau' = 4.75 +/- 0.82 s (n = 6). The difference in pO2 change with the time following tissue compression and pressure release reveals different dynamic mechanisms involved in the two transient phases. The elevated steady state pO(2) following reperfusion, which is approximately 20% higher than the pre-occlusion value, indicates localized reactive hyperaemia. Possible applications of O(2) microsensors in diseases, e.g. tumours, pressure ulcers, are also discussed.

Biosensing Techniques↗
PubMed2004

Concentration polarization of hyaluronan on the surface of the synovial lining of infused joints.

Hyaluronan (HA) in joints conserves the lubricating synovial fluid by making trans-synovial fluid escape almost insensitive to pressure elevation (e.g. effusions, joint flexion). This phenomenon, 'outflow buffering', was discovered during HA infusion into the rabbit knee joint cavity. It was also found that HA is partially reflected by the joint lining (molecular sieving), and that the reflected fraction R decreases as trans-synovial filtration rate Q is increased. It was postulated therefore that outflow buffering is mediated by HA reflection. Reflection creates a HA concentration polarization layer, the osmotic pressure of which opposes fluid loss. A steady-state, cross-flow ultrafiltration model was previously used to explain the outflow buffering and negative R-vs.-Q relation. However, the steady-state, cross-perfusion assumptions restricted the model's applicability for an infused, dead-end cavity or a non-infused joint during cyclical motion. We therefore developed a new, non-steady-state model which describes the time course of dead-end, partial HA ultrafiltration. The model describes the progressive build-up of a HA concentration polarization layer at the synovial surface over time. Using experimental parameter values, the model successfully accounts for the observed negative R-vs.-Q relation and shows that the HA reflected fraction (R) also depends on HA diffusivity, membrane area expansion and the synovial HA reflection coefficient. The non-steady-state model thus explains existing experimental work, and it is a key stage in understanding synovial fluid turnover in intact, moving, human joints or osteoarthritic joints treated by HA injections.

Animals↗
PubMed2004

Evidence for an oscillatory signature in atmospheric neutrino oscillations.

Muon neutrino disappearance probability as a function of neutrino flight length L over neutrino energy E was studied. A dip in the L/E distribution was observed in the data, as predicted from the sinusoidal flavor transition probability of neutrino oscillation. The observed L/E distribution constrained nu(micro)<-->nu(tau) neutrino oscillation parameters; 1.9x10(-3) 0.90 at 90% confidence level.

Journal Article↗
PubMed2004

Search for electron neutrino appearance in a 250 km long-baseline experiment.

We present a search for electron neutrino appearance from accelerator-produced muon neutrinos in the K2K long-baseline neutrino experiment. One candidate event is found in the data corresponding to an exposure of 4.8 x 10(19) protons on target. The expected background in the absence of neutrino oscillations is estimated to be 2.4+/-0.6 events and is dominated by misidentification of events from neutral current pi(0) production. We exclude the nu(micro) to nu(e) oscillations at 90% C.L. for the effective mixing angle in the 2-flavor approximation of sin((2)2theta(microe)( approximately 1/2sin((2)2theta(13))>0.15 at Deltam(2)(microe)=2.8 x 10(-3) eV(2), the best-fit value of the nu(micro) disappearance analysis in K2K. The most stringent limit of sin((2)2theta(microe)<0.09 is obtained at Deltam(2)(microe)=6 x 10(-3) eV(2).

Journal Article↗
PubMed2004

Limits on the neutrino magnetic moment using 1496 days of Super-Kamiokande-I solar neutrino data.

A search for a nonzero neutrino magnetic moment has been conducted using 1496 live days of solar neutrino data from Super-Kamiokande-I. Specifically, we searched for distortions to the energy spectrum of recoil electrons arising from magnetic scattering due to a nonzero neutrino magnetic moment. In the absence of a clear signal, we found micro(nu)</=(3.6x10(-10))micro(B) at 90% C.L. by fitting to the Super-Kamiokande day-night spectra. The fitting took into account the effect of neutrino oscillation on the shapes of energy spectra. With additional information from other solar neutrino and KamLAND experiments constraining the oscillation region, a limit of micro(nu)</=(1.1x10(-10))micro(B) at 90% C.L. was obtained.

Journal Article↗
PubMed2004

Molecular and functional characterization of a vasotocin-sensitive aquaporin water channel in quail kidney.

