PubMed Health⌕ Search

Biomedical subjects

F T Chew

Publications and source records attributed to F T Chew.

At least 19 recordsLinked to original sources
PubMed2005

Viability and adipogenic potential of human adipose tissue processed cell population obtained from pump-assisted and syringe-assisted liposuction.

BACKGROUND: Correcting soft tissue defects by autologous fat grafting has been a routine procedure in plastic surgery. Liposuction material for autologous fat grafting is normally obtained using a hand-held syringe. The pump-assisted liposuction technique is not used because of the belief that cells in the harvested fat tissue are necrotic from the physical forces created by the vacuum pump liposuction machine. OBJECTIVE: The metabolism and adipogenic potential of cultured mesenchymal precursor cells processed from pump and syringe lipoaspirates were studied. METHODS: Metabolic estimates were determined with alamarBlue assay. These cells were also induced along the adipogenic lineage with adipogenic induction factors. The extent of adipogenic differentiation was measured using a digital photo counting software. RESULTS: The cells obtained by pump-assisted liposuction are viable, have comparable metabolic activity and adipogenic potential which are comparable to cells using the syringe for aspiration. CONCLUSION: The implications of this study are that pump-assisted liposuction might be a possible alternative to aspirating adipose tissue for reimplantation during reconstruction procedures.

Adipocytes↗
PubMed2004

Economic burden of varicella in Singapore--a cost benefit estimate of implementation of a routine varicella vaccination.

Varicella is a common childhood illness that can result in significant morbidity and mortality. As early as 1995, recommendations for routine varicella vaccination have been published, but have not been universally implemented, with cost of vaccination as a major reason. Though available from 1996, the vaccine has yet to be routinely implemented in Singapore. We set out to assess the economic burden of varicella and the cost-benefit of adding a varicella vaccine to the existing immunization schedule in Singapore. In this study, using data from 1994--1995 the direct cost estimates were based on all levels of medical care; inpatient care, emergency room visits, primary health care and medication. Indirect costs were estimated from the cost of time lost by patients and their families attending to medical needs, as well as loss of productivity due to absenteeism. The cost of a vaccination program targeted at 15-month old infants receiving concomitant measles-mumps-rubella immunization was also assessed. The cost-benefit ratio was then estimated. The total cost of varicella in Singapore was estimated to be US$11.8 million per annum. The loss of productivity accounted for a large proportion of the total cost as a lot of parents took leave when their children were ill. The estimates of total cost represent approximately US$188 per varicella case per year. In comparison, the cost of a vaccination program was found to be US$3.3 million per annum. The cost per case averted was US$104. From a societal point of view, for every dollar invested in a vaccination program, we would save about US$2 dollars.

Acyclovir↗
PubMed2003

Laboratory assessment of the efficiency of encasing materials against house dust mites and their allergens.

BACKGROUND: The current recommendation to reduce mite allergen exposure for mite-sensitive individuals is to use allergen-impermeable bed coverings. As these covers are made of various kinds of materials, they vary in quality. The objective of this study was to investigate the efficiency of different covering materials against house dust mites and their allergens in vitro. METHODS: Four types of materials including (1) plastic cover, (2) polyurethane-coated cover, (3) non-woven covers, (4) tightly woven microfiber covers and a regular cotton bed sheet (as a control) were evaluated using three methods: (i) heat escape method, (ii) Siriraj chamber method and stereomicroscopy, scanning electron microscopy and (iii) enzyme-linked immunosorbent assay (ELISA). RESULTS: We found that there was a statistically significant difference in allergen permeability among four types of coverings (P < 0.001). In terms of the impermeability to mites and their allergens, plastic- and polyurethane-coated covers were observed to be the best, followed by non-woven, woven and cotton-based bed sheets. A regular cotton-based bed sheet allows a significant amount of leakage of mite allergens. Both woven and non-woven material are efficient barriers against mite allergen in terms of impermeability. However, with regard to mite colonization, non-woven covers have the drawback of mites being able to penetrate and colonize within the fabric fibers. Woven covers are therefore recommended because of their major advantages of not allowing the colonization of mites within the fabric, being easy to clean, and comfortable. CONCLUSION: The three assessment methods used in this study could be useful as a primary approach to evaluate the quality of covering materials in vitro using both pore size and ability to be colonized by mites on the materials as the key factors.

