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PubMed2005

Synthesis, physicochemical and pharmacokinetic characterization of calcium uronates.

Four calcium compounds containing uronic acids (D(+)-galacturonic and D(+)-glucuronic) in L:M ratio = 2 and 3 were isolated by applying novel (except for one complex) synthetic procedures. The compounds were characterized by elemental analysis, spectroscopic methods (diffuse reflectance and absorption UV-visible, IR, FIR), mass spectrometry, fast atom bombardment (FAB), thermal decomposition, thermogravimetry/derivative thermogravimetry (TG/DTG) data and differential scanning calorimetric studies (DSC). Two modes of water binding in the complexes, i.e., hydration and coordination-like, were established. Computer-aided analysis has shown that further investigations are needed in order to determine the applicability of calcium uronates as calcium carriers.

Calcium↗
PubMed2006

Cultural studies of Morchella elata.

The in vitro growth of Morchella elata was characterized with respect to the effects of a variety of substrates, isolates, developmental status of the parental ascoma, temperature, and pH. Optimal substrates for growth included sucrose, mannose and lactose, but the growth of some isolates was substantially reduced in some composite media. Maltose and potato-dextrose media limited growth and caused changes in colony morphology; mycelial pigmentation was black in the case of maltose, and mycelial margins were plumose in potato-dextrose cultures. Rapid growth was most reliably achieved in a composite medium containing 1:1 sucrose:mannose. Isolates derived from single ascospores shortly after ejection from ascomata varied in ability to grow in the various substrates. This may be related to variable maturity or dormancy; increasing growth rates correlated with pileus length in the parental ascomata, and ascomata that initially produced slower-growing or abortive colonies produced faster-growing colonies after storage at 20 degrees C for 96 wk. The growth of M. elata derived from recently ejected ascospores was optimal at 16-24 degrees C or above for a faster-growing isolate, and 20-24 degrees C or above for a slow-growing isolate. Although neither isolate grew at 8 degrees C or below in an initial experiment, spawn cultured on puffed wheat at 28 degrees C produced mycelia that proliferated when transferred to soil media and incubated at 8 degrees C. Growth of M. elata in liquid cultures adjusted with potassium hydroxide was optimal at pH 7.0, and was relatively sensitive to more acidic or alkaline pH. When calcium carbonate was used to adjust pH, optimal growth shifted to pH 7.7 or above, suggesting that wood ash and other calcium compounds may not only stimulate growth in natural settings, but also alter the optimal pH for proliferation of M. elata. Further studies with other substrate combinations and incubation conditions will be necessary to fully understand the connections between in vitro growth and the ecological behaviour of the fungus.

Ascomycota↗
PubMed2001

Evidence of calcium phosphate depositions in stenotic arteriovenous fistulas.

This study investigates vascular samples from patients with and without end-stage renal disease (ESRD) to determine the occurrence of calcium depositions. Findings in stenotic arteriovenous (AV)-fistula veins were compared with those of nonstenotic AV-fistula veins, non-AV-fistula veins, and atherosclerotic vessels. Calcium and phosphorus content was measured by means of scanning electron microscopy and its built-in method of energy-dispersive spectrometry (EDS) X-ray analysis. We found calcium and phosphorus in samples from AV fistulas with stenotic areas with a calcium/phosphorus molar ratio of 1. Based on EDS analysis and crystal shape comparison, we conclude that calcium phosphate precipitations in stenotic AV fistulas are brushites with the composition CaHPO(4)*2H(2)O. This specific calcium phosphate deposition was found solely in stenotic AV fistulas, not in nonstenotic AV-fistula veins or non-AV-fistula veins regardless of whether the patient had ESRD. Moreover, this calcium phosphate deposition was different from calcium compounds found in atherosclerotic samples. Whether the precipitation of brushite is primarily involved in the development of vascular-access stenosis or represents a secondary consequence cannot be determined from the present study.

