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PubMed1999

An electron probe x-ray microanalytical study of dentine minerals in sucrose-fed or glucocorticoid-medicated rats.

A high sucrose diet and glucocorticoid medication reduced dentine formation in molars of growing rats. This study was undertaken to determine whether the treatment schedules could have produced commensurate reductions in dentine minerals, and the particular concentrations of calcium (Ca) and phosphorus (P). Forty Spraque-Dawley rats were weaned at the age of 3 weeks. Tetracycline was injected i.p. to produce a fluorescent line which demarcated the preweaning from the postweaning dentine. The animals were then divided into two groups. Control rats were fed a commercial rat chow, test animals were fed a 43% sucrose diet. Half the animals in each group were also subjected to surgical implantation (s.c.) of cortisone pellets which released 0.42 mg into the circulation over a 24-hour period. At the end of the 6 week trials rats were killed and the mandibles were defleshed and prepared for electron probe microanalyzer. Each animal served as its own control, as the content of Ca, P, and total minerals were analyzed in the pre- and postweaning regions of dentine. During the preweaning there were no differences between the groups in any minerals. There was a slight reduction of minerals during the postweaning compared with the preweaning. During the postweaning, the sucrose diet significantly reduced the amount of Ca, P, and total minerals compared with the preweaning. During the postweaning, the sucrose diet reduced Ca compared with glucocorticoid medication and total minerals compared with other groups. On the contrary glucocorticoid medication seemed to compensate the reduction of minerals induced by the sucrose diet.

Animals↗
PubMed2005

Bone mineral measurements of subchondral and trabecular bone in healthy and osteoporotic rabbits.

INTRODUCTION: Experimental models of osteoporosis in rabbits are useful to investigate anabolic agents because this animal has a fast bone turnover with predominant remodelling over the modelling processes. For that purpose, it is necessary to characterize the densitometric values of each type of bony tissue. OBJECTIVE: To determine areal bone mass measurement in the spine and in trabecular, cortical and subchondral bone of the knee in healthy and osteoporotic rabbits. DESIGN: Bone mineral content and bone mineral density were measured in lumbar spine, global knee, and subchondral and cortical bone of the knee with dual energy X-ray absorptiometry using a Hologic QDR-1000/W densitometer in 29 skeletally mature female healthy New Zealand rabbits. Ten rabbits underwent triplicate scans for evaluation of the effect of repositioning. Osteoporosis was experimentally induced in 15 rabbits by bilateral ovariectomy and postoperative corticosteroid treatment for 4 weeks. Identical dual energy X-ray absorptiometry (DXA) studies were performed thereafter. RESULTS: Mean values of bone mineral content at the lumbar spine, global knee, subchondral bone and cortical tibial metaphysis were: 1934+/-217 mg, 878+/-83 mg, 149+/-14 mg and 29+/-7.0 mg, respectively. The mean values of bone mineral density at the same regions were: 298+/-24 mg/cm(2), 455+/-32 mg/cm(2), 617+/-60 mg/cm(2) and 678+/-163 mg/cm(2), respectively. Bone mineral content and bone density of healthy rabbits followed a normal distribution at the four skeletal regions studied. Precision after triplicate repositioning yielded a coefficient of variation ranging from 2.6% to 3.8%. The least significant change ranged between 7.3% and 10.7%. Bone mineral density measured at the four different skeletal regions correlated significantly. Bone mineral density in osteoporotic rabbits was significantly lower in the four regions studied than that in controls, rendering a T-score of, respectively, -2.0+/-1.1 in the lumbar spine, -2.2+/-2.1 in the global knee, -1.9+/-0.6 in the subchondral bone, and -5.7+/-3.1 in the cortical tibia (P<0.05). CONCLUSIONS: DXA is a reliable and precise method to evaluate the bone mass in rabbits. Our results also suggest that subchondral bone is a bone of mixed densitometric characteristics with marked cortical bone predominance.

