Heparin and air filters reduce embolic events caused by intra-arterial cerebral angiography - A prospective, randomized trial

Background-Intra-arterial cerebral angiography is associated with a low risk for neurological complications, but clinically silent ischemic events after angiography have been seen in a substantial number of patients.Methods and Results-In a prospective study, diffusion-weighted magnetic resonance imaging (DW-MRI) before and after intra-arterial cerebral angiography and transcranial Doppler sonography during angiography were used to evaluate the frequency of cerebral embolism. One hundred fifty diagnostic cerebral angiographies were randomized into 50 procedures, each using conventional angiographic technique, or systemic heparin treatment throughout the procedure, or air filters between the catheter and both the contrast medium syringe and the catheter flushing. There was no neurological complication during or after angiography. Overall, DW-MRI revealed 26 new ischemic lesions in 17 patients (11%). In the control group, 11 patients showed a total of 18 lesions. In the heparin group, 3 patients showed a total of 4 lesions. In the air filter group, 3 patients exhibited a total of 4 lesions. The reduced incidence of ischemic events in the heparin and air filter groups compared with the control group was significantly different (P=0.002). Transcranial Doppler sonography demonstrated a large number of microembolic signals that was significantly lower in the air filter group compared with the heparin and control groups (P=0.01), which did not differ from each other.Conclusions-Air filters and heparin both reduce the incidence of silent ischemic events detected by DW-MRI after intra-arterial cerebral angiography and can potentially lower clinically overt ischemic complications. This may apply to any intra-arterial angiographic procedure

Mtmr13/Sbf2-deficient mice: an animal model for CMT4B2

Charcot-Marie-Tooth (CMT) disease denotes a large group of genetically heterogeneous hereditary motor and sensory neuropathies and ranks among the most common inherited neurological disorders. Mutations in the Myotubularin-Related Protein-2 (MTMR2) or MTMR13/Set-Binding Factor-2 (SBF2) genes are associated with the autosomal recessive disease subtypes CMT4B1 or CMT4B2. Both forms of CMT share similar features including a demyelinating neuropathy associated with reduced nerve conduction velocity (NCV) and focally folded myelin. Consistent with a common disease mechanism, the homodimeric MTMR2 acts as a phosphoinositide D3-phosphatase with phosphatidylinositol (PtdIns) 3-phosphate and PtdIns 3,5-bisphosphate as substrates while MTMR13/SBF2 is catalytically inactive but can form a tetrameric complex with MTMR2, resulting in a strong increase of the enzymatic activity of complexed MTMR2. To prove that MTMR13/SBF2 is the disease-causing gene in CMT4B2 and to provide a suitable animal model, we have generated Mtmr13/Sbf2-deficient mice. These animals reproduced myelin outfoldings and infoldings in motor and sensory peripheral nerves as the pathological hallmarks of CMT4B2, concomitant with decreased motor performance. The number and complexity of myelin misfoldings increased with age, associated with axonal degeneration, and decreased compound motor action potential amplitude. Prolonged F-wave latency indicated a mild NCV impairment. Loss of Mtmr13/Sbf2 did not affect the levels of its binding partner Mtmr2 and the Mtmr2-binding Dlg1/Sap97 in peripheral nerves. Mice deficient in Mtmr13/Sbf2 together with known Mtmr2-deficient animals will be of major value to unravel the disease mechanism in CMT4B and to elucidate the critical functions of protein complexes that are involved in phosphoinositide-controlled processes in peripheral nerve

Production and characterization of monoclonal antibodies to the extracellular domain of PO

Seven monoclonal antibodies were raised against the immunoglobulin-like extracellular domain of PO (POED), the major protein of peripheral nervous system myelin. Mice were immunized with purified recombinant rat PO-ED. After fusion, 7 clones (POI-P07) recognizing either recombinant, rat, mouse, or human PO-ED were selected by ELlS A and were characterized by Western blot, immunohistochemistry, and a competition assay. Antibodies belonged to the IgG or IgM class, and P04-P07, reacted with PO in fresh-frozen and paraffin-embedded sections of human or rat peripheral nerve, but not with myelin proteins of the central nervous system of either species. Epitope specificity of the antibodies was determined by a competition enzyme-linked immunosorbent assay (ELISA) and a direct ELlS A using short synthetic peptides spanning the entire extracellular domain of PO. These assays showed that POl and P02 exhibiting the same reaction pattern in Western blot and immunohistochemistry reacted with different distant epitopes of PO. Furthermore, the monoclonal antibodies P05 and P06 recognized 2 different epitopes in close proximity within the neuritogenic extracellular sequence of PO. This panel of monoclonal antibodies, each binding to a different epitope of the extracellular domain of PO, will be useful for in vitro and in vivo studies designed to explore the role of PO during myelination and in demyelinating diseases of the peripheral nervous system

