Jeffrey S. Tepper

Comparative study of ozone (O3) uptake in three strains of rats and in the guinea pig

Ozone uptake was assessed in awake, spontaneously breathing Fischer-344 Sprague-Dawley, and Long-Evans rats and Hartley guinea pigs to provide data on the dosimetry of O3 in small laboratory animals. This information is needed for extrapolation of O3 toxicity data from experimental animals to man. Breathing measurements and O3 exposure data were obtained using a head-out body plethysmograph connected to a nose-only exposure system. The fractional uptake of O3 was computed by measuring flow and O3 concentration both upstream and downstream from the nose. The quantity of O3 removed by the animal, O2 consumption, CO2 production, and tidal breathing measurements were automatically recorded once each minute. All animal types were exposed for 1 hr to 0.3 ppm O3. Other Fischer-344 rats were also exposed for 1 hr to 0.0 or to 0.6 ppm O3. Exposure concentrations of O3 had no significant effect on percentage O3 uptake in Fischer-344 rats. Results showed that percentage O3 uptake (47%) did not differ significantly among the three strains of rats nor between the rats and the guinea pigs. Similarly, percentage O3 uptake was independent of animal age, lung weight, and lung volume as well as normal variations encountered in the resting breathing measures. However, species-specific ventilation and O3 concentration were the primary determinants of the accumulated lung dose of O3 during the exposures.

Acute Effects of Ozone on Heart Rate and Body Temperature in the Unanesthetized, Unrestrained Rat Maintained at Different Ambient Temperatures

AbstractThe present studies were conducted to investigate the concentration-response characteristics of acute ozone (O3) exposure on the cardiovascular and thermoregulatory function of the unanesthetized, unrestrained rat, and to examine the modulating effects produced by changes in ambient temperature (T a) on the induced toxic response. For all studies, groups of male Fischer 344 rats (n - 4-6/group) were implanted with radiotelemetry transmitters and allowed to recover overnight. The transmitters permitted continuous monitoring of electrocardiogram (ECG) and body core temperature (T co); heart rate (HR) was derived from the ECG signal. Frequency of breathing (f) was obtained in selected experiments using a barometric plethysmograph. All animals were monitored according to the following protocol: control (filtered air, 0.25 hr); exposure (O3, 2 hr); recovery (filtered air, 3–18 hr). For the concentration-response experiments, O3 concentration was varied from 0.25 to 1.0 ppm and all exposures were conduc...

Adaptation to Ozone in Rats and Its Association with Ascorbic Acid in the Lung

Ozone (O3) adaptation is a well-known, but poorly understood phenomenon that has been demonstrated in humans and laboratory animals. This study examined pulmonary function and bronchoalveolar lavage fluid (BALF) parameters in O3-adapted F-344 rats to explore possible mechanisms of adaptation. Of particular interest was ascorbic acid (AA), an antioxidant reported to be protective against O3 injury and found to be increased in O3-adapted rats. Adaptation was induced by exposure to 0.25 ppm O3, 12 hr/day for 6 or 14 weeks and evaluated with a challenge test, one that reexposed rats to 1.0 ppm O3 and measured attenuation in the O3 effect on frequency of breathing. Pulmonary function was assessed 1 day postexposure and adaptation and BALF were evaluated 1, 3, and 7 days postexposure. Results showed that forced vital capacity increased over time but decreased due to exposure and that the 14-week, O3-exposed rats had an increase in forced expiratory flow rate. All of the O3-exposed rats that were tested demonstrated adaptation on Postexposure Days 1, 3, and 7, but it was diminished on Day 7. Adaptation was also more pronounced in rats exposed for 14 weeks. Except for AA, BALF levels of total protein, potassium, lysozyme, uric acid, and alpha-tocopherol were unaffected by O3 exposure. Lactic acid dehydrogenase, alkaline phosphatase, glucose-6-phosphate dehydrogenase, and total glutathione were also assayed but were always below detectable limits. Ascorbic acid concentrations were elevated on Days 1, 3, and 7, showing postexposure patterns similar to those found for adaptation. Significant correlation was found between AA concentration and the magnitude of adaptation (r = 0.91, p < 0.002). We conclude that AA may play an important role in mechanisms associated with O3 adaptation in rats.

