Decrease In Calcium Concentration Research Articles

Doxorubicin-Induced Cardiac Toxicity Is Mediated by Lowering of Peroxisome Proliferator-Activated ReceptorδExpression in Rats

The present study investigates the changes of peroxisome proliferator-activated receptors δ (PPARδ) expression and troponin phosphorylation in heart of rats which were treated with doxorubicin (DOX). Wistar rats which were treated with DOX according to a previous method. The protein levels of PPARδ and troponin phosphorylation were measured using Western blot. The PPARδ expression in heart was markedly reduced in DOX-treated rats showing a marked decrease in cardiac dP/dT and cardiac output. Also, cardiac troponin phosphorylation was lowered in DOX-treated rats. Meanwhile, combined treatment with the agonist of PPARδ (GW0742) reversed the decrease of cardiac dP/dT and cardiac output in DOX-treated rats. Then, primary cultured cardiomyocytes from neonatal rats were used to measure the changes of calcium concentration in cells. In addition to both decrease of PPARδ expression and troponin phosphorylation in neonatal cardiomyocytes by DOX, a marked decrease of calcium concentration was also observed. Our results suggest the mediation of cardiac PPARδ in DOX-induced cardiotoxicity in rats. Thus, activation of PPARδ may restore the expression of p-TnI and the cardiac performance in DOX-induced cardio toxicity in rats.

Self Tuning of Hair Cell Bundle after Prolonged Deflection

Active hair bundle motility is one of the signatures of the amplification mechanism in non-mammalian hair cells. Here we impose high-amplitude deflections on the hair bundle for 0.1-50 seconds. Due to incompleteness of the adaptation mechanism, this is expected to change the opening probability of the transduction channels, thus mechanically bringing the bundle out of its equilibrium state. Recovery of hair bundle motion was characterized, and the effects of calcium on the feedback mechanism were investigated. Traces of hair bundle motility recorded immediately post stimulation show a slow drift towards the equilibrium position, without oscillatory motion. Bundles recover their innate oscillation between 0.1 - 1 second after cessation of the stimuli, and the quiescent time (Tq) shows a strong dependence on stimulus duration. Relaxation of hair bundles is fitted by the sum of two exponentials. The shorter of the time constants is found to be in the range ∼20-50 ms, consistent with myosin-motor dynamics. The longer time constant is significantly slower, ∼0.5-1 s. Decreased calcium concentration leads to a slower spontaneous oscillation, consistent with prior results in the field. The quiescent interval induced by deflection of hair bundles in a low-calcium environment is shorter, recovering more rapidly post stimulus cessation. Blockage of the extrusion pumps that regulate its concentration inside the stereocilia was likewise seen to prolong the induced quiescence, indicating that calcium accumulation may underlie the suppression of spontaneous motility.

The influence of operating parameters on the drug release and anti-bacterial performances of alginate wound dressings prepared by three-dimensional plotting

Three-dimensional plotting was used to manufacture fibrous alginate hydrogel wound dressings. Samples manufactured using varied operating parameters (increased air pressure, nozzle diameter, and layer increment or decreased calcium concentration, alginate concentration, and speed of the nozzle in the x and y directions) were compared to the control samples. The changes in the fiber size, porosity, tensile properties, degradation, swelling ratio, tetracycline release efficacy, water vapor transmission rate (WVTR), and bacterial inhibition potential due to alterations of the operating parameters were measured. The samples manufactured using altered operating parameters had larger fiber sizes and were less porous than the controls (p<0.05). A significantly higher Young's modulus, a larger ultimate tensile strength, less degradation, and lower swelling ratios were also found among some of the altered samples (p<0.05). The tetracycline release efficacies and bacterial inhibition potentials of the altered samples were not found to be significantly different from those of the controls. The WVTRs of most samples were slightly lower than those of common commercial dressings. When compared to films, the fibrous samples were able to absorb liquid faster and were less stiff, allowing for better conformation to the contours of the wounds. The fibrous samples also provided more sustained tetracycline release.

