Highly Selective Electrochemical Baeyer-Villiger Oxidation through Oxygen Atom Transfer from Water.

The Baeyer-Villiger oxidation of ketones is a crucial oxygen atom transfer (OAT) process used for ester production. Traditionally, Baeyer-Villiger oxidation is accomplished by thermally oxidizing the OAT from stoichiometric peroxides, which are often difficult to handle. Electrochemical methods hold promise for breaking the limitation of using water as the oxygen atom source. Nevertheless, existing demonstrations of electrochemical Baeyer-Villiger oxidation face the challenges of low selectivity. We report in this study a strategy to overcome this challenge. By employing a well-known water oxidation catalyst, Fe2O3, we achieved nearly perfect selectivity for the electrochemical Baeyer-Villiger oxidation of cyclohexanone. Mechanistic studies suggest that it is essential to produce surface hydroperoxo intermediates (M-OOH, where M represents a metal center) that promote the nucleophilic attack on ketone substrates. By confining the reactions to the catalyst surfaces, competing reactions (e.g., dehydrogenation, carboxylic acid cation rearrangements, and hydroxylation) are greatly limited, thereby offering high selectivity. The surface-initiated nature of the reaction is confirmed by kinetic studies and spectroelectrochemical characterizations. This discovery adds nucleophilic oxidation to the toolbox of electrochemical organic synthesis.

Low Catalyst Loading Enhances Charge Accumulation for Photoelectrochemical Water Splitting.

Solar water oxidation is a critical step in artificial photosynthesis. Successful completion of the process requires four holes and releases four protons. It depends on the consecutive accumulation of charges at the active site. While recent research has shown an obvious dependence of the reaction kinetics on the hole concentrations on the surface of heterogeneous (photo)electrodes, little is known about how the catalyst density impacts the reaction rate. Using atomically dispersed Ir catalysts on hematite, we report a study on how the interplay between the catalyst density and the surface hole concentration influences the reaction kinetics. At low photon flux, where surface hole concentrations are low, faster charge transfer was observed on photoelectrodes with low catalyst density compared to high catalyst density; at high photon flux and high applied potentials, where surface hole concentrations are moderate or high, slower surface charge recombination was afforded by low-density catalysts. The results support that charge transfer between the light absorber and the catalyst is reversible; they reveal the unexpected benefits of low-density catalyst loading in facilitating forward charge transfer for desired chemical reactions. It is implied that for practical solar water splitting devices, a suitable catalyst loading is important for maximized performance.

Atomically dispersed Ir catalysts exhibit support-dependent water oxidation kinetics during photocatalysis.

Heterogeneous water oxidation catalysis is central to the development of renewable energy technologies. Recent research has suggested that the reaction mechanisms are sensitive to the hole density at the active sites. However, these previous results were obtained on catalysts of different materials featuring distinct active sites, making it difficult to discriminate between competing explanations. Here, a comparison study based on heterogenized dinuclear Ir catalysts (Ir-DHC), which feature the same type of active site on different supports, is reported. The prototypical reaction was water oxidation triggered by pulsed irradiation of suspensions containing a light sensitizer, Ru(bpy)32+, and a sacrificial electron scavenger, S2O82-. It was found that at relatively low temperatures (288-298 K), the water oxidation activities of Ir-DHC on indium tin oxide (ITO) and CeO2 supports were comparable within the studied range of fluences (62-151 mW cm-2). By contrast, at higher temperatures (310-323 K), Ir-DHC on ITO exhibited a ca. 100% higher water oxidation activity than on CeO2. The divergent activities were attributed to the distinct abilities of the supporting substrates in redistributing holes. The differences were only apparent at relatively high temperatures when hole redistribution to the active site became a limiting factor. These findings highlight the critical role of the supporting substrate in determining the turnover at active sites of heterogeneous catalysts.

Coronavirus disease 2019 infection and cerebrovascular diseases: an update on the pathophysiology and management.

PURPOSE OF REVIEW: COVID-19 is an ongoing global pandemic since it was first discovered in 2020. Cerebral vascular disease and stroke are among the most common and devastating neurological manifestations of COVID-19. This review offers an up-to-date information on the possible underlying mechanism of COVID-19-related stroke, its diagnosis, and management. RECENT FINDINGS: The thromboembolism associated with COVID-19 infection is likely related to the cytokine storm with innate immune activation, pulmonary disease leading to hypoxia-induced ischemia, thrombotic microangiopathy, endothelial damage and multifactorial activation of the coagulation cascade. Currently, there is no clear guidelines on the use of antithrombotics for the prevention and treatment of this phenomenon. SUMMARY: COVID-19 infection can directly cause a stroke or facilitate the formation of thromboembolism in the presence of other medical conditions. Physicians treating patients with COVID-19 should stay vigilant about the signs and symptoms of stroke, detect and treat early.

