Use Of Ca2 Research Articles

Linolenic acid stimulates eryptosis and hemolysis through oxidative stress and CK1α/MLKL: protective role of melatonin, urea, and polyethylene glycol

Anticancer medications cause anemia in patients through ill-defined mechanisms, including hemolysis and eryptosis. Although α-linolenic acid (ALA) possesses anticancer properties against a variety of cancer cells, there is a dearth of evidence regarding how it modulates red blood cell (RBC) physiology. RBCs from healthy donors were subjected to anticancer concentrations of ALA (2.5, 5, 10, 20, 40, 80, and 100 μM) at 37 °C for 24 h, and colorimetric tests were used to determine hemolysis and acetylcholinesterase (AChE) activity. Meanwhile, flow cytometry was employed to identify eryptotic cells using annexin-V-FITC and forward scatter (FSC), Fluo4/AM to detect Ca2+, and H2DCFDA to assess oxidative stress. ALA significantly increased hemolysis and eryptosis in a concentration-dependent manner, along with elevated Fluo4 and DCF fluorescence, and erythrocyte sedimentation rate, and reduced FSC and AChE activity. Moreover, the addition of D4476, necrosulfonamide, melatonin, isosmotic urea, and polyethylene glycol 8000 – but not sucrose – significantly inhibited ALA toxicity. In conclusion, ALA stimulates hemolysis and eryptosis through Ca2+ buildup, oxidative stress, anticholinesterase activity, casein kinase 1α (CK1α), and mixed lineage kinase domain-like protein (MLKL). The anticancer activity of ALA may be potentiated by the use of Ca2+ channel blockers and chelators, antioxidants, and CK1α and MLKL inhibitors to ameliorate its toxicity to RBCs.

Morphological alterations of the neuronal Golgi apparatus upon seizures.

Epilepsy is one of the most common chronic neurological disorders, affecting around 50 million people worldwide, but its underlying cellular and molecular events are not fully understood. The Golgi is a highly dynamic cellular organelle and can be fragmented into ministacks under both physiological and pathological conditions. This phenomenon has also been observed in several neurodegenerative disorders; however, the structure of the Golgi apparatus (GA) in human patients suffering from epilepsy has not been described so far. The aim of this study was to assess the changes in GA architecture in epilepsy. Golgi visualisation with immunohistochemical staining in the neocortex of adult patients who underwent epilepsy surgery; 3D reconstruction and quantitative morphometric analysis of GA structure in the rat hippocampi upon kainic acid (KA) induced seizures, as well as in vitro studies with the use of Ca2+ chelator BAPTA-AM in primary hippocampal neurons upon activation were performed. We observed GA dispersion in neurons of the human neocortex of patients with epilepsy and hippocampal neurons in rats upon KA-induced seizures. The structural changes of GA were reversible, as GA morphology returned to normal within 24 h of KA treatment. KA-induced Golgi fragmentation observed in primary hippocampal neurons cultured in vitro was largely abolished by the addition of BAPTA-AM. In our study, we have shown for the first time that the neuronal GA is fragmented in the human brain of patients with epilepsy and rat brain upon seizures. We have shown that seizure-induced GA dispersion can be reversible, suggesting that enhanced neuronal activity induces Golgi reorganisation that is involved in aberrant neuronal plasticity processes that underlie epilepsy. Moreover, our results revealed that elevated cytosolic Ca2+ is indispensable for these KA-induced morphological alterations of GA in vitro.

Calcium regulates primary nitrate responseassociated gene transcription in a time- and dose-dependent manner.

