Whole genome sequencing of meticillin-resistant Staphylococcus aureus

BACKGROUND

Staphylococcus aureus is one of the major causes of community-acquired and hospital-acquired infections. It produces numerous toxins including superantigens that cause unique disease entities such as toxic-shock syndrome and staphylococcal scarlet fever, and has acquired resistance to practically all antibiotics. Whole genome analysis is a necessary step towards future development of countermeasures against this organism.

METHODS

Whole genome sequences of two related S aureus strains (N315 and Mu50) were determined by shot-gun random sequencing. N315 is a meticillin-resistant S aureus (MRSA) strain isolated in 1982, and Mu50 is an MRSA strain with vancomycin resistance isolated in 1997. The open reading frames were identified by use of GAMBLER and GLIMMER programs, and annotation of each was done with a BLAST homology search, motif analysis, and protein localisation prediction.

FINDINGS

The Staphylococcus genome was composed of a complex mixture of genes, many of which seem to have been acquired by lateral gene transfer. Most of the antibiotic resistance genes were carried either by plasmids or by mobile genetic elements including a unique resistance island. Three classes of new pathogenicity islands were identified in the genome: a toxic-shock-syndrome toxin island family, exotoxin islands, and enterotoxin islands. In the latter two pathogenicity islands, clusters of exotoxin and enterotoxin genes were found closely linked with other gene clusters encoding putative pathogenic factors. The analysis also identified 70 candidates for new virulence factors.

INTERPRETATION

The remarkable ability of S aureus to acquire useful genes from various organisms was revealed through the observation of genome complexity and evidence of lateral gene transfer. Repeated duplication of genes encoding superantigens explains why S aureus is capable of infecting humans of diverse genetic backgrounds, eliciting severe immune reactions. Investigation of many newly identified gene products, including the 70 putative virulence factors, will greatly improve our understanding of the biology of staphylococci and the processes of infectious diseases caused by S aureus.

Ultralight metallic microlattices

Ultralight (<10 milligrams per cubic centimeter) cellular materials are desirable for thermal insulation; battery electrodes; catalyst supports; and acoustic, vibration, or shock energy damping. We present ultralight materials based on periodic hollow-tube microlattices. These materials are fabricated by starting with a template formed by self-propagating photopolymer waveguide prototyping, coating the template by electroless nickel plating, and subsequently etching away the template. The resulting metallic microlattices exhibit densities ρ ≥ 0.9 milligram per cubic centimeter, complete recovery after compression exceeding 50% strain, and energy absorption similar to elastomers. Young's modulus E scales with density as E ~ ρ(2), in contrast to the E ~ ρ(3) scaling observed for ultralight aerogels and carbon nanotube foams with stochastic architecture. We attribute these properties to structural hierarchy at the nanometer, micrometer, and millimeter scales.

Structure of the rat osteocalcin gene and regulation of vitamin D-dependent expression

The osteocalcin gene encodes a 6-kDa polypeptide, which represents one of the most abundant noncollagenous bone proteins, and the present studies establish that osteocalcin mRNA is detected only in bone tissue. An osteocalcin gene was isolated from a rat genomic DNA library, and sequence analysis indicated that the mRNA is represented in a 953-nucleotide segment of DNA consisting of four exons and three introns. A modular organization of the 5' flanking sequences of the gene is reflected by the presence of at least three classes of regulatory elements, which include the following: (i) RNA polymerase II canonical sequences; (ii) a series of consensus sequences for hormone receptor binding sites and cyclic nucleotide responsive elements consistent with physiologic expression of the osteocalcin gene; and (iii) a 24-nucleotide sequence in the proximal promoter region with a CAAT motif as a central element. We have designated this highly conserved sequence as an "osteocalcin box" since only 2 nucleotide substitutions are found in the rat and human osteocalcin genes. We have demonstrated two factors regulating osteocalcin gene expression. First, a 200-fold increase occurs in normal fetal calvaria osteoblasts producing a mineralizing matrix, compared to confluent osteoblasts in a nonmineralizing matrix. Second, contained within the 600 nucleotides immediately upstream from the transcription start site are sequences that support a 10-fold stimulated transcription of the gene by 1,25-dihydroxyvitamin D.

