Stable Isotope Dilution Analysis (SIDA) to Determine Metabolites of Furan and 2-Methylfuran in Human Urine Samples: A Pilot Study

Furan and 2-methylfuran (2-MF) are food contaminants that are classified as potentially carcinogenic to humans. The main source of exposure for adults via food is coffee consumption. Furan and 2-MF are volatile, which complicates exposure assessment because their content measured in food prior to consumption does not afford a reliable dosimetry. Therefore, other ways of exposure assessment need to be developed, preferably by monitoring exposure biomarkers, e.g., selected metabolites excreted in urine. In this study, cis-2-buten-1,4-dial (BDA)-derived urinary furan metabolites Lys-BDA (l-2-amino-6-(2,5-dihydro-2-oxo-1H-pyrrol-1-yl)hexanoic acid), AcLys-BDA (l-2-(acetylamino)-6-(2,5-dihydro-2-oxo-1H-pyrrol-1-yl)hexanoic acid) and GSH-BDA (N-[4-carboxy-4-(3-mercapto-1H-pyrrol-1-yl)-1-oxobutyl]-l-cysteinyl-glycine cyclic sulfide), as well as acetyl acrolein (AcA, 2-oxo-pent-2-enal)-derived metabolites Lys-AcA (l-2-(acetylamino)-6-(2,5-dihydro-5-methyl-2-oxo-1H-pyrrol-1-yl)-hexanoic acid) and AcLys-AcA (l-2-amino-6-(2,5-dihydro-5-methyl-2-oxo-1H-pyrrol-1-yl)-hexanoic acid) and their stable isotopically labeled analogs, were synthesized and characterized through NMR and MS, and a stable isotope dilution analysis (SIDA) with UPLC-ESI-MS/MS was established. As a proof of concept, urinary samples of a four-day human intervention study were used. In the frame of this study, ten subjects ingested 500 mL of coffee containing 0.648 µmol furan and 1.059 µmol 2-MF. Among the furan metabolites, AcLys-BDA was the most abundant, followed by Lys-BDA and GSH-BDA. Exposure to 2-MF via the coffee brew led to the formation of Lys-AcA and AcLys-AcA. Within 24 h, 89.1% of the ingested amount of furan and 15.4% of the ingested amount of 2-MF were detected in the urine in the form of the investigated metabolites. Therefore, GSH-BDA, Lys-BDA, AcLys-BDA, Lys-AcA and AcLys-AcA may be suitable as short-term-exposure biomarkers of furan and 2-MF exposure.

A simulation-based module in pharmacology education reveals and addresses medical students' deficits in leading prescription talks

Although doctor-patient communication is essential for drug prescription, the literature reveals deficits in this area. An educational approach at the Cologne medical faculty aims at identifying and addressing those deficits in medical students.Fifth-year medical students first conducted a simulated prescription talk spontaneously. Subsequently, the conversation was discussed with peer students. A pharmacist moderated the discussion based upon a previously developed conversation guide. Afterwards, the same student had the conversation again, but as if for the first time. Conversations were video-recorded, transcribed and subjected to quantitative content analysis. Four days after the simulation, the students who conducted the talk, those who observed and discussed it, and students who did neither, completed a written test that focused on the content of an effective prescription talk.Content analysis revealed clear deficits in spontaneously led prescription talks. Even essential information as on adverse drug reactions were often lacking. Prescription talks became clearly more informative and comprehensive after the short, guided peer discussion. With regard to a comprehensive, informative prescription talk, the written test showed that both the students who conducted the talk and those who only observed it performed clearly better than the students who did not participate in the educational approach.Deficits regarding prescription talks are present in 5^th year medical students. We provide an approach to both identify and address these deficits. It thus may be an example for training medical students in simulated and clinical environments like the EACPT recommended to improve pharmacology education.

