Publications by authors named "Hans Stefan"

Article Synopsis
  • The study focuses on adult zebrafish that are blind due to mutations in the atoh7 gene, which prevents the formation of retinal ganglion cells (RGCs).
  • Researchers characterized the physical and behavioral traits of these mutants using various scientific techniques, noting distinct characteristics like dark pigmentation and reduced body size.
  • The findings highlight that these adult zebrafish serve as a valuable model for studying conditions like glaucoma and optic nerve aplasia by providing insights into retinal and tectal structure.
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Article Synopsis
  • Low-voltage electrical safety training is crucial for workers, but traditional lecture-based methods are often ineffective.
  • Virtual reality (VR) offers an immersive experience that enhances engagement and safety during training, making it a promising tool for industrial safety applications.
  • A study involving 18 participants showed that VR training led to improved knowledge retention and positive feedback, suggesting it is a viable alternative to traditional methods.
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Inflammation can lead to persistent and irreversible loss of retinal neurons and photoreceptors in mammalian vertebrates. In contrast, in the adult zebrafish brain, acute neural inflammation is both necessary and sufficient to stimulate regeneration of neurons. Here, we report on the critical, positive role of the immune system to support retina regeneration in adult zebrafish.

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Purpose: A better characterization of the dependence of the tissue sparing effect at ultra-high dose rate (UHDR) on physical beam parameters (dose, dose rate, radiation quality) would be helpful towards a mechanistic understanding of the FLASH effect and for its broader clinical translation. To address this, a comprehensive study on the normal tissue sparing at UHDR using the zebrafish embryo (ZFE) model was conducted.

Methods: One-day-old ZFE were irradiated over a wide dose range (15-95 Gy) in three different beams (proton entrance channel, proton spread out Bragg peak and 30 MeV electrons) at UHDR and reference dose rate.

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Trams are experiencing a resurgence with worldwide network expansion driven by the need for sustainable and efficient cities. Trams often operate in shared or mixed-traffic environments, which raise safety concerns, particularly in hazardous situations. This paper adopts an international, mixed-methods approach, conducted through two interconnected studies in Melbourne (Australia) and Birmingham (UK).

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The recently observed FLASH effect describes the observation of normal tissue protection by ultra-high dose rates (UHDR), or dose delivery in a fraction of a second, at similar tumor-killing efficacy of conventional dose delivery and promises great benefits for radiotherapy patients. Dedicated studies are now necessary to define a robust set of dose application parameters for FLASH radiotherapy and to identify underlying mechanisms. These studies require particle accelerators with variable temporal dose application characteristics for numerous radiation qualities, equipped for preclinical radiobiological research.

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In the lesioned zebrafish retina, Müller glia produce multipotent retinal progenitors that generate all retinal neurons, replacing lost cell types. To study the molecular mechanisms linking Müller glia reactivity to progenitor production and neuronal differentiation, we used single-cell RNA sequencing of Müller glia, progenitors and regenerated progeny from uninjured and light-lesioned retinae. We discover an injury-induced Müller glia differentiation trajectory that leads into a cell population with a hybrid identity expressing marker genes of Müller glia and progenitors.

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Morphogen gradients impart positional information to cells in a homogenous tissue field. Fgf8a, a highly conserved growth factor, has been proposed to act as a morphogen during zebrafish gastrulation. However, technical limitations have so far prevented direct visualization of the endogenous Fgf8a gradient and confirmation of its morphogenic activity.

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Impedance measurements are routinely performed during cochlear implantation (CI) after finalized electrode insertion. They may allow conclusions on the electrode's and implant's function. In the postoperative setting, the analysis of impedance changes enables the identification of scarring or inflammation processes around the electrode.

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The vertebrate inner ear is the sensory organ mediating hearing and balance. The entire organ develops from the otic placode, which itself originates from the otic-epibranchial progenitor domain (OEPD). Multiple studies in various species have shown the importance of the forkhead-box and distal-less homeodomain transcription factor families for OEPD and subsequent otic placode formation.

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Purpose: Optimal measurement settings to measure the medial olivocochlear reflex (MOCR) in humans have not yet been defined. The purpose of this study was to advance the representation of the MOCR in auditory brainstem response (ABR) as an addition to the current diagnostic portfolio.

Participants And Method: Twelve female and 14 male normal-hearing adults participated in the study.

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Introduction: The medial olivocochlear reflex (MOCR) is a part of the binaural processing strategies and influences the efferent auditory pathway in normal-hearing individuals. Patients with asymmetric hearing loss often benefit from a bimodal hearing solution with a cochlear implant (CI) and a hearing aid (HA). However, hearing performances may vary with some surprisingly high- or low-performing CI/HA users.

