PubMed Health⌕ Search

Biomedical subjects

B A Boehlecke

Publications and source records attributed to B A Boehlecke.

13 recordsLinked to original sources
PubMed2000

Characterization of an aerosol chamber for human exposures to endotoxin.

The objective of this study was to develop and characterize an exposure chamber in which human subjects could be exposed to low dust concentrations carrying an endotoxin coating. An exposure chamber, dust dispersion method, and endotoxin characterization technique were developed for inhalation exposures. A 6.27 m3 exposure chamber was designed and constructed from cinder block, glass windows, and Plexiglas. Using an acetone adhesion process, Enterobacter agglomerans were adsorbed onto respirable cellulose particles to create the endotoxin aerosol. The size distribution of the endotoxin-treated particles was verified using light microscopy and cascade impactors. A dry powder dust generator was refined to consistently disperse small quantities of the aerosol into the chamber to maintain dust concentrations at approximately 250 micrograms/m3. Dust levels during the chamber exposures were monitored using a portable continuous aerosol monitor (PCAM). During initial exposure runs, PCAM monitoring stations were positioned at different locations within a 0.5-meter matrix to document mixing patterns. Total dust and cascade impactor samples were collected throughout each exposure period to characterize the chamber operating system and insure the mean airborne dust concentration fulfilled target levels. A one-factor analysis of variance at the 95 percent confidence interval illustrated that there was not a statistically significant difference in the mean dust concentration throughout the exposure runs compared to the individual runs. Together the consistency of the total dust filters, endotoxin concentrations, and aerosol-monitoring instrument were adequate to allow use of the chamber for experimental studies involving human volunteers.

Aerosols↗
PubMed2000

Epidemiology and pathogenesis of sleep-disordered breathing.

Sleep-disordered breathing is common in the general population, but the observed prevalence depends on the criteria used to establish the diagnosis. Obesity is a strong risk factor, but other conditions such as allergic upper and lower airways disease may also be important. Differences in risk between the sexes and ethnic groups appear to be present even after established risk factors have been considered. The pathogenesis is likely mutifactorial with anatomic and physiologic factors of varying importance in different individuals. The natural history is uncertain, but without treatment or reduction in risk factors, some progression is likely. Ongoing epidemiologic investigations such as the Sleep Heart Health Study are beginning to provide important information on these questions.

Age Factors↗
PubMed1996

A mathematical model of bronchial absorption of vapors in the human lung and its significance in pharmacokinetic modeling.

This work formulates a model description of moderately soluble gas and vapor uptake in the bronchial region of the lung during initial inhalation exposure. The mass transport problem is solved using an iterative-analytical approach in which inhaled chemical is partitioned to alveolar blood-gas exchange, bronchial wall absorption, and exhalation. Results of 109 simulations allowed regression analysis to provide simple algebraic equations to describe the fraction of total inhaled mass taken up by the two alternative absorption pathways. These fractions are dependent on the chemical's solubility and liquid diffusivity. The derived relationships are then used in a modified physiologically based pharmacokinetic (PBPK) model which accounts for bronchial uptake. The results are compared to identical results from a traditional (unmodified) PBPK model to draw conclusions concerning the effect of bronchial uptake on systemic chemical distribution in addition to elevated bronchial tissue concentrations.

Absorption↗
PubMed1981

Silicosis in the 1980's.

At the request of the Mine Safety and Health Administration (MSHA), the National Institute for Occupational Safety and Health (NIOSH) recently investigated the health of workers at two silica flour mills. Both mills have a long history of failure to maintain workplace concentrations of dust containing free silica below the MSHA exposure standard. Thirty-seven percent of sixty-one workers and ex-workers with one or more years of silica dust exposure had chest radiographic evidence of silicosis. Because of the high prevalence of silicosis in workers at these two silica flour producers, MSHA silica dust measurements were reviewed for twenty-five other active U.S. silica flour producers. Eighty-nine percent of the work force in these 27 silica flour producers are employed at workplaces where more than twenty-five percent of the dust samples reviewed were above the exposure standard. Fifty-three percent of all samples were above the MSHA standard. No significant decline in silica dust levels occurred during the period (1974-1979) covered by the data supplied by MSHA. Based on the NIOSH study and MSHA data, it is apparent that the risk of silicosis is very high among workers in this industry. Prevention of this disease will require a concerted effort of government enforcement agencies, workers and management.

Dust↗
PubMed1981

Silicosis in silica flour workers.

In July 1979, the health of 86 current and ex-workers at 2 silica mining and milling operations in southern Illinois was examined using a respiratory questionnaire, spirometry, and chest radiographs. None of 25 current workers with less than 1 yr of exposure to silica dust had radiographic evidence of silicosis. For 61 current workers and ex-workers with 1 or more yr of exposure, chest radiographs showed 16 (26%) with simple silicosis and 7 (11%) with progressive massive fibrosis. Of these 23, 8 with simple silicosis and 3 with progressive massive fibrosis began work after the first Mine Safety and Health Administration inspection in 1973. These data and a review of federal dust inspection results between 1973 and 1979 showed that these cases of silicosis could have been prevented by effecting compliance with the existing dust standard.