Effect of the Shanghai Stroke Service System (4S) on the quality of stroke care and outcomes: A prospective quality improvement project.

BACKGROUND: In China, disparities in the quality of stroke care still exist and implementing quality improvement is still a challenge. AIM: The aim of the study was to determine whether the intervention by Shanghai Stroke Service System (4S) has helped improve adherence to stroke care guidelines and patient outcome. METHODS: The 4S is a regional stroke network with real-time data extraction among its 61 stroke centers in Shanghai. A total of 11 key performance indicators (KPIs) were evaluated. The primary outcomes were a composite measure and an all-or-none measure of adherence to 11 KPIs. The secondary outcomes were length of hospital stay and in-hospital mortality. RESULTS: The study enrolled 92,395 patients (mean age 69.0 ± 12.5 years, 65.2% men) with acute ischemic stroke hospitalized within 7 days of onset in Shanghai from January 2015 to December 2020. More patients received guideline recommended care between 2018 and 2020 than those between 2015 and 2017 (composite measure 87.1% vs 83.6%; absolute difference 2.9%, 95% confidence interval (CI) = [2.7%, 3.2%], p < 0.001; all-or-none measure 49.2% vs 44.8% patients; absolute difference 3.5%, 95% CI = [2.7%, 4.2%], p < 0.001). Further analysis of individual KPIs showed an absolute increase in six KPIs ranging from 3.4% to 8.9% (p < 0.001 for all comparisons). Compared with 2015-2017, hospital length of stay was shorter (10.95 vs 11.90 days; absolute difference -1.08, 95% CI = [-1.18, -0.99], p < 0.001), and in-hospital mortality was significantly reduced (risk ratio (RR) = 0.88, 95% CI = [0.79, 0.98], p = 0.01) in 2018-2020. CONCLUSION: The 4S intervention was associated with increased adherence to the stroke care guidelines, which further translated to improved clinical outcomes. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT02735226.

Stem cell treatment improves post stroke neurological outcomes: a comparative study in male and female rats.

BACKGROUND AND PURPOSE: The therapeutic potential of different stem cells for ischaemic stroke treatment is intriguing and somewhat controversial. Recent results from our laboratory have demonstrated the potential benefits of human umbilical cord blood-derived mesenchymal stem cells (MSC) in a rodent stroke model. We hypothesised that MSC treatment would effectively promote the recovery of sensory and motor function in both males and females, despite any apparent sex differences in post stroke brain injury. METHODS: Transient focal cerebral ischaemia was induced in adult Sprague-Dawley rats by occlusion of the middle cerebral artery. Following the procedure, male and female rats of the untreated group were euthanised 1 day after reperfusion and their brains were used to estimate the resulting infarct volume and tissue swelling. Additional groups of stroke-induced male and female rats were treated with MSC or vehicle and were subsequently subjected to a battery of standard neurological/neurobehavioral tests (Modified Neurological Severity Score assessment, adhesive tape removal, beam walk and rotarod). The tests were administered at regular intervals (at days 1, 3, 5, 7 and 14) after reperfusion to determine the time course of neurological and functional recovery after stroke. RESULTS: The infarct volume and extent of swelling of the ischaemic brain were similar in males and females. Despite similar pathological stroke lesions, the clinical manifestations of stroke were more pronounced in males than females, as indicated by the neurological scores and other tests. MSC treatment significantly improved the recovery of sensory and motor function in both sexes, and it demonstrated efficacy in both moderate stroke (females) and severe stroke (males). CONCLUSIONS: Despite sex differences in the severity of post stroke outcomes, MSC treatment promoted the recovery of sensory and motor function in male and female rats, suggesting that it may be a promising treatment for stroke.

Bell inequalities for entangled qubits: quantitative tests of quantum character and nonlocality on quantum computers.

