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171.
This editorial addresses the debate concerning the origin of adult nucleus pulposus cells in the light of profiling studies
by Minogue and colleagues. In their report of several marker genes that distinguish nucleus pulposus cells from other related
cell types, the authors provide novel insights into the notochordal nature of the former. Together with recently published
work, their work lends support to the view that all cells present within the nucleus pulposus are derived from the notochord.
Hence, the choice of an animal model for disc research should be based on considerations other than the cell loss and replacement
by non-notochordal cells. 相似文献
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173.
Mutant 5 S rRNA genes were expressed in Saccharomyces cerevisiae to further define the function of the ribosomal 5 S RNA. RNA synthesis and utilization were assayed using previously constructed markers which have been shown to be functionally neutral and easily detected by gel electrophoresis. Most mutations were found not to affect the growth rate because they were poorly expressed or could be accommodated effectively in the ribosomal structure. Two of the mutants, Y5A99U56U57 and Y5U90i5 adversely affected cell growth as well as protein synthesis in vitro. Polyribosome profiles in both of these mutants were substantially shorter, and an analysis of the ribosomal subunit composition revealed a significant imbalance with a 25-35% excess in 40 S subunits. Kinetic analyses of RNA labeling indicated very low cellular levels of mutant RNA either because it was poorly expressed (Y5U90i5) or rapidly degraded before being incorporated into mature 60 subunits (Y5A99U56U57). The results suggest that the 5 S RNA is required for the assembly of stable ribosomal 60 S subunits and raise the possibility that this RNA or, more likely, its corresponding ribonucleoprotein complex is critical for subunit assembly or even RNA processing. 相似文献
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Kevin B. Potts 《Journal of Mammalian Evolution》2010,17(3):221-222
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Yeast tRNA is a convenient substrate for the assay of the ribonucleolytic activity of human angiogenin. The optimal pH, [NaCl], and temperature for tRNA cleavage by angiogenin are approximately 6.8, 15-30 mM, and approximately 55 degrees C, respectively, as compared with approximately 8.0, 100-200 mM, and approximately 65 degrees C, respectively, for RNase A. Polyanions and metals both inhibit angiogenin and RNase A but to different extents. 相似文献
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