Evolution of a mesoporous bioactive glass scaffold implanted in rat femur evaluated by (45)Ca labeling, tracing, and histological analysis.

Mesoporous bioactive glass (MBG) as a biodegradable scaffold with a nanostructure has attracted significant attention. However, the in vivo evolution of MBG, which includes in situ degradation, the local effect induced by degradation, and the disposition of degradation products, remains unclear. In this study, we performed in situ labeling and synthesis of an MBG scaffold for the first time using (45)CaCl2. The obtained (45)Ca-MBG scaffolds possessed a mesoporous-macroporous cross-linked structure. These (45)Ca-MBG scaffolds were implanted in critical-sized rat femur defects (3 × 3 mm) for 1 day and for 1, 4, 8, and 12 weeks and analyzed by isotopic quantitative tracing. The results illustrated that the MBG scaffolds gradually degraded over time and persisted at a local level of approximately 9.63% at week 12. This finding suggests that only a very small amount of MBG-released calcium ions may have been transformed into calcium components of the new bone matrix. The research also confirmed that the active ingredients derived from the degradation of MBG scaffolds could actively regulate the mRNA expression levels of osteoblast-related genes in rat bone marrow-derived mesenchymal stem cells (rBMSCs) and promote bone regeneration in vivo. Moreover, through isotopic tracing of the entire body, (45)Ca, which disappeared in situ after implantation, could be detected in the heart, lungs, spleen, kidneys, intestines, and brain via the blood and was mainly accumulated in distal bone tissue, including the radius and cranium. However, (45)Ca radioactivity in the body tissues significantly decreased or disappeared after 12 weeks. Systemic toxicological studies on MBG scaffolds demonstrated the degradation products that spread to major organs did not cause abnormal histopathological changes. The above discoveries comprehensively address crucial issues regarding the application of MBG in vivo, and these findings provide a scientific basis for introducing a material with mesoporous structure into clinical applications.

Calcium-ammonium exchange experiments on clay minerals using a (45)Ca tracer technique in marine pore water.

Understanding cation exchange processes is important for evaluating early diagenetic and synsedimentary processes taking place in marine sediments. To quantify calcium (Ca) exchange and Ca-ammonium exchange in a seawater environment, we performed experiments with a radioactive (45)Ca tracer on clay mineral standards (Fithian illite, montmorillonite and kaolinite) and marine sediments from the North Atlantic Integrated Ocean Drilling Program Site U1306A in artificial seawater (ASW). The results show that equilibrium during the initial attachment of Ca as well as the exchange of Ca by [Formula: see text] is attained in less than 2 min. On average 8-20% of the exchangeable sites of the clay minerals were occupied by Ca in a seawater medium. The conditional selectivity coefficient, describing the [Formula: see text] exchange in ASW is mineral specific and it was determined to be 0.07 for montmorillonite, 0.05 for a natural marine sediment and 0.013 for Fithian illite.

Accurate determination of 4¹Ca concentrations in spent resins from the nuclear industry by accelerator mass spectrometry.

The radiological characterisation of nuclear waste is essential for managing storage sites. Determining the concentration of Long-Lived RadioNuclides (LLRN) is fundamental for their long-term management. This paper focuses on the measurement of low (41)Ca concentrations in ions exchange resins used for primary fluid purification in Pressurised Water Reactors (PWR). (41)Ca concentrations were successfully measured by Accelerator Mass Spectrometry (AMS) after the acid digestion of resin samples, followed by radioactive decontamination and isobaric suppression through successive hydroxide, carbonate, nitrate and final CaF2 precipitations. Measured (41)Ca concentrations ranged from 0.02 to 0.03 ng/g, i.e. from 0.06 to 0.09 Bq/g. The (41)Ca/(60)Co activity ratios obtained were remarkably reproducible and in good agreement with the current ratio used for resins management.

Activity standardisation of 45Ca and 204Tl using the new TDCR system at CMI.

A new triple-to-double coincidence ratio (TDCR) system has been established at CMI as an additional technique for primary activity standardisation. Details of the detectors and the electronics are given. Construction of the optical chamber was validated using measurement of a (3)H standard-the efficiency achieved with Ultima Gold was 58%. Several methods of efficiency variation (coloured bands painted on vial, positioning and photomultipliers defocussing) are compared. Activity concentrations of (204)Tl and (45)Ca were determined with the TDCR method and with the efficiency tracer technique. Advantages of the TDCR method compared to the efficiency tracing method and agreement between results are shown.

