Distribution Of 14C Research Articles

Cultured macrophages transfer surplus cholesterol into adjacent cells in the absence of serum or high-density lipoproteins

Cholesterol-laden macrophage foam cells are a hallmark of atherosclerosis. For that reason, cholesterol metabolism in macrophages has attracted considerable scrutiny, particularly the mechanisms by which macrophages unload surplus cholesterol (a process referred to as "cholesterol efflux"). Many studies of cholesterol efflux in macrophages have focused on the role of ABC transporters in moving cholesterol onto high-density lipoproteins (HDLs), but other mechanisms for cholesterol efflux likely exist. We hypothesized that macrophages have the capacity to unload cholesterol directly onto adjacent cells. To test this hypothesis, we used methyl-β-cyclodextrin (MβCD) to load mouse peritoneal macrophages with [13C]cholesterol. We then plated the macrophages (in the absence of serum or HDL) onto smooth muscle cells (SMCs) that had been metabolically labeled with [15N]choline. After incubating the cells overnight in the absence of HDL or serum, we visualized 13C and 15N distribution by nanoscale secondary ion mass spectrometry (NanoSIMS). We observed substantial 13C enrichment in SMCs that were adjacent to [13C]cholesterol-loaded macrophages-including in cytosolic lipid droplets of SMCs. In follow-up studies, we depleted "accessible cholesterol" from the plasma membrane of [13C]cholesterol-loaded macrophages with MβCD before plating the macrophages onto the SMCs. After an overnight incubation, we again observed substantial 13C enrichment in the SMCs adjacent to macrophages. Thus, macrophages transfer cholesterol to adjacent cells in the absence of serum or HDL. We suspect that macrophages within tissues transfer cholesterol to adjacent cells, thereby contributing to the ability to unload surplus cholesterol.

Exogenous Abscisic Acid Regulates Distribution of 13C and 15N and Anthocyanin Synthesis in 'Red Fuji' Apple Fruit Under High Nitrogen Supply.

In order to improve the problem of poor coloring caused by high fruit nitrogen in apple production, we studied the effects of different concentrations of abscisic acid (ABA: 0, 50, 100, and 150 mg/L) and fluridone (ABA biosynthesis inhibitor) on the fruit of ‘Red Fuji’ apple (Malus Domestica Borkh.) in the late stage of apple development (135 days after blooming) in 2017 and 2018. The effects of these treatments on the distribution of 13C and 15N and anthocyanin synthesis in fruit were studied. The results showed that the expression levels of ABA synthesis and receptor genes in the peel and flesh were upregulated by exogenous ABA treatment. An appropriate concentration of ABA significantly increased the expression of anthocyanin synthesis genes and transcription factors and increased the content of anthocyanin in the peel. The results of 13C and 15N double isotope labeling showed that exogenous ABA coordinated the carbon–nitrogen nutrient of apple fruit in the late stage of the development, reduced the accumulation of fruit nitrogen, increased the accumulation of fruit carbon and sugar, provided a substrate for anthocyanin synthesis, or promoted anthocyanin synthesis through the sugar signal regulation mechanism. Comprehensive analysis showed that the application of 100 mg/L ABA effectively improved the problem of poor coloring caused by high fruit nitrogen in the late stage of apple development and is beneficial to the accumulation of carbon in fruit and the formation of color.

Light energy utilization and distribution characteristics of flag leaf 13C assimilate in different spike-type wheat varieties and their responses to supplementary irrigation

