yoesh hickey sasai oversaw the. he is director of the research center for developmental biology. >> translator: these problems should not have occurred so i'm deeply ashamed of the fact that i could not catch the deficiencies that were in the thesis. >> he held a press conference in tokyo wednesday. it marked his first public appearance since the papers were published in the journal "nature" in january. sasai said he only took part in the last stage of writing the papers with haruko obokata who led the study. obokata and her team members claimed to have found a new way to create cells that can grow into any type of tissue. they said their method allowed mature animal cells to be reprogrammed. they named the phenomenon stimulus triggered acquisition of pluripotency or stap. scientists elsewhere questioned the findings, and investigators at riken who probed her work determined the study contained falsifications. they criticized sasai for not very fieing the legitimacy and accuracy of the data used in the papers. sasai