Allometric constraints on Sr/Ca and Ba/Ca partitioning in terrestrial mammalian trophic chains

In biological systems, strontium (Sr) and barium (Ba) are two non-essential elements, in comparison to calcium (Ca) which is essential. The Sr/Ca and Ba/Ca ratios tend to decrease in biochemical pathways which include Ca as an essential element, and these processes are termed biopurification of Ca. The quantitative pathway of the biopurification of Ca in relation to Sr and Ba between two biological reservoirs (R _n and R_{n -1}) is measured with an observed ratio (OR) expressed by the (Sr/Ca) _Rn /(Sr/Ca) _Rn-1 and (Ba/Ca) _Rn /(Ba/Ca) _Rn-1 ratios. For a mammalian organism, during the whole biopurification of Ca starting with the diet to the ultimate reservoir of Ca which is the bone, the mean values for OR_Sr and OR_Ba are 0.25 and 0.2, respectively. In this study, published Sr/Ca and Ba/Ca ratios are used for three sets of soils, plants, and bones of herbivorous and carnivorous mammals, each comprising a trophic chain, to illustrate the biopurification of Ca at the level of trophic chains. Calculated OR_Sr and OR_Ba of herbivore bones in relation to plants and of bones of carnivores in relation to bones of herbivores give OR_Sr=0.30±0.08 and OR_Ba=0.16±0.08, thus suggesting that trophic chains reflect the Sr/Ca and Ba/Ca fluxes that are prevalent at the level of a mammalian organism. The slopes of the three regression equations of log(Sr/Ca) vs. log(Ba/Ca) are similar, indicating that the process of biopurification of Ca with respect to Sr and Ba is due to biological processes and is independent of the geological settings. Modifications of the logarithmic expression of the Sr/Ca and Ba/Ca relationship allow a new formula of the biopurification process to be deduced, leading to the general equation OR_Ba=OR_Sr^1.79±0.33,where the allometric coefficient is the mean of the slopes of the three regression equations. Some recent examples are used to illustrate this new analysis of predator-prey relations between mammals. This opens up new possibilities for the utilization of Ba/Ca and Sr/Ca in addition to stable isotope ratios (¹³C and ¹⁵N) for the determination of the relative contribution of different food sources to an animals diet.     

Elemental and isotopic analyses of mammalian fauna from Southern Africa and their implications for paleodietary research

Elemental analyses of mammalian bone (e.g., strontium-calcium ratios, or Sr/Ca) distinguish between herbivores and carnivores; however, the relationships among herbivores are unclear. To study this question, a modern faunal sample from the Nagupande Tsetse Control Area (Zambezi drainage, Northwestern Zimbabwe) was used. This collection has the advantage of well-established geographical controls in addition to a varied fauna, which includes both bovids and suids. The grazing/browsing dietary status of each species was ascertained by means of isotopic analysis of carbon. Clear differences were seen in the δ¹³C of grazing and browsing animals; a specialized grazer was found to have significantly lower Sr/Ca than less specialized grazers and browsers. In this study it was also possible to examine differences in Sr/Ca by sex; female warthogs were found to have significantly lower Sr/Ca than males. The variation in certain animal groups was found to be abnormal. Implications for reconstruction of prehistoric human diets using trace-element techniques are discussed.     

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.     

西藏故如甲木墓地人群牙齿磨耗和食物结构的关系

西藏阿里故如甲木墓地位于阿里地区噶尔县,是迄今为止阿里地区发现的规模最大、埋葬最集中的古代墓葬群。2012-2014年由中国社会科学院考古研究所和西藏自治区文物保护研究所联合开展发掘工作,发现并清理了11座墓葬,其中8座墓葬的时代略早,约为公元3-4世纪。另外3座为公元7-9世纪的吐蕃时期墓葬。本文对时代略早的8座故如甲木墓地出土的人骨进行了牙齿磨耗的观察,计算了每颗牙齿的平均磨耗等级以及前后部牙齿的磨耗差别指数,并选择了7组不同时代、不同地点、不同生业类型的古代人群进行了比较分析。结果表明,故如甲木的古代人群牙齿磨耗与畜牧业人群的磨耗接近,这也符合故如甲木当时的生业类型,即以牧业为主,辅以青稞和谷物的种植栽培。从牙齿磨耗推测故如甲木的人群在食物结构中有足够的动物性食物,这与碳氮同位素的食物结构分析结果也是一致的。     

The concentration of Ca,Sr, Ba and Mn in successive needle age classes of Norway spruce [Picea abies (L.) Karst.]

