Comparison of dioxin-like-response in vitro and chemical analysis of emissions and materials.

Samples from industrial and domestic emissions and materials were investigated by using in vitro assays for dioxin-like-response (DLR) and chemical analysis. The results show a small part of persistent bioaccumulative toxicants (PBT) to be responsive in vitro. Clean-up procedures directed to persistence decrease the amount of inducing toxicants substantially. The comparison of biological in vitro (B) and chemical (A) analysis show ratios between B and A below 10 for DLR of persistent inductors. The consideration of PAH improved the knowledge about unknown less persistent agonists.

Liver tumor-promoting activity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in TCDD-sensitive and TCDD-resistant rat strains.

Risk assessment of dioxins is currently based on induction of liver tumors in rats. The toxicity of dioxins is characterized by large sensitivity differences among animal species and even strains of the same species, which complicates the risk assessment. The significance of these differences in dioxin-induced carcinogenicity is not known. We therefore studied the liver tumor-promoting activity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the sensitive Long-Evans (L-E) and the resistant Han/Wistar (H/W) rats differing >1000-fold in their sensitivity to the acute lethaity of TCDD. Female rats were partially hepatectomized, initiated with nitrosodiethylamine, and treated with TCDD for 20 weeks. Altered hepatic foci (AHF) were stereologically quantitated using glutathione S-transferase P as a marker. AHF were significantly (P < 0.001) and dose dependently increased in L-E rats at 10 and 100 ng/kg/day, but in H/W rats only at 1000 ng/kg/day and above, indicating a remarkable (approximately 100-fold) sensitivity difference between L-E and H/W rats. The same sensitivity difference but 10-fold less foci were observed between nonhepatectomized/noninitiated L-E and H/W rats. Induction of AHF was related to hepatotoxicity but not to cytochrome P4501A1 activity in the liver. Liver TCDD concentrations were similar in both strains. H/W rats are exceptionally resistant to induction of AHF by TCDD, and the resistance is associated with an altered transactivation domain of the aryl hydrocarbon receptor. Genetic differences may account for significant interindividual/intraspecies sensitivity differences in dioxin-induced carcinogenesis. Understanding the role of transactivation domain of the aryl hydrocarbon receptor in carcinogenesis is therefore likely to improve dioxin risk assessment.

A method to estimate the octanol-air partition coefficient of semivolatile organic compounds.

A multicolumn method for the estimation of the octanol-air partition coefficient (K(OA)) of semivolatile compounds is described. The method is based on the retention time of a compound on gas chromatographic columns of different selectivity and polarity. Log K(OA) values of polychlorinated biphenyls (PCB) were estimated with the novel multicolumn method. The results were in excellent agreement with previously published data using a generator column method. Therefore, we used our multicolumn method to estimate K(OA) for more than 100 PCB congeners.

Formation of octa- and heptachlorodibenzo-p-dioxins during semi anaerobic digestion of sewage sludge.

Octa- and heptachlorodibenzo-p-dioxins (OCDD and HpCDD) were formed during semi anaerobic digestion of sewage sludge at low temperature (20 degrees C). A twofold increase of OCDD and HpCDD was found after a digestion period of 192 days even if concentrations were corrected by corresponding accumulation factors caused by the degradation of biomass. Other polychlorinated dibenzo-p-dioxins and furans (PCDD/F) and polychlorinated biphenyls (PCB) were not increased. Under strictly anaerobic and aerobic conditions, however, no OCDD and HpCDD were formed. Semi anaerobic formation of OCDD and HpCDD may explain the prevalence of higher chlorinated PCDD in the homologues pattern typical for sewage sludge.

Quality criteria for the isotope dilution method with HRGC/MS.

The isotope dilution method is characterized by the use of appropiately labelled standard compounds in conjunction with mass spectrometry coupled to chromatographic systems. Although the isotope dilution method seems to be a simple procedure, some quality criteria for sample preparation, measurement and quantification have to be considered. Furthermore, archiving and documentation of analysis data as well as the use of reference materials to validate the analysis method are important with regard to European standard regulations for quality assurance. In view of this background and the increasing application tendency to environmental problems, essential quality critera for the isotope dilution method are presented and discussed, with special respect to sample extraction, separation performance and sensitivity. Also the quantification procedures are summarized.

Successful palliation by means of a bovine artery graft in a 4-day-old infant with type B interruption of aortic arch and right descending aorta.

In a 4-day-old baby a unique form of interrupted aortic arch was diagnosed, where the interruption was located between the right carotid and the right subclavian arteries in a right descending aorta. The additional large ductus was ligated, the VSD was palliated with pulmonary arterial banding. For the repair of the interrupted aortic arch with its long distance between the ascending and descending portions and the complicating proximity of the superior vena cava, a long pliable material had to be used. The anastomosis was successfully performed with a bovine arterial heterograft.