Phase-response curves and the circadian clock in Drosophila pseudoobscura

Abstract

The effects of light and temperature on the circadian rhythm of eclosion in Drosophila have been the subject of early investigation. In chronobiology Much before the clock gene was discovered in Drosophila melanogaster, Pittendrigh and Bruce (1957) proposed an explicit coupled-osculator model to account for transients. The model postulated that (1) the basic (A) oscilator was phase-shifted instantaneously by both light pulses, and that (in) the transients do not represent the time course and wave forn of the A oscillator Chandrashekaran performed two pulse experiments and reported that his results proferred unequivocal support to both the predictions of the coupled- oscillator model Chandrashekaran also proposed a 'dawn' and 'dusk' model for the phase-shifting effects of brief light pulses He was later able to empirically demonstrate that brief height pulses indeed shifted pbase With the 'off' transition ('dusk' effect) during the first half of the subjective night and with the "on' transition ('dawn' effect) during the second half of the subjective right further underlining the inherent dlfferences between the two halfes of the subjective right, Chandrashekaran could demonstrate that early and late subjective right phases of the Drosophila pseudoobscura is"circacdian rhythm require different energies of blue bright to evoke comparable magnitudes of delay and advance phase shifts in another scenes of experiments he demonstrated that there are reciprocal relations between the irradiance and duration of blue light pulses which could in combination severely attenuate the amplitude of the Drosophila pseudoobscum circadran rhythm Chandrashekaran also reported the most complete falluly of PRe for HTP and LTP of 3-, 6- and 12-h pulses and demonstrated that HT? and LTP PRe were minor images and that 6- and 12--h LTP Yielded PRE of the 'strong' type (type 0) and that all durations of HTP yielded PRe of the 'weak' type (type 1).