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Peripheral neurons that sense glucose relay signals of glucose availability to integrative clusters of neurons in the brain. However, the roles of such signalling pathways in the maintenance of glucose homoeostasis and their contribution to disease are unknown. Here we show that the selective activation of the nerve plexus of the hepatic portal system via peripheral focused ultrasound stimulation (pFUS) improves glucose homoeostasis in mice and rats with insulin-resistant diabetes and in swine subject to hyperinsulinemic-euglycaemic clamps. pFUS modulated the activity of sensory projections to the hypothalamus, altered the concentrations of metabolism-regulating neurotransmitters, and enhanced glucose tolerance and utilization in the three species, whereas physical transection or chemical blocking of the liver-brain nerve pathway abolished the effect of pFUS on glucose tolerance. Longitudinal multi-omic profiling of metabolic tissues from the treated animals confirmed pFUS-induced modifications of key metabolic functions in liver, pancreas, muscle, adipose, kidney and intestinal tissues. Non-invasive ultrasound activation of afferent autonomic nerves may represent a non-pharmacologic therapy for the restoration of glucose homoeostasis in type-2 diabetes and other metabolic diseases.

BackgroundThe brain predominantly expressed RING finger protein, Znf179, is known to be important for embryonic neuronal differentiation during brain development. Downregulation of Znf179 has been observed in motor neurons of adult mouse models for amyotrophic lateral sclerosis (ALS), yet the molecular function of Znf179 in neurodegeneration has never been previously described. Znf179 contains the classical C3HC4 RING finger domain, and numerous proteins containing C3HC4 RING finger domain act as E3 ubiquitin ligases. Hence, we are interested to identify whether Znf179 possesses E3 ligase activity and its role in ALS neuropathy.MethodsWe used in vivo and in vitro ubiquitination assay to examine the E3 ligase autoubiquitination activity of Znf179 and its effect on 26S proteasome activity. To search for the candidate substrates of Znf179, we immunoprecipitated Znf179 and subjected to mass spectrometry (MS) analysis to identify its interacting proteins. We found that ALS/ FTLD-U (frontotemporal lobar degeneration (FTLD) with ubiquitin inclusions)-related neurodegenerative TDP-43 protein is the E3 ligase substrate of Znf179. To further clarify the role of E3 ubiquitin ligase Znf179 in neurodegenerative TDP-43-UBI (ubiquitinated inclusions) (+) proteinopathy, the effect of Znf179-mediated TDP-43 polyubiquitination on TDP-43 protein stability, aggregate formation and nucleus/cytoplasm mislocalization were evaluated in vitro cell culture system and in vivo animal model.ResultsHere we report that Znf179 is a RING E3 ubiquitin ligase which possesses autoubiquitination feature and regulates 26S proteasome activity through modulating the protein expression levels of 19S/20S proteasome subunits. Our immunoprecipitation assay and MS analysis results revealed that the neuropathological TDP-43 protein is one of its E3 ligase substrate. Znf179 interactes with TDP-43 protein and mediates polyubiquitination of TDP-43 in vitro and in vivo. In neurodegenerative TDP-43 proteinopathy, we found that Znf179-mediated polyubiquitination of TDP-43 accelerates its protein turnover rate and attenuates insoluble pathologic TDP-43 aggregates, while knockout of Znf179 in mouse brain results in accumulation of insoluble TDP-43 and cytosolic TDP-43 inclusions in cortex, hippocampus and midbrain regions.ConclusionsHere we unveil the important role for the novel E3 ligase Znf179 in TDP-43-mediated neuropathy, and provide a potential therapeutic strategy for combating ALS/ FTLD-U neurodegenerative pathologies.

Netrin1 has been proposed to act from the floor plate (FP) as a long-range diffusible chemoattractant for commissural axons in the embryonic spinal cord. However, netrin1 mRNA and protein are also present in neural progenitors within the ventricular zone (VZ), raising the question of which source of netrin1 promotes ventrally directed axon growth. Here, we use genetic approaches in mice to selectively remove netrin from different regions of the spinal cord. Our analyses show that the FP is not the source of netrin1 directing axons to the ventral midline, while local VZ-supplied netrin1 is required for this step. Furthermore, rather than being present in a gradient, netrin1 protein accumulates on the pial surface adjacent to the path of commissural axon extension. Thus, netrin1 does not act as a long-range secreted chemoattractant for commissural spinal axons but instead promotes ventrally directed axon outgrowth by haptotaxis, i.e., directed growth along an adhesive surface.

