Evaluation of adrenal function in psittacine birds, using the ACTH stimulation test

The effect of ACTH (16 units) on plasma cortisol and corticosterone concentrations in healthy psittacine birds was evaluated. Plasma corticosterone significantly increased (P less than 0.01) from a mean (+/- SD) basal concentration of 3.25 +/ 3.6 ng/ml to 26.47 +/- 9.25 (one hour after ACTH administration) and 25.69 +/- 13.23 ng/ml (2 hours after ACTH administration). For maximal increase in plasma corticosterone as measured by radioimmunoassay (RIA), heat denaturation was necessary to release corticosteroids from steroid-binding proteins. As measured by RIA, plasma cortisol concentrations did not increase, whether or not the heat denaturation step was included. Addition of cortisol to avian plasma did not prevent accurate quantification of cortisol as measured by RIA. Plasma corticosterone concentrations in cockatoos, macaws, Amazon parrots, conures, and lorikeets before and after ACTH administration indicated that the ACTH stimulation test could be used to evaluate adrenal secretory capacity in psittacine birds.     

Equine thyroid function assessment with the thyrotropin-releasing hormone response test

The effect of thyrotropin-releasing hormone (TRH) on equine thyroid function was determined by quantifying serum thyroxine (T4) and 3,5,3'-triiodothyronine (T3) before and after TRH administration. Thyrotropin-releasing hormone was administered IV to adult horses (n = 5) and ponies (n = 6) at a dose of 1 mg or 0.5 mg, respectively. Serum T4 and T3 concentrations were determined before and 0.25, 0.5, 1, 2, 4, 6, 8, 12, and 24 hours after TRH administration. Serum T4 increased from a basal concentration of 24.4 +/- 8.7 ng/ml (mean +/- SD) to a maximum value of 48.2 +/- 10.2 by 4 hours after TRH administration. Serum T3 increased from a basal concentration of 0.44 +/- 0.18 ng/ml to a maximum value of 1.31 +/- 0.37 ng/ml by 2 hours after TRH administration. Seemingly, TRH increases serum concentrations of T4 and T3 and may be useful as a test of equine hypophysis-thyroid function.     

Thyroid-stimulating hormone in adult euthyroid and hypothyroid horses

The purpose of this study was to validate a thyroid-stimulating hormone (TSH) assay in a model of equine hypothyroidism. Thyrotropin-releasing hormone (TRH) stimulation tests were performed in 12 healthy adult mares and geldings, aged 4 to greater than 20 years. before and during administration of the antithyroid drug propylthiouracil (PTU) for 6 weeks. Serum concentrations of equine TSH, total and free thyroxine (T4), and total and free triiodothyronine (T3) were measured. Before PTU administration, mean +/- standard deviation baseline concentrations of TSH were 0.40 +/- 0.29 ng/mL. TSH increased in response to TRH, reaching a peak concentration of 0.78 +/- 0.28 ng/mL at 45 minutes. Total and free T4 increased from 12.9 +/- 5.6 nmol/L and 12.2 +/- 3.5 pmol/L to 36.8 +/- 11.4 nmol/L and 23.1 +/- 5.9 pmol/L, respectively, peaking at 4-6 hours. Total and free T3 increased from 0.99 +/- 0.51 nmol/L and 2.07 +/- 1.14 pmol/L to 2.23 +/- 0.60 nmol/l and 5.78 +/- 1.94 pmol/L, respectively, peaking at 2-4 hours. Weekly measurements of baseline TSH and thyroid hormones during PTU administration showed that total and free T, concentrations fell abruptly and remained low throughout PTU administration. Total and free T4 concentrations did not decrease dramatically until weeks 5 and 4 of PTU administration, respectively. A steady increase in TSH concentration occurred throughout PTU administration, with TSH becoming markedly increased by weeks 5 and 6 (1.46 +/- 0.94 ng/mL at 6 weeks). During weeks 5 and 6 of PTU administration, TSH response to TRH was exaggerated, and thyroid hormone response was blunted. Results of this study show that measurement of equine TSH in conjunction with thyroid hormone measurement differentiated normal and hypothyroid horses in this model of equine hypothyroidism.     

