Chorioallantoic membrane use as a non-lethal, non-invasive indicator of oviparous organism exposure to organochlorine contaminants
Bargar, Timothy Andrew
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The goals of this dissertation were to (1) describe the relationship between chemical levels in the chorioallantoic membrane (CAM), chick, and adult, and (2) show that data from residue analyses of CAMs can be used as a correlate of effect within neonates and adult oviparous organisms. Three different studies were done to address these goals. First, the effect of both chemical structure and chemical interaction on maternal excretion of organochlorines (OCs) into eggs was investigated. Actively laying adult white leghorn chickens (Callus domesticus) were injected with structurally different chemicals. Laid eggs were collected and analyzed for the dosed chemicals. Chemical structure significantly affected chemical excretion into the eggs while chemical interactions were less influential on excretion. Second, chemical distribution among three different egg compartments (embryo, CAM, yolk+albumin) during embryonic development was investigated. Fertile eggs from hens dosed with a chemical mixture were sacrificed at 9, 14, and 19 days of incubation corresponding to 43%, 67%, and 90% of embryonic development. Greater than 70% of the OC mass within the whole egg remained in the yolk-i-albumin, i.e., external to the embryo, through 90% of development. In addition, predominance of certain OCs in the CAM early in development decreased as development proceeded indicating chemical structure influenced distribution among the compartments. Third, the relationship of OC levels in the CAM to hepatic ethoxyresomfin-o-dealkylase (EROD) activity and plasma estradiol levels in both hens and chicks was investigated. Fertile eggs collected from hens were incubated until hatch. CAMs were removed from discarded eggshells for residue analyses. Blood and livers were removed from 1-week-old chicks, and from hens for biochemical assays. Hepatic EROD activity in both hens and chicks was significantly related with OC mass in CAMs while estradiol levels were not. This dissertation demonstrated that data from residue analyses of CAMs can be used to infer biological effect in both neonatal and adult oviparous organisms. It also shows that OC concentrations in eggs and adults may be predicted based on OC levels in eggs. Therefore, residue analyses of CAMs can be used for non-lethal, non-invasive assessment of oviparous organism exposure to organochlorines.