Stabilization of the shortest telomeres in myeloma cells. (A) Telomere distribution in a Southern blot smear. a indicates mean TRF of longer telomeres (⋄, kbp); b, mean TRF of shorter telomeres (□, kbp). Results showed that the distribution of longer telomeres and shorter telomeres was constant relative to the mean TRF in the 5.5- to 9.0-kbp range (B), and the patients' own granulocytes showed a similar relationship (C). Progressive shortening of the longest telomeres was seen in MM cells when mean TRF fell from 5.5 to 3.0 kbp, with stabilization of the shortest telomeres (B). This was not seen in the granulocytes, though the shortest mean TRF was 5.0 kbp or more (C). The lines shown in panels B and C were y = x reference lines.