Minimal Enrichment Research Articles

Trace Metal Concentrations in an Agricultural Watershed: Case Study in the Sumani Watershed, West Sumatera Indonesia

Selected trace metals investigation of agricultural soil at sawah, vegetable and river sediment in Sumani watershed, West Sumatra, Indonesia were conducted to determine their abundances and to assess contamination levels. pH, CEC and TC values indicates moderate to high soil fertility status. Average concentrations of Pb, Zn, Cu, TiO2, Fe2O3 and P2O5 were greater than those of Bulk Composition Crust (BCC) and UCC in most areas. Enrichment factor values at Sawah confirms depletion to minimal enrichment with most metals, while vegetable area indicates moderate enrichment with Pb, Cu and Rb, and depletion to minimal enrichment for Zn, Ni, Cr, V and Sr. Igeo values for Pb, at Sawah were unpolluted to moderately polluted but practically unpolluted for Zn, Cu, Ni, Cr, V, while vegetable area were moderately polluted with Pb, unpolluted to moderately polluted with Cu and Rb and and practically unpolluted for Zn, Ni, Cr, V and Sr. Elevated values of Pb in vegetable area, possibly due to volcanic ash from mount Talang, excess application of fertilizers and pesticides, and high contents of Pb in gasoline, Indonesia.

Metal contamination assessment in the urban stream sediments and tributaries of coastal area southwest Nigeria

A geochemical assessment of the fifty surface stream sediments from Ikorodu Southwest Nigeria was carried out to determine the level of contamination. The sediments were dried, disaggregated and sieved to Al > Ca > Na > Mg > K > P > Ti and were below the average shale concentration, except for Na in one sample. Results from factor and correlation analyses showed two groups of trace elements Ni, Co, Mn, U, Th, Sr, V, La, Cr, Ba, Sc, Ga, Cs, Nb, Rb, Y,Ce and Mo, Pb, Zn, As, Cd, Sb, Sn, Zr, which were from geogenic and anthropogenic sources, respectively. The enrichment factor showed that Cd, Bi, Pt, Mo and Ag were, for all samples, within background concentrations, except those of the Ogun River and the Owode Onirin, which showed significant enrichment of Cd, Zn, Cu, Pb and Ag, depletion to minimal enrichment for Bi, Mo and moderate enrichment for Pt. The contamination degree ranged between 1.25 and 143.79. The highest value was found at Owode Onirin and the lowest, at Igbonla 7. The geo-accumulation index showed that all the stream sediments ranged between practically uncontaminated to moderately to highly contaminated—with Pb, Sn, Zn, Cd, Cu, Cr, Zr and Ba. The potential ecological risk factor and environmental risk index (IER) showed that all of the samples were within the class of low to medium contamination risk, except samples from the Owode Onirin, which fell within the class of very high risk to extremely high risk respectively.

Heavy Metal Concentrations in Some Vegetables Grown in a Farm Treated with Urban Solid Waste in Kuru Jantar, Nigeria

The use of dumpsite soils as organic manure is wide spread in developing countries like Nigeria. This study investigates the concentration of some heavy metals in vegetables grown in a farm treated with dumpsite soils in Kuru Jantar, Nigeria. Soil samples and vegetables from the farm were collected and prepared using standard analytical procedures. The concentrations of metals in both soil and vegetables were determined using atomic absorption spectrophotometer (AAS). The results showed that the farm was polluted with the metals (Cd, Cr, Cu, Mu, Fe, Pb, Zn, Ni) determined. The Enrichment Factor (EF) showed that some metals had minimal enrichment while Cd (13.93) had significant enrichment at the farm. The Pollution index (PI) calculations showed that Original Research Article Nanven et al.; BJAST, 8(2): 139-147, 2015; Article no.BJAST.2015.192 140 at the farm, the contamination pollution ranged from very slight to very severe. The overall order of the metals at the dumpsite was Fe> Mn> Zn> Cu> Cr> Ni> Pb> Cd while the order of the metal concentrations at the farm was Fe> Mn> Zn> Ni> Cd> Pb. The data obtained in the study were analyzed using Pearson correlation analysis. The results showed perfect positive correlation values above 0.9 between the farm and the dumpsite, which indicated that there was a strong association or similarity between them. The metal concentrations in the vegetables analyzed showed that spinach decreased in the order Fe>Zn>Mn>Cd>Pb while in Cabbage, the order was Mn> Fe> Zn>Cu>Cd; in Radish, the order was Fe>Mn>Cu>Cr>Zn while in pepper, the order was Fe>Cu>Mn>Ni. In general, the metal concentrations were below the recommended limit of USEPA and FEPA standards for agricultural soils and vegetables except for Cd in vegetables. The concentrations were however higher in the farm than in the control. Thus, the farm was polluted with heavy metals from the dumpsite soils.

