scholarly journals Role of cytoplasmic calcium concentration in the bleaching adaptation of salamander cone photoreceptors.

1996 ◽  
Vol 490 (2) ◽  
pp. 293-303 ◽  
Author(s):  
H R Matthews ◽  
G L Fain ◽  
M C Cornwall
Keyword(s):  
Calcium Concentration ◽  
Cytoplasmic Calcium ◽  
Cone Photoreceptors

Albumin modulation of capillary permeability: role of endothelial cell [Ca2+]i

1993 ◽  
Vol 265 (1) ◽  
pp. H74-H82 ◽  
Author(s):  
P. He ◽  
F. E. Curry
Keyword(s):  
Endothelial Cells ◽  
Endothelial Cell ◽  
Calcium Concentration ◽  
Capillary Permeability ◽  
Common Mechanism ◽  
Cytoplasmic Calcium ◽  
Adsorption Model ◽  
Endothelial Cell Surface ◽  
Mesenteric Microvessels

Albumin is required in vascular perfusates to maintain the normal permeability of microvessel walls. The most common mechanism proposed for action of albumin involves binding to the endothelial cell surface to increase the resistance to water and solute flows through hydraulic pathways across the capillary wall. The results of the present experiments do not conform to this simple adsorption model. Ringer perfusion increased the hydraulic conductivity (Lp) of the wall of single perfused frog mesenteric microvessels by 4.0 +/- 0.5-fold. The increase in Lp was associated with an increase of cytoplasmic calcium concentration ([Ca2+]i) from 59 +/- 5 nM when albumin was in the perfusate to a transient peak of 181 +/- 13 nM, 1–2 min after Ringer perfusion. [Ca2+]i then fell back to close to 100 nM. Processes that reduced Ca2+ influx into endothelial cells (removal of extracellular Ca2+, membrane depolarization) reduced Ca2+ influx and attenuated the increase in [Ca2+]i. The same processes abolished the increase in Lp after Ringer perfusion and restored Lp to close to control values during Ringer perfusion. Thus Ca2+ entry into endothelial cells is required to initiate and maintain the increased permeability during Ringer perfusion.

Intracellular calcium levels in the Plasmodium berghei ookinete

Parasitology ◽  
2008 ◽  
Vol 135 (12) ◽  
pp. 1355-1362 ◽  
Author(s):  
I. SIDÉN-KIAMOS ◽  
C. LOUIS
Keyword(s):  
Intracellular Calcium ◽  
Plasmodium Berghei ◽  
Calcium Concentration ◽  
Insect Cells ◽  
Ionophore A23187 ◽  
Rodent Malaria Parasite ◽  
Calcium Indicators ◽  
Intracellular Ca

SUMMARYOokinetes are the motile and invasive stages of Plasmodium parasites in the mosquito host. Here we explore the role of intracellular Ca2+ in ookinete survival and motility as well as in the formation of oocysts in vitro in the rodent malaria parasite Plasmodium berghei. Treatment with the Ca2+ ionophore A23187 induced death of the parasite, an effect that could be prevented if the ookinetes were co-incubated with insect cells before incubation with the ionophore. Treatment with the intracellular calcium chelator BAPTA/AM resulted in increased formation of oocysts in vitro. Calcium imaging in the ookinete using fluorescent calcium indicators revealed that the purified ookinetes have an intracellular calcium concentration in the range of 100 nm. Intracellular calcium levels decreased substantially when the ookinetes were incubated with insect cells and their motility was concomitantly increased. Our results suggest a pleiotropic role for intracellular calcium in the ookinete.

scholarly journals The Role of Two-Pore Channels in Norepinephrine-Induced [Ca2+]i Rise in Rat Aortic Smooth Muscle Cells and Aorta Contraction

Cells ◽  
2019 ◽  
Vol 8 (10) ◽  
pp. 1144 ◽  
Author(s):  
Sergei K. Trufanov ◽  
Elena Yu. Rybakova ◽  
Piotr P. Avdonin ◽  
Alexandra A. Tsitrina ◽  
Irina L. Zharkikh ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Calcium Concentration ◽  
Muscle Cells ◽  
Rat Aorta ◽  
Structural Analogue ◽  
Aortic Smooth Muscle ◽  
Cis And Trans ◽  
High Degree

Second messenger nicotinic acid adenine dinucleotide phosphate (NAADP) triggers Ca2+ release via two-pore channels (TPCs) localized in endolysosomal vesicles. The aim of the present work is to evaluate the role of TPCs in the action of norepinephrine (NE), angiotensin II (AngII), vasopressin (AVP), and 5-hydroxytriptamine (5-HT) on free cytoplasmic calcium concentration ([Ca2+]i) in smooth muscle cells (SMCs) isolated from rat aorta and on aorta contraction. To address this issue, the NAADP structural analogue and inhibitor of TPCs, NED 19, was applied. We have demonstrated a high degree of colocalization of the fluorescent signals of cis-NED 19 and endolysosmal probe LysoTracker in SMCs. Both cis- or trans-NED 19 inhibited the rise of [Ca2+]i in SMCs induced by 100 μM NE by 50–60%. IC50 for cis- and trans-NED 19 were 2.7 and 8.9 μM, respectively. The inhibition by NED 19 stereoisomers of the effects of AngII, AVP, and 5-HT was much weaker. Both forms of NED 19 caused relaxation of aortic rings preconstricted by NE, with relative potency of cis-NED 19 several times higher than that of trans-NED 19. Inhibition by cis-NED 19 of NE-induced contraction was maintained after intensive washing and slowly reversed within an hour of incubation. Cis- and trans-NED 19 did not cause decrease in the force of aorta contraction in response to Ang II and AVP, and only slightly relaxed aorta preconstricted by 5-HT and by KCl. Suppression of TPC1 in SMCs with siRNA caused a 40% decrease in [Ca2+]i in response to NE, whereas siRNA against TPC2 did not change NE calcium signaling. These data suggest that TPC1 is involved in the NE-stimulated [Ca2+]i rise in SMCs. Inhibition of TPC1 activity by NED 19 could be the reason for partial inhibition of aortic rings contraction in response to NE.

