Activity Of Ca2 Research Articles

Effect of saponin on erythrocytes.

Saponins, naturally occurring glycosides and triterpene glycosides in plants, are considered useful in the prophylaxis and treatment of several disorders, including malignancy. The effect of these substances is partly attributable to induction of both apoptosis and necrosis. Saponin has previously been shown to trigger hemolysis. Erythrocytes may avoid hemolysis by entering programmed cell death or eryptosis, characterized by cell shrinkage and cell membrane scrambling, leading to phosphatidylserine exposure at the erythrocyte surface. Eryptosis is triggered by increase of cytosolic Ca(2+) activity ([Ca(2+)](i)). The present study explored, whether exposure of human erythrocytes to saponin modifies [Ca(2+)](i), ceramide formation, hemolysis, and eryptosis. Cell volume was estimated from forward scatter, phosphatidylserine exposure from annexin V binding, hemolysis from hemoglobin release, [Ca(2+)](i) from Fluo3-fluorescence, and ceramide utilizing specific antibodies. A 24 h exposure to saponin (15 µg/ml) resulted in a significant increase of annexin V binding and a significant stimulation of hemolysis. Saponin (15 µg/ml) further increased [Ca(2+)](i) and ceramide formation. Annexin V binding was significantly blunted but not abrogated in the nominal absence of extracellular Ca(2+). Saponin thus triggers cell membrane scrambling, an effect partially due to entry of extracellular Ca(2+) and ceramide formation.

Bax Inhibitor-1-Mediated Inhibition of Mitochondrial Ca2+ Intake Regulates Mitochondrial Permeability Transition Pore Opening and Cell Death

A recently studied endoplasmic reticulum (ER) stress regulator, Bax inhibitor-1 (BI-1) plays a regulatory role in mitochondrial Ca2+ levels. In this study, we identified ER-resident and mitochondria-associated ER membrane (MAM)-resident populations of BI-1. ER stress increased mitochondrial Ca2+ to a lesser extent in BI-1–overexpressing cells (HT1080/BI-1) than in control cells, most likely as a result of impaired mitochondrial Ca2+ intake ability and lower basal levels of intra-ER Ca2+. Moreover, opening of the Ca2+-induced mitochondrial permeability transition pore (PTP) and cytochrome c release were regulated by BI-1. In HT1080/BI-1, the basal mitochondrial membrane potential was low and also resistant to Ca2+ compared with control cells. The activity of the mitochondrial membrane potential-dependent mitochondrial Ca2+ intake pore, the Ca2+ uniporter, was reduced in the presence of BI-1. This study also showed that instead of Ca2+, other cations including K+ enter the mitochondria of HT1080/BI-1 through mitochondrial Ca2+-dependent ion channels, providing a possible mechanism by which mitochondrial Ca2+ intake is reduced, leading to cell protection. We propose a model in which BI-1–mediated sequential regulation of the mitochondrial Ca2+ uniporter and Ca2+-dependent K+ channel opening inhibits mitochondrial Ca2+ intake, thereby inhibiting PTP function and leading to cell protection.

Constitutive phosphorylation of myosin phosphatase targeting subunit-1 in smooth muscle.

Smooth muscle contraction initiated by myosin regulatory light chain (RLC) phosphorylation is dependent on the relative activities of Ca(2+)-calmodulin-dependent myosin light chain kinase (MLCK) and myosin light chain phosphatase (MLCP). We have investigated the physiological role of the MLCP regulatory subunit MYPT1 in bladder smooth muscle containing a smooth muscle-specific deletion of MYPT1 in adult mice. Deep-sequencing analyses of mRNA and immunoblotting revealed that MYPT1 depletion reduced the amount of PP1cδ with no compensatory changes in expression of other MYPT1 family members. Phosphatase activity towards phosphorylated smooth muscle heavy meromyosin was proportional to the amount of PP1cδ in total homogenates from wild-type or MYPT1-deficient tissues. Isolated MYPT1-deficient tissues from MYPT1(SM-/-) mice contracted with moderate differences in response to KCl and carbachol treatments, and relaxed rapidly with comparable rates after carbachol removal and only 1.5-fold slower after KCl removal. Measurements of phosphorylated proteins in the RLC signalling and actin polymerization modules during contractions revealed moderate changes. Using a novel procedure to quantify total phosphorylation of MYPT1 at Thr696 and Thr853, we found substantial phosphorylation in wild-type tissues under resting conditions, predicting attenuation of MLCP activity. Reduced PP1cδ activity in MYPT1-deficient tissues may be similar to the attenuated MLCP activity in wild-type tissues resulting from constitutively phosphorylated MYPT1. Constitutive phosphorylation of MYPT1 Thr696 and Thr853 may thus represent a physiological mechanism acting in concert with agonist-induced MYPT1 phosphorylation to inhibit MLCP activity. In summary, MYPT1 deficiency may not cause significant derangement of smooth muscle contractility because the effective MLCP activity is not changed.

