PubMed Health⌕ Search

Biomedical subjects

H M Wong

Publications and source records attributed to H M Wong.

10 recordsLinked to original sources
PubMed2006

Association between developmental defects of enamel and different concentrations of fluoride in the public water supply.

OBJECTIVES: To compare the prevalence and severity of developmental defects of enamel (DDE) among subjects whose maxillary incisors developed during periods with different concentrations of fluoride in the public water supply. METHODS: Standardized intra-oral photographs of random samples of 12-year-old children were collected in 1983, 1991 and 2001 (n = 1,990) in Hong Kong and assessed for DDE by a trained masked examiner. The fluoride concentrations in the public water supply at the times when the enamel on their maxillary incisors developed were 1.0, 0.7 and 0.5 ppm, respectively. RESULTS: The mouth prevalence of DDE for these children (based on the maxillary incisors) were 92.1, 55.8 and 35.2% in the years 1983, 1991 and 2001, respectively (p < 0.001). Most of these children were affected by diffuse opacities (89.3% in 1983, 48.5% in 1991 and 32.4% in 2001, p < 0.001). Marked differences in the mean number of teeth affected by DDE (p < 0.001) and in the maximum extent of DDE (p <or= 0.002) between 1983, 1991 and 2001 were also observed. CONCLUSIONS: A decrease in the prevalence and severity of DDE among the maxillary incisor teeth of the children corresponded to the reductions in the concentration of fluoride in the water during the time of enamel development.

Cariostatic Agents↗
PubMed2004

Declines in tobacco brand recognition and ever-smoking rates among young children following restrictions on tobacco advertisements in Hong Kong.

BACKGROUND: We compared the recognition of tobacco brands and ever-smoking rates in young children before (1991) and after (2001) the implementation of cigarette advertising restrictions in Hong Kong and identified continuing sources of tobacco promotion exposure. METHODS: A cross-sectional survey of 824 primary school children aged from 8 to 11 (Primary classes 3-4) living in two Hong Kong districts was carried out using self-completed questionnaires examining smoking behaviour and recognition of names and logos from 18 tobacco, food, drink and other brands common in Hong Kong. RESULTS: Ever-smoking prevalence in 2001 was 3.8 per cent (1991, 7.8 per cent). Tobacco brand recognition rates ranged from 5.3 per cent (Viceroy name) to 72.8 per cent (Viceroy logo). Compared with 1991, in 2001 never-smoker children recognized fewer tobacco brand names and logos: Marlboro logo recognition rate fell by 55.3 per cent. Similar declines were also seen in ever-smoker children, with recognition of the Marlboro logo decreasing 48 per cent. Recognition rates declined amongst both boys and girls. Children from non-smoking families constituted 51 per cent (426) of the sample, whereas 34.5 per cent (284), 8.5 per cent (70), 1.7 per cent (14) and 4.4 per cent (36) of the children had one, two, three or more than three smoking family members at home, respectively. Tobacco brand recognition rates and ever-smoking prevalence were significantly higher among children with smoking family members compared with those without. Among 12 possible sources of exposure to cigarette brand names and logos, retail stalls (75.5 per cent; 622), indirect advertisements (71.5 per cent; 589) and magazines (65.3 per cent; 538) were ranked the most common. CONCLUSION: Advertising restrictions in Hong Kong have effectively decreased primary-age children's recognition of tobacco branding. However, these children remain vulnerable to branding, mostly through exposure from family smokers, point-of-sale tobacco advertisement and occasional promotions. Action to curb these is now required.

Advertising↗
PubMed2001

Practice management: observations, issues, and empirical evidence.

