Adverse effects of psychological stress on physical and mental health, especially in older age, are well documented. How perceived stress relates to the epigenetic clock measure, DNA methylation age acceleration (DNAmAA), is less well understood and existing studies reported inconsistent results. DNAmAA was estimated from five epigenetic clocks (7-CpG, Horvath's, Hannum's, PhenoAge and GrimAge DNAmAA). Cohen's Perceived Stress Scale (PSS) was used as marker of psychological stress. We analyzed data from 1,100 Berlin Aging Study II (BASE-II) participants assessed as part of the GendAge study (mean age = 75.6 years, SD = 3.8 years, 52.1% women). In a first step, we replicated well-established associations of perceived stress with morbidity, frailty, and symptoms of depression in the BASE-II cohort studied here. In a second step, we did not find any statistically significant association of perceived stress with any of the five epigenetic clocks in multiple linear regression analyses that adjusted for covariates. Although the body of literature suggests an association between higher DNAmAA and stress or trauma during early childhood, the current study found no evidence for an association of perception of stress with DNAmAA in older people. We discuss possible reasons for the lack of associations and highlight directions for future research.
Weniger anzeigenClinical translation from bench to bedside often remains challenging even despite promising preclinical evidence. Among many drivers like biological complexity or poorly understood disease pathology, preclinical evidence often lacks desired robustness. Reasons include low sample sizes, selective reporting, publication bias, and consequently inflated effect sizes. In this context, there is growing consensus that confirmatory multicenter studies -by weeding out false positives- represent an important step in strengthening and generating preclinical evidence before moving on to clinical research. However, there is little guidance on what such a preclinical confirmatory study entails and when it should be conducted in the research trajectory. To close this gap, we organized a workshop to bring together statisticians, clinicians, preclinical scientists, and meta-researcher to discuss and develop recommendations that are solutionoriented and feasible for practitioners. Herein, we summarize and review current approaches and outline strategies that provide decision-critical guidance on when to start and subsequently how to plan a confirmatory study. We define a set of minimum criteria and strategies to strengthen validity before engaging in a confirmatory preclinical trial, including sample size considerations that take the inherent uncertainty of initial (exploratory) studies into account. Beyond this specific guidance, we highlight knowledge gaps that require further research and discuss the role of confirmatory studies in translational biomedical research. In conclusion, this workshop report highlights the need for close interaction and open and honest debate between statisticians, preclinical scientists, meta-researchers (that conduct research on research), and clinicians already at an early stage of a given preclinical research trajectory.
Weniger anzeigenBackground: Migraine frequency increases after the cessation of successful preventive treatment with CGRP(-receptor) monoclonal antibodies (mAbs). In this study, we aimed to evaluate the course of migraine after treatment resumption.
Methods: Patients with migraine, who started treatment with the same CGRP(-R) mAb after a three-month drug holiday were included in this analysis. We collected headache data at four prospective visits: 1) during the four weeks before the initial mAb treatment (baseline); 2) during the four weeks before the last mAb injection; 3) in weeks 13-16 of the drug holiday; 4) in weeks 9-12 after treatment restart. Outcomes were the changes in monthly migraine days (MMD), monthly headache days (MHD), monthly days with acute medication use (AMD) and Headache Impact Test-6 (HIT-6) scores across the observation period.
Results: This study included 39 patients (erenumab n = 16; galcanezumab/ fremanezumab n = 23). MMD decreased from 12.3 +/- 6.3 at the end of the drug holiday to 7.8 +/- 5.5 three months after treatment restart (p = 0.001). The improvement after treatment resumption was similar to the response in the initial treatment period (baseline: 12.3 +/- 6.3 MMD vs. 7.5 +/- 5.2 MMD before treatment interruption). MHD and AMD showed a significant improvement after treatment restart. HIT-6 scores decreased, indicating a diminished impact of headache on everyday life.
Conclusions: Reinitiation of treatment with CGRP(-R) mAbs after a drug holiday leads to a significant reduction of migraine frequency and medication use as well as improvement in quality of life.
Weniger anzeigenBackground: Art therapy is a form of complementary therapy to treat a wide variety of health problems. Existing studies examining the effects of art therapy differ substantially regarding content and setting of the intervention, as well as their included populations, outcomes, and methodology. The aim of this review is to evaluate the overall effectiveness of active visual art therapy, used across different treatment indications and settings, on various patient outcomes.
