Biomedical subjects

S W Chiu

Publications and source records attributed to S W Chiu.

At least 19 recordsLinked to original sources

PubMed2006

A comparison of the clinical effectiveness of spinal orthoses manufactured using the conventional manual method and CAD/CAM method in the management of AIS.

Spinal orthoses are commonly prescribed to patients with moderate AIS for prevention of further deterioration. In a conventional manufacturing method, plaster bandages are used to get patient's body contour and plaster cast is rectified manually. With the introduction of CAD/CAM system, a series of automated processes from body scanning to digital rectification and milling of positive model can be performed in a fast and accurate fashion. This project is to study the impact of CAD/CAM method as compared with the conventional method. In assessing the 147 recruited subjects fitted with spinal orthoses (43 subjects using conventional method and 104 subjects using CAD/CAM method), significant decreases (p<0.05) were found in the Cobb angles when comparing the pre-intervention data with that of the first year of intervention. Regarding the learning curve, Orthotists are getting more competent with the CAD/CAM technique in four years time. The mean productivity of the CAD/CAM method is 2.75 times higher than that of the conventional method. The CAD/CAM method could achieve similar clinical outcomes and with its high efficiency, could be considered as substitute for conventional methods in fabricating spinal orthoses for patients with AIS.

Adolescent↗

PubMed2005

Characterization of contamination in and toxicities of a shipyard area in Hong Kong.

This is the first integrated study on the contaminant characterization and toxicities of a shipyard area. This site in Hong Kong contained 3.6-33.4 mg kg(-1) dichlorodiphenyltrichloroethane and 5-79 g kg(-1) oil and grease. Other pollutants exceeding the Dutch intervention values were total polyaromatic hydrocarbons, total petroleum hydrocarbons, and metals Cu, Pb and Zn. These pollutants persisted partially owing to the poor fertility with <125 mg N kg(-1) and <530 mg P kg(-1) typical of coastal soil. Sediments collected within 100 m also showed contamination exceeding the China and Hong Kong intervention levels. The shipyard soil killed two bacteria Pseudomonas stutzeri and Acinetobacter sp. isolated from a clean coastal soil, inhibited germination of three exogenous plants Triticum aestivum, Brassica chinense and Lolium perenne, and inhibited proliferation of three indigenous bacteria: Methylobacterium sp., Pseudomonas aeruginosa and Bacillus cereus. Thus, ex situ remediation was needed.

Bacteria↗

PubMed2005

Conserved transcription factor binding sites of cancer markers derived from primary lung adenocarcinoma microarrays.

Gene transcription in a set of 49 human primary lung adenocarcinomas and 9 normal lung tissue samples was examined using Affymetrix GeneChip technology. A total of 3442 genes, called the set M AD, were found to be either up- or down-regulated by at least 2-fold between the two phenotypes. Genes assigned to a particular gene ontology term were found, in many cases, to be significantly unevenly distributed between the genes in and outside M AD. Terms that were overrepresented in M AD included functions directly implicated in the cancer cell metabolism. Based on their functional roles and expression profiles, genes in M AD were grouped into likely co-regulated gene sets. Highly conserved sequences in the 5 kb region upstream of the genes in these sets were identified with the motif discovery tool, MoDEL. Potential oncogenic transcription factors and their corresponding binding sites were identified in these conserved regions using the TRANSFAC 8.3 database. Several of the transcription factors identified in this study have been shown elsewhere to be involved in oncogenic processes. This study searched beyond phenotypic gene expression profiles in cancer cells, in order to identify the more important regulatory transcription factors that caused these aberrations in gene expression.

5' Flanking Region↗

PubMed2005

Resection of phaeochromocytoma extending into the right atrium in a patient with multiple endocrine neoplasia type 2A.

We report the first case of successful surgical resection of a malignant phaeochromocytoma with tumour extension into vena cava and right atrium in a patient with multiple endocrine neoplasia type 2A. A 21-year-old woman with genetic confirmation of multiple endocrine neoplasia type 2A syndrome was diagnosed with a very rare case of malignant phaeochromocytoma with tumour thrombus extension into vena cava and right atrium causing Budd-Chiari syndrome. It posed a challenge to the surgeons with regard to complete tumour resection and vascular control. Reviewing the limited literature, surgical resection by means of cardiopulmonary bypass with hypothermic circulatory arrest has been reported with success in phaeochromocytoma with advance vascular involvement. Adopting this approach, adrenalectomy with complete thrombus excision by inferior vena cava exploration and right atriotomy were performed successfully by a multidisciplinary team.

