Electro-Elastic Modeling of Thermal Spin Transition in Diluted Spin-Crossover Single Crystals.

Spin-crossover solids have been studied for many years for their promising applications as optical switches and reversible high-density memories for information storage. This study reports the effect of random metal dilution on the thermal and structural properties of a spin-crossover single crystal. The analysis is performed on a 2D rectangular lattice using an electro-elastic model. The lattice is made of sites that can switch thermally between the low-spin and high-spin states, accompanied by local volume changes. The model is solved by Monte Carlo simulations, running on the spin states and atomic positions of this compressible 2D lattice. A detailed analysis of metal dilution on the magneto-structural properties allows us to address the following issues: (i) at low dilution rates, the transition is of the first order; (ii) increasing the concentration of dopant results in a decrease in cooperativity and leads to gradual transformations above a threshold concentration, while incomplete spin transitions are obtained for big dopant sizes. The effects of the metal dilution on the spatiotemporal aspects of the spin transition along the thermal transition and on the low-temperature relaxation of the photo-induced metastable high-spin states are also studied. Significant changes in the organization of the spin states are observed for the thermal transition, where the single-domain nucleation caused by the long-range elastic interactions is replaced by a multi-droplet nucleation. As to the issue of the relaxation curves: their shape transforms from a sigmoidal shape, characteristic of strong cooperative systems, into stretched exponentials for high dilution rates, which is the signature of a disordered system.

External validation of a prediction model for estimating fat mass in children and adolescents in 19 countries: individual participant data meta-analysis.

OBJECTIVE: To evaluate the performance of a UK based prediction model for estimating fat-free mass (and indirectly fat mass) in children and adolescents in non-UK settings. DESIGN: Individual participant data meta-analysis. SETTING: 19 countries. PARTICIPANTS: 5693 children and adolescents (49.7% boys) aged 4 to 15 years with complete data on the predictors included in the UK based model (weight, height, age, sex, and ethnicity) and on the independently assessed outcome measure (fat-free mass determined by deuterium dilution assessment). MAIN OUTCOME MEASURES: The outcome of the UK based prediction model was natural log transformed fat-free mass (lnFFM). Predictive performance statistics of R2, calibration slope, calibration-in-the-large, and root mean square error were assessed in each of the 19 countries and then pooled through random effects meta-analysis. Calibration plots were also derived for each country, including flexible calibration curves. RESULTS: The model showed good predictive ability in non-UK populations of children and adolescents, providing R2 values of >75% in all countries and >90% in 11 of the 19 countries, and with good calibration (ie, agreement) of observed and predicted values. Root mean square error values (on fat-free mass scale) were <4 kg in 17 of the 19 settings. Pooled values (95% confidence intervals) of R2, calibration slope, and calibration-in-the-large were 88.7% (85.9% to 91.4%), 0.98 (0.97 to 1.00), and 0.01 (-0.02 to 0.04), respectively. Heterogeneity was evident in the R2 and calibration-in-the-large values across settings, but not in the calibration slope. Model performance did not vary markedly between boys and girls, age, ethnicity, and national income groups. To further improve the accuracy of the predictions, the model equation was recalibrated for the intercept in each setting so that country specific equations are available for future use. CONCLUSION: The UK based prediction model, which is based on readily available measures, provides predictions of childhood fat-free mass, and hence fat mass, in a range of non-UK settings that explain a large proportion of the variability in observed fat-free mass, and exhibit good calibration performance, especially after recalibration of the intercept for each population. The model demonstrates good generalisability in both low-middle income and high income populations of healthy children and adolescents aged 4-15 years.

Agreement and Precision of Deuterium Dilution for Total Body Water and Multicompartment Body Composition Assessment in Collegiate Athletes.

