Lead concentrations and lead and strontium stable-isotope ratios in teeth of European roe deer (Capreolus capreolus)

The study reports lead concentrations and lead and strontium stable-isotope ratios in mandibular molars of roe deer from three different areas in western Germany. Lead concentrations in third molars ranged between 0.23 and 36.61 μg/g (dry weight). Comparing lead concentrations in first molars and third molars in a group of ca. 1.5- or ca. 2.5-year-old individuals from the same area revealed an effect of tooth age on tooth lead content. The higher lead concentrations in the first molars were attributed to the longer period of lead accumulation by the dentin of these teeth compared with the later-forming third molars. Differences in lead isotopic signatures of the teeth were observed between the three areas, presumably reflecting variation in exposure to different sources of environmental lead. We also found marked variation in the ⁸⁷Sr/⁸⁶Sr isotope ratios of the teeth, with only a small overlap in values between two of the areas. Strontium isotope analysis alone or in combination with lead isotope analyses can be a useful means of assessing the provenance of deer teeth of unknown geographical origin.     

Incorporation of strontium into otoliths of an estuarine fish

Patterns of Sr/Ca variability in fish otoliths have been widely applied as tracers of movement between freshwater and marine habitats, with the assumption that low salinity habitats correspond to lower otolith levels of Sr/Ca. On the other hand, fluvial estuaries can contain steep gradients in Sr/Ca, and in some estuaries, freshwater values of Sr/Ca can exceed marine values, which are relatively constant across marine habitats. Therefore, to interpret Sr/Ca variability in otoliths of fish that move through estuaries, information is needed about both the incorporation of strontium into otoliths and the nature of the gradient of Sr/Ca in the water. We conducted four experiments to evaluate the incorporation of strontium into fish otoliths under estuarine conditions, using white perch (Morone americana) as a model estuarine fish. One laboratory and the two field experiments tested the relationship between Sr/Ca in the otolith and that in the water. A fourth experiment investigated the effect of salinity, independently of the water chemistry (Sr was manipulated while maintaining a constant salinity and Ca level). All four experiments supported a direct relationship between Sr/Ca in the otolith and the water, across a range of estuarine salinities. Results also indicated that the incorporation of strontium into otoliths of estuarine fishes should be constant across broad gradients of Sr/Ca in estuarine waters. While the experiments supported past applications of tracing estuarine and diadromous movements with otolith Sr/Ca chronologies, we emphasize the need to understand the underlying nature of Sr/Ca gradients in estuaries, which may limit or confound reconstructions of estuarine habitat use.     

应用氯化锶对小鼠卵母细胞孤雌活化的研究

目的　探讨小鼠卵母细胞孤雌激活的最佳作用条件。方法　将MⅡ期小鼠卵母细胞随机分为 2组 ,第一组 ,将小鼠卵母细胞分别放入 2、4、6、8、10mmol ml不同浓度的氯化锶激活液中 ,作用 6h ,观察激活率及囊胚发育率。第二组 ,将小鼠卵母细胞放入 10mmol ml氯化锶激活液中 ,分别作用 3、6、9h ,观察激活率及囊胚发育率。结果　第一组 ,激活率分别为 86 49%、82 6 1%、88 0 0 %、86 6 7%、81 18%。各组间差异无显著性。体内培养 72h回收囊胚 ,囊胚发育率分别为 0、31 42 %、43 33%、6 2 5 0 %、5 0 0 0 %。 6～ 10mmol mlSrCl2 激活液激活后囊胚发育率高于 0～ 4mmol ml(P <0 0 5 )。第二组 ,激活率分别为 82 86 %、89 6 1%、91.40 %。 72h囊胚发育率分别为 2 6 5 3 %、5 0 0 0 %、5 3 2 2 %。激活 6、9h的囊胚发育率高于激活 3h的囊胚发育率 (P <0 0 1)。结论　结果表明 ,6～ 10mmol ml的SrCl2 为卵母细胞孤雌活化的最佳作用浓度 ,6～ 9h的激活时间为最佳作用时间 ;表明SrCl2 的浓度和作用时间对小鼠卵母细胞的活化有显著的影响。     

Taxonomic character of plant species in absorbing and accumulating alkali and alkaline earth metals grown in temperate forest of Japan

