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At least 577 records · Page 32Linked to original sources
PubMed2003

Growth hormone increases bone mineral content in postmenopausal osteoporosis: a randomized placebo-controlled trial.

Eighty osteoporotic, postmenopausal women, 50-70 years of age, with ongoing estrogen therapy (HRT), were randomized to recombinant human growth hormone (GH), 1.0 U or 2.5 U/day, subcutaneous, versus placebo. This study was double-blinded and lasted for 18 months. The placebo group then stopped the injections, but both GH groups continued for a total of 3 years with GH and followed for 5 years. Calcium (750 mg) and vitamin D (400 U) were given to all patients. Bone mineral density and bone mineral content were measured with DXA. At 18 months, when the double-blind phase was terminated, total body bone mineral content was highest in the GH 2.5 U group (p = 0.04 vs. placebo). At 3 years, when GH was discontinued, total body and femoral neck bone mineral content had increased in both GH-treated groups (NS between groups). At 4-year follow-up, total body and lumbar spine bone mineral content increased 5% and 14%, respectively, for GH 2.5 U (p = 0.01 and p = 0.0006 vs. placebo). Femoral neck bone mineral density increased 5% and bone mineral content 13% for GH 2.5 U (p = 0.01 vs. GH 1.0 U). At 5-year follow-up, no differences in bone mineral density or bone mineral content were seen between groups. Bone markers showed increased turnover. Three fractures occurred in the GH 1.0 U group. No subjects dropped out. Side effects were rare. In conclusion, bone mineral content increased to 14% with GH treatment on top of HRT and calcium/vitamin D in postmenopausal women with osteoporosis. There seems to be a delayed, extended, and dose-dependent effect of GH on bone. Thus, GH could be used as an anabolic agent in osteoporosis.

Aged↗
PubMed1998

Bone mineral density in children with myelomeningocele.

BACKGROUND: Difficulties with ambulation in patients with myelomeningocele often lead to physical inactivity, osteoporosis, and subsequent development of pathologic fractures. OBJECTIVE: The purpose of this study was to examine bone mineral density and biochemical markers of bone metabolism in patients with myelomeningocele. DESIGN AND METHODS: A total of 35 patients between 6 and 19 years of age with myelomeningocele (ambulatory and nonambulatory) were randomly chosen at the Texas Scottish Rite Hospital for Children. We measured bone mineral density of the distal radius in these patients using single photon absorptiometry and measured the biochemical markers of bone metabolism including parathyroid hormone, 1,25 vitamin D, osteocalcin, urinary pyridinolines/deoxypyridinolines, and urinary calcium excretion. RESULTS: Bone mineral density of the distal radius in the patients with myelomeningocele was approximately 1 to 2 standard deviation units below the mean of the normal population. There were no significant differences between ambulators and nonambulators. However, bone mineral density of the 8 patients who suffered multiple fractures (19) was significantly lower than that for those remaining patients without fractures. Elevated urinary pyridinoline levels, which indicate elevated bone reabsorption, were found more frequently in both non- and limited ambulators than in full-time ambulators. Urinary calcium excretion also was greater than twofold higher in nonambulatory patients versus ambulatory patients. There were no other differences in the biochemical markers of bone metabolism (osteocalcin, parathyroid hormone, 1,25 vitamin D, and urinary deoxypyridinolines) between ambulators and nonambulators. Bone mineral density rises in normal growing children 6 to 19 years of age. When the boys and girls were considered separately, bone mineral density rises with age in boys, but not in girls. CONCLUSION: Patients with myelomeningocele have decreased bone mineral density and are at risk of suffering pathologic bone fractures. The measurement of bone mineral density may help to identify those patients at greatest risk of suffering multiple fractures. The urinary calcium excretion of nonambulators was higher than that of ambulators and likely contributes to their decreased bone mineral density. Bone mineral density increases with age in boys, but not in girls.

Adolescent↗
PubMed1992

Long-term excess of endogenous calcitonin in patients with medullary thyroid carcinoma does not affect bone mineral density.

