7,407 research outputs found
Long-term follow-up of asymptomatic or mildly symptomatic patients with severe degenerative mitral regurgitation and preserved left ventricular function
OBJECTIVES:
The timing for mitral valve surgery in asymptomatic patients with severe mitral regurgitation and preserved left ventricular function remains controversial. We analyzed the immediate and long-term outcomes of these patients after surgery.
METHODS:
From January 1992 to December 2012, 382 consecutive patients with severe chronic degenerative mitral regurgitation, with no or mild symptoms, and preserved left ventricular function (ejection fraction ≥ 60%) were submitted to surgery and followed for up to 22 years (3209 patient-years). Patients with associated surgeries, other than tricuspid valve repair, were excluded. Cox proportional-hazard survival analysis was performed to determine predictors of late mortality and mitral reoperation. Subgroup analysis involved patients with atrial fibrillation or pulmonary hypertension.
RESULTS:
Mitral valvuloplasty was performed in 98.2% of cases. Thirty-day mortality was 0.8%. Overall survival at 5, 10, and 20 years was 96.3% ± 1.0%, 89.7% ± 2.0%, and 72.4% ± 5.8%, respectively, and similar to the expected age- and gender-adjusted general population. Patients with atrial fibrillation/pulmonary hypertension had a 2-fold risk of late mortality compared with the remaining patients (hazard ratio, 2.54; 95% confidence interval, 1.17-4.80; P = .018). Benefit was age-dependent only in younger patients (<65 years; P = .016). Patients with atrial fibrillation/pulmonary hypertension (hazard ratio, 4.20, confidence interval, 1.10-11.20; P = .037) and patients with chordal shortening were at increased risk for reoperation, whereas patients with P2 prolapse (hazard ratio, 0.06; confidence interval, 0.008-0.51; P = .037) and patients with myxomatous valves (hazard ratio, 0.072; confidence interval, 0.008-0.624; P = .017) were at decreased risk.
CONCLUSIONS:
Mitral valve repair can be achieved in the majority of patients with low mortality (<1%) and excellent long-term survival. Patients with atrial fibrillation/pulmonary hypertension had compromised long-term survival, particularly younger patients (aged <65 years), and are at increased risk of mitral reoperation.info:eu-repo/semantics/publishedVersio
Single-Molecule Super-Resolution Imaging of T-Cell Plasma Membrane CD4 Redistribution upon HIV-1 Binding
The first step of cellular entry for the human immunodeficiency virus type-1 (HIV-1) occurs
through the binding of its envelope protein (Env) with the plasma membrane receptor CD4 and
co-receptor CCR5 or CXCR4 on susceptible cells, primarily CD4+ T cells and macrophages. Although
there is considerable knowledge of the molecular interactions between Env and host cell receptors
that lead to successful fusion, the precise way in which HIV-1 receptors redistribute to sites of
virus binding at the nanoscale remains unknown. Here, we quantitatively examine changes in the
nanoscale organisation of CD4 on the surface of CD4+ T cells following HIV-1 binding. Using singlemolecule super-resolution imaging, we show that CD4 molecules are distributed mostly as either
individual molecules or small clusters of up to 4 molecules. Following virus binding, we observe
a local 3-to-10-fold increase in cluster diameter and molecule number for virus-associated CD4
clusters. Moreover, a similar but smaller magnitude reorganisation of CD4 was also observed with
recombinant gp120. For one of the first times, our results quantify the nanoscale CD4 reorganisation
triggered by HIV-1 on host CD4+ T cells. Our quantitative approach provides a robust methodology
for characterising the nanoscale organisation of plasma membrane receptors in general with the
potential to link spatial organisation to function
Avoiding hologram bending in photorefractive crystals
coupled-wave theory predicts the bending of recorded hologram phase planes in most photorefractive crystals. Bent holograms occur in LiNbO3 and other photovoltaic crystals that are particularly interesting as holographic storage media and result in a reduced overall diffraction efficiency. We show that hologram bending in LiNbO3 can be avoided or at least sensibly reduced by use of an actively stabilized recording technique. (C) 1996 Optical Society of America21215215
Feedback-controlled running holograms in strongly absorbing photorefractive materials
We propose a mathematical model for the movement in absorbing materials of photorefractive holograms under feedback constraints. We use this model to analyze the speed of a fringe-locked running hologram in photorefractive sillenite crystals that usually exhibit a strong absorption effect. Fringe-locked experiments permit us to compute the quantum efficiency for the photogeneration of charge carriers in photorefractive crystals if the effect of bulk absorption and the effective value of the externally applied field are adequately taken into consideration. A Bi12TiO20 sample was measured with the 532-nm laser wavelength, and a quantum efficiency of Phi = 0.37 was obtained. Disregarding absorption leads to large errors in Phi. (C) 2000 Optical Society of America [S0740-3224(00)00209-5].1791517152
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Redefining Peptide 14D: Substitutional Analysis for Accelerated TB Diagnosis and Enhanced Activity against Mycobacterium tuberculosis.
Tuberculosis (TB) caused by Mycobacterium tuberculosis remains a predominant cause of mortality, especially in low- and middle-income nations. Recently, antimicrobial peptides have been discovered that at low concentrations could stimulate the growth of M. tuberculosis (hormetic response). In this study, such a peptide was used to investigate the effects on the time to positivity (TTP). A systematic substitution analysis of peptide 14D was synthesized using Spot synthesis technology, resulting in 171 novel peptides. Our findings revealed a spectrum of interactions, with some peptides accelerating M. tuberculosis growth, potentially aiding in faster diagnostics, while others exhibited inhibitory effects. Notably, peptide NH2-wkivfiwrr-CONH2 significantly reduced the TTP by 25 h compared to the wild-type peptide 14D, highlighting its potential in improving TB diagnostics by culture. Several peptides demonstrated potent antimycobacterial activity, with a minimum inhibitory concentration (MIC) of 20 µg/mL against H37Rv and a multidrug-resistant M. tuberculosis strain. Additionally, for two peptides, a strongly diminished formation of cord-like structures was observed, which is indicative of reduced virulence and transmission potential. This study underscores the multifaceted roles of antimicrobial peptides in TB management, from enhancing diagnostic efficiency to offering therapeutic avenues against M. tuberculosis
Feasibility of Noninvasive Positive Pressure Ventilation in the Treatment of Oxygen-Dependent COVID-19 Patients in Peru
Intensive care is expensive, and availability is limited. Low- and middle-income countries in particular have struggled to cope with the large influx of critically ill patients during the COVID-19 pandemic. Noninvasive respiratory support devices delivering continuous positive airways pressure (CPAP) require less resource and staff expertise compared with invasive mechanical ventilators and can be routinely used outside of intensive care units. This study assessed the use of the UCL-Ventura Wayrachi CPAP device in hospitalized patients with COVID-19 in Peru. A secondary analysis of data collected for a feasibility study commissioned by the Peruvian Ministry of Health was conducted. Data were collected from three hospitals, including patient demographics, clinical data, and outcomes. Forty-five patients were enrolled from July 16 to September 1, 2020. Eight patients (18%) were intolerant of the CPAP mask. Of the remainder, 18 (48.7%) improved and were discharged from hospital after 6 days. Eight (21.6%) died while on CPAP and 11 (29.7%) were eventually intubated, of whom two died. In total, 27 (60%) survived to hospital discharge. Participating physicians noted the device was easy to use and provided patient benefit, though voiced concerns about the strain on hospital oxygen supplies. In conclusion, the UCL Ventura Wayrachi CPAP device proved feasible in COVID-19 patients in Peru, and offered a bridging therapy for patients who required a ventilator when none were available
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