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Biomedical subjects

J S Tepper

Publications and source records attributed to J S Tepper.

23 records · Page 2Linked to original sources
PubMed1987

Cardiopulmonary effects in awake rats four and six months after exposure to methyl isocyanate.

Cardiopulmonary function was assessed four and six months after Fischer 344 rats were exposed to 2 hr to 0, 3, or 10 ppm methyl isocyanate (MIC). During assessment, the rats were challenged with 4 and 8% carbon dioxide (CO2) to stimulate ventilatory drive. Minute ventilation (VE) during CO2 challenge was increased in MIC-treated rats compared to controls when examined 4 months after exposure to 10 ppm MIC, suggesting a ventilation/perfusion inequality. An increase in maximum expiratory flow and a decrease in expiratory time indicated increased lung recoil in these rats. Evidence of pulmonary hypertension was observed in electrocardiograms (ECGs) and supported by postmortem analysis that showed a positive association between increased ECG abnormalities and increased right ventricular weights in the rats treated with 10 ppm MIC. At 6 months, forced expiratory flow-volume curves indicated persistent airway obstruction; however, no changes in inspiratory or expiratory resistance were evident. Decreased dynamic compliance and changes in two new measures of lung function (volume and time at zero expiratory intrapleural pressure) suggest that MIC-induced lung dysfunction also exhibited elements of a restrictive disease.

Airway Obstruction↗
PubMed1986

Determinants of behavioral response with ozone exposure.

Three separate experiments were performed to evaluate how the topography of a behavioral response and its consequences influence the behavioral effects produced by ozone (O3) exposure. The first experiment measured the responding of food-deprived rats working to obtain intermittent delivery of small pellets of food by completing an active response, wheel running. Low O3 concentrations (0.12 ppm) reduced the frequency of running responses maintained by this fixed-interval 10-min schedule of food delivery. The second experiment examined the effects of O2 on food-deprived rats performing a response (nose poking) that required minimal physical effort to produce deliveries of food pellets. Rats in this situation began to show reductions in responding at 0.5 ppm O3. A third experiment showed that responses requiring minimal physical effort, such as lever pressing, can be a sensitive index of O3 exposure if the response provides access to wheel running. We concluded that increased physical activity during exposure appeared to be an important variable in determining sensitivity to O3 exposure.

Animals↗
PubMed1985

Behavioral evaluation of the irritating properties of ozone.

The sensory irritant properties of ozone have been considered to be responsible for symptoms that occur in humans after exposure. This assumption has not been studied explicitly. One way to assess the aversive properties of airborne irritants is to give the exposed individual an opportunity to control the duration of exposure, i.e., escape from the irritant. Mice were trained to turn off 1000-ppm ammonia, a concentration that, in humans, is irritating to the upper airways. Each mouse could terminate irritant delivery for 1 min by inserting its nose five times into one of two conical response sensors. Daily exposure was limited to a maximum of twenty-five 1-min exposures, every other minute. After the determination of ammonia concentration-effect curves, ozone was substituted for ammonia. Ozone exposures were alternated every other day with ammonia as a control for any changes that might occur as a result of repeated ozone exposure. Ozone reliably maintained escape behavior. Additional mice with no history of ammonia termination were trained to terminate ozone exposure, indicating that the aversive properties of ozone were not dependent on previous experience with other airborne irritants. As the concentration of ozone increased from 0.25 to 24 ppm, the number of escape responses increased, and the duration of ozone tolerated decreased. Ozone concentrations of 0.5 ppm or greater were significantly more aversive than control.

Ammonia↗
PubMed1985

Alterations in behavior produced by inhaled ozone or ammonia.

Ozone, a lower-airway irritant, produces fatigue, lethargy, and increased respiratory rates in several species, including man. Ammonia, an upper-airway irritant, produces burning of the eyes, nose, and throat, and a decrease in respiratory rate. The effects of exposure to these two prototypical irritants were examined to see if behavioral changes during and after exposure occurred at concentrations comparable to those that produce symptoms in humans. Long-Evans rats and Swiss mice, individually housed in running wheels, were exposed either to ozone (0.08, 0.12, 0.25, or 0.5 ppm) or to ammonia (100 or 300 ppm) for 6 hr. Each animal's behavior was compared with its own control performance. Running in both species decreased in a concentration-related manner during exposure to either irritant. The decrease in running activity produced by high concentrations of ozone persisted for several hours after exposure. Concentrations of ammonia that eliminated running during exposure led to an increase in activity following exposure. At comparable concentrations of both compounds, activity in rats decreased more than in mice.

Ammonia↗