Non-classic androgen actions in Sertoli cell membrane in whole seminiferous tubules: effects of nandrolone decanoate and catechin.

Studies show a mechanism of action of testosterone, nandrolone and catechin as agonists of the membrane androgen receptor. The aim of this work is to investigate the non-classical effect of androgens and catechin in Sertoli cells from immature rats. The membrane potential of Sertoli cells in whole seminiferous tubules was recorded using a standard single microelectrode technique. It was performed a topical application of testosterone (1 µM), nandrolone (0.1, 0.5 and 1 µM) and the flavonoid catechin (0.1, 0.5 and 1 µM) alone and also after infusion with flutamide (1 µM), diazoxide (100 µM) or U73122 (1 µM). The immature testes were incubated for 5 min in KRb with (45)Ca(2+), with or without nandrolone (1 µM). The results were given as mean±SEM. The data were analyzed using ANOVA for repeated measures with Bonferroni post-test. Testosterone produces a depolarization in the membrane potential at 120 s after application. Catechin (1 µM) and nandrolone (1 µM) have shown a similar response to testosterone: depolarization at 120 s after the application. The same response of catechin and nandrolone was observed at different doses. The effects of testosterone, catechin and nandrolone were not affected after perfusion with flutamide. Perfusion with diazoxide and U73122 nullified the effect of nandrolone (1 µM) and catechin (1 µM). Nandrolone and testosterone increased (45)Ca(2+) uptake with or without flutamide within 5min. These results indicate that nandrolone and catechin act through a receptor on the plasmatic membrane, as well as testosterone, showing a non-classical pathway in Sertoli cells from immature rat testes.

(41)Ca in tooth enamel. Part I: a biological signature of neutron exposure in atomic bomb survivors.

The detection of (41)Ca atoms in tooth enamel using accelerator mass spectrometry is suggested as a method capable of reconstructing thermal neutron exposures from atomic bomb survivors in Hiroshima and Nagasaki. In general, (41)Ca atoms are produced via thermal neutron capture by stable (40)Ca. Thus any (41)Ca atoms present in the tooth enamel of the survivors would be due to neutron exposure from both natural sources and radiation from the bomb. Tooth samples from five survivors in a control group with negligible neutron exposure were used to investigate the natural (41)Ca content in tooth enamel, and 16 tooth samples from 13 survivors were used to estimate bomb-related neutron exposure. The results showed that the mean (41)Ca/Ca isotope ratio was (0.17 +/- 0.05) x 10(-14) in the control samples and increased to 2 x 10(-14) for survivors who were proximally exposed to the bomb. The (41)Ca/Ca ratios showed an inverse correlation with distance from the hypocenter at the time of the bombing, similar to values that have been derived from theoretical free-in-air thermal-neutron transport calculations. Given that gamma-ray doses were determined earlier for the same tooth samples by means of electron spin resonance (ESR, or electron paramagnetic resonance, EPR), these results can serve to validate neutron exposures that were calculated individually for the survivors but that had to incorporate a number of assumptions (e.g. shielding conditions for the survivors).

(41)Ca in Tooth Enamel. Part II: A means for retrospective biological neutron dosimetry in atomic bomb survivors.

(41)Ca is produced mainly by absorption of low-energy neutrons on stable (40)Ca. We used accelerator mass spectrometry (AMS) to measure (41)Ca in enamel of 16 teeth from 13 atomic bomb survivors who were exposed to the bomb within 1.2 km from the hypocenter in Hiroshima. In our accompanying paper (Wallner et al., Radiat. Res. 174, 000-000, 2010), we reported that the background-corrected (41)Ca/Ca ratio decreased from 19.5 x 10(-15) to 2.8 x 10(-15) with increasing distance from the hypocenter. Here we show that the measured ratios are in good correlation with gamma-ray doses assessed by electron paramagnetic resonance (EPR) in the same enamel samples, and agree well with calculated ratios based on either the current Dosimetry System 2002 (DS02) or more customized dose estimates where the regression slope as obtained from an errors-in-variables linear model was about 0.85. The calculated DS02 neutron dose to the survivors was about 10 to 80 mGy. The low-energy neutrons responsible for (41)Ca activation contributed variably to the total neutron dose depending on the shielding conditions. Namely, the contribution was smaller (10%) when shielding conditions were lighter (e.g., outside far away from a single house) and was larger (26%) when they were heavier (e.g., in or close to several houses) because of local moderation of neutrons by shielding materials. We conclude that AMS is useful for verifying calculated neutron doses under mixed exposure conditions with gamma rays.