Ecological risk assessment of metals contamination in the sediment of the Bamdezh wetland, Iran

Present survey investigates the intensity of heavy metals pollution (Ca, Fe, Ni, Cd, Pb, Zn, AS, Hg) in the sediments of Bamdezh wetland, Iran . The main objective of the study is quantification of heavy metal pollution intensity in this wetland. Bamdezh wetland is located in about 40 km northwest of Ahvaz, Iran. This wetland is a habitat and food source for aquatic ecosystem and migratory birds, also a significant resource of income for the locals. Anthropogenic portion of the metals was determined through five-step chemical sequential extraction. The results of partition studies revealed the arrangement of anthropogenic portions for the metals as follows: Cd (86 %) > Pb (80 %) > Ni (46 %) > Zn (44 %) > Fe (24 %). The mean enrichment factor values for various metals were between minimal enrichment and extremely enrichment. The values obtained from I poll index are indicative of a broad range from unpolluted to moderately polluted to moderately to strongly polluted. All stations can be interpreted as a very high degree of contamination using C d and high degree of contamination using mCd classification. PLI ranged from 1.22 at station 3 to 1.55 at station 4. Result of cluster analysis for Zn and LOI shows that these two elements are related together by high similarity coefficient. As LOI in the environment is the index of biological activity, then Zn should have biological origin. The dendrogram also showed that a part of Ca and Ni is derived from lithogenous source as they are linked to Fe.

Multi-element characterization and source identification of trace metal in road dust from an industrial city in semi-humid area of Northwest China

Concentrations and sources of multi-elements in road dusts from an industrial city of northwest China were determined. Dust samples have elevated concentrations of Co, Cr, Cu, Pb, Zn, Sr and Ba. The dusts were mainly moderate enrichment by Co and Pb, minimal enrichment to moderate enrichment by Sr and Zn, and deficiency to minimal enrichment by other trace metals. Mn, V, Y, La, Hf, Th and U originated from soil. Cu, Pb, Cr, Ba and Sr mainly derived from traffic. Co, Zr, Ni, Ga, As and Zn have mixed sources of nature, industry and traffic.

Surface Sediment Contamination by Uranium Mining/Milling Activities in South China

The distribution and the contamination level of uranium (U) and thorium (Th) radionuclides and potentially toxic metals, Cu, Li, Mn, Sr, and Zn were investigated in surface sediments from aquifer systems around a uranium industrial site in the northern Guangdong Province, China. Total contents of these elements and other major elements, including Fe, Al, Mg, Na, Ca, and K, were analyzed by inductively coupled plasma optical emission spectrometry. The results show that the contents of U, Th, Cu, and Mn are elevated in the sediments from a recipient stream that drains the industrial site and the reservoir downstream. Metal contents varied significantly among the sampling locations, and generally displayed a decreasing trend as the distance from the U industrial site increased. However, the highest level of U, Th, Cu, and Mn is observed in the terminal of the recipient stream, where is the inlet of a reservoir. Assessment of elemental enrichment in the sediments using enrichment factor and geoaccumulation index indicates that among the analyzed metals, U, Th, and Cu are the major contaminants, while contaminations of Li, Mn, Sr, and Zn which displayed depletion to minimal enrichment are not significant.

