Feasibility of thin-slice, low noise images created using multi-kernel synthesis to replace multiple image series in head CT.

BACKGROUND: SynthesiZed Improved Resolution and Concurrent nOise reductioN (ZIRCON) is a multi-kernel synthesis method that creates a single series of thin-slice computed tomography (CT) images displaying low noise and high spatial resolution, increasing reader efficiency and minimizing partial volume averaging. PURPOSE: To compare the diagnostic performance of a single set of ZIRCON images to two routine clinical image series using conventional CT head and bone reconstruction kernels for diagnosing intracranial findings and fractures in patients with trauma or suspected acute neurologic deficit. MATERIAL AND METHODS: In total, 50 patients underwent clinically indicated head CT in the ER (15 normal, 35 abnormal cases). A non-reader neuroradiologist established the reference standard. Three neuroradiologists reviewed two routine clinical series (head and bone kernels) and a single ZIRCON series, detecting intracranial findings or fractures and rating confidence (0-100). Sensitivity, specificity, and jackknife free-response receiver operating characteristic (JAFROC) figure of merit (FOM) were compared (limit of non-inferiority: -0.10). RESULTS: ZIRCON and conventional images demonstrated comparable performance for fractures (sensitivity: 51.5% vs. 54.5%; specificity: 40.2% vs. 34.2%) and intracranial findings (sensitivity: 88.2% vs. 91.4%; specificity: 77.2% vs. 73.7%).The estimated difference of JAFROC FOM demonstrated ZIRCON non-inferiority for acute pathologies overall (0.003 [95% CI=-0.051-0.057]) and fractures (0.048 [95% CI=-0.050-0.145]) but not for intracranial findings alone (-0.024 [95% CI=-0.100-0.052]). CONCLUSION: Thin-slice, low noise, and high spatial resolution images can be created to display intracranial findings and fractures replacing multiple images series in head CT with similar performance. Future studies in more patients and further algorithmic development are warranted.

Label-free, non-contact determination of resting membrane potential using dielectrophoresis.

Measurement of cellular resting membrane potential (RMP) is important in understanding ion channels and their role in regulation of cell function across a wide range of cell types. However, methods available for the measurement of RMP (including patch clamp, microelectrodes, and potential-sensitive fluorophores) are expensive, slow, open to operator bias, and often result in cell destruction. We present non-contact, label-free membrane potential estimation which uses dielectrophoresis to determine the cytoplasm conductivity slope as a function of medium conductivity. By comparing this to patch clamp data available in the literature, we have demonstratet the accuracy of this approach using seven different cell types, including primary suspension cells (red blood cells, platelets), cultured suspension cells (THP-1), primary adherent cells (chondrocytes, human umbilical mesenchymal stem cells), and adherent (HeLa) and suspension (Jurkat) cancer cell lines. Analysis of the effect of ion channel inhibitors suggests the effects of pharmaceutical agents (TEA on HeLa; DMSO and neuraminidase on red blood cells) can also be measured. Comparison with published values of membrane potential suggest that the differences between our estimates and values recorded by patch clamp are accurate to within published margins of error. The method is low-cost, non-destructive, operator-independent and label-free, and has previously been shown to allow cells to be recovered after measurement.

Associations Between the Superwoman Schema, Stress, and Cardiovascular Health Among African-American Women.

BACKGROUND: African-American (AA) women are less likely to achieve ideal cardiovascular (CV) health compared with women of other racial/ethnic subgroups, primarily due to structural and psychosocial barriers. A potential psychosocial construct relevant to ideal CV health is the superwoman schema (SWS). PURPOSE: We explored whether the SWS was associated with perceived stress, CV risk factors, and overall CV health among AA women. METHODS: This cross-sectional analysis of the FAITH! Heart Health+ Study was conducted among AA women with high cardiometabolic risk. Pearson correlation evaluated associations between SWS and CV risk factors (e.g., stress, hypertension, diabetes, etc.). The 35-item SWS questionnaire includes five domains. Stress was measured by the 8-item Global Perceived Stress Scale (GPSS). CV health was assessed using the American Heart Association Life's Simple 7 (LS7) rubric of health behaviors/biometrics. Data acquisition spanned from February to August 2022. RESULTS: The 38 women included in the analysis (mean age 54.3 [SD 11.5] years) had a high CV risk factor burden (71.1% hypertension, 76.3% overweight/obesity, 28.9% diabetes, 39.5% hyperlipidemia). Mean GPSS level was 7.7 (SD 5.2), CV health score 6.7 (SD 1.8), and SWS score 60.3 (SD 18.0). Feeling an "obligation to help others" and "obligation to present an image of strength" had strongest correlations with GPSS score among all SWS domains (r = 0.51; p = .002 and r = 0.39; p = .02, respectively). Correlation among the SWS domains and traditional CV risk factors was not statistically significant. CONCLUSION: Our findings suggest that an obligation to help others and to project an image of strength could be contributing to stress among AA women.

