Influx of Ca2+ into isolated secretory vesicles from adrenal medulla Influence of external K+ and Na+

Secretory vesic1es from adrenal medulla contain catecholamines, nuc1eotides and proteins, all of which are released into the extracellular fluid during exocytosis. Adrenal medullary secretory vesic1es also contain high concentrations of Ca'+ [1]. The mechanism of the aecumulation of Ca 2+ into the vesicles is largely unknown and the experimental data eoncerning the uptake of Ca'+ into isolated secretory vesicles are contradictory. It has been reported that secretory vesicle membranes are impermeable to Ca'+ [2], that secretory vesicles take up Ca 2+ independently of ATP [3] and that they possess an ATP-stimulated uptake system [4,5]. In earlier work relatively impure and unstable seeretory vesicle fractions were used for the determination of Ca 2+ -uptake. We have developed a method to isolate highly purified and stable secretory vesicles from bovine medulla [6]. With these vesic1es we repeated earlier Ca'+ -uptake experiments and found that: (i) The vesic1es take up <sCa2+ in K+-containingmedia; (ü) 4SCa2+ uptake is abolished in the presence ofNa+; (üi) nie Ca 2+ content of isolated secretory vesic1es is increased when incubated with Ca 2+ in media containing K+, but not in media containing Na +

Glucocorticoids rapidly inhibit oxytocin-stimulated adrenocorticotropin release from rat anterior pituitary cells, without modifying intracellular calcium transients

Glucocorticoid hormones suppress the secretion of ACTH evoked by secretagogues such as CRF and arginine vasopressin. In this study, we investigated the effects of glucocorticoids on ACTH release induced by oxytocin (OT) and on intracellular free calcium ion levels in corticotropes prepared from the adenohypophyses of female Wistar rats. Pulsatile additions of physiological concentration of OT (10 nM) to superfused anterior pituitary cells caused pulsatile ACTH release about 4-fold above basal secretion with similar peak amounts of ACTH during subsequent OT pulses. Exposure of the cells to corticosterone (100 nM) or to a selective glucocorticoid receptor agonist RU 28362 (100 nM) for 30 min suppressed OT-stimulated but not basal ACTH release by approximately 60%. Inhibition gradually disappeared during subsequent pulses of OT in the absence of corticosterone. Pretreatment with the selective antagonist RU 38486 (1 microM) completely blocked the inhibitory effect of corticosterone on OT-induced ACTH secretion. Changes in free cytosolic calcium levels in single cultured pituitary cells were measured using the calcium indicator Fura-2. OT caused calcium transients in corticotropes, which were identified by immunocytochemistry. They responded in a similar manner to a second OT stimulus when preincubated for 30 min with corticosterone (1 microM) or with RU 28362 (1 microM). Our data indicate that glucocorticoids, via glucocorticoid receptors, rapidly inhibit OT-stimulated ACTH secretion by corticotropes without affecting intracellular calcium transients due to OT. Therefore, we conclude that rapid inhibition of ACTH release by glucocorticoids interferes with cellular signal transduction beyond the step of calcium mobilization

Imaging Techniques for Relativistic Beams: Issues and Limitations

Characterizations of transverse profiles for low-power beams in the accelerators of the proposed linear colliders (ILC and CLIC) using imaging techniques are being evaluated. Assessments of the issues and limitations for imaging relativistic beams with intercepting scintillator or optical transition radiation screens are presented based on low-energy tests at the Fermilab A0 photoinjector and are planned for the Advanced Superconducting Test Accelerator at Fermilab.Comment: 8 pages, 11 Figures, LCWS1

The cause of the weak solar cycle 24

The ongoing 11-year cycle of solar activity is considerably less vigorous than the three cycles before. It was preceded by a very deep activity minimum with a low polar magnetic flux, the source of the toroidal field responsible for solar magnetic activity in the subsequent cycle. Simulation of the evolution of the solar surface field shows that the weak polar fields and thus the weakness of the present cycle 24 are mainly caused by a number of bigger bipolar regions emerging at low latitudes with a `wrong' (i.e., opposite to the majority for this cycle) orientation of their magnetic polarities in the North-South direction, which impaired the growth of the polar field. These regions had a particularly strong effect since they emerged within $\pm10^\circ$ latitude from the solar equator.Comment: 15 pages, 5 figures, accepted for publication in ApJ

Solar cycle 25: another moderate cycle?

Surface flux transport simulations for the descending phase of cycle 24 using random sources (emerging bipolar magnetic regions) with empirically determined scatter of their properties provide a prediction of the axial dipole moment during the upcoming activity minimum together with a realistic uncertainty range. The expectation value for the dipole moment around 2020 $(2.5\pm1.1\,$G) is comparable to that observed at the end of cycle 23 (about $2\,$G). The empirical correlation between the dipole moment during solar minimum and the strength of the subsequent cycle thus suggests that cycle 25 will be of moderate amplitude, not much higher than that of the current cycle. However, the intrinsic uncertainty of such predictions resulting from the random scatter of the source properties is considerable and fundamentally limits the reliability with which such predictions can be made before activity minimum is reached.Comment: 13 papges, 4 figures,Accepted for publication in ApJ

Possible pairing symmetries in SrPtAs with a local lack of inversion center

We discuss possible pairing symmetries in the hexagonal pnictide superconductor SrPtAs. The local lack of inversion symmetry of the two distinct conducting layers in the unit cell results in a special spin-orbit coupling with a staggered structure. We classify the pairing symmetry by the global crystal point group D_3d, and suggest some candidates for the stable state using a tight-binding model with an in-plane, density-density type pairing interaction. We may have some unconventional states like s+f-wave and a mixture of chiral d-wave and chiral p-wave. The spin orbit coupling is larger than the interlayer hopping, and the mixing between spin-singlet and triplet states can be seen in spite of the fact that the system has a global inversion center.Comment: 5 pages, 3 figure

Electroweak Absolute, Meta-, and Thermal Stability in Neutrino Mass Models

We analyze the stability of the electroweak vacuum in neutrino mass models containing right handed neutrinos or fermionic isotriplets. In addition to considering absolute stability, we place limits on the Yukawa couplings of new fermions based on metastability and thermal stability in the early Universe. Our results reveal that the upper limits on the neutrino Yukawa couplings can change significantly when the top quark mass is allowed to vary within the experimental range of uncertainty in its determination.Comment: 7 pages, 4 figures, match published versio