Longitudinal study of the socio-demographic determinants of changes in body weight and waist circumference in a multi-ethnic Asian population.

OBJECTIVE: To examine the changes in weight and waist circumference of adult Singaporeans between 1998 and 2005-2007, and the associations of these changes with demographic and socio-economic factors. METHODOLOGY: A prospective study, which followed up participants aged 18-69 years from the 1998 National Health Survey. Analysis was performed on data from 2483 individuals (53% of original sample) who returned for follow-up in 2005-2007. Body weight and waist circumference were measured both at baseline and follow-up. Logistic regression was used to examine factors associated with being overweight and obese at baseline. Linear regression was used to examine changes in weight and waist circumference over time. The variables examined were age, gender, ethnicity, marital status, educational level, housing and employment status, smoking, alcohol consumption and sports activities. RESULTS: Mean weight for the population increased over the follow-up period by 1.48 kg (s.d.=4.95) and mean waist circumference increased by 3.32 cm (s.d.=7.92). Cross-sectionally, those who were overweight or obese were more likely to be Malays or Indians, married, homemakers and have lower educational level. Prospectively, individuals who gained the most weight were younger, more likely to be ethnic minority groups and have the lowest body mass index (BMI) at baseline. They also appeared to be of higher socio-economic status (SES) based on housing type. These associations were statistically significant even after adjusting for other variables. CONCLUSION: Obesity prevention should start early in the younger age. Preventive programs need to reach out to Malay and Indian ethnic groups and those with higher SES. These findings should be used in designing messaging of preventive strategies.

Educational inequalities associated with health-related behaviours in the adult population of Singapore.

INTRODUCTION: Socioeconomic differences in health-related behaviours have been widely studied in the Western populations, but are seldom considered in Asian populations. We examined the effect of education attainment on health-related behaviours (physical activity, cigarette smoking and alcohol consumption) among non-institutionalised Singaporeans aged 18-69 years. METHODS: We used data from the Singapore National Health Survey 2004. Information on physical activity, cigarette smoking, alcohol consumption and sociodemographic characteristics was collected from 4,084 adults. Age-adjusted prevalence of the three health-related behaviours by educational attainment was calculated by the direct method. Logistic regression models, adjusted for age, gender, ethnic group and employment status, were used to estimate the odds ratio and 95% confidence interval, in order to study the prevalence of health-related behaviours according to educational attainment. RESULTS: The prevalence of physical inactivity, daily smoking and regular alcohol consumption was found to be consistently highest among men and women with the least education. Prevalence of physical inactivity and smoking was inversely related to educational attainment for both genders. However, no clear gradient was found between education and alcohol consumption for men and women. CONCLUSION: Less-educated Singaporeans were more likely to smoke daily, drink alcohol regularly or not to exercise regularly. Health promotion policies or programmes aimed at encouraging healthy lifestyles in the Singapore population should take into account the educational inequalities in these health-related behaviours.

Changes in the levels of major cardiovascular risk factors in the multi-ethnic population in Singapore after 12 years of a national non-communicable disease intervention programme.

INTRODUCTION: The National Healthy Lifestyle Programme, a population-wide non-communicable disease intervention programme, was started in 1992. A National Health Survey is carried out every six years to evaluate the impact of this programme on the cardiovascular risk factor profile of the resident population of Singapore. METHODS: The 2004 National Health Survey (NHS 04) was a population-based survey carried out over a period of four months from September to December 2004. A combination of disproportionate stratified sampling and systematic sampling was used to select a representative sample (n=7,078) for the survey. The reference population comprised 2.4 million multi-racial Singaporeans aged 18-69 years. Anthropometric and blood pressure measurements were carried out on all subjects and blood samples were taken for biochemical analysis. The results were compared with those of a similar survey conducted in 1998. RESULTS: A total of 4,084 Singapore residents took part in the survey, giving a response rate of 57.7 percent. The age-standardised prevalence of hypertension (greater than or equal to 140/90 mmHg) in Singapore residents aged 30-69 years decreased from 28.0 percent in 1998 to 24.0 percent (p-value is less than 0.001) in 2004. The prevalence of high total cholesterol (greater than or equal to 6.2 mmol/L) among those aged 18-69 years fell from 26.0 percent in 1998 to 18.1 percent (p-value is less than 0.001) in 2004. The prevalence of diabetes mellitus in residents aged 18-69 years in 2004 was 7.8 percent, compared to the 1998 level of 9.5 percent (p-value is less than 0.01). The level of obesity (body mass index is greater than or equal to 30 kg/sqm) increased slightly from 6.2 percent in 1998 to 6.8 percent (p-value equals 0.1627). The prevalence of daily smoking decreased from 15.0 percent in 1998 to 12.5 percent in 2004 (p-value is less than 0.001), while that of regular exercise increased from 17.0 percent to 25.0 percent (p-value is less than 0.001). Ethnic differences in the prevalence of diabetes mellitus, hypertension, hypercholesterolaemia, and exercise were observed. CONCLUSION: The NHS 04 results suggest that the National Healthy Lifestyle Programme significantly decreased daily smoking, high blood cholesterol and hypertension, and increased regular exercise over 1998 levels. The results also suggest that the programme stabilised the prevalence of obesity and diabetes mellitus.