Compared with women of other racial groups, African-American (AA) women in the USA have a higher cardiovascular (CV) disease burden and are at higher risk of maternal mortality from preventable CV health outcomes. The Giscombe Superwoman Schema (SWS) is a framework designed to characterize various aspects of the superwoman role that AA women may adopt to preserve themselves, their families, and their communities amidst the myriad of inequities that can compromise their ability to achieve ideal CV health. In this Brief Report, our team explored whether the SWS was associated with perceived stress, CV risk factors, and overall CV health among AA women. The study participants were AA women with high cardiometabolic risk residing in the Rochester and Minneapolis, St. Paul, Minnesota areas, recruited from the FAITH! Heart Health+ Study. We observed a positive association between the SWS and perceived stress levels, suggesting that the obligation to help others and to project an image of strength could be contributing to overall stress levels among AA women.

Single-Molecule Detection of the Encounter and Productive Electron Transfer Complexes of a Photosynthetic Reaction Center.

Small, diffusible redox proteins play an essential role in electron transfer (ET) in respiration and photosynthesis, sustaining life on Earth by shuttling electrons between membrane-bound complexes via finely tuned and reversible interactions. Ensemble kinetic studies show transient ET complexes form in two distinct stages: an "encounter" complex largely mediated by electrostatic interactions, which subsequently, through subtle reorganization of the binding interface, forms a "productive" ET complex stabilized by additional hydrophobic interactions around the redox-active cofactors. Here, using single-molecule force spectroscopy (SMFS) we dissected the transient ET complexes formed between the photosynthetic reaction center-light harvesting complex 1 (RC-LH1) of Rhodobacter sphaeroides and its native electron donor cytochrome c2 (cyt c2). Importantly, SMFS resolves the distribution of interaction forces into low (∼150 pN) and high (∼330 pN) components, with the former more susceptible to salt concentration and to alteration of key charged residues on the RC. Thus, the low force component is suggested to reflect the contribution of electrostatic interactions in forming the initial encounter complex, whereas the high force component reflects the additional stabilization provided by hydrophobic interactions to the productive ET complex. Employing molecular dynamics simulations, we resolve five intermediate states that comprise the encounter, productive ET and leaving complexes, predicting a weak interaction between cyt c2 and the LH1 ring near the RC-L subunit that could lie along the exit path for oxidized cyt c2. The multimodal nature of the interactions of ET complexes captured here may have wider implications for ET in all domains of life.

Rationale, design, and participant characteristics of the FAITH! Heart Health+ study: An exploration of the influence of the social determinants of health, stress, and structural racism on African American cardiovascular health.

