EC Ca Research Articles

Profile Distribution of Available Plant Nutrients in Western Hilly Tracts of Cuttack District, Odisha

Aims: An investigation was conducted to examine the distribution of available plant nutrients and the relationships between soil properties and available nutrient status in soil profiles in the Western Hilly Tracts of the Cuttack District, Odisha.
 Place and Duration of Study: The research area, i.e. the Narasinghpur block, is located in the western part of the Cuttack district in Odisha and is characterized by lateritic uplands and mountainous terrain. Three soil profiles were exposed i.e. upland, medium land and low land before the rainy season (February, 2020).
 Methodology: For experiments, five layers demarcated at 20cm intervals up to a depth of 100cm were sampled, processed, and stored. Several parameters, including particle size, pH, EC, OC, and available Ca, Mg, S, Fe, Mn, Cu, and Zn were analysed and interpreted using standard protocols.
 Results: Sand content decreased with pedon depth, whereas clay content showed the opposite trend. With increasing soil depth in all pedons, soil pH increased while EC and soil organic carbon content declined. The available Ca, Mg, and S in surface soils varied from 4.11 to 6.56 [cmol (p+)/kg], 2.15 to 3.54 [cmol (p+)/kg] and 9.85 to 12.06 mg kg-1, respectively. The corresponding subsurface ranges for these nutrients were 4.31 to 8.52 [cmol (p+)/kg], 2.41 to 4.52 [cmol (p+)/kg], and 6.95 to 11.41 mg kg-1, respectively. The available Fe, Mn, Cu, Zn, and B range in surface soils were 127.85-278.81, 68.48-144.98, 0.64-0.9, 0.54-0.63 and 0.37-0.47 mg kg-1, respectively. The subsurface ranges for these nutrients were 102.32–234.46, 53.21–118.28, 0.28–0.89, 0.17–0.50, and 0.29–0.91 mg kg-1. The status of micronutrients in the present study region was as follows: Fe > Mn > Cu > Zn > B. With increasing soil depth, available Ca and Mg increased, but available S, Fe, Mn, Cu, Zn and B declined. Positive correlations between available Fe, Mn, Cu, and Zn with the soil organic carbon content of the soil and negative correlations with the soil pH were observed.
 Conclusion: Plant nutrients in the research area varied with topography, although the differences between upland, medium land and lowland wasn't substantial. However, accelerated decomposition of soil organic matter and agricultural residues likely led to highermicronutrient concentrations at the soil's surface than subsurface.

Application of water quality index and multivariate statistical techniques for assessment of water quality around Yamuna River in Agra Region, Uttar Pradesh, India

Abstract In this research, water quality index and multivariate statistical techniques were carried out on 14 water quality parameters collected quarterly (four times/year) from nine water sources in Agra, Uttar Pradesh, India, for one year (May 2019–April 2020). The water quality parameters included are the concentration of hydrogen ions (pH), Electrical Conductivity, Turbidity, Total Dissolved Solids (TDS), Total Hardness, Total Alkalinity, Calcium, Sulphate, Chloride, Magnesium, Iron, COD, DO, and BOD. The water samples collected show that the mean values of physicochemical parameters are in the range set by WHO and BIS except for hardness in summer (1,680 mg/L), monsoon (832.22 mg/L), winter (1,876.66 mg/L), spring (1,535.55 mg/L); TDS in summer (1,000.33 mg/L), monsoon (683.44 mg/L), winter (1,087.66 mg/L), spring (776.66 mg/L); and sulphate in summer (927.22 mg/L), monsoon (446.77 mg/L), winter (925.77 mg/L), spring (944.88 mg/L), which indicate bad quality of water. The WQI values were calculated for three locations in different weather conditions. WQI values in summer, winter and spring are 630.90, 279.61, 279.91, showing that the river water is not suitable for drinking purposes whereas the WQI value in monsoon is 75.89, showing that water is fit for drinking purposes due to the dilution of the river water. A moderate positive correlation was observed for turbidity with total hardness, iron, total alkalinity, and sulphate. Negative correlation was observed with pH. Moderate correlation was seen with TDS–EC (0.608), TDS–Alkalinity (0.7794), EC–Ca (0.723), and strong correlation was observed for BOD–DO (0.941) and Ca–Mg (0.999). Principal component analysis revealed that five factors were significant (eigenvalue > 0.5) with total variance of 39.43%–85.19% respectively. The ICP-MS study of water samples from point sources indicate the presence of Ni2+, Cr6+, Co2+, Mn2+, Cu2+, and Zn2+ ions at higher concentrations.

