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)

Respiratory response of humans exposed to low levels of ozone for 6.6 hours.

Recent evidence suggests that prolonged exposures of exercising men to 0.08 ppm ozone (O3) result in significant decrements in lung function, induction of respiratory symptoms, and increases in nonspecific airway reactivity. The purpose of this study was to confirm or refute these findings by exposing 38 healthy young men to 0.08 ppm O3 for 6.6 h. During exposure, subjects performed exercise for a total of 5 h, which required a minute ventilation of 40 l/min. Significant O3-induced decrements were observed for forced vital capacity (FVC, -0.25 l), forced expiratory volume in 1 s (FEV1.0, -0.35 l), and mean expiratory flow rate between 25% and 75% of FVC (FEF25-75, -0.57 l/s), and significant increases were observed in airway reactivity (35%), specific airway resistance (0.77 cm H2O/s), and respiratory symptoms. These results essentially confirm previous findings. A large range in individual responses was noted (e.g., percentage change in FEV1.0; 4% increase to 38% decrease). Responses also appeared to be nonlinear in time under these experimental conditions.

Ozone concentration and pulmonary response relationships for 6.6-hour exposures with five hours of moderate exercise to 0.08, 0.10, and 0.12 ppm.

The magnitudes of pulmonary responses we previously observed (1) following 6.6-h exposures to 0.12 ppm ozone (O3) suggested that responses would also occur with similar exposures at lower O3 concentrations. The objective of this study was to determine the extent of pulmonary function decrements, respiratory discomfort, and increased airway reactivity to methacholine induced by exposure to O3 below 0.12 ppm. Separate 6.6-h chamber exposures to 0.00, 0.08, 0.10, and 0.12 ppm O3 included six 50-min periods of moderate exercise (VE approximately equal to 39 L/min, HR approximately equal to 115 bpm, and VO2 approximately equal to 1.5 L/min). Each exercise period was followed by 10 min of rest. A 35-min lunch break was included midway through the exposure. Although not intended as an exact simulation, the overall duration, intensity, and metabolic requirements of the exercise performed were representative of a day of moderate to heavy work or play. Preexposure FEV1 averaged 4.39 L, and essentially no change (+0.03 L) occurred with exposure to 0.00 ppm O3. Significant decreases (p less than 0.01) of -0.31, -0.30, and -0.54 L were observed with exposures to 0.08, 0.10, and 0.12 ppm, respectively. The provocative dose of methacholine required to increase airway resistance by 100% (PD100) was 58 cumulative inhalation units (CIU) following exposure to 0.00 ppm and was significantly reduced (p less than 0.01) to 37 CIU at 0.08, 31 CIU at 0.10, and 26 CIU at 0.12 ppm O3; reductions in PD100 are considered indicative of increases in nonspecific airway responsiveness.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary function, airway responsiveness, and respiratory symptoms in asthmatics following exercise in NO2.