Absorptiometry, Photon↗
PubMed2002

Small bowel resection in the rat: the effect upon bone and mineral metabolism.

BACKGROUND AND AIMS: We analyzed bone and mineral metabolism after long-segment small bowel resection in the rat to detect functional and morphological alterations and to determine the development of osteopathy. METHODS: Twelve-week-old male Lewis rats were randomized into short (8-week) or long (16-week) follow-up groups. Sham operation, resection of the proximal third of the small bowel, resection of the distal third of the bowel and resection of the entire jejunum and ileum were carried out. Nineteen days before the end of the experiment the animals were transferred into a metabolic cage to analyze weight gain/loss, food intake, and fecal excretion/24 h. At the end of the experiment the animals were killed; blood samples and bowel and bone specimens were collected, length, weight, volume, density, mineral content, and fracturing energy were determined, and bone histology was examined. The calcium/phosphorus ratio, nonmineralized tissue content and the ratio fracturing energy/mean bone density were calculated. RESULTS: After 8 weeks there were significant differences to the control group in body weight, weight gain, food efficiency, femur length, weight, volume, mineral content, mineral density, fracturing energy per bone volume, and bone density but not in bone calcium or magnesium. After 16 weeks there were differences in body weight, weight gain, food efficiency, femur length, weight, volume, bone mineral content and density, bone minerals, and nonmineralized tissue but not in fracturing energy; the average values of all these parameters were lower in the resected groups, and lowest in the group after resection of the entire jejunum and ileum. Bone histology showed a reduction in trabecular bone mass after long-segment small bowel resection. CONCLUSIONS: Long-segment small bowel resection causes a significant loss of body weight despite of a comparable mean chow ingestion resulting in a significant decreased food efficiency. We conclude that there is no inverse relationship of bone calcium content and the fracture risk, and that there is no severe mineralization defect after long-segment small bowel resection.

Animals↗
PubMed1998

Changes in mineral composition of rabbit corneas after alkali burn.

BACKGROUND: Mineral balance is essential for maintaining corneal transparency. In preliminary investigations, we found alterations of mineral concentrations in the human cornea after chemical burns. In this prospective study the mineral content of the rabbit cornea was quantified after experimental alkali burns. METHODS: Thirty-two eyes of rabbits were burnt for 30 s with 1 M NaOH. A short period of saline rinsing followed, but no further therapy was given. The eyes of 20 healthy rabbits served as a control. We measured the water content by weighing the cornea before and after drying. The mineral content of the cornea was determined in different stromal layers using energy-dispersive X-ray analysis in the scanning electron microscope. Groups of eight rabbits were examined on days 0, 1, 4 and 8 after the experimental burns. RESULTS: After alkali burns the mineral composition of the corneal stroma changed considerably. Sodium was present in high concentrations immediately after burning, up to 708 mmol/kg dry weight, and returned to normal on day eight. Chlorine increased significantly throughout the whole period. Sulphur concentrations stayed almost normal, showing only a minute loss of ground substance after alkali burn. A considerable and increasing edema could be concluded from the water content. CONCLUSIONS: Alkali burns resulted in a dramatic change of the corneal mineral content. Therapeutic intervention with appropriate solutions is required to restore and maintain the normal mineral composition of the denuded corneal stroma.

Animals↗
PubMed2005

Differential respirable dust related lung function effects between current and former South African coal miners.