BACKGROUND: African Americans (AAs) face cardiovascular health (CVH) disparities linked to systemic racism. The 2020 police killing of Mr. George Floyd in Minneapolis, Minnesota, alongside the COVID-19 pandemic, exacerbated adverse psychosocial factors affecting CVH outcomes among AAs. This manuscript describes the study protocol and participant characteristics in an ancillary study exploring the relationship between biopsychosocial factors and CVH among AAs. METHODS: Using a community-based participatory approach, a mixed-methods ancillary study of 58 AA participants from an overarching randomized control trial (RCT) was conducted. Baseline RCT health assessments (November 2020) provided sociodemographic, medical, and clinical data. Subsequent health assessments (February-December 2022) measured sleep quality, psychosocial factors (e.g., high-effort coping), biomarkers (e.g., cortisol), and cardiovascular diagnostics (e.g., cardio-ankle vascular index). CVH was assessed using the American Heart Association Life's Simple 7 (LS7) (range 0 to 14, poor to ideal) and Life's Essential 8 (LE8) scores (range 0 to 100, low to high). Correlations between these scores will be examined. Focus group discussions via videoconferencing (March to April 2022) assessed psychosocial and structural barriers, along with the impact of COVID-19 and George Floyd's killing on daily life. RESULTS: Participants were predominantly female (67%), with a mean age of 54.6 [11.9] years, high cardiometabolic risk (93% had overweight/obesity and 70% hypertension), and moderate LE8 scores (mean 57.4, SD 11.5). CONCLUSION: This study will enhance understanding of the associations between biopsychosocial factors and CVH among AAs in Minnesota. Findings may inform risk estimation, patient care, and healthcare policies to address CVD disparities in marginalized populations.

De novo design of proteins housing excitonically coupled chlorophyll special pairs.

Natural photosystems couple light harvesting to charge separation using a 'special pair' of chlorophyll molecules that accepts excitation energy from the antenna and initiates an electron-transfer cascade. To investigate the photophysics of special pairs independently of the complexities of native photosynthetic proteins, and as a first step toward creating synthetic photosystems for new energy conversion technologies, we designed C2-symmetric proteins that hold two chlorophyll molecules in closely juxtaposed arrangements. X-ray crystallography confirmed that one designed protein binds two chlorophylls in the same orientation as native special pairs, whereas a second designed protein positions them in a previously unseen geometry. Spectroscopy revealed that the chlorophylls are excitonically coupled, and fluorescence lifetime imaging demonstrated energy transfer. The cryo-electron microscopy structure of a designed 24-chlorophyll octahedral nanocage with a special pair on each edge closely matched the design model. The results suggest that the de novo design of artificial photosynthetic systems is within reach of current computational methods.

Photosynthetic control at the cytochrome b6f complex.

Photosynthetic control (PCON) is a protective mechanism that prevents light-induced damage to PSI by ensuring the rate of NADPH and ATP production via linear electron transfer (LET) is balanced by their consumption in the CO2 fixation reactions. Protection of PSI is a priority for plants since they lack a dedicated rapid-repair cycle for this complex, meaning that any damage leads to prolonged photoinhibition and decreased growth. The imbalance between LET and the CO2 fixation reactions is sensed at the level of the transthylakoid ΔpH, which increases when light is in excess. The canonical mechanism of PCON involves feedback control by ΔpH on the plastoquinol oxidation step of LET at cytochrome b6f. PCON thereby maintains the PSI special pair chlorophylls (P700) in an oxidized state, which allows excess electrons unused in the CO2 fixation reactions to be safely quenched via charge recombination. In this review we focus on angiosperms, consider how photo-oxidative damage to PSI comes about, explore the consequences of PSI photoinhibition on photosynthesis and growth, discuss recent progress in understanding PCON regulation, and finally consider the prospects for its future manipulation in crop plants to improve photosynthetic efficiency.

Optimization of upstream particle concentration from flow using AC electro-osmosis and dielectrophoresis.

There are many applications where upstream sample processing is required to concentrate dispersed particles in flow; this may be to increase the concentration (e.g., to enhance biosensor accuracy) or to decrease it (e.g., by removing contaminants from flow). The AC electrokinetic phenomenon, dielectrophoresis (DEP), has been used widely for particle trapping for flow, but the magnitude of the force drops reduces rapidly with distance from electrode edges, so that nm-scale particles such as viruses and bacteria are only trapped when near the electrode surface. This limits the usable flow rate in the device and can render the final device unusable for practical applications. Conversely, another electrokinetic phenomenon, AC electro-osmosis (ACEO), can be used to move particles to electrode surfaces but is unable to trap them from flow, limiting their ability for sample cleanup or trap-and-purge concentration. In this paper, we describe the optimization of ACEO electrodes aligned parallel to pressure-driven flow as a precursor/preconditioner to capture particles from a flow stream and concentrate them adjacent to the channel wall to enhance DEP capture. This is shown to be effective at flow rates of up to 0.84 ml min-1. Furthermore, the analysis of the 3D flow structure in the ACEO device by both simulation and confocal microscopy suggests that while the system offers significant benefits, the flow structure in the volume near the channel lid is such that while substantial trapping can occur, particles in this part of the chamber cannot be trapped, independent of the chamber height.

