Biomedical subjects

Honglian Shi

Publications and source records attributed to Honglian Shi.

At least 19 recordsLinked to original sources

PubMed2007

Cerebral tissue oxygenation and oxidative brain injury during ischemia and reperfusion.

The brain requires glucose and oxygen to maintain neuronal metabolism and function. Cerebral ischemia causes heterogeneous changes in tissue oxygenation and cellular metabolism, with a region of decreased blood flow, the penumbra, surrounding a severely damaged ischemic core. Because oxygenation is central in ischemic neuronal death, it is critical to understand exactly what actual changes occur in interstitial oxygen tension (pO2) in ischemic regions during stroke, particularly the penumbra and ischemic core. Cerebral ischemia induces a complex series of molecular pathways involving signaling mechanisms, gene transcription, and protein formation. Free radicals and oxidative stress have been suggested to be involved in each of the steps in the injury cascade. The goal of this review paper is to summarize the current literature concerning our understanding about cerebral tissue oxygenation changes after cerebral ischemia and reperfusion, the subsequent cellular and physiological changes in response to alteration in tissue oxygenation, and treatment strategies utilized to minimize the detrimental effects caused by stroke.

Antioxidants↗

PubMed2006

Effects of glucose concentration on redox status in rat primary cortical neurons under hypoxia.

Reduced supply of glucose involves in many pathological conditions such as stroke and contributes to ischemic injuries. In contrast, hyperglycemia has also been regarded as an important factor in causing and exaggerating stroke damage. Although the molecular mechanism(s) of imbalanced glucose-induced cellular injuries under low oxygen conditions are not clear, oxidative stress has been implicated in both hypo- and hypeglycemic damage. Redox status is critical for the regulation of cellular signaling and cell survival. The effects of glucose levels on redox status are not well understood in neurons under hypoxia. The purpose of this study was to determine the effects of glucose concentration on the redox status of rat primary neurons under hypoxia. The cellular redox status was determined from GSH/GSSG ratios, and oxidation of 2,3-dichlorofluorscein diacetate was used to assess levels of reactive oxygen species (ROS). We found that glucose levels were critical in regulating redox state in these neurons under hypoxia. The results showed that under hypoxic conditions: (1) there was an optimal glucose concentration (25mM) at which neurons maintained a reducing environment and showed the lowest levels of ROS and cell death; (2) in the concentration range of 0-25mM, the presence of glucose increased cellular GSH/GSSG ratio and reduced ROS and cell death; and (3) over-supply of glucose (25-100mM) elevated ROS levels, produced an oxidizing environment, and increased cell death. These results suggest that cellular redox status regulated by glucose may play an important role in glucose-mediated cellular responses in hypoxia.

Animals↗

PubMed2006

Acetoxymethoxycarbonyl nitroxides as electron paramagnetic resonance proimaging agents to measure O2 levels in mouse brain: a pharmacokinetic and pharmacodynamic study.

Measurement of O(2) concentration and distribution in brain is essential to understanding the pathophysiology of stroke. Low-frequency electron paramagnetic resonance (EPR) spectroscopy with a paramagnetic probe is an attractive imaging modality that can potentially map O(2) concentration in the brain. In a previous study, we demonstrated that, after intraperitoneal administration of 3-acetoxymethoxycarbonyl-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (1) to mice, this nitroxide crossed the blood-brain barrier into brain tissue where, after hydrolysis, 3-carboxy-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (2) was liberated and entrapped. This pilot study suggested that nitroxide 1 is a proimaging agent that can deliver nitroxide 2 to brain tissue, where O(2) levels can be estimated. In the present study, we conducted a series of pharmacokinetic and pharmacodynamic experiments designed to assess the uptake of structurally disparate nitroxides into brain tissue and retention, after hydrolysis, of the anions of the corresponding nitroxide acids. From these findings, nitroxide 1 and trans-3,4-di(acetoxymethoxycarbonyl)-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (5) meet the requirement as EPR proimaging agents for mapping O(2) distribution in the brain following stroke.

Animals↗

PubMed2006

Ebselen induced C6 glioma cell death in oxygen and glucose deprivation.

