Mineralization Of Hard Tissues Research Articles

Mineral content of calcified tissues in cystic fibrosis mice.

Although abnormal hard tissue mineralization is a recognized complication of cystic fibrosis (CF), the pathogenesis leading from the defective cystic fibrosis transmembrane conductance regulator (CFTR) protein is poorly understood. We hypothesized that CFTR plays a direct role in the mineralization of bone and teeth and tested the hypothesis using CF mouse models [CFTR(-) mice]. In vivo measurements by dual-emission X-ray absorpitometry (DEXA) indicated that bone mineral density (BMD) was reduced in CF mice as compared to gender-matched littermates. However, no change was evident after correction of BMD for the covariant of body weight. The latter finding was confirmed in isolated femurs and nasal bones by standard dry-ashing and instrumental neutron activation analysis (INAA). INAA of the continuously growing hypsodont incisor teeth from CFTR(-) mice revealed reduced Ca and normal P in the enamel layer--a finding consistent with changes in the deciduous teeth of CF children. Interestingly, enamel fluoride was increased in the CFTR(-) incisors and may associate with abnormal enamel crystallite formation. The iron content of the incisor enamel was reduced, explaining the loss of yellow pigmentation in CFTR(-) incisors. In contrast to the incisors, the mineral content of the slow-growing brachydont molar teeth was not different between CFTR(-) and CFTR(+) mice. It was concluded that CFTR does not play a direct role in the mineralization of bones or brachydont teeth in mice. Functional CFTR is apparently required for normal mineralization of the hypsodont incisors. However, multiple changes in the mineral composition of the CF incisors suggest an indirect role for CFTR, perhaps by maintaining a normal salivary environment for continuous tooth eruption.

Abnormal dissolution of octacalcium phosphate crystals at constant undersaturation

The dissolution of octacalcium phosphate (OCP), a possible important precursor phase in the in vivo mineralization of hard tissue, has been studied at 37°C over a range of undersaturations using a constant composition method (CC). The rate decreases markedly with time despite the sustained driving force, and eventually it approaches zero even though crystals remain in the undersaturated solutions. These OCP crystals will not dissolve when exposed to calcium phosphate solutions of the same undersaturations. However, the dissolution reaction resumes if the undersaturations are changed. Furthermore, at low undersaturation, the CC OCP dissolution curves show characteristic stepwise profiles. These interesting unpredicted phenomena persuade us to examine in more detail current crystal growth/dissolution models.

Biochemical characterization of purified carbonic anhydrase from the octocoral Leptogorgia virgulata

Carbonic anhydrase (CA) has been isolated and purified from the octocoral Leptogorgia virgulata (Lamarck) in an effort to investigate its role in the mineralization and demineralization of spicules and other calcified hard tissues. Affinity-chromatography using Prontosil-derivatized carboxymethylcellulose (CM) Bio-Gel A provided a one-step purification for 30 kdalton polypeptides with carbonic anhydrase activity. Four distinct polypeptides (designated α, β, γ, and δ) are separated from one another at this molecular weight by two-dimensional gel electrophoresis. The specific activity of the L. virgulata CA is on average 57.5±1.5 U g-1, is inhibitable by 10-6 M acetazolamide, and is unaffected by 5mM dithiotheitol. The amino acid composition of these polypeptides is similar to that of mammal, bird, reptile, fish and arthropod species. Antiserum made against the L. virgulata CA reacts specifically with the 30 kdalton polypeptides in western blots, and crossreacts with human CA I and II. Antiserum against avian CA II crossreacts with the L. virgulata 30 kdalton polypeptides. This is the first report of the characterization of a purified CA from an octocoral, and production of a CA antiserum to a species in the phylum Cnidaria.

Treatment of condylar fractures: Arguments for a standardization of result criteria

Biomaterials based on bioinspired mineralization are expected to offer osteoconductive and osteoinductive scaffolds for bone regeneration. An important role in the mediation of in vivo biomineralization process is played by highly anionic non-collagenous phosphoproteins (NCP) bound to the collagen matrix. Inspired by this fact, synthetic analogues of the NCPs like polyvinyl phosphonic acid which provide surface nucleation sites have been employed successfully for mineralization of hard tissues. In this study, electrospun nanofibrous scaffolds of partially phosphorylated polyvinyl alcohol (PPVA) are prepared and studied for matrix mineralization and maturation of human pre-osteoblasts like MG63 cells. Partial phosphorylation was found to affect many solution properties of PVA like increase in surface tension, conductivity and semi-crystalline intermolecular hydrogen bond formations narrowing down the electrospinning window for PPVA. In vitro mineralization under SBF treatment was uniform along the length of fibers on PPVA nanofibers. Further, MG63 cells showed increased adherence and proliferation on PPVA nanofibers and the expression of alkaline phosphatase activity and cell-matrix calcium levels were about two times higher than PVA nanofibers. The study established fabrication of electrospun nanofibers of a partially phosphorylated polymer, PVA resulting in improved osteoconduction and expression of early markers of osteoinduction in MG63 cells.

