In vivo monitoring of norepinephrine and hydroxyl free radical generation by ferrous iron in the myocardium with a microdialysis technique

1. We examined in vivo monitoring of norepinephrine and hydroxyl radical generation in rat myocardium with a microdialysis technique. For this purpose, we designed the microdialysis probe holding system which includes loose fixation of the tube and synchronization of the movement of the heart and the probe. 2. The hydroxyl free radical (.OH) reacts with salicylate and generates 2,3- and 2,5-dihydroxybenzoic acid (DHBA) which can be measured electrochemically in picomole quantity by high performance liquid chromatography (HPLC). 3. After probe implantation, norepinephrine concentration of dialysate decreased over the first 150 min and then reached an almost steady level. A positive linear correlation between the ferrous iron and .OH formation trapped as 2,3-DHBA (R2 = 0.960) and 2,5-DHBA (R2 = 0.982) was observed using the microdialysis technique. 4. The present results indicate that non-enzymatic oxidation in the extracellular fluid may play a key role in hydroxyl radical generation by ferrous iron.     

Evidence of hydroxyl free radical generation by calcium overload in rat myocardium

Although calcium (Ca2+) is important in cardiac dysfunction and has also been reported as a source of oxidative toxicity, the connection between Ca2+ overload and oxygen free radicals in the myocardium is not clear. We have investigated whether Ca2+ overload generates hydroxyl free radicals in rat ventricle. HPLC with electrochemical detection was used to measure the levels of 2,3- and 2,5-dihydroxybenzoic acid (DHBA) formed when the hydroxyl free radical reacts with salicylate. Ringer's solution containing salicylic acid (0.5 nmol microL-1 min-1) was infused through a microdialysis probe in the region of the left anterior descending coronary artery of the rat ventricle. A positive linear correlation was obtained between Ca2+ and hydroxyl free radical formation trapped as 2,3-DHBA (r2 = 0.976) and 2,5-DHBA (r2 = 0.982) in the myocardial dialysate. The administration of ouabain (1 mg kg-1, i.v.), a Ca2+ elevator, into the femoral vein significantly increased the level of 2,3- and 2,5-DHBA. These results indicate that Ca2+ overload generates hydroxyl free radicals in rat heart.     

Hydroxyl radical production in the brain after CO hypoxia in rats

Reactive oxygen species (ROS) have been implicated in the pathogenesis of neuronal injury after carbon monoxide (CO) poisoning. Severe CO poisoning is treated with hyperbaric oxygen (HBO), which eliminates CO quickly from hemoglobin and body tissue stores, but has a potential to increase ROS generation. In this study, the effects of HBO on generation of highly reactive hydroxyl radical (HO.) in the brain after CO poisoning in rats was investigated using nonenzymatic hydroxylation of salicylic acid to 2,3 dihydroxybenzoic acid (2,3-DHBA) as a probe. In control studies, the concentrations of 2,3-DHBA after HBO in brain mitochondria and postmitochondrial supernatant (cytosol) were similar to air-exposed animals. After CO poisoning, 2,3-DHBA concentration increased in brain mitochondria but not in the cytosol. After CO exposure and HBO administration at 1.5 atmospheres absolute (ATA), a decrease in 2,3-DHBA production was detected in brain mitochondria. After CO and HBO at 2.5 ATA, 2,3-DHBA concentration increased in both mitochondria and cytosol. The oxidant scavenger dimethylthiourea (DMTU) and the monoamine oxidase (MAO) inhibitor pargyline, administered to CO poisoned rats after HBO at 2.5 ATA, diminished 2,3-DHBA production in both subcellular compartments. These findings indicate that brain HO. production can be either diminished or accelerated after severe CO poisoning depending on the oxygen partial pressure employed during therapy.     

