Three phase elimination of oxytetracycline in veal calves; the presence of an extended terminal elimination phase

The pharmacokinetics of oxytetracycline were studied after both intravenous (i.v.) and intramuscular (i.m.) administration to a group of five veal calves. Blood samples were taken frequently during the terminal elimination phase in order to calculate a reliable elimination rate constant. Because of the low limit of quantification of the method of analysis used, oxytetracycline plasma concentrations could be monitored over a 12-day period of time.
After the intravenous administration of oxytetracycline, data were fitted according a three-compartment model. After i.m. administration, plasma-concentration-time curves could best be described by a two-compartment model. It was demonstrated that a very slow terminal elimination phase was present both after i.v. and i.m. administration with a half-life of approximately 95 h. The data show that this phase cannot be explained by slow absorption from the injection site and that release of oxytetracycline incorporated into bone is not a likely explanation.     

RADIONUCLIDE THYROID IMAGING IN 135 CATS WITH HYPERTHYROIDISM*

Thyroid scanning was performed in 135 hyperthyroid cats and 13 normal cats with technetium-99m as pertechnetate (^99mTcO₄) or with radioactive iodine (¹³¹I). Of the hyperthyroid cats, enlargement and increased radionuclide accumulation were found in one thyroid lobe in 38 (27%) and in both lobes in 97 (73%). In two hyperthyroid cats with thyroid carcinoma, extension of tumor into the thoracic cavity was detected. In normal and hyperthyroid cats the radionuclide images produced with ^99mTcO₄ and ¹³¹I were similar; however, the quality of the ^99mTcO₄ scans was usually better than that of the ¹³¹I scans.     

Colour Dilution Alopecia (CDA) in Ten yorkshire Terriers

Abstract— Clinical laboratory investigations as well as light, electron microscopic and X-ray microanalytical studies on skin biopsy specimens and hair from 10 yorkshire terriers suffering from Colour Dilution Alopecia (CDA) were carried out. Biochemical data detected a marked melanin reduction in hair from affected areas. Histologically, melanin clumps were mainly evident in the epidermal basal layer cells as well as inside the bulb and hair shaft. Ultrastructurally, basal keratinocytes were overloaded by fully melanized melanosomes disrupting cytoplasmic structures. Intracytoplasmic and free melanosomes were also evident in all cutaneous layers. Scanning electron microscopy showed holes and bulges scattered in the hair shaft. X-Ray microanalysis demonstrated silicate particles in the more superficial cuticular holes and calcium in the deeper fractured layers. Based on these observations a new hypothesis on the pathogenetic mechanism(s) of alopecia is proposed. Résumé— Diverses investigations, microscopie optique, microscopie électronique, études microanalytiques aux rayons X ont été réalisées sur des biopsies cutanées et des poils provenant de dix yorkshire Terriers présentant une Alopécie des Robes Diluées. Les examens biochemiques montrent une diminution nette de la mélanine dans les poils provenant des régions malades. Des aggrégate de mélanine sont observés dans les cellules de l'assise basale épidermique ainsi qu'à l'intérieur des bulbes pileux et des tiges pilaires. Sur le plan ultrastructural, les kératinocytes basaux montrent une surcharge en mélanosomes détruisant ainsi les structures cytoplasmiques. Des mélanosomes libres et intra-cytoplasmiques sont également observés dans toutes les couches épidermiques. La microscopie électronique à balayage montrent des trous et des bosses dispersés dans la gaine folliculaine. Des analyses en rayons X démontrent la présence de particules de silicate dans les trous les plus superficiels de la cuticule et du calcium dans les couches plus profondes. A partir de ces observations, une nouvelle hypothèse sur la pathogénie de dette alopécie est proposée. [Roperto F., Cerundolo, R., Restucci, B., Vincensi, M. R., De Caprariis, D., De Vico, G., Maiolino, P. Colour dilution alopecia (CDA) in ten yorkshire Terriers (Alopécie des robes diluées (ARD) chez dix yorkshire Terriers). Resumen— Se llevaron a cabo análisis clinicos asi como estudios microanaliticos con rayos X y microscopia electrónica sobre biopsias cutáneas tomadas a diez yorkshire Terriers que padecian de Alopecia de Color Diluido (CDA). Los estudios bioquimicos detectaron una fuerte reducción en melanina en el pelo de las zonas afectadas. A nivel histológico, los agregados de melanina se localizaban principalmente en la capa basal de la epidermis asi como en el bulbo piloso y en en pelo. A nivel ultraestructural, los queratinocitos basales estaban sobrecargados de melanosomas totalmente melanizados, alterando su estructura citoplasmática. También se identificaron melanosomas en forma libre o a nivel intracitoplasmático en todas las capas cutáneas. La microscopia electrónica de escáner mostró cavidades y prominencias diseminadas a lo largo del pelo. Mediante microanalisis por rayos X se detectaron partículas de silicato en las cavidades cuticulares más superficiales y calcio en las capas més profundas. Teniendo en cuenta estos hallazgos, se propone una nueva hipótesis sobre el/los mecanismo/s patogénico/s de la alopecia. [Roperto F., Cerundolo, R., Restucci, B., Vincensi, M. R., De Caprariis, D., De Vico, G., Maiolino, P. Colour dilution alopecia (CDA) in ten yorkshire Terriers (Alopecia de color diluido (CDA) en diez yorkshire Terriers).     

