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Biomedical subjects

S Corbett

Publications and source records attributed to S Corbett.

At least 19 recordsLinked to original sources
PubMed2006

Childhood asthma and return to school in Sydney, Australia.

OBJECTIVES: To describe the seasonal pattern of hospital admissions for childhood asthma in Sydney, Australia and investigate the relationship between these admissions and time of return to school. STUDY DESIGN: Time-series analysis of daily hospital admissions for childhood asthma in Sydney from 1994 to 2000. METHODS: We defined the time series of all asthma-related hospital admissions in Sydney between 1994 and 2000 for age groups 1-4 and 5-14 years. We analysed the time series for each age group using a generalized additive model with a log-link function, an offset term and quasi-likelihood estimation. Daily admissions were modelled using penalised regression splines adjusting for long term trends, school terms and holidays, weekday and influenza epidemics. RESULTS: After adjusting for potential confounding, the risk of asthma admission increased to a peak between 2 and 4 weeks after the first day of school in each term and varied between 1.5 and 3 times the risk prior to return to school for both age groups. The largest increase in asthma risk occurring in term one after the long summer holiday. The increase in admission risk began soon after the first day of school of each term for school age children 5-14 years, but not in pre-school age children 1-4 years. CONCLUSIONS: Returning to school after term holidays is strongly associated with increased risk of hospital admissions for asthma in children, especially following the long summer holiday. Preventive measures focused on return to school have the potential to substantially decrease admissions for asthma in children.

Absenteeism↗
PubMed2005

Dealing with lead in Broken Hill--trends in blood lead levels in young children 1991-2003.

The objective of the study was to investigate trends in blood lead concentrations in preschool children between 1991 and 2003, as part of the evaluation strategy of a public health lead management program in Broken Hill, Australia. Since 1991, all Broken Hill children aged 1-4 years have been offered at least annual blood lead screening as part of a community-wide lead management program. Recruitment of children was promoted throughout the period using local media and distribution of promotional material from health care centres and preschool, childcare, and educational facilities around the city. Venous blood samples were collected using standard procedures and analyses were subjected to internal and external quality control programs. Because the frequency distribution of blood lead levels are skewed, geometric rather than arithmetic means were used for comparative purposes. Trend analysis was based on age and sex standardised mean blood lead levels. The number of 1- to 4-year-old children screened ranged between 496 and 948 in any one year and response rates varied between 39% and 73%. The age-sex standardised mean blood lead level decreased from 16.3 microg/dL to 7.1 microg/dL between 1991 and 2003. Overall, blood lead levels declined by 56% over 13 years. These reductions were consistently observed irrespective of age or where a child lived in the town. The rate of decline has slowed since 1997. We conclude that substantial progress has been made in dealing with the lead problem in Broken Hill children, although the rate of decline of blood lead levels has slowed. Continued public health action is still needed to bring the proportion of young children with significantly elevated blood lead levels (>15 microg/dL) down from the 2003 figure of 12% to the NHMRC community-based target for lead in young Australians of 5%.

Child, Preschool↗
PubMed2005

Impact of ambient air pollution on birth weight in Sydney, Australia.

BACKGROUND: Studies in Asia, Europe, and the Americas have provided evidence that ambient air pollution may have an adverse effect on birth weight, although results are not consistent. METHODS: Average exposure during pregnancy to five common air pollutants was estimated for births in metropolitan Sydney between 1998 and 2000. The effects of pollutant exposure in the first, second, and third trimesters of pregnancy on risk of "small for gestational age" (SGA), and of pollutant exposure during pregnancy on birth weight were examined. RESULTS: There were 138,056 singleton births in Sydney between 1998 and 2000; 9.7% of babies (13,402) were classified as SGA. Air pollution levels in Sydney were found to be quite low. In linear regression models carbon monoxide and nitrogen dioxide concentrations in the second and third trimesters had a statistically significant adverse effect on birth weight. For a 1 part per million increase in mean carbon monoxide levels a reduction of 7 (95% CI -5 to 19) to 29 (95% CI 7 to 51) grams in birth weight was estimated. For a 1 part per billion increase in mean nitrogen dioxide levels a reduction of 1 (95% CI 0 to 2) to 34 (95% CI 24 to 43) grams in birth weight was estimated. Particulate matter (diameter less than ten microns) in the second trimester had a small statistically significant adverse effect on birth weight. For a 1 microgram per cubic metre increase in mean particulate matter levels a reduction of 4 grams (95% CI 3 to 6) in birth weight was estimated. CONCLUSION: These findings of an association between carbon monoxide, nitrogen dioxide, and particulate matter, and reduction in birth weight should be corroborated by further study.