Increased 3-nitrotyrosine in brains of Apo E-deficient mice

Apolipoprotein E (Apo-E) is linked to the pathogenesis of Alzheimer's disease. Apo-E deficient mice have increased lipid peroxidation in plasma. In the present study we examined two markers of oxidative stress in brains of Apo-E deficient mice. The ratios of 2,3 and 2,5 dihydroxybenzoic acid (DHBA)/salicylate, an index of hydroxyl radical generation, were unchanged except for an increase in 2.5-DHBA/salicylate in the cerebellum. 3-Nitroxyrosine is a marker for nitration of proteins produced by peroxynitrite. Concentrations of 3-nitrotyrosine were significantly increased in the cerebral cortex, hippocampus, brainstem and cerebellum of Apo-E deficient mice. These results suggest the Apo-E may modulate oxidative stress produced by peroxynitrite.     

Making people want dentistry

AIM: To examine sera for the presence of salicylic acid and 2,3- and 2,5-dihydroxybenzoic acids (2,3- and 2,5-DHBA), in individuals not taking salicylate drugs. METHODS: Extracts of acidified serum samples were analysed by high performance liquid chromatography with electro-chemical detection. The chromatographic conditions were altered, and the retention times of the unknown compounds compared against authentic salicylic acid, 2,3-DHBA, and 2,5-DHBA. Serum samples (some spiked with salicylic acid) were incubated with salicylate hydroxylase and analyses undertaken. An extract of acidified serum was derivatised using N-methyl-N-trimethylsilyltrifluoroacetamide and the salicylic acid derivative identified by gas chromatography-mass spectrometry. RESULTS: Salicylic acid, 2,3-DHBA, and 2,5-DHBA were identified as being normal constituents of serum. CONCLUSIONS: Salicylic acid, 2,3-DHBA, and 2,5-DHBA possess anti-inflammatory properties. The finding that these compounds are present as normal constituents of serum, possibly arising from diet, raises important questions as to their role in the promotion of health.     

Left ventricular regional systolic motion in patients with right ventricular pressure overload

The highly reactive and cytotoxic hydroxyl radical (OH) was found by electrochemical detection to be produced in reactions involving hydrogen peroxide (H2O2) and the nitric oxide (NO) donor diethylamine- NO complex. Using aromatic hydroxylation of salicylate as a specific indicator of OH, three salicylate hydroxylation products were identified; catechol, 2,3- and 2,5-dihydroxybenzoic acid. Four additional compounds were detected but not identified. The interactions of H2O2 and NO represent a biologically feasible reaction mechanism that can account for OH-induced damage in cellular environments where transition metal ions are unavailable for participation in the superoxide-mediated Fenton reaction. The ability of the NO/H2O2 complex to generate OH independently of iron or other transition metals provides a new focus for studies concerned with the origin of tissue-specific damage caused by oxygen-derived species.     

Consequences of prolonged inhalation of ozone on F344/N rats: collaborative studies. Part XIII. A comparison of changes in the tracheobronchial epithelium and pulmonary acinus in male rats at 3 and 20 months

