ELEMENTAL ANALYSIS OF PRECIPITATES FORMED IN NUCLEI BY ANTIMONATE-OSMIUM TETROXIDE FIXATION

Elements retained in cervical lymph nodes, isolated hepatic nuclei and salt-impregnated gels by fixation with antimonate- or pyrophosphate-containing and other osmium tetroxide solutions were assayed by nuclear activation analysis or by atomic absorption spectrophotometry. Salts preserved by the antimonate-osmium tetroxide fixative in lymph nodes, isolated nuclei and a KCl-enriched gel consisted almost entirely of potassium antimonate. The K + in the precipitates in these specimens appeared to derive partially from that in the fixative solution and partially from that in the specimen. Salts preserved by the antimonate-osmium tetroxide fixative in an NaCl-supplemented gel consisted partly of potassium antimonate derived from the fixative as in unsupplemented gels and partly of sodium antimonate. The Na + precipitated in this gel amounted to less than one-half that originally present. In comparison the pyrophosphate-osmium tetroxide solution retained higher levels of K + in lymph nodes, nuclei and the KCl gel, but the potassium pyrophosphate was not evident as electron-opaque precipitates. The latter fixative was less effective in preserving Na + in the NaCl gel. The pyrophosphate-containing fixative, which was about twice as efficient as the antimonate-containing solution in retaining the divalent cations, preserved 70% of the Mg ++ and 100% of the Ca ++ added to gels.