Adrenal Gland Neoplasms↗

PubMed2004

A distinctive ribonuclease from fresh fruiting bodies of the medicinal mushroom Ganoderma lucidum.

A ribonuclease with an N-terminal sequence distinct from other mushroom ribonucleases was isolated from fresh fruiting bodies of the medicinal mushroom Ganoderma lucidum. The ribonuclease was adsorbed on DEAE-cellulose and Q-Sepharose, and unadsorbed on CM-Sepharose. It possessed a molecular mass of 42 kDa as judged by gel filtration by fast protein liquid chromatography on Superdex 75 and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Its molecular mass was similar to that of straw mushroom ribonuclease but much higher compared with those of other mushroom ribonucleases. The ribonuclease was unique among mushroom ribonucleases in that it exhibited the highest potency toward poly(U), followed by poly(A). Its activity toward poly(G) and poly(C) was about one-half of that toward poly(A) and one-quarter of that toward poly(U). A pH of 4.0 and a temperature of 60 degrees C were required for optimal activity of the enzyme. The optimum pH was low compared with those reported for other mushroom ribonucleases.

Agaricales↗

PubMed2004

Sphingomyelin-cholesterol domains in phospholipid membranes: atomistic simulation.

We have carried out an atomic-level molecular dynamics simulation of a system of nanoscopic size containing a domain of 18:0 sphingomyelin and cholesterol embedded in a fully hydrated dioleylposphatidylcholine (DOPC) bilayer. To analyze the interaction between the domain and the surrounding phospholipid, we calculate order parameters and area per molecule as a function of molecule type and proximity to the domain. We propose an algorithm based on Voronoi tessellation for the calculation of the area per molecule of various constituents in this ternary mixture. The calculated areas per sphingomyelin and cholesterol are in agreement with previous simulations. The simulation reveals that the presence of the liquid-ordered domain changes the packing properties of DOPC bilayer at a distance as large as approximately 8 nm. We calculate electron density profiles and also calculate the difference in the thickness between the domain and the surrounding DOPC bilayer. The calculated difference in thickness is consistent with data obtained in atomic force microscopy experiments.

Algorithms↗

PubMed2003

Structure of sphingomyelin bilayers: a simulation study.

We have carried out a molecular dynamics simulation of a hydrated 18:0 sphingomyelin lipid bilayer. The bilayer contained 1600 sphingomyelin (SM) molecules, and 50,592 water molecules. After construction and initial equilibration, the simulation was run for 3.8 ns at a constant temperature of 50 degrees C and a constant pressure of 1 atm. We present properties of the bilayer calculated from the simulation, and compare with experimental data and with properties of dipalmitoyl phosphatidylcholine (DPPC) bilayers. The SM bilayers are significantly more ordered and compact than DPPC bilayers at the same temperature. SM bilayers also exhibit significant intramolecular hydrogen bonding between phosphate ester oxygen and hydroxyl hydrogen atoms. This results in a decreased hydration in the polar region of the SM bilayer compared with DPPC. Since our simulation system is very large we have calculated the power spectrum of bilayer undulation and peristaltic modes, and we compare these data with similar calculations for DPPC bilayers. We find that the SM bilayer has significantly larger bending modulus and area compressibility compared to DPPC.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2003

Removal of biocide pentachlorophenol in water system by the spent mushroom compost of Pleurotus pulmonarius.