Spatial Distribution Patterns and Potential Sources of Heavy Metals in Soils of a Crude Oil-Polluted Region in China

Twenty-two soil samples were collected at the subregional scale (50 km2) around Gudao Town, a typical oil-producing region of the Shengli Oilfield in the Yellow River Delta, China to determine the spatial distribution patterns and potential sources of heavy metals in soils of crude oil-polluted regions. The concentrations of total petroleum hydrocarbons (TPHs) and heavy metals as well as other soil properties were determined and the enrichment factor values were calculated for the heavy metals measured. Principal component analysis (PCA) and cluster analysis (CA) were used to estimate potential sources contributing to the concentrations of heavy metals in the soils. The results revealed that the soils were slightly alkaline (pH = 7.33–8.05) and high in salinity (1.43–41.30 g kg−1), TPHs (0.51–28.40 g kg−1) and organic matter (1.74–31.50 g kg−1). The mean concentrations of the measured heavy metals Cu, Zn, Pb, Cd, Cr, Ni and V were 18.4, 78.2, 20.8, 0.19, 56.6, 26.3 and 62.1 mg kg−1, respectively. Although the concentrations of all the metals measured in this study were not high enough to exceed the national control standards, there was a significant enrichment of Cd in the study area and Zn and Ni were in the category of deficiency to minimal enrichment. The spatial distribution patterns of Cu, Cr, Ni and V were similar and partially affected by oil exploitation and petroleum hydrocarbon spills. Potential sources of Cr, Ni, V and Cu in the soils were both natural sources and petroleum hydrocarbon spills, while Zn, Pb and Cd were probably from anthropogenic sources such as farming activities and traffic.

The use of legume seed for expression and storage of high value proteins

There is an ever growing need for the use of recombinant proteins both in medicine and industry; however their widespread use is limited by the lack of production capacity. Transgenic plants offer the possibility to produce and deliver recombinant proteins on a large scale with low production costs and with minimal purification or enrichment requirements. Among crop plants, legumes have great potential as a protein production platform because of their naturally high protein content, nutritional value, independence of N-nutrition, pollen containment, available processing technology, storage stability etc. There have been several proof-of-principle attempts to produce large amounts of recombinant protein in seed of both soybean and pea, however, our knowledge of processes regulating the foreign protein production and deposition is still limited.

Reliable Metabolic Flux Estimation in Escherichia coli Central Carbon Metabolism Using Intracellular Free Amino Acids.

13C metabolic flux analysis (MFA) is a tool of metabolic engineering for investigation of in vivo flux distribution. A direct 13C enrichment analysis of intracellular free amino acids (FAAs) is expected to reduce time for labeling experiments of the MFA. Measurable FAAs should, however, vary among the MFA experiments since the pool sizes of intracellular free metabolites depend on cellular metabolic conditions. In this study, minimal 13C enrichment data of FAAs was investigated to perform the FAAs-based MFA. An examination of a continuous culture of Escherichia coli using 13C-labeled glucose showed that the time required to reach an isotopically steady state for FAAs is rather faster than that for conventional method using proteinogenic amino acids (PAAs). Considering 95% confidence intervals, it was found that the metabolic flux distribution estimated using FAAs has a similar reliability to that of the PAAs-based method. The comparative analysis identified glutamate, aspartate, alanine and phenylalanine as the common amino acids observed in E. coli under different culture conditions. The results of MFA also demonstrated that the 13C enrichment data of the four amino acids is required for a reliable analysis of the flux distribution.

