Till and McCulloch
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- 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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