Nitrate (NO3-) is the primary source of nitrogen preferred by most arable crops, including wheat. The pioneering experiment on primary nitrate response (PNR) was carried out three decades ago. Since then, much research has been carried out to understand the NO3- signaling. Nitrate is sensed by the dual affinity NO3- transceptor NPF6.3, which further relays the information to a master regulator NIN-like protein 7 (NLP7) through calcium-dependent protein kinases (CPK10, CPK30, CPK32), highlighting the importance of calcium ion (Ca2+) as one of the important secondary messengers in relaying the NO3- signaling in Arabidopsis. In a previous study, we found that Ca2+ regulates nitrogen starvation response in wheat. In this study, 10days old NO3--starved wheat seedlings were exposed to various treatments. Our study on time course changes in expression of PNR sentinel genes; NPF6.1, NPF6.2, NRT2.1, NRT2.3, NR, and NIR in wheat manifest the highest level of expression at 30min after NO3- exposure. The use of Ca2+ chelator EGTA confirmed the involvement of Ca2+ in the regulation of transcription of NPFs and NRTs as well the NO3- uptake. We also observed the NO3- dose-dependent and tissue-specificregulation of nitrate reductase activity involving Ca2+ as a mediator. The participation of Ca2+ in the PNR and NO3- signaling in wheat is confirmed by pharmacological analysis, physiological evidences, and protoplast-based Ca2+ localization.

P-218 Does Artificial Oocyte Activation (AOA) improve the outcome beyond fertilization rate in ICSI cycles?

Abstract Study question Does CultActive© improve reproductive outcomes of ICSI cycles in cases of low fertilization rate and normal fertilization rate? Summary answer The application of CultActive© after ICSI improves fertilization rates only in clinical indication of fertilization failure. What is known already Oocyte activation deficiency is attributed in the majority of cases to fertilization failure in ICSI cycles, and these can be corrected by increasing initial levels of calcium (Ca2+) using assisted oocyte activation techniques (AOA), such as the use of Ca2+ ionophores. These agents enhance intracellular calcium release and increase the membrane permeability facilitating the influx of extracellular Ca2+, which initiates the activation cascade. Previous results suggest that Ca2+ ionophore treatment can increase the live birth rate after failed ICSI cycles in couples with poor fertilization rates, embryo developmental arrest, and also increase the number of good quality embryos. Study design, size, duration This was a retrospective observational study. There were 30 patients included and the first group consisted of 30 ICSI cycles, 231 oocytes and 56 embryos (without AOA). The second group consisted of the same patients (n = 30) with 30 ICSI cycles using AOA, 219 oocytes and 47 embryos. Subgroups were defined according to clinical indications (normal fertilization rate group: ≥ 65 % and low fertilization rate group: <65% ). All data was collected from January-December 2022. Participants/materials, setting, methods 450 oocytes were assessed in the study. 231 oocytes belonged to the pre-AOA and 219 belonged to the AOA. The oocytes were exposed for 15 minutes after ICSI in a solution containing the Ca2+ ionophore A23187, CultActive© (Gynemed, Germany). Fertilization, good quality blastocyst formation and pregnancy rate were analyzed.Good quality blastocyst were defined as ≥ 3BB. Statistical significance was analyzed using the Paired Student T test (p < 0.05 was considered statistically significant). Main results and the role of chance The cohort of patients with normal fertilization rate (without clinical indications),was not significantly different. The AOA treatment gave a fertilization rate of 61% compared to 71% of the control cycles (p = 0.1398). There was no increase in the number of good quality blastocysts formation when the study group was compared to the control (p = 0.1660). In the cohort of patients with an indication of low fertilization, a significantly higher fertilization rate was recorded compared to the control (51% and 37%, respectively p = 0.0238). There were no significant difference in the quantity of good quality blastocysts compared with the control (p = 0.3328). Regardless of normal or low fertilization rates there was no significant difference in pregnancy rate when CultActive© was used in treatment (p > 0.05). Limitations, reasons for caution There are limitations in our study. First, the retrospective design and limited study population are major limitations. The data should be interpreted cautiously in the subgroup analyses due to potential bias, specifically the small population in the group without clinical indication. Wider implications of the findings AOA was only beneficial for couples with poor fertilization. Embryo quality and pregnancy rate did not improve with CultActiveive©. External variation was minimized by using the same patients in each cohort. This suggests AOA should not be used without clinical indication or for poor embryo quality/blastulation rate. Trial registration number not applicable

Subvacuum environment-enhanced cell migration promotes wound healing without increasing hypertrophic scars caused by excessive cell proliferation.

