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J D Brain

Publications and source records attributed to J D Brain.

At least 55 records · Page 3Linked to original sources
PubMed1991

Pulmonary surfactant as a vehicle for intratracheal delivery of technetium sulfur colloid and pentamidine in hamster lungs.

Tracheal instillation of pentamidine in a surfactant vehicle may be an effective direct method of antibiotic delivery to the lungs. In 10 healthy hamsters, we compared the pulmonary distribution of 99mTc sulfur colloid (TcSC) mixed with pentamidine, using as a vehicle either surfactant (n = 5) or saline (n = 5). Each animal was instilled with 0.25 ml/kg of suspension containing 0.0018 mCi TcSC and pentamidine mixed with either surfactant or saline. After 4 h of spontaneous respiration, the lungs were excised, inflated to TLC, dried, and sliced into 3-mm cross sections from apex to base. Autoradiographs were examined to evaluate 99mTc distribution. The surfactant group had detectable radioactivity in 93% of all slices compared with 72% in the saline group (p = 0.02). Six slices per animal (43% of total) and their corresponding autoradiographs were analyzed for distribution of radioactivity. Lung slice area was determined by planimetry, and autoradiograph area was determined by video densitometry. We calculated the fraction of each lung slice with detectable radioactivity. The surfactant group had 41% of the lung slice areas exposed compared with 21% in the saline group (p = 0.02). The coefficient of variation of radioactive intensities within each slice was used as an index of spatial uniformity. There was a trend towards more uniform distribution in the surfactant group, with a narrower range of variation of intensities (1.51 to 2.56) than the saline group (1.95 to 6.47). We conclude that a surfactant vehicle significantly increases airspace deposition of TcSC and pentamidine instilled intratracheally in normal hamster lungs, and may improve uniformity of spread.

Animals↗
PubMed1991

Pulmonary deposition: determinants and measurement techniques.

Evaluating the response of animals to a toxic or therapeutic agent requires the knowledge of the dose of the agent in the respiratory tract. Dose is the amount retained in the lungs. It is the difference between the amount deposited and the amount cleared. Many factors influence the amount of and the site of deposition in the respiratory tract. For particles, the characteristics of the aerosol, most importantly size, the physiology of the animal, most importantly breathing pattern, and the geometry of the respiratory tract all play a role in determining local dose. These factors and their relative importance in determining regional deposition are discussed. Finally, ways in which dose can be measured in the respiratory tract are explored. These range from simple estimates of total dose using whole lung digests to the precise localization of dose in well-defined lung compartments using morphometry or in cellular or subcellular compartments using electron energy loss spectroscopy. The techniques utilized by an investigator depend on the amount of resolution desired. Their use and implementation in inhalation studies are the key to fully understanding the response of an animal to an inhaled toxic or therapeutic agent.

Aerosols↗
PubMed1990

Selective down-regulation of alveolar macrophage oxidative response to opsonin-independent phagocytosis.

We have compared the oxidative response of alveolar macrophages (AM) during opsonin-dependent and independent phagocytosis by using multiparameter flow cytometry. The respiratory burst of AM during phagocytosis was quantitated by the intracellular oxidation of the nonfluorescent precursors dichlorofluorescin diacetate (DCFH) or hydroethidine (HE, a reduced precursor of ethidium) to their fluorescent (oxidized) counterparts. After loading freshly isolated normal hamster AM with DCFH or HE, red or green fluorescent beads, respectively, were added to the shaking cell suspensions. Ingestion of opsonized particles by AM caused a marked increase in oxidation of both DCFH and HE proportional to the number of beads ingested. In contrast, uptake of one to three unopsonized particles per cell led to inhibition of oxidative activity compared to control cells incubated without particles. AM ingesting four or more unopsonized particles showed some increase in oxidative metabolism, but far less than that with identical numbers of particles in opsonin-dependent ingestion. Similar results were obtained using fluorescent labeled staphylococcal bacteria. Using three-color flow cytometry to study cells ingesting both types of particles, cells first ingesting unopsonized beads were also found to have an inhibited oxidative response to subsequently ingested opsonized particles. The mitochondrial poison antimycin inhibited most of the intracellular oxidative response to either type of phagocytosis. The remaining antimycin-insensitive, membrane derived respiratory burst of AM was also substantially diminished after phagocytosis of unopsonized particles vs similar numbers of opsonized particles. The greatly increased mitochondrial respiration in AM during phagocytosis of opsonized particles may be related to bactericidal mechanisms. Killing of ingested Staphylococcus by AM was markedly impaired in the presence of antimycin. The results suggest that AM may ingest the numerous, unopsonized inert particles that are inhaled without generation of potentially toxic oxygen metabolites, while retaining the capacity to undergo a respiratory burst after ingesting opsonized particles and bacteria. The mechanism(s) for this distinct response may include generation of an inhibitor of intracellular oxidative metabolism.

