Use of stored carbon reserves in growth of temperate tree roots and leaf buds: analyses using radiocarbon measurements and modeling

Characterizing the use of carbon (C) reserves in trees is important for understanding regional and global C cycles, stress responses, asynchrony between photosynthetic activity and growth demand, and isotopic exchanges in studies of tree physiology and ecosystem C cycling. Using an inadvertent, whole-ecosystem radiocarbon (¹⁴C) release in a temperate deciduous oak forest and numerical modeling, we estimated that the mean age of stored C used to grow both leaf buds and new roots is 0.7 years and about 55% of new-root growth annually comes from stored C. Therefore, the calculated mean age of C used to grow new-root tissue is ∼0.4 years. In short, new roots contain a lot of stored C but it is young in age. Additionally, the type of structure used to model stored C input is important. Model structures that did not include storage, or that assumed stored and new C mixed well (within root or shoot tissues) before being used for root growth, did not fit the data nearly as well as when a distinct storage pool was used. Consistent with these whole-ecosystem labeling results, the mean age of C in new-root tissues determined using 'bomb-¹⁴C' in three additional forest sites in North America and Europe (one deciduous, two coniferous) was less than 1–2 years. The effect of stored reserves on estimated ages of fine roots is unlikely to be large in most natural abundance isotope studies. However, models of root C dynamics should take stored reserves into account, particularly for pulse-labeling studies and fast-cycling roots (<1 years).     

Diet and diversity at later medieval Fishergate: the isotopic evidence

We present the results of stable carbon and nitrogen isotope analysis of bone collagen for 155 individuals buried at the Later Medieval (13th to early 16th century AD) Gilbertine priory of St. Andrew, Fishergate in the city of York (UK). The data show significant variation in the consumption of marine foods between males and females as well as between individuals buried in different areas of the priory. Specifically, individuals from the crossing of the church and the cloister garth had consumed significantly less marine protein than those from other locations. Isotope data for four individuals diagnosed with diffuse idiopathic skeletal hyperostosis (DISH) are consistent with a diet rich in animal protein. We also observe that isotopic signals of individuals with perimortem sharp force trauma are unusual in the context of the Fishergate dataset. We discuss possible explanations for these patterns and suggest that there may have been a specialist hospital or a local tradition of burying victims of violent conflict at the priory. The results demonstrate how the integration of archaeological, osteological, and isotopic data can provide novel information about Medieval burial and society.     

Stable carbon isotope composition of bone hydroxylapatite: significance in paleodietary analysis

The stable carbon isotope composition of the structural carbonate derived from animal bone hydroxylapatite (δ¹³C_B-HA) could record an animal’s diet. These records provide critical evidence for different paleontological disciplines, e.g., paleodiet analyses, and paleoclimate reconstructions. Compared to those of other body tissues, such as bone collagen or teeth enamel hydroxylapatite, δ¹³C_B-HA values record information on the whole diet of an animal in its last years. δ¹³C_B-HA can be applied to fossil animals of various body sizes. The δ¹³C analytical instruments available only require that prepared bone samples be approximately 2–5 mg for precise measurement, allowing δ¹³C_B-HA analysis to be feasible on most vertebrate fossils without destructive sampling, especially on small mammals or birds whose teeth are not large enough for sampling or are lost. Moreover, δ¹³C_B-HA can be used from different times or under less than ideal burial environments. For fossils dating back to Devonian or buried in hot and humid regions, dietary information has been completely lost in bone collagen during post-depositional processes but still remained in the δ¹³C_B-HA values because hydroxylapatite is less influenced by diagenetic effects after deposition. In addition, systematic methods such as X-ray diffraction and Fourier transform infrared spectroscopy have been developed to qualitatively or semiquantitatively assess the influence of diagenesis on bone hydroxylapatite to ensure the credibility of the δ¹³C_B-HA values. With the above merits, δ¹³C_B-HA analysis is therefore becoming an increasingly important method in paleodiet-related research. Currently, applications of the δ¹³C_B-HA method on fossil animals are primarily focused on two aspects, namely, paleodietary reconstruction of fossil animals with uncertain diets and paleoenvironmental reconstruction based on the δ¹³C_B-HA values of fossil herbivores. The published researches, combined with our new results from early birds, demonstrate the considerable significance of the δ¹³C_B-HA method in paleontological and paleoenvironmental research. Notably, the δ¹³C_B-HA-based paleodietary analysis of early vertebrates, especially the large number of small birds or mammals discovered in the past decades would be an important work in the near future.     

