DIFFERENTIAL SISTER-CHROMATID EXCHANGE RESPONSE IN PHYTOHEMAGGLUTININAND POKEWEED STIMULATED LYMPHOCYTES OF GOAT (CAPRA-HIRCUS L)

A differential sister chromatid exchange (SCE)/cell response was obser ved between phytohemagglutinin (PHA) and pokeweed (PKW) stimulated blo od lymphocytes of goat (Capra hircus L) exposed to final concentration s of 0.1, 0.25, 0.5, 1, 2.5 and 5 mu g/mL of BUdR. At 0.1 mu g/mL of B UdR, the two mitogens gave very similar SCE/cell responses: the SCE me an values were 3.17 +/- 1.93 for PHA and 3.28 +/- 1.76 for PKW, and th e frequency distributions fit very well the Poisson probability functi on with both mitogens. For 0.25 mu g/mL and increasing BUdR concentrat ions, SCE/cell rates for pokeweed mitogen were significantly higher th an those of PHA. At 5 mu g/mL of BUdR, the SCE/cell response was 8.68 +/- 3.24 for PKW and 6.96 +/- 3.45 for PHA, and the difference was sta tistically significant (P = 0.0001); for both mitogens the SCE/cell fr equency distributions fit the Poisson probability function only by ado pting a Poisson 'mixture' model, which takes into account the presence of two different subpopulations of cells.