Biomedical subjects

M Brauer

Publications and source records attributed to M Brauer.

80 records · Page 5Linked to original sources

PubMed1975

Removal of intact follicles from immature mice ovaries.

A method was devised with the purpose of preparing significant amounts of isolated intact follicles suitable for "in vitro" studies on the protein synthesis machinery of mammalian oocytes. Ovaries of immature mice(8-14-days old), free of annexes and surrounding fat are squashed gently on a wire screen placed over the rim of a centrifuge tube. This step is followed by washing the screen in a saline-gelatin solution which is centrifuged twice at low speed to separate intact follicles from smaller ovarian components. At the mentioned ages about 170-190 follicles of 80 mu in diameter are found in the ovary. 20% of this population comes out intact from the screen which means that 30 ovaries may yield about 1,000 free follicles. The samples were examined under the light microscope to check their homogeneity and in the electron microscope to see whether squashing introduced changes in the cell cytoplasm. No significant changes were observed. This method is therefore considered useful as a previous step to studying, at the molecular level, the metabolic phenomena related to oocyte growth and further differentiation.

Animals↗

PubMedDate not supplied

Platelet factor 4 (PF4) in septicaemia.

The plasma concentrations of platelet factor 4 were measured in ten patients with septicaemia. In the acute phase the platelet factor 4 values were elevated (27.1 +/- 20.1 ng/ml; mean +/- SD; normal values 4.7 +/- 1.2 ng/ml), and declined significantly after treatment with antibiotics and surgical therapy, respectively (10.6 +/- 7.3 ng/ml; p less than 0.005). The determination of prothrombin time, fibrinopeptide A, AT III and platelet counts demonstrated a coagulation disorder in the acute phase of septicaemia in all patients; a thrombocytopenia (less than 100,000/mm3) was observed in three cases. We suggest that the measurement of platelet factor 4 concentration could be useful as an in vivo indicator and as a follow-up parameter of increased platelet activation.

Adult↗

PubMedDate not supplied

Monitoring personal fine particle exposure with a particle counter.

Numerous epidemiological studies have demonstrated associations between ambient combustion-source particulates and adverse health outcomes. In order to better understand exposure to particles, we evaluated a portable particle counter for its ability to measure short-term peaks in personal particle exposure associated with various activities, such as proximity to vehicular traffic. In a series of laboratory and field measurements, a hand-held particle counter was evaluated by collecting simultaneous filter samples of particulate matter less than 2.5 microns (PM2.5) using a personal monitor. Time activity information was collected using a Personal Digital Assistant (PDA) which allows for linking of exposure events and particle measurements with 1 min temporal resolution. Laboratory and field experiments comparing the particle counter with the personal PM2.5 samples indicated low correlations (R2 < or = 0.39) for all size ranges. Despite these rather poor correlations, field measurements collected during different commuting modes (walking/cycling, car, bus, subway) and in different microenvironments indicated the ability of the particle counter to measure short-term particle exposures, especially those associated with combustion sources. Stratifying the measured particle counts by proximity to different particle sources enabled us to identify activities/microenvironments which were associated with higher exposures. Outdoor particle counts were significantly higher than indoor counts for particles smaller than 5.0 microns. Significantly elevated particle exposures were associated with proximity to environmental tobacco smoke (ETS), cooking emissions, wood smoke and with travel in vehicles powered with internal combustion engines.

Air Pollution↗

PubMedDate not supplied

Assessment of indoor fine aerosol contributions from environmental tobacco smoke and cooking with a portable nephelometer.

Personal monitoring studies have indicated that environmental tobacco smoke (ETS) and cooking are major indoor particulate sources in residential and nonindustrial environments. Continuous monitoring of fine particles improves exposure assessment by characterizing the effect of time-varying indoor sources. We evaluated a portable nephelometer as a continuous monitor of indoor particulate levels. Simultaneous sampling with the nephelometer and PM2.5 impactors was undertaken to determine the relationship between particle light scattering extinction coefficient (sigma(sp)) and particle mass concentration in field and environmental chamber settings. Chamber studies evaluated nephelometer measurements of ETS and particles produced from toasting bread and frying foods. Field measurements were conducted in 20 restaurants and bars with different smoking restrictions, and in five residential kitchens. Additional measurements compared the nephelometer to a different mass measurement method, a piezobalance, in a well-characterized residence where various foods were cooked and ETS was produced. Since the piezobalance provides 2-min average mass concentration measurements, these comparisons tested the ability of the nephelometer to measure transient particle concentration peaks and decay rate curves. We found that sigma(sp) and particle mass were highly correlated (R2 values of 0.63-0.98) over a large concentration range (5-1600 microg/m3) and for different particle sources. Piezobalance and gravimetric comparisons with the nephelometer indicated similar sigma(sp) vs. mass slopes (5.6 and 4.7 m2/g for piezobalance and gravimetric comparisons of ETS, respectively). Somewhat different sigma(sp) vs. particle mass slopes (1.9-5.6 m2/g) were observed for the different particle sources, reflecting the influence of particle composition on light scattering. However, in similar indoor environments, the relationship between particle light scattering and mass concentration was consistent enough to use independent nephelometer measurements as estimates of short-term mass concentrations. A method to use nephelometer measurements to determine particulate source strengths is derived and an example application is described.

