Electron Tomography and Correlative Approaches in Platelet Studies

Blood platelets play a central role in the arrest of bleeding and the development of thrombosis. Unraveling the complex processes of platelet biogenesis from megakaryocytes, platelet adhesion, aggregation, and secretory responses are important topics in the field of hemostasis and thrombosis. Analysis of the ultrastructural changes that occur during these processes is essential for understanding the rapid membrane dynamics and has contributed substantially to our present knowledge of platelet formation and functioning. Recent developments in real-time imaging, correlative light and electron microscopy imaging (CLEM), and 3D (cryo) electron microscopy and tomography offer exciting opportunities to improve studies of the platelet adhesive responses and secretion at the ultrastructural level in a close to native environment. In this chapter we discuss and illustrate cryo preparation techniques (high-pressure freezing, vitrification), correlative LM and EM workflows, and 3D cryo-electron tomography that we apply in our current research projects

Electron Tomography and Correlative Approaches in Platelet Studies

Blood platelets play a central role in the arrest of bleeding and the development of thrombosis. Unraveling the complex processes of platelet biogenesis from megakaryocytes, platelet adhesion, aggregation, and secretory responses are important topics in the field of hemostasis and thrombosis. Analysis of the ultrastructural changes that occur during these processes is essential for understanding the rapid membrane dynamics and has contributed substantially to our present knowledge of platelet formation and functioning. Recent developments in real-time imaging, correlative light and electron microscopy imaging (CLEM), and 3D (cryo) electron microscopy and tomography offer exciting opportunities to improve studies of the platelet adhesive responses and secretion at the ultrastructural level in a close to native environment. In this chapter we discuss and illustrate cryo preparation techniques (high-pressure freezing, vitrification), correlative LM and EM workflows, and 3D cryo-electron tomography that we apply in our current research projects

Perceptual Information Integration: Hypothetical Role of Astrocytes

In perceptual processes, signals carrying information about a stimulus are transmitted through multiple processing lines to populations of receptive neurons and thalamocortical circuits, leading to the formation of a spatial ensemble of local field potentials. This paper addresses the problem of how the brain integrates patterns embodied in local fields to (re) construct the stimulus in a conscious episode. Four examples of human perception are given to illustrate the requirements of the integrative process. Considering the strategic position of astrocytes, mediating somatic signals carried by blood flow and information carried by the neuronal network, as well as their intrinsic information processing capabilities, these cells seem ideally placed to integrate spatially distributed information. The amplitude-modulated calcium waveform in astrocytes is a multiscale phenomenon, simultaneously operating on temporal scales of milliseconds and seconds, as well as in micro and macro spatial scales. Oscillatory synchrony, constructive wave interference and communication by means of ionic antennae are proposed to constitute a neuro-astroglial self-organizing mechanism capable of perceptual integration and adding a feeling-like quality to information content. A proposal for constructing an artificial astrocyte is described, which would be capable of testing the hypothesis of astrocytic information integration made earlier.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)São Paulo State Univ, UNESP, Inst Biosci, São Paulo, BrazilSão Paulo State Univ, UNESP, Inst Biosci, São Paulo, Brazi