Accumulation Of Calcium Phosphate Research Articles

Sustainable biomaterials for tissue engineering: electrospun polycaprolactone fibers enriched with freshwater snail calcium carbonate and waste human hair keratin

AbstractThis study focuses on developing a sustainable and biocompatible polycaprolactone (PCL)‐based scaffold for bone tissue engineering through electrospinning, utilizing calcium carbonate (CaCO3) from Pomacea canaliculata shells and keratin from human hair, known for stimulating bone regeneration. The isolated CaCO3 has been identified to demonstrate two polymorphs, vaterite and calcite, as determined by X‐ray diffraction. The isolation of keratin from human hair was confirmed through sodium dodecyl sulfate polyacrylamide gel electrophoresis and Fourier transform infrared spectroscopy analysis, revealing the presence of α‐keratin structures around 45–50 kDa and β‐keratin structures around 55–60 kDa. According to scanning electron microscope observations, the addition of keratin to PCL fibers reduced their diameter from 457 ± 345 to 371 ± 103 nm. Further addition of calcium carbonate led to a mean diameter of 258 ± 76 nm. The melting temperature of PCL fibers containing keratin and CaCO3 was determined to be 76.17 °C via differential scanning calorimetry, while thermogravimetric analysis, conducted at temperatures up to 600 °C, revealed a remaining ash content of 9.59%. Calcium phosphate accumulation was observed to initiate on PCL fibers containing keratin and CaCO3 following a 7‐day exposure to simulated body fluid. The fibers exhibit cytocompatibility, showing no toxicity while supporting the growth and proliferation of Saos‐2 osteosarcoma cells. The results suggest that the innovative incorporation of keratin and CaCO3 into PCL nanofibers could serve as a bioactive matrix compared to pure PCL matrices, thereby offering enhanced potential for bone tissue engineering applications. © 2024 The Author(s). Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

A case of tracheobronchopathia ostochondorplastica.

Tracheobronchopathia osteochondroplastica (TO) is a disorder caused by the accumulation of calcium phosphate in the submucosa of large airways. Benign proliferation of bone and cartilage lead to the narrowing of airways. Bronchoscopy is the diagnostic test for TO. It shows characteristic smooth nodules emerging from tracheal rings that never involves the posterior membranous wall.

Calcification in Werner syndrome associated with lymphatic vessels aging.

In addition to the symptoms of aging, the main symptoms in Werner syndrome (WS), a hereditary premature aging disease, include calcification of subcutaneous tissue with solid pain and refractory skin ulcers. However, the mechanism of calcification in WS remains unclear. In this study, the histological analysis of the skin around the ulcer with calcification revealed an accumulation of calcium phosphate in the lymphatic vessels. Moreover, the morphological comparison with the lymphatic vessels in PAD patients with chronic skin ulcers demonstrated the ongoing lymphatic remodeling in WS patients because of the narrow luminal cross-sectional area (LA) of the lymphatic vessels but the increment of lymphatic microvessels density (MLVD). Additionally, fluorescence immunohistochemical analysis presented the cytoplasmic distribution and the accumulation of WRN proteins in endothelial cells on remodeling lymphatic vessels. In summary, these results point out a relationship between calcification in lymphatic vessels and the remodeling of lymphatic vessels and suggest the significance of the accumulation of WRN mutant proteins as an age-related change in WS patients. Thus, cytoplasmic accumulation of WRN protein can be an indicator of the decreasing drainage function of the lymphatic vessels and the increased risk of skin ulcers and calcification in the lymphatic vessels.

