Date of Award:

5-1-1996

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Committee Chair(s)

James A. Gessaman

Committee

James A. Gessaman

Committee

Edward W. Evans

Committee

William A. Brindley

Committee

Jimmie R. Parrish

Abstract

Detecting exposure to anticholinergic pesticides involves measuring levels of cholinesterase (ChE) activity. There are few published values for plasma ChE activity from wild avian species, yet reference levels of ChE activity are vital for nonlethal bioassays to determine exposure to carbamate or organophosphate pesticides. I used plasma samples from 102 sharp-shinned hawks (Accipiter striatus) and 45 Cooper's hawks (A. cooperii) captured during autumn migration to establish reference levels of cholinesterase activity. I evaluated the use of a spectrophotometer (SPEC) and 96-well optical microplate reader (MPR) for determining plasma cholinesterase activity from migrating hawks. The SPEC was more precise, both on same-day trials and between days, in measuring ChE activity. The variance in the MPR may have been the result of fluctuating temperatures between ChE activity measurements performed on different days. I also examined the differences between the SPEC and MPR methods measuring standardized amounts of eel brain acetylcholinesterase (AChE) and plasma ChE activity from pigeon and hawk samples analyzed on the same day. ChE activity run over several days ranged from 0.970-2.467 μmol/in/ml plasma for sharp-shinned and Cooper's hawks. Sharp-shinned and Cooper's hawks differ significantly in size both between species, and between genders within a species. I tested whether ChE activity differed between the two species, and between gender and age groups within each species. Sharp-shinned hawks had higher ChE activity than Cooper's hawks. Mean AChE activity was significantly higher in after-hatch-year sharp-shinned hawks when compared to hatch-year sharp-shinned hawks. This relationship did not hold for Cooper's hawks. Gender had no relationship to ChE activity in either species. The percentage of AChE in plasma ChE had the same relationship as mean AChE activity in sharp-shinned hawks, whereas there was a significant difference in the percentage of AChE between the genders of Cooper's hawks. Cholinesterase I50 activity was established using the organophosphate paraoxon. These values were 8.95 x 10-9 M and 5.11x10-9 M for sharp-shinned hawks and Cooper's hawks, respectively.

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