Role of Cardiolipin Content and Acyl Chain Composition in Mitochondrial-Mimicking Monolayers

Cardiolipin (CL) is a mitochondrial phospholipid that plays a fundamental role in maintaining inner membrane (IMM) structure-function. In several metabolic diseases, CL is shown to undergo alterations in content and acyl chain composition, though there is still debate as to which alteration is the major contributor to pathology. Therefore, this study distinguished the roles of CL content and acyl chain composition on influencing IMM biophysical organization. We utilized Langmuir monolayers to study lipid packing properties of CL, from which we conducted secondary analyses on membrane properties such as elasticity, thermodynamics of mixing, and miscibility. Our data demonstrated that a decrease in CL content and extreme acyl chain remodeling impaired biophysical properties of mitochondrial-mimicking monolayers. However, modest acyl chain remodeling did not have a significant impact on these properties. These findings are crucial for the better design of CL-specific, mitochondrial-targeted therapeutics for metabolic diseases.Bachelor of Science in Public Healt

Exploring the potential of ChatGPT as a supplementary tool for providing orthopaedic information

Purpose: To investigate the potential use of large language models (LLMs) in orthopaedics by presenting queries pertinent to anterior cruciate ligament (ACL) surgery to generative pre-trained transformer (ChatGPT, specifically using its GPT-4 model of March 14th 2023). Additionally, this study aimed to evaluate the depth of the LLM’s knowledge and investigate its adaptability to different user groups. It was hypothesized that the ChatGPT would be able to adapt to different target groups due to its strong language understanding and processing capabilities. Methods: ChatGPT was presented with 20 questions and response was requested for two distinct target audiences: patients and non-orthopaedic medical doctors. Two board-certified orthopaedic sports medicine surgeons and two expert orthopaedic sports medicine surgeons independently evaluated the responses generated by ChatGPT. Mean correctness, completeness, and adaptability to the target audiences (patients and non-orthopaedic medical doctors) were determined. A three-point response scale facilitated nuanced assessment. Results: ChatGPT exhibited fair accuracy, with average correctness scores of 1.69 and 1.66 (on a scale from 0, incorrect, 1, partially correct, to 2, correct) for patients and medical doctors, respectively. Three of the 20 questions (15.0%) were deemed incorrect by any of the four orthopaedic sports medicine surgeon assessors. Moreover, overall completeness was calculated to be 1.51 and 1.64 for patients and medical doctors, respectively, while overall adaptiveness was determined to be 1.75 and 1.73 for patients and doctors, respectively. Conclusion: Overall, ChatGPT was successful in generating correct responses in approximately 65% of the cases related to ACL surgery. The findings of this study imply that LLMs offer potential as a supplementary tool for acquiring orthopaedic knowledge. However, although ChatGPT can provide guidance and effectively adapt to diverse target audiences, it cannot supplant the expertise of orthopaedic sports medicine surgeons in diagnostic and treatment planning endeavours due to its limited understanding of orthopaedic domains and its potential for erroneous responses. Level of evidence: V

Docosahexaenoic acid regulates the formation of lipid rafts: A unified view from experiment and simulation

Docosahexaenoic acid (DHA, 22:6) is an n-3 polyunsaturated fatty acid (n-3 PUFA) that influences immunological, metabolic, and neurological responses through complex mechanisms. One structural mechanism by which DHA exerts its biological effects is through its ability to modify the physical organization of plasma membrane signaling assemblies known as sphingomyelin/cholesterol (SM/chol)-enriched lipid rafts. Here we studied how DHA acyl chains esterified in the sn-2 position of phosphatidylcholine (PC) regulate the formation of raft and non-raft domains in mixtures with SM and chol on differing size scales. Coarse grained molecular dynamics simulations showed that 1-palmitoyl-2-docosahexaenoylphosphatylcholine (PDPC) enhances segregation into domains more than the monounsaturated control, 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC). Solid state 2H NMR and neutron scattering experiments provided direct experimental evidence that substituting PDPC for POPC increases the size of raft-like domains on the nanoscale. Confocal imaging of giant unilamellar vesicles with a non-raft fluorescent probe revealed that POPC had no influence on phase separation in the presence of SM/chol whereas PDPC drove strong domain segregation. Finally, monolayer compression studies suggest that PDPC increases lipid-lipid immiscibility in the presence of SM/chol compared to POPC. Collectively, the data across model systems provide compelling support for the emerging model that DHA acyl chains of PC lipids tune the size of lipid rafts, which has potential implications for signaling networks that rely on the compartmentalization of proteins within and outside of rafts

Do kids with forearm fractures need opioids at discharge from the emergency department? Analgesic prescribing and pain control following closed reduction of pediatric forearm fractures

