Prodromal neuroinflammatory, cholinergic and metabolite dysfunction detected by PET and MRS in the TgF344-AD transgenic rat model of AD: a collaborative multi-modal study.

Mouse models of Alzheimer's disease (AD) are valuable but do not fully recapitulate human AD pathology, such as spontaneous Tau fibril accumulation and neuronal loss, necessitating the development of new AD models. The transgenic (TG) TgF344-AD rat has been reported to develop age-dependent AD features including neuronal loss and neurofibrillary tangles, despite only expressing APP and PSEN1 mutations, suggesting an improved modelling of AD hallmarks. Alterations in neuronal networks as well as learning performance and cognition tasks have been reported in this model, but none have combined a longitudinal, multimodal approach across multiple centres, which mimics the approaches commonly taken in clinical studies. We therefore aimed to further characterise the progression of AD-like pathology and cognition in the TgF344-AD rat from young-adults (6 months (m)) to mid- (12 m) and advanced-stage (18 m, 25 m) of the disease. Methods: TgF344-AD rats and wild-type (WT) littermates were imaged at 6 m, 12 m and 18 m with [18F]DPA-714 (TSPO, neuroinflammation), [18F]Florbetaben (Aß) and [18F]ASEM (α7-nicotinic acetylcholine receptor) and with magnetic resonance spectroscopy (MRS) and with (S)-[18F]THK5117 (Tau) at 15 and 25 m. Behaviour tests were also performed at 6 m, 12 m and 18 m. Immunohistochemistry (CD11b, GFAP, Aß, NeuN, NeuroChrom) and Tau (S)-[18F]THK5117 autoradiography, immunohistochemistry and Western blot were also performed. Results: [18F]DPA-714 positron emission tomography (PET) showed an increase in neuroinflammation in TG vs wildtype animals from 12 m in the hippocampus (+11%), and at the advanced-stage AD in the hippocampus (+12%), the thalamus (+11%) and frontal cortex (+14%). This finding coincided with strong increases in brain microgliosis (CD11b) and astrogliosis (GFAP) at these time-points as assessed by immunohistochemistry. In vivo [18F]ASEM PET revealed an age-dependent increase uptake in the striatum and pallidum/nucleus basalis of Meynert in WT only, similar to that observed with this tracer in humans, resulting in TG being significantly lower than WT by 18 m. In vivo [18F]Florbetaben PET scanning detected Aß accumulation at 18 m, and (S)-[18F]THK5117 PET revealed subsequent Tau accumulation at 25m in hippocampal and cortical regions. Aß plaques were low but detectable by immunohistochemistry from 6 m, increasing further at 12 and 18 m with Tau-positive neurons adjacent to Aß plaques at 18 m. NeuroChrom (a pan neuronal marker) immunohistochemistry revealed a loss of neuronal staining at the Aß plaques locations, while NeuN labelling revealed an age-dependent decrease in hippocampal neuron number in both genotypes. Behavioural assessment using the novel object recognition task revealed that both WT & TgF344-AD animals discriminated the novel from familiar object at 3 m and 6 m of age. However, low levels of exploration observed in both genotypes at later time-points resulted in neither genotype successfully completing the task. Deficits in social interaction were only observed at 3 m in the TgF344-AD animals. By in vivo MRS, we showed a decrease in neuronal marker N-acetyl-aspartate in the hippocampus at 18 m (-18% vs age-matched WT, and -31% vs 6 m TG) and increased Taurine in the cortex of TG (+35% vs age-matched WT, and +55% vs 6 m TG). Conclusions: This multi-centre multi-modal study demonstrates, for the first time, alterations in brain metabolites, cholinergic receptors and neuroinflammation in vivo in this model, validated by robust ex vivo approaches. Our data confirm that, unlike mouse models, the TgF344-AD express Tau pathology that can be detected via PET, albeit later than by ex vivo techniques, and is a useful model to assess and longitudinally monitor early neurotransmission dysfunction and neuroinflammation in AD.

Investigation of the effect of taurine supplementation on muscle taurine content in the mdx mouse model of Duchenne muscular dystrophy using chemically specific synchrotron imaging.

