Ocular Lesions in Red-Tailed Hawks ( Buteo jamaicensis) With Naturally Acquired West Nile Disease.

Ocular lesions are common in red-tailed hawks with West Nile (WN) disease. These lesions consist of pectenitis, choroidal or retinal inflammation, or retinal necrosis, but detailed investigation of the ocular lesions is lacking. Postmortem examination of the eyes of 16 red-tailed hawks with naturally acquired WN disease and 3 red-tailed hawks without WN disease was performed using histopathology, immunohistochemistry for West Nile virus (WNV) antigen, glial fibrillary acid protein, cleaved caspase-3, and the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling method. Retinal lesions were classified as type I or type II lesions. Type I lesions were characterized by lymphoplasmacytic infiltrates in the subjacent choroid with degeneration limited to the outer retina (type Ia lesion) or with degeneration and necrosis of the outer retina or outer and inner retina (type Ib lesion) while retinal collapse, atrophy, and scarring were hallmarks of type II lesions. Type II retinal lesions were associated with a more pronounced choroiditis. Although not statistically significant, WNV antigen tended to be present in larger quantity in type Ib lesions. Type I lesions are considered acute while type II lesions are chronic. The development of retinal lesions was associated with the presence of an inflammatory infiltrate in the choroid. A breakdown of the blood-retina barrier is suspected to be the main route of infection of the retina. Within the retina, virus appeared to spread via both neuronal and Müller cell processes.

The effect of chicken, pigeon, and turkey demineralized bone matrix (DBM) implanted in ulnar defects fixed with the intramedullary-external skeletal fixator (IM-ESF) tie-in in pigeons (Columba livia): histological evaluations.

Avian demineralized bone matrix (ADBM) powder prepared from chicken, pigeon, and turkey sources induced bone formation via endochondral and intramembranous processes, as in mammalian studies. There were no significant differences in percentage of new bone, percentage of cartilage, surface-forming osteoblast area, or osteoclast count between gaps treated with chicken, pigeon, and turkey DBM. However, there was a significantly (p<0.05) higher percentage of inflammatory area in gaps treated with chicken DBM than in gaps treated with pigeon DBM.

Further studies on the use of allopurinol to reduce plasma uric acid concentrations in the Red-tailed Hawk (Buteo jamaicensis) hyperuricaemic model.

The present paper reports the effects of allopurinol in a raptor hyperuricaemic model. The study was performed as a follow-up to previous experiments wherein allopurinol was used in doses of 100 and 50 mg/kg, and was proved to be toxic at these higher dose rates. To investigate whether 25 mg/kg (semel in die) s.i.d. allopurinol is a safe and effective dose in Red-tailed Hawks (Buteo jamaicensis) to reduce plasma uric acid concentrations, experimental studies were performed using the physiologically occurring postprandial hyperuricaemia. Preprandial and postprandial plasma concentrations of xanthine, hypoxanthine, allopurinol, oxypurinol and uric acid were established by high-performance liquid chromatography at various time intervals after receiving allopurinol (25 mg/kg SID) or placebo. No significant differences were observed between the experimental and the control group. These results indicate that this dose is safe to administer; however, this dose failed to cause a significant effect on plasma uric acid concentrations. Because of the low therapeutic ratio of allopurinol in Red-tailed Hawks, follow-up studies have concentrated on an alternative for the treatment of hyperuricaemia, namely urate oxidase.

Investigations into the uricolytic properties of urate oxidase in a granivorous (Columba livia domestica) and in a carnivorous (Buteo jamaicensis) avian species.

To study the uricolytic properties of urate oxidase in granivorous and carnivorous birds, experiments were conducted in pigeons (Columba livia domestica) and Red-tailed Hawks (Buteo jamaicensis). Plasma concentrations of allantoin and uric acid were determined at various times in experimental groups before and after receiving 100, 200, and 600 U/kg urate oxidase once daily and were compared with controls. All regimens caused a significant decrease in plasma uric acid concentrations within 2 days after the first administration, when compared with controls. Furthermore, both doses used in Red-tailed Hawks (200 and 100 U/kg) caused a significant postprandial suppression of plasma uric acid concentrations. Plasma allantoin concentrations were significantly higher when compared with controls. The ability of urate oxidase to prevent the physiological postprandial hyperuricaemia in Red-tailed Hawks and to reduce plasma uric acid concentrations to undetectable levels, shows the great potential of this drug for treating avian hyperuricaemia.

Synovial chondromatosis in raptors.