Cell migration and proliferation are conducive to wound healing; however, regulating cell proliferation remains challenging, and excessive proliferation is an important cause of scar hyperplasia. Here, we aimed to explore how a subvacuum environment promotes wound epithelisation without affecting scar hyperplasia. Human immortalized keratinocyte cells and human skin fibroblasts were cultured under subvacuum conditions (1/10 atmospheric pressure), and changes in cell proliferation and migration, target protein content, calcium influx, and cytoskeleton and membrane fluidity were observed. Mechanical calcium (Ca2+ ) channel blockers were used to prevent Ca2+ influx for reverse validation. A rat wound model was used to elucidate the mechanism of the subvacuum dressing in promoting healing. The subvacuum environment was observed to promote cell migration without affecting cell proliferation; intracellular Ca2+ concentrations and PI3K, p-PI3K, AKT1, p-AKT 1 levels increased significantly. The cytoskeleton was depolymerized, pseudopodia were reduced or absent, and membrane fluidity increased. The use of Ca2+ channel blockers weakened or eliminated these changes. Animal experiments confirmed these phenomena and demonstrated that subvacuum dressings can effectively promote wound epithelisation. Our study demonstrates that the use of subvacuum dressings can enhance cell migration without affecting cell proliferation, promote wound healing, and decrease the probability of scar hyperplasia.

Medical Treatment of Chronic Pain

Antinociceptive therapy for chronic neuropathic pain is anecdotal in nature based on a physician's preference. However, evidence-based therapy is expected, following the chronic pain guideline established in 2021, supported by 10 pain-associated Japanese medical societies. The guideline strongly recommends the use of Ca2+-channel α2δ ligands (pregabalin, gabapentin, and mirogabalin) and duloxetine for pain relief. International guidelines also recommend administration of tricyclic antidepressants as first-line agents. Recent studies have described three classes of medicines that show comparable antinociceptive effects in painful diabetic neuropathy. Furthermore, a combination of first-line agents can improve efficacy. Antinociceptive medical therapy should be individualized based on the patient's condition and adverse effect profile of each medication.

Fluorescence-Based Assay for TRPV1 Channels.

The transient receptor potential vanilloid 1 ion channel (TRPV1) is a ligand-gated nonselective calcium-permeant cation channel involved in the detection of a wide variety of chemical and physical noxious stimuli, ranging from exogenous and endogenous ligands to noxious heat (>42°C) and low pH (pH<5.2). Due to its central role in pain and hyperalgesia, TRPV1 is considered a relevant therapeutic target for the development of analgesic and anti-inflammatory drugs potentially useful to relieve chronic, neuropathic, and inflammatory pain and to treat disorders such as inflammatory bowel disease. In this view, the availability of in vitro assays for the screening of novel TRPV1 modulators is highly desirable. Since TRPV1 activation leads to an increase in the intracellular calcium (Ca2+) levels, the use of Ca2+ fluorescent indicators represent a valuable and sensitive tool for monitoring such intracellular changes. In this chapter, we describe methods for recording and monitoring Ca2+ signals through the fluorescent indicators Fluo-4 acetoxymethyl (AM) and Fura-2AM in HEK-293 cells transfected with TRPV1 or other thermoTRP channels.

Improvement of Lignocellulolytic Enzyme Production Mediated by Calcium Signaling in Bacillus subtilis Z2 under Graphene Oxide Stress.