Both mammals and birds can concentrate urine hyperosmotic to plasma via a countercurrent multiplier mechanism, although evolutionary lines leading to mammals and birds diverged at an early stage of tetrapod evolution. We reported earlier (Nishimura H, Koseki C, and Patel TB. Am J Physiol Regul Integr Comp Physiol 271: R1535-R1543, 1996) that arginine vasotocin (AVT; avian antidiuretic hormone) increases diffusional water permeability in the isolated, perfused medullary collecting duct (CD) of the quail kidney. In the present study, we have identified an aquaporin (AQP) 2 homolog water channel in the medullary cones of Japanese quail, Coturnix coturnix (qAQP2), by RT-PCR-based cloning techniques. A full-length cDNA contains an 822-bp open reading frame that encodes a 274-amino acid sequence with 75.5% identity to rat AQP2. The qAQP2 has six transmembrane domains, two asparagine-proline-alanine (NPA) sequences, and putative N-glycosylation (asparagine-124) and phosphorylation sites (serine-257) for cAMP-dependent protein kinase. qAQP2 is expressed in the membrane of Xenopus laevis oocytes and significantly increased its osmotic water permeability (P(f)), inhibitable (P < 0.01) by mercury chloride. qAQP2 mRNA (RT-PCR) was detected in the kidney; medullary mRNA levels were higher than cortical levels. qAQP2 protein that binds to rabbit anti-rat AQP2 antibody is present in the apical/subapical regions of both cortical and medullary CDs from normally hydrated quail, and the intensity of staining increased only in the medullary CDs after water deprivation or AVT treatment. The relative density of the approximately 29-kDa protein band detected by immunoblot from the medullary cones was modestly higher in water-deprived/AVT-treated quail. The results suggest that 1) medullary CDs of quail kidneys express a mercury-sensitive functioning qAQP2 water channel, and 2) qAQP2 is at least partly regulated by an AVT-dependent mechanism. This is the first clear identification of AQP2 homolog in nonmammalian vertebrates.

Algorithms↗
PubMed2004

Genomic analysis reveals RhoC as a potential marker in hepatocellular carcinoma with poor prognosis.

Hepatocellular carcinoma (HCC) is one of the most malignant human tumours because of its high incidence of metastasis. The mechanisms underlying the metastasis of HCC, however, remain poorly understood. In this study, we performed cDNA microarray analysis to profile gene expression patterns in two subtypes of HCC, solitary large HCC (SLHCC) and nodular HCC (NHCC), which differ significantly in the incidence of metastasis. Among 668 genes that were differentially expressed, we focused on RhoC, whose expression was significantly decreased in SLHCC compared to NHCC. The expression of RhoC in HCC and pericarcinomatous liver tissues (PCLT) was analysed at both the mRNA and protein levels by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting. In addition, immunohistochemistry was also performed on 94 cases of HCC with follow-up information. Collectively, our data indicate that the expression of RhoC significantly increased in HCC compared to PCLT; extrahepatic metastatic lesions expressed significantly higher levels of RhoC than the corresponding intrahepatic HCC tissues. There is a highly significant correlation of the RhoC expression levels with tumour vein invasion, number of tumour nodes and the status of differentiation. Significantly, the HCC patients with RhoC-positive expression had shorter survival than those with RhoC-negative expression. Together, our findings suggest a strong correlation between the expression of RhoC and HCC metastasis, implicating RhoC as a potential prognosis marker and therapeutic target for HCC.

Biomarkers, Tumor↗
PubMed2004

Single nucleotide polymorphisms and haplotypes of histamine N-methyltransferase in patients with gastric ulcer.

INTRODUCTION: Histamine plays a crucial role in the regulation of gastric acid secretion, which is involved in the pathogenesis of peptic ulcer. Histamine N-methyltransferase (HNMT) is the major metabolizing enzyme for histamine inactivation in human stomach. OBJECTIVE: This study aims to determine whether there exists a relationship between HNMT gene polymorphisms and the risk for gastric ulcer (GU). METHODS: 118 GU patients and 154 ethnically matched control subjects were enrolled and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assays were developed to genotype all these subjects for the T-1637C, C-411T, C314T and A1097T point mutations in HNMT gene. Haplotypes were reconstructed from the genotype data. RESULTS: Frequencies of the variant alleles in cases and controls were 0.398 vs 0.396 for T-1637C, 0.144 vs 0.110 for C-411T, 0.034 vs 0.042 for C314T, and 0.242 vs 0.273 for A1097T, respectively, with no significant difference for any locus between the two groups (all P > 0.05). Also the frequencies of genotypes, haplotypes and haplotype pairs based on these polymorphisms did not differ significantly between cases and controls. CONCLUSION: This study provided no evidence for the involvement of HNMT polymorphisms in the susceptibility to GU.