Driving native-like zonal enthesis formation in engineered ligaments using mechanical boundary conditions and β-tricalcium phosphate

Fibrocartilaginous entheses are structurally complex tissues that translate load from elastic ligaments to stiff bone via complex zonal gradients in the organization, mineralization, and cell phenotype. Currently, these complex gradients necessary for long-term mechanical function are not recreated in soft tissue-to-bone healing or engineered replacements, contributing to high failure rates. Previously, we developed a culture system that guides ligament fibroblasts to develop aligned native-sized collagen fibers using high-density collagen gels and mechanical boundary conditions. These constructs are promising ligament replacements, however functional ligament-to-bone attachments, or entheses, are required for long-term function in vivo. The objective of this study was to investigate the effect of compressive mechanical boundary conditions and the addition of beta-tricalcium phosphate (βTCP), a known osteoconductive agent, on the development of zonal ligament-to-bone entheses. We found that compressive boundary clamps, that restrict cellular contraction and produce a zonal tensile-compressive environment, guide ligament fibroblasts to produce 3 unique zones of collagen organization and zonal accumulation of glycosaminoglycans (GAGs), type II, and type X collagen. Ultimately, by 6 weeks of culture these constructs had similar organization and composition as immature bovine entheses. Further, βTCP applied under the clamp enhanced maturation of these entheses, leading to significantly increased tensile moduli, and zonal GAG accumulation, ALP activity, and calcium-phosphate accumulation, suggesting the initiation of endochondral ossification. This culture system produced some of the most organized entheses to date, closely mirroring early postnatal enthesis development, and provides an in vitro platform to better understand the cues that drive enthesis maturation in vivo. Statement of significanceLigaments are attached to bone via entheses. Entheses are complex tissues with gradients in organization, composition, and cell phenotype. Entheses are necessary for proper transfer of load from ligament-to-bone, but currently are not restored with healing or replacements. Here, we provide new insight into how tensile-compressive boundary conditions and βTCP drive zonal gradients in collagen organization, mineralization, and matrix composition, producing tissues similar to immature ligament-to-bone attachments. Collectively, this culture system uses a bottom-up approach with mechanical and biochemical cues to produce engineered replacements which closely mirror postnatal enthesis development. This culture system is a promising platform to better understanding the cues that regulate enthesis formation so to better drive enthesis regeneration following graft repair and in engineered replacements.

Exploration of mechanisms for calcium phosphate precipitation and accumulation in nitrifying granules by investigating the size effects of granules

Calcium phosphate could be accumulated in aerobic granules, which attracts attention recently for phosphorus removal and recovery from wastewater. In this study, partial nitrifying granules with high calcium precipitate content were sorted into different size groups for characterization and evaluation to reveal the dynamic balance of granules at stead state and relevant calcium phosphate precipitation and accumulation mechanism. It was found that light yellow small granules without calcium precipitates but high microbial activity co-existed with deep brown granules with calcium precipitate of around 91% and low microbial activity. Characterization with specific oxygen uptake rates, specific ammonium oxidation rates, calcium and phosphate removal rates from solution, EPS contents, elemental compositions by energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and scanning electron microscopy (SEM) for different size groups of granules enabled a proposal of a new hypothesized mechanism for calcium precipitation and accumulation. With this proposed mechanism, it is believed that sufficient granule retention time in reactors was critical for the accumulation of calcium precipitates followed by a slow microbial growth rate of biomass due to mass transfer resistance. The co-precipitation of calcium carbonate and calcium phosphate mainly occurred in granules with a size less than 710 µm while calcium phosphate dominant minerals were accumulated in granules larger than 710 µm. The results and conclusions in this study shed light on the mechanisms of calcium phosphate accumulation in granules, which could be used to better operate and control aerobic granular sludge with calcium phosphates for phosphorus removal and recovery.