同位素富集-稀释法研究食性转变对鱼类不同组织N同位素转化率的影响

稳定同位素技术广泛地用于描绘生态系统中食物网的食物来源和营养级关系,但是消费者不同组织转化率的研究相对较少。通过锦鲤摄食人工添加15N蓝藻的食性转化实验,研究不同组织N同位素转化率的差异,探讨组织生长和代谢对同位素转化的相对贡献,为不同时间尺度的稳定同位素研究取样奠定基础。结果表明,通过42d的加富蓝藻饲喂,各组织的N稳定同位素发生显著变化。肝的δ15N为(19.3±1.4)‰,显著高于其它组织,其次为鱼鳍((15.6±1.0)‰)和血液((12.6±0.4)‰),肌肉的δ15N‰最低,为(9.9±0.7)‰。在随后的同位素稀释实验中,锦鲤的体重增加,相对生长速率为0.011d-1,鳍肉的转化率最快,达到11.4%/d,半衰期仅为6.1d,其次是血液和肝,肌肉的转化率最低,仅有3.8%/d,半衰期最长,为18.4d。代谢衰减指数c和-1不存在显著差异,表明锦鲤各组织的N同位素转化主要由组织生长引起。结论显示,同位素富集-稀释法可以有效评价鱼类食性转变对不同组织同位素转化的差异,鳍肉和血液同位素分析可以作为锦鲤食性转变快速追踪的手段。     

Modelling organic carbon turnover in cleared temperate forest soils converted to maize cropping by using 13C natural abundance measurements

In southwest France, thick humic acid loamy soils have developed from Quaternary silty alluvial deposits. On these soils, most forest lands have been converted to continuous intensive maize cropping and the loss of C upon conversion to intensive agriculture has been shown to be significant. The objective of this study was to determine if a study of natural ¹³C abundance in soil organic C makes possible an improved modelling of organic carbon turnover in the cultivated horizons of soils in this landscape in southwest France. A chronosequence study is realized by comparing C pools and C-13 natural abundance of three forest sites and 14 adjacent agricultural sites, whose ages of cultivation ranged from 3 to 32 yr. ¹³C ratio is found to increase with time of cultivation. The fraction of C coming from the maize crop increases during the first decades of cultivation, and reaches a plateau thereafter. This equilibrium level is reached after a few decades of cultivation. The decrease of the initial C pool is fitted by a simple model assuming that about half of this pool is mineralized during the first yr of cultivation whereas the other half decreases at a slower rate. Therefore, a general bi-compartmental model is proposed for describing the soil organic carbon dynamics in these soils after forest clearing and intensive maize cropping.     

人为营养物质输入对汉丰湖不同营养级生物的影响--稳定C、N同位素分析

以长江一级支流小江上游的汉丰湖为研究对象,设置了4个采样点(影响组:A, B;对照组:C, D),应用碳、氮稳定性同位素探讨人类生活污水和农业面源污染对汉丰湖水生生态系统中不同营养级水平生物类群的影响。结果表明:影响组POM(颗粒有机物)和螺类碳、氮稳定性同位素比值范围分别为-25.93‰--24.63‰、4.12‰-9.86‰,-14.28‰--21.60‰、7.97‰-19.99‰;对照组POM(颗粒有机物)和螺类碳、氮稳定性同位素比值范围分别为-25.62‰--22.51‰、0.01‰-6.56‰,-22.96‰--19.21‰、6.75‰-8.89‰;不同组间POM和初级消费者螺类碳同位素比值无明显空间变化(P>0.05), 而氮稳定性同位素比值空间变化显著(P<0.05)。因此,在汉丰湖食物网中,氮稳定性同位素特征更好地反应了营养物质(人为输入)吸收和富集的信息。与固着藻类、鱼类等相比,POM和软体动物螺类更适合作为环境评价的指示物。影响组A、B样点的部分生物类群已经受到了人为营养物质输入的影响,影响强度B样点区域>A样点区域。结果建议加强汉丰湖水环境保护,控制污水排放量及提高污水处理水平,对于保护小江和三峡库区水质具有十分重要的意义。     

Dietary quality predicts adult weight gain: findings from the Framingham Offspring Study

