Ambient air pollution and the risk of acute myocardial infarction and stroke: A national cohort study

We used a large national cohort in Canada to assess the incidence of acute myocardial infarction (AMI) and stroke hospitalizations in association with long-term exposure to fine particulate matter (PM_2.5), nitrogen dioxide (NO₂), and ozone (O₃). The study population comprised 2.7 million respondents from the 2006 Canadian Census Health and Environment Cohort (CanCHEC), followed for incident hospitalizations of AMI or stroke between 2006 and 2016. We estimated 10-year moving average estimates of PM_2.5, NO₂, and O₃, annually. We used Cox proportional hazards models to examine the associations adjusting for various covariates. For AMI, each interquartile range (IQR) increase in exposure was found to be associated with a hazard ratio of 1.026 (95% CI: 1.007-1.046) for PM_2.5, 1.025 (95% CI: 1.001-1.050) for NO₂, and 1.062 (95% CI: 1.041-1.084) for O₃, respectively. Similarly, for stroke, an IQR increase in exposure was associated with a hazard ratio of 1.078 (95% CI: 1.052-1.105) for PM_2.5, 0.995 (95% CI: 0.965-1.030) for NO₂, and 1.055 (95% CI: 1.028-1.082) for O₃, respectively. We found consistent evidence of positive associations between long-term exposures to PM_2.5, and O₃, and to a lesser degree NO₂, with incident AMI and stroke hospitalizations.

Does exposure to air pollution increase the risk of acute care in young children with asthma? An Ontario, Canada study

Owing to their greater outdoor activity and ongoing lung development, children are particularly vulnerable to the harmful effects of exposure to fine particulate matter (PM_2.5)_. However, the effects of PM_2.5 components are poorly understood. This study aimed to use a longitudinal birth cohort of children with physician-diagnosed incident asthma to investigate the effect of PM_2.5 components at birth on morbidity measured by health services utilization. Of 1277 Toronto Child Health Evaluation Questionnaire (T-CHEQ) participants, the study population included 362 children diagnosed with asthma who were followed for a mean of 13 years from birth until March 31, 2016, or loss-to-follow-up. Concentrations of PM_2.5 and its components were assigned based on participants' postal codes at birth. Study outcomes included counts of asthma, asthma-related, and all-cause health services use. Poisson regression in single-, two-, and multi-pollutant models was used to estimate rate ratios (RR) per interquartile range (IQR) increase of exposures. Covariates were included in all models to further adjust for potential confounding. The adjusted RR for sulfate (SO₄) and all-cause hospitalizations was statistically significant with RR = 2.23 (95% confidence interval [CI]: 1.25-3.96) in a multi-pollutant model with nitrogen dioxide (NO₂) and ozone (O₃). In multi-pollutant models with oxidants, the adjusted RRs for SO₄ of all-cause hospitalizations and emergency department (ED) visits were also statistically significant with RR = 2.31 (95% CI: 1.32-4.03) and RR = 1.39 (95% CI: 1.02-1.90), respectively. While unadjusted single-pollutant RRs for asthma-specific and asthma-related health services use with the SO₄ component of PM_2.5 were above one, none were statistically significant. This study found significant associations with exposure to SO₄ in PM_2.5 and all-cause acute care, chiefly for hospitalizations, in children with asthma.

Numerical modelling of birch pollen dispersion in Canada

Simulating allergenic tree pollen is important to protect sensitive population and to support bioaerosols monitoring effort. Using the regional air quality model GEM-MACH, a simulation was conducted adopting two new main hypotheses: 1) the use of vertical correlation concept to force the vertical dispersion (a method normally used in tracer data assimilation) and, 2) the use of a puff instead of a continuous pollen release. The simulation was compared with pollen observations in Montreal and with the corresponding statistical forecasts (issued daily by the Weather Network) at several locations in the province of Quebec and elsewhere. The comparison with the simulation was found satisfactory (outperform forecasts based on persistence or pollen calendar and is also superior to numerical simulation of tree pollen done elsewhere in North America). Simulation shows that, for the 2012 pollen season, the majority (88%) of the Betula pollen measured in Montreal originated from the Laurentides region. Another result of scientific importance obtained here is that Betula pollen episodes (observed or simulated birch pollen) in Montreal occur only when the average daily temperature is in the range of 10° to 18 °C. This research is considered as a first step in forecasting bioaerosols in Canada within an air quality model.

Self-rated stress, distress, mental health, and health as modifiers of the association between long-term exposure to ambient pollutants and mortality

BACKGROUND

Individual and neighbourhood-scale socioeconomic characteristics modify associations between exposure to air pollution and mortality. The role of stress, which may integrate effects of social and environmental exposures on health, is unknown. We examined whether an individual's perspective on their own well-being, as assessed using self-rated measures of stress and health, modifies the pollutant-mortality relationship.

METHODS

The Canadian Community Health Survey (CCHS)-mortality cohort includes respondents from surveys administered between 2001 and 2012 linked to vital statistics and postal codes from 1981 until 2016. Annual fine particulate matter (PM_2.5), nitrogen dioxide (NO₂), and ozone (O₃) exposure estimates were attached to a sample of cohort members aged 30-89 years (n = 398,300 respondents/3,848,400 person-years). We examined whether self-rated stress, distress, mental health, and general health modified associations between long-term exposure to each pollutant (three-year moving average with one-year lag) and non-accidental mortality using Cox survival models, adjusted for individual- (i.e. socioeconomic and behavioural) and neighbourhood-scale covariates.

RESULTS

In fully-adjusted models, the relationship between exposure to pollutants and mortality was stronger among those with poor self-rated mental health, including a significant difference for NO₂ (hazard ratio (HR) = 1.15, 95% CI 1.06-1.25 per IQR) compared to those with very good/excellent mental health (HR = 1.05, 95% CI 1.01-1.08; Cochran's Q = 4.01; p < 0.05). Poor self-rated health was similarly associated with higher pollutant-associated HRs, but only in unadjusted models. Stress and distress did not modify pollutant-mortality associations.

CONCLUSIONS

Poor self-rated mental and general health were associated with increased mortality attributed to exposure to ambient pollutants.

Active terahertz time differentiator using piezoelectric micromachined ultrasonic transducer array

The rapid growth of information technology is closely linked to our ability to modulate and demodulate a signal, whether in the frequency or in the time domain. Recent demonstrations of terahertz (THz) modulation involve active semiconductor metamaterial surfaces or use of a grating-based micromirror for frequency offset tuning. However, a wideband and active differentiator in the THz frequency band is yet to be demonstrated. Here, we propose a simple method to differentiate a THz pulse by inducing tiny phase changes on the THz beam path using a piezoelectric micromachined ultrasonic transducer array. We precisely demonstrate that the modulated THz signal detected after the piezoelectric device is proportional to the first-order derivative of the THz pulse. The proposed technique will be able to support a wide range of THz applications, such as peak detection schemes for telecommunication systems.

