Intramembrane protease PARL defines a negative regulator of PINK1- and PARK2/Parkin-dependent mitophagy

<p>Mutations in PINK1 and PARK2/Parkin are a main risk factor for familial Parkinson disease. While the physiological mechanism of their activation is unclear, these proteins have been shown in tissue culture cells to serve as a key trigger for autophagy of depolarized mitochondria. Here we show that ablation of the mitochondrial rhomboid protease PARL leads to retrograde translocation of an intermembrane space-bridging PINK1 import intermediate. Subsequently, it is rerouted to the outer membrane in order to recruit PARK2, which phenocopies mitophagy induction by uncoupling agents. Consistent with a role of this retrograde translocation mechanism in neurodegenerative disease, we show that pathogenic PINK1 mutants which are not cleaved by PARL affect PINK1 kinase activity and the ability to induce PARK2-mediated mitophagy. Altogether we suggest that PARL is an important intrinsic player in mitochondrial quality control, a system substantially impaired in Parkinson disease as indicated by reduced removal of damaged mitochondria in affected patients.</p

Nonlinear statistical iterative reconstruction for propagation-based phase-contrast tomography

Propagation-based phase-contrast tomography has become a valuable tool for visualization of three-dimensional biological samples, due to its high sensitivity and its potential in providing increased contrast between materials with similar absorption properties. We present a statistical iterative reconstruction algorithm for this imaging technique in the near-field regime. Under the assumption of a single material, the propagation of the x-ray wavefield—relying on the transport-of-intensity equation—is made an integral part of the tomographic reconstruction problem. With a statistical approach acting directly on the measured intensities, we find an unconstrained nonlinear optimization formulation whose solution yields the three-dimensional distribution of the sample. This formulation not only omits the intermediate step of retrieving the projected thicknesses but also takes the statistical properties of the measurements into account and incorporates prior knowledge about the sample in the form of regularization techniques. We show some advantages of this integrated approach compared to two-step approaches on data obtained using a commercially available x-ray micro-tomography system. In particular, we address one of the most considerable challenges of the imaging technique, namely, the artifacts arising from samples containing highly absorbing features. With the use of statistical weights in our noise model, we can account for these materials and recover features in the vicinity of the highly absorbing features that are lost in the conventional two-step approaches. In addition, the statistical modeling of our reconstruction approach will prove particularly beneficial in the ongoing transition of this imaging technique from synchrotron facilities to laboratory setups

X-ray imaging of a water bear offers a new look at tardigrade internal anatomy

Gefördert durch den Publikationsfonds der Universität Kasse

Instalación contra incendios de una nave industrial de impresión y artes gráficas

Propagation-based phase-contrast computed tomography has become a valuable tool for visualization of three-dimensional biological samples, due to its high contrast between materials with similar attenuation properties. However, one of the most-widely used phase-retrieval algorithms imposes a homogeneity assumption onto the sample, which leads to artifacts for numerous applications where this assumption is violated. Prominent examples are biological samples with highly-absorbing implants. Using synchrotron radiation, we demonstrate by the example of a guinea pig inner ear with a cochlear implant electrode, how a recently developed model-based iterative algorithm for propagation-based phase-contrast computed tomography yields distinct benefits for such a task. We find that the model-based approach improves the overall image quality, removes the detrimental influence of the implant and accurately visualizes the cochlea

Myoanatomy of the velvet worm leg revealed by laboratory-based nanofocus X-ray source tomography

X-ray computed tomography (CT) imaging has become popular for investigating, nondestructively and three-dimensionally, both external and internal structures of various specimens. However, the limited resolution of conventional laboratory-based CT systems (≥500 nm) still hampers the detailed visualization of features on the low nanometer level. We present a laboratory CT device and data processing pipeline to routinely and efficiently generate high-resolution 3D data (≈100 nm) without requiring synchrotron radiation facilities. Our setup is especially relevant for conducting detailed analysis of very small biological samples, as demonstrated for a walking appendage of a velvet worm. Comparative analyses of our CT data with those obtained from other popular imaging methods highlight the advantages and future applicability of the nanoCT setup