Acute and chronic regulation of circulating PTH: Significance in health and in disease

Circulating human parathyroid hormone (PTH) is immunoheterogenous. It is composed of 80% carboxyl-terminal (C) fragments and of 20% PTH(1-84). This composition contrasts with the biological activity of the hormone, which is only related to PTH(1-84), creating a paradox between circulating PTH composition and PTH bioactivity. PTH molecular forms are either secreted by the parathyroid glands or generated by the peripheral metabolism of PTH(1-84) in the liver. The kidney has a major role in the disposal of C-PTH fragments. Secretion of PTH molecular forms by the parathyroid glands is highly regulated under a variety of clinical conditions, suggesting that C-PTH fragments could exert some biological effects of their own. Recent data suggest that C-PTH fragments can exert biological actions opposite to those of PTH(1-84) by acting on a C-PTH receptor not yet cloned. They can decrease calcium concentration, phosphate excretion, bone resorption and 1,25(OH)₂ synthesis. The clinical implications of this new concept are reviewed.

Neuronal activities of Portulaca oleracea in adult rats

Portulaca oleracea (purslane) belonging to the family “Portulacaceae” was considered to be an anti-magic herb used to protect against variety of diseases. Here, we investigated the neuronal activities of P. oleracea in adult rats. Animals were treated with 1.5 ml/kg of aqueous extract of purslane (leaves and stem) for 12 days. Cerebellum, pons and medulla, cerebral cortex, thalamus and hypothalamus, midbrain and spinal cord were isolated to estimate the concentration of calcium, acetyl cholinesterase, dopamine, norepinephrine and serotonin in them. Purslane was able to induce a significant decrease in calcium concentration of the brain cortex. Dopamine, norepinephrine and serotonin were significantly altered in the studied brain regions after treatment of rats with purslane. Acetyl cholinesterase was increased in all brain regions except in the cerebellum. Our results suggest the potential role of purslane mediated changes in the neuronal tissues. Key words: Portulaca oleracea, leaves and stem, neurotransmitters, acetylcholinesterase, calcium, brain, rats.

Decrease in Calcium Concentration Triggers Neuronal Retinoic Acid Synthesis during Homeostatic Synaptic Plasticity

Blockade of synaptic activity induces homeostatic plasticity, in part by stimulating synthesis of all-trans retinoic acid (RA), which in turn increases AMPA receptor synthesis. However, the synaptic signal that triggers RA synthesis remained unknown. Using multiple activity-blockade protocols that induce homeostatic synaptic plasticity, here we show that RA synthesis is activated whenever postsynaptic Ca(2+) entry is significantly decreased and that RA is required for upregulation of synaptic strength under these homeostatic plasticity conditions, suggesting that Ca(2+) plays an inhibitory role in RA synthesis. Consistent with this notion, we demonstrate that both transient Ca(2+) depletion by membrane-permeable Ca(2+) chelators and chronic blockage of L-type Ca(2+)-channels induces RA synthesis. Moreover, the source of dendritic Ca(2+) entry that regulates RA synthesis is not specific because mild depolarization with KCl is sufficient to reverse synaptic scaling induced by L-type Ca(2+)-channel blocker. By expression of a dihydropyridine-insensitive L-type Ca(2+) channel, we further show that RA acts cell autonomously to modulate synaptic transmission. Our findings suggest that, in synaptically active neurons, modest "basal" levels of postsynaptic Ca(2+) physiologically suppress RA synthesis, whereas in synaptically inactive neurons, decreases in the resting Ca(2+) levels induce homeostatic plasticity by stimulating synthesis of RA that then acts in a cell-autonomous manner to increase AMPA receptor function.

Fertilisation azotée et phosphatée dans la production du bleuet nain sauvage au Québec

experiment. The density of stem, the number of flower buds and the height of the plants have only increased with N fertilization. In the sprout year, leaf N, P and potassium (K) concentrations increased with N and P. Phosphorus fertilizer only increased leaf P concentration. However, a high rate of N decreased leaf calcium and magnesium concentrations. Fruit yields were significantly correlated with plant height (r� 0.75), numberof flowerbuds ( r � 0.82), stem density (r � 0.52), and leaf N, P and K concentrations (r � 0.58, 0.57 and 0.72, respectively). The productivity of wild blueberry was strongly influenced by N fertilization and the interactions with P have been limited. This lack of response to P fertilization confirmed that the crop P requirements were limited and can be met by soil P.

