Mortality-Air Pollution Associations in Low Exposure Environments (MAPLE): Phase 2.

INTRODUCTION: Mortality is associated with long-term exposure to fine particulate matter (particulate matter ≤2.5 µm in aerodynamic diameter; PM2.5), although the magnitude and form of these associations remain poorly understood at lower concentrations. Knowledge gaps include the shape of concentration-response curves and the lowest levels of exposure at which increased risks are evident and the occurrence and extent of associations with specific causes of death. Here, we applied improved estimates of exposure to ambient PM2.5 to national population-based cohorts in Canada, including a stacked cohort of 7.1 million people who responded to census year 1991, 1996, or 2001. The characterization of the shape of the concentration-response relationship for nonaccidental mortality and several specific causes of death at low levels of exposure was the focus of the Mortality-Air Pollution Associations in Low Exposure Environments (MAPLE) Phase 1 report. In the Phase 1 report we reported that associations between outdoor PM2.5 concentrations and nonaccidental mortality were attenuated with the addition of ozone (O3) or a measure of gaseous pollutant oxidant capacity (Ox), which was estimated from O3 and nitrogen dioxide (NO2) concentrations. This was motivated by our interests in understanding both the effects air pollutant mixtures may have on mortality and also the role of O3 as a copollutant that shares common sources and precursor emissions with those of PM2.5. In this Phase 2 report, we further explore the sensitivity of these associations with O3 and Ox, evaluate sensitivity to other factors, such as regional variation, and present ambient PM2.5 concentration-response relationships for specific causes of death. METHODS: PM2.5 concentrations were estimated at 1 km2 spatial resolution across North America using remote sensing of aerosol optical depth (AOD) combined with chemical transport model (GEOS-Chem) simulations of the AOD:surface PM2.5 mass concentration relationship, land use information, and ground monitoring. These estimates were informed and further refined with collocated measurements of PM2.5 and AOD, including targeted measurements in areas of low PM2.5 concentrations collected at five locations across Canada. Ground measurements of PM2.5 and total suspended particulate matter (TSP) mass concentrations from 1981 to 1999 were used to backcast remote-sensing-based estimates over that same time period, resulting in modeled annual surfaces from 1981 to 2016.Annual exposures to PM2.5 were then estimated for subjects in several national population-based Canadian cohorts using residential histories derived from annual postal code entries in income tax files. These cohorts included three census-based cohorts: the 1991 Canadian Census Health and Environment Cohort (CanCHEC; 2.5 million respondents), the 1996 CanCHEC (3 million respondents), the 2001 CanCHEC (3 million respondents), and a Stacked CanCHEC where duplicate records of respondents were excluded (Stacked CanCHEC; 7.1 million respondents). The Canadian Community Health Survey (CCHS) mortality cohort (mCCHS), derived from several pooled cycles of the CCHS (540,900 respondents), included additional individual information about health behaviors. Follow-up periods were completed to the end of 2016 for all cohorts. Cox proportional hazard ratios (HRs) were estimated for nonaccidental and other major causes of death using a 10-year moving average exposure and 1-year lag. All models were stratified by age, sex, immigrant status, and where appropriate, census year or survey cycle. Models were further adjusted for income adequacy quintile, visible minority status, Indigenous identity, educational attainment, labor-force status, marital status, occupation, and ecological covariates of community size, airshed, urban form, and four dimensions of the Canadian Marginalization Index (Can-Marg; instability, deprivation, dependency, and ethnic concentration). The mCCHS analyses were also adjusted for individual-level measures of smoking, alcohol consumption, fruit and vegetable consumption, body mass index (BMI), and exercise behavior.In addition to linear models, the shape of the concentration-response function was investigated using restricted cubic splines (RCS). The number of knots were selected by minimizing the Bayesian Information Criterion (BIC). Two additional models were used to examine the association between nonaccidental mortality and PM2.5. The first is the standard threshold model defined by a transformation of concentration equaling zero if the concentration was less than a specific threshold value and concentration minus the threshold value for concentrations above the threshold. The second additional model was an extension of the Shape Constrained Health Impact Function (SCHIF), the eSCHIF, which converts RCS predictions into functions potentially more suitable for use in health impact assessments. Given the RCS parameter estimates and their covariance matrix, 1,000 realizations of the RCS were simulated at concentrations from the minimum to the maximum concentration, by increments of 0.1 µg/m3. An eSCHIF was then fit to each of these RCS realizations. Thus, 1,000 eSCHIF predictions and uncertainty intervals were determined at each concentration within the total range.Sensitivity analyses were conducted to