To clarify the differences in light energy utilization and distribution characteristics of flag leaf 13C assimilate in different spike-type wheat varieties and their responses to supplementary irrigation, we set three water treatments in a field experiment, including no irrigation during growth duration of wheat (W0), water-saving irrigation (W1, irrigating at jointing and anthesis of wheat to keep the relative moisture of 0-40 cm soil to 65% and 70%), full irrigation (W2, irrigating at jointing and anthesis of wheat to keep the relative moisture of 0-40 cm soil to 85% and 90%) with the medium-spike wheat cultivars Jimai 22 and Qingnong 2, large-spike wheat cultivars Shannong 23 and Shannong 30 as test materials. The effects of different water treatments on canopy light energy utilization and 13C assimilate distribution characteristics of two spike-type wheat varieties were examined. The results showed that leaf area index, canopy light interception rate, and light energy utilization rate of the two varieties at 2, 11, 20 and 31 days after anthesis were significantly higher than W0 treatment, but there was no significant change in each index when the irrigation increased to W2 treatment. The distribution of flag leaf 13C assimilates of Jimai 22 and Shannong 23 of W1 in grain was 159.34 and 171.1 g·hm-2 higher than W0, respectively, and the distribution ratio was 6.5% and 6.5%, with no significant difference compared with W2. The grain yields of both varieties under W1 were significantly higher than that under W0, but with no significant difference with W2. Under water-saving irrigation, the medium-spike cultivars had higher canopy photosynthetically active radiation interception and utilization ability at 2 and 11 days after anthesis and large-spike cultivars at 20 and 31 days after anthesis. The distribution amount and ratio of 13C assimilates in the grain of medium-spike variety Jimai 22 flag leaf were 6.8% and 2.7% lower than that of the large-spike variety Shannong 23.

The degradation and transformation of TBBPA-derived NER in soil

Tetrabromobisphenol A (TBBPA) is a kind of widely used brominated flame retardants. After entering to the soil, considerable TBBPA and its metabolites can form non-extractable residues (NER) under the flooded condition (F-NER) and oxic condition (O-NER). However, little is known about the stability and environmental behavior of these NERs in soil after long-term incubation. In this study, two 14C-TBBPA-NERs was used to study: (1) The fate of F-NER in oxic and oxic-flooded-oxic soil including their releasing, mineralization, degradation and the distribution of 14C in soil matrix in the presence or absence of rice root exudate; (2) the biotransformation different between the F-NER and O-NER in oxic-flooded-oxic soil in the presence or absence of rice root exudate. During 231 d incubation, slow biotransformation of F-NER was observed in oxic soil. More than 10% of F-NER was mineralized accompanied by the releasing of ester and ether-linked NER, while the extractable TBBPA and its metabolites kept quite low during the incubation (1%−6%). In addition, the appearance of rice root exudate inhabited the mineralization of F-NER in oxic soil at the end of the experiment. In oxic-flooded-oxic incubation, the mineralization of F-NER is consistent with oxic condition, while the more extractable radioactivity was observed in soil extracts during the flooded incubation. We proposed that higher extractable 14C may attribute to the released dibrominated products and BPA tended to accumulated in flooded soil, and these extractable residues removed fast after soil turns into oxic condition. Meanwhile, O-NER was more stable than F-NER in soil presented as lower mineralization and releasing of TBBPA and its metabolites during the incubation, and further analysis showed that ester and ether-linked NER also decreased slower in O-NER treatment. No obvious extractable 14C accumulated in soil extract during the flooded incubation. O-NER was more persistent in soil after long-term incubation than F-NER may attribute to the metabolism of TBBPA is different in oxic and flooded conditions. We proposed that during the formation of F-NER in soil, anaerobic metabolites such as debrominated products and BPA were bounding to the soil matrix with TBBPA, and after releasing, these metabolites can be removed fast during the aerobic incubation. While O-NER mainly contained TBBPA and its aerobic metabolites such as MeO-TBBPA and MeO-triBBPA, and these unpolar products were more persistent in environment. Therefore, our results demonstrated that the biotransformation of two NERs was different in soil, which was closely related to the metabolism of TBBPA. In addition, both redox conditions changing and the addition of root exudate can affect the bioavailability of F-NER especially in long-term incubation.

Effects of potassium supply on the growth, photosynthesis and 15N and 13C absorption and utilization of M9T337 seedling.

