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Protein-degradation rates in developing rat brain were estimated from the decay in total radioactivity in proteins labelled by a single intraperitoneal injection of NaH14CO3 to 5-day-old animals. In contrast with previous reports, our results indicate that degradation rates are lower in developing than in adult brain and suggest that in brain, as has been observed in liver, adrenal gland, muscle, cultured mammalian cells and bacteria, reduced rates of protein degradation contribute to the increase in protein content under conditions of rapid growth.

Electrolytic manganese dioxide (EMD) has been prepared with varying levels of incorporated K § in the range 54 to 5150 ppm K, by varying the amount of K § in the electrolyte. Higher acid concentrations or higher current densities decrease the amount of incorporated K § X-ray diffraction patterns reveal the presence of an a-MnO2 phase (containing potassium) as a minor component along with the usual ~-MnO2. Cyclic voltammograms in 9.0 mol dm -3 KOH (v = 0.5 mV s -1) show that the Mn(IV) reduction peaks shift to more negative potentials while the peak currents decrease with increasing K*, reflecting the increased levels of a-MnO2 in the EMD. Chronopotentiometry reveals that voltages (corrected for iR loss) measured during reduction at 0.02 A g-1 are lower for EMDs containing > 590 ppm K, consistent with the presence of ~-MnO= in the EMDs. Potassium levels -< 590 ppm K do not primafacie effect the electrochemical behavior of EMD under the conditions of this study:

The Influence of Potassium Ion on the Electrodeposition and Electrochemistry of Electrolytic Manganese Dioxide.-Electrolytic MnO2 is prepared in the presence of varying amounts of K+ in the electrodeposition bath. Depending on the K+ concentration in the bath, the acid concentration, and the current density, incorporation of 54-5150 ppm K+ is observed. The incorporation of K+ is accompanied by the formation of α-MnO2 as a minor component along with the usual γ-MnO2. Even small amounts of the αphase (¿ 3%) have observable effects on the electrochemical reduction of MnO2. Changes in the cathodic peaks can be correlated with the increase in the amount of α-MnO2. These parallel the decreased voltages observed during reduction as the α-MnO2 content increases. -(KAO, W.-H.; WEIBEL, V. J.; ROOT, M. J.; J.