scholarly journals The role of intracellular calcium phosphate in osteoblast-mediated bone apatite formation

2012 ◽  
Vol 109 (35) ◽  
pp. 14170-14175 ◽  
Author(s):  
S. Boonrungsiman ◽  
E. Gentleman ◽  
R. Carzaniga ◽  
N. D. Evans ◽  
D. W. McComb ◽  
...  
Keyword(s):  
Calcium Phosphate ◽  
Intracellular Calcium ◽  
Apatite Formation ◽  
Bone Apatite

The Role of Brushite and Octacalcium Phosphate in Apatite Formation

1992 ◽  
Vol 3 (1) ◽  
pp. 61-82 ◽  
Author(s):  
Mats S.-A. Johnsson ◽  
George H. Nancollas
Keyword(s):  
Calcium Phosphate ◽  
Octacalcium Phosphate ◽  
In Vivo Studies ◽  
Apatite Formation ◽  
Acidic Solutions ◽  
Phosphate Phase ◽  
Apatite Mineral

Studies of apatite mineral formation are complicated by the possibility of forming several calcium phosphate phases. The least soluble, hydroxyapatite (HAP), is preferentially formed under neutral or basic conditions. In more acidic solutions phases such as dicalcium phosphate dihydrate (Brushite, DCPD) and octacalcium phosphate (OCP) are often found. Even under ideal HAP precipitation conditions the precipitates are generally nonstoichiometric, suggesting the formation of calcium-deficient apatites. Both DCPD and OCP havea been implicated as possible precursors to the formation of apatite. This may occur by the initial precipitation of DCPD and/or OCP followed by transformation to a more apatitic phase. Although DCPD and OCP are often detected during in vitro crystallization, in vivo studies of bone formation rarely show the presence of these acidic calcium phosphate phases. In the latter case the situation is more complicated, since a large number of ions and molecules are present that can be incorporated into the crystal lattice or adsorbed at the crystallite surfaces. In biological apatite, DCPD and OCP are usually detected only during pathological calcification where the pH is often relatively low. In normal in vivo calcifications these phases have not been found, suggesting the involvement of other precursors or the formation of an initial amorphous calcium phosphate phase (ACP) followed by transformation to apatite.

scholarly journals The role of collagen in bone apatite formation in the presence of hydroxyapatite nucleation inhibitors

2010 ◽  
Vol 9 (12) ◽  
pp. 1004-1009 ◽  
Author(s):  
Fabio Nudelman ◽  
Koen Pieterse ◽  
Anne George ◽  
Paul H. H. Bomans ◽  
Heiner Friedrich ◽  
...  
Keyword(s):  
Apatite Formation ◽  
Bone Apatite

Muscle Fatigue: The Role of Intracellular Calcium Stores

2002 ◽  
Vol 27 (1) ◽  
pp. 83-96 ◽  
Author(s):  
David G. Allen ◽  
Akram A. Kabbara ◽  
Håkau Westerblad
Keyword(s):  
Creatine Kinase ◽  
Calcium Phosphate ◽  
Sarcoplasmic Reticulum ◽  
Intracellular Calcium ◽  
Muscle Fatigue ◽  
Calcium Release ◽  
Calcium Stores ◽  
Reduction In Force ◽  
Calcium Phosphate Precipitation

Force declines when muscles are used repeatedly and intensively and a variety of intracellular mechanisms appear to contribute to this muscle fatigue. Intracellular calcium release declines during fatigue and has been shown to contribute to the reduction in force. Three new approaches have helped to define the role of calcium stores to this decline in calcium release. Skinned fibre experiments show that when intracellular phosphate is increased the amount of Ca2+ released from the sarcoplasmic reticulum (SR) declines. Intact fibre experiments show that the size of the calcium store declines during fatigue and recovers on rest. Intact muscles which lack the enzyme creatine kinase, do not exhibit the usual rise of phosphate during fatigue and, under these conditions, the decline of Ca2+ release is absent or delayed. These results can be explained by the "calcium phosphate precipitation" hypothesis. This proposes that if phosphate in the myoplasm rises, it enters the SR and binds to Ca2+ as Ca2+ phosphate. The resultant reduction in free Ca2+ within the SR contributes to the reduced Ca2+ release during fatigue. Key words: sarcoplasmic reticulum, myoplasmic phosphate, calcium phosphate precipitation, creatine kinase, glycogen

Regulation of intracellular calcium in N1E-115 neuroblastoma cells: the role of Na+/Ca2+exchange

2002 ◽  
Vol 282 (5) ◽  
pp. C1000-C1008 ◽  
Author(s):  
Kara L. Kopper ◽  
Joseph S. Adorante
Keyword(s):  
Membrane Potential ◽  
Intracellular Calcium ◽  
Normal Cell ◽  
Buffer Capacity ◽  
Neuroblastoma Cells ◽  
Fold Increase ◽  
Scorpion Venom ◽  
Reverse Mode ◽  
Intracellular Ca