Serum concentrations of thyroxine and 3,5,3'-triiodothyronine before and after intravenous or intramuscular thyrotropin administration in dogs

Response to thyrotropin (TSH) was evaluated in 2 groups of mixed-breed dogs. Thyrotropin (5 IU) was administered IV to dogs in group 1 (n = 15) and IM to dogs in group 2 (n = 15). Venous blood samples were collected immediately before administration of TSH and at 2-hour intervals for 12 hours thereafter. In group 1, the maximum mean concentration (+/- SD) of thyroxine (T4; 7.76 +/- 2.60 micrograms/dl) and 3,5,3'-triiodothyroxine (T3; 1.56 +/- 0.51 ng/ml) was attained at postinjection hours (PIH) 8 and 6, respectively. However, the mean concentration of T4 at PIH 6 (7.21 +/- 2.39 micrograms/dl) was not different (P greater than 0.05) from the mean concentration at PIH 8. The maximum mean concentration of T4 (10.10 +/- 3.50 micrograms/dl) and T3 (2.22 +/- 1.24 ng/ml) in group 2 was attained at PIH 12 and 10, respectively. Because dogs given TSH by the IM route manifested pain during injection, had variable serum concentrations of T3 after TSH administration, and may require 5 IU to achieve maximal increases in serum T4 concentrations, IV administration of TSH is recommended. The optimal sampling time to observe maximal increases in T3 and T4 after IV administration of TSH was 6 hours. Repeat IV administration of TSH may cause anaphylaxis and, therefore, is not recommended.     

Measurement of thyroid hormones (thyroxine, T4; triiodothyronine, T3) in captive nondomestic felids.

The aim of this research was to obtain basic values for the evaluation of thyroid function in nondomestic felids. Serum thyroid hormone concentrations (thyroxine, T4; triiodothyronine, T3) were measured by radioimmunoassay in 145 cats, representing nine species of captive nondomestic felids: jaguar (Panthera onca), n = 49; puma (Puma concolor), n = 10; ocelot (Leopardus pardalis), n = 22; oncilla (Leopardus tigrinus), n = 12; geoffroy (Oncifelis geoffroyi), n = 4; jaguarundi (Herpailurus yaguarondi), n = 8; margay (Leopardus wiedii), n = 7; lion (Panthera leo), n = 26; and tiger (Panthera tigris), n = 7. For each species, mean +/- SEM of T3 and T4, respectively, were as follows: jaguar, 0.56 +/- 0.03 and 9.7 +/- 0.8 ng/ml; puma, 0.67 +/- 0.04 and 11.2 +/- 1.2 ng/ml; ocelot, 0.48 +/- 0.03 and 13.8 +/- 1.5 ng/ml; oncilla, 0.43 +/- 0.03 and 10.0 +/- 1.6 ng/ml; geoffroy, 0.44 +/- 0.04 and 8.0 +/- 0.16 ng/ml; jaguarundi, 0.7 +/- 0.03 and 5.0 +/- 1.0 ng/ml; margay, 0.48 +/- 0.04 and 12.2 +/- 2.3 ng/ml; lion, 0.43 +/- 0.02 and 5.7 +/- 2.6 ng/ml; and tiger, 0.66 +/- 0.03 and 12.6 +/- 0.9 ng/ml. Within species, T3 and T4 concentrations did not differ (P > 0.05) between males and females.     

