Radiation Micro Research Articles

Reaction of Sb on In/Si(111) surfaces: Heteroepitaxial InSb(111) formation

Sb deposition and reaction on In/Si(111) were investigated by low-energy electron microscopy, low-energy electron diffraction, synchrotron radiation micro X-ray photoelectron spectroscopy and synchrotron radiation X-ray photo-emission electron microscopy. The Sb deposition process strongly depends on the initial In/Si(111) phases such as √3×√3, √31×√31 and 4×1. On the In/Si(111) surface where two phases co-exist, the diffusion of In atoms, which are released by the attack of Sb, modifies the deposition and reaction process of Sb. On a mixed In/Si(111) √31×√31+4×1 surface, an InSb(111) 2×2 structure with elongated domains initially forms along steps. Then In atoms are replaced by Sb atoms and InSb(111) 2×2 transforms into Sb/Si(111) 2×1 by further reaction with Sb atoms. Here, the existence of the 4×1 phase promotes the formation of larger InSb(111) 2×2 domains.

Osteocyte lacunar properties in rat cortical bone: Differences between lamellar and central bone

Recently, the roles of osteocytes in bone maintenance have gained increasing attention. Osteocytes reside in lacunae that are interconnected by canaliculi resulting in a vast cellular network within the mineralized bone matrix. As the structure of the lacuno-canalicular network is highly connected to osteocyte function, osteocyte lacunar properties such as volume, shape, orientation, and density are now frequently reported in studies investigating osteocyte activity. Despite this increasing interest in lacunar morphometrics, many studies show a large spread in such values, suggesting a large inter-species but also inter-site variation in lacunar properties. Here, osteocyte lacunae in rat cortical bone have been studied using synchrotron radiation micro computed tomography (SR μCT) and backscattered electron (BE) microscopy. Quantitative lacunar geometric characteristics are reported based on the synchrotron radiation data, differentiating between circumferential lamellar bone and a central, more disordered bone type. From these studies, no significant differences were found in lacunar volumes between lamellar and central bone, whereas significant differences in lacunar orientation, shape and density values were observed. The 3D nature of the SR μCT data sets furthermore revealed that lacunae in central bone, which appear to be poorly aligned in transverse 2D cross sections, are in fact highly aligned along the bone long axis. These results demonstrate the importance of using 3D methods to investigate anisotropic biological materials such as bone and that the appropriate choice of subregions for high resolution imaging is not trivial.

Effects of low-intensity pulsed ultrasound on new trabecular bone during bone-tendon junction healing in a rabbit model: a synchrotron radiation micro-CT study.

This study was designed to evaluate the effects of low-intensity pulsed ultrasound on bone regeneration during the bone–tendon junction healing process and to explore the application of synchrotron radiation micro computed tomography in three dimensional visualization of the bone–tendon junction to evaluate the microarchitecture of new trabecular bone. Twenty four mature New Zealand rabbits underwent partial patellectomy to establish a bone–tendon junction injury model at the patella–patellar tendon complex. Animals were then divided into low-intensity pulsed ultrasound treatment (20 min/day, 7 times/week) and placebo control groups, and were euthanized at week 8 and 16 postoperatively (n = 6 for each group and time point). The patella–patellar tendon specimens were harvested for radiographic, histological and synchrotron radiation micro computed tomography detection. The area of the newly formed bone in the ultrasound group was significantly greater than that of control group at postoperative week 8 and 16. The high resolution three dimensional visualization images of the bone–tendon junction were acquired by synchrotron radiation micro computed tomography. Low-intensity pulsed ultrasound treatment promoted dense and irregular woven bone formation at week 8 with greater bone volume fraction, number and thickness of new trabecular bone but with lower separation. At week 16, ultrasound group specimens contained mature lamellar bone with higher bone volume fraction and thicker trabeculae than that of control group; however, there was no significant difference in separation and number of the new trabecular bone. This study confirms that low-intensity pulsed ultrasound treatment is able to promot bone formation and remodeling of new trabecular bone during the bone–tendon junction healing process in a rabbit model, and the synchrotron radiation micro computed tomography could be applied for three dimensional visualization to quantitatively evaluate the microarchitecture of new bone in bone–tendon junction.

