A dynamic model of calcium signaling in mast cells and LTC4 release induced by mechanical stimuli

Mast cells （MCs） play an important role in theimmune system. It is known that mechanical stimuli caninduce intracellular Ca2＋ signal and release a variety ofmediators, including leukotriene C4 （LTC4）, leading toother cellular and physiological changes. In this paper, wepresent a mathematical model to explore signalling path-ways in MCs, by including cellular mechanisms for intra-cellular Ca2＋ increase and LTC4 release in response tomechanical stimuli, thapsigargin （TG, SERCA pumpinhibitor）, and LTC4 stimuli. We show that （i） mechanicalstimuli activate mechano-sensitive ion channels and induceinward ion fluxes and Ca2＋ entry which increases intra-cellular Ca2＋ concentration and releases LTC4; （ii） TGinhibits SERCA pumps, empties the internal Ca2＋ stores,which activates Ca2＋ release-activated Ca2＋ channels andresults in sustained intracellular Ca2＋ increase; and （iii）LTC4 activates receptors on MCs surface and increasesintracellular Ca2＋ concentration. Our results are consistentwith experimental observations, and furthermore, they alsoreveal that mechanical stimuli can increase intracellularCa2＋ even when LTC4 release is blocked, which suggests afeed forward loop involved in LTC4 production. This studymay facilitate our understanding of the mechanotransduc-tion process in MCs and provide a useful modeling tool forquantitatively analyzing immune mechanisms involvingMCs.     

Heterotrimeric G protein participated in modulation of cytoplasmic calcium concentration in pollen cells

Cytoplasmic free calcium concentration([Ca2+]c) in pollen cells of Lilium daviddi is measured with confocal laser scanning microscopy to investigate the effect of heterotrimeric G protein (G protein) on [Ca2+]c and the possible signal transduction pathway of G protein triggering cellular calcium signal. After application, cholera toxin (CTX), an agonist of G protein, triggers a transient increase of [Ca2+]c in pollen cells, and evokes a spatial-temporal characteristic calcium dynamics; while pertussis toxin (PTX), a G protein antagonist, leads to the decrease of [Ca2+]c. Both L-type Ca2+ channel blocker verapamil and inhibitor of IP3 receptor heparin inhibit CTX-induced [Ca2+]c increase. The results show that G protein may play a role in the modulation of [Ca2+]c through enhancing the extracellular Ca2+ influx and releasing of Ca2+ from intracellular stores.     

Effect of Aβ1-40 on membrane permeability and intracellular free Ca2+ of nerve cells

The effects of soluble and fibrillar Aβ1-40 on membrane permeability and intracellular free Ca2+ of nerve cells were investigated by the laser confocal microscopy. Results indicate that: i) Effects of soluble and fibrillar Aβ1-40 on cell membrane permeability are both concentration-de- pendent. Soluble Aβ1-40 increases membrane permeability only at concentration of 3 ?mol/L, while the toxic effect of fibrillar Aβ1-40 is much stronger, its evident effect begins from 1 ?mol/L. When its concentration rose to 3 ?mol/L, not only the membrane permeability increased, but also the nuclear membrane broke seriously. ii) Both soluble and fibrillar Aβ1-40 at high concentrations increased the intracellular free Ca2+, and the increased amplitudes are concentration-dependent. However, the fibrillar one induces the increase of intracellular Ca2+ much quicker and synchronously. These results indicate that some correlation exists between the neurotoxicity of high concentration soluble and fibrillar Aβ1-40 and the change of physico-chemical properties and intracellular Ca ion imbalance.     

大鼠胰腺β细胞内葡萄糖钙信号调控机制

用fura-2显微荧光法测量细胞内自由钙浓度[Ca2+]i,在单个大鼠胰腺β细胞上探讨了葡萄糖诱发的[Ca2+]i初期下降相(GIDP)、钙振荡和钙库释放的影响因素.实验中发现,非刺激浓度的葡萄糖(5 mmol/L)仍可导致β细胞特有的GIDP.GIDP与去极化无关,也不受外钙的影响,但能被内质网钙泵抑制剂thapsigargin抑制,提示此过程可能缘于钙库对胞浆Ca2+的摄取.在胞内钙振荡过程中移去胞外液中的Ca2+,振荡会逐渐停止;若施加thapsigargin,钙振荡仍能继续维持,说明钙振荡主要缘于外钙内流,钙库在钙振荡维持中的作用不大.无外钙条件下,葡萄糖诱导的钙库释放能被钠通道阻断剂TTX所抑制,而高钾对钙库的释放作用却不受TTX的影响,这提示膜去极化可以直接诱导钙库释放.因此,细胞膜去极化、外钙内流、胞内钙库的摄取和释放共同协调着β细胞内的Ca2+平衡.     

