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Biomedical subjects

K Donaldson

Publications and source records attributed to K Donaldson.

At least 109 records · Page 6Linked to original sources
PubMed1995

Supercoiled plasmid DNA as a model target for assessing the generation of free radicals at the surface of fibres.

The ability of respirable amosite and crocidolite asbestos, refractory ceramic fibres (RCFs) and man made vitreous fibres (MMVFs) to cause free radical injury to plasmid, phiX174 RFI DNA was assessed. The amosite and crocidolite asbestos caused substantial damage to the DNA and, in the main, the free radicals responsible for the asbestos-mediated DNA damage were hydroxyl radicals as determined by inhibition with mannitol. Asbestos fibre-mediated damage to the DNA was completely ameliorated by the chelation of fibre-associated iron by pre-treatment of fibres with desferrioxamine-B, confirming the importance of iron in the production of free radicals. MMVFs and RCFs produced modest free radical damage to the DNA, which was prevented by mannitol but not by iron chelation.

Asbestos, Amosite↗
PubMed1995

Bromo-deoxyuridine (BRDU) uptake in the lungs of rats inhaling amosite asbestos or vitreous fibres at equal airborne fibre concentrations.

Rats were exposed, by inhalation, to target airborne fibre concentrations of 1000 f/ml (PCOM fibres by WHO criteria) of a long amosite asbestos sample and a vitreous fibre sample; the target was closely attained for both fibre samples. The size distributions of the two fibre samples was closely similar. Rats were placed in the chambers for 7 hours and then, following a further 16 hours in room air, were injected with bromo-deoxyuridine (BRDU). The presence of BRDU-positive cells in terminal bronchioles/alveolar ducts was assessed in blocks taken from various parts of the left lung, from apex to base. There were significant differences in the proliferative responses between animals but there were also significant differences between the treatments. Lungs from rats exposed to vitreous fibres showed no greater response than the controls, but there was a markedly greater proliferative response in the lungs of rats inhaling long amosite. There was a decreasing gradient of proliferative response from the apex of the lung to the base with all treatments. This could be explained by different degrees of deposition in different areas of the lung. Similar amounts of fibre accumulated in the lungs of rats exposed to the two fibre types and it is unlikely that dissolution could be important over the timescale used here. We conclude that, when amosite asbestos deposits in the lungs of rats it stimulates a proliferative response and that deposition of an equal number of similar-sized vitreous fibres has no effect.

Air Pollutants↗
PubMed1995

Detection of surface free radical activity of respirable industrial fibres using supercoiled phi X174 RF1 plasmid DNA.

The ability of a number of respirable industrial fibres, amosite and crocidolite asbestos, refractory ceramic fibres (RCFs) and man-made vitreous fibres (MMVFs) to cause free radical injury to plasmid phi X174 RFI DNA was assessed. The oxidative DNA damage was observed as depletion of supercoiled DNA after fibre treatment was quantified by scanning laser densitometry. The mechanism of fibre-mediated damage was determined by the use of the specific hydroxyl radical scavenger mannitol and the iron chelator desferrioxamine-B. The amosite and crocidolite asbestos caused substantial damage to DNA that was dose-related. The free radicals responsible for the asbestos-mediated DNA damage were hydroxyl radicals, as determined by inhibition with mannitol. Asbestos fibre-mediated damage to DNA was completely ameliorated by the chelation of fibre-associated iron with desferrioxamine-B. The amount of Fe(II) and Fe(III) released by equal numbers of the different fibre types at equal fibre number was determined. The fibres released very small amounts of Fe(II) and there were no significant differences between the fibre types. The fibres released substantial amounts of Fe(III); MMVF 21 released significantly more Fe(III) than any of the other fibres and short fibre amosite also released more Fe(III) than three of the MMVFs and two of the RCFs. When ability to release Fe(II) and Fe(III) was compared with ability to cause DNA damage there was not a good correlation, because only the long amosite and crocidolite caused substantial free radical injury to DNA; this contrasts with MMVF 21 and short amosite being the two fibres that released the greatest amounts of iron. The loss of ability to damage DNA in DSF-B-treated asbestos fibres shows that iron at the surface of asbestos fibres definitely has a role in generating hydroxyl radicals. However, it is clear that some fibres, such as short amosite and MMVF 21, release large quantities of iron without causing free radical damage, whilst neither long amosite nor crocidolite released more iron than the other fibres. The exact role of iron in fibre reactivity therefore remains unresolved, but fibre-bound iron not released from the surface of asbestos could be important. Further research is under way to investigate this possibility.

