Purinergic Signaling Controls Spontaneous Activity in the Auditory System throughout Early Development

Spontaneous bursts of electrical activity in the developing auditory system arise within the cochlea before hearing onset and propagate through future sound-processing circuits of the brain to promote maturation of auditory neurons. Studies in isolated cochleae revealed that this intrinsically generated activity is initiated by ATP release from inner supporting cells (ISCs), resulting in activation of purinergic autoreceptors, K+ efflux, and subsequent depolarization of inner hair cells. However, it is unknown when this activity emerges or whether different mechanisms induce activity during distinct stages of development. Here we show that spontaneous electrical activity in mouse cochlea from both sexes emerges within ISCs during the late embryonic period, preceding the onset of spontaneous correlated activity in inner hair cells and spiral ganglion neurons, which begins at birth and follows a base to apex developmental gradient. At all developmental ages, pharmacological inhibition of P2Y1 purinergic receptors dramatically reduced spontaneous activity in these three cell types. Moreover, in vivo imaging within the inferior colliculus revealed that auditory neurons within future isofrequency zones exhibit coordinated neural activity at birth. The frequency of these discrete bursts increased progressively during the postnatal prehearing period yet remained dependent on P2RY1. Analysis of mice with disrupted cholinergic signaling in the cochlea indicate that this efferent input modulates, rather than initiates, spontaneous activity before hearing onset. Thus, the auditory system uses a consistent mechanism involving ATP release from ISCs and activation of P2RY1 autoreceptors to elicit coordinated excitation of neurons that will process similar frequencies of sound.Fil: Babola, Travis A.. University Johns Hopkins; Estados UnidosFil: Li, Sally. University Johns Hopkins; Estados UnidosFil: Wang, Zhirong. University Of Georgetown; Estados UnidosFil: Kersbergen, Calvin J.. University Johns Hopkins; Estados UnidosFil: Elgoyhen, Ana Belen. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Coate, Thomas M.. University Johns Hopkins; Estados UnidosFil: Bergles, Dwight E.. University Johns Hopkins; Estados Unido

Traitements immunosuppresseurs en transplantation rénale.

La transplantation rénale tient une place fondamentale dans la prise en charge de l’insuffisance rénale terminale, elle améliore la qualité de vie et la survie des patients comparativement à la dialyse. Cela est rendu possible grâce aux progrès considérables d’immunosuppression. Longtemps, l’objectif principal de l’immunosuppression a été de diminuer l’incidence du rejet aigu cellulaire en inhibant la fonction des lymphocytes T et lymphocyte B. Les épisodes de rejets aigus prédisposent au rejet chronique et à la perte du greffon au long cours. Dans ce travail nous avons décrit, l’insuffisance rénale terminale qui indique la greffe, le déroulement de la réponse allo-immune par les différentes voies de signalisation ainsi que la classification des différentes thérapeutiques immunosuppressives selon leurs sites d’action. Cependant, les traitements immunosuppresseurs présentent certaines complications immunologiques et non immunologiques, conduisant à une mauvaise fonction rénale, réduisant la survie du greffon et la survie du patient. A cet effet, différentes stratégies ont été adoptées dans le but de préserver la fonction rénale. Parmi les traitements actuellement disponibles, on associe classiquement : un inhibiteur de la calcineurine, un antiprolifératif avec ou sans corticoïde ou alternativement un inhibiteur de signal de prolifération. Aussi pendant la période initiale de la greffe, un traitement d’induction par des globulines anti-lymphocytaires polyclonales ou anticorps monoclonaux anti-récepteurs de l’IL2 est utilisé. De ces stratégies immunosuppressives, les protocoles d’immunosuppression ont été mis au point pour mieux répondre aux besoins des patients. Ce qui permet d’envisager la perspective d’une individualisation du traitement immunosuppresseur

Cochlear purinergic receptors contribute to in vivo spontaneous activity in the developing auditory system