The tissue-specific nuclear matrix protein, NMP-2, is a member of the AML/CBF/PEBP2/runt domain transcription factor family: interactions with the osteocalcin gene promoter

The nuclear matrix protein, NMP-2, was originally identified as an osteoblast-specific DNA-binding complex localized exclusively to the nuclear matrix. NMP-2 was shown to recognize two binding sites, site A (nt-605 to -599) and site B (nt -441 to -435), in the rat bone-specific osteocalcin gene promoter. This study shows that the NMP-2 binding sites A and B as well as a third NMP-2 binding site (nt -135 to -130) constitute a consensus sequence, ATGCTGGT, and represent an AML-1 recognition motif. AML-1 is a member of the AML transcription factor family which is associated with acute myelogenous leukemia and binds to the sequence TGCTGGT via its DNA-binding runt domain. Electrophoretic mobility shift assays reveal that a component of NMP-2 is a member of the AML/PEBP2/runt domain transcription factor family based on cross-competition with AML-1 consensus oligonucleotide. Limited immunoreactivity of NMP-2 with a polyclonal N-terminal AML-1 antibody and inability of the AML-1 partner protein CBF-beta to form complexes with NMP-2 indicate that NMP-2 is not identical to AML-1 but represents a variant AML/PEBP2/runt domain protein. Western and Northern blots reveal the presence of multiple AML-related proteins and AML-1 transcripts in several osseous cell lines. Furthermore, our results indicate that AML family members may selectively partition between nuclear matrix and nonmatrix compartments. Because proteins that contain a runt domain are implicated in tissue-specific transcriptional regulation, our results support the concept that the nuclear matrix mediates osteoblast-specific expression of the osteocalcin gene.

A natural BH3 mimetic induces autophagy in apoptosis-resistant prostate cancer via modulating Bcl-2-Beclin1 interaction at endoplasmic reticulum

A natural BH3-mimetic, small-molecule inhibitor of Bcl-2, (-)-gossypol, shows promise in ongoing phase II and III clinical trials for human prostate cancer. In this study we show that (-)-gossypol preferentially induces autophagy in androgen-independent (AI) prostate cancer cells that have high levels of Bcl-2 and are resistant to apoptosis, both in vitro and in vivo, but not in androgen-dependent (AD) cells with low Bcl-2 and sensitive to apoptosis. The Bcl-2 inhibitor induces autophagy through blocking Bcl-2-Beclin1 interaction, together with downregulating Bcl-2, upregulating Beclin1, and activating the autophagic pathway. The (-)-gossypol-induced autophagy is dependent on Beclin1 and Atg5. Our results show for the first time that (-)-gossypol can also interrupt the interactions between Beclin1 and Bcl-2/Bcl-xL at endoplasmic reticulum, thus releasing the BH3-only pro-autophagic protein Beclin1, which in turn triggers the autophagic cascade. Oral administration of (-)-gossypol significantly inhibited the growth of AI prostate cancer xenografts, representing a promising new regimen for the treatment of human hormone-refractory prostate cancer with Bcl-2 overexpression. Our data provide new insights into the mode of cell death induced by Bcl-2 inhibitors, which will facilitate the rational design of clinical trials by selecting patients who are most likely to benefit from the Bcl-2-targeted molecular therapy.