Group IIA secretory phospholipase A2 stimulates exocytosis and neurotransmitter release in pheochromocytoma-12 cells and cultured rat hippocampal neurons.

Recent evidence shows that secretory phospholipase A2 (sPLA2) may play a role in membrane fusion and fission, and may thus affect neurotransmission. The present study therefore aimed to elucidate the effects of sPLA2 on vesicle exocytosis. External application of group IIA sPLA2 (purified crotoxin subunit B or purified human synovial sPLA2) caused an immediate increase in exocytosis and neurotransmitter release in pheochromocytoma-12 (PC12) cells, detected by carbon fiber electrodes placed near the cells, or by changes in membrane capacitance of the cells. EGTA and a specific inhibitor of sPLA2 activity, 12-epi-scalaradial, abolished the increase in neurotransmitter release, indicating that the effect of sPLA2 was dependent on calcium and sPLA2 enzymatic activity. A similar increase in neurotransmitter release was also observed in hippocampal neurons after external application of sPLA2, as detected by changes in membrane capacitance of the neurons. In contrast to external application, internal application of sPLA2 to PC12 cells and neurons produced blockade of neurotransmitter release. Our recent studies showed high levels of sPLA2 activity in the normal rat hippocampus, medulla oblongata and cerebral neocortex. The sPLA2 activity in the hippocampus was significantly increased, after kainate-induced neuronal injury. The observed effects of sPLA2 on neurotransmitter release in this study may therefore have a physiological, as well as a pathological role.

Secretory phospholipase A2 activity in the normal and kainate injected rat brain, and inhibition by a peptide derived from python serum.

The present study aimed to elucidate sPLA(2) activity in the normal and kainate-lesioned hippocampus using selective inhibitors of sPLA(2). In normal rats the highest levels of sPLA(2) were observed in the hippocampus, pons, and medulla, followed by the cerebral neocortex and caudate nucleus. After intracerebroventricular kainate injections an increase in total PLA(2) activity was observed in the rat hippocampus. Using a selective sPLA(2) inhibitor 12-epi-scalaradial, sPLA(2) activity was found to be significantly increased by 2.5-fold on the side of the intracerebroventricular injection compared to the contralateral side. A peptide P-NT.II, derived from the amino acid sequence of "PLA(2)-inhibitory protein," discovered in the serum of the reticulated python, also showed potent sPLA(2) inhibitory activity in homogenates from the kainate-injected hippocampus. These results show that there is a high level of sPLA(2) activity in the normal hippocampus, pons, and medulla oblongata, and that the level increases further in the hippocampus after kainate-induced excitotoxic injury. The increased PLA(2) activity was inhibited by P-NT.II, indicating a potential use of this peptide as a PLA(2) inhibitory agent in the brain.

Seroprevalence of IgG antibodies against Chlamydia pneumoniae in Chinese, Malays and Asian Indians in Singapore.