An increase in exoenzyme production can be enhanced by environmental stresses such as graphene oxide (GO) stress, but the link between the two events is still unclear. In this work, the effect of GO as an environmental stress factor on exoenzyme (lignocellulolytic enzyme, amylase, peptidase, and protease) biosynthesis was investigated in Bacillus subtilis Z2, and a plausible mechanism by which cytosolic Ca2+ regulates lignocellulolytic enzyme production in B. subtilis Z2 subjected to GO stress was proposed. The filter paper-hydrolyzing (FPase [representing total cellulase]), carboxymethylcellulase (CMCase [representing endoglucanase]), and β-glucosidase activities and extracellular protein concentration of the wild-type strain under 10 μg/mL GO stress were 1.37-, 1.64-, 1.24-, and 1.16-fold those of the control (without GO stress), respectively. Correspondingly, the transcription levels of lignocellulolytic enzyme genes, cytosolic Ca2+ level, and biomass concentration of B. subtilis were all increased. With lignocellulolytic enzyme from B. subtilis used to hydrolyze alkali-pretreated rice straw, the released reducing sugar concentration reached 265.53 mg/g, and the removal rates of cellulose, hemicellulose, and lignin were 52.4%, 30.1%, and 7.5%, respectively. Furthermore, transcriptome data revealed that intracellular Ca2+ homeostasis played a key role in regulating the levels of gene transcription related to the synthesis of lignocellulolytic enzymes and exoenzymes. Finally, the use of Ca2+ inhibitors (LaCl3 and EDTA) and deletion of spcF (a calmodulin-like protein gene) further demonstrated that the overexpression of those genes was regulated via calcium signaling in B. subtilis subjected to GO stress. IMPORTANCE To effectively convert lignocellulose into fermentable sugars, high lignocellulolytic enzyme loading is needed. Graphene oxide (GO) has been shown to promote exoenzyme (lignocellulolytic enzyme, amylase, peptidase, and protease) production in some microorganisms; however, the regulatory mechanism of the biosynthesis of lignocellulolytic enzymes under GO stress remains unclear. In this work, the lignocellulolytic enzyme production of B. subtilis under GO stress was investigated, and the potential mechanism by which B. subtilis enhanced lignocellulolytic enzyme production through the calcium signaling pathway under GO stress was proposed. This work revealed the role of calcium signaling in the production of enzymes under external environmental stress and provided a direction to facilitate lignocellulolytic enzyme production by B. subtilis.

P–279 Effect of Ca2+ ionophore A23187 (calcymicin) on fertilization rates, embryo development and pregnancy in human assisted reproduction cycles

Abstract Study question Does Calcymicin improve reproductive outcomes of ICSI cycles in cases of fertilization failure and/or embryo blockage indications? Summary answer The application of the Calcymicin after ICSI improves reproductive outcomes, especially in cases with clinical indication of fertilization failure. What is known already According to the bibliography, deficiencies in the oocyte activation process frequently lead to failed ICSI cycles, and these can be corrected by increasing initial levels of calcium (Ca2+) in the oocyte using assisted oocyte activation techniques (AOA), such as the use of Ca2+ ionophores. Ca2+ Ionophores have been shown to trigger an initial Ca2+ spike in the ooplasm that activates Ca2+/Calmodulin dependent protein kinase II, which initiates the cascade of cellular events leading to oocyte activation. Previous results suggest that Ca2+ ionophore treatment can give live offspring after failed ICSI cycles. Study design, size, duration 270 oocytes collected from 17 patients who presented cycles with low fertilization rates and/or embryo blockage or poor quality embryos (according to ASEBIR’s embryo classification criteria) were retrospectively analyzed. Oocytes were divided into two groups, a control group that underwent conventional IVF/ICSI and another group that underwent an ICSI cycle with AOA. Study groups were defined according to clinical indications and subgroups according to AOA or control. All data were collected from 2017 until 2020. Participants/materials, setting, methods Among the 270 oocytes of the study sample, 142 belonged to the control group and 128 belonged to the AOA group. The AOA group oocytes were activated for 15 minutes immediately after ICSI using a prepared solution containing the Ca2+ ionophore A23187, CultActive© (Gynemed, Germany). Fertilization rate and type, blastocyst formation rate, blastocyst quality, embryo kinetics, and pregnancy rates were analyzed, all of them were compared to FIV/ICSI cycles without oocyte activation (control group). Main results and the role of chance In the analyses of the whole sample of oocytes, the AOA treatment gave a fertilization rate of 72.5%, which was significantly higher compared to 53.8% of the control cycles (p = 0.002). Good quality blastocysts and pregnancy rates were also significantly higher than the control (p = 0.01). In the group with an indication of fertilization failure, a significantly higher fertilization rate was recorded compared to the control (65% and 33%, respectively). A higher rate of abnormal embryos with three pronuclei was also found compared to the control (p &amp;lt; 0.001). There were no significant differences in blastocyst formation rates, quality, or embryo kinetics (p &amp;gt; 0.05). In the group with an indication of embryo blockage/poor embryo quality, a significantly higher rate of good quality blastocysts and lower blastulation time were recorded compared to the control (p &amp;lt; 0.05). Limitations, reasons for caution The safety of the AOA technique with Ca2+ ionophore has not been fully demonstrated. In our study, none of the newborns had malformations, and gestational weeks and birth weights were normal. However, further studies on the safety of this technique are needed to implement it routinely in human reproduction clinics. Wider implications of the findings: According to these findings, an increase in the initial levels of calcium in the oocyte through the application of the Ca2+ ionophore A23187 after ICSI improves the results of failed assisted reproduction cycles, especially in the case of those diagnosed with fertility failure, which is a clear indication for AOA. Trial registration number Not applicable