EFFECT OF SOIL CONDITIONRES ON SELECTIVITY COEFFICIENT IN SOME SALT AFFECTED SOILS

This study was carried out at Soil. Sci. Dept. Faculty of Agriculture, Menoufia University, Egypt during years of 2016 and 2017 on five salt affected soils of El-Hamoul area, Kafr El-Sheikh Governorate, North Nile, Delta, Egypt to study the changes in their chemical properties affected by compost as soil conditioner at application rates of 0, 1, 2 and 3% under incubation conditions (0, 3 and 6 months ) at room temperature on soil pH, EC, CEC, ESP and the content of soluble cations (Na+ , Ca2+, Mg2+ and K+), soluble anions (Cl- , CO32-, HCO3- and SO42-), exchangeable cations (Na, Ca, K and Mg) and OM at the same time the selectivity coefficient for the exchangeable cations in the five soils in relation with the studied treatments were calculated. Increasing rate of added compost as well as incubation period resulted in a decrease in soil pH, ESP, the content of soluble Na+ and Cl- and exchangeable Na but resulted in an increase in OM, CEC, EC and exchangeable cations Ca, K and Mg. Also, there are wide variations in the found selective coefficients according to the studied treatments. In general compost application improved the chemical properties of salt affected soil and increased exchangeable Ca than other cations.

Assessment of long-term soil dynamics at manured fields with field measurement and interviews: a case study in the semi-arid Ethiopian Rift Valley

ABSTRACTAssessment of long-term (more than 20 years) soil fertility dynamics is rare in Sub-Saharan Africa (SSA). It is because soil quality assessments have been conducted in research stations, which are difficult to continue in the long term mainly due to lack of funds in SSA. Farmers in the semi-arid Ethiopian Rift Valley (NERV) cultivate maize with long-term manure application to the fields (aradas). The history of manure application was carefully ascertained from farmers, and 40 manured aradas for 20 years and more and 40 unmanured fields were selected. Soil chemical properties (SOC, total N, Olsen P, CEC, exchangeable cations, EC, and pH) were analyzed, while on-site NO3-N and soil physical properties (soil compaction, saturated hydraulic conductivity, and water retention capacity) were measured. The manured aradas increased SOC, total N, P, CEC, K, Na, Mg, EC, and NO3-N and lowered Ca and pH. The arada soils lowered soil compaction and bulk density and increased porosity. No consistent changes in hydraulic conductivity and water retention capacity were observed, probably because of plough pans underlying the surface soil layer across NERV. Soil quality assessment to diagnose farmers’ long-term manure application based on field measurement and interviews can be an appropriate approach in SSA.

Linking Hyperpolarization to Endothelial Cell Calcium Events in Arterioles

Our understanding of the relationship between EC membrane potential and Ca(2+) entry has been shaped historically by data from cells in culture. Membrane hyperpolarization was associated with raised cytoplasmic [Ca(2+) ] ascribed to the increase in the inward electrochemical gradient for Ca(2+) , as ECs are generally thought to lack VGCC. Ca(2+) influx was assumed to reflect the presence of an undefined Ca(2+) "leak" channel, although the original research articles with isolated ECs did not elucidate which Ca(2+) influx channel was involved or indeed if a transporter might contribute. Overall, these early studies left many unanswered questions, not least whether a similar mechanism operates in native ECs that are coupled to each other and, in many smaller arteries and arterioles, to the adjacent vascular SMCs via gap junctions. This review discusses whether Ca(2+) leak through constitutively active EC Ca(2+) channels or a more defined, gated pathway might underlie the reported link between enhanced Ca(2+) entry and hyperpolarization. Electrophysiological evidence from ECs in isolation is compared with those in intact arteries and arterioles and the possible physiological relevance of EC Ca(2+) entry driven by hyperpolarization discussed.