Animals↗
PubMed1990

The cell biology and pathogenic role of pulmonary intravascular macrophages.

Pulmonary intravascular macrophages (PIMs) are an extensive population of mature phagocytic cells adherent to the pulmonary capillary endothelium in selected species. They are not prevalent in lungs of commonly studied laboratory animals, such as rodents, and thus have only been recently appreciated. However, their potential role in host defense and acute lung injury has attracted interest, since a number of studies have demonstrated pulmonary localization of circulating particles, microbes, and endotoxin by PIMs. Those animal species, such as ruminants, that provide useful models of pathogen (or endotoxin)-induced acute lung injury demonstrate rapid pulmonary uptake of bacteria by PIMs. Inflammatory mediators released by activated PIMs may initiate the process and provoke accumulation of neutrophils and platelets. This review summarizes the morphological characteristics of PIMs and their species distribution. The role of these members of the mononuclear phagocyte system, both beneficial and potentially pathogenic, is reviewed. The question of whether PIMs have a role in acute lung injury in humans is also discussed.

Animals↗
PubMed1990

Effect of exercise on redistribution and clearance of inhaled particles from hamster lungs.

Does exercise alter the redistribution and clearance of particles from the lungs? Sedentary hamsters and hamsters that were exercise trained by voluntary wheel running for the previous 5 wk were exposed to a 198Au-labeled aerosol for 25 min. Six trained and 6 sedentary animals were killed within 5 min after the exposure (day 0); the same number were killed 5 days later. The trained hamsters ran ad libitum during those 5 days. The lungs of all animals were excised, dried at total lung capacity, sliced into 1-mm-thick sections, and dissected into pieces that were counted for radioactivity and weighed. On day 0, trained hamsters had 80% more particles per milligram of lung than sedentary hamsters, although both were exposed under identical conditions of restraint. After five days, exercising hamsters cleared 38% of the particles present at day 0, whereas sedentary animals removed only 15%. Significant clearance was observed from the middle lung regions of sedentary hamsters and from all lung regions in exercising hamsters. We conclude that exercise can enhance the redistribution and clearance of particles from the lungs; the mechanisms responsible are as yet unclear.

Aerosols↗
PubMed1990

Breathing and lung mechanics in hamsters: effect of pentobarbital anesthesia.

An adaptation of the method reported by Skornik, Heimann, and Jaeger (Toxicol. Appl. Pharmacol. 59: 314-323, 1981) was used to evaluate pulmonary mechanics in intact awake hamsters. Lung volume changes were measured with a pressure plethysmograph, and pleural pressure was estimated by the use of a saline-filled esophageal catheter. We report data for normal awake hamsters studied at 18, 20, 22, 32, and 98 wk of age. Age-related differences were observed in tidal volume, dynamic compliance, and pulmonary resistance. To determine to what extent pulmonary mechanics are changed by anesthesia, hamsters were measured during spontaneous breathing while awake and while anesthetized. We found that anesthesia had a marked effect on the breathing pattern of normal hamsters. Twenty-five minutes after injection of pentobarbital sodium (70 mg/kg ip), tidal volume, dynamic compliance, pulmonary resistance, breathing frequency, and minute ventilation were 66, 40, 375, 60, and 41% of the corresponding awake values. Anesthesia always provoked a significant and dose-related decrease in tidal volume and an increase in respiratory period, together resulting in a profound decrease in minute ventilation. These significant differences from the awake values call into question the value of measurements in anesthetized animals. The methods described here yield reasonable and repeatable measurements and, because no anesthesia or surgery is required, they can be used in longitudinal studies when repeated measurements in the same animal over long periods of time can help define pathological changes or the effectiveness of various interventions.

Age Factors↗
PubMed1990

Effect of sulfur dioxide on pulmonary macrophage endocytosis at rest and during exercise.