Hydroponic experiment was carried out on M9T337 seedlings using 15N and 13C isotope tracer technology to study the effects of different potassium supply levels (K0, K1, K2, K3 and K4 were equivalent to 0, 3, 6, 9 and 12 mmol·L-1, respectively) on the growth, photosynthetic characteristics and 15N and 13C absorption and utilization of M9T337 seedlings. The results showed that dry mass, root length, root surface area, number of tips and root activity of M9T337 seedlings under the K2 level were significantly higher than those under other levels. The net photosynthetic rate (Pn) of leaves increased at low K+ concentration and then decreased with the increases of potassium supply level, and reached the maximum value at K2 treatment (15.5 μmol CO2·m-2·s-1). At the 30th day after treatment, the activities of nitrate reductase (NR) and carbon metabolism enzyme were highest in K2 treatment, and lowest in K0 treatment. With the increases of potassium application rate, the 13C accumulation of seedlings were first increased and then decreased, with the 13C distribution rate of each organ being the most balanced at K2 treatment. There were significant differences in 15N uptake and utilization rate among treatments. 15N uptake and utilization rates of seedlings under K2 treatment were the highest, which were 16.1 mg and 17.9%, respectively. Therefore, too low or too high potassium supply could inhibit seedling root growth and leaf photosynthesis, which was not conducive to carbon and nitrogen absorption. Appropriate potassium supply could improve root activity and net photosynthetic rate, enhance nitrate reductase (NR) and carbon metabolic enzyme activity, and promote carbon and nitrogen metabolism.

Effects of organic fertilizer application on accumulation and distribution of assimilates in winter wheat

To understand the effects of organic fertilizer addition on accumulation and distribution of winter wheat assimilates, we compared organic carbon content in soil and wheat plants, photosynthetic characteristics and assimilation transformation under two different fertilizer treatments, CF (chemical fertilizer only) and OF (organic fertilizer with chemical fertilizer), using 13CO2 pulse labeling method. The results showed that OF increased soil organic carbon content and wheat photosynthetic parameters, resulting in higher organic carbon content and total dry biomass accumulation in wheat plants compared with CF treatment. Compared marking to maturity with that on the 7th day after the same marking, the content and distribution rate of 13C in leaves and stems of two treatments decreased; the 13C content in spikes increased at jointing stage and filling stage, decreased at anthesis stage, and the 13C distribution rate increased at all stages. OF treatment was more beneficial for the transportation of photosynthetic product from leaves to spikes at filling stage, with higher 13C distribution rate in spikes compared with CF treatment. The results of correlation analysis showed that dry matter accumulation was significantly positively correlated with the net input of 13C content and its distribution rate, but negatively correlated with organic carbon content in plants. The net input of 13C content was significantly positively correlated with its distribution rate, and negatively correlated with Fv/Fm and Pn. In conclusion, organic fertilizer application could increase the content of organic carbon in soil, improve wheat plants photosynthetic capacity and transportation of photosynthetic product to spikes, and ultimately increase dry matter accumulation in wheat spikes.

Effects of multiple times of topdressing nitrogen application under equal level on utilization and distribution characteristics of 15N and 13C in winter jujube

We explored the effects of multiple times of topdressing nitrogen application under equal level on the characteristics of absorption, utilization, accumulation, and distribution of 15N and 13C in four-year-old potted winter jujube during fruit developmental periods using the stable isotope tra-cer technology. The results showed that with the increases of nitrogen application times, the 15N derived from fertilizer (Ndff) in each organ significantly increased at the fruit maturity. The distribution rates of 15N in reproductive organ (fruit) and vegetative organs (leaf, deciduous spur, new branch, and fine root) were highest under four-time application, and lowest under one-time application. The opposite pattern was observed in storage organs (trunk, perennial branch, and coarse root). The 15N utilization rate under four-time application was 27.4% and 15.5% higher than one-time and two-time application, respectively. The more times N being applied, the more total N content and 15N absorption amount of plant. Soil 15N abundance and total N content continued to drop under one-time application and increased at the beginning and then declined with the time under two-time application. The relatively stable soil 15N abundance and total N content appeared in four-time application, which was significantly higher than those in the other treatments in later treatment stages. The chlorophyll content, leaf nitrogen content and photosynthetic rate displayed an order of four-time application > two-time application > one-time application during fruit white-mature period to fruit harvest period. The accumulation and distribution of 13C varied across different treatments. Increasing nitrogen application times would promote more 13C being transported to fruit and storage organs but decrease that in annual vegetative organs. Our findings indicated that four-time nitrogen application could enhance and optimize the accumulation and distribution of photosynthetic products by ensuring steady and adequate supply of nitrogen and improving the absorption and utilization of nitrogen during fruit development period, which facilitates the growth, yield and quality of winter jujube.