Pentachlorophenol (PCP) has been widely used as a wood preservative since 1980s. Although it has been banned worldwide, residues of PCP are still commonly found. The spent compost of oyster mushroom Pleurotus pulmonarius (SMC) which was a degraded paddy straw-based substrate, contained 25% chitin. Five percentage of the SMC could remove 89.0 +/- 0.4% of 100 mg PCPl(-1) within 2 days at room temperature predominantly by biodegradation. The maximum removal capacity was 15.5 +/- 1.0 mg g(-1) SMC. The sorption kinetics of PCP by SMC can be described by the Freundlich monolayer model with a theoretical sorption capacity similar to that found for chitin. A PCP-degradative bacterium was isolated from the SMC. Yet, biodegradation was predominantly contributed by the immobilized ligninolytic enzymes secreted by the mushroom to the SMC. Degradation of PCP involves dechlorination, methylation, carboxylation and ring cleavage as verified by GC-MSD and ion chromatography. Thus, the SMC has a potential for treating PCP-contaminated water.

Adsorption↗

PubMed2003

Use of spent mushroom compost to bioremediate PAH-contaminated samples.

Spent mushroom compost (SMC) is a bulky waste byproduct of mushroom industry and produced abundantly. The SMC of Pleurotus pulmonarius immobilized laccase (0.88 mmoles min(-1) g(-1)) and manganese peroxidase (0.58 mmoles min(-1) g(-1)) of which the optimal temperatures were 45 and 75 degrees C, respectively. In laboratory test, complete degradative removal of individual naphthalene, phenanthrene, benzo[a]pyrene and benzo[g,h,i]perylene (200 mg PAH kg(-1) sandy-loam soil) by 5% SMC was obtained in two days under continuous shaking at 80 degrees C. The SMC-treated PAH samples had significantly reduced or removed their toxicities as revealed by the Microtox bioassay. These results were confirmed by gas chromatography-mass spectrometry analysis on the breakdown products. A phthalic derivative which is reported as a degradative product of PAHs by ozonation or ligninolysis was also detected in the SMC-treated samples. The results demonstrate the potential in employing SMC in ex situ bioremediation.

Adsorption↗

PubMed2003

Gender difference in self-esteem of Hong Kong Chinese with cardiac diseases.

Self-esteem is an indicator of a person's subjective quality of life due to its close relationship to a person's behavioural competence, positive self-experience, and sense of self-actualization. The present study aimed to investigate the basis of self-esteem in people with cardiac diseases, according to gender, after their cardiac surgery. The findings showed that there were prominent gender differences in the subjects' self-esteem. Women (aged<60) showed statistically significant higher ratings in the importance of 11 life events importance and the satisfaction of three life events than men. The study also found cultural uniqueness: Hong Kong Chinese (both men and women) with cardiac diseases generally indicated that social (interpersonal) self-concept dimensions were more important than achievement (personal) self-concept dimensions in their life perception. These findings are noteworthy for setting optimum goals of rehabilitation apart from return to work.

Adaptation, Psychological↗

PubMed2002

Cholesterol-induced modifications in lipid bilayers: a simulation study.

We present analysis of new configurational bias Monte Carlo and molecular dynamics simulation data for bilayers of dipalmitoyl phosphatidyl choline and cholesterol for dipalmitoyl phosphatidyl choline:cholesterol ratios of 24:1, 47:3, 11.5:1, 8:1, 7:1, 4:1, 3:1, 2:1, and 1:1, using long molecular dynamics runs and interspersed configurational bias Monte Carlo to ensure equilibration and enhance sampling. In all cases with cholesterol concentrations above 12.5% the area per molecule of the heterogeneous membrane varied linearly with cholesterol fraction. By extrapolation to pure cholesterol, we find the cross-sectional area of cholesterol in these mixtures is approximately 22.3 A(2). From the slope of the area/molecule relationship, we also find that the phospholipid in these mixtures is in a liquid ordered state with an average cross-sectional area per lipid of 50.7 A(2), slightly above the molecular area of a pure phospholipid gel. For lower concentrations of cholesterol, the molecular area rises above the straight line, indicating the "melting" of at least some of the phospholipid into a fluid state. Analysis of the lateral distribution of cholesterol molecules in the leaflets reveals peaks in radial distributions of cholesterols at multiples of approximately 5 A. These peaks grow in size as the simulation progresses, suggesting a tendency for small subunits of one lipid plus one cholesterol, hydrogen bonded together, to act as one composite particle, and perhaps to aggregate with other composites. Our results are consistent with experimentally observed effects of cholesterol, including the condensation effect of cholesterol in phospholipid monolayers and the tendency of cholesterol-rich domains to form in cholesterol-lipid bilayers. We are continuing to analyze this tendency on longer timescales and for larger bilayer patches.

