Lymph Node Yield is Associated with Improved Overall Survival and Increased Time to Recurrence in Node-Negative Pancreatic Ductal Adenocarcinoma Following Neoadjuvant Therapy.

OBJECTIVE: To determine if lymph node yield (LNY) is associated with improved overall survival (OS) and time to recurrence (TTR) in patients with node-negative pancreatic ductal adenocarcinoma (PDAC) treated with neoadjuvant therapy (NAT). BACKGROUND: Lymph node yield has been associated with survival in solid gastrointestinal cancers, including PDAC. METHODS: Patients with pathological T stage I-III, node-negative (N0), PDAC treated with NAT followed by pancreatoduodenectomy were identified in the Massachusetts General Hospital (MGH) pancreatectomy database and the National Cancer Database (NCDB). A cutoff point of 22 nodes was identified in the NCDB using the point with the optimal (log-rank test) split. Overall survival and TTR were evaluated using univariate and multivariable analyses. RESULTS: In the MGH cohort, 233 node-negative patients following NAT were included. A LNY ≥ 22 was associated with prolonged median OS (59 months vs. 25 months, P<0.001) and prolonged TTR (32 months vs. 14 months, P=0.019). On multivariable analysis, LNY was an independent predictor of survival (HR 0.97, 95% CI 0.95-0.99, P=0.034) per sampled node. In the NCDB, 2,029 node-negative patients following NAT were included. A LNY ≥ 22 was associated with prolonged median OS (49 months vs. 33 months, P<0.001). On multivariable analysis, LNY was an independent predictor of survival (HR 0.99, 95% CI 0.98-0.99, P<0.001) per sampled node. CONCLUSION: Lymph node yield was associated with improved oncologic outcomes in patients treated with NAT followed by pancreatoduodenectomy in two independent datasets. Responsible mechanisms by which LNY impacts the outcomes of node-negative patients following NAT warrant further exploration.

Ca2+ permeation through C-terminal cleaved, but not full-length human Pannexin1 hemichannels, mediates cell death.

Pannexin1 hemichannels (Panx1 HCs) are found in the membrane of most mammalian cells and communicate the intracellular and extracellular spaces, enabling the passive transfer of ions and small molecules. They are involved in physiological and pathophysiological conditions. During apoptosis, the C-terminal tail of Panx1 is proteolytically cleaved, but the permeability features of hemichannels and their role in cell death remain elusive. To address these topics, HeLa cells transfected with full-length human Panx1 (fl-hPanx1) or C-terminal truncated hPanx1 (Δ371hPanx1) were exposed to alkaline extracellular saline solution, increasing the activity of Panx1 HCs. The Δ371hPanx1 HC was permeable to DAPI and Etd+, but not to propidium iodide, whereas fl-hPanx1 HC was only permeable to DAPI. Furthermore, the cytoplasmic Ca2+ signal increased only in Δ371hPanx1 cells, which was supported by bioinformatics approaches. The influx of Ca2+ through Δ371hPanx1 HCs was necessary to promote cell death up to about 95% of cells, whereas the exposure to alkaline saline solution without Ca2+ failed to induce cell death, and the Ca2+ ionophore A23187 promoted more than 80% cell death even in fl-hPanx1 transfectants. Moreover, cell death was prevented with carbenoxolone or 10Panx1 in Δ371hPanx1 cells, whereas it was undetectable in HeLa Panx1-/- cells. Pretreatment with Ferrostatin-1 and necrostatin-1 did not prevent cell death, suggesting that ferroptosis or necroptosis was not involved. In comparison, zVAD-FMK, a pancaspase inhibitor, reduced death by ~60%, suggesting the involvement of apoptosis. Therefore, alkaline pH increases the activity of Δ371hPanx1HCs, leading to a critical intracellular free-Ca2+ overload that promotes cell death.

Increased Absorption of Thyroxine in a Murine Model of Hypothyroidism Using Water/CO2 Nanobubbles.