Adult↗
PubMed1998

Crystallization, fluoridation and some properties of apatite thin films prepared through rf-sputtering from CaO-P2O5 glasses.

Using calcium phosphate glass targets with the CaO/P2O5 molar ratios of 1.50-0.50, much lower than the stoichiometric value of 3.3 for hydroxyapatite, thin films of stoichiometric hydroxy-, nonstoichiometric oxyhydroxy- and Ca-deficient oxyhydroxy-apatites were prepared on alumina ceramic substrates by rf-sputtering followed by post-annealing. Based on the present results, a phase diagram for CaO-P2O5 at low temperatures in the ambience of air was depicted for thin films. The ambient H2O vapor had an influence on the phase diagram: Tricalcium phosphate was changed to apatite in the presence of H2O vapor. Dense fluorohydroxyapatite thin films were prepared by fluoridation of those apatite thin films at a low temperature such as 200 degrees C. In the present report, some functional properties of thin films thus prepared were also shown.

Aluminum Oxide↗
PubMed1999

Calcium phosphate formation on porous sol-gel-derived SiO2 and CaO-P2O5-SiO2 substrates in vitro.

Sol-gel-derived SiO2 and CaO-P2O5-SiO2 have been shown to be bioactive and bone bonding. In this study bioactive sol-gel-derived SiO2 and CaO-P2O5-SiO2 systems were tested for in in vitro bioactivity. The calcined ceramic monoliths were immersed in a simulated body fluid and analyzed to follow the hydroxyapatite formation on the ceramic surface. Apatite-forming ability was investigated in terms of structural changes by changing the composition and the preparation method. The role of Ca and P dopants in the substrate structure is complicated, and careful characterization is needed. The composition and structure together determine the in vitro bioactivity. The pore structure was analyzed using N2-adsorption/desorption isotherms. The results indicate that a great mesopore volume and a wide mesopore size distribution favor hydroxycarbonate apatite nucleation and a great surface area is not needed. The performed preparation process for silica in a basic environment provides a convenient way to prepare a mesoporous material.

Adsorption↗
PubMed1990

[Trials of remineralization of artificially produced enamel lesions].

The purpose of the study was checking in vitro whether after application of calcifying preparations remineralization occurs of artificially damaged enamel prisms. The study was carried out on 32 enamel samples obtained from 8 human teeth. For remineralization saturated solutions were used of phosphate-calcium compounds in the form of fluid or gel. The degree of demineralization and remineralization of enamel was assessed on the basis of images of enamel breaks in JSM-50A scanning microscope. Partial remineralization of artificially damaged enamel was found. Detailed evaluation of the remineralization progress requires extension of investigation methods.

Calcium Phosphates↗
PubMed1995

Effect of casein-based semi-synthetic food on renal acid excretion and acid-base state of blood in dogs.

Urinary acid excretion and blood acid-base state were determined in dogs fed a casein-based semi-synthetic food (SSF), to which different amounts of salts had been added, in comparison with feeding normal dog food. Net acid excretion (NAE) and inorganic acid excretion (IAE) increased during SSF feeding. IAE was higher than the acid load calculated from the sulphur and phosphorus content of the casein. This higher IAE appeared to be due to the presence of calcium and magnesium phosphate in the diet, because calcium and magnesium may be in part precipitated as carbonate, leaving phosphate to be absorbed as phosphoric acid. Acid excretion decreased by addition of CaO. When no neutral Na+ and K+ salts were added, the increase in NAE was accompanied by a metabolic acidosis. K+ was more effective in attenuating the acidosis than Na+. On the basis of these findings a diet can be made which imposes a known acid load, and provides stable baseline values. Hence, any additions that influence the acid-base balance can be properly studied. The data obtained in these and future studies utilising this diet may be of help in optimising the composition of nutrient solutions to be used in the care of critically ill patients.

Absorption↗
PubMed1994

Flash photolysis studies of the localization of calcium release sites in rat parotid isolated acinar cells.

