Morphine, but not methadone, inhibits microsomal prostaglandin E synthase-1 and prostaglandin-endoperoxide synthase 2 in lipopolysaccharide-stimulated horse synoviocytes.

Osteoarthritis (OA) is one of the main locomotor disorders in horses. Although nonsteroidal anti-inflammatory drugs are the first-line treatment for OA, opioids could also be used. In previous studies, opioids showed promising anti-inflammatory and analgesic effects. In this study, we aimed to investigate the effects of two opioids (morphine and methadone) against inflammation in lipopolysaccharide (LPS)-stimulated synoviocytes by analyzing microsomal prostaglandin E synthase-1 (mPGES-1) and prostaglandin-endoperoxide synthase 2 (PTGS2) expression. Synoviocytes were obtained from the joints at the distal limbs of dead animals. The cytotoxic effects of LPS, morphine, and methadone were investigated by using a cell viability assay with crystal violet dye. Synoviocytes were treated with LPS, LPS plus morphine, or LPS plus methadone for 3, 6, and 12 h, and mPGES-1 and PTGS2 expression was measured using real-time polymerase chain reaction. LPS, and morphine did not affect the viability of synoviocytes, even at high concentrations. LPS treatment increased mPGES-1 and PTGS2 expression, whereas morphine inhibited the increase in mPGES-1 and PTGS2 expression in LPS-stimulated synoviocytes. Methadone did not inhibit mPGES-1 or PTGS2 expression. These results suggest that morphine may exhibit anti-inflammatory effect; therefore, it might be beneficial for the treatment of OA.

Multirresistência antimicrobiana em cepas de Escherichia coli isoladas de cadelas com piometra / Antimicrobial multi-resistance of Escherichia coli strains isolated from bitches with pyometra

The antimicrobial sensibility of Escherichia coli strains isolated from the uterine content of bitches was evaluated. Fifteen E. coli strains were tested in relation to their susceptibility to different antimicrobials. The results demonstrated 100 percent of resistance to all tested drugs, being a quite conflicting finding compared to other works, which observed variable resistance of those bacteria to different antimicrobials but not the same multi-resistance pattern. The detection of those multi-resistance strains configures a problem, with important implications on the antimicrobial therapy. Therefore, additional investigations for a best characterization and extension of this problem are needed.

Uso de atracúrio para o bloqueio da musculatura extrínseca do bulbo ocular em cães submetidos à anestesia inalatória sob ventilação espontânea / Blocking of ocular bulb extrinsic musculature by atracurium in inhalant anesthetized dogs under spontaneous breathing

Comparou-se o bloqueio da musculatura extrínseca do bulbo ocular com três doses de atracúrio em cães submetidos à anestesia inalatória sob ventilação espontânea. Em estudo cego, foram utilizados seis cães, pré-medicados com 0,1mg/kg de acepromazina intravenoso (IV), anestesiados com 5mg/kg de propofol, entubados e mantidos sob anestesia inalatória com 1,5 por cento de isofluorano e submetidos a quatro tratamentos: não tratados (controle), tratados com 25µg/kg (G25) de atracúrio IV, com 50µg/kg (G50) de atracúrio IV e com 75µg/kg (G75) de atracúrio IV. Mensuraram-se: pressão parcial de CO2 expirado (ETCO2), freqüência cardíaca (FC), freqüência respiratória (ƒ), saturação arterial de oxiemoglobina (SatO2) e tempo de centralização do bulbo ocular. Nos grupos tratados com atracúrio, o ETCO2 aumentou aos 5min, e permaneceu aumentado até 10min em G50 e até 20min em G75, sendo este o único tratamento cuja concentração de ETCO2 apresentou-se acima de 50mmHg. Não houve reinalação de CO2 em nenhum grupo. Em G75, observou-se aumento crescente da ƒ até os 40min e considerável bradicardia após 10min; ambos retornaram aos valores basais após esse período. A centralização do bulbo ocular foi crescente de acordo com a dose: G25, 38±13min; G50, 65±16,4 min; G75, 78±27min, mas não houve diferença estatística entre G50 e G75. Conclui-se que G50 apresentou bloqueio satisfatório sem promover intensa e prolongada hipercapnia nos animais.