Effects of deuteration on transamination and oxidation of hyperpolarized 13C-Pyruvate in the isolated heart.

This study was designed to determine the effects of deuteration in pyruvate on exchange reactions in alanine aminotransferase (ALT), lactate dehydrogenase (LDH) and flux through pyruvate dehydrogenase (PDH). Although deuteration of a 13C enriched substrate is commonly used to increase the lifetime of a probe for hyperpolarization experiments, the potential impact of kinetic isotope effects on such substitutions has not been studied in detail. Metabolism of deuterated pyruvate was investigated in isolated rat hearts. Hearts were perfused with a 1:1 mixture of [U-13C3]pyruvate and [2-13C1]pyruvate or a 1:1 mixture of [U-13C3]pyruvate plus [2-13C1, U-2H3]pyruvate for 30 min before being freeze clamped. Another set of hearts received [2-13C1, U-2H3]pyruvate and was freeze-clamped at 3 min or 6 min. Tissue extracts were analyzed by 1H and 13C{1H} NMR spectroscopy. The chemical shift isotope effect of 2H was monitored in the 13C NMR spectra of the C2 resonance of lactate and alanine plus the C5 of glutamate. There was little kinetic isotope effect of 2H in pyruvate on flux through PDH, LDH or ALT as detected by the distribution of 13C, but the distribution of 2H differed markedly between alanine and lactate. At steady-state, alanine was a mixture of deuterated species, while lactate was largely perdeuterated. Consistent with results at steady-state, hearts freeze-clamped at 3 min or 6 min showed rapid removal of deuterium in alanine but not in lactate. Metabolism of hyperpolarized [1-13C1]pyruvate was compared to [1-13C1,U-2H3]pyruvate in isolated hearts. Consistent with the results from tissue extracts, there was little effect of deuteration on the kinetics of appearance of lactate, alanine or bicarbonate, but there was a small, time-dependent upfield chemical shift in the HP[1-13C1]alanine signal reflecting exchange of methyl deuterons with water protons. Together, these results demonstrate that (1) the kinetics of pyruvate metabolism in hearts detected by 13C NMR are not affected by replacement of the pyruvate methyl protons with deuterons and (2) that the loss of deuterium from the methyl position occurs rapidly during the conversion of pyruvate to alanine. The majority of the deuterium atoms are lost on the time-scale of a hyperpolarization experiment.

Effects of Different Chemical Forms of Nitrogen on the Quick and Reversible Inhibition of Soybean Nodule Growth and Nitrogen Fixation Activity.