Fourteen raptors, consisting of 13 great horned owls (Bubo virginianus) and one red-tailed hawk (Buteo jamaicensis), from central and north central Minnesota, western Wisconsin, and eastern South Dakota (USA) were admitted to a raptor rehabilitation center between June 1992 and June 1995, with perisynovial and synovial chondromatosis affecting multiple joints. Birds were severely debilitated primarily due to loss of shoulder motion. The etiology of these lesions in raptors is unknown.

Exogenous stages of Eimeria bemricki n. sp. (Apicomplexa: Eimeriidae) from the great gray owl, Strix nebulosa (Foster).

Exogenous stages of a new species of Eimeria are described from feces of a captive great gray owl, Strix nebulosa, held at the Gabbert Raptor Center, University of Minnesota, St. Paul, Minnesota. Oocysts (n = 100) of Eimeria bemricki are spherical to subspherical, 19.2 x 19.0 (21.5-16.0 x 21.0-16.0) microm, with ovoidal sporocysts (n = 100), 10.0 x 6.5 (12.0-7.0 x 7.0-5.5) microm and sporozoites (n = 20), 8.2 x 3.2 (6.8-10.1 x 2.5-3.9) microm. Stieda bodies, substieda bodies, polar bodies, and sporocyst residua are present, but micropyle, oocyst residuum, and parastieda bodies are absent. Three refractile bodies are contained in each sporozoite.

Further studies on allopurinol-induced hyperuricaemia and visceral gout in red-tailed hawks (Buteo jamaicensis).

To investigate the usefulness of allopurinol for the treatment of hyperuricemia in birds, experimental studies were performed using the physiologically occurring post-prandial hyperuricaemia in birds of prey as a model. Pre-and post-prandial plasma concentrations of allopurinol, oxypurinol, xanthine, hypoxan-thine and uric acid were established by high performance liquid chromatography in red-tailed hawks (RTH, Buteo jamaicensis) at various time intervals after receiving allopurinol (50 mg/kg SID) or placebo. The dosage used caused slight, but significantly elevated plasma uric acid concentrations compared to controls, as well as vomiting in the majority of treated birds. Markedly elevated plasma concentrations of oxypurinol, xanthine and hypoxanthine were seen in experimental birds. Toxic signs were attributed to oxypurinol, the active (and toxic) metabolite of allopurinol. Xanthinuria was considered to be the cause of the observed renal function disorder. Extrapolation of data from studies in humans and combining these with those of the present study suggest that the maximum dose of allopurinol that can be safely administered to RTH is about half the dose given in the present study, but this needs verification.

Analysis of Cytokinin Metabolism in ipt Transgenic Tobacco by Liquid Chromatography-Tandem Mass Spectrometry.

The endogenous levels of the major, naturally occurring cytokinins in Pisum sativum ribulose-1,5-bisphosphate carboxylase small subunit promoter-isopentenyl transferase gene (Pssu-ipt)-transformed tobacco (Nicotiana tabacum L.) callus were quantified using electrospray-liquid chromatography-tandem mass spectrometry during a 6-week subcultivation period. An ipt gene was expressed under control of a tetracycline-inducible promoter for a more detailed study of cytokinin accumulation and metabolism. Activation of the ipt in both expression systems resulted in the production of mainly zeatin-type cytokinins. No accumulation of isopentenyladenine or isopentenyladenosine was observed. In Pssu-ipt-transformed calli, as well as in the tetracycline-inducible ipt leaves, metabolic inactivation occurred through O-glucoside conjugation. No significant elevation of cytokinin N-glucosides levels was observed. Side-chain reduction to dihydrozeatin-type cytokinins was observed in both systems. The levels of the endogenous cytokinins varied in time and were subject to homeostatic regulatory mechanisms. Feeding experiments of ipt transgenic callus with [3H]isopentenyladenine and [3H]isopentenyladenosine mainly led to labeled adenine-like compounds, which are degradation products from cytokininoxidase activity. Incorporation of radioactivity in zeatin riboside was observed, although to a much lesser extent.

Levels of endogenous cytokinins, indole-3-acetic acid and abscisic acid during the cell cycle of synchronized tobacco BY-2 cells.

Correlation between cell cycle progression and endogenous levels of plant hormones was studied in synchronized tobacco BY-2 cell suspension cultures. Sixteen different cytokinins, indole-3-acetic acid (IAA) and abscisic acid (ABA) were extracted using solid-phase anion exchange chromatography in combination with immunoaffinity purification, and quantified by mass spectrometry. No significant correlation could be identified for IAA and ABA. In contrast, there were sharp peaks in the levels of specific cytokinins (zeatin- and dihydrozeatin-type) at the end of the S phase and during mitosis. The levels of other cytokinins analyzed, including zeatins N- and O-glucosides, remained low, suggesting that the increased amounts of their corresponding non-glucosylated form resulted from de novo synthesis. These findings suggest that zeatin- and dihydrozeatin-type cytokinins might play a specific regulatory role in the progression of the plant cell cycle. One hypothesis to explain cytokinin action is based on a specific interaction with kinases that regulate cell cycle progression, as has been recently shown for the cytokinin analogue olomoucine.

