Aktiini-välitteisten liikkuvuuden rooli ääreis-astrosyyttejen kehityskulkussa synaptisessa toiminnassa

Among other glial cell types such as microglia, oligodendrocytes and radial glia, astrocytes are known to be involved in brain function; metabolically supporting neurons, regulating blood flow dynamics, participating in the development of pathological states, sensing and modulating synaptic activity. At the same time the complex astrocytic morphology, with a number of highly ramified peripheral processes located near the synaptic terminals, suggests them as a possible source for morpho-functional plasticity in the brain. This thesis summarizes the work on the in vitro development and further in vivo implementation, using a gene delivery system, of a tool for suppressing activity-dependent astrocytic motility. Calciuminduced astrocyte process outgrowth and its dependence on Profilin-1, novel in vivo gene delivery approaches, a demonstration of astrocytic motility in vivo and the independence of visual processing from astrocytic motility rates are the main findings of the project. The results described in this work increase our understanding of the interactions occurring between astrocytes and neurons as well as the consequences for brain function.Glia-soluihin kuuluvat astrosyytit ovat tiedettävästi osa aivojen toimintaa. Astrosyytit tukevat metabolisesti neuroneita, säätelevät verenkierron dynamiikkaa, ovat hyvin läsnä patoloogisten tilojen kehittymisessä, mukana aistimassa ja muuntamassa synaptista aktiivisuutta. Samanaikaisesti astrosyyttejen kompleksi morfologia, läheinen sijainti synaptisien terminalejen kanssa viittaavat mahdolliseen morfo-funtionaaliseen muovautumiseen aivoissa. Tämä väitöskirja keskittyy töihin jotka kehittävät in vitro ja in vivo tekniikoita jolla voidaan käyttää geeni jakelu menetelmää joka vaimentaa astrosyyttejen liikkuvuutta. Keskeiset havainnot tässä väitöskirjassa ovat astrosyyttejen kasliumin indusoima haarottuminen joka on riippuvainen Profiliini-1:stä ja havainnollistaminen astrosyyttejen liikkuvuudesta in vivo menetelmillä ja astrosyyttejen liikkuvuus aste joka on itsenäinen visuaalisesta prosessoinnista. Kuvaillut tulokset tässä väitöskirjassa kohentavat meidän ymmärrystä astrosyytetjen ja neuronejen välisestä kanssakäymisestä ja niiden seuraamus aivojen toiminnassa

Chronic imaging through "transparent skull" in mice

Growing interest in long-term visualization of cortical structure and function requires methods that allow observation of an intact cortex in longitudinal imaging studies. Here we describe a detailed protocol for the "transparent skull" (TS) preparation based on skull clearing with cyanoacrylate, which is applicable for long-term imaging through the intact skull in mice. We characterized the properties of the TS in imaging of intrinsic optical signals and compared them with the more conventional cranial window preparation. Our results show that TS is less invasive, maintains stabile transparency for at least two months, and compares favorably to data obtained from the conventional cranial window. We applied this method to experiments showing that a four-week treatment with the antidepressant fluoxetine combined with one week of monocular deprivation induced a shift in ocular dominance in the mouse visual cortex, confirming that fluoxetine treatment restores critical-period-like plasticity. Our results demonstrate that the TS preparation could become a useful method for long-term visualization of the living mouse brain.Peer reviewe

Microglia complement signaling promotes neuronal elimination and normal brain functional connectivity

Complement signaling is thought to serve as an opsonization signal to promote the phagocytosis of synapses by microglia. However, while its role in synaptic remodeling has been demonstrated in the retino-thalamic system, it remains unclear whether complement signaling mediates synaptic pruning in the brain more generally. Here we found that mice lacking the Complement receptor 3, the major microglia complement receptor, failed to show a deficit in either synaptic pruning or axon elimination in the developing mouse cortex. Instead, mice lacking Complement receptor 3 exhibited a deficit in the perinatal elimination of neurons in the cortex, a deficit that is associated with increased cortical thickness and enhanced functional connectivity in these regions in adulthood. These data demonstrate a role for complement in promoting neuronal elimination in the developing cortex

Heparin-Binding Growth-Associated Molecule (Pleiotrophin) Affects Sensory Signaling and Selected Motor Functions in Mouse Model of Anatomically Incomplete Cervical Spinal Cord Injury

