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PubMed2005

A comparative study of the metastable equilibrium solubility behavior of high-crystallinity and low-crystallinity carbonated apatites using pH and solution strontium as independent variables.

UNLABELLED: Using solution strontium and pH as independent variables, the metastable equilibrium solubility (MES) behavior of two carbonated apatite (CAP) samples has been examined, a high-crystallinity CAP (properties expected to be similar to dental enamel) and a low-crystallinity CAP (properties expected to be similar to bone mineral). CAP samples were prepared by precipitation/digestion: (CAP A: high-crystallinity, 1.3 wt% CO3, synthesized at 85 degrees C; CAP B: low-crystallinity, 6.4 wt% CO3, synthesized at 50 degrees C). Baseline MES distributions were determined in a series of 0.1 M acetate buffers containing only calcium and phosphate (no strontium) over a broad range of solution conditions. To assess the influence of strontium, MES profiles were determined in a similar fashion with 20, 40, 60, and 80% of the solution calcium being replaced on an equal molar basis by solution strontium. To determine the correct function governing CAP dissolution, ion activity products (IAPs) were calculated from the compositions of buffer solutions based on the hydroxyapatite template (Ca(10-n)Sr(n)(PO4)6(OH)2 (n = 0-10)) and the calcium/hydroxide deficient hydroxyapatite template (Ca(9-n)Sr(n)(HPO4)(PO4)5OH (n = 0-9)). FINDINGS: (a) for CAP A, at high solution strontium/calcium ratios, the MES profiles were essentially superimposable when the solution IAPs were calculated using the stoichiometry of Ca6Sr4(PO4)6(OH)2 and for CAP B by a stoichiometry of Ca7Sr2(HPO4)(PO4)5OH; (b) for CAP A, at low strontium/calcium ratios, the stoichiometry yielding MES data superpositioning was found to be that of hydroxyapatite and for CAP B, that of calcium/hydroxide deficient hydroxyapatite. When other stoichiometries were assumed, good superpositioning of the data was not possible.

Apatites↗
PubMed2004

Assessment of strontium and calcium levels in Pakistani diet.

To cope with nuclear emergency effectively due to ingestion of fission fragment (90)Sr, adequacy of nutritionally and radiologically important elements strontium and calcium was studied in typical Pakistani diet and baseline analytical data were generated. Concentrations of strontium and calcium were measured by using inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and atomic absorption spectrometry (AAS) techniques. Daily dietary intake of strontium and calcium varied from 0.9 to 5.7 mg and 217 to 713 mg with the geometric mean value x geometric standard deviation of 2.6 x 1.7 and 487.1 x 1.4 mg d(-1), respectively. The average Sr concentration in the Pakistani diet was 1.4 times higher while Ca concentration was 0.4 times lower than the recommended values of the International Commission on Radiological Protection (ICRP). The calculated Sr/Ca ratio 5.3E-03 was also higher than the ICRP value. The study depicts that the strontium concentration in the Pakistani diet is adequate, while the calcium concentration is inadequate according to international standards and needs improvement.

Calcium, Dietary↗
PubMed2005

Preparation of TiO2-SiO2 mixed gel spheres for strontium adsorption.

A simple external gelation process, taking full advantage of the gelation features of titanium and silica, was developed to prepare TiO2-SiO2 mixed gel spheres suitable for strontium adsorption. The source solutions used for the process were prepared from different mixtures of 1M TiCl4 and 1M Na2SiO3 solutions and converted into droplets in a gelation column. The suitable spheres for strontium adsorption were obtained using a hexone (methyl isobutyl ketone) solution as the drop formation medium and ammonia as the gelling agent. The mixed oxide gels were identified and characterized by DTA/TGA, FTIR and XRD analysis. The parameters affecting the strontium adsorption, such as weight ratio of TiO2, pH, temperature, shaking time and selectivity towards competing ions were investigated. Sorption data have been interpreted in terms of Freundlich, Langmuir and Dubinin-Radushkevich equations. Thermodynamic parameters for the sorption system have been determined at four different temperatures. The value of DeltaH degrees =39.553 kJ/mol and DeltaG degrees =-16.687 kJ/mol at 296 K prove that the sorption of strontium on mixed oxide gel is an endothermic and a spontaneous process.

