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Biomedical subjects

J A Last

Publications and source records attributed to J A Last.

At least 73 records · Page 4Linked to original sources
PubMed1987

Modification by ozone of lung tumor development in mice.

Mice, either strain A/J or Swiss Webster, were exposed for 18 weeks either to filtered air or to 0.4 or 0.8 ppm ozone for 8 hours daily. Subgroups in each test group received a single ip injection of 1,000 mg urethan/kg or 0.9% sodium chloride vehicle 1 day prior to initiation of the exposure regimen. Tumor incidence in Swiss Webster mice was 0-3% in groups not receiving urethan and was 61-74% in groups receiving urethan. In A/J mice, the corresponding values were 9-38% and 100%, respectively. Exposure to ozone caused a decrease in the number of tumors per lung in urethan-treated mice of both strains, in a dose-dependent manner. There seemed to be a specific decrease in tumors derived from alveolar type II cells in the A/J mice given urethan plus ozone. Most interesting, perhaps, was a significant increase in the number of tumors per lung in A/J mice exposed to 0.8 ppm ozone without urethan, confirming a previous report by others. The corresponding ozone effect on lung tumor development was not observed in Swiss Webster mice.

Air Pollution↗
PubMed1986

Effects of silica on lung collagen.

A single intratracheal injection of 50 mg crystalline silica (quartz) into rats produces silicosis. This animal model may be used to study collagen metabolism during the early, middle, and late phases of lung injury, corresponding respectively to the stages of lung injury, development of discrete granulomas, and development of mature silicotic nodules. The early phase is characterized by a rapid increase in the rate of synthesis of lung collagen (within one week of instillation) and increased deposition of excess lung collagen (significant increases within two weeks of instillation). Later phases are characterized by a continuing increase in deposition of excess lung collagen for at least one year after instillation. Silica-induced fibrosis is unique among all the animal models (and in most human fibrotic diseases) thus far examined, in that the excess collagen deposited in the lung contains normal ratios of the two major collagen types of the lung: types I and III. This collagen is nonetheless biochemically different from normal lung collagen. There are reproducible and characteristic differences in the intermolecular cross-links of the collagen in lungs from rats injected with silica. Within one month of silica instillation (the earliest time point examined thus far), an increased hydroxylysine content of collagen can be appreciated. The reducible dysfunctional cross-links are also more likely to be derived from hydroxylysine (i.e. the ratio of dihydroxylated to monohydroxylated cross-links increases). Within four months of silica instillation (and increasingly thereafter), increased amounts of the mature trifunctional cross-link hydroxypyridinium (derived from three residues of hydroxylysine) can also be appreciated, seemingly paralleling the evolution of mature silicotic nodules in these lungs. These changes in cross-linking of lung collagen seem to be common to all the animal models of pulmonary fibrosis examined, and are also consistent with changes occurring in human fibrotic lungs. Preliminary observations suggest that the locus of cross-linking remains the same: hydroxylysine replaces lysine in the primary structure of a specific collagen alpha chain to form the altered cross-links. Thus, there may be molecular markers for the collagen of fibrosis in diseased lungs.

Animals↗
PubMed1986

Changes in collagen cross-linking in bleomycin-induced pulmonary fibrosis.

Collagen cross-linking was analyzed in lungs of rats, two, four, and ten weeks after intratracheal instillation of 1.5 units of bleomycin. Similar analyses were performed on lungs of mice 18 months after intratracheal instillation of bleomycin with or without subsequent exposure to 70% oxygen (O2) for 72 hours. Lungs were analyzed to determine the content of the reduced difunctional cross-links dihydroxylysinonorleucine (DHLNL) and hydroxylysinonorleucine (HLNL) and of the nonreducible trifunctional cross-link hydroxypyridinium (OHP). Ratios of DHLNL:HLNL were elevated in the rat lungs at two and four weeks, due to increased levels of DHLNL. There were no changes in the difunctional cross-links in any of the mouse lungs. Hydroxypyridinium content was elevated in the rat lungs at ten weeks and in the mouse lungs exposed to bleomycin and oxygen. We conclude that increases in DHLNL may serve as an early indicator that potentially "fibrotic collagen" is being synthesized in lungs acutely exposed to fibrogenic stimuli, while increases in OHP may serve as a permanent marker of a fibrogenic event that could have occurred months to years earlier.

