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Biomedical subjects

S C Wong

Publications and source records attributed to S C Wong.

At least 19 recordsLinked to original sources
PubMed2007

Biochemical severity of thyroid ectopia in congenital hypothyroidism demonstrates sexual dimorphism.

BACKGROUND: A recent study suggested that sexual dimorphism affects initial thyroid function in congenital hypothyroidism (CH) but differs according to aetiology of CH. AIMS: To determine if sexual dimorphism was associated with biochemical severity of CH and its aetiology in our large British population. METHODS: We examined retrospectively the initial thyroid function tests of 140 infants diagnosed with CH from screening. All infants underwent Tc-pertechnetate radionuclide scans at diagnosis to establish the aetiology of CH prior to commencement of treatment. Patients were classified into athyreosis, ectopia and presumed dyshormonogenesis on the basis of thyroid scans. A comparison of males and females were made within the three aetiological groups for gestational age, birth weight, initial dose of levothyroxine (LT4), screening TSH, confirmatory plasma thyroxine (T4), confirmatory plasma TSH and age of TSH suppression. RESULTS: There was no significant difference between sexes for gestation, birth weight and initial treatment dose in all aetiological subgroups. In thyroid ectopia, screening TSH and confirmatory plasma TSH were significantly higher in females compared with males (P < 0.01), while confirmatory plasma T4 were significantly lower in females (P < 0.05). No difference was detected between males and females in athyreosis and dyshormonogenesis subgroups for screening TSH, confirmatory plasma TSH and total T4. CONCLUSION: Sexual dimorphism influenced the biochemical severity of thyroid ectopia in congenital hypothyroidism in our British population. However, this effect was not apparent in patients with athyreosis or dyshormonogenesis. Further advances in the molecular genetics of CH are essential to evaluate this phenomenon further.

Choristoma↗
PubMed2006

Essence of conservation forms in the traveling wave solutions of higher-order traffic flow models.

This paper shows the essence of conservation forms when applying the weak solution theory to solve the traveling wave solution of a wide cluster in the Payne-Whitham (PW) model. The consideration of the conservation form for the acceleration equation is an important ingredient in the development of higher-order traffic flow models, but it is largely ignored in the research community. To fix the idea, we define two conservation forms for the same PW model, and consequently derive two solutions with different sets of characteristic parameters of the wide cluster. The analytical results are in good agreement with those that are obtained from numerical simulations. Moreover, these two solutions are also shown to be asymptotic to those of the well-known Kühne and Kerner-Konhaüser models with a viscosity term. More importantly, the careful treatment of the conservation form for the acceleration equation closes the important gap in the literature. Without the conservation form, the solution obtained depends very much on the design of numerical schemes, and can be quite arbitrary and may not adequately conform to the physically relevant properties.

Journal Article↗
PubMed2006

Association between setting quantified road safety targets and road fatality reduction.

Since the 1980s, many countries have set quantified road safety targets as part of their comprehensive road safety strategies. This paper studies the association between the setting of quantified road safety targets and road fatality reduction over the past two decades. Both aggregate and disaggregate levels of hypothesis tests are performed on data from 14 countries that set road safety targets during the period 1981-1999. A before-and-after analysis of the treatment and comparison groups is conducted, and the results show that the majority of countries with quantified road safety targets experienced a reduction in road fatalities in this period. Overall, the establishment of quantified road safety targets is found to have an appreciable association with an improvement in road safety.

Accidents, Traffic↗
PubMed2006

The role of pro-inflammatory cytokines in inflammatory bowel disease growth retardation.

Childhood inflammatory bowel disease (IBD) especially those with Crohn disease is commonly complicated by faltering growth and pubertal delay. Pro-inflammatory cytokines are often elevated in IBD and may affect linear growth and puberty either systemically or at the level of the growth plate. Further study of the underlying mechanisms of the deleterious effects of cytokines on the growth plate may improve management of faltering growth in childhood IBD. Well-controlled clinical studies of the respective effect of nutritional support, immunomodulatory therapy, biological agents and growth and puberty promoting agents on managing faltering growth also require further attention.

Adolescent↗
PubMed2006

Cytokine actions in growth disorders associated with pediatric chronic inflammatory diseases (review).

