Soft X-ray induced radiation damage in thin freeze-dried brain samples studied by FTIR microscopy.

In order to push the spatial resolution limits to the nanoscale, synchrotron-based soft X-ray microscopy (XRM) experiments require higher radiation doses to be delivered to materials. Nevertheless, the associated radiation damage impacts on the integrity of delicate biological samples. Herein, the extent of soft X-ray radiation damage in popular thin freeze-dried brain tissue samples mounted onto Si3N4 membranes, as highlighted by Fourier transform infrared microscopy (FTIR), is reported. The freeze-dried tissue samples were found to be affected by general degradation of the vibrational architecture, though these effects were weaker than those observed in paraffin-embedded and hydrated systems reported in the literature. In addition, weak, reversible and specific features of the tissue-Si3N4 interaction could be identified for the first time upon routine soft X-ray exposures, further highlighting the complex interplay between the biological sample, its preparation protocol and X-ray probe.

Combined in-situ imaging of structural organization and elemental composition of substantia nigra neurons in the elderly.

Human dopaminergic system in general, and substantia nigra (SN) neurons, in particular, are implicated in the pathologies underlying the human brain aging. The interplay between aberrations in the structural organization and elemental composition of SN neuron bodies has recently gained in importance as selected metals: Fe, Cu, Zn, Ca were found to trigger oxidative-stress-mediated aberration in their molecular assembly due to concomitant protein (alpha-synuclein, tau-protein) aggregation, gliosis and finally oxidative stress. In the present study, we demonstrate an integrated approach to the analysis of the structural organization, assembly, and metals' accumulation in two distinct areas of SN: in the neuromelanin neurons and neuropil. By using the highly brilliant source of PETRA III and the Kirkpatrick-Baez nano-focus, large area histological brain slices are scanned at the sub-neuronal resolution, taking advantage of continuous motor movement and reduced acquisition time. Elemental analysis with synchrotron radiation based X-ray Fluorescence (SRXRF) is combined with X-ray Phase Contrast Imaging (XPCI) to correct for inherent aberrations in the samples' density and thickness, often referred to as the mass thickness effect. Based on the raw SRXRF spectra, we observed the accumulation of P, S, Cl, K, Ca, Fe, Cu and Zn predominantly in the SN neurons. However, upon the mass thickness correction, the distributions of Cl became significantly more uniform. Simultaneously with the fluorescence signal, the Small Angle X-ray Scattering (SAXS) is recorded by a pixel detector positioned in the far-field, enabling fast online computation of the darkfield and differential phase contrast (DPC). The data has demonstrated the SN neurons and neuropil produces excellent contrast which is due to their different mass density and scattering strength, indicative of differences in local structure and assembly therein. In all, the results show that combined SRXRF-XPCI-SAXS experiments can robustly serve as a unique tool for understanding the interplay between the chemical composition and structural organization that may drive the biochemical age-related processes occurring in the human dopaminergic system.

Investigation of biochemical composition of adrenal gland tumors by means of FTIR.

The application of Fourier transform infrared (FTIR) microspectroscopy for the analysis of biomolecular composition of adrenal gland tumors is described. Samples were taken intraoperatively from three types of adrenal lesions: adrenal adenoma (ACA), adrenal cortical hyperplasia (ACH), both derived from adrenal cortical cells, and pheochromocytoma (Ph) derived from chromaffin cells of the adrenal medulla. The specimens were cryo-sectioned and freeze-dried. Since the investigated lesions originated from different cell types, it was predictable that they might differ in biomolecular composition. The experimental results were used to determine which absorption bands differentiate the analyzed samples the most. The main difference was observed in the lipid functional groups. The experimental results indicated that the level of lipids was higher in both the adenoma and the hyperplasia samples compared to pheochromocytomas. In contrast, the level of proteins was higher in the pheochromocytomas. Furthermore, differences within the range of nucleic acids and carbohydrates were observed in the studied adrenal gland tumor types.