Animals↗
PubMed1986

Synergistic interaction of ozone and respirable aerosols on rat lungs. II. Synergy between ammonium sulfate aerosol and various concentrations of ozone.

Pulmonary responses after continuous exposure of rats to concentrations of ozone (O3) ranging from 0.12 to 0.64 ppm were quantified by measuring tissue collagen synthesis rate, tissue protein and DNA content, and various constituents of bronchoalveolar lavage fluid. After 7 days of exposure to 0.64 ppm of O3, lung collagen synthesis rate and tissue content of protein and DNA were elevated. After shorter durations of exposure to 0.64 ppm of O3, significant elevations were observed in the protein content and the activities of lactate dehydrogenase, acid phosphatase, and N-acetyl-beta-D-glucosaminidase from lavage fluid. After exposure of rats to 0.20 ppm of O3 for 7 days, changes could be detected in both lung collagen synthesis rate and tissue protein content. Total lavagable protein content, a sensitive indicator for O3-induced effects upon the lung, was significantly elevated in lungs of rats exposed to 0.12 or 0.20 ppm of O3. To examine whether a synergistic interaction occurred between 0.20 or 0.64 ppm of O3 and acid aerosols, rats were continuously exposed to O3 with and without concurrent exposure to 5 mg/m3 of ammonium sulfate. A synergistic interaction between 0.20 ppm of O3 and ammonium sulfate aerosol was observed by measurement of total lavagable protein and of lung collagen synthesis rate. These results demonstrate that ammonium sulfate aerosol interacts synergistically with O3 at concentrations of O3 that approach ambient levels.

Aerosols↗
PubMed1986

Synergistic interaction of ozone and respirable aerosols on rat lungs. I. Importance of aerosol acidity.

A synergistic interaction, as defined by biochemical and morphological criteria, between ozone (or NO2) and respirable aerosols of ammonium sulfate or sulfuric acid has been described previously. Experiments in the present paper show that it is the acidity, not the sulfate content, of the aerosol that is responsible for such synergy; neutral aerosols of Na2SO4 or NaCl do not elicit synergistic effects when combined with ozone. Aerosol size (and, therefore, site of deposition in the lung) is also an important determinant of synergy with ozone; 0.5 micron mass median aerodynamic diameter (MMAD) aerosols are effective whereas 0.02 micron MMAD aerosols are not. The synergistic interaction between ozone and acidic aerosols could be demonstrated by biochemical and toxicological criteria in addition to those we have previously reported, for example increases in whole lung protein content and free (acid-soluble) proline content of lungs. A synergistic interaction has been demonstrated at concentrations of 0.64 ppm (1.3 mg/m3) of ozone and 1 mg/m3 of acid aerosol in this study. We conclude that acidity of an aerosol determines whether or not it interacts synergistically with ozone, and that an aerosol size that impacts maximally upon the alveolar duct region of the lung is most active with ozone.

Aerosols↗
PubMed1986

Comparative sensitivity of measurements of lung damage made by bronchoalveolar lavage after short-term exposure of rats to ozone.