Morbidity and Mortality of Invertebrates, Amphibians, Reptiles, and Mammals at a Major Exotic Companion Animal Wholesaler

The authors formally investigated a major international wildlife wholesaler and subsequently confiscated more than 26,400 nonhuman animals of 171 species and types. Approximately 80% of the nonhuman animals were identified as grossly sick, injured, or dead, with the remaining in suspected suboptimal condition. Almost 3,500 deceased or moribund animals (12% of stock), mostly reptiles, were being discarded on a weekly basis. Mortality during the 6-week “stock turnover” period was determined to be 72%. During a 10-day period after confiscation, mortality rates (including euthanasia for humane reasons) for the various taxa were 18% for invertebrates, 44.5% for amphibians, 41.6% for reptiles, and 5.5% for mammals. Causes of morbidity and mortality included cannibalism, crushing, dehydration, emaciation, hypothermic stress, infection, parasite infestation, starvation, overcrowding, stress/injuries, euthanasia on compassionate grounds, and undetermined causes. Contributing factors for disease and injury included poor hygiene; inadequate, unreliable, or inappropriate provision of food, water, heat, and humidity; presumed high levels of stress due to inappropriate housing leading to intraspecific aggression; absent or minimal environmental enrichment; and crowding. Risks for introduction of invasive species through escapes and/or spread of pathogens to naive populations also were identified.

SEGUE 1: AN UNEVOLVED FOSSIL GALAXY FROM THE EARLY UNIVERSE

We present Magellan/MIKE and Keck/HIRES high-resolution spectra of six red giant stars in the dwarf galaxy Segue 1. Including one additional Segue 1 star observed by Norris et al. (2010), high-resolution spectra have now been obtained for every red giant in Segue 1. Remarkably, three of these seven stars have metallicities below [Fe/H] = -3.5, suggesting that Segue 1 is the least chemically evolved galaxy known. We confirm previous medium-resolution analyses demonstrating that Segue 1 stars span a metallicity range of more than 2 dex, from [Fe/H] = -1.4 to [Fe/H] = -3.8. All of the Segue 1 stars are alpha-enhanced, with [alpha/Fe] ~ 0.5. High alpha-element abundances are typical for metal-poor stars, but in every previously studied galaxy [alpha/Fe] declines for more metal-rich stars, which is typically interpreted as iron enrichment from supernova Ia. The absence of this signature in Segue 1 indicates that it was enriched exclusively by massive stars. Other light element abundance ratios in Segue 1, including carbon-enhancement in the three most metal-poor stars, closely resemble those of metal-poor halo stars. Finally, we classify the most metal-rich star as a CH star given its large overabundances of carbon and s-process elements. The other six stars show remarkably low neutron-capture element abundances of [Sr/H] < -4.9 and [Ba/H] < -4.2, which are comparable to the lowest levels ever detected in halo stars. This suggests minimal neutron-capture enrichment, perhaps limited to a single r-process or weak s-process synthesizing event. Altogether, the chemical abundances of Segue 1 indicate no substantial chemical evolution, supporting the idea that it may be a surviving first galaxy that experienced only one burst of star formation.

Protein kinetic signatures of the remodeling heart following isoproterenol stimulation

Protein temporal dynamics play a critical role in time-dimensional pathophysiological processes, including the gradual cardiac remodeling that occurs in early-stage heart failure. Methods for quantitative assessments of protein kinetics are lacking, and despite knowledge gained from single-protein studies, integrative views of the coordinated behavior of multiple proteins in cardiac remodeling are scarce. Here, we developed a workflow that integrates deuterium oxide (2H2O) labeling, high-resolution mass spectrometry (MS), and custom computational methods to systematically interrogate in vivo protein turnover. Using this workflow, we characterized the in vivo turnover kinetics of 2,964 proteins in a mouse model of β-adrenergic-induced cardiac remodeling. The data provided a quantitative and longitudinal view of cardiac remodeling at the molecular level, revealing widespread kinetic regulations in calcium signaling, metabolism, proteostasis, and mitochondrial dynamics. We translated the workflow to human studies, creating a reference dataset of 496 plasma protein turnover rates from 4 healthy adults. The approach is applicable to short, minimal label enrichment and can be performed on as little as a single biopsy, thereby overcoming critical obstacles to clinical investigations. The protein turnover quantitation experiments and computational workflow described here should be widely applicable to large-scale biomolecular investigations of human disease mechanisms with a temporal perspective.