It has been reported that supply of nitrate to culture solution rapidly and reversibly inhibits nodule growth and nitrogen fixation activity of soybean. In this study, the effects of ammonium, urea, or glutamine on nodule growth and nitrogen fixation activity are compared with that for nitrate. Soybean plants were cultivated with a nitrogen-free nutrient solution, then 1 mM-N of nitrate, ammonium, glutamine, or urea were supplied from 12 DAP until 17 DAP. Repression of nodule growth and nitrogen fixation activity at 17 DAP were observed by ammonium, urea, and glutamine like nitrate, although the inhibitory effects were milder than nitrate. The removal of nitrogen from the culture solutions after nitrogen treatments resulted in a recovery of the nodule growth. It was found that the glutamine treatment followed by N-free cultivation gave highest nitrogen fixation activity about two times of the control. Tracer experiments with 15N and 13C were performed to evaluate the translocation of N and C to the different tissues. Culture solutions containing a 15N-labeled nitrogen source were supplied from 21 DAP, and the whole shoots were exposed to 13CO2 for 60 min on 23 DAP, and plants were harvested on 24 DAP. The percentage distribution of 15N in nodules was highest for ammonium (1.4%) followed by glutamine (0.78%), urea (0.32%) and nitrate (0.25%). The percentage distribution of 13C in the nodules was highest for the control (11.5%) followed by urea (5.8%), glutamine (2.6%), ammonium (2.3%), and nitrate (2.3%). The inhibitory effects of nitrogen compounds appeared to be related to a decrease in photoassimilate partitioning in the nodules, rather than 15N transport into the nodules. The free amino acid concentrations after nitrogen treatments were increased in the nodules and leaves by nitrate, in the roots by ammonium, in the stems by urea, and the roots, stems, and leaves by glutamine treatment. The concentrations of asparagine, aspartate, and glutamine were increased after nitrogen treatments. By the long-term supply of nitrogen for 2-weeks, nitrate significantly increased the lateral roots and leaf growth. The long-term supply of urea and glutamine also promoted the lateral roots and leaf growth, but ammonium suppressed them.

Species-dependent effects of earthworms on the fates and bioavailability of tetrabromobisphenol A and cadmium coexisted in soils

The activity of e-waste recycling often causes the combined pollution of tetrabromobisphenol A (TBBPA) and cadmium (Cd) in soils. In this study, the effects of their co-existence on each other's fate, further reflecting the bioavailability, were analyzed in the presence of two ecologically different earthworm species, endogeic Metaphire guillelmi and epigeic Eisenia fetida. Mineralization of 14C-TBBPA combined with 10 mg Cd kg−1 was suppressed by the presence of M. guillelmi, whereas a facilitating effect was produced by the combination of 1 mg Cd kg−1 in the soil-E. fetida system after a 14-day exposure. The uptake of 14C-TBBPA by M. guillelmi (17% of initial amount) and by E. fetida (10%) dominantly contributed to significant (P < 0.05) decrease of extractable (more bioavailable) 14C residues in soils both with and without Cd spiked, while the mineralization of 14C-TBBPA in the soils was negligible (<0.4%). Meanwhile the amendments of the two earthworm species exerted different impact on 14C distribution in bound residues. In general, co-exposure to Cd did not significantly (P > 0.05) influence the accumulation and metabolism of TBBPA in the earthworms. Both earthworms accumulated only ~7% of Cd in soil, however, the bioavailable Cd determined by the diffusive gradients in thin films technique declined by ~46% in the presence of M. guillelmi, and a much smaller decrease was determined in the presence of E. fetida. Amendment of TBBPA at environmental levels did not alter the accumulation and subcellular distribution of Cd in both earthworms unless that at high doses. The results highlighted the importance of considering the difference of the earthworm species and the interaction of pollutants in soil-risk assessments of such combined contamination. CapsuleM. guillelmi displayed greater effect on the fate of TBBPA and Cd co-existed in soils than E. fetida, while the accumulation, metabolism, or distribution of the two pollutants in earthworms did not significantly alter due to interactions between the two pollutants.

Dynamics of maize straw residue 13C incorporation into aggregates of a Mollisol as affected by long-term fertilization