Consequences of exposure of rats for 2 days or less to O3 at various concentrations between 0.12 and 0.96 ppm were measured using several assays performed on bronchoalveolar lavage fluid. Changes in apparent lung permeability were assessed by measurement of recovery of labelled bovine serum albumin in lung lavage fluid after intravenous injection ("permeability index"). The relative sensitivity of this assay was compared with the sensitivity of measurements of changes in protein and of enzyme content in lavage fluid. Permeability index increased in an exposure concentration-dependent manner after 6 or 24 h of exposure to O3 at or above levels of 0.4 ppm. Permeability index was also increased after 2 days of exposure to 0.2 ppm of O3. The activities of lactate dehydrogenase, acid phosphatase, and N-acetyl-beta-D-glucosaminidase in lung lavage fluid were less sensitive indicators of O3 damage than was altered permeability index. Increased lactate dehydrogenase activity could only be detected after continuous exposure of rats for at least 1 day to 0.64 (or higher) ppm of O3, while acid phosphatase and N-acetyl-beta-D-glucosaminidase activities were increased after exposure of rats to O3 at 0.4 ppm or above for 1 day. Activities of these enzymes were not increased after 6 h of exposure to 0.64 ppm of O3 or after 2 days of exposure to 0.2 ppm. Increased lavage protein content was the most sensitive measurement of the consequences of O3 exposure to rats in these protocols. The lavagable protein content increased after exposure of rats to O3 for 6 h at 0.4 ppm and for 1 or 2 days of exposure to 0.12 ppm, the current peak hourly National Ambient Air Quality standard for O3. While the biological significance of these observations remains to be determined, measurement of lavage protein content is a simple, sensitive indicator of acute changes in the lung caused by exposure to environmentally relevant concentrations of O3.

Acetylglucosaminidase↗
PubMed1986

Lung collagen and elastin after ozone exposure in vitamin B-6-deficient rats.

The effects of vitamin B-6 deficiency and ozone exposure on selected features of connective tissue metabolism in lung were investigated in groups of weanling male rats fed one of three diets: B-6-supplemented, fed ad lib; B-6-deficient, fed ad lib; or B-6-supplemented, restricted to the food intake of deficient rats for 5 weeks. Also, perinatal rat pups were studied that were nursed from dams fed one of the 3 diets from parturition to day 15 of lactation. During the final week of each experiment, half of the rats in each of the groups were exposed to 0.64 ppm of ozone (23.5 h per day). The collagen and elastin content, collagen synthesis rate, total protein synthesis rate, and lysyloxidase activity of lungs were measured. Perinatal pups rendered vitamin B-6-deficient were particularly sensitive to ozone exposure (65% died as compared to fewer than 5% of the ad lib or food-restricted controls). When L-proline incorporation into collagen and total protein was investigated using lung minces, food restriction and B-6-deficiency resulted in about one-half the incorporation normally observed. Total lung lysyl oxidase activity was also decreased in B-6-deficient and food-restricted rats compared to B-6-supplemented rats fed ad lib. Exposure to ozone resulted in increased lysyl oxidase activity and collagen synthesis in lungs from B-6-supplemented rats, but such responses were not observed in B-6-deficient or food-restricted (FR) rats exposed to ozone.

Aging↗
PubMed1986

Collagen crosslinking in lungs of rats with experimental silicosis.

Rats were intratracheally instilled with 50 mg of size-fractionated crystalline quartz to induce silicosis. Lungs were analyzed 1, 4, 6, and 9 months after instillation for their content of the reduced difunctional collagen crosslinks dihydroxylysinonorleucine (DHLNL) and hydroxylysinonorleucine (HLNL), of the nonreducible trifunctional (mature) crosslink, hydroxypyridinium (OHP), and of hydroxylysine. Ratios of DHLNL: HLNL were elevated in silicotic lung collagen at all times sampled, due both to increased levels of DHLNL and decreased amounts of HLNL. Hydroxylysine content of collagen in the silicotic lungs was also increased as compared with age-matched control rats. Hydroxypyridinium content of silicotic lung collagen was less than control values at 1 month, but was significantly increased to about 120%, 150%, and 175% of the age-matched control values at 4, 6, and 9 months after silica instillation, respectively. The increased levels of OHP in lung collagen were temporally correlated with the appearance of mature silicotic nodules in these lungs. We conclude that the large amounts of excess collagen deposited in silicotic lungs differs biochemically from normal lung collagen despite maintenance of the normal ratio of major collagen types in silicotic lungs.