Air Pollutants, Occupational↗
PubMed1995

Differential release of superoxide anions by macrophages treated with long and short fibre amosite asbestos is a consequence of differential affinity for opsonin.

OBJECTIVE: To investigate the ability of short and long fibre samples of amosite asbestos to stimulate superoxide production in isolated rat alveolar macrophages, and to determine how opsonisation with rat immunoglobulin might modify this response. METHODS: Macrophages were isolated from rat lung by bronchoalveolar lavage and challenged with both opsonised and non-opsonised long and short fibres of amosite asbestos. Release of superoxide anions was measured by the spectrophotometric reduction of cytochrome c, in the presence and absence of superoxide dismutase. RESULTS: Both long and short fibre samples of amosite asbestos without opsonisation were ineffective in stimulating isolated rat alveolar macrophages to release superoxide anions in vitro. After opsonisation with immunoglobulin, however, a dramatic enhancement of release of superoxide anion was seen with long fibres, but not short, which confirms the importance of fibre length in mediating biological effects. The increased biological activity of the long fibre sample is explained by increased binding of the opsonin to the fibre surface as, at equal mass, the long fibres bound threefold more immunoglobulin than the short fibres. CONCLUSION: Opsonisation is an important factor in modulation of the biological activity of fibres at the cellular level. Differences in binding of opsonin to samples of fibre previously considered to be identical apart from length, suggest that surface reactivity needs to be taken into account when fibres are compared. Binding of biological molecules, in vivo, may thus be an important modifying factor in the pathological processes initiated by fibres.

Animals↗
PubMed1995

Neutrophil sequestration in rat lungs.

BACKGROUND: The transit of neutrophils through the pulmonary microvasculature is prolonged compared with red blood cells and is increased further during cigarette smoking and in exacerbations of chronic obstructive pulmonary disease. The increased residence time (sequestration) of neutrophils in the pulmonary capillaries in these conditions may be the first step leading to the accumulation of cells within the lung interstitium and in the bronchoalveolar space, so potentiating lung damage. A rat model has been developed to investigate the factors which may influence neutrophil transit through the lung microvasculature. METHODS: Intratracheal instillation of the heat killed organism Corynebacterium parvum was used to induce an acute neutrophil alveolitis. Neutrophils and red blood cells were isolated from donor rats, labelled with two distinct radioisotopes, and then reinjected into recipient rats to assess their transit through the pulmonary circulation. To ascertain whether peripheral blood neutrophils were minimally altered by the isolation procedure their functional status in vitro was compared with that of inflammatory neutrophils in a number of assays commonly used as descriptors of neutrophil activation. The influence of neutrophil activation on the accumulation of cells in the lungs was assessed by comparing the lung sequestration of control neutrophils, isolated from peripheral blood, with that of inflammatory neutrophils obtained from bronchoalveolar lavage of inflamed rat lungs. Lung sequestration of neutrophils was defined as the fold increase in the ratio of neutrophils labelled with chromium-51 to red blood cells labelled with technetium-99m in lung tissue compared with the same ratio in peripheral blood. RESULTS: Sequestration of peripheral blood neutrophils occurred in control rat lungs as shown by a 17.5 (2.1) fold increase in the ratio of neutrophils to red blood cells in the pulmonary circulation compared with the ratio of these cells in the peripheral circulation. When inflammatory neutrophils, obtained by bronchoalveolar lavage from C parvum-treated animals, were injected into control rats, the increase was 90.6 (11.0) fold. Induction of an inflammatory response in the lung tissue of the recipient rat also caused an increase in the sequestration of control neutrophils compared with the same cells in control rat lungs which was, however, less marked than when inflammatory neutrophils were used (34.7 (4.7) fold). The mean (SE) pressure developed on filtration of inflammatory neutrophils in vitro through a millipore filter (7.53 (0.2) cm H2O) was greater than that of peripheral blood neutrophils (1.18 (0.2) cm H2O). Increased filtration pressure indicates a decrease in cell deformability and suggests that this may be a contributory factor to the increased sequestration of inflammatory neutrophils in the pulmonary vasculature. CONCLUSIONS: This study shows that there is sequestration of neutrophils in the pulmonary vasculature in normal rat lungs which increases in acute lung inflammation and when inflammatory neutrophils are injected into control animals. In this model changes in the neutrophil, such as cell deformability, may have a more important role in inducing increased neutrophil sequestration than the inflammatory response in the lungs.