examine associations between PM2.5 and mortality when in the presence of, or stratified by tertile of, O3 or Ox. Additionally, associations between PM2.5 and mortality were assessed for sensitivity to lower concentration thresholds, where person-years below a threshold value were assigned the mean exposure within that group. We also examined the sensitivity of the shape of the nonaccidental mortality-PM2.5 association to removal of person-years at or above 12 µg/m3 (the current U.S. National Ambient Air Quality Standard) and 10 µg/m3 (the current Canadian and former [2005] World Health Organization [WHO] guideline, and current WHO Interim Target-4). Finally, differences in the shapes of PM2.5-mortality associations were assessed across broad geographic regions (airsheds) within Canada. RESULTS: The refined PM2.5 exposure estimates demonstrated improved performance relative to estimates applied previously and in the MAPLE Phase 1 report, with slightly reduced errors, including at lower ranges of concentrations (e.g., for PM2.5 <10 µg/m3).Positive associations between outdoor PM2.5 concentrations and nonaccidental mortality were consistently observed in all cohorts. In the Stacked CanCHEC analyses (1.3 million deaths), each 10-µg/m3 increase in outdoor PM2.5 concentration corresponded to an HR of 1.084 (95% confidence interval [CI]: 1.073 to 1.096) for nonaccidental mortality. For an interquartile range (IQR) increase in PM2.5 mass concentration of 4.16 µg/m3 and for a mean annual nonaccidental death rate of 92.8 per 10,000 persons (over the 1991-2016 period for cohort participants ages 25-90), this HR corresponds to an additional 31.62 deaths per 100,000 people, which is equivalent to an additional 7,848 deaths per year in Canada, based on the 2016 population. In RCS models, mean HR predictions increased from the minimum concentration of 2.5 µg/m3 to 4.5 µg/m3, flattened from 4.5 µg/m3 to 8.0 µg/m3, then increased for concentrations above 8.0 µg/m3. The threshold model results reflected this pattern with -2 log-likelihood values being equal at 2.5 µg/m3 and 8.0 µg/m3. However, mean threshold model predictions monotonically increased over the concentration range with the lower 95% CI equal to one from 2.5 µg/m3 to 8.0 µg/m3. The RCS model was a superior predictor compared with any of the threshold models, including the linear model.In the mCCHS cohort analyses inclusion of behavioral covariates did not substantially change the results for both linear and nonlinear models. We examined the sensitivity of the shape of the nonaccidental mortality-PM2.5 association to removal of person-years at or above the current U.S. and Canadian standards of 12 µg/m3 and 10 µg/m3, respectively. In the full cohort and in both restricted cohorts, a steep increase was observed from the minimum concentration of 2.5 µg/m3 to 5 µg/m3. For the full cohort and the <12 µg/m3 cohort the relationship flattened over the 5 to 9 µg/m3 range and then increased above 9 µg/m3. A similar increase was observed for the <10 µg/m3 cohort followed by a clear decline in the magnitude of predictions over the 5 to 9 µg/m3 range and an increase above 9 µg/m3. Together these results suggest that a positive association exists for concentrations >9 µg/m3 with indications of adverse effects on mortality at concentrations as low as 2.5 µg/m3.Among the other causes of death examined, PM2.5 exposures were consistently associated with an increased hazard of mortality due to ischemic heart disease, respiratory disease, cardiovascular disease, and diabetes across all cohorts. Associations were observed in the Stacked CanCHEC but not in all other cohorts for cerebrovascular disease, pneumonia, and chronic obstructive pulmonary disease (COPD) mortality. No significant associations were observed between mortality and exposure to PM2.5 for heart failure, lung cancer, and kidney failure.In sensitivity analyses, the addition of O3 and Ox attenuated associations between PM2.5 and mortality. When analyses were stratified by tertiles of copollutants, associations between PM2.5 and mortality were only observed in the highest tertile of O3 or Ox. Across broad regions of Canada, linear HR estimates and the shape of the eSCHIF varied substantially, possibly reflecting underlying differences in air pollutant mixtures not characterized by PM2.5 mass concentrations or the included gaseous pollutants. Sensitivity analyses to assess regional variation in population characteristics and access to healthcare indicated that the observed regional differences inconcentration-mortality relationships, specifically the flattening of the concentration-mortality relationship over the 5 to 9 µg/m3 range, was not likely related to variation in the makeup of the cohort or its access to healthcare, lending support to the potential role of spatially varying air pollutant mixtures not sufficiently characterized by PM2.5 mass concentrations. CONCLUSIONS: In several large, national Canadian cohorts, including a cohort of 7.1 million unique census respondents, associations were observed between exposure to PM2.5 with nonaccidental mortality and several specific causes of death. Associations with nonaccidental mortality were observed using the eSCHIF methodology at concentrations as low as 2.5 µg/m3, and there was no clear evidence in the observed data of a lower threshold, below which PM2.5 was not associated with nonaccidental mortality.

