Multiple redox switches of the SARS-CoV-2 main protease in vitro provide opportunities for drug design.

Besides vaccines, the development of antiviral drugs targeting SARS-CoV-2 is critical for preventing future COVID outbreaks. The SARS-CoV-2 main protease (Mpro), a cysteine protease with essential functions in viral replication, has been validated as an effective drug target. Here, we show that Mpro is subject to redox regulation in vitro and reversibly switches between the enzymatically active dimer and the functionally dormant monomer through redox modifications of cysteine residues. These include a disulfide-dithiol switch between the catalytic cysteine C145 and cysteine C117, and generation of an allosteric cysteine-lysine-cysteine SONOS bridge that is required for structural stability under oxidative stress conditions, such as those exerted by the innate immune system. We identify homo- and heterobifunctional reagents that mimic the redox switching and inhibit Mpro activity. The discovered redox switches are conserved in main proteases from other coronaviruses, e.g. MERS-CoV and SARS-CoV, indicating their potential as common druggable sites.

Development and Evaluation of an MRI Artifact-Free Aneurysm Clip.

BACKGROUND AND OBJECTIVES: The digital subtraction angiography is still the gold standard in the follow-up after aneurysm surgery, although it remains a repeating invasive technique with accumulating X-ray exposure. An alternative magnetic resonance angiography has the disadvantage of metal-related artifacts. A metal-free aneurysm clip could overcome this problem. Recent advances in manufacturing technologies of fiber-reinforced plastics might allow developing a prototype of a metal-free clip. METHODS: The prototype was formed out of carbon fiber-reinforced polyetheretherketone (CF-PEEK) in accordance with the standard clip design. In vivo and in vitro studies were performed to analyze the central nervous system biocompatibility. The prototype was tested in a phantom in a 3 T MRI scanner and microtomography scanner. For in vivo assessment, the left renal artery of rats was either ligated with a suture, clipped with a regular titanium clip or with the CF-PEEK prototype clip. The animals underwent standard MRI sequences and magnetic resonance angiography and assessment by a blinded neuroradiologist. RESULTS: Phantom studies showed no signs of artifacts. The prototype showed a reliable clamping and reopening after clip application, although the clamping force was reduced. In vivo studies showed a successful occlusion of the renal artery in all cases in the magnetic resonance angiography. Clip artifacts were statistically significant reduced in the prototype group (P < .01). CF-PEEK showed no signs of impaired biocompatibility compared with the titanium samples in vitro and in vivo. CONCLUSION: Former attempts of metal-free aneurysm clips did not meet the criteria of the standard clip design. In this study, the practicability of this new CF-PEEK artifact-free aneurysm clip has been proven. The further fabrication developments should overcome the problem of a reduced clamping force in the future. After clinical approval, it will improve the magnetic resonance image quality and might help to reduce the amount of digital subtraction angiography in the follow-up.

Proton Release Reactions in the Inward H+ Pump NsXeR.

Directional ion transport across biological membranes plays a central role in many cellular processes. Elucidating the molecular determinants for vectorial ion transport is key to understanding the functional mechanism of membrane-bound ion pumps. The extensive investigation of the light-driven proton pump bacteriorhodopsin from Halobacterium salinarum(HsBR) enabled a detailed description of outward proton transport. Although the structure of inward-directed proton pumping rhodopsins is very similar to HsBR, little is known about their protonation pathway, and hence, the molecular reasons for the vectoriality of proton translocation remain unclear. Here, we employ a combined experimental and theoretical approach to tracking protonation steps in the light-driven inward proton pump xenorhodopsin from Nanosalina sp. (NsXeR). Time-resolved infrared spectroscopy reveals the transient deprotonation of D220 concomitantly with deprotonation of the retinal Schiff base. Our molecular dynamics simulations support a proton release pathway from the retinal Schiff base via a hydrogen-bonded water wire leading to D220 that could provide a putative gating point for the proton release and with allosteric interactions to the retinal Schiff base. Our findings support the key role of D220 in mediating proton release to the cytoplasmic side and provide evidence that this residue is not the primary proton acceptor of the proton transiently released by the retinal Schiff base.

A novel minimally invasive and press-fit method for symphysiodesis - a biomechanical analysis.