Carnosine inhibits carbonic anhydrase IX-mediated extracellular acidosis and suppresses growth of HeLa tumor xenografts.

BackgroundCarbonic anhydrase IX (CA IX) is a transmembrane enzyme that is present in many types of solid tumors. Expression of CA IX is driven predominantly by the hypoxia-inducible factor (HIF) pathway and helps to maintain intracellular pH homeostasis under hypoxic conditions, resulting in acidification of the tumor microenvironment. Carnosine (β-alanyl-L-histidine) is an anti-tumorigenic agent that inhibits the proliferation of cancer cells. In this study, we investigated the role of CA IX in carnosine-mediated antitumor activity and whether the underlying mechanism involves transcriptional and translational modulation of HIF-1α and CA IX and/or altered CA IX function.MethodsThe effect of carnosine was studied using two-dimensional cell monolayers of several cell lines with endogenous CA IX expression as well as Madin Darby canine kidney transfectants, three-dimensional HeLa spheroids, and an in vivo model of HeLa xenografts in nude mice. mRNA and protein expression and protein localization were analyzed by real-time PCR, western blot analysis, and immunofluorescence staining, respectively. Cell viability was measured by a flow cytometric assay. Expression of HIF-1α and CA IX in tumors was assessed by immunohistochemical staining. Real-time measurement of pH was performed using a sensor dish reader. Binding of CA IX to specific antibodies and metabolon partners was investigated by competitive ELISA and proximity ligation assays, respectively.ResultsCarnosine increased the expression levels of HIF-1α and HIF targets and increased the extracellular pH, suggesting an inhibitory effect on CA IX-mediated acidosis. Moreover, carnosine significantly inhibited the growth of three-dimensional spheroids and tumor xenografts compared with untreated controls. Competitive ELISA showed that carnosine disrupted binding between CA IX and antibodies specific for its catalytic domain. This finding was supported by reduced formation of the functional metabolon of CA IX and anion exchanger 2 in the presence of carnosine.ConclusionsOur results indicate that interaction of carnosine with CA IX leads to conformational changes of CA IX and impaired formation of its metabolon, which in turn disrupts CA IX function. These findings suggest that carnosine could be a promising anticancer drug through its ability to attenuate the activity of CA IX.

Gas phase hydroxylation of benzene with air–ammonia mixture over copper-based phosphate catalysts

The direct gas phase hydroxylation of benzene to phenol over copper-based phosphate catalysts has been studied. Nitrous oxide and air–ammonia mixtures were used as oxidizing agents. It has been found that nitrous oxide can be replaced by air–ammonia mixture without significant deterioration of the phenol yield. Nanostructured Ca–Cu phosphate catalysts with a dominant mixed pyrophosphate structure, prepared in the presence of suitable surfactants were found highly active and selective. Using surfactant-modified phosphate catalysts with sponge-like structure above 95% selectivity and about 6.5% and 4.2% phenol yields were achieved at the benzene WHSV 1h−1 and under not optimized reaction conditions using N2O and air–ammonia mixture as oxidizing agents, respectively. These catalysts, compared with unmodified ones, were found to be much more resistant toward deactivation caused by the chemical reduction of catalytically active copper phase during the catalytic test. The activity of the spongy Ca–Cu phosphate catalyst after 37h on stream decreased only by about 25%. In contrast, over similar unmodified Ca–Cu phosphate catalyst the phenol yield already after 8h on stream drops to about one third of the initial value.

