Exposure Of Human Subjects Research Articles

Whole-Body Exposure System Using Horn Antennas With Dielectric Lens at 28 GHz

In the revised international guidelines and standard for human protection from electromagnetic fields, the permissible specific absorption rate (SAR) for whole-body exposure has been extended from 3 or 10 GHz to 300 GHz. The rationale for this revision is the extrapolation from findings of conventional radio-frequency exposure and infrared radiation. However, experiments of whole-body exposure in human subjects are limited to a few studies, which were conducted below 6 GHz. In this study, an exposure system at 28 GHz targeting a wide area of the human back was developed, which consists of two horn antennas with a dielectric lens. The effectiveness of the proposed exposure system was evaluated by computational dosimetry and experiments. The computed power absorption and measured distributions in the wave absorber and the back of the human subject were in good agreement. Under the compliance with the local exposure limits, the whole-body average SAR was 0.35 W/kg, which is comparable to the limit for whole-body exposure of 0.4 W/kg for occupational exposure in the international guidelines and standard. The developed exposure system would be useful to evaluate the thermophysiological response to whole-body exposure above 6 GHz.

Association between Arsenic Level, Gene Expression in Asian Population, and In Vitro Carcinogenic Bladder Tumor.

The IARC classified arsenic (As) as “carcinogenic to humans.” Despite the health consequences of arsenic exposure, there is no molecular signature available yet that can predict when exposure may lead to the development of disease. To understand the molecular processes underlying arsenic exposure and the risk of disease development, this study investigated the functional relationship between high arsenic exposure and disease risk using gene expression derived from human exposure. In this study, a three step analysis was employed: (1) the gene expression profiles obtained from two diverse arsenic-exposed Asian populations were utilized to identify differentially expressed genes associated with arsenic exposure in human subjects, (2) the gene expression profiles induced by arsenic exposure in four different myeloma cancer cell lines were used to define common genes and pathways altered by arsenic exposure, and (3) the genetic profiles of two publicly available human bladder cancer studies were used to test the significance of the common association of genes, identified in step 1 and step 2, to develop and validate a predictive model of primary bladder cancer risk associated with arsenic exposure. Our analysis shows that arsenic exposure to humans is mainly associated with organismal injury and abnormalities, immunological disease, inflammatory disease, gastrointestinal disease, and increased rates of a wide variety of cancers. In addition, arsenic exerts its toxicity by generating reactive oxygen species (ROS) and increasing ROS production causing the imbalance that leads to cell and tissue damage (oxidative stress). Oxidative stress activates inflammatory pathways leading to transformation of a normal cell to tumor cell specifically; there is significant evidence of the advancing changes in oxidative/nitrative stress during the progression of bladder cancer. Therefore, we examined the relation of differentially expressed genes due to exposure of arsenic in human and bladder cancer and developed a bladder cancer risk prediction model. In this study, integrin-linked kinase (ILK) was one of the most significant pathways identified between both arsenic exposed population which plays a key role in eliciting a protective response to oxidative damage in epidermal cells. On the other hand, several studies showed that arsenic trioxide (ATO) is useful for anticancer therapy although the mechanisms underlying its paradoxical effects are still not well understood. ATO has shown remarkable efficacy for the treatment of multiple myeloma; therefore, it will be helpful to understand the underlying cancer biology by which ATO exerts its inhibitory effect on the myeloma cells. Our study found that MAPK is one of the most active network between arsenic gene and ATO cell line which is involved in indicative of oxidative/nitrosative damage and well associated with the development of bladder cancer. The study identified a unique set of 147 genes associated with arsenic exposure and linked to molecular mechanisms of cancer. The risk prediction model shows the highest prediction ability for recurrent bladder tumors based on a very small subset (NKIRAS2, AKTIP, and HLA-DQA1) of the 147 genes resulting in AUC of 0.94 (95% CI: 0.744-0.995) and 0.75 (95% CI: 0.343-0.933) on training and validation data, respectively.

Para-aminosalicylic acid significantly reduced tenofovir exposure in human subjects: Mismatched findings from in vitro to in vivo translational research.