External pH regulates the inward K+ channels in Brassica pollen protoplasts

Patch-clamp whole-cell recording techniques were used to investigate the regulation of the inward K* channels by external pH in Brassica pollen protoplasts. The inward K+ currents, conductance and voltage-independent maximum conductance were not significantly affected when the external pH was changed from 5.8 to 4.5. However, compared with the results obtained at pH 5.8, the inward K+ currents and conductance were significantly inhibited at pH 8 .5 . The activation kinetics of the inward K * channels was also significantly regulated by external pH. The channel activation time was shorter at the lower external pH than that at higher pH. Since external pH is a critical factor to regulate pollen germination, the results suggest that external pH regulation of the inward K+ channels may be one of potential physiological mechanisms for the regulation of pollen germination.     

Effect of calcium ions on the secondary structures of photosystemⅡ and its relations with photoinhibition

Calcium ions play an important role in the oxygen_evolving process of photosystem Ⅱ as demonstrated in many experiments. The changes of the secondary structures of PS Ⅱ induced by the depletion of Ca 2+ were reported. The results indicated that the removal of Ca 2+ led to the transition of α helix to turns and sheet structures. While Ca 2+ was re_added to the media, only the structures changed to turns could be recovered. The protein conformational changes of PS Ⅱ during the donor side photoinhibition induced by the depletion of Ca 2+ were also studied. This showed that the protein conformational changes differed between the control and Ca 2+ _depleted samples in a short period of illumination (within 10 min). However, the changes became similar when the illumination time was increased.     

Polysaccharide separation mechanism in polysulfone-Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> magnetic composite membranes

Polysulfone (PSF)-Fe3O4 composite membranes were prepared by the phase-inversion process and their polysaccharide separation mechanism was explored using chondroitin sulfate (CS) and dextran. The mechanism was analyzed from constraints on the magnetic field and geometric deformation. It was found that variations in dextran rejection from 58% to 46% were mainly influenced by the geometric deformation of the composite membrane, while the magnetic field had a significant influence on variations in CS rejection from 82% to 35%. The results indicate that it is possible to continuously separate different types of polysaccharide with a composite membrane by adjusting the external magnetic field.     

Pure metal extraction from molten oxide slag by short-circuit galvanic cell

The oxygen-ion-permeable membrane galvanic short-circuit method has been developed, in which pure metal was directly extracted from the molten oxide slag, and no external voltage is applied. The galvanic cell employed in the experiment was as follows: graphite rod|[O]_{Fe+C saturation}|ZrO₂(MgO)|(FeO)_(siag)|Fe rod. The reduction current in the galvanic cell consisted of an external short-circuit current and an interior short-circuit current in the oxygen-ion-permeable membrane. The real-time variation of external circuit reduction ratio of the molten slag could be obtained from the curve of the external circuit current to the time.     

Amyloid precursor protein-mediated modulation of capacitive calcium entry

Alzheimer’s disease(AD) is a progressive neurodegenerative disorder.In the present study,the function of amyloid precursor protein(APP) in modulating capacitive calcium entry(CCE),a refilling mechanism for depleted intracellular calcium stores,was investigated.CCE in neural 2a(N2a) cells stably expressing wild-type human APP was lower than in wild-type N2a cells,while CCE in APP knockout mouse embryonic fibroblast(MEF) cells was higher than in their wild-type counterparts.We demonstrate that wild-type APP depresses CCE.Furthermore,using N2a cells transfected with C-terminal APP fragments,we show that these fragments anchored in the cell membrane play an important role in CCE depression.     

Synthesis and characterization of cadmium-calcium hydroxyapatite solid solutions

A series of cadmium-calcium hydroxyapatite solid solutions was prepared by an aqueous precipitation method. By various means, the characterizations confirmed the formation of continuous solid solutions over all ranges of Cd/(Cd+Ca) atomic ratio. In the results, both lattice parameters a and c display slight deviations from Vegard’s rule when the Cd/(Cd+Ca) atomic ratio is greater than 0.6. The particles change from smaller acicular to larger hexagonal columnar crystals as the Cd/(Cd+Ca) atomic ratio increases from 0–0.60 to 0.60–1.00. The area of the phosphate peak for symmetric P-O stretching decreases with the increase in Cd/(Cd+Ca) atomic ratio, and the peak disappears when the Cd/(Cd+Ca) atomic ratio is greater than 0.6; the two phosphate peaks of P-O stretching gradually merge together for the Cd/(Cd+Ca) atomic ratio near 0.60. These variations can be explained by a slight tendency of larger Cd ions to occupy M(2) sites and smaller Ca ions to prefer M(1) sites in the structure.     