An animal model for Charcot-Marie-Tooth disease type 4B1

Charcot-Marie-Tooth disease (CMT) comprises a family of clinically and genetically very heterogeneous hereditary peripheral neuropathies and is one of the most common inherited neurological disorders. We have generated a mouse model for CMT type 4B1 using embryonic stem cell technology. To this end, we introduced a stop codon into the Mtmr2 locus within exon 9, at the position encoding amino acid 276 of the MTMR2 protein (E276X). Concomitantly, we have deleted the chromosomal region immediately downstream of the stop codon up to within exon 13. The resulting allele closely mimics the mutation found in a Saudi Arabian CMT4B1 patient. Animals homozygous for the mutation showed various degrees of complex myelin infoldings and outfoldings exclusively in peripheral nerves, in agreement with CMT4B1 genetics and pathology. Mainly, paranodal regions of the myelin sheath were affected, with a high degree of quantitative and qualitative variability between individuals. This pathology was progressive with age, and axonal damage was occasionally observed. Distal nerve regions were more affected than proximal parts, in line with the distribution in CMT. However, we found no significant electrophysiological changes, even in aged (16-month-old) mice, suggesting that myelin infoldings and outfoldings per se are not invariably associated with detectable electrophysiological abnormalities. Our animal model provides a basis for future detailed molecular and cellular studies on the underlying disease mechanisms in CMT4B1. Such an analysis will reveal how the disease develops, in particular, the enigmatic myelin infoldings and outfoldings as well as axonal damage, and provide mechanistic insights that may aid in the development of potential therapeutic approache

Describing the Lived Experiences of K-12 Teachers Addressing the Unique Needs of Black and Marginalized Twice-Exceptional Students: A Transcendental Phenomenological Study

The purpose of this phenomenological study was to describe the lived experiences of K-12 teachers addressing the unique needs of Black and marginalized twice-exceptional students in the United States. At this stage in the research, Black and marginalized twice-exceptional (2e) students are minority students that are gifted students that have a disability. The theory guiding this study was the teacher expectancy theory. This study was a transcendental phenomenological study. The study took place in the United States. Pseudonyms were used to protect the identities of the participants. The central research question asked, what are the lived experiences of teachers addressing the unique needs of Black and marginalized 2e students? Lesson plans, individual interviews, and observations were used to collect data. These data collections helped me understand the teachers’ lived experiences. The data was analyzed by coding to find the emerging themes from the participant’s responses. Also, triangulation and data reduction were used to analyze the data. The research revealed that teachers were unsure of how to support 2e students, lacked training and support, remained optimistic, and obstacles to success. It was recommended for future studies that researchers describe the lived experiences of Native American 2e students and female 2e students, that each state creates policies to support 2e students, and administration becomes trained in how to support 2e students so they could train their teachers

The Gdap1 knockout mouse mechanistically links redox control to Charcot-Marie-Tooth disease

Mutations in the mitochondrial fission factor GDAP1 are associated with severe peripheral neuropathies, but why the CNS remains unaffected is unclear. Using a Gdap1−/− mouse, Niemann et al. demonstrate that a CNS-expressed Gdap1 paralogue changes its subcellular localisation under oxidative stress conditions to also act as a mitochondrial fission facto

Myelin is dependent on the Charcot-Marie-Tooth Type 4H disease culprit protein FRABIN/FGD4 in Schwann cells

Studying the function and malfunction of genes and proteins associated with inherited forms of peripheral neuropathies has provided multiple clues to our understanding of myelinated nerves in health and disease. Here, we have generated a mouse model for the peripheral neuropathy Charcot-Marie-Tooth disease type 4H by constitutively disrupting the mouse orthologue of the suspected culprit gene FGD4 that encodes the small RhoGTPase Cdc42-guanine nucleotide exchange factor Frabin. Lack of Frabin/Fgd4 causes dysmyelination in mice in early peripheral nerve development, followed by profound myelin abnormalities and demyelination at later stages. At the age of 60 weeks, this was accompanied by electrophysiological deficits. By crossing mice carrying alleles of Frabin/Fgd4 flanked by loxP sequences with animals expressing Cre recombinase in a cell type-specific manner, we show that Schwann cell-autonomous Frabin/Fgd4 function is essential for proper myelination without detectable primary contributions from neurons. Deletion of Frabin/Fgd4 in Schwann cells of fully myelinated nerve fibres revealed that this protein is not only required for correct nerve development but also for accurate myelin maintenance. Moreover, we established that correct activation of Cdc42 is dependent on Frabin/Fgd4 function in healthy peripheral nerves. Genetic disruption of Cdc42 in Schwann cells of adult myelinated nerves resulted in myelin alterations similar to those observed in Frabin/Fgd4-deficient mice, indicating that Cdc42 and the Frabin/Fgd4-Cdc42 axis are critical for myelin homeostasis. In line with known regulatory roles of Cdc42, we found that Frabin/Fgd4 regulates Schwann cell endocytosis, a process that is increasingly recognized as a relevant mechanism in peripheral nerve pathophysiology. Taken together, our results indicate that regulation of Cdc42 by Frabin/Fgd4 in Schwann cells is critical for the structure and function of the peripheral nervous system. In particular, this regulatory link is continuously required in adult fully myelinated nerve fibres. Thus, mechanisms regulated by Frabin/Fgd4-Cdc42 are promising targets that can help to identify additional regulators of myelin development and homeostasis, which may crucially contribute also to malfunctions in different types of peripheral neuropathie