Summary Absorption and accumulation of alkali (Li, Na, K, Rb, Cs) and alkaline earth (Mg, Ca, Sr, Ba) metals were investigated as taxonomic characteristics (in 62 plant species). Leaf and soil samples were collected from 9 sites in temperature forest in Japan and the above mentioned elements were analyzed. Considerable differences were found among species in their ability to accumulate alkali and alkaline earth metals. Very high concentrations of Li (45 ppm, D.W.), K (37×10³ ppm), Rb (159 ppm) and Cs (8.2 ppm) were detected inLastrea japonica which were about 412, 12, 27 and 6 times higher than those of the species with the lowest concentrations. Na content was high inAcer micranthum (358 ppm) which was 16 times higher than species with the lowest concentration. Other species containing high levels of alkali metals wereHydrangea macrophylla, Struthiopteris niponica, Clethra barbinervis. Mean discrimination ratio (D.R.) for all investigated plant species for Li, Na, Rb, and Cs to K were 1.7, 0.44, 0.9 and 1.8 respectively. High concentrations of alkaline earth metals Ca (36×10³ ppm), Sr (345 ppm), and Ba (241 ppm) were found in the leaves ofHydrangea paniculata which were about 31, 84, and 72 times higher than those for the species with the lowest concentration. Mg was very high inStruthiopteris niponica (83×10² ppm). Other species with high concentrations of alkaline earth metals belonged to the genus Viburnum. Mean D.Rs. for Mg, Sr, and Bavs Ca were 1.0, 0.7 and 0.08. Principal component analysis of interrelationships between the mineral content in leaf tissues indicated that these elements could be classified into 2 groups with respect to their accumulation behavior in plants. The alkali metals K, Li, Rb, and Cs behaved similarly in their accumulation in leaves but Na behaved independently. Alkaline earth metals Ca, Mg, Sr, and Ba were also found to behave similarly in their accumulation. Factors scores of 1st and 2nd components revealed three groups of plant species: alkaliphilic, alkaline earthphilic, and neutral (non-accumulators).     

Novel open-framework architecture in strontium(II) phosphonate

Hydrothermal reaction of strontium nitrate with N,N′-piperazine-bis(methylenephosphonic acid) (H₄L) afforded a novel three-dimensional strontium(II) diphosphonate, namely, [Sr(H₂L)(H₂O)₂] · 3H₂O (1). The structure of compound 1 can be viewed as a pillar-layered architecture in which 1D chains of [Sr(PO₃)] along a-axes are further crosslinked by the piperazine bismethylene spacers along b- and c-axes.     

An Akt-dependent increase in canonical Wnt signaling and a decrease in sclerostin protein levels are involved in strontium ranelate-induced osteogenic effects in human osteoblasts

Sclerostin is an important regulator of bone homeostasis and canonical Wnt signaling is a key regulator of osteogenesis. Strontium ranelate is a treatment for osteoporosis that has been shown to reduce fracture risk, in part, by increasing bone formation. Here we show that exposure of human osteoblasts in primary culture to strontium increased mineralization and decreased the expression of sclerostin, an osteocyte-specific secreted protein that acts as a negative regulator of bone formation by inhibiting canonical Wnt signaling. Strontium also activated, in an apparently separate process, an Akt-dependent signaling cascade via the calcium-sensing receptor that promoted the nuclear translocation of β-catenin. We propose that two discrete pathways linked to canonical Wnt signaling contribute to strontium-induced osteogenic effects in osteoblasts.     

Synthesis and pharmacokinetics of strontium fructose 1,6-diphosphate (Sr-FDP) as a potential anti-osteoporosis agent in intact and ovariectomized rats