Amino Acids↗
PubMed1986

Early cellular events in pulmonary fibrosis.

In this review we have surveyed recent investigations of early cellular events in pulmonary fibrosis both in animal models and in human diseases. Analysis of the interactions of the numerous cell types in the lung following injury is an almost overwhelmingly complex enterprise. In the animal models experimental design has a profound effect on results, making it difficult to compare studies when species, fibrogenic agent, dose, route of exposure, schedule of administration, time course, and analytical methods may not be equivalent. In human diseases we are rarely able to obtain data at precisely the same time point in the course of the disease even among patients in the same study, and possible confounding variables present are legion. Transcending these difficulties for the moment, can we draw any conclusions from our current knowledge of early cellular interactions in pulmonary fibrosis? What is striking is not that there are so many agents that can potentially induce pulmonary fibrosis, but that the lung has such capabilities for recovery. Although the major effector cells may all initially participate in damaging the lung and initiating fibrosis, there is evidence that they may also have the capacity to participate in subsequent repair. Macrophages may initially recruit fibroblasts and stimulate them to proliferate, only to suppress them subsequently. Macrophage production of prostaglandins can lead to suppression of macrophage, neutrophil and lymphocyte responses, thus attenuating tissue injury and the development of fibrosis. Neutrophils may initially release toxic metabolites and enzymes that damage parenchyma. However, there is evidence that they may later play a role in attenuating fibrosis, perhaps through collagenase secretion, or through as yet unknown mechanisms. Lymphocytes may initially participate in a number of damaging ways by secreting chemoattractants for other cells and participating in destructive autoimmune processes. However, there is evidence that subpopulations of T cells may dramatically shift during the course of fibrosis, leading to attenuation of the process. It may thus be useful to consider irreversible pulmonary fibrosis as the end result of a process in which the balance of normal injury/repair mechanisms is disrupted. There is clearly no single "fibrogenic event." Rather, there seem to be a number of places where disruption of balance/repair processes may begin. In diseases of unknown etiology such as sarcoidosis or IPF, loss of control may occur at the genetic level, leading to the destructive alveolitis that is the apparent precursor of fibrosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

Biosynthesis of collagen crosslinks: in vivo labelling of neonatal skin, tendon, and bone in rats.

Collagen crosslinks in neonatal rats were labelled in vivo by a single intraperitoneal injection of 200 microCi of [14C]lysine. Rats were killed at times ranging from 30 minutes to 10 weeks after injection. Whole skin, tendon, and bone were analyzed, after reduction and hydrolysis, for collagen crosslink content by HPLC. Crosslinks and amino acids were visualized by their incorporation of radioactivity from [14C]lysine and also fluorometrically by post-column derivatization with o-phthalaldehyde. The incorporation of 14C from labelled lysine into the principal difunctional reducible crosslinks, N6.6'-dehydro-5,5'-dihydroxylysinonorleucine and N6.6'-dehydro-5-hydroxylysinonorleucine, increased most rapidly between 4 and 12 hours after injection, results similar to those observed by others studying crosslink biosynthesis in vitro. Incorporation of 14C into the tetrafunctional crosslink histidinohydroxymerodesmosine proceeded more slowly than it did for the difunctional crosslinks. Values for the amount of radioactivity incorporated into the various crosslinks reached an apparent constant value between 3 and 5 days after injection for all three tissues studied. These values remained approximately constant for the duration of the experiment except for HHMD in tendon, which showed an increase in incorporated radioactivity at 8 and 10 weeks after injection. Direct chemical quantification of these same crosslinks by determination of the fluorescence of their o-phthalaldehyde adducts was also performed. We conclude that in vivo labelling of collagen crosslinks can be studied, at least in rapidly growing neonates, after a single injection of radioactive lysine. The results of such studies support previous suggestions by others about the rate of formation of difunctional crosslinks based upon studies using in vitro systems. Our results further suggest that formation of the tetrafunctional reducible crosslink histidinohydroxymerodesmosine proceeds relatively rapidly in vivo. Finally, we conclude that such labelled crosslinks are apparently quite stable after biosynthesis, suggesting the possibility of studies of the metabolic fate of collagen crosslinks over appreciable fractions of the lifetime of a rat.

