Tractostorm: The what,why, and how of tractography dissection reproducibility

Investigative studies of white matter (WM) brain structures using diffusion MRI (dMRI) tractography frequently require manual WM bundle segmentation, often called “virtual dissection.” Human errors and personal decisions make these manual segmentations hard to reproduce, which have not yet been quantified by the dMRI community. It is our opinion that if the field of dMRI tractography wants to be taken seriously as a widespread clinical tool, it is imperative to harmonize WM bundle segmentations and develop protocols aimed to be used in clinical settings. The EADC‐ADNI Harmonized Hippocampal Protocol achieved such standardization through a series of steps that must be reproduced for every WM bundle. This article is an observation of the problematic. A specific bundle segmentation protocol was used in order to provide a real‐life example, but the contribution of this article is to discuss the need for reproducibility and standardized protocol, as for any measurement tool. This study required the participation of 11 experts and 13 nonexperts in neuroanatomy and “virtual dissection” across various laboratories and hospitals. Intra‐rater agreement (Dice score) was approximately 0.77, while inter‐rater was approximately 0.65. The protocol provided to participants was not necessarily optimal, but its design mimics, in essence, what will be required in future protocols. Reporting tractometry results such as average fractional anisotropy, volume or streamline count of a particular bundle without a sufficient reproducibility score could make the analysis and interpretations more difficult. Coordinated efforts by the diffusion MRI tractography community are needed to quantify and account for reproducibility of WM bundle extraction protocols in this era of open and collaborative science.     

Inhibition of angiogenesis by antibody blocking the action of proangiogenic high-molecular-weight kininogen

Summary.  Previously we demonstrated that domain 5 (D5) of high-molecular-weight kininogen (HK) inhibits neovascularization in the chicken chorioallantoic membrane (CAM) assay and further found that kallikrein cleaved HK (HKa) inhibited FGF2-and VEGF-induced neovascularization, and thus was antiangiogenic. In this study, we sought to demonstrate whether uncleaved HK stimulates neovascularization and thus is proangiogenic. The chick chorioallantoic membrane was used as an in ovo assay of angiogenesis. Low-molecular-weight kininogen stimulates angiogenesis, indicating that D5 is not involved. Bradykinin stimulates neovascularization equally to HK and LK and is likely to be responsible for the effect of HK. A murine monoclonal antibody to HK (C11C1) also recognizes a similar component in chicken plasma as detected by surface plasmon resonance. Angiogenesis induced by FGF2 and VEGF is inhibited by this monoclonal antibody and is a more potent inhibitor of neovascularization induced by VEGF than an integrin α_vβ₃ antibody (LM 609). Our postulate that C11C1 inhibits the stimulation of angiogenesis by HK was confirmed when either C11C1 or D5 completely inhibited angiogenesis in the CAM induced by HK. Growth of human fibrosarcoma (HT-1080) on the CAM was inhibited by GST-D5 and C11C1. These results indicate HK is proangiogenic probably by releasing bradykinin and that a monoclonal antibody directed to HK could serve as an antiangiogenic agent with a potential for inhibiting tumor angiogenesis and other angiogenesis-mediated disorders.     

Assessment of the efficacy of teriparatide treatment for osteoporosis on lumbar fusion surgery outcomes: a systematic review and meta-analysis

Neurosurgical Review - Treatment of osteoporosis with medications like teriparatide, a parathyroid hormone, is known to improve bone density and reduce the risk of osteoporotic vertebral fractures....     

Photorealistic imaging of left atrial appendage occlusion/exclusion

Recent improvements in 3D TEE post processing rendering techniques referred to as TrueVue (Philips Medical Systems, Andover, MA, USA). It allows for novel photorealistic imaging of cardiac structures including left atrial appendage (LAA) and its closure devices. Here we present TrueVue images of the LAA prior to and after LAA exclusion/occlusion using various percutaneous and surgical techniques. TrueVue may improve delineation of LAA anatomy prior to occlusion as well as visualization of occluder device position within the LAA.     