Oxidation‐ and CaMKII‐Mediated Sarcoplasmic Reticulum Ca2+ Leak Triggers Atrial Fibrillation in Aging

Advanced age is a well-recognized predisposition to atrial fibrillation (AF). However, the cellular electrophysiological changes that underlie the heightened susceptibility to AF in aged individuals remain poorly understood. Sarcoplasmic reticulum (SR) Ca(2+) leak that results from posttranslational modification of type 2 ryanodine receptor channels (RyR2) has been implicated in arrhythmogenesis. We hypothesize that aging alters atrial myocytes Ca(2+) homeostasis and RyR2 function, which create a substrate for AF initiation. We examined the susceptibility to AF in aged (24 months) and young adult (4-5 months) mice using an intraesophageal atrial electrical stimulation protocol. Aged mice showed significant higher AF induction rate (43.3%, n = 30) than young adults (8.8%, n = 34, P < 0.01). In accordance with these in vivo findings, significantly increased diastolic SR Ca(2+) leak and arrhythmogenic Ca(2+) activities with reduced SR Ca(2+) content were observed in aged atrial myocytes. Western blot showed RyR2 oxidation and phosphorylation at Ser2814 (Ca(2+) /calmodulin-dependent protein kinase II [CaMKII] site), but not phosphorylation at Ser2808 (protein kinase A [PKA] and CaMKII site), were increased in aged atrial myocytes. The selective CaMKII inhibitor (KN-93), as well as the antioxidant reagent (DTT) reversed the diastolic Ca(2+) leak and the frequency of spontaneous Ca(2+) transients in aged atrial myocytes, whereas PKA inhibition with H-89 was ineffective. Aging increases both the oxidation and CaMKII-phosphorylation of RyR2, which result in diastolic SR Ca(2+) leak and facilitate AF initiation. These results contribute to the electrophysiological remodeling of aged atria and suggest a therapeutic strategy for AF treatment in aging.

Theoretical Construction of Sports Information Management and Research on Application System Development

Among the activities of sports management, planning and decision can't run without information, which is also regarded as main basis among organizing and controlling management process .Information systems development must be based on needs of users sports information, by using the methods of software engineering, according to the steps of systems analysis, systems design, systems evaluation and implementation. The purpose of this paper is to grasp the sport science information management concepts, basic theoretical characteristics, content, to provide scientific construction and management for all levels sports organization.. In this paper, structured analysis method to complete the website of CBA and the development of sports information management systems.

Regulation of the Ca -independent phospholipase A2 in liver mitochondria by changes in the energetic state

The effect of electron transport chain redox status on activity of the mitochondrial Ca(2+)-independent phospholipase A2 (iPLA2) has been examined. When oxidizing NAD-linked substrates, the enzyme is not active unless deenergization occurs. Uncoupler, rotenone, antimycin A, and cyanide are equally effective at upregulating the enzyme, while oligomycin is ineffective. Thenoyltrifluoroacetone causes deenergization and activates the enzyme, but only if succinate is the respiratory substrate. These findings show that the mitochondrial iPLA2 responds to the energetic state overall, rather than to the redox status of individual electron transport chain complexes. With NAD-linked substrates, and using rotenone to deenergize, iPLA2 activation can be reversed by adding succinate to reestablish a membrane potential. For this purpose, ascorbate plus N,N,N'N'-tetramethyl-phenylenediamine can be used instead of succinate and is equally effective. With succinate as substrate, the membrane potential can be reduced in a graded and stable fashion by adding increasing concentrations of malonate, which is a competitive inhibitor of succinate utilization. A partial and stable activation of the iPLA2 accompanies partial deenergization. These findings suggest that in addition to the several functions that have been proposed, the mitochondrial iPLA2 may help to coordinate local capillary blood flow with changing energy demands.

Catalase, carbonic anhydrase and xanthine oxidase activities in patients with mycosis fungoides

Mycosis fungoides (MF) is the most common form of cutaneous T-cell lymphoma. In several studies the relationship between catalase (CAT), human cytosolic carbonic anhydrases (CA; hCA-I and hCA-II) and xanthine oxidase (XO) enzyme activities have been investigated in various types of cancers but carbonic anhydrase, catalase and xanthine oxidase activities in patients with MF have not been previously reported. Therefore, in this preliminary study we aim to investigate CAT, CA and XO activities in patients with MF. This study enrolled 32 patients with MF and 26 healthy controls. According to the results, CA and CAT activities were significantly lower in patients with mycosis fungoides than controls (p < 0.001) (p < 0.001). There was no significant difference in XO activity between patient and control group (p = 0.601). Within these findings, we believe these enzyme activity levels might be a potentially important finding as an additional diagnostic biochemical tool for MF.

