Effect Of Ca Ions Research Articles

The Effect of Ca Ions for Bacteria

Myelodysplastic syndrome (MDS) is clonal hematopoietic stem cell disorders characterized clinically by ineffective hematopoiesis...

Characterization and biocompatibility of a calcium-containing AZ31B alloy as a biodegradable material

Magnesium has attracted notability as a biodegradable material. Several studies have reported that magnesium containing calcium (Ca) had biosafety with higher mechanical properties. However, Mg–1Ca alloy showed non-uniform corrosion properties with bone. In this study, various Ca amounts were added to commercial magnesium alloy AZ31B to improve the corrosion resistance and microstructure. AZ31B billet was prepared by casting without Ca. The AZ31B alloy ingots were melted and recasted with Ca quantities at 1.5 and 2.5 wt%. Extrusion ingots were pressed out to a plate with thickness of 5 mm and width of 80 mm at 1650 °C. The microstructure of the alloy was observed by optical microscopy and SEM. The composition of the alloy was analyzed by EDX. To examine the corrosion properties, potentiodynamic polarization was used to measure the corrosion potential and current density. Osteoblast cells MC3T3-E1 were incubated with the samples to allow cell attachment and MTT assay. The microstructure of alloys was homogeneously distributed over the surface and observed phase boundary. Preliminary elemental analysis suggested that the second phases were Al2Ca and Mg2Ca. Grain refinement by extrude casting was obtained for AZ31B–xCa. The corrosion resistant of AZ31B–xCa by current density was greater than the AZ31B because the standard electrode potential of Mg phase was lower than Mg2Ca. In vitro studies showed that the reduction of corrosion resistance and mechanical ability of the magnesium alloy after addition of Ca were not correlated with bioactivity. In particular, AZ31B–1.5Ca had higher formation of biomimetic substances and lower cytotoxicity, even though it had more vulnerable mechanical properties than AZ31B. Based on this result, the effect of Ca ion on commercial alloy AZ31B, mechanical properties, and bioactivity as biodegradable implant were discussed.

Кінетика інгібіторної дії калікс[4]арену С-90 на активність транспортної Ca2+,Mg2+-АТР ази плазматичної мембрани гладеньком’язових клітин

In experiments on the suspension of myometrium cell plasma membrane, processed by 0.1% digitonin, the inhibitory action of calix[4]arene C-90 (5,11,17,23-tetra(threeftor)methyl(phenilsulphonilimino)-methylamino-25,26,27,28-tetrapropoxy-calix[4]arene) on the activity of Ca2+,Mg2+-ATPase was investigated. The authors also examined the influence of calix[4]arene in different concentration on affinity of enzyme (Ca2,Mg2+-ATPase) for the ATP and ions of Mg and Ca, and its influence on cooperative effect and maximum velocity of ATP hydrolysis. It is shown that calix[4]arene does not influence the affinity of Ca2+,Mg2+-ATPase for the ATP, which means that these two compounds have different binding centers. Also calix[4]arene has no influence on affinity and cooperative effect of Ca ions, if it is used in concentration lower than 50 μM. Calix[4]arene slightly increases coefficient of Ca2+,Mg2+-ATPase activation by magnesium chloride. In all three cases, where ATP, Mg and Ca ions are used to test the impact of calix[4]arene, maximum velocity of ATP hydrolysis significantly decreases. All these results clarify that calix[4]arene implements its inhibitory action through mechanism of uncompetitive inhibition of Ca2+,Mg2+-ATPase activity.

An ATR-FTIR study of sulphate sorption on magnetite; rate of adsorption, surface speciation, and effect of calcium ions

The adsorption of sulphate on magnetite was studied in-situ using ATR-FTIR spectroscopy. Synthetic magnetite particles were deposited on a ZnSe internal reflection element and the spectra of sulphate adsorbed at pH 4–8.5 were recorded. Two different ionic strengths were used viz. 0.01 M and 0.1 M NaCl. The spectra of adsorbed sulphate on magnetite coated ZnSe were compared with the spectra of sulphate solutions at the same pH values and in contact with uncoated ZnSe. The spectrum of adsorbed sulphate at pH 4 showed three maxima at 979, 1044, and 1115 cm −1 indicating a monodentate adsorption in which the T d symmetry of SO 4 2 − is lowered to C 3v. At pH 6.5, sulphate adsorbed as an outer-sphere complex with two weak bands appearing at 1102 and 980 cm −1. Moreover, spectra of the adsorbed sulphate at pH 4 were recorded as a function of time and sulphate concentration. The equilibrium absorbance at different concentrations fitted a Langmuir type adsorption isotherm. The Langmuir affinity constant K at pH 4 was determined from the slope and intercept of the Langmuir plot to be K = 1.2344 × 10 4 M − 1 and the Gibbs free energy of adsorption Δ G ads 0 was estimated from this value to be −33.3 kJ/mol. Kinetic analysis indicated that adsorption at pH 4 is fast, whilst the desorption kinetic at the same pH is very slow. In addition, the effect of Ca ions on sulphate adsorption was also studied. It was shown that Ca ions increased the sulphate adsorption on magnetite at pH 8.5.