Tenofovir and para-aminosalicylic acid (PAS) may be coprescribed to treat patients with concomitant infections of human immunodeficiency virus and Mycobacterium tuberculosis bacteria. Both drugs are known to have remarkable renal uptake transporter-mediated clearance. Owing to the lack of clinical studies on drug-drug interaction between the 2 drugs, we conducted a translational clinical study to investigate the effect of PAS on tenofovir pharmacokinetics (PK). Initially, we studied in vitro renal uptake transporter-mediated drug-drug interactions using stably transfected cells with human organic anion transporters (OAT1 and OAT3). Later, we estimated clinical drug interactions using static and physiologically based PK modelling. Finally, we investigated the effects of PAS-calcium formulation (PAS-Ca) on tenofovir disoproxil fumarate PK in healthy male Korean subjects. PAS inhibited OAT1- and OAT3-mediated tenofovir uptake in vitro. The physiologically based PK drug-drug interaction model suggested a 1.26-fold increase in tenofovir peak plasma concentration when coadministered with PAS. By contrast, an open-label, randomized, crossover clinical trial evaluating the effects of PAS-Ca on tenofovir PK showed significantly altered geometric mean ratio (90% confidence intervals) of maximum plasma concentration (Cmax ) and area under the curve (AUC0-inf ) by 0.33 (0.28-0.38) and 0.29 (0.26-0.33), respectively. Our study findings suggest that the PAS-Ca formulation significantly reduced systemic exposure to tenofovir through an unexplained mechanism, which was contrary to the initial prediction. Caution should be exercised while predicting in vivo PK profiles from in vitro data, particularly when there are potential confounders such as pharmaceutical interactions.

4141 Molecular Signatures of Cocaine Toxicity in Postmortem Human Brain and Neurons

OBJECTIVES/GOALS: The goal of this project is to identify new therapeutic targets and biomarkers to treat or prevent cocaine toxicity by investigating proteomic, transcriptomic and epigenetic signatures of cocaine exposure in human subjects. METHODS/STUDY POPULATION: Cocaine is a highly addictive neurotoxic substance, and it is estimated that 1.9 million Americans are current users of cocaine. To study the molecular effects of cocaine, we generated preliminary proteomics and next-generation RNA sequencing (RNAseq) data from human postmortem dorsolateral prefrontal cortex (Broadmann area 9 or BA9) of 12 cocaine-exposed subjects and 17 controls. Future directions for this project include RNAseq and DNA methylation analysis of neuronal nuclei sorted from human postmortem BA9 and a human induced pluripotent stem cell-derived neuron (hiPSN) model of cocaine exposure from the same postmortem subjects from whom we have brain samples. RESULTS/ANTICIPATED RESULTS: We found alterations in neuronal synaptic protein levels and gene expression, including the serotonin transporter SLC6A4, and synaptic proteins SNAP25, SYN2, SYNGR3. Pathway analysis of our results revealed alterations in specific pathways involved with neuronal function including voltage-gated calcium channels, and GABA receptor signaling. In the future, we expect to see an enhancement in neuron-specific gene expression signatures in our sorted neuronal nuclei and our hiPSN model of cocaine exposure. The hiPSN model will help elucidate which effects are due to acute versus chronic exposure of cocaine. DISCUSSION/SIGNIFICANCE OF IMPACT: Neuronal signatures found with this analysis can help us understand mechanisms of cognitive decline in long-term cocaine users as well as the acute effects on the brain of cocaine taken in overdose. With this work and future proposed studies, we can discover novel clinical biomarkers for cocaine neurotoxicity in patients with cocaine use disorder and determine readouts for future therapeutic development on cocaine addiction and overdose.

Development and validation of an analytical method for the determination of 17β-estradiol residues in muscle of tambaqui (Colossoma macropomum Cuvier, 1818) by LC-MS/MS and its application in samples from a fish sexual reversion study

Tambaqui (Colossoma macropomum Cuvier, 1818) is the main native fish species farmed in Brazil, and 17β-estradiol (E2) is a natural steroid hormone commonly used for the production of female fish monosex population, which, in tambaqui, shows a higher growth rate than the male. Thus, to assess whether the fish meat of treated tambaqui contains hormonal residue levels, a high-performance liquid chromatography coupled with electrospray tandem mass spectrometry (LC-MS/MS) method for the determination of E2 residues in fish muscle was developed and validated. A QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) dispersive solid phase extraction method was used for the sample preparation. The chromatographic separation was performed in a Poroshel EC-18 reverse phase column. The mobile phase was a mixture of acetonitrile with 0.01% ammonium hydroxide (A) and water with 0.01% ammonium hydroxide (B). The ratio of A:B phases was 60:40 (v/v) used in an isocratic mode. The method validation was performed according to Commission Decision 2002/657/EC and Veterinary International Conference Harmonization (VICH GL49). Since matrix effects were observed, matrix-matched analytical curves are recommended for quantitation. The linearity, selectivity, intraday and interday precision, accuracy, decision limit, detection capability, and detection and quantitation limits of the method are reported. The limits of detection and quantitation were 0.3 ng/g and 1.0 ng/g, respectively. At these limits and slaughtering fish 7 months after the end of the treatment, the muscle of tambaqui did not show detectable hormone residue level. Thus, consumption of tambaqui edible tissue from fish treated with E2 for the purpose of sexual reversion is unlikely to represent a risk associated with the exposure of human subjects as residue levels of this hormone are not detected in the fish muscle.

