Till and McCulloch

• The dawn of experimental measurement of stem cells

• Brief biographies of

  • Ernest McCulloch MD (1925 – 2011)

  • James Till PhD (1931 - ), physics/biophysics

  • Andrew Becker MD/PhD (1935 - 2015)

  • Lou Siminovitch PhD (1920 - 2021)

• Background on radiation sensitivity

• Colony forming unit - spleen assay

• in vitro CFU assays

• 1st paper in 1961

  • nodules

  • multilineages

  • suspected clonal origin

  • Estimate CFUs per donor cell

  • impact of radiation on CFU

• 1963

  • Use radiation-induced chromosomal changes etst hypothesis of clonal origin of nodules

• 1964/65: test self-renewal capacity of CFUs

• Number and type of colonies as a function of incubation time

• Number of colonies highly heterogeneous

  • Not soley due to technical artificats or spleen variation

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