Sources, variability and parameterizations of intra-city factors obtained from dispersion-normalized multi-time resolution factor analyses of PM2.5 in an urban environment

Ambient fine particulate matter (PM_2.5) data of similar continuously monitored species at two air monitoring sites with different characteristics within the City of Toronto were used to gauge the intra-city variations in the PM composition over a largely concurrent period spanning two years. One location was <8 m from the side of a major highway while the other was an urban background location. For the first time, multi-time resolution factor analysis was applied to dispersion-normalized concentrations to identify and quantify source contributions while reducing the influence of local meteorology. These factors were particulate sulphate (pSO4), particulate nitrate (pNO3), secondary organic aerosols (SOA), crustal matter (CrM) that were common to both sites, a hydrocarbon-like organic matter (HOM) exclusive to the urban background site, three black carbon related factors (BC, BC-HOM at the highway site, and a brown carbon rich factor (BC-BrC) at the urban background site), biomass burning organic matter (BBOM) and brake dust (BD) factors exclusive to the highway site. The PM_2.5 composition was different between these two locations, over only a 10 km distance. The sum of SOA, pSO4 and pNO3 at the urban background site averaged 57% of the PM_2.5 mass while the same species represented 43% of the average PM_2.5 mass at the highway site. Local or site-specific factors may be of greater interest for control policy design. Thus, regression analyses with potential explanatory, site-specific variables were performed for results from the highway site. Three model approaches were explored: multiple linear regression (MLR), regression with a generalized reduced gradient (GRG) algorithm, and a generalized additive model (GAM). GAM gave the largest fraction of variance for the locally-found factors at the highway site. Heavy-duty vehicles were most important for explaining the black carbon (BC and BC-HOM) factors. Light-duty vehicles were dominant for the brake dust (BD) factor. The auxiliary modelling for the local factors showed that the traffic-related factors likely originated along the main roadways at their respective sites while the more regional factors, - pSO4, pNO3, SOA, - had sources that were both regional and local in origin and with contributions that varied seasonally. These results will be useful in understanding ambient particulate matter sources on a city scale that will support air quality management planning.

Syk mediates airway contractility independent of leukocyte function

BACKGROUND

Syk, an immune regulatory tyrosine kinase, plays a role in inflammatory disease processes. We recently reported a role for epithelial expression of Syk in the airways hyper-responsiveness in response to air pollution in a mouse model of asthma. The aim of this study was to further investigate the role of Syk in airway contractility in response to methacholine (MCh) and particulate matter (PM) air pollutants, in the absence of underlying inflammation.

METHODS

We used Syk(flox/flox) //rosa26CreER(T) (2) conditional Syk knockout mice to evaluate respiratory mechanics and MCh responsiveness following PM exposure in vivo using the ventilator-based flexiVent system.

RESULTS

While total and differential cell counts in bronchoalveolar lavage fluid were similar between the Syk(flox/flox) and Syk(del/del) mice, central airways respiratory resistance (RN ) to MCh was significantly augmented following PM exposure between Syk-intact (Syk(flox/flox) ) and Syk-deficient (Syk(del/del) ) mice (RN (max) : 2.06 ± 0.29 vs. 1.29 ± 0.10, respectively; p < 0.05, n = 8-10/group). We employed live videomicroscopy to investigate changes in airway luminal diameter using ex vivo lung slices, which were devoid of circulating leukocytes. MCh reduced the airway luminal area of Syk(flox/flox) mice to 81.1 ± 1.4% of baseline, which was virtually abrogated in Syk(del/del) mice (luminal area = 93.2 ± 0.5%, n = 5/group, p < 0.05). In response to PM exposure, Syk(flox/flox) airways contracted to 73.8 ± 2.7% of baseline luminal diameter, whereas Syk(del/del) airways exhibited minimal contractility to PM and MCh (90.0 ± 1.3% of baseline, n = 5/group, p < 0.05).

CONCLUSIONS

These observations suggest that Syk mediates airway contractility in the normal and allergic airways, independent of its role and function in leukocytes, and supports a paracrine role for airway epithelial Syk in modulating airway smooth muscle activity.

