Reconstitution of Arp2/3-nucleated actin assembly with proteins CP, V-1, and CARMIL.

Actin polymerization is often associated with membrane proteins containing capping-protein-interacting (CPI) motifs, such as capping protein, Arp2/3, myosin I linker (CARMIL), CD2AP, and WASHCAP/Fam21. CPI motifs bind directly to actin-capping protein (CP), and this interaction weakens the binding of CP to barbed ends of actin filaments, lessening the ability of CP to functionally cap those ends. The protein V-1/myotrophin binds to the F-actin-binding site on CP and sterically blocks CP from binding barbed ends. CPI-motif proteins also weaken the binding between V-1 and CP, which decreases the inhibitory effects of V-1, thereby freeing CP to cap barbed ends. Here, we address the question of whether CPI-motif proteins on a surface analogous to a membrane lead to net activation or inhibition of actin assembly nucleated by Arp2/3 complex. Using reconstitution with purified components, we discovered that CARMIL at the surface promotes and enhances actin assembly, countering the inhibitory effects of V-1 and thus activating CP. The reconstitution involves the presence of an Arp2/3 activator on the surface, along with Arp2/3 complex, V-1, CP, profilin, and actin monomers in solution, recreating key features of cell physiology.

Cardiopulmonary resuscitation employing only abdominal compressions in infants after cardiac surgery: A secondary sub-analysis of the ICU-RESUS study.

Importance: Patients with underlying cardiac disease form a considerable proportion of pediatric patients who experience in-hospital cardiac arrest. In pediatric patients after cardiac surgery, CPR with abdominal compressions alone (AC-CPR) may provide an alternative to standard chest compression CPR (S-CPR) with additional procedural and physiologic advantages. Objective: Quantitatively describe hemodynamics during cardiopulmonary resuscitation (CPR) and outcomes of infants who received only abdominal compressions (AC-CPR). Design: This is a sub-group analysis of the prospective, observational cohort from the ICU-RESUS trial NCT028374497. Setting & Patients: A single site quaternary care pediatric cardiothoracic intensive care unit enrolled in the ICU-RESUS trial. Patients less than 1 year of age with congenital heart disease who required compressions during cardiac arrest. Interventions: Use of AC-CPR during cardiac arrest resuscitation. Measurements and Main Results: Invasive arterial line waveforms during CPR were analyzed for 11 patients (10 surgical cardiac and 1 medical cardiac). Median weight was 3.3 kg [IQR 3.0, 4.0]; and median duration of CPR was 5.0 [3.0, 20.0] minutes. Systolic (median 57 [IQR 48, 65] mmHg) and diastolic (median 32 [IQR 24, 43] mmHg) blood pressures were achieved with a median rate of 114 [IQR 100, 124] compressions per minute. Return of spontaneous circulation was obtained in 9 of 11 (82%) patients; 2 patients (18%) were cannulated for extracorporeal cardiopulmonary resuscitation (ECPR) and 6 (55%) survived to hospital discharge with favorable neurologic outcome. Conclusions: AC-CPR may offer an alternative method to maintain perfusion for infants who experience cardiac arrest. This may have particular benefit in pediatric patients after cardiac surgery for whom external chest compressions may be harmful due to anatomic and physiologic considerations.

Reconstitution of Arp2/3-Nucleated Actin Assembly with CP, V-1 and CARMIL.

Actin polymerization is often associated with membrane proteins containing capping-protein-interacting (CPI) motifs, such as CARMIL, CD2AP, and WASHCAP/Fam21. CPI motifs bind directly to actin capping protein (CP), and this interaction weakens the binding of CP to barbed ends of actin filaments, lessening the ability of CP to functionally cap those ends. The protein V-1 / myotrophin binds to the F-actin binding site on CP and sterically blocks CP from binding barbed ends. CPI-motif proteins also weaken the binding between V-1 and CP, which decreases the inhibitory effects of V-1, thereby freeing CP to cap barbed ends. Here, we address the question of whether CPI-motif proteins on a surface analogous to a membrane lead to net activation or inhibition of actin assembly nucleated by Arp2/3 complex. Using reconstitution with purified components, we discovered that CARMIL at the surface promotes and enhances actin assembly, countering the inhibitory effects of V-1 and thus activating CP. The reconstitution involves the presence of an Arp2/3 activator on the surface, along with Arp2/3 complex, V-1, CP, profilin and actin monomers in solution, recreating key features of cell physiology.