Cooperative activating effects of metal ion and Brønsted acid on a metal oxo species.

Metal oxo (M Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O) complexes are common oxidants in chemical and biological systems. The use of Lewis acids to activate metal oxo species has attracted great interest in recent years, especially after the discovery of the CaMn4O5 cluster in the oxygen-evolving centre of photosystem II. Strong Lewis acids such as Sc3+ and BF3, as well as strong Brønsted acids such as H2SO4 and CF3SO3H, are commonly used to activate metal oxo species. In this work, we demonstrate that relatively weak Lewis acids such as Ca2+ and other group 2 metal ions, as well as weak Brønsted acids such as CH3CO2H, can readily activate the stable RuO4− complex towards the oxidation of alkanes. Notably, the use of Ca2+ and CH3CO2H together produces a remarkable cooperative effect on RuO4−, resulting in a much more efficient oxidant. DFT calculations show that Ca2+ and CH3CO2H can bind to two oxo ligands to form a chelate ring. This results in substantial lowering of the barrier for hydrogen atom abstraction from cyclohexane.

ASIC1a inhibits cell pyroptosis induced by acid-induced activation of rat hepatic stellate cells.

The activation of hepatic stellate cells (HSCs) is associated with liver fibrosis, the pathological feature of most forms of chronic hepatic damage, and is accompanied by abnormal deposition of the extracellular matrix (ECM). During the pathological process, acid‐sensing ion channel 1a (ASIC1a), which is responsible for Ca2+ transportation, is involved in the activation of HSCs. It has previously been identified that ASIC1a is related to pyroptosis in articular chondrocytes. However, it remains unclear whether ASIC1a restrains pyroptosis during liver fibrosis. Here, we determined that the levels of pyroptosis‐associated speck‐like protein, gasdermin D, caspase‐1, nucleotide‐binding oligomerization domain (NOD)‐like receptor 3, and apoptosis‐associated speck‐like protein (ASC) decreased, while the level of α‐smooth muscle actin and collagen‐I increased upon introduction of ASIC1a into an acid‐induced model. Inhibition or silencing of ASIC1a and the use of Ca2+‐free medium were able to promote the pyroptosis of activated HSCs, which reduced their deposition. In summary, our study indicates that ASIC1a inhibits pyroptosis of HSCs and that inhibition of ASIC1a may be able to promote pyroptosis to relieve liver fibrosis.

Mechanisms Involved in Osmotic Backwashing of Fouled FO Membranes

Organic matter leads to one of the biggest problems in membranes: fouling. Developing efficient cleaning processes is therefore crucial. This study systematically examines how alginic acid fouling formed under different physical and chemical conditions affect osmotic backwashing cleaning efficiency in forward osmosis (FO). The fouling layer thickness before and after osmotic backwashing was measured by confocal laser scanning microscopy in order to assess cleaning efficiency, along with pure water flux (PWF) measurements. Osmotic backwashing was found to be very efficient. In the absence of Ca2+ in the feed solution, the alginate fouling thickness was fouling layer thickness down to Backwashing also became less effective when the initial membrane fouling flux increased using a draw solution (DS) of 4 M NaCl, with 91 μm of fouling remaining, despite a fullPWF restoration. The use of Ca2+ in the osmotic backwashing DS caused the fouling layer to expand and not be removed due to flux reversal and the interaction between the alginic acid layer and Ca2+. A reduction in the PWF recovery was obtained, showing the type of salt used for backwashing has a severe influence on cleaning efficiency.

