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PubMed2001

Placental calcification: a metastatic process?

Placental calcification commonly increases with gestational age. The mechanism of apatite mineralization probably involves one of three known mechanisms of tissue calcification: physiological (like bone), dystrophic (ischaemia-related) or metastatic (mineralization in a supersaturated environment). This study was designed to determine the mechanism of calcification by examining (1) the mineral content of placental calcifications in comparison to other physiological and pathological apatites, and (2) the expression of bone morphogenetic proteins (BMPs), which are important in physiological calcification, across gestational age. By energy-dispersive x-ray analysis (EDXA), the Ca/P weight ratio for apatitic mineral from mature calcifications was 2.00+/-0.05 (s.e.), which is similar to that for stones formed in a metastatic, supersaturated environment and lower than that observed in physiological calcification. Biologically active BMP, which was determined by bioassay, was demonstrated in mature and postmature placentae. The BMPs PLAB, PDF and related protein INSL-4 were identified by semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR), but their mRNA expression was independent of gestational age (7-41 weeks of gestation). We conclude that (1) the identified BMPs were not related directly to placental calcification, which argues against physiological calcification, and (2) the chemical composition of the apatitic mineral was suggestive of rapid formation in a supersaturated environment, which is consistent with a metastatic mechanism of calcification.

Animals↗

PubMed2004

Calcium oxalate crystal localization and osteopontin immunostaining in genetic hypercalciuric stone-forming rats.

BACKGROUND: The inbred genetic hypercalciuric stone-forming (GHS) rats develop calcium phosphate (apatite) stones when fed a normal 1.2% calcium diet. The addition of 1% hydroxyproline to this diet does not alter the type of stone formed, while rats fed this diet with 3% hydroxyproline form mixed apatite and calcium oxalate stones and those with 5% hydroxyproline added form only calcium oxalate stones. The present study was designed to determine the localization of stone formation and if this solid phase resulted in pathologic changes to the kidneys. METHODS: GHS rats were fed 15 g of the standard diet or the diet supplemented with 1%, 3%, or 5% hydroxyproline for 18 weeks. A separate group of Sprague-Dawley rats (the parental strain of the GHS rats), fed the standard diet for a similar duration, served as an additional control. At 18 weeks, all kidneys were perfusion-fixed for structural analysis, detection of crystal deposits using the Yasue silver substitution method, and osteopontin immunostaining. RESULTS: There were no crystal deposits found in the kidneys of Sprague-Dawley rats. Crystal deposits were found in the kidneys of all GHS rats and this Yasue-stained material was detected only in the urinary space. No crystal deposits were noted within the cortical or medullary segments of the nephron and there was no evidence for tubular damage in any group. The only pathologic changes occurred in 3% and 5% hydroxyproline groups with the 5% group showing the most severe changes. In these rats, which form only calcium oxalate stones, focal sites along the urothelial lining of the papilla and fornix of the urinary space demonstrated a proliferative response characterized by increased density of urothelial cells that surrounded the crystal deposits. At the fornix, some crystals were lodged within the interstitium, deep to the proliferative urothelium. There was increased osteopontin immunostaining in the proliferating urothelium. CONCLUSION: Thus in the GHS rat, the initial stone formation occurred solely in the urinary space. Tubular damage was not observed with either apatite or calcium oxalate stones. The apatite stones do not appear to cause any pathological change while those rats forming calcium oxalate stones have a proliferative response of the urothelium, with increased osteopontin immunostaining, around the crystal deposits in the fornix.

Animal Feed↗

PubMed1978

A study of the mineral phase of cementifying fibroma.

Physico-chemical study of a case of cementifying fibroma in the mandible of 78-year-old woman was carried out by X-ray diffraction analysis and thermogravimetric and differential-thermal analyses (TGA-DTA). The center of the tumor consisted of masses of acellular cementum-like tissues; while the periphery consisted of cementicle-like tissues. X-ray powder diffraction patterns showed that the mineral phase of these tissues was apatitic in nature. X-ray line broadening analysis revealed that the crystallinity of apatite of the cementum-like tissue was higher than that of apatite of cementicle-like tissue, and lower than that of bone apatite obtained from the same patient. Furthermore, TGA-DTA studies showed that the mineral (ash) value of cementum-like tissue was slightly higher than that of bone.

Aged↗

PubMed1978

Binding of dyes to hydroxyapatite treated with cetylpyridinium chloride or cetrimonium bromide.