Thyroxine (T4) is a drug extensively utilized for the treatment of hypothyroidism. However, the oral absorption of T4 presents certain limitations. This research investigates the efficacy of CO2 nanobubbles in water as a potential oral carrier for T4 administration to C57BL/6 hypothyroid mice. Following 18 h of fasting, the formulation was administered to the mice, demonstrating that the combination of CO2 nanobubbles and T4 enhanced the drug's absorption in blood serum by approximately 40%. To comprehend this observation at a molecular level, we explored the interaction mechanism through which T4 engages with the CO2 nanobubbles, employing molecular simulations, semi-empirical quantum mechanics, and PMF calculations. Our simulations revealed a high affinity of T4 for the water-gas interface, driven by additive interactions between the hydrophobic region of T4 and the gas phase and electrostatic interactions of the polar groups of T4 with water at the water-gas interface. Concurrently, we observed that at the water-gas interface, the cluster of T4 formed in the water region disassembles, contributing to the drug's bioavailability. Furthermore, we examined how the gas within the nanobubbles aids in facilitating the drug's translocation through cell membranes. This research contributes to a deeper understanding of the role of CO2 nanobubbles in drug absorption and subsequent release into the bloodstream. The findings suggest that utilizing CO2 nanobubbles could enhance T4 bioavailability and cell permeability, leading to more efficient transport into cells. Additional research opens the possibility of employing lower concentrations of this class of drugs, thereby potentially reducing the associated side effects due to poor absorption.

Surveillance Endoscopy in Pediatric Esophageal Atresia: Toward an Evidence-Based Algorithm.

BACKGROUND: Individuals with esophageal atresia (EA) have lifelong increased risk for mucosal and structural pathology of the esophagus. The use of surveillance endoscopy to detect clinically meaningful pathology has been underexplored in pediatric EA. We hypothesized that surveillance endoscopy in pediatric EA has high clinical yield, even in the absence of symptoms. STUDY DESIGN: The medical records of all patients with EA who underwent at least 1 surveillance endoscopy between March 2004 and March 2023 at an international EA referral center were retrospectively reviewed. The primary outcomes were endoscopic identification of pathology leading to an escalation in medical, endoscopic, or surgical management. Logistic regression analysis examined predictors of actionable findings. Nelson-Aalen analysis estimated optimal endoscopic surveillance intervals. RESULTS: Five hundred forty-six children with EA underwent 1,473 surveillance endoscopies spanning 3,687 person-years of follow-up time. A total of 770 endoscopies (52.2%) in 394 unique patients (72.2%) had actionable pathology. Esophagitis leading to escalation of therapy was the most frequently encountered finding (484 endoscopies, 32.9%), with most esophagitis attributed to acid reflux. Barrett's esophagus (intestinal metaplasia) was identified in 7 unique patients (1.3%) at a median age of 11.3 years. No dysplastic lesions were identified. Actionable findings leading to surgical intervention were found in 55 children (30 refractory reflux and 25 tracheoesophageal fistulas). Significant predictors of actionable pathology included increasing age, long gap atresia, and hiatal hernia. Symptoms were not predictive of actionable findings, except dysphagia, which was associated with stricture. Nelson-Aalen analysis predicted occurrence of an actionable finding every 5 years. CONCLUSIONS: Surveillance endoscopy uncovers high rates of actionable pathology even in asymptomatic children with EA. Based on the findings of the current study, a pediatric EA surveillance endoscopy algorithm is proposed.

The impact of surgical-oncologic textbook outcome in patients with stage I to III pancreatic ductal adenocarcinoma: A cross-validation study of two national registries.