A limitation of the NTP/HEI Collaborative Ozone Project conducted with F344/N rats at the Battelle Pacific North-west Laboratories in Richland, WA (1991-1993) was that the study used only one time point (20 months) to examine the chronic effects of exposure to ozone. Issues the design of that study could not address were (1) the status of cellular differentiation at earlier time points during the course of ozone exposure; (2) whether changes that appeared to be compensatory after 20 months of exposure were due to ozone, or were aspects of the natural aging process in rats; (3) the inability to define adequately which effects were related specifically to the prolonged duration of exposure; and (4) how and what changes brought about by the natural aging process may have overridden or confounded a clear definition of the effects of exposure to ozone at ambient concentrations (e.g., 0.12 parts per million [ppm]), which are of most concern with long-term exposure to this pollutant. The present study examined the effects of a 3-month exposure to ozone under conditions identical to those of the 20-month NTP/HEI Collaborative Ozone Project. In our facilities at the University of California, Davis, we exposed 42 male F344/N rats to either filtered air or 0.12 or 1.0 ppm ozone. After 3 months of exposure to 1.0 ppm ozone, changes in the distribution of superoxide dismutase (SOD) in the copper-zinc (Cu-Zn) form were shown by a pattern of reduced staining in terminal bronchioles and the centriacinar region; and the manganese (Mn) form of SOD was elevated within the centriacinar region. Further analysis by transmission electron microscopy and immunogold labeling confirmed that Mn SOD was elevated within epithelial type II cells immediately distal to the bronchiole-alveolar duct, junction (BADJ). The trachea, three major bronchi, and a short-length and long-length airway path relative to the trachea were examined by morphometric techniques. The pulmonary acini arising from each of these two paths were also examined morphometrically as a function of distance into the alveolar duct. Cellular changes occurring in each of these anatomical regions after 3 months of exposure were analyzed and compared to the changes noted after the 20-month ozone exposures. We found significant increases in the volume density of nonciliated epithelial cells lining the trachea and caudal bronchi as well as in the proximal and terminal bronchioles of the cranial region at a concentration of 1.0 ppm ozone after both 3 and 20 months of exposure. Remodeling of the centriacinar region, particularly within the cranial region of the lungs after exposure to 1.0 ppm ozone, was statistically significant at both 3 and 20 months. No statistically significant effects were noted following exposure to 0.12 ppm ozone for either 3 or 20 months. An important finding was that age did not influence the effect of ozone on the lungs of rats. We conclude that long-term exposure to ozone, rather than the effects of aging, lead to significant alterations of epithelial cell populations lining the airways and centriacinar region of the lung. Marked cellular changes were noted after exposure to 1.0 ppm ozone, but not to 0.12 ppm.     

Relationship of inhaled ozone concentration to acute tracheobronchial epithelial injury, site-specific ozone dose, and glutathione depletion in rhesus monkeys

Acute pulmonary epithelial injury produced by short-term exposure to ozone varies by site within the tracheobronchial tree. To test whether this variability is related to the local dose of ozone at the tissue site or to local concentrations of glutathione, we exposed adult male rhesus monkeys for 2 h to filtered air or to 0.4 or 1.0 ppm ozone generated from 18O2. Following exposure, lungs were split into lobes and specimens were selected by microdissection so that measurements could be made on airway tissue of similar branching history, including trachea, proximal (generation one or two) and distal (generation six or seven) intrapulmonary bronchi, and proximal respiratory bronchioles. One half of the lung was lavaged for analysis of extracellular components. In monkeys exposed to filtered air, the concentration of reduced glutathione (GSH) varied throughout the airway tree, with the proximal intrapulmonary bronchus having the lowest concentration and the parenchyma having the highest concentration. Exposure to 1.0 ppm ozone significantly reduced GSH only in the respiratory bronchiole, whereas exposure to 0.4 ppm increased GSH only in the proximal intrapulmonary bronchus. Local ozone dose (measured as excess 18O) varied by as much as a factor of three in different airways of monkeys exposed to 1.0 ppm, with respiratory bronchioles having the highest concentration and the parenchyma the lowest concentration. In monkeys exposed to 0.4 ppm, the ozone dose was 60% to 70% less than in the same site in monkeys exposed to 1.0 ppm. Epithelial disruption was present to some degree in all airway sites, but not in the parenchyma, in animals exposed to 1.0 ppm ozone. The mass of mucous and ciliated cells decreased in all airways, and necrotic and inflammatory cells increased. At 0.4 ppm, epithelial injury was minimal, except in the respiratory bronchiole, where cell loss and necrosis occurred, and was 50% that found in monkeys exposed to 1.0 ppm ozone. We conclude that there is a close association between site-specific O3 dose, the degree of epithelial injury, and glutathione depletion at local sites in the tracheobronchial tree.     