Modulatory effects of magnetic vestibular stimulation on resting-state networks can be explained by subject-specific orientation of inner-ear anatomy in the MR static magnetic field

Strong static magnetic fields, as used in magnetic resonance imaging (MRI), stimulate the vestibular inner ear leading to a state of imbalance within the vestibular system that causes nystagmus. This magnetic vestibular stimulation (MVS) also modulates fluctuations of resting-state functional MRI (RS-fMRI) networks. MVS can be explained by a Lorentz force model, indicating that MVS is the result of the interaction of the static magnetic field strength and direction (called "B0 magnetic field" in MRI) with the inner ear's continuous endolymphatic ionic current. However, the high variability between subjects receiving MVS (measured as nystagmus slow-phase velocity and RS-fMRI amplitude modulations) despite matching head position, remains to be explained. Furthermore, within the imaging community, an "easy-to-acquire-and-use" proxy accounting for modulatory MVS effects in RS-fMRI fluctuations is needed. The present study uses MRI data of 60 healthy volunteers to examine the relationship between RS-fMRI fluctuations and the individual orientation of inner-ear anatomy within the static magnetic field of the MRI. The individual inner-ear anatomy and orientation were assessed via high-resolution anatomical CISS images and related to fluctuations of RS-fMRI networks previously associated with MVS. More specifically, we used a subject-specific proxy for MVS (pMVS) that corresponds to the orientation of the individual inner-ear anatomy within the static magnetic field direction (also called "z-direction" in MR imaging). We found that pMVS explained a considerable fraction of the total variance in RS-fMRI fluctuations (for instance, from 11% in the right cerebellum up to 36% in the cerebellar vermis). In addition to pMVS, we examined the angle of Reid's plane, as determined from anatomical imaging as an alternative and found that this angle (with the same sinus transformation as for pMVS) explained considerably less variance, e.g., from 2 to 16%. In our opinion, an excess variability due to MVS should generally be addressed in fMRI research analogous to nuisance regression for movement, pulsation, and respiration effects. We suggest using the pMVS parameter to deal with modulations of RS-fMRI fluctuations due to MVS. MVS-induced variance can easily be accounted by using high-resolution anatomical imaging of the inner ear and including the proposed pMVS parameter in fMRI group-level analysis.

Toxicological testing of syringaresinol and enterolignans

Lignans are secondary plant constituents with dibenzylbutane skeletons found in cereals, oilseeds, and nuts. Two members of this class, syringaresinol (Syr) and secoisolariciresinol (Seco), occur at relatively high levels in cereals and processed food products as well as in coniferous trees. In vitro studies have shown that Seco and its metabolites enterodiol (END) and enterolactone (ENL), which are formed by intestinal microbes, exhibit strong antioxidant activity because of their phenolic character. The biological activity and discussion of dietary supplementation with these substances led to questions about the potential adverse health effects of these compounds, which are explored here. Syr and the metabolites END and ENL were investigated by combining structural information generated in silico with practical testing in vitro. An in silico structure-activity analysis was performed using ToxTree and NexusPrediction to suggest plausible mechanisms of toxicity and estimate toxicological endpoints of these compounds. Structural alerts were generated based on the presence of phenolic units with coordinating substituents that could potentially form quinoid structures, promote reactive oxygen species (ROS) formation, bind to cellular structures, or damage chromosomes. To assess the in silico results, the cytotoxicity and genotoxic potential of the studied compounds were tested in vitro using the resazurin reduction and comet assays, respectively. Incubating HepG2 and HT29 cells for 1 h or 24 h with 0–100 μM Syr, END, or ENL induced no cytotoxic effects. Additionally, even the highest tested concentrations of END and ENL showed no modulation of background and total DNA damage. The initial in silico screen thus generated structural alerts linked to toxicological endpoints, but experimental assessments of the studied compounds revealed no detectable toxicity, demonstrating the need for individual mechanistic experimental verification of in silico predictions. This approach makes it possible to connect known biological activity, such as reported antioxidative effects, to underlying mechanisms such as proton abstraction or donation. This in turn can yield insights – for example, that a compound's tendency to act as a pro- or anti-oxidant (and hence to exert adverse or beneficial health effects) may depend on its concentration and the cellular state.

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Potential of toxicologic mechanisms: cellular stress and chromosomal damage were identified in silico for syringaresinol, enterdiol and enterlactone.

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However, in confirmatory in vitro assays (cytotoxicity, DNA damage and DNA strand breaks) in HepG2 and HT29 cells no such toxicities were induced by physiological and higher concentrations of syringaresinol and enterolignans.