Neurons in the developing auditory system exhibit spontaneous bursts of activity before hearing onset. How this intrinsically generated activity influences development remains uncertain, because few mechanistic studies have been performed in vivo. In this thesis, we use macroscopic calcium imaging in unanesthetized mice to show that neurons responsible for processing similar frequencies of sound exhibit highly synchronized activity throughout the auditory system during this critical phase of development. Spontaneous activity normally requires synaptic excitation of spiral ganglion neurons (SGNs). Unexpectedly, tonotopic spontaneous activity was preserved in a mouse model of deafness in which glutamate release from hair cells is abolished. SGNs in these mice exhibited enhanced excitability, enabling direct neuronal excitation by supporting cell-induced potassium transients. These results indicate that homeostatic mechanisms maintain spontaneous activity before hearing onset, which may help preserve the auditory nerve and promote maturation of at least some aspects of sound processing circuits in the brain, thereby improving the performance of cochlear implants and the outcome of therapies designed to correct mutations causing inherited deafness. We also identified unique genetic profiles for three subtypes of SGNs that innervate inner hair cells, consistent with electrophysiologically distinct subtypes observed in adults. Additionally, in mouse models of deafness we found disruptions in activity patterns before hearing onset that were concurrent with failures of subtype to specify, suggesting this early activity is critical for SGN maturation. Ultimately, we want to know how maturation defects alter sound processing, but these mice are deaf, making these experiments impossible. However, we have recently identified another key component, the purinergic P2Y1 receptor, responsible for generating intrinsically generated activity within the cochlea. Mice lacking this receptor have normal hearing thresholds. We predict that removing this receptor will alter neuron specification and maturation, leading to deficits in circuit refinement and auditory processing. Taken together, these studies have allowed visualization of large-scale neural activity before hearing begins and revealed a critical role for precisely patterned spontaneous activity in circuit maturation. Understanding this activity and how it instructs cellular development may provide a basis for understanding complex auditory processing disorders in children, whose causes remain unknown and underexplored

Cochlear purinergic receptors contribute to in vivo spontaneous activity in the developing auditory system

Neurons in the developing auditory system exhibit spontaneous bursts of activity before hearing onset. How this intrinsically generated activity influences development remains uncertain, because few mechanistic studies have been performed in vivo. In this thesis, we use macroscopic calcium imaging in unanesthetized mice to show that neurons responsible for processing similar frequencies of sound exhibit highly synchronized activity throughout the auditory system during this critical phase of development. Spontaneous activity normally requires synaptic excitation of spiral ganglion neurons (SGNs). Unexpectedly, tonotopic spontaneous activity was preserved in a mouse model of deafness in which glutamate release from hair cells is abolished. SGNs in these mice exhibited enhanced excitability, enabling direct neuronal excitation by supporting cell-induced potassium transients. These results indicate that homeostatic mechanisms maintain spontaneous activity before hearing onset, which may help preserve the auditory nerve and promote maturation of at least some aspects of sound processing circuits in the brain, thereby improving the performance of cochlear implants and the outcome of therapies designed to correct mutations causing inherited deafness. We also identified unique genetic profiles for three subtypes of SGNs that innervate inner hair cells, consistent with electrophysiologically distinct subtypes observed in adults. Additionally, in mouse models of deafness we found disruptions in activity patterns before hearing onset that were concurrent with failures of subtype to specify, suggesting this early activity is critical for SGN maturation. Ultimately, we want to know how maturation defects alter sound processing, but these mice are deaf, making these experiments impossible. However, we have recently identified another key component, the purinergic P2Y1 receptor, responsible for generating intrinsically generated activity within the cochlea. Mice lacking this receptor have normal hearing thresholds. We predict that removing this receptor will alter neuron specification and maturation, leading to deficits in circuit refinement and auditory processing. Taken together, these studies have allowed visualization of large-scale neural activity before hearing begins and revealed a critical role for precisely patterned spontaneous activity in circuit maturation. Understanding this activity and how it instructs cellular development may provide a basis for understanding complex auditory processing disorders in children, whose causes remain unknown and underexplored