Hydroxyapatite Precipitation and Accumulation in Granules and Its Effects on Activity and Stability of Partial Nitrifying Granules at Moderate and High Temperatures

Precipitation and accumulation of calcium phosphate in granular sludge has attracted research attention recently for phosphate removal and recovery from wastewater. This study investigated calcium phosphate accumulation from granulation stage to steady state by forming heterotrophic granules at different COD/N ratios at 21 and 32 °C, respectively, followed by the transformation of heterotrophic granules to partial nitrifying granules. It was found that mature granules accumulated around 60–80% minerals in granules, much higher than young granules with only around 30% ash contents. In addition, high temperature promoted co-precipitation of hydroxyapatite and calcite in granules with more calcite than hydroxyapatite and only 4.1% P content, while mainly hydroxyapatite was accumulated at the moderate temperature with 7.7% P content. The accumulation of minerals in granules at the high temperature with 75–80% ash content also led to the disintegration and instability of granules. Specific ammonium oxidation rates were reduced, as well, from day 58 to day 121 at both temperatures due to increased mineral contents. These results are meaningful to control or manipulate granular sludge for phosphorus removal and recovery by forming and accumulating hydroxyapatite in granules, as well as for the maintenance of microbial activities of granules.

Biological Cell Investigation of Structured Nitinol Surfaces for the Functionalization of Implants.

Expandable implants including shape memory alloy (SMA) elements have great potential to minimize the risk of implant loosening and to increase the primary stability of bone anchoring. Surface structuring of such elements may further improve these properties and support osteointegration and bone healing. In this given study, SMA sheets were processed by deploying additive and removal manufacturing technologies for 3D-printed surgical implants. The additive technology was realized by applying a new laser beam melting technology to print titanium structures on the SMA sheets. The removal step was realized as a standard process with an ultrashort-pulse laser. The morphology, metabolic activity, and mineralization patterns of human bone marrow stromal cells were examined to evaluate the biocompatibility of the new surface structures. It was shown that both surface structures support cell adhesion and the formation of a cytoskeleton. The examination of the metabolic activity of the marrow stromal cells on the samples showed that the number of cells on the laser-structured samples was lower when compared to the 3D-printed ones. The calcium phosphate accumulation, which was used to examine the mineralization of marrow stromal cells, was higher in the laser-structured samples than in the 3D-printed ones. These results indicate that the additive- and laser-structured SAM sheets seem biocompatible and that the macrostructure surface and manufacturing technology may have positive influences on the behavior of the bone formation. The use of the new additive technique and the resulting macrostructures seems to be a promising approach to combine increased anchorage stability with simultaneously enhanced osteointegration.

Rapid calcification propensity testing in blood using a temperature controlled microfluidic polymer chip.

Phosphate toxicity is a major threat to cardiovascular health in chronic kidney disease. It is associated with oxidative stress, inflammation and the accumulation of calcium phosphate commonly known as calcification in soft tissues leading to functional disorders of blood vessels. An improved calcification propensity test for the assessment of phosphate toxicity was developed, which measures the velocity of calcium phosphate mineralization from colloidal precursors in vitro. This so called T50 test measures the transformation from a primary into a secondary form of nanosized colloidal plasma protein-calcium phosphate particles known as calciprotein particles. The T50 test in its previous form required a temperature controlled nephelometer and several hours of continuous measurement, which precluded rapid bed side testing. We miniaturized the test using microfluidic polymer chips produced by ultrasonic hot embossing. A cartridge holder contained a laser diode for illumination, light dependent resistor for detection and a Peltier element for thermo control. Increasing the assay temperature from 37°C to 75°C reduced the T50 test time 36-fold from 381 ± 10 min at 37°C to 10.5 ± 0.3 min at 75°C. Incorporating sputtered micro mirrors into the chip design increased the effective light path length, and improved signal-to-noise ratio 9-fold. The speed and reproducibility of the T50 chip-based assay run at 75°C suggest that it may be suitable for rapid measurements, preferably in-line in a dialyser or in a portable microfluidic analytic device with the chip inserted as a disposable cartridge.

Skin Cutibacterium acnes Mediates Fermentation to Suppress the Calcium Phosphate-Induced Itching: A Butyric Acid Derivative with Potential for Uremic Pruritus.