Air pollution and the development of posttransplant chronic lung allograft dysfunction

Chronic lung allograft dysfunction (CLAD) is the leading cause of mortality following lung transplantation. We conducted a retrospective cohort study including 397 bilateral lung recipients transplanted in from 1996 to 2009 to determine the association between ambient air pollution, CLAD and mortality. Pollution exposure was assessed using satellite-based estimates of nitrogen dioxide, distance to major roadway and total length of roadways around a patient's home. Cumulative exposures to ozone and particulate matter were estimated from concentrations measured at fixed-site stations near patients' homes using inverse distance weighted interpolation. Cox proportional hazards models were used to estimate the associations of CLAD with air pollution exposure, adjusting for various individual and neighborhood characteristics. During the follow-up, 185 patients developed CLAD (47%) and 101 patients died (25%). Fifty-four deaths (53%) were due to CLAD. We observed an association between CLAD development and road density within 200 m of a patient's home (HR 1.30 [95% CI 1.07-1.58]). Although based on a subgroup of 14 patients, living within 100 m of a highway was associated with a high risk for developing CLAD (HR 4.91 [95% CI 2.22, 10.87]). These data suggest that exposure to traffic-related air pollution is associated with development of CLAD among lung transplant recipients.

Particle dose estimation from frying in residential settings

Fumes produced during frying have been implicated as a potential cause for the increased incidence of adenocarcinoma. Particulate matter exposure has also been linked with other pulmonary and coronary disease. This study investigated the contribution of frying in residential settings to ultrafine and fine particulate matter (UFP, PM2.5, respectively) exposure in homes. Production rates of 44 +/- 26 particles (pt)/cm3 s (mean +/- standard deviation) and 0.13 +/- 0.12 microg/m3 s were found for UFP and PM2.5, respectively, from frying a variety of foods at medium heat in a loft-style apartment. Rates of 290 +/- 150 pt/cm3 s and 3.5 +/- 4.9 microg/m3 s were found for UFP and PM2.5, respectively, from frying with vegetable oil alone in five homes; the higher rates were ascribed to differences between the homes rather than the absence of food. The elimination of UFP and PM2.5 was found to be primarily through exhaust fans in these homes, and it was found to follow a first-order process with an elimination rate constant of 6.1 x 10(-4) +/- 2.5 x 10(-4) s(-1). The dose to an individual from frying was estimated based on the measured production and elimination rates and found to be significant when compared with the typical daily dose incurred within a home because of outside sources.

PRACTICAL IMPLICATIONS

The contribution of indoor sources to particulate matter exposure in homes remains poorly understood. Yet common household activities such as frying may produce substantial concentrations of potentially toxic particles. Because of the potential adverse health impacts associated with exposure to air pollution, potentially vulnerable individuals may be advised to remain indoors at certain times so as to reduce their overall exposure. Such interventions can be negated without proper guidance regarding the exposure involved in various indoor activities such as cooking. This paper outlines a methodology to estimate the dose to particulate matter incurred during frying and shows that this can represent a significant source of daily exposure.

Full pedigree quantitative trait locus analysis in commercial pigs using variance components

In commercial livestock populations, QTL detection methods often use existing half-sib family structures and ignore additional relationships within and between families. We reanalyzed the data from a large QTL confirmation experiment with 10 pig lines and 10 chromosome regions using identity-by-descent (IBD) scores and variance component analyses. The IBD scores were obtained using a Monte Carlo Markov Chain method, as implemented in the LOKI software, and were used to model a putative QTL in a mixed animal model. The analyses revealed 61 QTL at a nominal 5% level (out of 650 tests). Twenty-seven QTL mapped to areas where QTL have been reported, and eight of these exceeded the threshold to claim confirmed linkage (P < 0.01). Forty-two of the putative QTL were detected previously using half-sib analyses, whereas 46 QTL previously identified by half-sib analyses could not be confirmed using the variance component approach. Some of the differences could be traced back to the underlying assumptions between the two methods. Using a deterministic approach to estimate IBD scores on a subset of the data gave very similar results to LOKI. We have demonstrated the feasibility of applying variance component QTL analysis to a large amount of data, equivalent to a genome scan. In many situations, the deterministic IBD approach offers a fast alternative to LOKI.

Identification of quantitative trait loci for production traits in commercial pig populations

The aim of this study was to investigate methods for detecting QTL in outbred commercial pig populations. Several QTL for back fat and growth rate, previously detected in experimental resource populations, were examined for segregation in 10 different populations. Two hundred trait-by-population-by-chromosome tests were performed, resulting in 20 tests being significant at the 5% level. In addition, 53 QTL tests for 11 meat quality traits were declared significant, using a subset of the populations. These results show that a considerable amount of phenotypic variance observed in these populations can be explained by major alleles segregating at several of the loci described. Thus, despite a relatively strong selection pressure for growth and back fat traits in these populations, these alleles have not yet reached fixation. The approaches used here demonstrate that it is possible to verify segregation of QTL in commercial populations by limited genotyping of a selection of informative animals. Such verified QTL may be directly exploited in marker-assisted selection (MAS) programs in commercial populations and their molecular basis may be revealed by positional candidate cloning.