Floral development and expression of floral homeotic genes are influenced by cytokinins.

Tobacco plants that are somatic mosaics for the expression of a cytokinin-synthesizing gene have viviparous leaves. Epiphyllous buds can be either vegetative or floral. Floral adventitious buds can be either normal or abnormal. Abnormalities of floral development correlate with: (i) a local activation of the cytokinin-synthesizing gene, (ii) a drastic increase in floral cytokinin content, and (iii) a decrease in the steady-state levels of mRNA homologous of the homeotic genes DEFA, GLO and PLENA of Antirrhinum majus. Thus, these data show in planta that cytokinins, a class of phytohormones, are able to alter the development of floral organs and to decrease the expression of three homeotic floral genes.

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.

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.

Effect of diet and population density on male turkeys under various environmental conditions. 1. Turkey growth and health performance.

The performance of 1,312 male market turkeys (Large White, Nicholas strain) from 0 to 20 wk of age fed diets varying in feed form and energy level was measured under two stocking densities (.21 or .46 m2 per bird) and four lighting and temperature programs. The four diets were 1) corn and soybean meal with 1% supplemental fat, mash (CSM); 2) as 1, pelleted (CSP); 3) as Diet 1 but with 1, 2, 4, 6, and 8% supplemental fat during 0 to 4, 4 to 8, 8 to 12, 12 to 16, and 16 to 20 wk of age, respectively (CSF); and 4) as Diet 1 but with barely included at 0, 20, 35, 50, and 65% during the respective 4-wk age periods (CSB). The four light and temperature programs were 1) Environment A with intermittent light [4 [2 h light (L):4 h dark (D)]] in combination with cycling temperature at 7 and 21 C during light and dark photoperiod, respectively; Environment B with intermittent light, 21 C; Environment C with continuous light (18L:6D) and cycling temperature of 7 to 21 C; and Environment D with intermittent light, 7 C. Lighting and temperature programs started at 1 and 4 wk of age, respectively. Body weights at 20 wk of age decreased (P less than .05) with increasing temperature (13.86 versus 12.26 kg for Environments D and B, respectively) with cycling temperature intermediate (13.51 kg for Environment A). Intermittent light (P less than .05) improved BW and feed conversion by 3.4 and 2.0%, respectively, compared with continuous light. Rearing males at .21 m2 per bird versus .46 m2 per bird decreased weight (P less than .05) by 5.5%. Twenty-week BW of males fed the CSP (13.52 kg) and CSF (13.58 kg) diets were greater (P less than .05) than those fed CSM (12.90 kg) and CSB (12.69 kg) diets. Significant (P less than .05) interactions between diet, environment, and density were not detected for most performance characteristics. Environmental measurements indicated higher dust and ammonia levels in the warm environment (B). Isolates of aspergillus and incidence of airsacculitis at time of processing were greatest in Environment B.

The avian ceca: obligate combustion chambers or facultative afterburners? The conditioning influence of diet.

Changes in the anatomy and microbiology of the gut of many galliforme birds are influenced by the amount of crude fiber in the diet; the response is biphasic. As crude fiber in the diet increases, the bird compensates for the dilution of dietary energy content by increasing the amount it eats, which causes an increase in gizzard size. After exceeding a threshold in fiber content, where the metabolizable energy intake is limited by the sheer bulk of the food consumed relative to the ability of the bird to ingest food, there is an increase in hindgut size and a change in the microflora that allows extraction of energy from cellulose through the production of volatile fatty acids (VFAs). The result is a change in the apparent digestibility of the diet. Altering the energy demands through the application of environmental stressors, such as lowered temperature, may alter a hypothalamic or other regulatory mechanism setpoint at which hindgut hypertrophy occurs. The time frame required for such changes is between 4 and 8 weeks. Studies to determine digestibility of nutrients or the response of the gut of birds to altered diets must allow a sufficient period of time for gut adaptation prior to assessing its function. Other factors, such as age, photoperiod, and environmental factors, may affect the response of the gut.

Ketamine-xylazine anesthesia in red-tailed hawks with antagonism by yohimbine.