Pruritus and inflammation associated with accumulation of calcium phosphate (CaP) under the skin are common problems among dialysis patients with chronic kidney disease (CKD). The role of skin commensal microbiota in the CaP-induced uremic pruritus remains uncharacterized. Skin Cutibacterium acnes (C. acnes) can solubilize CaP by the production of short-chain fatty acids (SCFAs), such as butyric acid, through glucose fermentation. Like butyric acid, the N-[2-(2-Butyrylamino-ethoxy)-ethyl]-butyramide (BA-NH-NH-BA), a butyric acid derivative, remarkably induced acetylation of histone H3 lysine 9 (AcH3K9) in keratinocytes. Topical application of fermenting C. acnes, butyric acid or BA-NH-NH-BA onto mouse skin effectively ameliorated CaP-induced skin itching, interleukin (IL)-6 up-regulation in keratinocytes, and extracellular signal-regulated kinase (ERK) 1/2 activation in dorsal root ganglia (DRG). Activation of ERK 1/2 by CaP was markedly reduced in IL-6 knockout mice. Genus Cutibacterium was detected in relatively low abundance in itchy skin of patients with CKD. Our results identify a role for the skin fermenting C. acnes in ameliorating CaP-induced activation of IL-6/p-ERK signaling and resulting skin inflammation. Furthermore, we provide evidence for the potential therapeutic efficacy of BA-NH-NH-BA as a postbiotic for the treatment of uremic pruritus.