The role of ionic release from NovaMin (calcium sodium phosphosilicate) in tubule occlusion: an exploratory in vitro study using radio-labeled isotopes.

OBJECTIVE: The primary objective of this work was to develop a method of quantifying the levels and source of calcium and phosphate deposited on dental hard tissue from a novel calcium phosphosilicate (NovaMin) material using neutron activation analysis (NAA). A second objective was to explore the utility of radiotracing to determine dentin porosity following exposure to calcium phosphosilicate. METHODS: Neutron activation was used to create isotopes of Ca and P in the calcium phosphosilicate particles. Gamma radiation emitted from these isotopes was used to identify and measure their uptake (concentration) onto dental hard tissue. Three experiments were conducted to explore calcium and phosphate uptake to dental hard tissue: 1) a dose response to quantify the relative levels of calcium and phosphate deposited on dental hard tissue as a function of calcium phosphosilicate dose; 2) the effect of calcium phosphosilicate particle size on the relative levels of calcium and phosphate uptake; and 3) the permeability of calcium phosphosilicate-treated dentin by employing the radiotracer technetium. For all experiments, extracted bovine incisors were employed as the test substrate. RESULTS: The results indicate there is a strong dose relationship between the wt% and particle size of calcium phosphosilicate in the dentifrice formulation and new Ca and P deposition. At above 5.0 wt% calcium phosphosilicate, there appears to be an exponential increase in the number of counts from the tooth surface. Finer particle size calcium phosphosilicate appears to deposit much higher levels of Ca and P than the larger range of particle sizes. The results from the technetium study show that when treated with the dentifrice slurry containing calcium phosphosilicate, dentin shows only a slight amount of technetium infiltration, indicating a lowering of dentin permeability. CONCLUSION: This exploratory study has demonstrated that NAA and the use of radio isotopes have utility in monitoring the uptake of Ca and P into both dentin and enamel tooth structure. The data generated from these studies have shown that there is a dose dependence and particle size effect for calcium phosphosilicate on the deposition of calcium and phosphate to dental hard tissue.

Effects of the simultaneous application of potassium and calcium on the soil-to-Chinese cabbage transfer of radiocesium and radiostrontium.

Pot experiments were carried out in a greenhouse to investigate how effectively the transfer of radiocesium and radiostrontium from soil to Chinese cabbage could be reduced by applying K and Ca simultaneously to the soil. The sources of these elements were KCl and Ca(OH)(2) at agrochemical grades. Varying dosages of K and Ca were tested for an acid loamy soil treated with a mixed solution of (137)Cs and (85)Sr at two different times - 3 d before sowing and 32 d after sowing. For the pre-sowing deposition, the soil-to-plant transfer of (137)Cs decreased sharply with increasing dosages of K and Ca (K/Ca, g m(-2)) from 4.8/46 up to 22.4/215 but the (85)Sr transfer had the greatest reduction at a dosage of 12.8/123. At this dosage, an about 60% reduction occurred for each radionuclide. Plant growth was inhibited from the dosage of 22.4/215, above which all the plants died young. Both dosages of 4.8/46 and 12.8/123 tested following the growing-time deposition produced around 95% reductions for (137)Cs and 50% reductions for (85)Sr. In the second year after the 12.8/123 applications, the effects for (85)Sr were almost the same as in the first year, whereas those for (137)Cs were diminished slightly for the pre-sowing deposition and markedly for the growing-time deposition. Considerably (K) or slightly (Ca) higher doses than 12.8/123 would be allowable for the maximum TF reductions achievable without a growth inhibition.