Abstract Objective The purpose of this 2‐part study is to determine opioid prescribing patterns and opioid use and pain control after discharge following closed reduction of pediatric forearm fractures. Methods A retrospective study was conducted from December 2016 to January 2018 at a level 1 trauma center to determine opioid prescribing habits for patients 1–17 years old with forearm fractures treated with closed reduction. A prospective study was then conducted from August 2019 to October 2020 to determine pain control and opioid use after discharge. Data were collected through chart review and with telephone surveys on post‐discharge days 1, 3, and 5 to collect pain scores and opioid use. Results Fifty patients with a median age of 8 (interquartile range [IQR], 5–11) years old and 51 patients with a mean age of 9 (IQR, 6–11) years old were included in the retrospective and prospective cohorts, respectively. From the retrospective study, 21 patients (42%) were prescribed a median of 10 opioid doses (IQR, 8–12) at discharge. From the prospective study, 12 patients (24%) were discharged with a median of 8 opioid doses (IQR, 5.5–10), for a total of 98 total doses. Of those, only 7 doses (7%) were used by 3 patients. Higher weight and initial pain score were associated with increased rates of opioid prescription. Conclusions Pediatric patients who undergo closed reduction of a forearm fracture under procedural sedation in the emergency department are prescribed approximately 14 times the amount of opioid that is used. We propose that prescribing only non‐opioid analgesics to these patients would afford equivalent pain control without the side‐effects and abuse potential of opioid use at an early age

Tips and Tricks for Anatomic ACL Reconstruction With Soft-Tissue Quadriceps Tendon and Remnant Repair

Background: Quadriceps tendon (QT) autograft represents an excellent option for anterior cruciate ligament (ACL) reconstruction (ACLR), with minimal donor site morbidity and failure rates comparable with bone-patellar tendon-bone (BPTB) autograft. This video aims to provide technical tips for ACLR using all-soft-tissue QT autograft. Indications: ACLR with QT autograft is indicated in young, active ACL-injured patients who desire a return to sport. It represents a viable option in both primary and revision ACLR, as well as in skeletally immature patients. It is particularly indicated in those who kneel frequently, such as wrestlers or laborers, due to the lower incidence of postoperative anterior knee pain. Technique Description: A vertical incision is used to harvest a 10 mm × 70 mm partial thickness, all-soft-tissue QT graft. Care is taken not to violate the capsule or musculature. If necessary, graft size is modified based on preoperative magnetic resonance imaging (MRI) measurement of the notch width. The graft is then prepared with continuous loop suspensory fixation on the femoral side and draw sutures on the tibial side. The lateral femoral notch is debrided to allow for visualization of the posterior wall to enable anatomic tunnel placement. When possible, the tibial stump is preserved. The femoral tunnel is drilled via an anteromedial portal and the tibial tunnel via a tibial guide. The graft is then passed through the tibial stump into the femur. It is fixed on the tibial side with a PEEK interference screw in full extension with application of a posterior drawer. Results: Outcomes following ACLR with QT autograft are excellent, with laxity and patient-reported outcomes comparable with those following ACLR with BPTB and hamstring autograft. Furthermore, QT ACLR has been shown to result in less donor site morbidity than BPTB autograft, and lower rates of failure and infection compared with hamstring autograft. Conclusion: ACLR with QT autograft is a good option in young, active patients in both the primary and revision settings. Advantages of QT ACLR include less donor site morbidity than BPTB, and lower rates of failure compared with hamstring autograft in young patients. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication

OxPAPC stabilizes liquid-ordered domains in biomimetic membranes

Long-chain polyunsaturated fatty acids (PUFAs) are prone to nonenzymatic oxidation in response to differing environmental stressors and endogenous cellular sources. There is increasing evidence that phospholipids containing oxidized PUFA acyl chains control the inflammatory response. However, the underlying mechanism(s) of action by which oxidized PUFAs exert their functional effects remain unclear. Herein, we tested the hypothesis that replacement of 1-palmitoyl-2-arachidonyl-phosphatidylcholine (PAPC) with oxidized 1-palmitoyl-2-arachidonyl-phosphatidylcholine (oxPAPC) regulates membrane architecture. Specifically, with solid-state 2H NMR of biomimetic membranes, we investigated how substituting oxPAPC for PAPC modulates the molecular organization of liquid-ordered (Lo) domains. 2H NMR spectra for bilayer mixtures of 1,2-dipalmitoylphosphatidylcholine-d62 (an analog of DPPC deuterated throughout sn-1 and -2 chains) and cholesterol to which PAPC or oxPAPC was added revealed that replacing PAPC with oxPAPC disrupted molecular organization, indicating that oxPAPC does not mix favorably in a tightly packed Lo phase. Furthermore, unlike PAPC, adding oxPAPC stabilized 1,2-dipalmitoylphosphatidylcholine-d6-rich/cholesterol-rich Lo domains formed in mixtures with 1,2-dioleoylphosphatidylcholine while decreasing the molecular order within 1,2-dioleoylphosphatidylcholine-rich liquid-disordered regions of the membrane. Collectively, these results suggest a mechanism in which oxPAPC stabilizes Lo domains—by disordering the surrounding liquid-disordered region. Changes in the structure, and thereby functionality, of Lo domains may underly regulation of plasma membrane-based inflammatory signaling by oxPAPC