Assessing spatial distribution, sources, and potential ecological risk of heavy metals in surface sediments of the Nansi Lake, Eastern China

The study is conducted to investigate the spatial distribution, sources and ecological risk of seven heavy metals in surface sediments of Nansi Lake, Eastern China. A total of 29 samples were collected in surface sediments of Nansi Lake, and were analyzed for three nutrients (TN, TOC and TP), two major metals (Al and Fe), as well as seven trace metals (As, Cd, Cr, Cu, Hg, Pb and Zn). The mean concentrations of As, Cd, Cr, Cu, Hg, Pb, Zn, Fe and Al were 14.41, 0.22, 71.10, 30.1, 0.048, 29.14, 90.2, 30,816 and 70,653 mg kg−1, respectively, and the mean contents of these metals were higher than the background values with the exception of Cu and Fe. The spatial distribution indicated that the contents of all seven heavy metals were characterized by relatively higher contents in the upper lake than the lower lake. The hotspots with high values of As, Cd and Hg were associated with the river mouths, and the hotspots of Pb were mainly located around the dam in the central part, while no significant associations were displayed between spatial distribution of Cr, Cu, Zn and the river mouths. The mean enrichment factor (EF) values of As, Cd, Hg and Pb were 2.03, 2.93, 3.21 and 2.18, respectively, showing their moderate enrichment, while Cr, Cu and Zn with mean EF values of 1.19, 0.89 and 1.01 were deficiency to minimal enrichment. Multivariate and geostatistical analyses suggested that PC1 controlled by Cr, Cu and Zn was a lithogenic component, and come from parent rocks leaching. PC2 including Cd and partially Hg represented the factor from industrial wastewater discharge. PC3 showed elevated loadings of As and partially Cd, and could be attributed to the agricultural practices. While PC4 including Pb and partially Hg, was dominated by coal combustion. The results of potential ecological risk suggested that sediment environment of Nansi Lake suffered from high ecological risk.

Influence of phosphorus scavenging by iron in contrasting dimictic lakes

Internal regulatory controls of phosphorus (P) via iron (Fe) scavenging were quantified in four contrasting dimictic Wisconsin lakes: Mendota (eutrophic, calcareous), Fish (mesotrophic, calcareous), Devil’s (mesotrophic, noncalcareous), and Sparkling (oligotrophic, noncalcareous). Hypolimnetic enrichment of P was highest in Mendota and Devil’s and least in Fish and Sparkling. This enrichment was attributed mainly to internal loading in the noncalcareous lakes and regeneration of sedimenting epilimnetic P in the calcareous lakes. Differences in Fe scavenging efficiencies at fall turnover were related to hypolimnetic Fe:P molar ratios as well as Fe availability and its control by sulfate–sulfide chemistries. In the noncalcareous lakes with high hypolimnetic Fe enrichment (Fe:P &gt; 2), 45% of whole-lake total P was removed. P removal was low (&lt;20%) in the two calcareous lakes with minimal Fe enrichment (Fe:P &lt; 2). These differences in hypolimnetic P enrichment and subsequent Fe scavenging at fall turnover help to explain the differences in the amount of P available for subsequent spring and summer primary production as well as the differences in trophic state of the four lakes.

A local PUFEM modeling of stress singularity in sliding contact with minimal enrichment for direct evaluation of generalized stress intensity factors

The order of stress singularity around sharp corners is studied by solving the characteristic equation numerically. The corresponding displacement and stress fields around the sharp corners, which accurately satisfy the compatibility of deformation and stress states on the two sides of the slave corner, are derived for various contact configurations. The dominant mode of infinite asymptotic stress field for contact problems is then implemented with minimum enrichments (2 functions for each enriched node), for the first time, within the framework of partition of unity finite element. An increased rate of convergence is achieved and the generalized stress intensity factor can be obtained directly from the additional unknowns. Numerical examples demonstrate the superior accuracy of the present approach to capture the sliding contact stress singularities near sharp corners.

