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PubMed2006

NMR study of strontium binding by a micaceous mineral.

The nature of strontium binding by soil minerals directly affects the transport and sequestration/remediation of radioactive strontium species released from leaking high-level nuclear waste storage tanks. However, the molecular-level structure of strontium binding sites has seldom been explored in phyllosilicate minerals by direct spectroscopic means and is not well-understood. In this work, we use solid-state NMR to analyze strontium directly and indirectly in a fully strontium-exchanged synthetic mica of nominal composition Na(4)Mg(6)Al(4)Si(4)O(20)F(4). Thermogravimetric analysis, X-ray diffraction analysis, and NMR evidence supports that heat treatment at 500 degrees C for 4 h fully dehydrates the mica, creating a hydrogen-free interlayer. Analysis of the strontium NMR spectrum of the heat-treated mica shows a single strontium environment with a quadrupolar coupling constant of 9.02 MHz and a quadrupolar asymmetry parameter of 1.0. These quadrupolar parameters are consistent with a highly distorted and asymmetric coordination environment that would be produced by strontium cations without water in the coordination sphere bound deep within the ditrigonal holes. Evidence for at least one additional strontium environment, where proton-strontium couplings may occur, was found via a (1)H-(87)Sr transfer of populations by double resonance NMR experiment. We conclude that the strontium cations in the proton-free interlayer are observable by (87)Sr NMR and bound through electrostatic interactions as nine coordinate inner-sphere complexes sitting in the ditrigonal holes. Partially hydrated strontium cations invisible to direct (87)Sr NMR are also present and located on the external mica surfaces, which are known to hydrate upon exposure to atmospheric moisture. These results demonstrate that modern pulsed NMR techniques and high fields can be used effectively to provide structural details of strontium binding by phyllosilicate minerals.

Journal Article↗
PubMed1991

Evaluation of the effects of chelation therapy with time following strontium exposure to mice.

The effect of increasing the time interval between strontium exposure and chelation therapy was studied in male Swiss mice. Diethylenetriaminepentaacetic acid (DTPA), ethyleneglycol-bis-(beta-amino-ethylether)-N,N'-tetraacetic acid (EGTA), 4,7,13,16,21,24-hexaoxa-1,10-diazabycyclo[8.8.8]-hexacosane (Kryptofix 222), tartaric acid, and 1,13-bis(8-chinolyl)-1,4,7,10,13-pentaoxatridecan (Kryptofix 5) were administered intraperitoneally at 0, 6, 12, and 24 h after subcutaneous injection of 1,139 mg/kg of strontium nitrate. Chelating agents were given at doses equal to one-fourth of their respective LD50 values. Daily elimination of strontium into urine and feces was determined for five days after which time the animals were killed, and the concentration of strontium was determined in various tissues. Only Kryptofix 222 was capable of increasing the total urinary elimination of strontium when given immediately after strontium exposure, whereas the amount of total strontium excreted into the feces was significantly enhanced by treatment with EGTA at 0 or 24 h after strontium injection, or with Kryptofix 222 at 6 h after strontium exposure. However, Kryptofix 222, tartaric acid, and Kryptofix 5 reduced the concentration of strontium in bone at 0, 6, or 12 h after strontium injection, whereas at 24 h only Kryptofix 5 significantly lowered the concentration of the metal in bone. The results of this study indicate that the length of time before initiating chelation therapy for strontium removal may influence remarkably the effectiveness of this therapy.

Animals↗
PubMed2002

Strontium overload and toxicity: impact on renal osteodystrophy.

