Meet the authors: Jonathan Philpott and Carrie L. Partch.

Here, Molecular Cell talks to first author Jonathan Philpott and co-corresponding author Carrie Partch about their paper, "PERIOD phosphorylation leads to feedback inhibition of CK1 activity to control circadian period" (in this issue of Molecular Cell) and their scientific journeys until now.

PERIOD phosphorylation leads to feedback inhibition of CK1 activity to control circadian period.

PERIOD (PER) and Casein Kinase 1δ regulate circadian rhythms through a phosphoswitch that controls PER stability and repressive activity in the molecular clock. CK1δ phosphorylation of the familial advanced sleep phase (FASP) serine cluster embedded within the Casein Kinase 1 binding domain (CK1BD) of mammalian PER1/2 inhibits its activity on phosphodegrons to stabilize PER and extend circadian period. Here, we show that the phosphorylated FASP region (pFASP) of PER2 directly interacts with and inhibits CK1δ. Co-crystal structures in conjunction with molecular dynamics simulations reveal how pFASP phosphoserines dock into conserved anion binding sites near the active site of CK1δ. Limiting phosphorylation of the FASP serine cluster reduces product inhibition, decreasing PER2 stability and shortening circadian period in human cells. We found that Drosophila PER also regulates CK1δ via feedback inhibition through the phosphorylated PER-Short domain, revealing a conserved mechanism by which PER phosphorylation near the CK1BD regulates CK1 kinase activity.

Transplantation Outcomes with Donor Hearts after Circulatory Death.

BACKGROUND: Data showing the efficacy and safety of the transplantation of hearts obtained from donors after circulatory death as compared with hearts obtained from donors after brain death are limited. METHODS: We conducted a randomized, noninferiority trial in which adult candidates for heart transplantation were assigned in a 3:1 ratio to receive a heart after the circulatory death of the donor or a heart from a donor after brain death if that heart was available first (circulatory-death group) or to receive only a heart that had been preserved with the use of traditional cold storage after the brain death of the donor (brain-death group). The primary end point was the risk-adjusted survival at 6 months in the as-treated circulatory-death group as compared with the brain-death group. The primary safety end point was serious adverse events associated with the heart graft at 30 days after transplantation. RESULTS: A total of 180 patients underwent transplantation; 90 (assigned to the circulatory-death group) received a heart donated after circulatory death and 90 (regardless of group assignment) received a heart donated after brain death. A total of 166 transplant recipients were included in the as-treated primary analysis (80 who received a heart from a circulatory-death donor and 86 who received a heart from a brain-death donor). The risk-adjusted 6-month survival in the as-treated population was 94% (95% confidence interval [CI], 88 to 99) among recipients of a heart from a circulatory-death donor, as compared with 90% (95% CI, 84 to 97) among recipients of a heart from a brain-death donor (least-squares mean difference, -3 percentage points; 90% CI, -10 to 3; P<0.001 for noninferiority [margin, 20 percentage points]). There were no substantial between-group differences in the mean per-patient number of serious adverse events associated with the heart graft at 30 days after transplantation. CONCLUSIONS: In this trial, risk-adjusted survival at 6 months after transplantation with a donor heart that had been reanimated and assessed with the use of extracorporeal nonischemic perfusion after circulatory death was not inferior to that after standard-care transplantation with a donor heart that had been preserved with the use of cold storage after brain death. (Funded by TransMedics; ClinicalTrials.gov number, NCT03831048.).

Biochemical mechanisms of period control within the mammalian circadian clock.

Genetically encoded biological clocks are found broadly throughout life on Earth, where they generate circadian (about a day) rhythms that synchronize physiology and behavior with the daily light/dark cycle. Although the genetic networks that give rise to circadian timing are now fairly well established, our understanding of how the proteins that constitute the molecular 'cogs' of this biological clock regulate the intrinsic timing, or period, of circadian rhythms has lagged behind. New studies probing the biochemical and structural basis of clock protein function are beginning to reveal how assemblies of dedicated clock proteins form and evolve through post-translational regulation to generate circadian rhythms. This review will highlight some recent advances providing important insight into the molecular mechanisms of period control in mammalian clocks with an emphasis on structural analyses related to CK1-dependent control of PER stability.

