Specific activity, dioxin

Muelder and Shadoff (3) prepared C-2,3,7,8-Cl4-DBpD (0.9 mCi/ mmole) by chlorination of C-2,7-dichlorodibenzo-p-dioxin made from potassium C-2,4-dichlorophenate. The preparation of tritium-labeled 2,3,7,8-Cl4-DBpD is justified because the radiolabeled intermediates are less expensive and more accessible and because a higher specific activity is potentially attainable. Here, we consider the optimal conditions for the reaction sequence designed to obtain products of high chemical and radiochemical purity shown at the top of p. 8. 

Plant uptake is one of several routes by which an organic contaminant can enter man s food chain. The amount of uptake depends on plant species, concentration, depth of placement, soil type, temperature, moisture, and many other parameters. Translocation of the absorbed material into various plant parts will determine the degree of man s exposure—i.e., whether the material moves to an edible portion of the plant. Past experience with nonpolar chlorinated pesticides suggested optimal uptake conditions are achieved when the chemical is placed in a soil with low adsorptive capacity e.g., a sand), evenly distributed throughout the soil profile, and with oil producing plants. Plant experiments were conducted with one set of parameters that would be optimal for uptake and translocation. The uptake of two dioxins and one phenol (2,4-dichlorophenol (DCP)) from one soil was measured in soybean and oats (7). The application rates were DCP = 0.07 ppm, DCDD 0.10 ppm, and TCDD = 0.06 ppm. The specific activity of the com-... 

Brownlee LJ, Evans CH, Hollebone BR. 1986. The relative induction of mixed-function oxidase specific activity to carbon-hydrogen and carbon-carbon 1 bond strengths in polychlorinated derivatives of dibenzo-p-dioxin. J Appl Toxicol 6 67-72. 

Measurement of the specific activity of the 14-C dioxin by GC/EC allowed calculation of the amount of dioxin that was dissolved. 

On the other hand, sludge samples showed a slight increase (two- to threefold) of dioxin-like activity after the fungal treatment, reaching values above the mg/L BNF equivalent mark. This data can be interpreted as an indicator for bio-activation of some compounds, other than UV filters, present in the sludge by the treatment with T. versicolor. These results emphasize the need of a broad screening of biological assays tests, as they differ in their capacity to detect specific hazardous effects. 

Funatake, C.J. et al., 2004. Early consequences of 2,3,7,8-trtrachlorodibenzo-p-dioxin exposure on the activation and survival of antigen-specific T cells. 

Mechanism-specific in vitro bioassays, e.g. for dioxin-like or estrogenic activity, can fill in specific gaps left open by chemical analysis. They may detect unknown compounds, compounds that are present in levels below the limit of detection for chemical analysis, quantify mixture effects or quantify the presence of certain elasses of eompounds in a more cost effective way. Although... 

An additional screening test for TCDD-like (aryl hydrocarbon receptor, AhR, active) chemicals has been developed (Garrison et al. 1996) and is available commercially (Anonymous 1997). Dubbed the CALUX (for chemically activated luciferase gene expression) system, the assay is based on recombinant cell lines into which researchers have inserted a firefly luciferase gene. When exposed to dioxin-like compounds, the recombinant cells luminesce. The method is sensitive to ppt levels of 2,3,7,8-TCDD equivalents in blood, serum, and milk (Anonymous 1997). Samples testing positive can be subjected to more definitive and specific analytical testing. 

Pongratz I, Stromstedt P-E, Mason GGF, et al. 1991. Inhibition of the specific DNA binding activity of the dioxin receptor by phosphatase treatment. J Biol Chem 266 16813-16817. 

Randerath K, Putman KL, Randerath E, et al. 1990. Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on 1-compounds in hepatic DNA of Sprague-Dawley rats Sex specific effects and structure-activity relationships. Toxicol Appl Pharmacol 103 271-280. 

Specifications require a statement as to the content of the active ingredient. It is also important that the content of impurities be defined if these interfere with the active ingredient, or are phytotoxic, such as -nitrophenol in para-thion or are corrosive to packages or machinery or induce chemical degradation or are unduly hazardous to man or the environment, such as chlorinated dioxins or nitrosamines. 

The development, validation, and application of TEFs have been reviewed regularly since 1984 by Safe [25,36,37]. The limitations of this approach have been identified [38]. To assess the relative potencies and to derive consensus on TEFs for PCDDs, PCDFs, and dioxin-like PCBs, the WHO-European Centre for Environmental and Health (WHO-ECEH) and the International Program on Chemical Safety (IPCS) have initiated a project and published their interim report [39]. The most important limitations, namely possible synergism or antagonism among dioxins and its stereo isomers and the lack of pharmacokinetic consideration, have been addressed in this report. USEPA researchers [40] showed that the relative potency of PCBs, PCDFs, and 2,3,7,8-TCDD is tissue specific and thus estimates of TEFs based on hepatic EROD activity is limited. Additionally, limitations of TEFs based on mammalian models to aquatic species have been demonstrated [41]. The international initiative on TEFs has recognized these pitfalls and recommended development of TEFs for fish and other wildlife. 

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