Effect of 1-24ACTH administration on sheep blood granulocyte functions

The objective of the present study was to determine the efficiency of blood neutrophils (PMN) taken from sheep during acute stress. Ten healthy Charolle sheep were sampled before treatment (T0) and 1 (T1), 2 (T2), 24 (T24) and 48 (T48) hours after 1-24ACTH administration. Ten sheep serving as the controls were sampled at the same time intervals, using saline solution instead of 1-24ACTH. At each time sampling, rectal temperature, heart rate, cortisol, glucose, non-esterified fatty acids (NEFA), total and differential leukocyte counts were evaluated. PMN were isolated after centrifugation of whole blood and hypotonic lysis of RBC. Chemotaxis was evaluated on a modified Boyden chamber using a nitrate cellulose filter and both Zymosan activated serum (ZAS) and interleukin-8 (IL-8) as chemoattractants. Phagocytosis was measured using both non-opsonized latex beads and fluoresceinated yeasts opsonized with homologous serum. Superoxide (O(-)2) production was evaluated by measuring superoxide dismutase-inhibitable reduction of ferricytochrome C, and adherence by a colorimetric assay of acid phosphatase activity of adherent cells. The administration of 1-24ACTH induced an acute stress reaction, indicated by the presence of clinical, biochemical and hematological changes. Adherence significantly increased from T0 to T2 in treated sheep. This might be responsible for the depression of non-specific immunity in stressed animals. Studies using stressors other than 1-24 ACTH are needed to verify the influence of other components of the stress reaction on PMN functions.     

Contribution of æ1-acid glycoprotein to plasma protein binding of some basic antimicrobials in pigs

Protein binding kinetics of basic antimicrobials including trimethoprim (TMP), erythromycin (EM), lincomycin (LM) and clindamycin (CM) were studied using porcine plasma, albumin and æ-acid glycoprotein (AGP). Rosenthal plots of these basic drugs in porcine plasma suggest saturable and non-saturable binding. Dissociation constants (K_d) and binding capacity (B_max) for saturable binding were as follows: TMP, K_d= 8.58 μmol/L, B_max= 5.26 μmol/L; EM, k_d= 2.72 μmol/L, B_max= 3.06 μmol/L; LM, k_d= 3.96 μmol/L, B_max= 6.58 μmol/L and CM, k_d= 4.43 μmol/L, B_max= 21.7 μmol/L. The proportionality constants (B_max2/k_d2) for non-saturable binding were 0.29 in TMP, 0.52 in EM, 0.17 in LM and 3.2 in CM. The k_ds of the drugs in porcine AGP solution were determined by a fluorescence quenching method, using 1-anilino-8-naphthalene sulphonate (ANS) as a fluorescent probe: 9.51 μmol/L in TMP, 1.89 μmol/ L in EM, 4.48 μmol/L in LM and 9.69 μmol/L, in CM. Comparable kd values between porcine plasma and AGP solution indicated that AGP is a major saturable binder in porcine plasma. Binding property to porcine albumin presented linearity, showing the following proportionality constants: 0.23 in TMP, 0.38 in EM, 0.01 in LM and 0.76 in CM. The comparable proportionality constants of TMP and EM between porcine plasma and albumin solution indicate that albumin is a major non-saturable binder, whereas proportionality constants of LM and CM in albumin solution compared to those in porcine plasma were low, implying another non-saturable binder, i.e. lipoprotein. Simulation curve of drug-binding percentage vs. AGP concentrations showed that in pigs under a pathologic state, or during early growth stage with high AGP levels, AGP could be a main contributor to drug-plasma protein binding for all drugs examined. The increase of AGP from normal to pathological concentrations induced a decrease in the unbound fraction: LM > CM > EM > TMP in order of AGP contribution to drug binding. Therefore, the disposition and efficacy of basic antimicrobials which bind to AGP with high affinity could be markedly influenced by altered AGP levels, implying AGP contribution to pharmacokinetics and pharmacodynamics.     

