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Biomedical subjects

H Cowie

Publications and source records attributed to H Cowie.

8 recordsLinked to original sources
PubMed1990

Contrasting bronchoalveolar leukocyte responses in rats inhaling coal mine dust, quartz, or titanium dioxide: effects of coal rank, airborne mass concentration, and cessation of exposure.

The aim of this study was to determine the bronchoalveolar leukocyte response to airborne coal mine dust; quartz and titanium dioxide were used as positive and negative controls, respectively. Groups of rats were exposed to airborne mass concentrations of 10 and 50 mg/m3 of the dusts for 7 hr/day, 5 days/week and their bronchoalveolar space was lavaged at time points between 2 and 75 days of exposure, to assess the leukocyte response. This study revealed time-dependent and airborne mass concentration-dependent recruitment of neutrophils and macrophages into the bronchoalveolar region with coal mine dust inhalation but no real difference in the magnitude of the response between coal mine dusts from collieries mining coal of different rank and quartz content although the maximum quartz content in the dusts used was 6%. The inflammatory response was much less than that produced by quartz, at similar airborne mass concentrations, and more than that produced by titanium dioxide which was, in general, a poor inflammogen in the rat lung. Groups of rats were exposed to the airborne dusts for 32 or 75 days, then removed from the exposure chambers, and allowed to recover by breathing room air for a further 64 days. During this recovery period there was marked progression of the leukocyte response with quartz and persistence of the response with coal mine dust. Chronic recruitment of leukocytes to the lungs of individuals inhaling coal mine dust is likely to be an important factor in the development of coal workers' pneumoconiosis.

Administration, Inhalation↗
PubMed1989

Accumulation of mixed mineral dusts in the lungs of rats during chronic inhalation exposure.

The effects of mixed dust exposure on pulmonary clearance during chronic exposure has been investigated using rats exposed to combinations of toxic and relatively nontoxic dusts: quartz (at respirable dust concentrations of 1 and 10 mg/m3) plus titanium dioxide (at 30 and 20 mg/m3, respectively), and amosite asbestos (2.5 mg/m3) plus titanium dioxide (15 mg/m3). The rats were exposed for 5 days per week, and for up to 16 weeks (for quartz) or up to 32 weeks (for asbestos). The lung burdens were compared with previously published results for exposure to single dusts under the same exposure regimens. The main feature of all these comparisons was the absence of significant differences between the lung burdens (at 3, 10, and 38 days postexposure) for single-dust and mixed-dust exposures. There was, however, some reduction in the postexposure clearance (as shown by the lung burdens at 94, 150, and 260 days postexposure) of titanium dioxide which appeared to be due to the presence of quartz in the lung. For the quartz plus titanium dioxide experiments, the lymph nodes were dissected and analyzed separately. These results showed that transfer to lymph nodes accounted for most of the postexposure clearance for titanium dioxide, and almost all for the quartz.

Animals↗
PubMed1988

Pulmonary clearance of UICC amosite fibres inhaled by rats during chronic exposure at low concentration.

Clearance of UICC amosite asbestos from the lungs during chronic--that is, repeated--exposure was investigated by using the scanning electron microscope to measure lung burdens from rats which had inhaled amosite asbestos at an approximately constant concentration of 0.1 mg/m3 or, equivalently, 20 fibres/ml for seven hours a day, five days a week for up to 18 months. The lung burdens were compared with previous results for higher exposure concentrations of 1 and 10 mg/m3. Those previous lung burdens had been measured using other analytical methods (infrared spectrophotometry) that were not suitable for the new lower lung burdens. Taken together, these results showed lung burdens rising pro rata with exposure concentration and exposure time. This accumulation of lung burden has been described by a kinetic model that takes account of the sequestration of material at locations in the lung from where it cannot be cleared. Unlike some earlier models in which lung burdens eventually reach a plateau with equilibrium between deposition and clearance during chronic exposure, this sequestration model shows lung burdens continuing to rise with exposure time. The latest results reported here support the application of such a model to lower exposure concentrations closer to those of asbestos in workplaces.

