摘要:

The induction of drug‐metabolizing enzymes for different dietary flavonoids has been shown previously. The purpose of this study was to determine the threshold effect of these components. Rats were fed diets containing flavone, flavanone, or tangeretin at different levels (20, 50, 200, 500, and 200 ppm). Flavone induced ethoxyresorufin and pentoxyresorufin dealkylase activities at 500 ppm and arylhydrocarbon hydroxylase at 200 ppm. Epoxide hydrolase and glutathion transferase were increased at 200 ppm. UDP‐glucuronyl transferases were enhanced at 20 ppm. Flavanone induced pentoxyresorufin dealkylase and arylhydrocarbon hydroxylase at the greatest level. In contrast, epoxide hydrolase and conjugating enzymes were increased at the lowest dose. Significant induction was seen only for ethoxyresorufin deethylase and UDP‐glucuronyl transferase with diets containing 2000 ppm tangeretin. We conclude that the threshold effect depends on the chemical structure of the flavonoid and the enzyme activity. Low threshold doses for conjugating enzymes may be important for the anticarcinogenicity properties of these compounds.

ISSN:0098-4108    

DOI:10.1080/15287399209531604

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The T1/2for whole‐body elimination of [3H]‐2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) derived radioactivity in ring‐necked pheasant hatchlings was 13 d, whereas in adult hen pheasants that were not producing eggs it was 378 d. All TCDD‐derived radioactivity in hen tissues was from the parent compound. The oral bioavailability of TCDD in the adult hen pheasant varied with the environmental matrix, with 30% of the dose absorbed from a suspension of earthworms, 33% absorbed from a soil suspension, 41% absorbed from a suspension of paper mill sludge, and 58% absorbed from a suspension of crickets. A cumulative dose of 1.0 μg TCDD/kg body weight, administered as weekly doses of 0.1 μg/kg for 10 wk, did not adversely affect hen condition or

ISSN:0098-4108    

DOI:10.1080/15287399209531605

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Although several epidemiological studies have provided evidence that airborne sulfate particles can produce adverse health effects in susceptible individuals, there is only limited data demonstrating respiratory effects in human volunteers and experimental animals at near ambient concentrations. We have demonstrated previously that the mixing of metal oxide particles with SO2under humid conditions produces acid‐coated particles that are significantly more potent in causing pulmonary function changes than pure acid droplets. The present study examined the nonspecific airway responsiveness to acetylcholine in guinea pigs exposed to acid‐coated zinc oxide particles. One and a half hours after a 1‐h exposure to the aerosols or a control atmosphere, pulmonary resistance (RL) was measured in awake, spontaneously breathing animals before and during a challenge with increasing doses of iv acetylcholine (Ach). The provocative infusion rate of Ach that resulted in a 100% increase in RL(PR100) was significantly decreased (p < .05) in animals exposed to sulfuric acid‐coated metal oxide particles (approximately 30 μg/m3sulfate) compared to control animals exposed to furnace gases (79.6 ± 19.4 vs. 179.6 ± 16.2 μg/kg/min, mean ± SE, respectively). The PR100of animals exposed to SO2(109.1 ± 45.4) or metal oxide particles (106.7 ± 38.1) alone was not significantly different from that of furnace gas control animals, indicating that the acid coating on the metal oxide particles and not the particles themselves or the SO2was responsible for the decrease in the PR100‐Moreover, a 10‐fold greater amount of total sulfate as a pure aqueous sulfuric acid aerosol was necessary to produce a decrease in PR100(88.6 ± 11.0 μg/kg/min) equivalent to that produced by coated particles. These results suggest that acute exposure to near‐ambient concentrations of sulfuric acid under conditions that promote the formation of acid as a surface coating in respirable particles can induce a nonspecific airway hyperresponsiveness. In a similar manner, a dose‐dependent significant decrease in PR100was also produced in animals exposed to sodium sulfite droplets. Thus a single exposure to different forms of sulfur oxide aerosols can induce an alteration in the responsiveness of airway smooth muscle in the guinea pig.

ISSN:0098-4108    

DOI:10.1080/15287399209531606

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We previously demonstrated that combined treatment of mice with crude oil and longwave ultraviolet radiation (UVA) led to the depletion of IA‐positive cells from the epidermis. In the present study, we have developed an in vitro screening assay for combined effects of purified petrochemicals and UVA on epidermal IA and Thy‐1 expression. This method involves removal of skin from donor mice prior to treatment with chemicals and UVA (20,000 J/m2), followed by in vitro culture and subsequent immunoperoxidase staining. In this study, a complete correlation was observed in terms of IA‐positive cell density among similarly treated cultured skin and live mice. In vivo and in vitro studies both indicated that anthracene but not phenanthrene or benzo[a]pyrene led to significant depletion of both epidermal Langerhans cells and Thy‐1‐positive dendritic cells when followed by UVA treatment. The in vitro assay developed for this study should prove to be a valuable tool for the screening of a wide variety of chemicals for contact photosensitizing activity.

ISSN:0098-4108    

DOI:10.1080/15287399209531607

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Hen pheasants(Phasianus colchicus)injected with graded single doses of TCDD (6.25, 25, or 100 μg/kg) exhibited delayed‐onset body weight loss and mortality—classic signs of the wasting syndrome. The lowest single dose of TCDD to produce this effect was 25 μg/kg. When hen pheasants were treated weekly with far lower doses of TCDD (0.01–1.0 μg/kg/wk) for 10 wk, signs of the wasting syndrome and mortality were also produced. The lowest cumulative TCDD dose required to produce the response, using a weekly dosing regimen, was 10 μg/kg. Furthermore, using this dosing regimen, egg production by hens treated withacumulative TCDD dose of 10 μg/kg was reduced, as was hatchability of their eggs. We conclude that hen pheasants are responsive to the overt toxic effects of TCDD and that the lowest cumulative dose of TCDD that produces overt signs of toxicity, 10 μg/kg, also reduces egg production and egg hatchability.

ISSN:0098-4108    

DOI:10.1080/15287399209531608

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

HARNESSING SCIENCE FOR ENVIRONMENTAL REGULATION J. D. Graham, Ed.Praeger Publishers, New York, 1991. 239 pp., $39.95

ISSN:0098-4108    

DOI:10.1080/15287399209531609

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0098-4108    

DOI:10.1080/15287399209531603

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor