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Suxamethonium and Critical Illness Polyneuropathy
Administration of suxamethonium to patients with critical illness polyneuropathy may produce life-threatening hyper-kalaemia. A questionnaire to assess the awareness of this problem was sent to all UK intensive care units. A clinical scenario suggestive of critical illness polyneuropathy was accompanied by a list of possible drugs used to facilitate endotracheal intubation. Most respondents (68.7%) chose suxamethonium while 20.4% avoided any muscle relaxant. This result suggests a worrying lack of appreciation of the dangers of suxamethonium use in critical illness polyneuropathy.
Challenging barriers to surgical access in lower and middle-income countries
The Lancet Commission on Global Surgery suggests that five billion people do not have access to safe, affordable surgical and anaesthesia care when needed.1 This is most evident in lower- and middle-income countries where 9 out of 10 people do not have access to basic surgical care.1.
Delayed Acclimatization of the Ventilatory Threshold in Healthy Trekkers
Objective To test the hypothesis that acclimatization to high altitude results in an improvement of the ventilatory threshold (VT). Methods Eight lowlanders underwent cardiopulmonary exercise testing with a cycle ergometer to determine VT and peak oxygen uptake (Vo2peak) in Coventry, United Kingdom (altitude: 80 m), on arrival in Leh, India (altitude: 3500 m), and after 12 days of acclimatization that included a 5-day high altitude trek up to 4770 m. Results Vo2peak fell on arrival at 3500 m and remained depressed at 12 days. VT was depressed on arrival at high altitude and was further depressed at 12 days. VT as a proportion of the Vo2peak was decreased on arrival at high altitude, and after acclimatization, this relationship was further decreased. Conclusions Individuals who are sedentary or not participating in regular physical training appear to require a longer period of acclimatization than trained athletes. With the increasing numbers participating in high-altitude trekking and charity climbs of peaks, such as Mt. Kilimanjaro, this information has clinically significant practical implications for those leading or acting as medical advisors.
Human VCP mutant ALS/FTD microglia display immune and lysosomal phenotypes independently of GPNMB
Abstract Background Microglia play crucial roles in maintaining neuronal homeostasis but have been implicated in contributing to amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). However, the role of microglia in ALS/FTD remains incompletely understood. Methods Here, we generated highly enriched cultures of VCP mutant microglia derived from human induced pluripotent stem cells (hiPSCs) to investigate their cell autonomous and non-cell autonomous roles in ALS pathogenesis. We used RNA-sequencing, proteomics and functional assays to study hiPSC derived VCP mutant microglia and their effects on hiPSC derived motor neurons and astrocytes. Results Transcriptomic, proteomic and functional analyses revealed immune and lysosomal dysfunction in VCP mutant microglia. Stimulating healthy microglia with the inflammatory inducer lipopolysaccharide (LPS) showed partial overlap with VCP mutant microglia in their reactive transformation. LPS-stimulated VCP mutant microglia displayed differential activation of inflammatory pathways compared with LPS-stimulated healthy microglia. Conserved gene expression changes were identified between VCP mutant microglia, SOD1 mutant mice microglia, and postmortem ALS spinal cord microglial signatures, including increased expression of the transmembrane glycoprotein GPNMB. While knockdown of GPNMB affected inflammatory and phagocytosis processes in microglia, this was not sufficient to ameliorate cell autonomous phenotypes in VCP mutant microglia. Secreted factors from VCP mutant microglia were sufficient to activate the JAK-STAT pathway in hiPSC derived motor neurons and astrocytes. Conclusions VCP mutant microglia undergo cell autonomous reactive transformation involving immune and lysosomal dysfunction that partially recapitulate key phenotypes of microglia from other ALS models and post mortem tissue. These phenotypes occur independently of GPNMB. Additionally, VCP mutant microglia elicit non cell autonomous responses in motor neurons and astrocytes involving the JAK-STAT pathway.
The ALS/FTD-related C9orf72 hexanucleotide repeat expansion forms RNA condensates through multimolecular G-quadruplexes
AbstractAmyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are neurodegenerative diseases that exist on a clinico-pathogenetic spectrum, designated ALS/FTD. The most common genetic cause of ALS/FTD is expansion of the intronic hexanucleotide repeat (GGGGCC)n in C9orf72. Here, we investigate the formation of nucleic acid secondary structures in these expansion repeats, and their role in generating condensates characteristic of ALS/FTD. We observe significant aggregation of the hexanucleotide sequence (GGGGCC)n, which we associate to the formation of multimolecular G-quadruplexes (mG4s) by using a range of biophysical techniques. Exposing the condensates to G4-unfolding conditions leads to prompt disassembly, highlighting the key role of mG4-formation in the condensation process. We further validate the biological relevance of our findings by detecting an increased prevalence of G4-structures in C9orf72 mutant human motor neurons when compared to healthy motor neurons by staining with a G4-selective fluorescent probe, revealing signal in putative condensates. Our findings strongly suggest that RNA G-rich repetitive sequences can form protein-free condensates sustained by multimolecular G-quadruplexes, highlighting their potential relevance as therapeutic targets for C9orf72 mutation-related ALS/FTD.
Estimating the effectiveness of routine asymptomatic PCR testing at different frequencies for the detection of SARS-CoV-2 infections
AbstractBackgroundRoutine asymptomatic testing using RT-PCR of people who interact with vulnerable populations, such as medical staff in hospitals or care workers in care homes, has been employed to help prevent outbreaks among vulnerable populations. Although the peak sensitivity of RT-PCR can be high, the probability of detecting an infection will vary throughout the course of an infection. The effectiveness of routine asymptomatic testing will therefore depend on testing frequency and how PCR detection varies over time.MethodsWe fitted a Bayesian statistical model to a dataset of twice weekly PCR tests of UK healthcare workers performed by self-administered nasopharyngeal swab, regardless of symptoms. We jointly estimated times of infection and the probability of a positive PCR test over time following infection; we then compared asymptomatic testing strategies by calculating the probability that a symptomatic infection is detected before symptom onset and the probability that an asymptomatic infection is detected within 7 days of infection.ResultsWe estimated that the probability that the PCR test detected infection peaked at 77% (54–88%) 4 days after infection, decreasing to 50% (38–65%) by 10 days after infection. Our results suggest a substantially higher probability of detecting infections 1–3 days after infection than previously published estimates. We estimated that testing every other day would detect 57% (33–76%) of symptomatic cases prior to onset and 94% (75–99%) of asymptomatic cases within 7 days if test results were returned within a day.ConclusionsOur results suggest that routine asymptomatic testing can enable detection of a high proportion of infected individuals early in their infection, provided that the testing is frequent and the time from testing to notification of results is sufficiently fast.
Drug screening with human SMN2 reporter identifies SMN protein stabilizers to correct SMA pathology
Spinal muscular atrophy (SMA), the leading genetic cause of infant mortality, is caused by reduced levels of functional survival motor neuron (SMN) protein. To identify therapeutic agents for SMA, we established a versatile SMN2-GFP reporter line by targeting the human SMN2 gene. We then screened a compound library and identified Z-FA-FMK as a potent candidate. Z-FA-FMK, a cysteine protease inhibitor, increased functional SMN through inhibiting the protease-mediated degradation of both full-length and exon 7–deleted forms of SMN. Further studies reveal that CAPN1, CAPN7, CTSB, and CTSL mediate the degradation of SMN proteins, providing novel targets for SMA. Notably, Z-FA-FMK mitigated mitochondriopathy and neuropathy in SMA patient–derived motor neurons and showed protective effects in SMA animal model after intracerebroventricular injection. E64d, another cysteine protease inhibitor which can pass through the blood–brain barrier, showed even more potent therapeutic effects after subcutaneous delivery to SMA mice. Taken together, we have successfully established a human SMN2 reporter for future drug discovery and identified the potential therapeutic value of cysteine protease inhibitors in treating SMA via stabilizing SMN proteins.
Outcomes After Acute Plasma Exchange for Myelin Oligodendrocyte Glycoprotein Antibody-Associated Disease.
BACKGROUND AND OBJECTIVES: Data on the plasma exchange (PLEX) in myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) are limited. Herein, we evaluate outcomes after PLEX in MOGAD. METHODS: This international multicenter retrospective cohort study included patients from 18 tertiary care centers in 6 countries. Inclusion criteria included fulfillment of the 2023 International MOGAD panel criteria, receipt of at least 3 sessions of PLEX, and follow-up of ≥3 months after PLEX. Patients with coexisting neuroinflammatory disorders were excluded. We assessed the frequency of complete recovery (CR), clinically significant improvement (CSI), visual acuity (VA), and Expanded Disability Status Scale (EDSS). Logistic regression analyses were performed to identify predictors of CR and CSI. RESULTS: Of 234 patients, 135 (58%) were female. The median (interquartile range [IQR]) age at attack was 34 (IQR 22-49) years, and 42 (17%) were children. In 165 of 243 (68%), the attack treated with PLEX was the first attack. Attack phenotypes included 161 optic neuritis (235 eyes), 77 myelitis, 24 acute disseminated encephalomyelitis, 15 brainstem/cerebellar, 3 cerebral-cortical encephalitis attack, and 1 cerebral polyfocal deficit-36 with >1 core phenotypes. A total of 239 (99%) attacks were also treated with corticosteroids and 32 (13%) with IV immunoglobulins. VA in optic neuritis improved from 20/400 (20/70-hand motion) to 20/20 (20/20-20/30), p < 0.001, and EDSS decreased from a median of 4.0 (3.0-6.5) to 1.0 (0.0-2.5), p < 0.001. Of 229 attacks without subsequent attacks within 3 months, 100 (44%) achieved CR and 213 (93%) CSI. The probability of CR was decreased with advanced age (adjusted odd ratio [95% CI] 0.97 [0.96-0.99] per year), higher EDSS worsening from baseline (0.66 [0.54-0.81] per 0.5 increment) and delayed PLEX (0.98 [0.96-0.99] per day). Advanced age (0.97 [0.96-0.99] per year) and delayed PLEX (0.95 [0.94-0.96] per day) decreased the probability of CSI. DISCUSSION: We observed favorable outcomes after PLEX in MOGAD attacks. However, advanced age and delayed initiation of PLEX were associated with a reduced probability of improvement. The absence of a control group limits our ability to differentiate PLEX effects from spontaneous recovery, prior corticosteroid response, or long-term immunotherapy. Future prospective studies are needed to assess the impact of PLEX on improvement. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that PLEX is associated with favorable clinical outcomes in patients with MOGAD.