Adolescent↗
PubMed2004

Randomized controlled trial of Siberian ginseng for chronic fatigue.

BACKGROUND: Chronic fatigue greatly affects quality of life and is a common reason for consulting a physician. Since conventional therapy is often of limited help, fatigued patients may use herbal treatments. This randomized controlled trial evaluated the effectiveness of Siberian ginseng. METHOD: Subjects were recruited from advertisements in Iowa (82%) and members of chronic fatigue syndrome support groups (18%). Potential subjects were required to have substantial fatigue > or = 6 months with no identifiable cause. The mean change in a fatigue measure was compared for placebo and Siberian ginseng at 1 and 2 months. Comparisons were for all subjects and for subjects with characteristics previously identified in the literature as important for categorizing chronic fatigue. RESULTS: Ninety-six subjects were randomized to treatment groups, and 76 provided information at 2 months of follow-up. Fatigue among subjects assigned to either placebo or Siberian ginseng was substantially reduced during the study, but differences between treatment groups were not statistically significant in the full sample. Fatigue severity and duration had a statistically significant interaction with response to Siberian ginseng at the P < 0.05 level. Treatment was effective at 2 months for 45 subjects with less severe fatigue (P = 0.04 unadjusted for multiple comparisons) and for 41 subjects with fatigue for > or = 5 years (P = 0.09 unadjusted for multiple comparisons). CONCLUSION: Overall efficacy was not demonstrated. However, the findings of possible efficacy for patients with moderate fatigue suggests that further research may be of value.

Adult↗
PubMed2004

Effective donor lymphohematopoietic reconstitution after haploidentical CD34+-selected hematopoietic stem cell transplantation in children with refractory severe aplastic anemia.

Peritransplant toxicity and a delay in effective immune reconstitution have limited the utility of alternate donor transplantation for children with refractory severe aplastic anemia. We have assessed the effectiveness of infusing large numbers of highly purified haploidentical CD34+ cells after immunoablative conditioning in three patients who had failed intensive immunosuppression, lacked unrelated donors, and had active or recent serious infections. One patient rejected the first infusion, but engrafted after a second infusion from the same donor. This patient died 4 months after hematopoietic stem cell transplantation with no evidence of lymphoid reconstitution. Two patients experienced mixed chimerism requiring treatment with antibodies and/or donor lymphocyte infusion. Both currently survive more than 1 year after transplantation with normal blood counts, 100% donor engraftment, effective lymphoid reconstitution, and no chronic graft-versus-host disease. We observed functional thymopoiesis as measured by lymphocyte immunophenotyping, T cell receptor excision circles and T cell receptor Vbeta spectratyping complexity analysis. Further study is required to validate the initial promise of these preliminary observations.

Anemia, Aplastic↗
PubMed2004

Prothrombin Shanghai: hypoprothrombinaemia caused by substitution of Gla29 by Gly.

Prothrombin deficiency is a rare bleeding disorder inherited as an autosomal recessive trait. In this study, we reported a Chinese family with hereditary prothrombin deficiency. The proposita had a prolonged activated partial thromboplastin time (APTT, 71.6 s) and prothrombin time (PT, 28.0 s). The coagulation factors activities were normal except that prothrombin coagulation activity was markedly reduced, and the prothrombin antigen level was moderately decreased. Nucleotide sequencing of amplified DNA revealed a novel mutation, Glu (GAG) to Gly (GGG) at residue 29, which normally undergoes gamma-carboxylation within the Gla domain of prothrombin. The proposita was identified as homozygous, while her father, mother and maternal grandmother were heterozygous for the mutation. Gla29 has been demonstrated as one of the key residue for Ca2+-binding, membrane interaction and biological activity of prothrombin.

Amino Acid Substitution↗
PubMed2004

Persistent primitive trigeminal artery associated with aneurysm: report of two cases and review of the literature.

We present two cases of persistent primitive trigeminal artery (PPTA) associated with a giant aneurysm originating at the opening of the PPTA on the internal carotid artery (ICA). In one case, opening of the PPTA occurred 4 months after balloon occlusion of the ICA, when a giant aneurysm located at the cavernous segment of the ICA was being treated. The PPTA was occluded successfully using a Guglielmi detachable coil (GDC). A vertebral artery approach was taken. This is the first report of the opening of a PPTA associated with contrast filling of the aneurysm after balloon occlusion of the parent artery. The possibility of contrast filling of the aneurysm via potential PPTA should therefore be considered in the event of an ICA aneurysm with parent artery occlusion.

Balloon Occlusion↗