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  • Understanding Medical Research

    27 October 2017

    Understanding Medical Research: The Studies That Shaped Medicine is an exciting new title that offers a unique and valuable approach to understanding historically influential studies in important areas of medicine.

  • IgG-specific cell-based assay detects potentially pathogenic MuSK-Abs in seronegative MG.

    11 May 2018

    OBJECTIVE: To increase the detection of MuSK-Abs using a CBA and test their pathogenicity. METHODS: Sera from 69 MuSK-RIA-positive patients with myasthenia gravis (MG) (Definite MuSK-MG), 169 patients negative for MuSK-RIA and AChR-RIA (seronegative MG, SNMG), 35 healthy individuals (healthy controls, HCs), and 16 NMDA receptor-Ab-positive (NMDAR-Ab) disease controls were tested for binding to MuSK on a CBA using different secondary antibodies. RESULTS: Initially, in addition to 18% of SNMG sera, 11% of HC and 19% of NMDAR-Ab sera showed positive binding to MuSK-transfected cells; this low specificity was due to anti-IgG(H+L) detection of IgM bound nonspecifically to MuSK. Using an IgG Fc gamma-specific secondary antibody, MuSK-Abs were detected by CBA in 68/69 (99%) of Definite MuSK-MG, 0/35 HCs, 0/16 NMDAR-Ab, and 14/169 (8%) of SNMG sera, providing increased sensitivity with high specificity. The RIA-negative, CBA-positive MuSK-IgG sera, but not IgM-MuSK-binding sera, reduced agrin-induced AChR clustering in C2C12 myotubes, qualitatively similar to RIA-positive MuSK-Abs. CONCLUSIONS: An IgG-specific MuSK-CBA can reliably detect IgG MuSK-Abs and increase sensitivity. In the MuSK-CBA, IgG specificity is essential. The positive sera demonstrated pathogenic potential in the in vitro AChR-clustering assay, although less effective than Definite MuSK-MG sera, and the patients had less severe clinical disease. Use of IgG-specific secondary antibodies may improve the results of other antibody tests. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that an IgG-specific MuSK-CBA identifies patients with MG.

  • Robotic mouse

    12 January 2018

    © Springer Science+Business Media Dordrecht 2013. Gene targeting is a very powerful approach for the generation of clinically relevant mouse models to elucidate the underlying molecular basis of cerebellar disorders. However, with the etiology of the vast majority of these conditions still unknown, a complementary approach based on large-scale random mutagenesis is now being employed to identify new genes and downstream signaling pathways that control neuronal cell death and survival in the cerebellum. This chapter presents the characterization of the robotic mouse, a novel model of autosomal dominant cerebellar Ataxia isolated from an N-ethyl-N-nitrosourea (ENU) mutagenesis screen, which shows general growth retardation, adult-onset region-specific Purkinje cell (PC) loss, cataracts, and defects in early T-cell maturation. The mutated protein ALL1-fused gene from chromosome 4 (AF4), which functions as a cofactor of RNA polymerase II (Pol II) elongation and disruptor of telomeric silencing-1 (DOT1)-mediated chromatin remodeling during transcription, abnormally accumulates in PCs of the cerebellum due to a slower turnover by the ubiquitin-proteasome pathway. This results in the sustained transcriptional repression of the PC survival factor insulin-like growth factor 1 (IGF-1) and deficits in downstream signaling activation, leading to degeneration and eventually death of PCs. The identification of AF4 and DOT1 as the first transcriptional negative regulators of IGF-1 expression in the cerebellum opens new avenues of research into the manipulation of this pathway for the treatment of cerebellar Ataxia. In addition, the functional conservation among the AF4-related proteins implies that deregulation of transcriptional elongation and chromatin remodeling may also underlie the pathogenesis of other disorders of the central nervous system (CNS), in particular mental retardation. The robotic mouse has revealed a critical novel function for AF4 in the cerebellum which could not have been predicted otherwise, and has been instrumental in the elucidation of the relevant transcriptional regulatory mechanisms.

  • Multiparametric measurement of cerebral physiology using calibrated fMRI.

    7 May 2018

    The ultimate goal of calibrated fMRI is the quantitative imaging of oxygen metabolism (CMRO2), and this has been the focus of numerous methods and approaches. However, one underappreciated aspect of this quest is that in the drive to measure CMRO2, many other physiological parameters of interest are often acquired along the way. This can significantly increase the value of the dataset, providing greater information that is clinically relevant, or detail that can disambiguate the cause of signal variations. This can also be somewhat of a double-edged sword: calibrated fMRI experiments combine multiple parameters into a physiological model that requires multiple steps, thereby providing more opportunity for error propagation and increasing the noise and error of the final derived values. As with all measurements, there is a trade-off between imaging time, spatial resolution, coverage, and accuracy. In this review, we provide a brief overview of the benefits and pitfalls of extracting multiparametric measurements of cerebral physiology through calibrated fMRI experiments.