Growth disorders are commonly observed in children suffering from chronic inflammatory diseases such as Juvenile Idiopathic Arthritis (JIA) and Inflammatory Bowel Disease (IBD). These disorders range from general growth retardation to local acceleration of growth in the affected limb and are associated with the increased production of pro-inflammatory cytokines. In this article, we review how cytokines influence child growth by exerting a local effect at the level of the growth plate, and through systemic effects throughout the whole body.

Arthritis, Juvenile↗
PubMed2005

High-resolution numerical approximation of traffic flow problems with variable lanes and free-flow velocities.

This paper develops macroscopic traffic flow models for a highway section with variable lanes and free-flow velocities, that involve spatially varying flux functions. To address this complex physical property, we develop a Riemann solver that derives the exact flux values at the interface of the Riemann problem. Based on this solver, we formulate Godunov-type numerical schemes to solve the traffic flow models. Numerical examples that simulate the traffic flow around a bottleneck that arises from a drop in traffic capacity on the highway section are given to illustrate the efficiency of these schemes.

Journal Article↗
PubMed2005

Would relaxing speed limits aggravate safety? A case study of Hong Kong.

This paper studies the effect of the changed speed limits on accident counts for major roadways in the urban environment of Hong Kong. In 1999-2002, the speed limits of a number of sections of roadway were reviewed and increased. Nineteen of them were major roadways. Their speed limits were raised by 10-20 km/h from 50 to 70 km/h. Before and after studies were carried out to investigate the changes in accident counts with respect to the set of carefully chosen comparison groups. Qualification tests for these comparison groups were conducted to confirm their suitability for the studies. In the majority of the treatment sites, the accident counts were worse after the increase in speed limits, both for the category of fatal, serious and slight (FSS) accidents, and for the category of fatal and serious (FS) accidents. Overall, the relaxation of the speed limit from 50 to 70 km/h increased the FSS accident counts by 15% and the FS accident counts by 1%. The relaxation of the speed limit from 70 to 80 km/h increased the FSS accident counts by 18% and the FS accident counts by 36%.

Accidents, Traffic↗
PubMed2005

Celecoxib induces dose dependent growth inhibition in nasopharyngeal carcinoma cell lines independent of cyclooxygenase-2 expression.

Celecoxib is a cyclooxygenase-2 (COX-2) selective non-steroidal anti-inflammatory drug (NSAID) which has been shown to be capable of inhibiting the growth of various cancer cell lines. However, studies of its effect on the growth of nasopharyngeal carcinoma (NPC) cells are scarce. In this study, we investigated the effect of celecoxib on cell growth using three NPC cell lines: HK-1, Hone-1 and CNE-2. Our results showed that while all 3 cell lines expressed the COX-2 mRNA as determined by reverse transcription-polymerise chain reaction (RT-PCR), western blot analysis showed that only HK-1 expressed the COX-2 protein. Using MTT assay, celecoxib was found to inhibit growth in all 3 cell lines in a dose dependent manner. The IC(50) of celecoxib were 41.04 +/- 1.22, 49.68 +/- 1.12 and 51.74 +/- 3.89 microM for CNE-2, Hone-1 and HK-1 cells, respectively. This growth inhibitory effect was found to be independent of the cell line's COX-2 protein expression level of the cells lines. In HK-1 cells, the expression of the cell cycle regulatory protein, cyclin D1, was down regulated by incubation with 80 microM celecoxib for 24 hrs.

Blotting, Western↗
PubMed2004

Multivariate analysis on factors affecting suppression of thyroid-stimulating hormone in treated congenital hypothyroidism.

AIMS: To determine the factors which influence the suppression of thyroid-stimulating hormone (TSH) in infants with congenital hypothyroidism (CH) following treatment. METHODS: We examined retrospectively the patterns of thyroid function tests from diagnosis to 3 years of age in 140 infants diagnosed with CH from screening. Patients were classified into 3 groups: athyreosis, ectopia and presumed dyshormonogenesis on the basis of thyroid scans. Adequate TSH suppression was defined as plasma TSH concentration <6 mU/l. The factors affecting the suppression of TSH at 6 months and 1 year of age which were evaluated were: initial confirmatory plasma TSH, initial plasma thyroxine (T4), mean age of starting treatment with L-T4, dose of L-T4 at diagnosis, 6 weeks, 3 months and 6 months, and aetiology of the congenital hypothyroidism. Variables were then entered in a stepwise logistic regression model for TSH suppression at 6 months and 1 year of age. RESULTS: All infants had radionuclide scans prior to treatment: athyreosis (n = 39), ectopia (n = 78) and dyshormonogenesis (n = 23). 58% of patients had persistently raised TSH at 6 months of age while 31% of patients had a persistently raised TSH at 1 year of age. There was a significant delay in the normalisation of plasma TSH in athyreosis and ectopia groups compared with dyshormonogenesis. Multiple regression analysis for TSH suppression at 6 months of age found plasma T4 levels and aetiology of CH as independent factors affecting the timing of TSH suppression. Aetiology of CH was the only independent factor affecting TSH suppression at 1 year of age. CONCLUSION: At 6 months of age, plasma T4 levels at 6 weeks and 3 months, and aetiology of CH were independent factors affecting timing of TSH suppression. However, by 1 year of age, the aetiology of CH was the only independent factor affecting suppression of TSH.