Temporal patterns of lipolytic regulators in adipose tissue after acute growth hormone exposure in human subjects: A randomized controlled crossover trial

ObjectiveGrowth hormone (GH) stimulates lipolysis, but the underlying mechanisms remain incompletely understood. We examined the effect of GH on the expression of lipolytic regulators in adipose tissue (AT). MethodsIn a randomized, placebo-controlled, cross-over study, nine men were examined after injection of 1) a GH bolus and 2) a GH-receptor antagonist (pegvisomant) followed by four AT biopsies. In a second study, eight men were examined in a 2 × 2 factorial design including GH infusion and 36-h fasting with AT biopsies obtained during a basal period and a hyperinsulinemic-euglycemic clamp. Expression of GH-signaling intermediates and lipolytic regulators were studied by PCR and western blotting. In addition, mechanistic experiments in mouse models and 3T3-L1 adipocytes were performed. ResultsThe GH bolus increased circulating free fatty acids (p < 0.0001) together with phosphorylation of signal transducer and activator of transcription 5 (STAT5) (p < 0.0001) and mRNA expression of the STAT5-dependent genes cytokine-inducible SH2-containing protein (CISH) and IGF-1 in AT. This was accompanied by suppressed mRNA expression of G0/G1 switch gene 2 (G0S2) (p = 0.007) and fat specific protein 27 (FSP27) (p = 0.002) and upregulation of phosphatase and tensin homolog (PTEN) mRNA expression (p = 0.03). Suppression of G0S2 was also observed in humans after GH infusion and fasting, as well as in GH transgene mice, and in vitro studies suggested MEK-PPARγ signaling to be involved. ConclusionsGH-induced lipolysis in human subjects in vivo is linked to downregulation of G0S2 and FSP27 and upregulation of PTEN in AT. Mechanistically, in vitro data suggest that GH acts via MEK to suppress PPARγ-dependent transcription of G0S2. ClinicalTrials.govNCT02782221 and NCT01209429.

A novel method for evaluating the effect of pollution on the human skin under controlled conditions.

Generally considered as a major risk factor for various respiratory diseases, air pollution can also have a significant impact on the skin. To date, there is a plethora of cosmetics products with "anti-pollution" claims. However, these claims have not been fully substantiated with robust scientific evidence and currently there is no standardized method in place for validating the anti-pollution efficacy of cosmetics products. This article discusses an innovative Controlled Pollution Exposure System (CPES) which allows quantified administration of pollutants on the skin and analysis of their direct impact. Using CPES, human subjects were exposed to ambient dust and ozone and sebum were sampled and analyzed for biomarkers. Following exposure of human subjects' skin to either ambient dust(100-450μg/cm3 ) or ozone(100-1000ppb), analysis of sebum revealed a significant decrease in squalene concentration, and significant increases in squalene monohydroperoxide and malondialdehyde concentration. The findings demonstrate cutaneous oxidative stress induced by ambient dust and ozone. The findings also demonstrate the efficacy of CPES to accurately measure the direct effect of controlled gaseous and particulate pollutants on human skin and indicate that squalene, squalene monohydroperoxide and malondialdehyde may serve as potent biomarkers for evaluating potential anti-pollution claims of cosmetics products.

Abstract CT013: Osimertinib displays high brain exposure in healthy subjects with intact blood-brain barrier: a microdose positron emission tomography (PET) study with 11C-labelled osimertinib