An overview of selected emerging outdoor airborne pollutants and air quality issues: The need to reduce uncertainty about environmental and human impacts

According to the literature, it is estimated that outdoor air pollution is responsible for the premature death in a range from 3.7 to 8.9 million persons on an annual basis across the world. Although there is uncertainty on this figure, outdoor air pollution represents one of the greatest global risks to human health. In North America, the rapid evolution of technologies (e.g., nanotechnology, unconventional oil and gas rapid development, higher demand for fertilizers in agriculture) and growing demand for ground, marine and air transportation may result in significant increases of emissions of pollutants that have not been carefully studied so far. As a result, these atmospheric pollutants insufficiently addressed by science in Canada and elsewhere are becoming a growing issue with likely human and environmental impacts in the near future. Here, an emerging pollutant is defined as one that meets the following criteria: 1) potential or demonstrated risk for humans or the environment, 2) absence of Canada-wide national standard, 3) insufficient routine monitoring, 4) yearly emissions greater than one ton in Canada, 5) insufficient data concerning significant sources, fate, and detection limit, and 6) insufficiently addressed by epidemiological studies. A new methodology to rank emerging pollutants is proposed here based on weighting multiple criteria. Some selected emerging issues are also discussed here and include the growing concern of ultrafine or nanoparticles, growing ammonia emissions (due to rapid expansion of the agriculture), increased methane/ethane/propane emissions (due to the expanding hydraulic fracturing in the oil and gas sector) and the growing transportation sector. Finally, the interaction between biological and anthropogenic pollution has been found to be a double threat for public health. Here, a multidisciplinary and critical overview of selected emerging pollutants and related critical issues is presented with a focus in Canada.Implications: This overview paper provides a selection methodology for emerging pollutants in the atmospheric environment. It also provides a critical discussion of some related issues. The ultimate objective is to inform about the need to 1) address emerging issues through adequate surface monitoring and modeling in order to inform the development of regulations, 2) reduce uncertainties by geographically mapping emerging pollutants (e.g., through data fusion, data assimilation of observations into air quality models) which can improve the scientific support of epidemiological studies and policies. This review also highlights some of the difficulties with the management of these emerging pollutants, and the need for an integrated approach.

Early life exposure to air pollution and incidence of childhood asthma, allergic rhinitis and eczema

Rationale

There is growing evidence that air pollution may contribute to the development of childhood asthma and other allergic diseases. In this follow-up of the Toronto Child Health Evaluation Questionnaire (T-CHEQ) study, we examined associations between early life exposures to air pollution and incidence of asthma, allergic rhinitis and eczema from birth through adolescence.

Methods

1286 T-CHEQ participants were followed from birth until outcome (March 31, 2016) or loss to follow-up, with a mean of 17 years of follow-up. Concentrations of nitrogen dioxide (NO₂), ozone (O₃) and particulate matter with a 50% cut-off aerodynamic diameter of 2.5 µm (PM_2.5) from January 1, 1999 to December 31, 2012 were assigned to participants based on their postal codes at birth using ground observations, chemical/meteorological models, remote sensing and land-use regression models. Study outcomes included incidence of physician-diagnosed asthma, allergic rhinitis and eczema. Cox proportional hazard regression models were used to estimate hazard ratios per interquartile range of exposures and outcomes, adjusting for potential confounders.

Results

Hazard ratios of 1.17 (95% CI 1.05–1.31) for asthma and 1.07 (95% CI 0.99–1.15) for eczema were observed for total oxidants (O₃ and NO₂) at birth. No significant increase in risk was found for PM_2.5.

Conclusions

Exposures to oxidant air pollutants (O₃ and NO₂) but not PM_2.5 were associated with an increased risk of incident asthma and eczema in children. This suggests that improving air quality may contribute to the prevention of asthma and other allergic disease in childhood and adolescence.

This study found that exposure to total oxidants at birth increased the risk of developing asthma by 17% and eczema by 7%. Adverse impacts of exposure to air pollutants, particularly ozone and nitrogen dioxide, may have their origins in early life.http://bit.ly/33PClYN

Variability in ambient ozone and fine particle concentrations and population susceptibility among Canadian health regions

Objectives

To estimate the proportion of the Canadian population that is more susceptible to adverse effects of ozone (O₃) and fine particle (PM_2.5) air pollution exposure and how this varies by health region alongside ambient concentrations of O₃ and PM_2.5.

Methods

Using data from the census, the Canadian Community Health Survey, vital statistics and published literature, we generated cross-sectional estimates for 2014 of the proportions of the Canadian population considered more susceptible due to age, chronic disease, pregnancy, outdoor work, socio-economic status, and diet. We also estimated 2010–2012 average concentrations of O₃ and PM_2.5. Analyses were conducted nationally and for 110 health regions.

Results

Restrictive criteria (age < 10 or ≥ 75; asthma, chronic obstructive pulmonary disease, heart disease, or diabetes; pregnancy) suggested that approximately one third of the Canadian population is more susceptible, while inclusive criteria (restrictive plus age 10–19 and 65–74, outdoor work, less than high school education, low vitamin C intake) increased this proportion to approximately two thirds. Across health regions, estimates ranged from 24.4% to 41.2% (restrictive) and 61.2% to 87.0% (inclusive). Ten health regions were in the highest quartile of both population susceptibility and O₃ or PM_2.5 concentrations, all of which were outside major urban centres.

Conclusions

A substantial proportion of the Canadian population exhibits at least one risk factor that increases their susceptibility to adverse effects of O₃ and PM_2.5 exposure. Both risk communication and management interventions need to be increasingly targeted to regions outside large urban centres in the highest quartiles of both susceptibility and exposure.

Electronic supplementary material

The online version of this article (10.17269/s41997-018-0169-8) contains supplementary material, which is available to authorized users.

Associations between Living Near Water and Risk of Mortality among Urban Canadians

BACKGROUND

Increasing evidence suggests that residential exposures to natural environments, such as green spaces, are associated with many health benefits. Only a single study has examined the potential link between living near water and mortality.

OBJECTIVE

We sought to examine whether residential proximity to large, natural water features (e.g., lakes, rivers, coasts, "blue space") was associated with cause-specific mortality.

METHODS

Our study is based on a population-based cohort of nonimmigrant adults living in the 30 largest Canadian cities [i.e., the 2001 Canadian Census Health and Environment Cohort) (CanCHEC)]. Subjects were drawn from the mandatory 2001 Statistics Canada long-form census, who were linked to the Canadian mortality database and to annual income-tax filings, through 2011. We estimated associations between living within of blue space and deaths from several common causes of death. We adjusted models for many personal and contextual covariates, as well as for exposures to residential greenness and ambient air pollution.