The effect of cetylpyridinium chloride (CPC) and cetrimonium bromide (CTAB) on the adsorption of some acidic food dyes to hydroxyapatite was studied. The dyes investigated were brilliant blue (FD&C Blue No. 1), tartrazine (FD&C Yellow No. 5), sunset yellow (FD&C Yellow No. 6) and amaranth (FD&C Red No. 2). The apatite had adsorbed 9.2 mumol CPC per g dry weight. The adsorbed CPC was in equilibrium with a free concentration of 20 microgram/ml (58 micrometer). The adsorption of CPC and CTAB to the apatite was followed by an increased ability of the crystals to bind the dyes. The dyes were very firmly adsorbed and were not released during a series of washings. Untreated apatite showed only a minor affinity for the dyes. The adsorbed dyes were easily washed out. CPC and CTAB showed the smae specific ability to increase the binding capacity of the apatite. The results are discussed and related to the formation of stains on the teeth in persons using quaternary ammonium compounds for mouthrinsing. A mechanism explaining the production of stains is proposed.

Adsorption↗

PubMed2005

Supramolecular assembly of amelogenin nanospheres into birefringent microribbons.

Although both tooth enamel and bone are composed of organized assemblies of carbonated apatite crystals, enamel is unusual in that it does not contain collagen nor does it remodel. Self-assembly of amelogenin protein into nanospheres has been recognized as a key factor in controlling the oriented and elongated growth of carbonated apatite crystals during dental enamel biomineralization. We report the in vitro formation of birefringent microribbon structures that were generated through the supramolecular assembly of amelogenin nanospheres. These microribbons have diffraction patterns that indicate a periodic structure of crystalline units along the long axis. The growth of apatite crystals orientated along the c axis and parallel to the long axes of the microribbons was observed in vitro. The linear arrays (chains) of nanospheres observed as intermediate states before the microribbon formation give an important indication as to the function of amelogenin in controlling the oriented growth of apatite crystals during enamel mineralization.

Amelogenesis↗

PubMed1985

An in vitro ultrastructural study of infectious kidney stone genesis.

A ureolytic strain of Proteus mirabilis, isolated from a patient with infectious kidney stones, produced struvite (MgNH4PO4 X 6 H2O) and apatite [Ca10(PO4)6CO3] crystals in vitro when grown in artificial urine. Surface-attached crystals were encased in a slime-like layer. Scanning electron microscopy revealed that surfaces submerged in the artificial urine were colonized by P. mirabilis. Bacteria-associated crystals appeared soon after colonization and eventually became coated with an amorphous substance. Energy-dispersive X-ray analysis of these crystals revealed the presence of Mg, Ca, and P which are major components of struvite and apatite. Transmission electron microscopy of surface scrapings revealed that the glycocalyx of P. mirabilis contained a large number of crystals. Based on these observations and previous work, a theory for infectious renal calculogenesis is proposed. The kidney is initially colonized by invading ureolytic pathogens. These pathogens secrete copious amounts of glycocalyx which facilitates adhesion of the organisms to the kidney, provides protection for these bacteria, and serves to bind struvite and apatite crystals that result from bacterial urease activity. Growth of these calcified microcolonies into mature stones is characterized by continued bacterial growth, incorporation of urinary mucoproteins into the matrix along with bacterial glycocalyx, and a continued deposition of struvite and apatite crystals due to the high pH. The mature stone, in effect, represents an enlarged "fossilized" bacterial microcolony.

Humans↗

PubMed1993

The hydroxyapatite ion activity product in acid solutions equilibrated with human enamel at 37 degrees C.

Five samples of powered enamel were each sequentially equilibrated 5 times at 37 degrees C with either 4 or 17 mmol/l H3PO4, in contact with air, and the ionic activity product for hydroxyapatite (IHA) estimated. There was evidence for preferential release of Mg and Na, especially in the first equilibrations. In two experiments, raised values of IHA were observed in the first equilibration but otherwise IHA was reasonable constant within experimental error and was much closer to the solubility product of hydroxyapatite than many previous estimates, mainly at 25 degrees C, suggest. The mean value of IHA for the majority fraction, averaged over all samples, was 1.7 (+/- 0.7) x 10(-58). Non-apatitic solids formed in all systems but solubility appeared nevertheless to be controlled by an apatitic phase: either the enamel mineral itself or apatite reprecipitated during the course of equilibration. High values of IHA reported previously may be due to use of conditions favouring dissolution only of more soluble factions or to metastability artifacts associated with control of solubility by non-apatitic phases.

