Conclusions.Conjugation of several xenobiotics with model substances and herbicides is proven in the earthworm E. fetida. However, E. fetida has only limited capabilities of detoxifying herbicidal compounds. Different isoforms of GST were involved and altered in their activity after treatment. Recommendations and Perspectives.The accumulation of GSconjugates and their determination via fluorescence microscopy is a quick and secure, additional marker for exposure that should be further developed to complement existing biotests. The described methods and endpoints might help to understand the complex reaction of earthworms towards herbicides and lead to an adapted test methodology. Methods. Herbicides were applied to soil containing earthworms. Animals were then collected, sacrificed and shock-frozen. Extracted protein was analyzed for glutathione S-transferase (GST) activity using CDNB (1-chloro-2,4-dinitrobenzene), DCNB (1,2-dichloro-4-nitrobenzene), pNBC (p-nitrobenzylchloride), PNOBC (p-nitrobenz-o-ylchloride) and selected herbicides. GST isoenzymes were partially purified by affinity chromatography and molecular weights were estimated by SDS-PAGE. KeywordsResults. In E. fetida protein extracts, GST activity towards model compounds ranked as CDNB>DCNB>PNBOC>PNBC. Fluorodifen was not conjugated at all, but fenoxaprop and metolachlor were conjugated at low rates. Furthermore, the GST isoenzyme pattern changed during the incubation with herbicides, either due to stress or as a defense reaction. After incubation with monochlorobimane, a strong fluorescence of the intestinal tract and the intersegments was observed, indicating organ-specific GST induction.Discussion. According to the author's knowledge, here, for the first time, evidence is presented that E. fetida GST are also capable of conjugating a wider range of xenobiotic substrates. Different forms of GST were observed and changes in GST isoforms due to the herbicide treatment were also noticed. GST conjugation rates varied between different herbicides used in this experiment. It might be assumed that herbicides may well be detoxified by earthworms, to a certain extent, but that they are also potent stress factors influencing the detoxification system of the animal. High doses or long exposure might lead to deleterious effects on earthworms and limit their survival rate. The use of the animals as bioindicators for herbicides and herbicide residues seems very promising, but is surely influenced by the lack of detoxification for some compounds.
In this study, three separate experiments were carried out to explore the potential of Epipremnum plants for Co-60 and Cs-137 uptake and rhizofiltration from solutions. Experiment I was carried out to screen the effects of different concentration (0-10 mM) of stable Co and Cs salts on some physiological components of the Epipremnum over 20 d. Data from the experiment showed that 1 mM of either Co or Cs had no adverse effects on the chlorophyll, soluble sugar, and protein of Epipremnum. Over 20 d at a high concentration (10 mM), some effects of Co or Cs were detectable but were not inhibitory. Experiment H showed an increase in the concentration ratios (CRs) of carrier-free Co-60 and Cs-137 relative to their concentration in the solution. Transport indexes (TIs) of Co-60 only increased with increasing its concentration in the solution. CRs increased with time and more than 50% of Co-60 and Cs-137 was detected at 5 d. Based on the data obtained from experiments I and II, both stable Co and Cs were used as carriers for Co-60 and Cs-137 to study their uptake and translocation in Experiment III. It was found that the Epipremnum plant had bioconcentration factors (BCFs) of 10.69 and 2.26 for Co and Cs, respectively. However, TI was 13.8 for Co and 35.6 for Cs. The accumulation of Co-60 and Cs-137 in the roots of Epipremnum might offer a method for Co-60 and Cs-137 rhizofiltration.
Wheat grain was treated with radiolabeled diflubenzuron at 100 ppm and stored for various periods; up to 6 months. The grain was surface washed, Soxhlet-extracted with methanol, and the residues determined. A relative constant amount of bound residues (4%), i.e., non-extractable radioactivity, was found 4 months after application and remained constant. More than 97% of the extractable radioactivity in the grain after 6 months was identified as diflubenzuron. When the bound residues were fed to rats, 47% of the administered dose was eliminated via the urine and the remainder via feces within 96 h. Diflubenzuron was the major component in the urine. Adding bound residues to housefly media resulted in a dose-dependent mortality of housefly pupae. Bound residues were biologically active, preventing the emergence of adult houseflies. Supercritical fluid extraction of the bound residues extracted 92% and 96% of the radioactivity associated with grain and feces, respectively. Only diflubenzuron was present in these extracts. The bioavailability and biological activity of bound residues of diflubenzuron have been demonstrated and the identity of the radioactivity was shown to be parent compound. Based on these findings, bound pesticide residues can no longer be ignored or overlooked in the evaluation of pesticide residues and their possible toxicological implications.
Wheat grain was treated with radiolabeled fenvalerate and stored for various periods; up to 6 months. The grain was surface washed, Soxhlet-extracted with methanol, and the residue determined.A relative constant amount of bound residues (6%), i.e., nonextractable radioactivity, was found 2 months after application and remained constant. Seventy-eight percent of the extractable radioactivity in grain after 6 months was identified as fenvalerate.When bound residues were fed to rats, 40% of the administered dose was eliminated through the urine and the remainder through the feces 1 Present address: M. E. Regional Radioisotope Center, Radioisotope Department, Dokki 12311, Cairo, Egypt. 223
Among the different types of microorganisms; the fungal biomass is considered as an effective mediator for bioremediation of heavy metals, due to its higher surface area and extensive hyphal density in the soil. About seven fungal spp. were isolated from the soil garden of the Middle Eastern Regional Radioisotope Center for Arab Countries (MERRCAC); however, a single isolate of Aspergillus japonicus with high potential of metals biosorption was selected for further research during this work. Soil analysis revealed that lead concentration was 5.25 mg/ l. The aims of the present study were to gamma irradiate A. japonicus with low doses of 50 to 250Gy, in order to enhance its heavy metal tolerance ability, and to increase its efficacy for removal of lead (Pb) from the soil. Results indicated that combined treatments of A. japonicus with lead and gamma irradiation doses displayed more enhancements of its biosorption capacity and gain in dry biomass than single treatment. Treatment with Pb (1950 mg/ l) in combination with gamma irradiation (100 Gy) proved to be optimum for increasing the biosorption capacity of this isolate. However, Pb at 650 mg/ l combined with gamma irradiation at 100 Gy was the optimum for gain in dry biomass. Fourier Transform Infrared Spectroscopic (FTIR) analysis showed that the fungal biomass includes in its surface hydroxyl, carboxyl and amine groups. On the other hand, Transmission electron microscope (TEM) examination of the irradiated A. japonicus cells demonstrated accumulation of electron dense Pb on the cell wall and within the fungal cells, this indicate that Pb 2+ accumulation by fungi occurs by two methods absorption inside the cell and adsorption on the cell wall. The current study expressed a potential new method for enhancing microbial biosorption using low doses of gamma radiation.
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