Massive intercostal hemorrhage after implantation of an intrapericardial ventricular assist device: A case report.

Left ventricular assist devices (LVADs) have become integral to the treatment of advanced heart failure. Surgical bleeding is a known complication of LVAD placement but is most associated with intraperitoneal pump locations. Here we describe a case of massive postoperative hemorrhage secondary to erosion of an intrapericardial LVAD into an intercostal artery with an associated rib fracture.

Secretory carcinoma in the parotid gland of a pediatric patient. A challenging diagnosis.

Secretory carcinoma is a rare, recently identified and recognized neoplasm in major salivary glands. Few cases have been described with only 16 pediatric cases in the literature. We present a case preoperatively identified as a benign parotid lesion whose management was delayed due to the COVID-19 pandemic. Post enucleation of the lesion, histology identified a secretory carcinoma. This led to further and more extensive surgery to ensure complete removal. Clinicians and histopathologists should be aware of secretory carcinoma in their differential, as a high index of suspicion is required to ensure appropriate investigations are performed to obtain the diagnosis. Early identification is important to allow timely appropriate surgery to be performed.

Surgical Ablation of Cardiac Tissue with Nanosecond Pulsed Electric Fields in Swine.

BACKGROUND: Myocardial tissue can be ablated by the application nanosecond pulsed fields (nsPEFs). The applied electric fields irreversibly permeabilize cell membranes and thereby kill myocytes while leaving the extracellular matrix intact. METHODS: In domestic pigs (n = 10), hearts were exposed via sternotomy and either ablated in vivo ([Formula: see text] = 5) or in excised, Langendorff-perfused hearts ([Formula: see text] = 5). The nsPEFs consisted of 6-36 pulses of 300 ns each, delivered at 3-6 Hz; the voltage applied varied from 10 to 12 kV. Atrial lesions were either created after inserting the bottom jaw of the bipolar clamp into the atrium via a purse string incision (2-3 lesions per atrium) or by clamping a double layer of tissue at the appendages (one lesion per atrium). Ventricular lesions were created after an incision at the apex. The transmurality of each lesion was determined at three points along the lesion using a triphenyl tetrazolium chloride (TTC) stain. RESULTS: All 27 atrial lesions were transmural. This includes 13/13 purse string lesions (39/39 sections, tissue thickness 2.5-4.5 mm) and 14/14 appendage lesions (42/42 sections, tissue thickness 8-12 mm). All 3 right ventricular lesions were transmural (9/9 sections, 18 pulses per lesion). Left ventricular lesions were always transmural for 36 pulses (3/3 lesions, 9/9 sections). All lesions have highly consistent width across the wall. There were no pulse-induced arrhythmias or other complications during the procedure. CONCLUSIONS: nsPEF ablation reliably created acute lesions in porcine atrial and ventricular myocardium. It has far better penetration and is faster than both radiofrequency ablation and cryoablation and it is free from thermal side effects.

Multicenter Registry Using Propensity Score Analysis to Compare a Novel Transport/Preservation System to Traditional Means on Postoperative Hospital Outcomes and Costs for Heart Transplant Patients.