BACKGROUND: Deuterium oxide (D2O) dilution is the criterion method for total body water (TBW) measurement, but results may vary depending on the specimen type, analysis method, and analyzing laboratory. Bioelectrical impedance (BIA) estimates TBW, but results may vary by device make and model. OBJECTIVES: We investigated the accuracy and precision of TBW estimates and how measurement conditions affected the accuracy of body composition using multicompartment body composition models. METHODS: Eighty collegiate athletes received duplicate TBW measures acquired from 3 BIA devices (S10, SFB7, and SOZO) and from unique D2O combinations of specimen type (saliva, urine), analysis methodology [Fourier transform infrared spectrophotometry (FTIR), isotope-ratio mass spectrometry (IRMS)], and 3 different laboratories. TBW measures were substituted into 2-compartment (2C) and 5-compartment (5C) body composition models. Criterion measures were compared using Lin's concordance correlation coefficient cutoff of poor (<0.90), moderate (0.90-0.95), substantial (0.95-0.99), and almost perfect (>0.99). RESULTS: Fifty-one participants (26 female) completed the protocol. Using IRMS saliva as the criterion TBW, all other measures produced a substantial or almost perfect agreement, except for SFB7 (poor) and SOZO (moderate). The 2C body composition measures using D2O and BIA produced poor agreement except for moderate agreement for lab 3 FTIR saliva. The 5C body composition measures using D2O produced a substantial agreement, whereas the BIA device S10 and SOZO had a moderate agreement, while the SFB7 had a poor agreement to the criterion. Test-retest precision varied between techniques from 0.3% to 1.2% for TBW. CONCLUSIONS: Small differences in TBW measurement led to significant differences in 2C models. The 5C models partially mitigate differences seen in 2C models when different TBW measures are used. Interchanging TBW measures in multicompartment models can be problematic and should be performed with these considerations.

Virus matrix interference on assessment of virucidal activity of high-touch surfaces designed to prevent hospital-acquired infections.

OBJECTIVES/PURPOSE: High-touch surfaces are a critical reservoir in the spread of nosocomial infections. Although disinfection and infection control protocols are well developed, they lack the ability to passively reduce the pathogenic load of high-touch surfaces. Copper and its alloys have been suggested as a surface that exhibit continuous biocidal effects. Antimicrobial studies on these surfaces are prevalent, while virucidal studies are not as well explored. The goal of this study was to first determine the virucidal activity of a copper-nickel-zinc alloy and to then examine the effect of soiling and virus preparation on virucidal activity. METHODS: A baculovirus vector was used as an easily quantifiable model of an infectious enveloped animal cell virus. Droplets containing virus were deposited on surfaces and allowed to stay wet using humidity control or were dried onto the surface. Virus was then recovered from the surface and assayed for infectivity. To examine how the composition of the droplet affected the survival of the virus, 3 different soiling conditions were tested. The first two were recommended by the United States Environmental Protection Agency and the third consisted of cell debris resulting from virus amplification. RESULTS: A copper-nickel-zinc alloy was shown to have strong virucidal effects for an enveloped virus. Copper, nickel, and zinc ions were all shown to leach from the alloy surface and are the likely cause of virucidal activity by this surface. Virucidal activity was achieved under moderate soiling but lost under high soiling generated by routine virus amplification procedures. The surface was able to repeatably inactivate dried virus droplets under moderate soiling conditions, but unable to do so for virus droplets kept wet using high humidity. CONCLUSION: Ion leaching was associated with virucidal activity in both wet and dried virus conditions. Soiling protected the virus by quenching metal ions, and not by inhibiting leaching. The composition of the solution containing virus plays a critical role in evaluating the virucidal activity of surfaces and surface coatings.

Improving the accuracy of chloride measurements through participation in regular external quality assessment programme.

BACKGROUND: A chloride test is an integral part of a basic metabolic panel that is essential for the assessment of a patient's acid-base and electrolyte status. While many methods are available commercially for the routine measurement of chloride, there is a need to address the accuracy and variability among the measurement results, especially with the prevalence of patients seeking treatment across different healthcare providers for alternative opinions. METHOD: A method based on sector field inductively coupled plasma isotope dilution mass spectrometry (SF-ICP-IDMS) was developed for the measurement of chloride in human serum. The SF-ICP-IDMS method was then used to assign the target values in the Health Sciences Authority (HSA) External Quality Assessment (EQA) Programme to evaluate the results of chloride test from participating clinical laboratories. RESULTS: The accuracy of the measurements was evaluated by comparing the results with the certified values of Electrolytes in Frozen Human Serum Certified Reference Materials (SRM 956c and SRM 956d) from the National Institute of Standards and Technology (NIST) at different chloride concentration levels. Over a five-year period from 2014-2018, the number of clinical laboratories which participated in the EQA Programme increased from 23 to 33. Comparison of robust means from the laboratories' results with our assigned target values revealed a reduction in relative deviation over time. The relationship between the deviation of each brand of clinical analysers and the chloride levels was established, where a larger deviation was uncovered at low chloride concentration. The SF-ICP-IDMS method was further demonstrated to be comparable with methods used by other metrology institutes in an international comparison organised by HSA under the auspice of the Consultative Committee for Amount of Substance - Metrology in Chemistry and Biology (CCQM). CONCLUSION: The use of metrologically traceable assigned target values enabled the study of method biasness from a small pool of dataset in each of the four brands of clinical analysers in HSA EQA Programme. This work underscores the need to improve the accuracy of chloride measurements by regular participation in an accuracy-based EQA Programme.

