Ion transport and regulation of respiratory tract fluid output in dogs.
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To investigate the regulation of respiratory tract fluid output (RTFO), we collected the RTFO in an anesthetized canine model after a series of pharmacological interventions (inhibition of Na(+)-K(+)-ATPase or Na(+)-K(+)-2Cl(-) cotransporter, 250 microl) and physiological challenges (ionic and/or osmotic perturbation in airway lumen, 250 microl). Whereas 250 microl of aerosolized 0.9% saline caused a transient increase in RTFO, a 250-microl bumetanide-induced increase in RTFO was evident for 18 min and a 250-microl acetylstrophanthidin-induced increase in RTFO persisted for at least 30 min. Dry air ventilation decreased the responses of RTFO to the saline (sham) and acetylstrophanthidin intervention but not the bumetanide intervention. Delivery of 250 mosmol/kgH(2)O ion-free mannitol (250 microl) caused marked increases in RTFO that were little affected by the administration of acetylstrophanthidin or bumetanide 30 min before these challenges. A 250-microl 550 mosmol/kgH(2)O ion-free mannitol challenge caused a more marked and prolonged increase in RTFO. Thus aerosol delivery of a low dose of a cardiac glycoside or a near-isosmotic, ion-free, impermeant osmolyte solution may be therapeutically useful by increasing the clearance of secretions from the tracheobronchial airways. (+info)
Cyclohexane as an alternative vapor of carbon tetrachloride for the assessment of gas removing capacities of gas masks.
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An alternative vapor was explored to replace carbon tetrachloride (CCl4) for testing breakthrough times of cartridges and canisters of gas masks in the National Approval Test of Respirators. Cyclohexane was single out as a candidate for the alternative vapor out of six vapors: trichloroethylene, n-pentane, n-hexane, n-heptane, toluene and cyclohexane from the viewpoints of similarity of vapor pressure and water-solubility to CCl4, lower toxicity than CCl4, and technical feasibility in generating an airflow of 30 L/min containing the vapor ranging from 300 to 5000 ppm. Breakthrough times of cartridges and canisters were examined by generating cyclohexane vapor in a test airflow of 30 L/min in comparison with CCl4 vapor under various test conditions with different vapor concentrations and relative humidities (RH). As the results, the breakthrough times of the cartridges and canisters for cyclohexane were found to almost coincide with those for CCl4 under all examined range of concentrations and RH. By an increase of humidity from 50% RH to 80% RH, the cartridges showed significant shortening of breakthrough times for both of CCl4 and cyclohexane, but the susceptibility of the breakthrough time of cyclohexane to humidity was also similar to that of CCl4. It was, therefore, concluded that cyclohexane can be recommended as the alternative vapor of CCl4 for testing the breakthrough times of gas mask cartridges and canisters in the National Approval Test. (+info)
Environmental factors and heatstroke.
(59/1457)
The objective of this study was to determine the extent of the influence of temperature and humidity on the number of heatstroke presentations. Three hundred and forty-five labourers presented to the Accident and Emergency Hospital in Abu Dhabi with heatstroke during a 3 month summer period. There was no significant predictive association between the maximum daily temperature and/or humidity and the presentation of heatstroke. There was no significant association with the maximum temperature on the previous day, day of the week or temperature trend. The largest statistical correlation was between the maximum temperature and humidity and the log of the number of cases. It is possible that there are other significant explanatory variables that we have not included in the model. (+info)
Effect of water potential on growth and iron oxidation by Thiobacillus ferrooxidans.
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The effect of water potential on the growth of two strains of Thiobacillus ferrooxidans was determined by adding defined amounts of sodium chloride or glycerol to the culture medium. The two strains differed slightly, and the most tolerant strain had a minimum water potential for growth of minus 15 to minus 32 bars when chloride was used and minus 6 bars when glycerol was used. In another approach, the limiting water potential was determined by equilibrating small amounts of culture medium with atmospheres of relative humidities equivalent to specific water potentials, and the ability of the organism to grow and oxidize ferrous iron was determined. Under these conditions, which are analogous to those which might control water potential in a coal refuse pile or copper leaching dump, the lower limit at which iron oxidation occurred was minus 23 bars. The water potential of some coal refuse materials in which T. ferooxidans was present were determined, and it was found that the water potentials at which the organism was active in these habitats were similar to those at which it was able to grow in culture. However, marked variation in water potential of coal refuse materials was found, presumably due to differences in clays and organic materials, and some coal refuse materials would probably never have water potentials at which the organism could grow. Some literature on the water potentials in copper leach dumps is reviewed, and it is concluded that control of water potential is essential to maximize the success of leaching operations. Because adequate drainage is necessary in a leach dump to ensure sufficient aeration, in many cases water availability in leach dumps may restrict the development of the bacterium necessary for the process. (+info)
Weighing imprecision and handleability of the sampling cassettes of the IOM sampler for inhalable dust.