Suppression of epileptiform activity by high frequency sinusoidal fields in rat hippocampal slices

1. Sinusoidal high frequency (20-50 Hz) electric fields induced across rat hippocampal slices were found to suppress zero-Ca2+, low-Ca2+, picrotoxin, and high-K+ epileptiform activity for the duration of the stimulus and for up to several minutes following the stimulus. 2. Suppression of spontaneous activity by high frequency stimulation was found to be frequency (< 500 Hz) but not orientation or waveform dependent. 3. Potassium-sensitive microelectrodes showed that block of epileptiform activity was always coincident with a stimulus-induced rise in extracellular potassium concentration during stimulation. Post-stimulus inhibition was always associated with a decrease in extracellular potassium activity below baseline levels. 4. Intracellular recordings and optical imaging with voltage-sensitive dyes showed that during suppression neurons were depolarized yet did not fire action potentials. 5. Direct injection of sinusoidal current into individual pyramidal cells did not result in a tonic depolarization. Injection of large direct current (DC) depolarized neurons and suppressed action potential generation. 6. These findings suggest that high frequency stimulation suppresses epileptiform activity by inducing potassium efflux and depolarization block.

IL6 derived from cancer-associated fibroblasts promotes chemoresistance via CXCR7 in esophageal squamous cell carcinoma

Various factors and cellular components in the tumor microenvironment are key drivers associated with drug resistance in many cancers. Here, we analyzed the factors and molecular mechanisms involved in chemoresistance in patients with esophageal squamous cell carcinoma (ESCC). We found that interleukin 6 (IL6) derived mainly from cancer-associated fibroblasts played the most important role in chemoresistance by upregulating C-X-C motif chemokine receptor 7 (CXCR7) expression through signal transducer and activator of transcription 3/nuclear factor-κB pathway. CXCR7 knockdown resulted in the inhibition of IL6-induced proliferation and chemoresistance. In addition, CXCR7 silencing significantly decreased gene expression associated with stemness, chemoresistance and epithelial-mesenchymal transition and suppressed the proliferation ability of ESCC cells in three-dimensional culture systems and angiogenesis assay. In clinical samples, ESCC patients with high expression of CXCR7 and IL6 presented a significantly worse overall survival and progression-free survival upon receiving cisplatin after operation. These results suggest that the IL6-CXCR7 axis may provide a promising target for the treatment of ESCC.

A role for osteocalcin in osteoclast differentiation

Specific cellular interactions with components of the extracellular matrix can influence cellular differentiation and development of many tissues. The extracellular matrix of bone is composed of organic constituents and a solid phase of calcium and inorganic phosphate (apatite). When implanted subcutaneously in rats, particles of bone matrix (BPs) recruit progenitors that differentiate into multinucleated cells with osteoclastic features. Because BPs deficient in osteocalcin, a bone matrix protein, were less efficient at promoting osteoclast formation than were normal BPs, we directly examined the influence of osteocalcin on osteoclast differentiation. We evaluated tissue responses to particles of synthetic crystalline apatite alone (Ap), having many of the features of native apatite of mature bone, or to apatite prepared with osteocalcin (Ap/OC), bovine serum albumin (Ap/BSA) or rat bone collagen (Ap/Col). Twelve days after subcutaneous implantation in normal rats, Ap, Ap/BSA, and Ap/Col particles generated a mild foreign body reaction with multinucleated cells in direct contact with the particles; these cells were negative for tartrate-resistant acid phosphatase (TRAP) activity and lacked ruffled borders. In contrast, Ap particles containing approximately 0.1% osteocalcin were partially resorbed and they generated more multinucleated cells that were TRAP-positive, were immunoreactive with an antibody against tartrate-resistant purple acid phosphatase, and displayed ultrastructural features of active osteoclasts including ruffled borders and clear zones. These data support the hypothesis that osteocalcin may function as a matrix signal in the recruitment and differentiation of bone-resorbing cells.

Selective expression of fos- and jun-related genes during osteoblast proliferation and differentiation

