Mass Spectral Library for DNA Adductomics.

Endogenous electrophiles, ionizing and non-ionizing radiation, and hazardous chemicals present in the environment and diet can damage DNA by forming covalent adducts. DNA adducts can form in critical cancer driver genes and, if not repaired, may induce mutations during cell division, potentially leading to the onset of cancer. The detection and quantification of specific DNA adducts are some of the first steps in studying their role in carcinogenesis, the physiological conditions that lead to their production, and the risk assessment of exposure to specific genotoxic chemicals. Hundreds of different DNA adducts have been reported in the literature, and there is a critical need to establish a DNA adduct mass spectral database to facilitate the detection of previously observed DNA adducts and characterize newly discovered DNA adducts. We have collected synthetic DNA adduct standards from the research community, acquired MSn (n = 2, 3) fragmentation spectra using Orbitrap and Quadrupole-Time-of-Flight (Q-TOF) MS instrumentation, processed the spectral data and incorporated it into the MassBank of North America (MoNA) database, and created a DNA adduct portal Web site (https://sites.google.com/umn.edu/dnaadductportal) to serve as a central location for the DNA adduct mass spectra and metadata, including the spectral database downloadable in different formats. This spectral library should prove to be a valuable resource for the DNA adductomics community, accelerating research and improving our understanding of the role of DNA adducts in disease.

Ferrate(VI) mediated degradation of the potent cyanotoxin, cylindrospermopsin: Kinetics, products, and toxicity.

The presence of cylindrospermopsin (CYN), a potent cyanotoxin, in drinking water sources poses a tremendous risk to humans and the environment. Detailed kinetic studies herein demonstrate ferrate(VI) (FeVIO42-, Fe(VI)) mediated oxidation of CYN and the model compound 6-hydroxymethyl uracil (6-HOMU) lead to their effective degradation under neutral and alkaline solution pH. A transformation product analysis indicated oxidation of the uracil ring, which has functionality critical to the toxicity of CYN. The oxidative cleavage of the C5=C6 double bond resulted in fragmentation of the uracil ring. Amide hydrolysis is a contributing pathway leading to the fragmentation of the uracil ring. Under extended treatment, hydrolysis, and extensive oxidation lead to complete destruction of the uracil ring skeleton, resulting in the generation of a variety of products including nontoxic cylindrospermopsic acid. The ELISA biological activity of the CYN product mixtures produced during Fe(VI) treatment parallels the concentration of CYN. These results suggest the products do not possess ELISA biological activity at the concentrations produced during treatment. The Fe(VI) mediated degradation was also effective in the presence of humic acid and unaffected by the presence of common inorganic ions under our experimental conditions. The Fe(VI) remediation of CYN and uracil based toxins appears a promising drinking water treatment process.

A culturally appropriate method for validating self-reported drug administration among indigenous people who use injection drugs.

Compared with other racial/ethnic groups in the United States (US), American Indians/Alaska Natives have one of the fastest climbing rates of drug overdose deaths involving stimulants. Validating the substances self-reported by Indigenous people who use injection drugs (IPWIDs) can present logistical and cultural challenges. While the collection of biospecimens (e.g., urine, blood, hair follicle) can be one way to cross-validate the substances self-reported by IPWIDs, the collection of biospecimens has been historically problematic when conducting substance use research with Indigenous North Americans. In our National Institutes of Health (NIH)-supported pilot research conducted with IPWIDs, we have documented low willingness to provide a biospecimen to a research team. This article demonstrates an alternative method for validating self-reported substances injected by IPWIDs that does not require the extraction of biospecimens from Indigenous bodies and spaces. The method described includes:•Collecting used, unwashed syringes from IPWIDs at the time of behavioral assessment,•Sampling the used syringe by washing the syringe needle/barrel with methanol,•Analyzing the samples with gas chromatography mass spectrometry (GC-MS) and liquid chromatography coupled to triple-quadrupole mass spectrometry (LC-QQQ-MS). This method offers a more culturally appropriate alternative to validate substances self-reported by IPWIDs during behavioral assessments.