BACKGROUND: Chlamydia pneumoniae, a bacterium that causes respiratory infections, is probably under-diagnosed. There is also interest in its possible role in the aetiology of coronary heart disease. This is the first population-based seroprevalence survey of C. pneumoniae infection in Singapore. METHODS: A random sample of 1,068 people aged 18-69 years was selected from the participants of the Singapore National Health Survey conducted in 1998. Sera and data on certain clinical measurements and conditions had been collected. IgG antibodies for C. pneumoniae were detected using an indirect microimmunofluorescence test and positivity graded. Seropositivity was defined as IgG titre >/=1:16. RESULTS: There were no statistically significant differences in the prevalence rates of seropositivity to C. pneumoniae for age group 18-69 years among the three ethnic groups, i.e. Chinese (males 76.7%, females 68.3%), Malays (males 75.4%, females 59.1%), and Asian Indians (males 74.6%, females 59.4%). The seropositivity rate for people aged 18-69 years in Singapore was 75.0% for males and 65.5% for females (difference of 9.5%, P < 0.001). In both genders combined, seropositivity increased from 46.5% in the age group 18-29 to reach a plateau of 78.9% in the age group 40-49, which remained stable to 60-69 years. There was no association of seropositivity with smoking, diabetes mellitus, hypertension or body mass index after adjustment for age and gender. CONCLUSION: The high prevalence rates in our study population and the higher rate in males compared to females are consistent with studies from other parts of the world. No significant difference in prevalence rates was observed among Chinese, Malays and Indians. The pattern of rising and levelling off of seropositivity with age suggests that C. pneumoniae infection occurs early in life, and in older ages the high level of seropositivity is probably maintained by re-infections or chronic infections. Chlamydia pneumoniae infection was not found to be associated with the cardiovascular risk factors examined.

Multiple phosphorylation sites in RGS16 differentially modulate its GAP activity.

Regulators of G-protein signaling (RGS) are GTPase-activating proteins (GAP) for activated Galpha subunits. We found that mouse RGS16, when expressed in HEK293T cells, is phosphorylated constitutively at serine 194 based on in vivo orthophosphate labeling experiments, while serine 53 is phosphorylated in a ligand-dependent manner upon stimulation by epinephrine in cells expressing the alpha2A adrenergic receptor. Phosphorylation on both sites impairs its GAP activity and subsequent attenuation on heterotrimeric G-protein-stimulated extracellular signal-regulated protein kinase activity. This is the first report of RGS functional downregulation by phosphorylation via a G-protein-coupled receptor.

The effects of seagrass (Zostera japonica) canopy structure on associated fauna: a study using artificial seagrass units and sampling of natural beds.

The importance of seagrass canopy to associated fauna was assessed by comparing the species richness, abundance and diversity of the epi- and infaunal macroinvertebrate assemblages in a seagrass (Zostera japonica Ascherson and Graebner) bed and the adjacent unvegetated area in Hong Kong. Seagrass cover had significant effects on the composition and abundance of the associated fauna and the amount of detritus accumulated on the sediment surface. Detritus abundance was significantly higher in the seagrass bed, and was positively correlated with both the above- and belowground biomass of Z. japonica. Both the abundance and species richness of the epi- and infauna were significantly positively correlated with the belowground biomass of the seagrass and detritus standing crop. Macrofaunal species richness was higher (118) in the seagrass bed than the adjacent unvegetated areas (70), with a higher degree of similarity between the infauna than the epifauna of the two habitats. While all species recorded from the unvegetated areas were found in the seagrass bed, 48 species occurred only in the seagrass-covered areas. Species richness of epifauna was significantly higher in the seagrass bed, but there was no difference between infaunal species of the two habitats. On the contrary, faunal (epi- and infauna) abundance was significantly higher in seagrass areas. The seagrass bed also supported species of small tellinid bivalves previously not recorded from Hong Kong. Artificial seagrass units (ASUs, 0.2 m(2)) with four combinations of leaf density and leaf length and a control (bare sand) were placed at short distances from natural patches of Z. japonica. The composition, abundance and biomass of the epibenthos associated with the ASUs and the control were recorded after 3 months in the field. While species richness did not differ among the treatments, total abundance of epibenthos was significantly higher in the high density-long leaves (HL) treatment than in the control. Results of a discriminant analysis using log-transformed abundance data suggest that the gastropod Clithon oualaniensis, the mussel Musculista senhousia and the crab Thalamita sp. were important species distinguishing the assemblages in the various treatments. All the three species were significantly more abundant in the HL treatment than in the low density-short leaves (LS) treatment and the control. By contrast, there was no significant difference in the biomass of the epifauna, but discriminant analysis again separated the five treatments based on the composition of the biomass, with the same three species identified as the most important discriminating species. The species richness and abundance of the epifauna associated with the ASUs were similar to the adjacent unvegetated areas, but significantly lower than in the Zostera patches. The physical canopy structure of Z. japonica beds increased the abundance of the epibenthos, potentially through provision of canopy and indirectly through trapping of detritus.