BACKGROUND: Using national registries, we aimed to evaluate oncologic textbook outcomes in pancreatic ductal adenocarcinoma patients. METHODS: Patients with stage I to III pancreatic ductal adenocarcinoma and surgical resection from 2010 to 2020 in the US and Germany were identified using the National Cancer Database and National Cancer Registries data. The surgical-oncologic textbook outcome was defined as complete oncologic resection with no residual tumor and ≥12 harvested lymph nodes. The composite endpoint was defined as surgical-oncologic textbook outcome and receipt of perioperative systemic and/or radiation therapy. RESULTS: In total, 33,498 patients from the National Cancer Database and 14,589 patients from the National Cancer Registries were included. In the National Cancer Database, 28,931 (86%) patients had complete oncologic resection with no residual tumor, and 11,595 (79%) in the National Cancer Registries. 8,723 (26%) patients in the National Cancer Database and 556 (4%) in the National Cancer Registries had <12 lymph nodes harvested. The National Cancer Database shows 26,135 (78%) underwent perioperative therapy and 8,333 (57%) in the National Cancer Registries. Surgical-oncologic textbook outcome was achieved in 21,198 (63%) patients in the National Cancer Database and in 11,234 (77%) patients from the National Cancer Registries. 16,967 (50%) patients in the National Cancer Database and 7,878 (54%) patients in the National Cancer Registries had composite textbook outcome. Median overall survival in patients with composite textbook outcomes was 32 months in the National Cancer Database and 27 months in the National Cancer Registries (P < .001). In contrast, those with non-textbook outcomes had a median overall survival of 23 months in the National Cancer Database and 20 months in the National Cancer Registries (P < .001). CONCLUSION: Surgical-oncologic textbook outcomes were achieved in > 50% of stage I to III pancreatic ductal adenocarcinoma for both the National Cancer Database and the National Cancer Registries. Failure to achieve textbook outcomes was associated with impaired survival across both registries.

Tumor Size Reduction and Serum Carbohydrate Antigen 19-9 Kinetics After Neoadjuvant FOLFIRINOX in Patients With Pancreatic Ductal Adenocarcinoma.

BACKGROUND: Changes in tumor size and serum carbohydrate antigen 19-9 are commonly reported markers used to assess response to neoadjuvant therapy in pancreatic ductal adenocarcinoma. We evaluated the impact of the percentual tumor size reduction and carbohydrate antigen 19-9 kinetics on resectability and response to neoadjuvant FOLFIRINOX. METHODS: This was an institutional analysis of patients with non-metastatic (upfront resectable, borderline resectable, and locally advanced) pancreatic ductal adenocarcinoma who underwent neoadjuvant FOLFIRINOX. Resectability, pathologic response, disease recurrence, and overall survival were evaluated. RESULTS: Among 193 patients who completed FOLFIRINOX, 60% underwent resection, and 91% were R0. Pathologically, complete, and near-complete responses were achieved in 4% and 40% of patients, respectively. Tumor size reduction (odds ratio 1.02 per 1%, P = .024) and normalization of carbohydrate antigen 19-9 (odds ratio 2.61, P = .035) were associated with increased odds of resectability. Concerning pathologic response, tumor size reduction (odds ratio 1.03 per 1%, P = .018) was associated with increased odds of a complete and near-complete response. Lastly, in resected patients, a postoperative increase in carbohydrate antigen 19-9 after prior normalization after neoadjuvant therapy were at an increased risk of recurrence (hazard ratio 9.58, P < .001) and worse survival (hazard ratio 10.4, P < .001) compared to patients who maintained normalization. CONCLUSION: In patients with non-metastatic pancreatic ductal adenocarcinoma who underwent neoadjuvant therapy, tumor size reduction was a significant predictor of resectability and pathologic response, including complete and near complete responses, whereas serum carbohydrate antigen 19-9 normalization predicted resectability, disease recurrence, and survival. Patients with a postoperative carbohydrate antigen 19-9 rise after prior normalization after administration of neoadjuvant therapy were at an increased risk of recurrence and worse overall survival.

Liver transplantation in Latin America: reality and challenges.

Healthcare systems in Latin America are broadly heterogeneous, but all of them are burdened by a dramatic rise in liver disease. Some challenges that these countries face include an increase in patients requiring a transplant, insufficient rates of organ donation, delayed referral, and inequitable or suboptimal access to liver transplant programs and post-transplant care. This could be improved by expanding the donor pool through the implementation of education programs for citizens and referring physicians, as well as the inclusion of extended criteria donors, living donors and split liver transplantation. Addressing these shortcomings will require national shifts aimed at improving infrastructure, increasing awareness of organ donation, training medical personnel, and providing equitable access to care for all patients.

