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Axonal outgrowth and guidance require numerous extracellular cues and intracellular mediators that transduce signals in the growth cone to regulate cytoskeletal dynamics. However, the way in which cytoskeletal effectors respond to these signals remains elusive. Here, we demonstrate that Porf-2, a neuron-expressed RhoGTPase-activating protein, plays an essential role in the inhibition of initial axon growth by restricting the expansion of the growth cone in a cell-autonomous manner. Furthermore, the EphB1 receptor is identified as an upstream controller that binds and regulates Porf-2 specifically upon extracellular ephrin-B stimulation. The activated EphB forward signal deactivates Rac1 through the GAP domain of Porf-2, which inhibits growth cone formation and brakes axon growth. Our results therefore provide a novel GAP that regulates axon growth and braking sequentially through Eph receptor-independent and Eph receptor-dependent pathways.

Originally conceived at ESRF and first deployed in 2005 MXCuBE, Macromolecular Xtallography Customized Beamline Environment, has with its successor MXCuBE2, become a successful international collaboration. The aim of the collaboration is to develop a beamline control application for macromolecular crystallography (MX) that are independent of underlying instrument control software and thus deployable at the MX beamlines of any synchrotron source. The continued evolution of the functionality offered at MX beamlines is to a large extent facilitated by active software development. New demands and advances in technology have led to the development of a new version of MXCuBE, MXCuBE3, The design of which was inspired by the results of a technical pre-study and user survey. MXCuBE3 takes advantage of the recent development in web technologies such as React and Redux to create an intuitive and user friendly application. The access to the application from any web browser further simplifies the operation and natively facilitates the execution of remote experiments., Proceedings of the 16th Int. Conf. on Accelerator and Large Experimental Control Systems, ICALEPCS2017, Barcelona, Spain

The purpose of this work was to investigate the effects of hemispheric location, gender and age on susceptibility value, as well as the association between susceptibility value and diffusional metrics, in deep gray matter. Iron content was estimated in vivo using quantitative susceptibility mapping. Microstructure was probed using diffusional kurtosis imaging. Regional susceptibility and diffusional metrics were measured for the putamen, caudate nucleus, globus pallidus, thalamus, substantia nigra and red nucleus in 42 healthy adults (age range 25-78 years). Susceptibility value was significantly higher in the left than the right side of the caudate nucleus (P = 0.043) and substantia nigra (P < 0.001). Women exhibited lower susceptibility values than men in the thalamus (P < 0.001) and red nucleus (P = 0.032). Significant age-related increases of susceptibility were observed in the putamen (P < 0.001), red nucleus (P < 0.001), substantia nigra (P = 0.004), caudate nucleus (P < 0.001) and globus pallidus (P = 0.017). The putamen exhibited the highest rate of iron accumulation with aging (slope of linear regression = 0.73 × 10(-3) ppm/year), which was nearly twice those in substantia nigra (slope = 0.40 × 10(-3) ppm/year) and caudate nucleus (slope = 0.39 × 10(-3) ppm/year). Significant positive correlations between the susceptibility value and diffusion measurements were observed for fractional anisotropy (P = 0.045) and mean kurtosis (P = 0.048) in the putamen without controlling for age. Neither correlation was significant after controlling for age. Hemisphere, gender and age-related differences in iron measurements were observed in deep gray matter. Notably, the putamen exhibited the highest rate of increase in susceptibility with aging. Correlations between susceptibility value and microstructural measurements were inconclusive. These findings could provide new clues for unveiling mechanisms underlying iron-related neurodegenerative diseases.

With the rapid development of china railway, ZPW-2000A track circuit has been widely used. Tuning area, which is an important part of the ZPW-2000A track circuit, is not only the relationship between the signal transmission quality, and determine the effect of electrical insulation between adjacent sections. Therefore, the study of fault diagnosis aspects for tuning area is urgent and significant. In this paper, using the theory of transmission line a model of track circuit is built, the comparison of the actual data and experimental data of the track surface voltage envelope curve shows the correctness of this model. Owning to the good time-frequency characteristics of wavelet and the nonlinear mapping features of neural network, a fault diagnosis of ZPW-2000A tuning area based on the wavelet neural network(WNN) is proposed. Combined with the practical failure situation of railway site, the fault diagnosis method in this paper can accurately identify failure modes of tuning area.

