PubMed · 5774213
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Analytical guides.. https://doi.org/10.1080/00028896909343088
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With microtubule-associated proteins (MAPs) BeSO4 and MgSO4 stimulated tubulin polymerization as compared to a reaction mixture without exogenously added metal ion, while beryllium fluoride had no effect (E. Hamel et al., 1991, Arch. Biochem. Biophys. 286, 57-69). Effects of both cations were most dramatic at GTP concentrations in the same molar range as the tubulin concentration. We have now compared effects of beryllium and magnesium on tubulin-nucleotide interactions in both unpolymerized tubulin and in polymer. Polymer formed with magnesium had properties similar to those of polymer formed without exogenous cation, except for a 20% lower stoichiometry of exogenous GTP incorporated into the latter. In both polymers the incorporated GTP was hydrolyzed to GDP. Stoichiometry of GTP incorporation into polymers formed with beryllium or magnesium was identical, but much of the GTP in the beryllium polymer was not hydrolyzed. The beryllium polymer was more stable than the magnesium polymer. Beryllium also differed from magnesium in only weakly enhancing the binding of GTP in the exchangeable site of unpolymerized tubulin, while neither cation affected GDP exchange at the site. If both cations were present in a reaction mixture, polymer stability was little changed from that of the beryllium polymer, but most of the GTP incorporated into polymer was hydrolyzed. Six additional metal salts (AlCl3, CdCl2, CoCl2, MnCl2, SnCl2, and ZnCl2) also stimulated MAP-dependent tubulin polymerization, but enhanced polymer stability did not correlate with polymer GTP content. We postulate that enhanced polymer stability is a consequence of cation binding directly to tubulin and/or polymer while deficient GTP hydrolysis in the presence of beryllium, as well as aluminum and tin, is a consequence of tight binding of cation to GTP in the exchangeable site.
In this study, mesh monitors cast from experimental compositions of a Ni-Cr-Be alloy are evaluated by the application of image analysis techniques. Castability values obtained by this method are then contrasted with those from three commonly employed manual counting procedures. While castability values obtained by all methods reflect the effect of compositional variations, a comparison of results with respect to evaluation method indicates that the image analysis technique consistently yields higher castability values, especially evident in the poorly casting groups. The apparent explanation for these observed differences is that with imaging, segments that are partially cast to varying degrees are not arbitrarily eliminated from the data, as is the usual practice in manual counting methods; therefore, castability values obtained by using the imaging technique will very closely reflect an actual alloy volume of each cast monitor.
Induction of chromosome aberrations in G0 lymphocytes of peripheral human blood exposed to 235U and d(50)+Be neutron radiation was studied. Dose--effect relationships for different types of chromosome aberrations were analyzed. Linear dependence of the effect was established for the studied neutron radiation, except for the yield of dicentrics exposed to d(50)+Be neutrons. Accordingly to the yield of dicentrics, the relative biological efficiency (RBE) of 235U and d(50)+Be neutrons was 19.5 and 4.14, respectively.