Although the prevalence of aluminium-related bone diseases has declined, osteomalacia still persists at a low prevalence. The redistribution of bone disease prevalence corresponds to evolving regimens in the treatment of renal disease. Studies have demonstrated an association between the accumulation of strontium in bone and the presence of osteomalacia. The uptake of strontium has been shown to be dose-dependent, with distribution mainly in newly formed compact and cancellous bone. Animal studies demonstrated that high doses of strontium induced alterations of mineralization and, in a rat model of chronic renal failure, high strontium doses induced mineralization defects, with a corresponding 160-fold accumulation of strontium in bone. Studies indicated that the accumulation of metals in bone might be synergistic. Aluminium bone content was shown to be higher when both aluminium and strontium were administered compared with when only strontium was given. Studies in dialysis patients demonstrated that strontium levels and strontium/calcium ratios were elevated in the bone of osteomalacia patients compared with other types of renal osteodystrophy. In certain dialysis centres of developing countries, high strontium levels present in dialysis fluids correlated with strontium serum content. At these centres, the use of acetate-based concentrates may have been the source of strontium-contaminated dialysis fluids. In a recent study of bone biopsies taken from patients of French dialysis centres, strontium content was increased in bone of osteomalacic patients compared with other bone diseases and with controls. Several other trace elements have been found to accumulate in the bone of uraemic patients, with significant concern regarding associated pathology. Environmental and medical exposure to such trace metals should be evaluated to establish toxic thresholds and to eliminate the possibility of associated renal osteopathies.

Animals↗
PubMed1987

Activation of skinned muscle fibers by calcium and strontium ions.

Intact and mechanically skinned skeletal muscle fibers of the crab Carcinus maenas have been used. The aim of the experiments was to determine the origin of the mechanical activity recorded in intact crab muscle fibers exhibiting an inward strontium current in strontium solution without calcium. To do so, the effect of strontium ions in inducing activation of contractile proteins and calcium release from the sarcoplasmic reticulum has been studied. The properties of the sarcoplasmic reticulum membrane towards strontium ions, i.e., the efficiency of the calcium ATPase towards strontium ions and the capability to release strontium ions have been investigated. Results show that the contractile proteins have a lower affinity for strontium than for calcium ions. However, the maximum bound strontium is identical to the maximum bound calcium. As for the sarcoplasmic reticulum, strontium ions can induce a calcium release and also can be taken up by the calcium ATPase and be released. We concluded that the mechanical activity in intact fibers bathed in a strontium medium has two origins: first, a direct and partial activation of the contractile proteins by strontium ions flowing through the calcium channel; second, a contractile proteins activation of calcium ions released by the sarcoplasmic reticulum by a "strontium-induced calcium release" mechanism.

Animals↗
PubMed2004

A novel cation-sensing mechanism in osteoblasts is a molecular target for strontium.

UNLABELLED: Defining the molecular target for strontium in osteoblasts is important for understanding the anabolic effects of this cation on bone. The current studies demonstrate that a G-protein-mediated response to strontium persists in osteoblasts that lack CASR, suggesting a predominant role for a novel cation-sensing receptor in mediating the osseous response to strontium. INTRODUCTION: Strontium has anabolic effects on bone and is currently being developed for the treatment of osteoporosis. The molecular target for strontium in osteoblasts has not been determined, but the existence of CASR, a G-protein-coupled receptor calcium-sensing receptor, raises the possibility that strontium actions on bone are mediated through this or a related receptor. MATERIALS AND METHODS: We used activation of a transfected serum response element (SRE)-luciferase reporter in HEK-293 cells to determine if CASR is activated by strontium. In addition, we examined strontium-mediated responses in MC3T3-E1 osteoblasts and osteoblasts derived from wild-type and CASR null mice to determine if other cation-sensing mechanisms are present in osteoblasts. RESULTS AND CONCLUSIONS: We found that strontium stimulated SRE-luc activity in HEK-293 cells transfected with full-length CASR but not in cells expressing the alternatively spliced CASR construct lacking exon 5. In contrast, we found that MC3T3-E1 osteoblasts that lack CASR as well as osteoblasts derived from CASR null mice respond to millimolar concentrations of strontium. The response to strontium in osteoblasts was nonadditive to a panel of extracellular cations, including aluminum, gadolinium, and calcium, suggesting a common mechanism of action. In contrast, neither the CASR agonist magnesium nor the calcimimetic NPS-R568 activated SRE activity in osteoblasts, but the response to these agonists was imparted by transfection of CASR into these osteoblasts, consistent with the presence of distinct cation-sensing mechanisms. Co-expression of the dominant negative Galphaq(305-359) minigene also inhibited cation-stimulated SRE activity in osteoblasts lacking known CASR. These findings are consistent with strontium activation of a novel Galphaq-coupled extracellular cation-sensing receptor in osteoblasts with distinct cation specificity.

