Cryo-Electron Tomography of Reconstituted Biomolecular Condensates

The assembly of membraneless compartments by phase separation has recently been recognized as a mechanism for spatial and temporal organization of biomolecules within the cell. The functions of such mesoscale assemblies, termed biomolecular condensates, depend on networks of multivalent interactions between proteins, their structured and disordered domains, and commonly also include nucleic acids. Cryo-electron tomography is an ideal tool to investigate the three-dimensional architecture of such pleomorphic interaction networks at nanometer resolution and thus form inferences about function. However, preparation of suitable cryo-electron microscopy samples of condensates may be prone to protein denaturation, low retention of material on the sample carrier, and contamination associated with cryo-sample preparation and transfers. Here, we describe a series of protocols designed to obtain high-quality cryo-electron tomography data of biomolecular condensates reconstituted in vitro. These include critical screening by light microscopy, cryo-fixation by plunge freezing, sample loading into an electron microscope operated at liquid nitrogen temperature, data collection, processing of the data into three-dimensional tomograms, and their interpretation.

Successful single lung fontan operation in 2 children: case reports

We report on 2 children, aged 3 and 4 years, with single ventricle physiology who underwent Fontan operation in the presence of a single right lung successfully with good midterm outcome. Therefore, the absence of one lung is not a contraindication for a Fontan palliation in selected patients with optimal hemodynamics.

Results of Pediatric Cardiac Transplantation - Long-Term Results of a 15-Year Experience

INTRODUCTION

Heart transplantation (HTx) has increasingly become a therapeutic option for end-stage heart failure of any origin in children. Short- and mid-term results are promising. However, long-term outcome has been a matter of concern because of acute or chronic rejection and side effects of immunosuppression. We performed a retrospective study of up to 15-years of follow-up on this patient entity.

METHODS

Between 1988 and 2004, 58 HTx were performed in 55 children (cardiomyopathy (DCM) 32, congenital heart disease (CHD) 23, Re-HTx 3). Mean age was 9.1 +/- 7.2 years (4 days - 17.9 years). Twenty-nine patients had a total of 51 previous operations.

RESULTS

Operative mortality was 4/58 (6.8 %) due to primary graft failure. Late mortality was 7/54 (12.1 %) due to acute rejection (2), pneumonia (2), intracranial hemorrhage (1), suicide (1) and lymphoma (1). Mean follow-up was 5.2 +/- 4.2 years. One-, 5-, and 10-year survival was 86 %, 80 % and 80 %, respectively, and improved significantly after 1995 (92 % and 92 %; p = 0.04). Survival was comparable for DCM and CHD patients (1-year: 88 % vs. 82 %; p = 0.19; 5-years: 84 % vs. 77 %; p = 0.12). Three patients with therapy resistant rejection and assisted circulation required retransplantation and are alive. Freedom from acute rejection was 46 % with primary cyclosporine immunosuppression and 63 % with tacrolimus. Ninety-eight percent of the survivors are at home and in excellent cardiac condition.

CONCLUSION

Pediatric heart transplantation is a curative treatment for DCM and CHD with excellent clinical mid-term results. However, further follow-up is necessary to evaluate long-term side effects of immunosuppressants. Donor shortage remains a problem.

Anatomically positioned aorta ascending-descending bypass grafting via left posterolateral thoracotomy for reoperation of aortic coarctation

OBJECTIVE

Operation for aortic recoarctation and/or residual hypoplastic arch represents a surgical challenge because of surrounding scar tissue in the coarctation area, hazard of spinal cord ischemia due to aortic cross-clamping, laceration of the recurrent nerve, and the choice of the best approach. We demonstrate the first results of an anatomically guided technique via the prior left thoracotomy approach without establishment of cardiopulmonary bypass.

METHODS

Since 1989, five patients underwent anatomically positioned ascending-descending bypass grafting for treatment of recoarctation. Indication was a non-dilatable hypoplastic aortic arch segment; in two cases an additional isthmic restenosis was present. Inclusion criteria for our technique was an aorta ascending diameter large enough to allow partial clamping. Primary repair of aortic coarctation was end-to-end anastomosis in four patients and patch angioplasty in one. Mean age at primary repair was 5.5 years and at reoperation 16.1 years. Systolic pressure gradients at rest ranged from 35 to 70 mmHg; upper extremity hypertension was present in all patients. Operative technique consisted of performing a dacron or PTFE aorta ascending-descending bypass graft parallel to the aortic arch, size 18 or 20 mm in diameter, via the prior left thoracotomy.

RESULTS

There were no intraoperative complications and all patients survived. Postoperative complications were left lung atelectasis with necessity of reintubation, pericardial effusion, and transient left diaphragm elevation, each in one patient. After 7-90 months all patients are free of symptoms, have normal blood pressure (with two patients being under anti-hypertensive medication), and have no echocardiographically measurable pressure gradients.