Assessment of the impact of hydrolysis on bound sulfonamide residue determination in honey using stable isotope dilution ultrahigh performance liquid chromatography tandem mass spectrometry.

In this study, an analytical method based on isotope dilution-liquid chromatography tandem mass spectrometry (ID-LC-MS/MS) was developed as a candidate reference method for the determination of sulfonamides (SAs) in honey. To guarantee the accuracy and authenticity, the impact of hydrolysis on bound SA residues was first investigated by enabling (i) identification of sugar-bound SAs, (ii) clarifying the binding reaction rule between the SAs and sugar, (iii) detection of free SAs and sugar-bound SAs, and (iv) preparation of SA-contaminated honey. Thus, the efficiency of different hydrolysis conditions was assessed by comparing the bound SA content before and after hydrolysis. In addition, optimization of the sample pretreatment procedures and LC conditions to minimize matrix effects by separation from significant matrix interferences was also performed. Satisfactory results in terms of hydrolysis efficiency (approximately 88.3%-99.2%), extraction efficiency (84.2%-105.3%), recovery (95.9%-103.1%), and limit of quantification (0.6-1.5 µg·kg-1) were obtained.

Validation of bioelectrical impedance analysis for body composition assessment in children with obesity aged 8-14y.

BACKGROUND & AIMS: The aim was to generate a predictive equation to assess body composition (BC) in children with obesity using bioimpedance (BIA), and avoid bias produced by different density levels of fat free mass (FFM) in this population. METHODS: This was a cross-sectional validation study using baseline data from a randomized intervention trial to treat childhood obesity. Participants were 8 to 14y (n = 315), underwent assessments on anthropometry and BC through Air Displacement Plethysmography (ADP), Dual X-Ray Absorptiometry and BIA. They were divided into a training (n = 249) and a testing subset (n = 66). In addition, the testing subset underwent a total body water assessment using deuterium dilution, and thus obtained results for the 4-compartment model (4C). A new equation to estimate FFM was created from the BIA outputs by comparison to a validated model of ADP adjusted by FFM density in the training subset. The equation was validated against 4C in the testing subset. As reference, the outputs from the BIA device were also compared to 4C. RESULTS: The predictive equation reduced the bias from the BIA outputs from 14.1% (95%CI: 12.7, 15.4) to 4.6% (95%CI: 3.8, 5.4) for FFM and from 18.4% (95%CI: 16.9, 19.9) to 6.4% (95% CI: 5.3, 7.4) for FM. Bland-Altman plots revealed that the new equation significantly improved the agreement with 4C; furthermore, the observed trend to increase the degree of bias with increasing FM and FFM also disappeared. CONCLUSION: The new predictive equation increases the precision of BC assessment using BIA in children with obesity.

Effects of Breastfeeding on Maternal Body Composition in Moroccan Lactating Women during Twelve Months after Birth Using Stable Isotopic Dilution Technique.