Soil aggregates play a crucial role in the sequestration of soil organic carbon (SOC). Returning crop residues to soil is known to strongly influence soil C stocks, but the specific contribution of crop residues to soil aggregates influenced by long-term fertilization remains largely unknown. This study investigated the effects of long-term fertilization on the distribution of 13C-labeled maize straw residue in different aggregate size fractions and their retention in soils over a 1-year incubation. The dynamic variation and the distribution of maize straw-derived 13C in soil aggregates were monitored using a 13C stable isotope mass-balance approach. The following three fertilization treatments were selected: (1) without fertilization (CK), (2) mineral fertilizer (NPK), and (3) cow manure with mineral fertilizer (NPKM). Soil samples were collected from the surface layer (0–20 cm) of a long-term field experiment of Mollisols (Luvic Phaeozem) in 2015 at Gongzhuling, Jilin Province, China, which was established in 1980. Soils were incubated for 360 days at 25 °C, with or without 13C-labeled maize straw and destructively collected on the days of 45, 90, 135, 180, and 360. Soil aggregates were separated into two fractions (macroaggregates, > 250 μm; microaggregate, NPK > CK for all soil aggregates after the 360-day incubation. Our results illustrated that long-term application of manure with mineral fertilizer helps to stabilize or increase the retention of exogenous C in the soil aggregates.

Uptake and translocation of 14C-Carbamazepine in soil-plant systems

Carbamazepine (CBZ) is an antiepileptic drug that is frequently detected in wastewater treatment plants, soil and plants after irrigation with treated wastewater or application of biosolids. However, little information is available on the fate and uptake of CBZ in edible vegetables. In this study, radioautographic visualization of the 14C distribution revealed that 14C-CBZ can be taken up by all three ready-to-eat vegetables. Furthermore, a mass-balance study was conducted to evaluate the dynamic processes of the uptake and translocation of CBZ by 14C labeling. 14C-CBZ was gradually taken up with the growth of vegetables, with maximum uptake ratios of 2.19 ± 0.15, 2.86 ± 0.24 and 0.25 ± 0.05% of applied 14C in celery, carrot and pak choi, respectively. The bioconcentration factors (BCFs) based on 14C measurements ranged from 7.6 to 26.1 for celery, 3.6–12.9 for carrot, and 4.4–44 for pak choi. 14C-CBZ was easily translocated from the roots to the leaves and/or stems. The amendment of biosolids had a significant inhibitory effect on the uptake and translocation of 14C-CBZ from soil.

Metabolism of the Strobilurin Fungicide Mandestrobin in Wheat.

The metabolic fate of a new fungicide, mandestrobin, labeled with 14C at the phenoxy or benzyl ring was examined in wheat after a single spray application at 300 g/ha. Mandestrobin penetrated into foliage over time, with both radiolabels showing similar 14C distribution in wheat, and 2.8-3.3% of the total radioactive residue remained on the surface of straw at the final harvest. In foliage, mandestrobin primarily underwent mono-oxidation at the phenoxy ring to produce 4-hydroxy or 2-/5-hydroxymethyl derivatives, followed by their subsequent formation of malonylglucose conjugates. In grain, the cleavage of its benzyl phenyl ether bond was the major metabolic reaction, releasing the corresponding alcohol derivative, while the counterpart 2,5-dimethylphenol was not detected. The constant RS enantiomeric ratio of mandestrobin showed its enantioselective metabolism to be unlikely on/in wheat.

Lateral Marsh Edge Erosion as a Source of Sediments for Vertical Marsh Accretion

AbstractWith sea level rise accelerating and sediment inputs to the coast declining worldwide, there is concern that tidal wetlands will drown. To better understand this concern, sources of sediment contributing to marsh elevation gain were computed for Plum Island Sound estuary, MA, USA. We quantified input of sediment from rivers and erosion of marsh edges. Maintaining elevation relative to the recent sea level rise rate of 2.8 mm yr−1 requires input of 32,299 MT yr−1 of sediment. The input from watersheds is only 3,210 MT yr−1. Marsh edge erosion, based on a comparison of 2005 and 2011 LiDAR data, provides 10,032 MT yr−1. This level of erosion is met by &lt;0.1% of total marsh area eroded annually. Mass balance suggests that 19,070 MT yr−1 should be of tidal flat or oceanic origin. The estuarine distribution of 14C and 13C isotopes of suspended particulate organic carbon confirms the resuspension of ancient marsh peat from marsh edge erosion, and the vertical distribution of 14C‐humin material in marsh sediment is indicative of the deposition of ancient organic carbon on the marsh platform. High resuspension rates in the estuarine water column are sufficient to meet marsh accretionary needs. Marsh edge erosion provides an important fraction of the material needed for marsh accretion. Because of limited sediment supply and sea level rise, the marsh platform maintains elevation at the expense of total marsh area.