Studies have shown that ebselen is an antiinflammatory and antioxidative agent. Its protective effect has been investigated in oxidative stress related diseases such as cerebral ischemia in recent years. However, experimental evidence also shows that ebselen causes cell death in several different cell types. Whether ebselen will have a beneficial or detrimental effect on cells under ischemic condition is not known. Herein, we studied the effect of ebselen on C6 glioma cells under oxygen and glucose deprivation (OGD), an in vitro ischemic model. We found that ebselen significantly enhanced cell death after 3 h of OGD as observed by lactase dehydrogenase (LDH) release and cellular morphological changes. Further studies revealed that depletion of cellular glutathione level by the combined action of ebselen and OGD played a role in enhanced cell death as demonstrated by the following evidence: (1) cellular GSH was significantly depleted by the combined effort of ebselen and OGD, compared to that of ebselen or OGD insult alone; (2) exogenous addition of N-acetyl cysteine completely diminished the cell damage induced by ebselen and OGD; (3) supplement of glucose, which provides cellular reducing agents and thus maintains cellular GSH level, to the OGD medium diminished C6 cell damage induced by ebselen. We conclude that depleting cellular glutathione plays an important role in ebselen-induced cell death with OGD. Our results suggest that ebselen can have a beneficial or toxic effect, depending on the availability of GSH.

Animals↗

PubMed2005

Evaluation of spin trapping agents and trapping conditions for detection of cell-generated reactive oxygen species.

Electron paramagnetic resonance with spin trapping is a useful technique to detect reactive oxygen species, such as superoxide radical anion (O2*-), a key species in many biological processes. We evaluated the abilities of four spin traps in trapping cell-generated O2*-: 5-tert-butoxycarbonyl-5-methyl-1-pyrroline N-oxide (BMPO), 2-diethoxyphosphoryl-2-phenethyl-3,4-dihydro-2H-pyrrole N-oxide (DEPPEPO), 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO), and 5,5-dimethyl-1-pyrroline N-oxide (DMPO). Optimal experimental conditions for obtaining maximal signal intensity of O2*- adduct in a cellular system were first studied. The maximal intensities of BMPO, DEPMPO, and DMPO adducts were similar while DEPPEPO did not trap cell-generated O2*- induced by 1,6-benzo[a]pyrene quinone in a human mammary epithelial cell line (MCF-10A). BMPO and DEPMPO adducts were more stable, considering the stability of their maximal signal, than DMPO adduct in the tested cellular systems. In addition, we observed that O2*- spin adducts were reduced to their corresponding hydroxyl adducts in the cellular system. The selection of optimal spin trap in trapping cell-generated O2*- is discussed.

Cell Line↗

PubMed2005

Generation of hydrogen peroxide during brief oxygen-glucose deprivation induces preconditioning neuronal protection in primary cultured neurons.

Although reactive oxygen species (ROS) have been implicated in ischemic preconditioning (IPC)-induced neuronal protection, several key questions concerning ROS remain to be elucidated. The purpose of this study is to obtain direct evidence for the formation of specific ROS species generated by IPC, and to determine the specific species that is responsible for the observed neuronal protection. Primary cultured cortex neurons from rat embryos were preconditioned with 10 min of oxygen-glucose deprivation (OGD), which increased the intracellular levels of superoxide and hydrogen peroxide. This preconditioning markedly induced neuronal protection against 2-hr OGD stimuli. Preconditioning with exogenous ROS by the administration of xanthine/xanthine oxidase (X/XO), or hydrogen peroxide was also found to induce IPC-like neuronal protection. Administration of hydrogen peroxide scavengers, such as catalase, glutathione, or the thiol reductant N-(2-mercaptopriopionyl)-glycine, all reduced the increase in the intracellular hydrogen peroxide levels, which effectively eliminated IPC- or exogenous ROS-induced neuronal protection. In contrast, administration of the membrane-permeable superoxide dismutase mimic Mn(III)tetrakis(1-methyl-4-pyridyl)porphyrin pentachloride was able to block the increase of intracellular superoxide levels during IPC, but did not abolish either IPC- or exogenous X/XO preconditioning-induced neuronal protection. These findings strongly suggest that IPC enhances the generation of superoxide, which is then converted to hydrogen peroxide, and that hydrogen peroxide is likely the main trigger involved in the mechanism of IPC-induced neuronal protection.

Animals↗

PubMed2005

PUMA overexpression induces reactive oxygen species generation and proteasome-mediated stathmin degradation in colorectal cancer cells.