A novel strontium compound has been synthesized by the reaction of fructose-1,6-diphosphate with strontium (Sr-FDP). The compound was characterized and confirmed with elemental analyses and spectroscopic (IR, NMR) methods. The pharmacokinetic profiles of Sr-FDP were investigated in Sprague-Dawley rats following oral administration at a dose of 110, 220, and 440 mg/kg respectively. Pharmacokinetic differences were also compared in intact rats and ovariectomized rats with and without estrogen supplement. Strontium concentrations in plasma, urine, tissue and feces were determined by graphite furnace atomic absorption spectroscopy (GFAAS). The results showed that Sr-FDP was absorbed rapidly with T_max < 1 h in all the groups with AUC_0-∞ proportional to the oral dose. The pharmacokinetic profiles were characterized by long half-life, a large apparent volume of distribution. The highest Sr concentration was observed in the bone at 6 h, and the level of Sr decreased close to the baseline in heart, liver, spleen, lung, intestine, brain and kidney after 12 h. The cumulative amounts of Sr over 96 h were found to be ~ 3% in urine, but ~ 70% in feces suggesting that the parent drug was mainly excreted from the intestine. The C_max and AUC_0-∞ of Sr-FDP in ovariectomized rats were significantly decreased compared to those in intact rats, and this trend was ameliorated by using 17-beta-estradiol (E₂) treatment in the ovariectomized rats.     

Strontium and paleodietary research: A review

The measurement of skeletal strontium/calcium (Sr/Ca) ratios can provide information on the proportion of meat and vegetable foods in the diets of prehistoric peoples. This information is based in the well-documented reduction of Sr/Ca ratios in terrestrial food chains. The reduction, and therefore the paleodietary technique, is complicated by (a) differences in Sr/Ca ratios entering food chains, and (b) metabolic considerations such as age, pregnancy, etc. Changes in Sr/Ca ratios during interment may also obscure biological Sr/Ca levels. The theoretical basis of the technique, its complications, and practical use by anthropologists are reviewed, in an attempt to define the quality of information currently and potentially available from Sr/Ca analyses.     

The structure of the 11-coordinate barium complex of the pendant-donor macrocycle 1,4,7,10-tetrakis(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane: an analysis of the coordination numbers of barium(II) in its complexes

The crystal structure of [Ba(DOTAM)Cl]₂(ClO₄)₂ · 2.7H₂O, is reported, where DOTAM is 1,4,7,10-tetrakis(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane [triclinic, space group, , a=937.6(2), b=1050.4(2), c=1476.6(3) pm, α=110.41(2), β=97.48(2), γ=97.75(2)°, Z=2, R=0.0423]. The structure consists of a dimer held together by four oxygen atoms bridging between the two Ba atoms. Each Ba is 11-coordinate, coordinated to four nitrogens from the macrocyclic ring, and four oxygens from the four pendant amide groups of DOTAM. In addition, each Ba has a coordinated chloride ion, as well as two bridging amide oxygens from the other member of the dimer. An analysis of the coordination numbers (CN) of Ba(II) complexes is presented. It is found that the CN of Ba(II) complexes ranges from 3 to 12, and is most commonly 9 with unidentate ligands. Higher coordination numbers of 10 and above are promoted by either polydentate ligands of denticity greater than six, or the presence of several ligands such as nitrate or acetate that form four-membered chelate rings. Lower coordination numbers of seven and below are promoted by increasingly large substitutents attached directly to the donor atoms of the ligand.     

Photochemistry of bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)strontium tetraglyme solutions for eventual liquid phase photochemical deposition

The mechanism of Sr(hfac)₂TG (hfac = 1,1,1,5,5,5,hexafluoro-2,4-pentanedionato and TG, tetraglyme = 2,5,8,11,14-pentaoxapentadecane) photodegradation was investigated in methanol and dichloromethane at 254 and 300 nm. In methanol, photodegradation led to SrF₂ through the attack of fluoride on the metal, occurring from the CF₃ group in the intraligand excited state π-π*. In dichloromethane, a mixture of SrCl₂ and SrF₂ was obtained in proportions dependent on the initial complex concentration and irradiation wavelength. SrF₂ was formed by photoexcited species of the complex with the same mechanism occurring in methanol. SrCl₂ was formed by a solvent-initiated reaction at 254 nm, involving substitution of ligand by chloride ion, coming from photochemical solvent decomposition, whereas at 300 nm it was formed by a solvent-assisted reaction, involving an electron transfer to solvent from excited ligand in triplet state.The photochemical kinetics were followed by UV spectrophotometry, the photodecomposition products were recognized by ESI-mass, XRD and XPS. The Sr(hfac)₂TG photodegradation was usefully exploited to obtain pure thin films or mixture of SrCl₂ and SrF₂ by the LPPD technique, operating in suitable experimental conditions. The films were characterized by SEM, XPS and XRD.