RESUMO
BACKGROUND: Since 1962, the tobacco variety Nicotiana tabacum cv. Bel-W3 has been used worldwide as an ozone (O3) bio-indicator. The use of indicator plants to monitor O3 pollution has proven problematic when trying to correlate the severity of injury to ambient O3 concentration. The aim of the present study was to study factors affecting the O3 sensitivity of Nicotiana tabacum cv. Bel-W3 seedlings. RESULTS: In chronic O3 pre-exposure tests, tobacco plants were cultured from seeds in charcoal-filtered air (CF) and noncharcoal-filtered ambient air (NF) for 21 days. During these periods, the mean O3 concentrations of the CF and NF treatments were 5.5 ± 0.2 and 14.7 ± 0.4 ppb h-1, respectively (p < 0.001). At the end of the culturing period, no O3-induced foliar injury was observed in any of the plants. The O3 sensitivity of the tobacco plants was determined by exposing the plants to 150 ppb O3 for 8 hours in a fumigation chamber. The leaf injury index percentages (LII%) of indicator plants via the CF and NF treatments were 58.0 ± 3.2% and 43.1 ± 4.0%, respectively (p < 0.01). Twenty-one-day-old tobacco seedlings grown in NF air were used to test the effects of exposed leaves on O3 sensitivity. After removing the cotyledons and all true leaves, the NF seedlings with their apical buds intact were transferred to CF air. After another 7 days of culturing, the newly developed leaves were approximately 1 cm in length. After O3 treatment, the LII% values of the newly developed leaves from the untreated and defoliated seedlings were 2.5 ± 1.7% and 27.6 ± 1.3%, respectively (p < 0.001). In acute O3 exposure tests, 21-day-old seedlings grown in CF air were fumigated with 150 ppb O3 for 8 hours in one day or for 4 hours/day in two consecutive days. The LII% values for the two groups were 63.5 ± 7.4% and 20.1 ± 4.3%, respectively (p < 0.001). CONCLUSIONS: The present findings suggest that plant pre-exposure to O3 is a critical factor influencing O3 sensitivity and that exposed leaves obtain acquired tolerance against O3 injury later on.
RESUMO
OBJECTIVES: To evaluate the efficacy of a hybrid artificial liver support system in the treatment of chronic severe hepatitis. METHODS: The hybrid artificial liver support system (HALSS) consisted of a bioreactor containing more than 5 x 10(9) porcine hepatocytes and plasma exchange device. 15 patients with chronic severe viral hepatitis were treated with the hybrid system. RESULTS: All the patients experienced a reduction in symptoms, such as fatigue, abdominal distention or ascites. After each treatment serum total bilirubin decreased markedly (from 493.5 micromol/L+-139.8 micromol/L to 250.9 micromol/L+-91.3 micromol/L, t=8.695, P<0.001), while prothrombin activity increased (from 24.5%+-8.4% to 30.6%+-6.3%, t=3.325, P<0.01). There were 11 patients whose progress of hepatocytes necrosis stopped after HALSS treatment, and finally they recovered completely. Four patients died of their worsen conditions. No serious adverse events were noted in the 15 patients. CONCLUSION: HALSS is a reliable hepatic support device for chronic severe hepatitis.
