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J D Brain

Publications and source records attributed to J D Brain.

At least 73 records · Page 4Linked to original sources
PubMed1988

Pulmonary effects of blood replacement with a perfluorochemical emulsion followed by exposure to 85% oxygen or air.

Perfluorochemical emulsions (PCE) have been used as blood substitutes because of their high solubility coefficient for oxygen. However, concerns for their clinical use include both the hyperoxia required by PCE to improve oxygen delivery to tissues and the effects of PCE on lung tissue. We addressed 3 questions: (1) What are the combined effects on the lungs of PCE blood replacement and hyperoxia? (2) Does reduction of circulating white cells by PCE blood replacement modify the injurious effects of hyperoxia? (3) Does PCE alone alter the lungs? Adult rats received either partial or complete PCE blood replacement or no PCE and were then exposed to 85% oxygen for 5 days. Other rats received partial PCE or no PCE and breathed air for 5 days. Morphometric and morphologic analyses demonstrated that lung injury was primarily caused by hyperoxia, independent of PCE treatment. Statistical analyses of the data indicated no synergistic effects between PCE and hyperoxia; furthermore, transient reduction of blood inflammatory elements by PCE blood replacement did not modify the extent of injury that occurred later. Importantly, however, rats that received partial PCE and air exposure were virtually identical to those that received no PCE and air exposure. Five days after blood replacement, PCE components were most often seen within alveolar and interstitial macrophages and infrequently within endothelial and epithelial cells. Although PCE itself may have produced functional alterations in lung cells, direct effects were not morphologically evident. Our results suggest that, if PCE are used at moderate FIO2, such as 0.6 or less, structural changes in the lungs could be minimized.

Air↗
PubMed1988

Isolation and antigenic identification of hamster lung interstitial macrophages.

Lung interstitial macrophages (IMs) are a large, distinctive population of cells with important proliferative capacities. Characterization of their role in health and disease has been hampered by inadequate methods to separate interstitial from residual alveolar macrophages (AMs) in preparations of individual mononuclear cells from lung tissue. In this study, a specific cell-surface antigen (HAM1) present on more than 90% of hamster AMs, but not expressed by hamster IMs, was used to distinguish these populations. After collagenase digestion of lung tissue slices from exhaustively lavaged and perfused hamster lungs, mononuclear phagocytes were isolated by density gradient centrifugation. The mean yield of lung digest macrophages (3.9 +/- 1.9 (SD) x 10(6] was comparable to the yield of lavaged AMs (4.2 +/- 1.9 x 10(6]. The proliferative capacity of lavaged AMs, blood monocytes, and lung digest macrophages was compared using a soft-agar colony-forming unit (CFU) assay. Both lung digest macrophages and blood monocytes had significantly more CFUs (68.7 +/- 2.6 and 53.5 +/- 8.4 CFU/10(3) cells [mean +/- SEM], respectively) than did AMs (16.5 +/- 1.7) (p less than 0.01). To further define the composition of the lung digest macrophage population, flow cytometric analysis of fixed cells from six experiments was performed using a mouse monoclonal antibody specific for the HAM1 antigen found only on AMs. The lung digest macrophage population consisted of both antigen-negative IMs (78.2% +/- 3.7% [SEM]; n = 6) and antigen-positive, residual AMs (21.8% +/- 3.7%). Morphometric counts confirmed that substantial numbers of AMs are left behind after lavage and contribute to macrophages obtained from lung tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Pulmonary removal of circulating endotoxin results in acute lung injury in sheep.