CONCLUSIONS

Anatomically positioned aorta ascending-descending bypass grafting via the prior left posterolateral thoracotomy without cardiopulmonary bypass is a safe and efficient method for operation of complex recoarctation in patients with an acceptable size of the aorta ascendens.

Experience with an adjustable pulmonary artery banding device in two cases: initial success--midterm failure

Retraining of the left ventricle in congenitally corrected TGA or after Senning or Mustard operation is necessary when right-ventricular failure is developing and an arterial switch operation is indicated. As these hearts have little tolerance of marginal overbanding, a long-term adjustable pulmonary artery banding device would lower stress and risk of training. Although the inserted device (Osypka) allowed convenient intraoperative pressure ratio adjustment, mid-term adjustment failed due to dysfunction of the system.

Closure of atrial septal defects via limited right anterolateral thoracotomy as a minimal invasive approach in female patients

OBJECTIVE

The closure of atrial septal defects via sternotomy is a low-risk and high-benefit procedure. Limited right anterolateral thoracotomy is an alternative approach with regard to cosmetic aspects. However, it is discussed that a lateral approach is not appropriate for more complex lesions and is associated with an increased incidence of phrenic nerve damage.

METHODS AND RESULTS

The perioperative and long-term outcomes (mean follow-up time: 73.2 months) of 87 female patients, mean age 20.4 years (range: 3-56 years), operated on for all types of atrial septal defects via limited right anterolateral thoracotomy between 1982 and 1993, were analysed retrospectively. Special features of the operation technique were a limited skin incision, protection of mammary gland tissue, prevention of phrenic nerve damage, and aortic cannulation in all patients. There were no intraoperative complications. Postoperative complications occurred in 12/87 patients including one rethoracotomy for postoperative bleeding and one late pericardial tamponade due to coumadine overdose. Follow-up was assessed by a survey obtained by the patients or their parents, and their family doctors in 79 patients (90.8%) Cardiac symptoms, mostly supraventricular arrhythmias, were observed in 13.9%. Echocardiography revealed mild tricuspid valve regurgitation (one patient) and mild mitral valve incompetence (one patient with ostium primum defect); there were no residual shunts. Cosmetic results were considered good and excellent in 87.3% and satisfactory in 8.9%. Three patients (3.8%) complained of a broad scar. Anaesthetic areas and optional scar pain were quite frequent (16.5%), whereas restriction of shoulder movement, breast asymmetry and scoliosis were rare. In summary, only one patient, suffering from intercostal neuralgia, would prefer sternotomy.

CONCLUSION

Limited right anterolateral thoracotomy has a high cosmetic acceptance and was proven to be safe and effective for closure of any kind of atrial septal defects. Therefore, it is recommended as standard approach for atrial septal defects especially in female patients. reserved.

Pulmonary artery stenosis after systemic-to-pulmonary shunt operations

OBJECTIVE

Systemic-to-pulmonary shunt operations are still required for palliation of certain congenital heart defects. The aim of this study was to analyze the incidence and etiology of the development of pulmonary artery stenosis after these procedures.

METHODS AND RESULTS

Pre- and post-operative angiograms of 59 patients who underwent 54 peripheral and 12 central shunt operations were analyzed retrospectively. Patients without prior cardiovascular interventions (group I, n = 47) were differentiated from patients with prior interventions (group II, n = 12). In group I, all peripheral shunts were inserted contralaterally to the ductus arteriosus. Follow-up for all patients was 1.8 years (4 days-7.8 years). Pulmonary artery stenosis was diagnosed in 12/59 patients (20.3%, group I 12/47; group II 0) after a time interval of 4 days up to 5.3 years and only after Blalock-Taussig shunts (one classical, 11 modified) (12/40 = 30%). The stenoses were located ipsilaterally to the shunt in 7/12 and contralaterally in 5/12. Statistical analysis did not show any impact of age, weight, sex, shunt type or size, pulmonary artery diameters, Nakata and McGoon indices and prior interventions on the development of pulmonary artery stenosis. However, a patent ductus arteriosus and administration of Prostaglandin E1 had a significant impact on the development of pulmonary artery stenosis on the side of the ductus arteriosus.

CONCLUSION

Pulmonary artery stenosis is not a rare event after systemic-to-pulmonary shunt operations. A patent ductus arteriosus with or without administration of Prostaglandin E1 is related to pulmonary artery stenosis on the side of the ductus arteriosus. Pulmonary artery stenosis on the side of a peripheral shunt may be caused by inappropriate surgical technique, increased intimal proliferation, or pulmonary artery kinking. Treatment depends on severity of cyanosis and on further surgical plans.