Mortality-Air Pollution Associations in Low-Exposure Environments (MAPLE): Phase 1.

INTRODUCTION: Fine particulate matter (particulate matter ≤2.5 µm in aerodynamic diameter, or PM2.5) is associated with mortality, but the lower range of relevant concentrations is unknown. Novel satellite-derived estimates of outdoor PM2.5 concentrations were applied to several large population-based cohorts, and the shape of the relationship with nonaccidental mortality was characterized, with emphasis on the low concentrations (<12 µg/m3) observed throughout Canada. METHODS: Annual satellite-derived estimates of outdoor PM2.5 concentrations were developed at 1-km2 spatial resolution across Canada for 2000-2016 and backcasted to 1981 using remote sensing, chemical transport models, and ground monitoring data. Targeted ground-based measurements were conducted to measure the relationship between columnar aerosol optical depth (AOD) and ground-level PM2.5. Both existing and targeted ground-based measurements were analyzed to develop improved exposure data sets for subsequent epidemiological analyses.Residential histories derived from annual tax records were used to estimate PM2.5 exposures for subjects whose ages ranged from 25 to 90 years. About 8.5 million were from three Canadian Census Health and Environment Cohort (CanCHEC) analytic files and another 540,900 were Canadian Community Health Survey (CCHS) participants. Mortality was linked through the year 2016. Hazard ratios (HR) were estimated with Cox Proportional Hazard models using a 3-year moving average exposure with a 1-year lag, with the year of follow-up as the time axis. All models were stratified by 5-year age groups, sex, and immigrant status. Covariates were based on directed acyclical graphs (DAG), and included contextual variables (airshed, community size, neighborhood dependence, neighborhood deprivation, ethnic concentration, neighborhood instability, and urban form). A second model was examined including the DAG-based covariates as well as all subject-level risk factors (income, education, marital status, indigenous identity, employment status, occupational class, and visible minority status) available in each cohort. Additional subject-level behavioral covariates (fruit and vegetable consumption, leisure exercise frequency, alcohol consumption, smoking, and body mass index [BMI]) were included in the CCHS analysis.Sensitivity analyses evaluated adjustment for covariates and gaseous copollutants (nitrogen dioxide [NO2] and ozone [O3]), as well as exposure time windows and spatial scales. Estimates were evaluated across strata of age, sex, and immigrant status. The shape of the PM2.5-mortality association was examined by first fitting restricted cubic splines (RCS) with a large number of knots and then fitting the shape-constrained health impact function (SCHIF) to the RCS predictions and their standard errors (SE). This method provides graphical results indicating the RCS predictions, as a nonparametric means of characterizing the concentration-response relationship in detail and the resulting mean SCHIF and accompanying uncertainty as a parametric summary.Sensitivity analyses were conducted in the CCHS cohort to evaluate the potential influence of unmeasured covariates on air pollution risk estimates. Specifically, survival models with all available risk factors were fit and compared with models that omitted covariates not available in the CanCHEC cohorts. In addition, the PM2.5 risk estimate in the CanCHEC cohort was indirectly adjusted for multiple individual-level risk factors by estimating the association between PM2.5 and these covariates within the CCHS. RESULTS: Satellite-derived PM2.5 estimates were low and highly correlated with ground monitors. HR estimates (per 10-µg/m3 increase in PM2.5) were similar for the 1991 (1.041, 95% confidence interval [CI]: 1.016-1.066) and 1996 (1.041, 1.024-1.059) CanCHEC cohorts with a larger estimate observed for the 2001 cohort (1.084, 1.060-1.108). The pooled cohort HR estimate was 1.053 (1.041-1.065). In the CCHS an analogous model indicated a HR of 1.13 (95% CI: 1.06-1.21), which was reduced slightly with the addition of behavioral covariates (1.11, 1.04-1.18). In each of the CanCHEC cohorts, the RCS increased rapidly over lower concentrations, slightly declining between the 25th and 75th percentiles and then increasing beyond the 75th percentile. The steepness of the increase in the RCS over lower concentrations diminished as the cohort start date increased. The SCHIFs displayed a supralinear association in each of the three CanCHEC cohorts and in the CCHS cohort.In sensitivity analyses conducted with the 2001 CanCHEC, longer moving averages (1, 3, and 8 years) and smaller spatial scales (1 km2 vs. 10 km2) of exposure assignment resulted in larger associations between PM2.5 and mortality. In both the CCHS and CanCHEC analyses, the relationship between nonaccidental mortality and PM2.5 was attenuated when O3 or a weighted measure of oxidant gases was included in models. In the CCHS analysis, but not in CanCHEC, PM2.5 HRs were also attenuated by the inclusion of NO2. Application of the indirect adjustment and comparisons within the CCHS analysis suggests that missing data on behavioral risk factors for mortality had little impact on the magnitude of PM2.5-mortality associations. While immigrants displayed improved overall survival compared with those born in Canada, their sensitivity to PM2.5 was similar to or larger than that for nonimmigrants, with differences between immigrants and nonimmigrants decreasing in the more recent cohorts. CONCLUSIONS: In several large population-based cohorts exposed to low levels of air pollution, consistent associations were observed between PM2.5 and nonaccidental mortality for concentrations as low as 5 µg/m3. This relationship was supralinear with no apparent threshold or sublinear association.

Long-term exposure to traffic-related air pollution and selected health outcomes: A systematic review and meta-analysis.