Dust-related dose-response decrements in lung function among coal miners have been reported in several studies, with varying magnitudes across populations. Few studies have compared differences between current and former coal miners. No studies on dose response relationships with lung function have been conducted in South African coal mines, one of the top three producers of coal internationally. The objectives of this study were (1) to describe the relationship between respirable dust exposure and lung function among current and former South African coal miners and to determine whether differential dust related effects were present between these employment categories; (2) to examine dust related dose response relationships, controlling for potential confounding by smoking and a history of tuberculosis (TB). Six hundred and eighty-four current and 188 ex-miners from three bituminous coal mines in Mpumalanga Province were studied. Interviews assessing work histories, smoking profiles and other risk factors were conducted. Work histories were also obtained from company records. Standardised spirometry was performed by trained technicians. Cumulative respirable dust exposure (CDE) estimates were constructed from company-collected sampling and measurements conducted by the researchers. Regression models examined the associations of CDE with per cent predicted FEV(1) and FVC, controlling for smoking, past history of TB and employment status. A statistically significant decline in FEV(1) of 1.1 and 2.2 ml/mg-year/m(3) was found in representative 40-year-old, 1.7-m tall current and former miners, respectively. Significant differences were found between the highest and medium exposure categories. Ex-miners had a lower mean per cent predicted lung function than current miners for each cumulative exposure category, suggesting a "healthy worker" effect. Past history of TB contributed to 21 and 14% declines in per cent predicted FEV(1) and FVC, respectively. Thus, in this cohort, a dose-related decline in lung function was associated with respirable dust exposure, with a magnitude of effect similar to that seen in other studies and important differences between current and former employees. A "healthy worker" effect may have attenuated the magnitude of this relationship. TB was a significant contributor to lung function loss.

Adult↗
PubMed2001

Effect of saliva substitutes on mineral content of demineralized and sound dental enamel.

The aim of this in vitro study was to evaluate the effects of commercially available saliva substitutes on the mineral content of pre-demineralized and sound enamel. From 56 bovine incisors 224 enamel specimens were prepared and hand-polished. The specimens were partially covered with nail varnish (control of sound enamel). In group 1, 112 samples were demineralized (18 days; 37 degrees C; pH 5.0) and a portion of the demineralized area was likewise covered with nail varnish. Subsequently, 16 specimens were exposed (14 days; 37 degrees C) to 10 ml of each of several different saliva substitutes (Artisial; Glandosane; Oralube; Saliva medac), or mouthwash solutions (Biotène; Meridol), respectively. Non-carbonated, fluoride-containing mineral water (Eptinger) was used as control. In group 2, the 112 sound enamel specimens were immersed directly in the solutions (without a demineralization period). After immersion, the specimens were cut perpendicular to the surface, and slabs (110 microns) were ground. Contact microradiographs were obtained and studied with a digital image-analyzing system. A dedicated software (TMR 1.24) was used to calculate the mineral content. Sound enamel (group 2) was significantly demineralized after immersion in Biotène and Glandosane (P < 0.001; Kruskal-Wallis). In group 1, mineral loss after storage in Biotène and Glandosane was significantly increased (P < 0.001), compared with the mineral content after demineralization. All other solutions revealed a significant mineral gain (P < 0.01; Wilcoxon), with the most pronounced effects after use of Oralube and mineral water (both containing calcium, phosphates, and fluorides). Therefore, administration of products similar to the last named can be recommended for dentate patients with salivary gland hypofunction.

Animals↗
PubMed2004

Respiratory symptoms and obstructive lung diseases in iron ore miners: report from the obstructive lung disease in northern Sweden studies.

This is a population-based study on the prevalence of respiratory symptoms assessed by a mail questionnaire. The objective was to examine if work in an iron mine increased the risk of airway symptoms or obstructive diseases. The exposed group consisted of 114 previous or current male miners. Referents, 2472 males from the province, had never been employed by the mining company or worked as miners. Age, smoking and a family history of asthma were considered as possible confounders. The miners had an increased risk for respiratory symptoms (OR=2.2, 95% CI=1.4-3.1) including recurrent wheeze (OR= 2.4, 95% CI= 1.5-3.9), longstanding cough (OR= 1.8, 95% CI = 1.0-3.2), and for physician-diagnosed chronic bronchitis (OR=2.2, 95% CI= 1.0-4.5). Attacks of shortness of breath and asthma manifestations were similar between miners and referents. Higher risks in miners were found particularly among the non-smokers for physician-diagnosed chronic bronchitis (OR=9.2, 95% CI= 3.0-28) and for symptoms as well. A family history of asthma was less common among miners (9.2% vs. 17%, p < 0.05). We conclude that miners in a modern underground iron mine had an increased risk of respiratory symptoms. In contrast to other studies, this increased risk was particularly found in nonsmokers. A family history of asthma may be an important confounder in occupational studies of respiratory diseases.