Specific mechanism of use-dependent channel block of calcium-permeable AMPA receptors provides activity-dependent inhibition of glutamatergic neurotransmission

This study examined the blocking action of the selective channel blocker of calcium-permeable (CP) AMPA receptors, N1-(1-phenylcyclohexyl)pentane-1,5-diaminium bromide (IEM-1925), on excitatory postsynaptic currents in rat neostriatal and cortical neurons and in fly neuromuscular junctions. In both preparations, the blocking of CP-AMPA receptor currents increased along with the stimulation frequency. The continuous presence of kainate, which activates AMPA receptors, in the external solution also caused an enhanced blocking effect. Likewise, decrease of the synaptic release by lowering calcium concentration resulted in significant reduction of the blocking action. The activity dependence of the block is explained using the guarded receptor model. The drug molecule can only bind if the channel is open. After the channel has closed, the drug molecule remains trapped inside. However, the trapped molecule slowly egresses from closed channels to the cytoplasm. The total block effect is determined by the equilibrium between accumulation of the drug in the open channels and relief from the closed channels. Therefore, the conditions that favour the open state result in enhanced inhibition. This significant finding reveals a new way to modulate CP-AMPAR-mediated transmission using a physiologically relevant approach. Moreover, it allows the involvement of CP-AMPARs in the physiological and pathological processes – such as high-frequency synaptic activity or increase of the steady-state glutamate concentration – to be examined.

Effects of Lanthanum on Calcium and Magnesium Contents and Cytoplasmic Streaming of Internodal Cells of Chara corallina

Biological and environmental effects of lanthanide series of elements have received much attention recently due to their wide applications. In this study, effects of La(3+) treatments on calcium and magnesium concentrations as well as cytoplasmic streaming of internodal cells of Chara corallina were investigated. At all treatment concentrations (10, 100, and 1,000 μM), La(3+) significantly decreased calcium concentrations in the cell-wall fractions after 5-h treatments. Calcium concentrations in the cell contents and magnesium concentrations in the cell-wall fractions were reduced by 100 and 1,000 μM La(3+) treatments. However, cytoplasmic streaming as an indicator of [Ca(2+)](cyt) was only inhibited at the highest La(3+) concentration (1,000 μM). The results suggest that La(3+) may affect cellular calcium homeostasis by actions other than as a simple Ca(2+) antagonist. La(3+) could partially compensate for calcium deficiency at certain concentrations.

Calcium carbonate–hydrolyzed soy protein complexation in the presence of citric acid

The influence of hydrolyzed soy proteins on calcium carbonate stabilization was studied in citric acid solution. Calcium–soy proteins interactions were characterized using a calcium ion selective electrode, turbidity, and Isothermal Titration Calorimetry. Once the meta-stable phase was reached or just after soy protein addition, spray-drying was performed and SEM, XRD, and XPS analysis were carried out on spray-dried powders. In citric acid solution calcite crystals were eroded giving rise to smaller amorphous particles. In the presence of soy proteins, complexation exothermic in nature occurred with the mineral phase, which prevented CaCO 3 from recrystallisation and kept the system in an amorphous state. SEM performed on spray-dried powder showed that soy proteins were swollen in presence of mineral phase and resulted in a decrease of calcium concentration at the extreme surface of the studied powders as demonstrated by XPS.