Probing droplets with biological colloidal suspensions on smart surfaces by synchrotron radiation micro- and nano-beams

Droplets with colloidal biological suspensions evaporating on substrates with defined wetting properties generate confined environments for initiating aggregation and self-assembly processes. We describe smart micro- and nanostructured surfaces, optimized for probing single droplets and residues by synchrotron radiation micro- and nanobeam diffraction techniques. Applications are presented for Ac-IVD and β-amyloid (1–42) peptides capable of forming cross-β sheet structures. Complementary synchrotron radiation FTIR microspectroscopy addresses secondary structure formation. The high synchrotron radiation source brilliance enables fast raster-scan experiments.

Study of the distribution of actinides in human tissues using synchrotron radiation micro X-ray fluorescence spectrometry.

This study aims at evaluating the capabilities of synchrotron radiation micro X-ray fluorescence spectrometry (SR micro-XRF) for qualitative and semi-quantitative elemental mapping of the distribution of actinides in human tissues originating from individuals with documented occupational exposure. The investigated lymph node tissues were provided by the United States Transuranium and Uranium Registries (USTUR) and were analyzed following appropriate sample pre-treatment. Semi-quantitative results were obtained via calibration by external standards and demonstrated that the uranium concentration level in the detected actinide hot spots reaches more than 100 μg/g. For the plutonium hot spots, concentration levels up to 31 μg/g were found. As illustrated by this case study on these unique samples, SR micro-XRF has a high potential for this type of elemental bio-imaging owing to its high sensitivity, high spatial resolution, and non-destructive character.

Characterization of zinc and calcium spatial distribution at the fibrocartilage of rabbit patella-patellar tendon complex: A synchrotron radiation micro X-ray fluorescence study

Characterization of zinc and calcium spatial distribution at the fibrocartilage of rabbit patella-patellar tendon complex: A synchrotron radiation micro X-ray fluorescence study

Distribution of selected elements in calcific human aortic valves studied by microscopy combined with SR-μXRF: Influence of lipids on progression of calcification

Calcified heart valves display a significant imbalance in tissue content of trace and essential elements. The valvular calcification is an age-related process and there are data suggesting involvement of lipids. We studied elemental composition and lipid distribution in three distinct regions of calcified human aortic valves, representing successive stages of the calcific degeneration: normal, thickened (early lesion) and calcified (late lesion), using SR-μXRF (Synchrotron Radiation Micro X-Ray Fluorescence) for elemental composition and Oil Red O (ORO) staining for demonstration of lipids. Two-dimensional SR-μXRF maps and precise point spectra were compared with histological stainings on consecutive valve sections to prove topographical localization and colocalization of the examined elements and lipids. In calcified valve areas, accumulation of calcium and phosphorus was accompanied by enhanced concentrations of strontium and zinc. Calcifications preferentially developed in lipid-rich areas of the valves. Calcium concentration ratio between lipid-rich and lipid-free areas was not age-dependent in early lesions, but showed a significant increase with age in late lesions, indicating age-dependent intensification of lipid involvement in calcification process. The results suggest that mechanisms of calcification change with progression of valve degeneration and with age.

Trabecular microfractures in the femoral head with osteoporosis: Analysis of microcallus formations by synchrotron radiation micro CT