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This study serves as a cautionary tale of using in silico prediction of toxicity mechanisms. Experimental verification of in silico predictions is needed as these methodologies are still under development.

VOLT: a novel open-source pipeline for automatic segmentation of endolymphatic space in inner ear MRI

Background

Objective and volumetric quantification is a necessary step in the assessment and comparison of endolymphatic hydrops (ELH) results. Here, we introduce a novel tool for automatic volumetric segmentation of the endolymphatic space (ELS) for ELH detection in delayed intravenous gadolinium-enhanced magnetic resonance imaging of inner ear (iMRI) data.

Methods

The core component is a novel algorithm based on Volumetric Local Thresholding (VOLT). The study included three different data sets: a real-world data set (D1) to develop the novel ELH detection algorithm and two validating data sets, one artificial (D2) and one entirely unseen prospective real-world data set (D3). D1 included 210 inner ears of 105 patients (50 male; mean age 50.4 ± 17.1 years), and D3 included 20 inner ears of 10 patients (5 male; mean age 46.8 ± 14.4 years) with episodic vertigo attacks of different etiology. D1 and D3 did not differ significantly concerning age, gender, the grade of ELH, or data quality. As an artificial data set, D2 provided a known ground truth and consisted of an 8-bit cuboid volume using the same voxel-size and grid as real-world data with different sized cylindrical and cuboid-shaped cutouts (signal) whose grayscale values matched the real-world data set D1 (mean 68.7 ± 7.8; range 48.9–92.8). The evaluation included segmentation accuracy using the Sørensen-Dice overlap coefficient and segmentation precision by comparing the volume of the ELS.

Results

VOLT resulted in a high level of performance and accuracy in comparison with the respective gold standard. In the case of the artificial data set, VOLT outperformed the gold standard in higher noise levels. Data processing steps are fully automated and run without further user input in less than 60 s. ELS volume measured by automatic segmentation correlated significantly with the clinical grading of the ELS (p < 0.01).

Conclusion

VOLT enables an open-source reproducible, reliable, and automatic volumetric quantification of the inner ears’ fluid space using MR volumetric assessment of endolymphatic hydrops. This tool constitutes an important step towards comparable and systematic big data analyses of the ELS in patients with the frequent syndrome of episodic vertigo attacks. A generic version of our three-dimensional thresholding algorithm has been made available to the scientific community via GitHub as an ImageJ-plugin.

Absorption of Anthocyanin Rutinosides after Consumption of a Blackcurrant ( Ribes nigrum L.) Extract

The dominant anthocyanins in blackcurrant are delphinidin-3-O-rutinoside and cyanidin-3-O-rutinoside. Data on their absorption and distribution in the human body are limited. Therefore, we performed a human pilot study on five healthy male volunteers consuming a blackcurrant ( Ribes nigrum L.) extract. The rutinosides and their degradation products gallic acid and protocatechuic acid were determined in plasma and urine. The rutinosides' concentrations peaked in both plasma and urine samples within 2 h of extract ingestion. The recoveries of delphinidin-3-O-rutinoside and cyanidin-3-O-rutinoside from urine samples were 0.040 ± 0.011% and 0.048 ± 0.016%, respectively, over a 48 h period. Protocatechuic acid concentration increased significantly after ingestion of the blackcurrant extract. Our results show that after ingestion of a blackcurrant extract containing delphinidin-3-O-rutinoside and cyanidin-3-O-rutinoside, significant quantities of biologically active compounds circulated in the plasma and were excreted via urine. Furthermore, these results contribute to the understanding of anthocyanin metabolism in humans.

"Hopefully, I will never forget that again" - sensitizing medical students for drug safety by working on cases and simulating doctor-patient communication