Methods: We will include randomised controlled studies with an active art therapy intervention, defined as any form of creative expression involving a medium (such as paint etc.) to be actively applied or shaped by the patient in an artistic or expressive form, compared to any type of control. Any treatment indication and patient group will be included. A systematic literature search of the Cochrane Library, EMBASE (via Ovid), MEDLINE (via Ovid), CINAHL, ERIC, APA PsycArticles, APA Psyclnfo, and PSYNDEX (all via EBSCOHost), ClinicalTrials.gov and the WHO's International Clinical Trials Registry Platform (ICTRP) will be conducted. Psychological, cognitive, somatic and economic outcomes will be used. Based on the number, quality and outcome heterogeneity of the selected studies, a meta-analysis might be conducted, or the data synthesis will be performed narratively only. Heterogeneity will be assessed by calculating the p-value for the chi' test and the I-2 statistic. Subgroup analyses and meta-regressions are planned.
Discussion: This systematic review will provide a concise overview of current knowledge of the effectiveness of art therapy. Results have the potential to (1) inform existing treatment guidelines and clinical practice decisions, (2) provide insights to the therapy's mechanism of change, and (3) generate hypothesis that can serve as a starting point for future randomised controlled studies.
Weniger anzeigenBackground: People with depression often present with concurrent cognitive impairment. Computerized cognitive training (CCT) is a safe and efficacious strategy to maintain or enhance cognitive performance in a range of clinical populations. However, its efficacy in people with depression and how it varies across populations and design factors are currently unclear.
Methods: We searched MEDLINE, EMBASE, and PsycINFO from inception to 13 July 2021 for randomised controlled trials examining the efficacy of CCT vs any control condition on cognitive, mood, psychiatric symptoms, psychosocial, and daily functioning in adults with depression. Eligible samples include studies specifically targeting people with major depressive disorder as well as those with other diagnoses where at least 50% of the sample meets the clinical criteria for depression, with the exception of major psychiatric disorders or dementia. The primary outcome is change in the overall cognitive performance. Multivariate analyses will be used to examine the effect sizes on each outcome category as well as possible effect modifiers and correlations between categories. The risk of bias will be assessed using the Cochrane risk of bias tool version 2.
Discussion: To the best of our knowledge, this will be the first systematic review and meta-analysis of narrowly defined CCT across clinical populations with depression. We aim to investigate not only whether CCT is efficacious for cognition, but also how such effects vary across design factors, what other clinically relevant outcomes might respond to CCT, and the extent to which they differ across populations.
Weniger anzeigenFrailty is very common in old age and often associated with adverse events. Transitioning between frailty states is possible in both directions (improvement and worsening) offering targets for interventions. Frailty is more prevalent in women, but little is known about the impact of gender on frailty transition. The aim of this study is to identify gender differences for frailty transition in older adults and to develop gender-stratified prognostic prediction models for frailty transition. We performed a longitudinal analyses of the Berlin Initiative (cohort) Study with a frailty follow-up of 2.1 years. Description of frailty transition using the frailty phenotype and development of prognostic prediction models using multivariable logistic regressions for transition (improvement or worsening) stratified by gender following the TRIPOD statement were performed. In total, the study population consisted of 1158 community-dwelling adults with a mean age of 84.4 years and of whom 55% were women. Out of 1158 participants 225 (19%) were robust, 532 (46%) prefrail and 401 (35%) frail. After 2.1 (IQR 2.0-2.3) years, half of the participants had transitioned between frailty states. Men worsened more often and those who were already frail died more often than women. Gender-stratified prediction models for frailty transition demonstrated that some predictors (age, self-rated health, cognitive impairment, baseline frailty status) were included in all models. While stroke, diabetes mellitus, smoking and glomerular filtration rate were unique predictors in the models for females, osteoarthritis, hospitalization and education were predictors in the models for males. There are gender differences in frailty transition rates, patterns and prediction. This supports the importance of considering gender when addressing frailty and targeting interventions in old age.