Identifying Ryanodine Receptor Modulators: from High-Throughput Screening to Single Channel Recording

The ryanodine receptor Ca2+-release channels (RyRs) are central to cytoplasmic Ca2+ signalling in particular in the skeletal muscle of both mammals and insects. Regarding the latter, several insecticides target RyRs but recent studies have shown that specific RyR point mutations can confer insecticide resistance. Consequently, research for new RyR modulators remains crucial for crop protection. The full-length coding sequence of the Plutella xylostella RyR was synthesized and cloned into suitable mammalian expression vector. We engineered HEK-293 expressing the insect target and functionally selected stable clones by the use of Ca2+-sensitive fluorescence. In order to exclude any endogenous non-specific response, a related mock clone was also generated in parallel. Stimulation of the cells to activate the RyR elicited a Ca2+ mobilization, which was detected as a fluorescence increase using a FLIPR-TETRA instrument. This RyR cell-based assay was validated with RyR ligands and putative blockers and further optimized to make it suitable for high throughput screening. Drug discovery programs, which may involve the screening of >105 compounds, requires a high fidelity method of determining the effect of putative hits on the function of the target protein. Since RyR expression is targeted to internal membranes, patch-clamp of the nuclear membrane has been previously shown to be an effective method of isolating them for single-channel recording. We therefore set up this very challenging technique to measure the RyR activity single-channel properties (conductance, open probability -Po- and dwell time distribution) and to show the modulatory effect of Ca2+ on these above-mentioned parameters. From cell cloning to Mode of Action determination, we develop an assay funnel, optimized for hit sensitivity and specificity that is easily scalable to larger compound libraries.

Mitochondrial permeability transition pore is involved in oxidative burst and NETosis of human neutrophils

Neutrophils release neutrophil extracellular traps (NETs) in response to numerous pathogenic microbes as the last suicidal resource (NETosis) in the fight against infection. Apart from the host defense function, NETs play an essential role in the pathogenesis of various autoimmune and inflammatory diseases. Therefore, understanding the molecular mechanisms of NETosis is important for regulating aberrant NET release. The initiation of NETosis after the recognition of pathogens by specific receptors is mediated by an increase in intracellular Ca2+ concentration, therefore, the use of Ca2+ ionophore A23187 can be considered a semi-physiological model of NETosis. Induction of NETosis by various stimuli depends on reactive oxygen species (ROS) produced by NADPH oxidase, however, NETosis induced by Ca2+ ionophores was suggested to be mediated by ROS produced in mitochondria (mtROS).Using the mitochondria-targeted antioxidant SkQ1 and specific inhibitors of NADPH oxidase, we showed that both sources of ROS, mitochondria and NADPH oxidase, are involved in NETosis induced by A23187 in human neutrophils. In support of the critical role of mtROS, SkQ1-sensitive NETosis was demonstrated to be induced by A23187 in neutrophils from patients with chronic granulomatous disease (CGD). We assume that Ca2+-triggered mtROS production contributes to NETosis either directly (CGD neutrophils) or by stimulating NADPH oxidase. The opening of the mitochondrial permeability transition pore (mPTP) in neutrophils treated by A23187 was revealed using the electron transmission microscopy as a swelling of the mitochondrial matrix. Using specific inhibitors, we demonstrated that the mPTP is involved in mtROS production, NETosis, and the oxidative burst induced by A23187.

Production of potassium sulphate by conversion of phosphogypsum and potassium carbonate

This work shows the possibility of obtaining potassium sulfate by converting phosphogypsum and potassium carbotane by the reaction CaSO4 + K2CO3 → ↓ CaCO3 + K2SO4. The optimal conditions for this process are determined. It is shown that in an aqueous medium at a temperature of 20 °C, a stoichiometric ratio of the initial components, the rotation speed of the stirrer 200 rpm for 15-30 min, the degree of use of Ca2+ ions is 94-95 %. Potassium sulfate contained in the liquid phase is transferred into the solid phase by evaporation and subsequent crystallization.

