1,721,002 research outputs found
Determination of dexamethasone in milk of dairy cows by immuno-enzymatic assay
No full textEight lactating cows received 3 im injections at 24 h intervals of a commercial formulation containing dexamethasone. Each treatment provided 25 μg/kg bw/d of dexamethasone acetate, equivalent to 22.6 mg of dexamethasone. Milk samples were obtained before treatment (5 d), during the treatment period, and for up to 22 milking after the last injection. The concentrations of dexamethasone in the milk samples were determined by a commercial competitive immunoenzymatic assay for corticosteroids (detection limit 0.15 ng dexamethasone/ml). The conventional therapeutic dose of dexamethasone acetate caused milk drug concentrations exceeding the tolerated maximum residue limit (0.3 mg/kg). A withdrawal time of 3-3.5 d for dexamethasone in milk provided sufficient protection for consumer health. The commercial enzyme immunoassay kit employed in this study was sufficiently sensitive, easy to use, and appropriate to monitor the use of dexamethasone in lactating animals
Identificazione dei ß-recettori coinvolti nella lipolisi nel tessuto adiposo sottocutaneo di vitello
No full textAdrenergic regulation of vascular smooth muscle tone in calf digital artery
No full textRadioligand binding studies and functional assays on isolated smooth muscle preparations were performed in order to obtain a biochemical and functional characterization of the beta-adrenoceptor (beta-AR) subtypes involved in regulation of the smooth muscle relaxation of the calf's common digital artery. The results indicate that the common digital artery possesses two beta-AR populations (40% beta(1) and 60% beta(2)) and the beta(2)-subtype appears to predominate as far as function is concerned. Only the beta(2)-AR agonists clenbuterol and fenoterol caused dose-related relaxant effects, antagonized by propranolol, when tested in preparations precontracted both with PGF(2alpha) (1.4 x 10(-5) m) and noradrenaline (1.2 x 10(-6) m). In noradrenaline precontracted preparations the beta(1)-AR selective agonists dobutamine and xamoterol caused vasodilation which was not antagonized by (+/-)propranolol. While the functional relaxant effects of dobutamine may be attributed to its potent competitive alpha-AR blocking activity, further investigations are required to explain the effect of xamoterol. The vasodilator effect of (+/-)isoproterenol was irregular. The recorded contractile effects, mainly at dosages greater than 10(-6) m, suggest the loss of drug selectivity for beta-AR and alpha-AR activation. Indirect evidence indicates that the alpha-adrenoceptor (alpha-AR) population in this tissue which produces a strong contraction is functionally dominant over the beta-AR, suggesting limited therapeutic benefit for beta-AR drugs to control blood flow disorders in the calf's distal limb
Recettori adrenergici coinvolti nell’effetto vasodilatante dell’isossisuprina sull’arteria digitale comuna di cavallo.
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NK2 receptor involvement in tachykinin-induced contraction of equine ileum circular smooth muscle
No full textComparative pharmacokinetics of ampicillin-sulbactam combination in calves and sheep
No full textThe pharmacokinetics of ampicillin and sulbactam administered in combination were studied in calves and sheep. The animals were administered an aqueous solution of ampicillin/sulbactam (2:1, w/w) intravenously and intramuscularly at doses of 13.2 and 6.6 mg.kg-1, respectively. A microbiological method was used to detect ampicillin, and HPLC was used to detect sulbactam in serum. Following intravenous (i.v.) administration, the distribution phases were rapid and similar (about 15 min) for both drugs in both species, whereas sulbactam in calves and ampicillin in sheep showed a faster elimination rate. After intramuscular (i.m.) administration both drugs showed peak concentrations higher in calves than in sheep; the peak time of sulbactam was shorter in calves than in sheep. No other significant differences in the pharmacokinetics of the combination were observed between the species after i.m. injection. The mean residence and absorption times, calculated by non-compartmental analysis, for both calves and sheep suggested that the differences in ampicillin and sulbactam pharmacokinetics could be attributable to the different molecular structures
Ruolo dei recettori tachichininici NK2 nella contrazione della muscolatura liscia circolare dell’ileo di cavallo
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