Amino Acids↗
PubMed1985

Deferoxamine injection does not affect bleomycin-induced lung fibrosis in rats.

Bleomycin is an antineoplastic agent that causes a dose-related lung fibrosis that limits its therapeutic effectiveness. It has been proposed that the cellular toxicity and antitumor effects of bleomycin occur by formation of O2-Fe(II)-bleomycin complexes that degrade DNA and release O2- and OH radicals that attack other cellular components. Twice daily injections of the iron chelator deferoxamine were utilized in an attempt to ameliorate bleomycin-induced lung fibrosis. They failed to diminish bleomycin-induced lung inflammation and fibrosis in rats.

Animals↗
PubMed1985

Peribronchiolar fibrosis in lungs of cats chronically exposed to diesel exhaust.

This study reports the quantitative changes in the pulmonary proximal acinar region following chronic exposure to diesel exhaust and following an additional 6 months in clean air. Cats (13 months of age) from a minimum disease colony were exposed to clean air (eight cats for 27 months and nine cats for 33 months), diesel exhaust for 8 hours/day, 7 days/week (nine cats for 27 months), or diesel exhaust for 27 months followed by 6 months in clean air (10 cats). Morphologic and morphometric evaluation using light microscopy and scanning and transmission electron microscopy revealed two major exposure-related lesions in proximal acinar regions of lungs of cats: peribronchiolar fibrosis associated with significant increases in lymphocytes, fibroblasts, and interstitial macrophages containing diesel particulate-like inclusions and bronchiolar epithelial metaplasia associated with the presence of ciliated and basal cells and alveolar macrophages containing diesel particulate-like inclusions. Peribronchiolar fibrosis was greater at the end of the 6 months in clean air following exposure, whereas the bronchiolar epithelial metaplasia was most severe at the end of exposure. Following an additional 6 months in clean air the epithelium more closely resembled the control epithelial cell population. The labeling index of terminal bronchiolar epithelium was significantly increased at the end of exposure but was not significantly different from controls or exposed cats following an additional 6 months in clean air. The ultrastructural appearance of epithelial cells remained relatively unchanged following diesel exhaust exposure with the exception of diesel particulate-like inclusions. Total lung collagen, expressed as hydroxyproline per left caudal lobe, was apparently increased (although the difference was not significant) in lungs of cats allowed to recover 6 months in clean air. Newly synthesized collagen (evaluated as the amount of cross-link-derived aldehydes in collagen) was significantly increased to more than twice the control values. The ratio of collagen aldehydes to hydroxyproline was also significantly increased. These observations imply that chronic exposure to diesel exhaust has a persistent fibrogenic effect on the proximal acinar region of the lung.

Animals↗
PubMed1984

Long-term consequences of exposure to ozone. I. Lung collagen content.

Lung collagen content of rats and monkeys (Macaca fascicularis) exposed to ozone for 1 to 13 weeks and for 1 year, respectively, was quantified by measurement of 4-hydroxyproline in hydrolysates of whole lungs. In addition, ratios of type I to type III collagen in the lungs of the same monkeys were also evaluated by cyanogen bromide peptide mapping techniques. We observed elevated levels of collagen in lungs of both species of animals exposed to ozone. We conclude that elevations in collagen synthesis rates in lungs of rats and monkeys acutely exposed to high levels of ozone are reflected by corresponding increases in lung collagen content over subchronic and chronic time frames. Preliminary results on young rats also suggest that removal of rats from atmospheres containing ozone does not cause reversal of such increases in lung collagen content. To the contrary, recovery periods of up to 6 weeks seem to exacerbate the observed increases in lung collagen content.

