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PubMed2006

Methods for assessing gastrointestinal absorption of strontium in humans by stable tracer techniques.

Intestinal absorption of strontium from an oral test dose was studied in 13 healthy human volunteers using double tracer techniques with two stable strontium isotopes as tracers. Defined amounts of one isotope were administered orally, while tracer amounts of the second isotope were injected intravenously. Two different methods were used to assess the total fraction absorbed (f1 value). Fractional intestinal strontium absorption can be calculated from the ratio of the two isotopes in plasma or urine samples (in this paper called the double-isotope method) or the convolution integral technique, since both methods provide an accurate estimate of fractional absorption and yield comparable results. The latter additionally provides information on the absorption kinetics in the gastrointestinal tract. The absorption varies with respect to the chemical form and to the amount administered. Absorption patterns are characteristically different for uptake from solutions or from whole meals.

Administration, Oral↗
PubMed2002

Atmospheric carbon dioxide levels for the last 500 million years.

The last 500 million years of the strontium-isotope record are shown to correlate significantly with the concurrent record of isotopic fractionation between inorganic and organic carbon after the effects of recycled sediment are removed from the strontium signal. The correlation is shown to result from the common dependence of both signals on weathering and magmatic processes. Because the long-term evolution of carbon dioxide levels depends similarly on weathering and magmatism, the relative fluctuations of CO2 levels are inferred from the shared fluctuations of the isotopic records. The resulting CO2 signal exhibits no systematic correspondence with the geologic record of climatic variations at tectonic time scales.

Journal Article↗
PubMed1992

Palliation of bone metastases in prostate cancer. Hemibody irradiation or strontium-89?

The palliation of bone pain is a common clinical problem once metastatic prostate cancer has escaped from hormonal control. This retrospective study compares the results of treatment using hemibody irradiation (HBI) at the Royal Marsden Hospital (27 cases) with isotope therapy using the bone-seeking isotope strontium-89 (89Sr) at Southampton General Hospital (51 cases). Prior to analysis patients were matched for potential prognostic factors (performance status, bone scan extent of disease, age, histology and duration of hormone response) to minimize the effect of treatment selection bias. Pain control assessed at 3 months was similar for HBI and matched 89Sr cases, with 63% and 52% respectively showing some benefit. Median survival was similar for these groups at 20 and 21 weeks respectively. The unmatched 89Sr group, which had more favourable prognostic factors, had a better outcome with 96% showing improvement in pain and with a median survival of 59 weeks. Subsequent univariate analysis demonstrated that performance status and extent of disease on bone scan were of overriding importance in determining outcome. Transfusion requirements were higher for the HBI group than for the matched 89Sr group (50% and 25% respectively) but other bone marrow toxicity was similar. Despite routine anti-emetic therapy 37% of patients treated with HBI had some nausea or vomiting. Although expensive, 89Sr appears as effective a treatment option as HBI. Response is most likely with either approach when patients have a good performance status and a limited extent of disease.

Actuarial Analysis↗
PubMed2003

Evidence for rapid climate change in the Mesozoic-Palaeogene greenhouse world.

The best-documented example of rapid climate change that characterized the so-called 'greenhouse world' took place at the time of the Palaeocene-Eocene boundary: introduction of isotopically light carbon into the ocean-atmosphere system, accompanied by global warming of 5-8 degrees C across a range of latitudes, took place over a few thousand years. Dissociation, release and oxidation of gas hydrates from continental-margin sites and the consequent rapid global warming from the input of greenhouses gases are generally credited with causing the abrupt negative excursions in carbon- and oxygen-isotope ratios. The isotopic anomalies, as recorded in foraminifera, propagated downwards from the shallowest levels of the ocean, implying that considerable quantities of methane survived upward transit through the water column to oxidize in the atmosphere. In the Mesozoic Era, a number of similar events have been recognized, of which those at the Triassic-Jurassic boundary, in the early Toarcian (Jurassic) and in the early Aptian (Cretaceous) currently carry the best documentation for dramatic rises in temperature. In these three examples, and in other less well-documented cases, the lack of a definitive time-scale for the intervals in question hinders calculation of the rate of environmental change. However, comparison with the Palaeocene-Eocene thermal maximum (PETM) suggests that these older examples could have been similarly rapid. In both the early Toarcian and early Aptian cases, the negative carbon-isotope excursion precedes global excess carbon burial across a range of marine environments, a phenomenon that defines these intervals as oceanic anoxic events (OAEs). Osmium-isotope ratios ((187)Os/(188)Os) for both the early Toarcian OAE and the PETM show an excursion to more radiogenic values, demonstrating an increase in weathering and erosion of continental crust consonant with elevated temperatures. The more highly buffered strontium-isotope system ((87)Sr/(86)Sr) also shows relatively more radiogenic signatures during the early Toarcian OAE, but the early Aptian and Cenomanian-Turonian OAEs show the reverse effect, implying that increased rates of sea-floor spreading and hydrothermal activity dominated over continental weathering in governing sea-water chemistry. The Cretaceous climatic optimum (late Cenomanian to mid Turonian) also shows evidence for abrupt cooling episodes characterized by episodic invasion of boreal faunas into temperate and subtropical regions and changes in terrestrial vegetation; drawdown of CO(2) related to massive marine carbon burial (OAE) may be implicated here. The absence of a pronounced negative carbon-isotope excursion preceding the Cenomanian-Turonian OAE indicates that methane release is not necessarily connected to global deposition of marine organic carbon, but relative thermal maxima are common to all OAEs. 'Cold snaps' have also been identified from the Mesozoic record but their duration, causes and effects are poorly documented.