Calcium↗

PubMed1981

The influence of carbonate on the atomic structure and reactivity of hydroxyapatite.

A series of synthetic carbonated and non-carbonated apatites was investigated using high resolution transmission electron microscopy, and their dissolution behavior was tested under sink conditions, using the rotating disc method. n-Beam lattice images of the apatite samples were of a resolution greater than has been previously reported, and revealed an increase in crystalline disorder with the incorporation of carbonate in the apatite structure. This resulted in an increased rate of dissolution and a decreased activation energy for dissolution for the carbonated apatites. Thus, carbonate increased the reactivity of hydroxyapatite.

Carbonates↗

PubMed1989

Crystal morphology and decalcification patterns compared in rat and human enamel and synthetic hydroxyapatite.

The purpose of this investigation was to compare morphology and dissolution patterns by ultrastructural examination of rat and human enamel crystals as well as synthetic apatite crystals. Mature enamel crystals were of particular interest, since crystal maturation appears to be inhibited in amelogenesis imperfecta. Specimens were isolated from developing and mature rat incisor enamel. Rat enamel, mature human enamel, and synthetic apatite were thin-sectioned without decalcification and examined by transmission electron microscopy. Some sections were exposed to acid, and selected synthetic apatite sections were further treated for removal of embedding plastic, followed by vacuum-shadow-coating with carbon. Results showed that cross-sections of rat, human, and synthetic crystals had a distortion in the flattened hexagonal outline in regions where the growth of one crystal impinged on another. Crystal dissolution occurred preferentially along the c-axis, producing a central defect or hole in the crystals. Preliminary studies with weak acid on mature human enamel indicate that the relatively soluble crystal core is quickly dissolved, while the outer shell remains intact over a much longer period of time. In the mature rat and human enamel, this crystal hole formation had a consistent dimension of approximately 10-nm thickness. The crystal hole dimension was the same size as crystals that are formed during the early secretory phase in rat amelogenesis. Acid-treated synthetic apatite also showed dissolution of the crystal core along the c-axis, but dimensions of the hole were not consistent.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2001

[Osteogenetic activity of BMP-3-coated titanium specimens of different surface texture at the orthotopic implant bed of giant rabbits].

INTRODUCTION: The successful combination of osteoinductive factors with current materials used in both endoprosthetics and implantology improves bony ingrowth and long-term stability of the chosen implants. The aim of the present experimental animal study was to clarify in what way faster bony integration can be achieved through additional BMP-3-coating of titanium test implants of different surface textures (hydroxy-apatite-coated or corundum-blasted). METHODS: Thirty of 60 cylindrical titanium test implants with a hydroxy-apatite or corundum-blasted surface were coated with 230 microg porcine, high-purified BMP-3-precipitate per implant to check their osteoinductive potential in a bioassay. In each case a BMP-3-coated and an uncoated control-device were implanted with a gap formation of 1 mm into the femoral part of the patellofemoral joint of the right and left leg of 30 adult giant rabbits. Serial saw slices of all explanted specimens were prepared, and the osseous integration of the implant and time-dependent bone neoformation were analyzed microscopically and histomorphometrically 14, 35, and 56 days after implantation. RESULTS: Coating of TiAl4V6-test devices with BMP-3 led in both groups after gap implantation to an improved osseointegration, that was histomorphological and histomorphometrical verifiable. Statistical evaluation using the t-test for matched samples showed 5 weeks after surgery a significant higher volume of new formed bone of the BMP-3-coated corundum-blasted or hydroxy-apatite-coated TiAl4V6 test devices compared to the non-coated controls of the same type (P < 0.01). Light microscopy demonstrated osseointegration without connective tissue membrane around the surface of the implants after 2, 5, and 8 weeks. Better osseointegration was achieved in the hydroxy-apatite-coated implants than in the corundum-blasted implants. CONCLUSIONS: Our results indicate that composite metal implants, as used in endoprosthetics and implantology, are suitable carriers for BMP-3 and improved fixation of the implants can be achieved.

Alloys↗

PubMed2003

[In vitro release of tetracycline hydrochloride from alpha-TCP cement].