Two experiments were conducted to determine respiratory responses of persons with asthma performing intermittent moderate exercise while exposed to low concentrations of NO2. In the first, preliminary experiment, 13 male subjects, aged 19-35, with mild asthma were exposed on separate days in a chamber (natural breathing, 20 degrees C, 40% RH) to 0.30 ppm NO2 and to a control or "clean air" exposure (0.0 ppm NO2). Exposure included three 10-min periods of moderate treadmill exercise (VE = 44.5 liter/min), each followed by symptom measurement and pulmonary function testing. The average decrease in FEV1 following the initial 10 min exercise in 0.30 ppm was 11% which was significantly greater (p less than 0.05) than that observed in clean air (7%). Differences in FVC and SRaw were not significantly different at this time. Slight cough and dry mouth and throat were apparent only after the first exercise in NO2. After the second and third exercises, decreases in FEV1 and FVC and increases in SRaw were significantly greater in 0.30 than in 0.0 ppm NO2. Individual subject responses were variable. These results suggested that some asthmatics who perform moderate exercise while exposed to 0.30 ppm NO2 may experience bronchoconstriction and reduction in spirometric performance. Because of these preliminary findings, a more comprehensive, concentration-response experiment was conducted. Twenty-one male volunteers with mild asthma were exposed for 75 min with natural breathing to 0.0, 0.15, 0.30, and 0.60 ppm NO2. Exposure included three 10-min periods of moderate treadmill exercise (VE = 43 liter/min), each exercise followed by symptoms measurement and pulmonary function testing. In addition, airway responsiveness was measured two hr after each exposure by methacholine bronchial challenge testing. In the control exposures (0.0 ppm NO2), the exercise alone caused substantial decrements in pulmonary function. These decrements (as measured by decreases in FEV1 and FVC, and increases in SRaw) were not increased relative to the control exposure after any exercise session in any concentration of NO2. Furthermore, there was no overall group-averaged indication of a concentration-related effect of the NO2 on pulmonary function. Likewise, symptoms reported after NO2 exposure were not significantly different from those reported in clean air. Group-averaged airway responsiveness after exercise in NO2 was also not different from responsiveness after exercise in clean air. For only two subjects was there any indication of a concentration-related increase in airway responsiveness due to exposure to NO2.(ABSTRACT TRUNCATED AT 400 WORDS)

The armadillo infundibulum: correlative histochemistry, scanning and transmission electron microscopy of the ventricular surface.

The ependymal and supraependymal cells of the armadillo infundibulum (INF) were investigated by correlative histochemistry, scanning and transmission electron microscopy. Eighteen armadillos (8 adult females, 6 adult males, 2 immature females and 2 immature males) were examined. The following supraependymal elements were observed: (a) individual pleiomorphic cells made up of neurons, macrophages, and astrocytic-glial cells; (b) numerous spherical blebs of various sizes occurring singly or in clusters; (c) axons, traversing the surface alone or in association with macrophages and other SEC; (d) multicellular clusters containing SEC, macrophages, axons and other cell types. There were neurosecretory axons or blebs on and below the ependymal cell layer and a unique arrangement of multipolar cells and their processes, traversing the INF floor for several millimeters. The presence of neurosecretory axons at the INF ventricular surface, spherical blebs and SEC in contact with one another via long filaments or vast networks of smaller axons on the surface and numerous macrophages in close apposition to possible metabolic and transport sites give evidence of organized activity in a regulatory system.

Transventricular blood vessels in the third ventricle of the armadillo brain.

Transventricular filaments were observed with scanning electron microscopy on the dorsolateral wall of the infundibular recess of the third ventricle of the armadillo brain. Two to seven transventricular filaments per animal were present in 6 of 18 animals. There were two types of transventricular filaments, ciliated and bare. Using transmission electron microscopy, we determined that these filaments consisted of a single, central capillary surrounded by ciliated ependymal cells and a small accumulation of axons in five animals. In one animal, a bare filament had a central capillary surrounded by a large accumulation of axons with no surrounding ependyma. The consistent location and structure of these filaments indicate a possible function for a small vascular network, as well as a possible commissural network connecting right and left hypothalami in the region of infundibular nuclei.

A histochemical and ultrastructural study of lipofuscin accumulation in thyroid follicular cells of aging domestic cats.

Enzyme activity and fine structure of thyroid follicular cells were investigated in domestic cats at ages: 2 and 8 months, and 1, 3, 5 and 8 years. The following major changes in the follicular cells with advancing age were observed: with histochemistry--an increase in acid phosphatase and beta-glucuronidase activities confined to numerous granules (vesicles); with electron microscopy -- an increase in colloid vesicles, the appearance and increase in size and number of lipofuscin vesicles, and the increase in number of follicular cells containing numerous colloid or lipofuscin vesicles. It is our opinion that the numerous enzymatically active granules of the older groups, observed with histochemistry, are synonymous with the lipofuscin vesicles and many of the colloid vesicles observed with electron microscopy. The cellular changes involving increased enzymatic activity and lipofuscin accumulation with advancing age would correlate with decreased thyroid function reported in the literature. These observations, therefore, would suggest increased autophagic activity involving organelle or unneeded product degradation.