Michael J. Hooper

AGE-DEPENDENT CHANGES IN PLASMA AND BRAIN CHOLINESTERASE ACTIVITIES OF EASTERN BLUEBIRDS AND EUROPEAN STARLINGS

Age-dependent changes in plasma and brain cholinesterase (ChE) activity were characterized in two altricial passerine species: eastern bluebirds (Sialia sialis) and European starlings (Sturnus vulgaris). Plasma acetylcholinesterase (AChE) activity declined rapidly immediately after hatching, while plasma butyrylcholinesterase (BChE) activity increased throughout the nestling period. These patterns continued after birds fledged, since the BChE : AChE ratio was higher in adult birds than fledglings. This is the first confirmation of age-dependent changes in plasma ChE activity in altricial species. Total plasma ChE activity increased with age in both species, which is the reverse of results previously reported for several precocial species. Brain ChE activity increased with age in both species, and did not reach asymptotic levels before young fledged. This corresponded with patterns previously documented in European starlings and three other altricial species. We propose that age and degree of precocity in young birds must be considered when examining sensitivity or evaluating field exposure of birds to ChE-inhibiting compounds.

Cyclophosphamide effects on immune function of European starlings.

We developed and tested a battery of immune function assays on adult European starlings (Sturnus vulgaris) exposed to the immunotoxicant cyclophosphamide (CY). Starlings were injected intraperitoneally for three consecutive days with saline or 20 mg/kg CY. Cyclophosphamide did not affect body mass or packed cell volume. However, spleen to body mass ratios and the number of viable spleen cells were lower in CY-treated birds when compared to controls. Peripheral white blood cell numbers were reduced in CY-treated starlings, and the decrease affected all cell types. Phagocytic ability of macrophages cultured from peripheral blood monocytes was impaired in cells from CY-treated birds. Additionally, CY treatment resulted in decreased lymphocyte blastogenesis to the T-cell mitogen Concanavalin A. The hemagglutination response to sheep erythrocytes was lower in birds that had received CY. Thus, these immunological methods detected chemically-induced immune dysfunction in starlings.