Weniger anzeigenThe aim of the study was to assess the influence of music on anxiety levels compared to standard patient care in patients undergoing venous catheter placement procedures. This prospective randomized controlled trial included patients undergoing placement procedures for peripherally inserted central venous catheters (PICC), ports and central venous catheters (CVC). Patients were randomly assigned to a music intervention group (MIG) and a control group (CTRL). State and trait anxiety levels were assessed as primary outcome using the state-trait anxiety inventory (STAI) before and after the procedures. Secondary outcomes comprised averaged heart rate for all participants and time of radiological surveillance for port placement procedures exclusively. 72 participants were included into the final analysis (MIG n = 40; CTRL n = 32). All procedures were successful and no major complications were reported. Mean levels for post-interventional anxieties were significantly lower in the MIG compared to the CTRL (34.9 +/- 8.9 vs. 44 +/- 12.1; p < 0.001). Mean heart rate in the MIG was significantly lower than in the CTRL (76.1 +/- 13.7 vs. 93 +/- 8.9; p < 0.001). Procedure time for port implantation was significantly longer in the MIG by 3 min 45 s (p = 0.031). Music exposure during central venous catheter placement procedures highly significantly reduces anxiety and stress levels and can be used to improve patients' overall experience in the angio suite.
Weniger anzeigenMotor signs such as dyspraxia and abnormal gait are characteristic features of autism spectrum disorder (ASD). However, motor behavior in adults with ASD has scarcely been quantitatively characterized. In this pilot study, we aim to quantitatively examine motor signature of adults with ASD without intellectual impairment using marker-less visual-perceptive motion capture. 82 individuals (37 ASD and 45 healthy controls, HC) with an IQ > 85 and aged 18 to 65 years performed nine movement tasks and were filmed by a 3D-infrared camera. Anatomical models were quantified via custom-made software and resulting kinematic parameters were compared between individuals with ASD and HCs. Furthermore, the association between specific motor behaviour and severity of autistic symptoms (Autism Diagnostic Observation Schedule 2, Autism Spectrum Quotient) was explored. Adults with ASD showed a greater mediolateral deviation while walking, greater sway during normal, tandem and single leg stance, a reduced walking speed and cadence, a greater arrhythmicity during jumping jack tasks and an impaired manual dexterity during finger tapping tasks (p < 0.05 and |D|> 0.48) compared to HC. Furthermore, in the ASD group, some of these parameters correlated moderately to severity of ASD symptoms. Adults with ASD seem to display a specific motor signature in this disorder affecting movement timing and aspects of balance. The data appear to reinforce knowledge about motor signs reported in children and adolescents with ASD. Also, quantitative motor assessment via visual-perceptive computing may be a feasible instrument to detect subtle motor signs in ASD and perhaps suitable in the diagnosis of ASD in the future.
Weniger anzeigenCardiovascular magnetic resonance imaging is the gold standard for cardiac function assessment. Quantification of clinical results (CR) requires precise segmentation. Clinicians statistically compare CRs to ensure reproducibility. Convolutional Neural Network developers compare their results via metrics. Aim: Introducing software capable of automatic multilevel comparison. A multilevel analysis covering segmentations and CRs builds on a generic software backend. Metrics and CRs are calculated with geometric accuracy. Segmentations and CRs are connected to track errors and their effects. An interactive GUI makes the software accessible to different users. The software's multilevel comparison was tested on a use case based on cardiac function assessment. The software shows good reader agreement in CRs and segmentation metrics (Dice > 90%). Decomposing differences by cardiac position revealed excellent agreement in midventricular slices: > 90% but poorer segmentations in apical (> 71%) and basal slices (> 74%). Further decomposition by contour type locates the largest millilitre differences in the basal right cavity (> 3 ml). Visual inspection shows these differences being caused by different basal slice choices. The software illuminated reader differences on several levels. Producing spreadsheets and figures concerning metric values and CR differences was automated. A multilevel reader comparison is feasible and extendable to other cardiac structures in the future.
Weniger anzeigenLumbar foraminal stenosis may be caused by osseous and soft tissue structures. Thus, both computed tomography (CT) and magnetic resonance imaging (MRI) play a role in the diagnostic algorithm. Recently, dual-energy CT (DECT) has been introduced for the detection of spinal disorders. Our study's aim was to investigate the diagnostic accuracy of collagen-sensitive maps derived from DECT in detecting lumbar foraminal stenosis compared with standard CT and MRI. We retrospectively reviewed CT, DECT, and MRI datasets in patients with vertebral fractures between January 2015 and February 2017. Images were scored for presence and type of lumbar neuroforaminal stenosis. Contingency tables were calculated to determine diagnostic accuracy and interrater agreement was evaluated. 612 neuroforamina in 51 patients were included. Intraclass correlation coefficients for interrater reliability in detecting foraminal stenoses were 0.778 (95%-CI 0.643-0.851) for DECT, 0.769 (95%-CI 0.650-0.839) for CT, and 0.820 (95%-CI 0.673-0.888) for MRI. Both DECT and conventional CT showed good diagnostic accuracy in detecting lumbar foraminal stenosis but low sensitivities in detecting discoid stenosis. Thus, even though previous studies suggest that DECT has high diagnostic accuracy in assessing lumbar disc pathologies, we show that DECT does not provide additional information for detecting discoid stenosis compared with conventional CT.