Carbon↗
PubMed2006

(137)Cs and (90)Sr uptake by sunflower cultivated under hydroponic conditions.

The (90)Sr and (137)Cs uptake by the plant Helianthus annuus L. was studied during cultivation in a hydroponic medium. The accumulation of radioactivity in plants was measured after 2, 4, 8, 16 and 32 days of cultivation. About 12% of (137)Cs and 20% of (90)Sr accumulated during the experiments. We did not find any differences between the uptake of radioactive and stable caesium and strontium isotopes. Radioactivity distribution within the plant was determined by autoradiography. (137)Cs was present mainly in nodal segments, leaf veins and young leaves. High activity of (90)Sr was localized in leaf veins, stem, central root and stomata. The influence of stable elements or analogues on the transfer behaviour was investigated. The percentage of non-active caesium and strontium concentration in plants decreased with the increasing initial concentration of Cs or Sr in the medium. The percentage of (90)Sr activity in plants decreased with increasing initial activity of the nuclide in the medium, but the activity of (137)Cs in plants increased. The influence of K(+) and NH(4)(+) on the uptake of (137)Cs and the influence of Ca(2+) on the uptake of (90)Sr was tested. The highest accumulation of (137)Cs (24-27% of the initial activity of (137)Cs) was found in the presence of 10 mM potassium and 12 mM ammonium ions. Accumulation of about 22% of initial activity of (90)Sr was determined in plants grown on the medium with 8 mM calcium ions.

Cesium Radioisotopes↗
PubMed1993

Strontium, a tracer to study the transport of calcium in mineralizing tissues by electron probe microanalysis.

In growth plate cartilage the mineralization starts extracellularly in the lower hypertrophic zone. The mineral formed is the calcium phosphate apatite. Enough calcium and phosphate must be available at the mineralization front as well as in regions with proceeding mineralization. There must be a transport of Ca (and phosphate) to these sites. Electron probe X-ray microanalysis is a well established method to analyze element concentrations in small volumes, but it cannot discriminate isotopes. Strontium is similar to Ca in its chemical and biological behaviour and is therefore a suitable tracer to investigate the transport of Ca. Small amounts of Sr (0.1 g per kg body weight) were administered intraperitoneally to young rats. After definite intervals of time ranging from 10 to 120 min, 2-4 rats were killed. On freeze dried cryosections the Sr/Ca ratio of the serum and of the intra- and extracellular space of the growth plate were measured. The Sr/Ca ratio reaches its maximum after about 10 min in the serum and after 20 min in the extracellular space of growth plate cartilage. The intracellular Sr/Ca ratio shows large variations because of the low intracellular Ca and Sr concentration, and is lower than the extracellular ratio for times shorter than 30 min. No significant differences were found between the different cell zones of the unmineralized growth plate cartilage. The results demonstrate that the transport of Ca to the growth plate cartilage is relatively fast and that in growth plate cartilage, Ca is transported extracellularly, not intracellularly.

Animals↗
PubMed1974

Deep sea sedimentation.

An important problem in the study of microparticles in the marine environment, suspended in the water column or deposited as sediment on the ocean bottom, is the determination of provenance of the microparticles-where did they come from and by what processes were they transported to the sampling location? Two techniques of possible interest to those concerned with tracing the origins and dispersion paths of asbestos particles are described. One utilizes variations in the naturally occurring rubidium-strontium isotope system and is used to characterize a bulk sample, i.e., a large number of particles. The other utilizes scanning electron microscopy to observe variations in surface texture of individual grains which, in the case of quartz particles in the natural environment, can be related to the transport processes to which they have been subjected.

