Systemically transplanted bone marrow stromal cells contributing to bone tissue regeneration

Bone marrow stromal cells (BMSCs) are a rich source of osteogenic progenitor cells. A fundamental question is whether systemically transplanted BMSCs participate in bone regeneration. Luciferase and GFP double-labeled BMSCs were transplanted into irradiated mice. Five weeks after transplantation, artificial bone wounds were created in the mandibles and calvaria of the recipients. Animals were sacrificed at weeks 2, 4, and 6 after surgery and the expressions of luciferase and GFP were determined using Xenogen IVIS Imaging System, immunohistochemical staining and RT-PCR. The results demonstrated that transplanted BMSCs can be detected in wound sites as early as 2 weeks and lasted the whole experimental period. Luciferase expression peaked at 2 weeks after surgery and decreased thereafter, exhibiting a similar expression pattern as that of BSP, while GFP expression was relatively stable during the experimental period. In conclusion, BMSCs can migrate to bone wound sites and participate in bone regeneration in orocraniofacial region.

Phase stability and pressure dependence of defect formation in Gd2Ti2O7 and Gd2Zr2O7 pyrochlores

We report dramatically different behaviors between isostructural Gd2Ti2O7 and Gd2Zr2O7 pyrochlore at pressures up to 44 GPa, in which the substitution of Ti for Zr significantly increases structural stability. Upon release of pressure, the Gd2Ti2O7 becomes amorphous. In contrast, the high-pressure phase of Gd2Zr2O7 transforms to a disordered defect-fluorite structure. First-principle calculations for both compositions revealed that the response of pyrochlore to high pressure is controlled by the intrinsic energetics of defect formation.

Improving energy accumulation of microbial fuel cells by metabolism regulation using Rhodoferax ferrireducens as biocatalyst

AIMS

To study the physiology and metabolism of microbial cells in the performance of microbial fuel cells (MFCs).

METHODS AND RESULTS

A dual-chamber MFCs was constructed, and Rhodoferax ferrireducens was used as biocatalyst. To examine the physiology of microbial cells in the performance of MFCs, the anode media containing planktonic cells was replaced with fresh media in which KH(2)PO(4) and/or NH(4)Cl were excluded. The replacing of anode media containing planktonic cells with fresh media excluded of KH(2)PO(4) and NH(4)Cl made the coulombic yield remarkably increased by a factor of 68% (from 29.1 to 46.8C). The results showed that the electricity could be generated with cells in biofilms as biocatalyst, and coulombic yield was improved by limiting cell growth via removal of ingredients in anode media. By supplementation of glucose to the anode media when current declined to baseline, MFCs achieved about same platform current values immediately. MFCs could continue to produce electricity for about 30 h even after glucose was below detection.

CONCLUSIONS

Biofilms and metabolism of glucose play important roles in the performance of MFCs. Coulombic yield of MFCs could be improved by regulating the media ingredients using the stable biofilms-electrode system.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first attempt to study the effect of ingredient compositions of anode media on the performance of MFCs. The observed results that MFCs continued to produce electricity after glucose was below detection was helpful to better understand the mechanism of microbial electricity production.

Effect of Structure and Thermodynamic Stability on the Response of Lanthanide Stannate Pyrochlores to Ion Beam Irradiation

The lanthanide stannates, Ln2Sn2O7, Ln=La-Lu and Y, have the isometric pyrochlore structure, A2B2O7, and their structural properties have been refined by Rietveld analysis of powder neutron and synchrotron X-ray diffraction data. In this study, the enthalpies of formation of selected stannate pyrochlores, Ln=La, Nd, Sm, Eu, Dy, and Yb, were measured by high-temperature oxide melt solution calorimetry. Their radiation response was determined by 1 MeV Kr2+ ion irradiation combined with in situ TEM observation over the temperature range of 25 to 1000 K. The enthalpy of formation from binary oxides of stannate pyrochlores became more endothermic (from -145 to -40 kJ/mol) as the size of the lanthanide in the A-site decreases. A more exothermic trend of the enthalpy of formation was observed in stannate pyrochlores with larger lanthanide ions, particularly La, possibly as a result of increased covalency in the Sn-O bond. In contrast to lanthanide titanate pyrochlores, Ln2Ti2O7, that are generally susceptible to radiation-induced amorphization and zirconate pyrochlores, Ln2Zr2O7, that are generally resistant to radiation-induced amorphization, the lanthanide stannate pyrochlores show a much greater variation in their response to ion irradiation. La, Nd, and Gd stannates experience the radiation-induced transformation to the aperiodic state, and the critical amorphization temperatures are approximately 960, 700, and 350 K, respectively. Y and Er stannate pyrochlores cannot be amorphized by ion beam irradiation, even at 25 K, and instead disorder to a defect fluorite structure. Comparison of the calorimetric and ion irradiation data for titanate, zirconate, and stannate pyrochlores reveals a strong correlation among subtle changes in crystal structure with changing composition, the energetics of the disordering process, and the temperature above which the material can no longer be amorphized. In summary, as the structure approaches the ideal, ordered pyrochlore structure, radiation-induced amorphization is more easily attained. This is consistent with an increasingly exothermic trend in the enthalpies of formation of pyrochlores from the oxides, that is, the greater the thermochemical stability of the pyrochlore structure, the more likely it will be amorphized upon radiation damage rather than recover to a disordered fluorite structure.