BACKGROUND: Exclusive breastfeeding during the first six months of an infant's life is an important factor for their optimal growth and health. Breastfeeding also has maternal benefits and can assist with postpartum weight loss. As shown by previous studies, postpartum weight retention can contribute to obesity. OBJECTIVE: To quantify the human milk and evaluate the effect of breastfeeding on maternal weight loss during the 12 months postpartum. METHOD: This study included 70-mother-baby pairs. Infants' intake of human milk and water from other sources, as well as the body composition of the mothers, were measured at the 1st, 3rd, 6th, 9th and 12th month postpartum by using the deuterium oxide dose-to-mother technique. RESULTS: There was a significant change in the mothers' body composition between the first and twelfth months in exclusive breastfeeding women compared to not-exclusive ones. Similarly, the difference between the quantities of human milk intake was highly significant in exclusive breastfeeding women compared to women who were not exclusively breastfeeding. CONCLUSION: Our results showed that exclusive breastfeeding for twelve months has a significant effect on postpartum weight loss among Moroccan women and that it is an effective way to control overweight and obesity among lactating women.

Validity of Bioimpedance Spectroscopy in the Assessment of Total Body Water and Body Composition in Wrestlers and Untrained Subjects.

Bioimpedance spectroscopy (BIS) is an easy tool to assess hydration status and body composition. However, its validity in athletes remains controversial. We investigated the validity of BIS on total body water (TBW) and body composition estimation in Japanese wrestlers and untrained subjects. TBW of 49 young Japanese male subjects (31 untrained, 18 wrestlers) were assessed using the deuterium dilution method (DDM) and BIS. De Lorenzo's and Moissl's equations were employed in BIS for TBW estimation. To evaluate body composition, Siri's 3-compartment model and published TBW/fat-free mass (FFM) ratio were applied in DDM and BIS, respectively. In untrained subjects, DDM and BIS with de Lorenzo's equation showed consistent TBW estimates, whereas BIS with Moissl's equation overestimated TBW (p < 0.001 vs. DDM). DDM and BIS with de Lorenzo's equation estimated FFM and percent of fat mass consistently, whereas BIS with Moissl's equation over-estimated and under-estimated them (p < 0.001 vs. DDM). In wrestlers, BIS with de Lorenzo's and Moissl's equations assessed TBW similarly with DDM. However, the Bland-Altman analysis revealed a proportional bias for TBW in BIS with de Lorenzo's equation (r = 0.735, p < 0.001). Body composition assessed with BIS using both equations and DDM were not different. In conclusion, BIS with de Lorenzo's equation accurately estimates the TBW and body composition in untrained subjects, whereas BIS with Moissl's equation is more valid in wrestlers. Our results demonstrated the usefulness of BIS for assessing TBW and body composition in Japanese male wrestlers.

Paper spray tandem mass spectrometry: A rapid approach for the assay of parabens in cosmetics and drugs.

A fast methodology for the assay of parabens in drug and cosmetic preparations has been presented. The procedure developed is based on paper spray tandem mass spectrometry and isotope dilution approach. For each investigated paraben, the corresponding labeled standard has been used in order to improve the accuracy and reproducibility of the analyses. The MS experiments have been performed under MRM conditions, monitoring the transitions [M-H]- → m/z 92 and [M-H]- → m/z 98, respectively, for each analyte and the corresponding labeled internal standard. The quantitative assay has been performed using a calibration curve built from 2 to 15 mg/L. The method accuracy, in all case near 100%, was evaluated using fortified samples at two concentration levels, which are representative of the lower and the higher portion of calibration curve. The good values of LOQ, LOD, and reproducibility confirm the consistency of the developed approach.

Assessment of body composition in Sri Lankan adults: development and validation of bioelectrical impedance prediction equation.

Bioelectrical impedance analysis (BIA) is a simple and quick method used for assessment of body composition (BC). Present study aims to develop and validate a BIA prediction equation for Sri Lankan adults. Healthy adults (≥18 years) were randomly selected for development and validation of the equation. BIA was performed using the Inbody 230 multifrequency analyzer. BC analysis was also evaluated by deuterium oxide (D2O) dilution. Prediction equations for TBW/FFM were derived by linear-regression analysis. Study population included 170 adults, of which 32.9% were males. Mean age and BMI were 43.2 ± 12.6 years and 24.1 ± 4.5 kg/m2, respectively. Final equation for TBW (r = 0.915, p < 0.001) and FFM (r = 0.906, p < 0.001) correlated significantly with values obtained by D2O dilution. Therefore, this equation is suitable for estimation of BC parameters, such as TBW, FM, FFM, and %BF in Sri Lankan adults, and is possibly appropriate for use in other South Asian populations, including those living in Western countries.