This work provides quantitative tests of the extent of violation of two inequalities applicable to qubits coupled into Bell states, using IBM's publicly accessible quantum computers. Violations of the inequalities are well established. Our purpose is not to test the inequalities, but rather to determine how well quantum mechanical predictions can be reproduced on quantum computers, given their current fault rates. We present results for the spin projections of two entangled qubits, along three axes A, B, and C, with a fixed angle θ between A and B and a range of angles θ' between B and C. For any classical object that can be characterized by three observables with two possible values, inequalities govern relationships among the probabilities of outcomes for the observables, taken pairwise. From set theory, these inequalities must be satisfied by all such classical objects; but quantum systems may violate the inequalities. We have detected clear-cut violations of one inequality in runs on IBM's publicly accessible quantum computers. The Clauser-Horne-Shimony-Holt (CHSH) inequality governs a linear combination S of expectation values of products of spin projections, taken pairwise. Finding S > 2 rules out local, hidden variable theories for entangled quantum systems. We obtained values of S greater than 2 in our runs prior to error mitigation. To reduce the quantitative errors, we used a modification of the error-mitigation procedure in the IBM documentation. We prepared a pair of qubits in the state |00〉, found the probabilities to observe the states |00〉, |01〉, |10〉, and |11〉 in multiple runs, and used that information to construct the first column of an error matrix M. We repeated this procedure for states prepared as |01〉, |10〉, and |11〉 to construct the full matrix M, whose inverse is the filtering matrix. After applying filtering matrices to our averaged outcomes, we have found good quantitative agreement between the quantum computer output and the quantum mechanical predictions for the extent of violation of both inequalities as functions of θ'.

Association of elevated hs-CRP and multiple infarctions with outcomes of minor stroke or TIA: subgroup analysis of CHANCE randomised clinical trial.

BACKGROUND AND PURPOSE: The relationship of high-sensitive C-reactive protein (hs-CRP) levels and infarction numbers with the prognosis of stroke is uncertain. This study evaluated the association of different hs-CRP levels and infarction numbers with the prognosis of acute minor ischaemic stroke or transient ischaemic attack (TIA). METHODS: A subset of 807 patients with both hs-CRP measurement and baseline MRI was included from the Clopidogrel in High-risk Patients with Acute Non-disabling Cerebrovascular Events trial. The primary efficacy outcome was the occurrence of an ischaemic stroke at the 1-year follow-up. Infarction numbers were classified as multiple acute infarctions (MAIs), single acute infarction and no acute infarction (NAI). The association between different hs-CRP levels with different infarction numbers and the risk of any outcome was analysed using multivariable Cox regression models. RESULTS: Among the 807 patients, 84 (10.4%) patients had a recurrent ischaemic stroke within 1 year. After adjustment for conventional confounding factors, patients with both elevated hs-CRP levels and MAIs were associated with approximately 4.7-fold of risk of ischaemic stroke within 1 year (16.7% vs 3.5%, HR 4.68, 95% CI 1.54 to 14.23, p=0.007), compared with those with non-elevated hs-CRP levels and NAI. Similar results were observed for the composite events. CONCLUSIONS: Combined elevated hs-CRP levels and MAIs may increase 1-year stroke risk stratification efficiency in patients with minor ischaemic stroke or TIA compared with using those markers alone, which indicated that the combination of inflammatory and imaging markers might improve the effectiveness of risk stratification concerning minor ischaemic stroke or TIA.ClinicalTrials.gov Registry (NCT00979589).

Blood Pressure Variability during Angiography in Patients with Ischemic Stroke and Intracranial Artery Stenosis.

Our aim was to investigate factors predicting blood pressure (BP) variability during diagnostic cerebral angiography and associations between BP variability and clinical outcomes in patients with acute and subacute ischemic stroke and intracranial artery stenosis. 114 patients with ischemic stroke and intracranial artery stenosis (stenosis rate >50%) were recruited. Patients who underwent cerebral angiography within 3 days and 3-14 days of disease onset are referred to be Group A and Group S, respectively. BP variability in Group A was defined as the coefficient of variance (CV) of BP. Univariate and multivariate regression analyses were used to identify predictors of CV of BP and associations between CV of BP and clinical outcomes at discharge. In Group A patients, advanced age was associated with increased CV of SBP and diastolic blood pressure (DBP), and antihypertensive use was associated with lower CV of SBP. Male was associated with lower CV of DBP. In Group S, higher CV of SBP was associated with hypertension and antihypertensive use. Males had lower CV of SBP than females. The calcium channel blocker was associated with lower CV of DBP. Higher scores of the Stroke Scale at admission were significantly associated with poor clinical outcomes for both groups, while BP variability was not. Factors associated with BP variability are significantly different between stroke patients undergoing angiography within 3 days vs. 3-14 days after disease onset. BP variability is not significantly associated with clinical outcomes at discharge.

Preserving stroke care during the COVID-19 pandemic: Potential issues and solutions.

