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The articular localisation of amyloid is not uncommon in Galliformes. In commercial brown layer chickens amyloid artropathy was first described in 1994 as a clinical problem with increasing importance associated with growth depression and lameness. Considering the clinical veterinary and the scientific relevance of amyloid artropathy, it was a subject of poultry research during the past eight years. The outcome of the various studies performed is described in the present update. The occurrence, nature, pathogenesis and possible etiological factors of chicken amyloid artropathy, the identification and characterization of the chicken joint amyloid protein and the gene involved are reported. Finally, the results of immunological studies, which provide a plausible explanation for the difference in breed susceptibility, and summarising conclusions are presented.  相似文献   
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Thirty-one outbreaks of Marek's disease (MD) were reported in the Netherlands and retrospectively analyzed. The outbreaks occurred mostly in vaccinated commercial layer and a few breeder flocks of several breeds; however, the cause of the outbreaks could not be established. Therefore, in a prospective study, the occurrence of true vaccine failures was assessed onfive hatcheries. The plaque-forming units (PFU) of MD vaccine per chicken dose were determined through in vitro assays on vacine ampoules (2 to 5 per hatchery) and samples of reconstituted vaccine (approximately 22 per hatchery). All forty reconstituted vaccine samples of hatcheries 1 and 4 showed PFU doses <10(3). In hatchery 4, 14 samples showed extreme low PFU (< or = 10 PFU). In hatcheries 2, 3, and 5, the numbers of MD vaccine suspensions with a titer > or = 10(3) PFU, which is the standard required, were 1 (5%), 17 (77%), and 3 (14%), respectively. Some vaccine ampoules showed < 10(3) PFU per chicken dose. This study shows the usefulness to assess the PFU per chicken dose of reconstituted MD vaccine and vaccine ampoules to unravel true vaccine failures, which could result in disease outbreaks in the field.  相似文献   
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Gold octamers (Au8) bound to oxygen-vacancy F-center defects on Mg(001) are the smallest clusters to catalyze the low-temperature oxidation of CO to CO2, whereas clusters deposited on close-to-perfect magnesia surfaces remain chemically inert. Charging of the supported clusters plays a key role in promoting their chemical activity. Infrared measurements of the stretch vibration of CO adsorbed on mass-selected gold octamers soft-landed on MgO(001) with coadsorbed O2 show a red shift on an F-center-rich surface with respect to the perfect surface. The experiments agree with quantum ab initio calculations that predict that a red shift of the C-O vibration should arise via electron back-donation to the CO antibonding orbital.  相似文献   
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Ammonites are prominent in macroevolutionary studies because of their abundance and diversity in the fossil record, but their paleobiology and position in the marine food web are not well understood due to the lack of preserved soft tissue. We present three-dimensional reconstructions of the buccal apparatus in the Mesozoic ammonite Baculites with the use of synchrotron x-ray microtomography. Buccal mass morphology, combined with the coexistence of food remains found in the buccal mass, suggests that these ammonites fed on plankton. This diet may have extended to all aptychophoran ammonites, which share the same buccal mass morphology. Understanding the role of these ammonites in the Mesozoic food web provides insights into their radiation in the Early Jurassic, as well as their extinction at the end of the Cretaceous/early Paleogene.  相似文献   
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Pathology of experimentally-induced, acute toxoplasmosis in macropods   总被引:1,自引:0,他引:1  
SUMMARY Thirteen Tammar wallabies (Macropus eugenii) were dosed orally with 500, 1000 or 10 000 oocysts of Toxoplasma gondii, as part of a vaccination trial. Eleven animals died of acute toxoplasmosis 9 to 15 days after challenge. The lesions were similar in all animals, consisting of foci of necrosis and inflammation in the intestines, lymphoid tissue, adrenal cortex, heart, skeletal muscle and brain, and severe generalised pulmonary congestion and oedema. Free and intracellular tachyzoites of Toxoplasma were associated with the lesions. The remaining 2 animals had shown no signs of disease when euthanased four months after challenge. Small, focal, non-suppurative inflammatory lesions were seen in brain, heart and skeletal muscle of these animals and chronic Toxoplasma infection was confirmed by mouse inoculation.  相似文献   
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