The effects of Ca ions, EGTA and storage time on myofibrillar protein degradation, levels of Ca 2+-dependent proteases and cathepsins B, H, L and D of ostrich skeletal muscle

The effect of Ca ions and ethylene glycol-bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA) on myofibrillar protein degradation showed that when ostrich iliotibialis lateralis muscle was incubated with 10 mM EGTA at 2–4 °C for 24 hr, the activity of extracted cathepsin H was unchanged compared with a buffer-incubated sample. Ca ++ had no effect on extracted cathepsin H activity, while that of Ca 2+-dependent protease (CDP) decreased significantly ( p < 0.05). Ca 2+-treatment enhanced post-mortem changes observed in myofibrillar protein patterns (production of fragments around 30 K) that were not observed in EGTA-incubated myofibrils. The effect of storage time on shear force, CDP activity, cathepsin B, D, H and L activities and the SDS-PAGE pattern of myofibrils showed a time-dependent reduction in CDP activity. Of the cathepsins studied only cathepsin H showed a reduction (40%) in activity. The most prominent component appearing on storage at 2–4 °C had a M r of 27 K. The incubation of myofibrils with CDP mimicked the post-mortem changes. CDP may be responsible for some of the post-mortem changes observed, although shear force measurements suggest these changes do not lead to significant tenderisation.

Root Cap Mucilage and Extracellular Calcium as Modulators of Cellular Growth in Postmitotic Growth Zones of the Maize Root Apex*

Abstract: The control of maize root growth by root cap mucilage and extracellular calcium (Ca) was examined. Special attention was paid to the influence of these factors on cellular aspects of root growth, such as cell shape and organization of the microtubular (MT) cytoskeleton. Externally supplied Ca impaired the transition of early post‐mitotic cells from a more‐or‐less apolar mode of expansion to a strictly anisotropic mode of elongation accompanied by their more rapid growth. However, this inhibitory effect of Ca was not associated with any re‐arrangement of the cortical MTs, their transverse arrays, with respect to the root axis, being maintained under these conditions. Root mucilage, collected from donor root caps and placed around root tips, exerted a similar effect on cell shapes as did externally supplied Ca. In contrast, roots grown in a medium of low Ca content, or from which the root cap mucilage was continually removed, had more elongated cell shapes in their post‐mitotic growth regions when compared to the control roots. These findings are consistent with a notion that Ca is present in the root cap mucilage in physiologically relevant amounts and can mediate growth responses in both the PIG region and the apical part of the elongation zone.Integrating several known effects of Ca ions on growth at the root apex, a hypothesis is proposed that a Ca‐mediated and MT‐independent control of cell growth in the PIG region might be involved in morphogenetic root movements (e.g. gravitropism), and that root growth responses could be initiated by an asymmetric distribution of extracellular calcium, or root cap slime, around the growing root tip.

Evidence for a specific site for modulation of calcium channel activation by external calcium ions.

We have investigated the effect of permeant ion species on activation of transiently expressed neuronal alpha1A Ca channels. Equimolar replacement of Ba with Ca resulted in a consistent depolarizing shift of the half-activation potential whose magnitude (&sim;10 mV) was constant over a range of 2 to 100 mM permeant ion, suggesting that the effects of Ca ions were fully developed at concentrations below 2 mM and indicating that Ba and Ca screened surface charges equally. In mixtures of Ba and Ca at constant divalent cation concentration the voltage-shift, as a function of Ca mole fraction, was well described by a model in which Ba and Ca compete for a single site but only Ca ions produce a gating effect. Overall, our data are consistent with Ca ions exerting their effects on activation via a specific regulatory site.

The Physical Mechanism of Sodium Conductance Change in Nerve: An Electron Transfer Model

Assuming that the nerve membrane contains electron transfer complexes and energy traps, many Na channel-related properties can be explained, including the Na activation-inactivation process, refractory state, recovery of excitability, effects of Ca ions and local anesthetics, heat production and absorption, anode break excitation, and the significance of positive afterpotential in repetitive firing. This model also suggests that the nerve impulse could be elicited by laser beams.

The role of Ca2+ in cross-bridge kinetics in chemically skinned rabbit psoas fibers.