One aim of this study is to use non-Gaussian diffusion kurtosis imaging (DKI) for capturing microstructural abnormalities in gray matter of Alzheimer's disease (AD). The other aim is to compare DKI metrics against thickness of cortical gray matter and volume of deep gray matter, respectively. A cohort of 18 patients with AD, 18 patients with amnestic mild cognitive impairment (MCI), and 18 normal controls underwent morphological and DKI MR imaging. Images were investigated using regions-of-interest-based analyses for deep gray matter and vertex-wise analyses for cortical gray matter. In deep gray matter, more regions showed DKI parametric abnormalities than atrophies at the early MCI stage. Mean kurtosis (MK) exhibited the largest number of significant abnormalities among all DKI metrics. At the later AD stage, diffusional abnormalities were observed in fewer regions than atrophies. In cortical gray matter, abnormalities in thickness were mainly in the medial and lateral temporal lobes, which fit the locations of known early pathological changes. Microstructural abnormalities were predominantly in the parietal and even frontal lobes, which fit the locations of known late pathological changes. In conclusion, MK can complement conventional diffusion metrics for detecting microstructural changes, especially in deep gray matter. This study also provides evidence supporting the notion that microstructural changes predate morphological changes. Hum Brain Mapp 38:2495-2508, 2017. © 2017 Wiley Periodicals, Inc.

BACKGROUND: The study aimed to compare the tolerability and efficacy of gefitinib combined with chemotherapy agents versus chemotherapy alone for the treatment of epidermal growth factor receptor (EGFR)–mutated lung adenocarcinoma in heavily pretreated patients. METHODS: The study was designed as a matched-pair case-control investigation to minimize intergroup heterogeneity. Patients were stratified into gefitinib plus chemotherapy and chemotherapy alone groups with matching for sex, age, ECOG performance status, progress-free survival (PFS) from previous EGFR tyrosine kinase inhibitor treatment, EGFR mutation types, and tumor metastasis status. RESULTS: Sixty-six patients were selected from our database using the matched-pair method. The median age was 61 years (95% confidence interval, 57-65 years). During a follow-up period of 14.5 months on average, the overall response rates of the gefitinib-integrated and chemotherapy alone groups were 9.1% and 6.5%, respectively (P > .05), whereas the corresponding disease-control rates were 39.4% and 30.3%, respectively (P > .05). No statistically significant differences in PFS (median, 4.2 vs 3.3 months; P = .06) and overall survival (median, 10.4 vs 7.9 months; P = .44) were observed between two groups. The 6-month survival rates of the gefitinib-integrated and chemotherapy alone groups were 21.2% and 12.1%, respectively (P < .05). Side effects were mild, and all treatments were well tolerated. CONCLUSIONS: Our results indicated that gefitinib-integrated therapy offered a trend to better PFS and an improved 6-month survival rate in heavily pretreated patients with metastatic EGFR-mutated lung adenocarcinoma. All treatments were well tolerated. Future prospective studies are warranted to confirm our findings.

The above article, published online on 3 May 2014 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the authors, the journal Editor in Chief, and Wiley Periodicals, Inc. The retraction has been agreed due to errors in the results of the published article. The authors stated in the Methods section that ‘. . . only clusters with a false discovery rate (FDR)-corrected P-value less than 0.05 were included.’ However, it was subsequently discovered that the FDG-correction had not been performed correctly. Had this been carried out in the right way, the difference between the case group and the control group in most of the presented regions would have been insignificant. REFERENCE 1. Gao J, Feng S-T, Wu B, Gong N, Lu M, Wu P-M, Wang H, He X, and Huang B. Microstructural Brain Abnormalities of Children of Idiopathic Generalized Epilepsy With Generalized Tonic-Clonic Seizure: A Voxel-Based Diffusional Kurtosis Imaging Study J mag res. 2014 May 3. doi: 10.1002/jmri.24647 [epub ahead of print]

Objective To describe the prevalence of synchronous second primary malignancy detected by PET/ CT in our clinical practice and its differentiating features from metastatic lesion. Methods All PET/CT scans from 1st October 2009 to 30th September 2010 were reviewed. The suspected cases of synchronous second primary malignancy detected by PET/CT were selected, and the histologically confirmed ones were being illustrated. Metachronous second primary cases were excluded. Results A total of 1522 scans were reviewed. sixty-eight cases were suspected to have a synchronous second primary while 8 were histologically confirmed. Seven (0.4%) of them were malignant and 1 was a benign tumor. These 7 cases were illustrated, and we found a significant difference in SUVmax values and site of occurrence unusual to metastasis that were the two main radiological features differentiating them from metastatic lesion. Conclusion Synchronous second primary malignancy could be missed without the use of whole body imaging. Its diagnosis is of utmost importance to prevent erroneous upstaging of disease and subsequent palliative treatment instead of curative surgery.