Air Pollutants↗
PubMed2002

Validation of the NFL-225 test for predicting 1-RM bench press performance in college football players.

BACKGROUND: The purpose of this study was to evaluate the accuracy of repetitions-to-fatigue (RTF) using an absolute load of 102.3 kg (225 lbs) to estimate one-repetition maximum (1-RM) bench press performance in college football players using various prediction equations. METHODS EXPERIMENTAL DESIGN: a prospective study on the association between muscular endurance and muscular strength. PARTICIPANTS: 260 players from NCAA Division IA (n=43), IAA (n=63), II (n=129), and red-shirts (n=25) were evaluated at the conclusion of a minimum of eight weeks of heavy-resistance training during the off-season. MEASURES: all subjects performed a 1-RM bench press and RTF using an absolute load of 102.3 kg. RESULTS: The Mayhew et al. NFL-225 equation nonsignificantly overestimated 1-RM from RTF by 0.5 kg, while the Chapman et al. NFL-225 equation significantly underpredicted by 3.2 kg, although both equations were comparable in the number of players predicted within +/-4.5 kg of actual 1-RM (52% vs 51%, respectively). Only two of nine RTF equations currently in use produced predicted 1-RM values that were not significantly different from actual 1-RM performance. CONCLUSIONS: Specific NFL-225 equations are more accurate in estimating 1-RM bench press from absolute muscle endurance in college football players than previous published RTF equations. The accuracy of prediction decreases at higher repetitions.

Adolescent↗
PubMed2001

February asthma outbreaks in NSW: a case control study.

OBJECTIVES: To investigate individual factors associated with an asthma outbreak among children aged one to 14 years in Sydney in February 1999. METHODS: A case control study was undertaken with cases (n=92) defined as all children admitted to Sydney Children's Hospital for asthma in February 1999. Unmatched controls (n=76) were all children admitted for asthma in the previous three months. We obtained information by a structured telephone survey of parents. Logistic regression analyses were used to determine odds ratios for risk factors for hospital admission. RESULTS: Mean age for hospital admission of 4.7 years for cases and 4.4 years for controls. The presence of one or more siblings reduced the risk of admission during an asthma outbreak (OR=0.59, 95% CI 0.37 to 0.93). Children with older siblings aged 10 to 14 years were also less likely to be admitted (OR=0.3, 95% CI 0.12 to 0.74). An age effect was observed. Other demographic, clinical and environmental characteristics, including smoking, were not associated with admission during the outbreak. CONCLUSIONS: The main findings of this study are the protective effect of siblings and an age-dependent effect in risk of hospital admission during an asthma outbreak. These findings are consistent with an infective cause of the outbreak. IMPLICATIONS: Children without siblings, particularly older siblings, appear to be at highest risk of hospital admission during an asthma outbreak. Environmental and other factors need to be examined to further explain the episodicity of such outbreaks and to determine means of predicting and preventing future episodes.

Adolescent↗
PubMed2001

Comparison of the BacT/Alert PF pediatric FAN blood culture bottle with the standard pediatric blood culture bottle, the Pedi-BacT.