Endotoxemia has often been associated with the development of the adult respiratory distress syndrome. Our previous studies have shown that sheep, a popular animal model for adult respiratory distress syndrome, have abundant resident pulmonary intravascular macrophages that rapidly remove inorganic particles and live bacteria from the circulating blood. In this study, we examine the fate of circulating endotoxin in sheep and correlated the site of uptake with early morphologic evidence of tissue injury. Mature sheep and rats received intravenous 125I-labeled lipopolysaccharide (LPS). The dose was 0.8 microgram/kg in sheep and 17.0 micrograms/kg in rats. 125I-LPS clearance from the blood was assayed by gamma-counting of blood samples drawn over 1 hour and was correlated with circulating leukocyte numbers. The distribution of 125I-LPS was determined by gamma-counting of samples of major organs and tissues at time of necropsy. Lungs and liver were examined morphologically in both species. The half-life of circulating 125I-LPS was 2.38 minutes in sheep, and 12.39 minutes in rats. The endotoxin content of the lungs after injection was 77.58% of the total recovered dose in sheep, but only 2.02% in rats. Neutrophil margination occurred in the lungs of both species. In sheep, almost 25 minutes elapsed before peripheral neutrophil numbers decreased by 50%, much longer than the time required for LPS sequestration in the lungs. Rapid LPS uptake by the sheep lungs was associated with early (10-minute) ultrastructural changes including signs of pulmonary intravascular macrophage activation and microvascular congestion. By 60 minutes, many capillaries were occluded with neutrophils, platelets, and fibrin. There was interstitial edema, and endothelial cells showed evidence of severe injury. We conclude that in contrast to the rat, the sheep clears circulating endotoxin more rapidly and preferentially sequesters it in the lungs. Subsequent release of mediators by activated pulmonary intravascular macrophages may then lead to influx of other inflammatory cells and cascading injury.

Animals↗
PubMed1987

Deposition and phagocytosis of inhaled particles in the gas exchange region of the duck, Anas platyrhynchos.

Little is known about the fate of inhaled aerosol particles in birds; even the anatomical location of phagocytic cells within the lungs has yet to be clearly demonstrated. We exposed 2 anesthetized, spontaneously breathing ducks to a non-toxic iron oxide aerosol (aerodynamic mass mean diameter = 0.18 micron; 460 mg/m3) for 1.75 h and 2 awake, resting ducks to less concentrated aerosol (38 mg/m3) for 6 h on two consecutive days. All 4 ducks were sacrificed 24 h after the end of the last exposure. Their lungs, as well as the lungs from a control duck not exposed to the aerosol, were fixed in situ by insufflation of osmium tetroxide vapor or by intravascular perfusion. Then samples of the gas exchange region were examined with a transmission electron microscope. We found iron oxide particles: trapped within the trilaminar substance that is unique to avian lungs and coats the atria and infundibula; within epithelial cells of the atria and initial portions of the infundibula; and within interstitial macrophages. Only occasionally, small amounts of particles were found in the air capillaries. We conclude that both epithelial cells and interstitial macrophages can phagocytize particles in avian lungs, and that there is some convective transport of aerosol to the atria and the initial portions of the infundibula.

Animals↗
PubMed1987

The pulmonary toxicity of talc and granite dust as estimated from an in vivo hamster bioassay.

A short-term animal bioassay was used to assess the toxicity of occupational dusts. We quantified pulmonary responses in hamsters exposed to granite (12% quartz) and talc (quartz and asbestos-free) dust collected from worksites. Personal samples collected on workers showed similar quartz content and particle-size distributions to the high-volume samples collected for bioassays, thus demonstrating that the particulates were representative of worker exposure. We measured biochemical and cellular indicators of injury in bronchoalveolar lavage fluid (BAL) of animals exposed to dust suspensions by intra-tracheal instillation. The assays measured release of cytoplasmic and lysosomal enzymes into the cell-free supernatant of BAL; levels of albumin and red blood cells; changes in macrophage and polymorphonuclear neutrophil cell numbers; and in situ macrophage phagocytosis. Dose-response (0.15, 0.75, and 3.75 mg/100 g body wt) and time-course (1-14 days postexposure) studies were performed. One day after exposure, both talc and granite dust resulted in elevated enzyme levels, pulmonary edema, and increased cell numbers in BAL. Macrophage phagocytosis was also inhibited. Based on earlier studies, response levels were either intermediate between nontoxic iron oxide and toxic alpha-quartz or comparable with alpha-quartz. The response to granite dust diminished fairly rapidly over time. By contrast, after talc exposure, there was a more persistent elevation in enzyme levels, and macrophage phagocytosis remained depressed. These results indicate that, when a similar mass was deposited in the lungs, talc caused more lung injury than did granite. Better estimates of exposure-dose relationships in talc and granite workers as well as longer-term animal studies are required to evaluate the harmfulness of these work environments at present-day exposure levels.

Animals↗
PubMed1987

Adjusting for confounded variables: pulmonary function and smoking in a special population.