Animals↗
PubMed1995

Glutathione homeostasis in alveolar epithelial cells in vitro and lung in vivo under oxidative stress.

We studied the acute effects of cigarette smoke condensate (CSC), H2O2, and tumor necrosis factor (TNF)-alpha on the glutathione (GSH) redox system in a human type II epithelial cell line (A549) in vitro. CSC, in vitro and in vivo after intratracheal instillation of CSC in the rat, produced a depletion of intracellular soluble GSH, concomitant with GSH-conjugate formation, without significant elevation of oxidized GSH (GSSG), protein-GSH mixed disulfides (PrSSG), nor any GSH efflux from the cells. By contrast, H2O2 (500 microM) after 5-min exposure to A549 cells caused significant depletion of intracellular GSH associated with an efflux of GSSG and a significant increase in the formation of PrSSG. TNF-alpha, in concentrations of 100 U/ml and 1,000 U/ml, produced a significant depletion of GSH in A549 cells after 4- and 24-h exposure, with an associated elevation of GSSG. The activities of glutathione peroxidase, gamma-glutamylcysteine synthetase, and glucose-6-phosphate dehydrogenase were significantly decreased in epithelial cells and in rat lungs after CSC exposure, without change in glutathione S-transferase and glutathione reductase activities. By contrast, H2O2 and TNF-alpha did not alter these enzyme activities in epithelial cells. Thus GSH depletion and alteration in enzyme activities in alveolar epithelial cells by CSC, H2O2, and TNF-alpha occur by different mechanisms.

Animals↗
PubMed1995

The role of tumor necrosis factor in increased airspace epithelial permeability in acute lung inflammation.

Increased airspace epithelial permeability is an early event in lung inflammation and injury. In this study, we have developed a rat model to study the mechanisms of the epithelial permeability to 125iodine-labeled bovine serum albumin (125I-BSA), instilled intratracheally during acute lung inflammation. Epithelial permeability was measured as the percentage of instilled 125I-BSA appearing in the blood. The increase in epithelial permeability induced by intratracheal instillation of heat-killed Corynebacterium parvum produced a peak influx of neutrophils into the bronchoalveolar space at 16 h, which occurred after the peak increase in epithelial permeability (8 h). The increased epithelial permeability induced by C. parvum did not appear to be protease- or oxidant-mediated. Depletion of peripheral blood neutrophils was achieved by an intravenous injection of anti-neutrophil polyclonal antibody. The consequent profound reduction in neutrophil and macrophage influx into the airspaces 8 h after instillation of C. parvum reduced the epithelial permeability to control values. Bronchoalveolar lavage (BAL) leukocytes from rats 8 h, but not 16 h, after treatment with C. parvum caused a modest increase in epithelial permeability when re-instilled intratracheally into control rat lungs. Separation of the leukocytes before re-instillation indicated that macrophages rather than neutrophils were predominantly responsible for the increased epithelial permeability. The presence of dramatically increased levels of tumor necrosis factor (TNF) in BAL 8 h in contrast to a slight increase in BAL 16 h after C. parvum, the release of TNF from 8 h macrophages, the increased epithelial permeability induced by TNF in epithelial monolayers in vitro, and the inhibition of C. parvum-induced epithelial permeability by TNF antibody support the premise that TNF is a major player in the increased epithelial permeability that occurs during C. parvum-induced acute alveolitis.