Heparin-binding growth-associated molecule (pleiotrophin) is a neurite outgrowth-promoting secretory protein that lines developing fiber tracts in juvenile CNS (central nervous system). Previously, we have shown that heparin-binding growth-associated molecule (HB-GAM) reverses the CSPG (chondroitin sulfate proteoglycan) inhibition on neurite outgrowth in the culture medium of primary CNS neurons and enhances axon growth through the injured spinal cord in mice demonstrated by two-photon imaging. In this study, we have started studies on the possible role of HB-GAM in enhancing functional recovery after incomplete spinal cord injury (SCI) using cervical lateral hemisection and hemicontusion mouse models. In vivo imaging of blood-oxygen-level-dependent (BOLD) signals associated with functional activity in the somatosensory cortex was used to assess the sensory functions during vibrotactile hind paw stimulation. The signal displays an exaggerated response in animals with lateral hemisection that recovers to the level seen in the sham-operated mice by injection of HB-GAM to the trauma site. The effect of HB-GAM treatment on sensory-motor functions was assessed by performance in demanding behavioral tests requiring integration of afferent and efferent signaling with central coordination. Administration of HB-GAM either by direct injection into the trauma site or by intrathecal injection improves the climbing abilities in animals with cervical hemisection and in addition enhances the grip strength in animals with lateral hemicontusion without affecting the spontaneous locomotor activity. Recovery of sensory signaling in the sensorimotor cortex by HB-GAM to the level of sham-operated mice may contribute to the improvement of skilled locomotion requiring integration of spatiotemporal signals in the somatosensory cortex.Peer reviewe

Ocular dominance plasticity restored in adult mice after chronic fluoxetine treatment.

<p>(A) Experimental timeline: the first imaging session (IOS 0) was performed before fluoxetine treatment, the next (IOS 1) before monocular deprivation, and the last (IOS 2) after 1 week of monocular deprivation (MD). (B) Chronic 4-week fluoxetine treatment combined with 1-week MD caused a dramatic decline in ODI (from 0.16±0.04, n = 8 to -0.05±0.04, n = 7; ANOVA, P<0.01), whereas fluoxetine treatment without MD failed to produce an effect on OD (IOS 0: 0.16 ± 0.04; IOS 1: 0.16 ± 0.04; one-way ANOVA, P>0.05). (C) Representative IOS data in fluoxetine-treated and water-treated groups before and after monocular deprivation (color images–phase map of retinotopy; b/w images–magnitude map of intrinsic signal). Activity patch of the eye contralateral is normally larger; the ipsilateral patch is smaller. After fluoxetine treatment combined with MD, the patches were similar in size due to weakening of the response to the closed contralateral eye. In controls after monocular deprivation, the patch size remained unchanged. Scale bar, 1 mm.</p

Transparent skull preparation allows injections through the skull.

<p>(A) Images of the intact TS. Left: surface vasculature photograph. Right: representative optical imaging data (color images–phase map of retinotopy; b/w images–magnitude map of intrinsic signal). (B) Corresponding images after saline injection through the TS. The injection site is indicated with arrows. Scale bar, 1 mm. (C) IOS data for post-injection signal normalized to the signal before skull drilling and injection (two-way ANOVA (F _{1, 10} = 4.591; P>0,05 for the factor “Injection”).</p

Density distribution of a dust cloud in three-dimensional complex plasmas

We propose a method of determination of the dust particle spatial distribution in dust clouds that form in three-dimensional (3D) complex plasmas under microgravity conditions. The method utilizes the data obtained during the 3D scanning of a cloud, and it provides reasonably good accuracy. Based on this method, we investigate the particle density in a dust cloud realized in gas discharge plasma in the PK-3 Plus setup onboard the International Space Station. We find that the treated dust clouds are both anisotropic and inhomogeneous. One can isolate two regimes in which a stationary dust cloud can be observed. At low pressures, the particle density decreases monotonically with the increase of the distance from the discharge center; at higher pressures, the density distribution has a shallow minimum. Regardless of the regime, we detect a cusp of the distribution at the void boundary and a slowly varying density at larger distances (in the foot region). A theoretical interpretation of the obtained results is developed that leads to reasonable estimates of the densities for both the cusp and the foot. The modified ionization equation of state, which allows for violation of the local quasineutrality in the cusp region, predicts the spatial distributions of ion and electron densities to be measured in future experiments

Procedure for TS surgery in mice.

<p>(A-D). Schematic view of experimental preparations: (A) Dorsal view on the mouse head with important landmarks and indication of the incision area; (B) Skull after clearing with cyanoacrylate glue obtained increased transparency; (C) Head holder implantation scheme; (D) Nail polish and dental cement application scheme. (E-J). Photographs of the TS surgery main steps (see the protocol for detailed description): (E) Skull after scalp incision (step 8 in the protocol); (F) Cleaned bone surface (steps 9–10); (G) Skull covered with cyanoacrylate glue and acryl (steps 14–19); (H) Head holder mounting (step 24); (I) Head holder fixation with dental cement (step 26); (J) Nail polish added to the window (step 27). (K) Overview of a mouse after the TS surgery.</p