RESULTS

Our cohort included approximately 1.3 million subjects at baseline, 106,180 of whom died from nonaccidental causes during follow-up. We found significant, reduced risks of mortality in the range of 12-17% associated with living within of water in comparison with living farther away, among all causes of death examined, except with external/accidental causes. Protective effects were found to be higher among women and all older adults than among other subjects, and protective effects were found to be highest against deaths from stroke and respiratory-related causes.

CONCLUSIONS

Our findings suggest that living near blue spaces in urban areas has important benefits to health, but further work is needed to better understand the drivers of this association. https://doi.org/10.1289/EHP3397.

Urban greenness and mortality in Canada's largest cities: a national cohort study

BACKGROUND

Findings from published studies suggest that exposure to and interactions with green spaces are associated with improved psychological wellbeing and have cognitive, physiological, and social benefits, but few studies have examined their potential effect on the risk of mortality. We therefore undertook a national study in Canada to examine associations between urban greenness and cause-specific mortality.

METHODS

We used data from a large cohort study (the 2001 Canadian Census Health and Environment Cohort [2001 CanCHEC]), which consisted of approximately 1·3 million adult (aged ≥19 years), non-immigrant, urban Canadians in 30 cities who responded to the mandatory 2001 Statistics Canada long-form census. The cohort has been linked by Statistics Canada to the Canadian mortality database and to annual income tax filings through 2011. We measured greenness with images from the moderate-resolution imaging spectroradiometer from NASA's Aqua satellite. We assigned estimates of exposure to greenness derived from remotely sensed Normalized Difference Vegetation Index (NDVI) within both 250 m and 500 m of participants' residences for each year during 11 years of follow-up (between 2001 and 2011). We used Cox proportional hazards models to estimate associations between residential greenness (as a continuous variable) and mortality. We estimated hazard ratios (HRs) and corresponding 95% CIs per IQR (0·15) increase in NDVI adjusted for personal (eg, education and income) and contextual covariates, including exposures to fine particulate matter, ozone, and nitrogen dioxide. We also considered effect modification by selected personal covariates (age, sex, household income adequacy quintiles, highest level of education, and marital status).

FINDINGS

Our cohort consisted of approximately 1 265 000 individuals at baseline who contributed 11 523 770 person-years. We showed significant decreased risks of mortality in the range of 8-12% from all causes of death examined with increased greenness around participants' residence. In the fully adjusted analyses, the risk was significantly decreased for all causes of death (non-accidental HR 0·915, 95% CI 0·905-0·924; cardiovascular plus diabetes 0·911, 0·895-0·928; cardiovascular 0·911, 0·894-0·928; ischaemic heart disease 0·904, 0·882-0·927; cerebrovascular 0·942, 0·902-0·983; and respiratory 0·899, 0·869-0·930). Greenness associations were more protective among men than women (HR 0·880, 95% CI 0·868-0·893 vs 0·955, 0·941-0·969), and among individuals with higher incomes (highest quintile 0·812, 0·791-0·834 vs lowest quintile 0·991, 0·972-1·011) and more education (degree or more 0·816, 0·791-0·842 vs did not complete high school 0·964, 0·950-0·978).

INTERPRETATION

Increased amounts of residential greenness were associated with reduced risks of dying from several common causes of death among urban Canadians. We identified evidence of inequalities, both in terms of exposures to greenness and mortality risks, by personal socioeconomic status among individuals living in generally similar environments, and with reasonably similar access to health care and other social services. The findings support the development of policies related to creating greener and healthier cities.

FUNDING

None.

Surface data assimilation of chemical compounds over North America and its impact on air quality and Air Quality Health Index (AQHI) forecasts

The aim of this paper is to analyze the impact of initializing GEM-MACH, Environment and Climate Change Canada's air quality (AQ) forecast model, with multi-pollutant surface objective analyses (MPSOA). A series of 48-h air quality forecasts were launched for July 2012 (summer case) and January 2014 (winter case) for ozone, NO₂, and PM_2.5. In this setup, the GEM-MACH model (version 1.3.8.2) was initialized with surface analysis increments (from MPSOA) which were projected in the vertical by applying an appropriate fractional weighting in order to obtain 3D analyses in the lower troposphere. Here, we have used a methodology based on sensitivity tests to obtain the optimum vertical correlation length (VCL). Overall, results showed that for PM_2.5, more specifically for sulfate and crustal materials, AQ forecasts initialized with MPSOA showed a very significant improvement compared to forecasts without data assimilation, which extended beyond 48 h in all seasons. Initializing the model with ozone analyses also had a significant impact but on a shorter time scale than that of PM_2.5. Finally, assimilation of NO₂ was found to have much less impact than longer-lived species. The impact of simultaneous assimilation of the three pollutants (PM_2.5, ozone, and NO₂) was also examined and found very significant in reducing the total error of the Air Quality Health Index (AQHI) over 48 h and beyond. We suggest that the period over which there is a significant improvement due to assimilation could be an adequate measure of the pollutant atmospheric lifetime.

Multi-pollutant surface objective analyses and mapping of air quality health index over North America

Air quality, like weather, can affect everyone, but responses differ depending on the sensitivity and health condition of a given individual. To help protect exposed populations, many countries have put in place real-time air quality nowcasting and forecasting capabilities. We present in this paper an optimal combination of air quality measurements and model outputs and show that it leads to significant improvements in the spatial representativeness of air quality. The product is referred to as multi-pollutant surface objective analyses (MPSOAs). Moreover, based on MPSOA, a geographical mapping of the Canadian Air Quality Health Index (AQHI) is also presented which provides users (policy makers, public, air quality forecasters, and epidemiologists) with a more accurate picture of the health risk anytime and anywhere in Canada and the USA. Since pollutants can also behave as passive atmospheric tracers, they provide information about transport and dispersion and, hence, reveal synoptic and regional meteorological phenomena. MPSOA could also be used to build air pollution climatology, compute local and national trends in air quality, and detect systematic biases in numerical air quality (AQ) models. Finally, initializing AQ models at regular time intervals with MPSOA can produce more accurate air quality forecasts. It is for these reasons that the Canadian Meteorological Centre (CMC) in collaboration with the Air Quality Research Division (AQRD) of Environment Canada has recently implemented MPSOA in their daily operations.

Ambient PM2.5, O₃, and NO₂ Exposures and Associations with Mortality over 16 Years of Follow-Up in the Canadian Census Health and Environment Cohort (CanCHEC)

BACKGROUND

Few studies examining the associations between long-term exposure to ambient air pollution and mortality have considered multiple pollutants when assessing changes in exposure due to residential mobility during follow-up.

OBJECTIVE

We investigated associations between cause-specific mortality and ambient concentrations of fine particulate matter (≤ 2.5 μm; PM2.5), ozone (O3), and nitrogen dioxide (NO2) in a national cohort of about 2.5 million Canadians.

