Search PubMed⌕ Search

Biomedical subjects

Y L Ng

Publications and source records attributed to Y L Ng.

29 records · Page 2Linked to original sources
PubMed1991

Male endocrine functions in workers with moderate exposure to lead.

Evidence for the effect of occupational exposure to lead on the male endocrine system is conflicting. This study evaluated the primary (testicular) and secondary (hypothalamo pituitary testicular) effects of exposure to lead in 122 current lead workers and 49 non-exposed workers. The mean current blood lead concentration was 35.2 (range 9.6-77.4) micrograms/dl in the exposed workers, and 8.3 (range 2.6-14.8) micrograms/dl in the non-exposed workers. Concentrations of plasma luteinising hormone (LH) and follicle stimulating hormone (FSH) were both significantly higher in the exposed workers, but testosterone (T) was not significantly different between the two groups. In older exposed workers, however (greater than or equal to 40 years), plasma T concentrations were significantly lower, but LH and FSH concentrations were not significantly different. Compared with non-exposed workers, those exposed for less than 10 years had significantly raised LH and FSH and normal T concentrations whereas those exposed for 10 or more years had significantly lower T, and normal LH and FSH concentrations. The concentrations of LH and FSH showed a moderate increase in relation to blood lead concentrations in the range of 10 micrograms/dl to 40 micrograms/dl and thereafter reached a plateau or declined. No apparent trend for plasma T concentrations occurred. No significant difference in prolactin (PRL) concentration was noted. It is concluded that moderate exposure to lead was associated in dose related fashion with small but measurable changes in male endocrine functions that reflected both primary and secondary effects of lead on the testes and the hypothalamo pituitary testicular axis.

Adolescent↗
PubMed1991

Pulmonary effects of polyvinyl chloride dust exposure on compounding workers.

Spirometry, chest radiography, environmental measurements, and a questionnaire on respiratory symptoms were used to evaluate the effects of exposure to polyvinyl chloride (PVC) dust on 171 Chinese and Malay PVC compounding workers in comparison with an unexposed reference group. Workers with high cumulative PVC dust exposure had a lower forced expiratory volume in 1 s and forced vital capacity, and a higher prevalence of radiological profusion of small opacities. Wheezing or chest tightness was also significantly more frequent in this group. Unlike previous studies, the PVC compounding workers in this study were exposed to only negligible amounts, if any, of vinyl chloride monomer or thermal degradation products of PVC such as hydrogen chloride, phosgene, or chlorine. The conclusion was drawn that a low grade of pneumoconiosis and a small degree of lung function impairment is associated with PVC dust exposure. Reversible airways obstruction is also likely and warrants further investigation.

Adult↗
PubMed1991

Diurnal variation in peak expiratory flow rate among polyvinylchloride compounding workers.

The diurnal variation in peak expiratory flow rate (PEFR) was studied in 24 mixers and 24 non-mixers in three polyvinylchloride (PVC) compounding plants and 24 non-PVC controls from a marine police workshop. The three groups (all men) were matched for age, race, and smoking. The mean respirable dust concentration (essentially PVC dust) was 1.6 mg/m3 for mixers and 0.4 mg/m3 for nonmixers. The mean diurnal variation in PEFR of the mixers was 6.5%. This was significantly higher than the 4.8% for non-mixers and 4.3% for the non-PVC controls. Six mixers had a diurnal variation of more than 15% on at least one day compared with none among the other two groups. Twenty nine per cent of mixers complained of wheezing compared with 4% of non-mixers and none among non-PVC workers. These differences were significant. Forced expiratory volume in one second (FEV1) for the mixers was 10% below the predicted values whereas that of non-PVC workers was 2% below predicted values. The study indicates a significant acute airway constriction from occupational exposure to PVC dust.

Adult↗
PubMed1991

Human xanthine oxidase antibody levels: variation between males and females in Chinese and Europeans.