The concentrations of Ca, Sr, Ba and Mn were determined in up to five successive needle age classes from 54 individual Norway spruce trees [Picea abies (L.) Karst] from nine different sites. The accumulation behaviour was found to be very nonuniform, going from an increase with needle age to a decrease; irregular patterns were also found. The type of accumulation is largely site specific. The increasing behaviour can in most cases be approximated by a simple arithmetic function. All four elements usually show the same accumulation pattern, the similarities being closest between Ca and Mn and least between Ca and Ba. It is postulated that the similarity between the four elements is due to their precipitation and storage as oxalates. The similarity between Ca, Sr and Ba is observed at all concentrations, that with Mn only at concentrations larger than 300 g/g. Mn at small concentrations (< 50 g/g) shows a decreasing pattern and no similarity at all with Ca, Sr and Ba, but behaves similar to mobile elements.     

Evaluation of the mobility and discrimination of Ca, Sr and Ba in forest ecosystems: consequence on the use of alkaline-earth element ratios as tracers of Ca

A comprehensive understanding of Ca cycling in an ecosystem is desirable because of the role of this element in tree mineral nutrition and its status as a major base cation on the soil exchange complex. The determination of the origin of Ca in forests is particularly indicated in regard of important changes linked to acid inputs and intensive logging. Natural strontium isotopes are increasingly used as tracers of Ca in forest ecosystems for qualitative and quantitative assessments. Nevertheless this method is limited to relatively simple systems with two sources of nutrients. Some recent studies coupled Sr/Ca or Sr/Ba ratios to Sr isotopic measurements in order to solve more complex systems. Such method has however associated with it some uncertainties: this approach assumed that Ca, Sr and Ba behave similarly throughout the ecosystem and does not take into account the Ca biopurification processes occurring in some tree’s organs which can alter element ratio. The present work focuses on two deciduous species covering large areas in Europe: European beech (Fagus sylvatica L.) and pedunculate oak (Quercus robur L.). In order to test the similarity of behaviour between Ca, Sr and Ba, their concentrations were measured extensively in the major compartments of two forest ecosystems. In parallel, the discrimination process inside tree organs was studied in 23 stands for beech and 10 stands for oak. We found that Sr and Ca behave similarly in all soil and tree compartments. By contrast, Ba and Ca appear to have contrasting behaviours, especially in streams, soil solution and soil exchange complex (no correlations between element concentrations). Sr/Ba and Ba/Ca ratios must therefore be used with care as tracer of Ca. The Ca biopurification is absent in roots and slight in bole wood but is large in bark, twigs and leaves. The discrimination factors (DF) between wood and leaves are characteristic of the two species studied and do not change significantly as a function of the soil Ca status (acidic or calcareous soils). Therefore, strontium–calcium DF can be used as a correction factor of the Sr/Ca ratio of leaves when this ratio is used in connection with Sr isotopic ratios. This correction allows to solve systems of tree nutrition with more than two sources of Ca.     

中西部幼儿肠道菌群与膳食关系的比较

目的探究中部和西部地区幼儿肠道菌群的结构差异与膳食的关系,为幼儿营养健康状况监测和营养改善工作提供有效的营养干预。方法选择“贫困地区儿童营养改善项目”河南汝阳和贵州福泉,随机抽取107名汉族健康幼儿为调查对象,食物摄入采用24 h消费调查方法。应用高通量测序技术对肠道菌群进行测序和生物信息分析,研究两县幼儿肠道菌群差异。结果两县幼儿肠道菌群组成结构较为一致,但Alpha多样性分析表明,贵州福泉县幼儿肠道物种丰富度和多样性高于河南汝阳县。细菌属水平分析中,两县幼儿肠道内均以拟杆菌属、普雷沃菌、柔嫩梭菌和双歧杆菌属为主导的菌群结构,但河南汝阳县幼儿肠道双歧杆菌属和乳杆菌属丰度显著高于贵州福泉县(12.36% vs. 7.44%;0.19% vs. 0.03%)。结论中西部地区幼儿肠道菌群结构差异不大,但有益菌含量存在显著差异,这为研究肠道菌群与膳食及营养健康状况之间的关系提供了依据。     

Carbon isotope fractionation between diet and bioapatite in ungulate mammals and implications for ecological and paleoecological studies