Use of recombinant human thyroid-stimulating hormone for thyrotropin-stimulation testing of euthyroid cats

OBJECTIVE: To evaluate response of euthyroid cats to administration of recombinant human thyroid-stimulating hormone (rhTSH). ANIMALS: 7 healthy cats. PROCEDURE: Each cat received each of 5 doses of rhTSH (0, 0.025, 0.050, 0.100, and 0.200 mg), IV, at 1-week intervals. Serum concentration of total thyroxine (TT4) and free thyroxine (fT4) was measured immediately before each injection (time 0) and 2, 4, 6, and 8 hours after administration of each dose. RESULTS: Overall TT4 response did not differ significantly among cats when administered doses were > or = 0.025 mg. Serum TT4 concentrations peaked 6 to 8 hours after administration for all doses > or = 0.025 mg. For all doses > or = 0.025 mg, mean +/- SEM TT4 concentration at 0, 6, and 8 hours was 33.9 +/- 1.7, 101.8 +/- 5.9, and 101.5 +/- 5.7 nmol/L, respectively. For all doses > or = 0.025 mg, mean fT4 concentration at 0, 6, and 8 hours was 38.7 +/- 2.9, 104.5 +/- 7.6, and 100.4 +/- 8.0 pmol/L, respectively. At 8 hours, the fT4 response to 0.025 and 0.050 mg was less than the response to 0.100 and 0.200 mg. Adverse reactions after rhTSH administration were not detected. CONCLUSIONS AND CLINICAL RELEVANCE: The TSH stimulation test can be performed in cats by IV administration of 0.025 to 0.200 mg of rhTSH and measurement of serum TT4 concentrations at time of injection and 6 or 8 hours later. Clinical validation of the TSH stimulation test would facilitate development of additional tests of thyroid gland function, such as a TSH assay.     

Endocrine responses of healthy parrots to ACTH and thyroid stimulating hormone

Effects of exogenous ACTH on plasma corticosterone and cortisol concentrations and the effects of thyroid stimulating hormone (TSH) on plasma triiodothyronine (T3) and thyroxine (T4) were determined in the following 3 species of parrots: red-lored Amazon (group 1), blue-fronted Amazon (group 2), and African gray (group 3). Each bird was given ACTH (0.125 mg/bird) IM, except for 3 to 4 birds in each group, which were given saline solution (controls). Blood samples were collected before and 90 minutes after ACTH stimulation. In group 1 (n = 12), mean plasma corticosterone concentrations increased significantly (P less than 0.001) from 1.06 microgram/dl (before ACTH) to 4.89 micrograms/dl (after ACTH); mean corticosterone concentrations increased in the control birds from 1.06 microgram/dl to 1.84 microgram/dl; and mean cortisol concentrations increased only slightly from 0.228 microgram/dl to 0.266 microgram/dl. In group 2 (n = 12), mean corticosterone concentrations increased significantly (P less than 0.001) from 2.09 micrograms/dl to 10.58 micrograms/dl; control mean corticosterone concentrations decreased slightly from 2.09 micrograms/dl to 1.77 microgram/dl; and mean cortisol concentrations increased from less than or equal to 0.16 microgram/dl to 0.266 microgram/dl. In group 3 (n = 12), mean plasma corticosterone concentrations increased significantly (P less than or equal to 0.001) from 2.33 micrograms/dl to 4.67 micrograms/dl; mean control plasma corticosterone concentrations decreased from 2.33 micrograms/dl to 1.68 microgram/dl; and plasma corticol concentrations were not detectable. Each bird was given TSH, IM (1 U/bird). Blood samples were collected before and 6 hours after TSH administration. Saline solution was not administered as controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Luteinizing hormone and progesterone concentrations and induction of estrus after use of norgestomet ear implants or constant infusion of gonadotropin-releasing hormone in anestrous, nonlactating dairy goats

