Global analyses of endonucleolytic cleavage in mammals reveal expanded repertoires of cleavage-inducing small RNAs and their targets.

In mammals, small RNAs are important players in post-transcriptional gene regulation. While their roles in mRNA destabilization and translational repression are well appreciated, their involvement in endonucleolytic cleavage of target RNAs is poorly understood. Very few microRNAs are known to guide RNA cleavage. Endogenous small interfering RNAs are expected to induce target cleavage, but their target genes remain largely unknown. We report a systematic study of small RNA-mediated endonucleolytic cleavage in mouse through integrative analysis of small RNA and degradome sequencing data without imposing any bias toward known small RNAs. Hundreds of small cleavage-inducing RNAs and their cognate target genes were identified, significantly expanding the repertoire of known small RNA-guided cleavage events. Strikingly, both small RNAs and their target sites demonstrated significant overlap with retrotransposons, providing evidence for the long-standing speculation that retrotransposable elements in mRNAs are leveraged as signals for gene targeting. Furthermore, our analysis showed that the RNA cleavage pathway is also present in human cells but affecting a different repertoire of retrotransposons. These results show that small RNA-guided cleavage is more widespread than previously appreciated. Their impact on retrotransposons in non-coding regions shed light on important aspects of mammalian gene regulation

Capitate Stress Injuries of Both Wrists in an Adolescent Female Gymnast: A Case Report

Gymnastic activities expose the wrist to a wide variety of overuse and acute stresses. Injuries to the distal radius are the most commonly reported gymnastic wrist condition; however, many other structures are at risk of injury from the sport’s high acute and overuse demands, including the carpal bones, most commonly the scaphoid. We describe a 17-year-old female, high-level gymnast in whom stress injuries to both capitate bones were ultimately diagnosed after initial symptoms of pain. This case demonstrated the need for prompt recognition, without which much chronic and debilitating injury would develop. For successful diagnosis, healthcare providers should carefully examine and evaluate reported wrist pain in high-level, adolescent gymnasts

Idiopathic Thrombocytopenic Purpura in a 21-Year-Old Collegiate Football Player: A Case Report

Muscle cramps are commonly observed in collegiate athlete-patients; however, the condition may be a symptom of severe disorders. In particular, idiopathic thrombocytopenic purpura (ITP) may be a possible diagnosis and involves a decreased number of platelets in the bloodstream. We describe a 21-year-old collegiate player of American football with initially presented with cramping of the neck, abdomen, and forearms. Although findings of physical examination were normal, results of laboratory tests indicated ITP, and the patient was hospitalized for 3 days until the platelet count increased. Because the levels continued to decrease at 6-month followup, splenectomy and use of rituximab agents have been discussed with the patient for treatment after the end of the football season, before which dexamethasone will be administered to maintain a minimum platelet count of 50. Physicians should consider coordinating traditional care and specialist consultation to help treat severe conditions such as thrombocytopenia in athlete-patients

An ELLAM approximation for advective–dispersive transport with nonlinear sorption

We consider an Eulerian-Lagrangian localized adjoint method (ELLAM) applied to nonlinear model equations governing solute transport and sorption in porous media. Solute transport in the aqueous phase is modeled by standard advection and hydrodynamic dispersion processes, while sorption is modeled with a nonlinear local equilibrium model. We present our implementation of finite volume ELLAM (FV- ELLAM) and finite element (FE-ELLAM) discretizations to the reactive transport model and evaluate their performance for several test problems containing self- sharpening fronts

Efficient steady-state solution techniques for variably saturated groundwater flow

We consider the simulation of steady-state variably saturated groundwater flow using Richards' equation (RE). The difficulties associated with solving RE numerically are well known. Most discretization approaches for RE lead to nonlinear systems that are large and difficult to solve. The solution of nonlinear systems for steady- state problems can be particularly challenging, since a good initial guess for the steady-state solution is often hard to obtain, and the resulting linear systems may be poorly scaled. Common approaches like Picard iteration or variations of Newton's method have their advantages but perform poorly with standard globalization techniques under certain conditions. Pseudo-transient continuation has been used in computational fluid dynamics for some time to obtain steady-state solutions for problems in which Newton's method with standard line-search strategies fails. It combines aspects of backward Euler time integration and Newton's method to select intermediate estimates of the steady-state solution. Here, we examine the use of pseudo-transient continuation as well as Newton's method combined with standard globalization techniques for steady-state problems in heterogeneous domains. We investigate the methods' performance with direct and preconditioned Krylov iterative linear solvers. We then make recommendations for robust and efficient approaches to obtain steady-state solutions for RE under a range of conditions