The objective of this study was to compare the accuracy of calculating the primary tumor volumes using a gradient-based method and fixed threshold methods on the standardized uptake value (SUV) maps and the net influx of FDG (Ki) maps from positron emission tomography-computed tomography (PET-CT) images.Newly diagnosed patients with head and neck cancer were recruited, and dynamic PET-CT scan and T2-weighted magnetic resonance imaging were performed. The maps of Ki and SUV were calculated from PET-CT images. The tumor volumes were calculated using a gradient-based method and a fixed threshold method at 40% of maximal SUV or maximal Ki. Four kinds of volumes, VOLKi-Gra (from the Ki maps using the gradient-based method), VOLKi-40% (from the Ki maps using the threshold of 40% maximal Ki), VOLSUV-Gra (from the SUV maps using the gradient-based method), and VOLSUV-40% (from the SUV maps using the threshold of 40% maximal SUV), were acquired and compared with VOLMRI (the volumes acquired on T2-weighted images) using the Pearson correlation, paired t test, and similarity analysis.Eighteen patients were studied, of which 4 had poorly defined tumors (PDT). The positron emission tomography-derived volumes were as follows: VOLSUV-40%, 2.1 to 41.2 cm (mean [SD], 12.3 [10.6]); VOLSUV-Gra, 2.2 to 28.1 cm (mean [SD], 13.2 [8.4]); VOLKi-Gra, 2.4 to 17.0 cm (mean [SD], 9.5 [4.6]); and VOLKi-40%, 2.7 to 20.3 cm (mean [SD], 12.0 [6.0]). The VOLMRI ranged from 2.9 to 18.1 cm (mean [SD], 9.1 [3.9]). The VOLKi-Gra significantly correlated with VOLMRI with the highest correlation coefficient (PDT included, R = 0.673, P = 0.002; PDT excluded, R = 0.841, P0.001) and presented no difference from VOLMRI (P = 0.672 or 0.561, respectively, PDT included and excluded). The difference between VOLKi-Gra and VOLMRI was also the smallest.The tumor volumes delineated on the Ki maps using the gradient-based method are more accurate than those on the SUV maps and using the fixed threshold methods.

Object Diffusional kurtosis imaging (DKI), a natural extension of diffusion tensor imaging (DTI), can characterize non-Gaussian diffusion in the brain. We investigated the capability of DKI parameters for detecting microstructural changes in both gray matter (GM) and white matter (WM) in patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD) and sought to determine whether these DKI parameters could serve as imaging biomarkers to indicate the severity of cognitive deficiency. Materials and Methods DKI was performed on 18 AD patients and 12 MCI patients. Fractional anisotropy, kurtosis and diffusivity parameters in the temporal, parietal, frontal and occipital lobes were compared between the two groups using Mann–Whitney U test. The correlations between regional DKI parameters and mini-mental state examination (MMSE) score were tested using Pearson's correlation. Results In ADs, significantly increased diffusivity and decreased kurtosis parameters were observed in both the GM and WM of the parietal and occipital lobes as compared to MCIs. Significantly decreased fractional anisotropy was also observed in the WM of these lobes in ADs. With the exception of fractional anisotropy and radial kurtosis, all the five other DKI parameters exhibited significant correlations with MMSE score in both GM and WM. Conclusion Bearing additional information, the DKI model can provide sensitive imaging biomarkers for assessing the severity of cognitive deficiency in reference to MMSE score and potentially improve early detection and progression monitoring of AD based on characterizing microstructures in both the WM and especially the GM.

Introduction Osteoarthritis (OA) of the knee is a common and disabling disease worldwide. Its prevalence is increasing in view of the aging population. Changes in collagen content, its orientation and GAG content in the articular cartilage with age are the major features in knee osteoarthritis. These changes in collagen and GAG contents show no manifestation in plain radiography and conventional magnetic resonance imaging (MRI). Nevertheless, early diagnosis of the knee osteoarthritis is of paramount importance clinically in view of the evolution of putative interventions in its early stage. The aim of this project is to identify the relationships between the two imaging biomarkers (i.e. T1ρ and T2 mappings) and the GAG concentration in living human symptomatic cartilage. Methodology 28 patients with clinical diagnosis of knee osteoarthritis were enrolled. 7 males and 16 females were recruited and their mean age was 68.1 (ranges from 53 to 84). Conventional PD sequence, T1ρ and T2 mappings were performed for each subject within 1 week before total knee arthroplasty. Articular cartilage from the lateral tibial plateau was harvested and the GAG content in cartilage was determined by using dimethylmethylene blue method. T1ρ mean and T2 values were calculated and correlate with GAG concentration statistically. Results The mean value T1ρ was 40.3 ± 13.5 ms, ranging from 15.3 to 69.3 ms and the mean value T2 was 31.0 ± 10.5 ms, ranging from 16.1 to 46.9 ms. The mean value of GAG content was 80.1 ± 33.3 mg, ranging from 24.9 to 166.0 mg while the mean value of GAG concentration was 267.4 ± 165.9 mg/cm3, ranging from 91.3 to 760.5 mg/cm3. T2 values were inversely correlated with GAG concentration with R2 = 0.375, p = 0.001 while T1ρ values were also inversely correlated with GAG concentration with R2 = 0.200, p = 0.025. Conclusion This in vivo study confirmed that T1ρ and T2 values correlate with the GAG concentration in living human knee cartilages which corroborate with the previous works. The later (T2 values) is found more reliable in our study and less controversial in literatures. We postulate that T2 values can serve as a non-invasive imaging biomarker in the progress of knee osteoarthritis in terms of both disease diagnosis and treatment response monitoring.