The standard method for cardiac allograft preservation for the past 50 years has been static storage using crushed ice. A heart transplant transportation system designed to improve preservation quality with temperature monitoring, the Paragonix SherpaPak Cardiac Transport System (SCTS), was evaluated for its impact on postoperative costs relative to conventional ice storage. Observational US multicenter registry data collected during the August 2015 to November 2021 timeframe from 12 transplant hospitals were analyzed using logistic regression analysis and propensity matching to balance measured baseline covariates and to reduce selection bias. Hospital cost and outcome data post-transplant were then evaluated using various statistical methods. One hundred seventy-four (174) patients were identified resulting in 87 matches. Baseline characteristics were similar between groups. The SCTS group had a significantly lower proportion of ICU days on post-transplant mechanical circulatory support ( p < 0.0001); significantly fewer patients on extracorporeal membrane oxygenation ( p = 0.017); and significantly fewer patients experiencing severe primary graft dysfunction (PGD) ( p = 0.03). Overall hospital plus mechanical circulatory support post-transplant costs were significantly lower by $26.7K in the CTS cohort ( p = 0.03). Use of the SCTS is associated with improved clinical outcomes resulting in significantly lower overall hospital care costs.

Three-year outcomes of the postapproval study of the AtriCure Bipolar Radiofrequency Ablation of Permanent Atrial Fibrillation Trial.

OBJECTIVES: The Cox Maze IV operation is commonly performed concomitant with other cardiac operations and effectively reduces the burden of atrial fibrillation. Prospective randomized trials have reported outcomes early and at 12 months, but only single-center late durability results are available. As part of the postapproval process for a bipolar radiofrequency ablation system, we sought to determine early and midterm outcomes of patients undergoing the Cox Maze IV operation. METHODS: A prospective, multicenter, single-arm study of 363 patients (mean age, 70 years, 82% valve surgery) with nonparoxysmal atrial fibrillation (mean duration, 60 months, 94% Congestive heart failure, Hypertension, Age ≥ 75, Diabetes, Stroke, VAScular disease, Age 65-74, Sex category ≥2) undergoing concomitant Maze IV atrial fibrillation ablation at 40 sites with 70 surgeons was performed between June 2010 and October 2014. Compliance with the study lesion set was 94.5%, and 99% had left atrial appendage closure. Freedom from atrial fibrillation was determined by extended monitoring, with a 48-hour Holter monitor minimum. RESULTS: There were no device-related complications. Freedom from atrial fibrillation off antiarrhythmic medications at 1, 2, and 3 years was 66%, 65%, and 64%, respectively, and including those using antiarrhythmics was 80%, 78%, and 76%, respectively. Warfarin was used in 49%, 44%, and 40%, respectively. CONCLUSIONS: In patients with nonparoxysmal atrial fibrillation, compliance with the protocol was high, and freedom from atrial fibrillation off antiarrhythmics was high and sustained to 3 years. The safety and effectiveness of the system and Cox Maze IV procedure support the Class I guideline recommendation for concomitant atrial fibrillation ablation in patients undergoing cardiac surgery.

First Branchial Cleft Anomalies: Awareness Is Key.

Two patients presented with fluctuant areas inferior to the pinna. The first required numerous procedures and investigations before a correct diagnosis was obtained. However, with awareness of this condition, the subsequent patient was quickly identified and managed appropriately. First branchial cleft abnormalities are uncommon, however, present with common symptoms. Their location and characteristics in paediatric patients is key to having it in the differential diagnosis. Consideration of this condition by ENT surgeons is key to prevent multiple invasive and futile operations in our paediatric cohort.

Casein kinase 1 dynamics underlie substrate selectivity and the PER2 circadian phosphoswitch.

Post-translational control of PERIOD stability by Casein Kinase 1δ and ε (CK1) plays a key regulatory role in metazoan circadian rhythms. Despite the deep evolutionary conservation of CK1 in eukaryotes, little is known about its regulation and the factors that influence substrate selectivity on functionally antagonistic sites in PERIOD that directly control circadian period. Here we describe a molecular switch involving a highly conserved anion binding site in CK1. This switch controls conformation of the kinase activation loop and determines which sites on mammalian PER2 are preferentially phosphorylated, thereby directly regulating PER2 stability. Integrated experimental and computational studies shed light on the allosteric linkage between two anion binding sites that dynamically regulate kinase activity. We show that period-altering kinase mutations from humans to Drosophila differentially modulate this activation loop switch to elicit predictable changes in PER2 stability, providing a foundation to understand and further manipulate CK1 regulation of circadian rhythms.

