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Biomedical subjects

J A Last

Publications and source records attributed to J A Last.

At least 91 records · Page 5Linked to original sources
PubMed1984

A mechanism of synergistic lung damage by ozone and a respirable aerosol.

A hitherto unexpected synergism between the oxidant air pollutants ozone or nitrogen dioxide and a respirable-sized aerosol of ammonium sulfate was previously observed during controlled exposures of rats to these substances. In this paper we examine biochemical and morphometric changes in lungs of rats exposed for 3, 7, or 14 days to ozone (0.64-0.96 ppm), with or without an accompanying aerosol (approximately 1 micrometer mass median aerodynamic diameter) of ammonium sulfate (5 mg/m3). After 3 days of exposure to the mixture of pollutants, rat lung macrophage and macrophage precursors (monocytes) were increased 2- to 3-fold, fibroblasts were increased 2-fold, and apparent collagen synthesis rates were increased 2.5-fold, fibroblasts were increased 2-fold, and apparent collagen synthesis rates were increased 2.5-fold, as compared with values from animals exposed to ozone alone. Continued exposure to ozone alone for 7 or 14 days seemed to mimic changes seen at 3 days with the mixture of pollutants. Total number of lesions per lung was the same for ozone exposure with and without accompanying aerosol; lesions were larger in lungs of rats exposed to ozone plus ammonium sulfate. Based on these findings and a review of the literature, a mechanism for ozone-aerosol synergism is proposed. We suggest that the lifetime of free radicals arising from interaction of oxidants such as ozone or nitrogen dioxide with molecules within the lung is increased by either local pH changes or changes in the local sulfate concentration (or both) caused by inhalation of the respirable aerosol.

Aerosols↗
PubMed1983

Elastin synthesis during perinatal lung development in the rat.

The rate of soluble elastin synthesis was estimated in lung explants from rats of differing ages to better define periods in lung development important to the deposition of lung elastin. Lungs from rat pups at days 1, 3, 7, 9, 12, 15, and 21 post-parturition and from adult rats were incubated in a defined medium containing L-[3H]valine. Following incubation, labelled soluble elastin (tropoelastin) was separated from other soluble proteins by coacervation and electrophoresis on polyacrylamide gels containing sodium dodecyl sulfate. The tropoelastin synthetic rate was then estimated after correcting for differences in recovery of radioactivity as tropoelastin and lung tissue L-[3H]valine specific activity. Maximal rates of elastin synthesis were observed in lung explants from 7-12-day-old rats. The rate of elastin synthesis during this period was 5-8-times the rate observed in adult rat lung (expressed per g of fresh lung) and represented approx. 2% of the total protein synthesis. Moreover, the values derived from lung explant culture for elastin synthesis were consistent with values for lung elastin deposition in the perinatal rat (5-10 micrograms elastin/h per g lung).

Aging↗
PubMed1983

Type V collagen. Quantitation in normal lungs and in lungs of rats with bleomycin-induced pulmonary fibrosis.

Type V collagen was first isolated in 1976; there is still controversy as to how many molecular species of type V collagen exist. Although its structural and functional roles remain unclear, reports of changes in the relative amount of type V collagen from that present in normal tissue have been reported in such diverse pathologic conditions as atherosclerotic aortas, prolapsed mitral valves, and fibrotic lungs. Methods for quantitating type V collagen relative to other collagens have consisted of solubilizing the collagen with pepsin and then analyzing the ratios of the intact chains by gel electrophoresis or by column chromatography. In tissues in which only a small percentage of the total collagen can be solubilized by pepsin, such analyses may not accurately reflect changes in the total collagen present. In this report, a method for quantitating type V collagen relative to types I and III collagens based on CNBr peptide mapping is presented. CNBr solubilizes virtually all the collagen present in any tissue. The method is applied to a model of bleomycin-induced pulmonary fibrosis in rats. It was found that type I collagen increased relative to types III and V collagens, which seemed to remain at values comparable to those observed in lungs from control (normal) rats, both in terms of newly synthesized collagen (collagen synthesized by lung minces during 4 h in culture) and total unlabeled lung collagen (collagen synthesized during the life of the animal).

Amino Acids↗
PubMed1983

Protein deficiency: effects on lung mechanics and the accumulation of collagen and elastin in rat lung.