Evaluation of Pretreatment and Extraction Parameters for the Analysis of Fentanyl in Hair Using Statistical Design of Experiments (DoE).

Optimal methods for hair analysis are often debated. Previous work in this laboratory demonstrated that the statistical technique known as Design of Experiments (DoE) is useful for such optimization. DoE evaluates both the individual roles and the combinatorial associations among multiple independent variables (i.e., hair pretreatment parameters) and a dependent variable (i.e., drug recovery from hair). In this study, hair externally contaminated with fentanyl underwent decontamination with combinations of parameters based on a 24 fractional factorial block design DoE matrix. The parameters of interest included aqueous wash solvent (1% sodium dodecyl sulfate (SDS) or water), organic wash solvent (dichloromethane or methanol), number of consecutive washes (one or three), sequence of washes (aqueous first or organic first) and wash time (30 s or 30 min). The optimal method for decontaminating fentanyl from the hair surface was found to be one 30-min wash with dichloromethane followed by one 30-min wash with water. Pretreatment parameters were optimized with a 23 full factorial DoE matrix using authentic hair reference material (HRM), which consisted of pooled drug user hair diluted to a known concentration of fentanyl with drug-free hair. The factors of interest were extraction solvent/sample weight ratio (12.5 or 25 µL/mg), hair particle size (pulverized or 1 mm segments) and extraction time (2 or 24 h). The most effective pretreatment method for fentanyl consisted of pulverizing the hair prior to a 2-h extraction in a 25 µL/mg extraction solvent volume/sample weight ratio. Finally, using the optimized pretreatment methods, fentanyl containing authentic HRM was extracted using aqueous base, solvent and enzymatic hair extraction methods, where it was determined that the aqueous base technique was most effective for recovery of fentanyl. These experiments further demonstrate the value of DoE and authentic HRM in method development for forensic hair analysis.

Evaluation of extraction parameters in authentic hair reference material using statistical design of experiments.

Optimal methods for forensic hair analysis are often debated, especially regarding extraction parameters that include incubation time, temperature, and size of extracted hair particles. To assess hair pretreatment parameters for analysis of drugs of abuse, the statistical technique known as Design of Experiments (DoE) is useful. DoE evaluates both the individual roles and the combinatorial associations between multiple variables and overall drug extraction efficiency. Previous reports have focused on incorporated hair reference material (HRM), which is prepared in the lab at a specified drug concentration. In contrast, authentic HRM, which is prepared by diluting hair from drug users with blank hair to achieve specific drug concentrations, is an effective matrix for standardization of forensic hair testing, since the drug is incorporated into the hair matrix via uptake from systemic distribution. In the present study, extraction parameters for authentic HRM samples containing multiple drugs (diazepam, alprazolam, cocaine, methamphetamine, oxycodone, hydrocodone, and morphine) and metabolites (nordiazepam, cocaethylene, norcocaine, hydroxycocaine, and 6-monoacetylmorphine) were optimized based on recovery using a 23 full factorial DoE matrix. The factors evaluated included extraction solvent volume/sample weight ratio (12.5 or 25 µL/mg), particle size (pulverized or cut into 1 mm snippets), and extraction time (2 or 24 h) using solvent swelling. DoE analysis revealed significant differences in the optimal combinations of extraction parameters for maximum recovery. However, for the majority of drugs and metabolites, the most effective extraction method consisted of pulverizing hair prior to a 2-h extraction with a 12.5 µL/mg extraction solvent volume/sample weight ratio.

DNA Aptamer-Cyanine Complexes as Generic Colorimetric Small-Molecule Sensors.

