Variations in the management of acute illness in children with congenital adrenal hyperplasia: An audit of three paediatric hospitals

Objective: Episodes of acute adrenal insufficiency (AI)/adrenal crises (AC) are a serious consequence of congenital adrenal hyperplasia (CAH). This study aimed to assess morbidity from acute illness in CAH and identify factors associated with use of IV hydrocortisone, admission and diagnosis of an AC. Method: An audit of acute illness presentations among children with CAH to paediatric hospitals in New South Wales, Australia, between 2000 and 2015. Results: There were 321 acute presentations among 74 children with CAH. Two thirds (66.7%, n=214) of these resulted in admission and 49.2% (n=158) of the patients received intravenous (IV) hydrocortisone. An AC was diagnosed in (9.0%). Prior to presentation, 64.2% (n=206) had used oral stress dosing and 22.1% (n=71) had been given intramuscular (IM) hydrocortisone. Vomiting was recorded in 61.1% (n=196), 32.7% (n=64) of whom had used IM hydrocortisone. Admission, AC diagnosis, and use of stress dosing varied significantly between hospitals. IM use varied from 7.0% in one metropolitan hospital to 45.8% in the regional hospital. Children aged up to 12 months had the lowest levels of stress dosing and IV hydrocortisone administration. A higher number of prior hospital attendances for acute illness was associated with increased use of IM hydrocortisone. Conclusion: Pre-hospital and in-hospital management of children with CAH can vary between health services. Children under 12 months have lower levels of stress dosing prior to hospital than other age groups. Experience with acute episodes improves self-management of CAH in the context of acute illness in educated patient populations

Generalizations of Markov Chain Discretizations

Markov chains have famously been a crucial tool in understanding stochastic processes and queuing systems, among many other applications. Both discrete-time chains and continuoustime chains have been important centers in both research and application. These two cases are described by transition matrices. Continuous-time chains are difficult to model because this matrix is rather hard to compute in general. One attack to this problem is approximating a continuous-time chain with one that evolves in discrete time. The transition matrix is still difficult to compute exactly but can also be approximated to any order. The first-order approximation of this quantity is well-known. In 2008, Rachel Irby studied the second-order approximation and compared its performance to that of the first-order counterpart. In this paper, we will generalize the results outlined in Rachel\u27s paper by using an approximation of any order. Specifically, we will study direct comparisons using norms. In addition, we will compare the continuous-time chain to its approximate model through the study of stationary and limiting distributions

A model for transition of 5 '-nuclease domain of DNA polymerase I from inert to active modes

Bacteria contain DNA polymerase I (PolI), a single polypeptide chain consisting of similar to 930 residues, possessing DNA-dependent DNA polymerase, 3'-5' proofreading and 5'-3' exonuclease (also known as flap endonuclease) activities. PolI is particularly important in the processing of Okazaki fragments generated during lagging strand replication and must ultimately produce a double-stranded substrate with a nick suitable for DNA ligase to seal. PolI's activities must be highly coordinated both temporally and spatially otherwise uncontrolled 5'-nuclease activity could attack a nick and produce extended gaps leading to potentially lethal double-strand breaks. To investigate the mechanism of how PolI efficiently produces these nicks, we present theoretical studies on the dynamics of two possible scenarios or models. In one the flap DNA substrate can transit from the polymerase active site to the 5'-nuclease active site, with the relative position of the two active sites being kept fixed; while the other is that the 5'-nuclease domain can transit from the inactive mode, with the 5'-nuclease active site distant from the cleavage site on the DNA substrate, to the active mode, where the active site and substrate cleavage site are juxtaposed. The theoretical results based on the former scenario are inconsistent with the available experimental data that indicated that the majority of 5'-nucleolytic processing events are carried out by the same PolI molecule that has just extended the upstream primer terminus. By contrast, the theoretical results on the latter model, which is constructed based on available structural studies, are consistent with the experimental data. We thus conclude that the latter model rather than the former one is reasonable to describe the cooperation of the PolI's polymerase and 5'-3' exonuclease activities. Moreover, predicted results for the latter model are presented

Lysine deserts prevent adventitious ubiquitylation of ubiquitin-proteasome components

In terms of its relative frequency, lysine is a common amino acid in the human proteome. However, by bioinformatics we find hundreds of proteins that contain long and evolutionarily conserved stretches completely devoid of lysine residues. These so-called lysine deserts show a high prevalence in intrinsically disordered proteins with known or predicted functions within the ubiquitin-proteasome system (UPS), including many E3 ubiquitin-protein ligases and UBL domain proteasome substrate shuttles, such as BAG6, RAD23A, UBQLN1 and UBQLN2. We show that introduction of lysine residues into the deserts leads to a striking increase in ubiquitylation of some of these proteins. In case of BAG6, we show that ubiquitylation is catalyzed by the E3 RNF126, while RAD23A is ubiquitylated by E6AP. Despite the elevated ubiquitylation, mutant RAD23A appears stable, but displays a partial loss of function phenotype in fission yeast. In case of UBQLN1 and BAG6, introducing lysine leads to a reduced abundance due to proteasomal degradation of the proteins. For UBQLN1 we show that arginine residues within the lysine depleted region are critical for its ability to form cytosolic speckles/inclusions. We propose that selective pressure to avoid lysine residues may be a common evolutionary mechanism to prevent unwarranted ubiquitylation and/or perhaps other lysine post-translational modifications. This may be particularly relevant for UPS components as they closely and frequently encounter the ubiquitylation machinery and are thus more susceptible to nonspecific ubiquitylation.</p