In a cross-sectional study of 39 patients with medullary thyroid carcinoma (MTC), we have investigated the effects of long-term calcitonin excess on bone mineral density. Bone mineral density was measured by dual X-ray absorptiometry at the lumbar spine between the second and fourth vertebra and by single photon absorptiometry at the distal forearm. The mean observation time of each patient between diagnosis of tumour and measurement of bone mineral density was 62.4 months (range 1-158 months). The mean calcitonin serum level was 14.4 micrograms/l at the time of measurement of bone mineral density. All patients were substituted with 150-200 micrograms L-thyroxine daily. At both sites, the mean bone mineral densities of all patients with MTC were not significantly different from controls. Patients with normal calcitonin levels (below 0.2 micrograms/l) after treatment had a normal bone mineral density of the spine but significantly (P less than 0.05) reduced bone mineral density values of the forearm. This was due to the decreased body surface areas of patients in this subgroup. Patients with multiple endocrine neoplasia type IIa had significantly higher bone mineral densities. Other bone-influencing factors, such as postoperative hypoparathyroidism, calcium intake, diarrhoea, menopause, tumour stage, previous anti-tumour treatment, or thyroxine substitution dose, did not affect bone mineral density. We thus conclude that long-term excess of endogenous calcitonin in patients with MTC has no positive effect on bone mineral density.

Absorptiometry, Photon↗
PubMed1999

Intermittent inhibition of dentin mineralization of rat incisors under continual infusion of 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP) using a subcutaneous mini osmotic pump.

The inhibitory effect of the continual administration of 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP) (8 mgP/kg/day) through a mini osmotic pump on dentin mineralization was examined in relation to the diurnal rhythm of the rat and compared with that of daily injections of same amounts of HEBP known to inhibit dentin mineralization. After daily injections of HEBP, a series of alternating rows of mineralized and non-mineralized dentin islands appeared in the newly formed portion of the crown-analogue of rat incisors. A similar phenomenon occurred under the continual administration of HEBP in rats raised either under regular environmental photofraction or constant lighting conditions. The average distance between the adjacent mineralized dentin islands was 521.0 +/- 51.3 microns in the injected rats. After continual HEBP administration, this was 426.0 +/- 13.2 microns and 416.5 +/- 19.4 microns under ordinary photofraction and constant light, respectively. Although the pattern of individual mineralized dentin islands tended to become irregular in nocturnal rats, no statistical difference was noted between the two values. Rows of mineralized and non-mineralized dentin islands also appeared in the root analogue dentin. No sign of the intermittent inhibition of mineralization was recognized in mesodermal hard tissues other than dentin in the HEBP-affected animals. These data implicate the presence of intrinsic cycles in dentin mineralization at the growing end of rat incisors independent of environmental photofraction as well as the ameloblast function.

Animals↗
PubMed2000

Localization of alkaline phosphatase and osteopontin during matrix mineralization in the developing cartilage of coccygeal vertebrae.

We observed the manner in which alkaline phosphatase (ALPase) and osteopontin were localized in the cartilage and intramembranous bone of coccygeal vertebrae during matrix mineralization, shedding considerable light on the manner in which they develop. In the cartilage matrix of coccygeal vertebrae, we observed the localization of ALPase activity in the boundary of the proliferative and the hypertrophic zones. Granular nodules of mineralization were consistently found in the boundary of both zones, and increased in size when close to the hypertrophic zone. While osteopontin was rarely present in the early stages of mineralization, its localization along the margins of mineralized matrices in the hypertrophic zone was prominent. In contrast to cartilage, mineralized nodules in the intramembranous bone in the mid-portion of the vertebra displayed osteopontin-immunoreactivity, indicating its early synthesis and subsequent accumulation to early-stage mineralized nodules. When blood vessels, accompanied by osteoblastic and osteoclastic cell populations, invaded the cartilage, osteopontin was localized in the lower region of the hypertrophic zone, despite its maintaining the localization of ALPase and early-stage mineralization. Thus, our investigation demonstrated ALPase activity consistent with early-stage mineralization in the cartilage matrix. However, the fact that osteopontin-localization could not be pinpointed might account for its multifunctionality as concerns both the regulation of mineralization and the attachment of migrating osteogenic and osteoclastic cells to the mineralized matrix.

Acid Phosphatase↗
PubMed1995

A prospective study on mortality among Japanese coal miners.