Controls on calcium isotope fractionation in sedimentary porewaters

The calcium isotopic composition of porewaters and authigenic carbonates in the anoxic sediments of a convergent continental margin drilled during Ocean Drilling Program (ODP) provides first insight into the different processes that control Ca geochemistry in clastic marine, organic-rich sedimentary environments. In 4 sites drilled during Leg 204 at Hydrate Ridge (Cascadia Margin, offshore Oregon/USA), sulfate is consumed during anaerobic oxidation of methane and of organic matter via sulfate reduction within the upper meters of the sedimentary section. These reactions promote the precipitation of authigenic carbonates through the generation of bicarbonate, which is reflected in a pronounced decrease in calcium concentration. Although Ca isotope fractionation is observed during carbonate precipitation, Ca concentration in the pore fluids from ODP Leg 204 is decoupled from Ca isotopy, which seems to be mainly controlled by the release of light Ca isotopes that completely overprint the carbonate formation effect. Different processes, such as the release of organically bound Ca, ion exchange and ion pair formation may be responsible for the released light Ca. Deeper within the sedimentary section, additional processes such as ash alteration influence the Ca isotopic composition of the porewater. Two sites, drilled into the deeper core of the accretionary prism, reveal the nature of fluids which have reacted with the oceanic basement. These deep fluids are characterized by relatively high Ca concentrations and low δ 44/40Ca ratios.

Instrumental neutron activation analysis of water hyacinth as a bioindicator along the Nile river, Egypt

Water hyacinth (Eichhornia crassipes) is known to accumulate elements from rivers and a good tool for water monitoring. To test the usefulness of such an aquatic plant as a bioindicator, we have determined the levels of Na, Ca, Cr, Fe, Co, Zn, As, Rb, Zr, Sb, Cs, La, Ce, Nd, Sm, Eu, Tb, Yb, Hf, Ta, Th, and U in water hyacinth around industrial facilities and along the studied area by instrumental neutron activation analysis. The concentrations of Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Cd, and Pb were determined in upstream river water and effluent factories. Contamination factor, and pollution load index was calculated. The results show that higher concentrations as well as bioaccumulation factors of these elements were observed in water hyacinth samples around the industrial facilities. On the other hand a decrease in calcium concentration was observed as a result of the thermal pollution of Nile river water. The pollution load index for the studied area was estimated to be 4.2.

Discerning the Role of Topography and Ion Exchange in Cell Response of Bioactive Tissue Engineering Scaffolds

Surface topography is known to have an influence on osteoblast activity. However, in the case of bioactive materials, topographical changes can affect also ion exchange properties. This makes the problem more complex, since it is often difficult to separate the strictly topographical effects from the effects of ionic fluctuations in the medium. The scope of this paper is to analyze the simultaneous effect of topography and topography-mediated ion exchange on the initial cellular behavior of osteoblastic-like cells cultured on bioactive tissue engineering substrates. Two apatitic substrates with identical chemical composition but different micro/nanostructural features were obtained by low-temperature setting of a calcium phosphate cement. MG63 osteoblastic-like cells were cultured either in direct contact with the substrates or with their extracts. A strong and permanent decrease of calcium concentration in the culture medium, dependent on substrate topography, was detected. A major effect of the substrate microstructure on cell proliferation was observed, explained in part by the topography-mediated ion exchange, but not specifically by the ionic Ca(2+) fluctuations. Cell differentiation was strongly enhanced when cells were cultured on the finer substrate. This effect was not explained by the chemical modification of the medium, but rather suggested a strictly topographical effect.

Inhalational Anesthetics Induce Cell Damage by Disruption of Intracellular Calcium Homeostasis with Different Potencies

The authors hypothesized that inhalational anesthetics induced cell damage by causing abnormal calcium release from the endoplasmic reticulum via excessive activation of inositol 1,4,5-trisphosphate (IP3) receptors, with isoflurane having greater potency than sevoflurane or desflurane. The authors treated DT40 chicken B lymphocytes with total IP3 receptor knockout or their corresponding wild-type control cells with equipotent exposure to isoflurane, sevoflurane, and desflurane. The authors then determined the degree of cell damage by counting the percentage of annexin V- or propidium iodide-positively stained cells or measuring caspase-3 activity. They also studied the changes of calcium concentrations in the endoplasmic reticulum, cytosol, and mitochondria evoked by equipotent concentrations of isoflurane, sevoflurane, and desflurane in both types of DT40 cells. Prolonged use of 2 minimal alveolar concentration sevoflurane or desflurane (24 h) induced significant cell damage only in DT40 wild-type and not in IP3 receptor total knockout cells, but with significantly less potency than isoflurane. In accord, all three inhalational anesthetics induced significant decrease of calcium concentrations in the endoplasmic reticulum, accompanied by a subsequent significant increase in the cytosol and mitochondrial calcium concentrations only in DT40 wild-type and not in IP3 receptor total knockout cells. Isoflurane treatment showed significantly greater potency of effect than sevoflurane or desflurane. Inhalational anesthetics may induce cell damage by causing abnormal calcium release from the endoplasmic reticulum via excessive activation of IP3 receptors. Isoflurane has greater potency than sevoflurane or desflurane to cause calcium release from the endoplasmic reticulum and to induce cell damage.