Methodological considerations for behavioral studies relying on response time outcomes through online crowdsourcing platforms.

This perspective paper explores challenges associated with online crowdsourced data collection, particularly focusing on longitudinal tasks with time-sensitive outcomes like response latencies. Based on our research, we identify two significant sources of bias: technical shortcomings such as low, variable frame rates, and human factors, contributing to high attrition rates. We explored potential solutions to these problems, such as enforcing hardware acceleration and defining study-specific frame rate thresholds, as well as pre-screening participants and monitoring hardware performance and task engagement over each experimental session. With this discussion, we intend to provide recommendations on how to improve the quality and reliability of data collected via online crowdsourced platforms and emphasize the need for researchers to be cognizant of potential pitfalls in online research.

Surgical Considerations in Adult Congenital Heart Disease Heart Failure.

Surgical intervention is often used in the management of heart failure in patients with adult congenital heart disease. This review addresses anatomic variations and complications due to prior surgical interventions, including sternal reentry, collateral vessels, and the neo-aortic root after the Damus-Kaye-Stansel procedure. Surgical considerations for systemic atrioventricular valvular surgery, Fontan revision, and advanced heart failure therapies including ventricular assist devices, heart transplant, and combined heart-liver transplant are discussed, with a focus on unique patient populations including those with systemic right ventricles and those with Fontan circulation.

Negative pressure therapy for ECMO cannula stabilization.

Cannula stabilization for extracorporeal membrane oxygenation (ECMO) is important for patient mobilization and rehabilitation. Limitations to mobilization on ECMO include staff discomfort and cannula instability. We utilized the technique of negative pressure therapy for ECMO cannula stabilization to improve mobilization. Negative pressure therapy for ECMO cannula stabilization can be utilized safely for a variety of cannulation sites in any patient age from newborns to adults. This wound management strategy may facilitate patient mobilization and rehabilitation therapies in addition to extending cannula site duration.

Biophysical Mechanism of Allosteric Regulation of Actin Capping Protein.

Actin capping protein (CP) can be regulated by steric and allosteric mechanisms. The molecular mechanism of the allosteric regulation at a biophysical level includes linkage between the binding sites for three ligands: F-actin, Capping-Protein-Interacting (CPI) motifs, and V-1/myotrophin, based on biochemical functional studies and solvent accessibility experiments. Here, we investigated the mechanism of allosteric regulation at the atomic level using single-molecule Förster resonance energy transfer (FRET) and molecular dynamics (MD) to assess the conformational and structural dynamics of CP in response to linked-binding site ligands. In the absence of ligand, both single-molecule FRET and MD revealed two distinct conformations of CP in solution; previous crystallographic studies revealed only one. Interaction with CPI-motif peptides induced conformations within CP that bring the cap and stalk closer, while interaction with V-1 moves them away from one another. Comparing CPI-motif peptides from different proteins, we identified variations in CP conformations and dynamics that are specific to each CPI motif. MD simulations for CP alone and in complex with a CPI motif and V-1 reveal atomistic details of the conformational changes. Analysis of the interaction of CP with wild-type (wt) and chimeric CPI-motif peptides using single-molecule FRET, isothermal calorimetry (ITC) and MD simulation indicated that conformational and affinity differences are intrinsic to the C-terminal portion of the CPI motif. We conclude that allosteric regulation of CP involves changes in conformation that disseminate across the protein to link distinct binding-site functions. Our results provide novel insights into the biophysical mechanism of the allosteric regulation of CP.

Experience With the Crescent• Right Atrial Jugular Dual Lumen Catheter for Pediatric Venovenous Extracorporeal Membrane Oxygenation: A Case Series.

The Crescent dual lumen right atrial (RA) cannula has recently been introduced for the support of pediatric patients in need of venovenous extracorporeal membrane oxygenation (VV ECMO) support. We present the first pediatric case series illustrating utility of the Crescent RA cannula in the pediatric patient population at a single institution over a 10 month period. From December 2021 to August 2022, six pediatric patients were adequately supported on seven VV ECMO runs at our institution with the Crescent RA cannula. ECMO cannulation, circuit design, anticoagulation management, ECMO circuit pressures, flow rates, and recirculation were similar to our standard of care for VV ECMO. The Crescent RA cannula can be used safely and effectively to provide adequate support for pediatric patients requiring VV ECMO.