We conducted a prospective study to clarify mortality patterns among Japanese coal miners in a former coal mining area. Subjects included 1,796 coal miners and 4,022 non-coal-miners, who were identified by a mail survey between 1987 and 1989, and then followed up from the date of the survey to April 30th, 1994. We applied Cox's proportional hazards model to compare the mortalities between coal miners and non-coal-miners. Among the coal miners, significantly high risk ratios were observed in all causes of death (risk ratio = 1.4, p < 0.05) and all malignant neoplasms (risk ratio = 1.5, p < 0.05). Risk ratios for all causes of death and all malignant neoplasms also rose with the length of experience in coal mining. Analysis of the results for sites of cancer showed that coal miners had high risk ratios for stomach cancer (risk ratio = 1.6), liver cancer (risk ratio = 1.4) and lung cancer (risk ratio = 1.6), though these ratios were not statistically significant. When the risk ratio for lung cancer was analyzed according to the length of experience in coal mining, coal miners with at least 15 years' experience had a significantly high risk ratio (risk ratio = 2.4, p < 0.05), though coal miners with less than 15 years' experience had almost the same risk as non-coal-miners.

Adult↗
PubMed2002

BMP-6 accelerates both chondrogenesis and mineral maturation in differentiating chick limb-bud mesenchymal cell cultures.

Chick limb-bud mesenchymal cells, plated in micromass culture, differentiate in vitro to form a cartilaginous structure analogous to the epiphyseal growth plate. When inorganic phosphate, Pi, is included in the medium such that the total Pi concentration is 4 mM, apatite mineral precipitates around the "hypertrophic" chondrocytes. These hypertrophic chondrocytes are characterized by their increased expression of type X collagen, alkaline phosphatase activity, and apoptosis, as well as by the ability of their extracellular matrices to support mineral deposition. Under standard mineralizing conditions (0.8 x 10(6)cells/micromass; 4 mM Pi, 1.3 mM Ca(2+), 10% FCS, and antibiotics) mineralization does not commence until day 14-16. Based on the ability of bone morphogenic protein 6 (BMP-6) to stimulate chondrocyte maturation in other systems, 100 ng/ml BMP-6 was added to chick limb-bud mesenchymal cell cultures 2 and 5 days after plating, and the effects of this addition on mineral accretion and the characteristics of the mineral and matrix determined. Addition of BMP-6 accelerated the differentiation of the mesenchymal cells to hypertrophic chondrocytes. In the presence of BMP-6 added on both days 2 and 5, mineralization (assessed on basis of (45)Ca uptake) commenced by day 12. Fourier transform infrared imaging (FTIRI) was used to monitor the mineral content and mineral crystallinity as a function of time from day 9 to 21 in cultures with and without exogenous BMP-6. While BMP-6 accelerated the rate of mineral accretion, and the crystals that were formed in the BMP-6 cultures were initially more mature, by day 21 the crystal size distribution in experimental and control cultures were not significantly different. This study, the first to report the detailed application of FTIRI to cell cultures, indicates the importance of the extracellular matrix in the control of crystal maturation.

Alkaline Phosphatase↗
PubMed1992

Mineral-matrix interactions in bone and cartilage.

Mineral-matrix interactions regulate the process of hydroxyapatite formation in bones and teeth. In mineralizing tissues, many anionic macromolecules bind to mineral. By means of this binding, such molecules are able to regulate the size and shape of the mineral crystals, determine the site of initial crystal deposition, and determine the type of mineral crystals deposited. Collagen, which provides a template for hydroxyapatite deposition; extracellular matrix vesicles, which provide a protected environment for crystal deposition; and noncollagenous matrix proteins that have high affinities for hydroxyapatite have all been shown to affect mineralization in vitro. Some of the noncollagenous proteins have been shown to be capable of promoting and inhibiting mineral formation and growth, depending on their concentration and whether they are immobilized or free in solution. This review surveys the current understanding of mineral-matrix relationships involved in endochondral, intramembranous, and appositional bone formation, outlining the way in which mineral deposition is controlled in mammalian calcified tissues. The structural basis for the interaction of the matrix molecules with hydroxyapatite is presented, as is the in vitro and in situ data implicating the matrix molecules that interact with hydroxyapatite to control mineralization.

Bone Matrix↗
PubMed2002

Bone material properties and mineral matrix contributions to fracture risk or age in women and men.

