OBJECTIVEIn this study, we examined the biodegradation of Dichloroethylene (DCE) by two strains of aerobic bacteria.

METHODSUsing batch experiments, we measured the biodegradation rates of DCE and the residual concentrations of DCE for each bacterial strain. The varying trends in biodegradation rates with different initial concentrations of DCE were fitted to kinetic models.

RESULTSThe biodegradation kinetics of DCE by the strain DT-X, which uses toluene as co-metabolic substrate, fitted the Monod model (corresponding parameters: v(max)=0.0075 h(-1), K(s)=2.12 mg/L). The biodegradation kinetics of DCE by the strain DT-M, which uses 1,1-Dichloroethylene as single substrate, fitted the Haldane model (parameters: v(max) =0.0046 h(-1), K(s)=4.25 mg/L, K(i)=8.47 mg/L).

CONCLUSIONThe substrate removal rate constant of 1,1-Dichloroethylene of the co-metabolic strain DT-X was much higher than that of strain DT-M. The substrate removal rates obtained from both bacterial strains in this study were higher than those reported in similar studies.

Bacteria, Aerobic ; metabolism ; Dichloroethylenes ; metabolism ; Kinetics

Accidents, Occupational ; Adult ; Dichloroethylenes ; poisoning ; Female ; Humans

OBJECTIVETo explore the effects of p,p'-DDE and beta-BHC on the apoptosis of Sertoli cells in vitro via activation of Caspase.

METHODSSertoli cells were treated in vitro for 24 hours with a serial concentrations of p,p'-DDE (10, 30 and 50 micromol/L), beta-BHC (10, 30 and 50 micromol/L) and p,p'-DDE + beta-BHC (10, 30 and 50 micromol/L). The inhibitory group was first treated with 100 micromol/L Caspase-3 inhibitor Ac-DEVD-CHO treating for 2 hours before 50 micromol/L p, p'-DDE + 50 micromol/L beta-BHC 24 hours-treatment. The vitality of Sertoli cells was determined by MTT and the apoptosis rate was measured by AO/EB double fluorescence staining. The expressions of Caspase-3, Caspase-8 and Caspase-9 were determined by RT-PCR.

RESULTSAverage optical density (A) values were 0.498 +/- 0.039, 0.481 +/- 0.065, 0.397 +/- 0.032 and 0.286 +/- 0.049 in p,p'-DDE groups (10, 30, 50 and 70 micromol/L), and 0.518 +/- 0.103, 0.490 +/- 0.060, 0.454 +/- 0.054 and 0.302 +/- 0.030 in beta-BHC groups (10, 30, 50 and 70 micromol/L). In the mixture-treated groups (10, 30 and 50 micromol/L), the average A values were 0.483 +/- 0.048, 0.473 +/- 0.058 and 0.337 +/- 0.052. Compared with the solvent control group (0.527 +/- 0.022) , 50 micromol/L group of p, p'-DDE, beta-BHC or their mixture caused a significant decrease of Sertoli cell viability (t values were 4.599, 2.716, 6.537 respectively, P < 0.05). AO/EB double fluorescence staining analysis showed that apoptosis rates of Sertoli cells were significantly increased with all treated groups. The expressions of Caspase-3, Caspase-8 and Caspase-9 were upregulated as the concentrations of p,p'-DDE, beta-BHC and their mixture were increased.

CONCLUSIONp,p'-DDE, beta-BHC and their mixture could induce the apoptosis of Sertoli cells in vitro which was associated with activation of Caspase-3 mediated by cleavage of Caspase-8 and Caspase-9.

Animals ; Apoptosis ; drug effects ; Caspase 3 ; metabolism ; Caspase 8 ; metabolism ; Caspase 9 ; metabolism ; Cells, Cultured ; Dichloroethylenes ; toxicity ; Lindane ; toxicity ; Male ; RNA, Messenger ; genetics ; Rats ; Rats, Sprague-Dawley ; Sertoli Cells ; drug effects ; metabolism