Biology subjects

Sandt, C.

Publications and source records attributed to Sandt, C..

4 recordsLinked to original sources

bioRxiv2022

Virtual histology of Alzheimer's Disease: why are amyloid-β plaques visible with X-ray phase-contrast imaging?

Amyloid-{beta} (A{beta}) plaques from Alzheimers Disease (AD) can be visualized ex vivo in label-free brain samples using synchrotron X-ray phase-contrast tomography (XPCT). However, for XPCT to be useful as a screening method for amyloid pathology, it is essential to understand which factors drive the detection of A{beta} plaques. The current study was designed to test the hypothesis that A{beta}-related contrast in XPCT could be caused by the A{beta} fibrils and/or by metals trapped in the plaques. This study probed the fibrillar and elemental compositions of A{beta} plaques in brain samples from different types of AD patients and AD models to establish a relationship between XPCT contrast and A{beta} plaque characteristics. XPCT, micro-Fourier-Transform Infrared spectroscopy and micro-X-Ray Fluorescence spectroscopy were conducted on human samples (genetic and sporadic cases) and on four transgenic rodent strains (mouse: APPPS1, ArcA{beta}, J20; rat: TgF344). A{beta} plaques from the genetic AD patient were visible using XPCT, and had higher {beta}-sheet content and higher metal levels than the sporadic AD patient, which remained undetected by XPCT. A{beta} plaques in J20 mice and TgF344 rats appeared hyperintense on XPCT images, while they were hypointense with an hyperintense core in the case of APPPS1 and ArcA{beta} mice. In all four transgenic strains, {beta}-sheet content was similar, while metal levels were highly variable: J20 (zinc and iron) and TgF344 (copper) strains showed greater metal accumulation than APPPS1 and ArcA{beta} mice. Hence, a positive contrast formation of A{beta} plaques in XPCT images appeared driven by biometal entrapment. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=143 SRC="FIGDIR/small/509706v2_ufig1.gif" ALT="Figure 1"> View larger version (48K): org.highwire.dtl.DTLVardef@56e672org.highwire.dtl.DTLVardef@1336d85org.highwire.dtl.DTLVardef@15b6690org.highwire.dtl.DTLVardef@1aaa6cb_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIAmyloid-{beta} plaques in the different forms of Alzheimers Disease have various contrasts in X-ray phase-contrast tomography C_LIO_LIIn transgenic rodents, a core-restricted, positive contrast is driven by the level of metal entrapment within plaques C_LIO_LIIn humans, greater and more diffuse metal accumulation lead to a positive contrast in a genetic case of AD C_LI

biophysics↗

bioRxiv2021

Plastic biodegradation: do Galleria mellonella larvae - bio-assimilate polyethylene? A spectral histology approach using isotopic labelling and infrared microspectroscopy.

Environmental pollution by non-biodegradable polyethylene (PE) plastics is of major concern, thus, organisms capable of bio-degrading PE are required. The larvae of the Greater Wax Moth, Galleria mellonella (Gm), were identified as a potential candidate to digest PE. In this study, we tested whether PE was metabolized by Gm larvae and could found in their tissues. We examined the implication of the larval gut microbiota by using conventional and axenic reared insects. First, our study showed that neither beeswax nor PE alone favour the growth of young larvae. We then used Fourier-Transform Infrared Microspectroscopy ({micro}FTIR) to detect deuterium in larvae fed with isotopically labelled food. Perdeuterated molecules were found in most tissues of larvae fed with deuterium labelled oil for 72 hours proving that {micro}FTIR can detect metabolization of 1-2 mg of deuterated food. No bio-assimilation was detected in the tissues of larvae fed with 1-5 mg of perdeuterated PED4 for 72 hours and 19-21 days, but micron sized PE particles were found in the larval digestive tract cavities. We evidenced weak bio-degradation of PE films in contact for 24 hours with the dissected gut of conventional larvae; and in the PED4 particles from excreted larval frass. Our study confirms that Gm larvae can bio-degrade PE but can not necessarily metabolize it.

ecology↗

bioRxiv2019

Identification of distinct pathological signatures induced by patient-derived α-synuclein structures in non-human primates

AO_SCPLOWBSTRACTC_SCPLOWDopaminergic neuronal cell death, associated with intracellular -synuclein (-syn)-rich protein aggregates (termed Lewy bodies), is a well-established characteristic of Parkinsons disease. Much evidence, accumulated from multiple experimental models has suggested that -syn plays a role in PD pathogenesis, not only as a trigger of pathology but also as a mediator of disease progression through pathological spreading. Here we have used a machine learning-based approach to identify unique signatures of neurodegeneration in monkeys induced by distinct -syn pathogenic structures derived from PD patients. Unexpectedly, our results show that, in non-human primates, a small amount of singular -syn aggregates is as toxic as larger amyloid fibrils present in the LBs, thus reinforcing the need for preclinical research in this species. Furthermore, our results provide evidence supporting the true multifactorial nature of PD as multiple causes can induce similar outcome regarding dopaminergic neurodegeneration.

neuroscience↗

bioRxiv2018

Synchrotron FTIR and Raman spectroscopy provide unique spectral fingerprints for Arabidopsis floral stem vascular tissues

Cell walls are highly complex structures that are modified during plant growth and development. For example, the development of phloem and xylem vascular cells, which participate in the transport of sugars and water as well as support, can be influenced by cell-specific cell wall composition. Here, we used synchrotron radiation-based infrared (SR-FTIR) and Raman spectroscopy to analyze the cell wall composition of wild-type and double mutant sweet11-1sweet12-1, which impairs sugar transport, Arabidopsis floral stem vascular tissue. The SR-FTIR spectra showed that in addition to modified xylem cell wall composition, phloem cell walls in the double mutant line were characterized by modified hemicellulose composition. Moreover, combining Raman spectroscopy with a Classification and Regression Tree (CART) method identified combinations of Raman shifts that could distinguish xylem vessels and fibers. Additionally, the disruption of SWEET11 and SWEET12 genes impacts xylem cell wall composition in a cell-specific manner, with changes in hemicelluloses and cellulose observed at the xylem vessel interface. These results suggest that the facilitated transport of sugars by transporters that exist between vascular parenchyma cells and conducting cells is important to ensuring correct phloem and xylem cell wall composition.\n\nHighlightCombining vibrational spectroscopy techniques and multivariate analysis shows that the disruption of SWEET genes impacts phloem cell wall composition and that the effect on xylem cell wall composition is cell-specific.

plant biology↗