Duchenne muscular dystrophy (DMD) is a lethal genetic muscle wasting disorder, which currently has no cure. Supplementation with the drug taurine has been shown to offer therapeutic benefit in the mdx model for DMD, however the mechanism by which taurine protects dystrophic muscle is not fully understood. Mdx muscle is deficient in taurine, however it is not known if this deficiency occurs in the extracellular space, in other cells present in the tissue (such as immune cells) or in the myofibre itself. Likewise, the tissue location of taurine enrichment in taurine treated mdx muscle is not known. In this study we applied X-ray absorption near edge spectroscopy (XANES) at the sulfur K-edge in an imaging format to determine taurine distribution in muscle tissue. XANES is the only technique currently capable of imaging taurine directly in muscle tissue, at a spatial resolution approaching myocyte cell size (20-50 µm). Using a multi-modal approach of XANES imaging and histology on the same tissue sections, we show that in mdx muscle, it is the myofibres that are deficient in taurine, and taurine supplementation ameliorates this deficiency. Increasing the taurine content of mdx myofibres was associated with a decrease in myofibre damage (as shown by the percentage of intact myofibres) and inflammation. These data will help drive future studies to better elucidate the molecular mechanisms through which taurine protects dystrophic muscle; they also support the continued investigation of taurine as a therapeutic intervention for DMD.

Seasonal Zinc Storage and a Strategy for Its Use in Buds of Fruit Trees.

Bud dormancy allows deciduous perennial plants to rapidly grow following seasonal cold conditions. Although many studies have examined the hormonal regulation of bud growth, the role of nutrients remains unclear. Insufficient accumulation of the key micronutrient zinc (Zn) in dormant buds affects the vegetative and reproductive growth of perennial plants during the subsequent year, requiring the application of Zn fertilizers in orchard management to avoid growth defects in fruit trees. However, the mechanisms of seasonal Zn homeostasis in perennial plants remain poorly understood. Here, we provide new insights into Zn distribution and speciation within reproductive and vegetative buds of apple (Malus domestica) and four other deciduous fruit trees (peach [Amygdalus persica], grape [Vitis vinifera], pistachio [Pistacia vera], and blueberry [Vaccinium spp.]) using microscopic and spectroscopic characterization techniques comprising synchrotron-based x-ray fluorescence and x-ray absorption near-edge-structure analyses. By establishing a link between bud development and Zn distribution, we identified the following important steps of Zn storage and use in deciduous plants: Zn is preferentially deposited in the stem nodes subtending apical and axillary buds; Zn may then be sequestered as Zn-phytate prior to dormancy; in spring, Zn effectively releases for use during budbreak and subsequent meristematic growth. The mechanisms of Zn homeostasis during the seasonal cycles of plant growth and dormancy described here will contribute to improving orchard management, and to selection and breeding of deciduous perennial species.

Redox Fluctuations and Organic Complexation Govern Uranium Redistribution from U(IV)-Phosphate Minerals in a Mining-Polluted Wetland Soil, Brittany, France.

Wetlands have been proposed to naturally attenuate U transfers in the environment via U complexation by organic matter and potential U reduction. However, U mobility may depend on the identity of particulate/dissolved uranium source materials and their redox sensitivity. Here, we examined the fate of uranium in a highly contaminated wetland (up to 4500 mg·kg-1 U) impacted by former mine water discharges. Bulk U LIII-EXAFS and (micro-)XANES combined with SEM-EDXS analyses of undisturbed soil cores show a sharp U redox boundary at the water table, together with a major U redistribution from U(IV)-minerals to U(VI)-organic matter complexes. Above the water table, U is fully oxidized into mono- and bidentate U(VI)-carboxyl and monodentate U(VI)-phosphoryl complexes. Minute amounts of U(VI)-phosphate minerals are also observed. Below the water table, U is fully reduced and is partitioned between U(IV)-phosphate minerals (i.e., ningyoite and a lermontovite-like phase), and bidentate U(IV)-phosphoryl and monodentate U(IV)-carboxyl complexes. Such a U redistribution from U-minerals inherited from mine water discharge deposits could result from redox cycling nearby the water table fluctuation zone. Oxidative dissolution of U(IV)-phosphate minerals could have led to U(VI)-organic matter complexation, followed by subsequent reduction into U(IV)-organic complexes. However, uranium(IV) minerals could have been preserved in permanently waterlogged soil.

Mineral density volume gradients in normal and diseased human tissues.