Aptamers are promising biorecognition elements for sensors. However, aptamer-based assays often lack the requisite levels of sensitivity and/or selectivity because they typically employ structure-switching aptamers with attenuated affinity and/or utilize reporters that require aptamer labeling or which are susceptible to false positives. Dye-displacement assays offer a label-free, sensitive means for overcoming these issues, wherein target binding liberates a dye that is complexed with the aptamer, producing an optical readout. However, broad utilization of these assays has been limited. Here, we demonstrate a rational approach to develop colorimetric cyanine dye-displacement assays that can be broadly applied to DNA aptamers regardless of their structure, sequence, affinity, or the physicochemical properties of their targets. Our approach should accelerate the development of mix-and-measure assays that could be applied for diverse analytical applications.

Quantitation and Validation of 34 Fentanyl Analogs from Liver Tissue Using a QuEChERS Extraction and LC-MS-MS Analysis.

Since 2013, drug overdose deaths involving synthetic opioids (including fentanyl and fentanyl analogs) have increased from 3,105 to 31,335 in 2018. Postmortem toxicological analysis in fentanyl-related overdose deaths is complicated by the high potency of the drug, often resulting in low analyte concentrations and associations with toxicity, multidrug use, novelty of emerging fentanyl analogs and postmortem redistribution. Objectives for this study include the development of a quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction and subsequent liquid chromatography-mass spectrometry--mass spectrometry analysis, validation of the method following the American Academy of Forensic Sciences Standards Board (ASB) standard 036 requirements and application to authentic liver specimens for 34 analytes including fentanyl, metabolites and fentanyl analogs. The bias for all 34 fentanyl analogs did not exceed ±10% for any of the low, medium or high concentrations and the %CV did not exceed 20%. No interferences were identified. All 34 analytes were within the criteria for acceptable percent ionization suppression or enhancement with the low concentration ranging from -10.2% to 23.7% and the high concentration ranging from -7.1% to 11.0%. Liver specimens from 22 authentic postmortem cases were extracted and analyzed with all samples being positive for at least one target analyte from the 34 compounds. Of the 22 samples, 17 contained fentanyl and metabolites plus at least one fentanyl analog. The highest concentration for a fentanyl analog was 541.4 µg/kg of para-fluoroisobutyryl fentanyl (FIBF). The concentrations for fentanyl (n = 20) ranged between 3.6 and 164.9 µg/kg with a mean of 54.7 µg/kg. The fentanyl analog that was most encountered was methoxyacetyl fentanyl (n = 11) with a range of 0.2-4.6 µg/kg and a mean of 1.3 µg/kg. The QuEChERS extraction was fully validated using the ASB Standard 036 requirements for fentanyl, metabolites and fentanyl analogs in liver tissue.

Assessing Hair Decontamination Protocols for Diazepam, Heroin, Cocaine and Δ9-Tetrahydrocannabinol by Statistical Design of Experiments.

Prior to toxicological analysis, hair as a matrix requires pre-treatment measures including decontamination, homogenization and extraction. Decontamination is performed to differentiate between drug present from superficial deposition and drug incorporated from systemic distribution following ingestion. There are many methods for decontamination of hair samples, mostly developed by empirically using a traditional "one factor at a time" approach, in which one independent variable at a time is changed to observe the effect on the dependent variable. The goal of the present work was to compare the efficacy of decontamination protocols using statistical "design of experiments" (DoE), which allows for analysis of multiple variables and interactions within a single experiment. Decontamination parameters included identity of aqueous and organic wash solutions, number of sequential aqueous and organic washes, order of aqueous and organic washes, and duration of each wash. DoE studies were completed to identify optimal decontamination conditions for four abused drugs with varying physiochemical properties. For this purpose, drug-free human hair was externally contaminated with diazepam, heroin, cocaine or Δ9-tetrahydrocannabinol. Each analyte was found to have a unique set of decontamination conditions that were most effective. These included three 30-min washes with methanol followed by three with 1% sodium dodecyl sulfide for diazepam, three 30-s washes with dichloromethane followed by one with water for heroin, one 30-s wash with 1% sodium dodecyl sulfate followed by three with dichloromethane for cocaine and three 30-min washes with water followed by one with methanol for Δ9-tetrahydrocannabinol. The results provide proof-of-principle for a DoE approach to identify effective parameters for hair decontamination for a physicochemically diverse group of drugs. The major advantage of DoE is to elucidate combinations of parameters that result in effective removal of surface contamination, a goal that would be challenging to accomplish using a one factor at a time approach.