Confounded variables present an obstacle to valid inference in many environmental and occupational studies. We describe a series of procedures that we used to address this problem in a study of pulmonary function and smoking. Subjects were drawn from the Multiple Risk Factor Intervention Trial (MRFIT), a prospective study of coronary heart disease. Confounding of smoking, hypertension, and hyperlipidemia was designed into the trial and was beyond the control of our ancillary study. We used statistical techniques to detect and characterize the pattern of confounding, identify important variables affecting pulmonary function, and perform appropriate adjustments for extraneous influences (i.e., other than smoking). Among the techniques we used were factor analysis, stepwise multiple regression, and bootstrap replication. Analysis of the adjusted pulmonary function measurements showed that they were satisfactorily standardized and free of artifact. Moreover, use of the adjusted values sharpened our statistical results concerning smoking, the ultimate object of the study. We contrast the use of external and internal standards and discuss methods for detecting, ruling out, or counteracting confounding.

Adult↗
PubMed1987

A new technique for collecting ambient diesel particles for bioassays.

This paper describes a new application of a viable aerosol sampler, the Liquid Electrostatic Aerosol Precipitator (LEAP), for the collection of diesel particles for bioassays of pulmonary toxicity and mutagenicity or carcinogenicity. Currently used methods (filtration, dry electrostatic precipitation) cause agglomeration of particles and increases in particle size up to twenty-fold, which may alter particle toxicity significantly. Collection of diesel particles with the LEAP preserved submicronic particle size. Differences in chemical composition of extracts of surface adsorbents as compared to particles collected on filters also were observed. This technique may be applicable for collection of other types of combustion products or oil mists that agglomerate when collected by filtration.

Air Pollutants↗
PubMed1987

Uptake of bloodborne bacteria by pulmonary intravascular macrophages and consequent inflammatory responses in sheep.

Bacteria are primarily removed from the bloodstream of most species by mononuclear phagocytic cells in the liver and spleen. We have recently described large numbers of pulmonary intravascular macrophages in several ruminant species that also remove inert particles from the bloodstream. To determine the role of these cells in removal of bacteria from the bloodstream, sheep and rats were injected intravenously with a single dose of Pseudomonas aeruginosa, and kinetics of clearance, relative uptake among organs, and morphologic changes in the lungs and liver 1 h after injection were compared. In rats, bacteria were removed primarily by the liver, and pathologic changes were found in hepatic sinusoids but not in the lungs. However, in sheep, bacteria were removed primarily by the lungs, and pulmonary capillaries became filled with neutrophils, platelets, and fibrin deposits. We propose that uptake of bacteria by pulmonary intravascular macrophages and subsequent release of inflammatory mediators are central to the pathologic changes produced in ruminant models of sepsis-induced adult respiratory distress syndrome.

Animals↗
PubMed1987

Emphysema alters the deposition pattern of inhaled particles in hamsters.

How does pulmonary emphysema affect aerosol deposition? Groups of awake hamsters with emphysema (intratracheal elastase, 0.2 mg/100 g body wt) and age-matched controls (intratracheal saline) were exposed for 30 minutes to an insoluble radioactive aerosol (0.45 mu aerodynamic diameter) at 30, 60, or 90 days after instillation. Immediately after exposure, the animals were sacrificed. The lungs were excised, dried at total lung capacity, and sliced into 1-mm thick sections. Each slice was cut into pieces, which were counted for radioactivity and weighed. Then a measure of the uniformity of deposition, the evenness index (EI), was calculated. With perfect uniformity, all EIs would be one. We found fewer particles in the emphysematous, as compared with the control, lungs at 60 or 90 days after elastase instillation. The deposited particles were distributed less uniformly throughout the emphysematous lungs than in the control lungs. In controls, the standard deviation (SD) of the EI distribution (mean 1.0) averaged 0.33 for the three times studied. In elastase animals, the SD increased to 0.48 at 30 days, and at 60 days and 90 days the distributions were no longer normally distributed. This increased heterogeneity of deposition was also manifested as a loss of the normal apex-base gradient observed in control animals, an increase in the amount of nonventilated parenchyma, enhanced airway deposition, and an altered lobar deposition pattern. Morphometric analysis showed an increase in the mean linear intercept (MLI) of emphysematous lungs as compared with control lungs. However, the author found no correlation between MLI, a measure of emphysema, and EI, a measure of deposition, quantified in the same lung pieces. It is concluded that the emphysematous lesions produced by elastase markedly alter the deposition of an inhaled submicrometric aerosol. Factors that may contribute to these changes include airway obstruction and differences in breathing pattern in emphysematous as compared with control animals.