Mapping of the prostate in endorectal coil-based MRI/MRSI and CT: A deformable registration and validation study

The endorectal coil is being increasingly used in magnetic resonance imaging (MRI) and MR spectroscopic imaging (MRSI) to obtain anatomic and metabolic images of the prostate with high signal-to-noise ratio (SNR). In practice, however, the use of endorectal probe inevitably distorts the prostate and other soft tissue organs, making the analysis and the use of the acquired image data in treatment planning difficult. The purpose of this work is to develop a deformable image registration algorithm to map the MRI/MRSI information obtained using an endorectal probe onto CT images and to verify the accuracy of the registration by phantom and patient studies. A mapping procedure involved using a thin plate spline (TPS) transformation was implemented to establish voxel-to-voxel correspondence between a reference image and a floating image with deformation. An elastic phantom with a number of implanted fiducial markers was designed for the validation of the quality of the registration. Radiographic images of the phantom were obtained before and after a series of intentionally introduced distortions. After mapping the distorted phantom to the original one, the displacements of the implanted markers were measured with respect to their ideal positions and the mean error was calculated. In patient studies, CT images of three prostate patients were acquired, followed by 3 Tesla (3 T) MR images with a rigid endorectal coil. Registration quality was estimated by the centroid position displacement and image coincidence index (CI). Phantom and patient studies show that TPS-based registration has achieved significantly higher accuracy than the previously reported method based on a rigid-body transformation and scaling. The technique should be useful to map the MR spectroscopic dataset acquired with ER probe onto the treatment planning CT dataset to guide radiotherapy planning.

Cortical potential imaging of brain electrical activity by means of parametric projection filter

OBJECTIVES

The objective of this study was to explore suitable spatial filters for inverse estimation of cortical potentials from the scalp electroencephalogram. The effect of incorporating noise covariance into inverse procedures was examined by computer simulations and tested in human experiment.

METHODS

The parametric projection filter, which allows inverse estimation with the presence of information on the noise, was applied to an inhomogeneous three-concentric-sphere model under various noise conditions in order to estimate the cortical potentials from the scalp potentials. The method for determining the optimum regularization parameter, which can be applied for parametric inverse techniques, is also discussed.

RESULTS

Human visual evoked potential experiment was carried out to examine the performance of the proposed restoration method. The parametric projection filter gave more localized inverse solution of cortical potential distribution than the truncated SVD and Tikhonov regularization.

CONCLUSION

The present simulation results suggest that incorporation of information on the noise covariance allows better estimation of cortical potentials, than inverse solutions without knowledge about the noise covariance, when the correlation between the signal and noise is low.

High-resolution spatio-temporal functional neuroimaging of brain activity

The past decades have shown extraordinary progress in our ability to noninvasively image the functions of the human brain. Of particular interest is the recent trend in combining information from electrophysiological and magnetic resonance imaging, which we termed eMRI, to achieve high-resolution functional neuroimaging in both space and time domains. In this article, we review the recent progress in high-resolution functional neuroimaging, in particular the multimodal integration of electroencephalography (EEG) and magnetic resonance imaging (MRI). The state-of-the-art EEG inverse solutions based on different brain electric source models and various approaches to integrate the information from MRI are reviewed. The remaining challenges, future trends, and potential applications of the high-resolution functional neuroimaging research are discussed.

