Biomedical subjects

G Ampleman

Publications and source records attributed to G Ampleman.

24 records · Page 2Linked to original sources

PubMed1999

Acute toxicity of 2,4,6-trinitrotoluene in earthworm (Eisenia andrei).

2,4,6-Trinitrotoluene (TNT) is an worldwide recalcitrant environmental contaminant and is toxic to a number of organisms including humans. This study examines the acute effects (lethal and biomass changes) of TNT on the oligochaetes species Eisenia andrei, using the 3-day filter paper, and the 7- and 14-day direct contact spiked soil (OECD artificial and forest soil) toxicity tests. Studies using the filter paper test indicated that the lethality of TNT could be detected in the range 1.5 to 14.2 microg/cm(2), with significant biomass (body weight) changes occurring at the lowest concentration. Acute effects (lethality) could not be measured when earthworms were placed on filter paper containing a saturated aqueous solution of TNT. This may indicate that with these exposure conditions, TNT may have been adsorbed to the filter paper, and that this matrix should be saturated with TNT before becoming available to the earthworms. Spiked soil toxicity tests indicated that the E. andrei lethality by TNT was >1.5 times higher when earthworms were exposed to TNT-spiked forest soil (LOEC:260 mg/kg; LC(50) 14 days 222.4 mg/kg) than to spiked OECD artificial soil (LOEC:420 mg/kg; LC(50) 14 days: 364.9 mg/kg). The sublethal effect on biomass change at the selected TNT concentrations in soil was not significant compared to controls. Results indicate that the bioanalytical methods described in this article could be used as TNT toxicity assessment tools. This soil quality test method gives valuable information for the screening of soil toxicity.

Animals↗

PubMed1999

Ecotoxicity characterization of dinitrotoluenes and some of their reduced metabolites.

In the present study, the toxic effects of 2,4-dinitrotoluene (2,4-DNT), 2,6-dinitrotoluene (2,6-DNT) and a selection of their respective metabolites were examined and compared to 2,4,6-trinitrotoluene (TNT) using the 15-min Microtox (Vibrio fischen) and 96-h freshwater green alga (Selenastrum capricomutum) growth inhibition tests. All of the compounds tested were less toxic than TNT. Using the Microtox assay, 2,6-DNT was more toxic than 2,4-DNT and the order of toxicity for 2,6-DNT and its metabolites was: 2,6-DNT > or = 2A-6NT >> 2,6-DAT; whereas that for 2,4-DNT was: 4A-2NT > 2A-4NT > 2,4-DNT > 2,4-DAT. For the algal test, 2,4-DNT was more toxic than 2,6-DNT and the order of toxicity for 2,4-DNT and its metabolites was: 2,4-DNT > 2,4-DAT approximately equal to 4A-2NT = 2A-4NT. The order of toxicity for 2,6-DNT and its reduced metabolites using the algal test was very similar to the Microtox bioassay. These results demonstrate that the reduced metabolites of 2,6-DNT tested in this study were less toxic than that of the parent compound, but certain partially reduced metabolites of 2,4-DNT can be more toxic than the parent molecule. These data put into question the general hypothesis that reductive metabolism of nitro-aromatics is associated with a sequential detoxification process.

Biodegradation, Environmental↗

PubMed1999

Biotransformation of 2,4,6-trinitrotoluene with Phanerochaete chrysosporium in agitated cultures at pH 4.5.

The biotransformation of 2,4,6-trinitrotoluene (TNT) (175 microM) by Phanerochaete chrysosporium with molasses and citric acid at pH 4.5 was studied. In less than 2 weeks, TNT disappeared completely, but mineralization (liberated 14CO2) did not exceed 1%. A time study revealed the presence of several intermediates, marked by the initial formation of two monohydroxylaminodinitrotoluenes (2- and 4-HADNT) followed by their successive transformation to several other products, including monoaminodinitrotoluenes (ADNT). A group of nine acylated intermediates were also detected. They included 2-N-acetylamido-4,6-dinitrotoluene and its p isomer, 2-formylamido-4, 6-dinitrotoluene and its p isomer (as acylated ADNT), 4-N-acetylamino-2-amino-6-nitrotoluene and 4-N-formylamido-2-amino-6-nitrotoluene (as acetylated DANT), 4-N-acetylhydroxy-2,6-dinitrotoluene and 4-N-acetoxy-2, 6-dinitrotoluene (as acetylated HADNT), and finally 4-N-acetylamido-2-hydroxylamino-6-nitrotoluene. Furthermore, a fraction of HADNTs were found to rearrange to their corresponding phenolamines (Bamberger rearrangement), while another group dimerized to azoxytoluenes which in turn transformed to azo compounds and eventually to the corresponding hydrazo derivatives. After 30 days, all of these metabolites, except traces of 4-ADNT and the hydrazo derivatives, disappeared, but mineralization did not exceed 10% even after the incubation period was increased to 120 days. The biotransformation of TNT was accompanied by the appearance of manganese peroxidase (MnP) and lignin-dependent peroxidase (LiP) activities. MnP activity was observed almost immediately after TNT disappearance, which was the period marked by the appearance of the initial metabolites (HADNT and ADNT), whereas the LiP activity was observed after 8 days of incubation, corresponding to the appearance of the acyl derivatives. Both MnP and LiP activities reached their maximum levels (100 and 10 U/liter, respectively) within 10 to 15 days after inoculation.