 The isotope enrichment ɛ* of ¹³C between tooth enamel of large ruminant mammals and their diet is 14.1 ± 0.5‰. This value was obtained by analyzing both the dental enamel of a variety of wild and captive mammals and the vegetation that comprised their foodstuffs. This isotope enrichment factor applies to a wide variety of ruminant mammals. Non-ruminant ungulates have a similar isotope enrichment, although our data cannot determine if it is significantly different. We also found a ¹³C isotope enrichment ɛ* of 3.1 ± 0.7‰ for horn relative to diet, and 11.1 ± 0.8‰ for enamel relative to horn for ruminant mammals. Tooth enamel is a faithful recorder of diet. Its isotopic composition can be used to track changes in the isotopic composition of the atmosphere, determine the fraction of C₃ or C₄ biomass in diets of modern or fossil mammals, distinguish between mammals using different subpathways of C₄ photosynthesis,and identify those mammals whose diet is derived from closed-canopy habitats. Received: 1 July 1998 / Accepted: 9 February 1999     

The relationship between bone marrow adipose tissue and bone metabolism in postmenopausal osteoporosis

Postmenopausal osteoporosis (PMOP) is a prevalent skeletal disorder associated with menopause-related estrogen withdrawal. PMOP is characterized by low bone mass, deterioration of the skeletal microarchitecture, and subsequent increased susceptibility to fragility fractures, thus contributing to disability and mortality. Accumulating evidence indicates that abnormal expansion of marrow adipose tissue (MAT) plays a crucial role in the onset and progression of PMOP, in part because both bone marrow adipocytes and osteoblasts share a common ancestor lineage. The cohabitation of MAT adipocytes, mesenchymal stromal cells, hematopoietic cells, osteoblasts and osteoclasts in the bone marrow creates a microenvironment that permits adipocytes to act directly on other cell types in the marrow. Furthermore, MAT, which is recognized as an endocrine organ, regulates bone remodeling through the secretion of adipokines and cytokines. Although an enhanced MAT volume is linked to low bone mass and fractures in PMOP, the detailed interactions between MAT and bone metabolism remain largely unknown. In this review, we examine the possible mechanisms of MAT expansion under estrogen withdrawal and further summarize emerging findings regarding the pathological roles of MAT in bone remodeling. We also discuss the current therapies targeting MAT in osteoporosis. A comprehensive understanding of the relationship between MAT expansion and bone metabolism in estrogen deficiency conditions will provide new insights into potential therapeutic targets for PMOP.     

Synthesis and characterization of bis(4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedionato) strontium and barium adducts with O- and N- ancillary ligands; crystal structure of Sr(tftb)2(batcp)

Complexes of type [M(tftb)₂L_n] [M=Sr; n=1, L=tetraglyme (4), 2,3-benzo-10-aza-1,4,7,13-tetraoxacyclopentadeca-2-ene (batcp) (5), n=2, L=2,2^′-bipyridine-N,N^′ (bipy) (6); M=Ba; n=1, L=tetraglyme (7), 2,3-benzo-10-aza-1,4,7,13-tetraoxacyclopentadeca-2-ene (batcp) (8); n=2, L=2,2^′-bipyridine-N,N^′ (bipy) (9)] were prepared by in situ reactions of 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (Htftb) (1) with M(OH)₂ [M=Sr (2a); Ba (2b)] in the presence of the ancillary ligands L (3a: L=tetraglyme; 3b: L=2,3-benzo-10-aza-1,4,7,13-tetraoxacyclopentadeca-2-ene (batcp); 3c: L=2,2^′-bipyridine-N,N^′ (bipy)) in aqueous ethanol. The compounds were obtained in high yields and characterized by elemental analysis, ¹H NMR, mass spectrometry and IR analysis. Molecular structure of the [Sr(tftb)₂(batcp)] (5) has been determined by X-ray single crystal analysis.     

Changes in Sr/Ca, Ba/Ca and 87Sr/86Sr ratios between trophic levels in two forest ecosystems in the northeastern U.S.A.

The variability and biologicalfractionation of Sr/Ca, Ba/Ca and ⁸⁷Sr/⁸⁶Srratios were studied in a soil–plant–invertebrate–bird food chain in two forested ecosystems withcontrasting calcium availability in the northeasternU.S.A. Chemical measurements were made of the soilexchange pool, leaves, caterpillars, snails, and boththe femurs and eggshells of breeding insectivorousmigratory songbirds. ⁸⁷Sr/⁸⁶Sr values weretransferred up the food chain from the soil exchangepool to leaves, caterpillars, snails and eggshellswithout modification. Adult birds were the oneexception; their ⁸⁷Sr/⁸⁶Sr values generallyreflected those of lower trophic levels at each site,but were lower and more variable, probably becausetheir strontium was derived in part from foods intropical winter habitats where lower⁸⁷Sr/⁸⁶Sr ratios are likely to predominate. Sr/Ca and Ba/Ca ratios decreased at each successive trophiclevel, supporting previous suggestions that Sr/Ca andBa/Ca ratios can be used to identify the trophic levelat which an organism is primarily feeding. The changesin Sr/Ca and Ba/Ca ratios we measured for vegetationand insects were comparable to similar measurementsmade previously (but based on single samples of eachorganism) in an alpine ecosystem. Changes in Sr/Ca andBa/Ca ratios between birds and their food have notpreviously been measured, but the values we obtainedwere similar to those for herbivorous and carnivorousmammals at similar trophic levels. Our results provideevidence that supports the use of Sr/Ca ratios in thedetermination of human paleodiets and suggests thatSr/Ca ratios may also provide a useful tool in studiesof modern food webs. Furthermore, our findings suggestthat ⁹⁰Sr from nuclear fallout will notbioaccumulate in forests and that changes in Sr/Caratios between trophic levels will need to beconsidered in some cases when using⁸⁷Sr/⁸⁶Sr as a tracer of calciumbiogeochemistry.     