Increased amounts of reactive oxygen species (ROS) induce apoptosis in mammalian cells. PUMA (P53 up-regulated modulator of apoptosis), a mitochondrial proapoptotic BH3-only protein, induces rapid apoptosis through a Bax- and mitochondria-dependent pathway. However, the molecular basis of PUMA-induced apoptosis is largely not understood. Using a combination of biophysical and biochemical methods and PUMA-inducible colorectal cells, DLD-1.PUMA, we showed that (a) PUMA-induced apoptosis is dose and time dependent; (b) PUMA-induced apoptosis is directly associated with ROS generation; (c) diphenyleneiodonium chloride, a ROS blocker, or BAX-inhibiting peptide, a suppressor of BAX translocation, decreased ROS generation and apoptosis in DLD-1.PUMA cells; (d) overexpression of PUMA induced up-regulation (>1.34-fold) of peroxiredoxin 1 and down-regulation (by 25%) of stathmin through proteasome-mediated degradation; and (e) hydrogen peroxide down-regulated stathmin and disrupted the cellular microtubule network. Our findings indicate that PUMA induces apoptosis, in part, through the BAX-dependent generation of superoxide and hydrogen peroxide. ROS overproduction and oxidative stress induce proteome-wise alterations, such as stathmin degradation and disorganization of the cell microtubule network, in apoptotic cells.

Apoptosis↗

PubMed2004

Oxidative stress and apoptosis in metal ion-induced carcinogenesis.

Epidemiological evidence suggests that exposure to certain metals causes carcinogenesis. The mechanisms of metal-induced carcinogenesis have been pursued in chemical, biochemical, cellular, and animal models. Significant evidence has accumulated that oxidative stress may be a common pathway in cellular responses to exposure to different metals. For example, in the last few years evidence in support of a correlation between the generation of reactive oxygen species, DNA damage, tumor promotion, and arsenic exposure has strengthened. This article summarizes the current literature on metal-mediated oxidative stress, apoptosis, and their relation to metal-mediated carcinogenesis, concentrating on arsenic and chromium.

Animals↗

PubMed2004

Xanthine oxidase activates pro-matrix metalloproteinase-2 in cultured rat vascular smooth muscle cells through non-free radical mechanisms.

Reactive oxygen species (ROS) have been implicated in the regulation of matrix metalloproteinases (MMPs). The xanthine/xanthine oxidase (X/XO) reaction has been widely used as a source of exogenous ROS in studying MMPs, but commercial XO has also been known to be contaminated by proteolytic activity, and MMPs are protease sensitive substrate. We have investigated the activation of proMMP-2 by X/XO in cultured vascular smooth muscle cells (SMCs). SMCs were incubated with X/XO (unpurified or purified) or XO alone for 24h. X/XO activated proMMP-2 in a dose-dependent manner. A similar profile was observed using XO. Purified XO produced lower amounts of active MMP-2 compared to unpurified XO. EPR study showed that X/XO, not XO itself, produced superoxide anion, which was completely scavenged by SOD. However, X/XO-induced proMMP-2 activation could not be inhibited by combination of SOD and catalase. Incubation with XO either in cell-free conditioned media or in cells resulted in similar amounts of active MMP-2, suggesting that membrane-type-MMPs were not involved in proMMP-2 activation. This was further confirmed by the lack of inhibitory effect of hydroxamate MMP inhibitor, BB1101. Aprotinin blocked unpurified XO-induced proMMP-2 activation in a dose-dependent manner, demonstrating the proteolytic activity contained in XO is essential. We conclude that proteolytic activity contained in XO, rather the ROS derived from X/XO, is responsible for proMMP-2 activation in cultured SMCs. The results also suggest that caution needs to be taken when interpreting the reported results on activation of MMPs where X/XO had been used as an "authentic" source of superoxide anion.

Animals↗

PubMed2004

Application of in vivo EPR in brain research: monitoring tissue oxygenation, blood flow, and oxidative stress.