Feasibility, Safety, and Efficacy of Aggressive Multimodal Management of Elderly Patients with Pancreatic Ductal Adenocarcinoma.

OBJECTIVE: We aimed to evaluate the safety and efficacy of NAT followed by surgical resection in patients with PDAC aged ≥75 years. SUMMARY BACKGROUND DATA: Whether administration of neoadjuvant therapy (NAT) followed by surgical resection in elderly patients with pancreatic ductal adenocarcinoma (PDAC) is safe and effective is unknown. METHODS: The present study is a three-part comparison of older (≥ 75 years) versus younger (< 75 years) patients in different settings throughout the continuum of PDAC care. The first analysis was a comparison of older versus younger consecutive patients with non-metastatic PDAC who were initiated on FOLFIRINOX. The second was a comparison of older vs. younger patients who underwent NAT followed by surgical resection, and the third and final analysis was a comparison of older patients who underwent either NAT followed by surgical resection vs. upfront surgical resection. Postoperative complications, overall survival (OS), and time to recurrence (TTR), were compared. Propensity-score matching (PSM) analysis was performed to adjust for potential confounders. RESULTS: In the first analysis, a lower proportion of older patients (n=40) were able to complete the intended neoadjuvant FOLFIRINOX (8) cycles compared to younger patients (n=214) (65.0% vs. 81.4%, P=0.021). However, older patients were just as likely to undergo surgical exploration as younger patients (77.5% vs 78.5%, P=0.89) as well as surgical resection (57.5% vs 55.6%, P=0.70). In the second analysis, PSM was conducted to compare older (n=54) vs. younger patients (n=54) who underwent NAT followed by surgical resection. There were no significant differences in postoperative complications between the matched groups. While there was a significant difference in overall survival (OS) between older and younger patients (median OS: 16.43 months vs. 30.83 months, P=0.002), importantly, there was no significant difference in time to recurrence (TTR, median: 7.65 months vs. 11.83 months, P=0.215). In the third analysis, older patients who underwent NAT followed by surgical resection (n=48) were compared with similar older patients who underwent upfront surgical resection (n=48). After PSM, there was a significant difference in OS (median OS: 15.78 months vs. 11.51 months, P=0.037) as well as TTR (median TTR: 8.81 months vs. 7.10 months, P=0.046) representing an association with improved outcomes that favored the neoadjuvant approach among older patients alone. CONCLUSIONS: This comprehensive three-part study showed that administration of NAT followed by surgical resection appears to be safe and effective among patients ≥ 75 years of age. An aggressive approach should be offered to older adults undergoing multimodal treatment of PDAC.

Sofosbuvir plus glecaprevir/pibrentasvir as salvage therapy after liver transplantation in NS5A inhibitor-experienced patients. A case series.

BACKGROUND: Treatment of chronic hepatitis C virus (HCV) infection with direct-acting antivirals achieves a sustained virologic response rate higher than 95%. However, virologic failure remains a clinical challenge, and data on retreatment are limited, especially in special populations such as liver transplant (LT) recipients. OBJECTIVES: This study evaluated the sofosbuvir plus glecaprevir-pibrentasvir (GLE/PIB) regimen in LT recipients who had failed to a nonstructural protein 5A (NS5A) inhibitor-based regimen. MATERIAL AND METHODS: Retrospective study of 111 liver transplant recipients between January 2018 and December 2020; 18 patients presented with HCV recurrent infection after LT, out of whom three had a history of at least one NS5A inhibitor-based regimen. Salvage therapy with sofosbuvir plus GLE/PIB was started for 12 weeks; baseline characteristics and outcomes were recorded. RESULTS: All three patients (100%) achieved an undetectable HCV viral load 12 weeks after treatment completion. No serious adverse events were observed. CONCLUSION: In our series, sofosbuvir plus GLE/PIB for 12 weeks is an effective and safe salvage therapy after LT in patients previously treated with NS5A inhibitors.