Adult↗
PubMed1996

A comparison of the mineral content of enamel and dentine in human premolars and enamel pearls measured by X-ray microtomography.

Mineral content gradients in two composite enamel pearls from permanent human upper molars were measured by X-ray microtomography (XMT) at a resolution of 15-30 microns. This non-destructive microscopic technique was used to make 15-microns thick XMT slices with 100-microns separation through one pearl and 250-microns separation through the other. Average mineral contents were calculated from the linear absorption coefficients determined from regions of the XMT slices assuming the inorganic component to be calcium hydroxyapatite. These values were compared with similar XMT studies of coronal enamel and dentine of upper permanent premolars. A mineral content gradient in the pearls, reducing from the enamel surface to the amelodentinal junction, was found; this was similar to that observed in the coronal enamel of the upper premolar. The mineral contents in the surface and deeper enamel regions of the pearl were similar to those observed in premolar enamel. In contrast, the mineral content for the dentine of the pearl was greatest at the amelodentinal junction, i.e. the gradient was in the opposite direction to that observed in premolar dentine. These results suggest that the process of mineralization of the pearl dentine differs from that in permanent control dentine. In addition, gradients in enamel and dentine mineral contents reducing from the tip of the pearl to the base of the pearl were found.

Bicuspid↗
PubMed1991

Mineralized nodule formation in rat bone marrow stromal cell culture without beta-glycerophosphate.

Rat bone marrow stromal cells were cultured in the presence of 10 nM dexamethasone and various concentrations of beta-glycerophosphate. At day 12-15, some nodules consisting of polygonal cells were formed in all culture conditions, and these nodules were mineralized 2-3 days later. beta-Glycerophosphate significantly enhanced nodule formation at concentrations of not less than 5 mM. The mineralized nodules formed in the absence of beta-glycerophosphate were examined using phase-contrast microscopy, undemineralized and demineralized tissue histology, histochemistry for alkaline phosphatase, immunohistochemistry for type I, II, and III collagen, energy dispersive X-ray microanalysis, electron diffraction, and Fourier transform infrared spectroscopy (FT-IR). Mineralized nodules had histological characteristic similar to bone. Cells associated with nodules exhibited high alkaline phosphatase activity, and extracellular matrix of the nodules predominantly consisted of type I collagen. X-Ray microanalysis showed the presence of Ca and P in the mineralized area, and electron diffraction pattern showed the mineral to have apatite crystal structure. Moreover FT-IR indicated that the mineral was a mixture of hydroxyapatite and carbonateapatite. From these observations, it is concluded that the mineralized nodules formed in our culture system are truly bone-like.

Alkaline Phosphatase↗
PubMed1985

Effect of pyrophosphate and two diphosphonates on 45Ca and 32Pi uptake and mineralization by matrix vesicle-enriched fractions and by hydroxyapatite.

