Cumulative radiation exposure from diagnostic imaging in intensive care unit patients.

AIM: To quantify cumulative effective dose of intensive care unit (ICU) patients attributable to diagnostic imaging. METHODS: This was a prospective, interdisciplinary study conducted in the ICU of a large tertiary referral and level 1 trauma center. Demographic and clinical data including age, gender, date of ICU admission, primary reason for ICU admission, APACHE II score, length of stay, number of days intubated, date of death or discharge, and re-admission data was collected on all patients admitted over a 1-year period. The overall radiation exposure was quantified by the cumulative effective radiation dose (CED) in millisieverts (mSv) and calculated using reference effective doses published by the United Kingdom National Radiation Protection Board. Pediatric patients were selected for subgroup-analysis. RESULTS: A total of 2737 studies were performed in 421 patients. The total CED was 1704 mSv with a median CED of 1.5 mSv (IQR 0.04-6.6 mSv). Total CED in pediatric patients was 74.6 mSv with a median CED of 0.07 mSv (IQR 0.01-4.7 mSv). Chest radiography was the most commonly performed examination accounting for 83% of all studies but only 2.7% of total CED. Computed tomography (CT) accounted for 16% of all studies performed and contributed 97% of total CED. Trauma patients received a statistically significant higher dose [median CED 7.7 mSv (IQR 3.5-13.8 mSv)] than medical [median CED 1.4 mSv (IQR 0.05-5.4 mSv)] and surgical [median CED 1.6 mSv (IQR 0.04-7.5 mSv)] patients. Length of stay in ICU [OR = 1.12 (95%CI: 1.079-1.157)] was identified as an independent predictor of receiving a CED greater than 15 mSv. CONCLUSION: Trauma patients and patients with extended ICU admission times are at increased risk of higher CEDs. CED should be minimized where feasible, especially in young patients

Spinal cord neuroepithelial progenitor cells display developmental plasticity when co-cultured with embryonic spinal cord slices at different stages of development

All neurons and glial cells of the vertebrate CNS are derived from embryonic neuroepithelial progenitor cells (NEP). Distinct modes of radial neuronal migration, locomotion, and somal translocation have been described in the cerebral cortex, but less is known about the migratory behavior of neuroepithelial cells and their neuronal and glial descendants in the developing spinal cord. Here a novel spinal cord slice co-culture was developed to investigate the migration and differentiation potential of NEPs in the developing spinal cord. E12 NEPs from eGFP transgenic mouse cells were co-cultured with E12, E14, E16, and E18 organotypic spinal cord slices. Time-lapse confocal microscopy and quantitative 3D image analysis revealed that the co-cultured E12 eGFP NEP cells differentiated at a faster rate with increasing age of embryonic spinal cord slice but migrated further in younger slices. Furthermore, it revealed fast tangentially migrating cells and slower radially migrating cells undergoing locomotion and somal translocation. The ability of NEP cells to alter their migration and differentiation within embryonic microenvironments of different ages highlights their developmental plasticity and ability to respond to temporally expressed extrinsic signals

An ex vivo model to quantitatively analyze cell migration in tissue

Background: Within the developing central nervous system, the ability of cells to migrate throughout the tissue parenchyma to reach their target destination and undergo terminal differentiation is vital to normal central nervous system (CNS) development. To develop novel therapies to treat the injured CNS, it is essential that the migratory behavior of cell populations is understood. Many studies have examined the ability of individual neurons to migrate through the developing CNS, describing specific modes of migration including locomotion and somal translocation. Few studies have investigated the mass migration of large populations of neural progenitors, particularly in the developing the spinal cord. Here, we describe a method to robustly analyze large numbers of migrating cells using a co-culture assay. Results: The ex vivo tissue model promotes the survival and differentiation of co-cultured progenitor cells. Using this assay, we demonstrate that migrating neuroepithelial progenitor cells display region specific migration patterns within the dorsal and ventral spinal cord at defined developmental time points. Conclusions: The technique described here is a viable ex vivo model to quantitatively analyze cell migration and differentiation. We demonstrate the ability to detect changes in cell migration within distinct tissue region across tissue samples using the technique described here

The Netrin/RGM receptor, neogenin, controls adult neurogenesis by promoting neuroblast migration and cell cycle exit

A comprehensive understanding of adult neurogenesis is essential for the development of effective strategies to enhance endogenous neurogenesis in the damaged brain. Olfactory interneurons arise throughout life from stem cells residing in the subventricular zone of the lateral ventricle. Neural precursors then migrate along the rostral migratory stream (RMS) to the olfactory bulb. To ensure a continuous supply of adult-born interneurons, precursor proliferation, migration, and differentiation must be tightly coordinated. Here, we show that the netrin/repulsive guidance molecule receptor, Neogenin, is a key regulator of adult neurogenesis. Neogenin loss-of-function (Neo(gt/gt)) mice exhibit a specific reduction in adult-born calretinin interneurons in the olfactory granule cell layer. In the absence of Neogenin, neuroblasts fail to migrate into the olfactory bulb and instead accumulate in the RMS. In vitro migration assays confirmed that Neogenin is required for Netrin-1-mediated neuroblast migration and chemoattraction. Unexpectedly, we also identified a novel role for Neogenin as a regulator of the neuroblast cell cycle. We observed that those neuroblasts able to reach the Neo(gt/gt) olfactory bulb failed to undergo terminal differentiation. Cell cycle analysis revealed an increase in the number of S-phase neuroblasts within the Neo(gt/gt) RMS and a significant reduction in the number of neuroblasts exiting the cell cycle, providing an explanation for the loss of mature calretinin interneurons in the granule cell layer. Therefore, Neogenin acts to synchronize neuroblast migration and terminal differentiation through the regulation of neuroblast cell cycle kinetics within the neurogenic microenvironment of the RMS