Relationship between lung inflammation, changes in lung function and severity of exposure in victims of the Bhopal tragedy

The world's worst chemical industrial disaster, which occurred at Bhopal on 2-3 December, 1984, resulted in considerable respiratory morbidity in the exposed population. Therefore, a study was planned to evaluate the relationship between lower respiratory tract inflammation, lung function and severity of exposure. Sixty patients exposed to methyl isocyanate and presenting with respiratory symptoms were studied using bronchoalveolar lavage (BAL) 1-7 yrs after the accident. Pulmonary function tests included forced vital capacity (FVC) and forced expiratory volume in one second (FEV1). An index of severity of exposure was derived retrospectively on the basis of the acute symptoms in the victims themselves or the occurrence of death among their family members. Total lung inflammatory cells (p < 0.01) and absolute numbers of macrophages (p = 0.01) and lymphocytes (p < 0.05) increased as severity of exposure increased. FEV1/FVC % (p = 0.05) was also significantly lower as severity of exposure increased. Moderately exposed subjects had significantly lower FEV1/FVC % (p < 0.05) compared to those mildly exposed. In nonsmokers, BAL neutrophils, both percentage and absolute numbers, showed significant negative correlations with FEV1 % predicted (rs = -0.350, p < 0.05; and rs = -0.374, p < 0.01, respectively). Neutrophil percentage was negatively correlated with FEV1/FVC % (rs = -0.378; p < 0.01). Absolute lymphocytes had significant negative correlations with FVC % pred (rs = -0.318; p < 0.05). Macrophages had significant positive correlations with FVC % pred (rs = 0.322; p < 0.05) and FEV1 % pred (rs = 0.433; p < 0.01). Radiographic abnormalities (International Labour Organization (ILO) classification) were associated with decline in FEV1 % pred (p < 0.05). This study suggests that pulmonary function abnormalities occur in gas-exposed subjects as a consequence of an abnormal accumulation of lung inflammatory cells (lymphocytes and neutrophils), and that the intensity of lung inflammation and reduction in pulmonary function are greater in severely exposed subjects. As it has been observed that decline in pulmonary function is associated with radiographic abnormalities, there is a suggestion that injury following toxic gas exposure can lead to irreversible lung damage.     

Oleamide potentiates benzodiazepine-sensitive gamma-aminobutyric acid receptor activity but does not alter minimum alveolar anesthetic concentration

Short-term exposure to ozone at peak ambient levels induces neutrophil influx and impairs lung function in healthy humans. In order to investigate the mechanisms contributing to neutrophil recruitment and to examine the role of T-cells in the acute inflammatory response, we exposed 12 healthy humans to 0.2 parts per million (ppm) of ozone and filtered air on two separate occasions for 2 h with intermittent periods of rest and exercise (minute ventilation = 30 L x min(-1)). Fibreoptic bronchoscopy was performed 6 h after the end of exposures. Total protein, tryptase, histamine, myeloperoxidase, interleukin (IL)-8 and growth-related oncogene-alpha (Gro-alpha) were measured and total and differential cell counts were performed in bronchoalveolar lavage (BAL) fluid. Flow cytometry was performed on BAL cells to study total T-cells, T-cell receptors (alphabeta and gammadelta), T-cell subsets (CD4+ and CD8+ cells) and activated T-cell subsets (CD25+). Using immunohistochemistry, neutrophils, mast cells, total T-cell numbers, T-cell subsets, CD25+ T-cells and leukocyte endothelial adhesion molecules including P-selectin, E-selectin, intercellular adhesion molecule (ICAM)-1 and vascular adhesion molecule (VCAM)-1 were quantified in the bronchial biopsies. Paired samples were available from nine subjects. Following ozone exposure there was a threefold increase in the proportion of polymorphonuclear neutrophils (PMNs) (p=0.07) and epithelial cells (p=0.05) in BAL fluid. This was accompanied by increased concentrations of IL-8 (p=0.01), Gro-alpha (p=0.05) and total protein (p=0.058). A significant positive correlation was demonstrated between the two chemokines and proportion of PMNs in BAL fluid. After ozone exposure there was a significant decrease in the CD4/CD8 ratio (p=0.05) and the proportion of activated CD4+ (p=0.01) and CD8+ T-cells (p=0.04). However, no significant changes were demonstrable in any of the inflammatory markers studied in the biopsies. Short-term exposure of healthy humans to 0.2 ppm ozone induced a neutrophil influx in peripheral airways at 6 h post exposure, but no apparent inflammatory response in proximal airways. This response seems to be mediated at least in part by interleukin-8 and growth-related oncogene-alpha.     

