Proton–hydride tautomerism in hydrogen evolution catalysis Quintana, Luis M. Aguirre; Johnson, Samantha I.; Corona, Sydney L. ...
Proceedings of the National Academy of Sciences - PNAS,
06/2016, Volume:
113, Issue:
23
Journal Article
Peer reviewed
Open access
Efficient generation of hydrogen from renewable resources requires development of catalysts that avoid deep wells and high barriers. Information about the energy landscape for H₂ production can be ...obtained by chemical characterization of catalytic intermediates, but few have been observed to date. We have isolated and characterized a key intermediate in 2e⁻ + 2H⁺ → H₂ catalysis. This intermediate, obtained by treatment of Cp*Rh(bpy) (Cp*, η⁵-pentamethylcyclopentadienyl; bpy, κ²-2,2′-bipyridyl) with acid, is not a hydride species but rather, bears η⁴-Cp*H as a ligand. Delivery of a second proton to this species leads to evolution of H₂ and reformation of η⁵-Cp* bound to rhodium(III). With suitable choices of acids and bases, the Cp*Rh(bpy) complex catalyzes facile and reversible interconversion of H⁺ and H₂.
Disruption of the blood-brain barrier (BBB) occurs in many diseases and is often mediated by inflammatory and neuroimmune mechanisms. Inflammation is well established as a cause of BBB disruption, ...but many mechanistic questions remain.
We used lipopolysaccharide (LPS) to induce inflammation and BBB disruption in mice. BBB disruption was measured using (14)C-sucrose and radioactively labeled albumin. Brain cytokine responses were measured using multiplex technology and dependence on cyclooxygenase (COX) and oxidative stress determined by treatments with indomethacin and N-acetylcysteine. Astrocyte and microglia/macrophage responses were measured using brain immunohistochemistry. In vitro studies used Transwell cultures of primary brain endothelial cells co- or tri-cultured with astrocytes and pericytes to measure effects of LPS on transendothelial electrical resistance (TEER), cellular distribution of tight junction proteins, and permeability to (14)C-sucrose and radioactive albumin.
In comparison to LPS-induced weight loss, the BBB was relatively resistant to LPS-induced disruption. Disruption occurred only with the highest dose of LPS and was most evident in the frontal cortex, thalamus, pons-medulla, and cerebellum with no disruption in the hypothalamus. The in vitro and in vivo patterns of LPS-induced disruption as measured with (14)C-sucrose, radioactive albumin, and TEER suggested involvement of both paracellular and transcytotic pathways. Disruption as measured with albumin and (14)C-sucrose, but not TEER, was blocked by indomethacin. N-acetylcysteine did not affect disruption. In vivo, the measures of neuroinflammation induced by LPS were mainly not reversed by indomethacin. In vitro, the effects on LPS and indomethacin were not altered when brain endothelial cells (BECs) were cultured with astrocytes or pericytes.
The BBB is relatively resistant to LPS-induced disruption with some brain regions more vulnerable than others. LPS-induced disruption appears is to be dependent on COX but not on oxidative stress. Based on in vivo and in vitro measures of neuroinflammation, it appears that astrocytes, microglia/macrophages, and pericytes play little role in the LPS-mediated disruption of the BBB.
The study sought to compare short-term outcomes in patients with femoropopliteal artery calcification receiving vessel preparation with intravascular lithotripsy (IVL) or percutaneous transluminal ...angioplasty (PTA) prior to drug-coated balloon (DCB) for symptomatic peripheral artery disease.
Endovascular treatment of calcified peripheral artery lesions is associated with suboptimal vessel expansion and increased complication risk. Although initial results from single-arm studies with IVL have been reported, comparative evidence from randomized trials is lacking for most devices in the presence of heavy calcification.
The Disrupt PAD III (Shockwave Medical Peripheral Lithoplasty System Study for PAD) randomized trial enrolled patients with moderate or severe calcification in a femoropopliteal artery who underwent vessel preparation with IVL or PTA prior to DCB or stenting. The primary endpoint was core lab-adjudicated procedural success (residual stenosis ≤30% without flow-limiting dissection) prior to DCB or stenting.