Clinical computed tomography provides a single mineral density (MD) value for heterogeneous calcified tissues containing early and late stage pathologic formations. The novel aspect of this study is that, it extends current quantitative methods of mapping mineral density gradients to three dimensions, discretizes early and late mineralized stages, identifies elemental distribution in discretized volumes, and correlates measured MD with respective calcium (Ca) to phosphorus (P) and Ca to zinc (Zn) elemental ratios. To accomplish this, MD variations identified using polychromatic radiation from a high resolution micro-computed tomography (micro-CT) benchtop unit were correlated with elemental mapping obtained from a microprobe X-ray fluorescence (XRF) using synchrotron monochromatic radiation. Digital segmentation of tomograms from normal and diseased tissues (N=5 per group; 40-60 year old males) contained significant mineral density variations (enamel: 2820-3095 mg/cc, bone: 570-1415 mg/cc, cementum: 1240-1340 mg/cc, dentin: 1480-1590 mg/cc, cementum affected by periodontitis: 1100-1220 mg/cc, hypomineralized carious dentin: 345-1450 mg/cc, hypermineralized carious dentin: 1815-2740 mg/cc, and dental calculus: 1290-1770 mg/cc). A plausible linear correlation between segmented MD volumes and elemental ratios within these volumes was established, and Ca/P ratios for dentin (1.49), hypomineralized dentin (0.32-0.46), cementum (1.51), and bone (1.68) were observed. Furthermore, varying Ca/Zn ratios were distinguished in adapted compared to normal tissues, such as in bone (855-2765) and in cementum (595-990), highlighting Zn as an influential element in prompting observed adaptive properties. Hence, results provide insights on mineral density gradients with elemental concentrations and elemental footprints that in turn could aid in elucidating mechanistic processes for pathologic formations.

Multiscale Speciation of U and Pu at Chernobyl, Hanford, Los Alamos, McGuire AFB, Mayak, and Rocky Flats.

The speciation of U and Pu in soil and concrete from Rocky Flats and in particles from soils from Chernobyl, Hanford, Los Alamos, and McGuire Air Force Base and bottom sediments from Mayak was determined by a combination of X-ray absorption fine structure (XAFS) spectroscopy and X-ray fluorescence (XRF) element maps. These experiments identify four types of speciation that sometimes may and other times do not exhibit an association with the source terms and histories of these samples: relatively well ordered PuO2+x and UO2+x that had equilibrated with O2 and H2O under both ambient conditions and in fires or explosions; instances of small, isolated particles of U as UO2+x, U3O8, and U(VI) species coexisting in close proximity after decades in the environment; alteration phases of uranyl with other elements including ones that would not have come from soils; and mononuclear Pu-O species and novel PuO2+x-type compounds incorporating additional elements that may have occurred because the Pu was exposed to extreme chemical conditions such as acidic solutions released directly into soil or concrete. Our results therefore directly demonstrate instances of novel complexity in the Å and µm-scale chemical speciation and reactivity of U and Pu in their initial formation and after environmental exposure as well as occasions of unexpected behavior in the reaction pathways over short geological but significant sociological times. They also show that incorporating the actual disposal and site conditions and resultant novel materials such as those reported here may be necessary to develop the most accurate predictive models for Pu and U in the environment.

The plastic nature of the human bone-periodontal ligament-tooth fibrous joint.

This study investigates bony protrusions within a narrowed periodontal ligament space (PDL-space) of a human bone-PDL-tooth fibrous joint by mapping structural, biochemical, and mechanical heterogeneity. Higher resolution structural characterization was achieved via complementary atomic force microscopy (AFM), nano-transmission X-ray microscopy (nano-TXM), and microtomography (MicroXCT™). Structural heterogeneity was correlated to biochemical and elemental composition, illustrated via histochemistry and microprobe X-ray fluorescence analysis (µ-XRF), and mechanical heterogeneity evaluated by AFM-based nanoindentation. Results demonstrated that the narrowed PDL-space was due to invasion of bundle bone (BB) into PDL-space. Protruded BB had a wider range with higher elastic modulus values (2-8GPa) compared to lamellar bone (0.8-6GPa), and increased quantities of Ca, P and Zn as revealed by µ-XRF. Interestingly, the hygroscopic 10-30µm interface between protruded BB and lamellar bone exhibited higher X-ray attenuation similar to cement lines and lamellae within bone. Localization of the small leucine rich proteoglycan biglycan (BGN) responsible for mineralization was observed at the PDL-bone interface and around the osteocyte lacunae. Based on these results, it can be argued that the LB-BB interface was the original site of PDL attachment, and that the genesis of protruded BB identified as protrusions occurred as a result of shift in strain. We emphasize the importance of bony protrusions within the context of organ function and that additional study is warranted.

Uranium(VI) interactions with mackinawite in the presence and absence of bicarbonate and oxygen.