Allergens↗
PubMed2003

The upper and lower airway responses to nasal challenge with house-dust mite Blomia tropicalis.

BACKGROUND: The house dust mite Blomia tropicalis (B. tropicalis) was found to be the most prevalent domestic mite in Singapore. However, its pathogenicity in allergic airway diseases remains to be investigated. METHODS: Twenty adults with persistent allergic rhinitis (PAR) were studied. Five had a history of asthma, and all were asymptomatic except one who was under treatment with low-dose inhaled corticosteroid. Nasal challenge was carried out by nasal spray with phosphate-buffered saline (PBS) and with increasing concentrations of crude B. tropicalis extracts (0.6, 6.0 and 60 micro g/ml) at 15 min intervals. Subjective symptom scores and absolute number of sneezes were recorded together with objective measurements of spirometry (forced expiratory volume in 1 s, FEV1) and acoustic rhinomanometry (volume of the nasal cavity). These were performed at baseline, 5 min after each incremental challenge, and 30 min, 1 h, 3 h, 5 h and 7 h after the last challenge. Meanwhile, concentrations of mediators in nasal secretions (tryptase, leukotriene C4 (LTC4) and eosinophil cationic protein (ECP)) were measured in nasal aspirate samples at similar time intervals. An identical (control) challenge procedure with PBS alone was repeated in seven patients after a washout period of at least 2 weeks. RESULTS: Significant increases in the subjective and objective nasal symptoms, together with a significant increase of tryptase and LTC4 concentrations in nasal secretion, were found 5 min after each challenge with B. tropicalis, but not with PBS. There was no definitive pattern of the late-phase nasal response in either subjective symptoms or objective measurements. Three patients (3/5) with a history of asthma showed a fall in FEV1 readings (33%, 22% and 11% from baseline, respectively) at 7 h post challenge with concomitant mild wheezing in the night. CONCLUSIONS: Our study demonstrates direct evidence of allergic nasal response to B. tropicalis in sensitized adults. It shows that nasal provocation may also provoke concomitant asthmatic symptoms during the late-phase reaction, especially in people with a history of asthma.

Adult↗
PubMed2002

Seasonal variation in respiratory syncytial virus chest infection in the tropics.

Respiratory syncytial virus (RSV) is the most important cause of lower respiratory tract infection (LRTI) in young children. We determined if there was a seasonal variation in Malaysia in the incidence of RSV infection in young children admitted with LRTI, and possible associations of RSV infection with local meteorological parameters. A total of 5,691 children, aged less than 24 months and hospitalized with LRTI (i.e., bronchiolitis and pneumonia) between 1982-1997, were included in this study. Nasopharyngeal samples were collected and examined for RSV by immunofluorescence, viral culture, or both. Seasonal variations were determined by analyzing the monthly RSV-positive isolation rate via time series analysis. Possible correlations with local meteorological parameters were also evaluated.RSV was isolated in 1,047 (18.4%) children. Seasonal variations in RSV infection rate were evident and peaked during the months of November, December, and January (test statistics [T] = 53.7, P < 0.001). This seasonal variation was evident for both bronchiolitis and pneumonia categories (T = 42.8 and 56.9, respectively, P < 0.001). The rate of RSV infection appeared to correlate with the monthly number of rain days (r = 0.26, P < 0.01), and inversely with the monthly mean temperature (r = -0.38, P < 0.001). In the tropics, seasonal variations in the incidence of RSV infection are evident, with an annual peak in November, December, and January. This information provides a guide for healthcare provisions and implementation of RSV prevention.

Humans↗
PubMed2001

Genetic susceptibility to asthma and atopy among Chinese in Singapore--linkage to markers on chromosome 5q31-33.