Pairwise efficiency: a new mathematical approach to qPCR data analysis increases the precision of the calibration curve assay.

BACKGROUND: The real-time quantitative polymerase chain reaction (qPCR) is routinely used for quantification of nucleic acids and is considered the gold standard in the field of relative nucleic acid measurements. The efficiency of the qPCR reaction is one of the most important parameters in data analysis in qPCR experiments. The Minimum Information for publication of Quantitative real-time PCR Experiments (MIQE) guidelines recommends the calibration curve as the method of choice for estimation of qPCR efficiency. The precision of this method has been reported to be between SD = 0.007 (three replicates) and SD = 0.022 (no replicates). RESULTS: In this article, we present a novel approach to the analysis of qPCR data which has been obtained by running a dilution series. Unlike previously developed methods, our method, Pairwise Efficiency, involves a new formula that describes pairwise relationships between data points on separate amplification curves and thus enables extensive statistics. The comparison of Pairwise Efficiency with the calibration curve by Monte Carlo simulation shows the two-folds improvement in the precision of estimations of efficiency and gene expression ratios on the same dataset. CONCLUSIONS: The Pairwise Efficiency nearly doubles the precision in qPCR efficiency determinations compared to standard calibration curve method. This paper demonstrates that applications of combinatorial treatment of data provide the improvement of the determination.

Unrecognized Elevations of Toxic Elements in Urine and Blood Highlight the Potential Need for a Broader Approach to Exposure Assessment.

Heavy metals testing remains an ongoing challenge for diagnosing acute or chronic exposure to heavy metals. In this study, we determined the positivity rates of single element and panel testing for toxic elements, and evaluated the potential utility of an expanded detection protocol for screening of toxic element exposures. The retrospective analysis included data from urine (n = 19,343) and blood (n = 196,019) specimens tested using inductively coupled plasma-mass spectrometry (ICP-MS) for arsenic, cadmium, lead and mercury (blood), and arsenic, cadmium, copper, lead, mercury and zinc (urine). Lead industrial monitoring in blood and cadmium exposure in blood and urine were included to represent directed single element ordering. The percent of positive results, defined as results greater than the upper limit of the reference interval was determined. For blood, the highest positivity was observed for lead occupational exposure monitoring (26.2%) whereas for urine, the highest positivity was observed for zinc testing (28.1%). Remarkably, reanalysis using an expanded panel, of 120 blood and 174 urine specimens originally negative identified 42% (50 of 120) of the blood specimens with at least one elevated result and 48% (83 of 174) of the urine specimens with at least one elevated result. Our results indicate that a broad elemental screening panel may help ensure easier identification of elemental exposure and may eliminate the need for additional follow-up sample collections.

Validation of rapid 4-component body composition assessment with the use of dual-energy X-ray absorptiometry and bioelectrical impedance analysis.

Background: The 4-component (4C) model is a criterion method for human body composition that separates the body into fat, water, mineral, and protein, but requires 4 measurements with significant cost and time requirements that preclude wide clinical use. A simplified model integrating only 2 measurements-dual-energy X-ray absorptiometry (DXA) and bioelectrical impedance analysis (BIA)-and 10 min of patient time has been proposed. Objective: We aimed to validate a rapid, simplified 4C DXA + BIA body composition model in a clinical population. Design: This was a cross-sectional observational study of 31 healthy adults. Participants underwent whole-body DXA, segmental BIA, air displacement plethysmography (ADP), and total body water (TBW) measurement by deuterium (D2O) dilution. 4C composition was calculated through the use of the Lohman model [DXA mineral mass, D2O TBW, ADP body volume (BV), scale weight] and the simplified model (DXA mineral mass and BV, BIA TBW, scale weight). Accuracy of percentage of fat (%Fat) and protein measurements was assessed via linear regression. Test-retest precision was calculated with the use of duplicate DXA and BIA measurements. Results: Of 31 participants, 23 were included in the analysis. TBWBIA showed good test-retest precision (%CV = 5.2 raw; 1.1 after outlier removal) and high accuracy to TBWD2O [TBWD2O = 0.956*TBWBIA, R2= 0.92, root mean squared error (RMSE) = 2.2 kg]. %Fat estimates from DXA, ADP, D2O, and BIA all showed high correlation with the Lohman model. However, only the 4C simplified model provides high accuracy for both %Fat (R2 = 0.96, RMSE = 2.33) and protein mass (R2= 0.76, RMSE = 1.8 kg). %Fat precision from 4C DXA + BIA was comparable with DXA (root mean square-SD = 0.8 and 0.6 percentage units, respectively). Conclusions: This work validates a simplified 4C method that measures fat, water, mineral, and protein in a 10-min clinic visit. This model has broad clinical application to monitor many conditions including over/dehydration, malnutrition, obesity, sarcopenia, and cachexia.