Accumulation of heavy metals in Spinacia oleracea irrigated with paper mill effluent and sewage

The present study on heavy metal contamination in soil and their accumulation in edible part (leaves) and roots of Spinacia oleracea (Spinach) on irrigation with paper mill effluent (PME)/sewage revealed that there was significant increase in the nickel (Ni, +227.17 %) content of the soil irrigated with PME, whereas in the soil irrigated with sewage chromium (Cr, +274.84 %), iron (Fe, +149.56 %), and cadmium (Cd, +133.39 %), contents were increased appreciably. The value of enrichment factor (EF) for Ni (3.27) indicated moderate enrichment in PME-irrigated soil. The EF of Fe, zinc (Zn), Cd, and Cr were <2 in PME effluent-irrigated soil which showed deficiency of minimal enrichment. In sewage irrigated soil, EF value for Cr, Fe, and Cd indicated moderate enrichment, while the values for Zn and Ni indicated deficiency of minimal enrichment. Among various metallic concentrations, the maximum concentration of Fe was observed in leaves (400.12 ± 11.47 mg/kg) and root (301.41 ± 13.14 mg/kg) of S. oleracea after irrigation with PME, whereas the maximum concentrations of Fe was found in leaves (400.49 ± 5.97 mg/kg) and root (363.94 ± 11.37 mg/kg) of S. oleracea after irrigation with sewage for 60 days. The bioaccumulation factor value was found maximum for Cd (2.23) in the plants irrigated with PME while that of Fe (0.90) in the plants irrigated with sewage. The undiluted use of PME/sewage for irrigation increased the concentration of Cr, Cd, Zn, Ni, and Fe metals which were accumulated in S. oleracea, posing a potential threat to human health from this practice of irrigation.

Distribution patterns of some heavy metals in the surface sediment fractions at northern Safaga Bay, Red Sea, Egypt

The distribution patterns, the index of geo-accumulations (MIgeo), and the enrichment ratios (ER n ) of the contaminant metals: Fe, Mn, Zn, Cu, Pb, and Ni were studied in gravel, sand, mud, coarse, medium, and fine sediment fractions of the uppermost layer of the bottom sediments collected from 12 stations covering the northern part of Safaga Bay. The distribution levels of these metals were increasing with grain size decreasing toward the central axis of the bay that extends NE–SW and southward to Safaga Harbour indicating that these metals concentrated mainly in the fine, very fine, and particulate fractions of sediments and to many anthropogenic sources. The geo-accumulation factor of Zn was more significant (MIgeo ≈ 0.62–4.23) relative to the other metals. The bay was classified as moderately to strongly polluted by Zn while it is unpolluted to moderately polluted with the other metals with accumulation sequence of: Zn>Ni>Cu>Mn≥Pb. Zn and Ni recorded the highest enrichment ratios (average ERZn ≈ 3.07 to 8.89; average ERNi ≈ 0.84 to 3.63) in the different sediment fractions relative the other metals. These enrichment ratios classified the bay as minimal enrichment, suggestive of no or minimal pollution, to significant enrichment, suggestive of a significant pollution signals with metals sequence of: Zn>Ni>Cu>Pb>Mn.

Viable circulating tumour cell detection using multiplex RNA in situ hybridisation predicts progression-free survival in metastatic breast cancer patients

Background:Current approaches for detecting circulating tumour cells (CTCs) in blood are dependent on CTC enrichment and are based either on surface epithelial markers on CTCs or on cell size differences. The objectives of this study were to develop and characterise an ultrasensitive multiplex fluorescent RNA in situ hybridisation (ISH)-based CTC detection system called CTCscope. This method detects a multitude of tumour-specific markers at single-cell level in blood.Methods:Healthy blood samples spiked with tumour cell lines were used as a model system for the development and initial characterisation of CTCscope. To demonstrate the feasibility of CTC detection in patient blood, duplicate blood samples were drawn from 45 metastatic breast cancer patients for analysis by CTCscope and the CellSearch system. The association of CTCs with the tumour marker CA15-3 and progression-free survival (PFS) were assessed.Results:CTCscope detected CTC transcripts of eight epithelial markers and three epithelial-mesenchymal-transition (EMT) markers for increased sensitivity. CTCscope was used to detect CTCs with minimal enrichment, and did not detect apoptotic or dead cells. In patient blood samples, CTCs detected by CellSearch, but not CTCscope, were positively correlated with CA15-3 levels. Circulating tumour cells detected by either CTCscope or CellSearch predicted PFS (CTCscope, HR (hazard ratio) 2.26, 95% CI 1.18–4.35, P=0.014; CellSearch, HR 2.50, 95% CI 1.27–4.90, P=0.008).Conclusion:CTCscope offers unique advantages over existing CTC detection approaches. By enumerating and characterising only viable CTCs, CTCscope provides additional prognostic and predictive information in therapy monitoring.