Polyamines cause plasma membrane depolarization, activate Ca2+-, and modulate H+-ATPase pump activity in pea roots.

Polyamines regulate a variety of cation and K(+) channels, but their potential effects on cation-transporting ATPases are underexplored. In this work, noninvasive microelectrode ion flux estimation and conventional microelectrode techniques were applied to study the effects of polyamines on Ca(2+) and H(+) transport and membrane potential in pea roots. Externally applied spermine or putrescine (1mM) equally activated eosin yellow (EY)-sensitive Ca(2+) pumping across the root epidermis and caused net H(+) influx or efflux. Proton influx induced by spermine was suppressed by EY, supporting the mechanism in which Ca(2+) pump imports 2 H(+) per each exported Ca(2+). Suppression of the Ca(2+) pump by EY diminished putrescine-induced net H(+) efflux instead of increasing it. Thus, activities of Ca(2+) and H(+) pumps were coupled, likely due to the H(+)-pump inhibition by intracellular Ca(2+). Additionally, spermine but not putrescine caused a direct inhibition of H(+) pumping in isolated plasma membrane vesicles. Spermine, spermidine, and putrescine (1mM) induced membrane depolarization by 70, 50, and 35 mV, respectively. Spermine-induced depolarization was abolished by cation transport blocker Gd(3+), was insensitive to anion channels' blocker niflumate, and was dependent on external Ca(2+). Further analysis showed that uptake of polyamines but not polyamine-induced cationic (K(+)+Ca(2+)+H(+)) fluxes were a main cause of membrane depolarization. Polyamine increase is a common component of plant stress responses. Activation of Ca(2+) efflux by polyamines and contrasting effects of polyamines on net H(+) fluxes and membrane potential can contribute to Ca(2+) signalling and modulate a variety of transport processes across the plasma membrane under stress.

A Limited Role for Carbonic Anhydrase in C4 Photosynthesis as Revealed by a ca1ca2 Double Mutant in Maize

Carbonic anhydrase (CA) catalyzes the first biochemical step of the carbon-concentrating mechanism of C4 plants, and in C4 monocots it has been suggested that CA activity is near limiting for photosynthesis. Here, we test this hypothesis through the characterization of transposon-induced mutant alleles of Ca1 and Ca2 in maize (Zea mays). These two isoforms account for more than 85% of the CA transcript pool. A significant change in isotopic discrimination is observed in mutant plants, which have as little as 3% of wild-type CA activity, but surprisingly, photosynthesis is not reduced under current or elevated CO2 partial pressure (pCO2). However, growth and rates of photosynthesis under subambient pCO2 are significantly impaired in the mutants. These findings suggest that, while CA is not limiting for C4 photosynthesis in maize at current pCO2, it likely maintains high rates of photosynthesis when CO2 availability is reduced. Current atmospheric CO2 levels now exceed 400 ppm (approximately 40.53 Pa) and contrast with the low-pCO2 conditions under which C4 plants expanded their range approximately 10 million years ago, when the global atmospheric CO2 was below 300 ppm (approximately 30.4 Pa). Thus, as CO2 levels continue to rise, selective pressures for high levels of CA may be limited to arid climates where stomatal closure reduces CO2 availability to the leaf.

Reduced Synaptic STIM2 Expression and Impaired Store-Operated Calcium Entry Cause Destabilization of Mature Spines in Mutant Presenilin Mice

Mushroom dendritic spine structures are essential for memory storage, and the loss of mushroom spines may explain memory defects in Alzheimer's disease (AD). Here we show a significant reduction in the fraction of mushroom spines in hippocampal neurons from the presenilin-1 M146V knockin (KI) mouse model of familial AD (FAD). The stabilization of mushroom spines depends on STIM2-mediated neuronal store-operated calcium influx (nSOC) and continuous activity of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII). We demonstrate that STIM2-nSOC-CaMKII pathway is compromised in KI neurons, in aging neurons, and in sporadic AD brains due to downregulation of STIM2 protein. We further establish that overexpression of STIM2 rescues synaptic nSOC, CaMKII activity, and mushroom spine loss in KI neurons. Our results identify STIM2-nSOC-CaMKII synaptic maintenance pathway as a novel potential therapeutic target for treatment of AD and age-related memory decline.