Developmental studies of oncogene expression and transgenic animal studies implicate c-fos and other fos and jun family members in the regulation of bone tissue formation. Therefore, to initiate experimental examination of the hypothesis that expression of fos- and jun-related genes is functionally coupled to modulation of gene expression which supports bone development, we determined levels of expression of the principle fos and jun family members during progressive differentiation of normal rat calvaria-derived osteoblasts within two contexts. First, cellular mRNA levels were quantitated under conditions where expression of serum-induced early response genes had returned to basal levels. Our findings demonstrate high levels of c-fos, c-jun, and jun B mRNA transcripts during the proliferative period of osteoblast development, while expression of fra-1 and fra-2 is enhanced during the differentiation period. jun D is constitutively expressed during the time course exhibiting only a 30% decline in levels postproliferatively, and fos B mRNA is undetectable by Northern blot analyses. Late in the developmental sequence, apoptosis is evident. At this time, fra-1 expression is completely downregulated, while c-fos, fra-2, c-jun, jun B, and jun D show a dramatic enhancement in expression. Second, we addressed differential expression of fos and jun family members in relation to serum responsiveness as a function of stages of phenotypic development. Proliferating cells exhibit a prolonged induction of fos and jun family members in response to serum. While in differentiated cells, which are refractory to growth stimulus even when exposed to fresh serum every 2 days, a spike in fos and jun expression is observed. Thus, our data demonstrate significant differences in basal and serum responsiveness of fos and jun family members over the course of osteoblast differentiation. These findings are consistent with multiple lines of evidence linking activity of these early response genes to regulation of cell growth and development of the bone tissue phenotype.

Infrequent recovery of HIV from but robust exogenous infection of activated CD4(+) T cells in HIV elite controllers

BACKGROUND. Human immunodeficiency virus (HIV) elite controllers are able to control infection with HIV-1 spontaneously to undetectable levels in the absence of antiretroviral therapy, but the mechanisms leading to this phenotype are poorly understood. Although low frequencies of HIV-infected peripheral CD4(+) T cells have been reported in this group, it remains unclear to what extent these are due to viral attenuation, active immune containment, or intracellular host factors that restrict virus replication. METHODS. We assessed proviral DNA levels, autologous viral growth from and infectability of in vitro activated, CD8(+) T cell-depleted CD4(+) T cells from HIV elite controllers (mean viral load, <50 copies/mL), viremic controllers (mean viral load, <2000 copies/mL), chronic progressors, and individuals receiving highly active antiretroviral therapy. RESULTS. Although we successfully detected autologous virus production in ex vivo activated CD4(+) T cells from all chronic progressors and from most of the viremic controllers, we were able to measure robust autologous viral replication in only 2 of 14 elite controllers subjected to the same protocol. In vitro activated autologous CD4(+) T cells from elite controllers, however, supported infection with both X4 and R5 tropic HIV strains at comparable levels to those in CD4(+) T cells from HIV-uninfected subjects. Proviral DNA levels were the lowest in elite controllers, suggesting that extremely low frequencies of infected cells contribute to difficulty in isolation of virus. CONCLUSIONS. These data indicate that elite control is not due to inability of activated CD4(+) T cells to support HIV infection, but the relative contributions of host and viral factors that account for maintenance of low-level infection remain to be determined.

Effect of short-term hypomagnesemia on the chemical and mechanical properties of rat bone

Magnesium is known to have an essential role in determining the properties of bone, but the way in which Mg exerts its actions remains unclear. Although long-term Mg deficiency is known to produce osteopenia, the effects of short-term Mg deficiency have not been established. To test the hypothesis that Mg deficiency results in an altered pattern of initial mineralization and concomitant altered bone properties, the radiographic, histologic, chemical, and mechanical properties of the bones of rats given a Mg-deficient diet were compared to those of rats pair-fed the same diet supplemented with Mg. Short-term Mg-deficiency in the diet of growing rats produced a significant decrease in both the trabecular bone volume and the mineral content of the newly formed metaphysis, a significant increase in the Ca:P ratio, and a slight, but significant increase in hydroxyapatite crystallite size and/or perfection in the metaphysis. Comparable, but not significant, trends were found in the diaphyses. Metaphyseal bone osteocalcin levels were reduced in the Mg-deficient rats and lipid was more easily extracted from their bones. No detectable alterations in radiographic microstructure were noted. Mechanically, a significant decrease in the maximum three-point bend strength of the femurs of Mg-deficient rats was observed. These data support the hypothesis that short-term Mg deficiency affects the pattern of bone mineral formation.