Body surface Laplacian mapping of atrial depolarization in healthy human subjects

In the present study, we report body surface Laplacian mapping of atrial depolarization under sinus rhythm in 8 healthy male subjects. For each subject, 95 unipolar disk electrodes with inter-electrode distance of 2 cm were used to record simultaneously potential ECGs over the anterior chest. The Laplacian ECG was then estimated during the P wave using a novel spline Laplacian technique. The body surface potential map (BSPM) and body surface Laplacian map (BSLM) at different time instants or time intervals of the P wave were constructed and compared. The present results showed that the BSPMs during the P wave were characterized by the rotation of a pair of positive/negative potential distribution from right to left around the anterior torso. On the other hand, the corresponding BSLMs revealed more spatial details, including two positive activities (denoted as P1 and P2, appeared in all 8 subjects), and three negative activities (denoted as N1, N2, and N3, appeared in 7, 7, and 4 subjects, respectively). The separation of these activities and their evolving patterns were also compared and confirmed by computer simulation using a realistic geometry heart-torso model. The above findings may be directly related to the underlying activation sequence during atrial depolarization in healthy subjects, suggesting the potential clinical applications of the Laplacian ECG technique.

Boundary element method-based cortical potential imaging of somatosensory evoked potentials using subjects' magnetic resonance images

A boundary element method-based cortical potential imaging technique has been developed to directly link the scalp potentials with the cortical potentials with the aid of magnetic resonance images of the subjects. First, computer simulations were conducted to evaluate the new approach in a concentric three-sphere inhomogeneous head model. Second, the corresponding cortical potentials were estimated from the patients' preoperative scalp somatosensory evoked potentials (SEPs) based on the boundary element models constructed from subjects' magnetic resonance images and compared to the postoperative direct cortical potential recordings in the same patients. Simulation results demonstrated that the cortical potentials can be estimated from the scalp potentials using different scalp electrode configurations and are robust against measurement noise. The cortical imaging analysis of the preoperative scalp SEPs recorded from patients using the present approach showed high consistency in spatial pattern with the postoperative direct cortical potential recordings. Quantitative comparison between the estimated and the directly recorded subdural grid potentials resulted in reasonably high correlation coefficients in cases studied. Amplitude difference between the estimated and the recorded potentials was also observed as indexed by the relative error, and the possible underlying reasons are discussed. The present numerical and experimental results validate the boundary element method-based cortical potential imaging approach and demonstrate the feasibility of the new approach in noninvasive high-resolution imaging of brain electric activities from scalp potential measurement and magnetic resonance images.

X-ray photoelectron spectroscopy study of disordering in Gd2(Ti1-xZrx)2O7 pyrochlores

The dramatic increases in ionic conductivity in Gd2(Ti1-xZrx)2O7 solid solution are related to disordering on the cation and anion lattices. Disordering in Gd2(Ti1-xZrx)2O7 was characterized using x-ray photoelectron spectroscopy (XPS). As Zr substitutes for Ti in Gd2Ti2O7 to form Gd2(Ti1-xZrx)2O7 (0.25 < x < or =0.75), the corresponding O 1s XPS spectrum merges into a single symmetric peak. This confirms that the cation antisite disorder occurs simultaneously with anion disorder. Furthermore, the O 1s XPS spectrum of Gd2Zr2O7 experimentally suggests the formation of a split vacancy.

Extracellular signal-regulated kinase (ERK) activation is required for GP Ibalpha-dependent endothelial cell migration

The GP Ib complex can participate in endothelial cell (EC) migration on von Willebrand factor (vWF) or the mixed matrix of vWF and type I collagen (vWF/collagen). In this study, viper venom proteins alboaggregin (albo) A or B blocked GP Ibalpha, and echistatin inhibited alphavbeta3 binding. Albo A, B and echistatin inhibited EC migration on vWF and vWF/collagen. Albo B or the anti-GP Ibalpha monoclonal antibody (mAb) 1b1 did not affect the migration of smooth muscle cells or fibroblasts, which lack GP Ib. EC also migrate on albo A- or albo B-coated dishes. PD98059, which blocks ERK activation, abolished EC migration on vWF, vWF/collagen, collagen or albo B. Soluble albo A or 1b1 dramatically inhibited ERK activation during EC migration on vWF or albo B. Echistatin inhibited ERK activation on vWF and vitronectin (VN), but not albo B. Thus, in addition to alphavbeta3, EC GP Ibalpha initiates ERK activation, and regulates ERK-induced EC migration on vWF.