Weniger anzeigenThe molecular responses to acute resistance exercise are well characterized. However, how cellular signals change over time to modulate chronic adaptations to more prolonged exercise training is less well understood. We investigated anabolic signaling and muscle protein synthesis rates at several time points after acute and chronic eccentric loading. Adult rat tibialis anterior muscle was stimulated for six sets of ten repetitions, and the muscle was collected at 0 h, 6 h, 18 h and 48 h. In the last group of animals, 48 h after the first exercise bout a second bout was conducted, and the muscle was collected 6 h later (54 h total). In a second experiment, rats were exposed to four exercise sessions over the course of 2 weeks. Anabolic signaling increased robustly 6 h after the first bout returning to baseline between 18 and 48 h. Interestingly, 6 h after the second bout mTORC1 activity was significantly lower than following the first bout. In the chronically exercised rats, we found baseline anabolic signaling was decreased, whereas myofibrillar protein synthesis (MPS) was substantially increased, 48 h after the last bout of exercise. The increase in MPS occurred in the absence of changes to muscle fiber size or mass. In conclusion, we find that anabolic signaling is already diminished after the second bout of acute resistance type exercise. Further, chronic exposure to resistance type exercise training results in decreased basal anabolic signaling but increased overall MPS rates.
Weniger anzeigenSubjective cognitive decline (SCD), as expressed by older adults, is associated with negative affect, which, in turn, is a likely risk factor for Alzheimer's Disease (AD). This study assessed the associations between negative affective burden, cognitive functioning, and functional connectivity in networks vulnerable to AD in the context of SCD. Older participants (60-90 years) with SCD (n = 51) and healthy controls (n = 50) were investigated in a cross-sectional study. Subclinical negative affective burden, quantified through a composite of self-reported negative affective factors, was related to cognitive functioning (self-perceived and objective) and functional connectivity. Seed-to-voxel analyses were carried out in default mode network (DMN) and salience network (SAL) nodes using resting-state functional magnetic resonance imaging. Greater negative affective burden was associated with lower self-perceived cognitive functioning and lower between-network functional connectivity of DMN and SAL nodes in the total sample. In addition, there was a significant moderation of SCD status. Greater negative affective burden related to higher functional connectivity within DMN (posterior cingulate-to-precuneus) and within SAL (anterior cingulate-to-insula) nodes in the SCD group, whereas in controls the inverse association was found. We show that negative affective burden is associated with functional brain alterations in older adults, regardless of SCD status. Specifically in the SCD phenotype, greater negative affective burden relates to higher functional connectivity within brain networks vulnerable to AD. Our findings imply that negative affective burden should be considered a potentially modifiable target for early intervention.
Weniger anzeigenThe rates of both maternal and fetal adverse outcomes increase significantly with higher body mass index. The aim of this study was to calculate national estimates of adverse maternal and fetal outcomes and associated hospitalization cost among obese pregnant women using a national database. This study was a retrospective analysis of data retrieved from Nationwide Inpatient Sample database, collected during 2010-2014. The primary outcomes of this study were adverse maternal and fetal outcomes, hospital length of stay, and hospitalization cost. There was a total of 18,687,217 delivery-related hospitalizations, of which 1,048,323 were among obese women. Obese women were more likely to have cesarean deliveries (aOR 1.70, 95% CI 1.62-1.79) and labor inductions (aOR 1.51, 95% CI 1.42-1.60), greater length of stay after cesarean deliveries (aOR 1.14, 95% CI 1.08-1.36) and vaginal deliveries (aOR 1.48, 95% CI 1.23-1.77). They were also more likely to have pregnancy-related hypertension, preeclampsia, gestational diabetes, premature rupture of membranes, chorioamnionitis, venous thromboembolism, excessive fetal growth, and fetal distress. Obese pregnant women had significantly greater risk for adverse obstetrical outcomes, which substantially increased the hospital and economic burden. Risk stratification of pregnant patients based on obesity could also help obstetricians to make better clinical decisions and improve patient outcomes.