Asbestos↗
PubMedDate not supplied

Topical application of beta-radiation to reduce intimal hyperplasia after carotid artery balloon injury in rabbit. A possible application for brachytherapy in vascular surgery.

PURPOSE: Endovascular brachytherapy for the prevention of intimal hyperplasia (IH) and restenosis after balloon/stent angioplasty has proven effective both in animal preparations and clinical trials. A variety of beta-emitting isotopes and catheter-based devices have been developed for the delivery of low-dose radiation in clinical coronary and peripheral trials. No platform, however, has yet been developed for brachytherapy in concert with vascular surgical operations. The purpose of this study was to evaluate the vascular histopathologic response following balloon injury to rabbit carotid arteries with and without topically applied low-dose beta-radiation. METHODS: The beta-emitting isotope strontium-90 (Sr-90) was conjugated onto the matrix of polypropylene (PLYP) mesh. Rabbit carotid arteries were balloon-injured with a #2 embolectomy catheter. Six carotid arteries were wrapped with nonradioactive PLYP mesh (controls) and Sr-90 ( approximately 90 microCi) PLYP mesh in order to deliver low-dose radiation to the vessel wall from the external (adventitial) surface. Tissue was harvested at 6 weeks and processed for histologic examination. RESULTS: There was consistent blockade of fibrocellular neointima formation with virtually no neointima present in all treated segments, compared to moderate neointima formation in controls. Medial thinning and smooth muscle cell (SMC) necrosis were also associated with topical brachytherapy. CONCLUSION: beta-Radiation applied by an externally wrapped PLYP mesh labeled with Sr-90 markedly suppressed neointima formation in an animal vascular surgical injury model. Further studies, however, are necessary to determine a suitable isotope and dosage for clinical application.

Administration, Topical↗
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↗
PubMed1986

The cytokinetic behavior of pulmonary alveolar macrophages in monocytopenic mice.

The cytokinetic behavior of pulmonary alveolar macrophages (PAM) was studied by pulse labeling with 3HTdB in mice made monocytopenic by a single intravenous injection of the bone-seeking isotope strontium-89 (89Sr). In the presence or absence of blood monocytes, PAM population size was unchanged for up to 1 month of chronic, severe monocytopenia. Pulse-labeling studies performed during monocytopenia show that in control mice PAM population half-times were 17.8 days with a potential doubling time of 39 days, whereas T1/2 was 14.8 days with a 28.5 day population doubling time for PAM in 89Sr-treated mice. Analysis of the halving times of the PAM mean grain count and the halving times of the most highly pulse-labeled cohorts suggested that PAM cell cycle times (Tc) were 5.1 days with a PAM rate of disappearance of 10.8%/day in 88Sr-treated mice and Tc of 6.6 days with a PAM rate of disappearance of 11.4%/day in 89Sr-treated mice. As measured by 3HTdR-labeling techniques, these cytokinetic values are in close approximation to each other, suggesting that 89Sr treatment did not significantly alter either PAM population size or cytokinetic behavior. Employing experimental values it was possible to construct a simple model of PAM population growth that supports the concept that the PAM population is self-renewing in the adult mouse. Taken together, the data show that a major portion of the resident PAM need not depend on the daily influx of peripheral blood monocytes to maintain themselves in a kinetically steady state.

Animals↗
PubMed2002

Sourcing sediment using multiple tracers in the catchment of Lake Argyle, Northwestern Australia.

Control of sedimentation in large reservoirs requires soil conservation at the catchment scale. In large, heterogeneous catchments, soil conservation planning needs to be based on sound information, and set within the framework of a sediment budget to ensure that all of the potentially significant sources and sinks are considered. The major sources of sediment reaching the reservoir, Lake Argyle, in tropical northwestern Australia, have been determined by combining measured sediment fluxes in rivers with spatial tracer-based estimates of proportional contributions from tributaries of the main stream entering the lake, the Ord River. The spatial tracers used are mineral particle magnetics, the strontium isotopic ratio, and the neodymium isotopic ratio. Fallout of 137Cs has been used to estimate the proportion of the sediment in Lake Argyle eroded from surface soils by sheet and rill erosion, and, by difference, the proportion eroded from subsurface soils by gully and channel erosion. About 96% of the sediment in the reservoir has come from less than 10% of the catchment, in the area of highly erodible soils formed on Cambrian-age sedimentary rocks. About 80% of the sediment in the reservoir has come from gully and channel erosion. A major catchment revegetation program, designed to slow sedimentation in the reservoir, appears to have had little effect because it did not target gullies, the major source of sediment. Had knowledge of the sediment budget been available before the revegetation program was designed, an entirely different approach would have been taken.