PROGRESSION OF PULMONARY ALVEOLAR MICROLITHIASIS TO PULMONARY HYPERTENSION AND COR PULMONALE

SESSION TITLE: Wednesday Fellows Case Report Posters SESSION TYPE: Fellow Case Report Posters PRESENTED ON: 10/23/2019 09:45 AM - 10:45 AM INTRODUCTION: Pulmonary alveolar microlithiasis (PAM) is a rare disease with less than 600 cases described in the literature. It is characterized by accumulation of calcium phosphate in the alveolar space. (1) Radiographic features are pathognomonic but clinical manifestations are non-specific. We present a case of PAM with progressive deterioration over 20 years leading to pulmonary hypertension (pHTN) and cor pulmonale. CASE PRESENTATION: A Caucasian female presented in her late 20s with pleurisy and based on imaging was diagnosed with sarcoidosis. She was relatively asymptomatic and went without treatment until her 40’s when she developed worsening dyspnea on exertion. PFTs showed mild restrictive lung disease (TLC 3.86L, 78% predicted) with a DLCO of 44%. CT Chest showed diffuse micronodular calcifications, consistent with PAM, not sarcoidosis. Her symptoms progressed over the next 10 years as lung function worsened, showing progressive restriction (TLC 2.97L, 57% predicted) with a DLCO of 4%. Her serial TTEs showed gradual development of right ventricular enlargement, right ventricular hypokinesis, and interventricular septum flattening. Patient underwent right heart catheterization, showing right atrial pressure 10 mmHg, pulmonary artery pressure 66/28 with mPAP 43 mmHg, LVEDP 13 mmHg and cardiac index 3.12 L/m/m2. A trial of tadalafil was attempted without improvement in symptoms and was discontinued. At age 68, the patient presented with acute on chronic hypoxemic respiratory failure with RV failure. CT Chest done demonstrated diffuse calcifications of the lung parenchyma, right ventricular septal bowing, and reflux of contrast into the hepatic veins. Despite aggressive diuresis and supportive care, the patient died from cardiopulmonary failure. DISCUSSION: This case illustrates the progression of PAM with clinical symptoms and radiographic features correlating with decline of pulmonary function, particularly restriction and diffusion capacity. Etiology of PAM remains unclear but has been linked to genetic mutations in SLC34A2 (1). Radiographic characteristics of fine sand-like micronodular calcifications, known as sandstorm, is pathognomonic. We captured the structural effect and strain on the right heart with development of pHTN, likely secondary to chronic hypoxia. Additionally, microliths can irritate alveolar walls, leading to destruction of alveolar capillaries and cause of pHTN. (2) PAM associated pHTN is rarely described as PAM is a rare entity and patients often die from respiratory failure prior to development of pHTN. Treatment is limited to case reports and is not defined (3). CONCLUSIONS: PAM associated with pHTN is infrequently described. Currently, there is still no effective treatment for PAM aside from lung transplant. The treatment of PAM associated pHTN is even more unclear and use of PAH-targeted therapy requires further studies. Reference #1: Lina M. Jönsson Å, Simonsen U, Hilberg O, Bendstrup E. Pulmonary alveolar microlithiasis: two case reports and review of the literature. European Respiratory Review. 2012;21(125):249. Reference #2: Ferreira Francisco FA, Pereira e Silva JL, Hochhegger B, Zanetti G, Marchiori E. Pulmonary alveolar microlithiasis. State-of-the-art review. Respiratory Medicine. 2013;107(1):1-9. Reference #3: Synetos A, Dilaveris P, Gialafos E, Giannopoulos G, Stefanadis C. Severe pulmonary hypertension due to pulmonary alveolar microlithiasis. International Journal of Cardiology. 2006;106(3):396-7. DISCLOSURES: No relevant relationships by Alexandra Haw, source=Web Response No relevant relationships by Ronak Shah, source=Web Response Speaker/Speaker's Bureau relationship with Bayer Please note: $5001 - $20000 Added 03/13/2019 by Paul Strachan, source=Web Response, value=Honoraria Speaker/Speaker's Bureau relationship with United Therapeutics Please note: $5001 - $20000 Added 03/13/2019 by Paul Strachan, source=Web Response, value=Honoraria Speaker/Speaker's Bureau relationship with Gilead Please note: $1001 - $5000 Added 03/13/2019 by Paul Strachan, source=Web Response, value=Honoraria Speaker/Speaker's Bureau relationship with Genentech Please note: $5001 - $20000 Added 03/13/2019 by Paul Strachan, source=Web Response, value=Honoraria Speaker/Speaker's Bureau relationship with Boehringer Ingelhein Please note: $5001 - $20000 Added 03/13/2019 by Paul Strachan, source=Web Response, value=Honoraria Stock Ownership relationship with Pfizer Please note: $5001 - $20000 Added 03/13/2019 by Paul Strachan, source=Web Response, value=nothing, I purchased stock Speaker/Speaker's Bureau relationship with Portola Please note: $1001 - $5000 Added 03/13/2019 by Paul Strachan, source=Web Response, value=Honoraria Stock Ownership relationship with Portola Please note: $5001 - $20000 Added 03/13/2019 by Paul Strachan, source=Web Response, value=nothing, I purchased stock Stock Ownership relationship with La Jolla Pharmaceuticals Please note: $1001 - $5000 Added 03/13/2019 by Paul Strachan, source=Web Response, value=nothing, I purchased stock Stock Ownership relationship with Seatle Genetics Please note: $5001 - $20000 Added 03/13/2019 by Paul Strachan, source=Web Response, value=nothing, I purchased stock PI relationship with United Therapeutics Please note: $5001 - $20000 Added 03/13/2019 by Paul Strachan, source=Web Response, value=Grant/Research Support PI relationship with Actelion Please note: $5001 - $20000 Added 03/13/2019 by Paul Strachan, source=Web Response, value=Grant/Research Support

Characterization of protein extracts from different types of human teeth and insight in biomineralization

