Low Concentrations Of Metabolites Research Articles

Temporal fiber-optic fluorescence study of FAD-NADH interactions in phantoms for potential applications in rapid liquid optical biopsy procedures

Body fluids carry several biomarkers and genetic material that enable the detection of carcinogenesis and tumor metastasis. Owing to this, liquid biopsy is gaining importance and entering clinical practice as an adjunct modality to the current standard of practice in cancer detection. Liquid biopsy involving specimens such as urine is non-invasive and has biomarkers reflecting the tumor microenvironment. We investigate the normal and altered levels of cellular metabolic by-products in liquid phantoms and demonstrate their photon-induced excited-state interaction behaviour for potential diagnostic applications. Short-span temporal analysis of metabolic by-products FAD and NADH in liquid phantoms with fiber optic fluorescence spectroscopy is carried out. The mixed liquid phantom of FAD and NADH, showed excited state interactions that manifested as simultaneous inverse variation in the fluorescence emission from FAD and NADH in varying pH environments. Linear discriminant analysis of the time-varying integrated fluorescence intensity resulted in a 100% accuracy in classifying liquid samples between high and low metabolite concentrations. An extension of application of the experiment model for analysis of body fluids such as urine is also discussed.

Anaerobic biodegradation of perfluorooctane sulfonate (PFOS) and microbial community composition in soil amended with a dechlorinating culture and chlorinated solvents

Perfluorooctane sulfonate (PFOS), one of the most frequently detected per- and polyfluoroalkyl substances (PFAS) occurring in soil, surface water, and groundwater near sites contaminated with aqueous film-forming foam (AFFF), has proven to be recalcitrant to many destructive remedies, including chemical oxidation. We investigated the potential to utilize microbially mediated reduction (bioreduction) to degrade PFOS and other PFAS through addition of a known dehalogenating culture, WBC-2, to soil obtained from an AFFF-contaminated site. A substantial decrease in total mass of PFOS (soil and water) was observed in microcosms amended with WBC-2 and chlorinated volatile organic compound (cVOC) co-contaminants — 46.4 ± 11.0 % removal of PFOS over the 45-day experiment. In contrast, perfluorooctanoate (PFOA) and 6:2 fluorotelomer sulfonate (6:2 FTS) concentrations did not decrease in the same microcosms. The low or non-detectable concentrations of potential metabolites in full PFAS analyses, including after application of the total oxidizable precursor assay, indicated that defluorination occurred to non-fluorinated compounds or ultrashort-chain PFAS. Nevertheless, additional research on the metabolites and degradation pathways is needed. Population abundances of known dehalorespirers did not change with PFOS removal during the experiment, making their association with PFOS removal unclear. An increased abundance of sulfate reducers in the genus Desulfosporosinus (Firmicutes) and Sulfurospirillum (Campilobacterota) was observed with PFOS removal, most likely linked to initiation of biodegradation by desulfonation. These results have important implications for development of in situ bioremediation methods for PFAS and advancing knowledge of natural attenuation processes.

Metabolomics-based analysis of the diatom Cheatoceros tenuissimus combining NMR and GC–MS techniques

Metabolomics, a recent addition to omics sciences, studies small molecules across plants, animals, humans, and marine organisms. Nuclear magnetic resonance (NMR) and gas chromatography-mass spectrometry (GC–MS) are widely used in those studies, including microalgae metabolomics. NMR is non-destructive and highly reproducible but has limited sensitivity, which could be supplemented by joining GC–MS analysis. Extracting metabolites from macromolecules requires optimization for trustworthy results. Different extraction methods yield distinct profiles, emphasizing the need for optimization. The results indicated that the optimized extraction procedure successfully identified NMR and GC–MS-based metabolites in MeOH, CHCl3, and H2O extraction solvents. The findings represented the spectral information related to carbohydrates, organic molecules, and amino acids from the water-soluble metabolites fraction and a series of fatty acid chains, lipids, and sterols from the lipid fraction. Our study underscores the benefit of combining NMR and GC–MS techniques to comprehensively understand microalgae metabolomes, including high and low metabolite concentrations and abundances.•In this study, we focused on optimizing the extraction procedure and combining NMR and GC–MS techniques to overcome the low NMR sensitivity and the different detected range limits of NMR and GC–MS.•We explored metabolome diversity in a tropical strain of the small cells’ diatom Cheatoceros tenuissimus.