Lone Aortic Insufficiency and Conduction Disease: A Marker of Reactive Arthritis

A 48‐year‐old male with history of chronic arthritis and uveitis presented with 1 year of progressively reduced exercise capacity and nonexertional chest pain. Physical examination was consistent with severe aortic insufficiency. An electrocardiogram demonstrated sinus rhythm with first degree atrioventricular block. Transthoracic and transesophageal echocardiography demonstrated severe lone central aortic insufficiency of a trileaflet valve due to leaflet thickening, retraction of leaflet margins and mild aortic root dilation in the setting of left ventricular dilatation. In addition, computed tomographic angiography revealed a small focal aneurysm of the distal transverse arch. He was found to be positive for the immunogenetic marker HLA‐B27. The patient subsequently underwent uncomplicated mechanical aortic valve replacement. The diagnosis of HLA‐B27 associated cardiac disease should be entertained in any individual with lone aortic insufficiency, especially if accompanied by conduction disease.     

Temperature changes and chondrocyte death during drilling in a bovine cartilage model and chondroprotection by modified irrigation solutions

Purpose

Drilling into cartilage/bone is often required for orthopaedic surgery. While drilling into bone has been studied, the response of cartilage has received little attention. We have measured cartilage and drill bit temperatures during drilling and quantified the zone of chondrocyte death (ZCD) around the hole in the presence/absence of irrigation solutions.

Methods

Drilling was performed using a 1.5-mm orthopaedic drill bit applied to bovine metatarsophalangeal joints and temperatures recorded by infrared camera. Osteochondral explants were then incubated with 5-chloromethylfluorescein diacetate (CMFDA) and propidium iodide (PI) to label living/dead chondrocytes respectively. The width of the ZCD was quantified by confocal laser scanning microscopy (CLSM) and image analysis.

Results

Without irrigation, the ZCD following drilling for two seconds was 135?±?15 μm and this increased (>fourfold, P?P?P?265 and 119 °C respectively, whereas the camera saturated at >282 °C during drilling for five seconds. With irrigation, the drill bit temperature was significantly reduced during drilling for two and five seconds (approx. 90 °C) with negligible change in cartilage temperature. Drilling while irrigating with hyperosmotic saline (600 mOsm) reduced (P?P?2+ saline (5 mM).

Conclusions

Reducing temperature during drilling by irrigation markedly suppressed, but did not abolish chondrocyte death. Optimising the irrigation solution by raising osmolarity and reducing Ca²⁺ content significantly reduced chondrocyte death during drilling and may be clinically beneficial.     

Selective degeneration of a physiological subtype of spinal motor neuron in mice with SOD1-linked ALS