Effect of dose of furosemide on plasma tCO2 changes in standardbred horses

Nine Standardbred horses of similar athletic fitness (six mares, three geldings), ranging from 4 to 11 years of age, were used to determine the effects of 0, 250, or 500 mg intravenously administered furosemide on plasma tCO₂ changes over time. All horses were either currently racing or in advanced stages of race training before entering a qualifying race. Horses were randomly allotted to one of the three treatment levels of furosemide during 3 consecutive weeks. Jugular venous samples were obtained from horses at rest in box stalls before and hourly for 6 hours after administration of furosemide. Body weights of horses ranged from 356 to 456 kg, and the mean was 417 kg. Thus, the dose of furosemide received by each horse ranged from 0.55 to 0.70 mg/kg body weight for the 250-mg injections and from 1.1 to 1.4 mg/kg body weight for the 500-mg injections. Furosemide caused metabolic alkalosis in the horses. Least square means (±SEM) were determined and horses had adjusted plasma tCO₂ of 32.2, 33.9, and 34.7 ± 0.41 for the 0-, 5-, and 10-mL doses of furosemide, respectively. The type 3 tests of hypotheses found that there was a difference (P < .0001) across time, a difference (P = .0016) according to furosemide dose, and a difference (P < .0001) according to treatment × hour. There was no difference (P > .05) according to week or treatment × week. These data suggest that either 250 or 500 mg furosemide given to Standardbred race horses induces statistically similar metabolic alkalosis.     

Pharmacokinetics of flunixin and its effect on prostaglandin F2α metabolite concentrations after oral and intravenous administration in heifers

Flunixin meglumine (FM) was administered either orally as granules or intravenously to six heifers in a two period crossover study. Single doses of 2.2 mg/kg body weight were used. Pharmacokinetic variables were calculated using statistical moment methods. The effect exerted by flunixin was measured as changes in the basal plasma concentration of the main metabolite of prostaglandin (PG) F_2α. After oral FM the arithmetic means of pharmacokinetic variables were: MRT = 12.7 h; MAT = 6.3 h; C _max= 0.9 μg/mL; t _max= 3.5 h. The bioavailability was 60% and the mean half-life (harmonic mean) was 6.2 h. Oral administration of FM inhibited as effectively as intravenous administration the prostaglandin biosynthesis. The concentration of the PG metabolite decreased almost as rapidly as after intravenous administration. The duration of the effect was prolonged and the PG metabolite concentration was significantly lower between 10 and 30 h after oral than after intravenous administration. The results indicate that oral dosing of flunixin, in the form of granules, can be an alternative to intravenous administration for therapeutic use in cattle.     

The effects of opioid and α2 adrenergic blockade on non-steroidal anti-inflammatory drug analgesia in sheep

The analgesic effects of the non-steroidal anti-Inflammatory drugs (NSAIDs) flunixin and dipyrone were assessed in healthy sheep with no pre-existing inflammation, and in sheep with a chronic inflammatory lesion, using a mechanical noxious stimulus. Saline and dexamethasone were given as controls. Blood taken from healthy sheep after NSAID administration was assayed for thromboxane B₂ (TxB₂) to compare the ability of these drugs to inhibit cyclo-oxygenase. Both flunixin and dipyrone produced a small but statistically significant rise in pain thresholds (18% and 21% of maximum possible effect respectively) in the healthy sheep which peaked at 30 min and had returned to pre-drug values by 2–3 h. In the lame sheep a similar effect occurred but the response was smaller, much more variable and tended to be prolonged. Saline and dexamethasone had no effect on thresholds over 6 h in either group of sheep. The rise in thresholds was prevented by pre-treatment with naloxone (an opioid antagonist) or attpamezole (an α₂-adrenergic antagonist) in the healthy sheep. Naloxone and atipamezole had no effect on thresholds when given alone to healthy sheep. Both NSAIDs Inhibited the production of TxB₂ to a similar extent. These results indicate that central mechanisms may be involved in NSAID analgesia.     

α1-acid glycoprotein and serum binding of drugs in healthy and diseased dogs

Inter-individual variation in drug serum protein binding was studied in healthy dogs and in dogs with inflammatory diseases for lidocaine, oxprenolol and propranolol, which bind mainly to alpha 1-acid glycoprotein (alpha 1-AGP), and for diazepam, digitoxin and phenytoin, which bind mainly to albumin. For the drugs mostly bound to alpha 1-AGP, in both groups of dogs binding varied considerably, and it was markedly higher in dogs with inflammatory disease. For the other drugs, the variation in binding was smaller and did not differ between the two groups of dogs. In both groups of dogs, the alpha 1-AGP concentration varied widely; it was higher in the serum of the dogs with inflammation, while the concentration of albumin was lower in these animals. There was a significant negative correlation between percentage free lidocaine, oxprenolol or propranolol and alpha 1-AGP concentration, suggesting that the inter-individual variation in binding of these drugs is due to the variation in alpha 1-AGP concentration. There was a marked intra-individual variation in lidocaine binding and in serum alpha 1-AGP concentration, studied over a period of 3 weeks in healthy dogs; a significant negative correlation between percentage free lidocaine and alpha 1-AGP concentration was obtained.     