Effects of dietary calcium and vitamin D 3 on weight gain and mineral composition of the blue tilapia ( Oreochromis aureus) in low-calcium water

Influences of dietary calcium and vitamin D 3 (cholecalciferol) were evaluated with fingerling blue tilapia using a 2×2 factorial design. Four purified diets were formulated to contain 34% crude protein from egg albumin and casein with 3.20 kcal available energy/g. The basal diet (0.2 g Ca/kg) was supplemented with either 0 or 7.5 g Ca/kg (from CaCl 2·2H 2O) and 0 or 2000 IU vitamin D 3/kg. Experimental diets were fed in triplicate to groups of blue tilapia initially averaging 2.30±0.09 g in 38-liter aquaria receiving water with <0.1 mg Ca/l for a period of 24 weeks. Significantly ( P<0.05) greater weight gain and concentrations of ash, calcium, phosphorus and magnesium in bone and scale tissues were observed for fish fed the calcium-supplemented diets compared to those fed diets without supplemental calcium regardless of vitamin D 3 supplementation. Fish fed the diet without supplemental vitamin D 3 but with supplemental calcium had a significant reduction in weight gain at the end of 12 weeks compared to those fed the diet supplemented with both nutrients; this trend continued in subsequent weeks although differences were not significant. Effects of vitamin D 3 on mineralization of hard tissues were negligible at all sampling periods. Dietary supplementation of vitamin D 3 was not required for tilapia to utilize dietary calcium for growth and tissue mineralization. Based on these results, dietary calcium had the most profound effects on growth and mineral composition of blue tilapia reared in low-calcium water and effects of vitamin D 3 were more subtle.

Hard Tissue Mineralization and Demineralization.S. Suga , N. Watabe

Previous articleNext article No AccessNew Biological BooksHard Tissue Mineralization and Demineralization. S. Suga , N. Watabe Stephen MannStephen Mann Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Quarterly Review of Biology Volume 69, Number 1Mar., 1994 Published in association with Stony Brook University Article DOIhttps://doi.org/10.1086/418483 Copyright 1994 The University of ChicagoPDF download Crossref reports no articles citing this article.

A structural approach to bone adhering of bioactive glasses

Some silicate glasses exhibit the property of bonding to bone. In vivo tests show that a layer of silica gel is always formed on the glass surface when the bonding is successful. From a comparison with the silicon chemistry of diatoms and connective tissues it is apparent that silicate chelates form an essential step in the formation and mineralization of hard tissues. The same kind of chelating is also demonstrated for silicate anions in binary melts. It is suggested that in implants, the silica gel formed on the glass surface not only acts as a chelating agent, but also is flexible enough to supply the correct atomic distances required by the crystal structure of bone apatite. The phosphate phase used in most bioactive glasses is suggested to act as a source for a phosphate buffer, which adjusts the surface acidity of the glass implant.

Effects of a low calcium maternal and weaning diet on the thickness and microhardness of rat incisor enamel and dentine

The deposition and mineralization of incisor hard tissues have been studied in rat pups nursed by mothers on a low calcium diet or weaned with the maternal diet. Animals were killed at 30 days (control and low calcium diets; maternally fed) or 60 days (after 30 days weaning on maternal diet). The degree of mineralization of enamel and dentine was evaluated by a microhardness method on thick transverse sections. The enamel and dentine thickness, and the diameters of the incisor sections and pulp cavity were measured on microradiographs from the sections. Microhardness values of enamel were similar in groups killed after 30 days maternal feeding, but the microhardness of root enamel was 73–74% less in the low calcium-diet weaned group. Peripulpar dentine had mean microhardness values lower than controls in the group fed maternally for 30 days, whereas the whole root dentine appeared significantly less hard in the low calcium-diet weaned group than in the controls. A significant reduction of the incisor bucco-lingual diameter was observed only in this last experimental group. Enamel thickness was significantly lower in the roots of both experimental groups and in the necks of the low calcium weaned group. The reduction in dentine thickness was greater (from −30 to −56%); in the root it was more evident on the lingual aspect. Thus calcium deficiency in the mother's diet did not influence either the deposition or the mineralization of the pup's incisor enamel and dentine. However, when the offspring were weaned with the maternal calcium-deficient diet, mineralization of the tooth hard tissue was retarded.