The coronavirus 2019 (COVID-19) pandemic requires drastic changes in allocation of resources, which can affect the delivery of stroke care, and many providers are seeking guidance. As caregivers, we are guided by 3 distinct principles that will occasionally conflict during the pandemic: (1) we must ensure the best care for those stricken with COVID-19, (2) we must provide excellent care and advocacy for patients with cerebrovascular disease and their families, and (3) we must advocate for the safety of health care personnel managing patients with stroke, with particular attention to those most vulnerable, including trainees. This descriptive review by a diverse group of experts in stroke care aims to provide advice by specifically addressing the potential impact of this pandemic on (1) the quality of the stroke care delivered, (2) ethical considerations in stroke care, (3) safety and logistic issues for providers of patients with stroke, and (4) stroke research. Our recommendations on these issues represent our best opinions given the available information, but are subject to revision as the situation related to the COVID-19 pandemic continues to evolve. We expect that ongoing emergent research will offer additional insights that will provide evidence that could prompt the modification or removal of some of these recommendations.

Low-dose versus standard-dose alteplase in acute ischemic stroke in Asian stroke registries: an individual patient data pooling study.

OBJECTIVE: To investigate the comparative efficacy and safety of the low-dose versus standard-dose alteplase using real-world acute stroke registry data from Asian countries. METHODS: Individual participant data were obtained from nine acute stroke registries from China, Japan, Philippines, Singapore, South Korea, and Taiwan between 2005 and 2018. Inverse probability of treatment weight was used to remove baseline imbalances between those receiving low-dose versus standard-dose alteplase. The primary outcome was death or disability defined by modified Rankin Scale scores of 2 to 6 at 90 days. Secondary outcomes were symptomatic intracerebral hemorrhage and death. Generalized linear mixed models with the individual registry as a random intercept were performed to determine associations of treatment with low-dose alteplase and outcomes. RESULTS: Of the 6250 patients (mean age 66 years, 36% women) included in these analyses, 1610 (24%) were treated with low-dose intravenous alteplase. Clinical outcomes for low-dose alteplase were not significantly different to those for standard-dose alteplase, adjusted odds ratios for death or disability: 1.00 (0.85-1.19) and symptomatic intracerebral hemorrhage 0.87 (0.63-1.19), except for lower death with borderline significance, 0.77 (0.59-1.01). CONCLUSIONS: The present analyses of real-world Asian acute stroke registry data suggest that low-dose intravenous alteplase has overall comparable efficacy for functional recovery and greater potential safety in terms of reduced mortality, to standard-dose alteplase for the treatment of acute ischemic stroke.

Exosomes Secreted by the Cocultures of Normal and Oxygen-Glucose-Deprived Stem Cells Improve Post-stroke Outcome.

Emerging stroke literature suggests that treatment of experimentally induced stroke with stem cells offered post-stroke neuroprotection via exosomes produced by these cells. Treatment with exosomes has great potential to overcome the limitations associated with cell-based therapies. However, in our preliminary studies, we noticed that the exosomes released from human umbilical cord blood-derived mesenchymal stem cells (MSCs) under standard culture conditions did not improve the post-stroke neurological outcome. Because of this apparent discrepancy, we hypothesized that exosome characteristics vary with the conditions of their production. Specifically, we suggest that the exosomes produced from the cocultures of regular and oxygen-glucose-deprived (OGD) MSCs in vitro would represent the exosomes produced from MSCs that are exposed to ischemic brain cells in vivo, and offer similar therapeutic benefits that the cell treatment would provide. We tested the efficacy of therapy with exosomes secreted from human umbilical cord blood (HUCB)-derived MSCs under in vitro hypoxic conditions on post-stroke brain damage and neurological outcome in a rat model of transient focal cerebral ischemia. We performed the TTC staining procedure as well as the neurological tests including the modified neurological severity scores (mNSS), the modified adhesive removal (sticky-tape), and the beam walking tests before ischemia and at regular intervals until 7 days reperfusion. Treatment with exosomes obtained from the cocultures of normal and OGD-induced MSCs reduced the infarct size and ipsilateral hemisphere swelling, preserved the neurological function, and facilitated the recovery of stroke-induced rats. Based on the results, we conclude that the treatment with exosomes secreted from MSCs at appropriate experimental conditions attenuates the post-stroke brain damage and improves the neurological outcome.

Exosomes Treatment Mitigates Ischemic Brain Damage but Does Not Improve Post-Stroke Neurological Outcome.