Independent and interactive effects of diet and entomopathogenic microsporidia on an outbreaking forest insect defoliator

Abstract Insect herbivore diet mediates interactions with entomopathogens, yet this is relatively unexplored for microsporidia. Here, we examine a diet‐mediated tri‐trophic interaction between an outbreaking forest defoliator, forest tent caterpillar (FTC) Malacosoma disstria Hübner and Nosema sp. microsporidia. We conducted two experiments where diet quality was manipulated by incorporating lyophilized aspen (Populus tremuloides Michaux) foliage into an artificial diet, which was compared to a standard artificial diet. Diet quantity varied between fully fed and partially starved conditions, simulating an outbreak scenario. Microsporidia infection occurred naturally or was induced via experimental inoculation. We assessed FTC survival, microsporidia infection and load, and sublethal effects of treatments on FTC traits. Plant secondary metabolite concentrations in aspen‐augmented diets varied between experiments. In Experiment 1, the aspen‐augmented diet contained lyophilized aspen foliage with low concentrations of secondary metabolites, which increased FTC survival and reduced microsporidia infection. Diet quality and infection load also interactively influenced adult wing traits in Experiment 1. In Experiment 2, the aspen‐augmented diet contained lyophilized aspen foliage with higher concentrations of secondary metabolites, which negatively affected FTC. No diet‐mediated interactions with microsporidia were observed in Experiment 2. Diet quality (Experiments 1 and 2), diet quantity (Experiment 2) and microsporidia infection (Experiments 1 and 2) directly influenced FTC survival and/or had sublethal effects on FTC that may have cascading effects on population dynamics and dispersal. We demonstrated that diet quality can mediate interactions between FTC and microsporidia, but these interactions depend on the defensive chemistry of the FTC diet. To our knowledge, this is the first study to report diet‐mediated interactions between an outbreaking forest pest and microsporidia and one of only a few studies to examine this tri‐trophic interaction among Lepidoptera.

Buprenorphine-Naloxone Maintenance and Lactation.

Breastfeeding among lactating people with opioid use disorder taking buprenorphine monotherapy is generally accepted, as low concentrations of buprenorphine and metabolites in human milk have been well-established. The use of buprenorphine-naloxone for pregnant and lactating people with opioid use disorder is expanding and there is no information available regarding the concentrations of naloxone and their metabolites in human milk to recommend the use of this combination medication during lactation. To determine the concentrations of buprenorphine and naloxone and their primary metabolites in human milk, maternal plasma, and infant plasma, among lactating buprenorphine-naloxone maintained people and their infants. Four lactating buprenorphine-naloxone maintained people provided plasma and human milk samples on Days 2, 3, 4, 14, and 30 postpartum. Infant plasma was obtained on Day 14. Concentrations of buprenorphine, norbuprenorphine and their glucuronide metabolites were present in maternal plasma and human milk at low concentrations, consistent with previous research in lactating buprenorphine monotherapy participants. Naloxone was not detected, or was detected at concentrations below the limit of quantification, in maternal plasma and in all except one human milk sample at Day 30. Naloxone was not detected or detected at concentrations below the limit of quantification in all infant plasma samples. Results support the use of buprenorphine-naloxone by lactating people who meet appropriate criteria for breastfeeding.

Contribution of endophytes towards improving plant bioactive metabolites: a rescue option against red-taping of medicinal plants.

Medicinal plants remain a valuable source for natural drug bioprospecting owing to their multi-target spectrum. However, their use as raw materials for novel drug synthesis has been greatly limited by unsustainable harvesting leading to decimation of their wild populations coupled with inherent low concentrations of constituent secondary metabolites per unit mass. Thus, adding value to the medicinal plants research dynamics calls for adequate attention. In light of this, medicinal plants harbour endophytes which are believed to be contributing towards the host plant survival and bioactive metabolites through series of physiological interference. Stimulating secondary metabolite production in medicinal plants by using endophytes as plant growth regulators has been demonstrated to be one of the most effective methods for increasing metabolite syntheses. Use of endophytes as plant growth promotors could help to ensure continuous supply of medicinal plants, and mitigate issues with fear of extinction. Endophytes minimize heavy metal toxicity in medicinal plants. It has been hypothesized that when medicinal plants are exposed to harsh conditions, associated endophytes are the primary signalling channels that induce defensive reactions. Endophytes go through different biochemical processes which lead to activation of defence mechanisms in the host plants. Thus, through signal transduction pathways, endophytic microorganisms influence genes involved in the generation of secondary metabolites by plant cells. Additionally, elucidating the role of gene clusters in production of secondary metabolites could expose factors associated with low secondary metabolites by medicinal plants. Promising endophyte strains can be manipulated for enhanced production of metabolites, hence, better probability of novel bioactive metabolites through strain improvement, mutagenesis, co-cultivation, and media adjustment.

