Occurrence of Major Perfluorinated Alkylate Substances in Human Blood and Target Organs

Human exposure to perfluorinated alkylate substances (PFASs) is usually assessed from the concentrations in serum or plasma, assuming one-compartment toxicokinetics. To characterize body distributions of major PFASs, we obtained and extracted tissue samples from 19 forensic autopsies of healthy adult subjects who had died suddenly and were not known to have elevated levels of PFAS exposure. As target organs of toxicological importance, we selected the liver, kidneys, lungs, spleen, and brain, as well as whole blood. Samples weighing about 0.1 g were analyzed by liquid chromatography coupled to triple mass spectrometers. Minor variations in PFAS concentrations were found between the kidney cortex and medulla and between lung lobes. Organ concentrations of perfluorooctanoic sulfonate (PFOS) and perfluorononanoate (PFNA) correlated well with blood concentrations, while perfluorooctanoate (PFOA) and perfluorohexanoic sulfonate (PFHxS) showed more variable associations. Likewise, the liver concentrations correlated well with those of other organs. Calculations of relative distributions were carried out to assess the interdependence of organ retentions. Equilibrium model predictions largely explained the observed PFAS distributions, except for the brain. Although the samples were small and affected by a possible lack of homogeneity, these findings support the use of blood-PFAS concentrations as a measure of PFAS exposure, with the liver possibly acting as the main organ of retention.

Paired Liver:Plasma PFAS Concentration Ratios from Adolescents in the Teen-LABS Study and Derivation of Empirical and Mass Balance Models to Predict and Explain Liver PFAS Accumulation

Animal studies have pointed at the liver as a hotspot for per- and polyfluoroalkyl substances (PFAS) accumulation and toxicity; however, these findings have not been replicated in human populations. We measured concentrations of seven PFAS in matched liver and plasma samples collected at the time of bariatric surgery from 64 adolescents in the Teen-Longitudinal Assessment of Bariatric Surgery (Teen-LABS) study. Liver:plasma concentration ratios were perfectly explained (r2 > 0.99) in a multilinear regression (MLR) model based on toxicokinetic (TK) descriptors consisting of binding to tissue constituents and membrane permeabilities. Of the seven matched plasma and liver PFAS concentrations compared in this study, the liver:plasma concentration ratio of perfluoroheptanoic acid (PFHpA) was considerably higher than the liver:plasma concentration ratio of other PFAS congeners. Comparing the MLR model with an equilibrium mass balance model (MBM) suggested that complex kinetic transport processes are driving the unexpectedly high liver:plasma concentration ratio of PFHpA. Intratissue MBM modeling pointed to membrane lipids as the tissue constituents that drive the liver accumulation of long-chain, hydrophobic PFAS, whereas albumin binding of hydrophobic PFAS dominated PFAS distribution in plasma. The liver:plasma concentration data set, empirical MLR model, and mechanistic MBM modeling allow the prediction of liver from plasma concentrations measured in human cohort studies. Our study demonstrates that combining biomonitoring data with mechanistic modeling can identify underlying mechanisms of internal distribution and specific target organ toxicity of PFAS in humans.

Free Versus Bound Concentration: Passive Dosing from Polymer Meshes Elucidates Drivers of Toxicity in Aquatic Tests with Benthic Invertebrates

Aquatic toxicity tests with benthic organisms are used to predict the toxicity of hydrophobic organic chemicals (HOCs) in sediments, assuming that the freely dissolved concentration (Cfree ) is a good surrogate of bioavailability in the exposure system. However, Cfree of HOCs is difficult to control in water-only setups. Moreover, the role of dissolved organic carbon (DOC) in the occurrence of toxicity needs clarification because DOC concentrations in sediment porewater can be substantially higher than in typical test water. We introduced biocompatible polyethylene meshes with high sorptive capacities and fast release kinetics as a novel passive dosing phase, which maintained Cfree and Cwater (i.e., free + DOC-bound) in Hyalella azteca water-only tests. Adding the supernatant fraction of peat to test water as a DOC source increased Cwater to an extent comparable to sediment porewater and significantly increased and decreased the observed toxicity of permethrin and benzo[a]pyrene, respectively, to H. azteca. This result indicates that DOC can both benefit and harm test species likely due to the increased health after ingestion of DOC and to the uptake of DOC-bound HOCs, respectively. Passive dosing in combination with the addition of sediment DOC surrogates may better reflect exposure and habitat conditions in sediment porewater than conventional aquatic tests. Environ Toxicol Chem 2022;00:1-10. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Cytotoxicity Burst? Differentiating Specific from Nonspecific Effects in Tox21 in Vitro Reporter Gene Assays