Biophysical Phenomena↗

PubMed2002

Post-transplantation lymphoproliferative disease in Chinese: the Queen Mary Hospital experience in Hong Kong.

Post-transplantation lymphoproliferative disease (PTLD) is an unique iatrogenic complication after bone marrow transplantation (BMT) and solid organ transplantation (SOTx). The pattern of EBV related lymphoma in Chinese is different from Caucasians. We surveyed the incidence, clinical and pathological spectrum of PTLD among 541 cases of allogeneic BMT, 145 cases of renal transplant, 35 cases of heart/lung transplantation and 146 cases of orthotopic liver transplantation (OLT). From 1994 to 2001, 13 consecutive cases of PTLD were diagnosed, ranging from disseminated NK cell lymphoma to localized plasmacytoma. Both donor and recipient derived PTLD was documented. Disease was often heralded by cytomegaloviral disease and antithymocyte globulin (ATG) usage. Two cases were diagnosed post-mortem, and six patients died of PTLD at a median of 3 months. Complete and partial remission was only achieved in 3 and 2 cases, respectively, despite a range of treatment (reduced immunosuppression, explantation, radiotherapy, combination chemotherapy, donor lymphocytes, autologous marrow infusion and rituximab). Most responding patients died subsequently of rejection, infection and graft versus host disease (GVHD). The incidence of PTLD is not increased in Chinese patients. However, some patients may be at increased risk, especially mismatched allogeneic BMT, parental OLT (especially involving young infants) and heavy ATG exposure.

Adolescent↗

PubMed2001

Combined Monte Carlo and molecular dynamics simulation of hydrated lipid-cholesterol lipid bilayers at low cholesterol concentration.

We have applied a hybrid equilibration and sampling procedure for the atomic level simulation of a hydrated lipid bilayer to systems consisting of dipalmitoyl phosphatidylcholine (DPPC) and cholesterol, and palmitoyl-oleyl phosphatidylcholine (POPC) at low (approximately 6%) cholesterol concentration. The procedure is applied to bilayers of 94 molecules of DPPC, 6 molecules of cholesterol, and 3205 water molecules, and to bilayers of 120 molecules of POPC, 8 molecules of cholesterol, and 4268 water molecules, at a temperature of 325 K. After equilibration, three separate 400-ps continuous molecular dynamics runs, separated by 10,000 configurational bias Monte Carlo steps, were carried out for each system. Properties of the systems were calculated and averaged over the three separate runs. Results of the simulations are presented and compared with experimental data and with other recent simulations of DPPC and cholesterol, and of pure DPPC, and pure POPC. Certain properties of the bilayers are indistinguishable from cholesterol-free bilayers, including lateral diffusion and electron density. Other properties, most notably the order parameter profile, show the effect of cholesterol even at low concentrations.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2000

Ganoderma extract activates MAP kinases and induces the neuronal differentiation of rat pheochromocytoma PC12 cells.

The pharmacology and clinical application of traditional Chinese medicine has been extensively documented. We have used an in vitro model system, PC12 cells, to demonstrate the presence of neuroactive compounds in Ganoderma lucidum (lingzhi). Ganoderma extract induced the neuronal differentiation of PC12 cells and prevented nerve growth factor-dependent PC12 neurons from apoptosis. Moreover, these effects of ganoderma might be mediated via the ras/extracellular signal-regulated kinase (Erk) and cAMP-response element binding protein (CREB) signaling pathways, as demonstrated by the phosphorylation of Erk1, Erk2 and CREB. Thus, our data not only present the first evidence of the presence of neuroactive compounds that mediate the neuronal differentiation and neuroprotection of the PC12 cells, but also reveal the potential signaling molecules involved in its action.

Animals↗

PubMed2000

Injection of vasodilators into arterial grafts through cardiac catheter to relieve spasm.