Animals↗
PubMed1988

Kinetics of the bronchoalveolar leucocyte response in rats during exposure to equal airborne mass concentrations of quartz, chrysotile asbestos, or titanium dioxide.

The kinetics of the bronchoalveolar response was assessed in rats exposed, at equal airborne mass concentration (10 mg/m3), to titanium dioxide--a non-pathogenic dust--and the two pathogenic mineral dusts quartz and chrysotile asbestos. Rats were killed at intervals over a 75 day exposure period and groups of rats exposed for 32 and 75 days after recovery for two months. Bronchoalveolar lavage was carried out and the lavage fluid characterised for cellular content, macrophage activation, and concentrations of free total protein, lactate dehydrogenase, and N-acetyl-beta-D-glucosaminidase. Inhalation exposure to the two pathogenic dusts resulted in an increased number of leucocytes, macrophage activation, and increased levels of free enzymes and total protein. The pattern and magnitude of the responses to quartz and chrysotile differed. Chrysotile caused less inflammation than quartz, and the main cellular response peaked around the middle of the period of dust exposure whereas the highest levels of enzymes occurred towards the end. The difference in timing suggests that macrophages were not available for lavage towards the end of the exposure, owing to their playing a part possibly in deposition of granulation tissue. Quartz caused a greater cellular and enzyme response than chrysotile, particularly towards the end of the dust exposure phase. There was a noticeable progression of inflammation in the quartz exposed groups left to recover for two months, but not in the chrysotile recovery groups.

Animals↗
PubMed1986

The in vitro cytotoxicity of asbestos fibers: I. P388D1 cells.

In this study, the cytotoxicity of 13 fibrous samples of known fiber number and dimensions has been established in P388D1 cells. The cells were exposed in vitro to dust concentrations of 10 or 50 micrograms/ml and, after incubation for 24 or 48 hours, any changes in cellular viability, lactate dehydrogenase, and glucosaminidase levels were determined. In general, there was a close association between the reduction in cellular viability and the loss of intracellular enzymes induced by each dust, the chrysotile asbestos samples proving more cytotoxic than the amphiboles. The cytotoxicity of the fibrous dusts was shown to be related to the number of fibers greater than 8 micron in length in the samples.

Animals↗
PubMed1986

In vitro assays for detecting carcinogenic mineral fibres: a comparison of two assays and the role of fibre size.

The activities of 13 carcinogenic fibrous dust samples were compared in two in vitro test systems using V79/4 and A549 cells. Eleven of the dusts had similar ranks in both assays but two samples had disparate results. The relationship between the fibre length and diameter distributions of 12 of the samples and their activity in each assay was examined. A significant association between fibre length and biological activity occurred in both assays. This relationship showed increasing strength of association with increasing fibre length. The only significant association between fibre diameter and activity in vitro was demonstrated with fibres greater than 0.2 micron in the A549 assay.

Carcinogens↗
PubMed1985

Study of lung function data by principal components analysis.

As a rational approach to the many lung function tests available, we have subjected the results of a battery of six lung function measurements made in 458 coalminers to the statistical technique of principal components analysis. By this means the six test results were reduced to three principal components without important loss of information. The first component appeared to represent lung size and the second the degree of airflow obstruction, and the third detected impairment of gas transfer factor in excess of that explained by the first two components. The values of the first principal component, used to select men with abnormal lung function, identified more younger men with functional abnormalities than a method based on comparison of observed and predicted values of forced expiration volume in one second. The values of the second and third principal components were used to classify types of functional abnormality. It is concluded that this statistical technique provides a sensitive method of identifying men with unusual lung function, particularly younger men, in a population and can be used to define and quantify different aspects of lung function.

Adult↗