1. The temporal relationship between cytosolic free Ca2+ concentration ([Ca2+]i) and activation of membrane current responses in single rat parotid acinar cells has been examined. Activation of muscarinic receptors by carbachol (CCh) at -40 mV (midway between EK and ECl under our experimental conditions) frequently evoked biphasic current responses, application of 2 microM CCh leading to rapid activation of an inward current followed by a slower outward current. 2. Photochemical release of inositol 1,4,5-trisphosphate (InsP3), from 'caged' InsP3, by a brief near-UV flash, evoked similar biphasic current responses at -40 mV. In contrast, elevation of [Ca2+]i by photolysis of the caged calcium compound nitr-5 at -40 mV activated only monophasic current responses. 3. These results can be explained by a model in which the InsP3-sensitive Ca2+ release sites are localized at the luminal pole of the cell, combined with a relative preponderance of Ca(2+)-activated Cl- channels at that pole, and a relative preponderance of Ca(2+)-activated K+ channels at the basal end.

Animals↗
PubMed1997

Intermetallic Hydrides as Zintl Phases: A(3)TtH(2) Compounds (A = Ca, Yb; Tt = Sn, Pb) and Their Structural Relationship to the Corresponding Oxides.

Shiny crystals of the isotypic title compounds are obtained in high yield from suitable proportions of AH(2), metal A, and Sn or Pb in welded Ta containers slowly cooled from 1100 degrees C. These were characterized by single-crystal X-ray diffraction for Ca(3)SnH(2) and Ca(3)PbH(2) (orthorhombic, Cmcm (No. 63), Z = 4, a = 8.866(1), 8.937(1) Å, b = 11.371(2), 11.470(2) Å, c = 5.220(1), 5.2551(7) Å, respectively). The structure contains distorted hcp layers of Ca(3)Tt between which hydrogen occupies all tetrahedral voids formed by Ca atoms. These tetrahedra share three edges to form double chains along the c axis that are separated by Tt atoms. Both calcium compounds are diamagnetic semiconductors, and the family can all be formulated in terms of oxidation states as Zintl phases (A(+2))(3)Tt(-4)(H(-))(2). Their structure may be derived from the hexagonal version of the cubic perovskitic Ca(3)SnO by distortions that split the octahedral site in the oxide into edge-sharing tetrahedral pairs.

Journal Article↗
PubMed2006

Physicochemical degradation studies of calcium phosphate glass ceramic in the CaO-P2O5-MgO-TiO2 system.

The aim of this work was to evaluate the in vitro degradation behaviour of a 45CaO-37P(2)O(5)-5MgO-13TiO(2) (mol.%) glass ceramic, under two different simulated physiological conditions: normal physiological pH 7.4, and pH 3.0, which was designed to simulate the acidic conditions produced by osteoclast cells. The in vitro testing was carried out at 37 degrees C for up to 42 days for the pH 7.4 solution and for up to 1 day for the pH 3.0 solution. The incorporation of TiO(2) into the glass structure leads to the precipitation of specific crystalline phases in the glass matrix, namely alpha- and beta-Ca(2)P(2)O(7), TiP(2)O(7) and CaTi(4)(PO(4))(6). The degradation testing at pH 3.0 showed a higher weight loss compared with degradation testing at pH 7.4; the weight loss under the acidic condition after 1 day (24 h) was about 10 times higher than the weight loss after 42 days of immersion at pH 7.4. The ionic release profile of Ca(2+), PO(4)(3-), Mg(2+) and Ti(4+) showed a continuous increase in concentration over all immersion times for both testing solutions. After 1 day of immersion at pH 3.0, the concentration levels of Mg(2+), Ca(2+), PO(4)(3-) were about six times higher than the levels achieved after 42 days of immersion at pH 7.4. The glass ceramic showed similar degradation to hydroxyapatite, and therefore has potential to be used in certain clinical applications where relatively slow resorption of the implant and replacement by bone is required, e.g. cranioplasty.