Mycotoxins in infant/toddler foods and breakfast cereals in the US retail market.

The objective of this study was to conduct a mycotoxin survey of commercial infant/toddler foods (cereals and teething biscuits) and breakfast cereals in the United States. A total of 215 retail samples were collected from three geographical locations and analysed for aflatoxins, fumonisins, deoxynivalenol, HT-2 toxin, ochratoxin A, T-2 toxin, and zearalenone using a stable isotope dilution liquid-chromatography tandem mass spectrometry (LC-MS/MS) method. One or more mycotoxins were found in 69% (101/147) of the infant/toddler foods and 50% (34/68) of breakfast cereals. Mycotoxin co-occurrence was observed in 12% of infant/toddler foods and 32% of breakfast cereals. However, the concentrations of detected mycotoxins were lower than the current FDA action and guidance levels. Aflatoxins and HT-2 toxin were not detected in any of the samples, while deoxynivalenol was the most frequently detected mycotoxin. Rice-based cereals appeared to be less susceptible to mycotoxin contamination than other cereal types.

Assessment of bioavailable B vitamin content in food using in vitro digestibility assay and LC-MS SIDA.

Standardized analytical methods, where each B vitamin is extracted from a given sample individually using separate procedures, typically ensure that the extraction conditions provide the maximum recovery of each vitamin. However, in the human gastrointestinal tract (GIT), the extraction conditions are the same for all vitamins. Here, we present an analytically feasible extraction protocol that simulates conditions in the GIT and provides a measure of the content of bioavailable vitamins using LC-MS stable isotope dilution assay. The results show that the activities of both human gastric and duodenal juices were insufficient to liberate absorbable vitamers (AV) from pure cofactors. The use of an intestinal brush border membrane (IBBM) fraction derived from the mucosal tissue of porcine small intestine ensured at least 70% AV recovery. The rate of AV liberation, however, was strongly dependent on the cofactor, e.g., in the case of NADH, it was magnitudes higher than in the case of thiamine diphosphate. For some vitamins in some food matrices, the use of the IBBM fraction assay resulted in lower values for the content of AV than conventional vitamin determination methods. Conventional methods likely overestimate the actual bioavailability of some vitamins in these cases. Graphical abstract Assessment of bioavailable B vitamin content in food.

Dietary supplementation of branched-chain amino acids increases muscle net amino acid fluxes through elevating their substrate availability and intramuscular catabolism in young pigs.

Branched-chain amino acids (BCAA) have been clearly demonstrated to have anabolic effects on muscle protein synthesis. However, little is known about their roles in the regulation of net AA fluxes across skeletal muscle in vivo. This study was aimed to investigate the effect and related mechanisms of dietary supplementation of BCAA on muscle net amino acid (AA) fluxes using the hindlimb flux model. In all fourteen 4-week-old barrows were fed reduced-protein diets with or without supplemental BCAA for 28 d. Pigs were implanted with carotid arterial, femoral arterial and venous catheters, and fed once hourly with intraarterial infusion of p-amino hippurate. Arterial and venous plasma and muscle samples were obtained for the measurement of AA, branched-chain α-keto acids (BCKA) and 3-methylhistidine (3-MH). Metabolomes of venous plasma were determined by HPLC-quadrupole time-of-flight-MS. BCAA-supplemented group showed elevated muscle net fluxes of total essential AA, non-essential AA and AA. As for individual AA, muscle net fluxes of each BCAA and their metabolites (alanine, glutamate and glutamine), along with those of histidine, methionine and several functional non-essential AA (glycine, proline and serine), were increased by BCAA supplementation. The elevated muscle net AA fluxes were associated with the increase in arterial and intramuscular concentrations of BCAA and venous metabolites including BCKA and free fatty acids, and were also related to the decrease in the intramuscular concentration of 3-MH. Correlation analysis indicated that muscle net AA fluxes are highly and positively correlated with arterial BCAA concentrations and muscle net BCKA production. In conclusion, supplementing BCAA to reduced-protein diet increases the arterial concentrations and intramuscular catabolism of BCAA, both of which would contribute to an increase of muscle net AA fluxes in young pigs.

