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Gazzola M.,University of Quebec | Henry C.,University of Quebec | Couture C.,University of Quebec | Marsolais D.,University of Quebec | And 5 more authors.
Respiratory Physiology and Neurobiology | Year: 2016

Studying airway smooth muscle (ASM) in conditions that emulate the in vivo environment within which the bronchi normally operate may provide important clues regarding its elusive physiological function. The present study examines the effect of lengthening and shortening of ASM on tension development in human bronchial segments. ASM from each bronchial segment was set at a length approximating in situ length (Linsitu). Bronchial tension was then measured during a slow cyclical strain (0.004 Hz, from 0.7 Linsitu to 1.3 Linsitu) in the relaxed state and at graded levels of activation by methacholine. In all cases, tension was greater at longer ASM lengths, and greater during lengthening than shortening. The threshold of methacholine concentration that was required for ASM to account for bronchial tension across the entire range of ASM lengths tested was on average smaller by 2.8 logs during lengthening than during shortening. The length-dependency of ASM tension, together with this lower threshold of methacholine concentration during lengthening versus shortening, suggest that ASM has a greater ability to resist airway dilation during lung inflation than to narrow the airways during lung deflation. More than serving to narrow the airway, as has long been thought, these data suggest that the main function of ASM contraction is to limit airway wall distension during lung inflation. © 2016 Elsevier B.V. Source


Pereira G.,University of Western Australia | Pereira G.,Cooperative Research Center for Asthma | Nassar N.,University of Western Australia | Nassar N.,University of Sydney | And 3 more authors.
Australian and New Zealand Journal of Public Health | Year: 2011

Background: This study, in a region with relatively low industrial activity, used a highly specific marker for traffic emissions, accounted for the inherent fetal growth potential, and used complete record linkage of births, midwife notifications, deaths, hospital morbidity and birth defect records. Methods: Clinical records were obtained for pregnancies between 2000 and 2006 in three areas of Perth, Western Australia (n=3,501). We used carbon monoxide as a marker for locally derived traffic emissions, and assessed exposure using the AusRoads dispersion model. Fetal growth was characterised by proportion of optimal birth weight and investigated using multivariate mixed-effects regression. Results: Exposure in the third trimester was associated with a -0.49% (sd=0.23%) change in proportion of optimal birth weight per 10 μg/m3 increase in locally derived traffic emissions. However, this result was confined to one of the three study areas due to elevated exposure misclassification among women in the other two areas. Among this group, a neonate who would have otherwise attained an optimal birth weight of 3.5 kg would be expected to be born 58 g lighter for an interquartile increase in third trimester exposure, which was approximately half of the effect observed for maternal smoking during pregnancy. Conclusion: We observed an association between maternal exposure to traffic emissions and reduced fetal growth. This effect was supported by sensitivity analyses but only observed in one of the three study areas. Further studies are required to corroborate our results. Source


Pereira G.,University of Western Australia | Pereira G.,Cooperative Research Center for Asthma | Cook A.,University of Western Australia | Cook A.,Cooperative Research Center for Asthma | And 4 more authors.
American Journal of Obstetrics and Gynecology | Year: 2012

We sought to investigate seasonal variation in fetal growth, accounting for important sociodemographic, biological, and environmental exposures. Records of births 1998 through 2006 in Perth, Western Australia were obtained (N = 147,357). We investigated small for gestational age and sex and the proportion of optimal birthweight (POBW) in relation to seasonal exposures (season, temperature, sunlight) by trimester of pregnancy. Adjustment was made for a wide range of risk factors. The POBW for neonates with third trimesters predominantly in summer was 0.18% (0.00-0.36%) lower than for those in winter. POBW decreased by 0.14% (0.01-0.27%) per interquartile range increase in third-trimester temperature (9.15°C). An interquartile range increase in temperature over pregnancy (0.73°C) was associated with an odds ratio of 1.02 (95% confidence interval, 1.001.05) for small for gestational age and sex. Reduced fetal growth was associated with elevated ambient temperatures throughout and late in pregnancy, independently of air pollution and other risk factors. Source


Almqvist C.,Karolinska Institutet | Almqvist C.,Woolcock Institute of Medical Research | Garden F.,Woolcock Institute of Medical Research | Kemp A.S.,Childrens Hospital | And 9 more authors.
Paediatric and Perinatal Epidemiology | Year: 2010

Variation in the observed association between pet ownership and allergic disease may be attributable to selection bias and confounding. The aim of this study was to suggest a method to assess disease-related modification of exposure and second to examine how cat acquisition or dog ownership in early life affects atopy and asthma at 5 years. Information on sociodemographic factors and cat and dog ownership was collected longitudinally in an initially cat-free Australian birth cohort based on children with a family history of asthma. At age 5 years, 516 children were assessed for wheezing, and 488 for sensitisation. Data showed that by age 5 years, 82 children had acquired a cat. Early manifestations of allergic disease did not foreshadow a reduced rate of subsequent acquisition of a cat. Independent risk factors for acquiring a cat were exposure to tobacco smoke at home odds ratio (OR) 1.92 95% confidence interval (CI) 1.13, 3.26, maternal education ≤12 years OR 1.95 1.08, 3.51 and dog ownership OR 2.23 1.23, 4.05 Cat or dog exposure in the first 5 years was associated with a decreased risk of any allergen sensitisation, OR 0.50 0.28, 0.88 but no association with wheeze OR 0.96 0.57, 1.61 This risk was not affected by age at which the cat was acquired or whether the pet was kept in- or outdoors. In conclusion, cat or dog ownership reduced the risk of subsequent atopy in this high-risk birth cohort. This cannot be explained by disease-related modification of exposure. Public health recommendations on the effect of cat and dog ownership should be based on birth cohort studies where possible selection bias has been taken into account. © 2010 Blackwell Publishing Ltd. Source


Drysdale M.,Queens University | Drysdale M.,Golder Associates | Bjorklund K.L.,University of Western Australia | Bjorklund K.L.,Cooperative Research Center for Asthma | And 6 more authors.
Environmental Geochemistry and Health | Year: 2012

Simulated lung fluids are solutions designed to mimic the composition of human interstitial lung fluid as closely as possible. Analysis of mineral dusts using such solutions has been used to evaluate the respiratory bioaccessibility of various elements for which solubility in the lungs is a primary determinant of reactivity. The objective of this study was to employ simulated lung fluid analysis to investigate the respiratory bioaccessibility of nickel in soils. Current occupational guidelines in Australia regulate nickel compounds in terms of water solubility, though this may not be an accurate estimation of the total nickel that will dissociate in the lungs. Surface soils were collected from the city of Kalgoorlie in Western Australia, the site of an operational nickel smelter and metal mining activities. The fraction of the samples less than 10 μm was extracted from the soil, and it was this sub-10-μm fraction that was found to hold most of the total nickel present in the soil. The fine fraction was analyzed using a simulated lung fluid (modified Gamble's solution) to isolate the nickel phases soluble in the lungs. In addition, a sequential extraction was employed to compare the bioaccessible fraction to those dissolved from different binding forms in the soil. In all samples, the simulated lung fluid extracted more nickel than the two weakest leaches of the sequential extraction combined, providing a more representative nickel bioaccessibility value than the current water leach method. © 2011 Springer Science+Business Media B.V. Source

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