Cryo-electron microscopy reveals hydrogen positions and water networks in photosystem II.

Photosystem II starts the photosynthetic electron transport chain that converts solar energy into chemical energy and thus sustains life on Earth. It catalyzes two chemical reactions: water oxidation to molecular oxygen and plastoquinone reduction. Coupling of electron and proton transfer is crucial for efficiency; however, the molecular basis of these processes remains speculative owing to uncertain water binding sites and the lack of experimentally determined hydrogen positions. We thus collected high-resolution cryo-electron microscopy data of fully hydrated photosystem II from the thermophilic cyanobacterium Thermosynechococcus vestitus to a final resolution of 1.71 angstroms. The structure reveals several previously undetected partially occupied water binding sites and more than half of the hydrogen and proton positions. This clarifies the pathways of substrate water binding and plastoquinone B protonation.

Adoption of hooped-battens in cold-formed steel built-up columns for superior axial performance.

Previous research on cold-formed steel (CFS) battened columns has identified the critical factors influencing their performance and accordingly, their limiting values for improved performance have been recommended. However, these studies involved connecting battens to the chords (channels) via their flanges, leaving the slenderest component disconnected from the web. This study introduces a novel hooped-batten (tubular-element) that links both webs and flanges of the chords together, thereby improving the structural integrity of the built-up system and curtailing the half-wave buckling length in the webs. As a result, axial strength and stability in these built-up columns may improve adequately. Firstly, a numerical model of a conventional CFS battened column was developed in ABAQUS and verified against test results on the same reported in literature. Afterward, the validated model was used to simulate the behaviour of CFS built-up columns with hooped-battens. Two key parameters i.e., unbraced chord slenderness and overall column slenderness were varied to explore their influence on the axial behaviour of built-up columns in terms of peak strengths, failure modes and load-displacement characteristics. The performance of the hooped-battened columns was compared with the identical conventional battened columns, which reflects that the former exhibits superior strength and stability characteristics over the latter.

Virulence properties of Listeria monocytogenes isolated from meat and meat contact surfaces in a slaughterhouse.

Listeria monocytogenes is a ubiquitous microorganism that is isolated from a variety of sources such as soil, water, decaying vegetation, sewage, animal feeds, silage, farm environments and food-processing environments. This study aimed to determine the prevalence, serogroups, biofilm formation, virulence factor genes, and genetic relationships of L. monocytogenes strains isolated from beef meat and meat contact surfaces obtained from a slaughterhouse in Burdur, Turkey. In this study, a total of 179 beef meat and meat contact surface samples were analyzed for the presence of L. monocytogenes by polymerase chain reaction (PCR). Out of a total of 179 beef meat and meat contact surface samples, 83 (46.37%) were found to be contaminated with L. monocytogenes, with the highest incidence (53.01%) occurring in beef meat. In the present study, most of the isolated strains belonged to serogroups IIB and IVB (lineage I). The L. monocytogenes strain also contained monoA-B, prfA, plcA, plcB, mpl, hlyA, actA, gtcA, dltA, Fri, flaA, InlA, InlC, InlJ, and iap genes. Biofilm formation was not determined in the tested samples at pH 5.5 and different temperatures (4°C, 10°C, 25°C, and 37°C). However, strong biofilm formation was observed in 6.45% (2/31) of the strains at pH 7.0 after 48 h incubation at 37°C, and in 3.22% (1/31) of the strains at pH 7.0 after 48 h incubation at 4°C and 10°C. Pulsed-field gel electrophoresis (PFGE) results showed that L. monocytogenes isolates were clonally related, and cross-contamination was present. In addition, PFGE results also revealed that AscI had more distinguishing power than the ApaI restriction enzyme. These results indicate that L. monocytogenes detected from meat and meat contact surfaces in the slaughterhouse pose a potential risk to public health.

On the simulation and interpretation of substrate-water exchange experiments in photosynthetic water oxidation.

Water oxidation by photosystem II (PSII) sustains most life on Earth, but the molecular mechanism of this unique process remains controversial. The ongoing identification of the binding sites and modes of the two water-derived substrate oxygens ('substrate waters') in the various intermediates (Si states, i = 0, 1, 2, 3, 4) that the water-splitting tetra-manganese calcium penta-oxygen (Mn4CaO5) cluster attains during the reaction cycle provides central information towards resolving the unique chemistry of biological water oxidation. Mass spectrometric measurements of single- and double-labeled dioxygen species after various incubation times of PSII with H218O provide insight into the substrate binding modes and sites via determination of exchange rates. Such experiments have revealed that the two substrate waters exchange with different rates that vary independently with the Si state and are hence referred to as the fast (Wf) and the slow (WS) substrate waters. New insight for the molecular interpretation of these rates arises from our recent finding that in the S2 state, under special experimental conditions, two different rates of WS exchange are observed that appear to correlate with the high spin and low spin conformations of the Mn4CaO5 cluster. Here, we reexamine and unite various proposed methods for extracting and assigning rate constants from this recent data set. The analysis results in a molecular model for substrate-water binding and exchange that reconciles the expected non-exchangeability of the central oxo bridge O5 when located between two Mn(IV) ions with the experimental and theoretical assignment of O5 as WS in all S states. The analysis also excludes other published proposals for explaining the water exchange kinetics.