The performance of the BacT/Alert PF (Organon-Teknika Corp., Durham, N.C.), a new nonvented pediatric FAN blood culture bottle, was compared to that of the original pediatric bottle, the Pedi-BacT, with matched aerobic cultures obtained from two separate facilities. A total of 244 clinically significant isolates were recovered from 4,015 compliant pairs. Among the positive cultures, 170 (70%) isolates were detected in both the BacT/Alert PF and the Pedi-BacT bottles, while 47 (19%) isolates were recovered in the BacT/Alert PF bottle only and 27 (11%) isolates were recovered in the Pedi-BacT bottle only. Although isolation of specific microorganisms was comparable for the two bottles, the total number of organisms recovered by the BacT/Alert PF was greater than that by the Pedi-BacT (P = 0.0272). In addition, more organisms were recovered by the BacT/Alert PF bottle from the blood of patients receiving antimicrobial therapy (P = 0.0180). Overall time to detection was similar for the two bottles; however, a significantly decreased mean time to detection was recorded for yeast from the BacT/Alert PF bottle (22.9 h; P = 0.0001) and staphylococci from the Pedi-BacT bottle (22.5 h; P = 0.0056). One false-negative culture and five false-positive cultures occurred with the Pedi-BacT bottle, compared to one false-positive culture with the BacT/Alert PF bottle. The BacT/Alert PF bottle is a reliable blood culture bottle for pediatric blood culture specimens and may offer improved recovery of microbes from patients on antimicrobial therapy. The use of the nonvented bottle will both facilitate bottle processing and decrease expenditures for materials due to the elimination of the venting needles required for the original vented bottles.

Adolescent↗
PubMed1999

Investigation of a cluster of leukaemia in the Illawarra region of New South Wales, 1989-1996.

OBJECTIVES: To investigate a cluster of leukaemia among young people and assess the plausibility of a disease-exposure relationship. DESIGN: Descriptive analysis of population-based leukaemia incidence data, review of evidence related to the causation of leukaemia, assessment of environmental exposures to known leukaemogens, and resulting risks of leukaemia. SETTING: Illawarra region of New South Wales, Australia, focusing on suburbs between the Port Kembla industrial complex and Lake Illawarra (the Warrawong area). MAIN OUTCOME MEASURES: Standardised incidence ratios (SIRs) for leukaemia; current measured and past estimated ambient air benzene concentrations; and expected leukaemia cases attributable to estimates of ambient air benzene concentrations. RESULTS: In 1989-1996, 12 leukaemia cases among Warrawong residents aged less than 50 years were observed, more than the 3.49 cases expected from the rate in the rest of the Illawarra region (SIR, 343.8; 99% CI, 141.6-691.7). These people lived in suburbs immediately to the south-southwest of a coke byproducts plant (a major industrial source of benzene, one of the few known leukaemogens). The greatest excess was among 15-24-year-olds (SIR, 1085.6; 99% CI, 234.1-3072.4). In 1996, ambient air concentrations of benzene averaged less than 1 part per billion (ppb). Since 1970, ambient air concentrations of benzene were estimated to have averaged up to 3 ppb, about one-thousandth of the level at which leukaemia risk has been identified in occupational epidemiological studies. Using the risk assessment model developed by the US Environmental Protection Agency, we estimate that past benzene levels in the Warrawong area could have resulted in 0.4 additional cases of leukaemia in 1989-1996. CONCLUSIONS: The excess occurrence of leukaemia in the Warrawong area in 1989-1996 is highly unusual. Current environmental benzene exposure and the reconstructed past environmental benzene exposure level are too low to explain the large excess of leukaemia. The cause of the cluster is uncertain.

Adolescent↗
PubMed1999

Improved validated assay for the determination of mefloquine and its carboxy metabolite in plasma, serum and whole blood using solid-phase extraction and high-performance liquid chromatography.