PURPOSE: Does the cylindrical shaped bone block allow a stable construct for the arthrodesis of the pubic symphysis compared to a rectangular shaped bone block. The cylindrical shaped bone block stabilized by a 3.5 symphyseal plate is inferior to the stabilization with an internal fixator. METHODS: This study analyzed the arthrodesis of the pubic symphysis on 24 synthetic pelvises, using a rectangular shaped bone block (control group) or a cylindrical shaped bone block, stabilized with a symphysis locking plate (n = 8) as the standard clinical procedure. Additionally we analyzed the stability using an internal fixator. RESULTS: This study showed that utilizing a cylindrical shaped synthetic bone graft results in a significant higher contact area and compression force compared to the classical rectangular shaped graft. Furthermore, the stabilization with an internal fixator had the tendency for increases of compression force and contact area, yet without a statistical significance, when compared to the plate fixation. CONCLUSION: The novel method of cylindrical symphysis resection and cylindrical bone block implantation allowed an increased biomechanical stability compared to using a classical rectangular bone graft, also resulting in higher contact area. Moreover, this technique would also allow a minimally invasive approach for this purpose, which in turn could preserve perisymphyseal ligaments, thereby improving healing in a clinical context.

Mechanisms of Cysteine-Lysine Covalent Linkage-The Role of Reactive Oxygen Species and Competition with Disulfide Bonds.

Recently, a new naturally occurring covalent linkage was characterised, involving a cysteine and a lysine, bridged through an oxygen atom. The latter was dubbed as the NOS bond, reflecting the individual atoms involved in this uncommon bond which finds little parallel in lab chemistry. It is found to form under oxidising conditions and is reversible upon addition of reducing agents. Further studies have identified the bond in crystal structures across a variety of systems and organisms, potentially playing an important role in regulation, cellular defense and replication. Not only that, double NOS bonds have been identified and even found to be competitive in relation to the formation of disulfide bonds. This raises several questions about how this exotic bond comes to be, what are the intermediates involved in its formation and how it competes with other pathways of sulfide oxidation. With this objective in mind, we revisited our first proposed mechanism for the reaction with model electronic structure calculations, adding information about the reactivity with alternative reactive oxygen species and other potential competing products of oxidation. We present a network with more than 30 reactions which provides one of the most encompassing pictures for cysteine oxidation pathways to date.

Occurrence, resistance patterns, and management of carbapenemase-producing bacteria in war-wounded refugees from Ukraine.

We analyzed consecutive clinical cases of infections due to carbapenemase-producing gram-negative bacteria detected in war-wounded patients from Ukraine who were treated at one university medical center in southwest Germany between June and December 2022. The isolates of multiresistant gram-negative bacteria were subjected to a thorough microbiological characterization and whole genome sequencing (WGS). We identified five war-wounded Ukrainian patients who developed infections with New Delhi metallo-ß-lactamase 1-positive Klebsiella pneumoniae. Two isolates also carried OXA-48 carbapenemases. The bacteria were resistant to novel antibiotics, such as ceftazidime/avibactam and cefiderocol. The used treatment strategies included combinations of ceftazidime/avibactam + aztreonam, colistin, or tigecycline. WGS suggested transmission during primary care in Ukraine. We conclude that there is an urgent need for thorough surveillance of multiresistant pathogens in patients from war zones.

Experiences in the Use of Motorized Intramedullary Nails after Complex Injuries to the Extremities. / Erfahrungen bei der Anwendung motorisierter Marknägel nach komplexen Extremitätenverletzungen.

The treatment of complex injuries of the extremities after comminuted fractures or non-unions is a challenging area in the field of trauma surgery. Internal, motorized implants nowadays enable a patient-oriented and progressive treatment of these cases. The present article aims to present modern treatment strategies of complex injuries of the extremities, support the use of novel, motorized intramedullary nails and provide experiences for the handling with lengthening nails or transport nails. For this purpose, the preoperative planning including selection of patients, presentation of internal lengthening and transport systems and the most important factors during preparation of the surgery are described. Moreover, critical steps during the implantation of motorized nails and also during potential follow-up interventions are highlighted and the postoperative protocol including precise recommendations for the transport und consolidation phase are provided. Finally, the experiences are illustrated by presentation of the four different cases. The use of internal, motorized implants represents the latest step in the treatment of complex injuries of the extremities. These implants improve the quality of life and the authors recommend its use. However, these implants require a high expertise and adaption of established treatment protocols in these challenging trauma cases. Follow-up analyses with a considerably large number of cases are necessary and the research on implants to solve persisting problems in the area of complex injuries of the extremities has to be pursued intensively.

