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BIO 304
Mar 28, 2023
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o Cajal's influence If you can understand and visualize neurons then you can understand information flow in the nervous system Even today scientists are invested in improving imaging technologies o Connectome of the nervous system provides a framework of possibility of information flow; but every synapse can be modulated (by hormones, chemicals, etc.) - need to understand the dynamic electrical activity to really understand things From the golgi technique and beyond: advances in imaging neurons and neural circuits o Advances in neural imaging: Fluorescent dyes Fluorescent dyes have electrons that absorb light and emit fluorescence as they drop back down to lower energy orbitals Ex. Lucifer yellow (used commonly in nervous system tissue) Many carbon bonds allows electrons to be bumped up Has spectrum of wavelengths that the photon is excited Around 425nm blue light (absorbing photons) Rightward shift where the light it emits is at 525 nm (greenish yellow) Unlike golgi stain, dyes can be used to label live neurons Passing voltage pulses through electrode pushes dye into neuron; can tell us where axons project Some dyes can cross gap junctions - why would that be useful? A lot of neurons can be connected through gap junctions/electrical coupling; tells whether two neurons are electrically connected to one another Some dyes can zoom into sub-cellular structures o MitoTracker: labels mitochondria red o LysoTracker: labels lysosome (where things in cell are broken down enzymatically) o Hoechst and DAPI: labels nucleus blue You can conjugate dyes to other molecules o Toxins such as phallacidin can be fluorescently dyed and when it binds to F-actin it will be labelled green o Advances in neural imaging: Protein and mRNA localization Each cell expresses genes differently; specific genes certain cell types use uniquely - can be used to identify specific cells Referred to as marker gene; mark cell types of interest Marker genes can be detected at the mRNA level In situ hybridization: let's you visualize mRNA in the cell Involves using antisense RNA molecule that complements target mRNA - now you can see at the
molecular level which cells are expressing the marker gene
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