Figure 4

Growth characteristics and cellular senescence of primary and recombinant cells derived from the loggerhead sea turtle. (A) Sequential passage and cell growth of primary A634 cells, recombinant A634 derived K4DT cells, primary A640 cells and recombinant A640 derived K4DT cells. At the start of each passage, 5 × 10⁴ cells of each cell line were added to triplicate cell culture wells. (B) Detection of senescence-associated β-galactosidase staining in primary A634 cells (upper panel) and A634 derived K4DT cells (lower panel) after 16 passages. The arrows indicate positive blue staining, denoting cellular senescence. (C) Incidence of positively stained primary A634 cells, recombinant A634 derived K4DT cells, primary A640 cells and recombinant A640 derived K4DT cells. The percentage of positively stained cells counted in six randomly selected microscopic fields is shown in the graph. The double asterisks indicate statistical significance at the 1% level.