Does calmodulin participate in the regulation of the Ca-pump of erythrocytes in vivo?

Using a highly effective chelator of Ca2+ and 45Ca, the concentration of Cai2+ in human and rat erythrocytes was measured both at normal and accelerated Ca2+ influx into the cells. No effect of the calmodulin-dependent reaction inhibitor R24571 was observed. The Ca-ATPase from saponin-treated erythrocytes was characterized by a high affinity for Ca2+ (K 0.5-0.7 microM). This value is 2-3 times as low as that for Ca2+ concentration causing a 50% increase of the Ca-ATPase activity in erythrocyte ghosts obtained during hypoosmotic hemolysis. The Ca-ATPase activity in saponin-treated erythrocytes did not change either under the effect of calmodulin or by R24571. It was assumed that calmodulin did not participate in the regulation of the Ca2+-pump operation in erythrocytes in vivo.     

Structural identity of active sites of RNases

It is known that the affinity of all nucleoside monophosphate isomers for RNAase active sites increases in the following order: 5'-NMP----3'-NMP----2'-NMP, irrespective of the RNAase type (pyrimidine-specific, guanine-specific or non-specific) and stage of activity (transferase, hydrolase). It is known also that the nucleotides with the same degree of isomerism have substantially the same conformation. It was thus supposed that the structure of active sites of RNAase has common features with a closer similarity in case of pyrimidine-specific (EC 3.1.4.22), guanine-specific (EC 3.1.4.8) and non-specific (EC 3.1.4.23) RNAases.     

Cellular immunity in pyelonephritis: inhibition of the spleen cell response to the mitogen concanavalin A

Spleen cells from rats given experimental pyelonephritis using Escherichia coli and Proteus mirabilis as infecting organisms were evaluated for their ability to respond to the mitogen Concanavalin A. Results indicate an 80% reduction in the response of animals with gross suppuration in the kidney, but no inhibition is observed in animals with kidney infection, but not renal abscesses. The inhibition is not, apparently, due to serum factors.