Adult↗
PubMed1981

The use of pulmonary function testing and questionnaires as epidemiologic tools in the study of occupational lung disease.

Pulmonary function testing and questionnaires are valuable tools in epidemiologic studies of occupational lung disease. Accurate equipment and standardized methodology are vital to obtain reproducible responses. For spirometry, the FVC and FEV show the least intrasubject variability and on questionnaires, occupational and smoking history are more reproducible than symptoms. The limitations of any method used to define a lower limit of normal should be kept in mind and, whenever possible, groups should be compared by use of the distribution of observations in the two groups--not just the prevalence of "abnormal" findings.

Adult↗
PubMed1981

Cotton dust and complement in vivo.

Cotton grown in Stoneville, Mississippi and harvested by three different methods was examined for anticomplementary activity in human serum in vivo. Subjects exposed to cotton dust in a model cardroom for six hours showed changes in C3c and CH50 after exposure to closed boll harvested, bract removed cotton dust when compared with a group of normal, unexposed controls. Decreases in C3c, :C4, and C3A were associated with decreases in FEV1 after exposure to closed boll harvested bract intact cotton dust. The data from this preliminary study suggest in vivo associations between inhalation of cotton dusts and complement which appear to be independent of endotoxin contamination. These findings suggest a relationship between cotton dust inhalation and complement-mediated respiratory impairment.

Adolescent↗
PubMed1980

Enhanced viral interferon induction by the mineral wollastonite.

The in vitro activity of the fibrous mineral wollastonite (CaSiO3) on the interferon system was investigated. Wollastonite enhanced the induction of interferon by influenza virus in mammalian (LLC-MK2) cell monolayers but the mineral per se did not induce interferon. The magnitude of enhanced interferon induction was dependent on mineral concentration, particle size, and its time and sequence of addition onto cell monolayers. A "synergistic effect" on viral induction of interferon was noted when cell cultures were interferon-primed and then treated with wollastonite. Interferon yields were significantly higher than those obtained by the use of either the primer or wollastonite alone. That influenza virus multiplied in wollastonite-treated cells to a level that was sevenfold less than that in normal cells was associated with increased interferon production. The ability of interferon to confer antiviral cellular resistance was not impaired by wollastonite. The findings of this study suggest that the incorporation of wollastonite in appropriate interferon inducer-host cell systems may be useful for augmenting interferon production.

Animals↗
PubMedDate not supplied

Silicon nephropathy mimicking Fabry's disease.

Percutaneous renal biopsy was performed in a surface coal miner with radiographic and histopathologic pulmonary changes consistent with acute silicolipoproteinosis who developed proteinuria and hematuria. Electron microscopic evaluation of the renal tissue specimen revealed a diffusely thickened glomerular basement membrane, foot process effacement, and dense lamellar inclusions in swollen glomerular epithelial cells, similar to those seen in Fabry's disease. However, normal levels of plasma alpha-galactosidase A, normal urinary sediment glycosphingolipids and the absence of the clinical characteristics of Fabry's disease excluded this diagnosis. This case illustrates that electron-dense lamellar inclusions, similar to those seen in Fabry's disease, may be seen in other entities such as nephropathy associated with silicosis.

Adult↗
PubMedDate not supplied

Do waste incinerators induce adverse respiratory effects? An air quality and epidemiological study of six communities.

The purpose of the study presented here was to simultaneously measure air quality and respiratory function and symptoms in populations living in the neighborhood of waste incinerators and to estimate the contribution of incinerator emissions to the particulate air mass in these neighborhoods. We studied the residents of three communities having, respectively, a biomedical and a municipal incinerator, and a liquid hazardous waste-burning industrial furnace. We compared results with three matched-comparison communities. We did not detect differences in concentrations of particulate matter among any of the three pairs of study communities. Average fine particulate (PM2.5) concentrations measured for 35 days varied across study communities from 16 to 32 micrograms/m3. Within the same community, daily concentrations of fine particulates varied by as much as eightfold, from 10 to 80 micrograms/m3, and were nearly identical within each pair of communities. Direct measurements of air quality and estimates based on a chemical mass balance receptor model showed that incinerator emissions did not have a major or even a modest impact on routinely monitored air pollutants. A onetime baseline descriptive survey (n = 6963) did not reveal consistent community differences in the prevalence of chronic or acute respiratory symptoms between incinerator and comparison communities, nor did we see a difference in baseline lung function tests or in the average peak expiratory flow rate measured over a period of 35 days. Based on this analysis of the first year of our study, we conclude that we have no evidence to reject the null hypothesis of no acute or chronic respiratory effects associated with residence in any of the three incinerator communities.

Adolescent↗