A mouse model of autism implicates endosome pH in the regulation of presynaptic calcium entry.

Psychoactive compounds such as chloroquine and amphetamine act by dissipating the pH gradient across intracellular membranes, but the physiological mechanisms that normally regulate organelle pH remain poorly understood. Interestingly, recent human genetic studies have implicated the endosomal Na+/H+ exchanger NHE9 in both autism spectrum disorders (ASD) and attention deficit hyperactivity disorder (ADHD). Plasma membrane NHEs regulate cytosolic pH, but the role of intracellular isoforms has remained unclear. We now find that inactivation of NHE9 in mice reproduces behavioral features of ASD including impaired social interaction, repetitive behaviors, and altered sensory processing. Physiological characterization reveals hyperacidic endosomes, a cell-autonomous defect in glutamate receptor expression and impaired neurotransmitter release due to a defect in presynaptic Ca2+ entry. Acute inhibition of synaptic vesicle acidification rescues release but without affecting the primary defect due to loss of NHE9

High-Throughput Liquid Chromatography–Tandem Mass Spectrometry Quantification of Glycosaminoglycans as Biomarkers of Mucopolysaccharidosis II

We recently developed a blood–brain barrier (BBB)-penetrating enzyme transport vehicle (ETV) fused to the lysosomal enzyme iduronate 2-sulfatase (ETV:IDS) and demonstrated its ability to reduce glycosaminoglycan (GAG) accumulation in the brains of a mouse model of mucopolysaccharidosis (MPS) II. To accurately quantify GAGs, we developed a plate-based high-throughput enzymatic digestion assay coupled with liquid chromatography–tandem mass spectrometry (LC-MS/MS) to simultaneously measure heparan sulfate and dermatan sulfate derived disaccharides in tissue, cerebrospinal fluid (CSF) and individual cell populations isolated from mouse brain. The method offers ultra-high sensitivity enabling quantitation of specific GAG species in as low as 100,000 isolated neurons and a low volume of CSF. With an LOD at 3 ng/mL and LLOQs at 5–10 ng/mL, this method is at least five times more sensitive than previously reported approaches. Our analysis demonstrated that the accumulation of CSF and brain GAGs are in good correlation, supporting the potential use of CSF GAGs as a surrogate biomarker for brain GAGs. The bioanalytical method was qualified through the generation of standard curves in matrix for preclinical studies of CSF, demonstrating the feasibility of this assay for evaluating therapeutic effects of ETV:IDS in future studies and applications in a wide variety of MPS disorders

The Michigan Appropriateness Guide for Intravenous Catheters in Pediatrics: miniMAGIC

Vascular access device decision-making for pediatric patients remains a complex, highly variable process. To date, evidence-based criteria to inform these choices do not exist. The objective of the Michigan Appropriateness Guide for Intravenous Catheters in pediatrics (miniMAGIC) was to provide guidance on device selection, device characteristics, and insertion technique for clinicians, balancing and contextualizing evidence with current practice through a multidisciplinary panel of experts.The RAND Corporation and University of California, Los Angeles Appropriateness Method was used to develop miniMAGIC, which included the following sequential phases: definition of scope and key terms, information synthesis and literature review, expert multidisciplinary panel selection and engagement, case scenario development, and appropriateness ratings by an expert panel via 2 rounds.The appropriateness of the selection, characteristics, and insertion technique of intravenous catheters commonly used in pediatric health care across age populations (neonates, infants, children, and adolescents), settings, diagnoses, clinical indications, insertion locations, and vessel visualization devices and techniques was defined. Core concepts including vessel preservation, insertion and postinsertion harm minimization (eg, infection, thrombosis), undisrupted treatment provision, and inclusion of patient preferences were emphasized.In this study, we provide evidence-based criteria for intravenous catheter selection (from umbilical catheters to totally implanted venous devices) in pediatric patients across a range of clinical indications. miniMAGIC also highlights core vascular access practices in need of collaborative research and innovation