Ryanodine receptor and capacitative Ca2+ entry in fresh preglomerular vascular smooth muscle cells

Ryanodine receptor and capacitative Ca2+ entry in fresh preglomerular vascular smooth muscle cells.BackgroundA multiplicity of hormonal, neural, and paracrine factors regulates preglomerular arterial tone by stimulating calcium entry or mobilization. We have previously provided evidence for capacitative (store-operated) Ca2+ entry in fresh renal vascular smooth muscle cells (VSMCs). Ryanodine-sensitive receptors (RyRs) have recently been identified in a variety of nonrenal vascular beds.MethodsWe isolated fresh rat preglomerular VSMCs with a magnetized microsphere/sieving technique; cytosolic Ca2+ ([Ca2+]i) was measured with fura-2 ratiometric fluorescence.ResultsRyanodine (3 μmol/L) increased [Ca2+]i from 79 to 138 nmol/L (P = 0.01). Nifedipine (Nif), given before or after ryanodine, was without effect. The addition of calcium (1 mmol/L) to VSMCs in calcium-free buffer did not alter resting [Ca2+]i. In Ca-free buffer containing Nif, [Ca2+]i rose from 61 to 88 nmol/L after the addition of the Ca2+-ATPase inhibitor cyclopiazonic acid and to 159 nmol/L after the addition of Ca2+ (1 mmol/L). Mn2+ quenched the Ca/fura signal, confirming divalent cation entry. In Ca-free buffer with Nif, [Ca2+]i increased from 80 to 94 nmol/L with the addition of ryanodine and further to 166 nmol/L after the addition of Ca2+ (1 mmol/L). Mn2+ quenching was again shown. Thus, emptying of the sarcoplasmic reticulum (SR) with ryanodine stimulated capacitative Ca2+ entry.ConclusionPreglomerular VSMCs have functional RyR, and a capacitative (store-operated) entry mechanism is activated by the depletion of SR Ca2+ with ryanodine, as is the case with inhibitors of SR Ca2+-ATPase

The Politics of (Dis-)location: Queer Migration, Activism, and Coalitional Possibilities

This paper deals with the interrelatedness of borders and queer identities, bodies, sexualities, and the politics of (dis-)location in the U.S. and Germany. Looking into the relations between bodies and borders and the different ways in which activist groups in the U.S. and in Germany have attempted to develop new (re-)configurations of corpo-realities, this article shows how these groups help develop global and embodied forms of citizenship that present new forms of coalitional activism. As can be seen, processes of de- and reterritorialization increase the need for building alliances, which can function both as coalitional moments and revolutionary connections, revealing what Mohanty calls the “the temporality of struggle” (122) in the politics of location

Sinus Node Dysfunction, Atrial Arrhythmias, and the Sinus Node Microcirculation

A patient with sinus node dysfunction (SND) developed atrial arrhythmias that were abolished after avoidance of nonsteroidal anti-inflammatory medication and by the institution of a deliberate, modest increase in blood pressure, suggesting that there was a vascular component to the rhythm disturbance. Published anatomical evidence for a unique sinus node microcirculation substantiates the premise that SND may be sensitive to arterial flow. Because physicians have been unaware of the presence of a unique sinus node microcirculation, recognition of its presence may alter the approach to treatment of patients with SND and atrial arrhythmias, particularly in the elderly and those with diabetes

Glia and alpha-synuclein in neurodegeneration: A complex interaction

Abstractα-Synucleinopathies (ASP) comprise adult-onset, progressive neurodegenerative disorders such as Parkinson's disease (PD), dementia with Lewy bodies (DLB) and multiple system atrophy (MSA) that are characterized by α-synuclein (AS) aggregates in neurons or glia. PD and DLB feature neuronal AS-positive inclusions termed Lewy bodies (LB) whereas glial cytoplasmic inclusions (GCIs, Papp–Lantos bodies) are recognized as the defining hallmark of MSA. Furthermore, AS-positive cytoplasmic aggregates may also be seen in astroglial cells of PD/DLB and MSA brains. The glial AS-inclusions appear to trigger reduced trophic support resulting in neuronal loss. Moreover, microgliosis and astrogliosis can be found throughout the neurodegenerative brain and both are key players in the initiation and progression of ASP. In this review, we will highlight AS-dependent alterations of glial function and their impact on neuronal vulnerability thereby providing a detailed summary on the multifaceted role of glia in ASP

Regularity and mass conservation for discrete coagulation-fragmentation equations with diffusion

We present a new a-priori estimate for discrete coagulation-fragmentation systems with size-dependent diffusion within a bounded, regular domain confined by homogeneous Neumann boundary conditions. Following from a duality argument, this a-priori estimate provides a global $L^2$ bound on the mass density and was previously used, for instance, in the context of reaction-diffusion equations. In this paper we demonstrate two lines of applications for such an estimate: On the one hand, it enables to simplify parts of the known existence theory and allows to show existence of solutions for generalised models involving collision-induced, quadratic fragmentation terms for which the previous existence theory seems difficult to apply. On the other hand and most prominently, it proves mass conservation (and thus the absence of gelation) for almost all the coagulation coefficients for which mass conservation is known to hold true in the space homogeneous case.Comment: 24 page