Abstract Introduction. Osimertinib is a third generation, CNS active, epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) used for treatment of patients with locally advanced and metastatic T790M mutation positive non-small cell lung cancer (NSCLC). Osimertinib has shown efficacy superior to that of EGFR-TKIs (erlotinib and gefitinib) in the first-line treatment of EGFR mutation-positive advanced NSCLC and with reduced risk of CNS progression (Soria et al 2017). Furthermore, rapid osimertinib response on brain metastases has been reported (Koba et al 2017). Preliminary examination in non-human primates using 11C-labeled osimertinib indicates penetration of the intact blood brain barrier (BBB) and a high brain exposure compared to other EGFR-TKI agents, which may potentially contribute to improved efficacy in patients with brain metastases compared to other TKIs (Ballard et al 2016). Aim. The aim of this positron emission tomography (PET) study was to measure the brain exposure of [11C]osimertinib administered intravenously in healthy volunteers with an intact BBB. Methods. Eight male healthy volunteers (age 52±8 years) were examined for ~90 minutes with PET after single intravenous microdose of [11C]osimertinib. Concentration of [11C]osimertinib was also measured in arterial and venous blood and plasma. Brain MRI was acquired and used for co-registration of the PET data and automatic delineation of regions of interest in the brain. PK parameters Cmax (brain), Tmax (brain) and AUC0-90 min brain/blood ratio were calculated. Results. In all healthy volunteers, [11C]osimertinib distributed to the brain rapidly, with mean Tmax=13 min (range 5-30 min), Cmax= 1.4±0.3 SUV (range 1-1.8) corresponding to 2.2±0.2% of injected radioactivity and AUC0-90 min brain/blood ratio=3.8±0.3 (range 3.3-4.1). [11C]Osimertinib was distributed in all regions of the brain with uptake being highest in putamen followed by thalamus, frontal cortex, temporal cortex, caudate, cerebellum and white matter. Conclusions. This study indicates that [11C]osimertinib has a good brain exposure in human subjects with intact BBB and may potentially contribute to the efficacy of treatment with osimertinib. In NSCLC, patients with brain metastasis may benefit from treatment with osimertinib due to favorable brain exposure of the drug. Future studies in patients with NSCLC are required to examine uptake and kinetic properties of [11C]osimertinib in brain metastases.

T50 - Longitudinal Epigenetic Analysis Of Clozapine Use In Treatment-Resistant Schizophrenia: Data From The Crestar Consortium

Background Approximately one-third of patients with schizophrenia are considered treatment-resistant. For these patients, the atypical antipsychotic drug clozapine is recommended as the only evidence based treatment available. However, there is still significant variability in treatment-response. Animal studies have demonstrated that clozapine influences histone modification and DNA methylation, and a recent EWAS study in humans identified multiple differentially methylated positions (DMPs) and differentially methylated regions (DMRs) in clozapine-exposed samples. We used a longitudinal, within-participant design to conduct genome-wide analysis of DNA methylation changes in treatment resistant patients over 6 months of clozapine use. Methods We recruited 20 participants with a diagnosis of treatment-resistant schizophrenia, before they were prescribed clozapine. We then collected whole-blood samples at baseline and follow-up (6 weeks, 12 weeks and 6 months after clozapine start date), alongside clinical assessments. We quantified DNA methylation at ~ 480,000 sites across the genome using the Illumina 450 K HumanMethylation array and following pre-processing, normalization and quality control, an epigenome-wide association study was performed comparing DNA methylation at each time point. Results Preliminary data demonstrates an overall reduction in DNA methylation in the 6 months of clozapine use, with multiple individual CpG sites showing changes in DNA methylation that were found to be significantly associated with length of time exposed to clozapine. During analysis of the first 10 patients, the most significant CpG site was located in the gene body of CRB1; CRB1 is expressed exclusively in the eye, and the central nervous system, and has been previously associated with Lever’s congenital amaurosis and retinitis pigmentosa. The findings and analysis for all 20 participants will be presented at the meeting. Discussion This is the first study to identify longitudinal epigenetic changes following clozapine exposure in human subjects, replicating findings in animal studies of decreased methylation. Recruitment is ongoing and further analysis will look at whether epigenetic changes are associated with treatment-response/adverse reactions. Ultimately, these data will help us understand the mechanisms involved in clozapine, potentially providing biomarkers to predict clozapine response.

Assessing Supersaturation and Its Impact on In Vivo Bioavailability of a Low-Solubility Compound ABT-072 With a Dual pH, Two-Phase Dissolution Method

ABT-072 is a candidate drug evaluated for treatment of hepatitis C virus. It is an acidic compound with extremely low intrinsic aqueous solubility. An in vitro dissolution-partition system, referred as biphasic test method, was used to characterize ABT-072 prototype formulations. This test used 2 aqueous dissolution media of pH 2 and 6.5 in a sequential manner to simulate the transition of drug in gastrointestinal tract. The biphasic test used in this work effectively differentiated various ABT-072 formulations derived from conventional and enabling technologies. In vitro profiles of these formulations indicate a complex interplay among the 3 competitive kinetic processes including dissolution, precipitation, and partition in the aqueous media. The relative amount of drug partitioned into the organic phase (i.e., octanol) from different formulations was found to be directly related to their in vivo exposures observed in both dogs and human subjects, respectively. An in vitro-in vivo relationship was obtained between ABT-072 concentrations in octanol at t = 2 h from these formulations and the relative bioavailabilities in dogs and human subjects. This work revealed the significance of polymeric precipitation inhibition by sustaining a supersaturated state of ABT-072 and its impact on in vivo exposure in human subjects.