Aerosols↗
PubMed1986

Immune opsonin-independent phagocytosis by pulmonary macrophages.

The uptake of albumin-coated latex particles by hamster pulmonary macrophages (PM) in vitro was investigated by using a new technique that combined flow cytometry and fluorescence microscopy to differentiate and quantitate bound vs ingested particles. In the absence of serum, PM avidly bound and ingested particles, whereas phagocytosis by hamster polymorphonuclear leukocytes (PMN) was less marked. In the presence of serum, phagocytosis by PM was slightly depressed, whereas phagocytosis by PMN was stimulated more than 10-fold. The binding of particles to PM in the absence of serum was pH, temperature, and trypsin sensitive and was dependent on the presence of extracellular Ca++ but not Mg++. The ingestion of particles by this immune opsonin-independent pathway was also temperature sensitive but was not affected by either pH or extracellular Ca++. Particle ingestion, but not binding, was inhibited by cytochalasin D and the divalent cation ionophore A23187.

Albumins↗
PubMed1986

Inhibition of immune opsonin-independent phagocytosis by antibody to a pulmonary macrophage cell surface antigen.

Unlike other hamster phagocytes, hamster pulmonary macrophages (PM) avidly ingest albumin-coated latex particles in the absence of serum. They also possess a highly specific cell surface antigen. To evaluate the relationship between these two characteristics, PM were incubated with mouse monoclonal antibody directed against the PM antigen. After unbound antibody was removed, the amount of bound antibody and the phagocytic capability of PM were measured by flow cytometry and fluorescence microscopy. Maximum antibody binding produced a 25% inhibition of ingestion. Particle attachment was not affected. This effect was antigen specific, since neither a nonspecific mouse myeloma protein of the same subclass nor a mouse antibody that bound to another hamster surface antigen had any effect on binding or ingestion. If antigen-specific F(ab')2 fragments were introduced both before and during the period of phagocytosis, the inhibition of particle ingestion approached 100%. Particle binding increased at low F(ab')2 concentrations but declined at higher concentrations. Because calcium may play a role in the ingestion process, the effect of antibody on 45Ca uptake was evaluated. It was observed that antigen-specific F(ab')2 fragments stimulated 45Ca uptake, whereas control antibodies did not. These results suggest that the antigen reacting with our anti-hamster PM monoclonal antibody is involved in immune opsonin-independent phagocytosis and that calcium participates in this phagocytic process.

Animals↗
PubMed1986

Intravascular pulmonary macrophages: a novel cell removes particles from blood.

Clearance of radiolabeled gold colloid from the blood and relative organ distribution of retained colloid and magnetic iron oxide particles were compared between rats and calves. When unanesthetized calves 1 wk of age were injected intravenously with these two particle types, uptake was predominantly pulmonary. In contrast, in the rat there was overwhelming hepatic uptake. Similar pulmonary localization of injected particulate material was found in adult goats. When lung tissue was examined by electron microscopy, injected iron oxide was found within intravascular pulmonary macrophages. The mononuclear phagocyte system removes particulate material of both exogenous and endogenous origin from the circulation; hepatic and splenic uptake of such material usually predominates. We found that, unlike the species previously studied, ruminants have actively phagocytic cells within the pulmonary vasculature. Thus pulmonary intravascular macrophages constitute an important part of the mononuclear phagocyte system in some species.

Animals↗
PubMed1986

Pulmonary intravascular macrophages in sheep. Morphology and function of a novel constituent of the mononuclear phagocyte system.