BACKGROUND: Asthma and atopy are complex genetic traits, influenced by the interaction of multiple genes and environmental factors. Linkage of these traits to chromosome 5q31-33 has been shown in other populations, but has not been well studied in the Chinese. We studied linkage between asthma and atopy with markers on chromosome 5q31-33 in the Singapore Chinese. This region contains many candidate genes, including the cytokine gene cluster. METHODS: We recruited 88 Chinese families with at least two affected offspring, totaling 373 subjects, with 125 and 119 sib-pairs for atopy and asthma, respectively. All individuals were genotyped with 19 polymorphic microsatellite markers spanning a distance of 41 cM along chromosome 5q31-33. Affected sib-pair and multipoint linkage analysis was performed. RESULTS: There was evidence for linkage of the asthma and atopy phenotypes with three markers, D5S2110, D5S2011, and D5S412 (P values of 0.001 to 0.00001). Multipoint analysis further substantiated this (nonparametric linkage scores of 1.8-2.9). These findings suggest that susceptibility genes for asthma and atopy are found in this region in the Chinese. CONCLUSION: This study has shown linkage of atopy and asthma to chromosome 5q31-33 in a heterogeneous Chinese population. These findings further substantiate the notion that chromosome 5q31-33 contains "universally" important susceptibility genes for these traits.

Adolescent↗
PubMed2001

Immunochemical characterization of edible bird's nest allergens.

BACKGROUND: We have previously described anaphylaxis induced by edible bird's nest (BN) and demonstrated that this condition is IgE mediated. OBJECTIVES: This study aimed at describing the immunochemical properties of the BN allergens. Comparative studies between 3 commercially available sources (according to the country of origin) of BN were also made. METHODS: Crude extracts of commercially available processed BN from Sarawak (Malaysia), Thailand, and Indonesia and fresh unprocessed BN from the caves of Sarawak were obtained by means of aqueous extraction. Specific IgE toward these sources were determined by using fluorescence allergosorbent tests (FASTs). Cross-reactivity studies between the 3 sources of commercially available processed BN were carried out by means of FAST inhibition. Immunochemical characterization by means of IgE immunoblot, periodate treatment, and heat stability studies were carried out on fresh unprocessed BN from Sarawak. RESULTS: Serum from allergic patients showed differences in IgE binding to the 3 sources of commercially available BN, with the highest levels of specific IgE recorded with the Sarawak source (P <.0001). Of these, only the Sarawak and Thailand sources showed considerable cross-reactivity. Further work on the unprocessed fresh Sarawak source identified a putative 66-kd major allergen containing several isoforms. Periodate treatment resulted in loss of IgE binding. Despite a progressive decline in the molecular weights of allergens on SDS-PAGE with increasing periods of boiling, IgE binding, as assessed by means of FAST, was not affected. N-terminal sequence of the major putative allergen (66 kd) showed homology to a domain of an ovoinhibitor precursor in chicken (SWISS-PROT accession No. P10184). CONCLUSIONS: We have described the immunochemical properties of BN allergens. Edible BN from different sources are allergenically dissimilar. The putative major allergen is a 66-kd protein.

Adolescent↗
PubMed2000

Piezoelectric quartz crystal based label-free analysis for allergy disease.