Drug release from alpha-TCP cement containing tetracycline hydrochloride (TTCH) was studied in vitro. Results from X-ray diffraction study indicated that TTCH did not prevent the hydration of alpha-TCP. In vitro drug release study showed that TTCH release could sustain over 1200 h, and the release was controlled by two mechanisms: (1) diffusion of free TTCH molecules through the porous cement (square-root-of-time kinetics); (2) dissociation of TTCH from the apatite-TTCH complex (zero-order kinetics). The mechanism controlling release would changed with the variety of the antibiotic content of cement pellets, as a result of TTCH adsorption and bonding on calcium phosphates. The first mechanism was predominantly for low concentration system TTCH-loaded apatite cement systems at the initial release period, and for high concentration TTCH-loaded apatite cement systems. As for low concentration TTCH-loaded apatite cement systems at later release stage, drug release was controlled by the coupling of the two mechanisms.

Anti-Bacterial Agents↗

PubMed1984

[Structural studies of infection stones: structure of the nuclei].

The composition and structure of nuclei of infection stones were investigated. Twenty seven out of 40 renal stones were found to contain struvite and/or carbonate apatite in the nuclei as well as peripheral layers, and 13 contained calcium oxalate. Some bladder stones also contained different substances in the nuclei. In some infection stones whose architecture was studied in thin section and with scanning electron microscopy, we found large numbers of bacteria in the nuclei composed of struvite and/or apatite. Though we could find no bacteria within the nuclear parts composed of oxalate, we found them in apatite layers outside the nuclei. Urea-splitting bacteria are suggested to participate both in the initial formation of struvite stones and in the diversion of oxalate stones into phosphate stones. Such bacteria may play important roles in stone formation, not only as promotors of crystallization of struvite and apatite but also as a component such as of an organic matrix.

Calcium Oxalate↗

PubMed1996

Ultrastructure of selected struvite-containing urinary calculi from dogs.

OBJECTIVE: To elucidate the ultrastructural details of struvite-containing urinary calculi from dogs. SAMPLE POPULATION: 38 specimens were selected from a collection of approximately 13,000 canine urinary calculi: 18 of these were composed entirely of struvite, and 20 consisted of struvite and calcium phosphate (apatite). PROCEDURE: Qualitative and quantitative analyses of specimens included use of plain and polarized light microscopy, x-ray diffractometry, scanning electron microscopy with backscattered electron imagery, x-ray fluorescence scans, and electron microprobe analysis. RESULTS: 4 textural types were recognized among struvite calculi, and 4 textural types of struvite-apatite calculi were described. Evidences of calculus dissolution were described from 4 calculi studied. CONCLUSIONS: The presence of small, well interconnected primary pores in struvite-containing urinary calculi from dogs appears to be a significant factor in determining the possible interaction of calculi with changes in the urine composition. The progress of dissolution from the calculus surface to the calculus interior appears to be largely affected by the primary porosity originally present between crystals forming the calculus framework. Apatite was observed to be more resistant to dissolution than struvite. CLINICAL RELEVANCE: The prevalence of fine concentric laminations having low porosity, and the common occurrence of apatite among struvite-containing urinary calculi from dogs may be 2 reasons why the efficacy of dietary and medicinal manipulations in dissolving urinary calculi is greater among cats than it is among dogs.

Animals↗

PubMed1997

Surface modifications of titanium in calcium-ion-containing solutions.

The surface of titanium was modified in calcium-ion-containing solutions to improve bone conductivity. Three kinds of aqueous solutions for the modification were prepared using calcium nitrate, calcium chloride, and calcium oxide. The pH values of the solutions were 3.9, 7.4, and 12.6, respectively. At first, anatase powder was immersed in the solutions of 7 days to confirm the effect of the solutions on the modification. As a result, calcium titanate was formed on the anatase powder, indicating that the titanium surface was possibly modified by the solutions. Titanium plates were then immersed in the solutions at ambient temperature for 7 days, washed by deionized water, and dried. X-ray photo-electron spectroscopy of surface-modified titanium revealed that the surface-modified layer contained calcium hydroxide and/or calcium titanate. The surface-modified layer in which titanium was modified was thickest in this order: calcium oxide, calcium chloride, and calcium nitrate solutions. Apatite was formed on the surface-modified titanium in Hanks' solution while apatite was undetected on unmodified titanium. Therefore, the surface modification of titanium may improve bone conductivity. The amount of apatite corresponded to the thickness of the surface-modified layer and the amount of calcium in the layer.

Apatites↗

PubMed2000

Bioactive macroporous titanium surface layer on titanium substrate.