ANTECEDENTES: El tratamiento del virus de la hepatitis C (VHC) crónica con antivirales de acción directa logra tasas de respuesta virológica sostenida superiores a 95 %. Sin embargo, el manejo del fracaso virológico sigue siendo un desafío clínico y la evidencia sobre el retratamiento es limitada, especialmente en poblaciones como los receptores de trasplante hepático (TH). OBJETIVO: Este estudio evaluó el régimen de sofosbuvir más glecaprevir/pibrentasvir (GLE/PIB) en receptores de TH en quienes falló el régimen basado en inhibidores de la proteína no estructural 5A (NS5A). MATERIAL Y MÉTODOS: Estudio retrospectivo de 111 pacientes trasplantados entre enero de 2018 y diciembre de 2020; 18 pacientes presentaron infección recurrente por VHC posterior al TH, tres de ellos tuvieron antecedentes de al menos un régimen basado en inhibidores de NS5A. Se inició terapia de rescate con sofosbuvir más GLE/PIB durante 12 semanas posterior al TH; se registraron las características basales de los pacientes y sus desenlaces. RESULTADOS: En los tres pacientes se logró obtener una carga viral indetectable de VHC a las 12 semanas de finalizar el tratamiento. No se observaron eventos adversos graves. CONCLUSIÓN: En nuestra serie, sofosbuvir más GLE/PIB durante 12 semanas demostró ser una terapia de rescate efectiva y segura posterior al TH en pacientes previamente tratados con inhibidores de NS5A.

Sofosbuvir más glecaprevir/pibrentasvir como terapia de rescate postrasplante hepático en pacientes con exposición previa a inhibidores de NS5A. Serie de casos / Sofosbuvir plus glecaprevir/pibrentasvir as salvage therapy after liver transplantation in NS5A inhibitor-experienced patients. A case series

Resumen Antecedentes: El tratamiento de la infección crónica por el virus de la hepatitis C (VHC) con antivirales de acción directa logra tasas de respuesta virológica sostenida superiores a 95 %. Sin embargo, el manejo del fracaso virológico sigue siendo un desafío clínico y la evidencia sobre el retratamiento es limitada, especialmente en poblaciones como los receptores de trasplante hepático (TH). Objetivo: Este estudio evaluó el régimen de sofosbuvir más glecaprevir/pibrentasvir (GLE/PIB) en receptores de TH en quienes falló el régimen basado en inhibidores de la proteína no estructural 5A (NS5A). Material y métodos: Estudio retrospectivo de 111 pacientes trasplantados entre enero de 2018 y diciembre de 2020; 18 pacientes presentaron infección recurrente por VHC posterior al TH, tres de ellos tuvieron antecedentes de al menos un régimen basado en inhibidores de NS5A. Se inició terapia de rescate con sofosbuvir más GLE/PIB durante 12 semanas posterior al TH; se registraron las características basales de los pacientes y sus desenlaces. Resultados: En los tres pacientes se logró obtener una carga viral indetectable de VHC a las 12 semanas de finalizar el tratamiento. No se observaron eventos adversos graves. Conclusión: En nuestra serie, sofosbuvir más GLE/PIB durante 12 semanas demostró ser una terapia de rescate efectiva y segura posterior al TH en pacientes previamente tratados con inhibidores de NS5A.

Abstract Background: Treatment of chronic hepatitis C virus (HCV) infection with direct-acting antivirals achieves a sustained virologic response rates higher than 95%. However, virologic failure remains a clinical challenge, and data on retreatment are limited, especially in special populations such as liver transplant (LT) recipients. Objective: This study evaluated the sofosbuvir plus glecaprevir-pibrentasvir (GLE/PIB) regimen in LT recipients who had failed to a nonstructural protein 5A (NS5A) inhibitor-based regimen. Material and methods: Retrospective study of 111 liver transplant recipients between January 2018 and December 2020; 18 patients presented with HCV recurrent infection after LT, out of whom three had a history of at least one NS5A inhibitor-based regimen. Salvage therapy with sofosbuvir plus GLE/PIB was started for 12 weeks; baseline characteristics and outcomes were recorded. Results: All three patients (100%) achieved an undetectable HCV viral load 12 weeks after treatment completion. No serious adverse events were observed. Conclusion: In our series, sofosbuvir plus GLE/PIB for 12 weeks is an effective and safe salvage therapy after LT in patients previously treated with NS5A inhibitors.