This work presents a piezoelectric (Pz) quartz crystal based label-free quantification of total IgE and allergen-specific IgE in human sera for allergy testing. An evaluation of the different brands of crystals was first initiated with respect to variability in mass sensitivity, frequency measurement reliability and stability, and surface roughness. Thereafter, for total IgE quantification. a direct assay format was adopted. By means of thioctic acid (TA) and coupling reagents, anti-human IgE antibodies were immobilized on AT-cut Pz crystals (10 MHz). The modified crystals could detect serum IgE directly corresponding to a downward frequency shift. The results showed that silver-coated crystals as compared with their gold-coated counterparts provided approximately 1.5 times higher mass detection sensitivity for total IgE in the range of 5-300 IU/ml with a linear regression line, y = 1.8957 x + 1.5603, R2 = 0.995. For the detection of allergen-specific IgE, a sandwiched assay format was used. As the allergen-modified sensor surface captured various classes of associated antibodies (IgE, IgG, etc) and interfering serum proteins as well, the initial frequency shift downwards caused by sera sample incubation would not be proportional to specific IgE levels. Thus, following sample incubation, a second incubation step with secondary anti-human IgE was added to recognize IgE from other bound substances. The frequency shift after secondary antibody binding reflected the amount of allergen-specific IgE proportionally. Compared with 10 MHz crystals, the 20 MHz counterparts provided approximately four times higher mass detection sensitivity for allergen specific IgE in the range of 0.15-17.5 IU/ml with a linear regression line, y = 50.525 x + 107.777, R2 = 0.954. Total IgE and allergen specific IgE assay results of real patients' sera using the Pz sensors agreed well with those obtained by commercially available test kits with correlation coefficient 0.96-0.98. The possibility of regenerating the quartz crystals for further re-use was also dealt with.

Allergens↗
PubMed2000

Evaluation of the allergenicity of tropical pollen and airborne spores in Singapore.

BACKGROUND: Sensitization to pollen and spores of the Southeast Asian tropical region is not well documented. This study evaluated the allergenicity of the tropical airspora in Singapore. METHODS: On the basis of the results of an aerobiologic survey of the airspora profile of Singapore, crude extracts of 23 main spore (fungal and fern) and pollen types were prepared. A total of 231 patients with asthma and/or allergic rhinitis and 76 healthy controls were evaluated by skin prick test (SPT). Total and specific IgE levels were also quantified by the fluorescence allergosorbent test (FAST). RESULTS: All 23 allergenic extracts tested elicited positive SPT responses. Among the patients with atopic diseases, extracts of oil-palm pollen (Elaeis guineensis) were observed to have the highest frequency of positive reactions (40%), followed by extracts of resam-fern spores (Dicranopteris linearis) (34%) and sea-teak pollen (Podocarpus polystachyus) (33.8%). Fungal spores with the highest SPT responses were Curvularia spp. (26-32%) and Drechslera-like spores (31%). Positive responses to these extracts correlated with total serum IgE levels of the subjects and were significantly associated with the presence of atopic disease. CONCLUSIONS: We have documented sensitization to tropical pollen and spores in our population. Its association with atopy suggests that it has a role in allergic diseases in the tropics.

Adolescent↗
PubMed2000

Edible "bird's nest"-induced anaphylaxis: An under-recognized entity?

The Chinese delicacy "bird's nest" is the most common cause of food-induced anaphylaxis requiring hospitalization among Chinese children in Singapore. This investigation has established an immunoglobulin E-mediated cause and has characterized the major putative allergens.

Adolescent↗
PubMed1999

Self-assembled monolayer-based piezoelectric crystal immunosensor for the quantification of total human immunoglobulin E.

This work presents a piezoelectric (Pz) immunosensor for the quantification of total human IgE in serum samples. The anti-human IgE is deposited on the surface of the 10 M Hz AT-cut gold coated crystal resonator by self-assembled technique, and serves as a receptor layer. The highly ordered self-assembled monolayers (SAMs) ensure well-controlled surface structure and offer many advantages to the performance of the sensor. The fabricated Pz sensor can quantitatively detect human serum IgE in the range of 5-300 IU/ml with high precision (CV < 8%). A total of 28 patient serum samples are detected by the Pz sensor, and the results agree well with those given by two commercially provided test kits (Total IgE FAST Test, Pharmacia-CAP). The correlation coefficients are 0.94 between FAST and Pz sensor, and 0.90 between CAP and Pz sensor, respectively. After regeneration with urea and glycine buffer the coated crystal can be reused five times without appreciable loss of activity. Compared with conventional cross-linking methods, nonspecific binding caused by the SAM binding method is three to five times less.

