A novel test system for the detection of mutagenic and recombinogenic activity of chemicals is described in detail. Drosophila melanogaster larvae trans-heterozygous for the mutations multiple wing hairs (mwh) and flare (flr) are exposed to the test compounds for various periods of time ranging from 96 hr to 1 hr. Induced mutations are detected as single mosaic spots on the wing blade of surviving adults that show either the multiple wing hairs or flare phenotype. Induced recombination leads to mwh and flr twin spots and also to a certain extent, to mwh single spots. Recording of the frequency and the size of the different spots allows for a quantitative determination of the mutagenic and recombinogenic effects. This and earlier studies with a small set of well-known mutagens indicate that the test detects monofunctional and polyfunctional alkylating agents (ethyl methanesulfonate, diepoxybutane, mitomycin C, Trenimon), mutagens forming large adducts (aflatoxin B1), DNA breaking agents (bleomycin), intercalating agents (5-aminoacridine, ICR-170), spindle poisons (vinblastine), and antimetabolites (methotrexate). In addition, the test detects mutagens unstable in aqueous solution (beta-propiolactone), gaseous mutagens (1,2-dibromoethane), as well as promutagens needing various pathways of metabolic activation (aflatoxin B1, diethylnitrosamine, dimethylnitrosamine, mitomycin C, and procarbazine). The rapidity and ease of performance as well as the low costs of the test necessitate a high priority for validation of this promising Drosophila short-term test.
An investigation was untertaken to evaluate the nutrient status of the River Rhine (two stations) and eight of its tributaries (total of ten samplings). Determinations of the following inorganic substances were made: PO:--P; NOj-N; NOs-N; NH$-N and Cll. In addition, pH and carbonate alkalinity were measured. Bioassays to obtain the algal growth potential (AGP) were carried out using periphyton from the River Rhine. A linear relationship could be established between NOj-N and the AGP, while the AGP showed a non-linear dependence on the PO&P concentration. The critical N/P ratio for N or P limitation of the algal growth in bioassays was evaluated graphically and by calculation. The results of the two methods are in good agreement: N is the limiting factor at NOj-N/ PO&P ratios less than 10, while P is limiting at ratios greater than 20. At values between 10 and 20 neither N nor P can be supposed with certainty to be limiting.
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