G. E. Duke

Effects of chronic exposure to sublethal concentrations of lead acetate on heme synthesis and immune function in red-tailed hawks.

Red-tailed hawks were exposed to sublethal levels of lead acetate for periods of 3 or 11 weeks. Alterations in the heme biosynthetic pathway were demonstrated after the first week of exposure to 0.82 mg lead per kilogram body weight per day. Activity of erythrocyte porphobilinogen synthase (aminolevulinic acid dehydratase) was depressed significantly and did not return to normal levels until 5 weeks after the termination of lead treatments. A rapid and relatively brief increase in erythrocyte free protoporphyrin and a slower but more prolonged increase in its zinc complex were also demonstrated with exposure to this dose of lead for 3 weeks. Less substantial decreases in hematocrit and hemoglobin levels occurred but only in the longer experiment with exposure to higher lead levels. Short term, low level lead exposure did not effect immune function significantly in the hawks, as measured by antibody titers to foreign red blood cells or by the mitogenic stimulation of T-lymphocytes. Increased lead exposure produced a significant decrease in the mitogenic response but had no effect on antibody titers.

Comparative Pharmacokinetics of Antifungal Drugs In Domestic Turkeys, Red-Tailed Hawks, Broad-Winged Hawks, and Great-Horned Owls

The present research was to test in vitro activity of thiabendazole, 5-fluorocytosine, and amphotericin B against 11 isolates of Aspergillus fumigatus from avian species. Additionally, the plasma concentrations of these drugs were determined in four avian species given a range of dosages by oral, intravenous, and intratracheal routes. Thiabendazole inhibited most isolates in vitro at concentrations between 25 and 50 micrograms/ml; however, there were no detectable inhibitory concentrations in the plasma of any species at any of the doses. The arithmetic mean minimum inhibitory in vitro concentration for 5-fluorocytosine against the 11 Aspergillus isolates was 2.73 micrograms/ml. Inhibitory concentrations of 5-fluorocytosine were found 2 and 6 hours post-administration in all species when given oral doses of 30 or 60 mg/kg as a single dose or when given three divided doses a day totaling 120 mg/kg. No inhibitory concentrations were found 24 hours post-administration. Inhibitory concentrations of amphotericin B were found only 2 and 6 hours post-administration in birds receiving three doses of 1.5 mg/kg at 2-hour intervals. The arithmetic mean minimum inhibitory in vitro concentration for amphotericin B against 11 isolates of A. fumigatus was 0.81 micrograms/ml.

Effect of sublethal lead exposure on gastric motility of red-tailed hawks

In order to determine the effects of low level lead exposure on gastric motility in raptors, strain gage transducers were surgically implanted on the serosal surface of the muscular stomach of three red-tailed hawks. The frequency and amplitude of gastric contractions during ingestion and early digestion were monitored for 1 week under control conditions and for 3 weeks while the birds were fed 0.82 or 1.64 mg lead (as lead acetate) per kg body weight each day. Exposure to these doses did not appreciably affect either the frequency or amplitude of gastric contractions in these birds. This low level lead exposure also had no consistent effect on the regular egestion of pellets of undigested material by hawks. Daily exposure to doses up to 6.55 mg lead/kg body weight did not affect the frequency or timing of pellet egestion, and exposure to 1.64 mg lead/kg did not affect the gastric contractions associated with pellet egestion. Although gastrointestinal dysfunction is often associated with clinical cases of acute lead toxicity, chronic exposure to these low levels of lead acetate did not significantly alter gastric motility in red-tailed hawks.

The influence of avian pancreatic polypeptide on gastric secretion and motility in red-tailed hawks (Buteo jamaicensis)

Abstract 1. 1. Red-tailed hawks were surgically prepared with a gastric cannula for collecting secretions, a strain gauge transducer on the gastric serosa to detect contractions and a jugular cannula for infusion of buffer or avian pancreatic polypeptide (aPP). 2. 2. Infusion ofaPP (15 ng/ml) caused no significant effects on gastric secretion and motility as compared to control infusions. 3. 3. Previous research indicated that gastric secretion and motility were significantly depressed in chickens by aPP, but not in humans or dogs by PP. 4. 4. Thus, PP effects may be more related to feeding habits (meal eating vs continuous feeding) and gastric digestion requirements (vigorous “mastication” by the gizzard of chickens but not hawks, humans or dogs) than to taxonomic relationships.

Influence of cholecystokinin, vasoactive intestinal peptide and secretin on plasma concentration of avian pancreatic polypeptide in laying hens.

The influence of saline infusion (i.v.) followed by infusion of either cholecystokinin, vasoactive intestinal peptide, or secretin on plasma concentration of avian pancreatic polypeptide (aPP) was studied in sixteen 18-26-week old Single Comb White Leghorn hens. Three concentrations were used for each hormone. Blood was drawn after both saline and hormone infusions and assayed for aPP content. No significant influence of any of the three hormones on plasma aPP level was found in either fed or fasted hens.