간척지 토양에서 퇴비처리가 벼의 생산 및 품질개선에 미치는 영향

This study was conducted to reduce the dependability of farmers on chemical fertilizers for rice cultivation. Soil chemical and biological properties were monitored before experiment and at the time of harvesting. The results showed that EC, available SiO2, and exchangeable Ca 2+ were decreased at the time of harvesting while pH, OM, and exchangeable K + and Mg 2+ were remain unchanged, compared with soil before experiment. Population of aerobic bacteria, Bacillus sp., and fungi were also increased at the time of harvesting in the paddy field, compared with before fertilization, in the treatment of 50% soil-testing fertilizer + 50% compost. Concentrations of N, P, and K in rice leaves increased with the fertilizers application, maximum increase was recorded in 50% soil-testing fertilizer + 50% compost. Non-significant difference was observed in the morphological parameters of rice among the treatments. The chlorophyll contents of rice leaf increased in a similar fashion up to 60 days, thereafter, sharp decrease was observed in all the treatments. Maximum yield (per 10a) was recorded in the field treated with 50% soil-testing fertilizer + 50% compost followed by standard applied fertilizer, 70% soil-testing fertilizer + 30% compost, soil-testing fertilizer and unfertilized plot. Amylose content showed non-significant difference within the treatments. Protein content increased with the use of fertilizers and best protein content was recorded in the treatment of 50% soil-testing fertilizer + 50% compost. It was concluded that the amount of the chemical fertilizer used was directly proportional to the protein content of rice grain. However, the palatability of rice grown in unfertilized field was better than the treatments but minimum yield was obtained. Hence, the treatment of 50% soil-testing fertilizer + 50% compost, was the best among the fertilizer combinations for rice cultivation as supported by the yield, protein and palatability index.

Intravital Macrozoom Imaging and Automated Analysis of Endothelial Cell Calcium Signals Coincident with Arteriolar Dilation in Cx40BAC‐GCaMP2 Transgenic Mice

Calcium signaling is integral to endothelium-dependent vasodilation. Our goal was to develop methods enabling automated analyses for accurately and objectively determining the dynamic relationship between EC Ca(2+) responses and arteriolar diameter in vivo. User-friendly software (DiaFluor) written in LabView was applied to images acquired at 15fps with a custom macrozoom intravital microscope to evaluate changes in EC Ca(2+) concomitant with arteriolar diameter. Transgenic Cx40(BAC) -GCaMP2 mice expressing a fluorescent Ca(2+) indicator molecule in arteriolar ECs enabled resolution of EC Ca(2+) signaling in response to ACh microiontophoresis (500nA, 100-1000msec pulse) from a micropipette (1μm tip) positioned adjacent to an arteriole in the superfused cremaster muscle preparation. A 100-msec pulse of ACh (1M) had little effect on EC Ca(2+) or arteriolar diameter. As pulse duration increased, vasodilation increased with fluorescence intensity (p<0.01). Based upon fluorescence responses (F/F(o)), the effective diffusion distance of ACh along arterioles increased from ∼100μm (250msec pulse) to ∼200μm (1000msec pulse) with a peak velocity of ∼150μm/sec. The novel imaging and software presented here are the first to enable automated simultaneous evaluation of EC Ca(2+) signaling and endothelium-dependent vasodilation in vivo.

Assessment of the impact of industrial effluents on the quality of irrigation water and changes in soil characteristics: The case of Kombolcha town