Total-body creatine pool size and skeletal muscle mass determination by creatine-(methyl-d3) dilution in rats

There is currently no direct, facile method to determine total-body skeletal muscle mass for the diagnosis and treatment of skeletal muscle wasting conditions such as sarcopenia, cachexia, and disuse. We tested in rats the hypothesis that the enrichment of creatinine-(methyl-d(3)) (D(3)-creatinine) in urine after a defined oral tracer dose of D(3)-creatine can be used to determine creatine pool size and skeletal muscle mass. We determined 1) an oral tracer dose of D(3)-creatine that was completely bioavailable with minimal urinary spillage and sufficient enrichment in the body creatine pool for detection of D(3)-creatine in muscle and D(3)-creatinine in urine, and 2) the time to isotopic steady state. We used cross-sectional studies to compare total creatine pool size determined by the D(3)-creatine dilution method to lean body mass determined by independent methods. The tracer dose of D(3)-creatine (<1 mg/rat) was >99% bioavailable with 0.2-1.2% urinary spillage. Isotopic steady state was achieved within 24-48 h. Creatine pool size calculated from urinary D(3)-creatinine enrichment at 72 h significantly increased with muscle accrual in rat growth, significantly decreased with dexamethasone-induced skeletal muscle atrophy, was correlated with lean body mass (r = 0.9590; P < 0.0001), and corresponded to predicted total muscle mass. Total-body creatine pool size and skeletal muscle mass can thus be accurately and precisely determined by an orally delivered dose of D(3)-creatine followed by the measurement of D(3)-creatinine enrichment in a single urine sample and is promising as a noninvasive tool for the clinical determination of skeletal muscle mass.

Asymmetry of 13C labeled 3-pyruvate affords improved site specific labeling of RNA for NMR spectroscopy.

Selective isotopic labeling provides an unparalleled window within which to study the structure and dynamics of RNAs by high resolution NMR spectroscopy. Unlike commonly used carbon sources, the asymmetry of 13C-labeled pyruvate provides selective labeling in both the ribose and base moieties of nucleotides using Escherichia coli variants, that until now were not feasible. Here we show that an E. coli mutant strain that lacks succinate and malate dehydrogenases (DL323) and grown on [3-13C]-pyruvate affords ribonucleotides with site specific labeling at C5′ (~95%) and C1′ (~42%) and minimal enrichment elsewhere in the ribose ring. Enrichment is also achieved at purine C2 and C8 (~95%) and pyrimidine C5 (~100%) positions with minimal labeling at pyrimidine C6 and purine C5 positions. These labeling patterns contrast with those obtained with DL323 E. coli grown on [1, 3-13C]-glycerol for which the ribose ring is labeled in all but the C4′ carbon position, leading to multiplet splitting of the C1′, C2′ and C3′ carbon atoms. The usefulness of these labeling patterns is demonstrated with a 27-nt RNA fragment derived from the 30S ribosomal subunit. Removal of the strong magnetic coupling within the ribose and base leads to increased sensitivity, substantial simplification of NMR spectra, and more precise and accurate dynamic parameters derived from NMR relaxation measurements. Thus these new labels offer valuable probes for characterizing the structure and dynamics of RNA that were previously limited by the constraint of uniformly labeled nucleotides.Electronic supplementary materialThe online version of this article (doi:10.1007/s10858-011-9582-5) contains supplementary material, which is available to authorized users.