Biomedical subjects

M I Gilmour

Publications and source records attributed to M I Gilmour.

33 records · Page 2Linked to original sources

PubMed1995

A murine model of cystic fibrosis.

We have generated a mouse line in which the cystic fibrosis transmembrane conductance regulator (CFTR) gene has been mutated by gene targeting. Like human cystic fibrosis (CF) patients, mice lacking a functional CFTR gene, referred to as CFTR(-/-) mice, show increased numbers of goblet cells and obstruction of glands with inspissated eosinophilic secretions. The obstruction of glands often results in the destruction of gland-containing tissues in these animals. However, unlike the case in human CF patients, the most severe pathological changes in these mice were found, on preliminary analysis, to be confined to the intestinal tract and gallbladder. Although respiratory failure is the primary cause of death among humans with CF, we found only minor pathological alterations in the lungs and upper airways of our CFTR(-/-) animals. Possible explanations for the apparent lack of respiratory disease are the young age at which the animals were examined and the pathogen-free environment in which they were housed. In this manuscript, we examine the respiratory and other organ systems of CFTR(-/-) mice that have survived to adulthood. We also report on initial experiments in which CFTR(-/-) mice have been exposed to bacterial pathogens, and we present data on a single animal that displayed severe respiratory disease.

Animals↗

PubMed1995

The effects of ozone on immune function.

A review of the literature reveals that ozone (O3) exposure can either suppress or enhance immune responsiveness. These disparate effects elicited by O3 exposure depend, in large part, on the experimental design used, the immune parameters examined as well as the animal species studied. Despite the apparent contradictions, a general pattern of response to O3 exposure can be recognized. Most studies indicate that continuous O3 exposure leads to an early (days 0-3) impairment of immune responsiveness followed, with continued exposures, by a form of adaptation to O3 that results in a re-establishment of the immune response. The effects of O3 exposure on the response to antigenic stimulation also depend on the time at which O3 exposure occurred. Whereas O3 exposure prior to immunization is without effect on the response to antigen, O3 exposure subsequent to immunization suppresses the response to antigen. Although most studies have focused on immune responses in the lung, numerous investigators have provided functional and anatomical evidence to support the hypothesis that O3 exposure can have profound effects on systemic immunity.

Animals↗

PubMed1993

A comparison of the pulmonary defenses against streptococcal infection in rats and mice following O3 exposure: differences in disease susceptibility and neutrophil recruitment.

Ozone (O3) exposure reduces alveolar macrophage (AM) phagocytosis in mice and increases their susceptibility to Streptococcus zooepidemicus. O3 exposure also decreases AM phagocytosis in rats but does not result in mortality to infection. To investigate the mechanism of disease protection in rats, antibacterial defenses of two strains of mice and F344 rats were compared. O3 exposure (3 hr, 0.4 or 0.8 ppm) and infection with S. zooepidemicus resulted in a dose-dependent proliferation of bacteria in the lungs of mice and high mortality. Polymorphonuclear leukocytes (PMNs) were observed in severely affected individuals 2 or more days postinfection and did not alter the fatal infection. In contrast, microbial inactivation was only impaired in O3-exposed rat lungs during the first 48 hr after infection. In these animals PMNs could be isolated from bronchoalveolar lavage fluid between 6 and 48 hr postinfection with the peak response occurring at 24 hr. Pretreatment with anti-PMN serum eliminated the neutrophil influx and impaired further the bactericidal activity in ozone-exposed rats. The results suggest that inhaled streptococci are cleared normally from the mouse lung by AMs. Following exposure to O3, AM phagocytosis is reduced and the mice develop a fatal infection. The persistence of bacteria in the lungs of O3-exposed rats triggers a transient influx of PMNs whose appearance corresponds with elimination of the bacteria. Differences in antimicrobial defenses between various experimental species and humans need to be better understood in order to predict effects of air pollutants on susceptibility to infection in man.