Adsorption↗
PubMed2005

Long term results of non-surgical, exclusive strontium-/yttrium-90 beta-irradiation of pterygia.

BACKGROUND AND PURPOSE: To evaluate long term results and to demonstrate safety and efficacy of non-surgical, exclusive strontium-/yttrium-90 beta irradiation of non-operated pterygia. PATIENTS AND METHODS: Between March 1977 and April 1999, 43 patients with 54 primary pterygia were treated with an exclusive strontium-/yttrium-90 beta-irradiation up to a total dose of 50 Gy divided in four fractions with one week apart. All patients were referred from the same ophthalmologist. The average follow-up were 112(+/-88 months (range, 12-321 months), median 96 months. RESULTS: The patients were referred with early symptomatic manifestations of pterygia with a mean horizontal diameter of 1.6+/-0.7 mm (range, 0.5-4.5 mm), which shrank to a mean diameter of 0.9+/-0.6 mm (range, 0-2.5 mm) after irradiation (P<0.005). There was a reduction of size in every pterygium, none of the 54 pterygia developed a recurrent growth and there were no patient with any late side effect. Following the strontium-/yttrium-90 application the process came up with an obliteration of the vessels, which resulted in a grey, thin and avascular pannus. CONCLUSIONS: Strontium-/yttrium-90 beta-irradiation as an exclusive, non-surgical treatment for early pterygia provides a significant reduction of the size of the irradiated pterygia, is a safe and effective therapy to prevent a recurrence and can be performed without late side effects.

Adult↗
PubMed2006

Laser sources for precision spectroscopy on atomic strontium.

We present a new laser setup designed for high-precision spectroscopy on laser cooled atomic strontium. The system, which is entirely based on semiconductor laser sources, delivers 200 mW at 461 nm for cooling and trapping atomic strontium from a thermal source, 4 mW at 497 nm for optical pumping from the metastable P23 state, 12 mW at 689 nm on linewidth less than 1 kHz for second-stage cooling of the atomic sample down to the recoil limit, 1.2 W at 922 nm for optical trapping close to the "magic wavelength" for the 0-1 intercombination line at 689 nm. The 689 nm laser was already employed to perform a frequency measurement of the 0-1 intercombination line with a relative accuracy of 2.3 x 10(-11), and the ensemble of laser sources allowed the loading in a conservative dipole trap of multi-isotopes strontium mixtures. The simple and compact setup developed represents one of the first steps towards the realization of a transportable optical standards referenced to atomic strontium.

Lasers↗
PubMed1997

Variations in the concentration of plutonium, strontium-90 and total alpha-emitters in human teeth collected within the British Isles.

Concentrations of plutonium-239, plutonium-240, strontium-90 and total alpha-emitters have been measured in children's teeth collected throughout Great Britain and Ireland. The concentrations of plutonium and strontium-90 were measured in batched samples, each containing approximately 50 teeth, using low-background radiochemical methods. The concentrations of total alpha-emitters were determined in single teeth using alpha-sensitive plastic track detectors. The results showed that the average concentrations of total alpha-emitters and strontium-90 were approximately one to three orders of magnitude greater than the equivalent concentrations of plutonium-239,240. Regression analyses indicated that the concentrations of plutonium, but not strontium-90 or total alpha-emitters, decreased with increasing distance from the Sellafield nuclear fuel reprocessing plant-suggesting that this plant is a source of plutonium contamination in the wider population of the British Isles. Nevertheless, the measured absolute concentrations of plutonium (mean = 5 +/- 4 mBq kg-1 ash wt.) were so low that they are considered to present an insignificant radiological hazard.

Adolescent↗
PubMed2000

Long-term results of fractionated strontium-90 radiation therapy for pterygia.

