Exposure Estimation for Risk Assessment of the Phthalate Incident in Taiwan

Background

In May 2011, di(2-ethylhexyl) phthalates (DEHP) and, to a lesser extent, di-iso-nonyl phthalate (DiNP) were found to have been illegally used for many years in Taiwan as clouding agents in foods including sports drinks, juice beverages, tea drinks, fruit jam/nectar/jelly, and health or nutrient supplements.

Objective

To estimate the DEHP exposure for the study participants for the follow-up epidemiological study and health risk assessment.

Methods

A total of 347 individuals possibly highly exposed to phthalate-tainted foods participated in the study. Exposure assessment was performed based on the participants'' responses to a structured questionnaire, self-report of exposure history, urinary metabolite concentrations, and DEHP concentration information in 2449 food records. A Bayesian statistical approach using Markov chain Monte Carlo simulation was employed to deal with the uncertainties in the DEHP concentrations of the contaminated foods and the participants'' likelihood of being exposed.

Results

An estimated 37% and 15% of children younger than 12 years old were exposed to DEHP at medium (20–50 μg / kg_bw / day) and high AvDIs (50–100 μg / kg_bw / day), respectively, prior to the episode (9% and 3% in adults, respectively). Moreover, 11% of children and 1% of adults were highly exposed (> 100 μg / kg_bw / day), with a maximum of 414.1 μg / kg_bw / day and 126.4 μg / kg_bw / day, respectively.

Conclusions

The phthalate exposure-associated adverse health effects for these participants warrant further investigation. The estimation procedure may be applied to other exposure assessment with various sources of uncertainties.     

Statistical properties of the traditional algorithm-based designs for phase I cancer clinical trials

Although there are several new designs for phase I cancer clinical trials including the continual reassessment method and accelerated titration design, the traditional algorithm-based designs, like the '3 + 3' design, are still widely used because of their practical simplicity. In this paper, we study some key statistical properties of the traditional algorithm-based designs in a general framework and derive the exact formulae for the corresponding statistical quantities. These quantities are important for the investigator to gain insights regarding the design of the trial, and are (i) the probability of a dose being chosen as the maximum tolerated dose (MTD); (ii) the expected number of patients treated at each dose level; (iii) target toxicity level (i.e. the expected dose-limiting toxicity (DLT) incidences at the MTD); (iv) expected DLT incidences at each dose level and (v) expected overall DLT incidences in the trial. Real examples of clinical trials are given, and a computer program to do the calculation can be found at the authors' website approximately linyo" locator-type="url">http://www2.umdnj.edu/ approximately linyo.     

Automatic model-based roentgen stereophotogrammetric analysis (RSA) of total knee prostheses

Conventional radiography is insensitive for early and accurate estimation of the mal-alignment and wear of knee prostheses. The two-staged (rough and fine) registration of the model-based RSA technique has recently been developed to in vivo estimate the prosthetic pose (i.e, location and orientation). In the literature, rough registration often uses template match or manual adjustment of the roentgen images. Additionally, possible error induced by the nonorthogonality of taking two roentgen images neither examined nor calibrated prior to fine registration. This study developed two RSA methods for automate the estimation of the prosthetic pose and decrease the nonorthogonality-induced error. The predicted results were validated by both simulative and experimental tests and compared with reported findings in the literature. The outcome revealed that the feature-recognized method automates pose estimation and significantly increases the execution efficiency up to about 50 times in comparison with the literature counterparts. Although the nonorthogonal images resulted in undesirable errors, the outline-optimized method can effectively compensate for the induced errors prior to fine registration. The superiority in automation, efficiency, and accuracy demonstrated the clinical practicability of the two proposed methods especially for the numerous fluoroscopic images of dynamic motion.     