Alternative Splicing↗
PubMed2000

X-Ray Absorption Spectroscopy of Strontium(II) Coordination.

Detailed analyses of crystalline, hydrated, and precipitated strontium compounds and an aqueous strontium solution by synchrotron extended X-ray absorption fine structure (EXAFS) were used to quantify local thermal and static disorder and to characterize strontium coordination in a variety of oxygen-ligated bonding environments. Analysis of anharmonic vibrational disorder (i.e., significant contribution from a third cumulant term (C(3)) in the EXAFS phase-shift function) in compounds with low and high static disorder around strontium showed that first-shell anharmonic contributions were generally not significant above experimental error in the EXAFS fits (R+/-0.02 Å with and without C(3)). The only case in which a significant apparent decrease in Sr-O distance was observed with increasing temperature, and for which a third cumulant term was significant, was for dilute strontium in aqueous solution. Empirical parameterization of Debye-Waller factor (sigma(2)) for strontium compounds as a function of backscatterer atomic number (Z), interatomic Sr-Z distance, and temperature of spectral data collection showed systematic increases in sigma(2) as a function of increasing temperature and Sr-Z bond length. At values of sigma(2) greater than approximately 0.025 Å(2) (for N<12 and R(Sr)-Z>3 Å), backscattering was generally not significant above noise levels in spectra of compounds of known crystal structure. Comparison of the EXAFS spectra of freshly precipitated SrCO(3) (spectra collected wet) to that of dry, powdered strontianite (SrCO(3)(s)) indicated no significant differences in the local atomic structure around strontium. Analysis of partially hydrated strontium in natural Ca-zeolite (heulandite) showed that strontium is substituted only in the calcium (Ca2) site. Backscattering from aluminum and silicon atoms in the zeolite framework were apparent in the EXAFS spectra at low and room temperature at distances from central strontium of <4.2 Å. Comparison of strontium structural coordination determined in this and previous studies suggests that previous EXAFS determinations of hydrated strontium may have underestimated first-shell interatomic distances and coordination numbers because minor contributions to the EXAFS phase-shift and amplitude functions were not accounted for, either theoretically or empirically. Copyright 2000 Academic Press.

Journal Article↗
PubMed2005

Strontium ranelate: a novel mode of action optimizing bone formation and resorption.

Strontium ranelate has been shown to decrease the risk of fractures in postmenopausal women. Its efficacy in clinical studies results from its unique mode of action, on both bone resorption and bone formation. Pharmacological studies in animals have shown that strontium ranelate decreases bone resorption and increases bone formation, resulting in increased bone mass. In ovariectomized rats, strontium ranelate prevented the reduction in bone mineral content and the decrease in trabecular bone volume induced by estrogen deficiency. In this model, strontium ranelate decreased bone resorption, whereas bone formation was maintained at a high level as documented by plasma biochemical markers and histomorphometric indices of bone formation. In the model of osteopenia induced by hind-limb immobilization in rats, strontium ranelate reduced histomorphometric parameters of bone resorption and partially prevented long-bone loss, as assessed by bone mineral content, bone volume, and biochemical indices of bone resorption. In intact mice, strontium ranelate increased bone formation and vertebral bone mass. In intact growing rats, strontium ranelate increased the bone trabecular volume without alteration of mineralization. The unique mode of action of strontium ranelate on bone formation and resorption was supported by in vitro studies. In rat calvaria culture systems and rat osteoblastic cell cultures, strontium ranelate enhanced preosteoblastic cell replication and increased collagen synthesis by osteoblasts. Moreover, strontium ranelate decreased bone resorption in organ cultures and decreased the resorbing activity of isolated mouse osteoclasts. The assessment of bone markers in a clinical trial [Spinal Osteoporosis Therapeutic Intervention (SOTI)] supports the mode of action of strontium ranelate: bone alkaline phosphatase levels increased and C-telopeptide of type I collagen levels decreased in treated patients compared with the placebo group at all time points. Thus, pharmacological and clinical studies suggest that strontium ranelate optimizes bone resorption and bone formation, resulting in increased bone mass, which may be of great value in the treatment of osteoporosis.