METHODS

We assigned estimates of annual concentrations of these pollutants to the residential postal codes of subjects for each year during 16 years of follow-up. Historical tax data allowed us to track subjects' residential postal code annually. We estimated hazard ratios (HRs) for each pollutant separately and adjusted for the other pollutants. We also estimated the product of the three HRs as a measure of the cumulative association with mortality for several causes of death for an increment of the mean minus the 5th percentile of each pollutant: 5.0 μg/m3 for PM2.5, 9.5 ppb for O3, and 8.1 ppb for NO2.

RESULTS

PM2.5, O3, and NO2 were associated with nonaccidental and cause-specific mortality in single-pollutant models. Exposure to PM2.5 alone was not sufficient to fully characterize the toxicity of the atmospheric mix or to fully explain the risk of mortality associated with exposure to ambient pollution. Assuming additive associations, the estimated HR for nonaccidental mortality corresponding to a change in exposure from the mean to the 5th percentile for all three pollutants together was 1.075 (95% CI: 1.067, 1.084). Accounting for residential mobility had only a limited impact on the association between mortality and PM2.5 and O3, but increased associations with NO2.

CONCLUSIONS

In this large, national-level cohort, we found positive associations between several common causes of death and exposure to PM2.5, O3, and NO2.

CITATION

Crouse DL, Peters PA, Hystad P, Brook JR, van Donkelaar A, Martin RV, Villeneuve PJ, Jerrett M, Goldberg MS, Pope CA III, Brauer M, Brook RD, Robichaud A, Menard R, Burnett RT. 2015. Ambient PM2.5, O3, and NO2 exposures and associations with mortality over 16 years of follow-up in the Canadian Census Health and Environment Cohort (CanCHEC). Environ Health Perspect 123:1180-1186; http://dx.doi.org/10.1289/ehp.1409276.

Iodine concentration in milk sampled from Canadian farms

A study was conducted to determine the iodine concentration in milk and the relationship between that concentration and milking and feeding management practices. Milk samples were collected from the bulk tanks of 501 farms in all provinces of Canada. With a view to obtaining further information about farm management, a questionnaire was completed at each of the selected farms. Total iodine concentration (organic and inorganic) in the milk was determined using inductively coupled plasma mass spectrometry. The farms were grouped for each of the variables and, based on significant differences in iodine concentrations, 15 variables were selected for further analysis. A general linear model was fitted, with milk iodine as the response variable to main and two-way interaction effects. The mean iodine concentration in Canadian milk was 304 ± 8.4 μg/kg, with concentrations ranging from 54 to 1,902 μg/kg. Analysis of the questionnaire data suggested that component feeding was associated with lower iodine levels in milk than the levels obtained with total mixed rations. Neither the use of mineral supplementation nor the form of supplementation affected iodine levels in milk. Washing and dipping the teats before milking affected iodine in milk. The method of application of the teat sanitizers appears to be important, given that spray applications (inline or hand spraying) were associated with higher levels than those observed with the dip-cup procedure. In conclusion, Canadian milk iodine concentration varies considerably and appears to be influenced by feeding and milking practices.

Assessing the emetic potential of PDE4 inhibitors in rats

1. Type 4 phosphodiesterase (PDE4) inhibitors mimic the pharmacological actions of alpha(2)-adrenoceptor antagonists. This has been postulated as the mechanism by which PDE4 inhibitors induce emesis and was also demonstrated by their ability to reverse xylazine/ketamine-induced anaesthesia. We further characterized this latter effect since it appears to reflect the emetic potential of PDE4 inhibitors. 2. Selective inhibitors of PDE 1, 2, 3, 4 and 5 were studied in rats, on the duration of anaesthesia induced by the combination of xylazine (10 mg kg(-1), i.m.) and ketamine (10 mg kg(-1), i.m.). PMNPQ (i.e. 6-(4-pyridylmethyl)-8-(3-nitrophenyl)quinoline) - PDE4 inhibitor: 0.01 - 3 mg kg(-1)), like MK-912 (alpha(2)-adrenoceptor antagonist: 0.01 - 3 mg kg(-1)), dose-dependently reduced the duration of anaesthesia. In contrast, vinpocetine (PDE1 inhibitor), EHNA (PDE2 inhibitor), milrinone (PDE3 inhibitor) and zaprinast (PDE5 inhibitor) had no significant effect at the doses tested (1 - 10 mg kg(-1)). Analysis of plasma and cerebrospinal fluid (CSF) of treated animals confirmed the absorption and distribution to the brain of the inactive inhibitors. 3. Neither MK-912 (3 mg kg(-1)) nor PMNPQ (0.1 - 1 mg kg(-1)) altered the duration of anaesthesia induced via a non-alpha(2)-adrenoceptor pathway (sodium pentobarbitone 50 mg kg(-1), i.p.). 4. Central NK(1) receptors are involved in PDE4 inhibitor-induced emesis. Consistently, [sar(9), Met(O(2))(11)]-substance P (NK(1) receptor agonist, 6 microg i.c.v.) reduced the duration of anaesthesia induced by xylazine/ketamine. 5. In summary, this model is functionally coupled to PDE4, specific to alpha(2)-adrenoceptors and relevant to PDE4 inhibitor-induced emesis. It therefore provides a novel way of evaluating the emetic potential of PDE4 inhibitors in rats.

Localization of phosphodiesterase-4 isoforms in the medulla and nodose ganglion of the squirrel monkey

Pre-clinical and clinical studies are currently underway to evaluate the potential of phosphodiesterase-4 (PDE4) inhibitors for the treatment of chronic obstructive pulmonary disease and other inflammatory conditions of the airways. The most common side effect associated with this class of compounds is emesis. The squirrel monkey provides a model for evaluating the efficacy of PDE4 inhibitors and their emetic potential. The distribution of three PDE4 isoforms (A, C and D) has been investigated in the squirrel monkey medulla and nodose ganglion to determine which isoform(s) could be responsible for the emetic adverse effects. The distribution of PDE4 isoforms was delineated using immunohistochemistry with antibodies specific for PDE4A, PDE4C and PDE4D and by in situ hybridization with isoform-selective riboprobes. PDE4A was present in the medulla where expression was mostly restricted to glial cells and the vasculature. PDE4C was not detected in either the medulla or nodose ganglion. Finally, the PDE4D isoform was localized to neurons in the nodose ganglion and found through many structures of medulla including the area postrema, neurons of the nucleus tractus solitarius and locus coeruleus. These data are consistent with a role for PDE4D in the emetic response.

The next generation of PDE4 inhibitors

A number of highly potent PDE4 inhibitors are being developed for the treatment of asthma, chronic obstructive pulmonary disease, rheumatoid arthritis, multiple sclerosis and Crohn's disease. Cilomilast (Ariflo, SB 207499, SmithKline Beecham), the most advanced member of the class in Phase III clinical trials, was reported to have a limited therapeutic window. Other inhibitors with improved profiles in preclinical models are entering into (or are in) clinical trials. The recent developments in understanding PDE4 catalysis, inhibitor binding and their emetic response should facilitate the design of the next generation of PDE4 inhibitors.