Objective: We tested the hypothesis that dietary quality, measured by adherence to the Dietary Guidelines, was related to weight change in adults. Research Methods and Procedures: Dietary intake was assessed among 2245 adult men and women (average age, 49 to 56 years) in the Framingham Offspring cohort. Three‐day dietary records were collected in 1984 to 1988 and again in 1991 to 1996. Weight change was measured over 8 years after each assessment. A five‐point diet quality index (DQI) was computed based on mean nutrient intake levels from each set of diet records. One DQI point was contributed for each of five nutrients if intake met Dietary Guidelines for total and saturated fat, cholesterol, sodium, and carbohydrate. Gender‐specific generalized estimating equations pooled data across the two assessments to relate DQI to 8‐year weight gain. Results: Men and women with higher DQI scores gained less weight during follow‐up (p < 0.05). Average gain over 8 years was ～3 pounds among those with highest scores, compared with 5 to 8 pounds among those with lower scores. Smoking cessation was an important predictor of weight gain, accounting for about a 5‐ to 9‐pound difference in weight gain. Discussion: A high‐quality diet, one that is consistent with the Dietary Guidelines, may help curb rising rates of obesity at the population level. Poor compliance with the Guidelines, rather than the guidelines themselves, is likely responsible for the weight gain observed in the American population. Adoption of an eating pattern consistent with the Dietary Guidelines should facilitate population weight control if sustained long term.     

Enhanced benthic activity in sandy sublittoral sediments: Evidence from 13C tracer experiments

In situ and on-board pulse-chase experiments were carried out on a sublittoral fine sand in the German Bight (southern North Sea) to investigate the hypothesis that sandy sediments are highly active and have fast turnover rates. To test this hypothesis, we conducted a series of experiments where we investigated the pathway of settling particulate organic carbon through the benthic food web. The diatom Ditylum brightwellii was labelled with the stable carbon isotope ¹³C and injected into incubation chambers. On-board incubations lasted 12, 30 and 132 h, while the in situ experiment was incubated for 32 h. The study revealed a stepwise short-term processing of a phytoplankton bloom settling on a sandy sediment. After the 12 h incubation, the largest fraction of recovered carbon was in the bacteria (62%), but after longer incubation times (30 and 32 h in situ) the macrofauna gained more importance (15 and 48%, respectively), until after 132 h the greatest fraction was mineralized to CO₂ (44%). Our findings show the rapid impact of the benthic sand community on a settling phytoplankton bloom and the great importance of bacteria in the first steps of algal carbon processing.     

Light and dark uptake and loss of 14C: methodological problems with productivity measurements in oceanic waters

Measurements of the uptake and loss of ⁴C in the light and in the dark in the Tasman and Coral Seas have revealed methodological problems with the estimation of productivity in these waters. Rates of productivity estimated without replication, time series incubations and dark controls frequently overestimated the true rates of autotrophic production. The data showed unexpectedly high rates of both uptake and loss in the dark in oligotrophic waters. In oligotrophic oceanic waters, dark incorporation of ¹⁴C sometimes equalled the uptake of ¹⁴C in the light bottle. Rapid uptake of isotope in the dark controls appeared to be the result of rapid bacterial growth and metabolism. This problem was exacerbated by agitation of the sample before or during the incubation. Tropical samples were particularly susceptible to problems arising from the agitation of the samples. Latitudinal gradients of dark uptake and loss were revealed in these incubations. The loss of label during 8–12 hours in the dark (after 12 hr in the light) was as high as 50% in subtropical waters. The loss was frequently unmeasurable (< 10%) in temperate waters. The time course of ¹⁴C uptake indicated active grazing in the bottles and suggested that most of the nighttime losses of label were due to grazing by microheterotrophs. Respiratory losses appeared to be small. Calculated values of the assimilation number (or photosynthetic capacity) which did not correct for dark ¹⁴C uptake were too high to be biochemically realistic. The errors were due to the heterotrophic uptake of label and the lack of dark controls. Rapid release of ¹⁴C in the dark after incubation in the light meant that the estimate of productivity was dependant on the trophic state of the sample and on the period of incubation.     

Victims and survivors: Stable isotopes used to identify migrants from the Great Irish Famine to 19th century London

Historical evidence documents mass migration from Ireland to London during the period of the Great Irish Famine of 1845–52. The rural Irish were reliant on a restricted diet based on potatoes but maize, a C₄ plant, was imported from the United States of America in 1846–47 to mitigate against Famine. In London, Irish migrants joined a population with a more varied diet. To investigate and characterize their diet, carbon and nitrogen isotope ratios were obtained from bone collagen of 119 and hair keratin of six individuals from Lukin Street cemetery, Tower Hamlets (1843–54), and bone collagen of 20 individuals from the cemetery at Kilkenny Union Workhouse in Ireland (1847–51). A comparison of the results with other contemporaneous English populations suggests that Londoners may have elevated δ¹⁵N compared with their contemporaries in other cities. In comparison, the Irish group have lower δ¹⁵N. Hair analysis combined with bone collagen allows the reconstruction of perimortem dietary changes. Three children aged 5–15 years from Kilkenny have bone collagen δ¹³C values that indicate consumption of maize (C₄). As maize was only imported into Ireland in quantity from late 1846 and 1847, these results demonstrate relatively rapid bone collagen turnover in children and highlight the importance of age‐related bone turnover rates, and the impact the age of the individual can have on studies of short‐term dietary change or recent migration. Stable light isotope data in this study are consistent with the epigraphic and documentary evidence for the presence of migrants within the London cemetery. Am J Phys Anthropol, 2013. © 2012 Wiley Periodicals, Inc.     