Multimodal Precision Imaging of Pulmonary Nanoparticle Delivery in Mice:Dynamics of Application, Spatial Distribution, and Dosimetry

Targeted delivery of nanomedicine/nanoparticles (NM/NPs) to the site of disease (e.g., the tumor or lung injury) is of vital importance for improved therapeutic efficacy. Multimodal imaging platforms provide powerful tools for monitoring delivery and tissue distribution of drugs and NM/NPs. This study introduces a preclinical imaging platform combining X‐ray (two modes) and fluorescence imaging (three modes) techniques for time‐resolved in vivo and spatially resolved ex vivo visualization of mouse lungs during pulmonary NP delivery. Liquid mixtures of iodine (contrast agent for X‐ray) and/or (nano)particles (X‐ray absorbing and/or fluorescent) are delivered to different regions of the lung via intratracheal instillation, nasal aspiration, and ventilator‐assisted aerosol inhalation. It is demonstrated that in vivo propagation‐based phase‐contrast X‐ray imaging elucidates the dynamic process of pulmonary NP delivery, while ex vivo fluorescence imaging (e.g., tissue‐cleared light sheet fluorescence microscopy) reveals the quantitative 3D drug/particle distribution throughout the entire lung with cellular resolution. The novel and complementary information from this imaging platform unveils the dynamics and mechanisms of pulmonary NM/NP delivery and deposition for each of the delivery routes, which provides guidance on optimizing pulmonary delivery techniques and novel‐designed NM for targeting and efficacy.ISSN:1613-6810ISSN:1613-682

Multimodal Precision Imaging of Pulmonary Nanoparticle Delivery in Mice: Dynamics of Application, Spatial Distribution, and Dosimetry

Targeted delivery of nanomedicine/nanoparticles (NM/NPs) to the site of disease (e.g., the tumor or lung injury) is of vital importance for improved therapeutic efficacy. Multimodal imaging platforms provide powerful tools for monitoring delivery and tissue distribution of drugs and NM/NPs. This study introduces a preclinical imaging platform combining X-ray (two modes) and fluorescence imaging (three modes) techniques for time-resolved in vivo and spatially resolved ex vivo visualization of mouse lungs during pulmonary NP delivery. Liquid mixtures of iodine (contrast agent for X-ray) and/or (nano)particles (X-ray absorbing and/or fluorescent) are delivered to different regions of the lung via intratracheal instillation, nasal aspiration, and ventilator-assisted aerosol inhalation. It is demonstrated that in vivo propagation-based phase-contrast X-ray imaging elucidates the dynamic process of pulmonary NP delivery, while ex vivo fluorescence imaging (e.g., tissue-cleared light sheet fluorescence microscopy) reveals the quantitative 3D drug/particle distribution throughout the entire lung with cellular resolution. The novel and complementary information from this imaging platform unveils the dynamics and mechanisms of pulmonary NM/NP delivery and deposition for each of the delivery routes, which provides guidance on optimizing pulmonary delivery techniques and novel-designed NM for targeting and efficacy

Correction for mechanical inaccuracies in a scanning Talbot-Lau interferometer

Grating-based X-ray phase-contrast and in particular dark-field radiography are promising new imaging modalities for medical applications. Currently, the potential advantage of dark-field imaging in early-stage diagnosis of pulmonary diseases in humans is being investigated. These studies make use of a comparatively large scanning interferometer at short acquisition times, which comes at the expense of a significantly reduced mechanical stability as compared to tabletop laboratory setups. Vibrations create random fluctuations of the grating alignment, causing artifacts in the resulting images. Here, we describe a novel maximum likelihood method for estimating this motion, thereby preventing these artifacts. It is tailored to scanning setups and does not require any sample-free areas. Unlike any previously described method, it accounts for motion in between as well as during exposures.</p