Giant unilamellar vesicles composed of a ternary mixture of phospholipids and cholesterol exhibit coexisting liquid phases over a range of temperatures and compositions. A significant fraction of lipids in biological membranes are charged. Here, we present phase diagrams of vesicles composed of phosphatidylcholine (PC) lipids, which are zwitterionic; phosphatidylglycerol (PG) lipids, which are anionic; and cholesterol (Chol). Specifically, we use DiPhyPG-DPPC-Chol and DiPhyPC-DPPG-Chol. We show that miscibility in membranes containing charged PG lipids occurs over similarly high temperatures and broad lipid compositions as in corresponding membranes containing only uncharged lipids, and that the presence of salt has a minimal effect. We verified our results in two ways. First, we used mass spectrometry to ensure that charged PC/PG/Chol vesicles formed by gentle hydration have the same composition as the lipid stocks from which they are made. Second, we repeated the experiments by substituting phosphatidylserine for PG as the charged lipid and observed similar phenomena. Our results consistently support the view that monovalent charged lipids have only a minimal effect on lipid miscibility phase behavior in our system.

OBJECT Syrinx size and location within the spinal cord may differ based on etiology or associated conditions of the brain and spine. These differences have not been clearly defined. METHODS All patients with a syrinx were identified from 14,118 patients undergoing brain or cervical spine imaging at a single institution over an 11-year interval. Syrinx width, length, and location in the spinal cord were recorded. Patients were grouped according to associated brain and spine conditions including Chiari malformation Type I (CM-I), secondary CM (2°CM), Chiari malformation Type 0 (CM-0), tethered cord, other closed dysraphism, and spinal tumors. Syringes not associated with any known brain or spinal cord condition were considered idiopathic. Syrinx characteristics were compared between groups. RESULTS A total of 271 patients with a syrinx were identified. The most common associated condition was CM-I (occurring in 117 patients [43.2%]), followed by spinal dysraphism (20 [7.4%]), tumor (15 [5.5%]), and tethered cord (13 [4.8%]). Eighty-three patients (30.6%) did not have any associated condition of the brain or spinal cord and their syringes were considered idiopathic. Syringes in patients with CM-I were wide (7.8 ± 3.9 mm) compared with idiopathic syringes (3.9 ± 1.0, p < 0.0001) and those associated with tethered cord (4.2 ± 0.9, p < 0.01). When considering CM-I–associated and idiopathic syringes, the authors found that CM-I–associated syringes were more likely to have their cranial extent in the cervical spine (88%), compared with idiopathic syringes (43%; p < 0.0001). The combination of syrinx width greater than 5 mm and cranial extent in the cervical spine had 99% specificity (95% CI 0.92–0.99) for CM-I–associated syrinx. CONCLUSIONS Syrinx morphology differs according to syrinx etiology. The combination of width greater than 5 mm and cranial extent in the cervical spine is highly specific for CM-I–associated syringes. This may have relevance when determining the clinical significance of syringes in patients with low cerebellar tonsil position.

Background Context: Lumbar radiofrequency ablation (RFA) is an intervention used to treat facet-mediated chronic low back pain. In some studies with methods consistent with clinical practice guidelines, RFA results in improvements in pain and functional limitations. However, in other studies, RFA demonstrates limited benefit. Despite unanswered questions regarding efficacy of RFA, its use is widespread. Purpose: To describe trends in the utilization and cost of lumbar RFA and lumbar facet injections. Study Design/ Setting: Retrospective cohort study. Patient Sample: The sample was derived from the IBM/Watson MarketScan ® Commercial Claims and Encounters Databases from 2007-2016. Outcome Measures: Longitudinal trends in the distribution and quantity of lumbar facet injections before lumbar RFA, corticosteroid administration during lumbar facet injections, progression to lumbar RFA after lumbar facet injections, lumbar RFA utilization, and costs of these interventions. Methods: Two primary cohorts were identified from patients who received lumbar RFA or lumbar facet injection procedures. Utilization rates per 100,000 enrollees were determined for both

Preoperative chronic opioid use is a predictor of TKR. Using this association and others, a TKA revision risk calculator was generated at http://www.bit.do/tka.

Strokes promote immunosuppression, partially from increased sympathetic activity. Altering sympathetic drive with β-blockers has variably been shown to improve stroke outcomes. This study adds to this literature using propensity score matching to limit confounding and by examining the effects of selective and non-selective β-blockers. Prospective data from acute ischemic stroke admissions at a single center from July 2010-June 2015 were analyzed. Outcomes included infection (urinary tract infection [UTI], pneumonia, or bacteremia), discharge modified Rankin Score (mRS), and in-hospital death. Any selective and non-selective β-blocker use during the first 3 days of admission were investigated with propensity score matching. A sensitivity analysis was also performed. This study included 1431 admissions. Any β-blocker use was associated with increased infections (16.4 vs. 10.7%, p = 0.030). Non-selective β-blocker use was associated with increased infections (18.9 vs. 9.7%, p = 0.005) and UTIs (13.0 vs. 5.5%, p = 0.009). Selective β-blocker use was not associated with infection. There were no associations between β-blocker use and in-hospital death or discharge mRS. In the sensitivity analysis, the association between non-selective β-blocker use and urinary tract infections persisted (12.5 vs. 4.2%, p = 0.044). No associations with death or mRS were found. Early β-blocker use after ischemic stroke may increase the risk of infection but did not change disability or mortality risk. The mechanism may be mediated by β-adrenergic receptor antagonism given the different effects seen with selective versus non-selective β-blocker use.