PDE4 inhibitors induce emesis in ferrets via a noradrenergic pathway

The objective of this work was to assess the role of alpha(2)-adrenoceptors in emesis induced by inhibitors of type 4 phosphodiesterase (PDE4) in ferrets. Pre-treatment with yohimbine, MK-912 or MK-467 (alpha(2)-adrenoceptor antagonists) caused sudden and unexpected vomiting. In contrast, clonidine (alpha(2)-adrenoceptor agonist) did not induce emesis at doses ranging from 62.5-250 microg/kg s.c. At the dose of 250 microg/kg, clonidine also provided protection against emesis induced by the PDE4 inhibitors, PMNPQ (i.e. 6-(4-pyridylmethyl)-8-(3-nitrophenyl)quinoline, CT-2450 and R-rolipram. It was postulated that PDE4 inhibitors trigger emesis by mimicking the pharmacological actions of alpha(2)-adrenoceptor antagonists. This hypothesis was strengthened by the demonstration that PDE4 inhibitors can reverse the hypnotic effect of an alpha(2)-adrenoceptor mediated anaesthetic regimen in rats and ferrets. Similar to alpha(2)-adrenoceptor antagonists, PMNPQ, R-rolipram and S-rolipram dose-dependently decreased the duration of anaesthesia in rats injected with the combination xylazine/ketamine. While subcutaneous injections of CT-2450 (3-30 mg/kg) were without effect, a central infusion (6 microg i.c.v.) decreased the duration of anaesthesia. These studies suggest that the ferret is an appropriate model to study emesis induced by PDE4 inhibitors and that these compounds trigger the emetic reflex via a noradrenergic pathway, mimicking the pharmacological actions of a pre-synaptic alpha(2)-adrenoceptor inhibition.

Selective potentiating effect of RS14203 on a serotoninergic pathway in anesthetized rats

The usefulness of selective inhibitors of type 4 phosphodiesterase (PDE4) in the treatment of inflammation and pulmonary diseases is limited by their side effects: nausea and vomiting. We studied the effect of three structurally diverse PDE4 inhibitors on the vagal nerve afferent and efferent fibers in anesthetized rats. The effects of RS14203, (R)-rolipram, and CT-2450 were evaluated on the von Bezold-Jarisch reflex (vagal afferent fibers) and in a model of vagal electrical stimulation (vagal efferent fibers). All three PDE4 inhibitors were administered at 1, 10, or 100 microg/kg (iv) 15 min prior to the induction of bradycardia by an iv injection of 2-methyl-5-HT (von Bezold-Jarisch reflex) or by vagal electrical stimulation. At 100 microg/kg, RS14203 significantly potentiated the 2-methyl-5-HT response. No statistically significant effects were observed with (R)-rolipram or CT-2450 at the doses studied. RS14203, (R)-rolipram, or CT-2450 (1-100 microg/kg iv) did not affect the bradycardia induced by vagal electrical stimulation. Consequently, our results show that RS14203 selectively facilitates serotoninergic neurotransmission in vagal afferent fibers. The emetic action of RS14203 may be mediated by this mechanism.

Substituted furans as inhibitors of the PDE4 enzyme

The synthesis and in vitro activity of a series of substituted furans as a novel structural class of PDE4 inhibitors is described. Comparison of emetic threshold with known PDE4 inhibitors is presented.

Emesis induced by inhibitors of type IV cyclic nucleotide phosphodiesterase (PDE IV) in the ferret

Emesis induced by inhibitors of type IV cyclic nucleotide phosphodiesterase (PDE IV) has been investigated in the ferret. The PDE IV inhibitors studied were: RS14203, R-rolipram and CT-2450 (i.e. (R)-N-[4-[1-(3-cyclopentyloxy-4-methoxyphenyl)-2-(4-pyridyl)ethyl]phenyl ]N'-ethylurea), in addition to the less active enantiomers S-rolipram and CT-3405. Following oral administrations, different emetic profiles were observed with time. Emesis induced by RS14203 exhibited a dose-response relationship but no such relationship was seen for R-rolipram or CT-2450. The incidence of emesis was positively influenced by the dose of PDE IV inhibitors administered, allowing a rank order of potency: RS14203 > R-rolipram > S-rolipram > CT-2450 > CT-3405. PDE IV inhibitor-induced emesis was abolished by the tachykinin NK1 receptor antagonist, CP-99,994. No peripheral release of substance P by PDE IV inhibitors seems to be involved in triggering the emetic reflex since L-743,310, which only has peripheral NK1 receptor antagonist activity, was without effect. The implication of 5-HT3 receptors in PDE IV inhibitor-induced emesis was variable. Our results suggest that the PDE IV inhibitors studied are mixed peripheral-central emetogens. PDE IV inhibition itself could be plausible mechanism of action of these agents. However, whether emesis is mediated via a specific isoform of PDE IV remains to be established.

Effect of inhibition of nitric oxide synthase on Pseudomonas aeruginosa infection of respiratory mucosa in vitro

We studied the effect of the nitric oxide synthase (NOS) inhibitor asymmetric dimethyl arginine (ADMA) and the inactive enantiomer N G-methyl-D-arginine (D-NMMA) on Pseudomonas aeruginosa infection of the respiratory mucosa in nasal turbinate organ cultures. We also investigated the effect of P. aeruginosa culture filtrate on the expression of inducible NOS (iNOS) messenger RNA (mRNA) by an epithelial cell line (A549). Organ cultures were preincubated with ADMA (0.1 to 4 x 10(-4) M) or D-NMMA (2 x 10(-4) M) for 30 min prior to bacterial infection. Infected organ cultures (8 h) had significantly (P <= 0.05) greater epithelial damage and fewer ciliated and unciliated cells than did control cultures. There was an increased level of nitrite in the medium feeding infected organ cultures as compared with control cultures. ADMA significantly (P <= 0.05) reduced both bacterially induced epithelial damage and loss of ciliated cells in a concentration-dependent manner. D-NMMA did not influence the effect of P. aeruginosa infection of the mucosa. ADMA, but not D-NMMA, significantly (P <= 0.04) reduced total bacterial numbers adherent to the respiratory mucosa. P. aeruginosa culture filtrates (24 h and 36 h) significantly (P = 0.02) increased iNOS with respect to glyceraldehyde-3-phosphate dehydrogenase mRNA expression. These results show that P. aeruginosa stimulates iNOS expression by a cell line and NO production by an organ culture. ADMA reduces mucosal damage and loss of ciliated cells, which suggests that NO may be a mediator of epithelial damage caused by P. aeruginosa.