Australia↗
PubMedDate not supplied

Multisyringe flow injection analysis of stable and radioactive strontium in samples of environmental interest.

A multisyringe flow injection (MSFIA) method for the determination of stable and radioactive strontium, using a solid phase resin (Sr-Resin), has been developed. Strontium concentrations are determined by atomic emission spectroscopy and by a low background proportional counter. The method has been applied to different samples (water, milk and soil) of environmental interest. The LLD of the stable and radioactive Sr were 10 microg/l and 0.01 Bq, respectively. The standard deviation of the separation procedure is 2% (n=10).

Animals↗
PubMed2003

Migration of a Late Cretaceous fish.

Late Cretaceous sediments from the Western Interior of North America yield exceptionally well preserved fossils that serve as proxies for the rapidly changing climate preceding the Cretaceous/Tertiary boundary (about 67-65 Myr ago). Here we reconstruct the ontogenetic history of a Maastrichtian-age fish, Vorhisia vulpes, by using the carbon, oxygen and strontium isotope ratios of four aragonite otoliths collected from the Fox Hills Formation of South Dakota. Individuals of V. vulpes spawned in brackish water (about 70-80% seawater) and during their first year migrated to open marine waters of the Western Interior Seaway, where they remained for 3 years before returning to the estuary, presumably to spawn and die. The mean delta(18)O from the marine growth phase of V. vulpes yields a seawater temperature of 18 degrees C, which is consistent with leaf physiognomy and general-circulation-model temperature estimates for the Western Interior during the latest Maastrichtian.

Animal Migration↗
PubMed2004

Recycling lower continental crust in the North China craton.

Foundering of mafic lower continental crust into underlying convecting mantle has been proposed as one means to explain the unusually evolved chemical composition of Earth's continental crust, yet direct evidence of this process has been scarce. Here we report that Late Jurassic high-magnesium andesites, dacites and adakites (siliceous lavas with high strontium and low heavy-rare-earth element and yttrium contents) from the North China craton have chemical and petrographic features consistent with their origin as partial melts of eclogite that subsequently interacted with mantle peridotite. Similar features observed in adakites and some Archaean sodium-rich granitoids of the tonalite-trondhjemite-granodiorite series have been interpreted to result from interaction of slab melts with the mantle wedge. Unlike their arc-related counterparts, however, the Chinese magmas carry inherited Archaean zircons and have neodymium and strontium isotopic compositions overlapping those of eclogite xenoliths derived from the lower crust of the North China craton. Such features cannot be produced by crustal assimilation of slab melts, given the high Mg#, nickel and chromium contents of the lavas. We infer that the Chinese lavas derive from ancient mafic lower crust that foundered into the convecting mantle and subsequently melted and interacted with peridotite. We suggest that lower crustal foundering occurred within the North China craton during the Late Jurassic, and thus provides constraints on the timing of lithosphere removal beneath the North China craton.

Journal Article↗
PubMed1975

Bone scanning: principles, technique and interpretation.

Bone scanning is most useful in the detection of bone metastases. The recent introduction of new radiopharmaceuticals and instrumentation has reduced the time needed to perform the study and its relative cost, while increasing the usefulness of the study in detecting roentgenographically occult diseases. Metastatic disease is used as the pathophysiologic model for understanding the principles of bone scanning. When a tumor invades bone, in addition to causing bone destruction, it also causes reactive bone formation or repair. It is here that radioisotopes are of considerable value, since some radionuclides are incorporated into the hydroxyapatite crystals of reactive bone. Bone repair is described as occurring in three phases. In Phase I, the roentgenogram shows no change in bone density, but the scan is abnormal. In Phase II, both scintigraphic and roentgenographic abnormalities increase, and in Phase III, when the osteoid has calcified completely, the roentgenogram shows radiodensities and the scan appears almost normal. Fewer than 5 per cent of patients have a normal scan in the presence of an abnormal roentgenogram. Presently, most bone scans are performed with phosphate compounds labeled with -99m-Tc. In the past, 85-Sr, 87M-Sr, and 18-F were more broadly used. Scanning may be performed on either a rectilinear scanner or a scintophoto (gamma) camera. Areas which are abnormal on bone scan should be interpreted with current roentgenograms in the light of clinical findings.

Autopsy↗