Association between ageing, brain chemistry and white matter volume revealed with complementary MRI and FTIR brain imaging.

Magnetic resonance imaging (MRI) is the gold standard method to study brain anatomy in vivo. Using MRI, subtle alterations to white matter structures in the brain are observed prior to cognitive decline associated with the ageing process, and neurodegenerative diseases such as Alzheimer's disease. Detection of such alterations provides hope for early clinical diagnosis. While MRI is essential to detect subtle alterations to brain structure in vivo, the technique is less suited to study and image the distribution of biochemical markers within specific brain structures. Consequently, the chemical changes that drive, or are associated with MRI-detectable alterations to white matter are not well understood. Herein, we describe (to the best of our knowledge) the first application of a complementary imaging approach that incorporates in vivo MRI with ex vivo Fourier transform infrared (FTIR) spectroscopic imaging on the same brain tissue. The combined workflow is used to detect and associate markers of altered biochemistry (FTIR) with anatomical changes to brain white matter (MRI). We have applied this combination of techniques to the senescence accelerated murine prone strain 8 (SAMP8) mouse model (n = 6 animals in each group, analysed across two ageing time points, 6 and 12 months). The results have demonstrated alterations to lipid composition and markers of disturbed metabolism during ageing are associated with loss of white matter volume.

Detection of intact insulin analogues in post-mortem vitreous humour-Application to forensic toxicology casework.

The application of proteomic techniques to forensic science widens the range of analytical capabilities available to forensic laboratories when answering complex toxicology problems. Currently, these techniques are underutilised in post-mortem toxicology because of the historic focus on smaller (<1,000 amu) drug molecules. Definitive confirmation of an insulin overdose by analysis of post-mortem biological matrices is rare and challenging, however can assist coronial investigations pertaining to accidental or intentional overdoses in both diabetic and nondiabetic populations. A semiautomated micro-solid phase extraction paired with mass spectrometry-based insulin methodology was developed and validated for routine use in a Forensic Coronial Toxicology Laboratory. This resulting work reports the first Australian cases where synthetic insulins were confirmed by mass spectrometry in the vitreous humour of Type 1 diabetics who intentionally or accidentally overdosed on their prescription medication glargine and aspart. The detection of glargine M1 in Case 1, aspart in Case 2 and glargine M1 was indicated in Case 3. This paper highlights advancements in forensic coronial toxicology and the promising potential of proteomic analysis in a forensic context.

Biospectroscopic Imaging Provides Evidence of Hippocampal Zn Deficiency and Decreased Lipid Unsaturation in an Accelerated Aging Mouse Model.

Western society is facing a health epidemic due to the increasing incidence of dementia in aging populations, and there are still few effective diagnostic methods, minimal treatment options, and no cure. Aging is the greatest risk factor for memory loss that occurs during the natural aging process, as well as being the greatest risk factor for neurodegenerative disease such as Alzheimer's disease. Greater understanding of the biochemical pathways that drive a healthy aging brain toward dementia (pathological aging or Alzheimer's disease), is required to accelerate the development of improved diagnostics and therapies. Unfortunately, many animal models of dementia model chronic amyloid precursor protein overexpression, which although highly relevant to mechanisms of amyloidosis and familial Alzheimer's disease, does not model well dementia during the natural aging process. A promising animal model reported to model mechanisms of accelerated natural aging and memory impairments, is the senescence accelerated murine prone strain 8 (SAMP8), which has been adopted by many research group to study the biochemical transitions that occur during brain aging. A limitation to traditional methods of biochemical characterization is that many important biochemical and elemental markers (lipid saturation, lactate, transition metals) cannot be imaged at meso- or microspatial resolution. Therefore, in this investigation, we report the first multimodal biospectroscopic characterization of the SAMP8 model, and have identified important biochemical and elemental alterations, and colocalizations, between 4 month old SAMP8 mice and the relevant control (SAMR1) mice. Specifically, we demonstrate direct evidence of Zn deficiency within specific subregions of the hippocampal CA3 sector, which colocalize with decreased lipid unsaturation. Our findings also revealed colocalization of decreased lipid unsaturation and increased lactate in the corpus callosum white matter, adjacent to the hippocampus. Such findings may have important implication for future research aimed at elucidating specific biochemical pathways for therapeutic intervention.

A Multimodal Spectroscopic Imaging Method To Characterize the Metal and Macromolecular Content of Proteinaceous Aggregates ("Amyloid Plaques").

Alzheimer's disease (AD) is a major international health and economic concern. A key pathological feature of AD is so-called "amyloid-ß-plaques", or "Aß-plaques", which are deposits of aggregated protein, enriched with the Aß fragment of amyloid precursor protein. Despite their name, the deposits are not pure Aß and have a heterogeneous, chemically complex composition that can include multiple proteins, lipids, and metal ions (Fe, Cu, or Zn). Despite extensive research, it is still uncertain whether Aß-plaques are a cause or a consequence of AD pathology. Further characterization of the elemental and biochemical composition within and surrounding Aß-plaques, and knowledge of how composition varies with disease state or progression, may provide important insight into the relationship between Aß-plaques and AD pathology. With this aim in mind, herein we demonstrate a multimodal spectroscopic imaging workflow to better characterize the complex composition of Aß-plaques. Our approach incorporates several spectroscopic imaging techniques, such as Fourier transform infrared spectroscopic imaging (FTIR), Raman microscopy, and X-ray fluorescence microscopy (XFM). While FTIR, Raman, and XFM have been used previously, mostly in isolation, to study Aß-plaques, application of all three techniques, in combination with histology and fluorescence microscopy, has not been reported previously. We demonstrate that a multimodal workflow, incorporating all three methods on adjacent or serial tissue sections, can reveal substantial complementary information about the biochemical and elemental composition of Aß-plaques. Information revealed by the method includes the relative content and distribution of aggregated protein, total lipid, lipid esters, cholesterol, and metals (Fe, Cu, or Zn).