Dielectric properties of human macrophages are altered by Mycobacterium tuberculosis infection.

The analysis of cell electrophysiology for pathogenic samples at BSL3 can be problematic. It is virtually impossible to isolate infected from uninfected without a label, for example green fluorescent protein, which can potentially alter the cell electrical properties. Furthermore, the measurement of highly pathogenic organisms often requires equipment dedicated only for use with these organisms due to safety considerations. To address this, we have used dielectrophoresis to study the electrical properties of the human THP-1 cell line and monocyte-derived macrophages before and after infection with non-labelled Mycobacterium tuberculosis. Infection with these highly pathogenic bacilli resulted in changes including a raised surface conductance (associated with reduced zeta potential) and increased capacitance, suggesting an increase in surface roughness. We have also investigated the effect of fixation on THP-1 cells as a means to enable study on fixed samples in BSL1 or 2 laboratories, which suggests that the properties of these cells are largely unaffected by the fixation process. This advance results in a novel technique enabling the isolation of infected and non-infected cells in a sample without labelling.

Targeted Training Reduces Search Errors but Not Classification Errors for Hepatic Metastasis Detection at Contrast-Enhanced CT.

RATIONALE AND OBJECTIVES: Methods are needed to improve the detection of hepatic metastases. Errors occur in both lesion detection (search) and decisions of benign versus malignant (classification). Our purpose was to evaluate a training program to reduce search errors and classification errors in the detection of hepatic metastases in contrast-enhanced abdominal computed tomography (CT). MATERIALS AND METHODS: After Institutional Review Board approval, we conducted a single-group prospective pretest-posttest study. Pretest and posttest were identical and consisted of interpreting 40 contrast-enhanced abdominal CT exams containing 91 liver metastases under eye tracking. Between pretest and posttest, readers completed search training with eye-tracker feedback and coaching to increase interpretation time, use liver windows, and use coronal reformations. They also completed classification training with part-task practice, rating lesions as benign or malignant. The primary outcome was metastases missed due to search errors (<2 seconds gaze under eye tracker) and classification errors (>2 seconds). Jackknife free-response receiver operator characteristic (JAFROC) analysis was also conducted. RESULTS: A total of 31 radiologist readers (8 abdominal subspecialists, 8 nonabdominal subspecialists, 15 senior residents/fellows) participated. Search errors were reduced (pretest 11%, posttest 8%, difference 3% [95% confidence interval, 0.3%-5.1%], P = .01), but there was no difference in classification errors (difference 0%, P = .97) or in JAFROC figure of merit (difference -0.01, P = .36). In subgroup analysis, abdominal subspecialists demonstrated no evidence of change. CONCLUSION: Targeted training reduced search errors but not classification errors for the detection of hepatic metastases at contrast-enhanced abdominal CT. Improvements were not seen in all subgroups.

Proton Gradient Regulation 5 is required to avoid photosynthetic oscillations during light transitions.

The production of ATP and NADPH by the light reactions of photosynthesis and their consumption by the Calvin-Benson-Bassham (CBB) cycle and other downstream metabolic reactions requires careful regulation. Environmental shifts perturb this balance, leading to photo-oxidative stress and losses in CO2 assimilation. Imbalances in the production and consumption of ATP and NADPH manifest themselves as transient instability in the chlorophyll fluorescence, P700, electrochromic shift, and CO2 uptake signals recorded on leaves. These oscillations can be induced in wild-type plants by sudden shifts in CO2 concentration or light intensity; however, mutants exhibiting increased oscillatory behaviour have yet to be reported. This has precluded an understanding of the regulatory mechanisms employed by plants to suppress oscillations. Here we show that the Arabidopsis pgr5 mutant, which is deficient in Proton Gradient Regulation 5 (PGR5)-dependent cyclic electron transfer (CET), exhibits increased oscillatory behaviour. In contrast, mutants lacking the NADH-dehydrogenase-like-dependent CET are largely unaffected. The absence of oscillations in the hope2 mutant which, like pgr5, lacks photosynthetic control and exhibits high ATP synthase conductivity, ruled out loss of these photoprotective mechanisms as causes. Instead, we observed slower formation of the proton motive force and, by inference, ATP synthesis in pgr5 following environmental perturbation, leading to the transient reduction of the electron transfer chain and photosynthetic oscillations. PGR5-dependent CET therefore plays a major role in damping the effect of environmental perturbations on photosynthesis to avoid losses in CO2 fixation.