Absorption and translocation of sulfometuron-methyl in sugarcane (Saccharum officinarum L.) at different growth stages

ABSTRACTIn Brazil, weed management in sugarcane fields is mainly done with the use of selective herbicide formulations. For many years, diuron+hexazinone was one of the main herbicide mixture formulations used in sugarcane. Later, sulfometuron-methyl was included in the same mixture, which was marketed as a new herbicide formulation for residual in-season weed control in sugarcane. The mixture diuron+hexazinone+sulfometuron-methyl has been widely used in commercial sugarcane fields in Brazil. However, recent field observations have shown that sugarcane plants at different growth stages varied in their phytotoxicity levels after treatment with diuron+hexazinone+sulfometuron-methyl. Greenhouse and laboratory studies were conducted to determine 14Csulfometuron-methyl absorption and translocation, as well as 14C distribution in sugarcane at two growth stages, 2 to 3 leaves and 5 to 6 leaves. 14Csulfometuron-methyl absorption by sugarcane did not differ between the two growth stages. Different patterns of 14C accumulation were observed, which may explain variations in sulfometuron-methyl phytotoxic responses observed in the field.

Effect of Prebloom Pruning on 13C and 15N Distribution during Early Spring in Sweet Cherry

In sweet cherry, highly advanced dwarf combinations using ‘Gisela’ rootstocks promote higher productivity than do more vigorous combinations but require maintaining the leaf area to fruit area (LA:F) ratio. An experiment using double isotopic enrichment with 13C and 15N was carried out in 5-year-old ‘Bing’/‘GI 6’ trees in a commercial orchard located in Santa Cruz, Chile (34°39′S; 71°19′W), and characterized by a Mediterranean climate. Forty whole sweet cherry trees (TR1) trained as central axes were pruned in winter [July 20, 60 days before full bloom (DBFB)] and another 40 trees were left without pruning (TR2). A single 13CO2 pulse and 15N-urea application to the mature leaves of individual 4-year-old branches on trees of both TRs was carried out during stage III (SIII). Winter pruning reduced yield by 44%, improved fruit quality [i.e., size, weight, and soluble solids content (SSC)] and induced the growth of extension shoots (ES) (i.e., number, length, and LA). For both TRs, fruits were stronger sinks for 13C-photoassimilates and 15N than were ES. ES of pruned trees had higher sink strength than ES of unpruned trees. Pruned trees developed more ES that were longer and that had higher LA compared with the ES of unpruned trees.

Improving quantitative 13C NMR performance by an adiabatic scheme

NMR is a primary method of measurement that provides quantitative traceable results without the need for a standard of the same measurand. Despite the advantages of the 1H nucleus, such as high sensitivity, short relaxation times and widespread distribution in organic compounds, some molecules present only labile H atoms, or the 1H peaks of a sample may overlap with impurities. With the CHORAD scheme – a combination of the pulse sequence CHORUS and adiabatic modulation for 1H decoupling – this study has shown that 13C NMR can be used for quantitative analyses with a bias smaller than 2% and expanded uncertainty of 0.7% (for a confidence level of 95%). Since 13C is found with significant non-statistic isotope fractionation, all the peaks of the sample and internal standard should be integrated and their bulk 13C abundances obtained by isotope ratio mass spectrometry (IRMS) must be considered to meet quantitative requirements. Future experimental work may be performed to test this procedure for complex matrix samples. This approach also proved to be suitable for studies of site-specific 13C distribution and led to better heteronuclear decoupling when compared with the use of adiabatic decoupling with ordinary hard 90° pulses, a combination extensively reported in the literature over the last decade. An examination of the molecules studied in this work and others from the literature revealed an overall trend in the 13C intramolecular profile – hydrogen-containing positions are often 13C-depleted. A potential contribution of 1JCH coupling to these results is discussed.