PURPOSE: The long-term safety and effectiveness of fractionated strontium-90 radiation therapy (RT) for pterygium were reviewed retrospectively. METHODS AND MATERIALS: Between 1984 and 1996, 399 patients with 490 pterygia were treated with a strontium-90 eye applicator following surgical removal of the pterygium. The median follow-up period was 61 months (range 2-178). Of the 490 pterygia, 452 were fresh, 17 were recurrences after surgical removal alone, and 21 were recurrences after surgical removal plus postoperative RT. Fractionated RT of 31-42 Gy/4-5 fractions/22-29 days was given for 95.1% of the pterygia. RESULTS: In total, 58 (11.8%) local recurrences of pterygia were noted. The median time of local recurrences was 10 months, ranging from 2 to 93 months, and 16 recurrences (28%) were noted later than 24 months after treatment. The interval between surgery and the start of RT (1-3 days vs. >3 days) and recurrent pterygia were significant variables for local control in the multivariate analysis, while total RT dose (7-29 Gy vs. 31-50 Gy) was a marginally significant variable. Late toxicities that may be associated with strontium-90 RT were scleromalacia (scleral thinning) in 4 eyes, adhesion of eyelids in 3 eyes, and scleral ulcer in 2 eyes. CONCLUSION: Fractionated strontium-90 RT of approximately 40 Gy/4-5 fractions was safe and effective for preventing recurrence of pterygia, when RT was started within 3 days of surgery.

Adult↗
PubMed1982

A comparisoin of the R25 modification of Rappaport s enrichment medium with strontium chloride B for salmonella isolation from sewage polluted natural water.

The relation of salmonella isolation efficiency and the size of inoculum introduced from a buffered peptone water culture of sewage polluted water into strontium chloride B medium was investigated. Two separate studies were made, one using enrichment at 37 degrees C, the other at 43 degrees C. From these trials, two inocula suitable for efficient salmonella isolation were determined. Using this information, strontium chloride B medium was compared with modified Rappaport's broth (R25). The inoculum used with R25 was 0.005 ml, determined in an earlier study. Two incubation temperatures were employed with strontium chloride enrichment (37 and 43 degrees C). Rappaport's medium was incubated at 37 degrees C only. Elevated temperature enrichment at 43 degrees C improved the performance of strontium chloride B, but Rappaport's broth still gave significantly better results. This supports earlier studies on simplification of salmonella isolation and standardization of routine technique on a single enrichment medium: Rappaport broth (R25) incubated at 37 degrees C.

Bacteriological Techniques↗
PubMed1976

An evaluation of selective broths based on the bi-selenite ion and on hypertonic strontium chloride in Salmonellae detection in egg products.

Of the 104 isolations of Salmonella sp. from egg pulp, 97 were obtained from strontium chloride M broth, 42 from strontium selenite broth and 57 from strontium selenite A broth. The results suggest that the first medium may be used more successfully than bi-selenite based media for enrichment and subsequent detection of salmonellae in egg products; however, the growth of S. pullorum was not satisfactory in strontium chloride M broth.

Culture Media↗
PubMed1999

Oestrogen has no short-term effect on intestinal strontium absorption in healthy postmenopausal women.

OBJECTIVE: Impaired intestinal calcium absorption in postmenopausal women is often indirectly linked to decreased serum 1,25(OH)2D or to intestinal resistance to its action rather than directly to low circulating oestrogen levels following the menopause. The purpose of this clinical study was to investigate the short-term effect of oral 17 beta-oestradiol on intestinal calcium absorption, with strontium as a marker. DESIGN AND PATIENTS: Twenty-five healthy postmenopausal women participated in this randomised double blind placebo controlled clinical trial. Twelve women received oestradiol therapy (2 mg/day) and thirteen placebo for 2 months. Fractional strontium absorption (Fc240) was assessed at baseline and after 2 months of oestradiol/placebo therapy. RESULTS: Intestinal strontium absorption (Fc240) was unchanged after treatment with 17 beta-oestradiol (10.1 +/- 5.0 vs. 10.2 +/- 3.8(%)). Serum total calcitriol (1,25(OH)2D) was unchanged after treatment with placebo (88 +/- 22 vs. 79 +/- 21 (pmol/l)) but increased after treatment with oestradiol (88 +/- 30 vs. 116 +/- 33 (pmol/l); P < 0.005). Serum vitamin D binding protein (DBP) increased after oestradiol but not after placebo treatment. The free serum 1,25(OH)2D index was calculated. This index did not change after oestrogen therapy (1.6 +/- 0.5 vs. 1.8 +/- 0.5). CONCLUSION: In healthy postmenopausal women, short-term suppletion with exogenous oral oestrogen did not influence intestinal calcium absorption as measured by the strontium absorption test.