Deconvolution of Sustained Neural Activity From Large-Scale Calcium Imaging Data.

Recent technological advances in light-sheet microscopy make it possible to perform whole-brain functional imaging at the cellular level with the use of Ca2+ indicators. The outstanding spatial extent and resolution of this type of data open unique opportunities for understanding the complex organization of neuronal circuits across the brain. However, the analysis of this data remains challenging because the observed variations in fluorescence are, in fact, noisy indirect measures of the neuronal activity. Moreover, measuring over large field-of-view negatively impact temporal resolution and signal-to-noise ratio, which further impedes conventional spike inference. Here we argue that meaningful information can be extracted from large-scale functional imaging data by deconvolving with the calcium response and by modeling moments of sustained neuronal activity instead of individual spikes. Specifically, we characterize the calcium response by a linear system of which the inverse is a differential operator. This operator is then included in a regularization term promoting sparsity of activity transients through generalized total variation. Our results illustrate the numerical performance of the algorithm on simulated signals; i.e., we show the firing rate phase transition at which our model outperforms spike inference. Finally, we apply the proposed algorithm to experimental data from zebrafish larvæ. In particular, we show that, when applied to a specific group of neurons, the algorithm retrieves neural activation that matches the locomotor behavior unknown to the method.

Deoxycholic acid and l-Phenylalanine enrich their hydrogel properties when combined in a zwitterionic derivative

HypothesisSodium Deoxycholate (NaDC) and Phenylalanine (Phe) are important biological hydrogelators. NaDC hydrogels form by lowering the pH or by increasing the ionic strength. Phe gels form from saturated solution by thermal induction and slow kinetics. The resulting gels hold great potential in medicine and biology as drug carriers and models for fundamental self-assembly in pathological conditions. Based on this background it was hypothesized that a Phe substituted NaDC could provide a molecule with expanded gelling ability, merging those of the precursors. ExperimentsWe coupled both building blocks in a zwitterionic derivative bearing a Phe residue at the C3 carbon of NaDC. The specific zwitterionic structure, the concurrent use of Ca2+ ions for the carboxyl group coordination and the pH control generate conditions for the formation of hydrogels. The hydrogels were analyzed by combining UV and circular dichroism spectroscopies, rheology, small angle X-ray scattering and atomic force microscopy. FindingsHydrogel appearance occurs in conditions that are uncovered in the case of the pure Phe and NaDC: self-standing gels form instantaneously at room temperature, in the 10–12 pH range and down to concentration of 0.17 wt%. Both thixotropic and shake resistant gels can form depending on the derivative concentration. The gels show an uncommon thermal stability in the scanned range of 20–60 °C. The reported system concurrently enriches the hydrogelation properties of two relevant building blocks. We anticipate some potential applications of such gels in materials science where coordination of metal ions can be exploited for templating inorganic nanostructures.

Genetically Encoded Fluorescence/Bioluminescence Bimodal Indicators for Ca2+ Imaging.

Fluorescent and bioluminescent genetically encoded Ca2+ indicators (GECIs) are an indispensable tool for monitoring Ca2+ dynamics in numerous cellular events. Although fluorescent GECIs have a high spatiotemporal resolution, their application is often confined to short-term imaging due to the external illumination that causes phototoxicity and autofluorescence from specimens. Bioluminescent GECIs overcome these pitfalls with enhanced compatibility to optogenetic manipulation and photophysiological processes; however, they are compromised for spatiotemporal resolution. Therefore, there has been a push toward the use of Ca2+ indicators that possess the advantages of both fluorescent and bioluminescent GECI for a wide range of applications. To address this, we developed a high-affinity bimodal GECI, GLICO, using a single fluorescent protein-based GECI combined with a split luciferase. Through this novel design, the fusion protein becomes bimodal and possesses Ca2+ sensing properties similar to those of its fluorescent ancestor and confers bioluminescence-based Ca2+ imaging. GLICO in bioluminescence mode has the highest dynamic range (2200%) of all bioluminescent GECIs. We demonstrated the performance of GLICO in studying cytosolic Ca2+ dynamics in different cultured cells in each mode. With the purpose of Ca2+ imaging in high Ca2+ content organelle, we also created a low-affinity variant, ReBLICO and performed Ca2+ imaging of the ER in both fluorescence and bioluminescence modes. The ability to switch between fluorescence and bioluminescence modes with a single indicator would benefit transgenic applications by presenting an opportunity for a wide range of live Ca2+ imaging in physiological and pathophysiological conditions.

