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Ohne Zusammenfassung Bergleiche Auguftheft diefer Bl?tter, in melchem gleichfalls auf die Wichtigfeit diefes Qegenftandes hingemiefen murde. Die Red.  相似文献   
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Observations on transplacental infection with bluetongue virus in sheep   总被引:1,自引:0,他引:1  
Twenty-four ewes were inoculated with 1 of 2 strains of bluetongue virus type 4 at 40, 60, or 80 days of gestation. Two ewes aborted, 2 ewes died, and 1 was killed during the experiment, but their fetuses were recovered. At term, 2 mummified fetuses, 4 dead lambs, and 17 clinically healthy lambs were produced by 12 sheep, and the remaining 7 sheep were barren. Porencephaly and cerebellar dysgenesis were found in term lambs born to sheep inoculated at 40 and 60 days of gestation. Radiographic examination of 12 fetuses showed developmental ages far less than their chronologic age; 8 fetuses had skeletal growth-retardation lines, which were also observed in the dead lambs. A systemic lymphoreticular hyperplasia was observed in the dead lambs and in all lambs at 12 weeks of age; in 4 of the latter, granulomatous reactions were present in the liver and kidney. Lungs of the full-term lambs were reduced in weight and showed poor alveolar development and mononuclear cell infiltration, which persisted in the 12-week-old lambs. It was concluded that bluetongue virus is capable of causing not only gross abnormalities of the CNS, but also generalized growth retardation and fetal lymphoreticular hyperplasia.  相似文献   
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Isolated dog neutrophils exposed to known chemotactic factors assumed a bipolar configuration in suspension. This response was initiated within 2 minutes with a gradual return to spherical shape. The rate of return to sphere was positively correlated with the dose of stimulant. Dog neutrophils exposed to N-formylmethionyl-leucyl-phenylalanine (fMLP) did not adapt to bipolar conformation and did not bind radiolabeled fMLP. These findings are consistent with other species (pig and cow) that also did not respond to fMLP.  相似文献   
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Crystalluria results from oversaturation of urine with crystallogenic substance. However, oversaturation may occur as a result of in vitro as well as in vivo events. The microscopic appearance of crystals only represents a tentative identification of their composition because variable conditions associated with their formation, growth, and dissolution may alter their appearance. Definitive identification is dependent on physical methods such as optical crystallography, x-ray diffraction, and electron microscopic analysis.  相似文献   
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