Chronic Exposure to a Simulated Urban Profile of Ozone Alters Ventilatory Responses to Carbon Dioxide Challenge in Rats

Male Fischer 344 rats were exposed to a simulated urban profile of ozone (O3) (9-hr ramped spike, integrated concentration = 0.19 ppm) for up to 78 weeks. Small, but statistically significant, changes in breathing patterns and mechanics in unanesthetized, restrained rats were observed at Weeks 1, 3, 13, 52, and 78 during postexposure challenge with 0, 4, and 8% carbon dioxide (CO2). The data indicate that O3 exposure caused an overall increase in expiratory resistance (Rc), but particularly at 78 weeks. This increase in Rc most likely accounts for the rats reduced ability to increase ventilation during CO2 challenge compared to control rats. Reductions in CO2-induced tidal volume increases were observed in all O3-exposed animals during postexposure challenges to 4 and 8% CO2. Cumulatively, over all time points, spontaneous frequency of breathing and CO2-induced hyperventilation were also reduced. The decrease in frequency was dependent on a significant increase in the inspiratory time relative to control without a change in expiratory time. Light microscopic evaluation of the lung did not reveal any lesions associated with O3 exposure at any time point. Although statistically significant effects were detected, the etiology of the above-mentioned functional changes remains speculative. The potential relevance of these data to acute and chronic O3 exposure in humans is also discussed.

Dietary vitamin A enhances sensitivity of the local lymph node assay

Murine assays such as the mouse ear swelling test (MEST) and the local lymph node assay (LLNA) are popular alternatives to guinea pig models for the identification of contact sensitizers, yet there has been concern over the effectiveness of these assays to detect weak and moderate sensitizers. Much work has been done to improve the sensitivity of the MEST, including the addition of a vitamin A acetate (VAA) enriched diet, which increases its sensitivity. Vitamin A acetate has been reported to increase the numbers of Langerhans cells (antigen presenting cells) in the skin, which could in turn enhance the cellular immune response. Because the LLNA relies on tritiated-thymidine incorporation by proliferating T cells during the induction phase, we have studied the potential of the VAA diet to enhance sensitivity of the LLNA. Results indicate that the VAA enriched diet significantly increased the LLNA sensitivity to formalin, eugenol, glutaraldehyde, trimellitic anhydride, and an azo dye at concentrations where no proliferation was observed in mice maintained on the standard diet. Maintenance on a VAA diet for 3 weeks prior to initiating the sensitization procedure was optimal. Thus, incorporation of a VAA diet improves the sensitivity of the LLNA as a quick, objective, and relatively inexpensive screen for detecting moderate and weak contact sensitizers.

Workshop on Status of Test Methods for Assessing Potential of Chemicals to Induce Respiratory Allergic Reactions

AbstractBecause of the association between allergy and asthma and the increasing incidence of morbidity and mortality due to asthma, there is growing concern over the potential of industrial chemicals to produce allergic reactions in the respiratory tract. Two classes of chemicals have been well studied in this area: diisocyanates and acid anhydrides. The Environmental Protection Agencys Office of Pollution Prevention and Toxics (OPPT) encounters such chemicals in their premanufacturing notice (PMN) program. This article is a summary of a workshop convened by OPPT in collaboration with EPAs Healtin Effects Research Laboratory to discuss presently available test methods that might be applied to potential chemical allergens during the PMN process, the types of chemicals that should be considered suspect, and the kinds of research and validation needed to improve our capability to make such predictions. Formal presentations by experts in the field summarized basic concepts associated with chemically mediat...

Toxicological and chemical evaluation of emissions from carpet samples

This study investigated findings that the off-gassing of certain carpets caused sensory and pulmonary irritation, changes in neurobehavioral signs, and death in exposed mice. Two standard test method measures--one for estimating sensory irritancy (ASTM-E981-84), the other for evaluating the neurotoxic potential of chemicals (functional observational battery)--were coupled with a postmortem assessment to ascertain the mechanism of toxicity. The postmortem evaluation included measurements of hemoglobin, serum clinical chemistries, blood and lung lavage white cell counts and differential, organ weights, and a gross necropsy with a microscopic evaluation of all major organs. The study evaluated three treatment groups composed of two preheated carpet emission exposures and one preheated air-control exposure. No toxic effects were associated with exposure to the off-gassing of the two tested carpets. Clinical chemistry and histopathological alterations were observed with exposure to either filter-air or carpet when compared to nonexposed unrestrained control mice, indicating that the exposure procedure caused significant effects unrelated to carpet emissions. A detailed chemical and microbial evaluation of the carpets and carpet emissions showed volatile organic compounds, pesticide residues, and microbiological flora, but at insufficient quantities to result in acute toxicity. Based on this assessment, there was no indication that exposure to emissions from these two carpets poses a serious health risk.