BACKGROUND

High-throughput screening of chemicals with in vitro reporter gene assays in Tox21 has produced a large database on cytotoxicity and specific modes of action. However, the validity of some of the reported activities is questionable due to the "cytotoxicity burst," which refers to the supposition that many stress responses are activated in a nonspecific way at concentrations close to cell death.

OBJECTIVES

We propose a pragmatic method to identify whether reporter gene activation is specific or cytotoxicity-triggered by comparing the measured effects with baseline toxicity.

METHODS

Baseline toxicity, also termed narcosis, is the minimal toxicity any chemical causes. Quantitative structure-activity relationships (QSARs) developed for baseline toxicity in mammalian reporter gene cell lines served as anchors to define the chemical-specific threshold for the cytotoxicity burst and to evaluate the degree of specificity of the reporter gene activation. Measured 10% effect concentrations were related to measured or QSAR-predicted 10% cytotoxicity concentrations yielding specificity ratios (SR). We applied this approach to our own experimental data and to ∼ 8,000 chemicals that were tested in six of the high-throughput Tox21 reporter gene assays.

RESULTS

Confirmed baseline toxicants activated reporter gene activity around cytotoxic concentrations triggered by the cytotoxicity burst. In six Tox21 assays, 37%-87% of the active hits were presumably caused by the cytotoxicity burst (SR < 1 ) and only 2%-14% were specific with SR ≥ 10 against experimental cytotoxicity but 75%-97% were specific against baseline toxicity. This difference was caused by a large fraction of chemicals showing excess cytotoxicity.

CONCLUSIONS

The specificity analysis for measured in vitro effects identified whether a cytotoxicity burst had likely occurred. The SR-analysis not only prevented false positives, but it may also serve as measure for relative effect potency and can be used for quantitative in vitro-in vivo extrapolation and risk assessment of chemicals. https://doi.org/10.1289/EHP6664.

Application of Experimental Polystyrene Partition Constants and Diffusion Coefficients to Predict the Sorption of Neutral Organic Chemicals to Multiwell Plates in in Vivo and in Vitro Bioassays

Sorption to the polystyrene (PS) of multiwell plates can affect the exposure to organic chemicals over time in in vitro and in vivo bioassays. Experimentally determined diffusion coefficients in PS ( D_PS) were in a narrow range of 1.25 to 8.0 · 10^-16 m² s^-1 and PS-water partition constants ( K_PS/w) ranged from 0.04 to 5.10 log-units for 22 neutral organic chemicals. A kinetic model, which explicitly accounts for diffusion in the plastic, was applied to predict the depletion of neutral organic chemicals from different bioassay media by sorption to various multiwell plate formats. For chemicals with log K_ow > 3, the medium concentrations decreased rapidly and considerably in the fish embryo toxicity assay but medium concentrations remained relatively constant in the cell-based bioassays with medium containing 10% fetal bovine serum (FBS), emphasizing the ability of the protein- and lipid-rich medium to compensate for losses by multiwell plate sorption. The PS sorption data may serve not only for exposure assessment in bioassays but also to model the contaminant uptake by and release from plastic packaging material and the chemical transport by PS particles in the environment.