The present study describes an efficient method for isolation and purification of protein extracts from four types of human teeth i.e. molar, premolar, canine, and incisor. Detailed structural characterization of these protein extracts was done by Fourier transform infrared spectroscopy (FTIR) and circular dichroism (CD) which showed that a major fraction of the proteins present are unstructured in nature including primarily random coils in addition to the other structures like extended beta (β) structure, poly-l-proline-type II (PPII) helix, turns, with only a small fraction constituting of ordered structures like alpha (α) helix and β sheets. These resultant labile structures give the proteins the necessary flexibility that they require to interact with a variety of substrates including different ions like calcium and phosphates and for other protein-protein interactions. We also did initial studies on the mineralization of calcium phosphate with the protein extracts. Nanoparticle tracking analysis (NTA) show an increase in the size of calcium phosphate accumulation in the presence of protein extracts. We propose that protein extracts elevate the crystallization process of calcium phosphate. Our current biophysical study provides novel insights into the structural characterization of proteins from human teeth and their implications in understanding the tooth biomineralization. As per our knowledge, this is the first report which focuses on the whole protein extraction from different types of human teeth as these extracts imitate the in vivo tooth mineralization.

Characterization and Optimization of the Seeding Process of Adipose Stem Cells on the Polycaprolactone Scaffolds.

The purpose of the current study was to evaluate the usefulness of adipose-derived stem cells (ASCs) for bone injury therapy. Lipoaspirates were collected from the abdomen regions of 17 healthy female donors (mean age 49 ± 6 years) using Coleman technique or Body-jet liposuction. In the present study, the primary objective was the in vitro characteristics of human ASCs. The secondary objective was the optimization of the cell seeding process on 3D-printed scaffolds using polycaprolactone (PCL) or polycaprolactone covered with tricalcium phosphate (PCL + 5% TCP). Biological evaluation of human ASC showed high efficiency of isolation obtaining a satisfying amount of homogeneous cell populations. Results suggest that ASCs can be cultured in vitro for a long time without impairing their proliferative capacity. Growth kinetics shows that the highest number of cells can be achieved in passage 5 and after the 16th passage; there is a significant decrease of cell numbers and their proliferative potential. The percentage of colony forming units from the adipose stem cells is 8% ± 0.63% (p < 0.05). It was observed that the accumulation of calcium phosphate in the cells in vitro, marked with Alizarin Red S, was increased along with the next passage. Analysis of key parameters critically related to the cell seeding process shows that volume of cell suspension and propagation time greatly improve the efficiency of seeding both in PCL and PCL + 5% TCP scaffolds. The cell seeding efficiency did differ significantly between scaffold materials and cell seeding methods (p < 0.001). Increased seeding efficiency was observed when using the saturation of cell suspension into scaffolds with additional incubation. Alkaline phosphatase level production in PCL + 5% TCP scaffold was better than in PCL-only scaffold. The study results can be used for the optimization of the seeding process and quantification methods determining the successful implementation of the preclinical model study in the future tissue engineering strategies.

The Effect of Bioinduced Increased pH on the Enrichment of Calcium Phosphate in Granules during Anaerobic Treatment of Black Water.

Simultaneous recovery of calcium phosphate granules (CaP granules) and methane in anaerobic treatment of source separated black water (BW) has been previously demonstrated. The exact mechanism behind the accumulation of calcium phosphate (Cax(PO4)y) in CaP granules during black water treatment was investigated in this study by examination of the interface between the outer anaerobic biofilm and the core of CaP granules. A key factor in this process is the pH profile in CaP granules, which increases from the edge (7.4) to the center (7.9). The pH increase enhances supersaturation for Cax(PO4)y phases, creating internal conditions preferable for Cax(PO4)y precipitation. The pH profile can be explained by measured bioconversion of acetate and H2, HCO3– and H+ into CH4 in the outer biofilm and eventual stripping of CO2 and CH4 (biogas) from the granule. Phosphorus content and Cax(PO4)y crystal mass quantity in the granules positively correlated with the granule size, in the reactor without Ca2+ addition, indicating that the phosphorus rich core matures with the granule growth. Adding Ca2+ increased the overall phosphorus content in granules >0.4 mm diameter, but not in fine particles (<0.4 mm). Additionally, H+ released from aqueous phosphate species during Cax(PO4)y crystallization were buffered by internal hydrogenotrophic methanogenesis and stripping of biogas from the granule. These insights into the formation and growth of CaP granules are important for process optimization, enabling simultaneous Cax(PO4)y and CH4 recovery in a single reactor. Moreover, the biological induction of Cax(PO4)y crystallization resulting from biological increase of pH is relevant for stimulation and control of (bio)crystallization and (bio)mineralization in real environmental conditions.