One aim of this study is to use non‐Gaussian diffusion kurtosis imaging (DKI) for capturing microstructural abnormalities in gray matter of Alzheimer's disease (AD). The other aim is to compare DKI metrics against thickness of cortical gray matter and volume of deep gray matter, respectively. A cohort of 18 patients with AD, 18 patients with amnestic mild cognitive impairment (MCI), and 18 normal controls underwent morphological and DKI MR imaging. Images were investigated using regions‐of‐interest‐based analyses for deep gray matter and vertex‐wise analyses for cortical gray matter. In deep gray matter, more regions showed DKI parametric abnormalities than atrophies at the early MCI stage. Mean kurtosis (MK) exhibited the largest number of significant abnormalities among all DKI metrics. At the later AD stage, diffusional abnormalities were observed in fewer regions than atrophies. In cortical gray matter, abnormalities in thickness were mainly in the medial and lateral temporal lobes, which fit the locations of known early pathological changes. Microstructural abnormalities were predominantly in the parietal and even frontal lobes, which fit the locations of known late pathological changes. In conclusion, MK can complement conventional diffusion metrics for detecting microstructural changes, especially in deep gray matter. This study also provides evidence supporting the notion that microstructural changes predate morphological changes. Hum Brain Mapp 38:2495–2508, 2017. © 2017 Wiley Periodicals, Inc.

The amygdala serves as emotional center to mediate innate fear behaviors that are reflected through neuronal responses to environmental aversive cues. However, the molecular mechanism underlying the initial neuron responses is poorly understood. In this study, we monitored the innate defensive responses to aversive stimuli of either elevated plus maze or predator odor in juvenile mice and found that glutamatergic neurons were activated in amygdala. Loss of EphB2, a receptor tyrosine kinase expressed in amygdala neurons, suppressed the reactions and led to defects in spine morphogenesis and fear behaviors. We further found a coupling of spinogenesis with these threat cues induced neuron activation in developing amygdala that was controlled by EphB2. A constitutively active form of EphB2 was sufficient to rescue the behavioral and morphological defects caused by ablation of ephrin-B3, a brain-enriched ligand to EphB2. These data suggest that kinase-dependent EphB2 intracellular signaling plays a major role for innate fear responses during the critical developing period, in which spinogenesis in amygdala glutamatergic neurons was involved.SIGNIFICANCE STATEMENTGeneration of innate fear responses to threat as an evolutionally conserved brain feature relies on development of functional neural circuit in amygdala, but the molecular mechanism remains largely unknown. We here identify that EphB2 receptor tyrosine kinase, which is specifically expressed in glutamatergic neurons, is required for the innate fear responses in the neonatal brain. We further reveal that EphB2 mediates coordination of spinogenesis and neuron activation in amygdala during the critical period for the innate fear. EphB2 catalytic activity plays a major role for the behavior upon EphB–ephrin-B3 binding and transnucleus neuronal connections. Our work thus indicates an essential synaptic molecular signaling within amygdala that controls synapse development and helps bring about innate fear emotions in the postnatal developing brain.

Quantitative susceptibility mapping (QSM) is a recently developed magnetic resonance imaging (MRI) technique for quantifying the spatial distribution of magnetic susceptibility within biological tissues. It first uses the frequency shift in the MRI signal to map the magnetic field profile within the tissue. The resulting field map is then used to determine the spatial distribution of the underlying magnetic susceptibility by solving an inverse problem. The solution is achieved by deconvolving the field map with a dipole field, under the assumption that the magnetic field results from a superposition of the dipole fields generated by all voxels and that each voxel has its own unique magnetic susceptibility. QSM provides an improved contrast-to-noise ratio for certain tissues and structures compared with its magnitude counterpart. More importantly, magnetic susceptibility directly reflects the molecular composition and cellular architecture of the tissue. Consequently, by quantifying magnetic susceptibility, QSM is becoming a quantitative imaging approach for characterizing normal and pathological tissue properties. This article reviews the mechanism that generates susceptibility contrast within tissues and some associated applications.