The health effects of traffic-related air pollution (TRAP) continue to be of important public health interest. Following its well-cited 2010 critical review, the Health Effects Institute (HEI) appointed a new expert Panel to systematically evaluate the epidemiological evidence regarding the associations between long-term exposure to TRAP and selected adverse health outcomes. Health outcomes were selected based on evidence of causality for general air pollution (broader than TRAP) cited in authoritative reviews, relevance for public health and policy, and resources available. The Panel used a systematic approach to search the literature, select studies for inclusion in the review, assess study quality, summarize results, and reach conclusions about the confidence in the evidence. An extensive search was conducted of literature published between January 1980 and July 2019 on selected health outcomes. A new exposure framework was developed to determine whether a study was sufficiently specific to TRAP. In total, 353 studies were included in the review. Respiratory effects in children (118 studies) and birth outcomes (86 studies) were the most commonly studied outcomes. Fewer studies investigated cardiometabolic effects (57 studies), respiratory effects in adults (50 studies), and mortality (48 studies). The findings from the systematic review, meta-analyses, and evaluation of the quality of the studies and potential biases provided an overall high or moderate-to-high level of confidence in an association between long-term exposure to TRAP and the adverse health outcomes all-cause, circulatory, ischemic heart disease and lung cancer mortality, asthma onsetin chilldren and adults, and acute lower respiratory infections in children. The evidence was considered moderate, low or very low for the other selected outcomes. In light of the large number of people exposed to TRAP - both in and beyond the near-road environment - the Panel concluded that the overall high or moderate-to-high confidence in the evidence for an association between long-term exposure to TRAP and several adverse health outcomes indicates that exposures to TRAP remain an important public health concern and deserve greater attention from the public and from policymakers.

Modeling the intraurban variability of ambient traffic pollution in Toronto, Canada.

The objective of this paper is to model determinants of intraurban variation in ambient concentrations of nitrogen dioxide (NO2) in Toronto, Canada, with a land use regression (LUR) model. Although researchers have conducted similar studies in Europe, this work represents the first attempt in a North American setting to characterize variation in traffic pollution through the LUR method. NO2 samples were collected over 2 wk using duplicate two-sided Ogawa passive diffusion samplers at 95 locations across Toronto. Independent variables employed in subsequent regression models as predictors of NO2 were derived by the Arc 8 geographic information system (GIS). Some 85 indicators of land use, traffic, population density, and physical geography were tested. The final regression model yielded a coefficient of determination (R2) of .69. For the traffic variables, density of 24-h traffic counts and road measures display positive associations. For the land use variables, industrial land use and counts of dwellings within 2000 m of the monitoring location were positively associated with NO2. Locations up to 1500 m downwind of major expressways had elevated NO2 levels. The results suggest that a good predictive surface can be derived for North American cities with the LUR method. The predictive maps from the LUR appear to capture small-area variation in NO2 concentrations. These small-area variations in traffic pollution are probably important to the exposure experience of the population and may detect health effects that would have gone unnoticed with other exposure estimates.

Diet modification to reduce phosphorus surpluses: a mass balance approach.

Diet modification to reduce phosphorus (P) concentrations in manures has been developed in response to environmental concerns over P losses from animal agriculture to surface waters. We used USDA-NASS statistics on animal numbers and crop production to calculate county scale mass balances for manure P production, P removed in harvested portion of crops, and the potential effects of diet modification. Although spreading manure evenly over all crop acreage within a county is unlikely to occur, these calculations give a good indication as to the impact diet modification to reduce P can have at a regional or national scale. There was a high degree of regional variability in manure P surpluses (e.g., with the large crop acreages in the grain belt leading to large P offtake in crops preventing most P surpluses). In 89% of counties, there was a deficit of manure P relative to crop P removal; therefore there was a manure P surplus in 11% of counties. Diet modification decreased the percentage of states with a manure P surplus from 11 to 8%, a decrease of approximately 27%. Diet modification decreased the percentage of counties with the greatest surpluses of manure P (>30 kg ha(-1)) from 3% of all counties to 1%. Diet modification to decrease manure P is an important part of strategies to alleviate environmental concerns associated with surplus manure P in many areas, but additional strategies to deal with manure P surpluses are needed in some areas.

Outcome of high-dose therapy and autologous transplantation in non-Hodgkin's lymphoma based on the presence of tumor in the marrow or infused hematopoietic harvest.

PURPOSE: To evaluate the outcomes in 65 consecutive patients with non-Hodgkin's lymphoma (NHL) undergoing high-dose therapy (HDT) and autologous transplantation based on initial marrow involvement and the presence or absence of minimal disease in the hematopoietic harvests. PATIENTS AND METHODS: Patients with any history of histologic evidence of marrow tumor underwent autologous peripheral-blood stem-cell transplantation (PSCT), whereas others underwent autologous bone marrow transplantation (ABMT). Patients who underwent ABMT were further segregated retrospectively into two groups depending on whether there was evidence by cell culture and/or Southern analysis of minimal tumor in the marrow harvest. RESULTS: Comparable proportions (58% to 60%) of patients in each of the two groups (PSCT and ABMT) achieved a complete clinical remission (CR) at 100 days. For patients who achieve a CR, the actuarial relapse-free survival rate at 5 years for PSCT patients who received a tumor-negative apheresis harvest was 64%, compared with 57% for patients who received a tumor-negative bone marrow harvest and 17% for patients who received a histologically negative but minimally contaminated bone marrow harvest. Lymphoma grade and phenotype were not significant predictors of outcome. CONCLUSION: The observation that survival was significantly better in the groups of patients who received tumor-negative harvests and worse for patients who received minimally contaminated harvests suggests that tumor cells, even at minimal levels, reinfused in the transplanted harvest are responsible for progression in a proportion of patients who achieve a CR following HDT, although other biologic characteristics of the tumor could also be important. A relatively good outcome can be achieved with HDT and PSCT, even in patients with a significant marrow tumor burden.

