Search PubMed⌕ Search

Biomedical subjects

T Huang

Publications and source records attributed to T Huang.

At least 19 recordsLinked to original sources
PubMed2006

Palladium monolayer and palladium alloy electrocatalysts for oxygen reduction.

We investigated the oxygen-reduction reaction (ORR) on Pd monolayers on various surfaces and on Pd alloys to obtain a substitute for Pt and to elucidate the origin of their activity. The activity of Pd monolayers supported on Ru(0001), Rh(111), Ir(111), Pt(111), and Au(111) increased in the following order: Pd/Ru(0001) < Pd/Ir(111) < Pd/Rh(111) < Pd/Au(111) < Pd/Pt(111). Their activity was correlated with their d-band centers, which were calculated using density functional theory (DFT). We found a volcano-type dependence of activity on the energy of the d-band center of Pd monolayers, with Pd/Pt(111) at the top of the curve. The activity of the non-Pt Pd2Co/C alloy electrocatalyst nanoparticles that we synthesized was comparable to that of commercial Pt-containing catalysts. The kinetics of the ORR on this electrocatalyst predominantly involves a four-electron step reduction with the first electron transfer being the rate-determining step. The downshift of the d-band center of the Pd "skin", which constitutes the alloy surface due to the strong surface segregation of Pd at elevated temperatures, determined its high ORR activity. Additionally, it showed very high methanol tolerance, retaining very high catalytic activity for the ORR at high concentrations of methanol. Provided its stability is satisfactory, this catalyst might possibly replace Pt in fuel-cell cathodes, especially those of direct methanol oxidation fuel cells (DMFCs).

Alloys↗
PubMed2006

Strain-induced bond buckling and its role in insulating properties of Cr-doped V2O3.

Structural transformations around both V and Cr atoms in (V1-xCrx)2O3 across its metal-insulator transition (MIT) at x approximately 0.01 are studied by extended x-ray absorption fine-structure technique. Our new results for Cr made possible by the use of a novel x-ray analyzer that we developed reveal the substitutional mechanism of Cr doping. We find that this system has a buckled structure with short Cr-V and long V-V bonds. This system of bonds is disordered around the average trigonal lattice ascertained by x-ray diffraction. Such local distortions can result in a long range strain field that sets in around dilute Cr atoms in microscopic regions. We suggest that such locally strained regions should be insulating even at small x. The possibility of local insulating regions within a metallic phase, first suggested by Rice and Brinkman in 1972, remains unaccounted for in modern MIT theories.

Journal Article↗
PubMed2006

FADD self-association is required for stable interaction with an activated death receptor.

Receptor-mediated programmed cell death proceeds through an activated receptor to which the death adaptor FADD and the initiator procaspases 8 and/or 10 are recruited following receptor stimulation. The adaptor FADD is responsible for both receptor binding and recruitment of the procaspases into the death-inducing signaling complex. Biochemical dissection of the FADD death effector domain and functional replacement with a coiled-coil motif demonstrates that there is an obligatory FADD self-association via the DED during assembly of the death-inducing signaling complex. Using engineered oligomerization motifs with defined stoichiometries, the requirement for FADD self-association through the DED can be separated from the caspase-recruitment function of the domain. Disruption of FADD self-association precludes formation of a competent signaling complex. On this basis, we propose an alternative architecture for the FADD signaling complex in which FADD acts as a molecular bridge to stitch together an array of activated death receptors.

Caspase 10↗
PubMed2006

Production, characterization, and applications of two novel monoclonal antibodies against human interleukin-28A.

Interleukin-28A (IL-28A) is a novel cytokine discovered in recent years and has been shown to have antiviral activity. In this study, IL-28A complementary DNA was inserted into prokaryotic expression vector pET-44 Ek/LIC. The Nus-S-His-tagged IL-28A fusion protein was expressed in Escherichia coli BL21 (DE3) in the soluble fraction. The fusion protein was purified by S-protein agarose affinity chromatography, and the fusion tag was removed from recombinant IL-28A by cleavage with thrombin. To prepare specific monoclonal antibody against human IL-28A, BALB/c mice were immunized with IL-28A, and hybridoma cell lines were obtained by fusing mouse spleen cells with myeloma NS-1 cells. Two strains of hybridoma cells, which produced the anti-human IL-28A antibodies 1B9 and 4B5 were obtained. They are IgM isotype and working in western blot analysis and enzyme-linked immunosorbent assay. In the present study, it was shown for the first time that human umbilical vein endothelial cells treated with interferon-alpha and poly(I:C) express IL-28A protein assessed by flow cytometry and immunofluorescent staining techniques. Immunohistochemistry showed that macrophage-like cells in colon and lung tissue and alveolar epithelial cells in lung tissue contain IL-28A, indicating a novel mechanism for both cell types to carry out their antivirus or antitumor functions.