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Endothelial specification is a key event during embryogenesis; however, when, and how, endothelial cells separate from other lineages is poorly understood. In zebrafish, Npas4l is indispensable for endothelial specification by inducing the expression of the transcription factor genes , , and . We generated a knock-in reporter in zebrafish to visualize endothelial progenitors and their derivatives in wild-type and mutant embryos.

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Despite decades of research, knowledge about the genes that are important for development and function of the mammalian eye and are involved in human eye disorders remains incomplete. During mammalian evolution, mammals that naturally exhibit poor vision or regressive eye phenotypes have independently lost many eye-related genes. This provides an opportunity to predict novel eye-related genes based on specific evolutionary gene loss signatures.

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Background And Purpose: Continuing recent experiments at the research electron accelerator ELBE at the Helmholtz-Zentrum Dresden-Rossendorf the influence of beam pulse structure on the Flash effect was investigated.

Materials And Methods: The proton beam pulse structure of an isochronous cyclotron (UHDR) and a synchrocyclotron (UHDR) was mimicked at ELBE by quasi-continuous electron bunches at 13 MHz delivering mean dose rates of 287 Gy/s and 177 Gy/s and bunch dose rates of 10Gy/s and 10 Gy/s, respectively. For UHDR, 40 ms macro pulses at a frequency of 25 Hz superimposed the bunch delivery.

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Sensorineural hearing loss is caused by the loss of sensory hair cells and/or their innervating neurons within the inner ear and affects millions of people worldwide. In mammals, including humans, the underlying cell types are only produced during fetal stages making loss of these cells and the resulting consequences irreversible. In contrast, zebrafish produce sensory hair cells throughout life and additionally possess the remarkable capacity to regenerate them upon lesion.

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In comparison to mammals, zebrafish are able to regenerate many organs and tissues, including the central nervous system (CNS). Within the CNS-derived neural retina, light lesions result in a loss of photoreceptors and the subsequent activation of Müller glia, the retinal stem cells. Müller glia-derived progenitors differentiate and eventually restore the anatomical tissue architecture within 4 weeks.

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Objective: During cochlear implantation, electrophysiological tests are performed to document safe technical functioning of implant and electrodes. In rare cases, the apical part of the electrode folds over during insertion. The data from transimpedance matrix (TIM) measurements enable the generation of a heat map or TIM profile measuring the spatial distribution of voltage.

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Zebrafish can achieve scar-free healing of heart injuries, and robustly replace all cardiomyocytes lost to injury via dedifferentiation and proliferation of mature cardiomyocytes. Previous studies suggested that Wnt/β-catenin signaling is active in the injured zebrafish heart, where it induces fibrosis and prevents cardiomyocyte cell cycling. Here, via targeting the destruction complex of the Wnt/β-catenin pathway with pharmacological and genetic tools, we demonstrate that Wnt/β-catenin activity is required for cardiomyocyte proliferation and dedifferentiation, as well as for maturation of the scar during regeneration.

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LRRK2 gain-of-function is considered a major cause of Parkinson's disease (PD) in humans. However, pathogenicity of LRRK2 loss-of-function in animal models is controversial. Here we show that deletion of the entire zebrafish lrrk2 locus elicits a pleomorphic transient brain phenotype in maternal-zygotic mutant embryos (mzLrrk2).

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Introduction: Intraoperative electrocochleography (ECochG) during cochlear implantation is a promising tool to preserve residual hearing. However, the time gap between insertion of the electrode and acoustic feedback from the audiologist to the surgeon can cause delay and subsequently irreparable damage to cochlear structures. In this feasibility study, for the first time, real-time visualization of intraoperative ECochG via digital microscope display directly to the surgeon was successfully performed in four patients.

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Purpose: Numerous endeavors have been undertaken to preserve hearing in cochlear implant (CI) patients. Particularly, optimization of electrode array design aims at preservation of residual hearing (RH). This study examines whether a slim perimodiolar (PM) electrode array could bear the capability to preserve hearing.

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Patients with irritability, temper outbursts, hyperactivity and mood swings often meet the dysregulation profile (DP) of the Child Behavior Checklist (CBCL) or the Strengths and Difficulties Questionnaire (SDQ), which have been investigated over the past few decades. While the DP has emerged as a transdiagnostic marker with a negative impact on therapeutic outcome and psychosocial functioning, little is known about its underlying mechanisms such as attention and emotion regulation processes. In this study, we tested whether adolescent psychiatric patients (n = 27) with the SDQ-DP show impaired emotional face processing for task-irrelevant stimuli compared to psychiatric patients without the SDQ-DP (n = 30) and non-clinical adolescents (n = 21).

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Conditional gene inactivation is a powerful tool to determine gene function when constitutive mutations result in detrimental effects. The most commonly used technique to achieve conditional gene inactivation employs the Cre/loxP system and its ability to delete DNA sequences flanked by two loxP sites. However, targeting a gene with two loxP sites is time and labor consuming.

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