Microcalorimetric studies on cell survival and repair after UV induced damage

Rate of heat production during cell proliferation following UV-irradiation of respiratory-deficient yeast cells was measured as a function of time (p-t curve) in a batch microcalorimeter. Following observations were made: (a) All growing cell cultures showed 3 distinct phases of heat production namely lag, exponential and declining phases of rate of heat production. (b) Duration of the lag phase is inversely proportional to the number of cells capable of proliferation. (c) After UV-irradiation, lag phase increased in a dose dependent manner. (d) Liquid-holding reactivation increased the surviving fraction and reduced the lag phase in p-t curves. Presence of 2-deoxy-D-glucose during liquid-holding prevented the reduction in lag phase due to the inhibition of repair processes.