  • Fast dynamic ventilation MRI of hyperpolarized 129 Xe using spiral imaging.

    14 May 2018

    PURPOSE: To develop and optimize a rapid dynamic hyperpolarized 129 Xe ventilation (DXeV) MRI protocol and investigate the feasibility of capturing pulmonary signal-time curves in human lungs. THEORY AND METHODS: Spiral k-space trajectories were designed with the number of interleaves Nint  = 1, 2, 4, and 8 corresponding to voxel sizes of 8 mm, 5 mm, 4 mm, and 2.5 mm, respectively, for field of view = 15 cm. DXeV images were acquired from a gas-flow phantom to investigate the ability of Nint  = 1, 2, 4, and 8 to capture signal-time curves. A finite element model was constructed to investigate gas-flow dynamics corroborating the experimental signal-time curves. DXeV images were also carried out in six subjects (three healthy and three chronic obstructive pulmonary disease subjects). RESULTS: DXeV images and numerical modelling of signal-time curves permitted the quantification of temporal and spatial resolutions for different numbers of spiral interleaves. The two-interleaved spiral (Nint  = 2) was found to be the most time-efficient to obtain DXeV images and signal-time curves of whole lungs with a temporal resolution of 624 ms for 13 slices. Signal-time curves were well matched in three healthy volunteers. The Spearman's correlations of chronic obstructive pulmonary disease subjects were statistically different from three healthy subjects (P < 0.05). CONCLUSION: The Nint  = 2 spiral demonstrates the successful acquisition of DXeV images and signal-time curves in healthy subjects and chronic obstructive pulmonary disease patients. Magn Reson Med 79:2597-2606, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

  • Increased cerebral functional connectivity in ALS: A resting-state magnetoencephalography study.

    10 May 2018

    OBJECTIVE: We sought to assess cortical function in amyotrophic lateral sclerosis (ALS) using noninvasive neural signal recording. METHODS: Resting-state magnetoencephalography was used to measure power fluctuations in neuronal oscillations from distributed cortical parcels in 24 patients with ALS and 24 healthy controls. A further 9 patients with primary lateral sclerosis and a group of 15 asymptomatic carriers of genetic mutations associated with ALS were also studied. RESULTS: Increased functional connectivity, particularly from the posterior cingulate cortex, was demonstrated in both patient groups compared to healthy controls. Directionally similar patterns were also evident in the asymptomatic genetic mutation carrier group. CONCLUSION: Increased cortical functional connectivity elevation is a quantitative marker that reflects ALS pathology across its clinical spectrum, and may develop during the presymptomatic period. The amelioration of pathologic magnetoencephalography signals might be a marker sensitive enough to provide proof-of-principle in the development of future neuroprotective therapeutics.

  • Cerebrospinal fluid macrophage biomarkers in amyotrophic lateral sclerosis.

    21 May 2018

    OBJECTIVE: The neurodegenerative disease, amyotrophic lateral sclerosis (ALS), is a heterogeneous clinical syndrome involving multiple molecular pathways. The development of biomarkers for use in therapeutic trials is a priority. We sought to use a high-throughput proteomic method to identify novel biomarkers in individual cerebrospinal fluid (CSF) samples. METHODS: Liquid chromatography/tandem mass spectrometry with label-free quantification was used to identify CSF proteins using samples from a well-characterized longitudinal cohort comprising patients with ALS (n = 43), the upper motor neuron variant, primary lateral sclerosis (PLS; n = 6), and cross-sectional healthy (n = 20) and disease controls (Parkinsons' disease, n = 20; ALS mimic disorders, n = 12). RESULTS: Three macrophage-derived chitinases showed increased abundance in ALS: chitotriosidase (CHIT1), chitinase-3-like protein 1 (CHI3L1), and chitinase-3-like protein 2 (CHI3L2). Elevated CHI3L1 was common to ALS and PLS, whereas CHIT1 and CHI3L2 levels differed. Chitinase levels correlated with disease progression rate (CHIT1, r = 0.56, p < 0.001; CHI3L1, r = 0.31; p = 0.028; CHI3L2, r = 0.29, p = 0.044). CHIT1, CHI3L1, and CHI3L2 levels correlated with phosphorylated neurofilament heavy chain (pNFH; r = 0.62, p < 0.001; r = 0.49, p < 0.001; r = 0.41, p < 0.001). CHI3L1 levels, but not CHIT1 or CHI3L2, increased over time in those with low initial levels (gradient = 0.005 log abundance units/month, p = 0.001). High CHIT1 was associated with shortened survival (hazard ratio [HR] 2.84; p = 0.009). Inclusion of pNFH in survival models left only an association of pNFH and survival (HR 1.26; p = 0.019). INTERPRETATION: Neuroinflammatory mechanisms have been consistently implicated through various experimental paradigms. These results support a key role for macrophage activity in ALS pathogenesis, offering novel target engagement and pharmacodynamic biomarkers for neuroinflammation-focused ALS therapy. Ann Neurol 2018;83:258-268.