Comparison between urban Toronto PM and selected materials: aerosol characterization using laser ablation/ionization mass spectrometry (LAMS)

Laser ablation/ionization mass spectrometry (LAMS) of particulate matter (PM) was undertaken on-line in order to extend and contrast PM characterization. Qualitative on-line LAMS results for certified materials and Toronto source materials demonstrated the versatility and limitations of the technique. The observation of organic and inorganic components of certified materials verified the proper working condition of the in-house on-line LAMS. Organic and inorganic components of Toronto source materials were also observed with the on-line LAMS. Common components identified from both types of materials were Na, Al, Ca, Fe, and K. Other recognized components were compared with marker elements reported for some common PM emission sources. An in-house off-line LAMS was used to analyze urban Toronto PM deposited on glass substrates, while the on-line LAMS analyzed individual urban Toronto PM particles that were introduced directly into the instrument. Scanning electron microscopy (SEM), X-ray spectrometry and inductively coupled plasma atomic emission spectrometry (ICP-AES) were used for confirmatory purposes. Organic and inorganic components of urban Toronto PM at their typical ng/m3 concentrations were successfully observed in mass spectra using both off-line LAMS and on-line LAMS. Identified ions unique to each analyzed material were compared to identified ions of urban Toronto PM. The ability of LAMS to analyze individual respirable PM particles (viz. < 2 microns), both for inorganic trace elements and for organic components, greatly extended our capability to characterize PM and also to achieve estimates of concentration contributions of each material.

Phosphorylation of cysteine string protein by protein kinase A. Implications for the modulation of exocytosis

Cyclic AMP-dependent protein kinase (PKA) enhances regulated exocytosis in neurons and most other secretory cells. To explore the molecular basis of this effect, known exocytotic proteins were screened for PKA substrates. Both cysteine string protein (CSP) and soluble NSF attachment protein-alpha (alpha-SNAP) were phosphorylated by PKA in vitro, but immunoprecipitation of cellular alpha-SNAP failed to detect (32)P incorporation. In contrast, endogenous CSP was phosphorylated in synaptosomes, PC12 cells, and chromaffin cells. In-gel kinase assays confirmed PKA to be a cellular CSP kinase, with phosphorylation occurring on Ser(10). PKA phosphorylation of CSP reduced its binding to syntaxin by 10-fold but had little effect on its interaction with HSC70 or G-protein subunits. Furthermore, an in vivo role for Ser(10) phosphorylation at a late stage of exocytosis is suggested by analysis of chromaffin cells transfected with wild type or non-phosphorylatable mutant CSP. We propose that PKA phosphorylation of CSP could modulate the exocytotic machinery, by selectively altering its availability for protein-protein interactions.

A direct inhibitory role for the Rab3-specific effector, Noc2, in Ca2+-regulated exocytosis in neuroendocrine cells

Rab proteins comprise a family of GTPases, conserved from yeast to mammals, which are integral components of membrane trafficking pathways. Rab3A is a neural/neuroendocrine-specific member of the Rab family involved in Ca(2+) -regulated exocytosis, where it functions in an inhibitory capacity controlling recruitment of secretory vesicles into a releasable pool at the plasma membrane. The effector by which Rab3A exerts its inhibitory effect is unclear as the Rab3A effectors Rabphilin and RIM have been excluded from for this role. One putative Rab3A effector in dense-core granule exocytosis is the cytosolic zinc finger protein, Noc2. We have established that overexpression of Noc2 in PC12 cells has a direct inhibitory effect upon Ca(2+)-triggered exocytosis in permeabilized cells. We demonstrate specific nucleotide-dependent binding of Noc2 to Rab3A and show that the inhibition of exocytosis is dependent upon this interaction since Rab3A binding-deficient mutants of Noc2 do not inhibit exocytosis. We propose that Noc2 may be a negative effector for Rab3A in regulated exocytosis of dense-core granules from endocrine cells.