The strength of bone is related to its mass and geometry, but also to the physical properties of the tissue itself. Bone tissue is composed primarily of collagen and mineral, each of which changes with age, and each of which can be affected by pharmaceutical treatments designed to prevent or reverse the loss of bone. With age, there is a decrease in collagen content, which is associated with an increased mean tissue mineralization, but there is no difference in cross-link levels compared to younger adult bone. In osteoporosis, however, there is a decrease in the reducible collagen cross-links without an alteration in collagen concentration; this would tend to increase bone fragility. In older people, the mean tissue age (MTA) increases, causing the tissue to become more highly mineralized. The increased bone turnover following menopause may reduce global MTA, and would reduce overall tissue mineralization. Bone strength and toughness are positively correlated to bone mineral content, but when bone tissue becomes too highly mineralized, it tends to become brittle. This reduces its toughness, and makes it more prone to fracture from repeated loads and accumulated microcracking. Most approved pharmaceutical treatments for osteoporosis suppress bone turnover, increasing MTA and mineralization of the tissue. This might have either or both of two effects. It could increase bone volume from refilling of the remodeling space, reducing the risk for fracture. Alternatively, the increased MTA could increase the propensity to develop microcracks, and reduce the toughness of bone, making it more likely to fracture. There may also be changes in the morphology of the mineral crystals that could affect the homogeneity of the tissue and impact mechanical properties. These changes might have large positive or negative effects on fracture incidence, and could contribute to the paradox that both large and small increases in density have about the same effect on fracture risk. Bone mineral density measured by DXA does not discriminate between density differences caused by volume changes, and those caused by changes in mineralization. As such, it does not entirely reflect material property changes in aging or osteoporotic bone that contribute to bone's risk for fracture.

Journal Article↗
PubMed1991

[Clinical study of concerning factors of decreased bone mineral content in hemodialysis patients].

We investigated bone mineral content and factors related to decreased bone mineral content in maintenance hemodialysis patients. Bone mineral contents, epsilon GS/D, radius-bone mineral content (R-BMC) and L3-bone mineral density (L3-BMD), were measured with a micro densitometer, a bone mineral analyzer and a dual energy quantative CT scanner, and relative bone mineral contents (% epsilon GS/D, %R-BMC and %L3-BMD) were calculated respectively. The desferrioaxmine infusion test was carried out for diagnosis of aluminium associated bone disease, and an elevated level of aluminium (delta aluminium) was observed. There was reverse correlation between epsilon GS/D and age in female hemodialysis patients. Serum bone gla protein, alkaline phosphatase and PTH-C levels were high in cases with increased epsilon GS/D and who were receiving little medication with activated Vitamin D in maintenance hemodialysis patients. A correlation was observed between delta aluminium and total medication of aluminium hydroxide-gel. Hemodialysis patients with bone pain had long term hemodialysis, high total medication of aluminium and high aluminium. Relative bone mineral contents (% epsilon GS/D, %R-BMD) were useful for estimating bone mineral content in hemodialysis patients. Hemodialysis patients were divided in four groups by PTH-C and delta aluminium levels as follow, 1) normal, 2) aluminium associated bone disease, 3) secondary hyperparathyroidism with aluminium associated bone disease, 4) secondary hyperparathyroidism. These results indicate that secondary hyperparathyroidism, and medication with aluminium may play a role in decreased bone mineral content in hemodialysis patients, and menopause may also be an important factor in female hemodialysis patients.

Adult↗
PubMed1997

Estimating lung cancer mortality from residential radon using data for low exposures of miners.

Some recent estimates of lung cancer risk from exposure to radon progeny in homes have been based on models developed from a pooled analysis of 11 cohorts of underground miners exposed to radon. While some miners were exposed to over 10,000 working level months (WLM), mean exposure among exposed miners was 162 WLM, about 10 times the exposure from lifetime residence in an average house and about three times the exposure from lifetime residence at the "action level" suggested by the U.S. Environmental Protection Agency. The extrapolation of lung cancer risk from the higher exposures in the miners to the generally lower exposures in the home is a substantial source of uncertainty in the assessment of the risk of indoor radon. Using the pooled data for the miners, analyses of lung cancer risk were carried out on data restricted to lower exposures, either <50 WLM or <100 WLM. In the pooled data, there were 115 lung cancer cases among workers with no occupational WLM exposure and 2,674 among exposed miners, with 353 and 562 lung cancer cases in miners with <50 WLM and <100 WLM, respectively. Relative risks (RRs) for categories of WLM based on deciles exhibited a statistically significant increasing trend with exposure in each of the restricted data sets. In the restricted data, there was little evidence of departures from a linear excess relative risk model in cumulative exposure, although power to assess alternative exposure-response trends was limited. The general patterns of declining excess RR per WLM with attained age, time since exposure and exposure rate seen in the unrestricted data were similar to the patterns found in the restricted data. Risk models based on the unrestricted data for miners provided an excellent fit to the restricted data, suggesting substantial internal validity in the projection of risk from miners with high exposures to those with low exposures. Estimates of attributable risk for lung cancer (10-14%) in the U.S. from residential radon based on models from the unrestricted data were similar to estimates based on the data for miners receiving low exposures.