Animals↗

PubMed1993

Pulmonary clearance and inflammatory response in C3H/HeJ mice after intranasal exposure to Pseudomonas spp.

The environmental release of engineered microorganisms has caused health and environmental concerns. In this study, an animal model was used to examine health effects following pulmonary exposure to environmental and clinical isolates. In order to rule out the possibility that an adverse response was caused by endotoxin, 50% lethal doses (LD50) were determined, when possible, with endotoxin-sensitive (C3HeB/FeJ) and endotoxin-resistant (C3H/HeJ) mice by using both environmental isolates (Pseudomonas aeruginosa BC16, BC17, BC18, and AC869 and Pseudomonas maltophilia BC6) and clinical isolates (P. aeruginosa PAO1 and DG1). The LD50 of strains AC869, DG1, and PAO1 are 1.05 x 10(7), 6.56 x 10(6), and 1.02 x 10(7) CFU, respectively, in C3HeB/FeJ mice and 1.05 x 10(7), 1.00 x 10(7), and 2.75 x 10(6) CFU, respectively, in C3H/HeJ mice. Strains BC17 and BC18 were not lethal to the animals. On the basis of the LD50 data, an appropriate sublethal dose (approximately 10(6) CFU) was selected. Animals were challenged intranasally with microorganisms, and clearance from the lungs and nasal cavity was determined. Strains BC17, BC18, and AC869 were not detected in lungs or nasal washes 14 days following treatment. Strains BC6, BC16, and DG1 were recovered from the nasal cavities at the end of the experiment. Only strain PAO1 was detected in lungs and in nasal cavities 14 days after treatment. At selected intervals following treatment, the percentages of polymorphonuclear leukocytes and lymphocytes in bronchoalveolar lavage samples were determined. P. aeruginosa AC869, PAO1, and DG1 elicited a relatively strong inflammatory response which was indirectly related to lung clearance.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Increased cholinergic antagonism underlies impaired beta-adrenergic response in ovalbumin-sensitized guinea pigs.

The goal of this study was to determine if the hyporesponsiveness to beta-adrenoceptor stimulation observed in ovalbumin-sensitized tracheal smooth muscle is due to increased cholinergic muscarinic tone or to a defect in the beta-adrenergic cascade itself. We examined the effects of ovalbumin-sensitization on the responsiveness of guinea pig tracheae to agents that mediate relaxation at various steps in the beta-adrenergic cascade when the tracheal tissue was preconstricted with either carbachol or histamine. Ovalbumin sensitization caused significant reductions in the maximal relaxations both to the beta-adrenergic agonist isoproterenol and to prostaglandin E2 (PGE2) in guinea pig trachealis when the tracheal tissue was preconstricted with the muscarinic agonist carbachol. In contrast, sensitization had no effect on the ability of PGE2 and isoproterenol to relax histamine contractions. Preconstricting the tissues with increasing concentrations of KCl reduced the effectiveness of isoproterenol to relax equally airway tissues from both sensitized and control animals. Forskolin-induced relaxations of trachealis muscle were not altered with sensitization. When tracheal tissues were precontracted with increasing concentrations of carbachol, the effectiveness of isoproterenol and PGE2 to relax airway tissues decreased. Functional antagonism of relaxations by muscarinic agonists was enhanced in the sensitized tissues, since the concentration of carbachol necessary to reduce beta-adrenoceptor-induced relaxations to the same degree as in the control animals was a log dose lower. These results suggest that the impaired beta-adrenoceptor response in sensitized tissues is not due to an intrinsic defect in the beta-adrenergic cascade but to an enhancement of a muscarinic cholinergic pathway.

Animals↗

PubMed1993

Ozone-enhanced pulmonary infection with Streptococcus zooepidemicus in mice. The role of alveolar macrophage function and capsular virulence factors.

