Development of a bioassay to test the possible role of thiamine disturbance as a mechanism behind pollution-induced reproductive failures in birds

A test system was developed to examine the effects of environmental contami nants on thiamine homeostasis in bird embryos. This system employs fresh ch icken egg yolk lipids as a vehicle for use in egg injection studies. Furazo lidone, an antibiotic suspected to interfere with thiamine metabolism, was used as a positive control to evaluate the utility of the test system. It w as determined that fresh chicken egg yolk lipids were preferable over chemi cal vehicles as it resulted in lower mortality rates (16% versus 23-62%) an d did not induce any observable effects in the embryo. Injection of 1 mg/eg g of furazolidone at day 0 of development resulted in decreased respiration followed by death, with mortality rates being twice as high as in carrier controls. In addition, transketolase activity, which was measured as an ind icator of thiamine availability in the body, was decreased 25% in brains of 19-day-old embryos. This mechanism may be of importance for effects of env ironmental contaminants in wild bird populations.