Air Pollutants, Radioactive↗
PubMed1997

Cyclosporin A and its non-immunosuppressive derivative exhibit a differential effect on cell-mediated mineralization in culture.

Chronic immunosuppressive treatment with cyclosporin A (CsA) is associated with decreased bone density. However, in culture, CsA inhibits osteoclast differentiation and bone resorption. This raises the question as to whether CsA also affects osteoblast function. Immunophilin, one of the CsA-binding cyclophilins that is implicated in the immunosuppressive action of CsA via calcineurin, is a peptidyl prolyl cis-trans isomerase (PPl). CsA also binds a mitochondrial membrane PPl which is implicated in controlling permeability transition pores. Therefore, in the present study we tested the effect of CsA on cell mediated mineralization in parallel with mitochondrial rhodamine retention as an indicator of mitochondrial membrane potential Rat marrow stromal cells were grown in dexamethasone (DEX) medium to stimulate mineralization in culture, and CsA was added to various cultures using different treatment schedules. Low dose (0.1 microM) CsA inhibited mineralization, compared to controls, when present in the cultures during days 3-11 of DEX stimulation. Contrarily, high dose CsA (1.0 microM) resisted the inhibitory effect of the low dose. SDZ 220-384 (SDZ), a non-immunosuppressive derivative of CsA which is known, like CsA, to bind to mitochondrial cyclophilin but does not inhibit calcineurin, was also tested. Both high and low doses of SDZ decreased mineralization when present in the cultures from day 3 or from day 0. The similar effect of the low CsA dose and SDZ on mineralization is in accord with their ability to block permeability transition pores. The differential effect, on day 21 mineralization, between high CsA dose and SDZ took place in parallel to their opposing effects on mitochondrial membrane potential. On days 4-8, mitochondrial rhodamine retention was higher under CsA than under SDZ. Under these conditions there was no significant difference between the effects of these drugs on cell proliferation measured on day 11; there was a minor decrease in specific alkaline phosphatase activity by SDZ, too small to explain the extent of mineralization inhibition by SDZ. These results suggest that permeability transition pores might be involved in controlling mineralization. Unlike SDZ, CsA exhibits an additional effect on the mitochondrial membrane potential and on mineralization when applied at a high dose on day 3. Therefore identifying the additional activity of high dose CsA, which is missing in SDZ, may be beneficial. Such activity is expected to resist changes in rhodamine retention and decreased mineralization induced by SDZ, and yet enable preservation of immunosuppressive activity of CsA.

Alkaline Phosphatase↗
PubMed1998

The pathogenic 16/6 idiotype in patients with silica associated systemic lupus erythematosus (SLE) and uranium miners with increased risk for development of SLE.

OBJECTIVE: To investigate the prevalence of the 16/6 idiotype (16/6 Id), a major cross reactive idiotype of anti-DNA antibodies involved in the pathogenesis of experimental lupus, in subjects with an exogenous risk for the development of systemic lupus erythematosus (SLE). METHODS: The titer of 16/6 Id was determined by ELISA in sera of uranium miners exposed to heavy quartz dust: 15 developed definite and 12 probable SLE, 34 had clinical symptoms, and 27 had only serological signs (medium to high titer anti-dsDNA antibodies) of possible connective tissue disease (CTD) development. RESULTS: The prevalence of 16/6 Id was higher in all groups compared to healthy blood donors. It was 18.5% in miners with SLE (definite and probable) and 22.2-26.5% in miners with clinical and/or serological signs for developing CTD. All 16/6 Id positive miners were positive for anti-dsDNA antibodies and other autoantibodies associated with CTD. The prevalence of 16/6 Id in anti-dsDNA positive miners correlated slightly with CTD/SLE symptoms: 55.6% in patients with SLE, 47.4% in miners with possible CTD/SLE, and 22.2% in miners without CTD symptoms. Further, at short term followup, disease progressed in 2 miners of the 16/6 Id positive, but not in 16/6 Id negative miners. CONCLUSION: The detection of 16/6 Id in miners exposed to quartz dust may indicate a higher risk for development of SLE, warranting further studies of the role of 16/6 Id in the development of SLE in a cohort with the same sex, ethnicity, geographic region, and occupation.