Levels of antibody specific for Xanthine oxidase (XODAb) of the immunoglobulin classes IgG, IgM and IgA have been determined in the sera of blood donors of Chinese and European ethnic origin by immunoassay. No significant differences were found between the two ethnic groups. Significant differences were found in the distribution, of XODAb IgM levels between Chinese males and females and European males and females (chi 2 = 8.262, P = 0.025; chi 2 = 9.423, P = less than 0.001). Since the age range of the female blood donors is 16-49 years, it was postulated that the higher IgM XODAb levels in the females was the result of autoimmunisation by endothelial Xanthine oxidase during menstruation. A group of post-menopausal women showed significantly lower IgM XODAb levels compared to the blood donors (chi 2 = 31.748, P = less than 0.0005). IgM levels in a group of older men were also significantly lower (chi 2 = 3.895, P = less than 0.05) but the difference was much less marked. Unlike the younger males and females there was no significant difference in the distribution of XODAb IgM levels between older males and females. The results seem to support the hypothesis of menstrual auto-immunisation.

Adolescent↗
PubMed1990

The other side of the corneal endothelium.

New high-magnification biomicroscopes, the specular microscope and now the in-tandem confocal microscope, provide new images of the corneal endothelium in vivo. These are not always easy to interpret, and correlation with the morphology of the endothelium as seen in dead, fixed specimens is necessary. One such image is of the anterior surface with the confocal microscope. It exhibits a mosaic of hexagonal cells. This surface has not been specifically investigated previously in fixed preparations and the in vivo appearance does not correlate with the structure deduced from transmission electron micrographs. These indicate that the bases of endothelial cells are in the form of thin processes that would not present an image of clearly defined cell outlines. Therefore, the anterior surface of corneal endothelium stripped from ox and human corneas has been examined with the scanning electron microscope. It was found that the basal cell membranes extend processes to neighbouring cells and that some of these seem to unite. The possibility that these findings are artefactual has been examined by comparing them with published transmission and scanning electron micrographs, and it has been concluded that the processes of the basal cell membranes are real.

Animals↗
PubMed1990

Enzyme-linked immunosorbent assay for determination of antibodies to xanthine oxidase.

An enzyme-linked immunosorbent assay (ELISA) was developed to detect IgG, IgA and IgM antibodies to xanthine oxidase. The method used xanthine oxidase to coat sample wells on microtitre plates. The anti-xanthine oxidase concentrations were determined by reference to standard curves constructed by coating plates with anti-IgG, anti-IgA and anti-IgM to capture antibodies of different classes in standard human serum. The standard curves for IgG, IgA and IgM had a working range of 0 to about 60 ng/ml, and all results with commercial quality control serum fell within expected ranges. The coefficients of variation (CV) for within-batch precision (n = 30) and between-batch precision (n = 20) for IgG and IgM were about 9% and 12% respectively. The detection limit was 2 ng/ml. The ELISA was applied to assay serum samples of 110 Chinese and 110 European healthy subjects. A positively-skewed distribution in their anti-xanthine oxidase IgG and IgM levels was observed.

Antibodies↗
PubMed1975

Effect of preservation on the elasticity of human aortic valve homografts.

The elastic properties of preserved human aortic homografts after different storage times in antibiotic-nutrient medium solution have been measured. There was a definite loss of elasticity within nine months leading to a rapid decrease after a year of preservation. It is likely that satisfactory valve function depends on its elasticity, and these studies indicate that aortic valves which have been exposed to antibiotic media for more than nine months should not be used in valve replacement surgery.

Anti-Bacterial Agents↗
PubMedDate not supplied

A novel application of NMR microscopy: measurement of water diffusion inside bioadhesive bonds.

The self-diffusion coefficient of water (D) inside bioadhesive bonds formed by dry and prehydrated hydrophilic matrices has been spatially resolved using nuclear magnetic resonance (NMR) microscopy. One-dimensional profiles showing the variation of D inside bioadhesive bonds were calculated from nine diffusion-weighted profiles obtained immediately after bond formation and every 5 min for 30 min. The resulting data indicated that the hydration state of a hydrophilic matrix can significantly and dramatically influence the dynamics of water movement inside a bioadhesive bond.

Dehydration↗