Therapeutic plasma exchange in pediatric intensive care: Indications,results and complications

Therapeutic plasma exchange (TPE) is an effective treatment method in selective indications. Secondary to access and technical features, it is more difficult to apply in pediatric population than adults. The aim of this study is investigate safety, clinical indications, and results of this method in critically ill pediatric patients who need TPE treatment. All of the TPE procedures performed in a pediatric intensive care unit providing tertiary care during 4 years (2015–2019) were evaluated retrospectively. TPE procedures (635) were performed for 135 patients. Median age was 34 months (10‐108). Ninety‐seven patients had mechanical ventilation support. Sepsis with multiple organ failure was the most frequent indication and accounted for 44.4% (n = 60) of the indications followed by hematological and neurological diseases (19.2% and 9.6% respectively). TPE was performed alone in 469 cases (73.9%), in combination with continuous renal replacement therapy in 154 cases (24.2%), and additional to extracorporeal membrane oxygenation in 12 cases (1.9%). Hematological disease and sepsis subgroups had the highest intubation rate, mechanical ventilation period, PRISM score, organ failure count, and mortality. Fresh frozen plasma (FFP) was the most frequently used replacement fluid in 90.4% of the procedures. The most frequent anticoagulant used in TPE was acid citrate dextrose solution (79.3%). Procedural complications were detected in 104 cases (16.3%) and occurred during TPE sessions. Overall survival rate was 78.5%. We found that the non‐survivor group had significantly higher rates of organ failures (P = 0.0001), higher PRISM scores on admission (P = 0.0001), and higher rates of invasive ventilation support needed (P = 0.012). TPE is a treatment method which can be safely provided in healthcare facilities with necessary medical and technical requirements. Although it is riskier to provide such treatment to critically ill children, complications can be minimized in experienced healthcare facilities. Overall results are good and can vary depending on indication.     

Functional Redundancy of SWI/SNF Catalytic Subunits in Maintaining Vascular Endothelial Cells in the Adult Heart

Rationale: Mating type switching/sucrose non-fermenting (SWI/SNF) chromatin-remodeling complexes utilize either BRG1 or BRM as a catalytic subunit to alter nucleosome position and regulate gene expression. BRG1 is required for vascular endothelial cell (VEC) development and embryonic survival, whereas BRM is dispensable. Objective: To circumvent embryonic lethality and study Brg1 function in adult tissues, we used conditional gene targeting. To evaluate possible Brg1-Brm redundancy, we analyzed Brg1 mutant mice on wild-type and Brm-deficient backgrounds. Methods and Results: The inducible Mx1-Cre driver was used to mutate Brg1 in adult mice. These conditional-null mutants exhibited a tissue-specific phenotype and unanticipated functional compensation between Brg1 and Brm. Brg1 single mutants were healthy and had a normal lifespan, whereas Brg1/Brm double mutants exhibited cardiovascular defects and died within 1 month. BRG1 and BRM were required for the viability of VECs but not other cell types where both genes were also knocked out. The VEC phenotype was most evident in the heart, particularly in the microvasculature of the outer myocardium, and was recapitulated in primary cells ex vivo. VEC death resulted in vascular leakage, cardiac hemorrhage, secondary death of cardiomyocytes due to ischemia, and ventricular dissections. Conclusions: BRG1-catalyzed SWI/SNF complexes are particularly important in cardiovascular tissues. However, in contrast to embryonic development, in which Brm does not compensate, Brg1 is required in adult VECs only when Brm is also mutated. These results demonstrate for the first time that Brm functionally compensates for Brg1 in vivo and that there are significant changes in the relative importance of BRG1- and BRM-catalyzed SWI/SNF complexes during the development of an essential cell lineage.     

Reaction mechanism of Drosophila cryptochrome

Cryptochrome (CRY) is a blue-light sensitive flavoprotein that functions as the primary circadian photoreceptor in Drosophila melanogaster. The mechanism by which it transmits the light signal to the core clock circuitry is not known. We conducted in vitro studies on the light-induced conformational change in CRY and its effect on protein–protein interaction and performed in vivo analysis of the lifetime of the signaling state of the protein to gain some insight into the mechanism of phototransduction. We find that exposure of CRY to blue light induces a conformation similar to that of the constitutively active CRY mutant with a C-terminal deletion (CRYΔ). This light-induced conformation has a half-life of ∼15 min in the dark at 25 °C and is characterized by increased affinity to Jetlag E3 ligase. In vivo analysis reveals that in the Drosophila S2 cell line, the signaling state induced by a millisecond light exposure has a half-life of 27 min in the dark at 0 °C during which period it is susceptible to degradation by the ubiquitin-proteasome system. These findings lead to a plausible model for circadian photoreception/phototransduction in Drosophila.