Comprehensive analysis of synthetic cannabinoids and metabolites in oral fluid by online solid-phase extraction coupled to liquid chromatography-triple quadrupole-mass spectrometry.

The class of novel psychoactive substances known as synthetic cannabinoids (SC) includes illicit compounds that are sprayed on plant material and smoked or sold as liquids to be vaporized in e-cigarettes. In toxicological analysis of SC, fast analytical methods are needed for the detection and confirmation of parent drugs and metabolites at very low levels. While various analytical methods have been developed for SC in blood and urine, few are available for alternative matrices such as oral fluid (OF). There are numerous advantages to using OF as a sample matrix for SC analysis, including non-invasive collection, lesser risk of adulteration, and presence of both parent drug and metabolites. Here we report a validated online solid-phase extraction (online SPE) method coupled to LC-QqQ-MS for rapid confirmation and quantitation of 72 structurally diverse SC parent drugs and metabolites in OF with 2.5 min of preconcentration time and a total elution time of < 10 min. The use of online SPE for sample pretreatment facilitates rapid and consistent processing and greatly increases sample throughput. The method was fully validated according to relevant guidelines (ANSI/ASB Standard 036). Bias and precision values were within ± 20% for all compounds in human OF matrix. Method detection and quantitation limits ranged from 0.4 to 3.8 ng/mL and from 1.1 to 11.6 ng/mL, respectively. Recovery, matrix effects, process efficiency, carryover, and stability were also within acceptable limits for the majority of compounds. Successful application of the method was demonstrated using blank human OF fortified with SC in addition to a set of authentic OF specimens previously tested by another laboratory. Graphical abstract.

Development of a DNA Adductome Mass Spectral Database.

Mass spectrometry-based DNA adductomics is an emerging approach for the human biomonitoring of hazardous chemicals. A mass spectral database of DNA adducts will be created for the scientific community to investigate the associations between chemical exposures, DNA damage, and disease risk.

Conodipine-P1-3, the First Phospholipases A2 Characterized from Injected Cone Snail Venom.

The phospholipase A2 (PLA2s) superfamily are ubiquitous small enzymes that catalyze the hydrolysis of phospholipids at the sn-2 ester bond. PLA2s in the venom of cone snails (conodipines, Cdpi) are composed of two chains termed as alpha and beta subunits. Conodipines are categorized within the group IX of PLA2s. Here we describe the purification and biochemical characterization of three conodipines (Cdpi-P1, -P2 and -P3) isolated from the injected venom of Conus purpurascens Using proteomics methods, we determined the full sequences of all three conodipines. Conodipine-P1-3 have conserved consensus catalytic domain residues, including the Asp/His dyad. Additionally, these enzymes are expressed as a mixture of proline hydroxylated isoforms. The activities of the native Conodipine-Ps were evaluated by conventional colorimetric and by MS-based methods, which provide the first detailed cone snail venom conodipine activity monitored by mass spectrometry. Conodipines can have medicinal applications such inhibition of cancer proliferation, bacterial and viral infections among others.

LC-MS/MS based detection and characterization of covalent glutathione modifications formed by reactive drug of abuse metabolites.