Metastatic Hurthle Cell Carcinoma of the thyroid presenting as a Breast Lump: A Case Report.

BACKGROUND: Hurthle cell carcinoma of the thyroid is a rare form of thyroid cancer. It may present as a low grade tumour or can present as a more aggressive metastatic carcinoma. Hurthle cell carcinoma has the highest incidence of metastasis among all differentiated thyroid cancers. Most commonly haematogenous spread to lungs, bones and brain, however spread to regional lymph nodes is not uncommon. The breast is a rare site for metastasis from extramammary sources. We present the first case of breast metastasis from Hurthle cell carcinoma of the thyroid. CASE PRESENTATION: We report a 77 year old lady who had total thyroidectomy and bilateral neck dissection followed by radiotherapy for a high grade metastatic Hurthle cell carcinoma of the thyroid. Ten months later she presented to the breast clinic with left breast lump and a lump at the left axilla. Fine needle aspiration cytology of the lumps and histology after wide local excision of the breast lump confirmed metastatic Hurthle cell carcinoma. CONCLUSION: The presence of breast lumps in patients with history of extramammary cancer should raise the possibility of metastasis.

Low-energy defibrillation with nanosecond electric shocks.

AIMS: Reliable defibrillation with reduced energy deposition has long been the focus of defibrillation research. We studied the efficacy of single shocks of 300 ns duration in defibrillating rabbit hearts as well as the tissue damage they may cause. METHODS AND RESULTS: New Zealand white rabbit hearts were Langendorff-perfused and two planar electrodes were placed on either side of the heart. Shocks of 300 ns duration and 0.3-3 kV amplitude were generated with a transmission line generator. Single nanosecond shocks consistently induced waves of electrical activation, with a stimulation threshold of 0.9 kV (over 3 cm) and consistent activation for shock amplitudes of 1.2 kV or higher (9/9 successful attempts). We induced fibrillation (35 episodes in 12 hearts) and found that single shock nanosecond-defibrillation could consistently be achieved, with a defibrillation threshold of 2.3-2.4 kV (over 3 cm), and consistent success at 3 kV (11/11 successful attempts). Shocks uniformly depolarized the tissue, and the threshold energy needed for nanosecond defibrillation was almost an order of magnitude lower than the energy needed for defibrillation with a monophasic 10 ms shock delivered with the same electrode configuration. For the parameters studied here, nanosecond defibrillation caused no baseline shift of the transmembrane potential (that could be indicative of electroporative damage), no changes in action potential duration, and only a brief change of diastolic interval, for one beat after the shock was delivered. Histological staining with tetrazolium chloride and propidium iodide showed that effective defibrillation was not associated with tissue death or with detectable electroporation anywhere in the heart (six hearts). CONCLUSION: Nanosecond-defibrillation is a promising technology that may allow clinical defibrillation with profoundly reduced energies.

The Society of Thoracic Surgeons 2017 Clinical Practice Guidelines for the Surgical Treatment of Atrial Fibrillation.