Plasma luteinizing hormone and progesterone concentrations, time to onset of estrus, and pregnancy rates were determined in nonlactating anestrous does given 1 of 4 treatments: subcutaneous ear implants containing 3 mg of norgestomet for 9 days (NOR; n = 6); subcutaneous administration, using osmotic minipumps, of 250 ng of gonadotropin-releasing hormone (GnRH)/h for 48 hours (GnRH; n = 6); 3 mg of NOR for 9 days, followed immediately by 250 ng of GnRH/h for 48 hours (NOR + GnRH; n = 6); or no treatment (control; n = 6). During the 72-hour period after removal of NOR or insertion of GnRH pumps, 6 of 6, 0 of 6, 6 of 6, and 3 of 6 does were observed in estrus at a mean (+/- 13.8) hours in groups NOR, GnRH, NOR + GnRH, and control, respectively. Time from end of treatment to peak concentrations of luteinizing hormone were 56 +/- 4.0, 28 +/- 4.7, 34 +/- 4.3, and 41 +/- 9.7 hours (mean +/- SE) for NOR, GnRH, NOR +/- GnRH, and control, respectively. Peak concentrations of luteinizing hormone were significantly greater and occurred significantly later in does given NOR. Progesterone concentrations in does that became pregnant increased to concentrations greater than or equal to 1.0 ng/ml 3 to 5 days after breeding and remained high. Functional corpora lutea (CL) was found in 6 does that did not become pregnant, 1 CL was associated with pseudopregnancy and 1 CL was associated with ovulation prior to placement of the GnRH pumps. Functional CL failed to form in 10 of the 12 doses in groups GnRH and control.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plasma concentrations of enrofloxacin in African grey parrots treated with medicated water

Plasma concentrations of enrofloxacin were measured four times during a 7-day treatment period in African grey parrots that were fed with enrofloxacin-medicated drinking water. Water medicated at doubling doses of 0.09, 0.19, 0.38, 0.75, 1.5, and 3.0 mg/ml achieved mean concentrations (+/- SEM) of 0.10 (+/- 0.05), 0.12 (+/- 0.05), 0.12 (+/- 0.03), 0.15 (+/- 0.05), 0.30 (+/- 0.11), and 0.20 (+/- 0.06) micrograms/ml, respectively. A portion of the administered enrofloxacin was metabolized to an equipotent metabolite, ciprofloxacin. Mean ciprofloxacin concentrations paralleled enrofloxacin concentrations but were lower, ranging from 0.04 to 0.27 micrograms/ml. Acceptance of medicated water was adequate at lower doses; however, at doses of 1.5 and 3.0 mg/ml, acceptance was unsatisfactory, and mean weight loss in these groups was significantly higher than the control group. Based on the concentrations achieved in these preliminary trials and the susceptibility patterns of gram-negative bacteria isolated from psittacine birds, drinking water medicated with enrofloxacin at 0.19-0.75 mg/ml might be effective for treating highly susceptible gram-negative bacterial infections in African grey parrots.     

Chlamydophila psittaci in free-living Blue-fronted Amazon parrots (Amazona aestiva) and Hyacinth macaws (Anodorhynchus hyacinthinus) in the Pantanal of Mato Grosso do Sul, Brazil

Chlamydophila psittaci (C. psittaci) infection was evaluated in 77 free-living nestlings of Blue-fronted Amazon parrots (Amazona aestiva) and Hyacinth macaws (Anodorhynchus hyacinthinus) in the Pantanal of Mato Grosso do Sul, Brazil. Tracheal and cloacal swab samples from 32 wild parrot and 45 macaw nestlings were submitted to semi-nested PCR, while serum samples were submitted to complement fixation test (CFT). Although all 32 Amazon parrot serum samples were negative by CFT, cloacal swabs from two birds were positive for Chlamydophila DNA by semi-nested PCR (6.3%); these positive birds were 32 and 45 days old. In macaws, tracheal and cloacal swabs were positive in 8.9% and 26.7% of the samples, respectively. Complement-fixing antibodies were detected in 4.8% of the macaw nestlings; macaw nestlings with positive findings were between 33 and 88 days old. These results indicate widespread dissemination of this pathogen in the two evaluated psittacine populations. No birds had clinical signs suggestive of chlamydiosis. To the best of our knowledge, this is the first report on C. psittaci in free-living Blue-fronted Amazon parrots and Hyacinth macaws in Brazil.     