An improved high-performance liquid chromatography method using a low silanol activity octadecylsilica column and a solid-phase extraction technique is validated for the simultaneous analysis of mefloquine and its carboxy metabolite in whole blood, plasma and serum. An octadecylsilica column with high silanol activity is compared to a column of low activity in terms of pH dependent variability of chromatographic retention times for mefloquine and its carboxy metabolite. The low silanol activity column showed a relatively large mobile phase pH range where retention times for both components are consistent. The solid-phase extraction procedure consists of a simple protein precipitation step followed by sample concentration and extraction using a C18 membrane disk. The inter- and intra-assay variability for a therapeutic concentration of mefloquine (1000 ng/ml) is less than 2% in whole blood, plasma and serum while carboxymefloquine (1000 ng/ml) is 2.3% or less. At concentrations as low as 100 ng/ml the inter-assay variability is 6.2% or less for both analytes. This method shows a robust analytical procedure for the simultaneous analysis of mefloquine and its carboxy metabolite where precise measurements are useful in pharmacokinetic studies and in estimating drug compliance.

Antimalarials↗
PubMed1998

Admission rates as an indicator of the prevalence of severe asthma in the community.

BACKGROUND: A reliable indicator of the prevalence of severe asthma in the community is needed to monitor population-based asthma control strategies. We examined the potential use of asthma admissions to hospital as such an indicator. METHODS: We recruited subjects from the Emergency Department (ED) of a children's hospital. The attending doctor completed the 'physician questionnaire' which included questions on the patient's asthma severity and interval severity/chronicity of asthma. The parent/guardian completed the 'parent questionnaire'. It included questions on demography, asthma knowledge and attitudes, asthma history and social support. We performed univariate and multiple logistic regression to determine predictors for hospital admission. RESULTS: Interval severity of asthma, pre-treatment severity of wheeze and low post-treatment pulse oximetry best predicted whether children presenting with asthma were admitted. Demographic variables, factors associated with access to health services and factors related to the asthma history and management were not significant predictors of admission. DISCUSSION: At the population level, it may be possible to utilise routine hospital admission rates as an indicator of the prevalence of severe asthma in the community, especially within the context of monitoring trends in asthma prevalence. Our study was conducted in a metropolitan tertiary paediatric hospital. The reliability of hospital admission rates as indicators of the prevalence of severe asthma in other hospital settings, in different population groups and over time remains to be established.

Adolescent↗
PubMed1998

Best estimate of the magnitude of mortality due to occupational exposure to hazardous substances.

OBJECTIVES: With a proportionate attributable risk approach, to estimate the magnitude of premature mortality induced by exposure to hazardous substances in the Australian workforce. METHODS: Estimates of the magnitude of mortality induced by exposure to hazardous substances in the Australian work-force were calculated by the proportionate attributable risk approach after careful consideration of options for methodological refinements. The main data sources used were unit mortality datasets (individual deidentified death records), and tabulations when these were unavailable. RESULTS: The estimated number of deaths that occurred in Australia each year from occupational exposure to hazardous substances was 2290; 78% of these were men. The rate of mortality attributable to occupational exposure to hazardous substances was three to four times greater in male workers than in female workers. Male (productive) person-years of life lost (PYLL) were generally eight times higher than female PYLL. Cancer was the prime cause of death, followed by renal, cardiovascular, neurological, and chronic respiratory disease. Acute toxic episodes accounted for a small proportion of mortality but yielded a much larger proportion of PYLL, reflecting the relatively young ages of those who experienced fatal effects. CONCLUSIONS: Although national estimates of the proportions of mortality attributable to occupational exposure to hazardous substances seemed to be validly derived, uncertainties remain associated with the lack of an empirical basis for derivation of proportionate risk fractions used in the calculations. The finding of an appreciable burden of mortality that is attributable to past occupational exposure to hazardous substances emphasises the necessity for occupational health and safety authorities to measure and reduce worksite exposures. There is also an incentive to encourage the construction of appropriately designed cohort studies across industries and occupational groupings so that, ultimately, risk estimates may be directly calculated and applied to total workforce data for the definitive estimation of the magnitude of harm induced by occupational exposure to hazardous substances.

Australia↗
PubMed1998

Air pollution and hospital admissions in Sydney, Australia, 1990 to 1994.

