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H Wever

Publications and source records attributed to H Wever.

11 recordsLinked to original sources
PubMed1999

Formation and identification of azaarene transformation products from aquatic invertebrate and algal metabolism.

The metabolism of two azaarenes, viz. acridine and phenanthridine, by aquatic organisms was studied in short-term and chronic laboratory tests. The identity of metabolites observed in the test waters was investigated with different analytical methods, including HPLC, GC and hyphenated LC- or GC-MS. The Zebra mussel (Dreissena polymorpha), one green alga species (Selenastrum capricornutum) and periphyton or bacteria transformed acridine into 9[10H]-acridinone. Phenanthridine was transformed into 5[6H]-phenanthridinone by midge (Chironomus riparius) larvae. The findings indicate that closely related isomers may undergo species-specific biotransformation. It was concluded that keto-metabolites are major products in the aquatic fate of benzoquinolines, which may be overlooked in the risk assessment of parent compounds. This study illustrates the typical problems with, as well as the potency of, chromatographic methods in the elucidation of metabolic routes of organic contaminants.

Acridines↗
PubMed1996

Monitoring and estimating concentrations of polychlorinated biphenyls, dioxins, and furans in cattle milk and soils of Rhine-Delta floodplains.

In the Rhine-Delta, accumulation of microcontaminants in floodplain foodwebs has received little attention in comparison with aquatic communities. Here, soil and cattle milk samples were taken from three floodplains and analyzed for polychlorinated biphenyls (PCBs), dibenzodioxins (PCDDs) and dibenzofurans (PCDFs). Based on 2,3,7, 8-tetrachlorodibenzodioxin equivalents, total PCDD and PCDF residues in milk did not exceed the quality standard of 0.006 microg/kg fat weight. This was still the case if non- and mono-ortho PCBs were added to the total. Yet, the floodplains investigated were only moderately polluted according to previous studies and one cannot exclude higher levels in milk from other floodplains. Bioconcentration ratios of milk fat vs soil organic matter were about 0.01 to 0.1 for persistent PCBs. These values are in accordance with a few literature data found for other persistent compounds. Yet, ratios are lower than expected from equilibrium partitioning. Ratios for PCDDs and PCDFs were even lower, possibly due to biotransformation.

Animals↗
PubMed1989

Selective retention of toxic polychlorinated dibenzo-p-dioxins and dibenzofurans in the liver of the rat after intravenous administration of a mixture.

A mixture of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), purified from fly ash from a municipal incinerator, was administered as a single intravenous dose to male rats. Livers were analyzed after 5 h, 1, 2, 4, 7 and 9 days for PCDD and PCDF content. Starting from t = 5 h 2,3,7,8-substituted congeners were the predominant PCDDs and PCDFs retained. 2,3,4,6,7-PnCDF was the only congener without 4 lateral chlorine atoms retained in the liver. For most of the 2,3,7,8-substituted congeners reliable half-lives could not be calculated due to the short experimental period. For only three 2,3,7,8-substituted congeners was a complete elimination from the liver found, within this time period. These congeners were 2,3,7,8-TCDF, 1,2,3,7,8- and 2,3,4,6,7-PnCDF with half-lives of less than 1, 2.1 and 1.6 days, respectively. The other PCDDs and PCDFs, without 4 lateral chlorine atoms, were not detected in the liver from 5 h to 9 days after i.v. administration. Based on the congeneric distribution patterns, it is suggested that besides metabolism, structural specific binding to the Ah-receptor and cytochrome P-450 complex might also be responsible for this selective liver retention.

Animals↗
PubMed1988

[Arterial regional chemotherapy of advanced breast cancer].

From October 1985 to November 1987, arterial regional chemotherapy with mitoxantrone was undertaken in 18 patients with primary far advanced carcinoma of the breast, of inflammatory or ulcerating type. Two patients had a bilateral carcinoma. Eight weeks after regional chemotherapy 18 of 20 tumours had become operable. Regression of tumour size by at least 50% (checked by mammography) was achieved in seven patients. Axillary lymphadenectomy gave negative results in 6 of 17 patients. Conversion of the receptor status occurred in only 2 of 12 patients. There were only few side effects: alopecia in 20%, leucopenia less than 2,500/microliters in 18%, thrombocytopenia less than 100,000/microliters in 7% patient. After a follow-up period of up to 28 months local recurrence was noted in two, distant metastases in three cases. A totally disease-free period was achieved in 14 patients.

Breast Neoplasms↗