Search

The purpose of this study was to determine the effects of sulfuric acid (H(2)SO(4)) alone and with ozone (O(3)) on rats. To accomplish this, rats were exposed for 8 hours daily to an atmosphere containing either nebulized H(2)SO(4), H(2)SO(4) plus 0.9 ppm O(3), or 0.9 ppm O(3). The atmosphere in the exposure chambers was maintained at a fairly constant temperature and humidity. Nebulized H(2)SO(4) was delivered uniformly to provide a particle size of about 0.3 micron mass median diameter (MMD) and a mass concentration of 2 mg/m(3). In preliminary experiments, animals exposed to 2 mg/m(3) of H(2)SO(4) daily for 82 days showed very slight morphologic injury to the respiratory tract. In contrast, biological effects were readily demonstrable in rats exposed to H(2)SO(4) plus O(3) or to O(3) alone, possibly with some enhancement of effect in animals exposed to the mixture. The effects observed were characteristic of the response to O(3) alone.

Auditory, visual and somatosensory evoked potentials (EPs), recorded epidurally from 31 chronically implanted male Long-Evans rats, were studied to examine the pattern of sensory effects caused by hypercapnia. Recordings were obtained before exposures, 10-20 min after the beginning of exposure to CO2 in synthetic air, and 30 min after the end of exposure. Previous recordings revealed no substantial effects of the extended recording period itself. Blood pH during an average exposure of 18.8% CO2 was about 7.1. During this level of CO2 exposure the somatosensory response was almost completely abolished, but the latencies of early detectable components were not affected. In contrast, the latencies of all brainstem auditory evoked response components and the 1-5 interwave time increased, whereas amplitudes were only slightly affected. Amplitudes and latencies of early and late components of the flash EP were decreased and lengthened, but the after-discharge components appeared to be most sensitive to CO2. Concentration-response relationships were examined by exposure of rats to 8 and 16% CO2. The most sensitive EP parameter was average amplitude of the late somatosensory EP components. These results suggest that EPs might be useful for assessing acute metabolic disturbances as well as more commonly assessed neurologic disorders.

Bleomycin is a primary fibrogenic agent which increases collagen content in a fibroblast system by a direct effect on fibroblasts. A mechanism for the increase in collagen content is an increase in the rate of collagen biosynthesis. This implies alteration of either collagen transcription or translation. Hyperoxia depresses collagen biosynthesis without changing collagen content. This implies that hyperoxia also depresses collagen degradation. The addition of phagocytes (macrophages) to hyperoxically exposed cells increases both collagen content and the rate of collagen biosynthesis. Hyperoxia is therefore a secondary fibrogenic agent. This suggests that mediators released from phagocytes alter collagen transcription or translation.

The amount of nitric oxide (NO) in the blood of residents of urban and suburban areas was measured under steady-state conditions by isotopic dilution with N15O, followed by field-ionization mass spectrometry. Approximately 20 nmoles of NO per ml of blood was characteristic of both smokers and nonsmokers, except for one of the eight subjects who had a significantly lower level. Monkeys (Macaca speciosa) had values comparable to those of seven human subjects, and rats had values like that of the unique human subject. Whether the origin of the NO was endogenous or exogenous was not determined.

Rats of similar age and size were exposed continuously to nitrogen dioxide (NO2) at a concentration of about 15 ppm in air for 1, 2, 3, and 4 wk and 2, 3, 4, 5, 7, 13, 15, and 17 months. Large increases in lung volume and lesions of the small airways and their epithelium and that of adjacent alveoli developed. The lesions in the terminal bronchioles involved hypersecretion and asggregation of cellular debris and free cells in their lumena. A calibrated grid fitted to an eyepiece was used to measure the diameters of all patent bronchioles at the proximal point of the first alveolar "break" in the respiratory bronchiole. The terminal bronchioles and their short respiratory bronchioles inthe NO2-exposed animals developed stenosis, which increased with time. The maximum change, occurring after 17 months of exposure, was a 45.6% reduction in bronchiolar diameter. Over-all constriction was underestimated because nonpatent sections of bronchioles were excluded The ratio of lung volume to bronchiolar diameter in exposed animals also increased with time as a result of the rising volume and the falling bronchiolar diameter. Probable are discussed.