OBJECTIVES: This study examined the effects of outdoor air pollutants on daily hospital admissions in Sydney, Australia. METHODS: A time-series analysis of counts of daily hospital admissions and outdoor air pollutants (1990 to 1994) was performed, by means of Poisson regression that allowed for overdispersion and autocorrelation. RESULTS: An increase in daily maximum 1-hour concentration of nitrogen dioxide from the 10th to the 90th percentile was associated with an increase of 5.29% (95% confidence interval = 1.07, 9.68) in childhood asthma admissions and 4.60%(-0.17,9.61) in chronic obstructive pulmonary disease (COPD) admissions. A similar increase in daily maximum 1-hour particulate concentration was associated with an increase of 3.01% (-0.38, 6.52) in COPD admissions. An increase from the 10th to the 90th percentile in daily maximum 1-hour nitrogen dioxide, daily maximum 1-hour ozone, and daily mean particulate was associated with an increase in heart disease admissions among those 65 years and older of 6.71% (4.25, 9.23), 2.45% (-0.37, 5.35), and 2.82% (0.90, 4.77), respectively. Heart disease and childhood asthma were primarily associated with nitrogen dioxide; COPD was associated with both nitrogen dioxide and particulates. CONCLUSIONS: Current levels of air pollution in Sydney are associated with increased hospitalization for respiratory and heart disease.

Adolescent↗
PubMed1998

Air pollution and daily mortality in Sydney, Australia, 1989 through 1993.

OBJECTIVES: This study examined the effects of outdoor air pollutants in Sydney, Australia, on daily mortality. METHODS: Time-series analysis was performed on counts of daily mortality and major outdoor air pollutants (particulates, ozone, and nitrogen dioxide) in Sydney (1989 to 1993) with adjustment for seasonal and cyclical factors. Poisson regression was calculated with allowance for overdispersion and autocorrelation. The effects of lagging exposure by 0 to 2 days were assessed with single- and multiple-pollutant models. RESULTS: An increase in daily mean particulate concentration from the 10th to the 90th centile was associated with an increase of 2.63% (95% confidence interval 0.87 to 4.41) in all-cause mortality and 2.68% (0.25 to 5.16) in cardiovascular mortality. An increase in daily maximum 1-hour ozone concentration from the 10th to the 90th centile was associated with an increase of 2.04% (0.37 to 3.73) in all-cause mortality and 2.52% (-0.25 to 5.38) in cardiovascular mortality. An increase in the daily mean nitrogen dioxide concentration from the 10th to the 90th centile was associated with an increase of 7.71% (-0.34 to 16.40) in respiratory mortality. Multiple-pollutant models suggest that the effects of particulates and ozone on all-cause and cardiovascular mortality, and of nitrogen dioxide on respiratory mortality, are independent of the effects of the other pollutants. CONCLUSIONS: Current levels of air pollution in Sydney are associated with daily mortality.

Air Pollutants↗
PubMed1989

Legionella pneumophila grows adherent to surfaces in vitro and in situ.

Legionella pneumophila continues to play a role in both community- and nosocomially-acquired pneumonia. We investigated the ability of L pneumophila to adhere to various types of materials such as those found in the hospital air-cooling and portable water distribution systems. Through the use of a unique sampling apparatus, we were able to regularly acquire planktonic and sessile samples and determine the numbers of bacteria present in both populations, in vitro and in situ. Portions of these apparatuses could be aseptically removed for examination by scanning electron microscopy, or for the determination of the number of viable adherent L pneumophila. The number of bacteria present in each sample was determined by direct plate count, with presumptive L pneumophila colonies being positively identified by direct fluorescent antibody staining techniques. The results demonstrated that not only are legionellae capable of colonizing various metallic and nonmetallic surfaces but that they are preferentially found on surfaces. Surface-adherent bacteria may play a profound role as a reservoir of these potential pathogens in aquatic environments. Furthermore, these results suggest that any comprehensive legionella monitoring program must include not only water samples but also an examination of the adherent populations.

Air Conditioning↗
PubMed1988

A cluster of cases of lymphoma in an underground colliery.