Test of soil extractants for their suitability in predicting Ca/Sr ratios in leaves and stems of sugar maple seedlings

Differential uptake and translocation of Ca and Sr in organisms have been reported, calling into question the use of Sr to track Ca cycling in the environment. We investigated the relationship between Ca/Sr ratios in soil extracts of various strengths (H₂O, NH₄Cl, and NH₄EDTA) and seedlings of sugar maple (Acer saccharum Marsh.) grown from natural regeneration on 37 sites. Our objectives were to determine if Ca/Sr ratios in soil extracts are correlated with those in sugar maple tissues, and what soil extractant best duplicate plant tissue Ca/Sr ratios. Leaves had higher Ca/Sr ratios than stems and the extractants did not produce equal Ca/Sr ratios: H₂O had the lowest Ca/Sr, and NH₄EDTA the highest. The relationships between soil extract Ca/Sr ratios and leaf and stem Ca/Sr ratios were significant and linear, but the slopes differed among extractants. The lowest slope (0.45) was observed for the water extract/leaves and the highest (2.15) for the NH₄EDTA extract/stem with discrimination factors ranging from 0.22 with NH₄EDTA to 1.59 for water. Leaf extracts were more strongly correlated with soil Ca/Sr than stem extracts (R ² of 0.57–0.7 vs. R ² of 0.45–0.6, respectively). These findings support the use of Ca/Sr ratios in plants to track their source of soil Ca, but they highlight the need to calibrate the relationships for the plant tissue and soil extractant used.     

Discrimination between receptor- and store-operated Ca influx in human neutrophils

Ca²⁺ and Sr²⁺ entry pathways activated by pro-inflammatory agonists FMLP, LTB₄ and PAF have been compared to thapsigargin in human neutrophils. 2-APB (10 μM) increased Ca²⁺ influx and to a greater extent in agonist than in thapsigargin stimulated neutrophils. This action of 2-APB was specific to Ca²⁺ because 2-APB did not augment Sr²⁺ entry in agonist and thapsigargin stimulated neutrophils. This suggests that Ca²⁺ and Sr²⁺ entry can be used to discriminate between receptor and non-receptor (store)-operated Ca²⁺ influx. Our data show for the first time that Pyr3 whilst partially inhibiting agonist induced Ca²⁺ influx almost completely abolished Ca²⁺ influx after thapsigargin stimulation.     

Copepod and microzooplankton grazing in mesocosms fertilised with different Si:N ratios: no overlap between food spectra and Si:N influence on zooplankton trophic level

We hypothesized that the trophic level of marine copepods should depend on the composition of the protist community. To test this hypothesis, we manipulated the phytoplankton composition in mesocosms and measured grazing rates of copepods and mesozooplankton in those mesocosms. Twelve mesocosms with Northeast Atlantic phytoplankton were fertilised with different Si:N ratios from 0:1 to 1:1. After 1 week, ten of the mesocosms were filled with natural densities of mesozooplankton, mainly calanoid copepods, while two remained as mesozooplankton-free controls. Both before and after the addition of copepods there was a positive correlation of diatom dominance with Si:N ratios. During the second phase of the experiment, copepod and microzooplankton grazing rates on different phytoplankton species were assessed by a modification of the Landry-Hassett dilution technique, where the bottles containing the different dilution treatments were replaced by dialysis bags incubated in situ. The results indicated no overlap in the food spectrum of microzooplankton (mainly ciliates) and copepods. Ciliates fed on nanoplankton, while copepods fed on large or chain-forming diatoms, naked dinoflagellates, and ciliates. The calculated trophic level of copepods showed a significantly negative but weak correlation with Si:N ratios. The strength of this response was strongly dependent on the trophic levels assumed for ciliates and mixotrophic dinoflagellates.     