Although oxygen levels are critical to tissue survival, monitoring tissue oxygen levels in vivo, in real time, remains a technical challenge. This is especially so for repetitive measurements in non-superficial tissue. There currently exist several techniques that can be utilized for tissue oxygen measurement, but technical difficulties have limited their usefulness and general application. Here we describe a relatively new method, electron paramagnetic resonance (EPR) oximetry, for in vivo measurement of brain tissue oxygen, as well as information on blood flow and oxidative stress. In this paper we report experiments designed to assess and illustrate the effectiveness of this new method. Using the unique capability of this approach, we have measured both absolute values and temporal changes of pO2 in ischemic penumbra and core during cerebral ischemia and reperfusion in a rat model. EPR oximetry with particulate probe sensitively reflected differential changes in oxygenation in the core and penumbra during ischemia, reperfusion and also hyperoxic conditions. Simultaneous two-site detection with particulate probes was also obtained with good spatial resolution. Additionally, EPR measurement of oxidative stress, EPR imaging of brain with nitroxide and triarylmethyl soluble probes are also described. These results demonstrate that EPR oximetry with particulate probe can provide accurate and reproducible measurements of localized pO2 in the brain, and it is a versatile and useful method in the measurement of tissue pO2 under a variety of physiological and pathophysiological conditions.

Animals↗

PubMed2004

Arsenite causes DNA damage in keratinocytes via generation of hydroxyl radicals.

Arsenic is an environmental and occupational toxin. Dermatologic toxicities due to arsenic exposure are well-documented and include basal cell and squamous cell carcinomas. However, the mechanism of arsenic-induced skin cancer is not well-understood. Recent studies indicate that arsenic exposure results in the generation of reactive oxygen species (ROS) and oxidative stress. Here, we examined the chemical nature of the specific ROS, studied the interrelationship among these species, and identified the specific species that is responsible for the subsequent DNA damage in a spontaneously immortalized keratinocyte cell line. We detected the formation of O(2)(*)(-) and H(2)O(2) in keratinocytes incubated with arsenite [As(III)] but not with arsenate. As(III)-induced DNA damage was detected in a concentration-dependent manner and evident at low micromolar concentrations. Catalase, an H(2)O(2) scavenger, eliminated H(2)O(2) and reduced the As(III)-mediated DNA damage. Superoxide dismutase, by enhancing the production of H(2)O(2) and (*)OH, significantly increased the As(III)-mediated DNA damage. Sodium formate, a competitive scavenger for (*)OH, and deferoxamine, a metal chelator, both reduced the DNA damage. These results suggest that exposure to arsenite generates O(2)(*)(-) and H(2)O(2), and (*)OH, derived from H(2)O(2), is responsible, at least in part, for the observed DNA damage. These findings demonstrate arsenic-induced formation of specific ROS and provide the direct evidence of (*)OH-mediated DNA damage in keratinocytes, which may play an important role in the mechanism for arsenic-induced skin carcinogenicity.

Animals↗

PubMed2004

Oxidative mechanism of arsenic toxicity and carcinogenesis.

Arsenic is a known toxin and carcinogen that is present in industrial settings and in the environment. The mechanisms of disease initiation and progression are not fully understood. In the last a few years, there has been increasing evidence of the correlation between the generation of reactive oxygen species (ROS), DNA damage, tumor promotion, and arsenic exposure. This article summarizes the current literature on the arsenic mediated generation of ROS and reactive nitrogen species (RNS) in various biological systems. This article also discusses the role of ROS and RNS in arsenic-induced DNA damage and activation of oxidative sensitive gene expression.

Animals↗

PubMed2004

Development of biomarkers based on diet-dependent metabolic serotypes: practical issues in development of expert system-based classification models in metabolomic studies.

Dietary restriction (DR)-induced changes in the serum metabolome may be biomarkers for physiological status (e.g., relative risk of developing age-related diseases such as cancer). Megavariate analysis (unsupervised hierarchical cluster analysis [HCA]; principal components analysis [PCA]) of serum metabolites reproducibly distinguish DR from ad libitum fed rats. Component-based approaches (i.e., PCA) consistently perform as well as or better than distance-based metrics (i.e., HCA). We therefore tested the following: (A) Do identified subsets of serum metabolites contain sufficient information to construct mathematical models of class membership (i.e., expert systems)? (B) Do component-based metrics out-perform distance-based metrics? Testing was conducted using KNN (k-nearest neighbors, supervised HCA) and SIMCA (soft independent modeling of class analogy, supervised PCA). Models were built with single cohorts, combined cohorts or mixed samples from previously studied cohorts as training sets. Both algorithms over-fit models based on single cohort training sets. KNN models had >85% accuracy within training/test sets, but were unstable (i.e., values of k could not be accurately set in advance). SIMCA models had 100% accuracy within all training sets, 89 % accuracy in test sets, did not appear to over-fit mixed cohort training sets, and did not require post-hoc modeling adjustments. These data indicate that (i) previously defined metabolites are robust enough to construct classification models (expert systems) with SIMCA that can predict unknowns by dietary category; (ii) component-based analyses outperformed distance-based metrics; (iii) use of over-fitting controls is essential; and (iv) subtle inter-cohort variability may be a critical issue for high data density biomarker studies that lack state markers.