Infrapopliteal Segments on Lower Extremity CTA: Prospective Intraindividual Comparison of Energy-Integrating Detector CT and Photon-Counting Detector CT.

BACKGROUND. The higher spatial resolution and image contrast for iodine-containing tissues of photon-counting detector (PCD) CT may address challenges in evaluating small calcified vessels when performing lower extremity CTA by energy-integrating detector (EID) CTA. OBJECTIVE. The purpose of the study was to compare the evaluation of infrapopliteal vasculature between lower extremity CTA performed using EID CT and PCD CT. METHODS. This prospective study included 32 patients (mean age, 69.7 ± 11.3 [SD] years; 27 men, five women) who underwent clinically indicated lower extremity EID CTA between April 2021 and March 2022; participants underwent investigational lower extremity PCD CTA later the same day as EID CTA using a reduced IV contrast media dose. Two radiologists independently reviewed examinations in two sessions, each containing a random combination of EID CTA and PCD CTA examinations; the readers assessed the number of visualized fibular perforators, characteristics of stenoses at 11 infrapopliteal segmental levels, and subjective arterial sharpness. RESULTS. Mean IV contrast media dose was 60.0 ± 11.0 (SD) mL for PCD CTA versus 139.6 ± 11.8 mL for EID CTA (p < .001). The number of identified fibular perforators per lower extremity was significantly higher for PCD CTA than for EID CTA for reader 1 (R1) (mean ± SD, 6.4 ± 3.2 vs 4.2 ± 2.4; p < .001) and reader 2 (R2) (8.8 ± 3.4 vs 7.6 ± 3.3; p = .04). Reader confidence for assessing stenosis was significantly higher for PCD CTA than for EID CTA for R1 (mean ± SD, 82.3 ± 20.3 vs 78.0 ± 20.2; p < .001) but not R2 (89.8 ± 16.7 vs 90.6 ± 7.1; p = .24). The number of segments per lower extremity with total occlusion was significantly lower for PCD CTA than for EID CTA for R2 (mean ± SD, 0.5 ± 1.3 vs 0.9 ± 1.7; p = .04) but not R1 (0.6 ± 1.3 vs 1.0 ± 1.5; p = .07). The number of segments per lower extremity with clinically significant nonocclusive stenosis was significantly higher for PCD CTA than for EID CTA for R1 (mean ± SD, 2.2 ± 2.2 vs 1.6 ± 1.7; p = .01) but not R2 (1.1 ± 2.0 vs 1.1 ± 1.4; p = .89). Arterial sharpness was significantly greater for PCD CTA than for EID CTA for R1 (mean ± SD, 3.2 ± 0.5 vs 1.8 ± 0.5; p < .001) and R2 (3.2 ± 0.4 vs 1.7 ± 0.8; p < .001). CONCLUSION. PCD CTA yielded multiple advantages relative to EID CTA for visualizing small infrapopliteal vessels and characterizing associated plaque. CLINICAL IMPACT. The use of PCD CTA may improve vascular evaluation in patients with peripheral arterial disease.

Energetic driving force for LHCII clustering in plant membranes.

