In spite of numerous publications on potential diagnostic application of circulating DNA and transrenal nucleic acid (Tr-NA) analysis, few, if any, tests based on this technology are available in clinical labs. This delay in test development and implementation is caused, at least in part, by the deficit in robust methods for isolation of short nucleic acid fragments from bodily fluids, as well as in techniques for analyzing these fragments. We have developed a new anion exchanger-based method for the isolation of cell-free nucleic acid fragments from large volumes of bodily fluids, and analyzed these fragments by PCR techniques specially designed to amplify "ultrashort" templates. The combination of these two techniques not only revealed the presence in urine of 10-150 bases or bp DNA and RNA fragments in addition to previously observed 150-200-bp DNA fragments and high molecular weight DNA, but also significantly increased the sensitivity of Tr-DNA detection. Additionally, we detected in urine a variety of miRNAs, including those excreted transrenally, thereby opening new diagnostic possibilities for Tr-NA analysis.

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2507of the ThzNilv-type structure decreases. This suggests that the degree of order of the ThzNi17-type structures of Pr2C017 and NdzC017 is lowest. Therefore, the ThzNi~v-type compounds for these R elements do not exist. The degree of order of the ThzNi~7-type structures of Ce2C0~7 and Ho2Co17 is nearly ideal. One therefore gets only traces of the ThzZnlv-type structure even after prolonged annealing at lower temperatures. Dy2C017 appears to lie in between these two extreme cases. This is the reason that both modifications i.e.ThzNit7+ThzZnlv-type, are obtained in almost equal proportions below 1200°C.Since those R elements, studied in this work are uniformly distributed throughout the whole rare-earth series, the results obtained for their AzB17 compounds can generally be applied to all the RzCox7 compounds (Fig. 1). Buschow (1966) and Givord, Givord & Lemaire (1972) have explained the polymorphism of RzCo~v in terms of the radii ratios of R and Co atoms. No doubt the atomic radii of R and Co atoms are important factors in the formation of RECO~7. However, the atomic ratio model alone cannot explain the polymorphism of R2Co17 over the rare-earth series and the degree of order of R2Co17 of the Th2Ni17-type structure.In our opinion, the valence-electron concentration and the electron-spatial correlation play a deciding role in the stabilization of one or more of the polymorphic forms of R2C0~7 for a particular R element at a particular temperature.