Alkaline Phosphatase↗
PubMed2005

[Strontium ranelate: a novel concept for the treatment of osteoporosis].

The di-strontium salt strontium ranelate, a novel orally active agent consisting of two atoms of stable strontium and the organic moiety ranelic acid, has been developed for the treatment of osteoporosis. It has been shown to enhance osteoblastic cell replication and increase collagen synthesis while decreasing pre-osteoclast differentiation and bone-resorbing activity of mature osteoclasts in vitro. Studies performed in healthy animals have shown that strontium ranelate not only increases bone mass at various skeletal sites but also improves mechanical properties of femoral, humeral and vertebral bones. In estrogen-deficient animals, strontium ranelate effectively inhibits increased bone resorption while maintaining bone formation. Similar results have been obtained from studies in hind limb-immobilized animals. Strontium ranelate has been investigated in a large phase III program which includes two extensive multinational, randomized, double-blind, placebo-controlled clinical trials for the treatment of severe postmenopausal osteoporosis. Before inclusion in these two studies, patients were subjected to a run-in study in order to initiate normalization of their calcium and vitamin D status. The SOTI study, aimed at assessing strontium ranelate's effect on the risk of vertebral fractures, revealed a significant reduction in the risk of new vertebral fractures in the group treated with strontium ranelate. The TROPOS study, which aimed at evaluating the effect of strontium ranelate on nonvertebral fractures, showed a significant reduction in the risk of new nonvertebral fractures and also, in a high-risk subgroup, a significant reduction in the risk of hip fractures. In both studies, the reduction in fracture risk was accompanied by an increase in bone mineral density. The increase remained significant also after correction of the bone mineral density for the higher atomic mass of strontium compared to calcium. Furthermore, an increase in serum levels of a bone formation marker and a decrease in serum levels of a bone resorption marker were observed. The spectrum of side effects comprised mild diarrhea, particularly within the first weeks of treatment, and also a slightly increased risk of venous thromboembolic events. Strontium ranelate thus appears to be a new, effective treatment to prevent fractures in postmenopausal osteoporosis with a novel mechanism of action. It can be expected for the near future that strontium ranelate will also be evaluated for other types of osteoporosis, such as male osteoporosis.

Animals↗
PubMed2004

Strontium ranelate: a new paradigm in the treatment of osteoporosis.

