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121.
Cardiovascular and respiratory functions were serially evaluated in ten healthy, fasting, spontaneously breathing, laterally recumbent adult horses during five hours of constant 1.06% alveolar halothane (equivalent to 1.2 times the minimum alveolar concentration for horses). Mean carotid arterial pressure was about 25% higher after one hour of constant-dose halothane than after 30 minutes of constant-dose (P less than 0.05), and remained increased throughout the study. Mean carotid arterial pressure peaked after 90 minutes, and was about 30% higher than at 30 minutes. Total peripheral vascular resistance initially increased (20% at one hour), then gradually returned to the 0.5-hour value over the next four hours. Cardiac output progressively increased with time (P less than 0.05; 20% by two hours; nearly 40% by five hours) because of an increase in stroke volume. An increase (P less than 0.05) in mixed venous PO2 accompanied the increase in cardiac output. Heart rate did not change significantly (P greater than 0.05). Some measures of ventilation changed significantly with time (P less than 0.05). After four and five hours of constant alveolar halothane, the PaCO2, inspired gas flow, and ratio of inspired vs expired gas flow were significantly higher than the 0.5-hour values. Inspiratory time significantly decreased, beginning at three hours. All horses recovered from anesthesia and recumbency without complications.  相似文献   
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Observations of erratic anthelmintic activity of fenbendazole against known standardised thiabendazole-resistant strains of Haemonchus contortus and Trichostrongylus colubriformis in sheep were investigated. Fenbendazole at a dose rate of 10 mg/kg body weight was administered by oral, intra-ruminal or intra-abomasal routes, and was most effective against both resistant strains following intra-ruminal administration. In addition thiabendazole, oxibendazole, fenbendazole, parbendazole and mebendazole plus two unrelated compounds, levamisole and morantel tartrate, were used at one and a half times their suggested or recommended therapeutic dose rate against thiabendazole-resistant strains of H contortus and T colubriformis in sheep; each drug being administered by the intra-ruminal or intra-abomasal routes. Fenbendazole was more effective against both strains following intra-ruminal administration. Parbendazole was more effective against the resistant strain of T colubriformis following intra-ruminal administration. At the dose rate chosen for the other benzimidazoles used against these resistant strains, there was no difference in anthelmintic efficacy due to route of administration. Levamisole was highly effective against both resistant strains, irrespective of the route of administration. In the groups treated with morantel tartrate, the results obtained were difficult to interpret due to mortalities and a highly variable response in the surviving sheep. Fenbendazole, thiabendazole and mebendazole when used at their suggested or recommended therapeutic dose rate in sheep, were highly effective against known thiabendazole-susceptible strains of H contortus and T colubriformis following both intra-ruminal or intra-abomasal administration.  相似文献   
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Sheep infected with benzimidazole resistant strains of Haemonchus contortus and Trichostrongylus colubriformis were used to compare the anthelmintic efficacy of fenbendazole given as a single dose or administered in a divided dose regime over five days. Statistical analysis showed no significant difference between the two methods of administration for H contortus. On the other hand, divided dose fenbendazole was significantly less effective than single doses against adult T colubriformis at dose rates of 5 and 7.5 mg/kg. In the case of H contortus a highly significant correlation coefficient between post treatment egg counts and worm counts (r = 0.789) was obtained. This suggests that reduction in faecal egg output following drug treatment would provide a useful field indication of anthelmintic performance of fenbendazole (and possibly related compounds) against benzimidazole resistant strains of this parasite.  相似文献   
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Long-term studies of megestrol acetate and chlormadinone acetate in 100 female dogs are in progress. Doses of zero, one, 10 and 25 times the expected human dose of megestrol acetate and 25 times the expected human dose of chlormadinone acetate (on a milligram per kilogram body weight basis) are being given daily. During the first 4 years, eight dogs from each of the five groups were killed. The principal gross findings included enlarged uteri with mucoid material in the lumina, mammary development in dogs given middle and high doses of megestrol acetate and chlormadinone acetate, and thickened gallbladder walls in dogs given high doses of each. Histologic evaluation showed inhibition of ovulation for progestogen-treated dogs and suppression of ovarian follicular development with the high doses. Cystic endometrial hyperplasia was slight in the low-dose dogs and moderate to severe in most of the high-dose dogs; a few also had ulcerative endometritis and pyometra. The mammary glands of dogs given the middle and high doses produced lobules, acini, and secretion exceeding natural metestrus. Slight to marked cystic mucinous hyperplasia occurred in the gallbladders of most dogs given the high doses. Tow high-dose megestrol dogs had clinical signs and microscopic pancreatic, renal, and ocular changes indicative of diabetes mellitus.  相似文献   
127.
Radiolabelled fenbendazole (FBZ) and thiabendazole (TBZ) were administered into the rumen or abomassum of sheep previously infected with benzimidazole-susceptible or resistant Haemonchus contortus and Trichostrongylus colubriformis. Plasma radioactivity was determined for 12 hours following anthelmintic administration and at the end of this time the incorporation of radiolabel into the parasites was determined.Incorporation of radiolabel from FBZ was significantly greater in susceptible than in resistant worms. However, with TBZ there was no significant difference. There were no significant differences in the incorporation between H. contortus and T. colubriformis. Incorporation of TBZ was greater than FBZ in the worms except after ruminal administration to sheep showing clinical parasitism resulting from infection with benzimidazole- susceptible worms. TBZ was administered at five times the dose rate as FBZ, and thus a lower proportion of the administered TBZ than FBZ was incorporated.With the exception of incorporation of TBZ by resistant worms, the route of administration had a major effect on incorporation by the parasites and on plasma levels. Based on plasma levels, TBZ appeared to be rapidly absorbed from both the rumen and abomasum, whereas FBZ was less readily absorbed from the rumen with the rate of absorption being markedly greater if FBZ was administered directly into the abomasum. The findings suggest that the rumen may act as a reservoir of FBZ prolonging the period of high anthelmintic concentration in the host. This may contribute to the high efficacy of this anthelmintic.  相似文献   
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