AbstractThe town of Kombolcha is found in the northern part of Ethiopia. It contains several large industries that drain their liquid waste to the nearby rivers. To assess the impact of the wastes on irrigation water quality water samples were just taken randomly to be used only as indicators. The samples of water were collected three times from three rivers that are locally called the Leyole Worka and Borkena. These rivers are used as sources of irrigation water for the nearby farmlands. Parameters of pH EC Ca+2 Mg+2 Na+ Cl− CO HCO BO and SAR were monitored in the irrigation water and the soils of the respective irrigated farmlands. Significant concentration differences (at P ≤ 0.05) in these parameters were detected in the two rivers receiving industrial effluents (Leyole and Worka) and they are compared against the control river water (Borkena). The mean values of the parameters in each irrigation water source samples were also compared with FAO guidelines for irrigation water quality. The Leyole and Worka are found to be polluted as compared to the control river (Borkena). Significant quality difference was observed in pH value and Na+ concentrations between the Borkena River and effluent‐contaminated irrigation water of the Leyole River. Moreover Na+ HCO and SAR were found to be beyond the safe limits to use in irrigation. Irrigation water from the Worka River was found to be significantly different from the control irrigation water in Na+ Mg+2 and SAR and the Na+ concentration and the values of pH and SAR have been identified to exceed the normal conditions for use in agriculture. The chemical parameters in the irrigation water were also found to have accumulated and changed the soil characteristics of the farmlands. Copyright © 2011 John Wiley &amp; Sons Ltd.

A mathematical model of vasoreactivity in rat mesenteric arterioles: I. Myoendothelial communication

To study the effect of myoendothelial communication on vascular reactivity, we integrated detailed mathematical models of Ca(2+) dynamics and membrane electrophysiology in arteriolar smooth muscle (SMC) and endothelial (EC) cells. Cells are coupled through the exchange of Ca(2+), Cl(-), K(+), and Na(+) ions, inositol 1,4,5-triphosphate (IP(3)), and the paracrine diffusion of nitric oxide (NO). EC stimulation reduces intracellular Ca(2+) ([Ca(2+)](i)) in the SMC by transmitting a hyperpolarizing current carried primarily by K(+). The NO-independent endothelium-derived hyperpolarization was abolished in a synergistic-like manner by inhibition of EC SK(Ca) and IK(Ca) channels. During NE stimulation, IP(3) diffusing from the SMC induces EC Ca(2+) release, which, in turn, moderates SMC depolarization and [Ca(2+)](i) elevation. On the contrary, SMC [Ca(2+)](i) was not affected by EC-derived IP(3). Myoendothelial Ca(2+) fluxes had no effect in either cell. The EC exerts a stabilizing effect on calcium-induced calcium release-dependent SMC Ca(2+) oscillations by increasing the norepinephrine concentration window for oscillations. We conclude that a model based on independent data for subcellular components can capture major features of the integrated vessel behavior. This study provides a tissue-specific approach for analyzing complex signaling mechanisms in the vasculature.

Selective Activation of the SK1 Subtype of Human Small-Conductance Ca2+-Activated K+ Channels by 4-(2-Methoxyphenylcarbamoyloxymethyl)-piperidine-1-carboxylic Acid tert-Butyl Ester (GW542573X) Is Dependent on Serine 293 in the S5 Segment

A new small molecule, 4-(2-methoxy-phenylcarbamoyloxymethyl)-piperidine-1-carboxylic acid tert-butyl ester (GW542573X), is presented as an activator of small-conductance Ca(2+)-activated K(+) (SK, K(Ca)2) channels and distinguished from previously published positive modulators of SK channels, such as 1-ethyl-2-benzimidazolinone (1-EBIO) and cyclohexyl-[2-(3,5-dimethylpyrazol-1-yl)-6-methyl-pyrimidin-4-yl]-amine (CyPPA), in several aspects. GW542573X is the first SK1-selective compound described: an EC(50) value of 8.2 +/- 0.8 microM (n = 6, [Ca(2+)](i) = 200 nM) was obtained from inside-out patches excised from hSK1-expressing HEK293 cells. Whole-cell experiments showed that hSK2 and hSK3 channels were more than 10 times, and hIK channels even more than 100 times, less sensitive to GW542573X. The Ca(2+)-response curve of hSK1 was left-shifted from an EC(50)(Ca(2+)) value of 410 +/- 20 nM (n = 9) to 240 +/- 10 nM (n = 5) in the presence of 10 microM GW542573X. In addition to this positive modulation, GW542573X activated SK1 in the absence of Ca(2+) and furthermore induced a 15% increase in the maximal current at saturating Ca(2+). Thus, GW542573X also acts as a genuine opener of the hSK1 channels, a mechanism of action (MOA) not previously obtained with SK channels. The differential potency on hSK1 and hSK3 enabled a chimera approach to elucidate site(s) important for this new MOA and selectivity property. A single amino acid (Ser293) located in S5 of hSK1 was essential, and substituting the corresponding Leu476 in hSK3 with serine conferred hSK1-like potency (EC(50) = 9.3 +/- 1.4 microM, n = 5). GW542573X may activate SK channels via interaction with "deep-pore" gating structures at the inner pore vestibule or the selectivity filter in contrast to 1-EBIO and CyPPA that exert positive modulation via the intracellular calmodulin binding domain.