Phosphate Starvation Alters Abiotic-Stress-Induced Cytosolic Free Calcium Increases in Roots.

Phosphate (Pi) deficiency strongly limits plant growth, and plant roots foraging the soil for nutrients need to adapt to optimize Pi uptake. Ca2+ is known to signal in root development and adaptation but has to be tightly controlled, as it is highly toxic to Pi metabolism. Under Pi starvation and the resulting decreased cellular Pi pool, the use of cytosolic free Ca2+ ([Ca2+]cyt) as a signal transducer may therefore have to be altered. Employing aequorin-expressing Arabidopsis (Arabidopsis thaliana), we show that Pi starvation, but not nitrogen starvation, strongly dampens the [Ca2+]cyt increases evoked by mechanical, salt, osmotic, and oxidative stress as well as by extracellular nucleotides. The altered root [Ca2+]cyt response to extracellular ATP manifests during seedling development under chronic Pi deprivation but can be reversed by Pi resupply. Employing ratiometric imaging, we delineate that Pi-starved roots have a normal response to extracellular ATP at the apex but show a strongly dampened [Ca2+]cyt response in distal parts of the root tip, correlating with high reactive oxygen species levels induced by Pi starvation. Excluding iron, as well as Pi, rescues this altered [Ca2+]cyt response and restores reactive oxygen species levels to those seen under nutrient-replete conditions. These results indicate that, while Pi availability does not seem to be signaled through [Ca2+]cyt, Pi starvation strongly affects stress-induced [Ca2+]cyt signatures. These data reveal how plants can integrate nutritional and environmental cues, adding another layer of complexity to the use of Ca2+ as a signal transducer.

Assessment of the calcium releasing machinery in oocytes that failed to fertilize after conventional ICSI and assisted oocyte activation.

Can oocyte-related activation deficiencies be evaluated in oocytes that failed to fertilize after intracytoplasmic sperm injection (ICSI) combined with assisted oocyte activation (AOA)? Evaluation of the spindle-chromosome complexes and intracellular distribution of inositol trisphosphate type 1 receptors (IP3R1) in in-vitro matured (IVM) and failed-to-fertilize oocytes from patients undergoing AOA. Assessment of the oocyte-related Ca2+ releasing capacity in response to Ca2+ ionophores and sperm microinjection in oocytes that failed to fertilize after ICSI or ICSI-AOA. IVM oocytes from patients undergoing conventional ICSI (control) and ICSI-AOA (study group) revealed a similar normalcy of spindle-chromosome complexes and distribution patterns of IP3R1. Failed-to-fertilize oocytes from both groups showed significant differences in proportion of normal or abnormal spindle-chromosome complex conformations. However, migration of IP3R1 was identified in a higher proportion of failed-to-fertilize oocytes after ICSI-AOA than after conventional ICSI. It was further observed that oocytes which failed to fertilize, either after ICSI or ICSI-AOA, mostly retain their capacity to respond to stimuli such as exposure to Ca2+ ionophores or to sperm microinjection. Evaluation of spindle-chromosome normalcy and distribution of IP3R1 does not help identify the presence of Ca2+ releasing deficiencies in these oocytes. However, oocyte Ca2+ analysis adds value in identifying Ca2+ releasing incapacity of oocytes that failed to fertilize after ICSI or ICSI-AOA. Some patients experiencing fertilization failure after ICSI-AOA present with a suspected activation deficiency downstream of the Ca2+ machinery, which cannot be overcome by ICSI-AOA based on the use of Ca2+ ionophores.