Polymer Micro Chips for the Analyses of Calcification Risk

Calcification is a pathological accumulation of calcium phosphate in soft tissues including blood vessels [1] where it can cause cardiovascular morbidity and mortality e.g. heart attack [2]. Mixing blood serum with supersaturated calcium and phosphate results in colloidal calcium protein particles (CPPs) undergoing a typical ripening process. The conversion time can be optically determined by light scatter measurements of smaller primary and larger secondary CPPs (Fig 1). The half-maximal conversion time T50 is a measure of the calcification risk in the patient. Here we report the miniaturization of the experimental setup on a polymer microchip fabricated by ultrasonic processing. Compared to the usual measurement of light scatter in a nephelometer, the analysis was accelerated by increasing the temperature. Furthermore, better reproducible results were obtained by using a staggered herringbone mixer to mix the reactants [3]. A Peltier element is employed to heat the chip. Using this setup, the analysis was shortened to 16.1 ± 1.1min compared to 279 ± 9min obtained in a nephelometer by increasing the temperature from 38°C to 52°C (Fig. 4).

The formation of an organic coat and the release of corrosion microparticles from metallic magnesium implants

Magnesium alloys have been proposed as prospective degradable implant materials. To elucidate the complex interactions between the corroding implants and the tissue, magnesium implants were analyzed in a mouse model and the response was compared to that induced by Ti and by the resorbable polymer polyglactin, respectively. One month after implantation, distinct traces of corrosion were apparent but the magnesium implants were still intact, whereas resorbable polymeric wound suture implants were already fragmented. Analysis of magnesium implants 2weeks after implantation by energy-dispersive X-ray spectroscopy indicated that magnesium, oxygen, calcium and phosphate were present at the implant surface. One month after implantation, the element composition of the outermost layer of the implant was indicative of tissue without detectable levels of magnesium, indicating a protective barrier function of this organic layer. In agreement with this notion, gene expression patterns in the surrounding tissue were highly similar for all implant materials investigated. However, high-resolution imaging using energy-filtered transmission electron microscopy revealed magnesium-containing microparticles in the tissue in the proximity of the implant. The release of such corrosion particles may contribute to the accumulation of calcium phosphate in the nearby tissue and to bone conductive activities of magnesium implants.

Quantitative evaluation of the effects of mitochondrial permeability transition pore modifiers on accumulation of calcium phosphate: comparison of rat liver and brain mitochondria

Mitochondria play a critical role in some forms of apoptosis, and the Ca 2+-dependent permeability transition (PT) is a key initiator of this process. We quantitatively examined major control mechanisms of PT in rat brain (RBM) and liver (RLM) mitochondria. Compared with RLM, RBM were less sensitive to cyclosporin A (CsA), but the combined action of CsA + ADP was much more pronounced in RBM. Carboxyatractyloside abrogated the effects of all mPTP inhibitors in RBM but not in RLM, where the effects of CsA were not reduced. Estimated H +/Ca 2+ ratios were 0.81 ± 0.01 for RLM and 0.84 − 0.93 for RBM, suggesting that Ca 2+ and Pi were sequestered in the matrix as CaHPO 4 and Ca 3(PO 4) 2 salts, and that RBM sequester more CaPi as the least soluble salt. We conclude that: (1) RBM and RLM differ in their baseline behavior of the PT and in their responses to PT modifiers, and (2) PT modifiers can be functionally divided into those which directly affect the mitochondrial PT pore and are not energy-dependent (CsA, free Ca 2+, ADP ex, and Mg 2+), and those which affect the energy-dependent calcium phosphate sequestration process (ADP mt, CATR, local anesthetics). We also conclude that ANT affects PT by changing mitochondrial capacity for energization.