Hepatitis B Seroprevalence Study 1999.

Hepatitis B is a disease of public health importance in Singapore. A study was conducted in 1999 to estimate the overall and gender-, age- and ethnic-specific prevalence of hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg) and antibody to hepatitis B surface antigen in the Singapore population. A cross-sectional sample of the Singapore population constituting 4,698 Singapore residents aged 18-69 years was surveyed. This was the first time a large-scale study has been conducted to assess the hepatitis B seroprevalence rates in the Singapore population. The overall prevalence of the HBsAg in the general population was estimated to be about 4%. About 13% of the HBsAg carriers were also HBeAg positive. Only about 40% of the population had immunity to hepatitis B virus either through immunisation or from previous exposure to the virus. There was still a large proportion (60%) of the population who had no immunity, especially the younger age group of 18-29 years where only 28% had immunity. There is a need to strengthen the hepatitis B immunisation programme to reach out to those who have no immunity, especially the young adults.

Specific induction of RGS16 (regulator of G-protein signalling 16) mRNA by protein kinase C in CEM leukaemia cells is mediated via tumour necrosis factor alpha in a calcium-sensitive manner.

The RGS (regulator of G-protein signalling) proteins are GTPase-activating proteins for activated Galpha subunits. We investigated the effects of protein kinase C (PKC) on RGS proteins in various T cell lines by treating them with PMA. mRNA levels of both RGS16 and tumour necrosis factor alpha (TNFalpha) were found to be up-regulated in CEM leukaemia cells in a PKC-dependent manner. Mezerein, a non-phorbol-ester activator of PKC, also elevated RGS16 and TNFalpha mRNA levels, while the specific PKC inhibitor Go6983 abrogated their expression. In view of the slower kinetics of PMA-induced RGS16 expression and the tight correlation between TNFalpha and RGS16 mRNA induction among the cell lines studied, we suggest that activation of PKC up-regulates RGS16 via TNFalpha. Indeed, addition of recombinant TNFalpha to CEM cells rapidly stimulated RGS16 mRNA expression independently of PKC. Furthermore, mobilization of calcium by A23187 and thapsigargin blocked the TNFalpha-mediated induction of RGS16, which was reversed by EGTA and by the immunosuppressants FK506 and cyclosporin A, suggesting that the calcineurin/NF-AT (nuclear factor of activated T cells) pathway may repress the up-regulation process. Our results demonstrate for the first time that activation of PKC induces RGS16 expression via TNFalpha in a calcium-sensitive manner, thereby implicating RGS16 in the regulation of T cell responses to inflammation.

Analysis of agonist function at fusion proteins between the IP prostanoid receptor and cognate, unnatural and chimaeric G-proteins.

Direct measures of G-protein activation based on guanine nucleotide exchange and hydrolysis are frequently impossible to monitor for receptors which interact predominantly with G(s)alpha. An isolated FLAG (Asp-Tyr-Lys-Asp-Asp-Asp-Asp-Lys)-epitope-tagged human IP prostanoid receptor and fusion proteins generated between this form of the receptor and the alpha subunits of its cognate G-protein G(s), G(i1), a G-protein which it fails to activate in co-expression studies, and a chimaeric G(i1)-G(s)6 (a form of G(i1) in which the C-terminal six amino acids were replaced with the equivalent sequence of G(s)) were stably expressed in HEK293 cells. These were detected by [(3)H]ligand-binding studies and by immunoblotting with both an anti-FLAG antibody and with appropriate antisera to the G-proteins. Each construct displayed similar affinity to bind the agonist iloprost. Iloprost stimulated adenylate cyclase activity in clones expressing both IP prostanoid receptor and the IP prostanoid receptor-G(s)alpha fusion protein, and both constructs were shown to interact with and activate endogenously expressed G(s)alpha. Addition of iloprost to membranes of cells expressing the isolated receptor resulted in a small stimulation of high-affinity GTPase activity. Iloprost produced no stimulation of GTPase activity which could be attributed to the IP prostanoid receptor-G(i1)alpha fusion. However, the fusion proteins containing either G(s)alpha or G(i1)-G(s)6alpha produced substantially greater stimulation of GTPase activity than the isolated IP prostanoid receptor. Treatment of cells expressing the IP prostanoid receptor-G(i1)-G(s)6alpha fusion protein with a combination of cholera and pertussis toxins allowed direct measurement of agonist activation of the receptor-linked G-protein. Normalization of such results for levels of expression of the IP prostanoid receptor constructs demonstrated a 5-fold higher stimulation of GTPase activity when using the G(s)alpha-containing fusion protein and a 9-fold improvement when using the fusion protein containing G(i1)-G(s)6alpha to detect G-protein activation compared with expression of the isolated receptor.