Aged↗
PubMed1998

[Bone mineral density in nursing infants and young children (0-4 years old) at the level of the lumbar spine. The normal patterns].

OBJECTIVE: A cross-sectional study of bone mineral density was conducted in a normal population of children with ages ranging from the neonatal period to 4 years with the aim of establishing normal bone mineral density (BMD) patterns. PATIENTS AND METHODS: Bone mineral content density was measured by dual-energy X-ray absorptiometry at the level of the lumbar spine (L2-L4) in 147 normal children (69 boys, 78 girls, age range: 15 days to 4 years) randomly selected from the urban area of Barcelona. RESULTS: Weight, length and height were in the normal age distribution. Bone mineral content values were corrected by the vertebral surface area scanned and expressed as bone mineral density values (grams of hydroxyapatite/cm2). Bone mineral density values increased progressively from birth to 4 years and values were similar in both sexes. A statistically significant correlation was found between BMD values and age (r = 0.82, p < 0.001), weight (r = 0.87, p < 0.001) and length or height (r = 0.79, p < 0.001). Lumbar bone mineral density values increased annually, but the periods of higher increase were observed during the first 2 years of life. Bone mineral density values showed a similar pattern to height growth velocity. CONCLUSIONS: We report normative data for bone mineral density at the lumbar spine in our normally-growing pediatric population from the neonatal period to 4 years. These data provide a tool for the study and follow-up of pediatric populations at risk for low bone mineralization during early childhood.

Absorptiometry, Photon↗
PubMed2026

Transformation of antibiotics mediated by iron-bearing minerals: A review.

Iron-bearing minerals are ubiquitous in water, sediments and soil, where their surface chemical properties and redox activity can play an important role in degradation of trace antibiotics. This review systematically summarizes the roles of various iron-bearing minerals in chemical transformation and microbial degradation of antibiotics and reaction mechanisms involved, and refines the critical idea for iron-driven control of antibiotics with trace level in natural environment. Overall, antibiotics removal in the presence of iron-bearing minerals involves combination of adsorption, surface oxidative degradation, photo-induced degradation, Fenton-like reaction and microbial degradation. Adsorption of antibiotics by Fe(III)-minerals involves electrostatic interaction, complexation, H-bonding, &#x3c0;-&#x3c0; interaction and hydrophobic interaction. Adsorbed antibiotics form complexes with Fe(III)-minerals, undergoing electron transfer to generate radical intermediates, subsequently generating final products through hydroxylation, dealkylation, and deamination. Additionally, Fe(III)-minerals can be excited to produce electrons and holes under sunlight and to produce antibiotics-degrading hydroxyl radical through O2 reduction, H2O oxidation and ligand-to-metal charge transfer. Reduced iron minerals can activate oxygen to participate in Fenton-like degradation reactions. Finally, antibiotics are mainly removed by bio-driven Fenton reaction and direct enzyme biodegradation. The presence of iron-bearing minerals can promote antibiotics microbial degradation by providing nutrients for microorganisms or by changing microbial activity and microbial community structure. Existing problems and future research directions are identified. New insights for application of iron-bearing minerals in transformation of antibiotics are proposed. The work aims to suggest new methods and insights for pollution control and remediation of emerging contaminants including trace antibiotics in the natural environment.

Anti-Bacterial Agents↗
PubMed1988

Differences in the kinetics of the mineralization process in endochondral and intramembranous osteogenesis in human fetal development.

