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1.
An absorbed enzyme immunoassay (EIA) test for Johne's disease in cattle was developed in which absorption of cross-reacting antibodies occurred as a rapid reaction in solution rather than overnight with whole organisms and a subsequent centrifugation step. Total test time was reduced to less than 2 h with a minimum of manipulations. The test was evaluated in cattle herds from Johne's disease-endemic and Johne's disease-free regions of Australia. Specificity was 99.8%. Calculations of sensitivity were affected by the history of the herd under test. However, the EIA detected in excess of 80% of animals before onset of clinical disease and 65% of faecal shedders were EIA positive on, or before, first detection of Mycobacterium paratuberculosis in their faeces. The test should aid epidemiological studies and be a useful tool in the management and control of Johne's disease.  相似文献   
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Winter wheat cultivars of varying height were intercrossed and the progeny were studied in field trials to determine whether the greater resistance to S. nodorum of the taller cultivars was fortuitous or the result of genetic association.
Variation in height, in resistance and in time of ear emergence was continuous, providing no evidence of the existence of individual genes of major effect. In F2 and backcross generations, the inheritance of all three characters was principally additive. Among random F3 and F4 families there was a clear tendency for tall straw and resistance to segregate together, proving that the association between these characters was not fortuitous and providing evidence of linkage or pleiotropy in their genetic control. There was a similar though less consistent tendency for late ear emergence and resistance to segregate together. There was substantial residual variation in resistance, not associated with variation in height or time of ear emergence, but its heritability was difficult to prove by comparisons between F3 and F4 generations, perhaps partly because of genotype x environment interaction.
It is proposed that resistance is under polygenic control and pleiotropy rather than linkage is suggested as the explanation of its genetic association with height and with time of ear emergence. The existence of genes affecting resistance independently of height and time of ear emergence is also inferred. It is suggested that they permit the breeding of resistant cultivars of any height, though with increasing difficulty as height is reduced.  相似文献   
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The clinical, radiological and histopathological features of 30 thyroid tumours in the dog are described. Ten tumours were considered suitable for surgical removal and in a follow-up period of between 14 and 36 months five dogs were still alive.  相似文献   
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Nine male dogs (10.3–13.5 kg body weight) were randomly assigned to three groups of three dogs each and administered ceftiofur sodium subcutaneously as a single dose of 0.22, 2.2, or 4.4 mg ceftiofur free acid equivalents/kg body weight. Plasma and urine samples were collected serially for 72 h and assayed for ceftiofur and metabolites (derivatized to desfuroylceftiofur acetamide) using high-performance liquid chromatography. Urine concentrations remained above the MIC 90 for Escherichia coll (4.0 μg/mL) and Proteus mirabilis (1.0 μg/mL) for over 24 h after doses of 2.2 mg/kg (8.1 μg/mL) and 4.4 mg/kg (29.6 μg/mL), the interval between treatments for ceftiofur sodium in dogs, whereas urine concentrations 24 h after dosing at 0.22 mg/kg (0.1 mg/Ib) were below the MIC 90 for E.coli and P. mirabills (0.6 μg/mL). Plasma concentrations were dose-proportional, with peak concentrations of 1.66 ± 0.0990 μg/mL, 8.91 ± 6.42 μg/mL, and 26.7 ± 1.07 μg/mL after doses of 0.22, 2.2, and 4.4 mg/kg, respectively. The area under the plasma concentration versus time curve, when normalized to dose, was similar across all dosage groups.  相似文献   
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Testosterone concentrations in stallions showed a seasonal trend with peak concentrations in the spring (April and May in Britain) and lowest concentrations in the period from December to February. The effect on this pattern of changing the length of the photoperiod at the end of the normal breeding season (mid-summer's day) was studied in 2 experiments. In the first experiment artificial illumination was organised from 21 June to mimic the effect of transfer to a southern hemisphere spring and summer, that is short days becoming longer. The stallions had low concentrations of testosterone in February and high concentrations in April. Concentrations in July, August and September were extremely low with a return to high values in late November/early December. In the second experiment, illumination was maintained at the equivalent of a 16 1/2-hour day from 21 June to mid December. These stallions had high testosterone concentrations in April, after which they fell until August, later rising to a maximum in October. These results are discussed in relation to transfer of stallions between the northern and southern hemispheres.  相似文献   
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