Immunomodulation by exogenous surfactant: effect on TNF-alpha secretion and luminol-enhanced chemiluminescence activity by murine macrophages stimulated with group B streptococci.

Group B streptococci (GBS) are important pathogens in neonatal sepsis and pneumonia. GBS stimulate alveolar macrophages to produce inflammatory cytokines and free oxygen radicals, which can damage the lungs. In several studies, use of exogenous surfactant in term babies has improved outcome related to sepsis and respiratory failure. The role(s) of exogenous surfactant in modulating the inflammatory response produced by this microbe was examined. Tumor necrosis factor alpha (TNF-alpha) production and luminol-enhanced chemiluminescence (LCL), a measure of respiratory burst, were investigated. For measuring TNF-alpha release, RAW 264.7 murine macrophages were pre-incubated with bovine surfactant and stimulated with either lipopolysaccharide, live or heat-killed GBS type Ia. LCL was measured after macrophages were pre-incubated with or without surfactant overnight, then stimulated with GBS or phorbol myristate acetate. Lipopolysaccharide and GBS stimulated TNF-alpha secretion from macrophages that was suppressed by exogenous surfactant in a dose-dependent fashion. GBS and phorbol myristate acetate also increased LCL from macrophages, which was significantly suppressed by pre-incubation of macrophages with exogenous surfactant. We conclude that GBS type Ia stimulates TNF-alpha release and LCL from RAW 264.7 cells and that these responses are suppressed by surfactant. Suppression of inflammatory mediators by exogenous surfactant might improve respiratory disease associated with GBS.

An in vitro investigation of the hematopoietic microenvironment in young and aged mice.

Dexter-type cultures derived from the bone marrow of young and aged mice were established as in vitro correlates to the hematopoietic microenvironment and inoculated two weeks later with fresh bone marrow-derived stem cells (colony-forming units, CFUs) from young, syngeneic mice. Such cultures allowed the observation, quantitation and evaluation of interactions between aged or young microenvironments and the young stem cells. The hematopoietic microenvironments derived from aged marrow were found to support a greater total nucleated cellularity and a significantly greater number of CFUs. Also, the production of CFUs on aged monolayers occurred at an elevated rate. Though cyclic variations in total cellularity were noted in all cultures, the granulocyte--macrophage lineage always predominated. Lymphocyte populations in all cultures were seen to decline rapidly with time as other cell types became more abundant. The number of megakaryocytes in the aged marrow-derived cultures was significantly elevated in the early time periods post-refeeding. Differences in the adherent cell population densities were noted with the aged monolayers being somewhat less dense. However, there were no differences in morphologically identifiable cell types comprising the adherent layers derived from marrow of young and old mice. From these results, we conclude that there are differences in the ability of aged versus young hematopoietic microenvironments to support normal young stem cells in vitro and that the microenvironmental influences present in the in vitro system are reflective of those seen in the in vivo marrow microenvironment.

Intestinal glucose uptake is increased in aged mice.

Carbohydrate metabolism is impaired in the aged. Whether this is related to impaired glucose uptake or to other factors remains unclear. We measured changes in proliferative activity, glucose uptake, and disaccharidase activity in the intestinal mucosa of mice aged 2, 12, 24, and 30+ months to evaluate glucose absorption and its relationship to intestinal structure and proliferative activity. In vitro glucose uptake was increased significantly in the 30+ month-old mice compared to the younger animals. Similarly, crypt cell production rate and thymidine uptake were also increased. However, there were no significant changes in intestinal weight and length and villus height and crypt depth. These findings suggest that altered carbohydrate absorption in the aged is related to factors other than diminished mucosal glucose uptake. Whether this increased function is related to structural changes in the gut remains unclear.

Ureaplasmal pneumonia and sepsis associated with persistent pulmonary hypertension of the newborn.

Ureaplasma urealyticum was isolated from the lower respiratory tract of three infants with persistent pulmonary hypertension of the newborn. In one, cultures positive for U urealyticum were obtained on multiple occasions from trachea, blood, and pleural fluid prior to the infant's death on postnatal day 6. Autopsy findings confirmed the presence of severe pneumonia and the organism was again recovered from multiple sites. A second infant had no apparent predisposing factors for development of persistent pulmonary hypertension of the newborn but U urealyticum and Staphylococcus epidermidis were recovered from the trachea antemortem and from lung tissue obtained during autopsy on the 12th postnatal day. The third infant had persistent pulmonary hypertension of the newborn and a pulmonary infiltrate within hours after birth with tracheal cultures positive for both U urealyticum and Mycoplasma hominis. Erythromycin was given for ten days, and the infant gradually improved. Prolonged ventilation with supplemental oxygen was necessary, and chronic lung disease developed. This is the first report of neonatal ureaplasmal pneumonia with sepsis and persistent pulmonary hypertension of the newborn as well as the first time a microorganism other than streptococci has been specifically implicated in the pathogenesis of persistent pulmonary hypertension of the newborn. Respiratory infections with U urealyticum or other bacteria should be considered as possible causative or contributory factors in infants with persistent pulmonary hypertension of the newborn.

