Recent studies have revealed that the growth rate of budding yeast and mammalian cells varies during the cell cycle. By linking a multitude of signals to cell growth, the highly conserved Target of Rapamycin Complex 1 (TORC1) and Protein Kinase A (PKA) pathways are prime candidates for mediating the dynamic coupling between growth and division. However, measurements of TORC1 and PKA activity during the cell cycle are still lacking. Following the localization dynamics of two TORC1 and PKA targets via time-lapse microscopy in hundreds of yeast cells, we found that the activity of these pathways towards ribosome biogenesis fluctuates in synchrony with the cell cycle even under constant external conditions. Mutations of upstream TORC1 and PKA regulators suggested that internal metabolic signals partially mediate these activity changes. Our study reveals a new aspect of TORC1 and PKA signaling, which will be important for understanding growth regulation during the cell cycle.

Recent studies have revealed that the growth rate of budding yeast and mammalian cells varies during the cell cycle. By linking a multitude of signals to cell growth, the highly conserved Target of Rapamycin Complex 1 (TORC1) and Protein Kinase A (PKA) pathways are prime candidates for mediating the dynamic coupling between growth and division. However, measurements of TORC1 and PKA activity during the cell cycle are still lacking. Following the localization dynamics of two TORC1 and PKA targets via time-lapse microscopy in hundreds of yeast cells, we found that the activity of these pathways towards ribosome biogenesis fluctuates in synchrony with the cell cycle even under constant external conditions. Mutations of upstream TORC1 and PKA regulators suggested that internal metabolic signals partially mediate these activity changes. Our study reveals a new aspect of TORC1 and PKA signaling, which will be important for understanding growth regulation during the cell cycle.

Atracurium is a novel his-quaternary (x~mpetitive neuromuscular blocking agent. The drug was designed to undergo lapid chemical inactivation by "Rofmann elimination" at physiological pH and temperature to form laudancsine. Beside hydrolysis, atracurium is metabollzed to a quaternary alcohol and acid and metholaudanosine, which all breakdown to laudanosine. ( I ) It is known that laudanosine can induce oonvulslons. We developed a method for the determination of atracuri~m and laudano6ine in one run: I ml serum, 50 ~I sulphuric acid I M, 0.1 ml internal standard (hexafluorenium bromide I0 mg 1 -I ) and 0.1 ml potassium iodide solution (50 g 1 -j) are mixed; 7.0 ml DCM was added and 50 ~i is injected into the HPLC. Eluens: acetonitrile + sodium sulphate 0.03 M = 25 + 75, + sulphuric acid I M to pa 3.5 ; column 150 x 4.6 ram, Nucleosil 5C18; detection LrV at 210 nm, and fluorescence Em.320 nm, Exc. 280 urn. Sensitivity in spiked calf's serum: atracurium 25 ~g.l -I and lau~anosine 5 ~g.l -I . With this method and with the more time consuming assay of Neill and Jones (2) (unlike their publication), we al~ys found two peaks from the pure su~stanoe atracurium. ~ two did not correspond with the known degradation p rgducts. By TiC we could confirm our findings. In Tracrium~ ampoules (atracurium for h~an i.v. injection) we found with our method atracurium and three degradation pLod.,cts.