Conjugation with the tripeptide glutathione (GSH) is a common mechanism of detoxification of many endogenous and exogenous compounds. This phenomenon typically occurs through the formation of a covalent bond between the nucleophilic free thiol moiety of GSH and an electrophilic site on the compound of interest. While GSH adducts have been identified for many licit drugs, there is a lack of information on the ability of drugs of abuse to adduct GSH. The present study utilized a metabolic assay with GSH as a nucleophilic trapping agent to bind reactive drug metabolites formed in situ. Extracted ion MS spectra were collected via LC-QqQ-MS/MS for all potentially significant ions and examined for fragmentation common to GSH-containing compounds, followed by confirmation of adduction and structural characterization performed by LC-QTOF-MS/MS. In addition to the two positive controls, of the 14 drugs of abuse tested, 10 exhibited GSH adduction, with several forming multiple adducts, resulting in a total of 22 individual identified adducts. A number of these are previously unreported in the literature, including those for diazepam, naltrexone, oxycodone and Δ9-THC.

Separation and Identification of Isomeric and Structurally Related Synthetic Cannabinoids Using 2D Liquid Chromatography and High Resolution Mass Spectrometry.

Novel psychoactive substances (NPS) are emerging drugs of abuse that are variations of existing compounds intended to cause a CNS psychotropic effect. Some NPS are so comparable in structure and physicochemical properties that they co-elute using traditional single column chromatographic techniques and therefore will not be detected as individual compounds. 2D liquid chromatography (2D-LC) has demonstrated applicability in difficult separations of small molecules and compounds in complex mixtures. It was hypothesized that this technique could also be used to separate co-eluting isomeric and structurally related, non-isomeric NPS, including synthetic cannabinoids (SC). Initial studies assessed several parameters, including column type, mobile phase, analysis time, gradient and flow rate, to optimize a 2D-LC method for separation and analysis of SC. The final comprehensive on-line 2D-LC method employed a Bonus-RP column in the first dimension (1D) coupled with UV detection and a biphenyl column in the second dimension (2D) coupled with QTOF-MS detection in full scan positive mode. To test the utility of the method, three SC mixes were created, each containing five compounds that were unresolvable in a traditional, 1D-LC separation; one mix with isomeric compounds and two with structurally related but non-isomeric compounds. Contour plots of UV absorbance in 1D and MS ion intensity in 2D demonstrated that all components in each mixture were successfully resolved using the 2D-LC separation method. This research serves as proof-of-concept for the application of 2D-LC to the separation of isomeric and structurally related SC. With further optimization and validation, 2D-LC may be a generally useful tool for separation of complex mixtures of NPS.

Rapid quantitative analysis of methylphenidate and ritalinic acid in oral fluid by liquid chromatography triple quadrupole mass spectrometry (LC-QqQ-MS).

Methylphenidate (MPH), which is metabolized into ritalinic acid (RA), is an amphetamine derivative largely used in the treatment of attention-deficit hyperactivity disorder, a neurological condition commonly diagnosed in early childhood. Ensuring that patients comply with clinical treatment is crucial and compliance is generally monitored in blood or urine specimens which, especially in the case of children, can be challenging to obtain on a repetitive basis. Here we report validation of a specific, non-invasive, and rapid dilute-and-shoot analytical method for the detection and quantitation of MPH and RA in oral fluid (OF). The method is based on liquid chromatography coupled to triple quadrupole MS with electrospray ionization utilizing dynamic MRM mode. Subject OF specimens were collected using a Quantisal™ device, processed, and diluted for analysis with seven-point quadratic calibration curves (weighting of 1/x) using MPH-d9 and (±)-threo-RA-d10 as internal standards. QC samples and diluted specimens showed intra- and inter-day bias and imprecision values no greater than ±12%. The LOD and LOQ for MPH were 0.1 and 0.5 ng/mL, respectively, and 0.2 ng/mL and 0.5 ng/mL for RA, respectively, indicating the validity of the method for identification and confirmation at low concentrations. Selectivity was specific for the analytes of interest and matrix effects were minimized through the use of internal standard based quantitation.

Proteomic Analysis of Thiol Modifications and Assessment of Structural Changes in Hemoglobin Induced by the Aniline Metabolites N-Phenylhydroxylamine and Nitrosobenzene.