Groups of weanling (approximately 50 g) or young adult (approximately 300 g) rats were fed ad libitum casein-based diets varying in protein content from 4 to 16%. A group was also fed the 16% protein diet in an amount on a daily basis restricted to that consumed by the protein-deficient group (4% protein). The rats were fed the diets for either 4 weeks (weanling) or 6 weeks (adults). Protein-deficient or "food-restricted" rats (whether weanling or adults) were smaller and had smaller lungs than rats fed ad libitum the diets containing 16% protein. The lung elastin content was more resistant to dietary manipulation than was the lung collagen content. Lung collagen was significantly decreased in both weanling and adult rats fed the 4% protein diet. In weanling rats, pressure-volume relationships derived from saline-filled lungs (analyzed by exponential curve-fitting methods) suggested that lungs from food-restricted rats may be less compliant than lungs from rats fed the control diet ad libitum. When expressed in absolute terms, lungs from protein-deficient rats also appeared to be less compliant than normal rats; however, on a relative basis (percentage of volume at a given recoil pressure or the expression of volume on a weight basis) differences in compliance were less apparent. It is proposed that in weanling rats the differences in lung composition and compliance are the result of retarded lung growth and perhaps development.

Age Factors↗
PubMed1983

Type I collagen content is increased in lungs of patients with adult respiratory distress syndrome.

Collagen in lung tissue was examined from patients with adult respiratory distress syndrome, from patients who did not have this disease but required mechanical ventilation and oxygen treatment, and from patients without overt lung disease. Cyanogen bromide peptide mapping techniques were used to determine the ratio of type I to type III collagen present in these lungs. In the fibrotic lungs from patients with adult respiratory distress syndrome a shift was found in the ratio of type I to type III from the normal value of 2:1 to a mean value of 3.4:1. In patients with normal lungs and those with other lung diseases collagen type ratios were normal. Our data suggest that (i) changes in lung collagen of patients with adult respiratory distress syndrome resemble those previously described in patients with idiopathic pulmonary fibrosis, although the changes occur much more rapidly in the former; (ii) the increased content of collagen in lungs of patients with adult respiratory distress syndrome shown by others is predominantly of type I collagen; and (iii) the stimulus to the lung to produce excess type I collagen relative to type III is not solely of iatrogenic origin--that is, resulting from oxygen or ventilator treatment.

Adult↗
PubMed1983

Potentiation of butylated hydroxytoluene-induced acute lung damage by oxygen. Cell kinetics and collagen metabolism.

Changes in cell proliferation and in collagen synthesis were studied in young adult male BALB/c mice injected intraperitoneally with 400 mg/kg of butylated hydroxytoluene (BHT) in corn oil or corn oil alone and immediately exposed to 70% oxygen or air for 6 days. Mice received [3H]thymidine either as a single injection 90 min before being killed or as a continual infusion via an osmotic minipump. Autoradiography was done 2 to 14 days after BHT injection, and cell kinetic studies were performed. In a similar experiment, mice were injected intraperitoneally with [3H]proline 3 h before being killed, and type l/type III collagen ratio in newly synthesized lung collagen was determined. We found that exposure to 70% oxygen immediately after the administration of BHT initially delayed the epithelial cell proliferation and the decrease in the percentage of newly synthesized type III collagen that occurred after BHT alone. Once the animals were removed from oxygen there was a compensatory burst of cell proliferation and a precipitous drop in the percentage of newly synthesized type III collagen. The proliferating cell population after removal from oxygen was primarily interstitial and not epithelial. When exposure to oxygen was delayed, cell proliferation was similar to that seen after BHT injection alone.

Animals↗
PubMed1983

Synergistic effects on rat lungs of mixtures of oxidant air pollutants (ozone or nitrogen dioxide) and respirable aerosols.

A hitherto unexpected synergism between the oxidant air pollutants ozone or nitrogen dioxide and a respirable-sized aerosol of ammonium sulfate was observed during controlled exposures of rats to these substances. Response of rat lungs to these pollutants was quantitated by measurement of apparent collagen synthesis rates in vitro by lung minces from exposed animals. Dose-response curves to either O3 or NO2 were altered in the presence of 5 mg/m3 of (NH4)2SO4 aerosol. Morphometric and histologic observations of lungs from rats exposed to high levels of ozone, with and without concurrent exposure to the (NH4)2SO4 particles, confirmed such synergistic effects. In a separate set of experiments, rats were exposed at near ambient levels to mixtures of ozone and sulfuric acid aerosol (submicron-sized aerosol). Potentiation of ozone effects on lung collagen synthesis rates was also observed in these experiments. These observations may have broad implications for the appropriate evaluation of laboratory data in the setting of ambient air quality standards and/or threshold limit values for occupational safety.