Biocompatible Materials↗
PubMed1973

[Histological and histochemical studies of knee joint cartilage in human embryos].

The authors examined some age and topographic peculiarities in the occurrence and microscopic characteristics of glucosamineglycanes, glycogen, lipids, calcium compounds and collagenous fibres during the course of the embryonal development of man. The deposition of glycogen and lipids in chondroblasts after the third-fourth week of embryonal development was indicated as well as the appearance of glucosamineglycanes in the intercellular substance during the same period. The role of the same substances in the differentiation of the cartilaginous tissue was stressed. The authors pointed out the well manifested PAS-reactivity of the superficial layer of the periosteum as a typical peculiarity of this formation.

Calcium↗
PubMed1996

The effect of HA, TCP and ALCAP bioceramic capsules on the viability of human monocyte and monocyte derived macrophages.

The relationship between various bioceramics used in surgical implantation and inflammatory cellular response has not been fully elucidated. The objective of this study was to investigate the effect of various biomedical ceramics such as tricalcium phosphate (TCP), hydroxyapatite (HA), and aluminum-calcium-phosphorous oxide (ALCAP) on the adherence and viability of human monocyte and monocyte derived macrophages in vitro. The monocytes were isolated from human peripheral blood and seeded at a density of 5 x 10(5) cells/well according to standard laboratory procedures. Cells were considered macrophages after remaining in culture for 24 hours. Cells were then plated in each microtiter well loaded with ceramic capsules (HA, TCP and ALCAP) and buffered control. At the end of 1, 2, 3, and 7 days the viability and cell number of monocyte or monocyte derived macrophages were determined using an established assay. Cell number was determined in control wells with known amounts of cell number, a standard curve was generated by plotting absorbance units versus cell number. Biochemical analysis was performed on the aliquots obtained from the experimental and control wells at the end of each phase of the investigation. The data from this experiment suggest that: (I) monocytes and macrophages are capable of adhering to the surface of HA, TCP and ALCAP in an in vitro environment for over a 7 day period. (II) Long term incubation of ceramic capsules with macrophages revealed that the cells experienced gradual disassociation phenomenon with a greater number of cell detachment seen in the ALCAP contained wells. (III) SEM analysis of representative capsules demonstrated that there is an increase in the number of micropores on the surface of the materials after contacting a cellular environment. This observation suggest that the material surface has been modified (TCP > HA = ALCAP). (IV) Biochemical analysis of aliquots at the end of each phase showed a significant change (P < 0.05) in the activity of catalase and superoxide dismutase (SOD). Information obtained from this study provided new insights on the interrelationship between bioceramics and the possible cell response during chronic inflammation at the site of implantation.

Aluminum Oxide↗
PubMed1999

Selective induction of LTP and LTD by postsynaptic [Ca2+]i elevation.

Long-term potentiation (LTP) and long-term depression (LTD), two prominent forms of synaptic plasticity at glutamatergic afferents to CA1 hippocampal pyramidal cells, are both triggered by the elevation of postsynaptic intracellular calcium concentration ([Ca2+]i). To understand how one signaling molecule can be responsible for triggering two opposing forms of synaptic modulation, different postsynaptic [Ca2+]i elevation patterns were generated by a new caged calcium compound nitrophenyl-ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid in CA1 pyramidal cells. We found that specific patterns of [Ca2+]i elevation selectively activate LTP or LTD. In particular, only LTP was triggered by a brief increase of [Ca2+]i with relatively high magnitude, which mimics the [Ca2+]i rise during electrical stimulation typically used to induce LTP. In contrast, a prolonged modest rise of [Ca2+]i reliably induced LTD. An important implication of the results is that both the amplitude and the duration of an intracellular chemical signal can carry significant biological information.

Animals↗
PubMed2004

Heat-pressed ionomer glass-ceramics. Part II. Mechanical property evaluation.