Acute Disease↗
PubMed1995

Deformability and CD11/CD18 expression of sequestered neutrophils in normal and inflamed lungs.

Neutrophil (PMN) sequestration in the pulmonary microvasculature precedes the migration of these cells into the airspaces in inflamed lungs. Intratracheal instillation of the heat-killed organism Corynebacterium parvum in the rat induces an alveolitis in which PMN constitute 70 to 80% of the total cell count in the bronchoalveolar lavage (BAL). This acute alveolitis results in increased sequestration in the pulmonary microvasculature of 51Cr-labeled PMN when compared with control lungs. The aims of this study were to confirm this increased pulmonary PMN sequestration using unlabeled cells and to assess the function and adhesion molecule expression of such sequestered PMN. We counted the number of PMN and erythrocytes obtained by pulmonary vascular lavage (PVL) and compared the ratio of these two cell types in PVL and peripheral blood (PB) as a measure of the sequestration of PMN in the pulmonary vasculature. Compared with control animals, PVL in C. parvum-treated rats had higher PMN counts, which could not be accounted for by the PB leukocytosis. Sequestration of PMN in the pulmonary microvasculature depends on several factors, including the upregulation of adhesion molecules on both PMN and endothelial surfaces and the ability of the cells to deform when passing through the microcirculation. Cells obtained from the PVL were less deformable than PB cells in control but not in C. parvum-treated animals. The expression of the CD18 integrin on PMN obtained from the PVL of C. parvum-treated animals was increased compared with cells from control animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Effect of long and short fibre amosite asbestos on in vitro TNF production by rat alveolar macrophages: the modifying effect of lipopolysaccharide.

The influence of long and short fibre amosite on the generation of tumor necrosis factor (TNF) by rat alveolar macrophages was investigated in vitro. TNF rich supernatants were prepared from macrophages cultured in F10 medium +2% Bovine Serum Albumin (BSA). Spontaneously released TNF from unstimulated macrophages and TNF rich supernatants from macrophages exposed to Lipopolysaccharide (LPS) and fibres were stored at -70 degrees C and then tested for their cytotoxicity towards L929 cells. Maximum spontaneously released TNF was obtained from 24 hour macrophage cultures. Short amosite fibres had no significant effect in stimulating alveolar macrophages to release TNF while the 50 micrograms dose of long fibres resulted in significantly increased release of TNF. Cotreatment of alveolar macrophages with LPS and fibres further enhanced the TNF production and maximum production was obtained with LPS +50 micrograms dose of long fibre resulted in significantly increased release of TNF. Co-treatment of alveolar macrophages with LPS and fibres further enhanced the TNF production and maximum production was obtained with LPS +50 micrograms of long fibre amosite. The present study indicates that fibre dimension is a major factor in in vitro dust activity and TNF has a possible active role to play in dust induced inflammation in vivo.

Animals↗
PubMed1995

Mathematical model of phagocytosis and inflammation after the inhalation of quartz at different concentrations.

A mathematical model was developed with several distinctive features to represent the various processes leading to silicosis. It assures the phagocytosis of quartz by the resident alveolar macrophages. It then models the necrosis of macrophages caused by the ingestion of quartz particles and the subsequent release of these clusters onto alveolar surfaces. The inflammatory recruitment of alveolar macrophages and neutrophils in response to the cell necrosis caused by the ingestion of quartz particles is described in a functional form and is included in the model. The model also describes the pathological and other biological reactions to quartz particles in the interstitium. Specifically, once the quartz particles arrive at the interstitium, they can be phagocytozed by interstitial macrophages. The pathological interaction between quartz and interstitial macrophages may lead to quartz particles being sequestered in silicotic nodules, and also cleared to the efferent lymph nodes.