Objective: This project is part of the "PJ-STArT-Block", a one-week course preparing 10^th semester medical students for their final practical year. The focus is on sensitizing students to aspects of medication safety by becoming aware of their skills and their deficits in terms of application and communication of pharmacological knowledge. The modules were evaluated regarding feasibility, acceptance and possible effects. Furthermore, the areas in which students see their pharmacological deficits or learning successes were gathered. Methods: In simulated physician-patient conversations, the students are to identify drug-related problems such as medication errors, adverse drug events or interactions. Together with their fellow students and under medical or pharmaceutical moderation, they then have to find solutions for the identified problems and communicate these solutions to the patients. Based on paper cases, students practice, reflect, and discuss the research of reliable information about drugs and medication therapy. The written evaluation included the evaluation by school grades and the possibility of comments in free text. A content analysis of interviews with students at the beginning of the project aimed to identify areas of pharmacology in which they see their own deficits. Results: Evaluation results including the free text comments indicate students' acceptance of our pharmacology modules. According to this, the students realize the importance of aspects relevant for medication safety. The areas mentioned in 35 interviews in which students localize deficits, correspond to the topics that were intended when conceiving the modules and which are important for medication safety (e.g. interactions, adverse drug effects, dosages). Conclusion: Implementation of context-based, application-oriented teaching formats as recently claimed for pharmacological education to improve the quality of prescriptions, is possible, as the Cologne example shows. The student evaluation turns out positively and indicates a critical self-reflection. The students identified various pharmacological deficits in themselves, which have since been confirmed and quantified in another study.

Beyond binary parcellation of the vestibular cortex - A dataset

The data-set presented in this data article is supplementary to the original publication, doi:10.1016/j.neuroimage.2018.05.018 (Kirsch et al., 2018). Named article describes handedness-dependent organizational patterns of functional subunits within the human vestibular cortical network that were revealed by functional magnetic resonance imaging (fMRI) connectivity parcellation. 60 healthy volunteers (30 left-handed and 30 right-handed) were examined on a 3T MR scanner using resting state fMRI. The multisensory (non-binary) nature of the human (vestibular) cortex was addressed by using masked binary and non-binary variations of independent component analysis (ICA). The data have been made publicly available via github (https://github.com/RainerBoegle/BeyondBinaryParcellationData).

Appraisal of the signal-to-noise-ratio of uni- and bipolar recordings of ocular vestibular evoked myogenic potentials

Ocular vestibular evoked myogenic potentials (oVEMPs) are a non-invasive method to investigate otolith function mediated via the superior vestibular nerve. However, the herein used recordings and protocols may alter within different studies. In particular the diverging use of electrode configuration regarding polarity or even electrode position varies across studies. Therefore, a systematic analysis and appraisal of the different electrode configuration seems mandatory. In this study we compared the quality of uni- and bipolar recordings based on the signal to noise ratio (SNR). We recoded oVEMPs using a uni- and bipolar electrode configuration simultaneously and compared the recorded amplitudes and latencies and calculated the SNR. The amplitudes recorded by the unipolar configurations were significantly (p < 0.01) increased compared to the bipolar configuration. However, the SNR of the bipolar setup was significantly better (p < 0.05) when compared to the unipolar setup. Additionally, we estimated a transfer function that enabled a comparison of uni- and bipolar recordings. To conclude, the variety of setups used for oVEMP recording hinder a comparison of results and unipolar electrode configurations have clear disadvantages.

On the impact of examiners on latencies and amplitudes in cervical and ocular vestibular-evoked myogenic potentials evaluated over a large sample (N = 1,038)

Vestibular-evoked myogenic potentials (VEMPs) are frequently used in the clinical diagnosis and research of vertigo syndromes. Altered latencies or amplitudes are typically interpreted as an indication of disturbance in the processing of vestibular stimuli along the otolithic pathways. Correct interpretation, however, can be difficult as VEMP amplitudes can vary greatly across subjects and across laboratories, likely because they are very sensitive to measurement conditions. Here, we attempted to quantify the impact of examiner differences on VEMP data. We collected data from 1,038 people using eight different experimental examiners, and investigated the effect of examiner on VEMP latencies and amplitudes. We found that the examiner collecting the data had a strong effect on outcome measures with significant differences (p < 0.001) in cVEMP and oVEMP latencies and in oVEMP amplitudes. No significant differences between examiners were found for the cVEMP amplitudes. When we compared the healthy and pathological sides of patients with a clinically diagnosed unilateral disease, no significant differences between sides were found. Given our results and the results reported in the literature, we conclude that the signal features of VEMPs are very sensitive to variables that may be influenced by the examiner. The field should therefore work on a better standard for VEMP recordings.