The ocular bulb extrinsic musculature blocking by the administration of three atracurium doses in isoflurane anesthetized dogs under spontaneous breathing was compared. In a blind study, six dogs were premedicated with 0.1mg/kg of acepromazine, anesthetized with 5mg/kg of propofol, intubated and maintained in inhalation anesthesia with 1.5 percent of isoflurane in 100 percent of oxygen. Afterwards, they were submitted to four treatments (control, G25:25µg/kg of atracurium IV, G50:50µg/kg IV and G75:75µg/kg IV). Heart rate (HR), breathing rate (BR), CO2 extrated (ETCO2), arterial saturation of oxyhaemoglobin (SatO2) and ocular bulb centralization time were measured. ETCO2 in all animals were increased at 5min keeping high until 10min in G50 and until 20min in G75 dogs; this was the unique animal group that showed results above 50mmHg of ETCO2. CO2 was not reinhaled by any animal. It was observed an increase in BR until 40min and a considerable bradycardia after 10min in G75 animals; both returned to basal levels thereon. The centralization time was crescent, according the doses (G25: 38±13min; G50: 65±16.4min; G75: 78±27min), but no difference between G50 and G75. It was showed that G50 dogs took a content ocular centralization without intense and prolonged hypercapnia.

Ação antiarrítmica do isofluorano em cães submetidos à arritmias ventriculares induzidas por cloreto de bário / Antiarrhytmic action of isoflurane in dogs submitted to ventricular arrhytmia by barium chloride

Avaliou-se a ação antiarrítmica do isofluorano em cães submetidos a arritmias ventriculares pelo uso de cloreto de bário, utilizando-se de seis cães, machos e fêmeas, que receberam uma dose de 3mg/kg de peso IV de cloreto de bário a 2,5 por cento (G1). O mesmo protocolo foi repetido, nos mesmos animais, sob anestesia geral com isofluorano (G2). Usou-se a eletrocardiografia computadorizada para avaliar o ritmo cardíaco, a duração e/ou amplitude das ondas e os intervalos eletrocardiográficos. Não se verificou alteração no ritmo cardíaco em G2, diferente de G1, que apresentou freqüentes arritmias ventriculares na forma de bigeminismo e taquicardia ventricular multifocal. Houve diferença significativa entre os grupos em relação à freqüência cardíaca nos minutos iniciais de observação, quando ocorreu aumento na freqüência cardíaca em G1. A utilização do isofluorano conferiu ação antiarrítmica em cães com arritmias induzidas pelo cloreto de bário, reforçando suas indicações a pacientes com risco considerável de desenvolvimento de arritmias ventriculares.

Antiarrhythmic action of isoflurane was evaluated in dogs submitted a ventricular arrhythmias by the use of barium chloride, using six dogs, males and females, that received 3mg/kgLW intravenous dose of barium chloride 2.5 percent solution (G1). The same protocol was repeated on the same animals, after general anesthesia with isoflurane (G2). Computerized electrocardiography was used to evaluate the cardiac rhythm, waves duration and/or amplitude and electrocardiographic intervals. No alteration on the cardiac rhythm in G2 animals was observed, different from G1 animals, that showed frequent ventricular arrhythmias in bigeminism form, as well as mutifocal ventricular tachycardia. Differences between groups in relation of cardiac frequency in the observed initial minutes were showed, occurring an increase in cardiac frequency in G1 animals. The utilization of isoflurane conferred antiarrhythmic action in dogs with arrhythmias barium chloride induced, reforcing its indication for patients with considerable risk of ventricular arrhythmias development.

Estudo da ação inflamatória aguda do tiopental intraperitoneal em ratos / Acute inflammatory action of tiopental intraperitoneal in rats

Determinou-se a ação inflamatória aguda do tiopental intraperitoneal (IP) utilizando-se 72 ratos, divididos em grupo-tratado (40mg/kg de tiopental a 2,5 por cento IP) e grupo-controle (0,25ml de solução fisiológica IP). Para determinar o processo inflamatório, colheu-se o lavado peritoneal às 2, 6, 12, 24 e 48h após a inoculação. Os animais foram anestesiados com isoflurano e submetidos à eutanásia por secção dos vasos cervicais. Administraram-se 5ml de solução fisiológica heparinizada por via IP e, após homogeneização, divulsionou-se o peritôneo e colheu-se a amostra. Determinaram-se a dosagem de proteínas plasmáticas (PP), a contagem global (CGL) e a diferencial (CDL) de leucócitos. Não foi observada diferença na PP entre os grupos em nenhum momento exceto às 2h. Entre os momentos, a dosagem foi superior às 6 e 12h nos dois grupos. Não houve diferença entre os grupos para a CGL. Entre os momentos, a CGL diferiu dos demais às 6h em ambos os grupos. Verificou-se o mesmo perfil para a CDL entre os grupos exceto para os eosinófilos às 6h. Entre os momentos, os valores foram diferentes em relação aos neutrófilos em ambos os grupos, às 6 e 12h. Observou-se reação inflamatória aguda no processo provavelmente desencadeada pela ação mecânica da injeção. A eosinofilia observada no grupo-tratado após 6h sugere uma certa ação irritante do tiopental.