Moment resisting glulam frames with long self-tapping screws

Hovedoppgaven i prosjektet har vært å arbeide videre med den tidligere opparbeidete rapporten gjennomført av Bjørnfot et al. (2015) og å teste de forskjellige løsninger i laben. Det var et ønske fra utbyggeren å benytte treverk i størst mulig grad. Dette har resultert i en problemstilling for utforming av momentstive forbindelser mellom tresøyler og limtrebjelker. Disse danner hoved-bæresystemet til deres boliger, slik at man i størst mulig grad kan unngå plasskrevende avstivningssystemer mellom aksene. Momentstive trerammer danner store frie arealer inne i boligene med ev. store glassflater for utsikt og lysforhold. Det finnes mange muligheter for utforming av slike knutepunkter og mange mulige geometrier, men oppgavens omfang har blitt begrenset til noen få interessante løsninger som allerede har vært drøftet i et tidligere oppdrag utført av Bjørnfot et al. (2015). Limtrerammene er hovedsakelig tenkt til å være et alternativ til tradisjonell avstivning med veggskiver. En del av oppgaven har omhandlet dimensjonering av limtrerammene etter NS-EN 1995-1-1 2008. Den andre delen av oppgaven har gått ut på testing av de forskjellige teoretiske løsninger, mens den tredje delen handler om sammenligning av testresultatene med de teoretisk utførte beregninger. Beregninger er blitt utført i alle tilfeller. Disse inkluderer lastvirkning på søylen, takkonstruksjon og fundament. Beregninger av kapasiteter i de forskjellige knutepunktstilfellene er blitt gjort i PTC Mathcad og Excel iht. respektive Eurokoder og litteratur. Det ble valgt å vurdere to forskjellige knutepunkter i limtrerammer: knutepunkt mellom søyle og limtrebjelke over 1. etasje og knutepunkt mellom søyle og bjelke over 2. etasje. Det er vurdert forskjellige aspekter rundt knutepunktene, slike som konstruksjonssikkerhet og utførelse. Gjennomførte beregninger viser at det er mulig å lage momentstive forbindelser ved bruk av limtre for prosjekter omhandlende småhus. Testgjennomføring har ikke bekreftet den teoretiske modellen, noe som åpner veien til videre forskning.The main task of this project has been to continue to work on a previously prepared report carried out by Bjørnfot et al. (2015) and test the various solutions in the lab. It was a request from the developer to use wood as much as possible by using glulam frames as main structure in their buildings. This has resulted in a problem regarding the design of moment resistant connections between glulam columns and beams that form the main bearing system of their catalogue houses and help them to avoid advanced stiffening systems between the axes. Thick wooden frames form large free areas inside the houses and give possibilities for large glass surfaces for the view and light conditions. There are many possibilities for the design of such frames and many possible geometries, but the group has limited the scope to a few interesting solutions that have already been discussed in a previous assignment. The glulam frames are principally intended to be an alternative to traditional stiffening with walls. The first part of the task has been designing glulam frames according to scientific publications. The second part of the assignment was testing of the different theoretical solutions. The group came across several execution problems such as predrilling angle or use of powerful machines to set wooden frames together. This has resulted in small failures while execution. The final part has been to evaluate the calculation model and the real test results. Calculations have been made in all cases. Calculations of capacities in the various joints have been made in PTC Mathcad and Excel according to respective Eurocodes and scientific literature. Two different nodes have been considered: the joint between the pillar and the glulam beam above the 1st floor and the joint between the column and the beam above the 2nd floor. Different aspects of the frame joints such as construction safety, design and execution on site were considered. Eight different test sets with different screw lengths and inclination angles were chosen. Each test set consisted of three frame corners. Completed calculations confirm that it is possible to use glulam and long self-tapping screws to make moment resistant connections for the structural systems of small houses. However, test results cannot be directly compared with theoretical calculations.M-B

Preservation of developmental spontaneous activity enables early auditory system maturation in deaf mice.

Intrinsically generated neural activity propagates through the developing auditory system to promote maturation and refinement of sound processing circuits prior to hearing onset. This early patterned activity is induced by non-sensory supporting cells in the organ of Corti, which are highly interconnected through gap junctions containing connexin 26 (Gjb2). Although loss of function mutations in Gjb2 impair cochlear development and are the most common cause of congenital deafness, it is not known if these variants disrupt spontaneous activity and the developmental trajectory of sound processing circuits in the brain. Here, we show in a new mouse model of Gjb2-mediated congenital deafness that cochlear supporting cells adjacent to inner hair cells (IHCs) unexpectedly retain intercellular coupling and the capacity to generate spontaneous activity, exhibiting only modest deficits prior to hearing onset. Supporting cells lacking Gjb2 elicited coordinated activation of IHCs, leading to coincident bursts of activity in central auditory neurons that will later process similar frequencies of sound. Despite alterations in the structure of the sensory epithelium, hair cells within the cochlea of Gjb2-deficient mice were intact and central auditory neurons could be activated within appropriate tonotopic domains by loud sounds at hearing onset, indicating that early maturation and refinement of auditory circuits was preserved. Only after cessation of spontaneous activity following hearing onset did progressive hair cell degeneration and enhanced auditory neuron excitability manifest. This preservation of cochlear spontaneous neural activity in the absence of connexin 26 may increase the effectiveness of early therapeutic interventions to restore hearing