Shewanella oneidensis MR-1 respires CdSe quantum dots for photocatalytic hydrogen evolution.

Living bio-nano systems for artificial photosynthesis are of growing interest. Typically, these systems use photoinduced charge transfer to provide electrons for microbial metabolic processes, yielding a biosynthetic solar fuel. Here, we demonstrate an entirely different approach to constructing a living bio-nano system, in which electrogenic bacteria respire semiconductor nanoparticles to support nanoparticle photocatalysis. Semiconductor nanocrystals are highly active and robust photocatalysts for hydrogen (H2) evolution, but their use is hindered by the oxidative side of the reaction. In this system, Shewanella oneidensis MR-1 provides electrons to a CdSe nanocrystalline photocatalyst, enabling visible light-driven H2 production. Unlike microbial electrolysis cells, this system requires no external potential. Illuminating this system at 530 nm yields continuous H2 generation for 168 h, which can be lengthened further by replenishing bacterial nutrients.

URMC-099 prophylaxis prevents hippocampal vascular vulnerability and synaptic damage in an orthopedic model of delirium superimposed on dementia.

Systemic perturbations can drive a neuroimmune cascade after surgical trauma, including affecting the blood-brain barrier (BBB), activating microglia, and contributing to cognitive deficits such as delirium. Delirium superimposed on dementia (DSD) is a particularly debilitating complication that renders the brain further vulnerable to neuroinflammation and neurodegeneration, albeit these molecular mechanisms remain poorly understood. Here, we have used an orthopedic model of tibial fracture/fixation in APPSwDI/mNos2-/- AD (CVN-AD) mice to investigate relevant pathogenetic mechanisms underlying DSD. We conducted the present study in 6-month-old CVN-AD mice, an age at which we speculated amyloid-ß pathology had not saturated BBB and neuroimmune functioning. We found that URMC-099, our brain-penetrant anti-inflammatory neuroprotective drug, prevented inflammatory endothelial activation, breakdown of the BBB, synapse loss, and microglial activation in our DSD model. Taken together, our data link post-surgical endothelial activation, microglial MafB immunoreactivity, and synapse loss as key substrates for DSD, all of which can be prevented by URMC-099.

Structural basis and synergism of ATP and Na+ activation in bacterial K+ uptake system KtrAB.

The K+ uptake system KtrAB is essential for bacterial survival in low K+ environments. The activity of KtrAB is regulated by nucleotides and Na+. Previous studies proposed a putative gating mechanism of KtrB regulated by KtrA upon binding to ATP or ADP. However, how Na+ activates KtrAB and the Na+ binding site remain unknown. Here we present the cryo-EM structures of ATP- and ADP-bound KtrAB from Bacillus subtilis (BsKtrAB) both solved at 2.8 Å. A cryo-EM density at the intra-dimer interface of ATP-KtrA was identified as Na+, as supported by X-ray crystallography and ICP-MS. Thermostability assays and functional studies demonstrated that Na+ binding stabilizes the ATP-bound BsKtrAB complex and enhances its K+ flux activity. Comparing ATP- and ADP-BsKtrAB structures suggests that BsKtrB Arg417 and Phe91 serve as a channel gate. The synergism of ATP and Na+ in activating BsKtrAB is likely applicable to Na+-activated K+ channels in central nervous system.

Quantum Dot Biomimetic for SARS-CoV-2 to Interrogate Blood-Brain Barrier Damage Relevant to NeuroCOVID Brain Inflammation.

Despite limited evidence for infection of SARS-CoV-2 in the central nervous system, cognitive impairment is a common complication reported in "recovered" COVID-19 patients. Identification of the origins of these neurological impairments is essential to inform therapeutic designs against them. However, such studies are limited, in part, by the current status of high-fidelity probes to visually investigate the effects of SARS-CoV-2 on the system of blood vessels and nerve cells in the brain, called the neurovascular unit. Here, we report that nanocrystal quantum dot micelles decorated with spike protein (COVID-QDs) are able to interrogate neurological damage due to SARS-CoV-2. In a transwell co-culture model of the neurovascular unit, exposure of brain endothelial cells to COVID-QDs elicited an inflammatory response in neurons and astrocytes without direct interaction with the COVID-QDs. These results provide compelling evidence of an inflammatory response without direct exposure to SARS-CoV-2-like nanoparticles. Additionally, we found that pretreatment with a neuro-protective molecule prevented endothelial cell damage resulting in substantial neurological protection. These results will accelerate studies into the mechanisms by which SARS-CoV-2 mediates neurologic dysfunction.

Neutrophilia with damage to the blood-brain barrier and neurovascular unit following acute lung injury.