MS-based proteomic analysis was combined with in silico quantum mechanical calculations to improve understanding of protein adduction by N-phenylhydroxylamine (PhNHOH) and nitrosobenzene (NOB), metabolic products of aniline. In vitro adduction of model peptides containing nucleophilic sidechains (Cys, His, and Lys) and selected proteins (bovine and human hemoglobin and ß-lactoglobulin-A) were characterized. Peptide studies identified the Cys thiolate as the most reactive nucleophile for these metabolites, a result consistent with in silico calculations of reactivity parameters. For PhNHOH, sulfinamides were identified as the primary adduction products, which were stable following tryptic digestion. Conversely, reactions with NOB yielded an additional oxidized adduct, the sulfonamide. In vitro exposure of human whole blood to PhNHOH and NOB demonstrated that only sulfinamides were formed. In addition to previously reported adduction of ß93Cys of human Hb, two novel sites of adduction were found; α104Cys and ß112Cys. We also report CD and UV-Vis spectroscopy studies of adducted human Hb that revealed loss of α-helical content and deoxygenation. The results provide additional understanding of the covalent interaction of aromatic amine metabolites with protein nucleophiles.

Isolation and characterization of Conohyal-P1, a hyaluronidase from the injected venom of Conus purpurascens.

Hyaluronidases are ubiquitous enzymes commonly found in venom and their main function is to degrade hyaluran, which is the major glycosaminoglycan of the extracellular matrix in animal tissues. Here we describe the purification and characterization of a 60kDa hyaluronidase found in the injected venom from Conus purpurascens, Conohyal-P1. Using a combined strategy based on transcriptomic and proteomic analysis, we determined the Conohyal-P1 sequence. Conohyal-P1 has conserved consensus catalytic and positioning domain residues characteristic of hyaluronidases and a C-terminus EGF-like domain. Additionally, the enzyme is expressed as a mixture of glycosylated isoforms at five asparagine sites. The activity of the native Conohyal-P1 was assess MS-based methods and confirmed by classical turbidimetric methods. The MS-based assay is particularly sensitive and provides the first detailed analysis of a venom hyaluronidase activity monitored with this method. The discovery of new hyaluronidases and the development of techniques to evaluate their performance can advance several therapeutic procedures, as these enzymes are widely used for enhanced drug delivery applications. BIOLOGICAL SIGNIFICANCE: Cone snail venom is a remarkable source of therapeutically important molecules, as is the case of conotoxins, which have undergone extensive clinical trials for several applications. In addition to the conotoxins, a large array of proteins have been reported in the venom of several species of cone snails, including enzymes that were found in dissected and injected Conus venom. Here we describe the isolation and characterization of the hyaluronidase Conohyal-P1 from the injected venom of C. purpurascens. We employed a combined transcriptomic and proteomic analysis to obtain the full sequence of this hyaluronidase. The activity of Conohyal-P1 was assessed by a mass spectrometry-based method, which provide the first detailed venom hyaluronidase activity analysis monitored by mass spectrometry allowing the visualization of the substrate degradation by the enzyme.

Diabetes Prevalence in Relation to Serum Concentrations of Polychlorinated Biphenyl (PCB) Congener Groups and Three Chlorinated Pesticides in a Native American Population.