Biophysical Mechanism of Allosteric Regulation of Actin Capping Protein.

Actin capping protein (CP) can be regulated by steric and allosteric mechanisms. The molecular mechanism of the allosteric regulation at a biophysical level includes linkage between the binding sites for three ligands: F-actin, Capping-Protein-Interacting (CPI) motifs, and V-1/myotrophin, based on biochemical functional studies and solvent accessibility experiments. Here, we investigated the mechanism of allosteric regulation at the atomic level using single-molecule Förster resonance energy transfer (FRET) and molecular dynamics (MD) to assess the conformational and structural dynamics of CP in response to linked-binding site ligands. In the absence of ligand, both single-molecule FRET and MD revealed two distinct conformations of CP in solution; previous crystallographic studies revealed only one. CPI-motif peptide association induced conformational changes within CP that propagate in one direction, while V-1 association induced conformational changes in the opposite direction. Comparing CPI-motif peptides from different proteins, we identified variations in CP conformations and dynamics that are specific to each CPI motif. MD simulations for CP alone and in complex with a CPI motif and V-1 reveal atomistic details of the conformational changes. Analysis of the interaction of CP with wildtype (wt) and chimeric CPI-motif peptides using single-molecule FRET, isothermal calorimetry (ITC) and MD simulation indicated that conformational and affinity differences are intrinsic to the C-terminal portion of the CPI-motif. We conclude that allosteric regulation of CP involves changes in conformation that disseminate across the protein to link distinct binding-site functions. Our results provide novel insights into the biophysical mechanism of the allosteric regulation of CP.

Preemptive stenting of the left pulmonary artery during comprehensive stage 2 procedure does not influence Fontan candidacy.

Objective: Pulmonary artery reconstruction during comprehensive stage 2 (CS2) procedure can be challenging. Since 2017, we have employed preemptive left pulmonary artery (LPA) stenting. We hypothesized that LPA stenting promotes adequate growth and without compromising Fontan candidacy. Herewith, we report our midterm results. Methods: From 2002 to 2020, 159 patients underwent CS2. Patients were divided as follows: no stent (n = 122; Group 1) and perioperative LPA stent (n = 37; Group 2). Group 2 was subdivided according to unplanned stent (n = 17; Group 2a) or preemptive stent (n = 20; Group 2b). Relevant perioperative data was reviewed. Nonparametric statistics were utilized. Results: Median age and weight at surgery and hospital length of stay after CS2 did not differ between groups. Median cardiopulmonary bypass and crossclamp times were significantly greater in Group 1 (265 vs 243 minutes [P = .021] and 46 vs 26 minutes [P = .008]). In-hospital mortality was similar between Groups 1 and 2 (9.0% vs 18.9%, respectively [P = .1348]). Group 2b demonstrated a superior survival compared to Group 2a (P = .0335) but not Group 1 (P > .9999). Preemptive stenting significantly increased median hilar LPA diameter at CS2 exit angiogram compared with no stenting (P < .0001). Groups 2a and 2b significantly increased the pre-Fontan diameter of the hilar LPA when compared with Group 1 (6.1 and 6.8 vs 5.7 mm, respectively [P < .0001]). A further 120 patients underwent Fontan operation (75%). Median follow-up for Groups 1 and 2 were 7.4 and 3.0 years, respectively. Conclusions: Perioperative LPA stenting during CS2 does not adversely affect pulmonary growth. Preemptive stenting seems advantageous for LPA growth in preparation for Fontan completion.

Surgical outcomes of infective endocarditis in pediatrics: Moving the needle to a contemporary, multidisciplinary approach.