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.

High-resolution EEG: a new realistic geometry spline Laplacian estimation technique

BACKGROUND

A new realistic geometry (RG) spline Laplacian estimation technique has been developed for high-resolution EEG imaging.

METHODS

Estimation of the parameters associated with the spline Laplacian is formulated by seeking the general inverse of a transfer matrix. The number of spline parameters, which need to be determined through regularization, is reduced to one in the present approach, thus enabling easy implementation of the RG spline Laplacian estimator.

RESULTS

Computer simulation studies have been conducted to test the feasibility of the new approach in a 3-concentric-sphere head model. The new technique has also been applied to human visual evoked potential data with a RG head model.

CONCLUSIONS

The present numerical and experimental results demonstrate the feasibility of the new approach and indicate that the RG spline Laplacian can be estimated easily from the surface potentials and the scalp geometry.

The novel BH-3 mimetic apogossypolone induces Beclin-1- and ROS-mediated autophagy in human hepatocellular carcinoma [corrected] cells

Apogossypolone (ApoG2), a novel derivative of gossypol, exhibits superior antitumor activity in Bcl-2 transgenic mice, and induces autophagy in several cancer cells. However, the detailed mechanisms are not well known. In the present study, we showed that ApoG2 induced autophagy through Beclin-1- and reactive oxygen species (ROS)-dependent manners in human hepatocellular carcinoma (HCC) cells. Incubating the HCC cell with ApoG2 abrogated the interaction of Beclin-1 and Bcl-2/xL, stimulated ROS generation, increased phosphorylation of ERK and JNK, and HMGB1 translocation from the nucleus to cytoplasm while suppressing mTOR. Moreover, inhibition of the ROS-mediated autophagy by antioxidant N-acetyl-cysteine (NAC) potentiates ApoG2-induced apoptosis and cell killing. Our results show that ApoG2 induced protective autophagy in HCC cells, partly due to ROS generation, suggesting that antioxidant may serve as a potential chemosensitizer to enhance cancer cell death through blocking ApoG2-stimulated autophagy. Our novel insights may facilitate the rational design of clinical trials for Bcl-2-targeted cancer therapy.

A cortical potential imaging analysis of the P300 and novelty P3 components

The P300 and Novelty P3 are positive components of the event related brain potential (ERP) with a latency of at least 300 ms, which are manifestations of brain activity evoked by deviant events. Spencer et al. [1999, 2001] demonstrated that these are two distinct components, both of which may be elicited, with different amplitudes, by both rare and novel events. However, the locations of the intracranial sources of the components remain unknown. We describe the application of cortical potential imaging (CPI) analysis to the data described by Spencer et al. [1999]. The ERPs were recorded from 15 healthy subjects presented with auditory oddball sequences. Cortical potential maps (CPMs) were reconstructed from the scalp potential maps (SPMs) corresponding to the P300 and Novelty P3 components by deblurring the smoothing effect of the head volume conductor. The reconstructed CPMs, derived from the SPMs by means of the CPI, showed localized areas of activity distributed in both the frontal and parietal lobes; the parietal region was active throughout the period of the late positivities. The reconstructed CPMs associated with novel events showed prominent activity at the frontal lobe (Novelty P3) followed by progressively pronounced parietal lobe activity (P300), and these two components can be well separated by the CPMs. These analyses show how the CPI can be used to relate the scalp electrical recordings to the underlying brain activity.

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.

Non-apatitic environments in bone mineral: FT-IR detection, biological properties and changes in several disease states

Resolution enhanced FT-IR spectroscopy shows that non-apatitic environments of phosphate and carbonate ions occur in bone mineral. The spectroscopic characteristics of these environments and their chemical and biological properties are reviewed. The potential effectiveness of FT-IR for the detailed study of bone mineral changes in bone disease is shown by analysis of several samples.