Child, Preschool↗
PubMed2004

A qualitative assessment methodology for road safety policy strategies.

This paper proposes a qualitative assessment methodology that is comprised of a cluster analysis and an autoregression analysis that assess the effects of various road safety strategies implemented in Hong Kong over the last 10 years. The cluster analysis is first used to group over a hundred road safety projects and programs into a smaller set of meaningful road safety policy strategy clusters. These strategies, together with the trend factor, seasonal pattern, car crashworthiness and meteorological data are then used in the autoregression analysis to relate to the fatality and casualty rates of drivers, passengers, motorcyclists, and pedestrians. This method allows the evaluation of the overall effects of the road safety strategies, and the effects and relative significance of each individual strategy. The evaluation method is described, and the main findings of the study are discussed.

Accident Prevention↗
PubMed2004

Lead contamination and isotope signatures in the urban environment of Hong Kong.

The source and the extent of Pb pollution in the urban environment of Hong Kong were investigated at five different urban settings selected on the basis of their annual average daily traffic (AADT) varying from less than 100 to 61,700. In addition, a small distant island without any traffic was selected to establish the possible baseline values. The surface environmental samples studied consisted of street and tunnel dusts, gully sediments, and a limited number of roadside topsoils. The analytical results clearly indicated variable degrees of Pb contamination in these urban settings. However, the level of contamination varied significantly among different types of samples collected at the same location. Pb concentrations of roadside topsoils (79+/-22 micrograms/g) and gully sediments (278+/-88 micrograms/g) were lower than those of the corresponding road dusts (327+/-54 micrograms/g). The Pb isotope compositions in different urban settings varied considerably. The bedrock in the small island had the lowest Pb concentration (12 micrograms/g) but with the highest 206Pb/207Pb ratio (1.2206), whereas the tunnel ceiling dusts with the highest level of Pb (1410 micrograms/g) had the lowest 206Pb/207Pb ratio (1.1062). Despite the significant differences in vehicle types and traffic volumes, and the presence of several different petroleum retailers in Hong Kong, the Pb isotope ratios of road dusts (206Pb/207Pb: 1.1553+/-0.0043, 208Pb/207Pb: 2.4408+/-0.0084) varied within a relatively narrow range among all the five urban sampling sites. On the other hand, the Pb isotopic compositions of gully sediments (206Pb/207Pb: 1.1515+/-0.0145, 208Pb/207Pb: 2.4322+/-0.0198) varied noticeably within the same setting, but were reasonably comparable across the different study sites. In general, the 206Pb/207Pb ratios of road dusts can be used to estimate the direct contribution from automobile emissions, whereas those of gully sediments might reflect the effects of the mixing of different anthropogenic sources. The Pb isotope signatures in the urban environment of Hong Kong clearly suggested that anthropogenic Pb in the environment originated from Pb ore with a low 206Pb/207Pb ratio (such as the Australian Pb ore and similar sources in Southeast Asia) were significantly different from those of the anthropogenic Pb present in the neighboring Pearl River Delta (PRD) region.

Air Pollutants↗
PubMed2004

Children with congenital hypothyroidism are at risk of adult obesity due to early adiposity rebound.