MINERAL ASSEMBLAGES, COMPOSITIONAL VARIATION, AND CRYSTAL STRUCTURE OF FERUVITIC TOURMALINE FROM A CONTAMINATED ANATECTIC PEGMATITE AT MIROŠOV NEAR STRÁŽEK, MOLDANUBIAN ZONE, CZECH REPUBLIC

Amphibole-bearing, simply zoned, anatectic pegmatite, up to 20 cm thick, cuts calc-silicate rocks at Mirosov, near Stražek, in the Moldanubian Zone of the Czech Republic. Common amphibole (K-rich magnesio-hornblende to ferro-hastingsite), plagioclase An 30–42 and titanite, along with accessory feruvitic tourmaline—Ca-rich schorl to Na-rich feruvite—are indicators of Ca and Fe-contamination from the host rock. Interstitial tourmaline from the outer unit (TU1) and tourmaline from graphic intergrowths with quartz in more evolved parts of the pegmatite (TU2) have similar chemical compositions (EMPA, LA-ICP-MS) with Ca = 0.37–0.58 apfu , Al = 4.77–5.77 apfu ; TU1 has higher Mg/(Mg + Fe tot ) = 0.52–0.41 compared to TU2 (0.39–0.15). TU1 is enriched in Ti, V, Cr, Sr, and TU2 in Li and Zn, respectively. Late microscopic veinlets of Na,Al,Mg-enriched tourmaline (TU3)—Ca-rich dravite/schorl—replace both TU1 and TU2. A combination of EMPA, single crystal XRD data, and bond-valence optimization applied to the TU2 data yielded the formula X (Ca 0.494 Na 0.451 □ 0.055 ) Y (Mg 0.422 +Al 0.365 Fe 2+ 1.143 Fe 3+ 0.952Mn 0.029 Ti 0.084 Zn 0.005 ) Z (Al 5.106 Fe 3+ 0.377 Mg 0.518 ) T (Si 5.879 Al 0.121 O 18 ) (BO 3 ) 3 [(OH) 2.656 O 1.286 F 0.058 ], which represents disordered Na,Fe 3+ -rich feruvite (to “ oxy-feruvite ”). Contaminated pegmatite from Mirosov and its Ca-rich tourmalines are similar to other simple pegmatites from the Moldanubian Zone which have been contaminated by Ca,Fe-rich host rocks. The chemical compositions of Ca-rich schorl to Na-rich feruvite from various geological environments are similar, showing only minor dominance of Ca over Na ( apfu Ca), low X-site vacancy, and low Al (mostly apfu Al), but highly variable in Mg/(Mg + Fe tot ). The formation of feruvite requires specific geochemical conditions with high activities of Ca and Fe, but rather low Mg, conditions typical for some contaminated granitic pegmatites.

GABAAReceptor-Mediated Bidirectional Control of Synaptic Activity, Intracellular Ca2+, Cerebral Blood Flow, and Oxygen Consumption in Mouse Somatosensory Cortex In Vivo

Neural activity regulates local increases in cerebral blood flow (ΔCBF) and the cortical metabolic rate of oxygen (ΔCMRO2) that constitutes the basis of BOLD functional neuroimaging signals. Glutamate signaling plays a key role in brain vascular and metabolic control; however, the modulatory effect of GABA is incompletely understood. Here we performed in vivo studies in mice to investigate how THIP (which tonically activates extrasynaptic GABAARs) and Zolpidem (a positive allosteric modulator of synaptic GABAARs) impact stimulation-induced ΔCBF, ΔCMRO2, local field potentials (LFPs), and fluorescent cytosolic Ca(2+) transients in neurons and astrocytes. Low concentrations of THIP increased ΔCBF and ΔCMRO2 at low stimulation frequencies. These responses were coupled to increased synaptic activity as indicated by LFP responses, and to Ca(2+) activities in neurons and astrocytes. Intermediate and high concentrations of THIP suppressed ΔCBF and ΔCMRO2 at high stimulation frequencies. Zolpidem had similar but less-pronounced effects, with similar dependence on drug concentration and stimulation frequency. Our present findings suggest that slight increases in both synaptic and extrasynaptic GABAAR activity might selectively gate and amplify transient low-frequency somatosensory inputs, filter out high-frequency inputs, and enhance vascular and metabolic responses that are likely to be reflected in BOLD functional neuroimaging signals.

