The Escherichia coli iron transporter, FepA, has a globular N terminus that resides within a transmembrane -barrel formed by its C terminus. We engineered 25 cysteine substitution mutations at different locations in FepA and modified their sulfhydryl side chains with fluorescein maleimide in live cells. The reactivity of the Cys residues changed, sometimes dramatically, during the transport of ferric enterobactin, the natural ligand of FepA. Patterns of Cys susceptibility reflected energy-and TonB-dependent motion in the receptor protein. During transport, a residue on the normally buried surface of the N-domain was labeled by fluorescein maleimide in the periplasm, providing evidence that the transport process involves expulsion of the globular domain from the -barrel. Porin deficiency much reduced the fluoresceination of this site, confirming the periplasmic labeling route. These data support the previously proposed, but never demonstrated, ball-and-chain theory of membrane transport. Functional complementation between a separately expressed N terminus and C-terminal -barrel domain confirmed the feasibility of this mechanism.FepA is a Gram-negative bacterial outer membrane (OM) 6 protein that transports ferric enterobactin (FeEnt) (1-3). The crystal structures of FepA (4) and other bacterial metal transporters (FhuA, BtuB,57)), contain a C-terminal, 22-stranded -barrel, placing them in the porin superfamily (5). Their ϳ150-residue globular N termini (N-domain; see Fig. 1) reside within their -barrels. This architecture is potentially consistent with the "ball-and-chain" mechanism of membrane transport, whereby the globule controls solute (ligand) uptake by moving in and out of the channel. This process was postulated for nervous system channels (6), but no demonstrated examples of ball-and-chain transport are known.FepA and its relatives are unlike other porins (7, 8), because they selectively adsorb metal chelates with high affinity (3, 9 -14). Ligand binding causes small conformational changes that activate them to transport competency (15-17), hence their designation "ligand-gated porin" (LGP). The requirements for metabolic energy (18 -20) and another cell envelope protein, TonB (21-24), in LGP mediated transport are well known but unaccounted for: the OM has no source of energy and cannot sustain an ion gradient because of its open porin channels (7); TonB is a minor cell envelope protein whose functions are not yet understood.In live cells, FepA binds and transports FeEnt via sub-reactions with different dependences on energy and TonB. (i) In the absence of ligand the receptor opens, and its flexible surface loops extend outward (25). (ii) FeEnt binds to FepA in a biphasic reaction (26) that begins with adsorption to aromatic amino acids in the loop extremities (27, 28). Multiple determinants in multiple loops, including L7 (25), converge on the iron complex, creating a closed conformation that associates the negatively charged (Ϫ3), catecholate iron center with basic and aromatic residues in the r...
In our heavily pretreated patient population with NSCLC, early phase clinical trials with IO demonstrated similar outcomes to those seen in larger clinical studies that also used immune checkpoint inhibitors. The addition of NLR to RMH and MDACC prognostic scores can identify patients with poor overall outcomes treated with early phase IO studies.
BackgroundHemolytic uremic syndrome associated with Shiga toxin-producing Escherichia coli O157:H7 has been widely known as a common cause of acute renal failure in children. There are only a few reports of sporadic Shiga toxin-producing Escherichia coli-hemolytic uremic syndrome in adults in the USA. Analyses from the 2011 outbreak of hemolytic uremic syndrome associated with Escherichia coli O104:H4 reported that mortality rates are highest in those patients with age >60-years old. Therefore, recognizing Shiga toxin-producing Escherichia coli-hemolytic uremic syndrome in older people can help early introduction of the appropriate therapy.Case presentationWe describe an 86-year-old Caucasian woman, initially treated as suspected thrombotic thrombocytopenic purpura, with worsening neurological and renal functions despite plasmapheresis (plasma exchange). A subsequent normal ADAMTS13 activity level and positive stool sample for Escherichia coli O157:H7 confirmed the diagnosis of Shiga toxin-associated hemolytic uremic syndrome. We shifted our management towards aggressive supportive care. Despite conventional treatment, hemolytic uremic syndrome unfortunately led to her death.ConclusionsOur case demonstrates the importance of recognizing Shiga toxin-producing Escherichia coli-hemolytic uremic syndrome as an etiology of microangiopathic hemolytic anemia in older people. According to the current literature, supportive care is the best approach for Shiga toxin-producing Escherichia coli-hemolytic uremic syndrome. Therapies such as plasma exchange and eculizumab (a complement inhibitor) are not shown to be effective in Shiga toxin-producing Escherichia coli-hemolytic uremic syndrome. There is a dire need to continue research to find better treatment options in this disease entity with a high mortality, particularly in older people.