Macrophages resident in the pulmonary capillaries of sheep avidly remove injected particles from the circulating blood. Both sheep and rats were injected intravenously with radiolabeled gold colloid and magnetic iron oxide particles. One hour later, particle uptake in various organs was quantified by gamma counting and magnetometry. Organ localization of both gold and iron oxide particles was predominantly hepatic in rats. In marked contrast, sheep had predominantly pulmonary uptake. Ultrastructural morphology showed that pulmonary iron oxide uptake was by intravascular macrophages. Pulmonary intravascular macrophages were present in ruminant lungs in large numbers. Lungs of sheep given no particles were fixed by intratracheal instillation of glutaraldehyde; randomly chosen tissue samples were routinely processed for electron microscopy and studied with stereological methods. We found that these macrophages occupied 15.3% of the intravascular volume, and had 15.9 m2 of free surface available for contact with blood. Intravascular macrophages were closely applied to 7.1% of the endothelial surface, including numerous short segments with 12 to 15 nm of membrane interspace, increased subplasmalemmal cytoplasmic density, and intercellular electron-dense material. We conclude that pulmonary intravascular macrophages in sheep comprise an important component of their mononuclear phagocyte system. Furthermore, we suggest that these macrophages, through phagocytic uptake of bacteria or endotoxin, may contribute to pulmonary inflammation and injury.

Animals↗
PubMed1985

Short-term regional clearance of an inhaled submicrometric aerosol in pulmonary fibrosis.

Regional clearance of submicrometric aerosol during 5 days was studied in control hamsters and in those with diffuse interstitial pulmonary fibrosis. Fibrosis was induced by treatment with bleomycin (1.6 U/kg) and oxygen (70% for 72 h) 80 days earlier. Diseased and control animals were exposed for 30 min to an insoluble colloidal 198Au aerosol (AMAD, 0.62 micron; sigma g, 1.35). Five diseased and 6 control animals were killed immediately (Day 0); 6 diseased and 6 control animals were killed 5 days later (Day 5). All lungs were excised, dried at TLC, sliced into 1-mm sections, and dissected into pieces. When compared with deposition in Day 0 control lungs, 26.3% of the particles had been cleared 5 days after exposure from the control lungs. Diseased animals cleared 44.6% of the particles (p less than 0.05, compared with Day 0 diseased animals). Examination of regional clearance on the basis of lobar differences, apex to base levels, and presence of airways also reflected increased clearance in the fibrotic animals. The parenchymal distribution of particle retention at Day 0 was less uniform in the fibrotic animals than in the control animals and was not significantly altered after 5 days of clearance in either group. Particle clearance may be greater in diseased lungs because of accelerated alveolar-bronchiolar transport of particles or particle-containing macrophages.

Aerosols↗
PubMed1985

Ultrastructural analysis of a specific hamster alveolar macrophage antigen.

Alveolar macrophages of hamsters have a cell surface antigen not found on other pulmonary cells or macrophages from other sites. A specific mouse monoclonal antibody and protein A-colloidal gold were used to study the distribution of this antigen at the ultrastructural level. By quantitating the number of antigenic sites per unit linear distance of membrane of the total cell surface, it was established that this antigen is randomly distributed on the plasma membrane. Cell-to-cell heterogeneity in antigen density was correlated with other ultrastructural features of lung macrophages studied morphometrically. A strong correlation (r = 0.77) between antigen density and secondary lysosome content was found, supporting the thesis that expression of this antigen increases with macrophage age. No apparent topographic relationship of surface antigen to any cytoplasmic organelles could be inferred from the ultrastructural morphology. This study also used immuno-ultrastructural techniques to visualize stages of the internalization of labeled antigen in live cells. While some cells retained a random distribution of antigen at 0 degrees C, most showed movement of antigenic sites away from pseudopodia to clusters on more linear (less ruffled) portions of cell surface. At 37 degrees C, the antigen was internalized and could be visualized within coated pits and endocytic vacuoles. Definition of the anatomic distribution of this antigen under various conditions provides a baseline for further ultrastructural investigations of the function of this antigen.

Animals↗
PubMed1984

Noninvasive studies of Kupffer cells in situ by magnetometry.

Magnetic iron oxide (gamma-Fe2O3) particles were injected intravenously into four male New Zealand white rabbits. Most of these particles were phagocytized by the Kupffer cells. When the animal was placed in a magnetic field, the particles in the liver became magnetized and aligned. After removal of the external magnetizing field, the particles collectively produced a remanent magnetic field which was measured at the body surface. The strength of this field was proportional to the amount of magnetic particles present in the liver; sequential measurements thus allowed us to describe their disappearance from the liver. After each magnetization, the remanent field rapidly decayed due to particle rotation (relaxation). Since the particles were confined in phagosomes or secondary lysosomes we conclude that movements of these organelles due to cytoplasmic motion caused relaxation. Magnetic particles might therefore serve as probes for cytoplasmic motility of Kupffer cells in situ.

Animals↗