THE COMPANYFemtonics is one of the most dynamically expanding manufacturers of two-photon laser scanning microscopy. We make unique, custom designed 2D systems and as a pioneer we have introduced real-time 3D imaging technology to the market. By our modularity, each Femtonics microscope fits the researcher’s own needs and it can suit a wide variety of biological applications. Our other advantage is our multidisciplinary team which continually enhance and confirm the scientific applicability of our new developments.
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Microglia are the main immune cells of the brain and contribute to common brain diseases. However, it is unclear how microglia influence neuronal activity and survival in the injured brain in vivo. Here we develop a precisely controlled model of brain injury induced by cerebral ischaemia combined with fast in vivo two-photon calcium imaging and selective microglial manipulation. We show that selective elimination of microglia leads to a striking, 60% increase in infarct size, which is reversed by microglial repopulation. Microglia-mediated protection includes reduction of excitotoxic injury, since an absence of microglia leads to dysregulated neuronal calcium responses, calcium overload and increased neuronal death. Furthermore, the incidence of spreading depolarization (SD) is markedly reduced in the absence of microglia. Thus, microglia are involved in changes in neuronal network activity and SD after brain injury in vivo that could have important implications for common brain diseases.
This paper published in Nature Methods demonstrates the capabilities of the Femto3D-AO microscope developed by Gergely Katona et al. The acousto-optic two photon microscope is equipped with an electrically tunable lens focusing the excitation point very fast to any locations in 3D under the objective without mechanical restrictions. Scanning can be done in a near-cubic-millimeter range with high spatial and sub-millisecond temporal resolution. The paper describes two scanning strategies implemented on the system: continuous 3D trajectory scanning allows to precisely follow neural processes over several hundred micrometers to image the propagation of action potentials or dendritic spikes. Random access scanning mode supports imaging evoked or spontaneous calcium-activity in hundreds of neurons simultaneously in vivo.
Roska’s lab (FMI, Basel) mapped the presynaptic network of a V1 orientation selective neuron by using a single-cell-iniciated, monosynaptically restricted, retrograde transsynaptic network tracing with rabies viruses. The labeled neurons expressed GCaMP6s, which allowed to image, in vivo, the visual motion-evoked activity of individual layer 2/3 pyramidal neurons and their whole presynaptic networks across layers in the primary visual cortex of the mice. For the measurement of this large number of neurons scattered across the width of the cortex they used a Femto3D-AO microscope. They found that the neurons within each layer exhibited similar motion direction preferences, forming layer-specific functional modules. In one third of the networks, the layer modules were locked to the direction preference of the postsynaptic neuron, whereas for other networks the direction preference varied by layer.