Topographic neuronal maps arise as a consequence of axon trajectory choice correlated with the localisation of neuronal soma, but the identity of the pathways coordinating these processes is unknown. We addressed this question in the context of the myotopic map formed by limb muscles innervated by spinal lateral motor column (LMC) motor axons where the Eph receptor signals specifying growth cone trajectory are restricted by Foxp1 and Lhx1 transcription factors. We show that the localisation of LMC neuron cell bodies can be dissociated from axon trajectory choice by either the loss or gain of function of the Reelin signalling pathway. The response of LMC motor neurons to Reelin is gated by Foxp1- and Lhx1-mediated regulation of expression of the critical Reelin signalling intermediate Dab1. Together, these observations point to identical transcription factors that control motor axon guidance and soma migration and reveal the molecular hierarchy of myotopic organisation.

Mathematical interest in electrical impedance tomography has been strong since the publication of Calderon's foundational paper. This paper introduced the idea of applying external voltage patterns to a medium such that, assuming that the medium is sufficiently close to a constant admittivity, the reconstruction can be accomplished directly by inverse Fourier transform. Motivated by Calderon's method, we have developed a variant of the algorithm which is applicable to the case of measurement on only a part of the boundary and on discrete electrodes. Here we determine voltage or current patterns to apply to the electrodes which optimally approximate Calderon's special functions in the interior. Furthermore, in three dimensions and higher, Calderon's method allows each point in Fourier space to be computed in a multiplicity of ways. We show that by making use of the inherent redundancy in our measurements, we can significantly improve the quality of the static images produced by our algorithm. Index Terms--Breast cancer screening, direct reconstruction, electrode models, image reconstruction, impedance imaging.

It has been known for some time that many tumors have a significantly different conductivity and permittivity from surrounding normal tissue. This high 'contrast' in tissue electrical properties, occurring between a few kilohertz and several megahertz, may permit differentiating malignant from benign tissues. Here we show the ability of electrical impedance spectroscopy (EIS) to roughly localize and clearly distinguish cancers from normal tissues and benign lesions. Localization of these lesions is confirmed by simultaneous, in register digital breast tomosynthesis (DBT) mammography or 3-D mammograms. Index Terms--Breast cancer detection, digital breast tomosynthesis (DBT) mammography, electrical impedance spectroscopy (EIS), electrical impedance tomography (EIT).

Phantoms are frequently used in medical imaging systems to test hardware, reconstruction algorithms, and the interpretation of data. This report describes and characterizes the use of powdered graphite as a means of adding a significant reactive component or permittivity to useful phantom media for electrical impedance imaging. The phantom materials produced have usable complex admittivity at the electrical impedance tomography (EIT) frequencies from a few kilohertz to 1 MHz, as measured by our EIT system (ACT4) and by a commercial bioimpedance analyzer (BIS 4000, Xitron). We have also studied a commercial ultrasound coupling gel, which is highly electrically conductive and semisolid but that permits objects to move within it. The mixture of agar-graphite and gel-graphite, increases in permittivity and conductivity are proportional to the graphite concentration. We also report the use of a porous polymer membrane to simulate skin. A thin layer of this membrane increased resistance and the characteristic frequency of the phantoms, providing a promising candidate to simulate the effect of skin and the layered structure of a breast or other anatomical structure. The graphite also provides a realistic level of 'speckle' in ultrasound images of the phantom, which may be useful in developing dual-mode imaging systems with ultrasound and the EIT. Index Terms--Electrical impedance tomography (EIT), graphite powder, high-permittivity phantom, porous polymer.

Electrical impedance tomography (EIT) is a developing imaging modality that is beginning to show promise for detecting and characterizing tumors in the breast. At Rensselaer Polytechnic Institute, we have developed a combined EIT-tomosynthesis system that allows for the coregistered and simultaneous analysis of the breast using EIT and X-ray imaging. A significant challenge in EIT is the design of computationally efficient image reconstruction algorithms which are robust to various forms of model mismatch. Specifically, we have implemented a scaling procedure that is robust to the presence of a thin highly-resistive layer of skin at the boundary of the breast and we have developed an algorithm to detect and exclude from the image reconstruction electrodes that are in poor contact with the breast. In our initial clinical studies, it has been difficult to ensure that all electrodes make adequate contact with the breast, and thus procedures for the use of data sets containing poorly contacting electrodes are particularly important. We also present a novel, efficient method to compute the Jacobian matrix for our linearized image reconstruction algorithm by reducing the computation of the sensitivity for each voxel to a quadratic form. Initial clinical results are presented, showing the potential of our algorithms to detect and localize breast tumors. Index Terms--Breast cancer screening, electrical impedance tomography, image reconstruction, inverse problems.