Octacalcium phosphate and apatite overgrowths: A crystallographic and kinetic study

Octacalcium phosphate (OCP) and apatite overgrowths were studied using scanning and transmission electron microscopy (SEM and TEM). Precipitates containing overgrowths were prepared using constant composition methods with either OCP or dental enamel apatite seeds. In some cases the OCP-apatite interface was imaged using high-resolution TEM at an approximate 2.5-Å resolution. Chemical analysis showed that OCP could be grown on apatite seeds under constant composition conditions, but that apatite growth on OCP although not kept at constant composition, indicated the growth of a phase more basic than OCP with a Ca P molar ratio of 1.50 ± 0.04. High-resolution TEM confirmed that this phase was “apatite-like.” The data show that it is possible to grow apatite on OCP and vice versa near physiological pH. Overgrowths of apatite and OCP are of biological interest as both phases appear to precipitate during hard tissue mineralization.

Effects of Low Ambient Calcium Levels on Whole-Body Ca2+ Flux Rates and Internal Calcium Pools in the Freshwater Cichlid Teleost,Oreochromis Mossambicus

ABSTRACTCalcium fluxes and internal calcium pools were measured in fed, rapidly growing, male tilapia, Oreochromis mossambicus, acclimated to 0·8 mmol l−1 (FW) and 0-2 mmol l−1 (LFW) Ca2+. Plasma calcium levels were slightly and significantly higher in the LFW tilapia, but muscle calcium concentrations were independent of ambient Ca2+. At the time of the experiments, the LFW fish were growing and accumulated calcium, although the calcium content of their hard tissues was reduced. The LFW fish had higher Ca2+ influx and efflux rates than the FW fish. The increase in the influx of Ca2+ in LFW fish was, however, substantially greater than the increase in the efflux of Ca2+, giving these fish a more than four-fold increase in net Ca2+ influx from the water: for a 20-g tilapia net uptake rates of Ca2+ from the water were 390 and 1620 nmol Ca2+ h−1 for FW-and LFW-adapted fish, respectively. These values were calculated to represent at least 69 % of the total calcium accumulated by these growing fish. This indicates that even in low-calcium water, tilapia absorb a significant amount of their calcium requirement directly from the water.The pool of readily exchangeable calcium in the bone of FW fish was estimated to be about 7 % of the total hard tissue calcium. In the fish acclimated to LFW, this percentage increased to about 15 % as total hard tissue mineralization decreased. This may indicate that tilapia can increase the mobility of their h

Recent information on the mineralization of hard tissues.

Recent information on the mineralization of hard tissues.

Effects of Hypophysectomy on the Occurrence and Calcifiability of Matrix Vesicles in the Epiphyseal Growth Plate of Immature Rats

In the cellular secretion theory of mineral deposition, extracellular matrix vesicles are believed to play an integral role in hard tissue mineralization (1). Membrane limited matrix vesicles arise from the plasma membrane of epiphyseal chondrocytes and tooth odontoblasts by a budding process (2, 3). Nutritional and hormonal factors have been postulated to play essential roles in mineral deposition and apparently have a direct effect on matrix vesicles of calcifying cartilage as concluded by Anderson and Sajdera (4). Immature (75-85 gm) Long-Evans hooded rats were hypophysectomized by the parapharyngeal approach and maintained fourteen (14) days post-surgery. At this time, the animals were anesthetized and perfusion fixed in cacodylate buffered 2.5% glutaraldehyde. The proximal tibias were quickly dissected out and split sagittally. One half was used for light microscopy (LM) and the other for electron microscopy (EM). The halves used for EM were cut into blocks approximately 1×3 mm. The tissue blocks were prepared for ultra-thin sectioning and transmission EM. The tissue was oriented so as to section through the epiphyseal growth plate from the zone of proliferating cartilage on down through the hypertrophic zone and into the initial trabecular bone. Sections were studied stained (double heavy metal) and unstained.

Effects of a single dose of fluoride on calcium metabolism.

Fluoride 27 mg was given perorally to 14 subjects. It was found that the serum fluoride concentration increased followed by a decrease to normal levels during 24 h. Serum concentrations of calcium and phosphate decreased initially whereas those of serum immunoreactive parathyroid hormone increased. After 24 h the measured quantities were within normal limits. The results are discussed with reference to mineralization of hard tissues and to fluoride treatment of osteoporotic patients.