(61/1457)
The weight stability of the sampling cassette of the IOM sampler for inhalable dust was tested in several weighing experiments. The results show that the reliability of repeated weighings was good, but the absorption of water vapour was slow and varied considerably among cassette specimen. The exponential time constant for water absorption was approximately 4 days, and 15-20 days were needed to obtain weight stability. With the help of cassette blanks the imprecision in dust weight could be held below 0.05 mg, if the cassettes were allowed one week's storage in the weighing room before weighing, both before and after sampling. The IOM sampling cassettes seem to consist of a few subsets, each with identical relative weight increase in a weighing room. To keep the variability low it is important that both the blanks and the cassettes used for sampling come from the same subset. Experiments indicate that the conducting plastic of the IOM sampling cassette may be replaced with another kind of plastic with similar electrical conductivity, but whose humidity absorption is 30 times lower. A lid, which is weighed with the cassette, was designed so that the potential dust loss from the cassette proper to the commercial transport clip was eliminated. A flow adapter, which simplifies the measurement of the air flow during personal sampling, was designed. (+info)
Individualized model of human thermoregulation for the simulation of heat stress response.
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A population-based dynamic model of human thermoregulation was expanded with control equations incorporating the individual person's characteristics (body surface area, mass, fat%, maximal O(2) uptake, acclimation). These affect both the passive (heat capacity, insulation) and active systems (sweating and skin blood flow function). Model parameters were estimated from literature data. Other data, collected for the study of individual differences (working at relative or absolute workloads in hot-dry [45 degrees C, 20% relative humidity (rh)], warm-humid [35 degrees C, 80% rh], and cool [21 degrees C, 50% rh] environments), were used for validation. The individualized model provides an improved prediction [mean core temperature error, -0.21 --> -0.07 degrees C (P < 0.001); mean squared error, 0.40 --> 0.16 degrees C, (P < 0.001)]. The magnitude of improvement varies substantially with the climate and work type. Relative to an empirical multiple-regression model derived from these specific data sets, the analytical simulation model has between 54 and 89% of its predictive power, except for the cool climate, in which this ratio is zero. In conclusion, individualization of the model allows improved prediction of heat strain, although a substantial error remains. (+info)
Interaction of microcrystalline cellulose and water in granules prepared by a high-shear mixer.
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Microcrystalline cellulose (MCC) granules were prepared by wet granulation using a high-shear mixer. Physical characteristics of the granules were investigated using near IR spectrometry, thermogravimetry and isothermal water vapor adsorption. Near IR spectra of dried MCC granules prepared for various granulation times exhibited different peak intensities at 1428, 1772, and 1920 nm, which were assigned to functional groups of cellulose or water. On isothermogravimetric analysis, the rate of dehydration of water was shown to decrease with granulation time. These results suggest that the physical structure of MCC could change during the granulation process, and the interaction between MCC and water was gradually strengthened. The isothermal water vapor adsorption curves suggested that the amorphous region of MCC would be divided by the strong shear force of the impeller, because the high adsorption ability of intact MCC in the low humidity region was diminished in granules collected following 5 and 10 min of granulation. It was suggested that MCC formed a network which caught water within its structure during the wet granulation process. (+info)
Home dampness, current allergic diseases, and respiratory infections among young adults.
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BACKGROUND: The relation between home dampness and respiratory symptoms among adults is well confirmed, but data on specific allergic diseases and respiratory infections is more limited. Individual factors that may enhance susceptibility to the effects of home dampness are mainly unknown. METHODS: The association between home dampness and current physician diagnosed asthma, allergic rhinitis, allergic conjunctivitis, atopic dermatitis, common colds, and bacterial respiratory infections was studied in a questionnaire survey of 10 667 Finnish first year university students aged 18-25 years. The dampness categories analysed were visible mould and visible mould or damp stains or water damage during the last year. In multivariate analyses adjustment was made for parental education, active and passive smoking, type and place of residence, pets, and wall to wall carpets. The interaction effect of atopic heredity and dampness was investigated. RESULTS: Visible mould or damp stains or water damage was reported by 15.0% of the respondents. In multivariate models there was a positive association between home dampness and current asthma, allergic rhinitis, and atopic dermatitis, as well as common colds > or =4 times per year and other respiratory infections, but not between home dampness and allergic conjunctivitis. The strongest association was found between exposure to visible mould and asthma (OR 2.21, 95% CI 1.48 to 3.28) and common colds (OR 1.49, 95% CI 1.18 to 1.87). The risk of current asthma in damp homes was highest among subjects with atopic heredity. CONCLUSIONS: The risk of current asthma, allergic rhinitis, and atopic dermatitis was higher in damp homes. Of the respiratory infections, the risk of common colds was most clearly increased. (+info)