A macroporous titanium surface layer is often formed on titanium and titanium alloy implants for morphological fixation of the implants to bone via bony ingrowth into the porous structure. The surface of titanium metal was recently shown to become highly bioactive by being subjected to 5.0 M-NaOH treatment at 60 degrees C for 24 h and subsequent heat treatment at 600 degrees C for 1 h. In the present study, the NaOH and heat treatments were applied to a macroporous titanium surface layer formed on titanium substrate by a plasma spraying method. The NaOH and heat treatments produced an uniform amorphous sodium titanate layer on the surface of the porous titanium. The sodium titanate induced a bonelike apatite formation in simulated body fluid at an early soaking period, whereby the apatite layer grew uniformly along the surface and cross-sectional macrotextures of the porous titanium. This indicates that the NaOH and heat treatments lead to a bioactive macroporous titanium surface layer on titanium substrate. Such a bioactive macroporous layer on an implant is expected not only to enhance bony ingrowth into the porous structure, but also to provide a chemical integration with bone via apatite formation on its surface in the body.

Apatites↗

PubMed2002

Bioactivity of three CaO-P2O5-SiO2 sol-gel glasses.

Three gel glasses containing 25 mol % of CaO and SiO(2) + P(2)O(5) contents (in mol %): 75 + 0 (S75); 72.5 + 2.5 (S72.5P2.5); and 70 + 5 (S70P5), respectively, were obtained, characterized, and studied when soaked in a simulated body fluid (SBF). The influence of composition in both textural properties (surface area and porosity) and in vitro behavior of glasses was studied. In as prepared S72.5P2.5 and S70P5 glasses, crystalline phosphate nuclei were detected through XRD and FTIR. In addition, N(2) adsorption and Hg porosimetry measurements showed that the surface area increased, whereas the pore volume and the pore diameter decreased as P(2)O(5) in glasses increased. These variations were explained on the basis of the withdrawal of calcium from the glass silica network, due to the calcium-phosphorous bonding. In vitro studies showed that the three compositions were bioactive, because an apatite layer was formed after soaking in SBF. S75 presented the highest initial reactivity but the lowest crystallization rate of the apatite-like phase. For S72.5P2.5, and S70P5 the amorphous calcium phosphate formation was slower than for S75, but the crystallization of apatite was observed after shorter periods in SBF. Furthermore, after 7 days of soaking, the layer thickness decreased as P(2)O(5) in glasses increased.

Apatites↗

PubMed1985

Interface reactions between machinable bioactive glass-ceramics and bone.

A new biomaterial for bone substitution, a "machinable bioactive glass-ceramic" has been developed. The material contains two main crystal phases, mica and apatite, and is therefore machinable and bioactive. It has the advantage to be workable by the surgeon, if necessary, during operation. The preparation method of this glass-ceramic is described. Different types of the material can be produced in dependence of the composition, nucleation, and crystallization of the basic glass. In vivo and in vitro investigations showed a characteristic solubility of the material. A Ca-phosphate-rich interface layer with apatite crystals (from the basic glass-ceramic) and a thickness of about 5-10 micrometers grows as solid-state reaction between glass-ceramic and bone. This interface reaction is interpreted as a chemical process which includes a slight solubility of the glass-ceramic and a solid state reaction between the stable apatite crystals in the glass-ceramic and the bone.

Aluminum Silicates↗

PubMed1992

Mechanism and strength of bonding between two bioactive ceramics in vivo.

A study was conducted to examine the mechanism and strength of bonding between two bioactive ceramic plates in vivo. Rectangular plates (15 mm X 10 mm X 2 mm) of Bioglass, apatite-wollastonite-containing glass ceramic (designated A-W.GC), and two types of hydroxyapatite sintered at 900 degrees C and 1200 degrees C (designated HA900 and HA1200) were prepared. Two plates of the same materials tied together with silk thread were implanted subcutaneously into rats. The force required to detach the mutually bonded bioactive ceramic plates was measured 4, 8, 12, and 24 weeks after implantation. The interface between the two bonded plates was examined by SEM-EPMA and thin-film x-ray diffraction analysis. At 24 weeks after implantation, the mutual bonding of Bioglass and A-W.GC was stronger than that of the two HA types. SEM-EPMA and thin-film x-ray diffraction analysis of the bonded area of Bioglass and A-W.GC plates showed bonding zones with apatite in the margins, and a bonding zone with calcite in the center. The greater strength of bonding of Bioglass and A-W.GC plates compared with the two types of HA plate 24 weeks after implantation is explained by the wider bonding zone provided by the calcite layer formed in the center of the plates, which is considered to have been perfused with PO4-poor body fluids resulting from PO4 consumption for apatite formation in the margins.

Animals↗