Inorganic pyrophosphate (PPi) and two diphosphonates, ethane-1-hydroxy-1, 1-diphosphonate (EHDP) and dichloromethylene diphosphonate (Cl2MDP), were found to inhibit in vitro mineralization induced by matrix vesicle-enriched fractions from chicken epiphyseal cartilage. Inhibitor concentrations from 0.20 to 20 microM caused a dosage-dependent decrease in 45Ca and 32Pi uptake by the vesicle fraction. These inhibitors were also tested in a hydroxyapatite (HA)-seeded system to help distinguish between effects on the mineral vs nonmineral portions of the vesicle fraction. The order of inhibition of the HA-seeded system was EHDP greater than PPi greater than Cl2MDP, except for inhibitor concentrations of 0.20 microM where EHDP was the least inhibitory. This variation may be due to differences in the binding of the inhibitors to HA crystals. In general, inhibition of HA mineralization was greatest during later time periods, whereas vesicle ion uptake was affected more during early stages of incubation. The differential effects of the three inhibitors were most obvious at the 2.0 microM concentration. With PPi substantial inhibition of HA-seeded mineralization was observed even in late stages of the study; in contrast, with time the vesicle fraction overcame this inhibition. This suggests that alkaline phosphatase, an enzyme notably enriched in matrix vesicles, catalyzed the hydrolysis of PPi, reducing its concentration to a level where mineralization could proceed. Our findings show that matrix vesicle-induced mineralization differs significantly from apatite-induced mineralization. The data support the concept that vesicle alkaline phosphatase acts, at least in part, to remove physiological crystal growth inhibitors.

Alkaline Phosphatase↗
PubMedDate not supplied

Strontium alters the complexed acidic phospholipid content of mineralizing tissues.

High dietary strontium induces rickets in both calcium-replete and calcium-deficient animals. To test the hypothesis that strontium directly perturbs complexed acidic phospholipid (CPLX) metabolism and thus, mineralization, the effect of strontium treatment on CPLX formation was studied in solution, in culture, and in growing rats. Synthetic CPLX containing calcium or strontium were found to be similar in composition. Strontium, however, appeared to incorporate into CPLX less avidly than calcium. Mineralizing chick limb bud mesenchymal cell cultures treated with strontium demonstrated a significantly increased CPLX content and decreased 45Ca uptake compared to calcium-treated cultures. Long bones from young growing rats fed a diet supplemented with strontium demonstrated defective mineralization based on radiologic and histologic analyses. Metaphyseal bone of strontium-fed rats contained significantly greater amounts of CPLX and had significantly lower ash weights compared with control bone. Thus, treatment of mineralizing tissues with strontium both in vitro and in vivo resulted in defective mineralization and an accumulation of CPLX. Strontium appears to perturb mineralization, in part, by a direct effect on the cells of mineralizing tissues.

Animals↗
PubMed2005

Influence of high concentrations of mineral salts on production process and NaCl accumulation by Salicornia europaea plants as a constituent of the LSS phototroph link.

Use of halophytes (salt-tolerant vegetation), in a particular vegetable Salicornia europaea plants which are capable of utilizing NaCl in rather high concentrations, is one of possible means of NaCl incorporation into mass exchange of bioregenerative life support systems. In preliminary experiments it was shown that S. europaea plants, basically, could grow on urine pretreated with physicochemical processing and urease-enzyme decomposing of urea with the subsequent ammonia distillation. But at the same time inhibition of the growth process of the plants was observed. The purpose of the given work was to find out the influence of excessive quantities of some mineral elements contained in products of physicochemical processing of urine on the production process and NaCl accumulation by S. europaea plants. As the content of mineral salts in the human liquid wastes (urine) changed within certain limits, two variants of experimental solutions were examined. In the first variant, the concentration of mineral salts was equivalent to the minimum salt content in the urine and was: K - 1.5 g/l, P - 0.5 g/l, S - 0.5 g/l, Mg - 0.07 g/l, Ca - 0.2 g/l. In the second experimental variant, the content of mineral salts corresponded to the maximum salt content in urine and was the following: K - 3.0 g/l, P - 0.7 g/l, S - 1.2 g/l, Mg - 0.2 g/l, Ca - 0.97 g/l. As the control, the Tokarev nutrient solution containing nitrogen in the form of a urea, and the Knop nutrient solution with nitrogen in the nitrate form were used. N quantity in all four variants made up 177 mg/l. Air temperature was 24 degrees C, illumination was continuous. Light intensity was 690 micromoles/m2s of photosynthetically active radiation. NaCl concentration in solutions was 1%. Our researches showed that the dry aboveground biomass of an average plant of the first variant practically did not differ from the control and totaled 11 g. In the second variant, S. europaea productivity decreased and the dry aboveground biomass of an average plant totaled 8 g. The increase of K quantity in the experimental solutions resulted in an elevated content of the element in the plants. The increase of K uptake in the second experimental variant was accompanied by a 30-50% decrease of Na content in comparison with the other variants. Comparative Na content in the other variants was practically identical. N, Mg and P content in the control and experimental variants was also practically identical. The increase of S quantity in the second experimental variant also increased S uptake by the plants. But Ca quantity, accumulated in aboveground plants biomass in the experimental variants was lower than in the control. NaCl uptake by plants, depending on the concentration of mineral salts in the experimental solutions, ranged from 8 g (maximum salt content) up to 15 g (minimum salt content) on a plant growth area that totaled 0.032 m2. Thus, high concentrations of mineral salts simulating the content of mineral salts contained in urine did not result in a significant decrease of S. europaea productivity. The present work also considers the influence of higher light intensity concentrations on productivity and NaCl accumulation by S. europaea plants grown on experimental solutions with high salt content.