Severity of prematurity and age impact early postnatal development of GABA and glutamate systems.

Gamma-aminobutyric acid (GABA) and glutamatergic system perturbations following premature birth may explain neurodevelopmental deficits in the absence of structural brain injury. Using GABA-edited spectroscopy (MEscher-GArwood Point Resolved Spectroscopy [MEGA-PRESS] on 3T MRI), we have described in-vivo brain GABA+ (+macromolecules) and Glx (glutamate + glutamine) concentrations in term-born infants. We report previously unavailable comparative data on in-vivo GABA+ and Glx concentrations in the cerebellum, the right basal ganglia, and the right frontal lobe of preterm-born infants without structural brain injury. Seventy-five preterm-born (gestational age 27.8 ± 2.9weeks) and 48 term-born (39.6 ± 0.9weeks) infants yielded reliable MEGA-PRESS spectra acquired at post-menstrual age (PMA) of 40.2 ± 2.3 and 43.0 ± 2weeks, respectively. GABA+ (median 2.44 institutional units [i.u.]) concentrations were highest in the cerebellum and Glx higher in the cerebellum (5.73 i.u.) and basal ganglia (5.16 i.u.), with lowest concentrations in the frontal lobe. Metabolite concentrations correlated positively with advancing PMA and postnatal age at MRI (Spearman's rho 0.2-0.6). Basal ganglia Glx and NAA, and frontal GABA+ and NAA concentrations were lower in preterm compared with term infants. Moderate preterm infants had lower metabolite concentrations than term and extreme preterm infants. Our findings emphasize the impact of premature extra-uterine stimuli on GABA-glutamate system development and may serve as early biomarkers of neurodevelopmental deficits.

The effect of modified atmospheres on the mitochondrial respiratory function and cytochrome c oxidase activity from Rhyzopertha dominica (F.)

The mitochondrial respiratory function and cytochrome c oxidase activity in the isolated mitochondria from Rhyzopertha dominica in hypoxia and hypercapnia was evaluated. Insects were exposed to three modified atmospheres treatments: hypoxia, hypercapnia, hypoxia-hypercapnia, and were compared to a control group (normoxia). Lactate concentration increased in insects under all conditions compared to the control group, which confirms that R. dominica switched its metabolism to anaerobic, supporting the effect of the modified atmospheres. Moreover, the respiratory function decreased in all modified atmospheres treatments up to 50% versus normoxia. Furthermore, all modified atmospheres treatments caused mitochondria uncoupling and a decrease up to three-fold in the cytochrome c oxidase activity compared to normoxia. Besides the lesser O2 availability, this response was possible due to low activity in the electron transport chain, low concentrations of metabolites that participate in the energy-gaining process (glycolysis and the Krebs cycle), or a decrease in ATP production. This information can contribute to the development of new environmental alternatives in order to exterminate or diminish pests in grain warehouses.

Warmer Ambient Temperatures Depress Detoxification and Food Intake by Marsupial Folivores

Ambient temperature is an underappreciated determinant of foraging behaviour in wild endotherms, and the requirement to thermoregulate likely influences food intake through multiple interacting mechanisms. We investigated relationships between ambient temperature and hepatic detoxification capacity in two herbivorous marsupials, the common ringtail possum (Pseudocheirus peregrinus) and common brushtail possum (Trichosurus vulpecula) that regularly feed on diets rich in plant toxins. As an indicator of hepatic detoxification capacity, we determined the functional clearance rate of an anaesthetic agent, Alfaxalone, after possums were acclimated to 10°C [below the thermoneutral zone (TNZ)], 18°C [approximately lower critical temperature (LCT)], and 26°C [approximately upper critical temperature (UCT)] for either 7 days or less than 24 h. We then measured intake of foods with high or low plant secondary metabolite (PSM) concentrations under the same temperature regimes. After 7 days of acclimation, we found a positive correlation between the functional clearance rate of Alfaxalone and ambient temperature, and a negative relationship between ambient temperature and intake of foods with high or low PSM concentrations for both species. The effect of ambient temperature on intake of diets rich in PSMs was absent or reduced when possums were kept at temperatures for less than 24 h. Our results underscore the effects of ambient temperature in hepatic metabolism particularly with respect intake of diets containing PSMs. Given that the planet is warming, it is vital that effects of ambient temperature on metabolism, nutrition and foraging by mammalian herbivores is taken into account to predict range changes of species and their impact on ecosystems.