Mucous cell metaplasia in rat nasal epithelium after a 20-month exposure to ozone: a morphometric study of epithelial differentiation

The present study was designed to examine the effects of long-term ozone exposure on nasal epithelia and intraepithelial mucosubstances (IM) throughout the nasal airways of F344/N rats. Animals were exposed to 0 (controls), 0.12, 0.5, or 1.0 ppm ozone, 6 h/day, 5 days/wk, for 20 mo. Rats were killed 1 wk after the end of the exposure, and nasal tissues were processed for light and electron microscopy. Standard morphometric techniques were used to determine epithelial cell densities and the amounts of IM in the surface epithelium lining the nasal airways. No mucous cells or IM were present in the epithelia lining the nasal lateral meatus and maxillary sinus of rats exposed to 0 or 0.12 ppm ozone. In contrast, rats exposed to 0.5 or 1.0 ppm ozone had marked mucous cell metaplasia (MCM) with numerous mucous cells and conspicuous amounts of IM in the surface epithelium lining these upper airways. Ozone-induced increases in total epithelial cells (i.e., epithelial hyperplasia) were present only in rats exposed to 1.0 ppm. The results of this study indicate that rats chronically exposed to 1.0 or 0.5 ppm, but not 0.12 ppm, ozone can develop marked MCM with significant increases in IM in both proximal and distal nasal airways. The epithelial changes observed throughout the nasal passages of ozone-exposed rats may be adaptive responses in an attempt to protect the upper and lower respiratory tract from further ozone-induced injury.     

Respiratory responses to repeated prolonged exposure to 0.12 ppm ozone

Repeated exposure to high concentrations of ozone results first in augmentation (typically on the second day) and then attenuation of pulmonary response in humans. To determine the effects of repeated prolonged low-concentration ozone exposure, we exposed 17 healthy nonsmoking male subjects to 0.12 ppm ozone for 6.6 h on 5 consecutive days. Subjects were also exposed once to filtered air. Volunteers exercised at a ventilation of approximately 39 L/min for 50 min of each hour during the exposure. Spirometry, plethysmography, and symptom responses were obtained before, during, and after each exposure. Nasal lavage and aerosol bolus dispersion were obtained before and after exposure. Spirometry decreased and symptoms increased on the first day. Responses were less on the second day compared with those on the first day, and they were absent compared with control values on the subsequent 3 days of ozone exposure. Percent change in FEV1 after ozone exposure compared with that after air exposure averaged -12.79, -8.73, -2.54, -0.6, +0.18% for Days 1 to 5 of ozone exposure, respectively. FEV1 responses ranged from a zero to 34% decrease on Days 1 and 2. After each exposure, we determined the ratio of SRaw after inhaling a fixed dose of methacholine to SRaw after inhaling saline aerosol, as an index of airway responsiveness. Airway responsiveness was significantly increased after each ozone exposure. The mean ratios were 2.22, 3.67, 4.55, 3.99, 3.24, and 3.74 for filtered air and ozone Days 1 to 5, respectively. Symptoms of cough and pain on deep inspiration increased significantly on ozone Day 1 only.(ABSTRACT TRUNCATED AT 250 WORDS)     

Contractile responses and structure of small bronchi isolated from rats after 20 months' exposure to ozone