COVID-19: a catalyst for the digitization of surgical teaching at a German University Hospital.

BACKGROUND: The summer semester 2020, had to be restructured due to the SARS-CoV-2 pandemic and the associated contact restrictions. Here, for the first time, the established lectures in lecture halls and small group seminars could not be conducted in presence as usual. A possible tool for the implementation of medical teaching, offers the use of eLearning, online webinars and learning platforms. At present it is unclear how the SARS-CoV-2 pandemic will affect surgical teaching, how digitization will be accepted by students, and how virtual teaching can be expanded in the future. METHODS: The teaching, which was previously delivered purely through face-to-face lectures, was completely converted to digital media. For this purpose, all lectures were recorded and were available to students on demand. The seminars were held as a twice a week occurring online webinar. The block internship was also conducted as a daily online webinar and concluded with an online exam at the end. At the end of the semester, a survey of the students was carried out, which was answered by n = 192 students with an anonymized questionnaire. The questionnaire inquires about the previous and current experience with eLearning, as well as the possibility of a further development towards a purely digital university. RESULTS: There were n = 192 students in the study population. For 88%, the conversion of classes to web-based lectures represented their first eLearning experience. For 77% of all students, the digitization of teaching led to a change in the way they prepare for class. 73% of the participating students are of the opinion that eLearning lectures should continue to be offered. 54% of the students felt that eLearning lectures made more sense than face-to-face lectures. A purely virtual university could be imagined by 41% of the students. CONCLUSION: The conversion of teaching represented the first contact with eLearning for most students. Overall, the eLearning offering was experienced as positive. Due to the new teaching structure, the way of learning had already changed during the semester. Based on the new eLearning content, the already existing formats can be further expanded in the future. Nevertheless, it turned out that the practical-surgical contents and skills cannot be adequately represented by purely online offers; for this, the development of hybrid practice-oriented teaching concepts is necessary.

[Fridays for future! - All days for surgery! : Thoughts of young surgeons on a modern promotion of the next generation]. / Fridays for future! ­ All days for surgery! : Denkanstöße der jungen Chirurgie für eine moderne Nachwuchsförderung.

In order to be able to exploit the increasing complexity of modern surgery as best as possible in the future, the focus of young surgeons is on horizontal networking in addition to vertical networking: More interdisciplinary cooperation, more diversity, more perspectives. Future effective project work thrives on the exchange of young specialist society forums, junior resident spokespersons and junior student representation. However, the increasing establishment of mentoring programs and the experiences from daily practice show that this does not work without the experience and the readiness of the "greats" to impart knowledge. This article sketches the current challenges for the next generation of surgeons in the three fields of surgical training, life and surgery as well as promotion of excellence in academic surgery.

How effective are different models of pelvic binders: results of a study using a Pelvic Emergency Simulator.

BACKGROUND: The application of pelvic binders in the preclinical and early clinical phase is advisable to avoid or treat C-problems in unstable and potential bleeding pelvic ring fractures, even if the clinical effectivity is not completely proved. The use for pathologies in the posterior pelvic ring is still debatable. QUESTIONS/PURPOSES: We determined if there is a difference in achievable compression in the dorsal pelvic ring depending on position and pelvic binder model. Can this effect be tested with a simplified artificial model? METHODS: We simulated a Tile type C fracture within the established pelvic emergency trainer and measured in a test series the effectivity of reduction with a non-invasive stabilization technique using 3 different pelvic binders. RESULTS: Any therapeutic effect of a pelvic binder with compression to the posterior pelvic ring requires at first a reduction maneuver. While the compression effect in the symphysis depends only on positioning of the binder, in the posterior pelvic ring, the result varies with the used model. The achievable pressure in the SI joint with a pelvic binder is only 20-25% (33.5-47 N) compared to the C-Clamp values (156 N). CONCLUSIONS: The use of pelvic binders for non-invasive pelvic ring stabilization, even with a posterior pathology, could be proven in a simplified fracture model. A proper fracture reduction and an adequate device positioning influence the effectiveness. CLINICAL RELEVANCE: The use of an emergency pelvic trainer even for a non-invasive maneuver is advisable.