Weniger anzeigenSleep is essential but places animals at risk. Filtering acoustic information according to its relevance, a process generally known as sensory gating, is crucial during sleep to ensure a balance between rest and danger detection. The mechanisms of this sensory gating and its specificity are not understood. Here, we tested the effect that sounds of different meaning have on sleep-associated ongoing oscillations. We recorded EEG and EMG from mice during REM and NREM sleep while presenting sounds with or without behavioural relevance. We found that sound presentation per se, in the form of a neutral sound, elicited a weak or no change in the power of sleep-state-dependent EEG during REM and NREM sleep. In contrast, the presentation of a sound previously conditioned in an aversive task, elicited a clear and fast decrease in the EEG power during both sleep phases, suggesting a transition to lighter sleep without awakening. The observed changes generally weakened over training days and were not present in animals that failed to learn. Interestingly, the effect could be generalized to unfamiliar neutral sounds if presented following conditioned training, an effect that depended on sleep phase and sound type. The data demonstrate that sounds are differentially gated during sleep depending on their meaning and that this process is reflected in disruption of sleep-associated brain oscillations without behavioural arousal.
Weniger anzeigenMachine learning models are widely applied to predict molecular properties or the biological activity of small molecules on a specific protein. Models can be integrated in a conformal prediction (CP) framework which adds a calibration step to estimate the confidence of the predictions. CP models present the advantage of ensuring a predefined error rate under the assumption that test and calibration set are exchangeable. In cases where the test data have drifted away from the descriptor space of the training data, or where assay setups have changed, this assumption might not be fulfilled and the models are not guaranteed to be valid. In this study, the performance of internally valid CP models when applied to either newer time-split data or to external data was evaluated. In detail, temporal data drifts were analysed based on twelve datasets from the ChEMBL database. In addition, discrepancies between models trained on publicly-available data and applied to proprietary data for the liver toxicity and MNT in vivo endpoints were investigated. In most cases, a drastic decrease in the validity of the models was observed when applied to the time-split or external (holdout) test sets. To overcome the decrease in model validity, a strategy for updating the calibration set with data more similar to the holdout set was investigated. Updating the calibration set generally improved the validity, restoring it completely to its expected value in many cases. The restored validity is the first requisite for applying the CP models with confidence. However, the increased validity comes at the cost of a decrease in model efficiency, as more predictions are identified as inconclusive. This study presents a strategy to recalibrate CP models to mitigate the effects of data drifts. Updating the calibration sets without having to retrain the model has proven to be a useful approach to restore the validity of most models.
Weniger anzeigenThe intestinal epithelium is one of the fastest renewing tissues in mammals. It shows a hierarchical organisation, where intestinal stem cells at the base of crypts give rise to rapidly dividing transit amplifying cells that in turn renew the pool of short-lived differentiated cells. Upon injury and stem-cell loss, cells can also de-differentiate. Tissue homeostasis requires a tightly regulated balance of differentiation and stem cell proliferation, and failure can lead to tissue extinction or to unbounded growth and cancerous lesions. Here, we present a two-compartment mathematical model of intestinal epithelium population dynamics that includes a known feedback inhibition of stem cell differentiation by differentiated cells. The model shows that feedback regulation stabilises the number of differentiated cells as these become invariant to changes in their apoptosis rate. Stability of the system is largely independent of feedback strength and shape, but specific thresholds exist which if bypassed cause unbounded growth. When dedifferentiation is added to the model, we find that the system can recover faster after certain external perturbations. However, dedifferentiation makes the system more prone to losing homeostasis. Taken together, our mathematical model shows how a feedback-controlled hierarchical tissue can maintain homeostasis and can be robust to many external perturbations.
Weniger anzeigenFractal analysis of dynamic, four-dimensional computed tomography myocardial perfusion (4D-CTP) imaging might have potential for noninvasive differentiation of microvascular ischemia and macrovascular coronary artery disease (CAD) using fractal dimension (FD) as quantitative parameter for perfusion complexity. This multi-center proof-of-concept study included 30 rigorously characterized patients from the AMPLIFiED trial with nonoverlapping and confirmed microvascular ischemia (n(micro) = 10), macrovascular CAD (n(macro) = 10), or normal myocardial perfusion (n(normal) = 10) with invasive coronary angiography and fractional flow reserve (FFR) measurements as reference standard. Perfusion complexity was comparatively high in normal perfusion (FDnormal = 4.49, interquartile range [IQR]:4.46-4.53), moderately reduced in microvascular ischemia (FDmicro = 4.37, IQR:4.36-4.37), and strongly reduced in macrovascular CAD (FDmacro = 4.26, IQR:4.24-4.27), which allowed to differentiate both ischemia types, p < 0.001. Fractal analysis agreed excellently with perfusion state (kappa = 0.96, AUC = 0.98), whereas myocardial blood flow (MBF) showed moderate agreement (kappa = 0.77, AUC = 0.78). For detecting CAD patients, fractal analysis outperformed MBF estimation with sensitivity and specificity of 100% and 85% versus 100% and 25%, p = 0.02. In conclusion, fractal analysis of 4D-CTP allows to differentiate microvascular from macrovascular ischemia and improves detection of hemodynamically significant CAD in comparison to MBF estimation.
