Twin reversed arterial perfusion sequence in a monochorionic monoamniotic twin pregnancy: a very rare condition

Background: Twin reversed arterial perfusion sequence (TRAP) is a very rare congenital anomaly. We present sonographic findings of TRAP sequence in the case of a multiparous woman with a monochorionic monoamniotic twin pregnancy who was referred to our unit for blood sugar control. Case presentation: The patient had a history of co-twin demise at 13 weeks of gestation without appropriate fetal surveillance afterwards. We found a monochorionic placentation with a normal appearing pump twin, an abnormal appearing co-twin without obvious cardiac activity and reversed arterial flow toward instead of away from the anomalous acardiac fetus. Therefore, the sonographic diagnosis of TRAP sequence was confirmed. Conclusions: We recommend considering the potential rare complications of monochorionic twin pregnancy which necessitates proper surveillance and intervention to monitor suitable growth of pump twin. © 2020, The Author(s)

Comparative Structural Analysis of Lipid Binding START Domains

Steroidogenic acute regulatory (StAR) protein related lipid transfer (START) domains are small globular modules that form a cavity where lipids and lipid hormones bind. These domains can transport ligands to facilitate lipid exchange between biological membranes, and they have been postulated to modulate the activity of other domains of the protein in response to ligand binding. More than a dozen human genes encode START domains, and several of them are implicated in a disease.We report crystal structures of the human STARD1, STARD5, STARD13 and STARD14 lipid transfer domains. These represent four of the six functional classes of START domains.Sequence alignments based on these and previously reported crystal structures define the structural determinants of human START domains, both those related to structural framework and those involved in ligand specificity.This article can also be viewed as an enhanced version in which the text of the article is integrated with interactive 3D representations and animated transitions. Please note that a web plugin is required to access this enhanced functionality. Instructions for the installation and use of the web plugin are available in Text S1

Control of intestinal stem cell function and proliferation by mitochondrial pyruvate metabolism.

Most differentiated cells convert glucose to pyruvate in the cytosol through glycolysis, followed by pyruvate oxidation in the mitochondria. These processes are linked by the mitochondrial pyruvate carrier (MPC), which is required for efficient mitochondrial pyruvate uptake. In contrast, proliferative cells, including many cancer and stem cells, perform glycolysis robustly but limit fractional mitochondrial pyruvate oxidation. We sought to understand the role this transition from glycolysis to pyruvate oxidation plays in stem cell maintenance and differentiation. Loss of the MPC in Lgr5-EGFP-positive stem cells, or treatment of intestinal organoids with an MPC inhibitor, increases proliferation and expands the stem cell compartment. Similarly, genetic deletion of the MPC in Drosophila intestinal stem cells also increases proliferation, whereas MPC overexpression suppresses stem cell proliferation. These data demonstrate that limiting mitochondrial pyruvate metabolism is necessary and sufficient to maintain the proliferation of intestinal stem cells

Harnessing the power of computational fluid dynamics for flow coefficient and rain resistance improvement of type 1 natural ventilators

Type 1 Natural Ventilators act like a shield protecting the building from rain intrusion while allowing air to flow from outside. Despite their wide applications, they are far from the ideal design, mainly due to a lack of data on their air discharge coefficient and rain defense effectiveness under different climatic conditions. According to ventilation standards, since experimental testing of different geometries and configurations of these ventilators are complex, difficult, and costly, this study aims to implement Computational Fluid Dynamics (CFD) tools to investigate their performance. To do this, a combination of 9 various louvre panels was designed with 1, 2, and 3 blades and 5, 10, and 12 cm pitches following type 1 Natural Ventilator design standards. Accordingly, a geometrical model including the louvre panel and the wind tunnel is created, meshed, and tested under different climatic conditions. A mesh independency study and a validation analysis were also done to confirm the validity of the data. The pressure loss and signs of water penetration were monitored while the louvre panel was subjected to an air stream into which water is introduced using an array of nozzles to simulate the wind-blown rain. The results showed that the CFD tool was a strong technique in determining the louvre panels\u27 performance. Accordingly, four categories were defined to separate louvers’ performance in case of their air discharge coefficient and rain defense effectiveness. Namely, category #1 included the 2-blade louvre with 10 and 15 cm pitch and the 3-blade louvre with 15 cm pitch with a relatively high discharge coefficient and rain defense. The result demonstrated that the discharge coefficients of all louvres were not sensitive to wind velocity in the range of 5–10 m/s compared to those in the velocities less than 5 m/s and higher than 10 m/s. In addition, the discharge coefficient decreases dramatically as the number of blades over the pitch ratio increases. Finally, according to the results of this study, it was understood that the choice of a louvre configuration is application specific; for instance for applications in which high airflow is the dominant requirement, louvres configuration in category 3, efficient for airflow only, are the best choices

Data mining the Protein Data Bank to identify and characterise chameleon coil sequences that form symmetric homodimer β-sheet interfaces

A protein’s environment may affect its secondary structure. In this study, the focus is on homodimers with symmetric β-sheet interfaces resulting from the conversion of coil sequences into β-strands. All homodimers in the Protein Data Bank relying on those chameleon sequences have been identified. Initial analysis based on sequential and structural features has revealed that many of those dimers display specific properties which could contribute to their detection. Such result is important since it could provide some insight on dimerisation and possibly aggregation mechanisms