Background: Links between acute lung injury (ALI), infectious disease, and neurological outcomes have been frequently discussed over the past few years, especially due to the COVID-19 pandemic. Yet, much of the cross-communication between organs, particularly the lung and the brain, has been understudied. Here, we have focused on the role of neutrophils in driving changes to the brain endothelium with ensuing microglial activation and neuronal loss in a model of ALI. Methods: We have applied a three-dose paradigm of 10µg/40µl intranasal lipopolysaccharide (LPS) to induce neutrophilia accompanied by proteinaceous exudate in bronchoalveolar lavage fluid (BALF) in adult C57BL/6 mice. Brain endothelial markers, microglial activation, and neuronal cytoarchitecture were evaluated 24hr after the last intranasal dose of LPS or saline. C57BL/6-Ly6g(tm2621(Cre-tdTomato)Arte (Catchup mice) were used to measure neutrophil and blood-brain barrier permeability following LPS exposure with intravital 2-photon imaging. Results: Three doses of intranasal LPS induced robust neutrophilia accompanied by proteinaceous exudate in BALF. ALI triggered central nervous system pathology as highlighted by robust activation of the cerebrovascular endothelium (VCAM1, CD31), accumulation of plasma protein (fibrinogen), microglial activation (IBA1, CD68), and decreased expression of proteins associated with postsynaptic terminals (PSD-95) in the hippocampal stratum lacunosum moleculare, a relay station between the entorhinal cortex and CA1 of the hippocampus. 2-photon imaging of Catchup mice revealed neutrophil homing to the cerebral endothelium in the blood-brain barrier and neutrophil extravasation from cerebral vasculature 24hr after the last intranasal treatment. Conclusions: Overall, these data demonstrate ensuing brain pathology resulting from ALI, highlighting a key role for neutrophils in driving brain endothelial changes and subsequent neuroinflammation. This paradigm may have a considerable translational impact on understanding how infectious disease with ALI can lead to neurodegeneration, particularly in the elderly.

Neutrophilia with damage to the blood-brain barrier and neurovascular unit following acute lung injury.

Background: Links between acute lung injury (ALI), infectious disease, and neurological outcomes have been frequently discussed over the past few years, especially due to the COVID-19 pandemic. Yet, much of the cross-communication between organs, particularly the lung and the brain, has been understudied. Here, we have focused on the role of neutrophils in driving changes to the brain endothelium with ensuing microglial activation and neuronal loss in a model of ALI. Methods: We have applied a three-dose paradigm of 10µg/40µl intranasal lipopolysaccharide (LPS) to induce neutrophilia accompanied by proteinaceous exudate in bronchoalveolar lavage fluid (BALF) in adult C57BL/6 mice. Brain endothelial markers, microglial activation, and neuronal cytoarchitecture were evaluated 24hr after the last intranasal dose of LPS or saline. C57BL/6-Ly6g(tm2621(Cre-tdTomato)Arte (Catchup mice) were used to measure neutrophil and blood-brain barrier permeability following LPS exposure with intravital 2-photon imaging. Results: Three doses of intranasal LPS induced robust neutrophilia accompanied by proteinaceous exudate in BALF. ALI triggered central nervous system pathology as highlighted by robust activation of the cerebrovascular endothelium (VCAM1, CD31), accumulation of plasma protein (fibrinogen), microglial activation (IBA1, CD68), and decreased expression of proteins associated with postsynaptic terminals (PSD-95) in the hippocampal stratum lacunosum moleculare, a relay station between the entorhinal cortex and CA1 of the hippocampus. 2-photon imaging of Catchup mice revealed neutrophil homing to the cerebral endothelium in the blood-brain barrier and neutrophil extravasation from cerebral vasculature 24hr after the last intranasal treatment. Conclusions: Overall, these data demonstrate ensuing brain pathology resulting from ALI, highlighting a key role for neutrophils in driving brain endothelial changes and subsequent neuroinflammation. This paradigm may have a considerable translational impact on understanding how infectious disease with ALI can lead to neurodegeneration, particularly in the elderly.

Hybrid Amyloid Quantum Dot Nanoassemblies to Probe Neuroinflammatory Damage.

Various oligomeric species of amyloid-beta have been proposed to play different immunogenic roles in the cellular pathology of Alzheimer's Disease. However, investigating the role of a homogenous single oligomeric species has been difficult due to highly dynamic oligomerization and fibril formation kinetics that convert between many species. Here we report the design and construction of a quantum dot mimetic for larger spherical oligomeric amyloid species as an "endogenously" fluorescent proxy for this cytotoxic species to investigate its role in inducing inflammatory and stress response states in neuronal and glial cell types.

Dissecting the Conformational Dynamics of the Bile Acid Transporter Homologue ASBTNM.

