Description of strains of Peptostreptococcus anaerobius isolated from subcutaneous abscesses in cats.

Strains of Peptostreptococcus, Streptococcus and of a Gram-positive coccus, which was initially isolated as an anaerobe but grew subsequently as a facultative organism, were isolated from subcutaneous abscesses in cats. The cat strains of Peptostreptococcus gave metabolic fermentation products in combinations described for P. anaerobius. The Streptococcus strains conformed to the group S. intermedius. The facultative organism described had the metabolic products of P. anaerobius but the distinctly different biochemical characteristics of S. intermedius and fits neither of the genera strictly.     

Erythropoietin increases c-myc mRNA by a protein kinase C-dependent pathway

The peptide hormone erythropoietin is a major regulator of red blood cell production. While red blood cell development has been studied intensively, little is known about the intracellular signaling events that follow the binding of erythropoietin to its receptor on the target cell. We report here that erythropoietin-induced activation of the immediate early gene c-myc requires protein kinase C and that the binding of erythropoietin causes rapid phosphorylation of the major protein kinase C substrate, p80. Our results also argue for modulation of activity of a second signal transduction element in addition to protein kinase C.     

A kinetic model of CD4+ lymphocytes with the human immunodeficiency virus (HIV).

This report describes a kinetic model of in vitro cytopathology involving interactions of human immunodeficiency virus (HIV) with CD4+ helper T lymphocytes. The model uses nonlinearly coupled, ordinary differential equations to simulate the dynamics of infected and uninfected cells and free virions. It is assumed that resting cells are more readily infected than activated cells, but once infected, only activated cells produce more virus. Resting cells can be activated by some appropriate stimulus (e.g. phytohemagglutinin, soluble antigen). The model predicts that the initial inoculum of virus is taken up by resting cells and without stimulation the system comes to a steady state of two populations, namely infected and uninfected cells. Stimulation of this system produces two additional populations, namely infected and uninfected activated cells which, along with the previous populations, exhibit cyclic behavior of growth, viral expression/release, and death. Additional stimuli enhance or diminish the cyclic behavior depending upon their occurrence in time. These simulations suggest a similar dynamics in human HIV infection and may explain a major factor responsible for the widely varying depletion rate of (CD4+) helper T cells in AIDS patients.     

Enzyme Promiscuity: Engine of Evolutionary Innovation

Catalytic promiscuity and substrate ambiguity are keys to evolvability, which in turn is pivotal to the successful acquisition of novel biological functions. Action on multiple substrates (substrate ambiguity) can be harnessed for performance of functions in the cell that supersede catalysis of a single metabolite. These functions include proofreading, scavenging of nutrients, removal of antimetabolites, balancing of metabolite pools, and establishing system redundancy. In this review, we present examples of enzymes that perform these cellular roles by leveraging substrate ambiguity and then present the structural features that support both specificity and ambiguity. We focus on the phosphatases of the haloalkanoate dehalogenase superfamily and the thioesterases of the hotdog fold superfamily.