Administration, Oral↗
PubMed1999

Strontium is a potent and selective inhibitor of sensory irritation.

BACKGROUND: Irritant contact dermatitis occurs following topical exposure to many chemicals found in cosmetics, personal care products, drugs, and during occupational exposure. Signs and symptoms may include sensory irritation (sting, burn, and/or itch), erythema, edema, and vesiculation. OBJECTIVE: In an attempt to discover new classes of anti-irritant compounds without anesthetic properties, I observed that topical application of strontium salts to intact skin produced potent suppression of sting, burn, and itch caused by many irritant chemicals. METHODS: Chemically and biologically unrelated irritants were applied with or without strontium salts to the skin of healthy women with self-reported sensitive skin in double-blind, vehicle-controlled, random-treatment assignment trials and sensory irritation was assessed. RESULTS: Strontium application as a pretreatment or mixed with the irritant substantially suppressed sensory irritation without local anesthetic side-effects. CONCLUSION: Strontium salts represent a new class of selective inhibitors of sensory irritation and irritant dermatitis.

Administration, Topical↗
PubMedDate not supplied

Strontium-90 in newborns and childhood disease.

Radioactive strontium-90 concentrations in baby teeth obtained from Suffolk County, New York, rose steadily during the 1980s. Recent levels of strontium-90 are similar to those reported for babies born in the late 1950s-at the height of atmospheric nuclear weapons testing in Nevada. Strontium-90 concentrations increased concomitantly with increases in cancer incidence among Suffolk children under the age of 5 y, a result that mimicked parallel trends observed in the 1950s and early 1960s. Given that effects of strontium-90 on developing cells are most pronounced during the fetal and infant periods, escalating levels should be viewed as a factor in the recent decline in various child health status measures.

Child Welfare↗
PubMed2004

Engineering strontium binding affinity in an EF-hand motif: a quantum chemical and molecular dynamics study.

Proteins with the ability to specifically bind strontium would potentially be of great use in the field of nuclear waste management. Unfortunately, no such peptides or proteins are known -- indeed, it is uncertain whether they exist under natural conditions due to low environmental concentrations of strontium. To investigate the possibility of devising such molecules, one of us (CV), in a previous experimental study, proposed starting from an EF-hand motif of the protein calmodulin and mutating some residues to change the motif's specificity for calcium into one for strontium. In this paper, which represents a theoretical complement to the experimental work, we analyzed small-molecule crystallographic structures and performed quantum chemical calculations to identify possible mutations. We then constructed seven mutant sequences of the EF-hand motif and analyzed their dynamical and binding behaviors using molecular dynamics simulations and free-energy calculations (using the MM/PBSA method). As a result of these analyzes we were able to isolate some characteristics that could lead to mutant peptides with enhanced strontium affinity.

Amino Acid Motifs↗
PubMed1969

Active calcium and strontium transport in human erythrocyte ghosts.

Both calcium and strontium could be transported actively from erythrocytes if adenosine triphosphate, guanosine triphosphate, or inosine triphosphate were included in the hypotonic medium used to infuse calcium or strontium into the cells. Acetyl phosphate and pyrophosphate were not energy sources for the transport of either ion. Neither calcium nor strontium transport was accompanied by magnesium exchange, and the addition of Mg(++) to the reaction medium in a final concentration of 3.0 mmoles/liter did not promote the transport of either ion. In the absence of nucleotide triphosphates, the addition of 1.5 mmoles/liter of Sr(++) to the reaction solution did not bring about active calcium transport and similarly 1.5 mmoles/liter of Ca(++) did not bring about active strontium transport. The inclusion of 1.5 mmoles/liter of Ca(++) or Sr(++) in the reaction medium did not interfere with the transport of the other ion when the erythrocytes were infused with adenosine triphosphate.

Adenosine Triphosphate↗
PubMed2006

Comparison of observed skeleton retention of strontium in average indian adult with the value predicted by the ICRP biokinetic model.