A liquid chromatographic–mass spectrometric (LC–MS) method for the analysis of the bis-pyridinium oxime ICD-585 in plasma: Application in a guinea pig model

In recent animal studies, several novel oxime compounds that are better than 2-PAM as antidotes against selected organophosphate (OP) nerve agents have been identified. The purpose of this study was to develop and validate a liquid chromatographic–mass spectrometric (LC–MS) method for analysis of the bis-pyridinium oxime ICD-585 (1-(2-hydroxyiminomethylpyridinium)-3-(4-carbamoylpyridinium)-propane) in plasma and to establish the utility of the method in a guinea pig model. Calibration curves were prepared using ICD-585-spiked plasma at concentrations from 0.156 to 10 μg/ml. Curves were run over a 1-month time frame and a total of 13 (n = 13) were generated. The lower limit of quantification (LLOQ) was determined to be 0.216 μg/ml. Intra- and inter-day variability was assessed by studying precision and accuracy. For intra-day studies, data from the precision determinations indicated that the % CV's ranged from 4.28 to 14.98%. The % error in the accuracy assessments ranged from ?8.73 to 4.61%. For inter-day studies, precision data ranged from 3.53 to 13.20%. The % error in the accuracy assessments ranged from 0.39 to 13.77%. Room temperature, freeze–thaw and autosampler stability was also examined. For all 3 stability studies, the compound remained within ±15% of the initial analysis. Application of the method was demonstrated by analyzing samples from guinea pigs challenged with sarin (GB) or cyclosarin (GF) (1× LD₅₀) followed with intramuscular ICD-585 (58 μM/kg, 21.8 mg/kg). At 55 min after oxime administration, mean (±SD) plasma concentrations were 15.98 (±4.88) μg/ml and 14.57 (±3.70) μg/ml in GB- and GF-exposed animals, respectively. In summary, studies have been carried out to verify the sensitivity, precision and accuracy of the assay as well as the stability of the analyte under various conditions. The method has been demonstrated to be applicable to the analysis of plasma from nerve agent-exposed guinea pigs.     

Chromosomal integration of a synthetic expression control sequence achieves poly‐γ‐glutamate production in a Bacillus subtilis strain

Poly‐γ‐glutamate (γ‐PGA) has applications in food, medical, cosmetic, animal feed, and wastewater industries. Bacillus subtilis DB430, which possesses the γ‐PGA synthesis ywsC‐ywtAB genes in its chromosome, cannot produce γ‐PGA. An efficient synthetic expression control sequence (SECS) was introduced into the upstream region of the ywtABC genes, and this resulted in γ‐PGA‐producing B. subtilis mutant strains. Mutant B. subtilis PGA6‐2 stably produces high levels of γ‐PGA in medium A without supplementation of extra glutamic acid or ammonium chloride. The mutant B. subtilis PGA 6‐2 is not only a γ‐PGA producer, but it is also a candidate for the genetic and metabolic engineering of γ‐PGA production. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

NADPH oxidase activity selectively modulates vascular endothelial growth factor signaling pathways

Vascular endothelial growth factor (VEGF) and reactive oxygen species (ROS) play critical roles in vascular physiology and pathophysiology. We have demonstrated previously that NADPH oxidase-derived ROS are required for VEGF-mediated migration and proliferation of endothelial cells. The goal of this study was to determine the extent to which VEGF signaling is coupled to NADPH oxidase activity. Human umbilical vein endothelial cells and/or human coronary artery endothelial cells were transfected with short interfering RNA against the p47(phox) subunit of NADPH oxidase, treated in the absence or presence of VEGF, and assayed for signaling, gene expression, and function. We show that NADPH oxidase activity is required for VEGF activation of phosphoinositide 3-kinase-Akt-forkhead, and p38 MAPK, but not ERK1/2 or JNK. The permissive role of NADPH oxidase on phosphoinositide 3-kinase-Akt-forkhead signaling is mediated at post-VEGF receptor levels and involves the nonreceptor tyrosine kinase Src. DNA microarrays revealed the existence of two distinct classes of VEGF-responsive genes, one that is ROS-dependent and another that is independent of ROS levels. VEGF-induced, thrombomodulin-dependent activation of protein C was dependent on NADPH oxidase activity, whereas VEGF-induced decay-accelerating factor-mediated protection of endothelial cells against complement-mediated lysis was not. Taken together, these findings suggest that NADPH oxidase-derived ROS selectively modulate some but not all the effects of VEGF on endothelial cell phenotypes.     