Biomass↗
PubMed2004

Age-related changes in physicochemical properties of mineral crystals are related to impaired mechanical function of cortical bone.

The measures of bone mass and architecture need to be supplemented with physicochemical and compositional measures for better assessment of fracture risk. In the current studies, we investigated the effects of physicochemical properties of mineral crystals on tissue and organ-level mechanical function of aging rat cortical bone. Our hypothesis was that age-related changes in physicochemical properties of mineral crystals are related to impaired elastic deformability of cortical bone tissue. Raman microspectroscopy was used to investigate the age-related changes in mineralization (relative amounts of mineral and organic matrix), the substitution of carbonate ions in phosphate positions (type-B carbonate substitution) and mineral crystallinity (the orderliness of crystal lattice) of femurs from young adult (3-month old), middle-aged (8-month old) and aged (24-month old) female Sprague-Dawley rats. Cross-sectional properties, the area and the moment of inertia at the mid-diaphysis, were histomorphometrically quantified and the elastic deformation capacity of femurs was quantified via three-point bending tests. It was observed that the elastic deformation capacity of aged rats was significantly impaired both at the tissue and the organ levels with increasing age. In parallel with this impairment in the elastic deformability and in support of our hypothesis, we found that increasing mineralization, increasing crystallinity and increasing type-B carbonate substitution were significantly correlated with decreasing elastic deformation capacity with age. We conclude that the measure of bone mass needs to be supplemented with measures reflecting the physicochemical status of mineral crystals for improved assessment of fracture susceptibility.

Aging↗
PubMed2004

Differential expression patterns of the dentin matrix proteins during mineralized tissue formation.

Sequential and reciprocal interactions between the oral ectoderm and neural crest-derived mesenchyme are responsible for tooth development. During dentin formation, there are three components that are necessary for proper mineralization, namely, collagen which forms a scaffold, noncollagenous proteins that can specifically bind to the collagen template and function as a mineral nucleator and crystalline calcium phosphate deposited in an ordered manner. It is well established that noncollagenous proteins play an important role during mineralized tissue formation. Here we demonstrate by in situ hybridization techniques that the noncollagenous dentin matrix proteins 1, 2 (DMP1, 2) and dentin sialoprotein (DSP) have characteristic temporal and spatial expression patterns within odontogenic tissues during dentin mineralization. DMP1, DMP2 and DSP mRNA are expressed in the odontoblasts at specific and overlapping time points and are thus presumably used for different functions during dentin formation. In developing rat incisors and molars, high levels of expression of DMP2 mRNA were seen in polarized odontoblasts and preameloblasts, while DSP mRNA was expressed at significantly lower levels and was expressed by highly differentiated odontoblasts. However, their expression was continuously maintained during the mineralization of the organic matrix. In the adult rats, DMP2 and DSP mRNA was also detected in the osteoblasts. The expression of DMP1 mRNA was found to coincide with the start of the mineral nucleation process and gradually decreased during the maturation of the mineralized matrix during odontogenesis. In this study, we have also correlated the expression of these proteins relative to the presence of type I collagen and calcium phosphate crystals. Thus, the temporal and spatial differences between DMP1, DMP2 and DSP might implicate a direct demonstration of the functional difference between these three genes during calcified tissue formation.