Progression of influenza viral infection through the murine respiratory tract: the protective role of sleep deprivation.

Sleep deprivation is reported to have both beneficial and harmful effects upon host defenses. In the work reported herein, we address the effects of sleep deprivation on the mucosal anti-influenza defenses of both immune and nonimmune BALB/c mice. Sleep deprivation does not depress existing mucosal antiviral defenses in the respiratory tracts of BALB/c mice; in fact, it may actually be beneficial. Nasal mucosal immunity is not adversely affected in immune mice by sleep deprivation. In nonimmune mice, sleep deprivation slows or prevents the progress of nasal influenza viral infection down the trachea into the lungs. By 72 hours post-infection, 12 of 12 control mice shed virus into bronchioalveolar lavages (BAL) while only 2 of 12 sleep deprived mice shed virus (p<0.001). BAL levels of IL-1beta and interferon alpha were increased in sleep deprived animals, suggesting that sleep deprivation may exert its beneficial effects on the respiratory tract by upregulating the production of antiviral cytokines.

Antibiotic susceptibilities and therapeutic options for Ureaplasma urealyticum infections in neonates.

The appreciation of Ureaplasma urealyticum as a human pathogen and documentation of antibiotic resistance have heightened interest in drug susceptibilities and treatment alternatives for patients infected with this organism. Neonates pose special problems when therapy must be considered because of potential toxicities, clinical unfamiliarity or lack of experience. Forty-three isolates of U. urealyticum obtained from the lower respiratory tracts of neonates were tested against chloramphenicol, ciprofloxacin, clindamycin, erythromycin, doxycycline, and gentamicin by a microbroth dilution technique in 10B broth. In vitro resistance was observed in 1 or more strains for each of the drugs tested, except for erythromycin (minimal inhibitory concentration (MIC) range, 0.125 to 4 micrograms/ml, MIC90 = 2 micrograms/ml). MIC90 values for the remaining five antibiotics were: doxycycline, 2 micrograms/ml; chloramphenicol, 8 micrograms/ml; ciprofloxacin, 8 micrograms/ml; clindamycin, 16 micrograms/ml; and gentamicin, 32 micrograms/ml. The effect of pH and/or media components on MICs was evaluated by comparing MICs of American Type Culture Collection reference strain Staphylococcus aureus 29213 obtained in Mueller-Hinton broth (pH 7.2 to 7.4) and 10B broth (pH 6.0). No appreciable effect was detected for ciprofloxacin, chloramphenicol or doxycycline, whereas gentamicin, erythromycin and clindamycin all had MICs elevated by one to several dilutions when tested in 10B broth. In some instances the difference was sufficient to alter the interpretation of the MIC. Clinical experience in treating neonatal ureaplasmal infections is reviewed along with recommendations for obtaining cultures, initiating and monitoring efficacy of therapy.

Mycoplasmal infections of cerebrospinal fluid in newborn infants from a community hospital population.

Mycoplasma hominis or Ureaplasma urealyticum have previously been isolated from cerebrospinal fluid (CSF) in 13 of 100 newborn infants tested from a high risk university hospital population where the mothers were of predominantly lower income and socioeconomic status and had often received little or no prenatal care. We sought to determine whether such infections occur in neonates born to women cared for mainly through private obstetric practices and who delivered in 4 suburban community hospitals. CSF cultures were done in 318 infants during an 8-month period. M. hominis was isolated from 9 and U. urealyticum from 5 CSF cultures. Four infants infected with U. urealyticum and 3 infected with M. hominis were born at term. One infant infected with U. urealyticum had a birth weight of less than 1000 g. In 5 infants clearance of the infecting organism was documented without specific treatment. Twelve infants had good perinatal outcomes regardless of treatment and 2 died. One death in a 2240-g infant infected with M. hominis was associated with Haemophilus influenzae sepsis and pneumonia. The other death occurred 3 days after birth in a 630-g infant infected with U. urealyticum who had evidence of meningitis and intraventricular hemorrhage. Results of this study suggest that mycoplasmas are common causes of neonatal CSF infections, not only in high risk populations, but also in the general population.

Serum concentrations of erythromycin after intravenous infusion in preterm neonates treated for Ureaplasma urealyticum infection.