Two forms of the membrane-bound state of the first C2 domain (C2A) of synaptotagminⅠand calcium-triggered membrane insertion

Neurotransmitter release from presynaptic neurons into the synaptic cleft is an essential step in neurotrans-mission. The release is triggered by Ca2+ and completed by the fusion of neurotransmitters containing synaptic vesicles with the presynaptic membrane. Over the last decades, there has been a virtual explosion in identifica-tion of proteins that play critical roles in the release proc-ess. The leading candidates proposed as the Ca2+-sensors that regulate fusion are members of the synapt…     

Two forms of the membrane-bound state of the first C2 domain (C2A) of synaptotagminⅠand calcium-triggered membrane insertion

The synaptic vesicle protein synaptotagmin I(syt I) is a vesicle transmembrane protein present in synaptic vesicles, which has been proposed as the Ca^2 sensor that regulates secretion. The C2A domain is the membrane proximal part of its cytoplasmic domain. The interaction between C2A and lipid bilayer has been considered to be essential for triggering neurotransmitter release. In the present work, the measurements of membrane surface tension and surface concentration showed that the C2A domain of syt I exhibited two membrane-bound states: the surface adsorption state and the membrane insertion state. The surface absorption state formed in a Ca2~-independent manner with lower affinity, while the membrane insertion state formed with high affinity was only found in the presence of Ca^2 . Both the Ca^2 -independent and Ca^2 -dependent syt I membrane interactions required anionic phospholipids, such as phosphatidylserine (PS). When expressed into rat pheo-chromocytoma (PC12) cells and human embryonic kidney (HEK-293) cells, as demonstrated by immunofluorescence staining and subcellular fractionation, most of the C2A was found at the plasma membrane, even when the cells weredepleted of Ca^2 by incubation with EGTA. These resultssuggested a new molecular mechanism of syt I as a Ca^2 sensor in membrane fusion. Ca^2 -independent surface adsorption might attach syt I to the release site during the docking or priming step. When intracellular Ca^2 increased,syt I triggered the neurotransmitter release following the Ca^2 -dependent penetration into the target membrane.     

Reductive immobilization of perrhenate in soil and groundwater using starch-stabilized ZVI nanoparticles

Perrhenate(ReO4-) was used as nonradioactive surrogate for the radionuclide pertechnetate(99TcO-4) to investigate the potential of using starch-stabilized zero valent iron(ZVI) nanoparticles for reductive immobilization of pertechnetate in soil and groundwater.Batch kinetic tests indicated that the starch-stabilized ZVI nanoparticles were able to reductively remove ～96% of perrhenate(10 mg/L) from water within 8 h.XRD analyses confirmed that ReO 2 was the reduction product.A pseudo-first-order kinetic model was able to interpret the kinetic data,which gave a pseudo first order rate constant(kobs) value of 0.43h-1 at pH 6.9 and room temperature(25℃).Increasing solution pH up to 8 progressively increased the reaction rate.However,highly alkaline pH(10) resulted in much inhibited reaction rate.Consequently,the optimal pH range was identified to be from 7 to 8.Increasing solution temperature from 15 to 45℃ increased k obs from 0.38 to 0.53 h-1.The classical Arrhenius equation was able to interpret the temperature effect,which gave a low activation energy value of 7.61 kJ/mol.When the ReO-4-loaded loess was treated with the stabilized nanoparticles suspension([Fe]=560 mg/L),the water leachable ReO-4 was reduced by 57% and nearly all eluted Re was in the form of ReO2.This finding indicates that starch-stabilized ZVI nanoparticles are promising for facilitating in situ immobilization of ReO-4 in soil and groundwater.     

