Current Topics in Cellular Regulation, Volume 21 examines the advances in the general area of cellular regulation. This book discusses the roles of eukaryotic initiation factor 2 ancillary factors in the regulation of eukaryotic protein synthesis initiation and phosphorylation state of eIF-2. The monoclonal antibodies to cap-binding proteins, criteria for establishment of the biological significance of ribosomal protein phosphorylation, and comparison with casein kinases from mammary gland are also elaborated. This text likewise covers the regulation of phosphoprotein phosphatases, poly(ADP-ribosyl)ation reactions in vitro, and induced commitment to terminal erythroid differentiation. Other topics include the turnover characteristics of lactate dehydrogenase and role of urea synthesis in the removal of metabolic bicarbonate and regulation of blood pH. This volume is useful to biologists and researchers interested in basic mechanisms involved in the regulation of diverse cellular activities.