A simple analytical method of determining 1-hydroxypyrene glucuronide in human urine by isotope dilution with ultra performance liquid chromatography-tandem mass spectrometry.

The glucuronide conjugate of 1-hydroxypyrene (1-OHP-G) is a sensitive and reliable index biomarker for assessing low exposure to polycyclic aromatic hydrocarbons (PAHs). A simple method for determining 1-OHP-G in human urine with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established and applied to evaluate the exposure level of PAHs of pregnant women in a large sample size. After the urine sample was extracted with ethyl acetate, 0.2 mL of the aqueous phase was diluted to 1.0 mL with 5 mmol/L ammonium acetate before injection. The chromatographic separation was performed on a C18 column with a gradient elution and identification was conducted on a tandem mass spectrometry with electrospray ionization in negative mode. 1-OHP-d9-G was used as an internal standard to improve precision. The method was validated and good linearity was obtained in the range of 0.1∼2.0 ng/mL. The limit of detection (LOD) and the limit of quantification (LOQ) of 1-OHP-G were 0.015 and 0.051 ng/mL. Intra-day and inter-day precision were 4.3 and 6.7 %, respectively. The spiked recoveries were 79.4∼106 % for urine samples. This method was rapid, sensitive, and very suitable for batch analysis of urine. Six hundred seventy-five urine samples of pregnant women from the cities of Fuzhou, Shenzhen, and Nanning of P.R. China were analyzed with the proposed method. The medians of 1-OHP-G concentration were 0.27 µg/g.cr (n = 201), 0.30 µg/g.cr (n = 212), and 0.51 µg/g.cr (n = 262) for the cities of Fuzhou, Shenzhen, and Nanning, respectively. 1-OHP-G concentrations in urine samples of pregnant women from the cities of Fuzhou and Shenzhen in coastal areas were both significantly lower than that of Nanning City in inland region (p < 0.001). Graphical Abstract The internal standard 1-OHP-d9-G and 2.0 mL of ethyl acetate were added to 1.0 mL of urine sample, after vortex vibration and centrifugation the aqueous phase was removed and diluted, and 5 µl of aliquot was analyzed by UPLC-MS/MS.

Body composition assessment in horses using bioimpedance spectroscopy.

Assessment of equine body composition using objective measurements is difficult owing to the large size of the animals and the costs involved. Bioelectrical impedance spectroscopy (BIS), a technique widely used for the assessment of body composition in humans, was investigated for practicality of use in horses. BIS uses algorithms that require values for the apparent resistivities of body fluids and body proportion factors (Kb), currently not available for horses. Aims of the present study were to derive resistivity coefficients and body proportion factors and to validate their use for prediction of body composition horses. Validation of coefficients and predictive power using a split-sample agreement study design using correlation and limits of agreement analysis. Whole body impedance measurements were performed on 35 standardbred horses, yearlings to 14 yr, concurrently with determination of total body water volume (TBW) by deuterium dilution and extracellular water volume (ECW) by bromide dilution. Kb was determined in an independent group of 38 mixed-breed, age, and sex horses. Mean apparent resistivity coefficients were 511.4 and 1415.9 ohm.cm for intracellular water and TBW, respectively. Mean Kb was 1.52 ± 0.1. Using these coefficients, TBW and fat-free mass could be predicted with limits of agreement (2SD) of ± 11.6%; mean fat-free mass and fat mass were under- and overestimated by 3.1% and 14.1%, respectively, compared to measured reference values although these differences were not statistically significant. BIS is a practical technique for the assessment of body composition in equids, but the relatively wide limits of agreement, particularly for fat mass, may limit its usefulness for predicting body composition in individual horses.