Erythromycin is receiving renewed attention as an alternative for treatment of neonatal infections caused by Ureaplasma urealyticum because of recently proved abilities of this organism to produce systemic disease in this population. Although erythromycin has been used clinically for almost 40 years, very little is known about its activity in the preterm neonate. Fourteen neonates, birth weights < or = 1500 g and < or = 15 days of age, from whom U. urealyticum was isolated from the lower respiratory tract were randomized to receive erythromycin lactobionate either 25 or 40 mg/kg/day in four divided doses at 6-hour intervals scheduled for a total of 10 days. Blood samples collected at multiple time points after initial and steady state doses were assayed for erythromycin by liquid chromatography. Minimal inhibitory concentrations (MICs) of erythromycin for the U. urealyticum isolates were determined. MICs ranged from 0.031 to 2 micrograms/ml; MIC90 = 2 micrograms/ml. Serum erythromycin concentrations met or exceeded most MICs, with peak values of 3.05 to 3.69 and 1.92 to 2.9 micrograms/ml for the 40- and 25-mg/kg/day dosage groups, respectively. Pharmacokinetic parameters were calculated after the initial dose and at steady state for both dosage groups and compared. No adverse effects thought to be related to administration of erythromycin were observed. These preliminary findings showed that erythromycin is well-tolerated, has favorable pharmacokinetic activity in the preterm neonate and should be further investigated for treatment of ureaplasmal infections.

Apparent synergism between radiation and the carcinogen 1,2-dimethylhydrazine in the induction of colonic tumors in rats.

We have evaluated the interaction of radiation and 1,2-dimethylhydrazine (DMH) with respect to colon carcinogenesis in the Fischer 344 rat and have demonstrated the utility of this model for future more detailed mechanistic studies. In initial experiments, single doses of abdomen-only radiation (9 Gy) or DMH (150 mg/kg) were employed alone or in combination. Radiation was administered 3.5 days prior to the DMH. At 8 months post-treatment, the incidence of DMH-induced colon tumors was doubled by prior radiation exposure. When the protocol was repeated employing a DMH dose of 135 mg/kg with a 6-month observation period, the incidence of tumors induced by DMH alone was reduced, but the combination of radiation plus DMH still resulted in an augmentation of tumor incidence. When the protocol of radiation plus DMH was repeated three times at monthly intervals, a 15-fold increase in tumor incidence (from 5 to 74%) was observed at 6 months post-treatment. This finding demonstrates an apparent synergy between the radiation and the chemical carcinogen. Throughout these studies, the appearance of carcinomas was associated with preexisting colonic lymphoid nodules. The reproducibility of tumor induction as well as range of tumor incidence generated by variations in this system may be adequately sensitive to examine the combination of much lower doses of radiation and/or chemical carcinogen. The relationship between existing lymphoid aggregates which alter local epithelial cell kinetics and which are associated with fenestrations in the basement membrane, and the development of colon cancer in congruent sites may assist in defining dose-response curves for combined agents as well as providing a system for evaluating the mechanisms underlying their interactions.

Stem and stromal cell reconstitution of lethally irradiated mice following transplantation of hematopoietic tissue from donors of various ages.

If the limited life span of hematopoietic tissues in vitro is due to a finite proliferative capacity of individual stem cells, one might expect tissues of young donors to possess a greater proliferative capacity and to contain a larger population of primitive stem cells than those of older donors. To test this hypothesis, we used 12- and 8-day spleen colony formation (CFU-s) to assay more and less primitive stem cell subpopulations of three murine hematopoietic tissues: fetal liver (FL) and weanling (WBM) and adult (ABM) bone marrow. Subsequently, the same assays and a stromal cell assay were performed on the bone marrow from groups of lethally irradiated mice reconstituted with these tissues. Comparison of the CFU-s content of the donor tissues revealed that FL contained a significantly greater proportion of primitive stem cells as evidenced by a (Day 12):(Day 8) CFU-s ratio of 3.0 +/- 1.0 as compared to 0.9 +/- 0.1 for WBM and ABM. In addition, at 21 weeks post-transplantation the CFU-s/femur values of the FL reconstituted group were significantly greater than those of the ABM and WBM reconstituted groups. These results suggest that fetal hematopoietic tissue contains a greater proportion of primitive stem cells and has a greater proliferative potential than hematopoietic tissue from older donors. No differences were seen in stromal cell reconstitution of the three experimental groups. In all cases, assayable fibroblast colony forming cells (CFU-f) remained at 20-40% of control values, even at 21 weeks postreconstitution.

Epithelial cell proliferation and uptake of radiolabeled urogastrone in the intestinal tissues following abdominal irradiation in the mouse.