Characteristics of the Na+/K+-ATPase from Torpedo californica expressed in Xenopus oocytes: a combination of tracer flux measurements with electrophysiological measurements

The Na+/K+-ATPase from electroplax of Torpedo californica was incorporated into the plasma membrane of Xenopus oocytes by microinjection of mRNA coding for the alpha- and beta-subunit of the enzyme; the mRNAs were obtained by in vitro translation of cloned cDNAs (Noguchi et al. (1988) FEBS Lett. 225, 27-32). (1) Measurements of ouabain-sensitive membrane current revealed that the Na+/K+-ATPase of Torpedo is less sensitive to ouabain than the endogenous enzyme. (2) The ouabain-sensitive membrane currents in mRNA-injected oocytes exhibit similar voltage dependence as the currents generated by the endogenous ATPase of Xenopus oocytes; in particular, the current-voltage relation exhibits a maximum and a negative slope at potentials more positive than +20 mV. (3) A maximum can also be detected if the rate of 22Na+ efflux is determined under different voltage-clamp conditions. If membrane current and rate of Na+2 efflux are determined simultaneously, a voltage-independent ratio between current and flux is obtained suggesting voltage-independent Na+-K+ stoichiometry. The data are compatible with a 3Na+-2K+ stoichiometry.     

河南淇县宋庄东周墓地人骨稳定同位素分析——东周贵族与殉人食谱初探

淇县宋庄东周墓地出土贵族和殉人骨骼遗存的稳定同位素分析是国内首例针对东周社会分化背景下不同社会阶层先民开展的食谱研究.稳定碳氮同位素分析结果表明,贵族阶层在主粮和肉食方面与殉人群体明显不同.贵族几乎完全以粟为主粮,食物中肉类含量很高;而殉人阶层整体食肉水平较低,主粮的内部差异显著,大部分个体都不同程度的食用了当时不受青...     

Metabolic targeted therapy of cancer: current tracer technologies and future drug design strategies in the old metabolic network

Targeted drugs tailored against genes and signaling proteins have formed the new era termed Targeted Therapies. Although the field is relatively young, since only about 5 years ago clinical trials started showing promise, there have are already been significant setbacks due to drug resistance caused by point mutations, alterations in gene expression or complete loss of target proteins with disease progression. Although new drugs are continuously designed and tried, it seems inevitable that genetic and signal protein targets pose too broad flexibility and variability, often changing target characteristics and thus escape treatments turning “magic bullets” into rather “wondering bullets”. This is especially true in cancer, where old and new targeted therapies continue to fail and the most recent ones do not offer much improvement on clinical outcome parameters. Metabolic targeted therapies are aimed at control points of the metabolic network by targeting particular enzymes of major macromolecule synthesis pathways in cancer. This review summarizes the potential benefits of targeted therapies in the metabolic network as applied with genetic and proteomic approaches. The metabolic target approach is most efficient if and when pathway flux information is available for drug target development using the stable isotope based dynamic metabolic profile (SIDMAP) of tumor cells, in vitro or in vivo.This revised version was published online in June 2005. The previous version did not contain colour images.     

Morphology,diet, and stable carbon isotopes: On the diet of Theropithecus and some limits of uniformitarianism in paleoecology