El papel de la formación cognitiva en la endourología: un ensayo controlado aleatorizado / The role of cognitive training in endourology: a randomised controlled trial

Introducción: La formación cognitiva es una modalidad de formación importante que permite al usuario ensayar un procedimiento sin realizarlo físicamente. Esto ha llevado a intereses recientes a incorporar la formación cognitiva en la educación quirúrgica, pero la investigación actualmente es limitada. El uso de la formación cognitiva en cirugía no es claro, por lo que este estudio tuvo como objetivo determinar si, en relación con una condición de control, el uso de la formación cognitiva mejora las habilidades quirúrgicas técnicas en un simulador de ureteroscopia y, si es así, si un método de formación cognitiva es superior. Métodos: Este estudio prospectivo y comparativo reclutó a 59 estudiantes de medicina y los asignó al azar a uno de los 3 grupos: formación de simulación de control solamente (n = 20), grupo de formación cognitiva de tarjetas educativas (n = 20) o grupo de formación cognitiva de imágenes mentales (n = 19). Todos los participantes completaron 3 tareas al inicio en el simulador URO Mentor, seguidas de la intervención cognitiva si se asignaron al azar para recibirla. Los participantes regresaron para realizar una tarea de evaluación en el simulador. Las medidas de resultado del informe de ejecución URO Mentor se usaron para el análisis y se realizó una encuesta cuantitativa a todos los participantes para evaluar la utilidad de la formación recibida. Resultados. Este estudio mostró que la formación cognitiva tiene efectos mínimos en las habilidades técnicas de los participantes. El grupo de imágenes mentales tuvo menos fallos de láser en la tarea de evaluación en comparación tanto con el grupo control como con el de tarjetas educativas (p = 0,017, p = 0,036, respectivamente). El grupo de tarjetas educativas calificó su preparación para ser más útil en comparación con el control (p = 0,0125). Otros parámetros analizados entre los grupos no alcanzaron significación estadística. Se descubrió que la formación cognitiva era factible y rentable cuando se llevaba a cabo además de la formación de simulación. Conclusión: Este estudio ha demostrado que el papel de la formación cognitiva en la adquisición de habilidades quirúrgicas es mínimo y que ninguna forma de entrenamiento cognitivo fue superior a otra. Se necesita investigar más para evaluar otras formas de realizar entrenamiento cognitivo

Introduction: Cognitive training is an important training modality which allows the user to rehearse a procedure without physically carrying it out. This has led to recent interests to incorporate cognitive training within surgical education but research is currently limited. The use of cognitive training in surgery is not clear-cut and so this study aimed to determine whether, relative to a control condition, the use of cognitive training improves technical surgical skills on a ureteroscopy simulator, and if so whether one cognitive training method is superior. Methods: This prospective, comparative study recruited 59 medical students and randomised them to one of three groups: control- simulation training only (n = 20), flashcards cognitive training group (n = 20) or mental imagery cognitive training group (n = 19). All participants completed three tasks at baseline on the URO Mentor simulator followed by the cognitive intervention if randomised to receive it. Participants then returned to perform an assessment task on the simulator. Outcome measures from the URO Mentor performance report was used for analysis and a quantitative survey was given to all participants to assess usefulness of training received. Results: This study showed cognitive training to have minimal effects on technical skills of participants. The mental imagery group had fewer laser misfires in the assessment task when compared to both control and flashcards group (P = .017, P = .036, respectively). The flashcards group rated their preparation to be most useful when compared to control (P = .0125). Other parameters analysed between the groups did not reach statistical significance. Cognitive training was found to be feasible and cost effective when carried out in addition to simulation training. Conclusion: This study has shown that the role of cognitive training within acquisition of surgical skills is minimal and that no form of cognitive training was superior to another. Further research needs to be done to evaluate other ways of performing cognitive training

Complete ossification of the superior transverse scapular ligament in an Turkish male adult / Osificación completa del ligamento escapular superior transverso en un hombre adulto de Turquía

Scapula has three margins and angles and located posterolateral of thorax. One of the anatomical structures of scapula is suprascapular notch located medial to coracoid process base. Suprascapular notch can be seen in different shapes and depths. Suprascapular notch is surrounded by transverse scapular ligament which is a short and strong ligament. Suprascapular notch creates an osteofibrosis passage with this structure within suprascapular nerve passes. It has been reported that this osteofibrosis structure can intirely or partially ossify. All lesions of nerves occured in course as result of exposure to compression, tension and bending are called entrapment neuropathy. Like other peripheral nerves, suprascapular nerve can be exposed to compression while passing suprascapular notch. As a result of this compression suprascapular entrapment neuropathy may occur. There are direct trauma, repetitive microtrauma, neurit, progressive compressive lesions in suprascapular entrapment neuropathies etiology. A suprascapular notch taken foramen shape can be a predisposing factor to entrapment neuropathy. In the retrospective screening from Necmettin Erbakan University, Meram Medical Faculty, Department of Radiology archive, a male patient at age 68 with suprascapular notch variation has been detected. This patient's right suprascapular notch had became foramen by an osseous bridge. Diameters of foramen has been measured as 5.27 mm transverse 6.48 mm vertical. We believe having detailed knowledge of suprascapular notch is significant as a possible course of back and shoulder pain is entrapment of suprascapular nerve in suprascapular notch causing nerve paralyses, and it will give a right direction to clinicians in surgical practices.