Plants capture and convert solar energy in a complex network of membrane proteins. Under high light, the luminal pH drops and induces a reorganization of the protein network, particularly clustering of the major light-harvesting complex (LHCII). While the structures of the network have been resolved in exquisite detail, the thermodynamics that control the assembly and reorganization had not been determined, largely because the interaction energies of membrane proteins have been inaccessible. Here, we describe a method to quantify these energies and its application to LHCII. Using single-molecule measurements, LHCII proteoliposomes, and statistical thermodynamic modeling, we quantified the LHCII-LHCII interaction energy as ~-5 kBT at neutral pH and at least -7 kBT at acidic pH. These values revealed an enthalpic thermodynamic driving force behind LHCII clustering. Collectively, this work captures the interactions that drive the organization of membrane protein networks from the perspective of equilibrium statistical thermodynamics, which has a long and rich tradition in biology.

Incidence of complications related to shoulder arthroplasties identified on computed tomography.

PURPOSE: Determine incidence of shoulder arthroplasty complications identified on computed tomography (CT). MATERIALS AND METHODS: Retrospective institutional database review of patients with shoulder arthroplasties who underwent CT between 01/2006-11/2021 at a tertiary academic referral center with subspecialized orthopedic shoulder surgeons. CT reports were reviewed for arthroplasty type and complication. Data were stratified and summarized. Associations between complications and arthroplasty types were determined with Chi-squared goodness of fit test. RESULTS: Eight hundred twelve CTs in 797 unique patients were included (438 (53.9%) females and 374 (46.1%) males; mean age 67 ± 11 years). There were 403 total shoulder arthroplasties (TSA), 317 reverse total shoulder arthroplasties (rTSA), and 92 hemiarthroplasties (HA). Complications were present in 527/812 (64.9%) and incidences were: loosening/aseptic osteolysis 36.9%, periprosthetic failure 21.6%, periprosthetic fracture 12.3%, periprosthetic dislocation 6.8%, joint/pseudocapsule effusion 5.9%, prosthetic failure 4.8%, infection 3.8%, and periprosthetic collection 2.1%. Complications per arthroplasty were: 305/403 (75.7%) TSAs, 176/317 (55.5%) rTSAs, and 46/92 (50%) HAs (p < 0.001). Periprosthetic fracture (20.8%), prosthetic dislocation (9.8%), and prosthetic failure (7.9%) were highest in rTSAs (p < 0.001, p < 0.013, p < 0.001, respectively). Loosening/aseptic osteolysis most frequent in TSAs (54.1%) (p < 0.001). Periprosthetic failure most frequent in HA (32.6%) (p < 0.001). Significant associations were identified with joint/pseudocapsule effusion and loosening/aseptic osteolysis (p = 0.04) and prosthetic dislocation (p < .001). CONCLUSION: In this single tertiary academic referral center cohort, the incidence of shoulder arthroplasty complication identified on CT was 64.9% and the most commonly occurring complication was loosening/aseptic osteolysis (36.9%). TSA had the highest incidence of complication (75.7%).

Twisted Carotenoids Do Not Support Efficient Intramolecular Singlet Fission in the Orange Carotenoid Protein.

Singlet exciton fission is the spin-allowed generation of two triplet electronic excited states from a singlet state. Intramolecular singlet fission has been suggested to occur on individual carotenoid molecules within protein complexes provided that the conjugated backbone is twisted out of plane. However, this hypothesis has been forwarded only in protein complexes containing multiple carotenoids and bacteriochlorophylls in close contact. To test the hypothesis on twisted carotenoids in a "minimal" one-carotenoid system, we study the orange carotenoid protein (OCP). OCP exists in two forms: in its orange form (OCPo), the single bound carotenoid is twisted, whereas in its red form (OCPr), the carotenoid is planar. To enable room-temperature spectroscopy on canthaxanthin-binding OCPo and OCPr without laser-induced photoconversion, we trap them in a trehalose glass. Using transient absorption spectroscopy, we show that there is no evidence of long-lived triplet generation through intramolecular singlet fission despite the canthaxanthin twist in OCPo.

Outcomes in patients with clinically suspected pedal osteomyelitis based on bone marrow signal pattern on MRI.