Inhaled SO2 may cause damage by injuring upper airways. To what extent can SO2 also alter pulmonary macrophage function in the parenchyma and what is the impact of exercise? We studied the effect of SO2 on pulmonary macrophage endocytosis in resting and in exercising animals by measuring the rates of macrophage endocytosis in situ for 1 h of a test particle of insoluble radioactive colloidal gold (198Au), 1, 24, or 48 h after inhalation exposure to SO2. Resting hamsters exposed for 4 h to 50 ppm SO2 had no significant reduction in macrophage endocytosis compared with air-breathing control hamsters. However, if hamsters were exposed to the same concentration of SO2 while continuously running (40 min at 0.9 km/h), macrophage endocytosis was significantly reduced 1 h after exposure even though the exposure time was only one-sixth as long. Twenty-four hours later, the percentage of gold ingested by pulmonary macrophages remained significantly depressed. By 48 h, the rate had returned to control values. Exercise alone did not affect endocytosis. Hamsters exposed to 50 ppm SO2, with or without exercise, also showed significant reductions in the number of lavaged macrophages. This decrease was greatest and most persistent in the SO2 plus exercise group. These data indicate that even when animals are exposed to water-soluble gases, which are normally removed by the upper airways, exercise can potentiate damage to more peripheral components of the pulmonary defense system such as the macrophage.

Animals↗
PubMed1990

In vitro dissolution of uniform cobalt oxide particles by human and canine alveolar macrophages.

Intracellular dissolution of inhaled particles is an important pathway of clearance of potentially toxic materials. To study this process, monolayers of human and canine alveolar macrophages (AM) were maintained alive and functional in vitro for more than 2 wk. Complete phagocytosis of moderately soluble, monodisperse 57Co3O4 test particles of four different sizes was obtained by optimizing the cell density of the monolayer and the particle-to-cell ratio. The fraction of the initial particle mass that was soluble increased over time when the particles were ingested by AM but remained constant when in culture medium alone. Smaller particle sizes had a faster characteristic intracellular dissolution rate constant than did larger particles. The dissolution rates differed between AM obtained from two human volunteers as compared to those obtained from six mongrel dogs. These in vitro dissolution rates were very similar to in vivo translocation rates previously obtained from human and canine lung clearance studies after inhalation of the same or similar monodisperse, homogeneous 57Co3O4 test particles. We believe an important clearance mechanism for inhaled aerosol particles deposited in the lungs can be simulated in vitro in a cell culture system.

Adult↗
PubMed1990

Oxidative metabolism in the alveolar macrophage: analysis by flow cytometry.

We evaluated the reagents dichlorofluorescin (DCFH) and hydroethidine (HE) for use in flow cytometric analysis of the respiratory burst of alveolar macrophages and monocytes. DCFH and HE are non-fluorescent precursors which can be oxidized intracellularly to the fluorescent compounds dichlorofluorescein and ethidium. Alveolar macrophages (AMs) loaded with either DCFH or HE were analyzed after phorbol myristate acetate (PMA) stimulation. The results, expressed as fmol/cell oxidation product (DCF or ethidium) after fluorometric standardization of the flow cytometer, show that both DCFH (273 +/- 48, mean increase over control +/- SE, fmol/cell, N = 9) and HE (416 +/- 54, N = 11) detected the substantial respiratory burst of hamster AMs. Similar results were obtained with normal human AMs. By using multiparameter analyses, the oxidative response of AMs ingesting opsonized fluorescent latex beads was measured in subpopulations ingesting increasing numbers of particles. A graded increase in oxidation of both DCFH and HE was found in response to increasing phagocytosis. Ingestion of fluoresceinated staphylyococcal bacteria caused similar changes in HE-loaded AMs. Inhibition of respiration with antimycin showed that approximately 95% of the increased oxidative metabolism of hamster AMs ingesting opsonized beads or bacteria was mitochondrial. The remaining 5% (10-40 fmol/cell) is membrane-derived oxidative activity quantitatively similar to that measured in assays of extracellular release of H2O2. Monocytes loaded with either DCFH or HE showed substantial increases in fluorescence after PMA stimulation (mean % increase over control +/- SE at 30 min: 464 +/- 104, DCFH, 505 +/- 156, HE). While DCHF is known to measure H2O2, HE is less well characterized. Exposure of cells to an extracellular source of both superoxide anion (O2-) and H2O2, xanthine oxidase-xanthine, resulted in marked oxidation of intracellular HE. Addition of both superoxide dismutase and catalase blocked this oxidation, indicating that HE can detect both O2- and H2O2. These agents can be useful probes for precise analysis of oxidative metabolism during phagocytosis in AMs and other mononuclear phagocytes.

