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Neuron parts identification question

  1. Apr 15, 2018 #1
  2. jcsd
  3. Apr 15, 2018 #2

    BillTre

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    It is a view through either a phase contrast or maybe a differential interference contrast microscope.
    The bright areas are "phase positive" where the interference is positive (making it very bright) rather than negative (darker than background).

    This is a cell culture so it is not easy to tell if the "string-looking-like parts" are axons (outgoing signal path from the neuron) or dendrites (incoming signal path). They are usually called neurites in cultured cells. Cultured cells are usually grown on a flat surface, which makes it easy to visualize all their parts at one time.
    It is a time-lapse movie which is why things are moving fast.

    I am guessing they are some kind of vesicles (membrane enclosed structures).
    They are moving fast because they are being "transported" probably along microtubules (pulled by little protein motors that latch on to the vesicle and move along the microtubule).
    Can't tell what their contents are, but that might have something to do with their brightness (due to how they interact with the light). Cells in culture are not always "normal" or an obvious member of a well defined cell type.

    The cell bodies (third paragraph) would usually be at the center of an array of neurites. Flat grey areas at the distal end of neurites are growth cones which put out a lot of small fine processes that "sense" their local environment and direct which way the neurite will be further extended. Growth cones and their fine processes contain a lot of actin. Actin can also move things around, but not so much in the neurites.
     
  4. Apr 15, 2018 #3

    Fervent Freyja

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    Points of electrical activity?
     
  5. Apr 15, 2018 #4

    BillTre

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    Probably not.
    Here and here are a couple of examples of electrical activity in neurons that is visualized with voltage sensitive dyes.
    The first one also shows two traces, one of the light intensity and the other an electrode measured voltage potential, but it does not indicate where in the picture the electrode is.
     
  6. Apr 15, 2018 #5

    Fervent Freyja

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    Phase contrast, you were right.
     
  7. Apr 15, 2018 #6
    Thanks.
    I guess this question was too advanced for me :sorry:. But there's an answer I hope others can understand.

    What I understood:
    • Neurons have two different physical paths: one for incoming traffic and one for outgoing traffic.
    • There are sacks called vesicles. That is the little rounded thing containing the little glowing things in the image.
    • Because this is a culture, it may not represent reality accurately.
    What I didn't understood:
    • Protein motors?
    • Actin? I looked at the Wikipedia article, but this is... this is too advanced.
     
  8. Apr 15, 2018 #7

    BillTre

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    There are many kinds of protein motors.
    They are encoded by genes and act as nanomachines that can move around in some way. They provide the physical motive forces in cells.
    Protein motors, in this case dynenin, move along the microtubules (which act like railroad tracks), dragging the vesicles along with them.
    Actin forms filaments in muscle, which myosin also moves along. This is what powers muscle contraction. There are of actin and myosin any varieties in vertebrates which are turned on in different cells and do additional other things.
     
  9. Apr 15, 2018 #8

    Fervent Freyja

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    Did anyone ever trace this video back to the originators or source of publication? I didn't find them when I tried.
     
  10. Apr 15, 2018 #9
    What video?
     
  11. Apr 15, 2018 #10

    Fervent Freyja

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    That the OP is questioning.
     
  12. Apr 15, 2018 #11

    BillTre

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    The original video is a pretty standard looking thing.
    There are many equivalent videos to that.
     
  13. Apr 15, 2018 #12
    Oh. That video. Lemme check... Loading....

    Aha, found it! If you hadn't asked I wouldn't have thought about tracing its origins. It's:

    In the description of the video is a description that says that the bright spot is a nucleus. Now I'm glad I asked this question :biggrin:. I mean, it didn't cross my mind to look for the original. Thanks.

    Edit: Although the video description is not using a certain tone. I felt the tone of the description like that of someone assuming. That's my perception.
     
  14. Apr 15, 2018 #13

    BillTre

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    If all those bright spots are nuclei there would have to be a lot of small cells around.
    Guess its possible.
     
  15. Apr 15, 2018 #14

    Fervent Freyja

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    Since phase contrast was used, I'm not sure if we could even visually pinloint what was nuclei or not! It would be different if the visual markers of "bright spots" had been altered with dyes to begin with, but I'm not sure after realizing it was phase constrast. Finding the original study and the methods used other than phase constrast might clue us on to what is happening in the video!
     
  16. Apr 15, 2018 #15

    Fervent Freyja

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    There is an impression of dyes being used, to me at least.
     
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