Effects of Combined Phosphorylation at Ser-617 and Ser-1179 in Endothelial Nitric-oxide Synthase on EC50(Ca2+) Values for Calmodulin Binding and Enzyme Activation

We have investigated the possible biochemical basis for enhancements in NO production in endothelial cells that have been correlated with agonist- or shear stress-evoked phosphorylation at Ser-1179. We have found that a phosphomimetic substitution at Ser-1179 doubles maximal synthase activity, partially disinhibits cytochrome c reductase activity, and lowers the EC(50)(Ca(2+)) values for calmodulin binding and enzyme activation from the control values of 182 +/- 2 and 422 +/- 22 nm to 116 +/- 2 and 300 +/- 10 nm. These are similar to the effects of a phosphomimetic substitution at Ser-617 (Tran, Q. K., Leonard, J., Black, D. J., and Persechini, A. (2008) Biochemistry 47, 7557-7566). Although combining substitutions at Ser-617 and Ser-1179 has no additional effect on maximal synthase activity, cooperativity between the two substitutions completely disinhibits reductase activity and further reduces the EC(50)(Ca(2+)) values for calmodulin binding and enzyme activation to 77 +/- 2 and 130 +/- 5 nm. We have confirmed that specific Akt-catalyzed phosphorylation of Ser-617 and Ser-1179 and phosphomimetic substitutions at these positions have similar functional effects. Changes in the biochemical properties of eNOS produced by combined phosphorylation at Ser-617 and Ser-1179 are predicted to substantially increase synthase activity in cells at a typical basal free Ca(2+) concentration of 50-100 nm.

Selective positive modulation of the SK3 and SK2 subtypes of small conductance Ca2+‐activated K+ channels

Positive modulators of small conductance Ca(2+)-activated K(+) channels (SK1, SK2, and SK3) exert hyperpolarizing effects that influence the activity of excitable and non-excitable cells. The prototype compound 1-EBIO or the more potent compound NS309, do not distinguish between the SK subtypes and they also activate the related intermediate conductance Ca(2+)-activated K(+) channel (IK). This paper demonstrates, for the first time, subtype-selective positive modulation of SK channels. Using patch clamp and fluorescence techniques we studied the effect of the compound cyclohexyl-[2-(3,5-dimethyl-pyrazol-1-yl)-6-methyl-pyrimidin-4-yl]-amine (CyPPA) on recombinant hSK1-3 and hIK channels expressed in HEK293 cells. CyPPA was also tested on SK3 and IK channels endogenously expressed in TE671 and HeLa cells. CyPPA was found to be a positive modulator of hSK3 (EC(50) = 5.6 +/- 1.6 microM, efficacy 90 +/- 1.8 %) and hSK2 (EC(50) = 14 +/- 4 microM, efficacy 71 +/- 1.8 %) when measured in inside-out patch clamp experiments. CyPPA was inactive on both hSK1 and hIK channels. At hSK3 channels, CyPPA induced a concentration-dependent increase in the apparent Ca(2+)-sensitivity of channel activation, changing the EC(50)(Ca(2+)) from 429 nM to 59 nM. As a pharmacological tool, CyPPA may be used in parallel with the IK/SK openers 1-EBIO and NS309 to distinguish SK3/SK2- from SK1/IK-mediated pharmacological responses. This is important for the SK2 and SK1 subtypes, since they have overlapping expression patterns in the neocortical and hippocampal regions, and for SK3 and IK channels, since they co-express in certain peripheral tissues.

