No abstract

TLC identification of presumptive ochratoxins A and B can be supplemented with overnight results obtained by a single and rapid bioassay of these toxins, using Bacillus cereus mycoides LSU as the test organism. Furthermore, this bioassay can provide an accurate quantitative estimation of ochratoxins. The calculated coefficient of variation was 5.9%. The optimal medium, conditions, and ochratoxin concentrations for this assay are suggested. This test is sensitive to as little as 1.5 and 3.0 µg ochratoxins A and B, respectively.

Fifty adult Coleomegilla maculata (De Geer) were fed on 250 ml of an aqueous solution of sodium acetate-1-C 4 which contained 600 micrograms of the salt; total C u was 10 microcuries. After 4 hr, the beetles were homogenized, the amino acids were extracted and separated by thinlayer chromatography, and the activity was measured, using a scintillation counter. Glycine, serine, aspartic acid, glutamic acid, proline, and lysine showed high activity , and are considered to have been synthesized in vivo. They are apparently nonessential, in contrast to threonine, phenylalanine, isoleucine, and valine, which are essential or derived exclusively from essential dietary constituents. The low activity shown by alanine, leucine, arginine, and histidine indicated a low level of C* incorporation. Three unknown ninhydrin-positive compounds were isolated, in addition to the 19 amino acids that were identified.