Trabecular bone microfracture pathogenesis and associated healing processes are not well understood. We analyzed the microcalluses that form subsequent to microfractures in patients with osteoporosis (OP) using synchrotron radiation micro CT (SRCT).Subchondral bone columns were extracted from the femoral heads of 11 female patients with a femoral neck fracture. SRCT scanning was performed with 5.9×5.9×5.9μm3 voxel size and the microcallus number was measured in a 5-mm cubic subchondral bone region. The trabecular bone microstructure was measured and its relationship to the microcallus number was analyzed. In addition, the degree of mineralization of the microcallus region and that of the rest of the trabecular bone were measured and compared.Microcallus formations were detected in all cases, with a mean microcallus number of 4.9 (range, 2–11). The microcallus number had a significantly negative correlation with bone volume fraction (BV/TV), trabecular thickness (Tb.Th), and degree of mineralization, and had a positive correlation with specific bone surface (BS/BV). The degree of mineralization of the microcallus region was lower than that of the rest of the trabecular bone and had a wider range of values.Microcallus formations were frequently detected in patients with OP, and more prevalent in the bone with thinner trabeculae, suggesting microfractures might occur due to activities of daily living as the OP progresses. The degree of mineralization of microcallus might represent the process of bone healing from immature woven bone to mature trabecular bone.

Amyloid β Peptide Conformational Changes in the Presence of a Lipid Membrane System

Here we are presenting a comparative analysis of conformational changes of two amyloid β peptides, Aβ(25-35) and Aβ(1-42), in the presence and absence of a phospholipid system, namely, POPC/POPS (1-palmitoyl-2-oleoylphospatidylcholine/palmitoyl-2-oleoylphospatidylserine), through Raman spectroscopy, synchrotron radiation micro Fourier-transform infrared spectroscopy, and micro X-ray diffraction. Ringlike samples were obtained from the evaporation of pure and mixed solutions of the proteins together with the POPC/POPS system on highly hydrophilic substrates. The results confirm the presence of a α-helical to β-sheet transition from the internal rim of the ringlike samples to the external one in the pure Aβ(25-35) residual, probably due to the convective flow inside the droplets sitting on highly hydrophilic substrates enhancing the local concentration of the peptide at the external edge of the dried drop. In contrast, the presence of POPC/POPS lipids in the peptide does not result in α-helical structures and introduces the presence of antiparallel β-sheet material together with parallel β-sheet structures and possible β-turns. As a control, Aβ(1-42) peptide was also tested and shows β-sheet conformations independently from the presence of the lipid system. The μXRD analysis further confirmed these conclusions, showing how the absence of the phospholipid system induces in the Aβ(25-35) a probable composite α/β material while its coexistence with the peptide leads to a not oriented β-sheet conformation. These results open interesting scenarios on the study of conformational changes of Aβ peptides and could help, with further investigations, to better clarify the role of enzymes and alternative lipid systems involved in the amyloidosis process of Aβ fragments.

English

Synchrotron radiation micro-computed tomography (SR micro-CT), considered superior to standard polychromatic micro-CT techniques, was used to assess the densities of bovine enamel white-spot lesions (WSL) treated in a 10-day pH cycling model with either: (A) Clinpro Tooth Crème (0.21% NaF plus TCP), (B) Clinpro 5000 (1.1% NaF plus TCP) or (C) Tom’s of Maine (0% NaF) dentifrice. Each day consisted of four 2 min treatments, one 4 h acid challenge (pH=5.0), and immersion in artificial saliva (pH=7.0) between these events. After 10 days, WSL specimens were evaluated for lesion depth using confocal microscopy and lesion density using SR micro-CT with depths ranging from 2.76 to 113.16 μm, in 2.76 μm slice increments. Statistical analyses (Student’s t-test) were performed at the 95% confidence level. SR micro-CT analyses revealed the NaF plus TCP dentifrices improved WSL densities relative to the fluoride-free toothpaste, and is consistent with an earlier study utilizing polychromatic micro-CT. In contrast to previous findings, SR micro-CT analyses also revealed significant differences in WSL densities treated with the two NaF dentifrices at enamel depths of 13.80, 16.56, and 19.32 μm. These findings suggest SR micro-CT may be especially suited for detecting density differences in lesions sensitive to fluoride-driven remineralization processes. Key words: Toothpaste, synchrotron radiation micro computed tomography (SR micro-CT), density, remineralization, fluoride, monochromatized X-ray beams, X-ray linear attenuation coefficient (X-ray LAC).