Short-term exposure to high concentrations of ozone has been shown to increase airway responsiveness in normal humans and in all laboratory animal species studied to date. While our knowledge concerning the pulmonary effects of single exposures to ozone has increased rapidly over recent years, the effects of repeated exposures are less understood. The goal of the present study was to determine whether airway responsiveness is increased after near-lifetime exposure to ozone. Airway segments representing approximately eighth generation airways were isolated from Fischer 344 rats of both genders that had been exposed for 6 hr per day, 5 days per week for 20 months to 0, 0.12, 0.5, or 1.0 parts per million (ppm) ozone. Circumferential tension development was measured in isolated airways in response to bethanechol, acetylcholine, and electrical field stimulation. Responsiveness of the airways to the contractile stimuli was described by the effective dose or frequency that elicited half-maximum contraction (ED50) and the maximum response. Since ozone exposure is associated with remodeling of peripheral airways, smooth muscle area was determined and tension responses were normalized to the area measurements. Before normalization of tension data to smooth muscle area, neither the ED50 nor maximum response of small bronchi to the contractile stimuli was altered after chronic ozone exposure. Smooth muscle area was greater in airways isolated from animals that had been exposed to 0.5 ppm ozone. After accounting for smooth muscle area, maximum responses of the small bronchi isolated from male rats were significantly reduced after 0.12 and 0.5 ppm ozone. Although not significant statistically, a similar trend was observed in airways isolated from female rats. These results suggest that the increase in airway responsiveness associated with acute ozone exposure does not persist during near-lifetime exposure. Although the mechanism responsible for the adaptation to the effects of O3 on airway responsiveness is unknown, the results indicate that smooth muscle cell function was compromised by the chronic exposure. The mechanism(s) responsible for mediating this effect and the relevance of these results to humans remains to be determined.     

Follow-up study of changes in respiratory function in the same workers after an additional 6 years of exposure to pollutants in the rubber industry

Follow-up study of respiratory function was carried out in a group of 311 male workers employed in one rubber industry. The prevalence of respiratory symptoms and ventilatory capacity were recorded over te period of six years. Lung function was measured by recording maximum expiratory flow-volume (MEFV) curves on which forced vital capacity (FVC), one-second forced expiratory volume (FEVI) and flow rates at 50% and the last 25% of the vital capacity (FEF50, FEF25) were read. The prevalence of all chronic respiratory symptoms was higher during the follow-up study although not statistically significant (p > 0.05). During both studies smokers had significantly higher prevalence of chronic cough, chronic phlegm and chronic bronchitis than nonsmokers (p < 0.05 or < 0.025). Measured values of ventilatory capacity were significantly lower than predicted normal values during both studies (p < 0.01). Percentage of predicted values were lower during the follow-up study in comparison to that during the initial study. The mean lowest percentages were obtained for FEF25 (initial study: 77.4%; follow-up study: 70.5%). Smokers had larger mean annual decrease of FVC: 0.073 L; FEVI: 0.063 L; FEF50: 0.100 L/s; FEF25: 0.085 L/s than nonsmokers (FVC: 0.063 L; FEVI: 0.058 L; FEF50: 0.083 L/s; FEF25: 0.058 L/s). Workers exposed for more than 10 years had larger mean annual decrease of ventilatory capacity tests than hose with shorter exposure. Our data indicate that exposure to noxious agents in rubber industry may be responsible for the development of chronic respiratory symptoms and chronic lung function changes.     

Hydroxyl radical formation in diabetic rats induced by streptozotocin

Production of hydroxyl radicals was examined in the diabetic rats induced by streptozotocin to prove its involvement to the pathogenesis of diabetes. Hydroxyl radicals generated in plasma, heart muscle, liver and brain of the hyperglycemic rats were quantitatively assayed by trapping hydroxyl radicals with salicylic acid as 2,3- and 2,5-dihydroxybenzoic acid. The concentrations of 2,3- and 2,5-dihydroxybenzoic acid were significantly increased in all the tissues of the diabetic rats. In the brain and heart muscle of the diabetic rats, the increase of 2,3-dihydroxybenzoic acid was more manifest than that of 2,5-dihydroxybenzoic acid, while in liver 2,5-dihydroxybenzoic acid increased markedly. All the values of 2,3-dihydroxybenzoic acid detected in the tissues of the diabetic rats were quite higher than those in control. Hydroxyl radical production and blood glucose concentration were depended almost linearly on the amount of streptozotocin injected to rats up to 60 mg/kg body weight. It was suggested that 2,3-dihydroxybenzoic acid was produced from hydroxyl radicals themselves, while 2,5-dihydroxybenzoic acid was produced by hydroxylation of salicylic acid not only with hydroxyl radicals, but also by enzymatic reaction of microsomal cytochrome-P450. Hydroxyl radical formation may account for some pathological process especially in the heart muscle and brain.     