WNT5a regulates epithelial morphogenesis in the developing choroid plexus

The choroid plexus (CP) is the predominant supplier of cerebral spinal fluid (CSF) and the site of the blood-CSF barrier and is thus essential for brain development and central nervous system homeostasis. Despite these crucial roles, our understanding of the molecular and cellular processes giving rise to the CPs within the ventricles of the mammalian brain is very rudimentary. Here, we identify WNT5a as an important regulator of CP development, where it acts as a pivotal factor driving CP epithelial morphogenesis in all ventricles. We show that WNT5a is essential for the establishment of a cohesive epithelium in the developing CP. We find that in its absence all CPs are substantially reduced in size and complexity and fail to expand into the ventricles. Severe defects were observed in the epithelial cytoarchitecture of all Wnt5a-/- CPs, exemplified by loss of apicobasally polarized morphology and detachment from the ventricular surface and/or basement membrane. We also present evidence that the WNT5a receptor, RYK, and the RHOA kinase, ROCK, are required for normal CP epithelial morphogenesis. Our study, therefore, reveals important insights into the molecular and cellular mechanisms governing CP development

Neogenin recruitment of the WAVE regulatory complex to ependymal and radial progenitor adherens junctions prevents hydrocephalus

Denudation of the ependyma due to loss of cell adhesion mediated by cadherin-based adherens junctions is a common feature of perinatal hydrocephalus. Junctional stability depends on the interaction between cadherins and the actin cytoskeleton. However, the molecular mechanism responsible for recruiting the actin nucleation machinery to the ependymal junction is unknown. Here, we reveal that loss of the netrin/RGM receptor, Neogenin, leads to severe hydrocephalus. We show that Neogenin plays a critical role in actin nucleation in the ependyma by anchoring the WAVE regulatory complex (WRC) and Arp2/3 to the cadherin complex. Blocking Neogenin binding to the Cyfip1/Abi WRC subunit results in actin depolymerization, junctional collapse, and denudation of the postnatal ventricular zone. In the embryonic cortex, this leads to loss of radial progenitor adhesion, aberrant neuronal migration, and neuronal heterotopias. Therefore, Neogenin-WRC interactions play a fundamental role in ensuring the fidelity of the embryonic ventricular zone and maturing ependyma

<i>Neo</i> is expressed on newborn cortical interneurons and the maturing calbindin and parvalbumin subpopulations.

<p>(A) 2 day cultures from the E14.5 MGE were immunolabeled with anti-Neo (H-175, green) and anti-βIII-tubulin (red; merge, yellow), a marker for newborn neurons. (B,C,D) MGE cells were isolated at E14.5, differentiated for 4 days and then colabeled with (B) anti-Neo (MAB1079, red) and anti-GAD65/67, a GABAergic interneuron marker (green; merge, yellow), (C) anti-Neo (MAB1079, red) and anti-calbindin (green; merge, yellow), or (D) anti-Neo (H-175, green) and anti-parvalbumin (red; merge, yellow).</p

RGMa-mediated repulsion of newborn interneurons is suppressed by Netrin-1.

<p>(A) The extent of interneuron migration was calculated as the ratio of the distal to proximal area (guidance ratio) occupied by migrating cells. (B–E) Anti-βIII-tubulin immunolabeling (red) revealed the extent of interneuron migration out of E14.5 MGE VZ explants placed adjacent to agarose blocks containing control HEK293 cells (B), cells producing Netrin-1 (C), RGMa (D) or RGMa + Netrin-1 (E). Note the significant increase in neuron density on the distal side of the explant in the presence of RGMa (D). (E) Quantification of the guidance ratio for newborn interneuron migration out of the MGE explants in response to guidance cues. Dotted lines indicate the body of the explant. Control, n = 10; Netrin-1, n = 8; RGMa, n = 12; RGMa + Netrin-1, n = 7. *p<0.5, **p<0.01.</p

<i>RGMa</i> and <i>Neo</i> are expressed by radial progenitors in the VZ of the ganglionic eminences.

<p>(A) Coronal sections of E14.5 embryos show that RGMa was restricted to the VZ and SVZ in the ganglionic eminences. (B) Low levels of Neo were detected on radial progenitors in the LGE and MGE VZ (arrows). Newborn neurons within the migratory corridor were also Neo-positive (arrowhead). Neurons in the cortical plate (cp) and striatum (st) expressed high levels of <i>Neo</i>. No immunoreactivity was seen with an isotype-matched IgG control antibody (inset). Colabeling of E14.5 MGE VZ cells cultured for 2 days with antibodies to Neo (H-175, green), the radial progenitor marker, GLAST (C, red; merge, yellow), the cell cycle marker, Ki67 (D, red; merge, yellow), or the M-phase marker, phospho-vimentin55 (E, red; merge, yellow). GE, ganglionic eminence. Scale bars: A, 670 µm; B, 1.00 mm.</p

RGMa does not influence neurogenic divisions or interneuronal fate.

<p>MGE cells were isolated at E14.5 and differentiated for 4 days in recombinant RGMa. (A) No significant difference was observed in the percentage of neurons generated in the presence of 200 or 400 ng/ml RGMa or in the absence of RGMa. (B) Addition of the RGMa inhibitory peptide (Pep2, 10 µM) or scrambled control peptide (ScPep, 10 µM) had no significant effect on the number of neurons generated in the presence or absence of RGMa. Number of neurons counted per condition >520.</p