Evaluation of Several Variations of the Mouse Ear Swelling Test (MEST) for Detection of Weak and Moderate Contact Sensitizers

The ability of a chemical to cause contact sensitization has traditionally been evaluated in animal models typically using the guinea pig. However, these methods are expensive and require subjective analysis of erythema, which makes evaluation of dyes difficult. The mouse ear swelling test (MEST) is a more quantitative and less costly method, but it has not always been reliable for the detection of moderate and weak sensitizers. To identify a MEST that can reliably detect weak sensitizers, several published MEST procedures were examined using the strong sensitizer 2,4-dinitrofluorobenzene (DNFB) and three weaker sensitizers, glutaraldehyde, formalin, and an azo dye (Solvent Red 1 [SR1]). Almost all variations of the MEST procedures detected the strong sensitizer (DNFB) after optimizing the chemical concentration and sensitizing procedure; however, only one protocol detected the weaker sensitizers, glutaraldehyde, formalin, and SR1. This sensitive MEST protocol required test animals to be fed a vitamin A-s...

Pulmonary Function Studies in the Rat Addressing Concentration Versus Time Relationships of Ozone

Recent data from human studies suggest that the current 1 hr National Ambient Air Quality Standard (NAAQS) for O3 may not be appropriate for exposures of several hours. Animal studies are being used to further investigate this issue: (1) A polynomial model has been developed to depict lung injury from the interaction of O3 concentration (C) and exposure duration (T). The model was derived from lung fluid protein values in rats exposed in a matrix design to 0.1 to 0.8 ppm O3 for 2, 4, or 8 hrs. Airway dysfunction was correlated only at the highest CxT products. (2) Rats, exposed to 0.5 or 0.8 ppm O3 for 2 or 7 hours with intermittent 8% CO2 to augment ventilation, were evaluated with static and dynamic lung function tests. Protein leakage into the airspace was also assessed. Although, the impact of T on O3toxicity appeared to be C-dependent, loss of function was not necessarily linear. Collectively, these studies provide a preliminary basis for the evaluation of duration of exposure on the pulmonary response to O3.

Evaluation of an Azo and Two Anthraquinone Dyes for Allergic Potential

Two dye mixtures and the individual component dyes were evaluated for the potential to induce contact or pulmonary hypersensitivity. These dye mixtures were suspect because of anecdotal reports of both pulmonary and contact hypersensitivity in assembly workers, and because the component dyes were structurally related to dyes known to be contact sensitizers. One mixture consisted of disperse blue 3 (DB3) and disperse red 11 (DR11), which are anthraquinones, and the other mixture contained DR11 and solvent red 1 (SR1), an azo dye. Contact hypersensitivity was examined using the local lymph node assay (LLNA) and a modified mouse ear swelling test (MEST). Both the MEST and the LLNA indicated that SR1 has weak contact-sensitizing potential. None of the other individual dye compounds or the two mixtures were identified as contact sensitizers by either method. To evaluate the mixtures as potential pulmonary allergens, guinea pigs were repeatedly exposed by inhalation (300 mg/m3, 6 hr/day) 5 days/week, for 1 week. Weekly exposures were repeated three times with 2 weeks of nonexposure time in between. Guinea pigs were then challenged through the jugular vein using a dye-dimethylsulfoxide mixture. During the challenge, breathing mechanics (dynamic compliance and resistance) were measured in mechanically ventilated animals. Changes in these measurements, indicative of bronchoconstriction, were not observed in animals exposed to either dye mixture, nor were antibodies detected in the sera of exposed animals using individual dye-specific enzyme-linked immunosorbent assays. In conclusion, two methods indicate that SR1 may have contact-sensitizing potential.(ABSTRACT TRUNCATED AT 250 WORDS)