Administration, Inhalation↗
PubMed1994

Mesothelial cell injury caused by pleural leukocytes from rats treated with intratracheal instillation of crocidolite asbestos or Corynebacterium parvum.

The pleural and peritoneal mesothelium is a major target in asbestos exposure where mesothelial cell proliferation, exfoliation, and neoplasia have been reported in workers and experimental animals. The objective of this study was to determine the role of pleural leukocytes in mesothelial cell damage caused by asbestos exposure. We therefore investigated detachment and lysis injury to mesothelial cells in vitro induced by leukocytes lavaged from the pleural space of rats exposed, by intratracheal instillation, to crocidolite asbestos. Our studies revealed that normal pleural leukocytes were composed of macrophages, lymphocytes, eosinophils, and mast cells. This population showed a small but significant recruitment of mast cells and eosinophils 3 to 14 days after instillation of crocidolite asbestos; there were also modestly increased levels of macrophages present 30 days after low doses of asbestos. One day after intratracheal instillation of 5 mg crocidolite asbestos, the pleural leukocytes caused detachment injury to mesothelial cells in vitro. This injury was markedly reduced 3 days after asbestos exposure and was undetectable by Day 14. One month after instillation of asbestos, despite doses of asbestos from 0.5 to 5 mg, pleural leukocytes showed no ability to injure mesothelial cells in vitro. In a parallel study, pleural inflammation was induced by intratracheal instillation of heat-inactivated Corynebacterium parvum. Transient mesothelial cell-detaching injury was again expressed by pleural leukocytes 1 day after C. parvum instillation. This was likely related to an increase in the percentage of neutrophils present on this day. These results show that a single administration of crocidolite asbestos, intratracheally, leads to transient activation of pleural leukocytes in terms of the ability of these cells to detach mesothelial cells from matrix. This finding implies that mesothelial cell proliferation and exfoliation found in individuals exposed to asbestos may result from persistent stimulation of pleural leukocytes caused by the continuous presence of asbestos in the lung.

Animals↗
PubMed1994

Biological activity of respirable industrial fibres treated to mimic residence in the lung.

The durability of fibres in the lung environment after deposition could be a key factor in determining whether they accumulate to a sufficient tissue dose to cause pathological change. There is a shortage of information on the relative durabilities of respirable industrial fibres of various types. We describe a strategy for assessing the ability of different fibre types to persist in the lung milieu and to retain their biological activity. This is particularly important for the development of mesothelioma, where the long latent time that characterises this disease would be expected to exclude, from culpability, fibres that are not durable. We have combined a pre-treatment step in pH 5.0 or 7.0 with an assay that relies on the ability of fibres to damage the mesothelium. The long-term aim is to assess the impact that treatment in various pH solutions has on (a) fibre size/number, (b) loss of key elements, (c) the ability to damage the mesothelium. Such information should enable us to better predict the potential of fibres to cause mesothelioma.

Administration, Inhalation↗
PubMed1994

The stabilization of a human IgM monoclonal antibody with poly(vinylpyrrolidone).

An IgM anti-group B Streptococcus monoclonal antibody (4B9) was found to undergo irreversible heat-induced aggregation at 50 degrees C. A variety of excipients was tested for their ability to inhibit antibody aggregation. The amount of 4B9 aggregation, which was determined by analysis on a size-exclusion HPLC, was significantly reduced in the presence of low concentrations [between 0.1 and 1.0% (w/v)] of poly(vinylpyrrolidone) (PVP) molecules ranging in molecular weight from 10 to 40 kDa. When the PVP concentration was greater than 1.0%, antibody aggregation was enhanced, and with the highest molecular weight PVP, antibody precipitation occurred. HPLC was used to show that more PVP was associated with the 4B9 at 50 degrees C than at 25 degrees C. Differential scanning calorimetry revealed that PVP concentrations greater than 2.0% decreased the antibody thermal transition temperature. Enzyme-linked immunosorbent assays were used to assess the effects of PVP on the antigen binding capacity of 4B9 and on 4B9 quantitation. At 4 degrees C, PVP solutions of up to 5.0% had no effect on either 4B9 quantitation or antigen binding. At 50 degrees C, however, less 4B9 was detected in the 5.0% PVP solution. The heat stabilization of the 4B9 antibody by low concentrations of PVP can be explained by a weak binding of PVP to the native protein. The PVP may sterically interfere with protein-protein interactions, thus reducing aggregation. Higher concentrations of PVP lead to protein aggregation and precipitation, probably by a volume-exclusion mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
PubMed1994

RU 486: an alternative to surgical abortion.