Analysis of adherent cell culture lysates with low metabolite concentrations using the Biocrates AbsoluteIDQ p400 HR kit

The AbsoluteIDQ p400 HR kit is a commercial product for targeted metabolomics. While the kit has been validated for human plasma and serum, adherent cell lysates have not yet been evaluated. We have optimized the detection of polar and lipid metabolites in cell lysates using the kit to enable robust and repeatable analysis of the detected metabolites. Parameters optimized include total cell mass, loading volume and extraction solvent. We present a cell preparation and analytical method and report on the performance of the kit with regard to detectability of the targeted metabolites and their repeatability. The kit can be successfully used for a relative quantification analysis of cell lysates from adherent cells although validated only for human plasma and serum. Most metabolites are below the limit of the Biocrates’ set quantification limits and we confirmed that this relative quantification can be used for further statistical analysis. Using this approach, up to 45% of the total metabolites in the kit can be detected with a reasonable analytical performance (lowest median RSD 9% and 13% for LC and FIA, respectively) dependent on the method used. We recommend using ethanol as the extraction solvent for cell lysates of osteosarcoma cell lines for the broadest metabolite coverage and 25 mg of cell mass with a loading volume of 20 µL per sample.

Backslopping Time, Rinsing of the Grains During Backslopping, and Incubation Temperature Influence the Water Kefir Fermentation Process.

For eight backslopping steps, eight series of water kefir fermentation processes differing in backslopping time and rinsing of the grains during each backslopping step and eight series of fermentation processes differing in incubation temperature and backslopping time were followed. Short backslopping times resulted in high relative abundances of Liquorilactobacillus nagelii and Saccharomyces cerevisiae, intermediate backslopping times in high relative abundances of Leuconostoc pseudomesenteroides, and long backslopping times in high relative abundances of Oenococcus sicerae and Dekkera bruxellensis. When the grains were rinsed during each backslopping step, the relative abundances of Lentilactobacillus hilgardii and Leuc. pseudomesenteroides increased and those of D. bruxellensis and Liql. nagelii decreased. Furthermore, rinsing of the grains during each backslopping step resulted in a slightly higher water kefir grain growth and lower metabolite concentrations. The relative abundances of Liquorilactobacillus mali were highest at 17°C, those of Leuc. pseudomesenteroides at 21 and 25°C, and those of Liql. nagelii at 29°C. With a kinetic modeling approach, the impact of the temperature and rinsing of the grains during the backslopping step on the volumetric production rates of the metabolites was determined.

Respiratory and allergic outcomes among 5-year-old children exposed to pesticides

BackgroundLittle is known about the effects of pesticides on children’s respiratory and allergic outcomes. We evaluated associations of prenatal and current pesticide exposures with respiratory and allergic outcomes in children...

Role of cytochrome P450 for vitamin D metabolisms in patients with neurodegenerative disorders

IntroductionWe previously reported lower serum 25-hydroxyvitamin D concentrations in patients with Alzheimer’s disease (AD), Parkinson’s disease (PD) and Multiple system atrophy (MSA) compared to healthy controls (HC), whereas 1,25-di-hydroxyvitamin D levels were solely lower in MSA patients. We investigate serum concentrations of P450 involved in Vitamin D(VD) hydroxylation to clarify the responsible hydroxylase for the low serum concentrations of VD metabolites. MethodsA total of 79 individuals were enrolled including 20 HC, 20 AD, 19 PD and 20 MSA patients. The serum concentrations of P450 involved in VD hydroxylation were assayed by ELISA. The data were analyzed by the nonparametric Kruskal-Wallis test between groups. ResultsThough CYP2R1 and CYP27A1 mediate 25-hydroxylation for VD, CYP2R1 is the main hydroxylase, and CYP27A1 is also involved in VD synthesis. CYP2R1 concentrations showed no differences among groups, while lower CYP27A1 concentrations were found in PD (p < 0.05) and MSA (p < 0.005) compared to HC and differences between AD and MSA (p < 0.05), however no differences between PD and MSA. CYP27B1 is the main 1α-hydroxylase for 25-hydroxyvitamin D and showed differences between HC and PD (p < 0.05), between HC and MSA (p < 0.005) and between PD and MSA (p = 0.055). CYP24A1, which inactivate 1,25-di-hydroxyvitamin D, showed no differences among groups. ConclusionsCYP27A1 might affect VD synthesis and cause low 25-hydroxyvitamin D levels in AD, PD and MSA patients. Low 1,25-di-hydroxyvitamin D levels in MSA patients might be caused by impaired feedback mediated by CYP27B1.