EXECUTIVE SUMMARY: Surgical ablation for atrial fibrillation (AF) can be performed without additional risk of operative mortality or major morbidity, and is recommended at the time of concomitant mitral operations to restore sinus rhythm. (Class I, Level A) Surgical ablation for AF can be performed without additional operative risk of mortality or major morbidity, and is recommended at the time of concomitant isolated aortic valve replacement, isolated coronary artery bypass graft surgery, and aortic valve replacement plus coronary artery bypass graft operations to restore sinus rhythm. (Class I, Level B nonrandomized) Surgical ablation for symptomatic AF in the absence of structural heart disease that is refractory to class I/III antiarrhythmic drugs or catheter-based therapy or both is reasonable as a primary stand-alone procedure, to restore sinus rhythm. (Class IIA, Level B randomized) Surgical ablation for symptomatic persistent or longstanding persistent AF in the absence of structural heart disease is reasonable, as a stand-alone procedure using the Cox-Maze III/IV lesion set compared with pulmonary vein isolation alone. (Class IIA, Level B nonrandomized) Surgical ablation for symptomatic AF in the setting of left atrial enlargement (≥4.5 cm) or more than moderate mitral regurgitation by pulmonary vein isolation alone is not recommended. (Class III no benefit, Level C expert opinion) It is reasonable to perform left atrial appendage excision or exclusion in conjunction with surgical ablation for AF for longitudinal thromboembolic morbidity prevention. (Class IIA, Level C limited data) At the time of concomitant cardiac operations in patients with AF, it is reasonable to surgically manage the left atrial appendage for longitudinal thromboembolic morbidity prevention. (Class IIA, Level C expert opinion) In the treatment of AF, multidisciplinary heart team assessment, treatment planning, and long-term follow-up can be useful and beneficial to optimize patient outcomes. (Class I, Level C expert opinion).

Damaged right internal jugular venous catheter status after Cox Maze IV procedure.

The Cox-Maze IV (CM-IV) procedure was introduced as a modification of the Cox-Maze III by using a bipolar radiofrequency clamp to replicate the majority of the long linear cut and sew lesions. The CM-IV maintained excellent success rates with low complication, and there are no reports of device-related complication in the literature. In this article, we present a patient who underwent aortic valve replacement with a concomitant CM-IV procedure. There was difficulty removing the right internal jugular catheter during the postoperative course, with evidence of catheter fracture on chest radiograph. Upon catheter removal by Interventional Radiology, the distal segment had sustained a radiofrequency burn strike that had melted the involved segment with significant loss of catheter integrity. Of the several events that have occurred in our high volume Maze program, this resulted in changing the anesthesia protocol by using shorter catheters that will be less likely to become caught in the jaws of the bipolar clamp during the performance of the intercaval line of the CM-IV.

Ablation of Myocardial Tissue With Nanosecond Pulsed Electric Fields.

BACKGROUND: Ablation of cardiac tissue is an essential tool for the treatment of arrhythmias, particularly of atrial fibrillation, atrial flutter, and ventricular tachycardia. Current ablation technologies suffer from substantial recurrence rates, thermal side effects, and long procedure times. We demonstrate that ablation with nanosecond pulsed electric fields (nsPEFs) can potentially overcome these limitations. METHODS: We used optical mapping to monitor electrical activity in Langendorff-perfused New Zealand rabbit hearts (n = 12). We repeatedly inserted two shock electrodes, spaced 2-4 mm apart, into the ventricles (through the entire wall) and applied nanosecond pulsed electric fields (nsPEF) (5-20 kV/cm, 350 ns duration, at varying pulse numbers and frequencies) to create linear lesions of 12-18 mm length. Hearts were stained either with tetrazolium chloride (TTC) or propidium iodide (PI) to determine the extent of ablation. Some stained lesions were sectioned to obtain the three-dimensional geometry of the ablated volume. RESULTS: In all animals (12/12), we were able to create nonconducting lesions with less than 2 seconds of nsPEF application per site and minimal heating (< 0.2°C) of the tissue. The geometry of the ablated volume was smoother and more uniform throughout the wall than typical for RF ablation. The width of the lesions could be controlled up to 6 mm via the electrode spacing and the shock parameters. CONCLUSIONS: Ablation with nsPEFs is a promising alternative to radiofrequency (RF) ablation of AF. It may dramatically reduce procedure times and produce more consistent lesion thickness than RF ablation.

The ABLATE Trial: Safety and Efficacy of Cox Maze-IV Using a Bipolar Radiofrequency Ablation System.