Animals↗
PubMed1984

Ozone exposure, food restriction and protein deficiency: changes in collagen and elastin in rodent lung.

Two groups of weanling or young adult rats were fed ad lib casein-based diets containing 4 or 16% protein. Food was restricted in a third group (fed the 16% protein diet) to the amount consumed daily by rats (adult or weanlings) fed the 4% diet. After 3 weeks (weanlings) or 1, 3 or 5 weeks (adults), one-half of the rats in each group were exposed to 0.64 ppm (1.28 mg/m3) of ozone for 7 days (23.5 h each day). Several parameters were then evaluated related to lung connective tissue metabolism including: (1) total lung hydroxyproline, (2) total lung elastin, (3) apparent rates for lung collagen synthesis and elastin accumulation and (4) lung and body weights. In general, the response to protein deficiency and food restriction was more pronounced than to ozone exposure. Protein deficiency and food restriction resulted in decreased lung size and collagen content. However, the ability of lung to respond to ozone (in relative terms) was not altered by changes in diet as assessed by changes in lung weight or the collagen synthetic rate.

Animals↗
PubMed1984

Elevated ratios of type I/III collagen in the lungs of chronically ventilated neonates with respiratory distress.

Increased synthesis of type I collagen, leading to increased ratios of type I to type III collagen in the lungs, has been observed in the lungs of animals with experimental pulmonary fibrosis. Similar changes in collagen type ratios have been observed in lungs of humans dying of idiopathic pulmonary fibrosis and of adult respiratory distress syndrome. In this study, lung collagen type ratios were examined in infants with acute and chronic lung disease. Tissue from the right lower lobes of neonates was obtained post mortem. Specific collagen types were quantitated by solubilization of lung collagen with CNBr and fractionation of the resulting mixture of peptides by column chromatography and polyacrylamide gel electrophoresis. Ratios of type I/III collagen were calculated for each lung sample using two independent pairs of marker peptides for these determinations. In some cases the ratio of type V to type III collagen in these same lung samples was also quantitated. We observed a significant increase in the ratio of type I/III collagen in infants with a premortem diagnosis of chronic lung disease, usually preceded by respiratory distress syndrome. We also observed two infants with large changes in collagen type ratios who might have had pulmonary fibroplasia secondary to intrauterine lung disease. These data suggest that there may be several subsets of infants with respiratory distress syndrome, each having a different prognosis.

Chronic Disease↗
PubMed1984

Collagen biosynthesis.

Collagen is the major structural protein of the lung. At least five genetically distinct collagen types have been identified in lung tissue. However, the precise role of collagen in nonrespiratory lung function is not well understood, in part because of the difficulties inherent in studying lung collagen, regardless of the type of assay used. A major problem is the insolubility of lung collagen; generally less than 20% of total lung collagen can be solubilized as intact chains, even with harsh extraction procedures. Since such collagen may not be representative of total lung collagen, errors in quantitating collagen types, for example, may arise from using such material. Measurement of total lung collagen content may also pose problems, unless appropriate parameters of normalization are chosen. Biopsy dry weight, protein content, and DNA content, for example, may all change in certain disease states. Despite these difficulties, a number of changes in lung collagen have been documented in experimental pulmonary fibrosis, including increased collagen content, increased collagen synthesis rates, and changes in collagen type ratios. Many questions remain. For example, why do diverse toxic substances appear to cause essentially the same fibrotic response, even though initial sites of damage may vary? Conversely, why do similar toxic substances, such as ozone and NO2, cause diverse responses (fibrosis and emphysema, respectively)? Much work remains to be done to elucidate the mechanisms underlying the lung's choice of response.

Air Pollutants↗