Ozone exposure has been shown to increase the susceptibility of mice to pulmonary bacterial infection. We report here the differences in susceptibility of two strains of mice (C3H/HeJ and C57Bl/6) to pulmonary challenge with Streptococcus zooepidemicus, and demonstrate an association between O3 exposure, reduced alveolar macrophage (AM) function, and increased mortality to infection. After a 3-h exposure to air or to 0.4 or 0.8 ppm O3, mice received an infection of bacteria by aerosol. Subsequent mortality observed over a 20-day period for any given exposure concentration was greater in the C3H/HeJ mice than in the C57Bl/6 mice. Phagocytosis assays identified the AM from O3-exposed lungs as having an impaired ability to engulf the bacteria. Baseline phagocytic activity in C3H/HeJ mice was lower than that in C57Bl/6 mice. Microbiologic assessment of the lungs at various times after infection revealed that the streptococci proliferated rapidly in the lungs of O3-exposed mice, grew more quickly upon isolation, and displayed a mucoid colony appearance indicative of increased encapsulation. In vitro assays confirmed that the encapsulated isolates prevented binding of the bacteria to AM, and reinfection of nonexposed mice with the encapsulated isolate resulted in increased mortality compared with infection with similar numbers of the original unencapsulated bacteria. We have demonstrated that O3 inhalation impairs AM activity in the lung. The streptococci are then able to proliferate and more fully express virulence factors, in particular, the antiphagocytic capsule, which prohibits the ingestion of bacteria by pulmonary phagocytes and leads to increased severity of infection.

Air Pollutants↗

PubMed1991

Serum antibody responses in mice to intermittent inhalation of ovalbumin dust.

Serum antibody production and induction of antibody tolerance were monitored in mice following intermittent inhalation of ovalbumin dust (mass concentration = 4.2 mg m-3; diameter of 80% of particles less than 2.6 microns). Repeated inhalation of microgram quantities of dust stimulated serum antibody production and development of tolerance. The sequence of these responses is analogous to that following oral presentation of antigen, but is produced by a much lower dose when antigen is presented via the respiratory tract.

Administration, Intranasal↗

PubMed1990

The airborne survival of Pasteurella haemolytica and its deposition in and clearance from the mouse lung.

Pasteurella haemolytica A1 was aerosolised by a Collison nebuliser in a Henderson apparatus and its survival in air was measured. The organism was fragile in aerosol and survived best at high humidity and warm temperature. Mice were exposed to the aerosol and clearance from the lung measured. Deposition in the mouse lung showed a good linear correlation with bacterial concentration in the spray suspension fluid. Clearance from the lung was rapid over 24 h although some bacteria could be detected 2 and 4 days after exposure. Mice which received a second exposure 2 weeks later exhibited accelerated clearance from the lung whereby no bacteria could be detected after 12 h. This was associated with serum IgG antibody production, and local and splenic lymphocyte responses to bacterial antigen in vitro.

Aerosols↗

PubMed1990

Suppression of alveolar macrophage membrane-receptor-mediated phagocytosis by model particle-adsorbate complexes: physicochemical moderators of uptake.

In order to assess the abilities of alveolar macrophages (AMs) to phagocytize adsorbent-adsorbate complexes, rat AMs were incubated in vitro with two carbon blacks that have 15-fold differences in specific surface areas (ASTM classification N339 less than Black Pearls 2000) sorbed with 0.5 and 1.0 monolayer coverages of a polar and semi-polar adsorbate (acrolein and benzofuran, respectively). One-half monolayer coverages of N339 with either adsorbates significantly suppressed the phagocytosis of the carbon black, whereas one monolayer coverage did not. Neither adsorbate at either coverages affected the phagocytosis of Black Pearls 2000. The capacity of macrophages to phagocytize a subsequent particle challenge via the Fc-membrane receptor was quantified following treatment of the macrophages with the carbon black-adsorbate complexes. Treatment of the macrophages with carbon black N339-adsorbates complexes at both coverages impaired Fc-receptor-mediated phagocytosis, whereas no effect was observed when the carbon black was Black Pearls 2000. The results of this study indicate that the surface properties of the particles, the chemical properties of the chemical pollutants, and the interactions between particles and pollutants play a major role in defining the biological effect of particle-pollutant complexes.