Algorithms↗

PubMed2004

Development of biomarkers based on diet-dependent metabolic serotypes: concerns and approaches for cohort and gender issues in serum metabolome studies.

Mathematical models that reflect the effects of dietary restriction (DR) on the sera metabolome may have utility in understanding the mechanisms of DR and in applying this knowledge to human epidemiological studies. Previous studies demonstrated both the feasibility of identifying biomarkers through metabolome analysis and the validity of our approach in independent cohorts of 6-month-old male and female ad libitum fed or DR rats. Cross-cohort studies showed that cohort-specific effects distorted the dataset. The present study extends these observations across the entire sample set, thereby validating our markers independently of specific cohorts. Metabolites originally identified in males were examined in females and vice-versa. DR's effect on the metabolome is partially gender-specific and is modulated by environmental factors. DR reduces inter-gender differences in the metabolome. Univariate statistical methods showed that 56/93 metabolites in the female samples and 39/93 metabolites in the male samples were significantly altered (using our previous cut-off criteria of p < or = 0.2) by DR. The metabolites modulated by DR present a wide spectrum of concentration, redox reactivity and hydrophilicity, suggesting that our serotype is broadly representative of the metabolome and that DR has broad effects on the metabolome. These studies, coupled with those in the preceding and following reports, also highlight the utility for consideration of the metabolome as a network of metabolites using appropriate data analysis approaches. The inter-cohort and inter-gender differences addressed herein suggest potential cautions, and potential approaches, for identification of multivariate biomarker profiles that reflect changes in physiological status, such as a metabolism that predisposes to increased risk of neoplasia.

Animals↗

PubMed2004

Development of biomarkers based on diet-dependent metabolic serotypes: characteristics of component-based models of metabolic serotypes.

Our research seeks to identify a serum profile, or serotype, that reflects the systemic physiologic modifications resultant from dietary restriction (DR), in part such that this knowledge can be applied for biomarker studies. Direct comparison suggests that component-based classification algorithms consistently out-perform distance-based metrics for studies of nutritional modulation of metabolic serotype, but are subject to over-fitting concerns. Intercohort differences in the sera metabolome could partially obscure the effects of DR. Further analysis now shows that implementation of component-based approaches (also called projection methods) optimized for class separation and controlled for over-fitting have >97% accuracy for distinguishing sera from control or DR rats. DR's effect on the metabolome is shown to be robust across cohorts, but differs in males and females (although some metabolites are affected in both). We demonstrate the utility of projection-based methods for both sample and variable diagnostics, including identification of critical metabolites and samples that are atypical with respect to both class and variable models. Inclusion of non-statistically different variables enhances classification models. Variables that contribute to these models are sharply dependent on mathematical processing techniques; some variables that do not contribute under one paradigm are powerful under alternative mathematical paradigms. In practical terms, this information may find purpose in other endeavors, such as mechanistic studies of DR. Application of these approaches confirms the utility of megavariate data analysis techniques for optimal generation of biomarkers based on nutritional modulation of physiological processes.

Animals↗

PubMed2004

Interstitial pO2 in ischemic penumbra and core are differentially affected following transient focal cerebral ischemia in rats.