The daily dietary intake of strontium and its content in skeleton, for an Indian adult population group were estimated by experimentally measuring its concentration in total cooked diet and autopsy skeleton samples using radiochemical neutron activation analysis. The data on daily dietary intake of strontium were used to compute its contents in skeleton using ICRP Publication 67 biokinetic model for strontium. The theoretically computed value of strontium (213.8 mg) compared favourably with the measured values (GM 181.2 mg) in an urban population group living in Mumbai representing an average Indian adult (Reference Indian Man).

Adult↗
PubMed1994

Bone formation markers and pain palliation in bone metastases treated with strontium-89.

In several bone disorders, including those with metastatic involvement, changes in procollagen type I C-terminal and type III N-terminal peptides are detected, as indications of altered bone metabolism. Assessment of bone turnover could play a role in the evaluation of response to Strontium-89 used as palliative treatment in symptomatic bone metastases from various primary tumors. A correlation between bone formation rate markers procollagen I and III and efficacy of ionic Strontium-89 was shown in a group of 13 patients who underwent treatment with 4 mCi of Strontium-89 for painful bone metastases: 5 from breast, 7 from prostate, and 1 from lung carcinoid cancer. Assessed as a modification of analgesic intake, pain, and ambulation, there were 6 complete remissions, 3 partial remissions, and 4 nonresponders. The duration of the response was from 2 to 11 months. Procollagen I and III levels were found to be highly abnormal in those with no benefit from Strontium-89 administration but were in the normal range or only slightly elevated in those achieving complete or partial pain control, thus correlating with the clinical response.

Adult↗
PubMed1994

Systemic administration of new therapeutic radioisotopes, including phosphorus, strontium, samarium, and rhenium.

New advances in systemic radionuclide therapy have increased the number of treatment options available for patients with painful osseous metastases. This form of therapy has three major appeals: 1) it addresses all sites of involvement; 2) selective absorption into bone limits irradiation of normal tissues; and 3) as a result, toxicity may be reduced and the therapeutic ratio improved. The clinical experience with radioactive phosphorus, strontium, samarium, and rhenium are reviewed. To date, the best studied and the only Food and Drug Administration approved agent is strontium-89. About 60% to 90% of patients treated with strontium-89 respond with complete or partial relief of pain for a median duration of 6 months. Large, prospectively randomized clinical trials have established the efficacy of strontium-89 as a first-line therapy and as an adjuvant to external-beam radiotherapy. Particularly advantageous is its usefulness in situations in which external-beam radiotherapy options have been exhausted and normal tissue tolerance has been reached. Newer radiopharmaceuticals are still under investigation.

Bone Neoplasms↗
PubMed2006

Modulation of the kinetics of evoked quantal release at mouse neuromuscular junctions by calcium and strontium.

The effects of calcium and strontium on the quantal content of nerve-evoked endplate currents and on the kinetic parameters of quantal release (minimal synaptic delay, value of main mode of synaptic delay histogram, and variability of synaptic delay) were studied at the mouse neuromuscular synapse. At low calcium ion concentrations (0.2-0.6 mmol/L), evoked signals with long synaptic delays (several times longer than the value of main mode) were observed. Their number decreased substantially when [Ca(2+)](o) was increased (i.e. the release of transmitter became more synchronous). By contrast, the early phase of secretion, characterized by minimal synaptic delay and accounting for the main peak of the synaptic delay histogram, did not change significantly with increasing [Ca(2+)](o). Hence, extracellular calcium affected mainly the late, 'asynchronous', portion of phasic release. The average quantal content grew exponentially from 0.09 +/- 0.01 to 1.04 +/- 0.07 with the increase in [Ca(2+)](o) without reaching saturation. Similar results were obtained when calcium was replaced by strontium, but the asynchronous portion of phasic release was more pronounced and higher strontium concentrations (to 1.2-1.4 mmol/L) were required to abolish responses with long delays. Treatment of preparations with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis acetoxymethyl ester (BAPTA-AM) (25 micromol/L), but not with ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid acetoxymethyl ester (EGTA-AM) (25 micromol/L), abolished the responses with long delays. The dependence of quantal content and synchrony of quantal release on calcium and strontium concentrations have quite different slopes, suggesting that they are governed by different mechanisms.

Action Potentials↗