La escápula tiene tres márgenes y tres ángulos, y se encuentra en la región posterolateral del tórax. Una de las estructuras anatómicas de la escápula es la incisura supraescapular situada medial a la base del proceso coracoides. La incisura supraescapular puede tener diferentes formas y profundidad. Está rodeada por el ligamento escapular transverso, un ligamento corto y fuerte. Con esta estructura, crea un pasaje osteofibroso por el cual pasa el nervio supraescapular. Se ha reportado que esta estructura osteofibrosa se puede osificar completa o parcialmente. Todas las lesiones de los nervios ocurren en su trayecto como resultado de la exposición a compresión, tensión y flexión, lo que se denomina neuropatía por atrapamiento. El nervio supraescapular puede estar expuesto a compresión al pasar por la incisura supraescapular, generando neuropatía por atrapamiento. Su etiología puede ser por traumatismo directo, microtraumatismo repetitivo y lesiones compresivas progresivas. Una incisura supraescapular de forma oval puede ser un factor predisponente para la neuropatía por atrapamiento. En un estudio retrospectivo realizado en la Universidad Necmettin Erbakan, Facultad de Medicina de Meram, Departamento de archivo de Radiología, se observó la imagen de un varón de 68 años con variación en la incisura supraescapular derecha, la cual se transformó en un foramen por un puente óseo. Los diámetros del foramen fueron 5,27 mm transversales y 6,48 mm verticales. Creemos que el conocimiento detallado de la incisura supraescapular es necesario en el diagnóstico y posible curso de dolor del hombro, debido al atrapamiento del nervio supraescapular en la incisura y la posible parálisis nerviosa, dando una guía a los clínicos en las prácticas quirúrgicas.

Oxidative stress status and plasma trace elements in patients with asthma or allergic rhinitis

Introduction: This study was conducted to evaluate the oxidant/antioxidant balance (oxidative stress status) and plasma essential trace element levels in patients with bronchial asthma or allergic rhinitis. Methods: A total of 94 individuals consisting of 19 allergic asthmatics; 17 non-allergic asthmatics; 22 patients with allergic rhinitis; and 36 healthy control people were enrolled into this study. Superoxide dismutase (CuZnSOD) and glutathione peroxidase (GSH-Px) activity as antioxidant defence mechanism parameters, along with malondialdehyde (MDA) as a marker of lipid peroxidation, were determined in erythrocytes of patient groups and controls. Plasma copperand zinc levels were also determined in all groups. Results: CuZnSOD activity was significantly lower in all groups of patients (p<0.001 for allergic asthmatics, p=0.008 for allergic rhinitis patients, and p<0.001 for non-allergic asthmatics) when compared to those of controls. Erythrocyte GSH-Px enzyme activity was not different when compared to that of the control group. Similarly, the patient groups had no difference from those of the controls with respect to erythrocyte MDA levels. While plasma Cu levels in all asthmatic patients were not different from those of the controls, allergic rhinitis patients had significantly elevated (p<0.001) Cu levels compared to those of the controls. No statistically significant difference was established between patient groups and controls with respect to plasma zinc levels. Conclusion: While defective CuZnSOD activity observed in all patients groups was expected to cause an increase in lipid peroxidation indicated by high MDA levels in these patients groups, the fact that MDA levels were not different from those of controls in all patient groups indicates that other components of anti-oxidant defence system preserve their functions in these patients. On the other hand, statistically significant difference between all patients groups and controls with respect to trace elements was only observed in allergic rhinitis patients who had higher levels of Cu than those of controls (AU)

Oxidative stress status in patients with chronic idiopathic urticaria

Aim: The controversial data related to oxidative stress status in patients with chronic idiopathic urticaria (CIU) have been reported. Therefore, the present study was aimed to contribute to this debate by determining oxidative stress markers along with some trace element levels inpatients with CIU. Methods: Twenty-five patients with CIU (10 males, 15 females) and 36 healthy controls were enrolled into the study. Erythrocyte lipid peroxidation status, scavenger enzyme activities and trace element levels were determined. Results: While erythrocyte MDA levels, erythrocyte GSH- Px activities and erythrocyte Zn levels showed no differences between the patient and control groups, a statistically significant decrease and increase were observed in erythrocyte CuZn-SOD activities and Cu levels, respectively, in the CIU patients when compared to those of the controls (p < 0.001 for both of them). Conclusion: In conclusion, an oxidative burden which can be relieved by some preserved antioxidant mechanisms seems to be present in patients with CIU even if they are clinically stable and it may probably have a role in the pathogenesis (AU)