Diclofenac and Its Acyl Glucuronide: Determination of In Vivo Exposure in Human Subjects and Characterization as Human Drug Transporter Substrates In Vitro.

Although the metabolism and disposition of diclofenac (DF) has been studied extensively, information regarding the plasma levels of its acyl-β-d-glucuronide (DF-AG), a major metabolite, in human subjects is limited. Therefore, DF-AG concentrations were determined in plasma (acidified blood derived) of six healthy volunteers following a single oral DF dose (50 mg). Levels of DF-AG in plasma were high, as reflected by a DF-AG/DF ratio of 0.62 ± 0.21 (Cmax mean ± S.D.) and 0.84 ± 0.21 (area under the concentration-time curve mean ± S.D.). Both DF and DF-AG were also studied as substrates of different human drug transporters in vitro. DF was identified as a substrate of organic anion transporter (OAT) 2 only (Km = 46.8 µM). In contrast, DF-AG was identified as a substrate of numerous OATs (Km = 8.6, 60.2, 103.9, and 112 µM for OAT2, OAT1, OAT4, and OAT3, respectively), two organic anion-transporting polypeptides (OATP1B1, Km = 34 µM; OATP2B1, Km = 105 µM), breast cancer resistance protein (Km = 152 µM), and two multidrug resistance proteins (MRP2, Km = 145 µM; MRP3, Km = 196 µM). It is concluded that the disposition of DF-AG, once formed, can be mediated by various candidate transporters known to be expressed in the kidney (basolateral, OAT1, OAT2, and OAT3; apical, MRP2, BCRP, and OAT4) and liver (canalicular, MRP2 and BCRP; basolateral, OATP1B1, OATP2B1, OAT2, and MRP3). DF-AG is unstable in plasma and undergoes conversion to parent DF. Therefore, caution is warranted when assessing renal and hepatic transporter-mediated drug-drug interactions with DF and DF-AG.

The Role of Drug Exposure in Clinical Development: To What Extent Is Pharmacokinetic Assessment Needed in a Drug Development Programme?

Drug development is a risky, lengthy and very expensive process. The centrepiece beneficiary of successful drug development rightfully is—and should always be—the patient. There is a perpetual effort to make pharmaceutical research and development simpler and faster in order to provide safe, efficacious and cost-effective drugs in a timely manner. As the candidate molecule progresses through various phases of clinical development (phases 1–3 and post-approval), data are generated that not only satisfy key regulatory requirements but also support internal investment risk assessments. There are some data (e.g. data on drug safety and tolerability) that are collected in all clinical trials of a molecule irrespective of whether the participants are healthy volunteers in phase 1 or patients in a phase 3 trial. There have been various advances over the last decade to conduct fewer but better-designed studies and obviate duplicate, unwarranted, underpowered and inconclusive trials, e.g. adaptive study designs and model-based drug development approaches. These are resource efficient and ethical approaches to avoid unnecessary drug exposure in human subjects. Drug exposure or pharmacokinetic data are typically collected in almost all phases of drug development and often have a profound impact on the drug development programme in terms of cost and time. Importantly, pharmacokinetic data may be required by federal regulations in many scenarios, or strong justification may be needed if sponsors do not plan to collect/provide such data [1]. However, it should not be difficult to comprehend that whether mandated or not, pharmacokinetic data are critical to guide drug development and are often the sole end point of interest for certain specific studies. In some cases, a pharmacokinetic bridging study may potentially replace a large efficacy trial, e.g. in a paediatric population. The quantification of the exposure–response relationship assessment lies at the heart of any determination of the safety and effectiveness of new drug candidates. Hence, pharmacokinetic studies are critical for characterizing any intrinsic or extrinsic factors that could affect drug exposure. The key studies conducted along the clinical journey of a candidate molecule are listed in Table 1, along with the criticality of drug exposure assessment in such studies. Each drug is unique, and these are not the only studies needed during development, nor are all of these studies always needed. Additionally, the sequence/timing of these studies is driven by drug safety, indication, benefit–risk assessment, the extent of ‘at risk’ investment a sponsor wants to make and the holistic perspective of existing and emerging data. It is also worth noting that not all studies are required to collect pharmacokinetic data to the same extent. While the majority of the listed studies employ a dense pharmacokinetic sampling strategy, confirmatory clinical and paediatric studies typically employ a modelbased approach (e.g. population analyses) to cut down pharmacokinetic sampling to the minimum essential level, or to avoid it completely, based on the question(s) to answer. Gibbons et al. present summary data from multiple studies in this issue, providing a snapshot of exposure to This comment refers to the papers available at doi:10.1007/s40262015-0271-5 and doi:10.1007/s40262-015-0283-1.