After 5 years of use in more than 100,000 European women, RU 486, an antiprogestin medication used as a medical abortifacient, has recently come under scrutiny in the United States. This article discusses the current and potential uses of RU 486. Also addressed are the history, advantages, and disadvantages of medical abortion (including the acceptability of the method from a woman-centered perspective); new clinical trials; and ethical issues.

Abortion, Induced↗
PubMed1994

Effect of cigarette smoke and its condensates on alveolar epithelial cell injury in vitro.

The oxidant-antioxidant balance in the airspaces of the lungs may be critical in protecting the lungs from the effects of cigarette smoke. We studied the effect of cigarette smoke and its condensates on the detachment, attachment, and proliferation of the A549 human alveolar epithelial cell line, in an in vitro model of cell injury and regeneration and the protective effects of antioxidants. Whole and vapor phase cigarette smoke decreased 51Cr-labeled A549 cell attachment, increased cell detachment, and decreased cell proliferation, as assessed by [3H]thymidine uptake. Freshly isolated rat type II alveolar epithelial cells showed an enhanced susceptibility to smoke-induced cell lysis when compared with the A549 cell line. Reduced glutathione (GSH) (400 microM) protected against the effects of cigarette smoke exposure on cell attachment, proliferation, and detachment. Depletion of intracellular GSH with buthionine sulfoxamine enhanced the epithelial cell detachment injury produced by smoke condensates. We conclude that cigarette smoke and its condensates cause an oxidant-induced injury to A549 human type II alveolar epithelial cells. Both intra- and extracellular GSH have important roles in protecting epithelial cells from the injurious effects of cigarette smoke.

Animals↗
PubMed1994

An investigation of the role of glutathione in increased epithelial permeability induced by cigarette smoke in vivo and in vitro.

Airspace epithelial permeability is known to increase in cigarette smokers. To study the role of the antioxidant reduced glutathione (GSH) in this phenomenon, we used an in vitro model of the epithelial permeability of a monolayer of human type II alveolar epithelial cells (A549 cell line). Both whole (WSC) and vapor (VSC) smoke condensates induced a recoverable, concentration-dependent increase in epithelial permeability to 125iodine-labeled bovine serum albumin (125IBSA), associated with a profound fall in intracellular GSH. Buthionine sulfoximine (BSO), a GSH synthesis inhibitor, decreased GSH levels in A549 epithelial cells, significantly increased A549 epithelial cell permeability, and enhanced both WSC and VSC-induced A549 epithelial cell permeability. Co-culturing epithelial cells and GSH (500 microM) reduced WSC-induced, but not VSC-induced A549 epithelial cell permeability. Increasing intracellular GSH also ameliorated the smoke-induced increased epithelial permeability. Concentrations of cigarette smoke condensate of < 20% increased A549 epithelial cell permeability without associated cell detachment and lysis, which was also the case with BSO-induced increased epithelial permeability. WSC and VSC, instilled intratracheally, significantly increased rat lung epithelial permeability to 125IBSA, 6 h postinstillation, associated with a significant recruitment of neutrophils into the airspaces. This was associated with a small increase in GSH in the lung tissue of VSC-treated rats. However, both WSC and VSC markedly reduced GSH in bronchoalveolar lavage (BAL) fluid. Reduction in lung GSH to 95% but not to 68% of control values by BSO increased lung epithelial permeability in vivo. However, there was no additive effect on epithelial permeability of WSC and BSO.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