title: [Quantitative analysis of cell cyclin E expression threshold].
abstract: OBJECTIVE
  It is important to analyze the threshold of cyclins when we research the mechanism of cell cycle progressing. However, there was no effective way to caculate quantitatively. This study was designed to analyze cyclin E expression threshold quantitatively.
  
  
  METHODS
  MOLT-4 cells were detected at different photomultiplier tube (PMT) voltage by cyclin E/DNA multiparameter flow cytometry. Using this method, MOLT-4 cells were detected at the same voltage after being treated with caffeine and cycloheximide (CHX), and then MOLT-4 cells and JURKAT cells were detected at the same voltage. Threshold of cyclin E was counted by using formula B2/A x C (A, B, C indicates the minimum, threshold, and maximum of cyclin E fluorescence intensity respectively).
  
  
  RESULTS
  Cyclin E threshold of MOLT-4 cells calculated by formula B2/A x C was invariable at different voltage. It decreased when cells treaded with caffeine and unchanged when treated with cycloheximide. At the same time, cyclin E threshold of JURKAT cells calculated by formula was much lower than that of Molt-4 cells.
  
  
  CONCLUSIONS
  Formula B2/A x C can be used to analyze cyclin E expression threshold quantitatively.
authors.affiliation: Molecular Medical Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, P. R. China.
authors.forename: Da-xing
authors.initials: DX
authors.lastname: Xie
authors.forename: Jian-hong
authors.initials: JH
authors.lastname: Wu
authors.forename: Yuan
authors.initials: Y
authors.lastname: Yu
authors.forename: Jian-ping
authors.initials: JP
authors.lastname: Gong
mesh_terms: D002110:Caffeine / Q000494:pharmacology; D019927:Cyclin E / Q000032:analysis* / Q000096:biosynthesis / Q000235:genetics; D003513:Cycloheximide / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D019169:Jurkat Cells; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D019927:Cyclin E; D011500:Protein Synthesis Inhibitors; D002110:Caffeine; D003513:Cycloheximide