Cellular Uptake Kinetics of Neutral and Charged Chemicals in in Vitro Assays Measured by Fluorescence Microscopy

Cellular uptake kinetics are key for understanding time-dependent chemical exposure in in vitro cell assays. Slow cellular uptake kinetics in relation to the total exposure time can considerably reduce the biologically effective dose. In this study, fluorescence microscopy combined with automated image analysis was applied for time-resolved quantification of cellular uptake of 10 neutral, anionic, cationic, and zwitterionic fluorophores in two reporter gene assays. The chemical fluorescence in the medium remained relatively constant during the 24-h assay duration, emphasizing that the proteins and lipids in the fetal bovine serum (FBS) supplemented to the assay medium represent a large reservoir of reversibly bound chemicals with the potential to compensate for chemical depletion by cell uptake, growth, and sorption to well materials. Hence FBS plays a role in stabilizing the cellular dose in a similar way as polymer-based passive dosing, here we term this process as serum-mediated passive dosing (SMPD). Neutral chemicals accumulated in the cells up to 12 times faster than charged chemicals. Increasing medium FBS concentrations accelerated uptake due to FBS-facilitated transport but led to lower cellular concentrations as a result of increased sorption to medium proteins and lipids. In vitro cell exposure results from the interaction of several extra- and intracellular processes, leading to variable and time-dependent exposure between different chemicals and assay setups. The medium FBS plays a crucial role for the thermodynamic equilibria as well as for the cellular uptake kinetics, hence influencing exposure. However, quantification of cellular exposure by an area under the curve (AUC) analysis illustrated that, for the evaluated bioassay setup, current in vitro exposure models that assume instantaneous equilibrium between medium and cells still reflect a realistic exposure because the AUC was typically reduced less than 20% compared to the cellular dose that would result from instantaneous equilibrium.

[Evaluation of specific stabilizing exercise in the treatment of low back pain and lumbar disk disease in outpatient rehabilitation]

AIM

The aim of the study was to evaluate the outcome of outpatient rehabilitation in patients with low back pain and lumbar disk disease with a specific stabilizing exercise of the M. multifidus and M. transversus abdominis.

METHOD

99 outpatients admitted to a rehabilitation unit were included in a prospective randomized controlled interventional trial. The interventional group consisted of 50 patients (34 male, 16 female; mean age 41.1 +/- 9.1, range; 21 - 54 years), 49 patients (31 male, 18 female; mean age 37.9 +/- 9.5, range; 19 - 55 years) were in the control group. Outcomes were assessed at the beginning and the end of the treatment and at a three month follow-up with the Oswestry Low Back Pain Disability Questionnaire, the Hannover Functional Ability Questionnaire FFbH-R, the pain scale SES and a numeric rating scale.

RESULTS

In both groups there was a significant functional improvement as measured with the Oswestry Score and the FFbH-R. The interventional group showed better values at the end of the treatment. Pain as well could be reduced significantly by the treatment, but no differences were noted between the two groups.

CONCLUSION

Outpatient rehabilitation improved functional capacity and pain in both groups. Advantages could be seen in the interventional group concerning functional status. The specific stabilizing exercise approach appears to be effective in conservative treatment programs of low back pain and lumbar disk disease.

cis- and trans-Neocnidilide; 1H- and 13C-NMR Data of Some Phthalides

The (1)H- and (13)C-NMR spectra of several naturally occurring phthalides are reported; among others, the new natural compound 3,3alpha- CIS-neocnidilide isolated from APIUM GRAVEOLENS L. (and also found to be present in ANETHUM GRAVEOLENS L.). For some compounds, data are compared with previously published data.

The essential oil in lamina and petiole of Heracleum dissectum leaves

The essential oils of lamina and petiole of Heracleum dissectum are described. Fifty-seven compounds have been identified by mass spectrometry and retention indices. Differences between the oils of the two organs were mainly quantitative.

Phthalides in Roots of Capnophyllum peregrinum and Peucedanum ostruthium

In extracts from roots of CAPNOPHYLLUM PEREGRINUM Z-ligustilide was found to be present and in similar extracts of PEUCEDANUM OSTRUTHIUM cnidilide, Z-ligustilide and senkyunolide were detected. The compounds were analyzed by TLC, GLC and GCMS.

Cyanogenesis in Passifloraceae

A novel cyclopentenoid cyanogenic bis-glycoside has been isolated from Passiflora capsularis L. Its structure has been tentatively determined as 4-boivinosyl tetraphyllin B. The name passicapsin is proposed for this compound. Linamarin has been isolated from Passiflora warmingii Mast. Extracts of Passiflora perfoliata L. yielded a (probably glycosidic) cyclopentenone dervative, which possibly originated from an unstable glycoside having a free alpha-hydroxynitrile group.