NOBUGS 2016 Proceedings, The MXCuBE project started in 2005 at ESRF [1], with the objective of providing crystallography beamlines’ users an easy-to-use software platform to run their experiments. The current MXCuBE is based on PyQt, however the usage of old PyQt libraries, as well as the lack of a clear separation between the application control logic and the graphical layer makes it very difficult to maintain, upgrade and extend the current version. This, together with the need of extended capabilities for the operation of the new crystallography beamlines (such as improved remote operation, multiple user handling, cross platform, etc.) pushed the members of the MXCuBE collaboration into the development of a new software based on modern technologies, MXCuBE v3. Taking into account the requirements, the path that best suited the needs is a web-based development. All the remote operation and cross platform needs fits in a natural way in a web environment. Thanks to the single page application paradigm the final user experience can be improved, and not be only a desktop application clone. Also, decoupling the application between client and server improves the code quality, since each element has a clear scope and makes it easier to maintenance, compared to the previous version of MXCuBE. Taking advantage of this new technology the user interface has been completely redesigned, with the aim of enhancing the user experience. The main technologies in use are python-flask web framework [2] for the backend, and React JavaScript library [3] for the frontend, enhanced with several third party libraries for both components. Low-level control is achieved via connection to Tango, Sardana and custom protocols, by means of the so-called “Hardware objects”, which are self-contained pieces of software which links to the underlying instrumentation control. These libraries are being reused from the previous version of MXCuBE. Currently, MXCuBE v3 is under an active development, mainly by MAXIV and ESRF, and has already achieved one of the first milestones defined in 2015, when the first data collection experiment was successfully performed in June 2016 during Biomax commissioning, Fig [fig:MXCuBE-v3-screenshot]. The next months are devoted to increase the stability of the application and to add new features that will be needed when the user operation starts. MXCuBE v3 will not only server as the experiment control environment at Biomax [4] beamline in MAXIV and other facilities in the near future, but also will serve as technological breakthrough for future developments for the whole facility. References: [1] Gabadinho J. et al. MxCuBE: a synchrotron beamline control environment customized for macromolecular crystallography experiments. J Synchrotron Radiat. 2010. [2] Python Flask microwebframework, http://flask.pocoo.org [3] React: a Javascript library for building user interfaces. https://facebook.github.io/react [4] Thunnissen M. et al. The macromolecular crystallography beamlines BioMAX and MicroMAX at the MAX IV laboratory. Acta Crystallographica Section A: Foundations and Advances. 2015.

We compared the parameters derived from diffusion-weighted imaging (DWI) and positron emission tomography/computed tomography (PET/CT) for treatment response evaluation and response prediction in patients with gastrointestinal stromal tumor (GIST). Seven patients with histologically proven metastatic disease were enrolled. DWI and PET/CT data were collected from all patients at diagnosis and from six at follow-up. All 37 lesions were identifiable in DWI with a sensitivity of 100%. To achieve higher accuracy, we used the apparent diffusion coefficient (ADC) of liver and background noise as thresholds for the measurement of the ADCs of lesions. Significant inverse correlations were found between ADCmean_thr (ADCmean with thresholds) and SUVmean (mean standardized uptake value) (R2 = 0.523, p

Innate emotion response to environmental stimuli is a fundamental brain function that is controlled by specific neural circuits. Dysfunction of early emotional circuits may lead to neurodevelopmental disorders such as autism and schizophrenia. However, how the functional circuits are formed to prime initial emotional behaviours remain elusive. We reveal here using gene-targeted mutations an essential role for ephrin-B3 ligand-like activity in the development of innate fear in the neonatal brain. We further demonstrate that ephrin-B3 controls axon targeting and coordinates spinogenesis and neuronal activity within the amygdala. The morphological and behavioural abnormalities in ephrin-B3 mutant mice are rescued by conditional knock-in of wild-type ephrin-B3 during the critical period when axon targeting and fear responses are initiated. Our results thus define a key axonal molecule that participates in the wiring of amygdala circuits and helps bring about fear emotion during the important adolescence period., The molecular mechanism underlying initial circuit wiring in amygdala is poorly understood. Here the authors show that ephrin-B3 is required for axon targeting and amygdala spinogenesis during a critical period in development, and plays an important role in amygdala mediated fear responses.