Apical sodium-dependent bile acid transporter (ASBT) catalyses uphill transport of bile acids using the electrochemical gradient of Na+ as the driving force. The crystal structures of two bacterial homologues ASBTNM and ASBTYf have previously been determined, with the former showing an inward-facing conformation, and the latter adopting an outward-facing conformation accomplished by the substitution of the critical Na+-binding residue glutamate-254 with an alanine residue. While the two crystal structures suggested an elevator-like movement to afford alternating access to the substrate binding site, the mechanistic role of Na+ and substrate in the conformational isomerization remains unclear. In this study, we utilized site-directed alkylation monitored by in-gel fluorescence (SDAF) to probe the solvent accessibility of the residues lining the substrate permeation pathway of ASBTNM under different Na+ and substrate conditions, and interpreted the conformational states inferred from the crystal structures. Unexpectedly, the crosslinking experiments demonstrated that ASBTNM is a monomer protein, unlike the other elevator-type transporters, usually forming a homodimer or a homotrimer. The conformational dynamics observed by the biochemical experiments were further validated using DEER measuring the distance between the spin-labelled pairs. Our results revealed that Na+ ions shift the conformational equilibrium of ASBTNM toward the inward-facing state thereby facilitating cytoplasmic uptake of substrate. The current findings provide a novel perspective on the conformational equilibrium of secondary active transporters.

Quantum Dots for Improved Single-Molecule Localization Microscopy.

Colloidal semiconductor quantum dots (QDs) have long established their versatility and utility for the visualization of biological interactions. On the single-particle level, QDs have demonstrated superior photophysical properties compared to organic dye molecules or fluorescent proteins, but it remains an open question as to which of these fundamental characteristics are most significant with respect to the performance of QDs for imaging beyond the diffraction limit. Here, we demonstrate significant enhancement in achievable localization precision in QD-labeled neurons compared to neurons labeled with an organic fluorophore. Additionally, we identify key photophysical parameters of QDs responsible for this enhancement and compare these parameters to reported values for commonly used fluorophores for super-resolution imaging.

Aspirin versus anticoagulation for prevention of venous thromboembolism major lower extremity orthopedic surgery: a systematic review and meta-analysis.

BACKGROUND: Hip fracture surgery and lower extremity arthroplasty are associated with increased risk of both venous thromboembolism and bleeding. The best pharmacologic strategy for reducing these opposing risks is uncertain. PURPOSE: To compare venous thromboembolism (VTE) and bleeding rates in adult patients receiving aspirin versus anticoagulants after major lower extremity orthopedic surgery. DATA SOURCES: Medline, Cumulative Index to Nursing and Allied Health Literature, and the Cochrane Library through June 2013; reference lists, ClinicalTrials.gov, and scientific meeting abstracts. STUDY SELECTION: Randomized trials comparing aspirin to anticoagulants for prevention of VTE following major lower extremity orthopedic surgery. DATA EXTRACTION: Two reviewers independently extracted data on rates of VTE, bleeding, and mortality. DATA SYNTHESIS: Of 298 studies screened, 8 trials including 1408 participants met inclusion criteria; all trials screened participants for deep venous thrombosis (DVT). Overall rates of DVT did not differ statistically between aspirin and anticoagulants (relative risk [RR]: 1.15 [95% confidence interval {CI}: 0.68-1.96]). Subgrouped by type of surgery, there was a nonsignificant trend favoring anticoagulation following hip fracture repair but not knee or hip arthroplasty (hip fracture RR: 1.60 [95% CI: 0.80-3.20], 2 trials; arthroplasty RR: 1.00 [95% CI: 0.49-2.05], 5 trials). The risk of bleeding was lower with aspirin than anticoagulants following hip fracture repair (RR: 0.32 [95% CI: 0.13-0.77], 2 trials), with a nonsignificant trend favoring aspirin after arthroplasty (RR: 0.63 [95% CI: 0.33-1.21], 5 trials). Rates of pulmonary embolism were too low to provide reliable estimates. CONCLUSION: Compared with anticoagulation, aspirin may be associated with higher risk of DVT following hip fracture repair, although bleeding rates were substantially lower. Aspirin was similarly effective after lower extremity arthroplasty and may be associated with lower bleeding risk. Journal of Hospital Medicine 2014;9:579-585. © 2014 Society of Hospital Medicine.

Comparing National Institutes of Health funding of emergency medicine to four medical specialties.