Identifying the Functional Role of EXC-1, a GTPase Required for Maintenance of Shape in Small Biological Tubes

Biological tubes require regular maintenance due to constant pressures exerted on them. Selfrepairing mechanisms that occur on the subcellular level are essential to the longevity and growth of the tubule shape. Loss of this structure has been shown to result in a number of different disorders such as Polycystic Kidney Disease (PKD). PKD is characterized by loss structure in the nephrons of the kidney, resulting in the formation of fluid-filled cysts associated complications. To gain a better understanding of the cellular mechanisms that underlie these repairing processes, we study the genetic model organism Caenorhabditis elegans. C. elegans contains many small tubules like those found in the vascular and renal systems of humans. The tube that we study is the excretory canal, which is made up of a single epithelial tube cell; this provides a simple cellular and genetic model to carry out tests. Members of the EXC family of proteins are essential for growth and consistent maintenance of the shape of the excretory canal. Mutations in the exc (EXcretory Canal abnormal) genes lose the ability to maintain proper structure and develop cystic abnormalities. One gene in this family, exc-1, encodes a homologue of the Immunity-Related GTPases (IRGP), which plays a role in membrane trafficking, autophagy and endosome formation in mammalian cells. Continuing this work, we want to gain conclusive evidence that exc-1 is in fact a functional GTPase by the creation of a transgenic vector, isolation of the protein, and then carrying out a biochemical assay to test our hypothesis

Studying the Structure and Stability of F141L Calmodulin Mutant in the Assessment of Cardiac Related Complications

Calmodulin (CaM) is a ubiquitous protein that carries many different important roles within eukaryotes organisms. Its most recognized role is its ability to efficiently sense and bind calcium (Ca2+) when there is an influx within the intracellular compartments of cells. By binding Ca2+, CaM is able to interact and signal many other proteins in a very quick manner. Being that it is such a nimble protein, it has great importance in the cells of cardiac and skeletal muscle. Within these spaces CaM binds Ca2+ and signals calmodulin-dependent protein kinase II (CaMKII), which then goes on to phosphorylate ryanodine receptor 2, thus controlling the Ca2+ flux. When the genes that code for CaM become mutated, many dangerous disease states manifest. Focusing on one mutant variant specifically, F141L, is phenotypically expressed by recurrent cardiac arrest (RCA) and early onset severe long QT (EsLQT). This being only one of many fatal cardiac related diseases arising from mutated CaM, there is much work going into the underpinnings of the biochemical and biophysical implications of such mutants. This study aims to further this understanding by creating mutated CaM protein by use of recombinant protein expression technology, then studying its structural dynamics. The assays that will be utilized will aim to look at the stability and structure of the F141L mutant. The stability test will be carried out by thermal denaturation and the structure by circular dichroism. Gaining a better understanding of these aspects will help in the production of possible pharmaceuticals targeting CaM related issues

Cyclic Scheduling Problems

For classical non-cyclic scheduling problems, we are given a set of operations,each of which has to be processed exactly once. The aim is to minimize or maximizea given objective function such as makespan or sum of all (weighted) completion times for a given set of constraints. The set of constraints is usually given by precedence constraints between the operations. In contrast to these problems, for cyclic scheduling problems we are given a set of operations, each of which has to be processed infinitely often. Such types of scheduling problems arise in different application areas like compiler design, manufacturing, digital signal processing, railway scheduling, timetabling, etc. The problem is to find a periodic schedule which minimizes a given objective function. There exist two objective functions which are important in this area of cyclic scheduling. The objective which is considered throughout this work is to minimize the time difference between two succeeding occurrences of one operation for a given set of constraints. This time difference is called cycle time. In this thesis, we develop a general framework to model and to describe cyclic scheduling problems with resource constraints. Furthermore, we extend the model to describe blocking constraints for cyclic scheduling problems. In order to solve the problem, we develop a local search approach

Identifying the Functional Role of EXC-1, a GTPase Required for Maintenance of Shape in Small Biological Tubes

Biological tubes require regular maintenance due to constant pressures exerted on them. Selfrepairing mechanisms that occur on the subcellular level are essential to the longevity and growth of the tubule shape. Loss of this structure has been shown to result in a number of different disorders such as Polycystic Kidney Disease (PKD). PKD is characterized by loss structure in the nephrons of the kidney, resulting in the formation of fluid-filled cysts associated complications. To gain a better understanding of the cellular mechanisms that underlie these repairing processes, we study the genetic model organism Caenorhabditis elegans. C. elegans contains many small tubules like those found in the vascular and renal systems of humans. The tube that we study is the excretory canal, which is made up of a single epithelial tube cell; this provides a simple cellular and genetic model to carry out tests. Members of the EXC family of proteins are essential for growth and consistent maintenance of the shape of the excretory canal. Mutations in the exc (EXcretory Canal abnormal) genes lose the ability to maintain proper structure and develop cystic abnormalities. One gene in this family, exc-1, encodes a homologue of the Immunity-Related GTPases (IRGP), which plays a role in membrane trafficking, autophagy and endosome formation in mammalian cells. Continuing this work, we want to gain conclusive evidence that exc-1 is in fact a functional GTPase by the creation of a transgenic vector, isolation of the protein, and then carrying out a biochemical assay to test our hypothesis