Rapid In Vivo Quantification of Creatine Kinase Activity by Phosphorous-31 Magnetic Resonance Spectroscopic Fingerprinting (31P-MRSF).

Creatine kinase (CK) plays an important role in tissue metabolism by providing a buffering mechanism for maintaining a constant supply of adenosine triphosphate (ATP) during metabolic perturbations. Phosphorous-31 magnetic resonance spectroscopy (31P-MRS) employing magnetization transfer techniques is the only noninvasive method for measuring the rate of ATP synthesis via creatine kinase. However, due to the low concentrations of phosphate metabolites, current 31P-MRS methods require long acquisition time to achieve adequate measurement accuracy. In this chapter, we present a new framework of data acquisition and parameter estimation, the 31P magnetic resonancespectroscopic fingerprinting (31P-MRSF) method, for rapid quantification of CK reaction rate constant in the hindlimb of small laboratory animals.

NIMG-16. DEEP LEARNING SUPER-RESOLUTION MR SPECTROSCOPIC IMAGING TO MAP TUMOR METABOLISM IN MUTANT IDH GLIOMA PATIENTS

Abstract Metabolic imaging can map spatially abnormal molecular pathways with higher specificity for cancer compared to anatomical imaging. However, acquiring high resolution metabolic maps similar to anatomical MRI is challenging in patients due to low metabolite concentrations, and alternative approaches that increase resolution by post-acquisition image processing can mitigate this limitation. We developed deep learning super-resolution MR spectroscopic imaging (MRSI) to map tumor metabolism in patients with mutant IDH glioma. We used a generative adversarial network (GAN) architecture comprised of a UNet neural network as the generator network and a discriminator network for adversarial training. For initial training we simulated a large data set of 9600 images with realistic quality for acquired MRSI to effectively train the deep learning model to upsample by a factor of four. Two types of training were performed: 1) using only the MRSI data, and 2) using MRSI and prior information from anatomical MRI to further enhance structural details. The performance of super-resolution methods was evaluated by peak SNR (PSNR), structure similarity index (SSIM), and feature similarity index (FSIM). After training on simulations, GAN was evaluated on measured MRSI metabolic maps acquired with resolution 5.2×5.2 mm2 and upsampled to 1.3×1.3 mm2. The GAN trained only on MRSI achieved PSNR = 27.94, SSIM = 0.88, FSIM = 0.89. Using prior anatomical MRI improved GAN performance to PSNR = 30.75, SSIM = 0.90, FSIM = 0.92. In the patient measured data, GAN super-resolution metabolic images provided clearer tumor margins and made apparent the tumor metabolic heterogeneity. Compared to conventional image interpolation such as bicubic or total variation, deep learning methods provided sharper edges and less blurring of structural details. Our results indicate that the proposed deep learning method is effective in enhancing the spatial resolution of metabolite maps which may better guide treatment in mutant IDH glioma patients.

Low and high molecular weight metabolite concentrations in relationship to adiposity in a multi-site, multi-racial cohort of children