Systemic exposure to and disposition of catechols derived from Salvia miltiorrhiza roots (Danshen) after intravenous dosing DanHong injection in human subjects, rats, and dogs.

DanHong injection is a Danshen (Salvia miltiorrhiza roots)-based injectable solution for treatment of coronary artery disease and ischemic stroke. Danshen catechols are believed to be responsible for the injection's therapeutic effects. This study aimed to characterize systemic exposure to and elimination of Danshen catechols in human subjects, rats, and dogs receiving intravenous DanHong injection. A total of 28 catechols were detected, with content levels of 0.002-7.066 mM in the injection, and the major compounds included tanshinol, protocatechuic aldehyde, salvianolic acid B, rosmarinic acid, salvianolic acids A and D, and lithospermic acid with their daily doses ≥10 μmol/subject. After dosing, tanshinol, salvianolic acid D, and lithospermic acid exhibited considerable exposure in human subjects and rats. However, only tanshinol had considerable exposure in dogs. The considerable exposure to tanshinol was due to its having the highest dose, whereas that to salvianolic acid D and lithospermic acid was due to their relatively long elimination half-lives in the human subjects and rats. Protocatechuic aldehyde and rosmarinic acid circulated in the bloodstream predominantly as metabolites; salvianolic acids A and B exhibited low plasma levels with their human plasma metabolites little or not detected. Tanshinol and salvianolic acid D were eliminated mainly via renal excretion. Elimination of other catechols involved hepatobiliary and/or renal excretion of their metabolites. Methylation was found to be the primary metabolism for most Danshen catechols and showed intercompound and interspecies differences in rate and degree in vitro. The information gained here is relevant to pharmacological and toxicological research on DanHong injection.

Effect of Exposure to Petroleum Fumes on Plasma Antioxidant Defense System in Petrol Attendants

Several studies have reported toxicological implications of inhalational exposure to petrol fumes in animal models; however, there is little or no documentation on the probable effect of exposure in human subjects. This study investigated the relationship between exposure to petrol fumes and lipid peroxidation and antioxidant levels among petrol station attendants in Ibadan, South-West Nigeria A total of 150 subjects consisting of 100 petrol attendants and 50 control subjects were recruited. Ten mL of blood was collected from ante-cubital vein of subjects for analysis. Results reveal that exposure to petrol fumes is associated with oxidative stress. Significant (p<0.001) elevation of malondialdehyde was associated with marked decreases in superoxide dismutase (p<0.01), catalase (p<0.001) and glutathione (p<0.05) when compared with the control. Chain breaking antioxidant vitamins results include significant (p<0.05) decreases in vitamin E and no significant difference in vitamin C (p>0.05) when compared with control. Also there was a significant decrease in total protein (p<0.05) but no significant difference in albumin (p>0.05) in petrol attendants compared with the control. Our findings imply that exposure to petroleum fumes is a risk factor and is associated with oxidative stress which raises the need for public awareness about the health hazards in order to enable petrol attendants to take necessary precautionary measures.

Microstructural changes in the substantia nigra of asymptomatic agricultural workers

Parkinson's disease (PD) is marked by the loss of dopamine neurons in the substantia nigra (SN). Although the exact etiology is unknown, sporadic PD is hypothesized to be a result of genetic susceptibility interacting with environmental insult. Epidemiological studies suggest that pesticide exposure is linked to higher PD risk, but there are no studies demonstrating SN changes with chronic pesticide exposure in human subjects. Thus, high resolution T2-weighted magnetic resonance imaging (MRI) and diffusion tensor (DTI) images were obtained from 12 agricultural workers with chronic pesticide exposure, 12 controls, and 12 PD subjects. Neither controls nor pesticide-exposed subjects, had any parkinsonian symptoms. Exposure history to pesticides was assessed by a structured questionnaire. DTI measures in the SN, including fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD), were obtained for all subjects and compared among groups. Compared to controls, PD patients showed the expected significant changes in all DTI measurements in the SN. The pesticide-exposed subjects, compared to controls, had significantly lower FA values (p=0.022, after multiple comparisons correction), but no significant differences in RD, MD, or AD measures. The study is the first to demonstrate microstructural changes in the SN of human subjects with chronic pesticide exposure. The changes detected by MRI may mark “one of the hits” leading to PD, and underlie the increased risk of PD in pesticide users found in epidemiological studies. Further human studies assisted by these imaging markers may be useful in understanding the etiology of PD.