Facility type is associated with improved perioperative and oncologic outcomes after minimally invasive surgery for pancreatic cancer.

BACKGROUND: This study sought to evaluate outcome differences by facility type in patients who underwent minimally invasive surgery (MIS) for pancreatic ductal adenocarcinoma (PDAC). METHODS: The National Cancer Database was used to identify patients with clinical stage I-III PDAC who underwent MIS from 2010 to 2019 in academic or community facilities. RESULTS: Of 6806 patients who fulfilled inclusion criteria; 1788 (26.3%) were treated at community facilities and 5018 (74.7%) at academic facilities. Patients treated at academic facilities were more likely to receive care at a high-volume facility (62% vs. 32%, p < 0.001), undergo a Whipple (64% vs. 61%, p < 0.001), and be clinical stage II (42% vs. 38%) and III (5.6% vs. 4.9%, p = 0.001). Treatment at academic facilities was predictive of receiving neoadjuvant therapy (OR 2.08, p < 0.001), negative margin resection (OR 0.80, p = 0.004), lower 90-day mortality (OR 0.72, p = 0.02), decreased length of stay (IRR 0.96, p < 0.001), and longer OS (HR 0.88, p = 0.002). CONCLUSION: Patients who underwent MIS for PDAC at academic facilities experienced an association with improved perioperative and oncologic outcomes than those treated in community facilities.

Identification of high-risk features in mucinous cystic neoplasms of the pancreas.

BACKGROUND: Mucinous cystic neoplasms of the pancreas are uncommon tumors that have the potential of becoming cancer. There is no consensus regarding the high-risk features of these tumors. Our study aimed to identify the preoperative demographic, clinical, or radiologic factors that can predict the presence of high-grade dysplasia or invasive carcinoma in mucinous cystic neoplasms of the pancreas. METHODS: We identified 157 patients who underwent resection and fulfilled the pathologic criteria for mucinous cystic neoplasms of the pancreas in a prospectively maintained database spanning 3 decades (1990-2020). Multivariable logistic regression was used to identify predictors of high-grade dysplasia or invasive carcinoma in mucinous cystic neoplasms of the pancreas. RESULTS: The rate of high-grade dysplasia or invasive carcinoma was 11%. Tumor size ≥4 cm (P < .001), mural nodularity (P = .04), and a serum CA 19-9 level >37 U/mL (P < .001) were associated with high-grade dysplasia or invasive carcinoma. In the multivariable analysis, tumor size ≥4 cm (odds ratio 16.9, 95% confidence interval 2.04-140, P = .009) and a CA 19-9 level >37 U/mL (odds ratio 5.68, 95% confidence interval 1.52-21.3, P = .010) were predictors of high-grade dysplasia or invasive carcinoma. There were no tumors with high-grade dysplasia or invasive carcinoma in patients with tumor size <4 cm in the absence of an elevated CA 19-9 or mural nodularity. CONCLUSION: Tumors with a size ≥4 cm and/or a high CA 19-9 level should be considered for prompt surgical resection. Conversely, tumors <4 cm with no other high-risk features have a negligible risk for high-grade dysplasia or invasive carcinoma and may benefit from nonoperative surveillance. Mural nodularity is an additional suspicious feature. These findings may contribute to future guidelines.

Immunotolerance in liver transplantation: a primer for the clinician.

The use of immunosuppressive medications for solid organ transplantation is associated with cardiovascular, metabolic, and oncologic complications. On the other hand, the development of graft rejection is associated with increased mortality and graft dysfunction. Liver transplant recipients can withdraw from immunosuppression without developing graft injury while preserving an adequate antimicrobial response - a characteristic known as immunotolerance. Immunotolerance can be spontaneously or pharmacologically achieved. Contrary to the classic dogma, clinical studies have elucidated low rates of true spontaneous immunotolerance (no serologic or histological markers of immune injury) among liver transplant recipients. However, clinical, serologic, and tissue biomarkers can aid in selecting patients in whom immunosuppression can be safely withdrawn. For those who failed an immunosuppression withdrawal trial or are at high risk of rejection, pharmacological interventions for immunotolerance induction are under development. In this review, we provide an overview of the mechanisms of immunotolerance, the clinical studies investigating predictors and biomarkers of spontaneous immunotolerance, as well as the potential pharmacological interventions for inducing it.

