Biology subjects

Diekmann, R.

Publications and source records attributed to Diekmann, R..

3 recordsLinked to original sources

bioRxiv2023

Effect of caffeine and other xanthines on liver sinusoidal endothelial cell ultrastructure

Xanthines such as caffeine and theobromine are among the most consumed psychoactive stimulants in the world, either as natural components of coffee, tea and chocolate, or as food additives. The present study assessed if xanthines affect liver sinusoidal endothelial cells (LSEC). Cultured primary rat LSEC were challenged with xanthines at concentrations typically obtained from normal consumption of xanthine-containing beverages, food or medicines; and at higher concentrations below the in vitro toxic limit. The fenestrated morphology of LSEC were examined with scanning electron and structured illumination microscopy. All xanthine challenges had no toxic effects on LSEC ultrastructure as judged by LSEC fenestration morphology, or function as determined by endocytosis studies. All xanthines in high concentrations (150 g/mL) increased fenestration frequency but at physiologically relevant concentrations, only theobromine (8 g/mL) showed an effect. LSEC porosity was influenced only by high caffeine doses which also shifted the fenestration distribution towards smaller pores. Moreover, a dose-dependent increase in fenestration number was observed after caffeine treatment. If these compounds induce similar changes in vivo, age-related reduction of LSEC porosity can be reversed by oral treatment with theobromine or with other xanthines using targeted delivery.

cell biology↗

bioRxiv2021

Photon-free (s)CMOS camera characterization for artifact reduction in high- and super-resolution microscopy

Modern implementations of widefield fluorescence microscopy often rely on sCMOS cameras, but this camera architecture inherently features pixel-to-pixel variations. Such variations lead to image artifacts and render quantitative image interpretation difficult. Although a variety of algorithmic corrections exists, they require a thorough characterization of the camera, which typically is not easy to access or perform. Here, we developed a fully automated pipeline for camera characterization based solely on thermally generated signal, and implemented it in the popular open-source software Micro-Manager and ImageJ/Fiji. Besides supplying the conventional camera maps of noise, offset and gain, our pipeline also gives access to dark current and thermal noise as functions of the exposure time. This allowed us to avoid structural bias in single-molecule localization microscopy (SMLM), which without correction is substantial even for scientific-grade, cooled cameras. In addition, our approach enables high-quality 3D super-resolution as well as live-cell time-lapse microscopy with cheap, industry-grade cameras. As our approach for camera characterization does not require any user interventions or additional hardware implementations, numerous correction algorithms demanding camera characterization become easily applicable.

biophysics↗

bioRxiv2019

Organotypic slice culture model demonstrates interneuronal spreading of alpha-synuclein aggregates

Here we describe the use of an organotypic hippocampal slice model for studying -synuclein aggregation and inter-neuronal spreading initiated by injection of preformed -synuclein filaments (PFFs). PFF injection at dentate gyrus templates the endogenous -synuclein to form aggregates in axons and cell bodies that spread to CA3 and CA1 regions. Aggregates were insoluble and phosphorylated at serine 129, recapitulating Lewy pathology features found in Parkinsons disease and other synucleinopathies. The spreading of the aggregates were favoring the anterograde direction in the slice model. The model allowed development of slices expressing only serine-129 phosphorylation-deficient human -synuclein (S129G) using adeno-associated viral (AAV) vector in -synuclein knockout slices. Processes of aggregation and spreading of -synuclein were thereby shown to be independent of phosphorylation at serine 129. We provide methods and highlight crucial steps for PFF microinjection and characterization of aggregate formation and spreading. Slices derived from genetically engineered mice or manipulated by using viral vectors allow testing of hypotheses on mechanisms involved in formation of -synuclein aggregates and their prion-like spreading.

neuroscience↗