Animals↗
PubMed2006

Evidence for lower variability of coronary artery calcium mineral mass measurements by multi-detector computed tomography in a community-based cohort--consequences for progression studies.

PURPOSE: To compare the measurement variability for coronary artery calcium (CAC) measurements using mineral mass compared with a modified Agatston score (AS) or volume score (VS) with multi-detector CT (MDCT) scanning, and to estimate the potential impact of these methods on the design of CAC progression studies. MATERIALS AND METHODS: We studied 162 consecutive subjects (83 women, 79 men, mean age 51 +/- 11 years) from a general Caucasian community-based cohort (Framingham Heart Study) with duplicate runs of prospective electrocardiographically-triggered MDCT scanning. Each scan was independently evaluated for the presence of CAC by four experienced observers who determined a "modified" AS, VS and mineral mass. RESULTS: Of the 162 subjects, CAC was detected in both scans in 69 (42%) and no CAC was detected in either scan in 72 (45%). Calcium scores were low in the 21/162 subjects (12%) for whom CAC was present in one but not the other scan (modified AS < 20 in 20/21 subjects, mean AS 4.6 +/- 1.9). For all three quantification algorithms, the inter- and intraobserver correlation were excellent (r > 0.96). However, the mean interscan variability was significantly different between mineral mass, modified AS, and VS (coefficient of variation 26 +/- 19%, 41 +/- 28% and 34 +/- 25%, respectively; p < 0.04), with significantly smaller mean differences in pair-wise comparisons for mineral mass compared with modified AS (p < 0.002) or with VS (p < 0.03). The amount of CAC but not heart rate was an independent predictor of interscan variability (r = -0.638, -0.614 and -0.577 for AS, VS, and mineral mass, respectively; all p < 0.0001). The decreased interscan variability of mineral mass would allow a sample size reduction of 5.5% compared with modified AS for observational studies of CAC progression and for randomized clinical trials. CONCLUSION: There is significantly reduced interscan variability of CAC measurements with mineral mass compared with the modified AS or VS. However, the measurement variability of all quantification methods is predicted by the amount of CAC and is inversely correlated to the extent of partial volume artifacts. Moreover, the improvement of measurement reproducibility leads to a modest reduction in sample size for observational epidemiological studies or randomized clinical trials to assess the progression of CAC.

Adult↗
PubMed2006

Tensile behavior of cortical bone: dependence of organic matrix material properties on bone mineral content.

A porous composite model is developed to analyze the tensile mechanical properties of cortical bone. The effects of microporosity (volksman's canals, osteocyte lacunae) on the mechanical properties of bone tissue are taken into account. A simple shear lag theory, wherein tensile loads are transferred between overlapped mineral platelets by shearing of the organic matrix, is used to model the reinforcement provided by mineral platelets. It is assumed that the organic matrix is elastic in tension and elastic-perfectly plastic in shear until it fails. When organic matrix shear stresses at the ends of mineral platelets reach their yield values, the stress-strain curve of bone tissue starts to deviate from linear behavior. This is referred as the microscopic yield point. At the point where the stress-strain behavior of bone shows a sharp curvature, the organic phase reaches its shear yield stress value over the entire platelet. This is referred as the macroscopic yield point. It is assumed that after macroscopic yield, mineral platelets cannot contribute to the load bearing capacity of bone and that the mechanical behavior of cortical bone tissue is determined by the organic phase only. Bone fails when the principal stress of the organic matrix is reached. By assuming that mechanical properties of the organic matrix are dependent on bone mineral content below the macroscopic yield point, the model is used to predict the entire tensile mechanical behavior of cortical bone for different mineral contents. It is found that decreased shear yield stresses and organic matrix elastic moduli are required to explain the mechanical behavior of bones with lowered mineral contents. Under these conditions, the predicted values (elastic modulus, 0.002 yield stress and strain, and ultimate stress and strain) are within 15% of experimental data.