Influence of route of administration on the plasma concentrations of ivermectin in reindeer

The concentration of ivermectin in the plasma of reindeer was measured after it was administered either topically as a pour-on preparation at 500 μg kg⁻¹ bodyweight at different seasons to animals of different ages, or after subcutaneous and oral doses of 200 μg kg⁻¹ bodyweight. The plasma concentrations of ivermectin were highest and least variable after it was administered subcutaneously.     

Feline epitheliotrophic T-cell lymphoma with paraneoplastic eosinophilia – immunochemotherapy with vinblastine and human recombinant interferon α2b

A cat with epitheliotrophic T‐cell lymphoma with paraneoplastic eosinophilia is described. Initial attempts to control the disease with conventional therapies failed. The addition of recombinant human interferon α_2b (rhINFα_2b) resulted in a clinical, haematogenous and sonographic improvement for 49 days. The overall survival time from initial diagnosis was 100 days. Relapse was correlated with the development of serum antibodies directed against rhINFα_2b. To our knowledge, this is the first report describing the clinical use of IFNα in the treatment of neoplasia in the cat.     

Changes in taurine levels in response to repeated administration of the β2-agonist salbutamol in lambs

Repeated oral administration of salbutamol to lambs for 28 days was found to decrease levels of taurine significantly in the serum and heart, and the mean excretion of taurine into urine was significantly less than in controls. Serum urea, low density lipoprotein and high density lipoprotein were also significantly reduced. Consistent with these changes, fat content in muscle was reduced, whereas protein content was not significantly changed. Body weight was not significantly changed by salbutamol treatment but heart and kidney weights (relative to body weight) were significantly increased. Salbutamol excretion in urine was relatively constant and residues were detected in certain organs and tissues, notably liver, bile and kidney. Changes in urinary and serum taurine level may reflect subtle changes in protein metabolism not detectable as changes in body weight or gross protein content.     

Effects of α2-adrenergic drugs on blood platelets in sheep

Xylazine (0.2 mg/kg, iv) alone or preceded by atipame-zole (0.125 μg/kg, iv) or by aspirin (10 μg/kg, iv) was administered to 18 sheep. Medetomidine (60 μg/kg, iv) was also administered to 12 sheep. Xylazine, but not medetomidine, significantly reduced the number of platelets. Both atipamezole and aspirin prevented this reduction. It was concluded that α₂-agonists would seem to produce platelet aggregation that may contribute to the development of the respiratory changes that follow the administration of α₂-agonists in sheep, but probably not always to a degree that could result in a significant decrease in the number of circulating platelets.     

Sedative action of the α2-agonist medetomidine in cats

Medetomidine, a novel alpha 2-agonist drug intended for small animal sedation, was injected intramuscularly at dose rates of 0.02, 0.06 and 0.18 mg/kg. Xylazine (3.0 mg/kg) and saline were used for comparison. The five treatments were tested in a Latin square design in five cats. Treatments differed significantly in three-way analysis of variance, medetomidine inducing an increase in drowsiness with a corresponding decrease in both aroused waking and sleep determined by polygraphical criteria. The duration of effect was dose-dependent. The effect of 0.18 mg/kg medetomidine was comparable to 3.0 mg/kg of xylazine. The drugs also induced bradycardia.     

Contribution of α1-acid glycoprotein to species difference in lincosamides-plasma protein binding kinetics