An apparent occupational outbreak of cases of non-Hodgkin's lymphoma among the employees of an underground colliery on the NSW south coast has been investigated. The employment register of the mine recorded that 1004 men had worked at the colliery from its opening in 1946 until December 31, 1986. In this period, this cohort of men had amassed 18,818 person-years. A person-years analysis of the mortality and morbidity of cancer showed a standardized incidence ratio for non-Hodgkin's lymphoma of 3.27 (95% confidence interval [CI], 1.31-6.74) and for Hodgkin's disease of 7.27 (95% CI, 1.98-18.59). All of the cases of non-Hodgkin's lymphoma were diagnosed after 1978. An excess of cases of cancer of the salivary gland also was present (standardized incidence ratio, 10.00; 95% CI, 1.21-36.10). The method of coal extraction, the geology and chemistry of the coal-seams that were mined and the general characteristics of the work-force at the colliery are similar to those at other collieries in the region. Furthermore, an exhaustive work-place environmental study at the colliery has failed to identify any plausible carcinogenic agent to which the findings of this study can be attributed. Coal-miners previously have not been shown to be at a greater risk of developing lymphoma or related malignancies, and the region in which the mine is located has lower prevalence rates of non-Hodgkin's lymphoma and Hodgkin's disease than does New South Wales as a whole.

Age Factors↗
PubMed1982

Protein synthesis initiation factors from human HeLa cells and rabbit reticulocytes are similar: comparison of protein structure, activities, and immunochemical properties.

Five initiation factors, eIF-2, eIF-3, eIF-4A, eIF-4B, and eIF-5, were purified from human HeLa cells. Methods of protein fractionation and assays for initiation factors which had been developed for rabbit reticulocytes were found to be suitable for HeLa factors. The initiation factors from HeLa cells are similar to or indistinguishable from the corresponding rabbit reticulocyte factors with respect to specific activities, molecular weights as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and subunit structure. The molecular weight of eIF-3 particles from both species is about 410000 as determined by equilibrium sedimentation analytical centrifugation. The partial protease fragmentation patterns of corresponding proteins also are similar and indicate that the primary sequences of the factors are related in the two species. Antisera raised in goats against rabbit eIF-3 and human eIF-2, eIF-4A, and eIF-4B cross-react with the cognate factors from both species. On the basis of immunoblotting techniques, eIF-4A is highly conserved, eIF-2 alpha, eIF-3, and eIF-4B are somewhat less conserved, and eIF-2 beta is the least conserved of the proteins examined. The functional, structural, and immunological results are all consistent with the view that initiation factors from different mammalian cells are very similar.

Animals↗
PubMed1981

The purification and characterization of multiple forms of protein synthesis eukaryotic initiation factors 2, 3, and 5 from rabbit reticulocytes.

Eukaryotic initiation factors 2, 3, and 5 (eIF-2, eIF-3, and eIF-5) each were purified or fractionated into a number of forms which differ in protein mass or composition. The various factor polypeptides were analyzed by partial protease digestion and the fragmentation patterns were compared to identify proteins related in primary structure. The digestion method was made more sensitive by prior radiochemical labeling of the proteins by iodination with 125I. At least four molecular weight forms of eIF-5 were found which ranged from 168,000 to 128,000. The lower molecular weight forms, nevertheless, were biologically active in in vitro assays. Analysis of a variety of eIF-3 preparations indicates that the presence or abundance of especially the higher molecular weight subunits varies considerably. Many of these components are related to one another in primary structure; five of the subunits greater than Mr = 90,000 appear to be derived from the 210 kilodalton subunit by limited proteolysis. Analysis of eIF-2 polypeptides shows that the alpha, beta, and gamma subunits give distinctively different partial protease digestion patterns and that some preparations contain a minor component (gamma') related to the gamma subunit which could be misidentified as the beta subunit. The results indicate that initiation factors may be cleaved into different active forms by proteases acting either in the intact cell or during the factor isolation and purification. Addition of the protease inhibitor, phenylmethanesulfonyl fluoride, prevents some, but not all of the proteolysis.

Animals↗