Study of caffeine in urine and saliva of horses subjected to urinary acidification.

The study of caffeine in racing horses has been of growing concern in veterinary sports medicine since the Association of Racing Commissioners International (ARCI) stated that it has no valid therapeutic use in racehorses. We examined the kinetic alterations in the urinary excretion and salivary secretion of caffeine in seven horses subjected to urinary acidification using ascorbic acid because this procedure can simulate the acidosis that follows anaerobic exercise. They participated in two treatment groups: the control group (SG) received 500 ml of saline and then 2.0 mg kg(-1) caffeine i.v. 30 min later; and the acidi fi ed group (AG) was subjected to urinary acidification with ascorbic acid at a dose of 0.5 g kg(-1) i.v. and then 2.0 mg kg(-1) caffeine i.v. 30 min later. Samples were collected 30 min before caffeine administration, immediately before caffeine administration (time zero) and at 0.25, 0.5, 1, 2, 4, 6, 8, 12, 24, 48 and 72 h afterwards. The samples were assayed by gas chromatography. The mean urinary pH for SG was 8.2, but for AG it was as low as 5.9 at 4 h, extending acidosis for up to 8 h. The kinetic curves for the two groups were similar for urinary excretion and salivary secretion. Differences occurred only in peak excretion and peak secretion in SG obtained at 1 h and 30 min, respectively, and in AG at 2 h and 1 h, respectively. This could be explained, in part, to the diuresis in AG compared with SG, resulting in less concentrated urine in the former group. The large difference between the pKa of caffeine and the pH of the medium may be responsible for the similar pharmacokinetics observed for the two groups.

Effects of caffeine on locomotor activity of horses: determination of the no-effect threshold.

Caffeine is the legal stimulant consumed most extensively by the human world population and may be found eventually in the urine and/or blood of race horses. The fact that caffeine is in foods led us to determine the highest no-effect dose (HNED) of caffeine on the spontaneous locomotor activity of horses and then to quantify this substance in urine until it disappeared. We built two behavioural stalls equipped with juxtaposed photoelectric sensors that emit infrared beams that divide the stall into nine sectors in a 'tic-tac-toe' fashion. Each time a beam was interrupted by a leg of the horse, a pulse was generated; the pulses were counted at 5-min intervals and stored by a microcomputer. Environmental effects were minimized by installing exhaust fans producing white noise that obscured outside sounds. One-way observation windows prevented the animals from seeing outside. The sensors were turned on 45 min before drug administration (saline control or caffeine). The animals were observed for up to 8 h after i.v. administration of 2.0, 2.5, 3.0 or 5.0 mg caffeine kg(-1). The HNED of caffeine for stimulation of the spontaneous locomotor activity of horses was 2.0 mg kg(-1). The quantification of caffeine in urine and plasma samples was done by gradient HPLC with UV detection. The no-effect threshold should not be greater than 2.0 microg caffeine ml(-1) plasma or 5.0 microg caffeine ml(-1) urine.

Comparison of the quantification of caffeine in human plasma by gas chromatography and ELISA

In the present study we evaluated the precision of the ELISA method to quantify caffeine in human plasma and compared the results with those obtained by gas chromatography. A total of 58 samples were analyzed by gas chromatography using a nitrogen-phosphorus detector and routine techniques. For the ELISA test, the samples were diluted to obtain a concentration corresponding to 50 per cent of the absorbance of the standard curve. To determine whether the proximity between the I50 of the standard curve and that of the sample would bring about a more precise result, the samples were divided into three blocks according to the criterion of difference, in modulus, of the I50 of the standard curve and of the I50 of the sample. The samples were classified into three groups. The first was composed of 20 samples with I50 up to 1.5 ng/ml, the second consisted of 21 samples with I50 ranging from 1.51 to 3 ng/ml, and the third of 17 samples with I50 ranging from 3.01 to 13 ng/ml. The determination coefficient (R² = 0.999) showed that the data obtained by gas chromatography represented a reliable basis. The results obtained by ELISA were also reliable, with an estimated Pearson correlation coefficient of 0.82 between the two methods. This coefficient for the different groups (0.88, 0.79 and 0.49 for groups 1, 2 and 3, respectively) showed greater reliability for the test with dilutions closer to I50.