About 300 samples of bone tissue from femoral diaphyses and from parietal bones of calvaria were collected from human fetuses aged from 6-8 to 40-41 weeks in order to compare the kinetics of the mineralization process in endochondral and intramembranous bone formation. The crystallinity of bone mineral was evaluated by the method based on electron spin resonance (ESR) spectrometry, and mineral content was measured after ashing of the samples. Highly significant differences in the kinetics of deposition of mineral (ash content) and maturation of deposited mineral (crystallinity coefficient) were found between parietal bones and femoral diaphyses in the course of fetal development. In the early stages of development (6-8 to 10-12 weeks), the content of mineral and its crystallinity in parietal bones were significantly lower than in femoral diaphyses. In the parietal bones a gradual increase in both values was observed until they reached a plateau at the age of 30 weeks. On the other hand, in femoral diaphyses of 6-8-week-old fetuses mineral content was high and deposited mineral showed a high degree of crystallinity. Both these values did not change significantly until birth. The differences in kinetics of the mineralization process between the weight-bearing bones and bones that are not exposed to the influence of strong external forces are most probably genetically conditioned. The collected data supply embryological information and might be used in the future for evaluation of pathologic changes in skeletal development.

Embryonic and Fetal Development↗
PubMed1994

The loci of mineral in turkey leg tendon as seen by atomic force microscope and electron microscopy.

Transmission electron micrographs of fully mineralized turkey leg tendon in cross-section show the ultrastructure to be more complex than has been previously described. The mineral is divided into two regions. Needlelike-appearing crystallites fill the extrafibrillar volume whereas only platelike crystallites are found within the fibrils. When the specimen is tilted through a large angle, some of the needlelike-appearing crystallites are replaced by platelets, suggesting that the needlelike crystallites are platelets viewed on edge. If so, these platelets have their broad face roughly parallel to the fibril surface and thereby the fibril axis, where the intrafibrillar platelets are steeply inclined to the fibril axis. The projection of the intrafibrillar platelets is perpendicular to the fibril axis. The extrafibrillar volume is at least 60% of the total, the fibrils occupying 40%. More of the mineral appears to be extrafibrillar than within the fibrils. Micrographs of the mineralized tendon in thickness show both needlelike-appearing and platelet crystallites. Stereoscopic views show that the needlelike-appearing crystallites do not have a preferred orientation. From the two-dimensional Fourier transform of a selected area of the cross-sectional image, the platelike crystallites have an average dimension of 58 nm. The needlelike-appearing crystallites have an average thickness of 7 nm. The maximum length is at least 90 nm. Atomic force microscopy (AFM) of unstained, unmineralized turkey leg tendon shows collagen fibrils very much like shadow replicas of collagen in electron micrographs. AFM images of the mineralized tendon show only an occasional fibril. Mineral crystallites are not visible. Because the collagen is within the fibrils, the extrafibrillar mineral must be embedded in noncollagenous organic matter. When the tissue is demineralized, the collagen fibrils are exposed. The structure as revealed by the two modalities is a composite material in which each component is itself a composite. Determination of the properties of the mineralized tendon from the properties of its elements is more difficult than considering the tendon to be just mineral-filled collagen.

Animals↗
PubMed2004

X-ray microtomographic study of mineral concentration distribution in deciduous enamel.

OBJECTIVE: To determine the mineral concentration distribution in deciduous enamel by quantitative X-ray microtomography (XMT). DESIGN: Tooth rods ( approximately 2 mm x 2 mm) were removed from the mid-buccal region of 11 deciduous molars. Three XMT slices were taken at 1.5, 2.0 and 2.5 mm from the amelocemental junction. The distribution and variation in mineral concentration of enamel were studied from the XMT images. RESULTS: The mean mineral concentration for all the teeth was 2.81 (S.D. = 0.065) g cm(-3). There was no notable difference in the mean mineral concentration values between the three XMT slices of each tooth. However, there was up to 8% variation between different teeth (2.69-2.92 g cm(-3)). Gradients of increasing mineral concentration from the amelodentinal junction (ADJ) to the external surface were found, ranging from 0.08 to 0.60 mg cm(-3) microm(-1) with a mean of 0.366 mg cm(-3) microm(-1). The mineral concentration gradients in the occlusal slices were steeper than those in the cervical slices. The difference in mineral concentration between the inner and outer enamel ranged from 1.5 to 8.7%. CONCLUSION: In view of the large variation in both the means and the gradients of mineral concentration in deciduous molars, the mineral distribution of each experimental tooth should be measured as baseline data in studies of caries progression.

Dental Enamel↗