Animals↗
PubMed2005

The effect of fetal gender on the false-positive rate of Down syndrome by maternal serum screening.

OBJECTIVES: (1) To further explore if there is a difference in maternal serum levels of alpha-fetoprotein (AFP), human chorionic gonadotrophin (hCG) and estriol (uE3) between fetal genders. (2) To determine if these differences influence false-positive rates of Down syndrome screening in pregnancies with male or female fetuses. METHODS: This is a descriptive study of women screened at the Ontario Maternal Serum Screening program between 1993 and 1995. The women were grouped by fetal gender and ethnicity. Serum levels of the three markers and screening false-positive rates for Down syndrome were compared between fetal genders in women of different ethnicity respectively. RESULTS: Complete data were available for 110 306 pregnancies. In all three ethnic groups, MSAFP levels were significantly decreased and MShCG levels were significantly increased in women with female fetuses. The level of MSuE3 was similar between genders. The difference in false-positive rates of Down syndrome between genders was not statistically significant. CONCLUSIONS: This is the largest study comparing false-positive rates between fetal genders. In contrast to previous studies, the differences in the serum marker levels between fetal genders do not influence the false-positive rates for Down syndrome.

Adult↗
PubMed2005

The influence of risk estimates obtained from maternal serum screening on amniocentesis rates.

OBJECTIVE: To investigate the influence of Down syndrome risk estimates obtained from maternal serum screening (MSS) on women's choices regarding amniocentesis. METHODS: Women who screened positive for Down syndrome by an Ontario MSS program between 1993 and 1998 were grouped on the basis of their risk estimate and ethnicity. Amniocentesis uptake rates between the groups were compared in order to determine how the MSS risk estimate influenced uptake. RESULTS: Analysis of 16 792 women showed that amniocentesis uptake rates increased as the estimated risk increased. Uptake in women < or = 35 was higher than that for older women (70% vs 60%, p = 0.001). Uptake in Caucasian and Asian women was higher than the uptake in Black women (67% vs 49%, p = 0.001). Women aged 35 years or older were more likely to proceed with amniocentesis if the MSS risk estimate was higher than their age-specific risk. CONCLUSION: The increase in amniocentesis rate paralleled the increase in MSS risk estimate for Down syndrome. Risk-specific amniocentesis rates are higher in women aged less than 35 years. Women aged 35 years or older whose risk estimate by MSS is lower than their age-specific risk are less likely to opt for amniocentesis.

Adolescent↗
PubMed2003

Using Down syndrome serum screening results to predict low birthweight.

OBJECTIVE: To investigate the use of prenatal maternal serum screening results for Down syndrome, for the prediction of low (<2500 g) and very low (<1500 g) birthweight. DESIGN: Record linkage of maternal serum screening results with the corresponding birth records. PARTICIPANTS: 42 259 women whose pregnancies had been screened for the risk of Down syndrome. SETTING: Three East London maternity units, between February 1989 and August 1998. RESULTS: Estimates were made of the effectiveness of single markers only for the prediction of low birthweight, and of multiple markers together with mother's weight and smoking habit. As reported previously, high levels of the single markers alpha-fetoprotein and total human chorionic gonadotrophin, inhibin A, and low levels of unconjugated oestriol were associated with low birthweight. However, the best prediction was obtained when multiple serum markers comprising alpha-fetoprotein, unconjugated oestriol, and inhibin A were used in combination together with mother's weight and adjustment for smoking habit. For a false-positive rate of 5%, this combination predicted 23% of low birthweight and 39% of very low birthweight babies, possibly the best method of prediction to date. CONCLUSION: Prediction of low birthweight derived from Down syndrome screening could be used, for little extra cost, to advise on place of delivery or to select candidates for randomised clinical trials of low birthweight prevention.

Adult↗
PubMed2003

Maternal serum screening in Ontario using the triple marker test.