Rapid and reliable high-performance liquid chromatographic method for analysing human plasma serotonin, 5-hydroxyindoleacetic acid, homovanillic acid and 3,4-dihydroxyphenylacetic acid

The simultaneous measurement of homovanillic acid, 3,4-dihydroxyphenylacetic acid, serotonin and 5-hydroxyindoleacetic acid in human plasma by an ultrafiltration and microbore high-performance liquid chromatography—electrochemical detection technique is established. Conventional preparation of blood is very tedious and time-consuming, but isocratic separation of the analytes in plasma ultrafiltrates using a microbore column could be achieved within 10 min. Hence, theoretically, over 140 analyses can be performed in a working day. The detection limit (signal-to-noise ratio = 3) of this method is about 0.1–0.5 pg per injection for all analytes. The required volume of plasma samples can be less than 100 μl. Hence, blood loss is minimal, especially in repeated blood sampling. This rapid, simple and sensitive method can, therefore, be used as a routine clinical tool in the simultaneous measurement of plasma homovanillic acid, 3,4-dihydroxyphenylacetic acid, serotonin and 5-hydroxyindoleacetic acid.     

Multiple Factors from Bradykinin-Challenged Astrocytes Contribute to the Neuronal Apoptosis: Involvement of Astroglial ROS, MMP-9, and HO-1/CO System

Bradykinin (BK) has been shown to induce the expression of several inflammatory mediators, including reactive oxygen species (ROS) and matrix metalloproteinases (MMPs), in brain astrocytes. These mediators may contribute to neuronal dysfunction and death in various neurological disorders. However, the effects of multiple inflammatory mediators released from BK-challenged astrocytes on neuronal cells remain unclear. Here, we found that multiple factors were released from brain astrocytes (RBA-1) exposed to BK in the conditioned culture media (BK-CM), including ROS, MMP-9, and heme oxygenase-1 (HO-1)/carbon monoxide (CO), leading to neuronal cell (SK-N-SH) death. Exposure of SK-N-SH cells to BK-CM or H₂O₂ reduced cell viability and induced cell apoptosis which were attenuated by N-acetyl cysteine, indicating a role of ROS in these responses. The effect of BK-CM on cell viability and cell apoptosis was also reversed by immunoprecipitation of BK-CM with anti-MMP-9 antibody (MMP-9-IP-CM) or MMP2/9 inhibitor, suggesting the involvement of MMP-9 in BK-CM-mediated responses. Astroglial HO-1/CO in BK-CM induced cell apoptosis and reduced cell viability which was reversed by hemoglobin. Consistently, the involvement of CO in these cellular responses was revealed by incubation with a CO donor CO-RM2 which was reversed by hemoglobin. The role of HO-1 in BK-CM-induced responses was confirmed by overexpression of HO-1 in SK-N-SH infected with Adv-HO-1. BK-CM-induced cell apoptosis was due to the activation of caspase-3 and cleavage of PARP. Together, we demonstrate that BK-induced several neurotoxic factors, including ROS, MMP-9, and CO released from astrocytes, may induce neuronal death through a caspase-3-dependent apoptotic pathway.     

Structure and function of human hemoglobin covalently labeled with periodate-oxidized adenosine triphosphate

Periodate-oxidized adenosine triphosphate (o-ATP), a ribose ring-opened dialdehyde derivative of ATP, reacts specifically with human deoxyhemoglobin to give a single major covalently modified product after reduction with sodium borohydride. This product, designated di-ATP Hb, was isolated using ion-exchange chromatography and shown to have incorporated two molecules of o-ATP/tetramer. Peptide mapping and x-ray crystallography at 2.8-A resolution indicate that a covalent adduct is formed between the ligand and residues Lys-82 EF6 of each beta chain in the organic phosphate-binding site of the molecule. di-ATP Hb exhibits a significantly decreased oxygen affinity (P50 = 20.8 mm Hg versus 5.8 mm Hg control; 50 mM 2-[bis(2-hydroxyethyl)amino]-2-(hydroxymethyl)-propane-1,3-diol, pH 7.4, 0.1 M C, 20 degrees C). The subunit cooper-activity of di-ATP Hb is also reduced (nmax = 1.9 versus 2.7 control).