Regulation of tumour cell fatty acid oxidation by n-6 polyunsaturated fatty acids

The aim of this study was to evaluate acute effects of ethyl tert-butyl ether (ETBE) in man after short-term exposure. ETBE may in the future replace methyl tert-butyl ether, a widely used oxygenate in unleaded gasoline. Eight healthy male volunteers were exposed to ETBE vapor for 2 h at four levels (0, 5, 25, and 50 ppm) during light physical exercise. The subjects rated irritative symptoms, discomfort, and central nervous system effects in a questionnaire. Ocular (eye redness, tear film break-up time, conjunctival epithelial damage, and blinking frequency), nasal (acoustic rhinometry and analysis of inflammatory markers and cells in nasal lavage fluid), and pulmonary (peak expiratory flow, forced expiratory volume in 1 s, forced vital capacity, vital capacity, and transfer factor) measurements were performed. Significantly increased ratings of solvent smell (p = 0.001, repeated-measures ANOVA) were seen during exposures and correlated to exposure levels. Furthermore, significantly elevated ratings of discomfort in throat and airways were seen during and after 50 ppm compared to the control exposure (p = 0.02). Increased nasal swelling (p = 0.001) and blinking frequency (p = 0.01) were noted at all exposure levels, but their magnitudes were not related to exposure levels. A slightly impaired pulmonary function was seen at 25 and 50 ppm, since forced vital capacity (p = 0.02) and vital capacity (p = 0.04) differed significantly from the clean air exposure. Although the impairments seemed to fall within normal inter- and intraindividual variation and have no clinical relevance as such, it cannot be excluded that other individuals may react more severely than eight healthy male volunteers in this study.     

Antioxidant supplementation and respiratory functions among workers exposed to high levels of ozone

Ozone exposure has been related to adverse respiratory effects, in particular to lung function decrements. Antioxidant vitamins are free-radical scavengers and could have a protective effect against photo-oxidant exposure. To evaluate whether acute effects of ozone on lung functions could be attenuated by antioxidant vitamin supplementation, we conducted a randomized trial using a double-blind crossover design. Street workers (n = 47) of Mexico City were randomly assigned to take daily a supplement (75 mg vitamin E, 650 mg vitamin C, 15 mg beta carotene) or a placebo and were followed from March to August 1996. Pulmonary function tests were done twice a week at the end of the workday. During the follow-up, the mean 1-h maximum ozone level was 123 ppb (SD = 40). During the first phase, ozone levels were inversely associated with FVC (beta = -1.60 ml/ppb), FEV1 (beta = -2.11 ml/ppb), and FEF25-75 (beta = -4.92 ml/ppb) (p < 0.05) in the placebo group but not in the supplement group. The difference between the two groups was significant for FVC, FEV1, and FEF25-75 (p < 0.01). During the second phase, similar results were observed, but the lung function decrements in the placebo group were smaller, suggesting that the supplementation may have had a residual protective effect on the lung. These results need to be confirmed in larger supplementation studies.     