T-type calcium channel Cav3.2 deficient mice show elevated anxiety, impaired memory and reduced sensitivity to psychostimulants

The fine-tuning of neuronal excitability relies on a tight control of Ca2+ homeostasis. The low voltage-activated (LVA) T-type calcium channels (Cav3.1, Cav3.2 and Cav3.3 isoforms) play a critical role in regulating these processes. Despite their wide expression throughout the central nervous system, the implication of T-type Cav3.2 isoform in brain functions is still poorly characterized. Here, we investigate the effect of genetic ablation of this isoform in affective disorders, including anxiety, cognitive functions as well as sensitivity to drugs of abuse. Using a wide range of behavioral assays we show that genetic ablation of the cacna1h gene results in an anxiety-like phenotype, whereas novelty-induced locomotor activity is unaffected. Deletion of the T-type channel Cav3.2 also triggers impairment of hippocampus-dependent recognition memories. Acute and sensitized hyperlocomotion induced by d-amphetamine and cocaine are dramatically reduced in T-type Cav3.2 deficient mice. In addition, the administration of the T-type blocker TTA-A2 prevented the expression of locomotor sensitization observed in wildtype mice. In conclusion, our data reveal that physiological activity of this specific Ca2+ channel is required for affective and cognitive behaviors. Moreover, our work highlights the interest of T-type channel blockers as therapeutic strategies to reverse drug-associated alterations.

High‐grade localized metasomatic alteration of the granitic gneiss surrounding a clinopyroxene‐rich pegmatoid dyke: Söndrum stenhuggeriet, Halmstad, SW Sweden

AbstractThe Söndrum stone quarry (Halmstad, SW Sweden) exposes a transition from migmatized granitic gneissic country rock into a foliated clinopyroxene‐free granitic gneiss, and then a central pegmatoid dyke dominated by clinopyroxene megacrysts. This transition zone represents a fracture‐controlled, fluid‐alteration zone that developed under conditions of 650–700 °C and 790 MPa. Mineral chemical trends in F, Cl, Fe, Ti, Mn and Y are interpreted as documenting a fluid infiltration event associated with the formation of the pegmatoid dyke. Fluid inclusions from the pegmatoid dyke are CO2 dominant, whereas in the surrounding country rock they are dominated by H2O‐NaCl‐CaCl2. Fluid inclusions from the intermediate foliated clinopyroxene‐free granitic gneiss are a mixture of the two types. The pegmatoid dyke appears to have originated from a high Ca activity, Fe‐Mg enriched, fluid‐rich granitic melt with a CO2 component, which was emplaced along a tectonic fracture in a regionally migmatized granitic gneiss in the lower crust. This was accompanied by limited partial melting of the surrounding granitic gneiss. The Ca activity of the melt was high enough to allow for the formation of clinopyroxene megacrysts as opposed to orthopyroxene. H2O‐enriched fluids expelled from the crystallizing pegmatoid dyke, which retained the majority of the CO2 helping to stabilize the clinopyroxene. The expelled fluids coarsened and chemically affected the surrounding country rock resulting in trends in the mineral and fluid inclusion chemistry seen today in the foliated and regional granitic gneiss.