Both native coronary artery and coronary bypass grafts may develop vasospasm after coronary artery bypass grafting. We recommend that whenever there is a high suspicion of vasospasm in arterial grafts and the native coronary artery unresponsive to or not suitable for usual vasodilator therapy, prompt selective graft arteriogram should be performed. Intraluminal injection of vasodilators such as calcium antagonists in combination with nitroglycerin may provide an effective antispastic therapy and this procedure could be lifesaving as demonstrated in the present report.

Aged↗

PubMed2000

A rare complication of PTCS: ruptured balloon with retained broken catheter.

This report describes a rare situation in which a retained ruptured balloon with broken catheter was caught in an incompletely opened stent during a percutaneous transluminal coronary stenting (PTCS) procedure in a 84 year old gentleman. A short, warm heart bypass and single cross clamping coronary artery bypass grafting procedure was performed.

Aged↗

PubMed1999

Combined Monte Carlo and molecular dynamics simulation of fully hydrated dioleyl and palmitoyl-oleyl phosphatidylcholine lipid bilayers.

We have applied a new equilibration procedure for the atomic level simulation of a hydrated lipid bilayer to hydrated bilayers of dioleyl-phosphatidylcholine (DOPC) and palmitoyl-oleyl phosphatidylcholine (POPC). The procedure consists of alternating molecular dynamics trajectory calculations in a constant surface tension and temperature ensemble with configurational bias Monte Carlo moves to different regions of the configuration space of the bilayer in a constant volume and temperature ensemble. The procedure is applied to bilayers of 128 molecules of POPC with 4628 water molecules, and 128 molecules of DOPC with 4825 water molecules. Progress toward equilibration is almost three times as fast in central processing unit (CPU) time compared with a purely molecular dynamics (MD) simulation. Equilibration is complete, as judged by the lack of energy drift in 200-ps runs of continuous MD. After the equilibrium state was reached, as determined by agreement between the simulation volume per lipid molecule with experiment, continuous MD was run in an ensemble in which the lateral area was restrained to fluctuate about a mean value and a pressure of 1 atm applied normal to the bilayer surface. Three separate continuous MD runs, 200 ps in duration each, separated by 10,000 CBMC steps, were carried out for each system. Properties of the systems were calculated and averaged over the three separate runs. Results of the simulations are presented and compared with experimental data and with other recent simulations of POPC and DOPC. Analysis of the hydration environment in the headgroups supports a mechanism by which unsaturation contributes to reduced transition temperatures. In this view, the relatively horizontal orientation of the unsaturated bond increases the area per lipid, resulting in increased water penetration between the headgroups. As a result the headgroup-headgroup interactions are attenuated and shielded, and this contributes to the lowered transition temperature.

Lipid Bilayers↗

PubMed1999

Simulation study of a gramicidin/lipid bilayer system in excess water and lipid. I. Structure of the molecular complex.

This paper reports on a simulation of a gramicidin channel inserted into a fluid phase DMPC bilayer with 100 lipid molecules. Two lipid molecules per leaflet were removed to insert the gramicidin, so the resulting preparation had 96 lipid molecules and 3209 water molecules. Constant surface tension boundary conditions were employed. Like previous simulations with a lower lipid/gramicidin ratio (Woolf, T. B., and B. Roux. 1996. Proteins: Struct., Funct., Genet. 24:92-114), it is found that tryptophan-water hydrogen bonds are more common than tryptophan-phospholipid hydrogen bonds. However, one of the tryptophan NH groups entered into an unusually long-lived hydrogen bonding pattern with two glycerol oxygens of one of the phospholipid molecules. Comparisons were made between the behavior of the lipids adjacent to the channel with those farther away. It was found that hydrocarbon chains of lipids adjacent to the channel had higher-order parameters than those farther away. The thickness of the lipid bilayer immediately adjacent to the channel was greater than it was farther away. In general, the lipids adjacent to the membrane had similar orientations to those seen by Woolf and Roux, while those farther away had similar orientations to those pertaining before the insertion of the gramicidin. A corollary to this observation is that the thickness of the hydrocarbon region adjacent to the gramicidin was much thicker than what other studies have identified as the "hydrophobic length" of the gramicidin channel.

Biophysical Phenomena↗