Adsorption↗

PubMed1989

The effect of titanium dioxide inhalation on the pulmonary clearance of Pasteurella haemolytica in the mouse.

Four inhalation exposure chambers were designed and built in which up to 80 mice per chamber could be accommodated. Exposure for several weeks to an inert inorganic particulate aerosol of titanium dioxide at a respirable aerosol concentration of 20 mg m-3 impaired the clearance of Pasteurella haemolytica in proportion to the duration of exposure. Other groups exposed to a lower respirable concentration of 2 mg m-3 exhibited similar clearance rates relative to mice maintained in clean air. A recovery experiment showed that inhalation of TiO2 at 20 mg m-3 for 10 days impaired bacterial clearance at least 10 days after cessation of exposure to TiO2.

Administration, Inhalation↗

PubMed1989

Pulmonary clearance of Pasteurella haemolytica and immune responses in mice following exposure to titanium dioxide.

The effects of dust inhalation on immune responses in mice to aerosolized Pasteurella haemolytica were investigated. Animals exposed to titanium dioxide dust (TiO2) at a respirable aerosol concentration of approximately 20 mg m-3 for 20 hr per day, before or after aerosol vaccination, had impaired pulmonary bacterial clearance relative to animals kept in clean air. Additionally, lymphocytes from the local (mediastinal) lymph nodes had depressed responses to bacterial antigen in vitro in mice exposed to dust immediately after vaccination. However, there were no differences in the splenic lymphocyte responses between groups, while serum antibody responses were low and variable. A second experiment showed that aerosol vaccinated and nonvaccinated animals, which were exposed to a respirable aerosol concentration of TiO2 at 20 mg m-3 immediately after inoculation with a bacterial aerosol, had impaired clearance compared to their respective controls maintained in clean air.

Aerosols↗

PubMed1988

Effects of inhaled titanium dioxide dust on the lung and on the course of experimental Legionnaires' disease.

Guinea-pigs were exposed for 14 days to an aerosol of titanium dioxide (TiO2) dust to produce macrophage blockade. Groups of the animals were later infected by aerosol with Legionella pneumophila. Histological and ultrastructural studies showed that TiO2 dust alone was inert and non-fibrogenic and even at 6 weeks induced no pathological lesions in the lungs, apart from accumulation of macrophages in interalveolar septa. The macrophage blockade by TiO2 did not alter the animals' susceptibility to Legionnaires' disease nor increase mortality. The blockade was effective in the early stages of the infection and limited multiplication of L. pneumophila in the lungs. Later blood monocytes were recruited into the lungs, where they phagocytosed Legionellae, resulting in lung counts comparable to those of TiO2-free control animals.

Animals↗

PubMedDate not supplied

TNF-alpha enhanced allergic sensitization to house dust mite in brown Norway rats.

We have recently demonstrated that pulmonary exposure to residual oil fly ash (ROFA) resulted in enhanced sensitization to house dust mite (HDM) and augmented the development of allergic lung disease after allergen challenge. This effect was associated with increased tumor necrosis factor alpha (TNF-alpha), a macrophage- and epithelial cell-derived cytokine that promotes granulocyte migration to the lung. The present study examined whether exogenous administration of TNF-alpha enhances sensitization to HDM. One day prior to pulmonary sensitization with 10 microg HDM (5 microg each on days 1 and 3), female Brown Norway rats were instilled via the trachea with either 2.0 microg recombinant rat TNF-alpha, 2.0 microg bovine serum albumin (BSA), or 1,000 microg ROFA, and were challenged with 10 microg HDM 14 days later. Antigen-induced immediate bronchoconstriction responses, antigen-specific immunoglobulin E (IgE) titers, lymphocyte proliferation, (cytokines (TNF-alpha and interleukin [IL]-13), and eosinophils were elevated in rats treated with ROFA or TNF-alpha compared with BSA-treated controls after HDM challenge. Intratracheal administration of anti-TNF-alpha monoclonal antibody during ROFA exposure did not reduce ROFA-enhanced lymphocyte proliferation or IgE titers, but had a trend for reduced pulmonary inflammation. This study demonstrates that TNF-alpha has similar adjuvant activity as ROFA, but other factors may fulfill this function when TNF-alpha activity is blocked.