BACKGROUND: The primary objective of this study is to provide objective, empirical, evidence-based practice management information. This is a hitherto under-researched area of considerable interest for both the practitioner and educator. METHODS: A questionnaire eliciting a mix of structured and free text responses was administered to a random sample of 480 practitioners who are members of the American Academy of Periodontology. Potential respondents not in private practice were excluded and the next listed person substituted. RESULTS: The results provide demographic and descriptive information about some of the main issues and problems facing practice managers, central to which are information technology (IT), financial, people management, and marketing. Human resource and marketing management appear to represent the biggest challenges. CONCLUSIONS: Periodontists running practices would prefer more information, development, and support in dealing with IT, finance, marketing, and people management. The empirical evidence reported here suggests that although tailored educational programs on key management issues at both undergraduate and postgraduate levels have become ubiquitous, nevertheless some respondents seek further training opportunities. Evidence-based practice management information will be invaluable to the clinician considering strategic and marketing planning, and also for those responsible for the design and conduct of predoctoral and postdoctoral programs.

Attitude of Health Personnel↗
PubMed1999

Controlled release of human immunoglobulin G. 2. Morphological characterization.

Human immunoglobulin G (IgG) serves as an important chemotherapeutic agent for a number of immunological ailments and as a carrier in the targeted delivery of other therapeutic agents. This paper deals with the characterization of IgG-dispersed monolithic matrixes of different geometries, prepared using a nonbiodegradable polymer carrier EVAc. The morphological changes associated with the matrix during drug release was studied using scanning electron microscopy, polarizing microscopy, atomic force microscopy, and X-ray photoelectron microscopy, and the results were compared. The study answered the burst effect problem significantly and illustrated the potential of these techniques in understanding the morphological structure of matrixes and mode of release kinetics.

Delayed-Action Preparations↗
PubMed1998

Preliminary validation and reliability of the Modified Child Dental Anxiety Scale.

An 8-question Modified Child Dental Anxiety Scale was developed to assess children's concerns about specific dental procedures. These dental situations include examination, scale and polish, injection, filling, extraction, and relative and general anaesthesia. A question about how the child felt generally when visiting the dentist was also included. Children (n = 314) from two schools in Liverpool, ages 8 to 15 years, completed a questionnaire including the modified scale, Corah's Dental Anxiety Scale, the Dental Fear Survey Schedule for Children, and background questions (age, sex and previous dental experience). The internal consistency was favourable (alpha = .84) and test-retest reliability acceptable. This initial study suggests that the scale may be useful in trials to assess the benefits of interventions to assist children receive dental treatment.

Adolescent↗
PubMed1996

ELISA for the detection of serum and saliva IgA against the BMRFI gene product of Epstein-Barr virus.

The BMRF1 protein is an Epstein-Barr virus (EBV) DNA polymerase accessory protein that forms part of the early antigen diffuse (EA-D) component. An enzyme-linked immunosorbent assay (ELISA) was developed for the detection of IgA antibody to the BMRF1 protein of EBV in saliva and serum samples. The assay was shown to be specific for nasopharyngeal carcinoma (NPC) patients and, when used with saliva alone, to have a sensitivity comparable to an existing indirect immunoperoxidase assay for early antigens. The sensitivity of the assay could be significantly enhanced to 86% by the use of paired saliva and serum samples.

Antibodies, Viral↗
PubMed1995

Role of calcium in thromboxane B2-mediated injury to rabbit gastric mucosal cells.

A sustained increase in cytosolic Ca2+ can damage gastric mucosal cells. The present study has examined the role of Ca2+ in thromboxane B2 (TXB2)-mediated damage of rabbit isolated gastric mucosal cells. Cells were isolated from rabbit oxyntic mucosa by collagenase-EDTA digestion. Cell metabolic activity and cell damage were estimated by alamar blue dye absorbance and trypan blue uptake, respectively. Cellular Ca2+ was monitored by indo-1 dye fluorescence. Addition of TXB2 (10(-6) and 10(-8) M) to the cell suspension resulted in a decrease in metabolic activity, and this effect was reduced when Ca2+ was removed from the incubation medium. TXB2 addition to the incubation medium resulted in an increase in cytosolic Ca2+ and incubation of cells with the intracellular Ca2+ chelator, BAPTA-AM (20 microM), reduced cell injury in response to TXB2. Incubation of cells with the Ca2+ ionophore A23187 (1-25 microM) resulted in a dose-dependent increase in trypan blue uptake and a reduction in cell metabolism. Cell injury in response to A23187 were exacerbated by addition of TXB2 (10(-8) M) to the cell suspension. TXB2 treatment reduced cellular content of reduced glutathione (GSH), while exogenous GSH addition (10 mM) reduced TXB2-mediated cell injury. These data demonstrate that TXB2 can directly injure gastric mucosal cells. Gastric mucosal cellular damage in response to TXB2 is mediated in part by a disruption of Ca2+ homeostasis as well as a reduction in cellular GSH content.