Phosphodiesterase expression in human epithelial cells

Epithelial cells play a critical role in airway inflammation and have the capacity to produce many inflammatory mediators, including bioactive lipids and proinflammatory cytokines. Intracellular levels of cAMP and cGMP are important in the control of inflammatory cell function. These cyclic nucleotides are inactivated via a family of phosphodiesterase (PDE) enzymes, providing a possible site for drug intervention in chronic inflammatory conditions. We studied the expression of PDE activity in an epithelial cell line (A549) and in primary human airway epithelial cells (HAECs). We measured PDE function using specific inhibitors to identify the PDE families present and used RT-PCR to elucidate the expression of PDE isogenes. Both A549 cells and HAECs predominantly expressed PDE4 activity, with lesser PDE1, PDE3, and PDE5 activity. RT-PCR identified HSPDE4A5 and HSPDE4D3 together with HSPDE7. Inhibition of PDE4 and PDE3 reduced secretion by these cells. Epithelial PDE may be an important target for PDE4 inhibitors in the development of the control of asthmatic inflammation, particularly when delivered via the inhaled route.

Inhaled corticosteroids increase interleukin-10 but reduce macrophage inflammatory protein-1alpha, granulocyte-macrophage colony-stimulating factor, and interferon-gamma release from alveolar macrophages in asthma

We determined the effect of inhaled corticosteroid, budesonide, on the release of the anti-inflammatory cytokine, interleukin-10 (IL-10), and of pro-inflammatory cytokines, macrophage inflammatory protein-1alpha (MIP-1alpha), interferon-gamma (IFN-gamma), and granulocyte-macrophage colony-stimulating factor (GM-CSF), from blood monocytes and alveolar macrophages of mild asthmatic subjects in a double-blind, cross-over, placebo-controlled study. Budesonide reduced bronchial hyperresponsiveness and improved baseline FEV1. Alveolar macrophages were obtained by bronchoalveolar lavage performed at the end of each treatment phase. IL-10 from blood monocytes was not altered, but both IL-10 mRNA and protein expression from alveolar macrophages stimulated by lipopolysaccharide and IL-1beta were increased after corticosteroid therapy. By contrast, alveolar macrophages released significantly less MIP-1alpha, IFN-gamma, and GM-CSF after steroid treatment. In comparison to alveolar macrophages from normal nonasthmatic volunteers, those from asthmatic patients released more MIP-1alpha, IFN-gamma, and GM-CSF but lower amounts of IL-10 particularly at baseline and after IL-1beta stimulation. The ability of steroids to inhibit pro-inflammatory cytokines but to enhance the anti-inflammatory cytokine such as IL-10 may contribute to their beneficial actions in asthma. Asthma is characterized by alveolar macrophages exhibiting both an enhanced capacity to release pro-inflammatory cytokines and a reduced capacity to produce IL-10.

Human airway smooth muscle cells express and release RANTES in response to T helper 1 cytokines: regulation by T helper 2 cytokines and corticosteroids

RANTES is a basic 8-kDa polypeptide of the C-C chemokine subfamily with strong chemotactic activity for eosinophils, lymphocytes, and monocytes. We determined the regulation of RANTES production by human airway smooth muscle cells in culture. While TNF-alpha, but not IFN-gamma, increased RANTES mRNA expression and protein release, the combination of TNF-alpha and IFN-gamma caused a greater degree of expression and release in a time- and dose-dependent manner. Sequential treatment of airway smooth muscle cells with TNF-alpha and IFN-gamma showed that IFN-gamma sensitized the cells to the stimulatory effect of TNF-alpha. Using a modified Boyden chamber technique, RANTES separated by reverse-phase liquid chromatography from cell culture supernatants of airway smooth muscle cells stimulated by TNF-alpha and IFN-gamma showed a strong chemoattractant effect on human eosinophils, an effect inhibited by an anti-RANTES Ab. RANTES production induced by TNF-alpha and IFN-gamma was inhibited partly by the Th2-derived cytokines, IL-4, IL-10, and IL-13, as well as by dexamethasone. Our studies indicate that, in addition to contractile responses and mitogenesis, airway smooth muscle cells have synthetic and secretory potential with the release of RANTES. They may participate in chronic airway inflammation by interacting with both Th1- and Th2-derived cytokines to modulate chemoattractant activity for eosinophils, activated T lymphocytes, and monocytes/macrophages.

Human airway smooth muscle cells express and release RANTES in response to T helper 1 cytokines: regulation by T helper 2 cytokines and corticosteroids

RANTES is a basic 8-kDa polypeptide of the C-C chemokine subfamily with strong chemotactic activity for eosinophils, lymphocytes, and monocytes. We determined the regulation of RANTES production by human airway smooth muscle cells in culture. While TNF-alpha, but not IFN-gamma, increased RANTES mRNA expression and protein release, the combination of TNF-alpha and IFN-gamma caused a greater degree of expression and release in a time- and dose-dependent manner. Sequential treatment of airway smooth muscle cells with TNF-alpha and IFN-gamma showed that IFN-gamma sensitized the cells to the stimulatory effect of TNF-alpha. Using a modified Boyden chamber technique, RANTES separated by reverse-phase liquid chromatography from cell culture supernatants of airway smooth muscle cells stimulated by TNF-alpha and IFN-gamma showed a strong chemoattractant effect on human eosinophils, an effect inhibited by an anti-RANTES Ab. RANTES production induced by TNF-alpha and IFN-gamma was inhibited partly by the Th2-derived cytokines, IL-4, IL-10, and IL-13, as well as by dexamethasone. Our studies indicate that, in addition to contractile responses and mitogenesis, airway smooth muscle cells have synthetic and secretory potential with the release of RANTES. They may participate in chronic airway inflammation by interacting with both Th1- and Th2-derived cytokines to modulate chemoattractant activity for eosinophils, activated T lymphocytes, and monocytes/macrophages.

Inhibition of inducible nitric oxide synthase expression by interleukin-4 and interleukin-13 in human lung epithelial cells

Nitric oxide produced by the inducible enzyme, nitric oxide synthase (iNOS), is implicated in immunological and inflammatory processes. We determined the effects of T-helper (Th)2-derived cytokines on the induction of iNOS from an epithelial A549 cell line and human airway epithelial cells stimulated by a mixture of interleukin-1 beta (IL-1 beta), interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha). Interleukin-4 (IL-4) and interleukin-13 (IL-13) but not interleukin-10 (IL-10) inhibited both iNOS mRNA expression and nitrite release in A549 cells. On human airway epithelial cells, IL-4 and IL-13 reduced iNOS mRNA expression. Dexamethasone also inhibited both iNOS expression and nitrite release. Th2 cytokines, IL-4 and IL-13, inhibit iNOS upregulation by Th1 cytokines, indicating an important reciprocal role of Th1 and Th2 T-cell subsets on lung epithelial cells.