OBJECTIVES: To summarise the experience and evaluate the performance of the Ontario maternal serum screening (MSS) programme. SETTING: The Ontario MSS programme between October 1993 and September 2000. METHODS: This study used information collected in the Ontario MSS database, which contains data on each screened pregnancy. In the Ontario MSS programme, women are screened between 15 and 20 weeks of gestation. The risk cut-off for Down's syndrome was >or= 1 in 385 at term and women with a serum alpha-fetoprotein >or= 2.2 multiples of the unaffected population median were defined as screen-positive for open neural tube defects. RESULTS: Between 1 October 1993 and 30 September 2000, 428410 women residing in Ontario were screened for open neural tube defects, and 423895 women were screened for Down's syndrome and trisomy 18. Approximately 48% of all pregnant women in the province had MSS. The uptake rate of amniocentesis following a positive Down's syndrome screening was 67%. Of 717 cases of Down's syndrome ascertained in the screened population, 531 were detected by MSS, giving a term detection rate (DR) of 70.6%, with a false-positive rate (FPR) of 7.2%. For neural tube defects, the DR was 72.7%, with a FPR of 2.0%. The screen also detected 50% of cases of trisomy 18 at term, with a FPR of 0.2%. Coincidentally, 113 cases of chromosome aneuploidies other than Down's syndrome and trisomy 18 were detected. DISCUSSION: In the Ontario MSS programme, MSS performed as expected in the detection of Down's syndrome, open neural tube defects and trisomy 18. MSS is an effective and practical method for large-scale second trimester screening for Down's syndrome, open neural tube defects and trisomy 18, and the MSS database is an extremely useful tool in monitoring the performance of this screen.

Amniocentesis↗
PubMed2003

Distribution of technetium-99m-labelled QVAR delivered using an Autohaler device in children.

QVAR, an extrafine hydrofluoroalkane/beclomethasone dipropionate formulation, has been shown to double lung deposition in adults. The aim of the present study was to assess the total body deposition and distribution of technetium-99m-labelled (99mTc) QVAR in children after inhalation via an Autohaler. Sixteen male asthmatic children (5-14 yrs) inhaled labelled drug (<4 MBq 99mTc; 100 microg beclomethasone dipropionate) via an Autohaler within 30 min after salbutamol (200 microg) administration. Simultaneous anterior and posterior planar scintigraphic scans (120 s acquisition time) were collected after inhalation of labelled drug. Mean+/-SD lung deposition of labelled drug (attenuation-corrected; percentage of ex-actuator dose) was 36.9+/-9.2, 46.5+/-11.6 and 54.1+/-10.7% in children aged 5-7, 8-10 and 11-14 yrs, respectively. Combined oropharyngeal and gastrointestinal deposition was 59.7+/-8.2, 48.9+/-12.3 and 40.3+/-11.8%. Lung deposition positively correlated with the forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). Gastrointestinal dose negatively correlated with the FEV1, FVC, height and age. In older children (11-14 yrs), lung deposition was almost identical to that reported in adults using QVAR. In children aged 5-10 yrs, lung deposition using QVAR was greater than the levels measured using other commercial aerosol delivery systems. Oropharygeal and gastrointestinal deposition was inversely related to age.

Administration, Inhalation↗
PubMed2002

Reliability of the comet assay in cryopreserved human sperm.

BACKGROUND: Although the comet assay has potential value for measuring DNA damage in large epidemiological human sperm studies, it is impractical to perform the assay daily on fresh semen samples. Therefore, before its use in epidemiological studies, the reliability of the comet assay in measuring DNA damage in cryopreserved sperm should be compared with that in fresh human sperm. METHODS: Semen samples from 16 men were cryopreserved in liquid nitrogen (LN) using four methods: flash freezing with and without cryopreservative, and programmable freezing with and without cryopreservative. Neutral microgel electrophoresis was performed and comets were stained with YOYO-1. Comet length was measured using an eyepiece micrometer at x400 magnification. RESULTS: The highest correlation was between comet assay results obtained from fresh human semen compared with semen flash frozen without cryopreservative (R = 0.88). However, the method of cryopreservation, as compared with other sources of variability, accounted for only 6% of the variability. Inter-individual variability accounted for 20%, and individual sperm-to-sperm variability within an ejaculate accounted for 65%. CONCLUSIONS: Flash-freezing in LN without cryopreservative most closely reproduced the results obtained using fresh human semen samples, and thereby represents the most appropriate cryopreservation method for human semen in epidemiological studies utilizing the neutral comet assay.

Adult↗
PubMed2002

A computational fluid dynamic and experimental study of an ozone contactor.

A computational fluid dynamic (CFD) model of an ozone contacting chamber in the Umgeni Water Wiggins Waterworks in Durban, South Africa, has been set up and verified by experimental tracer tests, as part of an investigation to optimise the control and disinfection efficiency of the contactor. The effect of gas injection was modelled by increasing the turbulent intensity at the reactor inlet. Experimental tracer responses which were used as partial verification of the model correspond very closely to model predictions.

Disinfectants↗
PubMed2002

Pilot-scale study of an anaerobic baffled reactor for the treatment of domestic wastewater.