OBJECTIVES: A series of ionomer glasses based on the formula: 4.5SiO2-1.5P2O5-(X)Al2O3-4.5CaO-0.5CaF2, were investigated where X was varied from 3.0 to 1.5 in order to develop heat pressable dental ceramics. METHODS: The glasses were heat-pressed and then subjected to different heat-treatment cycles. The mechanical properties of the glass-ceramics were investigated, specimens were tested for hardness, fracture toughness (indentation method) and flexural strength (biaxial method). RESULTS: Good mechanical properties were obtained for heat-treatments at lower temperatures (i.e. 1150 degrees C). At intermediate heat-treatment temperatures the glass-ceramics were highly crystalline which did not favor the mechanical properties. There appears to be an inverse relationship between fracture toughness and flexural strength. High fracture toughness values of 2.7 (0.4) MPam0.5 were produced for the X = 2.8 glass heat-treated for 8 h at 1150 degrees C, the flexural strength was lowest for this heat-treatment. High flexural strengths of 194.4 (75.0) MPa were obtained by heat-treating the same glass for 1 h at 1150 degrees C. Increasing the hold time increases crystal size thereby increasing the extent of microcracking in the glass-ceramic thus lowering the flexural strength. Microcracks appear to increase the fracture toughness of the glass-ceramics probably by a crack termination mechanism. SIGNIFICANCE: Good flexural strength and high fracture toughness are attainable in this system, but appear to be mutually exclusive in the materials studied. With further investigation this system could provide clinically useful materials.

Acrylic Resins↗
PubMedDate not supplied

Intracellular calcium suppresses mechano-electrical transduction current in chick cochlear hair cells.

Intracellular calcium concentration ([Ca2+]i) was elevated by photolysis of the caged calcium compound, Nitr-5, and by use of the intrapipette perfusion technique in hair cells dissociated from the chick cochlea. An increase in [Ca2+]i induced an outward-going current at a membrane potential of -40 mV, as recorded with an intracellular medium of 160 mM KCl. This current was carried by the Ca2+-activated K+ current. In contrast, an increase of [Ca2+]i induced an inward-going current at -50 mV with a 160 mM CsCl-based intracellular medium. This inward-going current was carried by the Ca2+-activated non-selective cation current. The amplitude of the mechano-electrical transduction current was suppressed by the increase of [Ca2+]i, achieved both by photolysis and by use of the intrapipette perfusion method.

Animals↗
PubMed1990

Ca2(+)-induced Ca2+ release as examined by photolysis of caged Ca2+ in single ventricular myocytes.

In cardiac muscle, entry of Ca2+ through the voltage-gated Ca2+ channel and its interaction with an intracellular site are thought to trigger the release of the intracellular Ca2+ pools and to activate contraction. The availability of a novel "caged calcium" compound, and its effective use in neuronal and heart cells to modulate Ca2+ channel and contraction, made it possible to examine directly the Ca2(+)-induced Ca2+ release hypothesis in intact mammalian cardiac myocytes. We used the caged Ca2+ compound DM-nitrophen, which on photolysis, rapidly (less than 200 microseconds) changes its Ca2(+)-binding affinity from 3 X 10(-9) to 2 X 10(-3) M at pH 7.0. In isolated whole cell clamped guinea pig ventricular myocytes dialyzed with unphotolyzed DM-nitrophen (Ca2+ buffered to values less than 10(-7) M), we found that a 160-microseconds light pulse photoreleased sufficient Ca2+ to activate contraction. Photorelease of Ca2+ failed to activate significant contraction in myocytes pretreated with caffeine, supporting the idea that the release of Ca2+ from intracellular pools was necessary to generate tension. However, photorelease of Ca2+ after the depolarization-induced Ca2+ release failed to suppress contraction, as predicted from the Ca2(+)-induced inactivation hypothesis. The failure to suppress contraction was not sufficient to definitively reject the Ca2(+)-induced inactivation hypothesis, since the intracellular Ca2+ concentration may not have risen sufficiently to inactivate the release channel.

Acetates↗