Biomechanical Phenomena↗
PubMed2006

Zoledronic acid initiated during the first year of androgen deprivation therapy increases bone mineral density in patients with prostate cancer.

PURPOSE: Androgen deprivation therapy in patients with prostate cancer is associated with bone loss and an increased risk of fractures. Zoledronic acid protects against bone mineral density loss when initiated concurrently with androgen deprivation therapy. We evaluated the effect of zoledronic acid initiated subsequent to androgen deprivation therapy on bone mineral density and biochemical markers of bone turnover. MATERIALS AND METHODS: Patients with prostate cancer without bone metastases who had received androgen deprivation therapy for 12 months or less were randomized to 4 mg zoledronic acid or placebo intravenously every 3 months for 1 year. Patients were stratified according to androgen deprivation therapy duration (less than 6 vs 6 to 12 months). The primary end point was the change in femoral neck and lumbar spine bone mineral density in the 2 groups. The secondary end point was the change in serum bone specific alkaline phosphatase and urine N-telopeptide levels. Total hip bone mineral density was also measured. RESULTS: The 120 patients with prostate cancer received zoledronic acid (61) or placebo (59). Compared with placebo, zoledronic acid increased femoral neck, total hip and lumbar spine bone mineral density yearly by 3.6% (p = 0.0004), 3.8% (p <0.0001) and 6.7% (p <0.0001), respectively. The effects of zoledronic acid on bone mineral density at these 3 sites were not differentiated according to androgen deprivation therapy duration. Additionally, mean bone specific alkaline phosphatase and N-telopeptide levels were decreased in the zoledronic acid group (each p <0.0001) and were increased in the placebo group (p <0.0001 and p = 0.004, respectively). CONCLUSIONS: Zoledronic acid increased bone mineral density and suppressed bone turnover markers in patients with prostate cancer without bone metastases when initiated during year 1 of androgen deprivation therapy.

Adenocarcinoma↗
PubMed2001

Ultrastructure of early mineral deposition during hyaline layer formation in rat molars.

There is no consensus on whether the first mineralized layer, the hyaline layer, that is juxtaposed to root dentine is a variety of dentine or cementum or even a tissue of epithelial origin. Some suggest that there is no intermediate tissue between the acellular extrinsic fibre cementum (AEFC) and the root dentine. Here, to study hyaline layer formation and mineralization we examined by transmission electron microscopy the early stages of root development in upper molars from 10 to 13 day old Wistar rats. In addition to conventionally processed material, undemineralized and unstained sections were examined, which showed the deposition of fine mineral crystals in contact with the mineralized surface of root dentine. Early mineralization of the hyaline layer occurred in the region of the inner basement membrane, which persisted between the inner cellular layer of Hertwig's epithelial root sheath and the outer mineralized root dentine. When the root sheath began its fragment, collagen fibrils from the developing periodontal ligament began to insert into the mineralising hyaline layer, which was 0.5-0.8 micron wide. As the fragmentation of the root sheath HERS increased, more collagen fibrils appeared intermingled with the mineralising hyaline layer. In more advanced stages, when the hyaline layer had become fully mineralized and the formation of the AEFC began, the hyaline layer could no longer be identified. Thus, the hyaline layer is clearly discernible at early stages of periodontal development. Subsequently, it is masked by intermingling of cementum and dentine and therefore it is not possible to detect it in the formed roots of rat molars.

Animals↗