As the neural network becomes wired, postsynaptic signaling molecules are thought to control the growth of dendrites and synapses. However, how these molecules are coordinated to sculpt postsynaptic structures is less well understood. We find that ephrin-B3, a transmembrane ligand for Eph receptors, functions postsynaptically as a receptor to transduce reverse signals into developing dendrites of mouse hippocampal neurons. Both tyrosine phosphorylation-dependent GRB4 SH2/SH3 adaptor-mediated signals and PSD-95-discs large-zona occludens-1 (PDZ) domain-dependent signals are required for inhibition of dendrite branching, whereas only PDZ interactions are necessary for spine formation and excitatory synaptic function. PICK1 and syntenin, two PDZ domain proteins, participate with ephrin-B3 in these postsynaptic activities. PICK1 has a specific role in spine and synapse formation, and syntenin promotes both dendrite pruning and synapse formation to build postsynaptic structures that are essential for neural circuits. The study thus dissects ephrin-B reverse signaling into three distinct intracellular pathways and protein-protein interactions that mediate the maturation of postsynaptic neurons.

Purpose: We investigated the incidence of lymph node metastasis in gastrointestinal stromal tumor (GIST) patients in our PET/CT database. The demographic data and characteristics of the primary tumor were evaluated in GIST patients with or without lymph node metastasis. Materials and Methods: We reviewed our PET/CT database from January 1, 2007 to November 30, 2010 by using keyword search, and identified GIST with lymph node metastasis according to our standard of reference. Statistical analysis was conducted between GIST group with or without lymph node metastasis based on the age, sex, primary tumor size, and primary tumor location. Results: A total of 29 GIST patients were found in our database. Six of them had lymph node metastasis, corresponding to 20.7%. When considering only the adult patients, the incidence was 17% (5 out of 28). There were 4 males and 1 female, with the mean age of 66.8 years old, which was 8 years older than the group without lymph node metastasis. Of the 5 adult metastasis patients, 4 had their primary tumor located at very rare sites other than stomach or small bowel. Statistical analysis using Fisher exact test of rare location showed significance between the 2 groups with P = 0.004. The mean size of the primary tumor in the group with lymph node metastasis was 5.2 cm, which was 2.9 cm less than the group without metastasis. No statistical significance was found in age, sex, or size of primary tumor between the 2 groups. Conclusion: The incidence of lymph node metastasis in GISTs in our database is 20.7%, which is surprisingly higher than we thought from other previous studies. In contrast to the group without lymph node metastasis, these patients tend to be of older ages and had rare location of the primary tumor. This result supports further study with larger sample size.

It has been suggested that ephrin-B proteins have receptor-like roles in the control of axon pathfinding by repulsion, although it is largely unknown how the reverse signals are coupled to downstream intracellular molecules and how they induce cytoskeletal reorganization at the axon terminal. We found that ephrin-B3 (EB3) was able to function as a repulsive guidance receptor and mediate stereotyped pruning of murine hippocampal mossy fiber axons during postnatal development. Targeted intracellular point mutants showed that axon pruning requires tyrosine phosphorylation-dependent reverse signaling and coupling to the SH2/SH3 adaptor protein Grb4 (also known as Nckbeta/Nck2). Furthermore, we found that the second SH3 domain of Grb4 is required and sufficient for axon pruning/retraction by mediating interactions with Dock180 and PAK to bring about guanine nucleotide exchange and signaling downstream of Rac, respectively. Our results reveal a previously unknown pathway that controls axon pruning and elucidate the biochemical mechanism by which ephrin-B reverse signals regulate actin dynamics to bring about the retraction of growth cones.

RATIONALE Tandem mass (MS/MS) spectra generated by collision-induced dissociation (CID) typically lack redundant peptide sequence information in the form of e.g. b- and y-ion series due to frequent use of sequence-specific endopeptidases cleaving C- or N-terminal to Arg or Lys residues. METHODS Here we introduce arginyl-tRNA protein transferase (ATE, EC 2.3.2.8) for proteomics. ATE recognizes acidic amino acids or oxidized Cys at the N-terminus of a substrate peptide and conjugates an arginine from an aminoacylated tRNAArg onto the N-terminus of the substrate peptide. This enzymatic reaction is carried out under physiological conditions and, in combination with Lys-C/Asp-N double digest, results in arginylated peptides with basic amino acids on both termini. RESULTS We demonstrate that in vitro arginylation of peptides using yeast arginyl tRNA protein transferase 1 (yATE1) is a robust enzymatic reaction, specific to only modifying N-terminal acidic amino acids. Precursors originating from arginylated peptides generally have an increased protonation state compared with their non-arginylated forms. Furthermore, the product ion spectra of arginylated peptides show near complete 2× fragment ladders within the same MS/MS spectrum using commonly available electrospray ionization peptide fragmentation modes. Unexpectedly, arginylated peptides generate complete y- and c-ion series using electron transfer dissociation (ETD) despite having an internal proline residue. CONCLUSIONS We introduce a rapid enzymatic method to generate peptides flanked on either terminus by basic amino acids, resulting in a rich, redundant MS/MS fragment pattern., Rapid Communications in Mass Spectrometry, 28 (24), ISSN:1097-0231, ISSN:0951-4198