In vitro, strontium ranelate increases collagen and non-collagenic protein synthesis by mature osteoblast-enriched cells. The effects of strontium ranelate on bone formation were confirmed as the drug enhanced preosteoblastic cell replication. In the isolated osteoclast, a preincubation of bone slices with strontium ranelate induced a dose-dependent inhibition of the bone resorbing activity of treated rat osteoclast. Strontium ranelate dose-dependently inhibited preosteoclast differentiation. The drug was administered in 160 early postmenopausal women, in a 24-month, double-blind, placebo-controlled, prospective randomised study. At the conclusion of the study, the percentage variation of lumbar bone mineral density (BMD) from baseline was significantly different in the group receiving strontium ranelate 1000 mg/day as compared with placebo (+5.53 versus -0.75%, respectively). Increase in total hip and neck BMD averages were 3.2 and 2.5%, respectively. The effect of strontium ranelate in postmenopausal women with established osteoporosis was assessed during a multinational, prospective, double-blind, randomised, placebo-controlled trial. Strontium ranelate (500, 1000, 2000 mg/day) or placebo were given to 353 Caucasian women with prevalent vertebral osteoporosis. At the conclusion of this 2-year study, the annual increase in lumbar BMD of the group receiving strontium ranelate 2000 mg was 7.3% (p < 0.001). A significant increase in bone alkaline phophatase (p = 0.002) over a 6-month period and a significant decrease in N-telopeptide crosslinks (p = 0.004) throughout the 2-year period were seen in the group receiving 2000 mg of strontium ranelate. During the second year of treatment, the dose of 2000 mg was associated with a 44% reduction in the number of patients experiencing a new vertebral deformity. Bone histomorphometry showed no mineralisation defects. The primary analysis of the SOTI study, evaluating the effect of strontium ranelate 2000 mg on vertebral fracture rates, revealed a 41% reduction in the relative risk of patients experiencing a first new vertebral fracture with strontium ranelate throughout the 3-year study. The TROPOS study showed a significant reduction in the risk of experiencing a first non-vertebral fracture in the group treated with strontium ranelate throughout the 3-year study. A reduction in the risk of experiencing a hip fracture was also demonstrated in the patients treated for > or = 18 months.

Animals↗
PubMed1979

Diet and status at Chalcatzingo: some empirical and technical aspects of strontium analysis.

Determination of the levels of particular trace elements preserved in bone provides a potential pathway for reconstructing the diet of extinct primate species and archaic human groups. Strontium is one of the most useful trace elements for dietary reconstruction but several empirical properties of strontium must be considered during the interpretation of results. (1) Strontium is distributed unevenly throughout the physical environment. (2) Plants, in general, do not discriminate against strontium. (3) During ionic transfer across biological membranes, strontium is discriminated against by terrestrial vertebrates. (4) It is unlikely that strontium would be selectively removed from bone mineral during diagenesis. A particular difficulty in trace element analysis is caused by interaction between analytical technique and sample matrix. To assess this problem the skeletal population from Chalcatzingo was analyzed by two techniques: atomic absorption spectrometry and neutron activation analysis. The results from the two techniques compared favorably indicating that the pattern of bone strontium levels could be accepted as an accurate reflection of the distribution of bone strontium within the population. After demonstrating the internal accuracy of the results, the bone strontium level and position of social rank within Chalcatzingo were compared. Ethnographic and archaeological evidence on chiefdoms and states indicate that dietary differences in the amount of meat consumed occur between social ranks. The relative social ranks were reconstructed by using a "pattern analysis" of the burial goods accompanying each individual. The individuals accompanied by jade had the lowest mean bone strontium level (X = 532). Those individuals buried with a shallow dish had a slightly higher level (X = 635). A third group, which had no grave goods, had the highest mean bone strontium level (X = 700) which suggests that their diet contained less meat than was available to the rest of the community.

Anthropology, Physical↗
PubMed1976

Comparison between strontium and calcium uptake by the fragmented sarcoplasmic reticulum.

The ATP-supported uptake of strontium by the fragmented sarcoplasmic reticulum is monophasic and proceeds more rapidly than the fast uptake of calcium. Strontium uptake is not activated by Pi. The accumulation of strontium is nearly proportional to the external strontium concentration even in the millimolar range. Internal and external strontium quickly equilibrate. One mole of strontium is stored for every mole of ATP split by the Sr2+-activated ATPase. In the absence of oxalate most of the strontium is taken up with a transport ratio of one. On the opposite, the transport ratio of calcium decreases immediately, especially when ADP is not instantaneously phosphorylated to ATP. In this case, energy conversion is uncoupled more effectively by the simultaneous action of ADP and free internal calcium, resulting in the interruption of the fast uptake. After depletion of ATP most of the stored strontium is released and the remaining fraction appears to be not exchangeable. Strontium activates the slow uptake of calcium, but reduces the amplitude of the fast uptake. The calcium induced release of strontium, and vice versa, is partial and transient. The strontium activated ATPase does not transport calcium at low ionic calcium concentrations.