Animals↗

PubMedDate not supplied

Suppression and recovery of the alveolar macrophage phagocytic system during continuous exposure to 0.5 ppm ozone.

Short-term exposures to ozone (O3) are known to impair pulmonary antibacterial defenses and alveolar macrophage (AM) phagocytosis in a dose-related manner. To determine the effect of prolonged O3 exposure, Swiss mice were exposed continuously to 0.5 ppm O3. At 1, 3, 7, and 14 days, intrapulmonary killing was assessed by inhalation challenge with Staphylococcus aureus or Proteus mirabilis and by comparing the number of viable bacteria remaining in the lungs at 4 h between O3-exposed and control animals. To evaluate the effects of O3 on the functional capacity of the AMs, Fc-receptor mediated phagocytosis was assessed. Ozone exposure impaired the intrapulmonary killing of S. aureus at 1 and 3 days; however, with prolonged exposure, the bactericidal capacity of the lungs returned to normal. This trend of an initial suppression followed by recovery was reflected in the phagocytic capacity of the AMs. In contrast to S. aureus, when P. mirabilis was used as the challenge organism, O3 exposure had no suppressive effect on pulmonary bactericidal activity, which correlated with an increase in the phagocytic cell population in the lungs. Morphologic examination of the lavaged macrophages showed that after 1 day of O3 exposure, the AMs were more foamy, and contained significantly more vacuoles. There was also a significant increase in binucleated cells at 3 days. These studies demonstrate that continuous exposure to O3 modulates AM-dependent lung defenses and points to the importance of the challenge organism and exposure protocol in establishing the adverse effect of O3.

Animals↗

PubMedDate not supplied

Factors that influence the suppression of pulmonary antibacterial defenses in mice exposed to ozone.

Exposure to ozone (O3) has been shown to increase susceptibility of mice to bacterial infection; however, the underlying mechanism has not been well elucidated. This study investigated the effect of O3 exposure on the ability of mice to combat an infectious challenge of Streptococcus zooepidemicus. Following a 3-h exposure to either air, 0.4 ppm O3, or 0.8 ppm O3, 5- and 9-week-old mice received an aerosol infection of bacteria. Intrapulmonary killing of the bacteria was impaired in the O3-exposed mice. The effect was most severe at the higher dose of O3 in the younger mice, and showed good correlation to subsequent mortality assessed over a 20-day period. Alveolar macrophages (AM) from O3-exposed mice had an impaired ability to phagocytose the bacteria. Additionally, prostaglandin E2 (PGE2) levels, which are known to depress AM function, were increased in the bronchoalveolar lavage fluid of the younger mice following exposure to O3, while pretreatment with indomethacin in the drinking water blunted the increased of PGE2 and reduced O3 enhanced mortality from 53 to 33%. The data show that O3 inhalation can reduce the defensive capability of the murine lung and that this is associated with a reduction in AM phagocytosis. The defect is more marked in young mice, suggesting that they may be more susceptible to oxidant exposure. Further studies are required to distinguish between direct toxicity of O3 on the AM and indirect suppression due to modulation of pharmacologic or inflammatory mediators.

Adjuvants, Immunologic↗