Exchangeability of orthophosphate and pyrophosphate in soils: a double isotopic labelling study

Liquid polyphosphate fertilisers have shown advantages in field experiments as a phosphorus (P) source for crops grown on calcareous soils. Polyphosphate fertilisers contain orthophosphate (oP), pyrophosphate (pP) and other condensed P species. A double labelling technique was developed using ion chromatography for separation of oP and pP, the major P species in polyphosphate fertilisers, in order to measure the isotopically exchangeable oP, pP and hydrolysed pP. Isotopically exchangeable P was measured in soils incubating for zero, three and 7 days after applying oP or pP to simulate a fertiliser band concentration at one g P kg−1 soil. The data from this incubation study suggest that pP addition initially resulted in less isotopically exchangeable P than oP addition but there was no significant difference in the total isotopically exchangeable P for the two different P sources after 7 days of incubation. The addition of pP to soil resulted in an increase in iron, aluminium and dissolved organic carbon in soil solution, and a decrease in calcium concentration in soil solution. This study has shown that the availability of P added as pP is governed by a complex series of processes that differ from the chemistry of oP reactions in soil.

Sistema radicular do capim-tanzânia adubado com potássio e magnésio

Um experimento em casa de vegetação foi conduzido no período da primavera de 2004 visando à obtenção de informações relativas aos atributos do sistema radicular de Panicum maximum Jacq. cv. Tanzânia adubado com combinações de potássio e magnésio em solução nutritiva. Utilizou-se o delineamento experimental de blocos ao acaso, com quatro repetições, em esquema fatorial 5² incompleto, com 13 combinações de doses de potássio e magnésio, em mmol/L: 0,4K/0,05Mg; 0,4K/1,35Mg; 0,4K/2,65Mg; 3,2K/0,70Mg; 3,2K/2,00Mg; 6,0K/0,05Mg; 6,0K/1,35Mg; 6,0K/2,65Mg; 8,8K/0,70Mg; 8,8K/2,00Mg; 11,6K/0,05Mg; 11,6K/1,35Mg e 11,6K/2,65Mg. Após o segundo corte das plantas, realizou-se a coleta das raízes, utilizando-se água corrente e água desionizada com auxílio de peneiras de 0,25 e 1,00 mm. As combinações de doses de potássio e de magnésio foram determinantes para a produção de matéria seca de raízes, o comprimento radicular, a concentração de magnésio nas raízes e as concentrações conjuntas de potássio, magnésio e cálcio. De forma isolada, as doses de potássio alteraram a superfície radicular, o comprimento e a superfície radicular específicos e a concentração de potássio nas raízes. As doses de magnésio, isoladamente, promoveram aumento na superfície radicular e decréscimo na concentração de cálcio nas raízes. As maiores respostas do sistema radicular do capim-tanzânia foram obtidas com o fornecimento de potássio de 6,0 a 8,8 mmol/L e de magnésio de 1,4 a 2,0 mmol/L na solução nutritiva. A participação do potássio foi de 35 a 53% e a do magnésio em torno de 20% na concentração total de potássio, magnésio e cálcio nas raízes.

