Biological Detection Methods Research Articles

Biological, chromatographical, and radioimmunological evidence for a melanotropin-like peptide in the central nervous system of Locusta migratoria

Our recent immunocytochemical study has demonstrated the existence of α-melanocyte stimulating hormone (α-MSH)-like material in the locust central nervous system. The aim of the present study was to further characterize α-MSH in the locust brain by its biological effect on frog skin and by high-pressure liquid chromatography in combination with radio-immunological and biological detection methods. Parallel radioimmunoassay (RIA) curves of crude nervous tissue extracts coupled with bioactivity in a very specific bioassay suggest similarity between the locust α-MSH-like substance and synthetic α-MSH. The highest concentration of α-MSH immunoreactive material in the central nervous system was found in the optic lobes, where α-MSH immunoreactive cell bodies are localized, as was previously shown by immunocytochemistry. High concentrations of α-MSH immunoreactive material were also detected in the thoracic ganglia of the locust ventral nervous system. The application of locust brain extracts to gel permeation HPLC resulted in a similar elution profile of the bioactive and immunologically active substances, both coeluting with synthetic α-MSH. As is the case for vertebrate brain material, reverse-phase HPLC revealed four α-MSH immunoreactive peaks. One of the peaks coelutes with monoacetyl-α-MSH and other RIA-positive material elutes at times close (but not identical) to the methionine sulfoxide forms of α-MSH. Peak three, however, elutes in a very different position from desacetyl-α-MSH. Peaks are absent in the position of desacetyl-α-MSH. Similarity between the locust α-MSH-related substance and authentic α-MSH is discussed.

Methods for the Detection of Trichothecenes

The trichothecenes are a group of fungal metabolites with a tetracyclic, sesquiterpenoid ring system and include a number of compounds which are highly toxic. These compounds are produced by various species of the imperfect fungi including members of the following genera: Calonectria, Fusarium, Myrothecium, Stachybotrys, Trichoderma, and Trichothecium. Both biological and chemical methods for detection of various trichothecenes are reviewed. Some of the bioassay techniques in use for the detection of the various trichothecenes include the rabbit dermal toxicity tests, cytotoxicity, and inhibition of protein synthesis tests; these are highly sensitive but lace specificity. The sensitivity of these tests for the T-2 toxin are 0.005 mug for rabbit skin toxicity, 0.03 mug/ml for inhibition of protein synthesis in rabbit reticulocytes, and less than 1 mug/ml for cytotoxicity to human karyoblast cells. In the present state of development of the chemical assay methods, thin layer and gas-liquid chromatography are specific for various trichothecenes but lack sensitivity. The lower detection limit of the trichothecenes on thin layer plates varies from 0.2 to 2-3 mug/spot while gas-liquid chrommatography has a reported sensitivity of approximately 0.05 mug/injection.