Opiate abuse is associated with long-lasting neural adaptative changes in the brain. Increasing evidence demonstrates that opiates significantly alter the function of the glutamatergic system, while how the system is regulated still remains elusive. In the present study, we studied the effect of morphine on extracellular glutamate concentration in the hippocampus, a nucleus rich of the glutamatergic neurons. The results showed that glutamate concentration in the extracellular fluid of the hippocampus was decreased following either acute or chronic treatment of morphine. However, naloxone-induced withdrawal increased glutamate concentration significantly. These results suggest an adaptation of the glutamatergic neuronal transmission in the hippocampus after morphine treatment.

Opiate abuse has been shown to cause adaptive changes in presynaptic release and protein phosphorylation-mediated synaptic plasticity, but the underlying mechanisms remain unclear. Neuronal SNARE proteins serve as important regulatory molecules underlying neural plasticity in view of their major role in the process of neurotransmitter release. In the present study, the expression of SNAP-25, a t-SNARE protein essential for vesicle release, was found to be dramatically regulated in hippocampus after chronic morphine treatment, which was visualized with two-dimensional gel electrophoresis. The spots of SNAP-25 in the gel were shifted along the dimension of isoelectric point, indicating a likely change of the post-transcriptional modification. Immunoblotting analysis with specific antibody to Ser187, a protein kinase C (PKC) phosphorylation site of SNAP-25, revealed that the specific phosphorylation was correspondingly decreased, which was correlated with morphine-induced inhibition of PKC activity. Moreover, the level of ternary complex of SNARE proteins in either synaptosomes or PC12 cells was significantly reduced after chronic morphine treatment. This suggests a causal relationship between the inhibition of PKC-dependent SNAP-25 phosphorylation and the down-regulation of SNARE complex formation after chronic morphine treatment. Further analysis of SNARE complex formed by transfection of the wild-type or Ser187 mutants of SNAP-25 showed that only wild-type-formed complex was inhibited by morphine treatment. Thus, these results indicate that chronic morphine treatment inhibits phosphorylation of SNAP-25 at Ser187 and leads to a down-regulation of SNARE complex formation, which presents a potential molecular mechanism for the alteration of exocytotic process and neural plasticity during opiate abuse.

Accumulating evidence has indicated that there might exist some correlation between opiate reward and certain kinds of learning and memory processes. The present study attempted to investigate the correlation between individual differences in morphine reward and capacities in spatial learning and spontaneous alternation. In the present studies, good-response (GR) and poor-response (PR) mice were respectively selected according to their performance in a spatial learning test involving the Morris water maze or in a spontaneous alternation task using the Y-maze. In a place preference conditioning procedure, morphine (3.0 mg/kg) produced significant conditioned place preference (CPP) in both GR and PR mice selected by using either the Morris water maze or the Y-maze. The PR mice selected with the Morris water maze showed significantly more CPP induced by morphine than the GR mice. However, no detectable difference was observed in morphine-induced CPP between the GR and PR mice selected with the Y-maze. These results suggested that the variation in morphine-induced CPP in mice is somehow differentially related to that of spatial learning but unlikely to that of spontaneous alternation.

How long does it take to equilibrate the unfolded state of a protein? The answer to this question has important implications for our understanding of why many small proteins fold with two state kinetics. When the equilibration within the unfolded state U is much faster than the folding, the folding kinetics will be two state even if there are many folding pathways with different barriers. Yet the mean first passage times (MFPTs) between different regions of the unfolded state can be much longer than the folding time. This seems to imply that the equilibration within U is much slower than the folding. In this communication we resolve this paradox. We present a formula for estimating the time to equilibrate the unfolded state of a protein. We also present a formula for the MFPT to any state within U, which is proportional to the average lifetime of that state divided by the state population. This relation is valid when the equilibration within U is very fast as compared with folding as it often is for small proteins. To illustrate the concepts, we apply the formulas to estimate the time to equilibrate the unfolded state of Trp-cage and MFPTs within the unfolded state based on a Markov State Model using an ultra-long 208 microsecond trajectory of the miniprotein to parameterize the model. The time to equilibrate the unfolded state of Trp-cage is ∼100 ns while the typical MFPTs within U are tens of microseconds or longer.