Humoral response to different SARS-CoV-2 vaccines in orthotopic liver transplant recipients.

BACKGROUND: The safety and efficacy data of the different types of available vaccines is still needed. The goal of the present analysis was to evaluate the humoral response to the COVID-19 vaccines in orthotopic liver transplant (OLT) recipients. METHODS: Participants were included from February to September 2021. No prioritized vaccination roll call applied for OLT patients. Controls were otherwise healthy people. Blood samples were drawn after 15 days of the complete vaccine doses. The samples were analyzed according to the manufacturer's instructions using the Liaison XL platform from DiaSorin (DiaSorin S.p.A., Italy), and SARS-COV-2 IgG II Quant (Abbott Diagnostics, IL, USA). RESULTS: A total of 187 participants (133 OLT, 54 controls, median age: 60 years, 58.8% women) were included for the analysis; 74.3% had at least one comorbidity. The serologic response in OLT patients was lower than in controls (median 549 AU/mL vs. 3450 AU/mL, respectively; p = 0.001). A positive humoral response was found in 133 OLT individuals: 89.2% with BNT162b2 (Pfizer-BioNTech), 60% ChAdOx1 nCOV-19 (Oxford-AstraZeneca), 76.9% with CoronaVac (Sinovac, Life Sciences, China), 55.6% Ad5-nCov (Cansino, Biologics), 68.2% Gam-COVID-Vac (Sputnik V) and 100% with mRNA-1273. In controls the serological response was 100%, except for Cansino (75%). In a multivariable model, personal history of COVID-19 and BNT162b2 inoculation were associated with the serologic response, while the use of prednisone (vs. other immunosuppressants) reduced this response. CONCLUSION: The serologic response to COVID-19 vaccines in OLT patients is lower than in healthy controls. The BNT162b2 vaccine was associated with a higher serologic response.

Mechanism of voltage sensing in Ca2+- and voltage-activated K+ (BK) channels.

In neurosecretion, allosteric communication between voltage sensors and Ca2+ binding in BK channels is crucially involved in damping excitatory stimuli. Nevertheless, the voltage-sensing mechanism of BK channels is still under debate. Here, based on gating current measurements, we demonstrate that two arginines in the transmembrane segment S4 (R210 and R213) function as the BK gating charges. Significantly, the energy landscape of the gating particles is electrostatically tuned by a network of salt bridges contained in the voltage sensor domain (VSD). Molecular dynamics simulations and proton transport experiments in the hyperpolarization-activated R210H mutant suggest that the electric field drops off within a narrow septum whose boundaries are defined by the gating charges. Unlike Kv channels, the charge movement in BK appears to be limited to a small displacement of the guanidinium moieties of R210 and R213, without significant movement of the S4.

Endogenous pannexin1 channels form functional intercellular cell-cell channels with characteristic voltage-dependent properties.