The relationship between ontogeny, morphology, and diet in the Chinese hook snout carp (Opsariichthys bidens)

The relationship of changes of body and mouth shape with diet during ontogeny in the Chinese hook snout carp Opsariichthys bidens was examined. Shape changes were analyzed using geometric morphometrics. Body shape changed from a shallow body to a deep body as size increased. Similarly, the head of O. bidens changed from an upward-pointing direction to a downward-pointing directing as size increased. The position of the eye also changed during ontogeny, with large individuals having an eye situated higher on the head than small individuals. The conspicuous symphyseal knob on the lower jaw of O. bidens results in a typical zigzag pattern of the jaw. The zigzag pattern became more pronounced as fish grew larger. No difference in body shape or jaw shape was found between males and females. The shape changes were associated with changes in diet, suggesting that diet choice over the course of ontogeny has a strong impact on body shape. Benthic macroinvertebrates and zooplankton dominated the diet of small individuals, medium-size individuals specialized in benthic macroinvertebrates, and fish dominated the diet of large individuals.     

Requirement of Ca2+ for the gelatinization of pectin solution by a proteinous cell wall-bound factor and solubilization of the gel by acid treatment

The cell wall-bound pectin-gelatinizing factor, whose existence was reported in a previous paper (Yamaoka and Sato, 1981), was found to be composed of a proteinous factor (PGF) and calcium ion. Magnesium ion could not replace Ca²⁺ whereas Sr²⁺ could replace Ca²⁺ and Ba²⁺ could cause gelation without the action of PGF. In the hypocotyl of soybean seedlings, the basal region contained more PGF than did the apical region. The gel of apple pectin formed by the action of PGF and Ca²⁺ was solubilized by acid treatment for some time after the gelation. It was also found that the gel became more and more resistant to acidity with time. The hardened gel was almost completely dissolved by boiling in 0.2 M NaCl solution. The idea that the gelation of apple pectinin vitro may simulate the gelation of pectin in the primary cell wall was discussed in view of the results and the phenomenon of acid growth.     

The relationship between biodiversity and ecosystem functioning in food webs

Recent theoretical and experimental work provides clear evidence that biodiversity loss can have profound impacts on functioning of natural and managed ecosystems and the ability of ecosystems to deliver ecological services to human societies. Work on simplified ecosystems in which the diversity of a single trophic level is manipulated shows that diversity can enhance ecosystem processes such as primary productivity and nutrient retention. Theory also strongly suggests that biodiversity can act as biological insurance against potential disruptions caused by environmental changes. However, these studies generally concern a single trophic level, primary producers for the most part. Changes in biodiversity also affect ecosystem functioning through trophic interactions. Here we review, through the analysis of a simple ecosystem model, several key aspects inherent in multitrophic systems that may strongly affect the relationship between diversity and ecosystem processes. Our analysis shows that trophic interactions have a strong impact on the relationships between diversity and ecosystem functioning, whether the ecosystem property considered is total biomass or temporal variability of biomass at the various trophic levels. In both cases, food-web structure and trade-offs that affect interaction strength have major effects on these relationships. Multitrophic interactions are expected to make biodiversity–ecosystem functioning relationships more complex and non-linear, in contrast to the monotonic changes predicted for simplified systems with a single trophic level.     

Relationship between diet and helminths in Gallotia caesaris (Sauria: Lacertidae)

Diet and helminth fauna were analysed in Gallotia caesaris, a small lacertid lizard endemic to El Hierro (Canary Islands, Spain) in order to study the evolutionary and functional relationships between the two traits. This species is omnivorous but consumed a high proportion (82.13%) of plant matter including not only seeds but also leaves and other vegetative parts. Helminth fauna included many helminth species typical of herbivorous reptiles. Both herbivory and helminth presence were higher than expected for a lizard of its size. Comparison with other lacertids suggests that both traits result from an adaptation to insular conditions but that some "evolutionary time" to develop them is needed. Canarian Gallotia lizards, a separate lineage evolving for a long time in insularity, constitutes the most advanced lacertid group in this way. Nevertheless, results for G. caesaris indicate that helminth fauna also changes seasonally tracking variation in diet (and herbivory) throughout the year, which suggests a dynamic interaction between diet and helminth parasites.     

Determination of foliar Ca/Sr discrimination factors for six tree species and implications for Ca sources in northern hardwood forests

Plant and Soil - Discrimination during foliar uptake between the alkaline earth elements Ca and Sr must be understood to fully utilize Ca/Sr and 87Sr/86Sr ratios as a monitor of Ca sources to...