Neuroinflammation is critically required as a regenerative cue of the adult zebrafish retina // Exploring the Mechanical Function of Cephalopod Septa

Date

May 25, 2018

Time

4:00 PM - 5:00 PM

Speaker

Michael Brand, Oliver Bludau // Igor Zlotnikov, Robert Lemanis

Affiliation

Predoc; Postdoc

Language

en

Main Topic

Biologie

Other Topics

Biologie, Medizin

Description

Abstract 1st talk Chronic inflammatory retinal diseases often cause neuronal loss in mammalian vertebrates. In contrast to mammals, neuronal inflammation in zebrafish is crucially important and sufficient to stimulate a regenerative response after traumatic brain injury. We have tested the hypothesis that the immune system contributes to adult retina regeneration in zebrafish. Leukocyte activation upon photoreceptor ablation was monitored using immunohistochemistry and transgenic reporter lines. Further, to investigate the role of the immune system during retina regeneration, we performed immunosuppression using dexamethasone in combination with sterile photoreceptor ablation. To elucidate whether stimulation of the immune system in the absence of lesion is sufficient to induce a regenerative response, we performed intravitreal injections of zymosan and flagellin. Several results show an activation of the immune system after light lesion such as significant accumulation of leukocytes at the lesion site, recruitment of neutrophils and morphological changes of microglia. Under immunosuppression, we observe a lower activation of the immune cells, significant reduction of cycling Müller glia as well as a striking decrease of overall proliferation. Conversely, immune stimulation in the absence of lesion resulted in a robust proliferative response and the up-regulation of regenerative marker genes in clusters of neuronal precursor cells. We conclude that neuronal inflammation occurs in the zebrafish retina following photoreceptor ablation. and is essential to initiate successful regeneration of photoreceptors. Abstract 2nd talk Ammonites are a group of extinct cephalopods whose long clade age, global distribution, and morphological diversity underlie their study in the fields of stratigraphy, ecology, evolutionary dynamics, extinction selectivity, and constructional morphology. However some fundamental aspects of their biology, such as habitat depth and mode of life, are still poorly understood. A prime example is the function of the complex septa unique to ammonites. The classical hypothesis states the increased complexity of these structures improved the resistance of the shell to implosion due to hydrostatic pressure, thus forms with more complex septa could inhabit deeper waters. Evidence of this mechanical function is limited to theoretical models, the results of which directly have contradicted each other. We circumvent these problems by combining high-resolution computed tomography, nanoindentation, and finite element analysis to test different septal morphologies against a hydrostatic loading. Combining computational mechanics and material testing permits the creation of more realistic models than were previously possible. Contrary to the expected results, shells with more complex septa seem to be weaker under hydrostatic loading, challenging the traditional interpretation of the function of septal complexity in ammonites.

Links

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Last modified: May 25, 2018, 9:48:08 AM