Animals↗
PubMed1989

Effect of cystic fibrosis on inhaled aerosol boluses.

An aerosol bolus undergoes changes in shape between its inspiration and expiration. In comparison with the inhaled bolus, the exhaled bolus is more spread because of convective mixing, may have a shift in the location of the mode caused by asymmetries of filling and emptying of lung units, and contains fewer particles because of particle deposition. We hypothesized that the extent of these changes is related to lung health. To examine this, 11 patients with cystic fibrosis (CF) and 11 healthy subjects inhaled 70 cm3 boluses containing 1 micron monodisperse particles that were inspired to volumetric penetrations (Vp) of 100 to 700 cm3. As each bolus was expired, we measured spreading (volumetric width at one-half aerosol concentration peak height), modal shift, and particle deposition. Patients with CF exhaled boluses that were broader than those exhaled by normal subjects at all penetrations examined. At a Vp of 600 cm3, patients had a mean bolus half-width that was 68% greater than that of healthy subjects (p less than 0.0001), and they exhaled the bolus mode 20% earlier (p less than 0.0002). Particle deposition was increased compared with that in normal subjects at all Vp. For example, mean deposition at a Vp of 600 cm3 was 46.2 +/- 2.6% (SE) for the patients versus 25.8 +/- 1.6% for the normal subjects (p less than 0.0001). Among the patients with CF, pulmonary function parameters indicating obstruction were significantly correlated with bolus spreading and aerosol deposition: the percent predicted FEV1/FVC was inversely correlated with spreading (r = -0.88, p less than 0.0004) and deposition (r = -0.84, p less than 0.0008).(ABSTRACT TRUNCATED AT 250 WORDS)

Aerosols↗
PubMed1989

Magnetometric estimation of organelle motion in hamster lung macrophages in vitro: the effects of temperature.

Pulmonary macrophages, containing ingested ferrimagnetic particles, were studied in vitro. Magnetic particles (Fe3O4) suspended in saline were repeatedly instilled intratracheally into the lungs of Syrian golden hamsters. Later the animals were sacrificed and pulmonary macrophages were harvested by repeated lung lavage. After monolayer cultures were established, the particles previously phagocytized by the macrophages were magnetized and aligned by applying an external field. After the external field was removed, the particles produced a remanent magnetic field which gradually decreased due to random misalignment of the particles (relaxation). When relaxation was measured at various incubation temperatures, we found that relaxation slowed as the temperature decreased; we believe that this reflects decreased organelle motion. These results provide direct evidence that relaxation measured previously in intact animals is related to intracellular movements. Magnetometry can be used to quantitate the motion of cell organelles and thus the influence of altered cytoplasmic rheology and cytoskeletal activity.

Animals↗
PubMed1988

Phagocytic and motile properties of endothelial cells measured magnetometrically: effects of endotoxin.

Endothelial cells lining the vasculature share some properties with macrophages and neutrophils in that they can take up material from the blood and are known to migrate, particularly during wound healing. We observed that endothelial cells isolated from bovine pulmonary arteries ingested magnetic iron oxide particles during culture in vitro. Using a non-optical, magnetometric method, we examined motions of magnetic-particle containing intracellular vacuoles. We demonstrated that these organelles move within endothelial cells, but at a slower rate than phagosomes within macrophages. Magnetometry was used to show that incubation with endotoxin (10 micrograms/ml) for 4 hr resulted in a decrease in cytoplasmic movement; yet the fluidity of the cytoplasm was increased, as measured by intracellular particle response to forced motion. We conclude that intracellular magnetic probe particles can detect vesicular motion in endothelial cells, and that endotoxin exposure can affect endothelial cells directly, altering their physical properties; these alterations precede ultrastructural evidence of cell death.

Animals↗
PubMed1988

Pulmonary disease from exposure to an artificial aluminium silicate: further observations.