Five red-tailed hawks (Buteo jamaicensis) were anesthetized at weekly intervals with intravenous ketamine hydrochloride (KET, 4.4 mg/kg) and xylazine hydrochloride (XYL, 2.2 mg/kg). Twenty min after anesthesia, yohimbine hydrochloride (YOH, 0.05, 0.10, 0.20 and 0.40 mg/kg) or a control was administered. All doses of YOH significantly reduced the head-up times (F = 20.84, df = 1,24, P less than 0.0001) and the standing times (F = 12.30, df = 1,24, P less than 0.0001), compared to the control group. The heart and respiratory rates following YOH (all doses) were significantly greater (P less than 0.01) than the anesthetized rates, but were comparable to the rates observed in restrained, unanesthetized hawks. Yohimbine did not appear to have any significant effect on body temperature. Based upon administration of 4.4 mg/kg KET and 2.2 mg/kg XYL, a dose of 0.10 mg/kg YOH was recommended to achieve antagonism without causing profound cardiovascular or respiratory changes.

Aspergillus and other human respiratory disease agents in turkey confinement houses.

The atmosphere of a turkey confinement house on a large Minnesota farm was examined over the course of a year in order to determine levels of airborne contaminants and to evaluate the hazard potential posed by the contaminants to farm workers. Air concentrations of total and respirable dust, ammonia, carbon monoxide, hydrogen sulfide, nitrogen dioxide, methane, and Aspergillus (a fungal respiratory disease agent) were evaluated. Inter- and intra-seasonal variations in confinement house contaminant concentrations were observed. The highest concentrations of dust, ammonia and Aspergillus occurred during the winter months when dust levels averaged 9.3 mg/m3 and ammonia levels averaged 35 parts per million (ppm). Aspergillus levels were lower than expected, never exceeding 73 colony forming units per cubic meter (cfu/m3). Ammonia levels were found to be particularly high during tilling of the confinement house when concentrations greater than 100 ppm were reached. Concentrations of carbon monoxide, hydrogen sulfide, nitrogen dioxide and methane were below detectable levels.

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.

The in vitro response of turkey lymphocytes to steroid hormones.

The in vitro mitogen response of whole blood turkey lymphocytes to various concentrations of steroid hormones was evaluated. Corticosterone (COS) at concentrations between 1 and 80 ng/ml significantly suppressed the proliferative response (3H-thymidine incorporation) to phytohemagglutinin (PHA) and concanavalin A (ConA). Non-mitogen-stimulated (NMS) cells were suppressed at concentrations of COS above 5 ng/ml. Progesterone significantly suppressed NMS cells at concentrations of 80 ng/ml, PHA-stimulated cells at concentrations of 500 ng/ml, and ConA-stimulated cells at concentrations of 1000 ng/ml. beta-Estradiol enhanced the response of NMS cells at concentrations of 500 ng/ml, had no effect on PHA-stimulated cells, and suppressed the response of ConA-stimulated cells at concentrations greater than 500 ng/ml. Testosterone affected only the ConA response, causing suppression at concentrations above 2000 ng/ml. Corticosterone and progesterone caused 80 and 95% suppression, respectively, of the proliferative response to ConA when compared with non-hormone-treated cells. The possible implications of steroid hormone-induced immunosuppression in the pathogenesis of aspergillosis is discussed.

Use of whole blood lymphocyte stimulation test for immunocompetency studies in bald eagles, red-tailed hawks, and great horned owls.

Mitogen-induced whole blood lymphocyte stimulation tests for immunocompetency studies in bald eagles (Haliaeetus leucocephalus), red-tailed hawks (Buteo jamaicensis), and great horned owls (Bubo virginianus) were developed. Combinations of incubation times, blood dilutions, concentrations of [3H]thymidine and [125I]2-deoxyuridine, antibiotics, phytohemagglutinin-P, and concanavalin A were tested for their effects on the stimulation index (SI). An antibiotic combination of gentamicin plus amphotericin B yielded low SI with lymphocytes from bald eagles, but not with lymphocytes from great horned owls or red-tailed hawks. Penicillin plus streptomycin caused no such depression of SI. Lymphocytes from all 3 species yielded maximum responses with a 48-hour prelabel and 12- to- 16 hour postlabel incubation period at 41 C and 1:20 blood dilution. Optimal mitogen concentrations for lymphocytes from bald eagles, red-tailed hawks, and great horned owls were 25 micrograms, 10 micrograms, and 10 micrograms of phytohemagglutinin-P/well, respectively, and 2.5 micrograms, 10 micrograms, and 10 micrograms of concanavalin A/well, respectively. Differences in SI were not seen between the 2 radioactive labels. The optimal concentration of the [3H]thymidine label ranged from 0.06 to 0.125 microCi/well.