Amyotrophic lateral sclerosis (ALS; Lou Gehrig’s disease) affects motor neurons (MNs) in the brain and spinal cord. Understanding the pathophysiology of this condition seems crucial for therapeutic design, yet few electrophysiological studies in actively degenerating animal models have been reported. Here, we report a novel preparation of acute slices from adult mouse spinal cord, allowing visualized whole cell patch-clamp recordings of fluorescent lumbar MN cell bodies from ChAT-eGFP or superoxide dismutase 1-yellow fluorescent protein (SOD1YFP) transgenic animals up to 6 mo of age. We examined 11 intrinsic electrophysiologic properties of adult ChAT-eGFP mouse MNs and classified them into four subtypes based on these parameters. The subtypes could be principally correlated with instantaneous (initial) and steady-state firing rates. We used retrograde tracing using fluorescent dye injected into fast or slow twitch lower extremity muscle with slice recordings from the fluorescent-labeled lumbar MN cell bodies to establish that fast and slow firing MNs are connected with fast and slow twitch muscle, respectively. In a G85R SOD1YFP transgenic mouse model of ALS, which becomes paralyzed by 5–6 mo, where MN cell bodies are fluorescent, enabling the same type of recording from spinal cord tissue slices, we observed that all four MN subtypes were present at 2 mo of age. At 4 mo, by which time substantial neuronal SOD1YFP aggregation and cell loss has occurred and symptoms have developed, one of the fast firing subtypes that innvervates fast twitch muscle was lost. These results begin to describe an order of the pathophysiologic events in ALS.Amyotrophic lateral sclerosis (ALS; Lou Gehrig’s disease) is a progressive and usually lethal neurodegenerative condition prominently featuring loss of motor neurons (MNs) and muscle denervation (1–3). Inherited forms of ALS, accounting for ∼10% of cases, potentially inform about disease mechanisms, including: protein folding and quality control [e.g., mutant superoxide dismutase 1 (SOD1), ubiquilin2, and VCP]; RNA binding proteins (e.g., TDP43, FUS, and HNRNPA1); or a DNA expansion (C9ORF72 hexanucleotide expansion). The clinical courses of the various heritable forms and the 90% of cases that are considered sporadic are not distinct, however, reflecting a potentially shared progressive loss of MNs and motor circuit dysfunction (4).ALS has been modeled in mice that are transgenic for a variety of mutant forms of SOD1, allowing for the study of the trajectory of the condition at various time points (5, 6). Among the studies conducted to date are a number addressing electrophysiological changes. From these studies, however, there does not appear to be a clear consensus on the changes that occur in MNs before and during the development of symptoms (7). For example, whereas research on the neuromuscular junction has revealed preferential denervation of fast twitch (type IIb) muscle fibers (8–10), the relationship of this selective susceptibility at the muscle level to pathophysiologic change in the spinal cord is not clear.A major challenge to understanding spinal cord physiology of the mouse models of ALS arises from difficulty in distinguishing the individual features of neurons in the anatomically and physiologically heterogeneous motor system. For example, the usefulness of in vivo recordings requires ensuring adequate sampling of anatomically and functionally heterogeneous spinal cord MNs. For the ex vivo alternative, slice physiology is challenging because most mouse models develop disease after 1 mo of age, a time when spinal cord tissue becomes more sensitive to ischemia (11, 12), making isolation of viable slices difficult. In addition, the spinal cord becomes heavily myelinated in the first few weeks of postnatal life (13), making visualization of individual neurons difficult. Hence, most research regarding cellular electrophysiology in mouse models of ALS has been carried out with primary cultures of embryonic (E13–14) spinal cord MNs (14) or induced pluripotent stem (iPS) cell-derived MNs (15). Although they provide a basis for further study, these models may lack the changes that occur progressively in the context of an intact spinal cord. These models may also lack the diversity of MN physiology present in the mature spinal cord.Here we studied a transgenic strain of ALS mice, G85R SOD1YFP (16), that develops motor symptoms by ∼3 mo of age, associated with progressive accumulation of aggregates in MN cell bodies (from ∼1 mo of age), attended by MN cell loss. The mice paralyze uniformly by 5–6 mo of age. We first developed, using ChAT- EGFP mice that express GFP fluorescence in MNs (17), an acute slice preparation of adult mouse spinal cord that yielded healthy MNs in animals up to and beyond 6 mo of age, readily visualized by their fluorescence, enabling whole cell patch-clamp recordings when coupled with differential interference contrast (DIC) imaging. This preparation allowed extensive characterization of normal MN electrophysiology and enabled grouping of MNs, distinguishing four firing types. We then recorded from MNs in slices from ALS animals at two time points: during the course of aggregation at 2–3 mo of age, before symptoms, and after the onset and initial progression of symptoms at 4 mo of age. At the early time, the four distinct clusters of MNs were present, albeit the fastest firing type (cluster 4) exhibited a significant hyperpolarization. At the later time point, this firing type was no longer detectable, with only the other three types observable, the fastest of which (cluster 3) was now hyperpolarized. Retrograde tracing from fast and slow twitch muscles of the lower extremity revealed that aggregates form preferentially in MN cell bodies attached to fast twitch muscle. These observations suggest a possible sequence of events in which hyperpolarization of the cluster 4 MNs, innervating fast twitch muscle, is associated with aggregate formation in these neurons, which then die, denervating fast twitch muscle.