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Preset larval Mercenaria mercenaria were exposed to nominal concentrations of 1 (control) to 495 microg Cu/L in artificial seawater and monitored for mortality, activity, development, and metamorphosis in sealed 30-mm plastic petri plates containing 1.5 ml of artificial seawater or toxicant solution. The plastic petri plates sorbed only about 2.6 microg/L at any dose and allowed direct observation of larval clams under a light microscope for a period of two weeks; control survivorship was in excess of 60% at 400 h. The dose-response curve for mortality for clams exposed to copper and fed Isochrysis galbana was characterized by survival similar to or better than controls at doses of 5 and 14 microg Cu/L, while doses of 7 and > or = 29 microg Cu/L exhibited mortality greater than controls. Values of lowest concentration at which 50% of the organisms died (LC50) were 62.4, 21.2, and 11.7 microg Cu/L, and the lowest observed adverse effect concentration values of 57, 29, and 29 microg Cu/L were determined at 48, 96, and 192 h, respectively. In contrast, activity, as judged by swimming, exhibited a typical exponentially decreasing response at these same concentrations. Experiments on the uptake of dissolved copper by I. galbana confirmed literature reports that these algae concentrate copper. Ingesting copper-containing algae was demonstrated to be a source of copper toxicity for larval clams.

1. A standard microbiological procedure for the assay of available amino acids in proteins using Tetrahymena pyriformis has been modified by evaluating cell growth from the tetrahymanol content of the cultures by gas-liquid chromatography (GLC). 2. This modification improves the precision of the method compared with cell-counting techniques and provided automatic injection facilities are available for the GLC, the procedure is not excessively time-consuming. 3. It has been confirmed that enzymic predigestion is essential for all except the most soluble proteins and a satisfactory method using pronase has been incorporated into the microbiological procedure. 4. After enzymic digestion of the sample, growth of Tetrahymena with many proteins can be measured turbidimetrically, but particulate matter still persists with a proportion of samples, particularly those of plant origin, and the GLC method is therefore more widely applicable. It is also more precise. 5. Good agreement has been obtained between a chick bioassay and the modified Tetrahymena assay for available lysine in eight different proteins, including heat-damaged fish meals. 6. The modified procedure appeared to give good results for available tryptophan and methionine. 7. When cystine was omitted from the standard culture medium it was possible to test for available methionine plus cystine, but further work is required to assess the reliability of this particular assay.

Background and Purpose: Tetanus neurotoxin has many potential therapeutic applications, due to its ability to increase localised muscle tone when injected directly into a muscle. It is a closely related molecule to botulinum neurotoxin (most commonly known as Botox), which has been widely used to release muscle tension for therapeutic and cosmetic applications. However, tetanus toxin has been relegated to the "maybe pile" for protein therapeutics as most of the population is vaccinated, leading to highly effective antibody-mediated protection against the toxin. The potential for tetanus-based therapeutics remains substantial if the problem of pre-existing immunity can be resolved. Experimental Approach: A well-established murine model of localised muscular contraction was utilised. We administered functional tetanus toxin combined with an immunogenic, but functionally inactive, decoy molecule. Key Results: Incorporation of the decoy molecule greatly reduces the dose of active toxin required to induce a localised increase in muscle tone in mice vaccinated with the human toxoid vaccine. Conclusion and Implications: Our results clearly demonstrate that the barriers to developing a tetanus toxin therapeutic are not insurmountable and the technology presented here is the first major step towards realising the therapeutic potential of this powerful neurotoxin. Opening the therapeutic potential of tetanus toxin will have huge implication for the wide range of diseases caused by low-tone muscle.