Aerosols↗

PubMedDate not supplied

Personal exposure to particles in Banská Bystrica, Slovakia.

Epidemiological studies have associated adverse health impacts with ambient concentrations of particulate matter (PM), though these studies have been limited in their characterization of personal exposure to PM. An exposure study of healthy nonsmoking adults and children was conducted in Banska Bystrica, Slovakia, to characterize the range of personal exposures to air pollutants and to determine the influence of occupation, season, residence location, and outdoor and indoor concentrations on personal exposures. Twenty-four-hour personal, at-home indoor, and ambient measurements of PM10, PM2.5, sulfate (SO4(2-)) and nicotine were obtained for 18 office workers, 16 industrial workers, and 15 high school students in winter and summer. Results showed that outdoor levels of pollutants were modest, with clear seasonal differences: outdoor PM10 summer/winter mean = 35/45 microg/m3; PM2.5 summer/winter mean = 22/32 microg/m3. SO4(2-) levels were low (4-7 microg/m3) and relatively uniform across the different sample types (personal, indoor, outdoor), areas, and occupational groups. This suggests that SO4(2-) may be a useful marker for combustion mode particles of ambient origin, although the relationship between personal exposures and ambient SO4(2-) levels was more complex than observed in North American settings. During winter especially, the central city area showed higher concentrations than the suburban location for outdoor, personal, and indoor measures of PM10, PM2.5, and to a lesser extent for SO4(2-), suggesting the importance of local sources. For PM2.5 and PM10, ratios consistent with expectations were found among exposure indices for all three subject groups (personal>indoor>outdoor), and between work type (industrial>students>office workers). The ratio of PM2.5 personal to indoor exposures ranged from 1.0 to 3.9 and of personal to outdoor exposures from 1.6 to 4.2. The ratio of PM10 personal to indoor exposures ranged from 1.1 to 2.9 and the ratio of personal to outdoor exposures from 2.1 to 4.1. For a combined group of office workers and students, personal PM10/PM2.5 levels were predicted by statistically significant multivariate models incorporating indoor (for PM2.5) or outdoor (for PM10) PM levels, and nicotine exposure (for PM10). Small but significant fractions of the overall variability, 15% for PM2.5 and 17% for PM10, were explained by these models. The results indicate that central site monitors underpredict actual human exposures to PM2.5 and PM10. Personal exposure to SO4(2-) was found to be predicted by outdoor or indoor SO4(2-) levels with 23-71% of the overall variability explained by these predictors. We conclude that personal exposure measurements and additional demographic and daily activity data are crucial for accurate evaluation of exposure to particles in this setting.

Adult↗

PubMedDate not supplied

Exposure of chronic obstructive pulmonary disease patients to particles: respiratory and cardiovascular health effects.

To examine hypotheses regarding air pollution health effects, we conducted an exploratory study to evaluate relationships between personal and ambient concentrations of particles with measures of cardiopulmonary health in a sample of patients with chronic obstructive pulmonary disease (COPD). Sixteen currently non-smoking COPD patients (mean age=74) residing in Vancouver were equipped with a particle (PM(2.5)) monitor for seven 24-h periods. Subjects underwent ambulatory heart monitoring, had their lung function and blood pressure (BP) measured, and recorded symptoms and medication use. Ambient PM(2.5), PM(10), sulfate, and gaseous pollutant concentrations were monitored at five sites within the study area. Although no associations between air pollution and lung function were statistically significant, an estimated effect of 3% and 1% declines in daily FEV(1) change (DeltaFEV(1)) for each 10 microg/m(3) increase in ambient PM(10) and PM(2.5), respectively, was observed. Increases of 1 microg/m(3) in personal or ambient sulfate were associated with 1.0% and 0.3% declines in DeltaFEV(1), respectively. Weak associations were observed between particle concentrations and increased supraventricular ectopic heartbeats and with decreased systolic BP. No consistent associations were observed between any particle metric and diastolic BP, heart rate, or heart rate variability (r-MSSD or SDNN), symptom severity, or bronchodilator use. Of the pollutants measured, ambient PM(10) was most consistently associated with health parameters; the use of personal exposures did not improve the strength of any associations or lead to increased effect estimates.