Strontium ranelate increases the formation of bone-like mineralized nodules in osteoblast cell cultures and leads to Sr incorporation into the intact nodules

We describe effects of strontium ranelate treatment on intact mineralized nodules produced in osteoblast cell cultures. We analyzed the matrix directly at the cell culture surfaces following treatment with 0.05 and 0.5 mM Sr(2+). This method allowed for data to be obtained from intact nodules, rather than from extracted samples. The bone-like nature of the matrix was evaluated by using attenuated total reflection Fourier transform infrared spectroscopy and the incorporation of Sr into the nodules was investigated by using both energy dispersive X-ray spectroscopy and synchrotron radiation micro X-ray fluorescence. We observed typical mineralized nodules in all of the cell cultures. However, the formation of these nodules was markedly increased in cultures treated with 0.5 mM Sr(2+). In all of the cultures, the nature of the intact matrix was similar to that described in native bone tissue, being comprised of a poorly crystalline CO3 (2-)-containing apatite and a collagenous matrix. This indicated that treatment had no deleterious effects on the matrix. Moreover, the nodules presented Ca and P as the main chemical components, confirming their bone-like mineralized nature. The incorporation of Sr into the nodules was clearly observed in the treated cultures, with their relative Sr content [Sr/(Ca+Sr) ratio] being markedly increased in a dose-dependent manner. Thus, strontium ranelate promoted an increase in the formation of mineralized nodules in osteoblast cell cultures while preserving the bone-like nature of the matrix at the tissue level. We further demonstrated that Sr was incorporated into the intact nodules formed during treatment.

Strontium Is Incorporated in Different Levels into Bones and Teeth of Rats Treated with Strontium Ranelate

The aim of this study was to evaluate the strontium incorporation into specific bones and teeth of rats treated with strontium ranelate. The relative strontium levels [Sr/(Ca + Sr) ratio] were obtained by synchrotron radiation micro X-ray fluorescence. The incisor teeth were further examined by energy dispersive X-ray spectroscopy (EDS) in a scanning electron microscope. The isolated mineral phase was investigated by EDS in a transmission electron microscope and X-ray diffraction. The strontium content was markedly increased in animals treated with strontium ranelate, with different incorporation levels found among specific bones, regions within the same bone and teeth. The highest strontium levels were observed in the iliac crest, mandible and calvaria, while the lowest were observed in the femoral diaphysis, lumbar vertebrae, rib and alveolar bone. The strontium content was higher in the femoral neck than in the diaphysis. The strontium levels also varied within the alveolar bone. High levels of strontium were found in the incisor tooth, with values similar to those in the iliac crest. Strontium was observed in both enamel and dentin. The strontium content of the molar tooth was negligible. Strontium was incorporated into the mineral substance, with up to one strontium replacing one out of 10 calcium ions within the apatite crystal lattice. The mineral from treated animals presented increased lattice parameters, which might be associated to their bone strontium contents. In conclusion, the incorporation of strontium occurred in different levels into distinct bones, regions within the same bone and teeth of rats treated with strontium ranelate.

Spatial distribution of tissue level properties in a human femoral cortical bone

The mechanical properties of cortical bone are determined by a combination bone tissue composition, and structure at several hierarchical length scales. In this study the spatial distribution of tissue level properties within a human femoral shaft has been investigated. Cylindrically shaped samples (diameter: 4.4mm, N=56) were prepared from cortical regions along the entire length (20–85% of the total femur length), and around the periphery (anterior, medial, posterior and lateral quadrants). The samples were analyzed using scanning acoustic microscopy (SAM) at 50MHz and synchrotron radiation micro computed tomography (SRμCT). For all samples the average cortical porosity (Ct.Po), tissue elastic coefficients (cij) and the average tissue degree of mineralization (DMB) were determined. The smallest coefficient of variation was observed for DMB (1.8%), followed by BV/TV (5.4%), cij (8.2–45.5%), and Ct.Po (47.5%). Different variations with respect to the anatomical position were found for DMB, Ct.Po and cij. These data address the anatomical variations in anisotropic elastic properties and link them to tissue mineralization and porosity, which are important input parameters for numerical multi-scale bone models.