Multiple intracellular signallings involved in regulation of on channels by GH releasing or inhibitory hormones in pituitary somatotropes

Influx of Ca2-via Ca2+ channels is the major step triggering exocytosis of pituitary somatotropes to release growth hormone (GH). Voltage-gated Ca2+ and K+ channels, the primary determinants of the influx of Ca2+ in somatotropes, are regulated by GH-releasing hornone (GHRH) and somatostatin (SRIF) through G protein-coupled signalling systems. Using whole-cell patch-clamp techniques, the changes of the Ca2+ and K+ currents in primary cultured somatotropes were recorded and signalling systems were studied using pharmacological reagents and intracellular dialysis of non-permeable molecules including antibodies and antisense oligonucleotides. GHRH increased both L-and T-types Ca2+ currents and decreased transient (I4) and delayed rectified (Ik) K+ currents. The increase in Ca2+ currents by GHRH was mediated by cAMP/protein kinase A system but the decrease in K+ currents required normal function of protein kinase C system. The GHRH-induced alteration of Ca2+ and K+ currents augments the influx of Ca2+ , leading to an increase in the [ Ca2+ ]I and the GH secretion. In contrary, a significant reduction in Ca2+ currents and increase in K currents were obtained in response to SRIF. The ion channel response to SRIF was demonstrated as a membrane delimited pathway and can be recorded by classic whole-cell configuration, Intracellular dialysis of anti-αi3 antibodies attenuated the increase in K + currents by SRIF whereas anti-αo antibodies blocked the reduction in the Ca2+ current by SRIF. Dialysis of antisense oligonucleotides specific for αo2 sub-units also attenuated the inhibition of SRIF on the Ca2+current. The Gi3 protein mediated the increase in K + currents and the Go2 protein mediated the reduction in the Ca2 +current by SRIF. The SRIF-induced alteration of Ca2 + and K + currents diminished the influx of Ca2+ , leading to a decrease in the [ Ca2+ ]I and the GH secretion. It is therefore concluded that multiple signalling systems are employed in the ion channel response to GHRH or SRIF in somatotropes, which leads to an increase or decrease in the GH secretion.     

The binding of the anticoagulation factor Ⅰ from the venom of Agkistrodon acutus to activated factor Ⅹ

Anticoagulation factor Ⅰ (ACF Ⅰ) from the venom of Agkistrodon acutus prolonged plasma prothrombin time (PPT) with dose-dependent manner and exhibited marked anticoagulant activity only at the concentration higher than its critical concentration (12 nmol/L). It was discovered that ACFⅠ formed a 1:1 complex with activated coagulation factor (FⅩa) in the presence of Ca2+ ions by the method of polyacrylamide gel electrophoresis. Both native ACFⅠ and decalcified ACFⅠ failed to form complexes with FⅩa in the absence of Ca2+. Sr2+ ions were able to replace Ca2+ ions in the binding of ACFⅠ to FⅩa, but both Ba2+ ions and Tb3+ ions were ineffective. ACFⅠ was a new member of the Ⅸ/Ⅹ-bp family in the C-type lectin superfamily, and had a amino acid composition similar to the other members of this family. It was composed of 251 amino acid residues with a molecular weight of 29 603.6 u on non-reducing condition, determined by MALDI-TOF-MS, and a molecular weight of 14.7 ku on reducing condition, determined by the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).     

New pyrometallurgical process of EAF dust treatment with CaO addition

The non-carbothermic zinc pyrometallurgical processing of electric arc furnace (EAF) dust was investigated on a laboratory scale. The main objective of this process was to convert highly stable zinc ferrite (ZnFe₂O₄), which accounts for more than half of total zinc in the EAF dust, into ZnO and Ca₂Fe₂O₅ by CaO addition. The EAF dust was mixed with CaO powder in various ratios, pressed into pellets, and heated in a muffle furnace in air at temperatures ranging from 700 to 1100℃ for a predetermined holding time. All ZnFe₂O₄ was transformed into ZnO and Ca₂Fe₂O₅ at a minimum temperature of 900℃ within 1 h when sufficient CaO to achieve a Ca/Fe molar ratio of 1.1 was added. However, at higher temperatures, excess CaO beyond the stoichiometric ratio was required because it was consumed by reactions leading to the formation of compounds other than ZnFe₂O₄. The evaporation of halides and heavy metals in the EAF dust was also studied. These components could be preferentially volatilized into the gas phase at 1100℃ when CaO was added.     