The combination of artificial neural networks and synchrotron radiation-based infrared micro-spectroscopy for a study on the protein composition of human glial tumors.

Protein-related changes associated with the development of human brain gliomas are of increasing interest in modern neuro-oncology. It is due to the fact that they might make some of these tumors highly aggressive and difficult to treat. This paper presents a methodology for protein-based analysis of human brain gliomas using synchrotron radiation based Fourier transform infrared spectroscopy (SRFTIR) coupled with artificial neural networks (ANNs). The main goal of this study was to optimize a set of ANNs to predict the secondary structure of proteins (alpha-helices, beta-sheets, beta-turns, bends, random coils) in brain gliomas, based on the amide I-II spectral range. All networks were tested and optimized to reach the standard error of prediction (SEP) lower than 5%. The results indicate that protein-related changes are associated with a tumor's malignancy grade. Particularly, the content of alpha helices increases with increasing malignancy grade, while the content of beta sheets decreases. We also found that proteomic information could be a useful marker to distinguish either between low and high grade tumors or between oligodendroglial- and astrocyte-derived ones. This demonstrates the applicability of FTIR coupled with ANNs to provide clinically relevant information.

Pigmented creatine deposits in Amyotrophic Lateral Sclerosis central nervous system tissues identified by synchrotron Fourier Transform Infrared microspectroscopy and X-ray fluorescence spectromicroscopy.

Amyotrophic Lateral Sclerosis (ALS) is an untreatable, neurodegenerative disease of motor neurons characterized by progressive muscle atrophy, limb paralysis, dysarthria, dysphagia, dyspnae and finally death. Large motor neurons in ventral horns of spinal cord and motor nuclei in brainstem, large pyramidal neurons of motor cortex and/or large myelinated axons of corticospinal tracts are affected. In recent synchrotron Fourier Transform Infrared microspectroscopy (sFTIR) studies of ALS CNS autopsy tissue, we discovered a small deposit of crystalline creatine, which has a crucial role in energy metabolism. We have now examined unfixed, snap frozen, post-autopsy tissue sections of motor cortex, brain stem, spinal cord, hippocampus and substantia nigra from six ALS and three non-degenerated cases with FTIR and micro-X-ray fluorescence (XRF). Heterogeneous pigmented deposits were discovered in spinal cord, brain stem and motor neuron cortex of two ALS cases. The FTIR signature of creatine has been identified in these deposits and in numerous large, non-pigmented deposits in four of the ALS cases. Comparable pigmentation and creatine deposits were not found in controls or in ALS hippocampus and substantia nigra. Ca, K, Fe, Cu and Zn, as determined by XRF, were not correlated with the pigmented deposits; however, there was a higher incidence of hot spots (Ca, Zn, Fe and Cu) in the ALS cases. The identity of the pigmented deposits remains unknown, although the absence of Fe argues against both erythrocytes and neuromelanin. We conclude that elevated creatine deposits may be indicators of dysfunctional oxidative processes in some ALS cases.

Implementation of X-ray fluorescence microscopy for investigation of elemental abnormalities in amyotrophic lateral sclerosis.

The abnormalities of metallochemical reactions may contribute to the pathogenesis of Amyotrophic Lateral Sclerosis (ALS). In the present work, an investigation of the elemental composition of the gray matter, nerve cells and white matter from spinal cord tissues representing three ALS cases and five non-ALS controls was performed. This was done with the use of the synchrotron microbeam X-ray fluorescence technique (micro-SRXRF). The following elements were detected in the tissue sections: P, S, Cl, K, Ca, Fe, Cu, Zn and Br. A higher accumulation of Cl, K, Ca, Zn and Br was observed in the nerve cell bodies than in the surrounding tissue. Contrary to all other elements, Zn accumulation was lower in the white matter areas than in the gray matter ones. The results of quantitative analysis showed that there were no general abnormalities in the elemental accumulation between the ALS and the control group. However, for individual ALS cases such abnormalities were observed for the nerve cells. We also demonstrated differences in the elemental accumulation between the analyzed ALS cases.