The distribution profile and oxidation states of biometals in APP transgenic mouse brain: dyshomeostasis with age and as a function of the development of Alzheimer's disease

The enrichment of transition metals in the brain and the dyshomeostasis of metals are thought to be important etiological factors for elderly people in a number of neurodegenerative diseases, including Alzheimer's disease (AD). However, the understanding of how biometals dynamically dysregulate in the stages of AD development, such as the exact time-dependent and site-dependent accumulation in the brain with AD progression, is still limited. Herein, by using the APP/V717I transgenic mouse model and age-matched mice as control, we offer distinctive in situ and quantitative images of metals (Cu, Fe, Zn and Ca) in brain sections by synchrotron radiation micro beam X-ray fluorescence (SR-μXRF). The images show that Fe and Ca increased with brain aging in both AD and control (CNT) mice, and Cu, Fe, Zn and Ca appeared significantly elevated in AD mice and showed an obvious age-dependent rise. Fe, Cu and Zn were obviously specifically enriched in the cortex and hippocampus, which were also the plaque-formation sensitive brain regions. Our results demonstrate that the enrichment of transition metals with age and metals' dyshomeostasis in specific regions may contribute together to the etiology and development of AD in elderly people. The XANES measurements of Cu and Fe show evidence that Cu may have redox properties in the AD brain.

Effects of vitamin K on the morphometric and material properties of bone in the tibiae of growing rats

Suboptimal vitamin K nutriture is evident during rapid growth. We aimed to determine whether vitamin K2 (menaquinone-4 [MK-4]) supplementation is beneficial to bone structure and intrinsic bone tissue properties in growing rats. Male Wistar rats (5 weeks old) were assigned to either a control diet (n = 8) or an MK-4–supplemented diet (22 mg d−1 kg−1 body weight, n = 8). After a 9-week feeding period, we determined the serum concentration ratio of undercarboxylated osteocalcin to γ-carboxylated osteocalcin and the urinary deoxypyridinoline level. All rats were then euthanized, and their tibiae were analyzed by micro–computed tomography for trabecular architecture and synchrotron radiation micro–computed tomography for cortical pore structure and mineralization. Fourier transform infrared microspectroscopy and a nanoindentation test were performed on the cortical midlayers of the anterior and posterior cortices to assess bone tissue properties. Neither body weight nor tibia length differed significantly between the 2 groups. Dietary MK-4 supplementation decreased the ratio of undercarboxylated osteocalcin to γ-carboxylated osteocalcin but did not affect deoxypyridinoline, indicating a positive effect on bone formation but not bone resorption. Trabecular volume fraction and thickness were increased by MK-4 (P < .05). Neither the cortical pore structure nor mineralization was affected by MK-4. On the other hand, MK-4 increased mineral crystallinity, collagen maturity, and hardness in both the anterior and posterior cortices (P < .05). These data indicate the potential benefit of MK-4 supplementation during growth in terms of enhancing bone quality.

Plant Cell Nucleolus as a Hot Spot for Iron

Many central metabolic processes require iron as a cofactor and take place in specific subcellular compartments such as the mitochondrion or the chloroplast. Proper iron allocation in the different organelles is thus critical to maintain cell function and integrity. To study the dynamics of iron distribution in plant cells, we have sought to identify the different intracellular iron pools by combining three complementary imaging approaches, histochemistry, micro particle-induced x-ray emission, and synchrotron radiation micro X-ray fluorescence. Pea (Pisum sativum) embryo was used as a model in this study because of its large cell size and high iron content. Histochemical staining with ferrocyanide and diaminobenzidine (Perls/diaminobenzidine) strongly labeled a unique structure in each cell, which co-labeled with the DNA fluorescent stain DAPI, thus corresponding to the nucleus. The unexpected presence of iron in the nucleus was confirmed by elemental imaging using micro particle-induced x-ray emission. X-ray fluorescence on cryo-sectioned embryos further established that, quantitatively, the iron concentration found in the nucleus was higher than in the expected iron-rich organelles such as plastids or vacuoles. Moreover, within the nucleus, iron was particularly accumulated in a subcompartment that was identified as the nucleolus as it was shown to transiently disassemble during cell division. Taken together, our data uncover an as yet unidentified although abundant iron pool in the cell, which is located in the nuclei of healthy, actively dividing plant tissues. This result paves the way for the discovery of a novel cellular function for iron related to nucleus/nucleolus-associated processes.