Surgeon anterior cruciate ligament reconstruction volume and rates of concomitant meniscus repair

Abstract Purpose The purpose of this study was to assess the effect of surgeon anterior cruciate ligament reconstruction (ACLR) volume on rates of ACLR with concomitant meniscus repair versus meniscectomy and subsequent meniscus surgeries. Methods A retrospective review was conducted from a database of all ACLR performed between 2015 and 2020 at a large integrated health care system. Surgeon volume was categorized as < 35 ACLR per year (low‐volume), and ≥ 35 ACLR per year (high‐volume). Rates of concomitant meniscus repair and meniscectomy were compared between low‐volume and high‐volume surgeons. Subgroup analyses compared the rates of subsequent meniscus surgery and procedure time based on surgeon volume and meniscus procedure type. Results A total of 3,911 patients undergoing ACLR were included. High‐volume surgeons performed concomitant meniscus repair statistically significantly more often than low‐volume surgeons (32.0% vs 10.7%, p < 0.001). Binary logistic regression indicated 4.15 times higher odds of meniscus repair among high‐volume surgeons. Subsequent meniscus surgery occurred more commonly following ACLR with meniscus repair among low‐volume surgeons (6.7% vs 3.4%, p = 0.047), but not high‐volume surgeons (7.0% vs 4.3%, p = 0.079). Low‐volume surgeons also had longer procedure times for concomitant meniscus repair (129.9 vs 118.3 min, p = 0.003) and meniscectomy (100.6 vs 95.9 min, p = 0.003). Conclusions Data from this study shows that surgeons with lower volume of ACLR select meniscus resection statistically significantly more often than higher‐volume surgeons. However, an abundance of literature is available to show that meniscus loss negatively affects the development of post‐traumatic osteoarthritis in patients Therefore, as demonstrated in this study by high‐volume surgeons, the meniscus should be repaired and protected whenever possible. Level of Evidence III

Proteolipid domains form in biomimetic and cardiac mitochondrial vesicles and are regulated by cardiolipin concentration but not monolyso-cardiolipin

International audienceCardiolipin (CL) is an anionic phospholipid mainly located in the inner mitochondrial membrane, where it helps regulate bioenergetics, membrane structure, and apoptosis. Localized, phase-segregated domains of CL are hypothesized to control mitochondrial inner membrane organization. However, the existence and underlying mechanisms regulating these mitochondrial domains are unclear. Here, we first isolated detergent-resistant cardiac mitochondrial membranes that have been reported to be CL-enriched domains. Experiments with different detergents yielded only nonspecific solubilization of mitochondrial phospholipids, suggesting that CL domains are not recoverable with detergents. Next, domain formation was investigated in biomimetic giant unilamellar vesicles (GUVs) and newly synthesized giant mitochondrial vesicles (GMVs) from mouse hearts. Confocal fluorescent imaging revealed that introduction of cytochrome c into membranes promotes macroscopic proteolipid domain formation associated with membrane morphological changes in both GUVs and GMVs. Domain organization was also investigated after lowering tetralinoleoyl-CL concentration and substitution with monolyso-CL, two common modifications observed in cardiac pathologies. Loss of tetralinoleoyl-CL decreased proteolipid domain formation in GUVs, because of a favorable Gibbs-free energy of lipid mixing, whereas addition of monolyso-CL had no effect on lipid mixing. Moreover, murine GMVs generated from cardiac acyl-CoA synthetase-1 knockouts, which have remodeled CL acyl chains, did not perturb proteolipid domains. Finally, lowering the tetralinoleoyl-CL content had a stronger influence on the oxidation status of cytochrome c than did incorporation of monolyso-CL. These results indicate that proteolipid domain formation in the cardiac mitochondrial inner membrane depends on tetralinoleoyl-CL concentration, driven by underlying lipid-mixing properties, but not the presence of monolyso-CL

Anatomic Flat Double-Bundle Medial Collateral Ligament Reconstruction

Several surgical techniques have been described to restore the anatomy of the medial collateral ligament, involving suture repair and reconstruction, with the latter having been associated with superior postoperative outcomes. Recently, a growing interest in anatomic isometric medial collateral ligament reconstruction (MCLR) has been developed, involving careful evaluation and finding the most appropriate location for the femoral placement of the allograft. Therefore, the purpose of this article is to describe anatomic MCLR aiming to restore medial knee stability by focusing on isometric positions within the native anatomy of the MCL