Protease-elicited TUNEL positivity of non-apoptotic fixed cells

István Gál, Tamás Varga, Ildikó Szilágyi, Margit Balázs, József Schlammadinger, Gábor Szabó

Research output: Contribution to journalArticle

29 Citations (Scopus)


The appearance of free DNA ends in the chromatin is usually considered an indication of advanced apoptosis. Unexpectedly, the nuclei of non- apoptotic cells derived from mouse thymuses could be specifically labeled by terminal transferase after proteinase K treatment of the fixed, cytocentrifuged samples. Artifactual mechanical or contaminating nucleolytic factors have been ruled out as players in the generation of free DNA ends. The phenomenon was detected in both formaldehyde- and ethanol-fixed specimens, in agarose-embedded fixed cells, and in chromatin spreads. By urea-agarose gel electrophoresis, the average single-strand size of the DNA molecules carrying the free ends was found between 50 and 250 kb. We suggest that ss discontinuities preexisting in the fixed normal cells are unmasked by protease treatment eliciting TUNEL (terminal transferase-mediated nick end- labeling) positivity.

Original languageEnglish
Pages (from-to)963-969
Number of pages7
JournalJournal of Histochemistry and Cytochemistry
Issue number7
Publication statusPublished - Jul 2000



  • Apoptosis
  • Chromatin
  • Fragmentation
  • Protease

ASJC Scopus subject areas

  • Anatomy
  • Histology

Cite this