Weniger anzeigenThe AbsoluteIDQ p400 HR kit is a commercial product for targeted metabolomics. While the kit has been validated for human plasma and serum, adherent cell lysates have not yet been evaluated. We have optimized the detection of polar and lipid metabolites in cell lysates using the kit to enable robust and repeatable analysis of the detected metabolites. Parameters optimized include total cell mass, loading volume and extraction solvent. We present a cell preparation and analytical method and report on the performance of the kit with regard to detectability of the targeted metabolites and their repeatability. The kit can be successfully used for a relative quantification analysis of cell lysates from adherent cells although validated only for human plasma and serum. Most metabolites are below the limit of the Biocrates' set quantification limits and we confirmed that this relative quantification can be used for further statistical analysis. Using this approach, up to 45% of the total metabolites in the kit can be detected with a reasonable analytical performance (lowest median RSD 9% and 13% for LC and FIA, respectively) dependent on the method used. We recommend using ethanol as the extraction solvent for cell lysates of osteosarcoma cell lines for the broadest metabolite coverage and 25 mg of cell mass with a loading volume of 20 mu L per sample.
Weniger anzeigenTransient receptor potential channel subfamily C, member 6 (TRPC6), a non-selective cation channel that controls influx of Ca2+ and other monovalent cations into cells, is widely expressed in the kidney. TRPC6 gene variations have been linked to chronic kidney disease but its role in acute kidney injury (AKI) is unknown. Here we aimed to investigate the putative role of TRPC6 channels in AKI. We used Trpc6(-/-) mice and pharmacological blockade (SH045 and BI-749327), to evaluate short-term AKI outcomes. Here, we demonstrate that neither Trpc6 deficiency nor pharmacological inhibition of TRPC6 influences the short-term outcomes of AKI. Serum markers, renal expression of epithelial damage markers, tubular injury, and renal inflammatory response assessed by the histological analysis were similar in wild-type mice compared to Trpc6(-/-) mice as well as in vehicle-treated versus SH045- or BI-749327-treated mice. In addition, we also found no effect of TRPC6 modulation on renal arterial myogenic tone by using blockers to perfuse isolated kidneys. Therefore, we conclude that TRPC6 does not play a role in the acute phase of AKI. Our results may have clinical implications for safety and health of humans with TRPC6 gene variations, with respect to mutated TRPC6 channels in the response of the kidney to acute ischemic stimuli.
Weniger anzeigenA newly developed UVC LED source with an emission wavelength of 233 nm was proved on bactericidal efficacy and skin tolerability. The bactericidal efficacy was qualitatively analysed using blood agar test. Subsequently, quantitative analyses were performed on germ carrier tests using the MRSA strain DSM11822, the MSSA strain DSM799, S. epidermidis DSM1798 with various soil loads. Additionally, the compatibility of the germicidal radiation doses on excised human skin and reconstructed human epidermis was proved. Cell viability, DNA damage and production of radicals were assessed in comparison to typical UVC radiation from discharge lamps (222 nm, 254 nm) and UVB (280-380 nm) radiation for clinical assessment. At a dose of 40 mJ/cm(2), the 233 nm light source reduced the viable microorganisms by a log(10) reduction (LR) of 5 log(10) levels if no soil load was present. Mucin and protein containing soil loads diminished the effect to an LR of 1.5-3.3. A salt solution representing artificial sweat (pH 8.4) had only minor effects on the reduction. The viability of the skin models was not reduced and the DNA damage was far below the damage evoked by 0.1 UVB minimal erythema dose, which can be regarded as safe. Furthermore, the induced damage vanished after 24 h. Irradiation on four consecutive days also did not evoke DNA damage. The radical formation was far lower than 20 min outdoor visible light would cause, which is classified as low radical load and can be compensated by the antioxidant defence system.
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