The levels of iron, zinc, and copper in the tissues of the pregnant rat, on d 12, 19, and 21 after impregnation have been determined and compared with controls. Iron levels decreased considerably in late pregnancy as a result of increased fetal requirements, thus diminishing iron stores in rat tissues, but maintaining the circulating plasma levels. Copper levels increased slightly at midpregnancy, but returned to control levels at the end of gestation. Zinc stores also increased slightly during early pregnancy, yet were decreased at the end of pregnancy, but to a lesser extent than those of iron. The data are explained on the basis of equilibrium between assimilation and fetal needs for copper, a slightly higher demand for zinc with altered equilibrium, and a much altered equilibrium for iron that provokes a dwindling of iron maternal reserves that is not compensated by dietary iron.
A kinetic study of the fl-glucosidase-catalysed reaction of a commercial cellulase preparation from Trichoderma viride is described. The Krn and Vmax values of the fl-glucosidase system were: (a) 0.SmM and 6.6 ~mol/min, respectively, using p-nitrophenyl fl-D-glucopyranoside (pNPG) as substrate; and (b) 2.5 mM and 8.1 ixmol/min, respectively, using cellobiose as subtrate. The glucose effect on initial reaction velocity agrees with a mixed-inhibition pattern. The inhibition constant (Ki) values were, 0.53 and 0.39 mM with p N P G and cellobiose as substrates, respectively. The temperature and pH optima were determined.
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