Aerosols↗
PubMed1983

Mucus glycoproteins secreted by respiratory epithelial tissue from cystic fibrosis patients.

Tracheae, bronchi, nasal epithelial, and nasal polyp tissue slices were incubated in tissue culture with [3H]-glucosamine, and the rate of secretion of labeled mucus glycoproteins was measured. Secretion rates were at least 3- to 6-fold higher for all of the samples from nine patients with cystic fibrosis (CF) who were studied, as compared with values for tissue slices from eight young subjects not affected with this disease. The secreted glycoproteins were further purified into one neutral and three acidic fractions by ion-exchange chromatography on DEAE-cellulose. The glycoproteins secreted by respiratory epithelial tissue from cystic fibrosis subjects contained relatively more of two acidic glycoprotein fractions. Double-label experiments with both [3H]-glucosamine and [35S]-sulfate as mucus glycoprotein precursors further substantiated the shift to more acidic components in the purified mucus glycoproteins and, in addition, suggested a higher level of sulfation of these same two acidic glycoprotein fractions. All four of the labeled glycoprotein fractions secreted by cultured human bronchi cochromatographed with authentic mucus glycoproteins purified from sputum of cystic fibrosis subjects by the same techniques. The differences between mucus glycoproteins from cultured CF airway tissue and mucus glycoproteins from other patients' tissue included relatively increased rates of production, level of sulfation, and greater acidity. Further applications of these in vitro techniques should allow the determination of the enzymatic and biochemical causes of these observed differences in the absence of such potentially confounding variables as concurrent airway infection or of oropharyngeal secretions.

Bronchi↗
PubMed1983

Biochemical alterations of lung structure as predictors of chronic lung disease.

This presentation reports on newer animal models and techniques that we and others have developed. These models attempt to predict in a reasonable experimental time frame the occurrence of structural changes in the lungs that are the basis of various chronic diseases. Since the major chronic diseases of the lung parenchyma involving what we think of as well-understood structural changes are pulmonary fibrosis and emphysema, I will discuss in detail ways of looking at effects of air pollutants on lung collagen and lung elastin metabolism.

Animals↗
PubMed1983

Anomalous electrophoretic behavior of a cyanogen bromide peptide from type III collagen.

The relationship between relative mobility on sodium dodecyl sulfate-polyacrylamide gels and the logarithm of molecular weight was linear for peptides derived by CNBr cleavage from purified collagen chains. One striking exception was found: when the CNBr peptide alpha 1(III)CB-8 was subjected to electrophoresis on a polyacrylamide slab gel calibrated with other peptides derived from the type III collagen chain, its relative mobility corresponded to a molecular weight of approximately 8,000. On a gel calibrated with globular proteins, its apparent molecular weight was 12,000. Its actual molecular weight, as determined by gel filtration and by amino acid analysis, is approximately 12,000. The dodecyl sulfate-protein binding ratio for this peptide did not differ from that of other collagenous peptides or globular proteins. Free electrophoretic mobilities and retardation coefficients were determined for selected collagenous peptides and globular proteins by electrophoresis on tube gels of different concentrations of acrylamide. By these indices, alpha 1(III)CB-8 resembled a globular protein rather than a collagenous peptide. Presumably, some difference in primary structure of this peptide results in conformational changes of its complex with dodecyl sulfate, such that the peptide-dodecyl sulfate complex behaves more like a globular protein than a collagenous peptide on polyacrylamide gels.

Amino Acids↗
PubMed1983

Interactions of ascorbic acid supplementation and bleomycin instillation on murine lung connective tissue metabolism.

The effects of ascorbic acid supplementation on the pulmonary toxicity induced by bleomycin were examined. Swiss-Webster mice were fed an ascorbate-free diet supplemented with ascorbic acid at 0%, 0.2%, or 1.0% of the diet for 2 weeks. Bleomycin (0.15 units) was instilled intratracheally and the mice were killed 1 week later. Bleomycin caused pulmonary inflammation and edema as noted by the increases in lung wet weight and lung wet-weight-to-dry-weight ratios. The activity of prolyl hydroxylase was increased 1.4-fold to 1.6-fold in response to bleomycin, but only minor increases were observed in the collagen and elastin content of the lung. Prior dietary ascorbic acid supplementation did not reverse the effects induced by bleomycin. Interestingly, each dietary level of supplemental ascorbic acid resulted in a slight increase in the elastin and collagen content of the lung in comparison with lungs from mice consuming no ascorbic acid in their diet. The data suggest that high levels of ascorbic acid supplementation may aggravate the response to bleomycin.

