A combined ultrastructural approach to the study of nuclear matrix thermal stabilization |
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Authors: | E. Falcieri P. Gobbi P. Sabatelli S. Santi F. Farabegoli R. Rana A. Cataldi N. M. Maraldi A. M. Martelli |
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Affiliation: | (1) Istituto di Anatomia Umana Normale, Università di Bologna, via Irnerio 48, I-40126 Bologna, Italy;(2) Istituto di Citomorfologia Normale e Patalogica del C.N.R. c/o I.O.R., via di Barbiano 1/10, I-40137 Bologna, Italy;(3) Laboratorio di Biologia Cellulare e Microscopia Electronica, c/o I.O.R., Bologna, Italy;(4) Dipartimento di Patologia Sperimentale, Università di Bologna, Bologna, Italy;(5) Istituto di Morfologia Umana Normale, Università di Chieti, Chieti, Italy |
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Abstract: | Summary Using mouse erythroleukaemia cells and different ultrastructural techniques, the morphology was investigated of the nuclear matrix obtained after incubation at 37° C of isolated nuclei. If purified nuclei were heated for 45 min at 37° C, the final matrix exhibited well-recognizable nucleolar remnants, an inner network and a peripheral lamina. Without such incubation only the peripheral lamina was seen surrounding homogeneous, finely granular material. Similar results were obtained with both araldite-embedded and freeze-fractured nuclear matrices, although in the latter case the loose granular material was not evident. Observations of araldite-embedded, heat-treated nuclei revealed clumping of heterochromatin in small, very electron-dense masses with large interchromatin spaces. These ultrastructural aspects were even more striking in freeze-fractured nuclei. Cytochemical matrix analysis by osmium-ammine staining for nucleic acids and DNase-gold labelling for DNA localization demonstrated that also matrix residual nucleic acids, mostly RNA, are stabilized by heat exposure of isolated nuclei. The results demonstrate that the morphology of heat-stabilized nuclear matrix is not artefactually affected during the preparation for conventional electron microscopy and suggest a possible involvement of nucleic acids in the heat-induced stabilization of the nuclear matrix. |
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