BACKGROUND: Infective endocarditis (IE) is an uncommon disease in children that, when present, is accompanied by significant morbidity and mortality. The presence of congenital heart disease often complicates management. The aim of the present study is to describe the characteristics and outcomes of children undergoing surgery for IE. METHODS: A retrospective chart review from 2004 to 2020 was conducted to identify consecutive patients younger than age 20 years with IE undergoing surgery. RESULTS: A total of 94 patients with IE were identified, of whom 47 underwent surgery at a median age of 16.7 years. Thirty-one patients (65.95%) had congenital heart disease. Vegetation and embolic phenomena occurred in 41 and 29 patients (87.23% and 61.7%), respectively, with the brain as most common location (57.1%). Native valve involvement had a greater tendency to embolize (P < .001). Staphylococcus spp was the most common organism (49%). The mitral valve was the most affected (31.9%). Seven (14.9%) patients had multivalvar involvement and valve replacement was the most common procedure performed (37 patients; 78.7%). There were 3 operative deaths (6.4%). Median length of hospital stay was 21 days. Risk factors for prolonged hospital stay were time to surgery in days (P < .001) and native valvar involvement (P = .05). Five patients (10.6%) had postoperative recurrent IE. Survival at 1 and 5 years was 93.6% and 89.4%, respectively. CONCLUSIONS: Children with IE can undergo surgery with acceptable results. The morbidity, but not mortality, is driven by embolic complications. Staphylococcus spp and native valve involvement are significant risk factors. VIDEO ABSTRACT.

Quality Report: Postoperative Guideline Implementation Reduces Length of Stay after Fontan Procedure.

Introduction: Patients following the Fontan procedure have a physiology that results in prolonged pleural effusion, often delaying hospital discharge. The hospital length of stay (LOS) of patients following the Fontan procedure at our institution was significantly longer than the Society of Thoracic Surgery benchmark. This quality improvement project aimed to decrease hospital LOS in patients following the Fontan procedure from a baseline of 23 days to 7 days by January 1, 2021, and sustain indefinitely. Methods: We implemented standardized postoperative clinical practice guidelines in April 2020. We designed guidelines using previously published protocols. Key features included an ambulatory PleurX drain (BD, Franklin Lakes, N.J.), diuresis with fluid restriction, and pulmonary vasodilation with supplemental oxygen and sildenafil. All patients were discharged from the hospital with a PleurX drain in place. We compared clinical outcome variables before and after guideline implementation. As a balancing measure, we tracked 30-day readmissions. Results: One hundred seven patients underwent the Fontan procedure before guideline implementation from January 2015 to January 2020, with an average hospital LOS of 23 days. Postguideline implementation, 35 patients underwent the Fontan procedure from April 2020 to July 2022, with an average hospital LOS of 8 days in 2020, which further improved to an average hospital LOS of 7 days. There was no change in 30-day readmission after guideline implementation (24% pre versus 23% post; P = 0.86). Conclusion: Implementing clinical practice guidelines for patients following the Fontan procedure led to an over 50% reduction in hospital LOS without increasing 30-day readmission.

Methylprednisolone for Heart Surgery in Infants - A Randomized, Controlled Trial.

BACKGROUND: Although perioperative prophylactic glucocorticoids have been used for decades, whether they improve outcomes in infants after heart surgery with cardiopulmonary bypass is unknown. METHODS: We conducted a multicenter, prospective, randomized, placebo-controlled, registry-based trial involving infants (<1 year of age) undergoing heart surgery with cardiopulmonary bypass at 24 sites participating in the Society of Thoracic Surgeons Congenital Heart Surgery Database. Registry data were used in the evaluation of outcomes. The infants were randomly assigned to receive prophylactic methylprednisolone (30 mg per kilogram of body weight) or placebo, which was administered into the cardiopulmonary-bypass pump-priming fluid. The primary end point was a ranked composite of death, heart transplantation, or any of 13 major complications. Patients without any of these events were assigned a ranked outcome based on postoperative length of stay. In the primary analysis, the ranked outcomes were compared between the trial groups with the use of odds ratios adjusted for prespecified risk factors. Secondary analyses included an unadjusted odds ratio, a win ratio, and safety outcomes. RESULTS: A total of 1263 infants underwent randomization, of whom 1200 received either methylprednisolone (599 infants) or placebo (601 infants). The likelihood of a worse outcome did not differ significantly between the methylprednisolone group and the placebo group (adjusted odds ratio, 0.86; 95% confidence interval [CI], 0.71 to 1.05; P = 0.14). Secondary analyses (unadjusted for risk factors) showed an odds ratio for a worse outcome of 0.82 (95% CI, 0.67 to 1.00) and a win ratio of 1.15 (95% CI, 1.00 to 1.32) in the methylprednisolone group as compared with the placebo group, findings suggestive of a benefit with methylprednisolone; however, patients in the methylprednisolone group were more likely than those in the placebo group to receive postoperative insulin for hyperglycemia (19.0% vs. 6.7%, P<0.001). CONCLUSIONS: Among infants undergoing surgery with cardiopulmonary bypass, prophylactic use of methylprednisolone did not significantly reduce the likelihood of a worse outcome in an adjusted analysis and was associated with postoperative development of hyperglycemia warranting insulin in a higher percentage of infants than placebo. (Funded by the National Center for Advancing Translational Sciences and others; STRESS ClinicalTrials.gov number, NCT03229538.).