OBJECTIVES: The purpose of this study was to compare National Institutes of Health (NIH) funding received in 2008 by emergency medicine (EM) to the specialties of internal medicine, pediatrics, anesthesiology, and family medicine. The hypothesis was that EM would receive fewer NIH awards and less funding dollars per active physician and per medical school faculty member compared to the other four specialties. METHODS: Research Portfolio Online Reporting Tools (RePORT) were used to identify NIH-funded grants to 125 of the 133 U.S. allopathic medical schools for fiscal year 2008 (the most recent year with all grant funding information). Eight medical schools were excluded because six were not open in 2008, one did not have a website, and one did not have funding data available by medical specialty. From RePORT, all grants awarded to EM, internal medicine, family medicine, anesthesiology, and pediatric departments of each medical school were identified for fiscal year 2008. The authors extracted the project number, project title, dollars awarded, and name of the principal investigator for each grant. Funds awarded to faculty in divisions of EM were accounted for by identifying the department of the EM division and searching for all grants awarded to EM faculty within those departments using the name of the principal investigator. The total number of active physicians per medical specialty was acquired from the Association of American Medical Colleges' 2008 Physician Specialty report. The total number of faculty per medical specialty was collected by two research assistants who independently counted the faculty listed on each medical school website. The authors compared the total number of NIH awards and total funding per 1,000 active physicians and per 1,000 faculty members by medical specialty. RESULTS: Of the 125 medical schools included in the study, 84 had departments of EM (67%). In 2008, NIH awarded over 9,000 grants and approximately $4 billion to the five medical specialties of interest. Less than 1% of the grants and funds were awarded to EM. EM had the second-lowest number of awards and funding per active physician, and the lowest number of awards and funding per faculty member. A higher percentage of grants awarded to EM were career development awards (26%, vs. a range of 11% to 19% for the other specialties) and cooperative agreements (26%, vs. 2% to 10%). In 2008, EM was the only specialty of the five not to have a fellowship or T32 training grant. EM had the lowest proportion of research project awards (42%, vs. 58% to 73%). CONCLUSIONS: Compared to internal medicine, pediatrics, anesthesiology, and family medicine, EM received the least amount of NIH support per active faculty member and ranked next to last for NIH support by active physician. Given the many benefits of research both for the specialty and for society, EM needs to continue to develop and support an adequate cohort of independent investigators.

A randomized controlled trial of the effect of service delivery information on patient satisfaction in an emergency department fast track.

OBJECTIVES: The objective was to determine the effect on patient satisfaction of providing patients with predicted service completion times. METHODS: A randomized controlled trial was conducted in an urban, community teaching hospital. Emergency department (ED) patients triaged to fast track on weekdays between October 26, 2009, and December 30, 2009, from 9 am to 5 pm were eligible. Patients were randomized to: 1) usual care (n = 342), 2) provided ED process information (n = 336), or 3) provided ED process information plus predicted service delivery times (n = 333). Patients in group 3 were given an "average" and "upper range" estimate of their waiting room times and treatment times. The average and upper range predictions were calculated from quantile regression models that estimated the 50th and 90th percentiles of the waiting room time and treatment time distributions for fast track patients at the study site based on 2.5 years of historical data. Trained research assistants administered the interventions after triage. Patients completed a brief survey at discharge that measured their satisfaction with overall care, the quality of the information they received, and the timeliness of care. Satisfaction ratings of very good versus good, fair, poor, and very poor were modeled using logistic regression as a function of study group; actual service delivery times; and other patient, clinical, and temporal covariates. The study also modeled satisfaction ratings of fair, poor, and very poor compared to good and very good ratings as a function of the same covariates. RESULTS: Survey completion rates and patient, clinical, and temporal characteristics were similar by study group. Median waiting room time was 70 minutes (interquartile range [IQR] = 40 to 114 minutes), and median treatment time was 52 minutes (IQR = 31 to 81 minutes). Neither intervention affected any of the satisfaction outcomes. Satisfaction was significantly associated with actual waiting room time, individual providers, and patient age. Every 10-minute increase in waiting room time corresponded with an 8% decrease (odds ratio [OR] = 0.92; 95% confidence interval [CI] = 0.89 to 0.95) in the odds of reporting very good satisfaction with overall care. The odds of reporting very good satisfaction with care were lower for several triage nurses and fast track nurses, compared to the triage nurse and fast track nurse who treated the most study patients. Each 10-minute increase in waiting room time was also associated with a 10% increase in the odds of reporting very poor, poor, or fair satisfaction with overall care (OR = 1.10; 95% CI = 1.06 to 1.14). The odds of reporting very poor, poor, or fair satisfaction with overall care also varied significantly among the triage nurses, fast track doctors, and fast track nurses. The odds of reporting very poor, poor, or fair satisfaction with overall care were significantly lower among patients aged 35 years and older compared to patients aged 18 to 34 years. CONCLUSIONS: Satisfaction with overall care was influenced by waiting room time and the clinicians who treated them and not by service completion time estimates provided at triage.