Effects of oral administration of levothyroxine sodium on serum concentrations of thyroid gland hormones and responses to injections of thyrotropin-releasing hormone in healthy adult mares

OBJECTIVE: To determine the effects of levothyroxine sodium (L-T4) on serum concentrations of thyroid gland hormones and responses to injections of thyrotropin-releasing hormone (TRH) in euthyroid horses. ANIMALS: 12 healthy adult mares. PROCEDURE: 8 horses received an incrementally increasing dosage of L-T4 (24, 48, 72, or 96 mg of L-T4/d) for weeks 1 to 8. Each dose was provided for 2 weeks. Four additional horses remained untreated. Serum concentrations of total triiodothyronine (tT3), total thyroxine (tT4), free T3 (fT3), free T4 (fT4), and thyroid-stimulating hormone (TSH) were measured in samples obtained at weeks 0, 2, 4, 6, and 8; 1.2 mg of TRH was then administered i.v., and serum concentrations of thyroid gland hormones were measured 2 and 4 hours after injection. Serum reverseT3 (rT3) concentration was also measured in the samples collected at weeks 0 and 8. RESULTS: Treated horses lost a significant amount of weight (median, 19 kg). Significant treatment-by-time effects were detected for serum tT3, tT4, fT3, fT4, and TSH concentrations, and serum tT4 concentrations were positively correlated (r, 0.95) with time (and therefore dosage) in treated horses. Mean +/- SD serum rT3 concentration significantly increased in treated horses (3.06 +/- 0.51 nmol/L for week 8 vs 0.74 +/- 0.22 nmol/L for week 0). Serum tT3, tT4, fT3, and TSH concentrations in response to TRH injections differed significantly between treated and untreated horses. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of levothyroxine sodium increased serum tT4 concentrations and blunted responses toTRH injection in healthy euthyroid horses.     

Serum disposition of exogenous progesterone after intramuscular administration in bitches

Progesterone was administered IM to 6 adult anestrous bitches at a dosage of 2 mg/kg of body weight. Serum progesterone concentrations were measured prior to progesterone administration and for 72 hours thereafter. The serum progesterone concentration time data were analyzed by use of a pharmacokinetics modeling computer program. The mean (+/- SD) peak serum progesterone concentration (34.3 +/- 7.8 ng/ml) was reached at 1.8 +/- 0.2 hours after progesterone administration. The mean serum progesterone concentration was 6.9 +/- 1.4 ng/ml at 24 hours and 2.0 +/- 0.4 ng/ml at 48 hours after progesterone administration. By 72 hours after administration, mean serum progesterone concentration was 0.9 +/- 0.2 ng/ml, which was comparable to serum progesterone concentrations prior to injection. The mean half-life of the absorption phase was 0.5 hours (range, 0.3 to 0.7 hours). The mean half-life of elimination was 12.1 hours (range, 9.5 to 13.8 hours). By analysis of the data, it was established that a dosage of 3 mg/kg, when the hormone was given IM to dogs once a day, would maintain serum progesterone concentration greater than 10 ng/ml.     

Serum concentrations of ionized calcium, vitamin D3, and parathyroid hormone in captive thick-billed parrots (Rhynchopsitta pachyrhyncha).

Serum collected from 68 thick-billed parrots (Rhynchopsitta pachyrhyncha) from 15 institutions was analyzed for ionized Ca (iCa), total Ca (tCa), P, total protein (TP), albumin (Alb), parathyroid hormone (PTH), and vitamin D3. Values were not distributed normally; 95% frequency intervals were as follows: iCa (0.82-1.3 mmol/L), tCa (1.37-2.09 mmol/L,), P (0.35-1.75 mmol/L), TP (21-39 g/L), Alb (9-13 g/L), PTH (0-65.68 pmol/L), and vitamin D3 (5.2-51 nmol/L). Sixty percent (+/-7.5%) of tCa was ionized. Female thick-billed parrots had significantly higher mean iCa (1.11 mmol/L, n = 22) than male thick-billed parrots (1.05 mmol/L, n = 32). tCa and iCa values in thick-billed parrots were lower than the reported values for other psittacine species. A significant positive linear relationship existed between Alb-TP and iCa-tCa ratios. A significant inverse linear relationship was also identified between the tCa-P ratio and PTH. These findings are consistent with known domestic avian Ca physiology.     