Objective: confluent T1 hypointense marrow signal is widely accepted to represent osteomyelitis on MRI. Some authors have suggested that non-confluent bone marrow signal abnormality should be considered early osteomyelitis. The purpose of this study was to address this issue by comparing the rate of osteomyelitis and amputation based on T1 marrow signal characteristics. Materials and methods: a total of 112 patients who underwent MRI of the foot for the evaluation of possible osteomyelitis were included. Patients were assigned to confluent T1 hypointense, reticulated T1 hypointense, and normal bone marrow signal groups. Results: patients with confluent T1 hypointense signal on MRI had significantly higher rates of osteomyelitis and amputation at 2 and 14 months post-MRI than the reticulated T1 hypointense group ( p < 0.001 ). Six patients had normal T1 signal, 16.7 % of whom had osteomyelitis and underwent amputation by 2 months post-MRI. Of 61 patients with reticulated T1 hypointense signal, 19.7 % had a diagnosis of osteomyelitis at 2 months post-MRI and 30.8 % had a diagnosis of osteomyelitis at 14 months post-MRI; moreover, 14.8 % and 31.5 % underwent amputation by 2 and 14 months post-MRI, respectively. Of 45 patients with confluent T1 hypointense signal, 73.3 % of patients had osteomyelitis at 2 months post-MRI and 82.5 % had osteomyelitis at 14 months post-MRI. In this group, 66.7 % underwent amputation by 2 months post-MRI and 77.8 % underwent amputation by 14 months post-MRI. Conclusions: over half of the patients with suspected pedal osteomyelitis who had reticulated or normal T1 bone marrow signal on MRI healed with conservative measures. Therefore, we recommend terminology such as "osteitis", "reactive osteitis", or "nonspecific reactive change" to describe bone marrow edema-like signal and reticulated hazy T1 hypointense signal without associated confluent T1 hypointensity. Moreover, we recommend that the MRI diagnosis of osteomyelitis is reserved for confluent T1 hypointense bone signal in the area of concern.

A training program to reduce reader search errors for liver metastasis detection in CT.

Detection of low contrast liver metastases varies between radiologists. Training may improve performance for lower-performing readers and reduce inter-radiologist variability. We recruited 31 radiologists (15 trainees, 8 non-abdominal staff, and 8 abdominal staff) to participate in four separate reading sessions: pre-test, search training, classification training, and post-test. In the pre-test, each radiologist interpreted 40 liver CT exams containing 91 metastases, circumscribed suspected hepatic metastases while under eye tracker observation, and rated confidence. In search training, radiologists interpreted a separate set of 30 liver CT exams while receiving eye tracker feedback and after coaching to increase use of coronal reformations, interpretation time, and use of liver windows. In classification training, radiologists interpreted up to 100 liver CT image patches, most with benign or malignant lesions, and compared their annotations to ground truth. Post-test was identical to pre-test. Between pre- and post-test, sensitivity increased by 2.8% (p = 0.01) but AUC did not change significantly. Missed metastases were classified as search errors (<2 seconds gaze time) or classification errors (>2 seconds gaze time) using the eye tracker. Out of 2775 possible detections, search errors decreased (10.8% to 8.1%; p < 0.01) but classification errors were unchanged (5.7% vs 5.7%). When stratified by difficulty, easier metastases showed larger reductions in search errors: for metastases with average sensitivity of 0-50%, 50-90%, and 90-100%, reductions in search errors were 16%, 35%, and 58%, respectively. The training program studied here may be able to improve radiologist performance by reducing errors but not classification errors.

STN7 is not essential for developmental acclimation of Arabidopsis to light intensity.