Stable stationary states of non-local interaction equations

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Endothelin-1, superoxide and adeninediphosphate ribose cyclase in shark vascular smooth muscle

In vascular smooth muscle (VSM) o

A Ca 2+-sensing receptor modulates shark rectal gland function

SUMMARY The elasmobranch Squalus acanthias controls plasma osmolality and extracellular fluid volume by secreting a hypertonic fluid from its rectal gland. Because we found a correlation between extracellular Ca2+ concentration and changes in cytosolic Ca2+ ([Ca2+]i), we sought the possible presence of a calcium-sensing receptor in rectal gland artery and tubules. Cytosolic Ca2+ of both tissues responded to the addition of external Ca2+ (0.8-5.3 mmol l-1) in a linear fashion. Spermine, Gd3+ and Ni2+, known agonists of the calcium-sensing receptor, increased [Ca2+]i. To assess the participation of inositol triphosphate (IP3) generation, sarcoplasmic/endoplasmic reticulum (SR/ER) Ca2+ depletion, and activation of store-operated Ca2+ entry, we utilized thapsigargin and ryanodine to deplete Ca2+ SR/ER stores and the inhibitory reagents TMB-8 and 2-APB to block IP3 receptors. In each case, these agents inhibited the [Ca2+]i response to agonist stimulation by approximately 50 %. Blockade of L-channels with nifedipine had no significant effect. Increases in ionic strength are known to inhibit the calcium-sensing receptor. We postulate that the CaSR stimulates Ca2+-mediated constriction of the rectal gland artery and diminishes cyclic AMP-mediated salt secretion in rectal gland tubules during non-feeding conditions. When the shark ingests sea water and fish, an increase in blood and interstitial fluid ionic strength inhibits the activity of the calcium-sensing receptor, relaxing the rectal gland artery and permitting salt secretion by the rectal gland tubules

Endothelin A and B receptors of preglomerular vascular smooth muscle cells

BACKGROUND: The endothelin (ET) receptors are subclassified into ET(A,) which are purely vasoconstrictive, and ET(B). The ET(B) receptors may cause either vasodilation by stimulating the release of nitric oxide from endothelial cells, or vasoconstriction of vascular smooth muscle cells (VSMC). The relative contribution of ET(A) and ET(B) receptors to calcium signaling and vasoconstriction in the renal microcirculation is not clear. Our goal was to study the cytosolic calcium concentration ([Ca(2+)](i)) responses of fresh rat preglomerular VSMC and afferent arterioles to agonists and antagonists of ET(A) and ET(B) receptors in rats. METHODS: Fresh VSMC and afferent arterioles were isolated using the magnetized microsphere/sieving technique, followed by gentle collagenase digestion. [Ca(2+)](i) was measured with fura-2 ratiometric fluorescence. RESULTS: Afferent arterioles and VSMC responded to ET-1 stimulation with a rapid peak increase in [Ca(2+)](i) (Delta= 287 +/- 81 and 342 +/- 55 nmol/L, respectively). The ET(B) receptor agonist IRL 1620 stimulated a rise in [Ca(2+)](i) in afferent arterioles (106 +/- 35 nmol/L); subsequent addition of ET-1 at the IRL 1620 nadir to stimulate ET(A) receptors caused a second peak that was twice as large (213 +/- 44 nmol/L). In VSMC, the ET(B) agonist peak increase was 99 +/- 12 nmol/L; addition of ET-1 then increased [Ca(2+)](i) by 294 +/- 23 nmol/L. The ET(B) inhibitor BQ-788 prevented stimulation of [Ca(2+)](i) by IRL 1620 in afferent arterioles and VSMC; subsequent stimulation of ET(A) receptors with ET-1 caused an increase in [Ca(2+)](i) (239 +/- 17 and 248 +/- 22 nmol/L). Pretreatment with the selective ET(A) inhibitor PD 156707 attenuated but did not abolish the responses to ET-1, suggesting that the residual [Ca(2+)](i) response was caused by ET(B) stimulation. CONCLUSION: These results indicate that fresh preglomerular VSMC as well as afferent arterioles have both ET(A) and ET(B) receptors, and that the rapid peak [Ca(2+)](i) responses to the ET(B) agonist IRL 1620 are less than half that of subsequent stimulation of ET(A) receptors with ET-1. The similarity of findings in isolated VSMC and afferent arterioles suggests that responses in VSMC in our arteriolar preparation overshadow any potential contribution of endothelial cells when reagents are administered abluminally

Growth behaviour of periodic tame friezes

We examine the growth behaviour of the entries occurring in n-periodic tame friezes of real numbers. Extending work of the last author, we prove that generalised recursive relations exist between all entries of such friezes. These recursions are parametrised by a sequence of so-called growth coefficients, which is itself shown to satisfy a recursive relation. Thus, all growth coefficients are determined by a principal growth coefficient, which can be read-off directly from the frieze. We place special emphasis on periodic tame friezes of positive integers, specifying the values the growth coefficients take for any such frieze. We establish that the growth coefficients of the pair of friezes arising from a triangulation of an annulus coincide. The entries of both are shown to grow asymptotically exponentially, while triangulations of a punctured disc are seen to provide the only friezes of linear growth