BACKGROUND: The Cox Maze-IV procedure (CMP-IV) has replaced the Cox Maze-III procedure as the most common approach for the surgical treatment of atrial fibrillation (AF). The Food and Drug Administration-regulated AtriCure Bipolar Radiofrequency Ablation of Permanent Atrial Fibrillation (ABLATE) trial sought to demonstrate the safety and efficacy of the CMP-IV performed with the Synergy ablation system (AtriCure, Inc, Cincinnati, OH). METHODS: Fifty-five patients (aged 70.5 ± 9.3 years), 92.7% of whom had nonparoxysmal AF, underwent CMP-IV to terminate AF during a concomitant cardiac surgical procedure. Lesions were created using the AtriCure Synergy bipolar radiofrequency ablation system. All patients were seen for follow-up visits after 30 days, 3 months, and 6 months, with 24-hour Holter monitoring at 6 months. Late evaluation was performed by 48-hour Holter monitoring at an average of 21 months. RESULTS: The primary efficacy endpoint, absence of AF (30 seconds or less) at 6-month follow-up off antiarrhythmic medications (Heart Rhythm Society definition), indicated 76% (38 of 50) were AF free (95% confidence interval: 62.6% to 85.7%). The primary safety endpoint, the rate of major adverse events within 30 days, was 9.1% (5 of 55; 95% confidence interval: 3.9% to 19.6%), with 3.6% mortality (2 of 55). Secondary efficacy endpoints included being AF free with antiarrhythmic drugs (6 months, 84%; 21 months, 75%), successful pulmonary vein isolation (100%), and AF burden at 6 and 21 months. The results, together with those for the secondary safety endpoint (6-month major adverse events), demonstrated that the Synergy system performs comparably to the cut-and-sew Cox Maze-III procedure. CONCLUSIONS: The CMP-IV using the AtriCure Synergy system was safe and effective for cardiac surgical patients who had persistent and longstanding persistent AF.

Combined minimally invasive mitral valve repair and direct coronary artery bypass: a new alternative to sternotomy.

A case is presented in which significant single-vessel coronary artery disease and severe mitral valve regurgitation were successfully managed using combined minimally invasive direct coronary artery bypass and mitral valve repair. Although the management of coronary artery disease with simultaneous mitral valve disease has traditionally been approached using a median sternotomy, this combined minimally invasive approach led to a successful outcome and may serve as an alternative methodology for patients who are appropriate candidates.

Isolated internal iliac artery aneurysm resection and reconstruction: operative planning and technical considerations.

Isolated iliac artery aneurysms are rare but dangerous aneurysms associated with a high incidence of rupture (between 14 and 70%). Rupture is frequently associated with an exceedingly high mortality primarily because of the elusive nature of the presenting symptoms and the resulting major delays in treatment. Accordingly these aneurysms are best managed aggressively. Although emerging endovascular techniques show promise surgical resection and reconstruction remains the gold standard for definitive management and has withstood the test of time with excellent durable and unparalleled results. That said, from an operative perspective these aneurysms are technically demanding and remain one of the more formidable technical challenges in vascular surgery. To highlight the key elements involved in a successful repair we present a right internal iliac artery aneurysm with an associated contralateral common iliac artery occlusion, review the necessary preoperative planning and the available surgical treatment options, and detail the technical steps leading to a successful reconstruction. Careful operative planning is critical. Inadequate preoperative studies, inadequate preoperative decision making, and a poorly formulated operative strategy can lead to catastrophic results. Some of the most feared complications include pelvic venous injury with resulting massive hemorrhage and postoperative pelvic ischemia (with resulting rectal and/or spinal cord ischemia) which occurs as a result of inadequate contralateral collateral pelvic blood flow when the internal iliac artery is not reimplanted. Accordingly the preoperative workup must include a careful analysis of the adequacy of the contralateral pelvic blood flow to supply collateral flow in the event that the internal iliac is not reimplanted. In the presence of compromised contralateral internal iliac perfusion, resection and reconstruction or an alternative form of pelvic revascularization is mandatory. Excellent and unencumbered exposure is mandatory for a safe and successful repair. The retroperitoneal approach as illustrated in this case is strongly recommended. Although it is challenging excellent results can be achieved by resection of the aneurysm and reconstruction.