OBJECTIVE: There is some evidence that children with congenital hypothyroidism (CH) are heavier than their reference population. There are few data on adults with CH. The timing of adiposity rebound (AR) in childhood has been shown to have strong correlations with adult obesity. Our aims were to study the timing of AR and factors affecting AR in children with CH. PATIENTS AND METHODS: The timing of AR was examined in a retrospective study of children with CH with growth data at least up to 5 years of age. The proportion of children with CH who reached AR by 37 months and by 49 months of age were compared with healthy children and children with acute lymphoblastic leukaemia (ALL) described in the literature. Correlation of timing of AR with body mass index (BMI) standard deviation score (SDS) at 10 years, initial severity of hypothyroidism and age at normalization of TSH were examined. Multiple logistic regression was used to identify independent factors associated with BMI > or = 20 (overweight) at 10 years of age. RESULTS: The study included 53 children (34 females and 19 males). AR had occurred by 37 months in 37.7% children with CH, in 42.7% children treated for ALL (CH vs. ALL, P = 0.58) and in 4.5% healthy British children (CH vs. normal, P < 0.0001). We found that 54.7% children with CH had reached AR compared with 21.4% of normal children (CH vs. normal, P < 0.0001) by the age of 49 months. Timing of AR showed significant negative correlation with BMI SDS at 10 years (r = -0.487, P = 0.01). There were no significant relationships between timing of AR and initial thyroid function or age at normalization of TSH. Multiple logistic regression analysis identified age at AR as an independent factor associated with BMI > or = 20 at 10 years of age (P = 0.04). CONCLUSIONS: Children with CH showed significantly earlier AR compared to normal British children. This showed significant negative correlation with BMI SDS at 10 years. AR in CH does not appear to be directly related to the initial severity of hypothyroidism or to treatment factors.

Age of Onset↗
PubMed2003

Recharging cationic DNA complexes with highly charged polyanions for in vitro and in vivo gene delivery.

The intravenous delivery of plasmid DNA complexed with either cationic lipids (CL) or polyethyleneimine (PEI) enables high levels of foreign gene expression in lung. However, these cationic DNA complexes cause substantial toxicity. The present study found that the inclusion of polyacrylic acid (pAA) with DNA/polycation and DNA/CL complexes prevented the serum inhibition of the transfection complexes in cultured cells. The mechanism mediating this increase seems to involve both particle size enlargement due to flocculation and electrostatic shielding from opsonizing serum proteins. The use of pAA also increased the levels of lung expression in mice in vivo substantially above the levels achieved with just binary complexes of DNA and linear PEI (lPEI) or CL and reduced their toxicity. Also, the use of a "chaser" injection of pAA 30 min after injection of the ternary DNA/lPEI/pAA complexes further aided this effort to reduce toxicity while not affecting foreign gene expression. By optimizing the amount of pAA, lPEI, and DNA within the ternary complexes and using the "chaser" injection, substantial levels of lung expression were obtained while avoiding adverse effects in lung or liver. These developments will aid the use of cationic DNA complexes in animals and for eventual human gene therapy.

Acrylic Resins↗
PubMed2002

Heavy metals in agricultural soils of the Pearl River Delta, South China.

There is a growing public concern over the potential accumulation of heavy metals in agricultural soils in China owing to rapid urban and industrial development and increasing reliance on agrochemicals in the last several decades. Excessive accumulation of heavy metals in agricultural soils may not only result in environmental contamination, but elevated heavy metal uptake by crops may also affect food quality and safety. The present study is aimed at studying heavy metal concentrations of crop, paddy and natural soils in the Pearl River Delta, one of the most developed regions in China. In addition, some selected soil samples were analyzed for chemical partitioning of Co, Cu, Pb and Zn. The Pb isotopic composition of the extracted solutions was also determined. The analytical results indicated that the crop, paddy and natural soils in many sampling sites were enriched with Cd and Pb. Furthermore, heavy metal enrichment was most significant in the crop soils, which might be attributed to the use of agrochemicals. Flooding of the paddy soils and subsequent dissolution of Mn oxides may cause the loss of Cd and Co through leaching and percolation, resulting in low Cd and Co concentrations of the paddy soils. The chemical partitioning patterns of Pb, Zn and Cu indicated that Pb was largely associated with the Fe-Mn oxide and residual fractions, while Zn was predominantly found in the residual phase. A significant percent fraction of Cu was bound in the organic/sulphide and residual phases. Based on the 206Pb/207Pb ratios of the five fractions, it was evident that some of the soils were enriched with anthropogenic Pb, such as industrial and automobile Pb. The strong associations between anthropogenic Pb and the Fe-Mn oxide and organic/sulphide phases suggested that anthropogenic Pb was relatively stable after deposition in soils.

Agriculture↗