Effect of phosphogypsum application on the growth and Ca uptake of Komatsuna Brassica rapa L. cv. Natsurakuten

(pp. 1–7) Application of phosphogypsum PG and limestone to Andisol were compared in terms of their effects on the growth and uptake of Ca in Komatsuna Brassica rapa L. cv. Natsurakuten. The studies were carried out in soil pot cultures, and both PG and limestone were applied to the Andisol at the rates of 0, 0.30, 0.75, 1.50 g kg−1 in the form of CaO. 1. Limestone application resulted in an increase in the soil pH. On the other hand, no change was observed in the case of PG application at pH 6.1 ± 0.1 regardless of the application rate. Both soil EC and water-soluble Ca increased in proportion to the PG application rate, and this increase was approximately 5 times greater than that observed when limestone was applied at 1.50 g kg−1. The w-Ca/ex-Ca ratio (water-soluble Ca: 1 M acetic acid-extractable Ca) was clearly increased from 0.12 up to 0.26 in PG, while the value was slightly decreased from 0.12 to 0.05 in limestone. 2. After 33 days cultivation, both top and root growth of Komatsuna were enhanced by PG application. Specifically, when PG was applied at the rates of 0.30, 0.75, and 1.50 g kg−1 the root fresh weight increased by 31, 14, and 6%, respectively, in comparison with limestone. The root development of Komatsuna was closely related to Ca uptake. Ca uptake by Komatsuna was closely correlated to water-soluble Ca in comparison with 1 M acetic acid-extractable Ca in the soil. In particular, Ca uptake was restricted under the low-water soluble Ca conditions 2.0 mmolc kg−1. Therefore, it was concluded that water-soluble Ca in the soil was useful as an index of plant-available Ca.

Ca 2+ communication through connexin 43 in lung capillaries

The extent to which endothelial (EC) cells support gap junctional intercellular communication (GJIC) remains unknown. To determine GJIC, by fluorescence microscopy we viewed septal capillaries of isolated, blood-perfused lungs from wild type (WT) mice, and from mice with targeted deletion of the gap junctional protein, connexin 43 (Cx43) in EC (Cx43-/-) (Liao, et al., PNAS, 2001). Lung artery, left atrial and airway pressures were held at 10, 3 and 5 cm H2O, respectively. We co-loaded vessels with the Ca2+ cage, NP-EGTA and the cytosolic Ca2+ (Ca2+cyt) indicator, fluo 4. At baseline, EC Ca 2+cyt was 88±17 gray levels. To increase Ca2+cyt focally, we targeted high-intensity UV light to a single EC of a septal capillary, thereby uncaging Ca2+ from NP-EGTA. In WT mice, uncaging increased EC Ca2+cyt locally as well as at a site 100 μm distant by 33±2 and 29±2 gray levels, respectively (mean±SE, n=3, P<0.05). By contrast, in Cx43-/- mice uncaging increased Ca2+cyt locally (n=3, P<0.05), but not at a distant site. Thus, the uncaging-induced Ca2+ signal was conducted 100 μm from the uncaging site in WT, but not in Cx43-/- mice. We conclude, EC of lung capillaries rapidly communicate Ca2+ signals through Cx43-containing gap junctions. Such spatial communication may amplify Ca2+-dependent proinflammatory responses in the lung capillary bed (supported by HL75503, HL57556).

Pre-B-cell-colony-enhancing factor is critically involved in thrombin-induced lung endothelial cell barrier dysregulation

Prior genomic and genetic studies identified pre-B-cell colony-enhancing factor (PBEF) as a novel candidate gene and biomarker in acute lung injury (ALI). As increased vascular permeability is a cardinal feature of ALI, we assessed the role of PBEF in in vitro vascular barrier regulation using confluent human pulmonary artery endothelial cell (HPAEC) monolayers. Reductions in PBEF protein expression (>70%) by siRNA significantly attenuated EC barrier dysfunction induced by the potent edemagenic agent, thrombin, reflected by reductions in transendothelial electric resistance (TER, ∼60% reduction). Furthermore, PBEF siRNA blunted thrombin-mediated increases in Ca 2+ entry, polymerized actin formation, and myosin light chain phosphorylation, events critical to the thrombin-mediated permeability response. Finally, PBEF siRNA also significantly inhibited thrombin-stimulated increase of IL-8 secretion in HPAEC, a chemokine known to induce actin fiber formation and intercellular gap formation of endothelial cells. Taken together, these studies demonstrate that PBEF may be required for complete expression of the thrombin-induced inflammatory response and reveal potentially novel role for PBEF in the regulation of EC Ca 2+-dependent cytoskeletal rearrangement and endothelial barrier dysfunction. Ongoing studies will continue to address the molecular mechanisms by which PBEF contributes to ALI susceptibility.