Selective activation of a chimeric Gi1/Gs G protein alpha subunit by the human IP prostanoid receptor: analysis using agonist stimulation of high affinity GTPase activity and [35S]guanosine-5'-O-(3-thio)triphosphate binding.

A FLAG-tagged form of the human IP prostanoid receptor was expressed stably in HEK 293 cells. This bound [3H]iloprost with high affinity and stimulated cAMP production when exposed to agonist. Iloprost produced weak stimulation of GTPase activity and [35S]guanosine-5'-O-(3-thio)triphosphate binding in membranes of these cells. Pretreatment of cells with pertussis toxin did not modify iloprost-mediated stimulation, but this was blocked by cholera toxin. The effects of iloprost were not increased by coexpression of either Gsalpha or Gi1alpha. In contrast, coexpression of a chimeric G protein alpha subunit in which the carboxyl-terminal six amino acids of Gi1alpha were altered to those of Gsalpha resulted in robust stimulation by iloprost. Because the chimeric G protein alpha subunit (Gi1/Gs6alpha) is not a substrate for either pertussis or cholera toxin, pretreatment of cells coexpressing the IP prostanoid receptor and Gi1/Gs6alpha with a mixture of these toxins resulted in resolution of the signal derived from activation of the chimeric G protein. Agonist-stimulated [35S]guanosine-5'-O-(3-thio)triphosphate binding and GTPase activity assays are the most commonly used strategies to examine interactions between G protein-coupled receptors and G proteins. These usually are not appropriate for receptors such as the IP prostanoid receptor that interact with G proteins with low rates of guanine nucleotide exchange and hydrolysis. Chimeric G proteins such as Gi1/Gs6alpha that allow appropriate receptor contacts to be converted to the higher nucleotide turnover rates typical of the Gi family G proteins can overcome this and offer a novel means to examine agonist function at such receptors.

Characterization of protein complexes formed on the repressor elements of the human tumor necrosis factor alpha gene.

Human tumor necrosis factor alpha (TNF-alpha) is an important cytokine responsible for pleiotropic effects in vivo. The expression of TNF-alpha is under both positive and negative regulation. Previously we showed that a 108 bp region (-280 to -172) in the TNF-alpha promoter represses TNF-alpha transcription in U937 cells. We also demonstrated that a smaller region of the promoter spanning base pairs -254 and -230 is sufficient for repressor function. This 25 bp TNF-alpha repressor site (TRS) contains a 10 bp sequence homologous to the binding site of activator protein AP-2, yet it does not bind the AP-2 protein. In this study, we demonstrate that this 10 bp core sequence is an essential element for the repressor function of the TRS. Using gel retardation analysis with the 108 bp repressor element and the TRS as probes, multiple specific DNA binding complexes have been identified from U937 nuclear extracts. The complexes B, C, and D on the 108 bp probe and the three major complexes on the 25 bp TRS probe are also present in Jurkat and Mono Mac 6 cells, and their abundance in these cell lines seems to correlate with their postulated repressor function. We have demonstrated that the major TRS binding proteins, with estimated MWs of 30-60 kD, copurify on a heparin agarose column and on a DNA affinity column conjugated with the 10 bp core sequence.

An evaluation of ultraviolet radiation personnel hazards from selected 400-watt high intensity discharge lamps.

A study of selected mercury and multi-vapor lamps, commonly used for working environment illumination, was underta ken to evaluate the scope of the ultraviolet personnel hazards one may expect under various operating conditions of the lamps. Spectral irradiance measurements were made for operating conditions with and without reflector-type luminaires, glass covers on luminaries and outer glass bulbs on the lamps.

An evaluation of fluorescent light sources for use in phototherapy of neonatal jaundice.

An evaluation of fluorescent lamps for use in the phototherapy of neonatal jaundice was undertaken by making spectral irradiance measurements of each lamp. Conclusions are drawn on the usefulness of current methods of measuring exposure dose to radiation from the lamps. UV hazards from the lamps are evaluated.