We have evaluated the rate of crypt cell production and uptake of radiolabeled recombinant human urogastrone (125I-rhUG) in the intestinal tissues of the mouse at 3, 5, 7, 9, and 12 days following irradiation of the abdomen with 9 Gy. At autopsy, the animals were injected intraperitoneally with 1 microgram/g body weight of the metaphase arrest agent, vincristine sulfate, and 25 muCi of 125I-rhUG (specific activity 1.7 muCi/micrograms) to quantify the rate of crypt cell production and uptake of radiolabeled urogastrone, respectively. The results indicated that the rate of crypt cell production was increased significantly in the irradiated animals compared to the unirradiated animals and showed a peak on the 3rd and 5th postirradiation days in small intestine and colon, respectively. The uptake of 125I-rhUG was increased significantly on the 3rd postirradiation day in the intestinal tissues but showed a bimodal pattern with peaks on the 3rd and 9th postirradiation days. These results suggest that there may be a close association between epithelial cell proliferation and uptake of 125I-rhUG, particularly in the early part of recovery of intestinal mucosa following irradiation. However, these data do not discriminate whether the increased uptake of 125I-rhUG is the cause or the effect of proliferation induced by an irradiation stimulus. Further analysis also revealed that there was no relationship between crypt depth and 125I-rhUG uptake. However, crypt depth was inversely correlated with villus height in the proximal small intestine but not in the ileum. Villus height was correlated inversely with 125I-rhUG uptake in the ileum and jejunum but not the duodenum. The rate of crypt cell production was strongly correlated with crypt depth throughout the intestine and inversely correlated with villus height. This suggests that villus-to-crypt inhibitory feedback may be a primary regulator of cellular proliferation in the crypts and the association of 125I-rhUG uptake with proliferation indirectly reflects this interaction.

Relative biological effectiveness measurements using murine lethality and survival of intestinal and hematopoietic stem cells after fermilab neutrons compared to JANUS reactor neutrons and 60Co gamma rays.

The relative biological effectiveness (RBE) of the 25-MeV (average energy) neutron beam at the Fermi National Accelerator Laboratory was measured using murine bone marrow (LD50/30) and gut (LD50/6) lethality and killing of hematopoietic colony forming units (CFU-S) or intestinal clonogenic cells (ICC). The reference radiation was 60Co gamma rays. The LD50/30 and LD50/6 for mice exposed to the Fermilab neutron beam were 6.6 and 8.7 Gy, respectively, intermediate between those of JANUS neutrons and 60Co gamma rays. The D0 values for CFU-S and ICC were 47 cGy and 1.05 Gy, respectively, also intermediate between the lowest values found for JANUS neutrons and the highest values found after 60Co gamma rays. The split-dose survival ratios for CFU-S at intervals of 1-6 hr between doses were essentially 1.0 for both neutron sources, while the corresponding split-dose survival ratio for 60Co gamma rays was consistantly above 1, reaching a maximum of 1.7 with a 1-hr interval between doses. The 3-hr split-dose survival ratios for ICC were 1.0 for JANUS neutrons, 1.85 for Fermilab neutrons, and 6.5 for 60Co gamma rays. The RBE estimates for LD50/30 were 1.5 and 2.3 for Fermilab and JANUS neutrons, respectively. Based on LD50/6, the RBEs were 1.9 (Fermilab) and 3.0 (JANUS). The RBEs for CFU-S D0 were 1.4 (Fermilab) and 1.9 (JANUS) and for jejunal microcolony D0 1.4 (Fermilab) and 2.8 (JANUS).

Patterns of Schistosoma haematobium egg distribution in the human lower urinary tract. II. Obstructive uropathy.

In a series of 32 unselected consecutive autopsies of Egyptian male adults, we found a significant prevalence of schistosomal obstructive uropathy (SOU) and of precursor lesions of stenosis, fibrosis and induration of the ureters (62.5%). Lower urinary tracts with obstructive uropathy had a significantly higher total egg burden (TEB) than did lower urinary tracts with any other type of gross lesion (i.e., benign prostatic hypertrophy, other urethral outlet obstruction, or SOU precursor lesions). In turn, lower urinary tracts with any type of gross change had higher egg burdens than did tracts which appeared grossly normal. Lower urinary tracts with any type of gross lesion had significantly larger seminal vesicles than did tracts which were grossly normal. Moreover, relative weight of seminal vesicles could be correlated with the S. haematobium egg burdens in the seminal vesicles. In a series of lower urinary tracts taken from unselected consecutive American autopsies, seminal vesicle weight could be correlated with increase in prostatic weight in those tracts with prostatic hypertrophy; the same correlation could not be found in tracts without prostatic hypertrophy. Thus, seminal vesicle hypertrophy appears to correlate with obstructive uropathy in general, not solely obstructive uropathy of schistosomal origin. Digital evaluation of seminal vesicle size may be useful in the clinical evaluation of such patients.

Patterns of Schistosoma haematobium egg distribution in the human lower urinary tract. I. Noncancerous lower urinary tracts.

Schistosoma haematobium egg burdens (eggs/g of tissue) of 17 anatomic segments of lower urinary tracts from 32 unselected Egyptian autopsies have been determined by tissue digestion and replicate counts of aliquots of the digestate. There were three anatomic patterns of egg distribution in these lower urinary tracts: apical, basal and diffuse. Regression of egg burdens of each of the anatomic segments as the dependent variable against egg burdens of the entire lower urinary burden yielded a good fit for 15 of 17 of these segments. Statistical analyses revealed that many of these equations for discrete anatomic segments can be combined, generally giving one equation for anatomic regions which are in continuity, indicating that the female worm lives and oviposits in specified venous plexes. These equations also suggest that there are differences in the rates, duration and onset of egg accumulation which may be responsible for schistosomal obstructive uropathy as a cause of death in fairly young individuals.