Difficulties in Differentiating Natural from Synthetic Alkaloids by Isotope Ratio Monitoring using 13C Nuclear Magnetic Resonance Spectrometry.

Within the food and pharmaceutical industries, there is an increasing legislative requirement for the accurate labeling of the product's origin. A key feature of this is to indicate whether the product is of natural or synthetic origin. With reference to this context, we have investigated three alkaloids commonly exploited for human use: nicotine, atropine, and caffeine. We have measured by 13C nuclear magnetic resonance spectrometry the position-specific distribution of 13C at natural abundance within several samples of each of these target molecules. This technique is well suited to distinguishing between origins, as the distribution of the 13C isotope reflects the primary source of the carbon atoms and the process by which the molecule was (bio)synthesized. Our findings indicate that labeling can be misleading, especially in relation to a supplied compound being labeled as "synthetic" even though its 13C profile indicates a natural origin.

Radiocarbon Dating Historical Mortars: Lime Lumps and/or Binder Carbonate?

ABSTRACTLime lumps and bulk mortars show different 14C contamination when analyzed in several CO2 fractions isolated from the effervescence of an ongoing hydrolysis reaction. Age profiles of both materials are therefore highly complementary and together they can provide a reliable date. Furthermore, they can also reveal the complexity of the radiocarbon (14C) distribution within the mortar and thus prevent over-interpretation of the data. The lime lump versus bulk mortar dating data presented here has been collected over 22 years, with only a small fraction of the results so far published internationally. Since there has been an increasing interest in mortar dating over recent years with a special focus on lime lumps, and since many laboratories have just begun mortar dating experiments, we wish to present some of the extensive data that already exist. Previously published data from 15 lime lumps (including 34 14C measurements from sequential dissolution) and 43 new 14C measurements from 17 lime lumps are presented here. The samples are from medieval Finland and Sweden, classical Rome and medieval Italy, and the Roman Jerash (Gerasa), Jordan.

Differences between nitrogen-tolerant and nitrogen-susceptible sweetpotato cultivars in photosynthate distribution and transport under different nitrogen conditions.

To characterize the differences in photosynthate distribution and transport between nitrogen(N)-tolerant and N-susceptible sweetpotato cultivars under different N conditions, three N levels, including 0 (N0), 120 (N120), and 240 kg ha−1 (N240), were used in field experiments with the Jishu26 (J26) and Xushu32 (X32) cultivars in 2015 and 2016. The results from both years revealed that high N application reduced the tuberous root yield, the tuber/vine rate of carbon-13 (13C), and top-to-base (three equal segments of stem divided from the fifth opened leaf of the shoot tip to the main stem, defined as the top, middle, and base parts, respectively) gradients such as sucrose, ammonia N and potassium along the stem. ‘J26’ showed a higher yield than ‘X32’ under N0 but lower yield than ‘X32’ under N120 and N240. It also exhibited a higher 13C distribution to tuberous roots compared with that of ‘X32’ under N0, and the opposite trend was observed under N120 and N240. Under N0, ‘J26’ showed a steep top-to-base amino acid gradient and a significantly lower top-to-base sucrose increase along the stem in the late growth stage. Under N120 and N240, ‘X32’ exhibited a greater top-to-base decrease in the ammonia N along the stem during the main growth stages, a steep top-to-base sucrose gradient along the stem in the early growth stage, and a lower top-to-base sucrose increase along the stem in the middle and late growth stages. The formation of a reasonable photosynthate distribution structure attributed to high yield was related to a desirable sucrose, ammonia N or K+ gradient downward along the stem. These results might help provide farmers with sweetpotato cultivars using less or no N fertilizer in soils of different fertility and enhance the knowledge of yield-related physiology.