The conductivity and permittivity of breast tumors are known to differ significantly from those of normal breast tissues, and electrical impedance tomography (EIT) is being studied as a modality for breast cancer imaging to exploit these differences. At present, X-ray mammography is the primary standard imaging modality used for breast cancer screening in clinical practice, so it is desirable to study EIT in the geometry of mammography. This paper presents a forward model of a simplified mammography geometry and a reconstruction algorithm for breast tumor imaging using EIT techniques. The mammography geometry is modeled as a rectangular box with electrode arrays on the top and bottom planes. A forward model for the electrical impedance imaging problem is derived for a homogeneous conductivity distribution and is validated by experiment using a phantom tank. A reconstruction algorithm for breast tumor imaging based on a linearization approach and the proposed forward model is presented. It is found that the proposed reconstruction algorithm performs well in the phantom experiment, and that the locations of a 5-mm-cube metal target and a 6-mm-cube agar target could be recovered at a target depth of 15 mm using a 32 electrode system. Index Terms--Breast imaging, electrical impedance tomography, mammography geometry, reconstruction algorithm.

• We tested TDP-43 expression in lateral motor column (LMC) neurons growing into a limb. • TDP-43 function loss/gain redirects LMC axon trajectory selection w/ opposite effects. • TDP-43 level changes LMC explant neurite growth preference against ephrin ligands. • Other ligand types including Netrin-1 and Semaphorin3 F were not involved in TDP-43-mediated LMC pathfinding. • TDP-43 is essential for the ephrin-mediated LMC axon trajectory into the limb. During the neural circuit formation, neuronal growth cones must be guided precisely to their neuronal or muscle targets, which can be achieved by the activation of membrane-bound guidance receptors at the periphery. However, the mechanisms that regulate the temporal availability of these receptors remain largely unknown. TAR DNA binding protein-43 (TDP-43) has been proposed to bind with the mRNAs of guidance receptors, thus prompting us to investigate its role in axon guidance of the spinal lateral motor column (LMC) neurons into the limb mesenchyme. We first identified the TDP-43 expression in the LMC neurons at the stage of axons growth into the limb using in situ mRNA hybridization. The loss and gain of TDP-43 function in chick LMC neurons redirected their axon trajectory with opposite effects. In mice, a spinal motor neuron-specific TDP-43 deletion led to the misrouting of LMC axons. Further, ectopic TDP-43 expression increased EphB protein levels in LMC neurons, suggesting that TDP-43 mediates LMC pathfinding by regulating EphB expression. Finally, TDP-43 levels influenced the growth preference of LMC neurites against ephrin-B, but not Netrin-1 and Semaphorin ligands. Our results demonstrate that TDP-43 is essential for the ephrinB:EphB signaling-mediated axon trajectory selection of LMC subtypes into the limb. [ABSTRACT FROM AUTHOR]

Background: Proper guidance of neuronal axons to their targets is required to assemble neural circuits during the development of the nervous system. However, the mechanism by which the guidance of axonal growth cones is regulated by specific intermediaries activated by receptor signaling pathways to mediate cytoskeleton dynamics is unclear. Vav protein members have been proposed to mediate this process, prompting us to investigate their role in the limb selection of the axon trajectory of spinal lateral motor column (LMC) neurons. Results: We found Vav2 and Vav3 expression in LMC neurons when motor axons grew into the limb. Vav2, but not Vav3, loss‐of‐function perturbed LMC pathfinding, while Vav2 gain‐of‐function exhibited the opposite effects, demonstrating that Vav2 plays an important role in motor axon growth. Vav2 knockdown also attenuated the redirectional phenotype of LMC axons induced by Dcc, but not EphA4, in vivo and lateral LMC neurite growth preference to Netrin‐1 in vitro. This study showed that Vav2 knockdown and ectopic nonphosphorylable Vav2 mutant expression abolished the Src‐induced stronger growth preference of lateral LMC neurites to Netrin‐1, suggesting that Vav2 is downstream of Src in this context. Conclusions: Vav2 is essential for Netrin‐1‐regulated LMC motor axon pathfinding through Src interaction. Key Findings: Spinal cord, motor neuron, axon guidance. [ABSTRACT FROM AUTHOR]