Regulation of phosphorylase kinase by low concentrations of Ca ions upon muscle contraction: the connection between metabolism and muscle contraction and the connection between muscle physiology and Ca-dependent signal transduction

It had long been one of the crucial questions in muscle physiology how glycogenolysis is regulated in connection with muscle contraction, when we found the answer to this question in the last half of the 1960s. By that time, the two principal currents of muscle physiology, namely, the metabolic flow starting from glycogen and the mechanisms of muscle contraction, had already been clarified at the molecular level thanks to our senior researchers. Thus, the final question we had to answer was how to connect these two currents. We found that low concentrations of Ca ions (10−7–10−4 M) released from the sarcoplasmic reticulum for the regulation of muscle contraction simultaneously reversibly activate phosphorylase kinase, the enzyme regulating glycogenolysis. Moreover, we found that adenosine 3′,5′-monophosphate (cyclic AMP), which is already known to activate muscle phosphorylase kinase, is not effective in the absence of such concentrations of Ca ions. Thus, cyclic AMP is not effective by itself alone and only modifies the activation process in the presence of Ca ions (at that time, cyclic AMP-dependent protein kinase had not yet been identified). After a while, it turned out that our works have not only provided the solution to the above problem on muscle physiology, but have also been considered as the first report of Ca-dependent protein phosphorylation, which is one of the central problems in current cell biology. Phosphorylase kinase is the first protein kinase to phosphorylate a protein resulting in the change in the function of the phosphorylated protein, as shown by Krebs and Fischer. Our works further showed that this protein kinase is regulated in a Ca-dependent manner. Accordingly, our works introduced the concept of low concentrations of Ca ions, which were first identified as the regulatory substance of muscle contraction, to the vast field of Ca biology including signal transduction

THE CHEMICAL NATURE OF GROWTH FACTORS REQUIRED BY MOSQUITO LARVAe: I. RIBOFLAVIN AND THIAMIN

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A Practical Liquid Medium for Cultivation of Trypanosoma cruzi in Large Volumes

In the media usually employed for the cultivation of Trypanosoma cruzi, the portion most favorable to the growth of this microorganism is the water of condensation formed on blood agar. This fluid is so small in amount that rubber caps are placed on tubes and flasks to conserve it during the incubation of cul-tures. In 1936 Kelser used such a medium for the production of diagnostic anti-gen for Chagas disease and demonstrated that the antigen had merit as a medical tool. However, the necessity of having aseptically drawn blood makes the preparation of large amounts of Kelser's medium difficult. In 1943 Miss Nylah Tom showed that a blood agar medium could be inspis-sated and sterilized in the autoclave at 15 pounds for 20 minutes. This discovery suggested the sequence of experiments by which we were able to arrive at a practical liquid medium for cultivation of Trypanosoma cruzi in large volumes. In this laboratory, Trypanosoma cruzi has been cultivated in 5-ml, 500-ml, and 5-liter volumes in a solution of 2 per cent of peptone, 0.5 per cent of sodium chloride, and 0.2 per cent of glucose (pH 7.5). Previously coagulated and drie