In patients receiving IVL (n = 153) or PTA (n = 153), procedural success was greater in the IVL group (65.8% vs. 50.4%; p = 0.01) and the percentage of lesions with residual stenosis ≤30% (66.4% vs. 51.9%; p = 0.02) was greater in the IVL group, while flow-limiting dissections occurred more frequently in the PTA group (1.4% vs. 6.8%; p = 0.03). Post-dilatation (5.2% vs. 17.0%; p = 0.001) and stent placement (4.6% vs. 18.3%; p < 0.001) were also greater in the PTA group. The rates of major adverse events (IVL: 0% vs. PTA: 1.3%; p = 0.16) and clinically driven target lesion revascularization (IVL: 0.7% vs. PTA: 0.7%; p = 1.0) at 30 days were comparable between groups.
IVL is an effective vessel preparation strategy that facilitates definitive endovascular treatment in calcified femoropopliteal arteries in patients with peripheral artery disease. (Shockwave Medical Peripheral Lithoplasty System Study for PAD Disrupt PAD III; NCT02923193).
The intrinsically disordered C-terminal peptide region of severe acute respiratory syndrome coronavirus 2 nonstructural protein-1 (Nsp1-CT) inhibits host protein synthesis by blocking messenger RNA ...(mRNA) access to the 40S ribosome entrance tunnel. Aqueous copper(II) ions bind to the disordered peptide with micromolar affinity, creating a possible strategy to restore protein synthesis during host infection. Electron paramagnetic resonance (EPR) and tryptophan fluorescence measurements on a 10-residue model of the disordered protein region (Nsp1-CT
), combined with advanced quantum mechanics calculations, suggest that the peptide binds to copper(II) as a multidentate ligand. Two optimized computational models of the copper(II)-peptide complexes were derived: One corresponding to pH 6.5 and the other describing the complex at pH 7.5 to 8.5. Simulated EPR spectra based on the calculated model structures are in good agreement with experimental spectra.
To assess safety and efficacy of the S.M.A.R.T. Vascular Stent System (Cordis Corp, Fremont, California) in obstructive superficial femoral artery (SFA) disease.
The single-arm, multicenter STROLL ...study (S.M.A.R.T. Nitinol Self-Expanding Stent in the Treatment of Obstructive Superficial Femoral Artery Disease) included 250 patients (250 lesions in SFA or proximal popliteal artery). The efficacy endpoint was primary patency defined by freedom from binary restenosis (peak systolic velocity ratio > 2.5) as derived by duplex ultrasound plus clinically driven target lesion revascularization (TLR) at 12 months.
Mean age of patients was 67.7 years ± 10.3; 47.2% of patients had diabetes; distribution of Rutherford/Becker classes 2, 3, and 4 was 45.8%, 51.4%, and 2.8%. Mean lesion length and reference vessel diameter were 77.3 mm ± 35.3 and 4.9 mm ± 0.7, respectively (23.6% cases with total occlusions). The 30-day freedom from major adverse events (death, index limb amputation, clinically driven TLR) was 100%. The 1-year primary patency was 81.7% by Kaplan-Meier estimate. The presence of diabetes or total occlusion had no effect on primary patency. Ankle-brachial index was 0.4-0.8 in 84.6% of patients at baseline and improved to > 0.8 in 81.0% of patients at 12 months. The proportion of patients in Rutherford/Becker class 3-4 was reduced from 54.2% at baseline to 8.0% at 12 months. Four patients (2.0%) experienced single-stent strut fracture (type I) at 1 year, without associated loss of stent patency.
The S.M.A.R.T. Vascular Stent System proved to be safe and effective for endovascular treatment of obstructive SFA and proximal popliteal artery disease, based on 1-year vessel patency and associated hemodynamic and clinical improvements.