Identification of Minimal HDV-Like Ribozymes with Unique Divalent Metal Ion Dependence in the Human Microbiome

HDV-like self-cleaving ribozymes have been found in a wide variety of organisms, implicated in diverse biological processes, and their activity typically shows a strong divalent metal dependence, but little metal specificity. Recent studies suggested that very short variants of these ribozymes exist in nature, but their distribution and biochemical properties have not been established. To map out the distribution of small HDV-like ribozymes, the drz-Spur-3 sequence was minimized to yield a core construct for structure-based bioinformatic searches. These searches revealed several microbial ribozymes, particularly in the human microbiome. Kinetic profile of the smallest ribozyme revealed two distinct metal binding sites, only one of which promotes fast catalysis. Furthermore, this ribozyme showed markedly reduced activity in Ca(2+), even in the presence of physiological Mg(2+) concentrations. Our study substantially expands the number of microbial HDV-like ribozymes and provides an example of cleavage regulation by divalent metals.

Increased Prostaglandin E_2 Has a Positive Correlation with Plasma Calcium during Goldfish Reproduction

somatic index (r=0.81, p<0.001), plasma Ca and plasma PGE2 levels (r=0.635, p<0.05), and plasma Ca and plasma TRAP activities (r=0.584, p<0.05) from the analysis using samples of both reproductive and non- reproductive stages. Taking these data into consideration, we suggested that PGE2 acts on osteoclasts and increases plasma Ca as a result of osteoclastic bone resorption, and we concluded that PGE2 is an important hormone in Ca metabolism during fish reproduction.

Spontaneous, Pro-Arrhythmic Calcium Signals Disrupt Electrical Pacing in Mouse Pulmonary Vein Sleeve Cells

The pulmonary vein, which returns oxygenated blood to the left atrium, is ensheathed by a population of unique, myocyte-like cells called pulmonary vein sleeve cells (PVCs). These cells autonomously generate action potentials that propagate into the left atrial chamber and cause arrhythmias resulting in atrial fibrillation; the most common, often sustained, form of cardiac arrhythmia. In mice, PVCs extend along the pulmonary vein into the lungs, and are accessible in a lung slice preparation. We exploited this model to study how aberrant Ca2+ signaling alters the ability of PVC networks to follow electrical pacing. Cellular responses were investigated using real-time 2-photon imaging of lung slices loaded with a Ca2+-sensitive fluorescent indicator (Ca2+ measurements) and phase contrast microscopy (contraction measurements). PVCs displayed global Ca2+ signals and coordinated contraction in response to electrical field stimulation (EFS). The effects of EFS relied on both Ca2+ influx and Ca2+ release, and could be inhibited by nifedipine, ryanodine or caffeine. Moreover, PVCs had a high propensity to show spontaneous Ca2+ signals that arose via stochastic activation of ryanodine receptors (RyRs). The ability of electrical pacing to entrain Ca2+ signals and contractile responses was dramatically influenced by inherent spontaneous Ca2+ activity. In PVCs with relatively low spontaneous Ca2+ activity (<1 Hz), entrainment with electrical pacing was good. However, in PVCs with higher frequencies of spontaneous Ca2+ activity (>1.5 Hz), electrical pacing was less effective; PVCs became unpaced, only partially-paced or displayed alternans. Because spontaneous Ca2+ activity varied between cells, neighboring PVCs often had different responses to electrical pacing. Our data indicate that the ability of PVCs to respond to electrical stimulation depends on their intrinsic Ca2+ cycling properties. Heterogeneous spontaneous Ca2+ activity arising from stochastic RyR opening can disengage them from sinus rhythm and lead to autonomous, pro-arrhythmic activity.

4-Functionalized 1,3-diarylpyrazoles bearing benzenesulfonamide moiety as selective potent inhibitors of the tumor associated carbonic anhydrase isoforms IX and XII

A library of 4-functionalized 1,3-diarylpyrazoles (3a–3h, 5a–5g and 6a–6g) was designed, synthesized and evaluated against four human carbonic anhydrase (CA, EC 4.2.1.1) isozymes representing two cytosolic isozymes hCA I and hCA II, and two transmembrane tumor associated ones, hCA IX and hCA XII. All the twenty two tested compounds exhibited excellent CA activity profile against the four CA isozymes when compared to the reference drug acetazolamide. Six of the tested compounds (3a–3b, 3f, 3h, 6a and 6b) displayed low nanomolar affinity (Ki < 5 nM) for hCA IX whereas seven compounds (3a–3b, 3d–3f, 3h and 6f) displayed Ki < 10 nM against hCA XII. In addition, they acted as selective CA inhibitors of isoforms IX and XII over the physiological isoforms I and II.