[Delegation and the Efficient Use of Medical Personnel - Ideas During Times of Physician Shortage]. / Überlegungen und Berechnungen zur Effizienz des Einsatzes von Ärzten für delegierbare, nichtärztliche Tätigkeiten ­ ein Denkanstoß in Zeiten des Nachwuchsmangels.

BACKGROUND: Patient care is a cost intensive process and an important fraction of these costs is the salary of medical staff. Efficient use, especially in times of physician shortage, should thus be of great importance to hospital management. We aim to calculate the costs and resulting saving potential from delegation of tasks, that are performed by medical personnel, but could in principle be delegated. MATERIALS AND METHODS: The calculation is based on the survey "Nachwuchsumfrage" of the Berufsverband and German Society of Surgery (n = 708). Satisfaction, limiting factors and time spent on tasks that could be delegated were assessed. From the average physician's salary and the salary of personnel that could be delegated to costs and potential savings were calculated. RESULTS: The surveyed surgeons spent an average of 124 min per day on tasks that could in principle be delegated. In total, costs through unused delegation were calculated at over 16,000 € per year and staff member, with a saving potential of up to 7,000 € despite full delegation. DISCUSSION: Our simple calculation shows the saving potential through adequate task delegation. Apart from the monetary aspects, a positive effect on physician staff satisfaction can be assumed, as unused delegation potential was the leading cause for decreased satisfaction.

[Case-based learning can improve the teaching quality in trauma surgery education : A survey analysis among medical students]. / Fallbasiertes Lernen kann die Lehrqualität im unfallchirurgischen Unterricht verbessern : Eine Umfrageanalyse unter Medizinstudierenden.

BACKGROUND: Medical education has always been challenging for students and teachers. Of growing importance is the promotion of knowledge of correlations and knowledge transfer from theoretical aspects into clinical practice. In order to achieve this aim, student-centered teaching concepts are increasingly being employed in the literature. OBJECTIVE: Can a trauma surgery practical seminar be improved by a case-based teaching concept? MATERIAL AND METHODS: For this purpose, standardized case studies and corresponding teaching materials, such as classification aids and treatment strategies, were made available to the students and lecturers. Using a two-staged evaluation the effects of the modified teaching design could be recorded and statistically analyzed. RESULTS: The seminar was considered to be relevant for the examinations. The teaching by the lecturers was found to be more competent and appeared more motivated. Overall, the seminar was rated better by the students. CONCLUSION: A case-based teaching concept can significantly improve the education in trauma surgery, when correctly and specifically implemented.

Macrophage-activating lipoprotein (MALP)-2 impairs the healing of partial tendon injuries in mice.

Tendon injuries are accounted for up to 50% of musculoskeletal injuries and often result in poor outcomes. Inflammation is a major hallmark of tendon regeneration. Therefore, we analyzed in this study whether the topical application of the pro-inflammatory mediator macrophage-activating lipoprotein (MALP)-2 improves the healing of partial tendon injuries. C57BL/6 mice underwent a partial tenotomy of the flexor digitorum longus tendon of the left hind limb, which was treated with a solution containing either 0.5 µg MALP-2 or vehicle (control). Repetitive gait analyses were performed prior to the surgical intervention as well as postoperatively on days 1, 3, 7, 14 and 36. The structural stability of the tendons was biomechanically tested on day 7 and 36. In addition, Western blot analyses were performed on isolated tendons that were treated in vitro with MALP-2 or vehicle. In both groups, partial tenotomy resulted in a pathological gait pattern during the initial postoperative phase. On day 7, the gait pattern normalized in vehicle-treated animals, but not in MALP-2-treated mice. Moreover, the tendons of MALP-2-treated mice exhibited a significantly reduced biomechanical stiffness after 7 and 36 days when compared to controls. Western blot analyses revealed a significantly higher expression of heme oxygenase (HO)-1 and lower expression of cyclin D in MALP-2-treated tendons. These findings indicate that MALP-2 delays the healing of injured tendons most likely due to increased intracellular stress and suppressed cell proliferation in this naturally bradytrophic tissue. Hence, the application of MALP-2 cannot be recommended for the treatment of tendon injuries.