Modulation of neurotransmitter release by dihydropyridine-sensitive calcium channels involves tyrosine phosphorylation

Cultured rat cerebellar granule cells depolarized by high KCl, display a large component of Ca2+ influx through L-type voltage-dependent Ca2+ channels as defined by a sensitivity to 1 microM nifedipine. This Ca2+ influx is not coupled to neurotransmitter exocytosis but has implications for neuronal development. KCl stimulation in the absence of external Ca2+ followed by the readdition of Ca2+ allows the coupling of a class of L-type Ca2+ channels to neurotransmitter exocytosis as assessed by loading of glutamatergic pools with [3H]-D-aspartate. KCl stimulation in the absence of external Ca2+ ('predepolarization') enhances tyrosine phosphorylation of several cellular proteins, and inhibitors of tyrosine kinases block both phosphorylation and the neurotransmitter release coupled to the L-type Ca2+ channel. More specifically, an inhibitor of src family tyrosine kinases, PP1, blocks the effects of predepolarization suggesting a role for a src family kinase in the process. Furthermore, L-type Ca2+ channel recruitment and modulation of release could be activated with the tyrosine phosphatase inhibitor sodium orthovanadate. The phosphoproteins enhanced by predepolarization, which include the cytoskeletal proteins focal adhesion kinase (FAK) and vinculin, are also highly phosphorylated early on in culture when neurite outgrowth occurs. As the neurons develop a network of neurites, both tyrosine phosphorylation and L-type Ca2+ channel activity decrease. These results show a novel mechanism for the recruitment of L-type Ca2+ channels and their coupling to neurotransmitter release which involves tyrosine phosphorylation. This phenomenon has a role in cerebellar granule cell development.

Measurement of PM10/2.5 fractionated respirable particles in urban Toronto by INAA, PIXE, ICP-AES, and LAMS. A comparison

The chemical analysis of urban Toronto airborne particulate matter (PM), size segregated into respirable PM10/2.5, is presented. The characterization of PM by use of proton-induced X-ray emission analysis (PIXE), and inductively coupled plasma-atomic emission spectrometry revealed elemental information; a newer laser ablation-ionization mass spectrometry approach has the potential to expand the chemical information from PM by analyzing both the inorganic and organic species. These PM analytical approaches will be continued in the future for studying (1) emission source identification, (2) inhalation health hazards, and (3) urban smog chemistry.

The Fate of Elements in Residential Composters

An investigation into the fate of elements during residential composting was conducted by studying an Envirocycle residential-type aerobic composter unit that was set up and operated at the University of Toronto's greenhouse facility. Source materials consisting of various fruits and vegetables were combined with Metropolitan Toronto Works Department's finished leaf compost (MWFLC), and composted over a 2-month period. Instrumental neutron activation analysis (INAA) was used to determine the concentrations of Al, As, Ba, Ca, Co, Cr, Fe, K, Mg, Mn, Na, Sb, Sr, Ti, V, and Zn in the source materials and the 2-month greenhouse finished compost (GHFC). Results indicate that the ratio of final element mass to input element mass was approximately 1, suggesting that elements are conserved during the composting process. One tailed t tests (0.05 level of significance) on element concentrations between the MWFLC and GHFC revealed that supplementing MWFLC with fruits and vegetables does not significantly change concentrations >25%. One-way analyses of variances conducted on Toronto residential compost samples revealed good homogeneity within an individual composter, although significant elemental variances occurred between separate composters. Incidentally, it was noticed that several of the Toronto residential compost samples had Cr levels that exceeded Ontario Ministry of Environment and Energy guideline values for municipal compost.

Role of cyclic AMP dependent protein kinase in cannabinoid receptor modulation of potassium "A-current" in cultured rat hippocampal neurons

Cannabinoid receptor agonists have been previously shown to enhance a potassium A-current (IA) in cultured rat hippocampal neurons. This effect has been further demonstrated to be dependent on G-protein linkage to adenylyl cyclase and levels of intracellular cyclic AMP (cAMP). The present study extends this analysis to the involvement of cAMP-dependent protein kinase (PKA) in this cascade. Specific activators and inhibitors of PKA were shown to have differential effects on the voltage dependence of IA. Specific activators of PKA produced a negative shift in voltage dependence of IA, whereas PKA inhibitors produced a positive shift in IA voltage dependence, the latter similar to that effected by the cannabinoid agonist WIN 55,212-2. Although the negative shift in IA induced by PKA stimulation could be reversed by PKA inhibitors, the positive shift produced by the PKA inhibitors alone was only 50-60% of the cannabinoid-produced shift in IA voltage dependence. This partial effect of PKA inhibition was confirmed by biochemical assays in the same cultured neurons that showed a similar 50-60% decrement in in vitro protein phosphorylation produced by PKA inhibitors. Results are discussed in terms of a diffusible second messenger linkage of the cannabinoid receptor to the A-current channel via the role of protein phosphorylation in modulation of IA.