A cross sectional analysis of the relation between exposure to an artificial aluminium silicate (alunite residue) and pulmonary function changes has been made in 32 subjects, 17 of whom had been previously reported and in whom there was suggestive evidence of a dose response relation between gas transfer and total silicate exposure. Longitudinal data were also available for nine subjects. No dose effect relation was observed in either analysis and only one of the three subjects previously observed to have an abnormal chest radiograph (the index subject) had deteriorated appreciably. Respirable particles of alunite residue were injected intratracheally into Syrian hamsters. No evidence of pulmonary toxicity was seen as judged by bronchoalveolar lavage measurements of the concentrations lactic dehydrogenase, albumin, and the lambda fraction of gold, and the numbers of macrophages, polymorphonuclear cells, and red blood cells (alpha-quartz and ferrous oxide were used as positive and negative controls). These results do not support a significant toxic effect of this aluminium silicate on the lungs.

Adolescent↗
PubMed1988

Convective mixing in human respiratory tract: estimates with aerosol boli.

Convective gas mixing in the respiratory tract of 17 healthy male subjects was studied by an aerosol bolus technique. The monodisperse 1 micron di(2-ethylhexyl)sebacate droplets we used behaved as a nondiffusing gas. As the bolus was inspired to different depths and then expired, we measured the extent to which the bolus spread. We found that the deeper the bolus penetrated into the lungs, the more it became dispersed. The half-width of the expired bolus was a linear function of the volume to which the bolus penetrated at volumetric penetrations of 100-800 cm3. This suggests that convective mixing is not confined to central airways but can also occur in the lung periphery.

Adult↗
PubMed1988

Comparison of particle clearance and macrophage phagosomal motion in liver and lungs of rats.

Magnetic particles and magnetometry were used to noninvasively measure motion of particle-containing organelles in macrophages as well as to monitor the disappearance of particles from tissues. We compared these parameters in the liver (where macrophages are attached to the endothelium) and in the lungs (where macrophages were mobile on epithelial surfaces). Submicrometric magnetic particles were injected intravenously (1.5 mg/kg) into rats; 94% was taken up by the liver. Rats were also instilled intratracheally (1.0 mg/kg) with the same particles. Ultrastructural analyses showed that almost all particles were ingested by macrophages in both organs. Periodically, the retained particles were magnetized and aligned with an external magnet. After the magnet was removed, the decay of the resulting remanent field (relaxation) was followed for 25 min. Relaxation parameters (t1/2 and lambda 0) in the liver were constant from 30 min to 30 days after particle administration, but relaxation in lungs showed a time-dependent increase during the 1st day due to the slower rate of particle phagocytosis. Relaxation in both organs primarily reflects the motion of particle-containing organelles as they are rotated by the cytoskeleton. Relaxation in the lungs may also reflect cell translocation or even changes in alveolar shape. Clearance of particles from the lungs or liver was measured by following B0 (initial magnetic field strength). After correction for growth, the clearance t1/2 was 17.7 and 27.3 days for the lungs and liver, respectively. Bulk transport of particles is probably a more important clearance mechanism in the lungs than in the liver.

Animals↗
PubMed1988

The pathophysiology of enhanced susceptibility to murine cytomegalovirus respiratory infection during short-term exposure to 5 ppm nitrogen dioxide.

To determine whether exposure to nitrogen dioxide (NO2) affects respiratory tract susceptibility to viral infection, CD-1 mice were inoculated intratracheally with murine cytomegalovirus (MCMV) during exposure to varying concentrations of NO2. Exposure lasted for 6 h per day; it began 2 consecutive days prior to instillation of MCMV and continued for 4 days after virus inoculation. Exposure to 5 ppm NO2 resulted in MCMV proliferation and a mild bronchopneumonia in some animals inoculated with 10(2) plaque-forming units of virus. Importantly, this inoculum was too low to produce either viral replication or histologic abnormalities in the lungs of air-exposed animals. We also found that the amount of virus required to infect animals exposed to 5 ppm of NO2 was 100-fold lower than that needed to consistently produce infection in air-exposed animals. Animals exposed to 5 ppm NO2 also exhibited depressed phagocytosis of colloidal Au198 in vivo as well as diminished macrophage destruction of instilled MCMV compared to air-exposed animals. These results demonstrate that exposure to 5 ppm NO2, although not associated with evidence of overt lung injury per se, is nevertheless capable of predisposing the lower respiratory tract to viral infection.

Animals↗