A simple, miniaturized algal assay procedure using microplates has been developed to assess aquatic toxicity with the green alga, Selenastrum capricornutum. Cell count‐generated EC50 data comparisons with the classic assay using flasks have indicated good agreement between the two methods following toxic assessment of various wastewater samples and metal solutions. Parametric comparisons (ATP us cell counts) with the microplate method show equally good correlation. The technique is highly versatile in conducting basic algal bioassays for varying times (4‐hour, 4‐day, 8‐day EC50's) and with differing parameters, depending on set objectives. Other interesting features of the microplate technique include handling rapidity, economy, space‐saving convenience, and automation potential.
Genuine needs for rapid, simple, and cost-efficient biotesting procedures to screen an ever-increasing number of chemicals and environmental samples are making the search for such assays a constant endeavor. With respect to genotoxicity screening, we compared, in this study, the performance of two novel assays (Vibrio fischeri M169 Mutatoxm assay and the Escherichia coli PQ37 SOS Chromotest kit assay) with two well-established Ames testing procedures (plate incorporation and fluctuation assays). Testing material included 14 chemicals (10 potentially directly acting and 4 indirectly acting compounds) reflecting different chemical classes (2 inorganics, 2 pesticides, 2 halogenated hydrocarbons, 2 alkylating agents, 2 aromatic amines, 1 chlorophenol, and 3 polycyclic aromatic hydrocarbons). Comparative assessment criteria included (1) interprocedural agreement in detecting presence or absence of genotoxicity, (2) accuracy in being able to recognize animal (non)carcinogens, and (3) sensitivity (detection of lowest actively genotoxic concentration). In terms of qualitative responses, both the SOS Chromotest (86% agreement) and Mutatox assays (93% agreement) were good predictors of the Ames testing mutagenicity. For their capability to correctly discriminate between (non)carcinogens, accuracy was 82% (9 of 11 chemicals) for Mutatox, 73% (8 of 11 chemicals) for Ames testing, and 64% (7 of 11 chemicals) for the SOS Chromotest. In general, the Salmonella-based assays proved more sensitive (6 times out of 9 chemicals) than the Mutatox (3 times out of 9 chemicals) and the SOS Chromotest (never more sensitive). Overall, this study demonstrates reliable performances by both the SOS Chromotest and Mutatox for chemical genotoxicity screening when results are referenced to the well-validated Ames assay. Although additional comparative data with other chemicals will be required, it appears likely that these more practical and cost-efficient procedures can be presently useful to screen genotoxic activity of various xenobiotics and environmental samples. 0 7994 by John Wi/ey & Sons, Inc.
The rate of nonenzymatie browning of dehydrated vegetables has been studied as a function of temperature, moisture content, and confining atmosphere. The browning proceeds in linear fashion up to, and for a reasonable distance beyond, the limit of palatability for dehydrated nonsulfited carrot, white potato, onion, and sweet potato. The effect of oxygen on the browning rates of these four dehydrated vegetables is relatively small. The browning rates vary exponentially with the reciprocal of the absolute temperature.
1441but which react rapidly with organic peroxides. It may be expected that a more reactive compound may be required for helped the project greatly by supplying many of the compounds evaluated. best antioxidant efficiency a t low temperatures than for use at high t.emperatures. A number of isolated facts seem to support this assumption. A systematic study of the change in relative stabilizing efficiency with temperature, for various antioxidants, would be of fundamental importance. ACKNOWLEDGMENTThe author is indebted to C. S. Myers of Bakelite Corporation, under whose direction this work was carried out, for his many helpful suggestions. The assistance given by many of the writer's associates of Bakelite Corporation is also gratefully acknowledged. The experimental procedure was based on information received from R. M. Koppenhoefer of the Socony Vacuum Sulfite disappearance in dehydrated sulfited carrot, white potato, and cabbage stored at temperatures ranging from 24' to 49' C. proceeds approximately as a first-order reaction. The apparent activation energies, calculated according to the Arrhenius equation, are high, ranging from 33 to 43 kg.-cal. The rate increases markedly as the moisture content is raised; for carrot and white potato at 38' C., the increases are about 3-and s-fold, respectively, over the moisture ranges of 5.4 to 8.0, and 5.3 to 9.2%. For sulfited vegetables stored in air as compared to similar samples stored in nitrogen, the respective rates of sulfite disappearance are in the ratio of about 1 to 1 at 49" C., and
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