Ozone-induced stimulation of pulmonary sympathetic fibers: a protective mechanism against edema

Tropospheric ozone exerts well-described toxic effects on the respiratory tract. Less documented, by contrast, is the ability of ozone to induce protective mechanisms against agents that are toxic to the lungs. In particular, interactions between ozone and the sympathetic nervous system have never been considered. Using a model of permeability edema in isolated perfused rabbit lungs, we report here that, immediately after exposure of rabbits to 0.4 ppm ozone for 4 hr, the pulmonary microvascular responses to acetylcholine and substance P are completely blocked. Several lines of evidence, including partial inhibition of the ozone-induced protective effect by several drugs (alpha2- and beta-adrenergic antagonists, neuropeptide Y antagonist, guanethidine), measured levels of released catecholamines in blood and urine and the in vitro response of isolated lungs exposed to 0.4 ppm ozone all seem to suggest that ozone can stimulate pulmonary adrenergic fibers and induce the local release of catecholamines and neuropeptide Y, this resulting in transient protection against pulmonary edema. We also showed that, 48 hr after the exposure, ozone increased the baseline microvascular permeability and the response to low concentrations of acetylcholine.     

The effect of nitrogen dioxide exposure on the release of surfactant isolated from neonatal rabbit type II pneumocytes in culture

Nitrogen dioxide (NO2) is a well-known environmental air toxin, produced from a variety of sources, including cigarette smoke. Because of the growing knowledge of the harmful effects of passive smoking on children, we decided to study the effect of NO2 exposure on the release of surfactant from isolated neonatal type II pulmonary epithelial cells. After isolation from 1 to 4 day old rabbits, type II epithelial cells were allowed to adhere for 18 hours, washed, media changed, and were exposed to either 5% CO2 in room air or NO2, 5 ppm, for 2 hours (all results mean +/- sd; comparisons, paired t-test). There was no difference in cell number or viability prior to exposure. Cells exposed to NO2 had an increase in LDH release [LDH activity in media/(LDH in media+cells) x 100], air 12.6 +/- 2.2%, NO2 21.7 +/- 3.7%, (p < 0.05). NO2-exposed cells also had an increase in total phospholipid (microgram/cell culture dish) in media compared to air exposed, air 170.13 +/- 7.54, NO2 195.15 +/- 11.2, (p < 0.05). 3H-choline incorporation as a precursor to disaturated phosphatidylcholine (DSPC) was also conducted during exposure to either air or NO2. Incorporation of 3H-choline into surfactant lipid was increased in media from cells after NO2 exposure compared to air, 58.23 +/- 15.16 air, 76.81 +/- 19.86 NO2 (cpm/microgram protein; p < 0.05). These results show that 2 hours of 5 ppm NO2 exposure is associated with an increase in release of surfactant from neonatal type II cells in culture.     

Monogenic determinants of familial Alzheimer''s disease: presenilin-2 mutations

An industry-wide pulmonary morbidity study was undertaken to evaluate the respiratory health of employees manufacturing refractory ceramic fibers at five US sites between 1987 and 1989. Refractory ceramic fibers are man-made vitreous fibers used for high temperature insulation. Of the 753 eligible current employees, 742 provided occupational histories and also completed the American Thoracic Society respiratory symptom questionnaire; 736 also performed pulmonary function tests. Exposure to refractory ceramic fibers was characterized by classifying workers as production or nonproduction employees and calculating the duration of time spent in production employment. The risk of working in the production of refractory ceramic fibers and having one or more respiratory symptoms was estimated by adjusted odds ratios and found to be 2.9 (95 percent confidence interval 1.4-6.2) for men and 2.4 (95 percent confidence interval 1.1-5.3) for women. The effect of exposure to refractory ceramic fibers on forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), the ratio of the two (FEV1/FVC), and forced expiratory flow (liters/second) between 25 percent and 75 percent of the FVC curve (FEF(25-75)) was evaluated by multiple regression analysis using transformed values adjusted for height, by dividing by the square of each individual's height. For men, there was a significant decline in FVC for current and past smokers of 165.4 ml (p < 0.01) and 155.5 ml (p = 0.04), respectively, per 10 years of work in the production of refractory ceramic fibers. For FEV1, the decline was significant (p < 0.01) only for current smokers at 134.9 ml. For women, the decline was greater and significant for FVC among nonsmokers, who showed a decrease of 350.3 ml (p = 0.05) per 10 years of employment in the production of refractory ceramic fibers. These findings indicate that there may be important sex differences in response to occupational and/or environmental exposure.