Adenosine Triphosphatases↗
PubMed2005

Long-term strontium ranelate administration in monkeys preserves characteristics of bone mineral crystals and degree of mineralization of bone.

UNLABELLED: In monkeys, long-term strontium ranelate administration results in a dose-dependent bone strontium uptake (mainly into newly formed bone) that preserves the degree of mineralization of bone and the bone mineral at the crystal level, showing its safety at bone mineral level. INTRODUCTION: Strontium ranelate simultaneously increases bone formation and decreases bone resorption, leading to prevention of bone loss and increase in bone mass and bone strength in normal and ovariectomized rats. This study investigated the interactions of stable strontium (Sr) with bone mineral in monkeys after long-term strontium ranelate treatment and after a period of treatment withdrawal. MATERIALS AND METHODS: Iliac bone was obtained from untreated monkeys, monkeys at the end of a 52-week strontium ranelate administration (200, 500, 1250 mg/kg/day orally), and in parallel groups 10 weeks after the end of strontium ranelate administration (same three doses; n = 3-7). Sr uptake and distribution in bone mineral were quantified by X-ray microanalysis, changes at the crystal level by X-ray diffraction, and the degree of mineralization of bone (DMB) by quantitative microradiography. RESULTS: After strontium ranelate administration, dose-dependent Sr uptake occurred into cortical and cancellous bone, with higher content (1.6 times) in new than in old bone. This Sr uptake decreased (50%) 10 weeks after treatment withdrawal; the decrease occurred almost exclusively in new bone. At the end of strontium ranelate treatment and after its withdrawal, a preservation of crystal characteristics was observed, suggesting that Sr was only faintly linked to crystals by ionic substitution and of DMB. CONCLUSIONS: These results show the absence of a deleterious effect of long-term strontium ranelate treatment on bone mineralization, confirming the histomorphometric observations made in postmenopausal osteoporotic women treated with strontium ranelate.

Animals↗
PubMed2006

Strontium ranelate for preventing and treating postmenopausal osteoporosis.

BACKGROUND: Strontium ranelate is a new treatment for osteoporosis therefore, its benefits and harms need to be known. OBJECTIVES: To determine the efficacy and safety of strontium ranelate for the treatment and prevention of postmenopausal osteoporosis. SEARCH STRATEGY: We searched MEDLINE (1996 to March 2005), EMBASE (1996 to week 9 2005), the Cochrane Library (1996 to Issue 1 2005), reference lists of relevant articles and conference proceedings from the last two years. Additional data was sought from authors. SELECTION CRITERIA: We included randomized controlled trials (RCTs) of at least one year duration comparing strontium ranelate versus placebo reporting fracture incidence, bone mineral density (BMD), health related quality of life or safety in postmenopausal women. Treatment (versus prevention) population was defined as women with prevalent vertebral fractures and/or lumbar spine BMD T score < -2.5 SD. DATA COLLECTION AND ANALYSIS: Two reviewers independently determined study eligibility, assessed trial quality and extracted the relevant data. Disagreements were resolved by consensus. RCTs were grouped by dose of strontium ranelate and treatment duration. Where possible, meta-analysis was conducted using the random effects model. MAIN RESULTS: Four trials met the inclusion criteria. Three included a treatment population (0.5 to 2 g of strontium ranelate daily) and one a prevention population (0.125 g, 0.5 g and 1 g daily). A 37% reduction in vertebral fractures (RR 0.63, 95% CI 0.56, 0.71) and a 14% reduction in non-vertebral fractures (RR 0.86, 95% CI 0.75, 0.98) were demonstrated over three years with 2 g of strontium ranelate daily in a treatment population. An increase in BMD was shown at all BMD sites after two to three years in both populations. Lower doses of strontium ranelate were superior to placebo and the highest dose demonstrated the greatest reduction in vertebral fractures and increase in BMD. An increased risk of diarrhea with 2 g of strontium ranelate was found; however, adverse events did not affect the risk of discontinuing treatment nor did it increase the risk of serious side effects, gastritis or death. Additional data suggests that the risk of vascular and nervous system side-effects is slightly increased with taking 2 g of strontium ranelate daily over three to four years. AUTHORS' CONCLUSIONS: There is silver level evidence (www.cochranemsk.org) to support the efficacy of strontium ranelate for the reduction of fractures (vertebral and to a lesser extent non-vertebral) in postmenopausal osteoporotic women and an increase in BMD in postmenopausal women with/without osteoporosis. Diarrhea may occur however, adverse events leading to study withdrawal were not significantly increased with taking 2 g of strontium ranelate daily. Potential vascular and neurological side-effects need to be further explored.