Abstract Background Surgical mitral valve repair (SMVR) remains the gold standard for severe degenerative mitral regurgitation (DMR). However, the results with transcatheter mitral valve repair ...(TMVR) in prohibitive-risk DMR patients have not been previously reported. Objectives This study aimed to evaluate treatment of mitral regurgitation (MR) in patients with severe DMR at prohibitive surgical risk undergoing TMVR. Methods A prohibitive-risk DMR cohort was identified by a multidisciplinary heart team that retrospectively evaluated high-risk DMR patients enrolled in the EVEREST (Endovascular Valve Edge-to-Edge Repair Study) II studies. Results A total of 141 high-risk DMR patients were consecutively enrolled; 127 of these patients were retrospectively identified as meeting the definition of prohibitive risk and had 1-year follow-up (median: 1.47 years) available. Patients were elderly (mean age: 82.4 years), severely symptomatic (87% New York Heart Association class III/IV), and at prohibitive surgical risk (STS score: 13.2 ± 7.3%). TMVR (MitraClip) was successfully performed in 95.3%; hospital stay was 2.9 ± 3.1 days. Major adverse events at 30 days included death in 6.3%, myocardial infarction in 0.8%, and stroke in 2.4%. Through 1 year, there were a total of 30 deaths (23.6%), with no survival difference between patients discharged with MR ≤1+ or MR 2+. At 1 year, the majority of surviving patients (82.9%) remained MR ≤2+ at 1 year, and 86.9% were in New York Heart Association functional class I or II. Left ventricular end-diastolic volume decreased (from 125.1 ± 40.1 ml to 108.5 ± 37.9 ml; p < 0.0001 n = 69 survivors with paired data). SF-36 quality-of-life scores improved and hospitalizations for heart failure were reduced in patients whose MR was reduced. Conclusions TMVR in prohibitive surgical risk patients is associated with safety and good clinical outcomes, including decreases in rehospitalization, functional improvements, and favorable ventricular remodeling, at 1 year. (Real World Expanded Multi-center Study of the MitraClip System REALISM; NCT01931956 )
Colorectal cancer (CRC) is a major cause of cancer mortality. Whereas some patients respond well to therapy, others do not, and thus more precise, individualized treatment strategies are needed. To ...that end, we analyzed gene expression profiles from 1,290 CRC tumors using consensus-based unsupervised clustering. The resultant clusters were then associated with therapeutic response data to the epidermal growth factor receptor-targeted drug cetuximab in 80 patients. The results of these studies define six clinically relevant CRC subtypes. Each subtype shares similarities to distinct cell types within the normal colon crypt and shows differing degrees of 'stemness' and Wnt signaling. Subtype-specific gene signatures are proposed to identify these subtypes. Three subtypes have markedly better disease-free survival (DFS) after surgical resection, suggesting these patients might be spared from the adverse effects of chemotherapy when they have localized disease. One of these three subtypes, identified by filamin A expression, does not respond to cetuximab but may respond to cMET receptor tyrosine kinase inhibitors in the metastatic setting. Two other subtypes, with poor and intermediate DFS, associate with improved response to the chemotherapy regimen FOLFIRI in adjuvant or metastatic settings. Development of clinically deployable assays for these subtypes and of subtype-specific therapies may contribute to more effective management of this challenging disease.
Tricuspid regurgitation (TR) is a prevalent disease with limited treatment options.
This is the first 30-day report of the U.S. single-arm, multicenter, prospective CLASP TR early feasibility study ...of the PASCAL transcatheter valve repair system in the treatment of TR.
Patients with symptomatic TR despite optimal medical therapy, reviewed by the local heart team and central screening committee, were eligible for the study. Data were collected at baseline, discharge, and the 30-day follow-up and were reviewed by an independent clinical events committee and echocardiographic core laboratory. Feasibility endpoints included safety (composite major adverse event MAE rate), echocardiographic, clinical, and functional endpoints.
Of the 34 patients enrolled in the study, the mean age was 76 years, 53% were women, the mean Society of Thoracic Surgeons score was 7.3%, 88% had atrial fibrillation/flutter, 97% had severe or greater TR, and 79% had New York Heart Association (NYHA) functional class III/IV symptoms. Twenty-nine patients (85%) received implants; at 30 days, 85% of them achieved a TR severity reduction of at least 1 grade, with 52% with moderate or less TR (p < 0.001). The MAE rate was 5.9%, and none of the patients experienced cardiovascular mortality, stroke, myocardial infarction, renal complication, or reintervention. Eighty-nine percent of the patients improved to NYHA functional class I/II (p < 0.001), the mean 6-min walk distance improved by 71 m (p < 0.001), and the mean Kansas City Cardiomyopathy Questionnaire score improved by 15 points (p < 0.001).
In this early experience, the repair system performed as intended, with substantial TR reduction, favorable safety results with a low MAE rate, no mortality or reintervention, and significant improvements in functional status, exercise capacity, and quality of life. (Edwards CLASP TR EFS CLASP TR EFS; NCT03745313)
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