Potassium, Calcium, and Magnesium Mineralization in Manure-Treated Soils

Studies into cation release in manured soils are very limited and poorly documented. The present investigation was therefore aimed at comparing the influence of manure application on cation [calcium (Ca), magnesium (Mg) and potassium (K)] mineralization in four different soils. Four sources of livestock manure: chicken manure (PM), cattle manure (CM), swine manure (SM), ostrich manure (OM) and a control (no manure) were added to the soils (Andosol, red–yellow soil, masa soil, and sandune soil) and incubated for 8 weeks at room temperature. Soils were sampled at weekly intervals and analyzed for pH, EC, and exchangeable Ca, Mg, and K. Soil pH increases ranging between 5.8 in CM and 6.6 in OM treatments were observed. Chicken manure increased EC from the mean initial level of 4.4 to 11.8 mS/m. Cumulative mineralized Ca and Mg was highest in red–yellow soil followed by masa soil. The lowest values for Ca (1.8 cmolc kg−1) and Mg (1.3 cmolc kg−1) were in Andosol.

Motor activity in the isolated jejunum of VR1 knockout mice

of Ca 2 ~ frorq the IP3 mediated stores of the SR, which in turn are replenished by continuous innux of EC Ca :+ via L-type Ca 2+ channels. Clasp muscle depends on both release of Ca 2+ from internal stores and influx of EC Ca 2+ for CC. Low intrinsic tone in the sling is likely a property of the contractile elements and their response to normal IC Ca 2+ levels. Sling muscles rely primarily on internal Ca 2+ stores for CC, and refilling of these internal stores by EC CaZ+ahrough a nifedipine-insensitive pathway.The role of these differences in the pathogenesis and treatment of disease states requires further study.

Reduced length-dependent cross-bridge recruitment in skinned fiber preparations of human failing myocardium

A depressed activity of myosin ATPase has been described in human failing myocardium. Since alterations in cross-bridge kinetics may affect both systolic and diastolic cardiac function, the present study simultaneously investigated Ca(2+)-dependent tension and actomyosin ATPase activity (MYO) in triton X-skinned fiber preparations of human non-failing (donor hearts, n=8) and failing (dilated cardiomyopathy, n=11) left ventricular myocardium at increasing sarcomeric length (1.9 and 2.1 microm, alpha-actinin staining). The MYO/tension ratio was analyzed as a parameter characterizing myofibrillar energetics. At a sarcomere length of 1.9 microm, the Ca(2+) sensitivity of tension was significantly increased in human failing compared to non-failing myocardium. In human non-failing myocardium, maximal Ca(2+)-activated tension [1.9 microm vs. 2.1 microm, 23.7 (1.9) vs. 28.3 (1.9) mN/mm(2)] and the Ca(2+) sensitivity of tension [EC(50)Ca(2+ )(pCa): 5.67 (0.06) vs. 7.07 (0.11)] were increased by increasing sarcomere length. This was accompanied by an enhancement in Ca(2+)-dependent MYO [+72 (11) vs. +101 (9) microM ADP/s] as well as an increase in the Ca(2+)-sensitivity of MYO [EC(50)Ca(2+ )(pCa): 5.84 (0.08) vs. 6.86 (0.08)]. In human failing myocardium, only Ca(2+) sensitivity of tension (but not of MYO) increased. Tension cost was increased in failing vs. non-failing tissue [1.9 microm: 4.18 (0.06) vs. 3.53 (0.06) (mN.s)/(mm(2). microM ADP); 2.1 microm: 4.28 (0.13) vs. 3.52 (0.05) (mN.s)/(mm(2). microM ADP)]. We concluded that, in human failing myocardium, the length-dependent force generation may be blunted due to an already increased Ca(2+) affinity of troponin C as well as an impairment of length-dependent cross-bridge recruitment.