Mackinawite, Fe(II)S, samples loaded with uranium (10(-5), 10(-4), and 10(-3) mol U/g FeS) at pH 5, 7, and 9, were characterized using X-ray absorption spectroscopy and X-ray diffraction to determine the effects of pH, bicarbonate, and oxidation on uptake. Under anoxic conditions, a 5 g/L suspension of mackinawite lowered 5 × 10(-5) M uranium(VI) to below 30 ppb (1.26 × 10(-7) M) U. Between 82 and 88% of the uranium removed from solution by mackinawite was U(IV) and was nearly completely reduced to U(IV) when 0.012 M bicarbonate was added. Near-neighbor coordination consisting of uranium-oxygen and uranium-uranium distances indicates the formation of uraninite in the presence and absence of bicarbonate, suggesting reductive precipitation as the dominant removal mechanism. Following equilibration in air, mackinawite was oxidized to mainly goethite and sulfur and about 76% of U(IV) was reoxidized to U(VI) with coordination of uranium to axial and equatorial oxygen, similar to uranyl. Additionally, uranium-iron distances, typical of coprecipitation of uranium with iron oxides, and uranium-sulfur distances indicating bidentate coordination of U(VI) to sulfate were evident. The affinity of mackinawite and its oxidation products for U(VI) provides impetus for further study of mackinawite as a potential reactive medium for remediation of uranium-contaminated water.

Imaging translocation and transformation of bioavailable selenium by Stanleya pinnata with X-ray microscopy.

Selenium hyperaccumulator Stanleya pinnata, Colorado ecotype, was supplied with water-soluble and biologically available selenate or selenite. Selenium distribution and tissue speciation were established using X-ray microscopy (micro-X-ray fluorescence and transmission X-ray microscopy) in two dimensions and three dimensions. The results indicate that S. pinnata tolerates, accumulates, and volatilizes significant concentrations of selenium when the inorganic form supplied is selenite and may possess novel metabolic capacity to differentiate, metabolize, and detoxify selenite concentrations surpassing field concentrations. The results also indicate that S. pinnata is a feasible candidate to detoxify selenium-polluted soil sites, especially locations with topsoil polluted with soluble and biologically available selenite.

A bacterium that can grow by using arsenic instead of phosphorus.

Life is mostly composed of the elements carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus. Although these six elements make up nucleic acids, proteins, and lipids and thus the bulk of living matter, it is theoretically possible that some other elements in the periodic table could serve the same functions. Here, we describe a bacterium, strain GFAJ-1 of the Halomonadaceae, isolated from Mono Lake, California, that is able to substitute arsenic for phosphorus to sustain its growth. Our data show evidence for arsenate in macromolecules that normally contain phosphate, most notably nucleic acids and proteins. Exchange of one of the major bio-elements may have profound evolutionary and geochemical importance.

Tracing copper-thiomolybdate complexes in a prospective treatment for Wilson's disease.

Wilson's disease is a human genetic disorder which results in copper accumulation in liver and brain. Treatments such as copper chelation therapy or dietary supplementation with zinc can ameliorate the effects of the disease, but if left untreated, it results in hepatitis, neurological complications, and death. Tetrathiomolybdate (TTM) is a promising new treatment for Wilson's disease which has been demonstrated both in an animal model and in clinical trials. X-ray absorption spectroscopy suggests that TTM acts as a novel copper chelator, forming a complex with accumulated copper in liver. We have used X-ray absorption spectroscopy and X-ray fluorescence imaging to trace the molecular form and distribution of the complex in liver and kidney of an animal model of human Wilson's disease. Our work allows new insights into metabolism of the metal complex in the diseased state.

Uranium biomineralization as a result of bacterial phosphatase activity: insights from bacterial isolates from a contaminated subsurface.

Uranium contamination is an environmental concern at the Department of Energy's Field Research Center in Oak Ridge, Tennessee. In this study, we investigated whether phosphate biomineralization, or the aerobic precipitation of U(VI)-phosphate phases facilitated by the enzymatic activities of microorganisms, offers an alternative to the more extensively studied anaerobic U(VI) bioreduction. Three heterotrophic bacteria isolated from FRC soils were studied for their ability to grow and liberate phosphate in the presence of U(VI) and an organophosphate between pH 4.5 and 7.0. The objectives were to determine whether the strains hydrolyzed sufficient phosphate to precipitate uranium, to determine whether low pH might have an effect on U(VI) precipitation, and to identify the uranium solid phase formed during biomineralization. Two bacterial strains hydrolyzed sufficient organophosphate to precipitate 7395% total uranium after 120 h of incubation in simulated groundwater. The highest rates of uranium precipitation and phosphatase activity were observed between pH 5.0 and 7.0. EXAFS spectra identified the uranyl phosphate precipitate as an autunite/meta-autunite group mineral. The results of this study indicate that aerobic heterotrophic bacteria within a uranium-contaminated environment that can hydrolyze organophosphate, especially in low pH conditions, may play an important role in the bioremediation of uranium.