Structural and functional connectivity mapping of the vestibular circuitry from human brainstem to cortex

Structural and functional interconnections of the bilateral central vestibular network have not yet been completely delineated. This includes both ipsilateral and contralateral pathways and crossing sites on the way from the vestibular nuclei via the thalamic relay stations to multiple "vestibular cortex" areas. This study investigated "vestibular" connectivity in the living human brain in between the vestibular nuclei and the parieto-insular vestibular cortex (PIVC) by combined structural and functional connectivity mapping using diffusion tensor imaging and functional connectivity magnetic resonance imaging in 24 healthy right-handed volunteers. We observed a congruent functional and structural link between the vestibular nuclei and the ipsilateral and contralateral PIVC. Five separate and distinct vestibular pathways were identified: three run ipsilaterally, while the two others cross either in the pons or the midbrain. Two of the ipsilateral projections run through the posterolateral or paramedian thalamic subnuclei, while the third bypasses the thalamus to reach the inferior part of the insular cortex directly. Both contralateral pathways travel through the posterolateral thalamus. At the cortical level, the PIVC regions of both hemispheres with a right hemispherical dominance are interconnected transcallosally through the antero-caudal splenium. The above-described bilateral vestibular circuitry in its entirety takes the form of a structure of a rope ladder extending from the brainstem to the cortex with three crossings in the brainstem (vestibular nuclei, pons, midbrain), none at thalamic level and a fourth cortical crossing through the splenium of the corpus callosum.

Age effects on the P300 potential and the corresponding fMRI BOLD-signal

Age has been reported to influence amplitude and latency of the P300 potential. Nevertheless, it is not yet fully understood which brain regions are responsible for these effects. The aim of this study was to investigate age-effects on the P300 potential and the simultaneously acquired BOLD signal of functional MRI. 32 healthy male subjects were investigated using an auditory oddball paradigm. The functional MRI data were acquired in temporal synchrony to the task. The evoked potential data were recorded during the intervals in between MR image acquisitions in order to reduce the influence of the scanner noise on the presentation of the tones and to reduce gradient artifacts. The age-effects were calculated by means of regression analyses. In addition, brain regions modulated by the task-induced amplitude variation of the P300 were identified (single trial analysis). The results indicated an age effect on the P300 amplitude. Younger subjects demonstrated increased parietal P300 amplitudes and increased BOLD responses in a network of brain regions including the anterior and posterior cingulate cortex, the insula, the temporo-parietal junction, the superior temporal gyrus, the caudate body, the amygdala and the parahippocampal gyrus. Single trial coupling of EEG and fMRI indicated that P300 amplitudes were predominantly associated with neural responses in the anterior cingulate cortex, the putamen and temporal brain areas. Taken together, the results indicate diminished neural responses in older compared to younger subjects especially in frontal, temporo-parietal and subcortical brain regions.

Long-range synchrony of γ oscillations and auditory hallucination symptoms in schizophrenia

Phase locking in the gamma-band range has been shown to be diminished in patients with schizophrenia. Moreover, there have been reports of positive correlations between phase locking in the gamma-band range and positive symptoms, especially hallucinations. The aim of the present study was to use a new methodological approach in order to investigate gamma-band phase synchronization between the left and right auditory cortex in patients with schizophrenia and its relationship to auditory hallucinations. Subjects were 18 patients with chronic schizophrenia (SZ) and 16 healthy control (HC) subjects. Auditory hallucination symptom scores were obtained using the Scale for the Assessment of Positive Symptoms. Stimuli were 40-Hz binaural click trains. The generators of the 40Hz-ASSR were localized using eLORETA and based on the computed intracranial signals lagged interhemispheric phase locking between primary and secondary auditory cortices was analyzed. Current source density of the 40 ASSR response was significantly diminished in SZ in comparison to HC in the right superior and middle temporal gyrus (p<0.05). Interhemispheric phase locking was reduced in SZ in comparison to HC for the primary auditory cortices (p<0.05) but not in the secondary auditory cortices. A significant positive correlation was found between auditory hallucination symptom scores and phase synchronization between the primary auditory cortices (p<0.05, corrected for multiple testing) but not for the secondary auditory cortices. These results suggest that long-range synchrony of gamma oscillations is disturbed in schizophrenia and that this deficit is related to clinical symptoms such as auditory hallucinations.