Presence Of Constant Concentration Research Articles

Double Diffusive Magneto-Free-Convection Flow of Oldroyd-B Fluid over a Vertical Plate with Heat and Mass Flux

The purpose of this research is to analyze the general equations of double diffusive magneto-free convection in an Oldroyd-B fluid flow based on the fundamental symmetry that are presented in non-dimensional form and are applied to a moving heated vertical plate as the boundary layer flow up, with the existence of an external magnetic field that is either moving or fixed consistent with the plate. The thermal transport phenomenon in the presence of constant concentration, coupled with a first order chemical reaction under the exponential heating of the symmetry of fluid flow, is analyzed. The Laplace transform method is applied symmetrically to tackle the non-dimensional partial differential equations for velocity, mass and energy. The contribution of mass, thermal and mechanical components on the dynamics of fluid are presented and discussed independently. An interesting property regarding the behavior of the fluid velocity is found when the movement is observed in the magnetic intensity along with the plate. In that situation, the fluid velocity is not zero when it is far and away from the plate. Moreover, the heat transfer aspects, flow dynamics and their credence on the parameters are drawn out by graphical illustrations. Furthermore, some special cases for the movement of the plate are also studied.

Information Content in Stochastic Pulse Sequences of Intracellular Messengers

Many cell signaling pathways rely on oscillatory messenger concentrations even to transduce aperiodic environmental changes. The universal second messenger calcium, Ca2+, often exhibits pulsatile behavior in the presence of constant concentrations of external ligands such as hormones or neurotransmitters. Even when the mean interpulse time is a function of the external ligand concentration, the pulse sequence is not regular. The analysis of intracellular Ca2+ pulses that involve Ca2+ release through inositol 1,4,5-trisphosphate (IP3) receptors led to a model with stochastic pulse firing with rate, lambda, and deterministic inhibition and recovery with rate, rho. In this paper we combine this model with recent observations that established an exponential relationship between lambda and the external ligand concentration, C. We compute analytically the mutual information between C and the interpulse time or the number of pulses using the least informative distribution for C in the limits of lambda/rho>1. We obtain that the mutual information is largest in the second limit. The difference between the two, however, is at most ~1 bit. Thus, the resolution with which the values of C can be discriminated at most doubles in one case with respect to the other. The generic features of the model and the exponential dependence of the firing rate with C are an indication that the Ca2+ signaling mechanism behaves as a noise-driven excitable system. Our results are thus applicable in this more general setting as well.

Calcium-sensitive Activity and Conformation of Caenorhabditis elegans Gelsolin-like Protein 1 Are Altered by Mutations in the First Gelsolin-like Domain

The gelsolin family of actin regulatory proteins is activated by Ca(2+) to sever and cap actin filaments. Gelsolin has six homologous gelsolin-like domains (G1-G6), and Ca(2+)-dependent conformational changes regulate its accessibility to actin. Caenorhabditis elegans gelsolin-like protein-1 (GSNL-1) has only four gelsolin-like domains (G1-G4) and still exhibits Ca(2+)-dependent actin filament-severing and -capping activities. We found that acidic residues (Asp-83 and Asp-84) in G1 of GSNL-1 are important for its Ca(2+) activation. These residues are conserved in GSNL-1 and gelsolin and previously implicated in actin-severing activity of the gelsolin family. We found that alanine mutations at Asp-83 and Asp-84 (D83A/D84A mutation) did not disrupt actin-severing or -capping activity. Instead, the mutants exhibited altered Ca(2+) sensitivity when compared with wild-type GSNL-1. The D83A/D84A mutation enhanced Ca(2+) sensitivity for actin severing and capping and its susceptibility to proteolytic digestion, suggesting a conformational change. Single mutations caused minimal changes in its activity, whereas Asp-83 and Asp-84 were required to stabilize Ca(2+)-free and Ca(2+)-bound conformations, respectively. On the other hand, the D83A/D84A mutation suppressed sensitivity of GSNL-1 to phosphatidylinositol 4,5-bisphosphate inhibition. The structure of an inactive form of gelsolin shows that the equivalent acidic residues are in close contact with G3, which may maintain an inactive conformation of the gelsolin family.

Interactions of bradykinin, prostaglandin E1, 5-hydroxytryptamine, histamine and adenosine-5'-triphosphate on the dry leakage response in rat skin.

Dye leakage in rats produced by intracutaneous injections of irritants was quantitated using an azovan blue technique. Concentration-response lines were obtained for irritants alone and in presence of constant concentrations of other irritants. 5-Hydroxytryptamine (5-HT) (10-7M) potentiated histamine, bradykinin and prostaglandin E1 (PGE1) but inhibited adenosine-5'-triphosphate (ATP). Histamine (10-5M) potentiated bradykinin, PGE1 and ATP. Bradykinin (10-6M) potentiated PGE1 only, but PGE1 (10-6M) potentiated bradykinin, 5-HT and histamine. ATP (10-4M) potentiated 5-HT, histamine and PGE1. Release of ATP during stimulation of sensory nerves might explain enhanced neurogenic oedema observed in skin surrounding an area pretreated with compound 48/80.