Spectroscopic investigations of carious tooth decay

We report on the elemental composition of healthy and infected part of human tooth using laser induced breakdown spectroscopy (LIBS). We have used prominent constituent transitions in laser-excited tooth to diagnose the state of the tooth. A nanosecond laser pulse (355 nm, 5 ns) was used as an ablating pulse and the sodium (3s 2S–3p 2P) at 588.99 and (3s 2S–3p 2P) at 589.99 nm, strontium (5s 21S–1s5P) at 460.55 nm, and calcium (3d 3D–4f 3F 0) at 452.55 nm transitions for spectroscopic analysis. The spectroscopic observations in conjunction with discriminate analysis showed that calcium attached to the hydroxyapatite structure of the tooth was affected severely at the infected part of the tooth. The position-time plots generated from two-dimensional (2D) images conclusively showed a decrease in calcium concentration in the infected region of the irradiated tooth. Using the technique, we could distinguish between the healthy and carious parts of the tooth with significant accuracy.

Interactions of total bone marrow cells with increasing quantities of macroporous calcium phosphate ceramic granules

The biological properties of synthetic calcium phosphate bioceramics have made them the third choice of material for bone reconstructive surgery, after autologous bone and allografts. Nevertheless, bioceramics lack the osteogenic properties that would allow them to repair large bone defects. One strategy in bone tissue engineering consists of associating a synthetic scaffold with osteogenic cells. Mesenchymal stem cells (MSC) are usually isolated from bone marrow cultured for several weeks and seeded on to a small quantity of bioceramic. We have studied the association of total bone marrow cells, harvested from femurs of rats, with increasing amounts of calcium phosphate ceramic granules (50-250 mg). A cell viability test indicated that a little quantity of bioceramics granules (50 mg) was less detrimental for culturing 1 million nucleated cells from the whole bone marrow population. Cell morphology, viability, adhesion and differentiation were studied after different culture periods. Among the heterogeneous population of bone marrow cells, only a limited amount of cells attached and differentiated on the bioceramics. To explain the influence of the amount of synthetic scaffold on cell viability, media calcium concentrations were measured. Low cell viability could be explained by calcium phosphate precipitation leading to a decrease in calcium concentrations observed with relatively large amounts of scaffold. This study showed that the chemical stability of the ceramic plays a critical role in the viability of bone marrow cells.

New Active vitamin D analogs and calcimimetics to control hyperparathyroidism in chronic renal failure

New vitamin D derivatives were introduced to clinical use for the treatment of secondary hyperparathyroidism. Patients who were treated by paricalcitol survived more than patients who were treated by calcitriol. Doxercalciferol and paricalcitriol could maintain suppressed parathyroid hormone (PTH) with less frequent hypercalcemic accidents. Cinacalcet suppressed serum PTH levels in dialysis patients and decreased serum calcium and phosphate concentrations. We must further investigate these new drugs' outcomes, by measuring mortality and morbidity.

Effects of acetylpuerarin on hippocampal neurons and intracellular free calcium subjected to oxygen–glucose deprivation/reperfusion in primary culture

This study was undertaken to find out the effects of acetylpuerarin on hippocampal neurons and intracellular free calcium in primary culture subjected to oxygen-glucose deprivation/reperfusion. According to different reperfusion time (1 h, 6 h, 12 h, 24 h), three concentrations (1.6 micromol l(-1), 0.4 micromol l(-1), 0.1 micromol l(-1)) of acetylpuerarin, and MK-801 (10 micromol l(-1)), a positive control drug, neurons were randomly divided into 21 groups. Each group was observed by inverted phase contrast microscope; neuron viability was measured by the reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT); intracellular Ca(2+) was observed by Fura-2/AM ester through fluorospectrophotometer. The injured neurons were protected and degeneration and necrosis were alleviated in treatment groups of acetylpuerarin and MK-801. Acetylpuerarin increased the neuron viability at high, middle and low concentrations. Fluorescence detection results showed that the calcium concentration in the group treated with acetylpuerarin and MK-801 was lowered in each reperfusion time. Our results demonstrated that acetylpuerarin could protect the hippocampal neurons from ischemia-reperfusion injury in rats by alleviating the morphological damage, increasing neuron viability and decreasing calcium concentration in neuron.