1 Alpha,25-dihydroxyvitamin D3 rapidly increases cytosolic calcium in clonal rat osteosarcoma cells lacking the vitamin D receptor

1 alpha,25-Dihydroxyvitamin D3 [1 alpha,25-(OH)2D3] rapidly increases cytosolic calcium in a variety of cell types. Although these rapid effects do not appear to directly involve genome activation, the requirement for the classic vitamin D receptor is unclear. Clonal rat osteosarcoma cells, ROS 17/2.8, respond to 1 alpha,25-(OH)2D3 with an increase in osteocalcin message but ROS 24/1 cells do not. The lack of the receptor for vitamin D in the ROS 24/1 cells has been confirmed by the absence of any detectable vitamin D-receptor complex binding to the vitamin D-responsive element (VDRE) of the osteocalcin gene and the absence of vitamin D receptor mRNA in the cells. Quin-2-loaded ROS 17/2.8 and ROS 24/1 cells were treated with 1 alpha,25-(OH)2D3 in the presence and absence of extracellular calcium and with the inactive epimer, 1 beta,25-dihydroxyvitamin D3 [1 beta,25-(OH)2D3]. The 1 alpha,25-(OH)2D3 increased cytosolic calcium in the ROS 17/2.8 and 24/1 cells after 5 minutes in a dose-responsive manner and in the presence and absence of extracellular calcium. Pretreatment of both cell lines with 1 beta,25-(OH)2D3 for 30 s blocked the hormone-induced rise in cytosolic calcium. The rapid effects of 1 alpha,25-(OH)2D3 on ROS cells with and without the vitamin D receptor and the ability of the inactive epimer to inhibit these effects indicate that the signaling system mediating the hormone's rapid actions is not the classic vitamin D receptor.

Changes in chromatin structure support constitutive and developmentally regulated transcription of the bone-specific osteocalcin gene in osteoblastic cells

Transcription of the osteocalcin gene, which encodes a 10 kDa bone-specific protein, is controlled by modularly organized basal regulatory sequences and hormone-responsive enhancer elements. We have previously shown that in the ROS 17/2.8 rat osteosarcoma cell line, which continuously expresses the osteocalcin gene, key regulatory elements reside in two DNase I hypersensitive sites that are fucntionally correlated with transcriptional activity. We now report that a specific nucleosomal organization supports this constitutive expression in ROS 17/2.8 cells, and that chromatin remodeling directly correlates with the developmentally regulated transcriptional activation of the osteocalcin gene during differentiation of normal diploid rat osteoblasts. By combining DNase I, micrococcal nuclease, and specific restriction endonuclease digestion analysis, we observed that the presence of DNAse I hypersensitive sites (-170 to -70 and -600 to -400) and a selective nucleosome positioning over the OC gene promoter are directly associated with developmental stage-specific transcriptional activation in bone-derived cells.

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.

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.

Altered binding of human histone gene transcription factors during the shutdown of proliferation and onset of differentiation in HL-60 cells

Two sites of protein-DNA interaction have been identified in vivo and in vitro in the proximal promoter regions of an H4 and an H3 human histone gene. In proliferating cells, these genes are transcribed throughout the cell cycle, and both the more distal site I and the proximal site II are occupied by promoter-binding factors. In this report we demonstrate that during the shutdown of proliferation and onset of differentiation of the human promyelocytic leukemia cell line HL-60 into cells that exhibit phenotypic properties of monocytes, histone gene expression is down-regulated at the level of transcription. In vivo occupancy of site I by promoter factors persists in the differentiated HL-60 cells, but protein-DNA interactions at site II are selectively lost. Furthermore, in vitro binding activity of the site II promoter factor HiNF-D is lost in differentiated cells, and nuclear extracts from differentiated cells do not support in vitro transcription of these histone genes. Our results suggest that the interaction of HiNF-D with proximal promoter site II sequences plays a primary role in rendering cell growth-regulated histone genes transcribable in proliferating cells. It appears that while cell-cycle control of histone gene expression is mediated by both transcription and mRNA stability, with the shutdown of proliferation and onset mRNA stability, with the shutdown of proliferation and onset of differentiation, histone gene expression is regulated at the transcriptional level.