Aged↗

PubMedDate not supplied

Ambient atmospheric particles in the airways of human lungs.

Epidemiologic studies linking particulate matter (PM) air pollution and adverse respiratory and cardiovascular effects have focused attention on the interactions of PM and lung cells. Information on the types, numbers, composition, sizes, and distribution of ambient particles in the airways is potentially useful for correlations with pathological and/or physiological changes, but relatively little is known about the extent to which ambient particles actually enter airway epithelial cells and are retained in airway walls and even less information is available about correlations with pathologic changes. Since many ambient particles are colorless and/or well below the level of resolution of light microscopy, definitive evaluation of particle burden in the airway wall requires analytical electron microscopy. Studies from the authors' laboratory suggest that in Vancouver, a city with relatively low PM levels, particle loads in the airway mucosa are nonetheless numerically substantial, typically in the range of 10(7) particles/g dry tissue. In most individuals particle concentrations in the larger airways show a clear increase in concentration with increasing airway generation (smaller airway diameter) as expected from deposition models; however, smoking disrupts this pattern in some subjects. Respiratory bronchioles accumulate particularly high particle loads, typically 25-100 times the concentrations seen in the mainstem bronchus. Similarly high concentrations are found in the large airway carinas, suggesting that these locations are likely sites for particle toxicity. The majority of particles in the airways in Vancouver lungs appear to be crustal in origin, with particular accumulation of silica in the airways compared to the parenchyma. Ultrafine particles, which have been postulated to be important in PM toxicity, are present in small numbers as singlet particles and are largely metals, perhaps representing combustion products, but carbonaceous chain aggregates are rarely found. Mean particle aerodynamic diameters vary from about 0.3 to 0.6 microm in different parts of the airways and, overall, the airways retain PM2.5 rather than PM10, a finding supporting the observation that, in some studies, adverse health effects appear to correlate better with PM2.5 than with PM10 concentrations. Preliminary examination of lungs of subjects from Mexico City, a location with relatively high ambient particle concentrations, indicates that the airway mucosa retains relatively large numbers of carbonaceous chain aggregates of ultrafine particles that appear to be combustion products and that presumably produce the numerous adverse effects documented for such products. Limited published data correlating visible particle load and airway mucus secretion, inflammation, and mural fibrosis suggest that high levels of air pollutant particles can induce chronic fibrotic responses in the airways, a phenomenon that might be linked to chronic airflow obstruction; this observation needs confirmation as well as correlation with specific types of particles.

Air Pollutants↗

PubMedDate not supplied

Assessment of indoor aerosols with an integrating nephelometer.

A portable nephelometer was used to assess particulate levels inside and outside of homes with indoor air impacted by biomass combustion. Simultaneous sampling with PM10 and PM2.5 inertial impactors was undertaken to determine the relationship between particle light scattering coefficient (sigma sp) and particle mass concentration. Measurements were conducted in 22 homes in rural Mexico and in 6 homes in rural British Columbia, Canada. In both areas, biomass combustion resulted in high levels of fine particulates, mainly indoors in Mexico and outdoors in British Columbia. Comparisons were made between the average of the nephelometer sigma sp (unheated nephelometer inlet stream) and the measured particle mass (PM10 and PM2.5) during a defined sampling duration. The two measurements were highly correlated (r2 values of 0.79-0.96) over a wide range of particle mass concentrations (10-1600 micrograms/m3). A stronger correlation was observed for PM2.5 than for PM10. Colocated outdoor nephelometer and impactor measurements were poorly correlated (r2 = 0.50). Substantially different relationships were observed between the Mexico and British Columbia particulate, indicating the importance of particle composition and ambient conditions as factors affecting light scattering, even indoors. However, in a given series of similar indoor environments, the relationship between particle light scattering and mass concentration is stable enough to use independent nephelometer measurements as estimates of mass concentrations. The fast-response, continuous measurement, portability and datalogging capabilities of this nephelometer, combined with its ease of use, make this an important measurement tool to be used in conjunction with traditional filter sampling in the assessment of indoor particle levels and the evaluation of sources.

Aerosols↗