State-Dependent Inhibition of Inactivation-Deficient Ca V 1.2 and Ca V 2.3 Channels By Mibefradil

The structural determinants of mibefradil inhibition were analyzed using wild-type and inactivation-modified Ca(V)1.2 (alpha1C) and Ca(V)2.3 (alpha1E) channels. Mibefradil inhibition of peak Ba2+ currents was dose- and voltage-dependent. An increase of holding potentials from -80 to -100 mV significantly shifted dose-response curves toward higher mibefradil concentrations, namely from a concentration of 108 +/- 21 microm (n = 7) to 288 +/- 17 microm (n = 3) for inhibition of half of the Ca(V)1.2 currents (IC(50)) and from IC(50) = 8 +/- 2 microm (n = 9) to 33 +/- 7 microm (n = 4) for Ca(V)2.3 currents. In the presence of mibefradil, Ca(V)1.2 and Ca(V)2.3 experienced significant use-dependent inhibition (0.1 to 1 Hz) and slower recovery from inactivation suggesting mibefradil could promote transition(s) to an absorbing inactivated state. In order to investigate the relationship between inactivation and drug sensitivity, mibefradil inhibition was studied in inactivation-altered Ca(V)1.2 and Ca(V)2.3 mutants. Mibefradil significantly delayed the onset of channel recovery from inactivation in CEEE (Repeat I + part of the I-II linker from Ca(V)1.2 in the Ca(V)2.3 host channel), in EC(AID)EEE (part of the I-II linker from Ca(V)1.2 in the Ca(V)2.3 host channel) as well as in Ca(V)1.2 E462R, and Ca(V)2.3 R378E (point mutation in the beta-subunit binding motif) channels. Mibefradil inhibited the faster inactivating chimera EC(IS1-6)EEE with an IC(50) = 7 +/- 1 microm (n = 3), whereas the slower inactivating chimeras EC(AID)EEE and CEEE were, respectively, inhibited with IC(50) = 41 +/- 5 microm (n = 4) and IC(50) = 68 +/- 9 microm (n = 5). Dose-response curves were superimposable for the faster EC(IS1-6)EEE and Ca(V)2.3, whereas intermediate-inactivating channel kinetics (CEEE, Ca(V)1.2 E462R, and Ca(V)1.2 E462K) were inhibited by similar concentrations of mibefradil with IC(50) approximately 55-75 microm. The slower Ca(V)1.2 wild-type and Ca(V)1.2 Q473K channels responded to higher doses of mibefradil with IC(50) approximately 100-120 microm. Mibefradil was also found to significantly speed up the inactivation kinetics of slower channels (Ca(V)1.2, CEEE) with little effect on the inactivation kinetics of faster-inactivating channels (Ca(V)2.3). A open-channel block model for mibefradil interaction with high-voltage-activated Ca2+ channels is discussed and shown to qualitatively account for our observations. Hence, our data agree reasonably well with a "receptor guarded mechanism" where fast inactivation kinetics efficiently trap mibefradil into the channel.

High-density lipoprotein increases intracellular calcium levels by releasing calcium from internal stores in human endothelial cells

Elevated levels of high-density lipoproteins (HDL) appear to delay or prevent the development of atherosclerosis. The intracellular signaling mechanisms activated by HDL in vascular cells are currently under active investigation. In this study the effects of HDL on endothelial intracellular Ca levels (EC Ca i) are investigated. We show that HDL, like low density lipoproteins (LDL), increases EC Ca i in a dose-dependent fashion by releasing Ca from internal stores. Neither apolipoprotein A-I (apo A-I) nor apolipoprotein A-II (apo A-II) was responsible for the increase in EC Ca i. HDL appeared to release Ca from the same internal stores as did LDL, since preincubation of EC with LDL prevented subsequent responses to HDL but not to the vasodilator ATP. In addition, preincubation of EC with pertussis toxin, an inhibitor of specific G proteins, as well as U73122, an inhibitor of phospholipase C, prevented a rise in EC Ca i in response to HDL. These findings suggest that HDL, like LDL, can modulate EC Ca i and that this occurs via a pertussis toxin-sensitive G protein-mediated pathway which involves phospholipase C.