The sinusoidal analysis method is applied to chemically skinned rabbit psoas preparations, and the effect of Ca ions on exponential processes is determined. The results are compared to the predictions of two classes of models, those in which the binding of Ca2+ to the thin filaments acts as a switch to fully activate a segment of the filament (switch hypothesis), and those in which the binding of Ca2+ results in a graded increase in activity in proportion to the fraction of sites occupied (graded hypothesis). Although qualitative features of our results are in accord with the switch hypothesis, quantitative examination of the results shows that there is an extra process (B'), which produces a W-shaped phase-frequency plot during partial activation. This result is consistent with the assumption that there are two activated states available to the thin filaments of structured muscle.

Effects of Ca ions on action potentials in immature cultured neurons from chick cerebral cortex.

Action potentials evoked by depolarizing pulses were studied in immature cultured cerebral cortical neurons from chick embryos. The majority of action potentials were rather small, and they were still elicited in the presence of 10(-7) gm/ml tetrodotoxin (TTX), but were almost completely abolished in NA+-free solution or by 10(-5) gm/ml TTX in Tyrode's solution. The elevation of external Ca2+ concentration not only increased the maximum rates of rise of action potentials in normal Tyrode's solution with and without low (10(-7) gm/ml) TTX but also regenerated action potentials in high (10(-5) gm/ml) TTX-containing Tyrode's solution or in Na+-free solution. These high Ca2+ effects were blocked by Mn2+ or Co2+. These results suggest that action potentials, which were predominantly Na-dependent, are partially contributed by Ca ions in immature chick cerebral cortical neurons.

The effect of Ca ions on the kinetics of actin-myosin interactions in glycerinated cray-fish muscle fibres

The effect of Ca ions on the kinetics of actin-myosin interactions in glycerinated cray-fish muscle fibres

Dual effect of external calcium on the frequency of miniature synaptic potentials in frog sympathetic ganglion cells

The effect of calcium on spontaneous transmitter release and on the release induced by tetanic stimulation and by raising the external potassium concentration ([K]0) was studied in sympathetic ganglion cells of Rana esculenta. 1. In standard Ringer's solution the frequency of miniature excitatory postsynaptic potentials (mepsp) ranged from 0.05--2.0 s-1 (0.05 +/- 0.09 s-1, n = 37) at room temperature. 2. At a [K]0 of 2.5 mM mepsp frequency was approximately linearly related to the logarithm of the external calcium concentration (log [Ca]0) (0.1 mM less than or equal to [Ca]0 less than or equal to 20 mM). 3. Duration and amplitude of the potentiation of transmitter release after tetanic preganglionic stimulation increased depending on [Ca]0. 4. Mepsp frequency was strongly dependent on [K]0 between 10 and 20 mM; the frequency being increased to about 40 times control level at a [K]0 of 20 mM. 5. Raising [Ca]0 up to 1.8 mM in high K solutions resulted in an increase in mepsp frequency followed by a decrease at higher [Ca]0. 6. These results are consistent with the idea that the effect of calcium on mepsp frequency depends on: (a) the driving force for calcium entry, (b) the effect of Ca ions on the potential gradient within the nerve membrane.

The Effect of Ca-Ions on the Kinetics of Rhodopsin Photoproduct Decay in the Living, Isolated Frog Retina

The Effect of Ca-Ions on the Kinetics of Rhodopsin Photoproduct Decay in the Living, Isolated Frog Retina

曹灰長石に対するDodecylammonium Chlorideの吸着に関する研究

The adsorption isotherms of dodecylammonium chloride on silica and labradorite at natural pH and for various pH values were determined using a radioactive form of the reagent. The effect of Ca ion and Na ion on the adsorption of dodecylammonium chloride on silica and labradorite was also investigated.The results of adsorption tests of dodecylammonium chloride on both silica and labradorite indicated that there is a significant difference between both adsorption mechanisms. Namely, dodecylammonium ions adsorb at Stern layer on quartz surface as counter ions, on the other hand, dodecylammonium ions mainly adsorb on the labradorite surface by ion exchange, viz, by exchanging Na ions or Ca ions which are lattice cations of labradorite.The effect of pH on the adsorption of dodecylammonium ion on both silica and labradorite showed a similar tendency, however, the mechanisms differ from each other. On silica surface, H ion is potential determining ion and so controls adsordtion of dodecylammonium ion as counter ion in the Stern Layer. On the other hand, since Na ion and Ca ion which are lattice cations of labradorite are exchanged easily by H ion in acldic side, H ion is a competitor to the dodecylammonium ion for labradorite surface.The effect of Ca ion on the adsorption of dodecylammonium chloride on silica and labradorite was less than the effecf of H ion, but it was signmcant.