A revised model for studying phosphorus and calcium kinetics in growing sheep.

The objective of the study was to revise a model of P kinetics proposed by Vitti et al. (2000) and extend its use to study Ca flows in growing sheep. Twelve Santa Ines male sheep, 8 mo of age, with average BW of 31.6 kg were injected with 32P and 45Ca to trace the movement of P and Ca in the body. The original model had 4 pools representing the gut, plasma, soft tissues, and bone. In the revised model, instantaneous values rather than averages for pool derivatives were incorporated, and the model was extended to represent absorption and excretion of phytate P explicitly. The amendments improved the model, resulting in higher flows between plasma and bone than between plasma and tissue and, therefore, a more accurate representation of P metabolism. Phosphorus and Ca metabolism were then assessed conjointly using the revised model. The results showed that P and Ca metabolism are closely related as evidenced by the ratio of these minerals in the bidirectional flows between plasma and bone and between plasma and tissue. Phytate P digestibility was 47%, and P retention was negative (-1.4 g/d), suggesting that a feed characteristic impaired P utilization and led to P deficiency. The revised model provides an improved prediction of P and Ca metabolism that can be used to assess mineral requirements and to estimate losses to the environment.

Counting individual 41Ca atoms with a magneto-optical trap.

Atom trap trace analysis, a novel method based upon laser trapping and cooling, is used to count individual atoms of 41Ca present in biomedical samples with isotopic abundance levels between 10(-8) and 10(-10). The method is calibrated against resonance ionization mass spectrometry, demonstrating good agreement between the two methods. The present system has a counting efficiency of 2x10(-7). Within 1 h of observation time, its 3-sigma detection limit on the isotopic abundance of 41Ca reaches 4.5x10(-10).

Transfer of alkaline earth elements in mothers' milk and doses from 45Ca, 90Sr and 226Ra.

An international programme of work is currently under way to develop methods for calculating doses to infants from ingestion of radionuclides present in mothers' milk. This paper considers the special case of the alkaline earth elements. Models have been developed for 45Ca, 90Sr and 226Ra and the sensitivity of results to various changes in parameter values is discussed. A complication when calculating doses from intakes of radium is that the International Commission on Radiological Protection has previously recommended that doses from decay products of radium should be calculated using element-specific biokinetic models (so-called independent biokinetics). An extension of this method to the models for breastfeeding is proposed. Preliminary estimates of the doses received by the infant for a number of maternal intake scenarios show that doses to the infant can exceed the corresponding adult dose, such as for 45Ca (ratio = 3.1) while, in other cases such as 90Sr, the infant dose can be a significant fraction of the adult dose.

A novel dual radio- and stable-isotope method for measuring calcium absorption in humans: comparison with the whole-body radioisotope retention method.

BACKGROUND: Dietary calcium absorption can be determined only with the use of isotope techniques. Currently used isotope techniques require exclusive equipment or are not true tracer approaches. OBJECTIVE: The objective was to compare a dual-isotope method combining radioisotopes and stable isotopes with a whole-body radioisotope retention method for measuring calcium absorption. DESIGN: Seven healthy adults aged 21-27 y consumed a test meal containing 63 +/- 14 (macro x +/- SD) mg Ca together with a water solution of (47)Ca (0.11 MBq). One hour after ingestion, 18 mg (44)Ca was administered intravenously. All feces and urine were collected for 5 and 6 d, respectively. Calcium absorption was estimated from whole-body retention of the radioisotope 12 times over 3 wk after ingestion and from the excretion of (47)Ca and (44)Ca in a 24-h urine sample collected on day 2. (44)Ca in urine was determined by inductively coupled plasma mass spectrometry. RESULTS: Mean (+/- SD) calcium absorption was 75 +/- 9% with the dual-isotope method and was 74 +/- 8% with the whole-body radioisotope retention method. There was a high degree of agreement between the methods. CONCLUSION: The dual-isotope method is a valid approach for measuring calcium absorption from a single meal.

Reconstruction of two victims' posturing based on the induced radioactivities in their bones in the criticality accident in Tokai-Mura, Japan.

