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N Itada

Publications and source records attributed to N Itada.

11 recordsLinked to original sources
PubMed1977

Carbonic anhydrase activity in intact red blood cells measured with 18O exchange.

We have used a stirred, temperature-regulated, reaction vessel separated by a Teflon membrane from the ion source of a mass spectrometer to monitor continuously the time course of disappearance of C18O16O, mass 46, at chemical equilibrium as the 18O exchanges with 16O in water. This instrument is sensitive to less than 0.01 mm Hg of partial pressure of C18O16O with a response time of less than 3 s. The equation of Mills and Urey was used to calculate the hydration velocity constant for uncatalyzed or catalyzed homogenous solutions from the exponential disappearance of mass 46. Addition of red blood cells to the reaction mixture produces biphasic (double exponential) disappearance curve for mass 46. A theory of this process has been developed which describes the time course of [C18O16O] as a function of the catalytic factor for intracellular carbonic anhydrase (A) and the permeability of the cell membrane to HCO3- (P) in addition to the known values; water volume of the cells in the suspension, extracellular pH, the extracellular hydration reaction velocity constant, ku, and dehydration reaction velocity constant, ku. Using this theory, A and P were estimated from the disappearance curve for mass 46 at different values of hematocrit in the reaction mixture, both by a trial and error curve fitting procedure and by a more convenient graphical linearization method. The values of A and P obtained were very sensitive to small amounts of lysis (less than 1%), but the graphical method of analysis minimized this effect. For the blood cells of five normal subjects suspended in 24 mM bicarbonate in 145 mM NaCl at pH 7.4 and 37 degrees, using the graphical method we obtained an average value of 9,906 for A as compared to 19,900 for a comparable concentration of hemolysate. Correcting for a lower pH and chloride concentration inside the cell the latter figure would reduce to 17,500, still 80% higher than the intracellular value. The reason for this discrepancy is not clear. The average permeability of the red cell to bicarbonate ion was 3 X 10(-4) cm/s.

Adult↗
PubMed1975

Cathodic oxygen consumption and electrically induced osteogenesis.

Small amounts of electric current stimulate bone formation in the region of a cathode. The purpose of this experiment is to compare changes in oxygen and hydroxyl ion concentration that occur at the cathode at current levels known to be capable of inducing osteogenesis (10-20 muamps) with those changes that occur at current levels known to be toxic to bone (100 muamps). An oxygen consumption chamber containing an oxygen electrode is fitted with two stainless steel electrodes which are connected to a constant current source. At the cathode, with a current of 100 muamps, oxygen is consumed at nearly stoichiometric rates. At higher current (100 muamps) levels, cathodic oxygen consumption gives way to hydrogen evolution. Cathodic hydroxyl ion production is directly proportional to current. It is concluded from these in vitro experiments that at 10-20 muamps the oxygen tension in the vicinity of the cathode is lowered and the pH is moderately increased. At 100 muamps the oxygen tension is not lowered, but the pH is increased dramatically. If these same changes occur in the vicinity of a cathode in vivo, then lowering the local tissue oxygen tension and raising the local pH may be mechanisms operative in electrically induced bone formation.

Chemical Phenomena↗