BACKGROUND/AIMS: Recent studies demonstrated that the treatment with mesenchymal stem cells (MSCs) obtained from the human umbilical cord blood improved survival, reduced brain damage, prevented apoptosis, suppressed inflammatory responses, downregulated the DNA damage-inducing genes, upregulated the DNA repair genes, and facilitated neurological recovery in stroke-induced animals. Emerging stroke literature supports the concept that the exosomes released from MSCs are the primary biological principles underlying the post-stroke neuroprotection offered by MSCs treatment. METHODS: Because the treatment with exosomes has a great potential to overcome the limitations associated with cell-based therapies, we tested the efficacy of exosomes secreted from HUCB-MSCs under standard culture conditions on post-stroke brain damage and neurological outcome in a rat model of ischemic stroke by performing TTC staining as well as the modified neurological severity scores, modified adhesive removal, beam-walking, and accelerating Rotarod performance tests before ischemia and at regular intervals until seven days reperfusion. RESULTS: Exosomes treatment attenuated the infarct size. Treatment with exosomes did not affect the post-stroke survival rate and body weight changes, but exacerbated the somatosensory and motor dysfunction and adversely affected the natural recovery that occurs without any treatment. CONCLUSION: Treatment with exosomes secreted from HUCB-MSCs under standard culture conditions attenuates the ischemic brain damage but does not improve the post-stroke neurological outcome.

Impact of Stroke Call on the Stroke Neurology Workforce in the United States: Possible Challenges and Opportunities.

BACKGROUND: The Stroke & Vascular Neurology Section of the American Academy of Neurology was charged to identify challenges to the recruitment and retention of stroke neurologists and to make recommendations to address any identified problems. The Section initiated this effort by determining the impact of stroke on-call requirements as a barrier to the recruitment and retention of vascular neurologists. METHODS: This is a cross-sectional survey of a sample of US Neurologists providing acute stroke care. RESULTS: Of the 900 neurologists who were sent surveys, 313 (35%) responded. Of respondents from institutions providing stroke coverage, 71% indicated that general neurologists and 45% indicated that vascular neurologists provided that service. Of those taking stroke call, 36% agreed with the statement, "I spent too much time on stroke call," a perception that was less common among those who took less than 12-hour shifts (P < .0001); 21% who participated in stroke call were dissatisfied with their current job. Forty-six percent indicated that their stroke call duties contributed to their personal feeling of "burnout." CONCLUSIONS: Although the reasons are likely multifactorial, our survey of neurologists providing stroke care suggests that over-burdensome on-call responsibilities may be contributing to the vascular neurology workforce burnout and could be affecting recruitment and retention of vascular neurologists. Strategies to reduce the lifestyle impact of stroke call may help address this problem.

The network of Shanghai Stroke Service System (4S): A public health-care web-based database using automatic extraction of electronic medical records.

Background Several stroke outcome and quality control projects have demonstrated the success in stroke care quality improvement through structured process. However, Chinese health-care systems are challenged with its overwhelming numbers of patients, limited resources, and large regional disparities. Aim To improve quality of stroke care to address regional disparities through process improvement. Method and design The Shanghai Stroke Service System (4S) is established as a regional network for stroke care quality improvement in the Shanghai metropolitan area. The 4S registry uses a web-based database that automatically extracts data from structured electronic medical records. Site-specific education and training program will be designed and administrated according to their baseline characteristics. Both acute reperfusion therapies including thrombectomy and thrombolysis in the acute phase and subsequent care were measured and monitored with feedback. Primary outcome is to evaluate the differences in quality metrics between baseline characteristics (including rate of thrombolysis in acute stroke and key performance indicators in secondary prevention) and post-intervention. Conclusions The 4S system is a regional stroke network that monitors the ongoing stroke care quality in Shanghai. This project will provide the opportunity to evaluate the spectrum of acute stroke care and design quality improvement processes for better stroke care. A regional stroke network model for quality improvement will be explored and might be expanded to other large cities in China. Clinical Trial Registration-URL http://www.clinicaltrials.gov . Unique identifier: NCT02735226.

Prevention of the Severity of Post-ischemic Inflammation and Brain Damage by Simultaneous Knockdown of Toll-like Receptors 2 and 4.

Toll-like receptor 2 (TLR2) and TLR4 belong to a family of highly conserved pattern recognition receptors and are well-known upstream sensors of signaling pathways of innate immunity. TLR2 and TLR4 upregulation is thought to be associated with poor outcome in stroke patients. We currently show that transient focal ischemia in adult rats induces TLR2 and TLR4 expression within hours and shRNA-mediated knockdown of TLR2 and TLR4 alone and in combination decreases the infarct size and swelling. We further show that TLR2 and TLR4 knockdown also prevented the induction of their downstream signaling molecules MyD88, IRAK1, and NFκB p65 as well as the pro-inflammatory cytokines IL-1ß, IL-6, and TNFα. This study thus shows that attenuation of the severity of TLR2- and TLR4-mediated post-stroke inflammation ameliorates ischemic brain damage.