A novel, calcium-induced triphasic current response in silent, non-bursting Aplysia neurons

The iontophoretic injection of Ca2+ ions into voltage-clamped, silent neurons of Aplysia californica results in a prolonged, triphasic current response. This response consists of: a tetraethylammonium-sensitive outward current during the injection; followed by an inward current 10-30 s after the end of the injection; and finally a long, slowly increasing outward current that lasts for several minutes before returning to baseline.

The ionic mechanism of the slow outward current in Aplysia neurons

A slow outward current associated with spike frequency adaptation has been studied in the giant Aplysia neurons R2 and LP1. The current was observed during 60-s voltage clamp commands to potentials just below spike threshold. The slow outward current shows a marked voltage dependence at membrane potential less negative than -40 mV. The slow outward current is associated with increased membrane conductance. The K+ sensitivity of the slow outward current was studied by varying the extracellular K+ concentration and also by measuring potassium efflux with a K+-sensitive electrode. Both procedures indicated that the slow outward current was K+ dependent. Tail currents following the activation of the slow outward current were examined. They were shown to have a similar potassium sensitivity as the slow outward current and had a reversal potential near the potassium equilibrium potential for these cells. The sensitivity of the slow outward current to known blockers of K+ currents, tetraethylammonium and 4-aminopyridine, was tested. The sensitivity was much less than that reported for other K+ currents. The sensitivity of the slow outward current to changes of the extracellular concentrations of Na+ and Cl- ions, as well as electrogenic pump inhibitors, was tested. The results indicate that the slow outward current is much less sensitive to these changes than to the manipulations of the extracellular K+ ion concentration. We tested the sensitivity of this current to manipulations of intracellular and extracellular Ca2+ ion concentrations. We found that the current persisted at a slightly reduced level in the absence of extracellular calcium or in the presence of calcium blocking agents, cobalt and lanthanum. Intracellular injection of the calcium chelator EGTA at a concentration sufficient to block the Ca2+-dependent K+ current, seen after a brief (1.4-s) burst of action potentials, had minimal effects on the slow outward current. Procedures thought to increase intracellular Ca2+ were tested. We found that exposure of the cell to solutions containing elevated Ca2+ concentrations for prolonged periods increased the slow outward current. Also, treatment with drugs thought to elevate intracellular Ca2+ increased the slow outward current. In conclusion, the slow outward current results from an increased K+ conductance.(ABSTRACT TRUNCATED AT 400 WORDS)

Septal inhibition of aversive emotional states

Two experiments were carried out to test the proposition that electrical stimulation of the septal region of the cat has the capacity to inhibit aversive emotional states. In the first experiment the source of aversive stimulation was electrical stimulation of various hypothalamic regions. The results were: (1) The animals would perform a learned response in order to obtain septal stimulation only if given concomitant aversive hypothalamic stimulation. (2) If septal stimulation was omitted the animal showed a conventional extinction effect. (3) If non-aversive hypothalamic stimulation was substituted for aversive stimulation the animal did not perform to obtain septal stimulation. In the second experiment a side preference was influenced by septal stimulation only when carbachol was administered to the hypothalamus, otherwise septal stimulation was neutral. It was concluded that these data provide evidence of an emotion inhibitory function of activity of the septal region.

The elderly in the wrong unit

Patients over 65 admitted from an area of North London forming the overlapping part of the catchment areas of a geriatric unit and a psychiatric unit were studied, with particular reference to misplacement in the inappropriate hospitals service and its consequences.The incidence of misplacement found was much lower than previously reported. In the geriatric unit 2.2% of admissions were definitely and 6.0% were probably misplaced. In the psychiatric unit 6.2% were definitely and a further 8.4% were probably misplaced. Misplacement did not materially affect the outcome. The striking differences that were found between the patterns of death and discharge in the geriatric and psychiatric units were determined principally by the type of illness leading to admission.The frequent coexistence of mental and physical disorders in the elderly patient, which this study confirms, indicates the need for further development of effective liaison at a local level between the geriatric, psychiatric, and social services.