Geladas were long supposed to be the only living primates feeding almost entirely on graminoids and accordingly display dramatic dental and manual adaptive traits. A recent study of Theropithecus gelada, the first in a relatively undisturbed habitat, revealed a more diverse diet, also incorporating large quantities of forbs. The peculiar adaptive traits of T. gelada are also observed in extinct Theropithecus as early as 3.7 Ma. Stable carbon isotopic data of extinct Theropithecus from eastern Africa indicate that specimens older than 3 Ma consumed a significant proportion of C₃ plants (on average ca. 40% of total food intake) whereas specimens younger than 2 Ma consumed more C₄ plants (on average ca. 80%). Recent paleobotanical evidence suggests that C₃ herbaceous plants were still present in non‐negligible proportions in Plio‐Pleistocene lowland tropical ecosystems. Together, the shared morphological adaptive traits of extant and extinct Theropithecus and the varied diets of extant T. gelada suggest that the paleodiets of Theropithecus may have been dominated by herbaceous plants, comprising both C₃ forbs and graminoids and C₄ graminoids. The changes in stable carbon isotopes could correspond to a replacement of C₃ plants by C₄ plants within the herbaceous strata rather than a shift from C₃ woody vegetation to C₄ graminoids. This synthesis highlights the need for a more exhaustive knowledge of the ecology of extant species to achieve meaningful paleodietary and paleoenvironmental reconstructions. A strong selectivity for food resources that are rare in the landscapes (as in T. gelada) should also be considered when interpreting stable carbon isotopes of extinct African mammals (and notably hominids).     

Root turnover and production by14C dilution: implications of carbon partitioning in plants

Summary Estimates of belowground net primary production (BNP) obtained by using traditional soil core harvest data are subject to a variety of potentially serious errors. In a controlled growth chamber experiment, we examined the aboveground-belowground, labile to structural tissue, and plant to soil dynamics of carbon to formulate a¹⁴C dilution technique for potential successful application in the field and to quantify sources of error in production estimates.Despite the fact that the majority of net¹⁴C movement between above- and belowground plant parts occurred between the initial labeling and day 5, significant quantities of¹⁴C were incorporated into cell-wall tissue throughout the growing period. The rate of this increase at late sampling dates was greater for roots than for shoots. Total loss of assimilated¹⁴C was 47% in wheat and 28% in blue grama. Exudation and sloughing in wheat and blue grama, respectively, was 15 and 6% of total uptake and 22 and 8% of total plant production.When root production estimates by¹⁴C dilution were corrected for the quantities of labile¹⁴C incorporated into structural carbon between two sampling dates, good agreement with actual production was found. The error associated with these estimates was ±2% compared with a range of –119 to –57% for the uncorrected estimates. Our results suggest that this technique has potential field application if sampling is performed the year after labelling.Sources of errors in harvest versus¹⁴C dilution estimates of BNP are discussed.     

Mutualistic mycorrhiza in orchids: evidence from plant-fungus carbon and nitrogen transfers in the green-leaved terrestrial orchid Goodyera repens

The roles of mycorrhiza in facilitating the acquisition and transfer of carbon (C) and nitrogen (N) to adult orchids are poorly understood. Here, we employed isotopically labelled sources of C and N to investigate these processes in the green forest orchid, Goodyera repens. Fungus-to-orchid transfers of C and N were measured using mass spectrometry after supplying extraradical mycelial systems with double-labelled [13C-15N]glycine. Orchid-to-fungus C transfer was revealed and quantified by radioisotope imaging and liquid scintillation counting of extraradical mycelium following 14CO2 fixation by shoots. Both 13C and 15N were assimilated by the fungus and transferred to the roots and shoots of the orchid. Contrary to previous reports, considerable quantities (2.6% over 72 h) of fixed C were shown to be allocated to the extraradical mycelium of the fungus. This study demonstrates, for the first time, mutualism in orchid mycorrhiza, bidirectional transfer of C between a green orchid and its fungal symbiont, and a fungus-dependent pathway for organic N acquisition by an orchid.     

Technical note: interpreting stable carbon isotopes in human tooth enamel: an examination of tissue spacings from South Africa

Stable isotope analysis of skeletal tissues is widely used in archeology and paleoanthropology to reconstruct diet. In material that is poorly preserved or very old, the tissue of choice is frequently tooth enamel, since this is less susceptible to diagenesis. The relationships between carbon isotope ratios in tooth enamel (δ(13) C(enamel) ), bone collagen (δ(13) C(collagen) ), and bone apatite (δ(13) C(bone apatite) ) are, however, not well understood. To elucidate these, we have measured all three indicators in archeological humans from the western and southern Cape coastal regions of South Africa. The correlation between δ(13) C(enamel) and δ(13) C(collagen) is good (R(2) = 0.71 if two outliers are excluded, n = 79). The correlation between δ(13) C(enamel) and δ(13) C(bone apatite) is weaker (R(2) = 0.37, n = 33) possibly due to bone diagenesis. No systematic offset between δ(13) C(bone apatite) and δ(13) C(enamel) was observed in this sample of archeological humans. Intertooth comparisons of δ(13) C(enamel) in three individuals showed little variation, despite the different ages of crown formation. Carbon isotope ratios in both enamel and bone collagen are good proxies for δ(13) C(diet) .