Microanatomy of secretory granule release from guinea pig tracheal goblet cells

The microanatomy of mucin granule release from epithelial goblet cells has been investigated in guinea pig tracheae. Using a tannic acid arrest procedure, granule release under basal conditions and after high K+ or acetylcholine (ACh) application was arrested and a variety of granule fusion sites were identified in ultrathin sections and freeze-fracture replicas. Rather than there being subclasses of secretory cells containing either electron-lucent granules (indicative of mucin) or smaller electron-dense (serous) granules, the majority of secretory cells in both control and treated groups contained granules with an electrondense core surrounded by an electron-lucent region. Granule release sites were of three principal types: (1) simple exocytosis, where the membranes of single granules fused directly with the plasma membrane to give an "omega" profile; (2) compound exocytosis, where granule membranes, fused together intracellularly, were found in continuity with the plasma membrane; and (3) apocrine-like secretion, which involved the loss of the central apical mass of granules together with elements of the cell cytoplasm. In treated preparations, there was an increase in the number of cells exhibiting fusion sites; the percentage showing simple fusions fell from 82% to 59% (with ACh) and 57% (with KCl), whereas the percentage of cells exhibiting compound and apocrine-like secretion increased. Dense cores were frequently retained at the sites of fusion and, despite the expansive decondensation of mucin known to occur, there was also evidence of some retention of the electron-lucent material.

Expression of RANTES in human airway epithelial cells: effect of corticosteroids and interleukin-4, -10 and -13

RANTES is a C-C chemokine with strong chemoattractant and activating properties for eosinophils, basophils and T lymphocytes. We investigated the expression of RANTES in human airway epithelial cells and its modulation. Epithelial cells obtained from tracheas of donor lungs were stimulated with interleukin-1 beta (IL-1 beta), tumour necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma) or with a mixture of the three cytokines ('cytomix'). Levels of mRNA and protein were assayed by Northern blot and radioimmunoassay, respectively. Each individual cytokine produced a small increase in RANTES protein: IL-1 beta 24 +/- 1 pM, TNF-alpha 13 +/- 7 pM and IFN-gamma 29 +/- 7 pM, but cytomix increased protein to 236 +/- 22 pM (P < 0.002) and mRNA expression by > 20-fold (P < 0.002). Both RANTES protein and mRNA expression were inhibited by dexamethasone (10(-6) M) (38 +/- 5%, P < 0.05 and 55 +/- 8%, P < 0.007, respectively), and by IL-4 (42 +/- 7%, P < 0.03 and 19 +/- 1%, not significant, respectively). No inhibitory effect was observed with IL-10 or IL-13. We also demonstrated in vivo expression of RANTES protein by epithelial cells in human airways using immunohistochemistry. Our data show that human airway epithelial cells can be stimulated to express and release RANTES, an effect that is inhibited by corticosteroids and IL-4, but not by IL-10 and IL-13.

Expression of inducible nitric oxide synthase mRNA in Brown Norway rats exposed to ozone: effect of dexamethasone

We studied the effects of ozone exposure and dexamethasone on inducible nitric synthase (iNOS) gene expression in Brown Norway rats in vivo. Using a murine iNOS cDNA probe, we detected a 4.4 kb iNOS mRNA by Northern analysis in rat lung. The iNOS signal was weak in control lungs, but increased in lungs exposed to ozone (3 ppm, 6 h). Ozone-induced iNOS mRNA expression was time-dependent, with maximal expression at 2 h, declining by 8 h and increasing again at 24 h postexposure. Dexamethasone significantly reduced the iNOS mRNA expression in the lungs of both controls and ozone-exposed rats. These results demonstrate that ozone inhalation induces iNOS expression in vivo, thus providing evidence at the molecular level for the possible involvement of nitric oxide generation in ozone-induced pulmonary inflammation or lung damage.

Plasma atrial natriuretic peptide during spontaneous bronchoconstriction in asthmatics

The aim of this work was to establish the role of endogeneous ANP during a spontaneous asthma attack. Forced expiratory lung volume in 1 s (FEV1), cardiovascular parameters, and plasma ANP, cAMP, and cGMP were measured for 60 min before and 10 min after treatment with a bronchodilator in 10 asthmatics. The results show that in the presence of moderate bronchoconstriction, FEV1 was 54 +/- 3% (+/-SE); ANP levels initially were slightly elevated at 47 +/- 10 pg/ml and decreased to 26 +/- 3 pg/ml (p < 0.05) over 60 min, with no change in FEV1. Following salbutamol inhalation, FEV1 increased to 77 +/- 4% with no change in ANP. We conclude that endogenous ANP does not act as a bronchodilator in asthmatics with moderate bronchospasm.

Effect of dehydration and hyperosmolal hydration on lignocaine and metabolites disposition in conscious rabbits

1. The present study aimed to investigate the effect of dehydration and hyperosmolal hydration on the disposition of lignocaine and two of its metabolites, monoethylglycinexylidide (MEGX) and glycinexylidide (GX). 2. Lignocaine was infused to three groups of conscious rabbits: controls, rabbits previously deprived of water for 48 h and rabbits receiving an infusion of 2.5% NaCl. 3. In dehydrated and hyperosmolal-hydrated rabbits, plasma osmolality was 321 +/- 1 and 313 +/- 1 mOsm kg-1, respectively (P < 0.01 compared to controls, 285 +/- 1 mOsm kg-1). In dehydrated animals, baseline values of plasma arginine vasopressin (AVP) concentrations and plasma renin activity (PRA) were higher than in controls, i.e. 12.4 +/- 1.4 pg ml-1 and 15.4 +/- 1.7 ng AI ml-1 h-1 vs. 3.4 +/- 0.2 pg ml-1 (P < 0.01), and 5.1 +/- 0.6 ng AI ml-1 h-1 (P < 0.01), respectively; atrial natriuretic peptide (ANP) decreased from 55 +/- 11 to 32 +/- 4 pg ml-1 (P < 0.05). Compared to controls, hyperosmolal hydration only increased AVP to 15.5 +/- 0.7 pg ml-1 (P < 0.01). 4. Under both experimental conditions, lignocaine plasma concentrations were almost double (P < 0.01) those in controls, due to a lower systemic clearance, e.g. 54 +/- 3 and 59 +/- 1 vs. 96 +/- 5 ml min-1 kg-1, respectively. Plasma levels of MEGX increased (P < 0.01) only in dehydrated animals, although GX plasma concentrations were augmented (P < 0.01) about three fold in both groups of animals. The changes in lignocaine plasma concentrations were correlated with AVP levels (R2 = 0.5168, P<0.001).5. To document the effect of AVP on hepatic plasma flow, another group of rabbits received on separate occasions two doses of AVP (17 and 84 ng kg-1) while receiving an infusion of in docyanine green. AVP reduced hepatic plasma flow from 38.9 +/-2.7 ml min-1 to 19.6 +/-2.5 ml min-1 (P<0.01).The predicted maximal AVP-induced decrease in hepatic plasma flow was 19.6 ml min-1 kg- 1(Emax), and AVP concentration eliciting 50% of Em.. (ED50) was 28.7 pg ml-1.6 It is concluded that both dehydration and hyperosmolal hydration alter the disposition of lignocaine and two of its metabolites.