Antigen-Antibody Reactions↗
PubMed1999

Association of ambient air-pollution levels with acute asthma exacerbation among children in Singapore.

BACKGROUND: Air-pollution levels have been shown to be associated with increased morbidity of respiratory diseases. METHODS: Data for ambient air-pollutant levels, meteorologic factors, and hospitalization or emergency room (ER) visits for acute asthma in Singapore children over a 5-year period (1990-4) were obtained and analyzed for associations by time-series methods. RESULTS: Throughout this period, the annual mean and 24-h mean levels for sulfur dioxide (SO2), nitrogen dioxide (NO2), and total suspended particles (TSP) and maximum 1-h daily average for ozone were generally within the air-quality guidelines established by the World Health Organization (WHO). However, positive correlation between levels of each of these pollutants and daily ER visits for asthma was observed in children aged 3-12 years, but not among adolescents and young adults (13-21 years old). The association with SO2 and TSP persisted after standardization for meteorologic and temporal variables. An adjusted increase in 2.9 ER visits for every 20 microg/m3 increase in atmospheric SO2 levels, lagged by 1 day, was observed on days when levels were above 68 microg/m3. With TSP, an adjusted increase of 5.80 ER visits for every 20 microg/m3 increase in its daily atmospheric levels, lagged by 1 day, was observed on days with levels above 73 microg/m3. Similar results were also obtained after controlling for autocorrelation by time-series analysis. CONCLUSIONS: These associations were observed even though the overall levels of all pollutants were generally within the air-quality guidelines established by the WHO. These findings suggest that asthmatic children are susceptible to increased levels of air pollutants, particularly SO2 and TSP, although the ambient levels are generally within "acceptable" ranges.

Acute Disease↗
PubMed1999

Sensitization to local dust-mite fauna in Singapore.

BACKGROUND: Recent studies showed the presence of a unique dust-mite fauna in the indoor environment of Singapore. Immediate hypersensitivity to these dust mites, along with other known indoor allergens, may play a role in the pathogenesis of allergic respiratory diseases. This study evaluated the sensitization rates of the local atopic population to these allergens. METHODS: The skin prick test was performed on a total of 391 individuals (289 patients with asthma and/or allergic rhinitis and 102 healthy controls) using extracts of six species of local dust mites (Austroglycyphagus malaysiensis, Blomia tropicalis, Dermatophagoides pteronyssinus, D. farinae, Sturnophagoides brasiliensis, and Tyrophagus putrescentiae) and 10 other common indoor allergens. Total serum IgE and specific IgE to these dust mites were also quantified with the fluorescence allergosorbent test (FAST). RESULTS: The sensitization rates among patients with asthma and/or allergic rhinitis to dust mites and other inhalant allergens tested (via skin prick tests) were as follow: B. tropicalis (96.2%), D. pteronyssinus (93.4%), D. farinae (92.3%), A. malaysiensis (78.2%), S. brasiliensis (71.6%), T. putrescentiae (71.3%), canary feathers (69.9%), Periplaneta americana (cockroach) (59.5%), Blattella germanica (cockroach) (56.4%), mosquito (Aedes sp.) (46.4%), dog epithelia (mixed breed) (34.3%), kapok seed (31.8%), cat hair (29.1%), Aspergillus fumigatus (20.8%), Penicillium notatum (18.0%), and Candida (Monilia) albicans (9.3%). All patients were observed to react to at least three of the six dust-mite extracts, with 254/289 (87.9%) reacting to at least five or to all six. Skin prick responses to the dust mites were found to correlate with the corresponding specific IgE levels quantified by FAST (P<0.001). In addition, specific IgE levels to D. pteronyssinus and D. farinae were highly correlated (Spearman's rank coefficient = 0.76, P<0.001), as were those to B. tropicalis and A. malaysiensis (r = 0.60, P<0.001). CONCLUSIONS: Asthma and/or allergic rhinitis patients were highly sensitized to the local dust-mite fauna. Thus, these dust mites should be considered important allergenic sources of this region.

Adolescent↗