BACKGROUND: Exposure to persistent organic pollutants (POPs) is known to increase risk of diabetes. OBJECTIVE: To determine which POPs are most associated with prevalence of diabetes in 601 Akwesasne Native Americans. METHODS: Multiple logistic regression analysis was used to assess associations between quartiles of concentrations of 101 polychlorinated biphenyl (PCBs) congeners, congener groups and three chlorinated pesticides [dichlorodiphenyldichloroethylene (DDE), hexachlorobenzene (HCB) and mirex] with diabetes. In Model 1, the relationship between quartiles of exposure and diabetes were adjusted only for sex, age, body mass index (BMI), and total serum lipids. Model 2 included additional adjustment for either total PCBs or total pesticides. RESULTS: Total serum PCB and pesticide concentrations were each significantly associated with prevalence of diabetes when adjusted only for covariates (Model 1), but neither showed a significant OR for highest to lowest quartiles after additional adjustment for the other (Model 2). When applying Model 2 to PCB congener groups and individual pesticides, there were significant omnibus differences between the four quartiles (all ps < 0.042) for most groups, with the exception of penta- and hexachlorobiphenyls, DDE and mirex. However, when comparing highest to lowest quartiles only non- and mono-ortho PCBs [OR = 4.55 (95% CI: 1.48, 13.95)], tri- and tetrachloro PCBs [OR = 3.66 (95% CI: 1.37, -9.78)] and HCB [OR = 2.64 (95% CI: 1.05, 6.61)] showed significant associations with diabetes. Among the non- and mono-ortho congeners, highest to lowest quartile of dioxin TEQs was not significant [OR = 1.82 (95% CI: 0.61, 5.40)] but the OR for the non-dioxin-like congeners was [OR = 5.01 (95% CI: 1.76, 14.24)]. CONCLUSION: The associations with diabetes after adjustment for other POPs were strongest with the more volatile, non-dioxin-like, low-chlorinated PCB congeners and HCB. Because low-chlorinated congeners are more volatile, these observations suggest that inhalation of vapor-phase PCBs is an important route of exposure. CITATION: Aminov Z, Haase R, Rej R, Schymura MJ, Santiago-Rivera A, Morse G, DeCaprio A, Carpenter DO, and the Akwesasne Task Force on the Environment. 2016. Diabetes prevalence in relation to serum concentrations of polychlorinated biphenyl (PCB) congener groups and three chlorinated pesticides in a Native American population. Environ Health Perspect 124:1376-1383; http://dx.doi.org/10.1289/ehp.1509902.

Changes in persistent organic pollutant levels from adolescence to young adulthood.

Elimination rates and their corresponding half-lives are conceptually important and intuitively accessible pharmacokinetic measures of toxicant elimination, but regression-based estimates are biased proportional to the degree of continuing (background) exposure. We propose an alternative estimator, the censored normal regression model, which uses all observations, but treats individuals whose initial level failed to exceed their follow-up level as censored observations to weight the regression estimates from those that declined between blood draws. In this manner, we derive the intrinsic elimination rate, the elimination rate free from ongoing exposure, as a parameter in a regression with an unobserved, latent dependent variable. We utilize sequential measurements of persistent organic pollutants (POPs) levels from adolescence to adulthood, a period of intense change in size and body composition, to quantify individual-level change within a community exposed to significant quantities of contaminants over an extended period of time. Although much research has been conducted on effects of POPs, far less attention has been given to vectors of intake and changes in toxicant levels during the life course. We apply exploratory factor analysis (EFA) to types and timing of consumption, along with physical behavioral characteristics, to identify a structure of seven underlying factors. Although several variables show factorial complexity, the latent constructs included an age/maturation and period-related factor, a nutritional composite, consumption prior to pregnancy, fish and fowl consumed during pregnancy, factors distinguishing body mass and weight from height, and bottom-feeding fish consumption. Unadjusted and adjusted half-lives using the censored normal regression estimator, as well as estimated half-lives from conventional log concentration regressions, are reported for PCB groupings, specific congeners, p,p'-DDE, and HCB.

Reductive and oxidative degradation of iopamidol, iodinated X-ray contrast media, by Fe(III)-oxalate under UV and visible light treatment.