A Novel System for Source Characterization and Controlled Human Exposure to Nanoparticle Aggregates Generated During Gas–Metal Arc Welding

The aim of this study was to achieve a method to perform detailed characterization and human exposure studies of nanosized and nanostructured aerosol particles. The source chosen was mild steel, active gas, arc welding fume. The setup consisted of a generation chamber, where welding can be performed, connected to an airtight stainless steel 22 m3 exposure chamber. Instrumentation, consisting of a tapered element oscillating microbalance, a scanning mobility particle sizer, and a sampler for electron microscopy and particle-induced X-ray emission analysis was connected to the stainless steel chamber. The feasibility of the system for human exposure studies was evaluated by exposing 31 human volunteers, in groups of three, to a test aerosol containing 1 mg/m3 welding fumes and to conditioned, filtered air. The results show that an aerosol that accurately represents dilute welding fume exposures that occur in workplaces can be produced in a controlled manner, and that the experimental setup can be used for 6 h, double-blind, exposures of human subjects. Particle mass concentration levels could be varied from <5 μg/m3 to more than 1000 μg/m3. Fumes from metal active gas welding showed a unimodal size distribution with a mean mobility diameter of 160 nm, transmission electron microscopy showed aggregates with a clearly nanosized structure. Copyright 2013 American Association for Aerosol Research

Modeling personal particle-bound polycyclic aromatic hydrocarbon (pb-pah) exposure in human subjects in Southern California

BackgroundExposure to polycyclic aromatic hydrocarbon (PAH) has been linked to various adverse health outcomes. Personal PAH exposures are usually measured by personal monitoring or biomarkers, which are costly and impractical for a large population. Modeling is a cost-effective alternative to characterize personal PAH exposure although challenges exist because the PAH exposure can be highly variable between locations and individuals in non-occupational settings. In this study we developed models to estimate personal inhalation exposures to particle-bound PAH (PB-PAH) using data from global positioning system (GPS) time-activity tracking data, traffic activity, and questionnaire information.MethodsWe conducted real-time (1-min interval) personal PB-PAH exposure sampling coupled with GPS tracking in 28 non-smoking women for one to three sessions and one to nine days each session from August 2009 to November 2010 in Los Angeles and Orange Counties, California. Each subject filled out a baseline questionnaire and environmental and behavior questionnaires on their typical activities in the previous three months. A validated model was used to classify major time-activity patterns (indoor, in-vehicle, and other) based on the raw GPS data. Multiple-linear regression and mixed effect models were developed to estimate averaged daily and subject-level PB-PAH exposures. The covariates we examined included day of week and time of day, GPS-based time-activity and GPS speed, traffic- and roadway-related parameters, meteorological variables (i.e. temperature, wind speed, relative humidity), and socio-demographic variables and occupational exposures from the questionnaire.ResultsWe measured personal PB-PAH exposures for 180 days with more than 6 h of valid data on each day. The adjusted R2 of the model was 0.58 for personal daily exposures, 0.61 for subject-level personal exposures, and 0.75 for subject-level micro-environmental exposures. The amount of time in vehicle (averaging 4.5% of total sampling time) explained 48% of the variance in daily personal PB-PAH exposure and 39% of the variance in subject-level exposure. The other major predictors of PB-PAH exposures included length-weighted traffic count, work-related exposures, and percent of weekday time.ConclusionWe successfully developed regression models to estimate PB-PAH exposures based on GPS-tracking data, traffic data, and simple questionnaire information. Time in vehicle was the most important determinant of personal PB-PAH exposure in this population. We demonstrated the importance of coupling real-time exposure measures with GPS time-activity tracking in personal air pollution exposure assessment.

