To elucidate the evolutionary dynamics of rDNA site number in polyploid plants, we determined 5S and 18S-5.8S-26S rDNA sites for ten species of Sanguisorba (2n=14, 28, 56) and a single species of each of three outgroup genera, Agrimonia (2n=28), Rosa (2n=14), and Rubus (2n=14) by the fluorescence in situ hybridization (FISH) method. We also estimated phylogenetic relationships among these species using matK chloroplast DNA (cpDNA) sequences, and reconstructed the evolutionary history of rDNA site number based on the maximum parsimony method. The 2n=14 and 2n=28 plants of all genera except Rosa carried two 5S rDNA sites, whereas Rosa and 2n=56 plants carried four sites. The 2n=14 plants had two 18S-5.8S-26S rDNA sites, whereas Sanguisorba annua and 2n=28 plants had four or six sites. Phylogenetic analysis showed that polyploidization from 2n=14 to 2n=28 has occurred once or three times in Sanguisorba and Agrimonia. The 5S rDNA sites duplicated during each ancestral polyploidization were evidently lost after each polyploidization. However, the duplicated 18S-5.8S-26S rDNA sites were all conserved after each polyploidization. Thus, the duplicated 5S rDNA sites tend to have been eliminated, whereas those of 18S-5.8S-26S rDNA tend to have been conserved in Sanguisorba. In the most parsimonious hypothesis, 2n=14 in S. annua is a secondary, putatively dysploid state, reduced from 2n=28.
Rhabdomyolysis is a severe adverse effect of hypolipidaemic agents such as statins and fibrates. We evaluated this muscular cytotoxicity with an in-vitro culture system. Cellular apoptosis was determined using phase-contrast and fluorescein microscopic observation with Hoechst 33342 staining. L6 rat myoblasts were treated with various statins and bezafibrate under various conditions. With statins only, skeletal cytotoxicity was ranked as cerivastatin > fluvastatin > simvastatin > atorvastatin > pravastatin in order of decreasing potency. Combined application of fibrates enhanced atorvastatin-induced myopathy, which causes little apoptosis alone. These results suggest that statins and fibrates synergistically aggravate rhabdomyolysis.
Summary It is well known that some amino acids inhibit bacterial growth. L -Serine is known to inhibit the growth of Escherichia coli by inhibition of homoserine dehydrogenase (EC 1.1.1.3). It has been reported that this L -serine inhibition may be prevented by the addition of L -isoleucine or L -threonine to the medium. In our study, however, recovery of the growth inhibition of Escherichia coli by L -serine occurred in the presence of several amino acids, especially L -phenylalanine. In an attempt to further elucidate this inhibition mechanism, different intermediates of aromatic amino acid biosynthesis were added to the growth medium. Recovery from the inhibition did not occur in the presence of prephenate but did occur when phenylpyruvate was added to the medium. The specific activity of prephenate dehydratase decreased in cells grown in the presence of L -serine. However, L -serine did not inhibit in vitro prephenate dehydratase activity, and the expression of pheA, which encodes the prephenate dehydratase, was not depressed by L -serine. We suggest that L -serine acts via another inhibition mechanism. Although this inhibition mechanism has not been fully elucidated, our results suggest that the addition of L -serine to the growth medium inhibits prephenate dehydratase synthesis and thus affects L -phenylalanine biosynthesis.
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