Animals↗
PubMed1994

Reduced glutathione modulates Ca(2+)-mediated damage to rabbit isolated gastric mucosal cells.

In the present study, we have examined the role of reduced glutathione (GSH) in the modulation of Ca2+ ionophore A-23187-induced gastric mucosal cellular disruption. Experiments were conducted using cells isolated from rabbit oxyntic mucosa. Cell injury was assessed by release of the lysosomal enzyme acid phosphatase, by trypan blue dye uptake, and by examination of lipid peroxidation. Cellular GSH was assessed spectrophotometrically by measuring total soluble reduced thiol content. Ionophore A-23187 (3-25 microM) induced a concentration-dependent injury to mucosal cells and a concentration-dependent reduction in cellular GSH content. Removal of Ca2+ from the incubation medium abolished both the disruptive action and the GSH-lowering effect of A-23187. Gastric cellular GSH content was reduced significantly by preincubation of cells with an agent that depletes reduced sulfhydryls, diethyl maleate (DEM; 1 mM). Furthermore, DEM significantly augmented cellular disruption in response to A-23187. Similarly, incubation of cells with L-cysteine (1 mM), a stimulant of glutathione synthesis, increased mucosal cellular GSH content and decreased the cellular disruptive effect of A-23187. Exogenous addition of GSH to the cell suspension significantly reduced Ca2+ ionophore-induced cellular disruption and hastened the recovery of cellular free Ca2+ concentration ([Ca2+]) to baseline values. Similarly, exogenous GSH reduced cellular disruption produced by cyclopiazonic acid and thapsigargin, agents that increase intracellular [Ca2+] ([Ca2+]i) by inhibiting Ca2+ sequestration. These data suggest that a sustained increase in [Ca2+]i contributes to the pathogenesis of gastric mucosal cellular injury. This effect appears to be mediated by a reduction in the cellular content of GSH.

Animals↗
PubMed1986

Assessment of mechanistic proposals for the binding of agonists to cardiac muscarinic receptors.

N-[3H]Methylscopolamine has been used to characterize muscarinic receptors in crude homogenates prepared from hearts of Syrian golden hamsters. The Hill coefficient is one for specific binding of the radioligand itself and for its inhibition by muscarinic antagonists; markedly lower values are obtained for its inhibition by muscarinic agonists. The binding patterns of agonists have been analyzed in terms of a mixture of sites differing in affinity for the drug and reveal the following. All agonists discern at least two classes of receptor in atrial and ventricular homogenates. The number of classes and the relative size of each differ for different agonists in the same region and for the same agonist in different regions. Atrial and ventricular affinities are in good agreement for some agonists but differ for others. Guanylyl imidodiphosphate (GMP-PNP) is without effect on the specific binding of the radioligand but alters the binding of carbachol via an apparent redistribution of receptors from one class to another; the apparent affinity at either class remains unchanged. Carbachol reveals two classes of sites in ventricular preparations, and the nucleotide mediates an interconversion from higher to lower affinity; three classes are revealed in atrial preparations, and the nucleotide eliminates the sites of highest affinity with a concomitant increase in the number of sites of lowest affinity. Taken together, the data are incompatible with the notion of different, noninterconverting sites; rather, there appear to be several possible states of affinity such that the equilibrium distribution of receptors among the various states is determined by the tissue, by the agonist, and by neurohumoral modulators such as guanylyl nucleotides. The effects of agonists and GMP-PNP cannot be rationalized in terms of a ternary complex model in which the low Hill coefficients arise from a spontaneous equilibrium between receptor (R) and G protein (G) and in which agonists bind preferentially to the RG complex.

Animals↗