Pharmacokinetics, inhibition of lymphoblast transformation, and toxicity of cyclosporine in clinically normal pigs

Pharmacokinetic variables were calculated from time-concentration data obtained after IV (10 mg/kg of body weight; n =9) and oral (12.5 mg/kg to group A [n = 3]; 25 mg/kg to group B [n = 3]; and 50 mg/kg to group C [n = 3] pigs) cyclosporine (formerly, cyclosporine A) administration. Resulting mean (+/- SD) pharmacokinetic variables were as follows: half life of distribution, 0.96 (+/- 0.7) hours; half life of elimination, 7.71 (+/- 2.6) hours; volume of distribution at steady state, 4.47 (+/- 2.22) L/kg; volume of the central compartment, 1.71 (+/- 0.78) L/kg; and systemic clearance, 8.95 (+/- 2.7) ml/kg/min. Oral bioavailability was: overall 57 (+/- 19) %; group A, 44 (+/- 11) %; group B, 78 (+/- 15) %; group C, 48 (+/- 6) %. Time to peak concentration was 3.55 (+/- 0.88) hours. During the 22 days of daily oral cyclosporine administration, blood 24-hour trough concentrations were: group A, 224.3 (+/- 78.4) ng/ml; group B, 640.7 (+/- 174.6) ng/ml; and group C, 2,344 (+/- 1,095) ng/ml. Lymphoblast transformation stimulation index was suppressed in all pigs except 1, which had a corresponding cyclosporine concentration of 92.4 ng/ml. Minimal, although statistically significant, decreases in serum albumin and magnesium concentrations and increases in serum creatinine and urea nitrogen concentrations were evident in pigs of some treatment groups. Histologic examination of necropsy specimens revealed mild hepatic necrosis (n = 1 pig), renal tubular dilatation (n = 5), and pulmonary inflammation (n = 2). Pigs given 25 and 50 mg of cyclosporine/kg failed to gain weight.     

Thyroid and adrenal function tests in adult male ferrets

Effects of thyroid-stimulating hormone (TSH) and thyrotropin-releasing hormone (TRH) on plasma concentrations of thyroid hormones, and effects of ACTH and dexamethasone on plasma concentrations of cortisol, were studied in adult male ferrets. Thirteen ferrets were randomly assigned to test or control groups of eight and five animals, respectively. Combined (test + control groups) mean basal plasma thyroxine (T4) values were different between the TRH (1.81 +/- 0.41 micrograms/dl, mean +/- SD) and TSH (2.69 +/- 0.87 micrograms/dl) experiments, which were performed 2 months apart. Plasma T4 values significantly (P less than 0.05) increased as early as 2 hours (3.37 +/- 1.10 micrograms/dl) and remained high until 6 hours (3.45 +/- 0.86 micrograms/dl) after IV injection of 1 IU of TSH/ferret. In contrast, IV injection of 500 micrograms of TRH/ferret did not induce a significant increase until 6 hours (2.75 +/- 0.79) after injection, and induced side effects of hyperventilation, salivation, vomiting, and sedation. There was no significant increase in triiodothyronine (T3) values following TSH or TRH administration. Combined mean basal plasma cortisol values were not significantly different between ACTH stimulation (1.29 +/- 0.84 micrograms/dl) and dexamethasone suppression test (0.74 +/- 0.56 micrograms/dl) experiments. Intravenous injection of 0.5 IU of ACTH/ferret induced a significant increase in plasma cortisol concentrations by 30 minutes (5.26 +/- 1.21 micrograms/dl), which persisted until 60 minutes (5.17 +/- 1.99 micrograms/dl) after injection. Plasma cortisol values significantly decreased as early as 1 hour (0.41 +/- 0.13 micrograms/dl), and had further decreased by 5 hours (0.26 +/- 0.15 micrograms/dl) following IV injection of 0.2 mg of dexamethasone/ferret.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of morphine on serum gonadotropin concentrations in postpartum beef cows