On 30 September 1999, three workers were severely exposed to neutrons and gamma rays in a criticality accident that occurred at a uranium conversion facility in Tokai-mura, Ibaraki Prefecture, Japan. Radiochemical analyses of 32P and 45Ca induced by neutrons in bone matrix were carried out after the deaths of two of the victims. It was found that more than several million becquerels of both nuclides had been produced in their body skeletons. Results showed non-homogeneous distributions of neutron fluence in the bodies, from which it could be deduced how both workers were positioned relative to the fission source during exposure, i.e., at the moment of the first nuclear excursion. For the victim who died first, the activities in the central part of his body were more than those of his extremities. Also, in the central part of his body, the right side showed more activities than the left side. As for the second man, the activities indicated rather uniform exposure to neutrons to the whole body although the geometrical distribution of the activity varied enough to assume his orientation. Such information on the geometrical distribution of neutron-induced radioactivities in the skeleton can be used to reconstruct the posturing of the victims, which is necessary to estimate their apparent absorbed doses.

IL-1- and TNF-induced bone resorption is mediated by p38 mitogen activated protein kinase.

We have previously shown that p38 mitogen-activated protein kinase (MAPK) inhibitors, which block the production and action of inflammatory cytokines such as tumor necrosis factor (TNF) and interleukin-1 (IL-1), are effective in models of bone and cartilage degradation. To further investigate the role of p38 MAPK, we have studied its activation in osteoblasts and chondrocytes, following treatment with a panel of proinflammatory and osteotropic agents. In osteoblasts, significant activation of p38 MAPK was observed following treatment with IL-1 and TNF, but not parathyroid hormone, transforming growth factor-beta (TGF-beta), 1,25(OH)(2)D(3), insulin-like growth factor-1 (IGF-1), or IGF-II. Similar results were obtained using primary bovine chondrocytes and an SV40-immortalized human chondrocyte cell line, T/C28A4. SB 203580, a selective inhibitor of p38 MAPK, inhibited IL-1 and TNF-induced p38 MAPK activity and IL-6 production (IC(50)s 0.3--0.5 microM) in osteoblasts and chondrocytes. In addition, IL-1 and TNF also activated p38 MAPK in fetal rat long bones and p38 MAPK inhibitors inhibited IL-1- and TNF-stimulated bone resorption in vitro in a dose-dependent manner (IC(50)s 0.3--1 microM). These data support the contention that p38 MAPK plays a central role in regulating the production of, and responsiveness to, proinflammatory cytokines in bone and cartilage. Furthermore, the strong correlation between inhibition of kinase activity and IL-1 and TNF-stimulated biological responses indicates that selective inhibition of the p38 MAPK pathway may have therapeutic utility in joint diseases such as rheumatoid arthritis (RA).

Bioassay for neutron-dose estimations of three patients in the JCO criticality accident in Tokai-mura by measuring beta-ray emitters.

The measurement of beta-emitters in biological samples (hair, urine and bone) from three patients in the JCO criticality accident was performed to assess the neutron dose to individuals. The result of the measurements of 32P in hair and urine collected immediately after the accident showed that sufficient 32P activities had been induced in the hair by fast neutrons and in the urine by thermal neutrons to know the severity of the exposure to the individuals and to the position. From the measurement of 32P and 45Ca in bone from various anatomical parts of two patients who died 82 and 210 days after the accident, it was suggested that the distribution of the induced beta-emitters activities could prove the position and posture of the patients at the moment of exposure.

Radiochemical analysis of 41Ca and 45Ca.

The radioactive isotopes of calcium, 41Ca (t1/2 = 1.03 x 10(5) yr) and 45Ca (t1/2 = 163 d), are produced by neutron capture in the stable isotopes 40Ca and 44Ca, respectively. These radionuclides are present in the environment due to the reactions between the galactic cosmic rays and the earth's surface, and in nuclear power plants by the activation of the structural components of nuclear reactor vessels. The aim of this paper is to propose a radiochemical separation method of 41Ca and 45Ca from the other beta gamma emitters present in radioactive materials, based on selective precipitation reactions. The activities were measured by liquid scintillation counting (LSC). The obtained decontamination factors are satisfactory for each radioactive component of the initial sample in that their activities in the final product were lower than the minimum detectable activity (MDA) due to the effectiveness of the radiochemical procedure. The sensitivity of the method allows the radiological characterization of 41Ca and 45Ca content in radioactive materials.