Comparison of the quantification of caffeine in human plasma by gas chromatography and ELISA.

In the present study we evaluated the precision of the ELISA method to quantify caffeine in human plasma and compared the results with those obtained by gas chromatography. A total of 58 samples were analyzed by gas chromatography using a nitrogen-phosphorus detector and routine techniques. For the ELISA test, the samples were diluted to obtain a concentration corresponding to 50% of the absorbance of the standard curve. To determine whether the proximity between the I50 of the standard curve and that of the sample would bring about a more precise result, the samples were divided into three blocks according to the criterion of difference, in modulus, of the I50 of the standard curve and of the I50 of the sample. The samples were classified into three groups. The first was composed of 20 samples with I50 up to 1.5 ng/ml, the second consisted of 21 samples with I50 ranging from 1.51 to 3 ng/ml, and the third of 17 samples with I50 ranging from 3.01 to 13 ng/ml. The determination coefficient (R2 = 0.999) showed that the data obtained by gas chromatography represented a reliable basis. The results obtained by ELISA were also reliable, with an estimated Pearson correlation coefficient of 0.82 between the two methods. This coefficient for the different groups (0.88, 0.79 and 0.49 for groups 1, 2 and 3, respectively) showed greater reliability for the test with dilutions closer to I50.

Efeitos do amitraz e da xilazina sobre algumas características fisiológicas de cavalos / Effect of amitraz and xylazine on some physiological variables of horses

Avaliaram-se os efeitos das injeçöes intravenosa (iv) de amitraz (0,1mg/kg) e xilazina (1mg/kg), em cavalos, sobre a atividade cardíaca, freqüência respiratória, atividade motora intestinal, temperatura retal, sudorese e freqüência de apreensäo de alimentos. O amitraz causou diminuiçäo significativa da atividade cardíaca, da freqüência respiratória e da movimentaçäo intestinal, mas esses efeitos näo foram täo pronunciados quanto os causados pela xilazina. O amitraz causou, também, relaxamento significativo da musculatura lisa retal, e um aparente aumento da sudorese e da freqüência de cavalos flagrados mastigando feno. A temperatura retal näo foi influenciada pelo amitraz. Os resultados indicam que o amitraz, na dose utilizada, näo causou efeitos colaterais severos em cavalos

Characterization of the antinociceptive and sedative effect of amitraz in horses.

Amitraz, an acaricide used to control ectoparasites in animals has a complex pharmacological activity, including alpha2-adrenergic agonist action. The purpose of this research was to investigate the possible antinociceptive and/or sedative effect of amitraz in horses. The sedative effect of the intravenous (i.v.) injection of dimethylformamide (DMF, 5 mL, control) or amitraz (0.05, 0.10, 0.15 mg/kg), was investigated on the head ptosis test. The participation of alpha2-adrenergic receptors in the sedative effect provoked by amitraz was studied by dosing yohimbine (0.12 mg/kg, i.v.). To measure the antinociception, xylazine hydrochloride (1 mg/kg, i.v., positive control) and the same doses of amitraz and DMF were used. A focused radiant light/heat directed onto the fetlock and withers of a horse were used as a noxious stimulus to measure the hoof withdrawal reflex latency (HWRL) and the skin twitch reflex latency (STRL). The three doses of amitraz used (0.05, 0.10 and 0.15 mg/kg) provoked a dose-dependent relaxation of the cervical muscles. The experiments with amitraz and xylazine on the HWRL showed that after i.v. administration of all doses of amitraz there was a significant increase of HWRL up to 150 min after the injections. Additionally, there was a significant difference between control (DMF) and positive control (xylazine) values up to 30 min after drug injection. On the other hand, the experiments on the STRL show that after administration of amitraz at the dose of 0.15 mg/kg, a significant increase in STRL was observed when compared with the control group. This effect lasted up to 120 min after injection. However, no significant antinociceptive effect was observed with the 0.05 and 0.10 mg/kg doses of amitraz or at the 1.0 mg/kg dose of xylazine.