Morphine (M), an opioid agonist, was administered to postpartum (PP) Angus cows to investigate opioid modulation of gonadotropin secretion. In Exp. 1, eight PP cows (36.9 +/- 2.3 d) received either M (1 mg/kg; n = 4) or saline solution (S) (n = 4) via i.v. injection 36 h after calf removal. Morphine decreased (P less than .01) the number of serum LH pulses (3.0 +/- 1.1 pre- vs .3 +/- .3 post-pulses/h) and, compared with pretreatment values (3.3 mg/ml), decreased (P less than .05) mean LH at 105 min (2.1 ng/ml) through 270 min 1.9 ng/ml +/- .4). Serum prolactin (PRL) increased (P less than .01) following M from 16.4 ng/ml to a peak of 59.3 ng/ml (+/- 3.9). Serum FSH concentrations were unaffected. In Exp. 2, M (.31 mg/kg i.v. injection followed by .15 mg/(kg.h) infusion; n = 6) or S (n = 6) treatments were given for 7 h beginning 36 h after calf removal. Serum LH was similar between groups during the pretreatment and the first 6 h of infusion, but M decreased (P less than .001) the number of serum LH pulses (.44 +/- .09 vs .06 +/- .04 pulses/h). Morphine increased (P less than .05) serum PRL. It is concluded that M differentially modulated gonadotropin secretion in the cow such that PRL increased, LH decreased and FSH was unchanged.     

Pharmacokinetics of marbofloxacin in blue and gold macaws (Ara ararauna)

OBJECTIVE: To determine the pharmacokinetics of marbofloxacin after single IV and orally administered doses in blue and gold macaws. ANIMALS: 10 healthy blue and gold macaws. PROCEDURES: In a crossover study, marbofloxacin (2.5 mg/kg) was administered orally (via crop gavage) to 5 birds and IV to 5 birds. Blood samples were obtained at 0, 0.5, 1, 3, 6, 12, 24, 48, 72, and 96 hours after marbofloxacin administration. After a 4-week washout period, the study was repeated, with the first 5 birds receiving the dose IV and the second 5 birds receiving the dose orally. Serum marbofloxacin concentrations were quantitated by use of a validated liquid chromatography-mass spectrometry assay. RESULTS: After oral administration, mean +/- SD area under the curve was 7.94 +/- 2.08 microg.h/mL, maximum plasma concentration was 1.08 +/- 0.316 microg/mL, and bioavailability was 90.0 +/- 31%. After IV administration of marbofloxacin, the apparent volume of distribution was 1.3 +/- 0.32 L/kg, plasma clearance was 0.29 +/- 0.078 L/h/kg, area under the curve was 9.41 +/- 2.84 microg.h/mL, and the harmonic mean terminal half-life was 4.3 hours. CONCLUSIONS AND CLINICAL RELEVANCE: Single IV and orally administered doses of marbofloxacin were well tolerated by blue and gold macaws. The orally administered dose was well absorbed. Administration of marbofloxacin at a dosage of 2.5 mg/kg, PO, every 24 hours may be appropriate to control bacterial infections susceptible to marbofloxacin in this species.     

Validation of a novel high-sensitivity radioimmunoassay procedure for measurement of total thyroxine concentration in psittacine birds and snakes.

OBJECTIVE: To validate a novel high-sensitivity radioimmunoassay (RIA) procedure developed to accurately measure the relatively low serum total thyroxine (T4) concentrations of birds and reptiles and to establish initial reference ranges forT4 concentration in selected species of psittacine birds and snakes. ANIMALS: 56 healthy nonmolting adult psittacine birds representing 6 species and 42 captive snakes representing 4 species. PROCEDURE: A solid-phase RIA designed to measure free T4 concentrations in dialysates of human serum samples was used without dialysis to evaluate total T4 concentration in treated samples obtained from birds and reptiles. Serum T4 binding components were removed to allow assay of undialyzed samples. Assay validation was assessed by determining recovery of expected amounts of T4 in treated samples that were serially diluted or to which T4 was added. Intra- and interassay coefficient of variation (CV) was determined. RESULTS: Mean recovery of T4 added at 4 concentrations ranged from 84.9 to 115.0% and 95.8 to 119.4% in snakes and birds, respectively. Intra- and interassay CV was 3.8 and 11.3%, respectively. Serum total T4 concentrations for 5 species of birds ranged from 2.02 to 768 nmol/L but ranged from 3.17 to 142 nmol/L for blue-fronted Amazon parrots; concentrations ranged from 0.21 to 6.06 nmol/L for the 4 species of snakes. CONCLUSIONS AND CLINICAL RELEVANCE: This new RIA method provides a commercially available, accurate, and sensitive method for measurement of the relatively low serum T4 concentrations of birds and snakes. Initial ranges for the species evaluated were established.     