Calcium absorption from small soft-boned fish.

The prevalence of osteoporosis in developing countries is low compared to most industrialised countries despite an apparent low Ca intake. It is possible, however, that food surveys have overlooked important Ca sources in developing countries. Small fish eaten with the bones can be a rich source of Ca, even though Ca from bone may be considered unavailable for absorption. In the present study, absorption of Ca from indigenous Bengali small fish was compared with the Ca absorption from milk. Ca absorption from single meals was determined in 19 healthy men and women (21-28 y). Each subject received two meal types on two separate occasions. Both meals consisted of white wheat bread, butter and ultra pure water with the main Ca source being either small Bengali fish (397 mg Ca in total) or skimmed milk (377 mg Ca in total). The meals were extrinsically labelled with 47Ca, and whole-body retention was measured on day 8, 12, 15 and 19 after intake of each meal. The labelling procedure was evaluated by an in vitro method. The calculated absorption of Ca as measured with 47Ca whole-body retention was 23.8 +/- 5.6% from the fish meal and 21.8 +/- 6.1% from the milk meal (mean +/- SD), which was not significantly different (p = 0.52). Even after correction for an incomplete isotope exchange, as indicated by the in vitro study, Ca absorption was similar from the two meal types. It was concluded that Ca absorption from small Bengali fish was comparable that from skimmed milk, and that these fish may represent a good source of Ca.

Chlorine and sodium perfusion and electrolyte balance in human tissue and tumours before and during neutron and photon radiotherapy.

Radiotherapy with nuclear reactor fission neutrons was applied in 49 cases of pretreated patients with superficial metastases or relapses from primary carcinoma. Measurements of the decay rates of the radiation-induced radioactivity of 49Ca, 38Cl and 24Na in the irradiated tissue resulted in values for the simultaneous local kinetics of chlorine and sodium, and in approximate data on the electrolyte masses. The electrolytes were present in non-exchangeable and exchangeable compartments of soft tissue. Exchange times of the intravascular to extravascular turnover and the frequencies of the exchange fractions were determined for a series of irradiations. The results have been interpreted in terms of the mean electrolyte exchange rates, of a standardized functional blood flow, and of the supply capacity of the vascular system. In the average of all cases, the regional perfusion was reduced by about 30% by irradiation up to 14 Gy (equivalent photon dose = 45 Gy) connected with an increase in the non-exchangeable fractions. After fractionated doses higher than 14 Gy, functional blood flow and supply capacity increased to 120%, and fixed electrolytes were removed from the irradiated tissue. Data on electrolyte kinetics and vascularity are compared with the literature.

Long-term effects of ovariectomy on the mechanical properties and chemical composition of rat bone.

One hundred Sprague-Dawley rats were ovariectomized (OVX) or sham-operated (Sham) at the age of 12 weeks. Eight or six animals from each group were sacrificed at the following time points: 0, 2, 4, 8, 16, 28, and 40 weeks. Mechanical testing of the bones showed that the maximal load of the femoral neck remained at the baseline level in OVX rats but clearly increased in Sham animals. However, after 28 weeks (at the age of 40 weeks) of ovariectomy, the femoral neck strength in Sham animals started to decrease, reaching the OVX level at the age of 1 year. The gain of torsional strength of the humerus was first slowed down after ovariectomy, but 16 weeks after operation this difference between the OVX and Sham animals disappeared. In OVX rats incorporation of 45 Ca2+ into the tibia and the number of osteoclasts on the trabecular bone surfaces were increased at 4-16 weeks and at 2-28 weeks, respectively, but they returned later to the levels observed in Sham animals. This indicates that the OVX-induced increase in bone turnover is transient. The trabecular bone volume at the distal femur decreased and the area of the marrow cavity in the distal third of the femur increased after OVX and did not show any recovery. Analysis of the inorganic composition of bone by energy-dispersion spectrometry showed that the percentage of magnesium was transiently decreased after OVX in both trabecular and cortical bone. Despite the OVX-induced loss of trabecular bone, increasing body weight or some metabolic changes may induce structural changes which may be responsible for maintaining the mechanical force of the femoral neck in aging OVX rats.