BACKGROUND AND AIM: Low molecular weight (LMW) and high molecular weight (HMW) phthalates are used in multiple everyday products, many of which are bioavailable to children. Evidence concerning the effects of these phthalates on child adiposity remain inconsistent. METHODS: Analyses included 540 racial/ethnically diverse children ages 4-8 in the Environmental Influences on Child Health Outcomes (ECHO) study, a follow-up of the NICHD Fetal Growth Studies. Urinary oxidative metabolites of three LMW and eleven HMW phthalates were determined using liquid chromatography tandem-mass spectrometry. Values were divided by molecular weight and summed to obtain composite LMW and HMW group values (nmol/ml) and natural log transformed. Outcomes were child’s body mass index (BMI) z-score, waist circumference z-score, and percent body fat. Linear regression models were adjusted for urine specific gravity, gender, age, race/ethnicity, birth weight, prolonged exclusive breastfeeding, physical activity, fast-food consumption, smoke exposure, neighborhood traffic, mother’s education and pre-pregnancy BMI. RESULTS:All children had LMW and HMW phthalate group levels at or above the limit of detection. LMW levels were not associated with BMI z-score (β [95% CI]: 0.010 [-0.037. 0.057]), waist circumference z-score (β [95% CI]: -0.002 [-0.046, 0.042]) or percent body fat (β [95% CI]: -0.009 [-0.025, -0.007]). There was evidence of a possible interaction with race (p=0.09), with increased LMW levels in Black children being positively associated with percent body fat (β [95% CI]: 0.005 [0.001, 0.010]). HMW levels were not associated with BMI z-score (β [95% CI]: -0.003 [-0.084, 0.078]), waist circumference z-score (β [95% CI]: 0.021 [-0.055, 0.097]) or percent body fat (β [95% CI]: 0.0003 [-0.008, 0.008]). CONCLUSIONS:In this largely null cross-sectional analysis only LMW phthalates in Black children were associated with percent body fat. Additional research is needed to identify possible interactions between LMW phthalates, HMW phthalates and joint exposure to related chemicals. KEYWORDS: Phthalates, Obesity and metabolic disorders, Children's environmental health

BIMG-22. DEEP LEARNING SUPER-RESOLUTION MR SPECTROSCOPIC IMAGING TO MAP TUMOR METABOLISM IN MUTANT IDH GLIOMA PATIENTS

Metabolic imaging can map spatially abnormal molecular pathways with higher specificity for cancer compared to anatomical imaging. However, acquiring high resolution metabolic maps similar to anatomical MRI is challenging due to low metabolite concentrations, and alternative approaches that increase resolution by post-acquisition image processing can mitigate this limitation. We developed deep learning super-resolution MR spectroscopic imaging (MRSI) to map tumor metabolism in patients with mutant IDH glioma. We used a generative adversarial network (GAN) architecture comprised of a UNet neural network as the generator network and a discriminator network for adversarial training. For training we simulated a large data set of 9600 images with realistic quality for acquired MRSI to effectively train the deep learning model to upsample by a factor of four. Two types of training were performed: 1) using only the MRSI data, and 2) using MRSI and prior information from anatomical MRI to further enhance structural details. The performance of super-resolution methods was evaluated by peak SNR (PSNR), structure similarity index (SSIM), and feature similarity index (FSIM). After training on simulations, GAN was evaluated on measured MRSI metabolic maps acquired with resolution 5.2×5.2 mm2 and upsampled to 1.3×1.3 mm2. The GAN trained only on MRSI achieved PSNR = 27.94, SSIM = 0.88, FSIM = 0.89. Using prior anatomical MRI improved GAN performance to PSNR = 30.75, SSIM = 0.90, FSIM = 0.92. In the patient measured data, GAN super-resolution metabolic images provided clearer tumor margins and made apparent the tumor metabolic heterogeneity. Compared to conventional image interpolation such as bicubic or total variation, deep learning methods provided sharper edges and less blurring of structural details. Our results indicate that the proposed deep learning method is effective in enhancing the spatial resolution of metabolite maps which may better guide treatment in mutant IDH glioma patients.

Spectral Wavelet-feature Analysis and Classification Assisted Denoising for enhancing magnetic resonance spectroscopy.

Magnetic resonance spectroscopy (MRS) is capable of revealing important biochemical and metabolic information of tissues noninvasively. However, the low concentrations of metabolites often lead to poor signal-to-noise ratio (SNR) and a long acquisition time. Therefore, the applications of MRS in detection and quantitative measurements of metabolites in vivo remain limited. Reducing or even eliminating noise can improve SNR sufficiently to obtain high quality spectra in addition to increasing the number of signal averaging (NSA) or the field strength, both of which are limited in clinical applications. We present a Spectral Wavelet-feature ANalysis and Classification Assisted Denoising (SWANCAD) approach to differentiate signal and noise peaks in magnetic resonance spectra based on their respective wavelet features, followed by removing the identified noise components to improve SNR. The performance of this new denoising approach was evaluated by measuring and comparing SNRs and quantified metabolite levels of low NSA spectra (e.g. NSA = 8) before and after denoising using the SWANCAD approach or by conventional spectral fitting and denoising methods, such as LCModel and wavelet threshold methods, as well as the high NSA spectra (e.g. NSA = 192) recorded in the same sampling volumes. The results demonstrated that SWANCAD offers a more effective way to detect the signals and improve SNR by removing noise from the noisy spectra collected with low NSA or in the subminute scan time (e.g. NSA = 8 or 16 s). The potential applications of SWANCAD include using low NSA to accelerate MRS acquisition while maintaining adequate spectroscopic information for detection and quantification of the metabolites of interest when a limited time is available for an MRS examination in the clinical setting.