Actin capping protein regulates postsynaptic spine development through CPI-motif interactions.

Dendritic spines are small actin-rich protrusions essential for the formation of functional circuits in the mammalian brain. During development, spines begin as dynamic filopodia-like protrusions that are then replaced by relatively stable spines containing an expanded head. Remodeling of the actin cytoskeleton plays a key role in the formation and modification of spine morphology, however many of the underlying regulatory mechanisms remain unclear. Capping protein (CP) is a major actin regulating protein that caps the barbed ends of actin filaments, and promotes the formation of dense branched actin networks. Knockdown of CP impairs the formation of mature spines, leading to an increase in the number of filopodia-like protrusions and defects in synaptic transmission. Here, we show that CP promotes the stabilization of dendritic protrusions, leading to the formation of stable mature spines. However, the localization and function of CP in dendritic spines requires interactions with proteins containing a capping protein interaction (CPI) motif. We found that the CPI motif-containing protein Twinfilin-1 (Twf1) also localizes to spines where it plays a role in CP spine enrichment. The knockdown of Twf1 leads to an increase in the density of filopodia-like protrusions and a decrease in the stability of dendritic protrusions, similar to CP knockdown. Finally, we show that CP directly interacts with Shank and regulates its spine accumulation. These results suggest that spatiotemporal regulation of CP in spines not only controls the actin dynamics underlying the formation of stable postsynaptic spine structures, but also plays an important role in the assembly of the postsynaptic apparatus underlying synaptic function.

Incidence of and Risk Factors for Aortic Arch Interventions After the Comprehensive Stage II Procedure for Hypoplastic Left Heart Syndrome.

Minimal data exist about the incidence and risk factors for arch intervention after comprehensive stage II (CSII). Goal of this study was to document incidence of arch interventions after CSII and determine if any differences existed between those who underwent an arch intervention (aiCSII) versus those did not have an intervention. Single-center retrospective chart review of all hypoplastic left heart syndrome patients who underwent a CSII between 6/1/2005 and 2/1/2020 was performed. Univariate analysis was conducted in addition to principal components analysis (PCA). One hundred patients were evaluated. Sixteen patients underwent 24 arch interventions. Age at initial arch reintervention was 1.3 ± 1.2 years (median 1.0 years, range 0.5-2.2 years). Univariate analysis showed that the aiCSII group were more likely to be female, to have had a retrograde arch intervention post-hybrid procedure, and to be younger at time of CSII. On echocardiograms, aiCSII group had significantly higher pre-CSII patent ductus arteriosus velocities, arch velocities on their 1st post-operative and discharge study post-CSII, and arch velocities pre-Fontan. Gradients were higher in the aiCSII via pre-Fontan catheterization. With PCA, echocardiographic and catheterization data remained significantly associated with aiCSII versus those who did not undergo an arch intervention (OR = 4.5 (1.9, 19.8), p = 0.008). Incidence of arch intervention post-CSII was 16%. Echocardiographic arch velocities during the CSII hospitalization were the strongest predictors for subsequent aortic arch interventions. Further studies are needed to determine any modifiable variables that may reduce the incidence of arch interventions.

Early Improvement in Clinical Status Following Ventricular Assist Device Implantation in Children: A Marker for Survival.