An algebraic approach to physical fields.

According to the algebraic approach to spacetime, a thoroughgoing dynamicism, physical fields exist without an underlying manifold. This view is usually implemented by postulating an algebraic structure (e.g., commutative ring) of scalar-valued functions, which can be interpreted as representing a scalar field, and deriving other structures from it. In this work, we point out that this leads to the unjustified primacy of an undetermined scalar field. Instead, we propose to consider algebraic structures in which all (and only) physical fields are primitive. We explain how the theory of natural operations in differential geometry-the modern formalism behind classifying diffeomorphism-invariant constructions-can be used to obtain concrete implementations of this idea for any given collection of fields. For concrete examples, we illustrate how our approach applies to a number of particular physical fields, including electrodynamics coupled to a Weyl spinor.

[Use of surgical simulators in further education-A nationwide analysis in Germany]. / Einsatz chirurgischer Simulatoren in der Weiterbildung ­ eine deutschlandweite Analyse.

BACKGROUND: In addition to learning theoretical knowledge, the medical specialist training in surgery necessitates the acquisition of practical surgical competences. Simulation-based teaching concepts represent an alternative to education and advanced training on patients. The aim of this study was to analyze the distribution and implementation of surgical simulators in German hospitals. METHODS: The data analysis was carried out based on an individual on-line questionnaire with a total of 19 standardized questions. This was sent to the senior surgeons in hospitals and clinics via the email distributors of specialist societies for surgery in Germany. RESULTS: A total of 267 complete datasets were analyzed (response rate 12%). Of the participants 84% reported that they were active in a teaching hospital. At the time of the investigation 143 surgical simulators were in use at 35% of the hospitals and clinics included in the evaluation. There were clear regional differences between the individual federal states. Of the participants, 21.1% did not have a simulator at the hospital but the acquisition of one was planned. Simulation training was most frequently used by students (41.1%) and physicians during further education (32.5%). Simulators were not integrated into advanced surgical training in 81.8%. Of the participating hospitals, 94% showed an interest in integration into surgical specialist training in the future. CONCLUSION: The results of this survey confirmed the special importance of simulation-based training for surgical education in German hospitals; however, at the same time there were clear deficits in information concerning user behavior and a deficiency in the perceived integration of simulation training in advanced training for surgery.

A novel press-fit minimally-invasive symphysiodesis technique.

OBJECTIVE: Instability of the pubic symphysis often results in a poor outcome and reduced mobility of the patient. In some cases, an arthrodesis of the pubic symphysis is required. Until today, there is no data published how many of these procedures are performed annually and there is also no data about the outcome after this extensive surgery. METHODS: We developed a novel surgical technique to address the arthrodesis of the pubic symphysis in a minimally invasive approach. Therefore, we used for this purpose modified instruments and performed the transplantation of a cylindrical bone substitute into the pubic symphysis, without an extensive approach or dissecting the anterior or posterior symphyseal ligaments. RESULTS: Using this novel technique, a minimally invasive symphysiodesis was achieved in radiological findings, after the procedure. CONCLUSION: Thus, this actually minimally invasive surgical technique seems to be a promising advancement for the arthrodesis of the pubic symphysis.

Flexor tendon grafts for pulley reconstruction - Morphological aspects.