Animals↗
PubMed1983

Experimental silicosis. II. Long-term effects of intratracheally instilled quartz on collagen metabolism and morphologic characteristics of rat lungs.

Rats received intratracheal instillations of 50 mg of silica (quartz, 0.5 mu particles). One, 2, 4, 5, 6, 9, and 12 months later, the lungs were evaluated histologically and by various biochemical measurements. The lung content of protein, proline, and hydroxyproline (collagen) were quantitated, as were the synthesis rates of lung collagen and the total lung protein (evaluated with lung minces in vitro. The ratio of newly synthesized and of total lung Type I to Type III collagen was also determined. These experiments were performed in parallel on rats free of chronic respiratory disease and a strain of conventional animals. The authors conclude that 1) the excess collagen deposited in granulomas and/or silicotic nodules as part of the fibrotic response of the lung is similar to normal lung collagen with respect to relative ratios of Types I and III present, in contrast to the response of the lung to oxidant pneumotoxins; 2) the response of the lung to silica continues for at least 1 year; 3) there are essentially no differences in the response of chronic respiratory disease-free Sprague-Dawley and conventional Wistar rats to intratracheally instilled silica. Both strains of rats develop silica-containing granulomas, mature silicotic nodules, and areas of alveolar lipoproteinosis associated with interstitial pneumonitis. Even 1 year after instillation of silica areas of granulomas, silicotic nodules and alveolar lipoproteinosis may be observed in most of the lungs studied; ie, these responses are not mutually exclusive.

Animals↗
PubMed1982

Long-term morphologic and biochemical features of experimentally induced lung fibrosis in the mouse.

Mice were injected with 400 mg. per kg. of butylated hydroxytoluene (BHT) and exposed to an atmosphere of 70 per cent oxygen for 6 days. Control groups were animals treated with BHT alone or injected with vehicle and kept for 6 days in either O2 or air. Animals were killed at various time intervals after BHT treatment, and the lung changes were evaluated with biochemical and morphologic techniques. In animals exposed to BHT + O2, there was initially a diffuse interstitial pneumonitis, increased levels of interstitial collagen, and a decreased ratio of type III to type I collagen. With time the inflammatory component subsided, and degenerative changes primarily consisting of dilation of terminal airways and of alveoli became apparent. Elevated levels of lung hydroxyproline persisted until the termination of the study at 1 year, although ratios of type III to type I collagen returned to normal. In animals treated with BHT alone, collagen accumulation and morphologic changes were similar, although much less severe. It is concluded that potentiation of acute lung injury by oxygen produces long-lasting morphologic and biochemical alterations in lung parenchyma.

Animals↗
PubMed1982

Experimental silicosis. I. Acute effects of intratracheally instilled quartz on collagen metabolism and morphologic characteristics of rat lungs.

Rats were intratracheally instilled with 50 mg of silica as quartz (0.5-mu particles) at day 0. One and 2 weeks later, lungs were evaluated histologically and by a variety of biochemical measurements. Protein, proline, and hydroxyproline content (as an index of total lung collagen) were quantitated, as were the lung collagen synthesis rate and the total lung protein biosynthesis rate (evaluated with lung minces in vitro). The ratio of newly synthesized Type I/Type III collagen was determined, as was the same ratio for total lung collagen. These experiments were performed in parallel on chronic respiratory disease-free rats and in a strain of conventional animals. The authors conclude that 1) changes in lung structure and composition can be appreciated as early as 1 week, the earliest time point studied, after intratracheal instillation of 50 mg of quartz; 2) observed morphologic changes during the first 2 weeks are consistent with biochemical changes; 3) there are essentially no differences in the response of chronic respiratory disease-free Sprague-Dawley and conventional Wistar rats to intratracheally instilled silica. Both strains of rats developed silica-containing granulomas, which ultimately developed into silicotic nodules, as well as areas of alveolar lipoproteinosis associated with interstitial pneumonitis.

Animals↗