. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CHLAMYDOMONAS CLOCK 653 CAFFEINE. THEOPHYLLINE 035 10 DRUG CONCENTRATION (mM) FIGURE 3. Period lengthening effects of caffeine and tlu-ophylline on both the + and - mating types of strain 137 F of Chlamydomonas rcinhardii. Each point represents the mean of two replicate samples. For 9 of the 12 points the standard deviations ranged from 0 to For the + mating type 5 mM and the 10 mM caffeine-treated samples, the standard deviations were and , respectively. For the -- mating type the standard deviation for treatm
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CHLAMYDOMONAS CLOCK 653 CAFFEINE. THEOPHYLLINE 035 10 DRUG CONCENTRATION (mM) FIGURE 3. Period lengthening effects of caffeine and tlu-ophylline on both the + and - mating types of strain 137 F of Chlamydomonas rcinhardii. Each point represents the mean of two replicate samples. For 9 of the 12 points the standard deviations ranged from 0 to For the + mating type 5 mM and the 10 mM caffeine-treated samples, the standard deviations were and , respectively. For the -- mating type the standard deviation for treatment with 10 mM caffeine was (Feldman, 1975), and when pulsed, it produced phase changes in the Phaseolus sleep movement rhythm (Mayer and Scherer, 1975). In our experiments caffeine was found to have a much greater effect on the biological timing process than did theophylline at equal concentrations. This is consistent with the results of Feldman (1975) on the conidiation rhythm of Neurospora. The period lengthening effect of these drugs suggests that they are acting at or close to the biological timing process. The best known effect of these drugs is the inhibition of cAMP phosphodiesterase, which results in an increase in cellular cAMP levels. Amrhein and Filner (1973) demonstrated that theophylline inhibits cyclic AMP phosphodiesterase in Chlamydomonas. However, other experiments suggest that the drugs may not be influencing the clock through their alteration of cAMP levels. Scott and Solomon (1973) found that in Neurospora, theophylline (5 mM) inhibited phosphodiesterase more effectively than caffeine; 83% of the phosphodiesterase activity remained in the caffeine-treated samples and only S2% of the activity remained in the theophylline- treated samples. If the action of the drugs on the timing mechanism of the clock is via their effects on cAMP phosphodiesterase, it is surprising that in Feldman's (1975) study on the conidiation rhythm of Xcitrospora and in this expe
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