OS0509 放射光μCTを用いた高強度鋼の転動疲労下のき裂検出(OS5-2 き裂進展・計測,OS-5 材料の疲労挙動と損傷評価1)

In the present study, synchrotron radiation micro computed tomography (SR μCT) imaging of SPring-8 was applied to the observation of delamination defects in high-strength steels under rolling contact fatigue. The rolling contact fatigue crack initiation occurs under surface and these defects propagate to the surface. The conventional technique, such as optical microscope and scanning microscope, cannot give us the crack initiation and growth behavior under the surface. Therefore, the shape of rolling contact fatigue defects was observed by SR μCT imaging. The specimen with an artificial defect, which simulates an inclusion, was used to the contact rolling fatigue tests. The broken and non-broken specimens were observed respectively by SR μCT. The delamination defects and cracks can be detected from the artificial defetct. It is found from these results that the defect initiation and propagation behavior in the rolling contact fatigue process can be discussed from the measurements by SR μCT imaging. The number of crack, location and size of crack obtained by the CT imaging coincide with those by polishing and SEM measurements. It is found from these results that the defect initiation and propagation behavior in the rolling contact fatigue process can be discussed from the measurements by SR μCT imaging.

Observation of Fatigue Crack Propagation Behavior under Torsional Loading by Using Synchrotron Radiation Micro-CT Imaging

In the present study, synchrotron radiation micro computed tomography (SR CT) imaging of SPring-8 was applied to the observation of the torsion fatigue crack propagation behavior. The transition of crack propagation from Mode II to I occurs under torsion fatigue. The conventional technique, such as optical microscope and scanning microscope, cannot give us the crack growth behavior under the surface. Therefore, the transition of crack propagation could not be discussed in detail. The compact torsion fatigue-testing machine was developed for fatigue testing at SPring-8, and thetorsion fatigue tests and measurements of SR micro-CT were carried out alternately. The shape of torsion fatigue cracks could be evaluated quantitatively and nondestructively. Transition of crack propagation from Mode II to Mode I under the surface could be observed. The condition of transition of crack propagation was discussed by using three-dimensional shape of cracks.

Study of Lead Level During Pregnancy by Application of Synchrotron Radiation Micro XRF

In order to study the daily Pb absorption in fetus and to monitor the main Pb sources in prenatal fetus, we have investigated several cases of Pb distribution along the longitudinal axis of fetal hair. The changes of Pb levels in the pregnancy period, even the daily changes of Pb levels can be detected in the hair. Therefore, by analyzing the Pb distribution curves in the fetal hair and the living habits of their mothers, the main sources of Pb in the prenatal fetus can be evaluated. In our study, the main sources of Pb in the two cases of prenatal fetus studied here should be from the polluted aquatics.

Observation of crack propagation under torsion fatigue tests by synchrotron radiation [formula omitted] imaging

In the present study, synchrotron radiation micro computed tomography (SR μCT) imaging of SPring-8 was applied to the observation of the torsion fatigue crack propagation behavior. The transition of crack propagation from Mode II to I occurs under torsion fatigue. The conventional technique, such as optical microscope and scanning microscope, cannot give us the crack growth behavior under the surface. Therefore, the transition of crack propagation could not be discussed in detail. The compact torsion fatigue-testing machine was developed for fatigue testing at SPring-8, and the torsion fatigue tests and measurements of SR micro-CT were carried out alternately. The shape of torsion fatigue cracks could be evaluated quantitatively and nondestructively. Transition of crack propagation from Mode II to Mode I under the surface could be observed. The condition of transition of crack propagation was discussed by using three-dimensional shape of cracks.