Iopamidol, widely employed as iodinated X-ray contrast media (ICM), is readily degraded in a Fe(III)-oxalate photochemical system under UV (350 nm) and visible light (450 nm) irradiation. The degradation is nicely modeled by pseudo first order kinetics. The rates of hydroxyl radical (OH) production for Fe(III)-oxalate/H2O2/UV (350 nm) and Fe(III)-oxalate/H2O2/visible (450 nm) systems were 1.19 ± 0.12 and 0.30 ± 0.01 µM/min, respectively. The steady-state concentration of hydroxyl radical (OH) for the Fe(III)-oxalate/H2O2/UV (350 nm) conditions was 10.88 ± 1.13 × 10(-14) M and 2.7 ± 0.1 × 10(-14) M for the Fe(III)-oxalate/H2O2/visible (450 nm). The rate of superoxide anion radical (O2(-)) production under Fe(III)-oxalate/H2O2/UV (350 nm) was 0.19 ± 0.02 µM/min with a steady-state concentration of 5.43 ± 0.473 × 10(-10) M. Detailed product studies using liquid chromatography coupled to Q-TOF/MS demonstrate both reduction (multiple dehalogenations) and oxidation (aromatic ring and side chains) contribute to the degradation pathways. The reduction processes appear to be initiated by the carbon dioxide anion radical (CO2(-)) while oxidation processes are consistent with OH initiated reaction pathways. Unlike most advanced oxidation processes the Fe(III)-oxalate/H2O2/photochemical system can initiate to both reductive and oxidative degradation processes. The observed reductive dehalogenation is an attractive remediation strategy for halogenated organic compounds as the process can dramatically reduce the formation of the problematic disinfection by-products often associated with oxidative treatment processes.

Relationships of polychlorinated biphenyls and dichlorodiphenyldichloroethylene (p,p'-DDE) with testosterone levels in adolescent males.

BACKGROUND: Concern persists over endocrine-disrupting effects of persistent organic pollutants (POPs) on human growth and sexual maturation. Potential effects of toxicant exposures on testosterone levels during puberty are not well characterized. OBJECTIVES: In this study we evaluated the relationship between toxicants [polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene (p,p´-DDE), hexachlorobenzene (HCB), and lead] and testosterone levels among 127 Akwesasne Mohawk males 10 to < 17 years of age with documented toxicant exposures. METHODS: Data were collected between February 1996 and January 2000. Fasting blood specimens were collected before breakfast by trained Akwesasne Mohawk staff. Multivariable regression models were used to estimates associations between toxicants and serum testosterone, adjusted for other toxicants, Tanner stage, and potential confounders. RESULTS: The sum of 16 PCB congeners (Σ16PCBs) that were detected in ≥ 50% of the population was significantly and negatively associated with serum testosterone levels, such that a 10% change in exposure was associated with a 5.6% decrease in testosterone (95% CI: -10.8, -0.5%). Of the 16 congeners, the more persistent ones (Σ8PerPCBs) were related to testosterone, whereas the less persistent ones, possibly reflecting more recent exposure, were not. When PCB congeners were subgrouped, the association was significant for the sum of eight more persistent PCBs (5.7% decrease; 95% CI: -11, -0.4%), and stronger than the sum of six less persistent congeners (3.1% decrease; 95% CI: -7.2, 0.9%). p,p´-DDE was positively but not significantly associated with serum testosterone (5.2% increase with a 10% increase in exposure; 95% CI: -0.5, 10.9%). Neither lead nor HCB was significantly associated with testosterone levels. CONCLUSIONS: Exposure to PCBs, particularly the more highly persistent congeners, may negatively influence testosterone levels among adolescent males. The positive relationship between p,p´-DDE and testosterone indicates that not all POPs act similarly. CITATION: Schell LM, Gallo MV, Deane GD, Nelder KR, DeCaprio AP, Jacobs A; Akwesasne Task Force on the Environment. 2014. Relationships of polychlorinated biphenyls and dichlorodiphenyldichloroethylene (p,p´-DDE) with testosterone levels in adolescent males. Environ Health Perspect 122:304-309; http://dx.doi.org/10.1289/ehp.1205984.