Effects of storage time on stability of salivary immunoglobulin A and lysozyme

BACKGROUND: In many research settings, storage of samples prior to analysis is unavoidable. This study investigates the effects of storage time on stability of salivary immunoglobulin A (IgA) and lysozyme. METHODS: Saliva samples were obtained from 30 healthy adults. Each sample was divided into five aliquots and stored at -30 degrees C until analysis. The samples were measured for IgA and lysozyme concentrations after 1, 2, 3, 8 and 12 months of storage using enzyme-linked immunosorbent assay. RESULTS: There was a decline in the concentrations of IgA and lysozyme with increasing storage time. Repeated measures analyses for both salivary IgA and lysozyme showed a significant difference after 8 months of storage as compared to the 1st month (p<0.05). IgA levels decreased significantly with % change in majority of the samples >10% after storage for 8 months or more. A similar pattern was observed for lysozyme with % change in majority of the samples >14% levels when the samples were assayed at 8th month and beyond (mean% change+/-S.D.>14%). CONCLUSION: Salivary IgA and lysozyme concentrations remain stable for up to 3 months when stored at -30 degrees C. These findings have important implications with regard to measurement validity of salivary biomarkers research.     

Postural stability and neurobehavioural effects of heat exhaustion among adult men

The medical complications of heat disorders, including haematological, cardiovascular and renal damage, have been well documented. However, very little has been written on its neurological complications. The objective of this study was to assess the effects of heat exhaustion on postural stability and neurobehavioral functions of men. The study is prospective in design and spans a 3-year period. All soldiers who were diagnosed to have heat exhaustion (cases) from 1 March 1998 to 31 August 1998 were included in the study. For each case, a healthy soldier (matched for age, ethnicity, years of education and military vocation) was recruited to serve as control. Each subject had a neurobehavioral assessment by using the Swedish Performance Evaluation System (SPES), a computerized test battery. The postural stability of the subjects was assessed using a computerized postural sway system. Findings for 37 heat exhaustion cases and 37 controls revealed that cases had a significantly higher prevalence of neurasthenia symptoms compared to the controls. There were significant (small) differences between the cases and controls in the neurobehavioral tests of choice reaction time, digit span and some parts of colour word stress and logical series measures. Postural stability in the cases was significantly poorer when in the “eyes-closed” condition, compared with the controls. Men with heat exhaustion, studied 2 weeks after the acute episode, had significantly more symptoms of neurasthenia, poorer performance in short-term memory and slower reaction time. The cases (as a group) had significantly poorer postural stability.     

Outdoor work and the risk of pterygia: a case-control study

Aim: To investigate the relationship between outdoor work and pterygium formation in a hospital-based case-control study in Singapore. Method: Sixty-one patients with pterygium (49 males, mean age 54.2 years) and 125 controls (41 males, mean age 50.2 years), excluding patients with cataract and age-related macular degeneration presenting at outpatient clinics of the Singapore National Eye Centre were interviewed face-to-face with a standard questionnaire. Demographic data and information on outdoor work and eye protection, were collected. Results: Thirty-eight subjects (20.4%) were outdoor workers and 148 (79.6%) were indoor workers. Outdoor workers were more likely to be male smokers and alcohol drinkers with lower family income and higher sunlight exposure than indoor workers. The crude odds ratio for pterygiumin outdoor workers was 7.0 (95% confidence interval 3.2, 15.3). The adjusted odds ratio was 4.2 (95% confidence interval 1.7, 10.1). Conclusion: There is a statistically significant association between outdoor work and pterygium formation, which may be related to the higher exposure to sunlight and dust in outdoor workers. Efforts may be made to educate outdoor workers to wear proper equipment to protect their eyes against excessive sunlight. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of 2-ethoxyethylacetate menstrual patterns of workers exposed to low levels of 2-ethoxyethylacetate (EGEEA)

The objectives of this study were to determine the exposure levels among workers who handle 2-ethoxyethylacetate (EGEEA) in the liquid crystal display (LCD) manufacturing industry and to study the menstrual patterns among the exposed workers compared to a referent group of workers. A total of 52 female exposed workers and 55 referents was studied. Detailed menstrual histories were obtained by personal interview using a structured questionnaire. All the exposed had individual 8-hour personal monitoring for EGEEA in the environment and start-of-shift and end-of-shift urine analysis for EGEEA concentration. The geometric mean end-of-shift urine EGEEA concentration was 0.16 mg/g creatinine. End-of-shift urine EGEEA was well correlated with the air concentration; r = 0.81 [p < 0.0001]. No significant differences were observed between the exposed and referent groups for duration of each menstrual cycle (period), duration (days) of the menses, and the amount of flow, even after adjusting for possible confounders viz. age, years of education, use of oral contraceptive pills, age at menarche, gravidity, and race. The workers in the LCD manufacturing industry were exposed to a mean TWA of 0.51 ppm of EGEEA. At this concentration, the findings did not reveal any significant difference between the menstrual patterns of the exposed and referent subjects. Am. J. Ind. Med. 31:148–152, 1997. © 1997 Wiley-Liss, Inc.     

Prevalence of respiratory symptoms in children and air quality by village in rural Indonesia

AIM: This study compared prevalence of respiratory symptoms in three Indonesian villages and related this to air quality. METHODS: We interviewed caregivers of 382 children, using the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire, and monitored air quality during the survey period. RESULTS: Respiratory symptom prevalence was highest in Kerinci (40.5%), followed by SP7 (33.3%) and Pelalawan (19.8%). Compared with Pelalawan, adjusted odds ratios were 3.17 (95% confidence interval, 1.43-7.07) for Kerinci, and 2.03 (1.04-3.96) for SP7. Ambient air quality levels were highest in Kerinci for PM10 and hydrocarbon (means: 102.9 microg/m3, 10.5 microg/m3), followed by SP7 (73.7 microg/m3, 6.3 microg/m3) and Pelalawan (26.1 microg/m3, 4.7 microg/m3). CONCLUSIONS: The higher prevalence of respiratory symptoms in Kerinci and SP7 could be the result of higher PM10 and hydrocarbon levels in these locations.     

Impairment of color vision among workers exposed to low concentrations of styrene

A field study was conducted among 21 male workers exposed to styrene of concentration below 30 ppm in a fiber-reinforced plastic boat manufacturing plant. Twenty-one male workers with similar age groupings, years of education, and social and occupational state served as referents. The mean end-of-shift urinary mandelic acid (MA) and phenylglycoxylic acid (PGA) for the exposed workers were 84 mg/g creatinine and 66 mg/g creatinine, respectively. The Lanthony D-15 Hue Desaturated Panel was used to evaluate color discrimination of the exposed and referent groups. The results of the test were expressed as total color difference score (TCDS). The exposed workers' mean TCDS (a higher score denotes poorer color discrimination ability) was significantly (p < 0.0006) higher than the referents'. Neurobehavioral tests were also conducted, using the World Health Organization's Neurobehavioral Core Test Battery (NCTB). All the results of the NCTB were poorer for the exposed than for the referents. However, significant differences were observed only for Digit Span, Digit Symbol, and Benton Visual Retention tests. These results suggest that low exposure to styrene could affect some psychometric performance and may impair color vision.