Extracellular ATP increases [Ca 2+]i in distal tubule cells. I. Evidence for a P2Y2 purinoceptor

2000 ◽  
Vol 279 (1) ◽  
pp. F92-F101 ◽  
Author(s):  
Michel Bidet ◽  
Guy De Renzis ◽  
Sonia Martial ◽  
Isabelle Rubera ◽  
Michel Tauc ◽  
...  
Keyword(s):  
Calcium Concentration ◽  
Distal Tubule ◽  
Calcium Flux ◽  
Free Calcium ◽  
Receptor Subtype ◽  
Cytoplasmic Calcium ◽  
P2y2 Receptor ◽  
Nucleotide Analogs ◽  
Flux Measurements ◽  
Free Calcium Concentration

Experiments were performed to characterize the P2 purinoceptor subtype responsible for cytoplasmic calcium mobilization in cells from the initial part of rabbit distal convoluted tubule (DCT). Free calcium concentration was measured in a DCT cell line (DC1) with the probe fura 2. Both ATP and UTP increased cytosolic Ca2+ concentration ([Ca2+]i; EC50 3 and 6 μM, respectively). The order of potency for nucleotide analogs was ATP = UTP > adenosine 5′- O-[thiotriphosphate] ≫ ADP > UDP, which is consistent with the pharmacology of the P2Y2 receptor subtype. The increased [Ca2+]iresponses to ATP and UTP were strongly inhibited by suramin. Pretreatment of cells with pertussis toxin (PTX) attenuated the action of both nucleotides. Inhibition of phospholipase C with U-73122 totally blocked the [Ca2+]i response to ATP. Thus ATP- and UTP-stimulated [Ca2+]i mobilization in DC1 cells appears to be mediated via the activation of P2Y2 purinoceptors coupled to a G protein mechanism that is partially sensitive to PTX. Calcium flux measurements showed that lanthanum- and nifedipine-sensitive calcium channels are involved in the [Ca2+]i response to ATP.

scholarly journals Voltage-clamp recordings of light responses from wild-type and mutant mouse cone photoreceptors

2019 ◽  
Vol 151 (11) ◽  
pp. 1287-1299 ◽  
Author(s):  
Norianne T. Ingram ◽  
Alapakkam P. Sampath ◽  
Gordon L. Fain
Keyword(s):  
Voltage Clamp ◽  
Mouse Retina ◽  
Cone Photoreceptors ◽  
Wild Type ◽  
Light Responses ◽  
Α Subunit ◽  
Background Light ◽  
Connexin 36 ◽  
Mouse Lines

We describe the first extensive study of voltage-clamp current responses of cone photoreceptors in unlabeled, dark-adapted mouse retina using only the position and appearance of cone somata as a guide. Identification was confirmed from morphology after dye filling. Photocurrents recorded from wild-type mouse cones were biphasic with a fast cone component and a slower rod component. The rod component could be eliminated with dim background light and was not present in mouse lines lacking the rod transducin-α subunit (Gnat1−/−) or connexin 36 (Cx36−/−). Cones from Gnat1−/− or Cx36−/− mice had resting membrane potentials between −45 and −55 mV, peak photocurrents of 20–25 picoamps (pA) at a membrane potential Vm = −50 mV, sensitivities 60–70 times smaller than rods, and a total membrane capacitance two to four times greater than rods. The rate of activation (amplification constant) was largely independent of the brightness of the flash and was 1–2 s−2, less than half that of rods. The role of Ca2+-dependent transduction modulation was investigated by recording from cones in mice lacking rod transducin (Gnat1), recoverin, and/or the guanylyl-cyclase–activating proteins (GCAPs). In confirmation of previous results, responses of Gnat1−/−;Gcaps−/− cones and triple-mutant Gnat1−/−;Gcaps−/−;Rv−/− cones recovered more slowly both to light flashes and steps and were more sensitive than cones expressing the GCAPs. Cones from all four mouse lines showed significant recovery and escaped saturation even in bright background light. This recovery occurred too rapidly to be caused by pigment bleaching or metaII decay and appears to reflect some modulation of response inactivation in addition to those produced by recoverin and the GCAPs. Our experiments now make possible a more detailed understanding of the cellular physiology of mammalian cone photoreceptors and the role of conductances in the inner and outer segment in producing cone light responses.

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