Carmichael’s Concise Review Coming Events


Due to COVID-19, please check to see if the listed events have been postponed or cancelled.


2021


RMS Event: International Microscopy Focus Lecture Series “A brief history of the impact of Transmission Electron Microscopy on Materials Science” Professor Sir Peter Hirsch


October 5, 2021 Virtual


www.rms.org.uk/rms-event-calendar/2021- events/imfls-professor-sir-peter-hirsch.html


RMS Event: Imaging ONEWORLD “Finding the needle in the haystack with 3D correlative light and electron microscopy” Dr. Lucy Collinson


October 11, 2021 Virtual


www.rms.org.uk/rms-event-calendar/2021-events/ imaging-oneworld-finding-the-needle.html


flowcytometryUK 2021 (formerly One Day flowcytometryUK) November 17–18, 2021


Virtual www.rms.org.uk/rms-event-calendar/2021- events/flowcytometryuk-2021.html


2021 Gordon Research Conference on Three-Dimensional Electron Microscopy


October 31–November 5, 2021 Waterville Valley, NH


www.grc.org/three-dimensional-electron- microscopy-conference/2021


Neuroscience 2021 (Hybrid) November 8–11, 2021 (virtual) November 13–16, 2021 (in person)


Chicago, IL and Virtual http://www.sfn.org/meetings/neuroscience-2021


2021 MRS Fall Meeting & Exhibit (Hybrid) November 29–December 2, 2021 (in person) December 6–8, 2021 (virtual)


Boston, MA and Virtual www.mrs.org/fall2021


Cell Bio Virtual 2021 December 1–10, 2021


Virtual https://www.ascb.org/cellbio2021


2022 Microscopy & Microanalysis 2022 July 31–August 4, 2022


Portland, OR www.microscopy.org/events/future.cfm


2023 Microscopy & Microanalysis 2023 July 24–28, 2023


Minneapolis, MN www.microscopy.org/events/future.cfm


2024 Microscopy & Microanalysis 2024


July 28–August 1, 2024 Cleveland, OH www.microscopy.org/events/future.cfm


8


Window to the Brain Allows Observation of Cellular Neural Activity


Stephen W. Carmichael Mayo Clinic, Rochester, MN 55905 carmichael.stephen@mayo.edu


Calcium indicators that are genetically encoded, along with transgenic


approaches to broadly express these indicators in the mammalian brain in a cell type-specific fashion, have enabled simultaneous imaging of multiple cortical regions. Studies have revealed how neural activity across several regions are coordinated in a variety of brain states and behaviors. For numerous technical reasons these studies have been done mostly in mice while their heads are immobilized. Clever manipulations allow the brain to be imaged during some behaviors, but these behaviors cannot be considered normal. Several head-mounted miniaturized imaging devices have been developed that allow resolution at the cellular level in freely moving animals but only from small fields of view (FOV). A head-mounted imaging device with a relatively large FOV has recently been engineered for useful imaging in rats, but there is a much larger array of genetic tools available for mice than for rats. In an elegant study, Mathew Rynes, Daniel Surinach, and others working in the laboratory of Suhasa Kodandaramaiah introduced the mini- mScope, a miniature fluorescence microscope capable of simultaneously imaging an 8 × 10 mm2


FOV with resolutions ranging from about 39 to


56 μm. Tis imaging device could be positioned on the head of a freely moving mouse. Rynes and Surinach, who co-led the effort, specified three criteria that


constrained the design of the mini-mScope. First, to permit free behavior and mobility, the overall weight of the device needed to be less than 4 grams, which is about 15% of the body weight of a mouse. Second, the device needed to image most of the dorsal cortex of the mouse brain. Tird, the imaging resolution needed to be sufficient to provide useful images of calcium activity dynamics across the FOV. Briefly, this was accomplished by first performing a large craniotomy over the dorsal cortex of an anesthetized animal, then covering the opening with a 3D-printed transparent shell that was glued in place. Magnets were placed to provide attachment of the mini-mScope before experiments were conducted. Tree blue light-emitting diodes (LEDs) and one green LED with appropriate filters were mated with a biconvex lens and a complementary metal oxide semiconductor (CMOS) sensor. Te device weighed 3.8 g and allowed a repertoire of behaviors, including grooming and rearing, indicating that the mice were relatively comfortable with the device in place. Since a single biconvex lens was used to image a convex surface, not all of the surface was in focus, and the optical resolution varied within the FOV. For some experiments, the team used a transgenic mouse (Ty1-GCaMP6f),


which expresses fluorescent reporters of calcium activity in excitatory neurons. Several studies demonstrated that


the mini-mScope acquired calcium


signals that are comparable to a conventional epifluorescence microscope. Specific stimuli (brief vibrations to a hind limb and flashes of white light in one eye [Figures 1 and 2]) evoked a robust increase in calcium activity in the


doi:10.1017/S1551929521001127 2021 September


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