Biodegradation, Environmental↗

PubMed1998

Development of a soil extraction procedure for ecotoxicity characterization of energetic compounds.

The acetonitrile-sonication extraction method (US EPA Method 8330) associated with aquatic-based toxicity tests was examined to study the ecotoxicity of energetic substances in soil. Three studies were carried out: (1) toxicological characterization of different energetic substances to select a representative toxicant and to validate the choice of bioassays; (2) choice of an appropriate solvent to transfer acetonitrile extracts to the bioassay incubation media; and (3) optimization of Method 8330 using soil samples spiked with the toxicant. Initial studies indicated that pure 2,4,6-trinitrotoluene (TNT) was toxic to Vibrio fischeri [Microtox; IC50 (15 min) of 4.2 microM], whereas RDX was less toxic (IC20 = 181 microM) and HMX was not toxic up to its limit of water solubility (< 22 microM). Selected pure TNT metabolites were less toxic than TNT. Similar results were found using the 96-h Selenastrum capricornutum growth inhibition test. The toxicity of pure TNT in different solvents (acetonitrile, acetone, and DMSO) and that from Method 8330-extracted TNT-spiked soil samples were compared to TNT dissolved in water. Data indicated that DMSO was the most appropriate solvent to transfer the acetonitrile extracts. A modified Method 8330 may be used in conjunction with bioassays and chemical analyses to examine the ecotoxicity of soils contaminated with energetic substances.

Acetone↗

PubMed1998

Characterization of metabolites in the biotransformation of 2,4,6-trinitrotoluene with anaerobic sludge: role of triaminotoluene.

The present study describes the biotransformation of 2,4,6-trinitrotoluene (TNT) (220 microM) by using anaerobic sludge (10%, vol/vol) supplemented with molasses (3.3 g/liter). Despite the disappearance of TNT in less than 15 h, roughly 0.1% of TNT was attributed to mineralization (14CO2). A combination of solid-phase microextraction-gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry identified two distinctive cycles in the degradation of TNT. One cycle was responsible for the stepwise reduction of TNT to eventually produce triaminotoluene (TAT) in relatively high yield (160 microM). The other cycle involved TAT and was responsible for the production of azo derivatives, e.g., 2,2',4,4'-tetraamino-6,6'-azotoluene (2,2',4, 4'-TA-6,6'-azoT) and 2,2',6,6'-tetraamino-4,4'-azotoluene (2,2',6, 6'-TA-4,4'-azoT) at pH 7.2. These azo compounds were also detected when TAT was treated with the anaerobic sludge but not with an autoclaved sludge, suggesting the biotic nature of their formation. When the anaerobic conditions in the TAT-containing culture medium were removed by aeration and/or acidification (pH 3), the corresponding phenolic compounds, e.g., hydroxy-diaminotoluenes and dihydroxy-aminotoluenes, were observed at room temperature. Trihydroxytoluene was detected only after heating TAT in water at 100 degrees C. When 13CH3-labeled TNT was used as the N source in the above microcosms, we were unable to detect 13C-labeled p-cresol or [13CH3]toluene, indicating the absence of denitration or deamination in the biodegradation process. The formation and disappearance of TAT were not accompanied by mineralization, suggesting that TAT acted as a dead-end metabolite.

Anaerobiosis↗

PubMedDate not supplied

Fate of explosives and their metabolites in bioslurry treatment processes.

Microcosm tests simulating bioslurry reactors with 40% soil content, containing high concentrations of TNT and/or RDX, and spiked with either [14C]-TNT or [14C]-RDX were conducted to investigate the fate of explosives and their metabolites in bioslurry treatment processes. RDX is recalcitrant to indigenous microorganisms in soil and activated sludge under aerobic conditions. However, soil indigenous microorganisms alone were able to mineralize 15% of RDX to CO2 under anaerobic condition, and supplementation of municipal anaerobic sludge as an exogenous source of microorganisms significantly enhanced the RDX mineralization to 60%. RDX mineralizing activity of microorganisms in soil and sludge was significantly inhibited by the presence of TNT. TNT mineralization was poor (< 2%) and was not markedly improved by the supplement of aerobic or anaerobic sludge. Partitioning studies of [14C]-TNT in the microcosms revealed that the removal of TNT during the bioslurry process was due mainly to the transformation of TNT and irreversible binding of TNT metabolites onto soil matrix. In the case of RDX under anaerobic conditions, a significant portion (35%) of original radioactivity was also incorporated into the biomass and bound to the soil matrix.

Biodegradation, Environmental↗