Negative chronotropic effect of the atrial natriuretic peptide in an anesthetized dog model

The effects of atrial natriuretic peptide (ANP) on heart rate and on the chronotropic response induced by angiotensin II were evaluated. The action of angiotensin II, injected into the sinus node artery, on heart rate was determined in anaesthetized and vagotomized dogs pretreated with beta-adrenoceptor antagonist (n = 9), before and after the infusion of physiological and pharmacological doses (10 and 50 ng/kg per min) of ANP. ANP plasma concentrations were determined by radioimmunoassay. Compared to the baseline concentration values (117 +/- 3 pg/ml), a slight increase was produced by the lower dose (293 +/- 45 pg/ml), whereas a significant augmentation was noted with the higher dose of ANP (1024 +/- 255 pg/ml). The basal heart rate and mean systemic arterial pressure were decreased (26.3 and 13.5%) during the intravenous infusion of the physiological dose of the peptide and were significantly reduced (32.5 and 29.2%, P < 0.05) by the administration of the pharmacological dose of ANP. Angiotensin II had a positive chronotropic effect (29 +/- 3 beats/min) that was significantly inhibited by the pharmacological dose of ANP. Our results suggest that ANP might have a role in the control of heart rate.

Effect of intravenous atrial natriuretic peptide on gas exchange in humans

The aim of this work was to establish whether a physiological increase in atrial natriuretic peptide (ANP) plasma levels affects pulmonary gas exchange in humans. Ten volunteers received an infusion of either ANP (4 pmol.kg-1.min-1) or physiological saline, for 60 min. Baseline measures of the alveolar-arterial PO2 difference and of the physiological dead space were within normal limits and remained stable during and after the infusion of ANP or saline, although plasma ANP and cGMP rose significantly (p < 0.01) (mean +/- SEM: ANP: 13.4 +/- 3.9 to 56.0 +/- 10.4 pmol/l; cyclic GMP: 3.8 +/- 0.3 to 17.0 +/- 3.8 nmol/l). We conclude that a physiological increase in plasma ANP does not affect pulmonary gas exchange significantly in humans.

Effect of atrial natriuretic peptide on bronchial tone in anesthetized rabbits

The effect of atrial natriuretic peptide (ANP) on histamine-induced bronchoconstriction was studied in vivo (in normoxic and in hypoxic rabbits) and in vitro. Thirty-two anesthetized rabbits, spontaneously breathing room air or 10% O2, received infusions of ANP (20, 40, or 80 ng/min/kg normoxia; 20 ng/min/kg hypoxia) or the vehicle for 100 min. After 75 min of ANP infusion, bronchoconstriction was induced inhaling histamine; respiratory resistance (Rrs) was measured prior to and until 20 min posthistamine. The results show that the histamine-induced increase in Rrs was significantly reduced by ANP 80 ng/kg/min in normoxia, and by ANP 20 ng/kg/min in hypoxia. In vitro, ANP had no effect on tracheal and bronchial smooth muscle precontracted with histamine or acetylcholine. These results show that ANP can decrease a histamine-induced bronchoconstriction in vivo but not in vitro, suggesting an indirect mechanism of action.

Muscarinic effect of atrial natriuretic peptide on rabbit airways

1. The aim of the present work was to investigate under which circumstances atrial natriuretic peptide (ANP) modulates airway resistance. 2. Of the six groups of rabbits (n = 5) studied, three received an infusion of ANP (80 ng min-1 kg-1 i.v.) for a period of 100 min, while the other three were infused with the vehicle. Before receiving the infusion of ANP or the vehicle, the animals were pretreated with atropine (0.5 mg kg-1 i.v.), propranolol (2 mg kg-1 i.v.) or not pretreated. After 75 min of infusion of ANP, bronchoconstriction was induced by inhalation of histamine. Respiratory resistance (Rrs) was measured before and 3, 5, 10, 15 and 20 min post-histamine challenge. 3. Following 75 min of ANP infusion, plasma ANP concentration increased from 153 +/- 52 (mean +/- s.e.mean) to 1441 +/- 203 pg ml-1 (P < 0.05) without affecting baseline Rrs. Control Rrs values (12.5-20.4 cmH2O l-1 s) were significantly increased following the inhalation of histamine (P < 0.001). By themselves, atropine, propranolol or ANP did not modify the histamine-induced increase in Rrs. However, when the animals were pretreated with atropine, ANP infusion significantly reduced the increase in Rrs induced by histamine (30 +/- 2 vs 51 +/- 6 cmH2O l-1 s; P < 0.05). 4. These data suggest that ANP has an indirect modulating effect on the airway smooth muscle and will decrease Rrs when muscarinic receptors are blocked.

Alteration in gas exchange related to body position

The diagnosis of alteration in gas exchange related to body position requires a deliberate evaluation of PaO2 responses. Body positions that improve V/Q matching and thus PaO2 need to be specified in patient care plans; individualized interventions are more useful than generic care plans that state, "turn q 2 h." Additionally, standard rotations for patients treated on mechanically rotating beds could be individualized according to gas exchange responses to the position changes. Routine documentation of patient body positions next to arterial blood gas results on flow sheets could prove valuable in the evaluation and treatment of hypoxemia in patients with pulmonary problems.

Alteration in gas exchange related to body position

The diagnosis of alteration in gas exchange related to body position requires a deliberate evaluation of PaO2 responses. Body positions that improve V/Q matching and thus PaO2 need to be specified in patient care plans; individualized interventions are more useful than generic care plans that state, "turn q 2 h." Additionally, standard rotations for patients treated on mechanically rotating beds could be individualized according to gas exchange responses to the position changes. Routine documentation of patient body positions next to arterial blood gas results on flow sheets could prove valuable in the evaluation and treatment of hypoxemia in patients with pulmonary problems.

The role of vasodilators in patients with progressive systemic sclerosis. Interstitial lung disease and pulmonary hypertension

The use of systemic vasodilator drugs in reducing pulmonary artery pressures in patients with pulmonary hypertension is controversial. The effect of hydralazine in four patients with pulmonary hypertension resulting from interstitial lung disease (group 1) and nifedipine in four patients with pulmonary hypertension secondary to progressive systemic sclerosis (group 2) was investigated. Hydralazine blunted exercise induced elevations in pulmonary arterial pressures in individual group 1 patients; nifedipine failed to effect significant salutory hemodynamic changes in any group 2 patients.