Large proportions of South Africans live in areas with inadequate sanitation and a poor infrastructure for waterborne sanitation. Service providers are looking for alternative wastewater treatment options. The anaerobic baffled reactor is being considered as a decentralised sanitation option in these areas. A 3,200 L reactor was built and is currently being evaluated at a wastewater treatment works. The reactor was built based on experiences gained from working with a laboratory reactor (10 L) and predicted flow patterns observed on a computational fluid dynamics model. The design and construction of the reactor will be discussed in this paper. The feed to the reactor consists of screen degritted sewage and the flow to the reactor is maintained by means of a programmable logic controller. The pilot-plant layout is discussed in this paper. Samples are analysed for chemical oxygen demand, pH, alkalinity, ammonia, phosphorus, solids and ash content. Reductions of between 70 and 80% are obtained for COD and the pH values for the effluent samples are within the discharge limits.

Bioreactors↗
PubMed2001

Deltopectoral skin flap as a free skin flap revisited: further refinement in flap design, fabrication, and clinical usage.

The deltopectoral skin flap is an axial flap; therefore, it can be fashioned as a free skin flap. Although color and texture of the skin are well suited for facial resurfacing, the structural features of inconsistent thickness of the skin, a short vascular pedicle, a minute caliber of the nutrient vessel, and donor site morbidity often preclude the use of this flap for this purpose. The deltopectoral skin flap fabricated as a free skin flap transferred by means of a microsurgical technique was used in 27 patients between 1985 and 1998 at our hospital. The anterior perforating branches of the internal mammary vessels were the primary nutrient vessels of the flap in seven instances. The external caliber of this artery varied between 0.6 mm and 1.2 mm, with an average size of 0.9 mm. The size of the accompanying vein varied between 1.5 mm and 3.2 mm, with an average of 2.3 mm. Coaptation of these vessels with those in the recipient site was technically difficult. Thrombosis occurred at the anastomotic site in three patients, requiring reoperation. Two flaps were saved. The flap failure was drastically reduced in the remaining 20 patients by including a segment of the internal mammary vessel when fabricating the vascular pedicle. The size of the internal mammary arterial segment averaged 2.1 mm, and the average size of the accompanying vein was 2.9 mm. The problem of a bulky flap was managed by surgical defatting/thinning of the flap at the time of flap fabrication and transfer. A V-to-Y skin flap advancement technique of wound closure was used in eight individuals. The flap donor-site morbidities were minimized with this method of wound closure.

Adult↗
PubMed2001

Expression of the Hoxa-13 gene correlates to hepatitis B and C virus associated HCC.

To study the Hoxa-13 gene in the liver, we examined its expression by RT-PCR in various liver cell lines, rat livers under different conditions, and human primary hepatocellular carcinomas (HCCs). The gene was found to be expressed in cell lines originating from liver stem-like cells, but not in cell lines originating from hepatocytes and bile duct epithelia. Expression was induced in rat livers after treatment with d-galactosamine, which is known to induce oval cell proliferation, but not after a two-thirds partial hepatectomy (2/3 PH) where induction of oval cell proliferation is thought not to occur. Expression of the gene correlated with human HCC samples associated with Hepatitis B or C virus infection in this small series. These results suggest that the Hoxa-13 gene may provide a potentially useful tool for elucidation of mechanisms involved in lineage-specific differentiation and carcinogenesis of liver stem cells.

Animals↗
PubMed2001

Endoscopic Nd:YAG laser therapy combined with local chemotherapy of superficial carcinomas of the oesophagus and gastric cardia.

The aim of this study was to explore the possibilities of non-surgical management for superficial carcinomas of the oesophagus and gastric cardia. Thirty-one patients with superficial oesophageal or gastric cardiac carcinomas, who refused or were unsuitable for surgery, received endoscopic Nd:YAG laser therapy combined with local injection of chemotherapeutic drugs 5-fluorouracil and mitomycin. After one to four sessions of treatment no cancer cells were detected by multiple biopsies and no complications such as bleeding or perforation occurred in any case. The 31 patients have been followed-up for 25-91 months (five cases for 91 months, eight cases for 79 months, four cases for 55 months, eight cases for 33 months and six cases for 25-31 months). All patients are surviving without sign of recurrence and no cancer cells were detected by endoscopic biopsies. Our findings indicate that this is an effective and safe therapeutic modality and may be considered as the first choice for those patients who refuse or are not suitable for surgery, and for those of older age and in poor condition.

Adult↗
PubMed2001

An unusual cystic appearance of disseminated low-grade gliomas.

We report five cases of pediatric disseminated low-grade gliomas of the brainstem or spinal cord that exhibited an unusual, cystic pattern. Leptomeningeal disease was present in three of these at diagnosis, and was detected shortly afterwards in the other two. Four patients are alive up to 5 years later, following minimal to no intervention, while one is dead.

Arachnoid Cysts↗