Blood Pressure Response to Controlled Diesel Exhaust Exposure in Human Subjects

Exposure to traffic-related air pollution is associated with risk of cardiovascular disease and mortality. We examined whether exposure to diesel exhaust increased blood pressure (BP) in human subjects. We analyzed data from 45 nonsmoking subjects, 18 to 49 years of age in double-blinded, crossover exposure studies, randomized to order. Each subject was exposed to diesel exhaust, maintained at 200 μg/m(3) of fine particulate matter, and filtered air for 120 minutes on days separated by ≥2 weeks. We measured BP pre-exposure, at 30-minute intervals during exposure, and 3, 5, 7, and 24 hours from exposure initiation and analyzed changes from pre-exposure values. Compared with filtered air, systolic BP increased at all of the points measured during and after diesel exhaust exposure; the mean effect peaked between 30 and 60 minutes after exposure initiation (3.8 mm Hg [95% CI: -0.4 to 8.0 mm Hg] and 5.1 mm Hg [95% CI: 0.7-9.5 mm Hg], respectively). Sex and metabolic syndrome did not modify this effect. Combining readings between 30 and 90 minutes, diesel exhaust exposure resulted in a 4.4-mm Hg increase in systolic BP, adjusted for participant characteristics and exposure perception (95% CI: 1.1-7.7 mm Hg; P=0.0009). There was no significant effect on heart rate or diastolic pressure. Diesel exhaust inhalation was associated with a rapid, measurable increase in systolic but not diastolic BP in young nonsmokers, independent of perception of exposure. This controlled trial in humans confirms findings from observational studies. The effect may be important on a population basis given the worldwide prevalence of exposure to traffic-related air pollution.

FMRI of Cocaine Self-Administration in Macaques Reveals Functional Inhibition of Basal Ganglia

Disparities in cocaine-induced neurochemical and metabolic responses between human beings and rodents motivate the use of non-human primates (NHP) to model consequences of repeated cocaine exposure in human subjects. To characterize the functional response to cocaine infusion in NHP brain, we employed contrast-enhanced fMRI during both non-contingent injection of drug and self-administration of cocaine in the magnet. Cocaine robustly decreased cerebral blood volume (CBV) throughout basal ganglia and motor/pre-motor cortex and produced subtle functional inhibition of prefrontal cortex. No brain regions exhibited significant elevation of CBV in response to cocaine challenge. Theses effects in NHP brain are opposite in sign to the cocaine-induced fMRI response in rats, but consistent with previous measurements in NHP based on glucose metabolism. Because the striatal ratio of D2 to D1 receptors is larger in human beings and NHP than rats, we hypothesize that the inhibitory effects of D2 receptor binding dominate the functional response in primates, whereas excitatory D1 receptor stimulation predominates in the rat. If the NHP accurately models the human response to cocaine, downregulation of D2 receptors in human cocaine-abusing populations can be expected to blunt cocaine-induced functional responses, contributing to the weak and variable fMRI responses reported in human basal ganglia following cocaine infusion.

The Association Between Serotonin Transporter Gene Promotor Polymorphism (5-HTTLPR) and Elemental Mercury Exposure on Mood and Behavior in Humans

A functional polymorphism in the serotonin transporter (5-HTT) gene-linked polymorphic region (5-HTTLPR) is reported to affect mood and behavior in humans. In this study, the effects of 5-HTTLPR polymorphism on neurobehavioral and mood domains that are known to be affected by elemental mercury (Hg°) exposure in human subjects were examined. The Behavioral Evaluation for Epidemiologic Studies (BEES) test battery was administered concurrently with urine and buccal-cell collections for 164 male dentists (DD) and 101 female dental assistants (DA) with occupational exposure to Hg° for an average of 19 and 10 yr, respectively. Geometric mean urinary mercury (Hg) levels in DD and DA were 2.52 (2.22) μg/L and 1.98 (1.98) μg/L, respectively. Corresponding indices of chronic occupational Hg° exposure, weighted for historical exposure, were 1212 (1877) and 316 (429). 5-HTTLPR status was 40% and 20% wild type, 40% and 56% single allelic substitution, and 20% and 24% double allelic substitution for the two genders. DD and DA were evaluated separately. Regression analyses controlled for age, premorbid intelligence, frequency of alcohol per week, and education. 5-HTTLPR polymorphism was associated with 5 behavioral measures in DD and with 12 behavioral measures in DA. Mood scores were more consistently associated with the variant in both groups. The strongest evidence for an additive effect for urinary Hg and 5-HTTLPR polymorphism in both groups was for tests of Finger TapAlternate and Hand SteadinessFactor1. Other significant additive effects that were less consistent across groups were also observed. These results add to the growing evidence of genetic determinants of mood and behavior that potentially increase susceptibility to Hg toxicity in humans.