Plants respond to changing light intensity in the short term through regulation of light harvesting, electron transfer, and metabolism to mitigate redox stress. A sustained shift in light intensity leads to a long-term acclimation response (LTR). This involves adjustment in the stoichiometry of photosynthetic complexes through de novo synthesis and degradation of specific proteins associated with the thylakoid membrane. The light-harvesting complex II (LHCII) serine/threonine kinase STN7 plays a key role in short-term light harvesting regulation and was also suggested to be crucial to the LTR. Arabidopsis plants lacking STN7 (stn7) shifted to low light experience higher photosystem II (PSII) redox pressure than the wild type or those lacking the cognate phosphatase TAP38 (tap38), while the reverse is true at high light, where tap38 suffers more. In principle, the LTR should allow optimisation of the stoichiometry of photosynthetic complexes to mitigate these effects. We used quantitative label-free proteomics to assess how the relative abundance of photosynthetic proteins varied with growth light intensity in wild-type, stn7, and tap38 plants. All plants were able to adjust photosystem I, LHCII, cytochrome b6 f, and ATP synthase abundance with changing white light intensity, demonstrating neither STN7 nor TAP38 is crucial to the LTR per se. However, stn7 plants grown for several weeks at low light (LL) or moderate light (ML) still showed high PSII redox pressure and correspondingly lower PSII efficiency, CO2 assimilation, and leaf area compared to wild-type and tap38 plants, hence the LTR is unable to fully ameliorate these symptoms. In contrast, under high light growth conditions the mutants and wild type behaved similarly. These data are consistent with the paramount role of STN7-dependent LHCII phosphorylation in tuning PSII redox state for optimal growth in LL and ML conditions.

Cryo-EM structure of the four-subunit Rhodobacter sphaeroides cytochrome bc1 complex in styrene maleic acid nanodiscs.

Cytochrome bc1 complexes are ubiquinol:cytochrome c oxidoreductases, and as such, they are centrally important components of respiratory and photosynthetic electron transfer chains in many species of bacteria and in mitochondria. The minimal complex has three catalytic components, which are cytochrome b, cytochrome c1, and the Rieske iron-sulfur subunit, but the function of mitochondrial cytochrome bc1 complexes is modified by up to eight supernumerary subunits. The cytochrome bc1 complex from the purple phototrophic bacterium Rhodobacter sphaeroides has a single supernumerary subunit called subunit IV, which is absent from current structures of the complex. In this work we use the styrene-maleic acid copolymer to purify the R. sphaeroides cytochrome bc1 complex in native lipid nanodiscs, which retains the labile subunit IV, annular lipids, and natively bound quinones. The catalytic activity of the four-subunit cytochrome bc1 complex is threefold higher than that of the complex lacking subunit IV. To understand the role of subunit IV, we determined the structure of the four-subunit complex at 2.9 Å using single particle cryogenic electron microscopy. The structure shows the position of the transmembrane domain of subunit IV, which lies across the transmembrane helices of the Rieske and cytochrome c1 subunits. We observe a quinone at the Qo quinone-binding site and show that occupancy of this site is linked to conformational changes in the Rieske head domain during catalysis. Twelve lipids were structurally resolved, making contacts with the Rieske and cytochrome b subunits, with some spanning both of the two monomers that make up the dimeric complex.

High cyclic electron transfer via the PGR5 pathway in the absence of photosynthetic control.

The light reactions of photosynthesis couple electron and proton transfers across the thylakoid membrane, generating NADPH, and proton motive force (pmf) that powers the endergonic synthesis of ATP by ATP synthase. ATP and NADPH are required for CO2 fixation into carbohydrates by the Calvin-Benson-Bassham cycle. The dominant ΔpH component of the pmf also plays a photoprotective role in regulating photosystem II light harvesting efficiency through nonphotochemical quenching (NPQ) and photosynthetic control via electron transfer from cytochrome b6f (cytb6f) to photosystem I. ΔpH can be adjusted by increasing the proton influx into the thylakoid lumen via upregulation of cyclic electron transfer (CET) or decreasing proton efflux via downregulation of ATP synthase conductivity (gH+). The interplay and relative contributions of these two elements of ΔpH control to photoprotection are not well understood. Here, we showed that an Arabidopsis (Arabidopsis thaliana) ATP synthase mutant hunger for oxygen in photosynthetic transfer reaction 2 (hope2) with 40% higher proton efflux has supercharged CET. Double crosses of hope2 with the CET-deficient proton gradient regulation 5 and ndh-like photosynthetic complex I lines revealed that PROTON GRADIENT REGULATION 5 (PGR5)-dependent CET is the major pathway contributing to higher proton influx. PGR5-dependent CET allowed hope2 to maintain wild-type levels of ΔpH, CO2 fixation and NPQ, however photosynthetic control remained absent and PSI was prone to photoinhibition. Therefore, high CET in the absence of ATP synthase regulation is insufficient for PSI photoprotection.