Comparative study of chloramphenicol absorption in calves after oral, intra-ruminal and intra-abomasal administration

The mechanisms responsible for the rapid decline of chloramphenicol plasma levels after oral administration in young calves during their first weeks of life were investigated. Chloramphenicol was administered by stomach tube, to four 2 week old calves on three consecutive days at a dose of 50 mg/kg. The plasma levels increased daily to a peak value on the third day. The minimum therapeutic concentration of 5 μg/ml, however, was barely obtained. Simultaneous estimation of the ruminal contents showed a parallel increase in chloramphenicol concentration. Thus it can be assumed that there is an inefficient absorption of chloramphenicol from the forestomachs of young calves. Chloramphenicol was not metabolized by the ruminal contents until the calves were 9 weeks old. Finally chloramphenicol was administered to 7 week old calves by the intra-abomasal route, intraruminal route and by mouth. Only with the intra-abomasal method could a therapeutically effective level be reached. This indicates that the rapid decline of chloramphenicol plasma levels in calves during their first weeks of life could be attributed to the delayed reticulo-rumen emptying and to inefficient absorption from the forestomachs.     

Bioavailability of three brands of digoxin tablets in dogs

As information on the comparative bioavailability of digoxin tablets in dogs is scarce, three brands of digoxin tablets, commercially available in Belgium, were compared in 6 healthy dogs in a cross-over randomized design. Each dog received 1 mg digoxin on four occasions (once intravenously and 3 times orally). The mean areas under the curve relative to the intravenous value were 80, 71 and 65%. For the 3 oral preparations peak plasma concentrations were reached within 1 hour after dosing and often within 30 minutes. The mean peak concentrations were 11.0, 10.0 and 8.1 ng/ml. The times for 50% dissolution were 4.5, 7.5 and 25 minutes. Although differences between brands were only significant for the dissolution rate, the same ranking order was present for all parameters. It is therefore concluded that it may be advisable not to switch a digitalized dog from one brand to another.     

Digoxin-quinidine interaction in the dog

In seven healthy dogs, digoxin was given as an oral loading dose (0.05 mg/kg/day) on the first day, followed by an oral maintenance dose (0.02 mg/kg/day) during the next 14 days. On the sixth day of digoxin treatment, oral quinidine (200 mg b.i.d.) was added until the tenth day. Plasma concentrations of digoxin and quinidine were measured; in three of the seven dogs ECG and physical signs of digitalis toxicity were evaluated. The average steady state plasma concentration of digoxin increased significantly ( P <0.01) during quinidine administration (from 1.4 to 2.3 ng/ml). On the days that digoxin was administered without quinidine, none of the dogs vomited nor was anorectic; the PQ-interval increased significantly ( P <0.01) between 0.01 and 0.03 s. When quinidine was added, vomiting and anorexia occurred but no further increases in die PQ-interval were seen.     

Angiographic features in a case of extensive arterial thrombosis in a dog

This report documents the diagnosis of an extensive thrombosis of the caudal portion of the aorta in a Dalmatian dog. By angiography a detailed study was made of the extent and localization of the thrombus.     

Fumigation toxicity of volatile natural and synthetic cyanohydrins to stored-product pests and activity as soil fumigants

Insecticidal fumigation toxicity of natural and synthetic cyanohydrins was evaluated with four stored-product pests: the lesser grain borer, Rhyzopertha dominica (F), the red flour beetle, Tribolium castaneum Herbst, the saw-toothed grain beetle Oryzaephilus surinamensis L, the maize weevil, Sitophilus zeamais (Motsch) and the house fly, Musca domestica L. The fumigation LC50 values were calculated by probit analysis. For house flies, all but one of the cyanohydrins tested were more potent than 1,3-dichloropropene (Telone). Three were as efficacious as chloropicrin. For the lesser grain borer, all cyanohydrins tested were more insecticidal than dichloropropene, and all but one were more potent than chloropicrin. Four were as insecticidal as dichlorvos. The acetate of 1-cyano-1-hydroxy-2-propene (CHP-ace) was also tested in soil for antifungal and antibacterial activity, and inhibition of weed seed germination. CHP-ace reduced the total soil bacterial and fungal counts significantly, and was effective in inhibiting the germination of weed seeds in soil, indicating a broad spectrum of activity as a soil fumigant.