Bone Density↗
PubMed2001

Stable strontium accumulation by earthworms: a paradigm for radiostrontium interactions with its cationic analogue, calcium.

The accumulation of stable strontium and its chemical analogue calcium by four species of earthworm, representing three distinct ecophysiological groups inhabiting celestite (SrSO4)-rich natural soils, was investigated. An increase in soil strontium concentration over a four-orders-of-magnitude range was accompanied by an increase in earthworm tissue strontium concentration. In contrast, no relationship between soil and tissue calcium concentrations was apparent, indicating that this essential cation is strongly regulated within earthworm tissues but that nonessential strontium burdens are not physiologically regulated. Concentration factors for strontium ranged from 0.1 to 1.42, with an inverse relationship between this parameter and soil strontium concentration. The use of concentration factors and discrimination coefficients lead to the conclusion that earthworms discriminate against strontium accumulation at increased soil calcium concentrations, such that strontium would be predicted to be more efficiently accumulated by worms inhabiting acidic, calcium-poor soils. Although few consistent trends in strontium and calcium concentration were apparent between earthworm species, the species with the highest calcium turnover (i.e., the litter-inhabiting Lumbricus rubellus) typically accumulated higher concentrations of strontium than representatives of contrasting ecophysiological classes. These findings are considered in the context of the distribution, retention, and cycling of radiostrontium in soils.

Animals↗
PubMed1980

The feasibility of dental strontium analysis for diet-assessment of human populations.

It has been suggested that bone and dental strontium contents of extinct terrestrial vertebrates vary in direct proportion to the strontium levels present in the animals' diets. It has been hypothesized that these trace quantities decrease as one moves upward along the food chain--herbivores having more strontium than primary carnivores, primary carnivores more than secondary carnivores, and so on. The present study was designed to determine the feasibility of dental strontium analysis for diet-assessment of human fossil populations. Human vegetarian and nonvegetarian teeth were analyzed for strontium. It was hoped that by comparing the strontium levels of these two groups, one might determine conclusively whether the nature of diet plays an important role in the determination of dental strontium levels within a species. Atomic absorption spectrophotometry was used to analyze seven vegetarian and seven nonvegetarian teeth. Strontium levels varied considerably within both groups of teeth and no significant difference in strontium levels existed between the vegetarian and nonvegetarian teeth. These results suggest that dental strontium analysis may not be a useful indicator of the dietary habits of human fossil populations.

Dental Enamel↗
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↗
PubMed2004

Activation and early parthenogenesis of bovine oocytes treated with ethanol and strontium.

