the effect of physiological concentrations of caffeine (purified from persian tea) on adenosine deaminase (ada) activity at physiological and pathological concentrations of adenosine (as substrate) in 50 mm tris-hcl buffer (ph 7.3) at 37°c was investigated, using uv-vis spectroscopy. ada exhibited a bi-phasic activity behavior and both phases showed positive cooperativities indicating adenosine...

Structural and dynamical fingerprints of evolutionary optimization in biological networks are still unclear. Here we analyze the dynamics of genetic regulatory networks responsible for the regulation of cell cycle and cell differentiation in three organisms or cell types each, and show that they follow a version of Hebb's rule which we have termed coherence. More precisely, we find that simulta...

Immunoreceptor tyrosine-based inhibition motifs (ITIMs) consist of a 6-amino acid stretch (ILV)xYxx(LV). ITIMs are expressed in the intracytoplasmic domain of transmembrane receptors, which extinguish cell activation induced by receptors bearing immunoreceptor tyrosine-based activation motifs. The recent identification of new members of the ITIM-bearing receptor family (such as the signal-regul...

FcgammaRI depends for its biological function on both the intracellular domain of the alpha-chain and associated Fc receptor (FcR) gamma-chains. However, functional protein effectors of FcgammaRI's intracellular domain have not been identified. In this study, we identified periplakin (PPL) as a selective interacting protein for the intracellular tail of FcgammaRI but no other activatory FcRs. T...

Although each statistical unit on which measurements are taken is unique typically there is not enough information available to account totally for its uniqueness. Therefore heterogeneity among units has to be limited by structural assumptions. One classical approach is to use random effects models, which assume that heterogeneity can be described by distributional assumptions. However, inferen...

Meta-analysis is a standard statistical method used to combine the conclusions of individual studies that are related and the results of single study alone can not answered to deal with issues. The data are summarized by one or more outcome measure estimates along with their standard errors. The multivariate model and the variations between studies are not considered in most articles. Here we d...

This paper sheds some light on the problems associated with random effects gravity approaches. Arguments for the superiority of a fixed effects model are given both along intuitive and econometric lines based on a Hausman test.  2000 Elsevier Science S.A. All rights reserved.

This paper uses data drawn from the English Football League to model separate hazard rates for club managers for the 2001/2, 2002/3 and 2003/4 seasons. On average over the three seasons, approximately one-third of managers involuntarily exited employment status with their club. We model the hazard using a standard logistic model exploiting information on the spell at risk rather than the indivi...

The melanocortin 1 receptor (MC1R) is a G-protein-coupled receptor (GPCR) crucial for the regulation of melanocyte proliferation and differentiation. MC1R activation by melanocortin hormones triggers the cAMP pathway and stimulates the extracellular-signal-regulated protein kinases ERK1 and ERK2 to promote synthesis of photoprotective eumelanin pigments, among other effects. Signaling from most...