Optical frequency standard based on a single 40Ca+

Research on the development of the optical frequency standard based on trapped and cold 40 Ca+ with the 4s2S1/2-3d2D5/2 clock transition at 729nm is reported. A single calcium ion was trapped and laser cooled in the Paul trap and stay in trap for more than 15 days. The linewidth of a 729nm laser was reduced to less than 10Hz by locking to a cavity for longer than 50 hours uninterruptedly. The overall systematic uncertainty of the clock transition has been characterized to be better than 6.5×10 16 . The absolute frequency of the clock transition was measured at 10 15 level using an optical frequency comb referenced to a Hydrogen maser, which was calibrated to the SI second through the global positioning system (GPS). The frequency value was 411042129776393.0(1.6)Hz after the correction of the systematic shifts.     

Cardiac protective role of a novel erythrocyte-derived depressing factor on rats and its Ca^2＋ mechanism

The cardiac protective role of a novel erythro-cyte-derived depressing factor (EDDF) on spontaneous hy-pertensive rats (SHR), calcium overload (CaO) rats and Wistar rats and its mechanism was evaluated. Mean artery pressure (MAP), heart rate (HR) and LVdp/dtmax were measured by physiological recorder. The effect of EDDF on the Ca2+-ATPase activity in myocardial sarcoplasmic reticu-lum (SR) of CaO rats was determined by inorganic phos-phate assay. Calcium transport in myocytes was measured by 45Ca2+ radioactive isotope measurement. The phosphoryla-tion levels of extracellular signal-regulated protein kinases (ERK1/2) in myocardial tissue of SHR and CaO rats were measured by Western blot method. And the ultrastructures of cardiac muscle cells were observed with the transmission electron microscope. The results indicated that EDDF could significantly decrease MAP, HR and LVdp/dtmax in a dose dependent manner (P < 0.05). It seems that the mechanism might relate with activating the Ca2+-APTase, enhancing the uptake and release of Ca2+ from SR (P < 0.05), decreasing the phosphorylation levels of ERK1/2 of myocytes (P < 0.01) and lightening the ultrastructural lesion of cardiac muscle cells. In CaO rats, the Ca2+-ATPase activity decreased clearly com-pared to control (64.99 7.16 vs 94.48 7.68 nmol·min-1 ·mg-1 protein, P < 0.01), while EDDF (100 mg/mL) could significantly increase the activity (87.93 ?9.54 vs 64.99 ?7.16, P < 0.05, n = 7). Both uptake and release rate of Ca2+ (祄ol 45Ca2+/g protein/min) from myocardial SR of CaO rats re-markably decreased compared to control (32.40 ?2.70 and 15.46 ?1.49 vs 61.09 ?10.89 and 25.47 ?4.29, P < 0.05); EDDF (100 mg/mL) could significantly stimulate their activi-ties (50.48 6.76 and 21.76 2.75 vs 32.40 2.70 and 15.46 1.49, P < 0.05). EDDF could evidently down-regulate the phosphorylation of ERK1/2 in myocardial tissue from SHR and CaO rats (P < 0.01), lighten the ultrastructural lesion of cardiac muscle cells of SHR as well. It is concluded that EDDF seems to play protective roles on both structure and function of heart, which closely related with amelioration of Ca2+ transport and inhibition of Ca2+-MAP kinase pathway.     

Effects of iron oxide on crystallization behavior and spatial distribution of spinel in stainless steel slag

Chromium plays a vital role in stainless steel due to its ability to improve the corrosion resistance of the latter. However, the release of chromium from stainless steel slag (SSS) during SSS stockpiling causes detrimental environmental issues. To prevent chromium pollution, the effects of iron oxide on crystallization behavior and spatial distribution of spinel were investigated in this work. The results revealed that FeO was more conducive to the growth of spinels compared with Fe₂...     

A nut-type ultrasonic motor and its application in the focus system

This article reports a screw-driven polyhedron linear ultrasonic motor （USM） of nut-type. It is comprised of a stator, which is a threaded metal nut bonded with piezoelectric plates on its external surface, and a rotor with external threads, which engage with the internal threads of the stator. A traveling wave in the plane is stimulated on the stator when harmonic electric signals are applied to the piezoelectric plates. The traveling wave drives the rotor to rotate, and the threads transform the rotation into a linear motion. The lens can be fixed in the rotor and realize the integrated design of the auto focus system. This structure can omit retarder and directly drive to obtain a high accuracy of positioning, and it is shockproof. A mini AF cellular phone module （8.5 mm×8.5 mm×5.9 mm） driven by this motor was made and an image resolution of 3-5 MP was obtained in the module prototypes of the cellular phone.