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Human interferons induce a protein of 15,000 daltons in human and bovine cells. This protein is located in the cytoplasm in a soluble form and is induced by concentrations of interferon which induce the antiviral state. Messenger RNA prepared from interferon-treated human and bovine cells contains a mRNA which yields on translation in vitro a protein similar in size to the 15-kDa protein induced by interferon in vivo. The human protein has been purified to homogeneity from interferon-treated human cells by ion-exchange chromatography and reverse-phase high-performance liquid chromatography. A comparison of the peptides generated by V8 protease from the human and bovine 15-kDa proteins reveals that the two proteins are similar but not identical.  相似文献   
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  总被引:8,自引:18,他引:8  
The use of protease inhibitors causes the accumulation of very large polypeptides (polyprotein) in tissue culture cells infected with either poliovirus or echovirus 12. The effectiveness of the inhibitor varies, depending on the cell line chosen. In infected monkey kidney cells, polyprotein is not cleaved when a chymotrypsin inhibitor is added, but in infected HeLa cells a trypsin inhibitor is most effective. Therefore, at least a part of the proteolytic activity is supplied by the host cell. Extracted viral polyprotein can be cleaved in vitro by trypsin or chymotrypsin. As estimated by migration in sodium dodecyl sulfate gels and antigenicity, chymotrypsin cleavage of the poliovirus polyprotein yields fragments which are similar to the in vivo product. The polyprotein is not in soluble form but is attached to a fast-sedimenting, membrane-bound structure. Proteolytic activities in cell extracts were assayed using polyprotein as substrate, and infected and uninfected extracts produced qualitatively dissimilar cleavages.  相似文献   
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Proteins and virus particles were separated by zonal electrophoresis or isoelectric focusing in glass tubes of small volume. The tubes were covered at the bottom with dialysis membranes and sucrose gradients containing either buffer or ampholytes were generated directly into them. When ampholytes were employed, reproducible pH gradients were generated during electrophoresis. After the separations were finished, dense sucrose was pumped into the bottom of each tube and the gradient was fractionated from the top; the recovery of virus was nearly complete.  相似文献   
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The genus Ceratocystis sensu stricto includes important fungal pathogens of woody and herbaceous plants. This genus is distinguished from species in Ceratocystis sensu lato by the presence of Chalara anamorphs. Ascospore shape has been used extensively in delineating Ceratocystis taxa, which show a large variety of ascospore shapes. Sequence analysis of one region of he 18S ribosomal RNA subunit and two regions of the 28S ribosomal RNA subunit showed that there was a majority of multiple substitutions at nucleotide sites and that there was a low transition/transversion ratio, T = 0.72. Both of these results suggest that these are well established, old species. Ascospore morphology, for the most part, was not congruent with the molecular phylogeny, and the use of morphological characters may be misleading in the taxonomy of these species.   相似文献   
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The hematoxylin and eosin stain is the most common method used in anatomic pathology, yet it is a method about which technologists ask numerous questions. Hematoxylin is a natural dye obtained from a tree originally found in Central America, and is easily converted into the dye hematein. This dye forms coordination compounds with mordant metals, such as aluminum, and the resulting lake attaches to cell nuclei. Regressive formulations contain a higher concentration of dye than progressive formulations and may also contain a lower concentration of mordant. The presence of an acid increases the life of the solution and in progressive solutions may also affect selectivity of staining. An appendix lists more than 60 hemalum formulations and the ratio of dye to mordant for each.  相似文献   
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