The occurrence of intercellular channels formed by pannexin1 has been challenged for more than a decade. Here, we provide an electrophysiological characterization of exogenous human pannexin1 (hPanx1) cell­cell channels expressed in HeLa cells knocked out for connexin45. The observed hPanx1 cell­cell channels show two phenotypes: O-state and S-state. The former displayed low transjunctional voltage (Vj) sensitivity and single-channel conductance of ∼175 pS, with a substate of ∼35 pS; the latter showed a peculiar dynamic asymmetry in Vj dependence and single-channel conductance identical to the substate conductance of the O-state. S-state hPanx1 cell­cell channels were also identified between TC620 cells, a human oligodendroglioma cell line that endogenously expresses hPanx1. In these cells, dye and electrical coupling increased with temperature and were strongly reduced after hPanx1 expression was knocked down by small interfering RNA or inhibited with Panx1 mimetic inhibitory peptide. Moreover, cell­cell coupling was augmented when hPanx1 levels were increased with a doxycycline-inducible expression system. Application of octanol, a connexin gap junction (GJ) channel inhibitor, was not sufficient to block electrical coupling between HeLa KO Cx45-hPanx1 or TC620 cell pairs. In silico studies suggest that several arginine residues inside the channel pore may be neutralized by hydrophobic interactions, allowing the passage of DAPI, consistent with dye coupling observed between TC620 cells. These findings demonstrate that endogenously expressed hPanx1 forms intercellular cell­cell channels and their unique properties resemble those described in innexin-based GJ channels. Since Panx1 is ubiquitously expressed, finding conditions to recognize Panx1 cell­cell channels in different cell types might require special attention.

Liver Transplantation in Mexico.

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The Emergence of New Catalytic Abilities in an Endoxylanase from Family GH10 by Removing an Intrinsically Disordered Region.

Endoxylanases belonging to family 10 of the glycoside hydrolases (GH10) are versatile in the use of different substrates. Thus, an understanding of the molecular mechanisms underlying substrate specificities could be very useful in the engineering of GH10 endoxylanases for biotechnological purposes. Herein, we analyzed XynA, an endoxylanase that contains a (ß/α)8-barrel domain and an intrinsically disordered region (IDR) of 29 amino acids at its amino end. Enzyme activity assays revealed that the elimination of the IDR resulted in a mutant enzyme (XynAΔ29) in which two new activities emerged: the ability to release xylose from xylan, and the ability to hydrolyze p-nitrophenyl-ß-d-xylopyranoside (pNPXyl), a substrate that wild-type enzyme cannot hydrolyze. Circular dichroism and tryptophan fluorescence quenching by acrylamide showed changes in secondary structure and increased flexibility of XynAΔ29. Molecular dynamics simulations revealed that the emergence of the pNPXyl-hydrolyzing activity correlated with a dynamic behavior not previously observed in GH10 endoxylanases: a hinge-bending motion of two symmetric regions within the (ß/α)8-barrel domain, whose hinge point is the active cleft. The hinge-bending motion is more intense in XynAΔ29 than in XynA and promotes the formation of a wider active site that allows the accommodation and hydrolysis of pNPXyl. Our results open new avenues for the study of the relationship between IDRs, dynamics and activity of endoxylanases, and other enzymes containing (ß/α)8-barrel domain.

Impact of the COVID-19 pandemic on the clinical training of last year medical students in Mexico: a cross-sectional nationwide study.

BACKGROUND: The COVID-19 pandemic has brought unprecedented changes to medical education. However, no data are available regarding the impact the pandemic may have on medical training in Mexico. The aim of our study was to evaluate and identify the medical school students' perceptions of the changes in their clinical training due to the pandemic in Mexico. METHODS: This was a cross-sectional study where a previous validated online survey was translated and adapted by medical education experts and applied to senior medical students from March to April of 2021. The 16-item questionnaire was distributed online combining dichotomous, multiple-choice, and 5-point Likert response scale questions. Descriptive and multivariate analyses were performed to compare the student's perceptions between public and private schools. RESULTS: A total of 671 responses were included in the study period. Most participants were from public schools (81%) and female (61%). Almost every respondent (94%) indicated it was necessary to obtain COVID-19 education, yet only half (54%) received such training. Students in private schools were less likely to have their clinical instruction canceled (53% vs. 77%, p = 0.001) and more likely to have access to virtual instruction (46% vs. 22%, p = 0.001) when compared to students from public schools. Four out of every five students considered their training inferior to that of previous generations, and most students (82%) would consider repeating their final year of clinical training. CONCLUSIONS: The impact of the COVID-19 on medical education in Mexico has been significant. Most final-year medical students have been affected by the cancellation of their in-person clinical instruction, for which the majority would consider repeating their final year of training. Efforts to counterbalance this lack of clinical experience with virtual or simulation instruction are needed.