Stroke causes heterogeneous changes in tissue oxygenation, with a region of decreased blood flow, the penumbra, surrounding a severely damaged ischemic core. Treatment of acute ischemic stroke aims to save this penumbra before its irreversible damage by continued ischemia. However, effective treatment remains elusive due to incomplete understanding of processes leading to penumbral death. While oxygenation is central in ischemic neuronal death, it is unclear exactly what actual changes occur in interstitial oxygen tension (pO2) in ischemic regions during stroke, particularly the penumbra. Using the unique capability of in vivo electron paramagnetic resonance (EPR) oximetry to measure localized interstitial pO2, we measured both absolute values, and temporal changes of pO2 in ischemic penumbra and core during ischemia and reperfusion in a rat model. Ischemia rapidly decreased interstitial pO2 to 32% +/- 7.6% and 4% +/- 0.6% of pre-ischemic values in penumbra and core, respectively 1 hour after ischemia. Importantly, whilst reperfusion restored core pO2 close to its pre-ischemic value, penumbral pO2 only partially recovered. Hyperoxic treatment significantly increased penumbral pO2 during ischemia, but not in the core, and also increased penumbral pO2 during reperfusion. These divergent, important changes in pO2 in penumbra and core were explained by combined differences in cellular oxygen consumption rates and microcirculation conditions. We therefore demonstrate that interstitial pO2 in penumbra and core is differentially affected during ischemia and reperfusion, providing new insights to the pathophysiology of stroke. The results support normobaric hyperoxia as a potential early intervention to save penumbral tissue in acute ischemic stroke.

Animals↗

PubMed2003

Benzo(a)pyrene quinones increase cell proliferation, generate reactive oxygen species, and transactivate the epidermal growth factor receptor in breast epithelial cells.

Polycyclic aromatic hydrocarbons, such as benzo(a)pyrene (BaP), are known mammary carcinogens in rodents and may be involved in human breast cancer. We have reported previously that BaP can mimic growth factor signaling and increase cell proliferation in primary human mammary epithelial cells and the human mammary epithelial cell line MCF-10A. BaP-quinones (BPQs) are important metabolites of BaP that have been associated with the production of reactive oxygen species. Using a model of epidermal growth factor (EGF) withdrawal in MCF-10A, we hypothesized that production of reactive oxygen species by BPQs could lead to the activation of the EGF receptor (EGFR). Here, we demonstrate through electron paramagnetic resonance spectroscopy and flow cytometry that 1,6-BPQ and 3,6-BPQ produce superoxide anion and hydrogen peroxide in MCF-10A cells. Furthermore, we show that BPQs increase EGFR, Akt, and extracellular signal-regulated kinase activity, leading to increased cell number in the absence of EGF. The BPQ-induced EGFR activity and associated cell proliferation were attenuated by the EGFR inhibitor AG1478, as well as by the antioxidant N-acetyl cysteine. Overexpression of catalase, but not Cu/Zn superoxide dismutase, reduced the extent of BPQ-dependent increased cell number and EGFR pathway activation. Moreover, the direct treatment of MCF-10A cells with hydrogen peroxide enhanced EGFR, Akt, and extracellular-regulated kinase phosphorylation that could be similarly inhibited by AG1478, N-acetyl cysteine, and catalase. Taken together, these data indicate that BPQs, through the generation of hydrogen peroxide, activate the EGFR in MCF-10A cells, leading to increased cell number under EGF-deficient conditions.

Benzopyrenes↗

PubMed2002

Attention to relative response across sequential electrodes improves quantitation of coulometric array.

HPLC separations coupled with coulometric electrode-based detectors offer potential to evaluate complex biological samples, but analytical approaches to such samples are still being defined. Coulometric electrode array systems use response ratio (as ratio conformity), for quantitation and qualitative characterization. We investigated the influence of changing the ratio conformity requirement (ratio window, RW) on quantitative consistency of the system. Sixty-one serum metabolites were analyzed in three cohorts of ad libitum/dietary restricted rats with two RW settings. RW 30 uses channels with <30% ratio variation (vs standard) to quantitate, whereas RW 100 generally uses all channels. Quantitation between the two approaches differed in 29/671, 61/976, and 264/976 metabolites in cohorts A, B, and C, respectively. The changes were 23.0 +/- 16.6, 31.9 +/- 28.6, and 23.6 +/- 17.1% (+/- SD). Correlation analysis showed that 11, 7, and 21% of the 61 metabolites had r(2) < 0.9 in cohorts A, B, and C, respectively. Inspection of HPLC chromatograms revealed that most of the metabolites with changed levels possessed common characteristics (e.g., shoulder peaks, low signal/noise ratios, coeluting peaks). Analysis demonstrated that RW 30 provided precise quantitation, whereas RW 100 did not. These data suggest that narrow ratio window increases quantitative accuracy in coulometric electrode array analysis of the metabolome(s) of complex biological samples (e.g., sera, mitochondria).

Animals↗