Efficient artificial activation is indispensable for the success of cloning programs. Strontium has been shown to effectively activate mouse oocytes for nuclear transfer procedures, however, there is limited information on its use for bovine oocytes. The present study had as objectives: (1). to assess the ability of strontium to induce activation and parthenogenetic development in bovine oocytes of different maturational ages in comparison with ethanol; and (2). to verify whether the combination of both treatments improves activation and parthenogenetic development rates. Bovine oocytes were in vitro matured for 24, 26, 28, and 30 h, and treated with ethanol (E, 7% for 5 min) or strontium chloride (S, 10mM SrCl(2) for 5h) alone or in combination: ethanol+strontium (ES) and strontium+ethanol (SE). Activated oocytes were cultured in vitro in synthetic oviductal fluid (SOF) medium and assessed for pronuclear formation (15-16 h), cleavage (46-48 h) and development to the blastocyst stage (D7). Treatment with ethanol and strontium promoted similar results regarding pronuclear formation (E, 20-66.7%; S, 26.7-53.3%; P>0.05) and cleavage (E, 12.8-40.6%; S, 16.1-41.9%; P>0.05), regardless of oocyte age. The actions of both strontium and ethanol were influenced by oocyte age: ethanol induced greater activation rates after 28 and 30 h of maturation (48.4 and 66.7% versus 20.0 and 23.3% for 24 and 26 h, respectively; P<0.05) and strontium after 30 h (53.3%) was superior to 24 and 26 h (26.7% for both). Blastocyst development rates were minimal in all treatments (0.0-6.3%; P>0.05), however, when the mean (+/-S.D.) cell number in blastocysts at the same maturational period was compared, strontium treatment was superior to ethanol for activation rates (82+/-5.7 and 89.5+/-7.8 versus 54 and 61, at 28 and 30 h, respectively). Improved results were obtained by combined treatments. The combination of ethanol and strontium resulted in similar pronuclear formation (ES, 36.7-83.9%; SE, 53.1-90.3%) and cleavage rates (ES, 31.3-81.3%; SE, 65.6-80.7%). Regarding embryo development, there was no difference (P>0.05) between treatments, and blastocysts were only obtained in treatment SE at 24 and 26 h (6.5% for both). It is concluded that, SrCl(2) induces activation and parthenogenetic development in bovine oocytes.

Animals↗
PubMed2005

Use of strontium for bovine oocyte activation.

Strontium efficiently activates mouse oocytes, however, there is limited information on its use in cattle. Thus, the objective of this study was to establish a suitable protocol for activating bovine oocyte with strontium. For pronuclear development, the absence of calcium and magnesium in the activation medium (TALP) with 10 and 50 mM strontium (34.4 and 53.1%, respectively) was superior to the complete TALP (6.5 and 19.4%, respectively). In all activation media, better results were observed with 25 and 50 mM strontium (21.9-53.1 and 19.4-53.1%, respectively). Incubation for 4 h promoted similar results in all strontium concentrations. However, strontium at 15, 20, and 25 mM for 6 and 8 h (40.7, 46.7, and 48.3%, and 29.3, 48.3, and 40.7%, respectively) were superior to control (15.5 and 10%, respectively). After in vitro maturation for 26 h, strontium (S; 20 mM in Ca2+- and Mg2+-free TALP for 6 h), ionomycin+strontium (IS), and strontium+ionomycin (SI) (60, 63.3, and 65%, respectively) were similar in pronuclear development and superior to ionomycin (I; 5 microM for 5 min; 36.7%). In treatments S and I, only 1 PN zygotes were observed. In treatment S, most of them had 1 and 2 PB (35.7 and 60.7%, respectively), and in treatment I, 0, 1, and 2 PB (14.3, 57.1, and 28.6%, respectively). Most of the zygotes in treatment IS and SI were 1 PN 2 PB (77.4 and 61.6%, respectively). The number of oocytes with clusters of cortical granules was similar in all treated groups (11-29%). Cortical granule exocytosis in treatment IS (68%) was similar to S (54%) and superior to I, SI, and control (27, 45, and 5.0%, respectively). Cleavage and blastocyst rates were similar for S, I, IS, and SI treatments (61.7-76.7, and 8.3-13.3%, respectively) and the same was observed for ICM, TE, and total cell number, and ICM/total cell ratio (22-25, 64-69, and 86-95, and 0.26-0.27). In conclusion, strontium may be efficiently applied for bovine oocyte activation at 20 mM in Ca2+- and Mg2+-free TALP medium for 6 h.

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