Influence of Rotation on Pulsar Radiation Characteristics

We present a relativistic model for pulsar radio emission by including the effect of rotation on coherent curvature radiation by bunches. We find that rotation broadens the width of leading component compared to the width of trailing component. We estimate the component widths in the average pulse profiles of about 24 pulsars, and find that 19 of them have a broader leading component. We explain this difference in the component widths by using the nested cone emission geometry. We estimate the effect of pulsar spin on the Stokes parameters, and find that the inclination between the rotation and magnetic axes can introduce an asymmetry in the circular polarization of the conal components. We analyze the single pulse polarization data of PSR B0329+54 at 606 MHz, and find that in its conal components, one sense of circular polarization dominates in the leading component while the other sense dominates in the trailing component. Our simulation shows that changing the sign of the impact parameter changes the sense of circular polarization as well as the swing of polarization angle.Comment: 20 pages, 4 Postscript figures, uses aastex.cls. Accepted for Publication in ApJ 200

Radio Emission by Particles due to Pulsar Spin

We present a relativistic model for the motion of charged particles in rotating magnetic field lines projected on to a plane perpendicular to the rotation axis. By making an approximation that the projected field lines are straight, an analytical expression is obtained for the particle trajectory. The motive behind developing this model is to elucidate some of the effects of rotation in pulsar profiles. There is a significant contribution to the curvature of particle trajectory due to the rotation of pulsar, which is in addition to the inherent curvature of the field lines. The asymmetry in the observed pulse shapes can be explained by considering the aberration-retardation effects. The single sign circular polarization that has been observed in many pulsars, might be due to the relative orientation of sight line with respect to the particle trajectory plane.Comment: 19 pages, 6 figues. Submitted to Astronomy and Astrophysic

Combined histamine H_1/H_2 receptor antagonists: Part II. Pharmacological hybrids with pheniramine- and tiotidine-like substructures,

Hybrid molecules combining the crucial structural features of both pheniramine-type histamine H1 receptor antagonists and guanidinothiazole-type H2 receptor antagonists have been synthesized and tested for in vitro pharmacological activity at the isolated ileum and the spontaneously beating right atrium of the guinea-pig. In the title compounds the basic side chain nitrogen of the H1 antagonist and the so-called ‘polar group' (cyanoguanidine, urea, or nitroethenediamine) of the H2 antagonist moiety have been linked by a polymethylene spacer. The new substances displayed high affinities to both histamine receptor subtypes and a dual type of antagonism (surmountable/insurmountable) characterized by a shift of the concentration response curves to the right accompanied by a depression of the maximal response to the agonist if the antagonist concentration was ≥100 nM. Highest combined histamine antagonist activities were found in the nitroethenediamine series with pKB values ranging from 8.16 to 9.04 in the ileum (H1) and 7.0–8.08 in the atrium (H2

Dissociations in the effects of beta2-adrenergic receptor agonists on cAMP formation and superoxide production in human neutrophils: Support for the concept of functional selectivity

In neutrophils, activation of the beta2-adrenergic receptor (beta2AR), a Gs-coupled receptor, inhibits inflammatory responses, which could be therapeutically exploited. The aim of this study was to evaluate the effects of various beta2AR ligands on adenosine-3',5'-cyclic monophosphate (cAMP) accumulation and N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP)-induced superoxide anion (O2*-) production in human neutrophils and to probe the concept of ligand-specific receptor conformations (also referred to as functional selectivity or biased signaling) in a native cell system. cAMP concentration was determined by HPLC/tandem mass spectrometry, and O2*- formation was assessed by superoxide dismutase-inhibitable reduction of ferricytochrome c. beta2AR agonists were generally more potent in inhibiting fMLP-induced O2*- production than in stimulating cAMP accumulation. (-)-Ephedrine and dichloroisoproterenol were devoid of any agonistic activity in the cAMP assay, but partially inhibited fMLP-induced O2*- production. Moreover, (-)-adrenaline was equiefficacious in both assays whereas the efficacy of salbutamol was more than two-fold higher in the O2*- assay. In contrast to the agonists, the effects of beta2AR antagonists were comparable between the two parameters on neutrophils. Differences between the data from neutrophils and recombinant test systems were observed for the beta2AR agonists as well as for the beta2AR antagonists. Lastly, we obtained no evidence for an involvement of protein kinase A in the inhibition of fMLP-induced O2*- production after beta2AR-stimulation, although, in principle, cAMP-increasing substances can inhibit O2*- production. Taken together, our data corroborate the concept of ligand-specific receptor conformations with unique signaling capabilities and suggest that the beta2AR inhibits O2*- production in a cAMP-independent manner