While clinical status at the time of ventricular assist device (VAD) implant can negatively affect outcomes, it is unclear if early improvement after implant can have a positive effect. Therefore, the objectives of this study were to describe the clinical status of pediatric patients supported with a VAD and determine the impact of clinical status on the 1-month follow-up form on survival and ability to discharge. This was a retrospective analysis of data collected prospectively by the Pediatric Interagency Registry for Mechanical Circulatory Support Registry (Pedimacs) Registry. The Pedimacs database was queried for patients implanted between September 19, 2012, and September 30, 2019, who were alive on VAD support at 1-month postimplant on either a paracorporeal pulsatile or intracorporeal continuous device. Four factors on the 1-month follow-up were the focus of this study: mechanical ventilation, supplemental nutritional support, inotropic support, and ambulatory status. These factors were regarded as present if detected between 1-week and 1-month postimplant and were analyzed to determine their impact on survival following 1 month of VAD support and on successful discharge from hospital in patients with implantable continuous-flow devices. The eligible study cohort consisted of 414 patients with a mean age of 9.6 ± 6.2 years, weight of 40.8 ± 32.3 kg with the majority being male (56.7%) and having cardiomyopathy (68%). An isolated left ventricular assist device (LVAD) was the most common implant (85.5%). At implant, 40% were ventilated, 57% required nutritional support, 93% were on inotropes, and 58% were nonambulating. On the 1-month postimplant form, there were significant improvements in all four categories (14% ventilator support, 46% nutritional support, 53% on inotropes, and 25% nonambulating). However, there was no significant early change in the percentage of patients requiring supplemental nutrition in the paracorporeal pulsatile devices (88% vs. 82%; p = 0.2). Presence of these clinical parameters in early follow-up postimplant had a significant negative impact on survival and on the ability of patients with continuous-flow devices to be discharged. Presence of four specific clinical parameters early after VAD placement is associated with worse overall survival and an inability to discharge patients on VAD support. Ongoing work is needed for optimization of patients before implant and aggressive rehabilitation after implant to help improve long-term outcomes.

Survival of Toddler with Aortoesophageal Fistula after Button Battery Ingestion.

Button batteries (BBs) are found in many households and are a source of esophageal foreign body in the pediatric population. Upon ingestion, significant caustic injury can occur within 2 hours leading to tissue damage and severe, potentially fatal sequelae. Aortoesophageal fistula (AEF) is a rare complication that nearly always results in mortality. We report a rare case of a toddler who developed an AEF after BB ingestion and survived following staged aortic repair. There should be a high index of suspicion for this complication with the history of BB ingestion and presence of hematemesis, hemoptysis, or melena.

Echocardiographic changes in patients with a cylinder mitral valve replacement: Preliminary analysis.

AIMS: Cylinder mitral valve construct (cMVC) is new technique for replacing the mitral valve compared to more traditional mitral valve replacement (MVR) procedures. Goal of this study was to describe echocardiographic changes over time in patients undergoing a cMVC. Secondary goal was to compare echocardiographic changes in patients that underwent a cMVC to a group of patients that underwent a MVR. METHODS: Retrospective analysis of patients undergoing a cMVC was performed. Demographics, discharge echocardiogram, and recent echocardiogram vales were evaluated. Age matched patients undergoing a MVR were assessed. Discharge and recent echocardiographic parameters were compared within the cMVC group. cMVC and MVR values were compared between groups. RESULTS: Five cMVC patients were studied. Age at surgery for the cMVC was 4.3 ± 4.2 years (median 2.2, .8-10.3 years). Time interval from hospital discharge echocardiogram to the most recent echocardiogram was 1.2 ± .7 years (median 1.0, .6-2.0 years). Mean mitral valve gradient significantly increased over time (3.6 ± 3.0 mm Hg vs 7.6 ± 2.9 mm Hg). There were significant improvements in left ventricular diameters, systolic sphericity index, shortening fraction, and ejection fraction over time. There were no significant differences in demographics, discharge echocardiogram values, and follow up echocardiogram values between the cMVC and MVR groups. CONCLUSION: In conclusion, echocardiographic indices of left ventricular function improved over time in patients undergoing cMVC. In addition, there were no significant differences between cMVC and MVR patients in echocardiographic values. Studies with a larger patient sample with longer follow up are needed to determine if cMVC continues to have comparable echocardiographic results to MVR.