Effect of naloxone on serum luteinizing hormone, cortisol and prolactin concentrations in anestrous beef cows

Two experiments were conducted with the opioid antagonist naloxone to determine the effect of opioid receptor blockade on hormone secretion in postpartum beef cows. In Exp. 1, nine anestrous postpartum beef cows were used to measure the effect of naloxone on serum luteinizing hormone (LH), cortisol and prolactin concentrations. Cows received either saline (n = 4) or 200 mg naloxone in saline (n = 5) iv. Blood samples were collected at 15-min intervals for 2 h before and after naloxone administration. Serum LH concentrations increased (P less than .01) in naloxone-treated cows from 1.8 +/- .04 ng/ml before treatment to 3.9 +/- .7 ng/ml and 4.2 +/- .5 ng/ml at 15 and 30 min, respectively, after naloxone administration. In contrast, LH remained unchanged in saline-treated cows (1.6 +/- .3 ng/ml). Serum cortisol and prolactin concentrations were not different between groups. In Exp. 2, 12 anestrous postpartum beef cows were used to examine the influence of days postpartum on the serum LH response to naloxone. Four cows each at 14 +/- 1.2, 28 +/- .3 and 42 +/- 1.5 d postpartum received 200 mg of naloxone in saline iv. Blood samples were taken as in the previous experiment. A second dose of naloxone was administered 2 h after the first, and blood samples were collected for a further 2 h. Serum LH concentrations increased (P less than .01) only in cows at 42 d postpartum.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of the effects of clomipramine on canine thyroid function tests

To evaluate the effect of long-term clomipramine administration on the hypothalamic-pituitary-thyroid axis in healthy dogs, 14 healthy adult dogs were enrolled in a prospective study. Clomipramine (3 mg/kg PO q12h) was administered to all dogs beginning on day 0, and continued for 112 days. Serum total thyroxine (T4), free thyroxine (fT4), 3,5,3'-triiodothyronine (T3), 3,3',5'-triiodothyronine (reverse T3; rT3), and thyroid-stimulating hormone (TSH) were measured on days 0, 7, 28, 42, 56, and 112. Thyrotropin-releasing hormone (TRH) response tests were performed concurrently. Significant decreases were noted in serum T4, f4, and rT3 concentrations beginning on day 28 through the end of the study period. The lowest mean (+/-SEM) concentrations of T4 (26 +/- 1.2 to 17 +/- 0.5 nmol/L) and rT3 (1.21 +/- 0.13 to 0.83 +/- 0.08 nmol/L) occurred at day 112, whereas the lowest mean fT4 (29 +/- 2.4 to 18 +/- 1.7 pmol/L) was found on day 56 of clomipramine treatment. The effect of treatment over time on serum T3 concentration also was significant, but the deviation in T3 from baseline was variable. No significant effect of clomipramine treatment was noted on either pre- or post-TRH TSH concentrations. The 35 and 38% decreases in serum T4 and fT4 concentrations, respectively, during clomipramine administration may lead to a misdiagnosis of hypothyroidism. Although no evidence of hypothyroidism was noted in this study population, subclinical hypothyroidism may have occurred. A longer duration of treatment might further suppress thyroid function, and concurrent illness or other drug administration might exacerbate clomipramine's effects.