Why an increase in activity of an enzyme in the Calvin–Benson cycle does not always lead to an increased photosynthetic CO2 uptake rate?—a theoretical analysis

AbstractOverexpressing Calvin–Benson cycle (CBC) enzyme shown to limit the flow of CO2 through the cycle is a major approach to improve photosynthesis. Though control coefficients of CBC enzymes vary under different environmental and developmental conditions, it is usually implicitly assumed that enzymes in the CBC have a monotonic impact on the CBC fluxes. Here, with a dynamic systems model of the photosynthetic carbon metabolism, we show that, for glycerate-3-phosphate kinase (PGAK), fructose-1,6-bisphosphatase (FBPase), fructose-1,6-bisphosphate aldolase (FBA) and transketolase (TKa), individually increasing activity of these CBC enzymes theoretically leads to an initial increase then decrease in the fluxes through the CBC. Also, the inhibition constants of adenosine diphosphate (ADP) for PGAK and of fructose-6-phosphate (F6P) for FBPase influence the CBC flux in a biphasic manner. These predicted enzymes showing a biphasic manner are always located in different subcycles of the CBC, which consume the shared substrates in the early steps in the CBC and produce intermediates used as substrates for enzymes in the later reactions. We show that the excessive increase in activities of enzymes in one subcycle consuming the shared metabolite could cause low concentrations of metabolites in the other subcycles, which results in low reaction rates of the later reactions and hence lowers overall CBC flux. This study provides a model to explain the underlying reasons that overexpression of enzymes in the CBC sometimes can negatively impact photosynthesis. We find that balanced activities of enzymes in the subcycles of the CBC are required to gain a higher efficiency of the CBC.

A Simple and High-Throughput LC-MS-MS Method for Simultaneous Measurement of Nicotine, Cotinine, 3-OH Cotinine, Nornicotine and Anabasine in Urine and Its Application in the General Korean Population.

Measuring nicotine metabolites is the most objective method for identifying smoke exposure. Liquid chromatography--tandem mass spectrometry (LC-MS-MS) can measure multiple metabolites and is sensitive enough to detect low concentrations of metabolites. Therefore, we developed a simple and high-throughput method for measuring nicotine, cotinine, trans-3'-hydroxycotinine (3-OH cotinine), nornicotine and anabasine for population-based studies using LC-MS-MS. Each 30 µL of urine sample was diluted with 90 µL of acetonitrile containing five deuterated internal standards. Chromatographic separation used a C18 column, and LC-MS-MS analysis was performed with a multiple reaction monitoring mode. The chromatographic run time for each sample was 6.5 min. The method was validated by evaluating selectivity, interference, limit of detection, lower limit of quantification, precision, accuracy, linearity, extraction recovery, matrix effect and carryover according to guidelines. Our methods required a short preparation time (∼20 min) while simultaneously measuring five markers for smoking status. No endogenous or exogenous interference was found. Our method showed excellent precision and accuracy: within-run coefficient of variation (CV) 2.9-9.4%, between-run CV 4.8-8.7% and bias -10.1 to 5.3%. Linear dynamic ranges were 1-10,000 ng/mL for nicotine, nornicotine and anabasine; 2-5,000 ng/mL for cotinine and 5-15,000 ng/mL for 3-OH cotinine. Extraction recovery was consistent (87-109%) across concentrations. No significant matrix effect or carryover was observed. The validated method was applied to 849 urine samples. In samples from the 125 current smokers, nicotine, cotinine, 3-OH cotinine, nornicotine and anabasine were detected in 97.6, 99.2, 98.4, 96.8 and 87.2%, respectively. No markers were detected in 93.9% of 609 nonsmokers. The overlapping detection of multiple markers made it possible to identify the smoking status even in current smokers with a low concentration of cotinine. Our LC-MS-MS method using a simple sample preparation technique is sensitive and effective for screening of smoking status in the general population.