BACKGROUND: Pulleys are crucial to convert flexor tendon excursion into angular motion at the metacarpophalangeal and interphalangeal joints. Loss of pulley function can lead to significant impairment of hand function and may require surgical reconstruction. This reconstruction can be achieved using different flexor tendons grafts, such as the intrasynovial flexor digitorum superficialis (FDS) or the extrasynovial palmaris longus (PL). However, there is limited knowledge on the micromorphology of human pulleys and the suitability of flexor tendon grafts for their reconstruction remains elusive. METHODS: In the present cadaver study A2 and A4 pulleys were compared with FDS and PL tendons by means of scanning electron microscopy (SEM), histology and immunohistochemistry. Surface morphology, core structure and vascularization of the specimens were analyzed. RESULTS: SEM imaging of the gliding surfaces revealed morphological differences between tendons and pulleys. Moreover, the core structure of FDS samples was characterized by bundles of individual collagen fibrils whereas PL tendons exhibited a less hierarchical microstructure. In contrast, pulleys consisted of lamellar sheets of densely packed collagen fibrils. Finally, immunohistochemical analyses revealed that the flexor tendons and pulleys contain similar numbers of CD31+ microvessels, indicating a comparable tissue vascularization. CONCLUSION: This study provides novel SEM and immunohistochemical insights into the micromorphology of human pulleys and flexor tendon grafts. Intrasynovial flexor tendons may be particularly suitable for pulley reconstruction and preserving the paratenon may be crucial for graft revascularization.

A novel internal fixation method for open book injuries of the pubic symphysis- A biomechanical analysis.

BACKGROUND: Pelvic fractures in adults are common injuries and account for up to 3.64% of all fractures. Usually, the treatment of open book injuries (Types B1.1 and B1.2 AO-Classification) is open reduction and plate stabilization using dynamic compression plates, with or without interlocking screws. These implants seem to enhance the outcome of such injuries, but also variety of complications occurs. To reduce complications and achieve appropriate reduction and stabilization, this study compared established stabilization techniques to a novel minimally invasive internal fixation method using an internal fixator system that is already being utilized for spinal fractures. METHODS: This study was performed on 32 composite pelvises in a bilateral stance biomechanical model. The pelvises were variously stabilized with an internal fixator, a 4.5 mm dynamic compression plate and a 3.5 mm symphyseal locking dynamic compression plate. The contact area and loading forces were assessed by a sensor film inside the symphyseal gap. FINDINGS: This study showed significantly greater reduction and loading capabilities of the internal fixator compared to the other implants (p < 0.05). There was also significantly greater contact area with the use of an internal fixator compared to the other implants (p < 0.05). The 3.5 mm interlocking plate showed significantly greater contact area compared to the 4.5 mm plate (p < 0.05). INTERPRETATION: The internal fixator that is already proven in spinal surgery is biomechanically superior to conventional implants used in pelvic surgery. The contact area analysis furthermore showed a more physiological loading pattern, which can improve ligamentous healing in a clinical context.

Evidence in surgical training - a review.

The first residency programs for surgical training were introduced in Germany in the late 1880s and adopted in 1889 by William Halsted in the United States [Cameron JL. William Stewart Halsted. Our surgical heritage. Ann Surg 1997;225:445-58.]. Since then, surgical education has evolved from a sheer volume of exposure to structured curricula, and at the moment, due to work time restrictions, surgical education is discussed on an international level. The reported effect of limited working hours on operative case volume has been variable [McKendy KM, Watanabe Y, Lee L, Bilgic E, Enani G, Feldman LS, et al. Perioperative feedback in surgical training: a systematic review. Am J Surg 2017;214:117-26.]. Experienced surgeons fear that residents do not have sufficient exposure to standard procedures. This may reduce the residents' responsibility for the treatment of the patient and even lead to a reduced autonomy at the end of the residency. Surgical education does not only require learning the technical skills but also human factors as well as interdisciplinary and interprofessional handling. When analyzing international surgical curricula, major differences even between countries of the European Union with more or less strict curricula can be found. Thus far, there is no study that analyzes the educational program of different countries, so there is no evidence which educational system is superior. There is also little evidence to distinguish the good from the average surgeon or the junior surgeons' progress during his residency training. Although some evaluation tools are already available, the lack of resources of most teaching hospitals often results in not using these tools as long it is not mandatory by a governmental program. Because of decreased working hours, increasing hospital costs, and increasing jurisdictional restrictions, teaching hospitals and teachers will have to change their sentiments and focus on their way of surgical education before governmental regulations will emerge leading to more regulation in surgical education. Some learning tools such as simulation, electronic learning, augmented reality, or virtual reality for a timely, sufficient and up to date surgical education. However, research and evidence for existing and novel learning tools will have to increase in the next years to allow surgical education for the future generation of surgeons around the world.