Changes in the elemental composition of Bioglass during its surface development in the presence or absence of proteins

The present study examined the elemental distribution with depth from the surface of Bioglass 45S5 immersed in simulated body fluid (SBF) in the presence or absence of proteins derived from foetal calf serum for 960 h using energy dispersive spectroscopy (EDS). The changes in elemental composition of the surface of Bioglass were also analysed with EDS for different immersion times (10 min to 960 h) before and after immersion in SBF with or without proteins. The presence of proteins consistently altered the elemental composition of Bioglass with depth from the surface, although the development of a silica rich layer was similar in both the presence or absence of proteins. In the presence of proteins the accumulation of calcium phosphate at the surface of Bioglass was slower, formed a narrower layer and had lower concentrations of calcium and phosphate than the calcium phosphate rich layer that developed in SBF alone.

Calcium phosphate formation within sol-gel prepared titania in vitro and in vivo.

Calcium phosphate formation is induced within sol-gel prepared titania and grows toward a calcium phosphate solution in which the titania is immersed. The implantation of this sol-gel prepared titania film coating on TiA16V4 core into the femurs of goats shows an accumulation of calcium phosphate within the titania film 12 weeks postoperatively, which leads to the connection of the titania film coating to the bone. Therefore, sol-gel prepared titania is probably bioactive. The results indicate that hydrated titania gel is able to generate calcium phosphate by intake of calcium and phosphate from the surrounding solution. Sufficient TiOH concentration at the titania surface is needed to start this process. Titanium could be bioactive, if its hydrolysis can be accelerated.

Ultrastructural localization of alkaline phosphatase in lactating rat mammary gland

Alkaline phosphatase is found in almost all nucleated mammalian cells as well as in many microorganisms. In animal tissues, it is often found associated with plasma membranes and also has been indirectly implicated in the accumulation of calcium-phosphate in calcifying tissue, osteoblasts and odontoblasts. In the secretion of milk, vesicles accumulate casein and colloidal calcium-phosphate, while in a separate pathway milk fat is secreted and bounded by the apical plasma membrane. Alkaline phosphatase is found in milk, and all milks contain both colloidal calcium-phosphate and fat globule membranes which are derived in part from the plasma membrane. Previous studies had suggested that mammary alkaline phosphatase is limited to nonsecretory myoepithelial cells, but recent work has indicated that intracellular alkaline phosphatase is cryptic. We therefore decided to investigate the cytochemical distribution of alkaline phosphatase in mammary secretory cells, and to determine if it could participate in calcium-phosphate accumulation in milk.

Phosphocitrate inhibits mitochondrial and cytosolic accumulation of calcium in kidney cells in vivo.

Synthetic 3-phosphocitrate, an extremely potent inhibitor of calcium phosphate crystallization as determined in a nonbiological physical-chemical assay, has many similarities to a mitochondrial factor that inhibits crystallization of nondiffracting amorphous calcium phosphate. In order to determine whether phosphocitrate can prevent uptake and crystallization of calcium phosphate in mitochondria in vivo, it was administered intraperitoneally to animals given large daily doses of calcium gluconate or parathyroid hormone, a regimen that causes massive accumulation and crystallization of calcium phosphate in the mitochondria and cytosol of renal tubule cells in vivo. Administration of phosphocitrate greatly reduced the net uptake of Ca2+ by the kidneys and prevented the appearance of apatite-like crystalline structures within the mitochondrial matrix and cytosol of renal tubule cells. Phosphocitrate, which is a poor chelator of Ca2+, did not reduce the hypercalcemia induced by either agent. These in vivo observations therefore indicate that phosphocitrate acts primarily at the cellular level to prevent the extensive accumulation of calcium phosphate in kidney cells by inhibiting the mitochondrial accumulation or crystallization of calcium phosphate.