In fura 2-loaded N1E-115 cells, regulation of intracellular Ca2+ concentration ([Ca2+]i) following a Ca2+ load induced by 1 μM thapsigargin and 10 μM carbonylcyanide p-trifluoromethyoxyphenylhydrazone (FCCP) was Na+ dependent and inhibited by 5 mM Ni2+. In cells with normal intracellular Na+ concentration ([Na+]i), removal of bath Na+, which should result in reversal of Na+/Ca2+exchange, did not increase [Ca2+]i unless cell Ca2+ buffer capacity was reduced. When N1E-115 cells were Na+ loaded using 100 μM veratridine and 4 μg/ml scorpion venom, the rate of the reverse mode of the Na+/Ca2+ exchanger was apparently enhanced, since an ∼4- to 6-fold increase in [Ca2+]ioccurred despite normal cell Ca2+ buffering. In SBFI-loaded cells, we were able to demonstrate forward operation of the Na+/Ca2+ exchanger (net efflux of Ca2+) by observing increases (∼ 6 mM) in [Na+]i. These Ni2+ (5 mM)-inhibited increases in [Na+]i could only be observed when a continuous ionomycin-induced influx of Ca2+ occurred. The voltage-sensitive dye bis-(1,3-diethylthiobarbituric acid) trimethine oxonol was used to measure changes in membrane potential. Ionomycin (1 μM) depolarized N1E-115 cells (∼25 mV). This depolarization was Na+dependent and blocked by 5 mM Ni2+ and 250–500 μM benzamil. These data provide evidence for the presence of an electrogenic Na+/Ca2+ exchanger that is capable of regulating [Ca2+]i after release of Ca2+ from cell stores.

Intracellular calcium levels in the Plasmodium berghei ookinete

Parasitology ◽  
2008 ◽  
Vol 135 (12) ◽  
pp. 1355-1362 ◽  
Author(s):  
I. SIDÉN-KIAMOS ◽  
C. LOUIS
Keyword(s):  
Intracellular Calcium ◽  
Plasmodium Berghei ◽  
Calcium Concentration ◽  
Insect Cells ◽  
Ionophore A23187 ◽  
Rodent Malaria Parasite ◽  
Calcium Indicators ◽  
Intracellular Ca

SUMMARYOokinetes are the motile and invasive stages of Plasmodium parasites in the mosquito host. Here we explore the role of intracellular Ca2+ in ookinete survival and motility as well as in the formation of oocysts in vitro in the rodent malaria parasite Plasmodium berghei. Treatment with the Ca2+ ionophore A23187 induced death of the parasite, an effect that could be prevented if the ookinetes were co-incubated with insect cells before incubation with the ionophore. Treatment with the intracellular calcium chelator BAPTA/AM resulted in increased formation of oocysts in vitro. Calcium imaging in the ookinete using fluorescent calcium indicators revealed that the purified ookinetes have an intracellular calcium concentration in the range of 100 nm. Intracellular calcium levels decreased substantially when the ookinetes were incubated with insect cells and their motility was concomitantly increased. Our results suggest a pleiotropic role for intracellular calcium in the ookinete.

Study of Bio-Mineralization of BCP with Compensation of Calcium and Phosphate Ions

2009 ◽  
Vol 610-613 ◽  
pp. 1391-1394
Author(s):  
Hua De Zheng ◽  
Ying Jun Wang ◽  
Qiang Ma ◽  
Cheng Yun Ning ◽  
Xiao Feng Chen
Keyword(s):  
Free Energy ◽  
Calcium Phosphate ◽  
Calcium Ions ◽  
Biphasic Calcium Phosphate ◽  
Porous Ceramic ◽  
Apatite Layer ◽  
Apatite Formation ◽  
Phosphate Ions

In the present study, an Intelligent Multi-parameter Simulated Evaluation in vitro （IMSE system） was used to study the deposition properties of apatite formation on the surface of biphasic calcium phosphate porous ceramic (BCP) from static and dynamic r-SBF. Results showed that apatite formed on the surface of BCP from static and dynamic r-SBF differed between each other. In static r-SBF, ions were transferred by diffusion, which could not compensate the consuming of calcium ions, and mist apatite layer was formed on the surface of samples. But in the dynamic r-SBF, simulated fluid was adjusted precisely and flowed forcedly, the concentrations of ions were homogeneous; with the compensation of ions, calcium and phosphate were supersaturated, and the free energy of apatite formation was negative, bone-like apatite sheets were formed on the surface of samples.

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