Protein binding kinetics of lincomycin (LM) and clindamycin (CM) were studied using plasma, albumin and α₁-acid glycoprotein (AGP) derived from humans, dogs, cattle and sheep. Based on Rosenthal plots of LM and CM, drug-binding property in plasma presented specific and non-specific binding, except for LM in cattle and sheep and for CM in sheep, where only non-specific binding was demonstrated. Dissociation constant (Kd) and binding capacity (Bmax) for specific binding and proportionality constant (PC) for non-specific binding were as follows: Kd = 3.14 μmol/L, Bmax = 15.28 μmol/L, PC = 0.19 for humans; Kd = 3.84 μmol/L, Bmax = 6.55 μmol/L, PC = 0.14 for dogs; PC = 0.12 for cattle; PC = 0.16 for sheep in LM and Kd = 0.94 μmol/L, Bmax = 12.24 μmol/L, PC = 4.98 for humans; Kd = 1.48 μmol/L, Bmax = 9.52 μmol/L, PC = 2.91 for dogs; Kd = 1.22 μmol/L, Bmax = 4.45 μmol/L, PC = 2.40 for cattle; PC = 1.48 for sheep in CM. The specific binding for each species was different, showing more difference in Bmax compared with Kd. The non-specific binding of LM was similar among species whereas that of CM was different, implying species difference. The drug-binding property of AGP for each species was all specific binding and the Kd was comparable to that obtained from plasma, indicating that AGP is a major specific binder in plasma. The lack of detection of specific binding for LM in cattle and sheep and for CM in sheep plasma could be attributable to a higher Kd and lower plasma AGP concentration compared with other species. The drug-binding property of albumin was characterized as all non-specific, without a great difference among species. Except for CM in sheep, the lower PC in albumin solution compared with that in plasma suggested the presence of another non-specific binder in plasma, i.e. lipoprotein. From the simulation of drug-binding percentage to AGP concentrations, AGP could be a major contributor to drug-plasma protein binding in pathological states. The degree of AGP-drug binding for each species could vary according to the degree of increase of AGP concentrations from a healthy to a pathological state, inducing a decrease in the unbound fraction (fp): 6.1 fold for dogs, 4.6 fold for humans, 1.8 fold for sheep and 1.4 fold for cattle in LM; 5.8 fold for dogs, 5.7 fold for cattle, 4.0 fold for humans and 1.5 fold for sheep in CM. Therefore, the disposition and efficacy of lincosamides affected by fp can be modified differently by the change of fp attributable to the alteration of plasma AGP concentration in each species.     

Utilization of F1 information in estimating QTL effects in F2 crosses between outbred lines

Quantitative trait loci (QTL) analysis in designed experiments is investigated using a mixed model framework through the modification of segment mapping techniques. Allele effects are modelled in the F₁ generation allowing the estimation of additive substitution effects while accounting for QTL segregation within lines and differences in mean QTL effects between lines. The resulting approach is called F₁ segment mapping. Simulation is used to illustrate the method and its properties. F₁ segment mapping has advantages over F₂ segment mapping in the derivation of exact additive genetic covariances and in the computation time for variance component estimation.     

Agreement of SpO2, SaO2 and ScO2 in anesthetized cynomolgus monkeys (Macaca fascicularis)

Objective To assess the agreement between three measurements of arterial oxygen saturation (SpO₂, SaO₂ and ScO₂) in anesthetized cynomolgus monkeys. Study Design Prospective study. Animals Eleven mature, male cynomolgus monkeys (Macaca fasicularis). Methods Monkeys were anesthetized with intramuscular ketamine followed by intravenous propofol. The trachea of each was intubated and the lungs ventilated. Arterial oxygen saturation was measured with a Nonin 8500 V pulse oximeter, using a lingual clip on the cheek. Arterial blood samples were taken from an indwelling catheter. Inspired oxygen concentration was varied from 12 to 20%, and 88 paired arterial blood samples and saturation measurements were taken. Arterial oxygen saturation in the blood samples was measured using a cooximeter. The saturation was also calculated from the arterial oxygen tension using the Adair equation. The results were compared using Bland and Altman's method. Results The pulse oximeter readings were 2.7% higher than that of the cooximeter, with a limit of agreement of ?3.9 to 9.3%. The pulse oximeter readings were 1.8% higher than the calculated saturation, with a limit of agreement of ?6.5% to 10.1%. The cooximeter readings were 0.9% lower than the calculated saturation, with a limit of agreement of ?5.6% to 3.8%. Conclusions The agreement between SpO₂ and other measurements of arterial oxygen saturation in this study is typical for this technique. The bias and limits of agreement are consistent with reports in other species. Clinical relevance The Nonin 8500 V is a useful pulse oximeter for clinical use in primates.     

The effect of xylazine on plasma thromboxane B2 concentration in sheep

α₂-adrenoceptor agonist drugs can cause respiratory changes leading to a short period of hypoxaemia in sheep. It has been suggested that this is due to transient platelet aggregation and pulmonary microembolism. If platelet aggregation were to follow platelet activation in response to the administration of α₂ agonists, plasma thromboxane levels would be expected to rise. This study was carried out to measure plasma thromboxane B₂ concentrations before and after the intravenous administration of the α₂-agonist drug xylazine at a dose of 0.1 mg/kg. It was found that the plasma thromboxane concentration rose by 320% and, furthermore, the rise was prevented by the prior administration of atipamezole hydrochloride (0.125 mg/kg), an α₂-adrenoceptor antagonist.