Background Little is known about agreement between patients and physicians on content and outcomes of clinical discussions. A common perception of content and outcomes may be desirable to optimize decision making and clinical care. Objective To determine patient-physician agreement on content and outcomes of coronary heart disease (CHD) prevention discussions. Design Cross-sectional survey nested within a randomized CHD prevention study. Setting and participants University internal medicine clinic; 24 physicians and 157 patients. Methods Following one clinic visit, we surveyed patients and physicians on discussion content, decision making, and final decisions about CHD prevention. For comparison, we audio-recorded, transcribed, and coded 20 patient-physician visits. We calculated percent agreement between patient/physician reports, patient/transcription reports, and physician/transcription reports. We calculated Cohen’s kappas to compare patient/physician perspectives. Results Patients and physicians agreed on whether CHD was discussed in 130 visits (83%; kappa=0.55; 95% CI .40–.70). When discussions occurred, they agreed about discussion content (pros versus cons) in 53% of visits (kappa=0.15; 95% CI −.01–.30), and physicians’ recommendations in 73% (kappa=0.44; 95% CI .28–.66). Patients and physicians agreed on final decisions to take medication in 78% (kappa=.58; 95% CI .45–.71) and change lifestyle in 69% (kappa=.38; 95% CI .24–.53). They agreed less often, 43%, (kappa=.13; 95% CI −.11–.37) about degree of involvement in decision making. Audio-recorded results were similar, but showed very low agreement between transcripts and patients’ and physicians’ self-report on discussion content and decision making. Conclusions Disagreements about clinical discussions and decision making may be common. Future work is needed to determine: how widespread such agreements are; whether they impact clinical outcomes; and the relative importance of the subjective experience versus objective steps of shared decision making.
Allogeneic hematopoietic cell transplantation (allo-HCT) is a potentially curative therapy for patients with multiple myeloma, as it provides a graft-versus-myeloma effect alongside a myeloma-free graft. Although reduced-intensity conditioning regimens decrease nonrelapse mortality (NRM), there is a paucity of data with regard to the ideal conditioning regimen in myeloma. We conducted a retrospective comparison of 3 different preparative regimens used for allo-HCT for multiple myeloma at our institution in recent clinical trials: busulfan/fludarabine (BuFlu), fludarabine/ melphalan 100 mg/m 2 (FM100), and fludarabine/melphalan 140 mg/m 2 (FM140). NRM, progression-free survival (PFS) at 3 years, and overall survival (OS) at 3 years were the primary endpoints. Secondary endpoints included time to engraftment, and the incidence of grades II through IV acute graft-versus-host disease and chronic graftversus-host disease. A total of 73 patients received allo-HCT with these regimens. NRM at 3 years was seen in 3 (21%), 5 (28%), and 6 (24%) patients in the BuFlu, FM100, and FM140 groups, respectively. Three-year PFS in the BuFlu, FM100, and FM140 groups was 16% (hazard ratio [HR], 1.2; 95% confidence interval [CI], 0.6 to 2.1), 26% (HR, 0.6; 95% CI, 0.3 to 1.2), and 11% (reference), respectively. Three-year OS in the BuFlu, FM100, and FM140 groups was 39% (HR, 1.1; 95% CI, 0.5 to 2.2), 43% (HR, 0.7; 95% CI, 0.3 to 1.4), and 32% (reference), respectively. High-risk cytogenetics and relapsed disease prior to allo-HCT were found to be independent predictors of inferior OS on multivariate analysis, with a HR of 2.1 (P = .02) and 2.6 (P = .004), respectively. In contrast, the preparative regimen did not emerge as a predictor of PFS or OS. Durable clinical remission can be achieved in 11% to 25% of patients with multiple myeloma with the use of allo-HCT without any significant difference in the safety or efficacy of the conditioning regimen. High-risk cytogenetics and relapsed disease prior to transplant were associated with inferior PFS and OS.
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