Diffusion tensor imaging has already been extensively used to probe microstructural alterations in white matter tracts, and scarcely, in deep gray matter. However, results in literature regarding age-related degenerative mechanisms in white matter tracts and parametric changes in the putamen are inconsistent. Diffusional kurtosis imaging is a mathematical extension of diffusion tensor imaging, which could more comprehensively mirror microstructure, particularly in isotropic tissues such as gray matter. In this study, we used the diffusional kurtosis imaging method and a white-matter model that provided metrics of explicit neurobiological interpretations in healthy participants (58 in total, aged from 25 to 84 years). Tract-based whole-brain analyses and regions-of-interest (anterior and posterior limbs of the internal capsule, cerebral peduncle, fornix, genu and splenium of corpus callosum, globus pallidus, substantia nigra, red nucleus, putamen, caudate nucleus, and thalamus) analyses were performed to examine parametric differences across regions and correlations with age. In white matter tracts, evidence was found supportive for anterior-posterior gradient and not completely supportive for retrogenesis theory. Age-related degenerations appeared to be broadly driven by axonal loss. Demyelination may also be a major driving mechanism, although confined to the anterior brain. In terms of deep gray matter, higher mean kurtosis and fractional anisotropy in the globus pallidus, substantia nigra, and red nucleus reflected higher microstructural complexity and directionality compared with the putamen, caudate nucleus, and thalamus. In particular, the unique age-related positive correlations for fractional anisotropy, mean kurtosis, and radial kurtosis in the putamen opposite to those in other regions call for further investigation of exact underlying mechanisms. In summary, the results suggested that diffusional kurtosis can provide measurements in a new dimension that were complementary to diffusivity metrics. Kurtosis together with diffusivity can more comprehensively characterize microstructural compositions and age-related changes than diffusivity alone. Combined with proper model, it may also assist in providing neurobiological interpretations of the identified alterations.

[1] to compare 46 AD patients with 94 age-matched healthy volunteers (Australian Imaging Biomarkers & Lifestyle study). AFD is proportional to the image intensity, which is related to the quantity of intra-axonal water, and is therefore sensitive to the number of axons within a voxel (density). To perform voxel-wise comparisons of AFD, images were non-linearly warped to a common template image. We incorporated morphology information by modulating the AFD in each voxel based on the change to a fibre bundle’s cross-sectional area (atrophy). Modulation ensures the AFD in template space encapsulates both sources of axonal loss (axon density as measured by the MRI signal, and volume loss due to atrophy). We investigated whole-brain group AFD differences with and without modulation using novel tractography-based statistics. Results: Significant AFD decreases in AD were observed in white matter bundles known to be involved in language and memory (Fig.1). As shown in columns 1 & 2, the group AFD difference is more extensive when morphology information is included via AFDmodulation. Since AFD differences are associated with a voxel and direction (shown by the direction-colour-encoded tractogram in Fig.1) population differences can be attributed to a specific fibre bundle in regions with crossing-fibres (e.g. Arcuate Fasciculus).The absence of differences in fibre density (column 1) within regions previously detected using FA suggests that FA decreases detected in AD are largely caused by atrophy-induced partial volume changes. Conclusions: By incorporating morphology information, AFD is potentially a more sensitive and interpretable biomarker of axon degeneration compared to existing diffusion MRI measures based on image intensity alone.[1] Raffelt et al.2012,59(4):3976-94.

To improve the accuracy of volume and apparent diffusion coefficient (ADC) measurements in diffusion-weighted magnetic resonance imaging (MRI), we proposed a method based on thresholding both the b0 images and the ADC maps.In 21 heterogeneous lesions from patients with metastatic gastrointestinal stromal tumors (GIST), gross lesion were manually contoured, and corresponding volumes and ADCs were denoted as gross tumor volume (GTV) and gross ADC (ADC(g)), respectively. Using a k-means clustering algorithm, the probable high-cellularity tumor tissues were selected based on b0 images and ADC maps. ADC and volume of the tissues selected using the proposed method were denoted as thresholded ADC (ADC(thr)) and high-cellularity tumor volume (HCTV), respectively. The metabolic tumor volume (MTV) in positron emission tomography (PET)/computed tomography (CT) was measured using 40% maximum standard uptake value (SUV(max)) as the lower threshold, and corresponding mean SUV (SUV(mean)) was also measured.HCTV had excellent concordance with MTV according to Pearson's correlation (r=0.984, P.001) and linear regression (slope = 1.085, intercept = -4.731). In contrast, GTV overestimated the volume and differed significantly from MTV (P=.005). ADC(thr) correlated significantly and strongly with SUV(mean) (r=-0.807, P.001) and SUV(max) (r=-0.843, P.001); both were stronger than those of ADC(g).The proposed lesion-adaptive semiautomatic method can help segment high-cellularity tissues that match hypermetabolic tissues in PET/CT and enables more accurate volume and ADC delineation on diffusion-weighted MR images of GIST.