Tighten Your Belt : Cells that line the surfaces and cavities of  your body are packed tightly together, like bricks…

Tighten Your Belt : Cells that line the surfaces and cavities of  your body are packed tightly together, like bricks in a wall. Your skin, the lining of your mouth or stomach, or blood vessels are springy..pulling back when stretched. How do they stay in shape?

⇛Scientists have discovered that each cell has a tiny belt that acts like a rubber band. Cables, made of actin filaments (in red) are crosslinked and connected together by alpha actinin (blue). The overlapping fluorescent signals color them purple in the image. Motor proteins, known as myosin (green), power this belt and keep it taut. They do this by pulling on the interdigitating cables so that they slide past each other. A variation of this same assembly makes your muscles contract!

⇛Notice the beautiful symmetry in the arrangement of these molecules all around the cell. Even the junctions, where three cells meet, maintains its ordered arrangement of cables and motors. This brought to mind the poet Blake (1757–1827):

“Tiger, tiger, burning bright

 In the forests of the night,

 What immortal hand or eye

 Dare frame thy fearful symmetry?”

⇛Reference: Ebrahim et al., 2013 NMII Forms a Contractile Transcellular Sarcomeric Network to Regulate Apical Cell Junctions and Tissue Geometry. Current Biology ▶ http://goo.gl/Pwp7F


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42 Responses to Tighten Your Belt : Cells that line the surfaces and cavities of  your body are packed tightly together, like bricks…

  1. Now I feel old and wrinkly… < winking >  ;-{))

  2. Jim Carver says:

    Wow, that is really cool. It’s funny…but I was just wondering about it the other day.

    Nice fix. 🙂

  3. Rajini Rao says:

    This is not the only trick that cells use to stay elastic. There are springy fibers known as elastin and collagen inside cells, that help too.

  4. Can it be true that symmetrical configurations expend the least amount of energy. I have often wondered why airplanes always travel a corridor and our highways are boring straight lines. Is nature predisposed to the principal of least action? If true, why are there mutations? And you brought to mind Penrose tiles, and logarithmic curves and Fibonacci sequences. Where is the symmetry in them?

  5. To me the great poet to expound symmetry was Blake who wrote:

    TO see a world in a grain of sand,

    And a heaven in a wild flower,

    Hold infinity in the palm of your hand,

    And eternity in an hour.

  6. Rajini Rao says:

    In the case of airplanes and highways, I’m guessing they are the shortest paths combined with the least resistance (wind, forests). Similarly, the symmetry in biology also arises from optimizing various stresses and forces. Did you see the article on the theory of bee hive cells being hexagons, Suhail Manzoor ? Let me find it for you.

  7. Rajini Rao says:

    Suhail Manzoor , that’s actually my favorite Blake quote. But I have a special fondness for Tyger because I had to memorize it in school 🙂

    Here is the theory about hexagonal bee hive cells: http://www.npr.org/blogs/krulwich/2013/05/13/183704091/what-is-it-about-bees-and-hexagons

  8. Jim Carver says:

    Rajini Rao So in plants would that be analogous to cellulose and lignin as a structural building block? 

  9. Rajini Rao says:

    Jim Carver , similar in shape but the building blocks of celllulose and lignin are not so elastic. Myosin is actually a motor…it rides on the highways of actin, pulling the cables together and keeping the belt taut. It burns ATP so it is an active energy burning process.

  10. No I have not Rajini Rao let me ask the Oracle Google. From a political perspective I believe its incumbent Upton us not too follow the principle pf least action for it leads to stasis and stagnation. We should aim for constant and continual mutation. But my position is untenable. Alas the human species prefers to be lazy 🙂

  11. Rajini Rao says:

    Hmm… Suhail Manzoor , I don’t think of biolgical principles of least action. Far from it. Rather, its more of a continual fine-tuning, tinkering and adjusting to get things just right. As the environmental demands change, biological systems adapt in a never-ending effort to optimize energy expenditure and efficiency.

  12. In what distant deeps or skies          

    Burnt the fire of thine eyes?  

    On what wings dare he aspire?  

    What the hand dare seize the fire?


  13. Cindy Brown says:

    tyger tyger burning bright.  not the usual quoted verses, though 😉

  14. Rajini Rao says:

    Jose M. G. Guerreiro , I also like:

    When the stars threw down their spears,

     And water’d heaven with their tears,

     Did He smile His work to see?

     Did He who made the lamb make thee?

  15. Rajini Rao says:

    Cindy Brown , the opening lines are quoted in my post 🙂 Hope you like the poem as much as I do!

  16. Rajini Rao , the honeycomb theory is so apt to your post. Natural selection does organise around the principle of least action I think. Look at our cities and our societies and cells and entire organism, indeed, I see the entire universe seeking to minimise the energy budget. And it does so through natural selection . thanks for the link. Hexagons rule 🙂 

  17. Cindy Brown says:

    I am going to hang my head in shame that I skimmed it quickly enough to miss that!



    (And obviously if I recognized the poem from the more obscure lines, I like it a lot! 🙂 )

  18. Rajini Rao says:

    I thought you would enjoy it, Suhail Manzoor 🙂

  19. Rajini Rao says:

    Let’s blame Google for making the pictures so big and hiding the text, Cindy Brown 😀

  20. Cindy Brown says:

    Works for me! 😀

  21. Here is a packing order akoin to cells at a cosmological scale Galaxy filament supercluster complexes

  22. Bill Carter says:

    Wonderful post Rajini Rao – As you know, I’d love to see engineering materials do something similar: Actively maintain structure through adjustment of mass and stress. Someday, perhaps!

  23. The hardest thing to get around Rajini Rao is the feedback look in evolution. There are no subject and object in biology, everything is connected and influences in both direction . I keep forgetting that 🙂 

  24. Rajini Rao says:

    Wow, that galaxy supercluster could easily be mistaken for a network of collagen fibers inside a cell: http://goo.gl/9ih9q

  25. Biology is poetry! Take that you particle physicists 😉

  26. Rajini Rao says:

    William Carter  you do a pretty good job in building on nature with the nanomaterials you come up with 🙂

  27. The symmetry between the cosmic and the living makes me want to break into a song and dance at times.

  28. Rajini Rao says:

    The Cell Biology Society teamed up with astronomers to come up with a series called Cellular or Celestial? I guessed most of them wrong 😛

  29. Rajini Rao says:

    Hehe, Patrick Armstrong , most of us need a motorized belt to keep our not-so-slim waistlines from falling out as well.

  30. How to we keep that belt tightened Rajini Rao I am agreeing with William McGarvey the sagging is beginning despite having muscles 🙂   Nourishment for the cells to keep the elasticity (or is that just fate)  😦

  31. Mary T says:

    This makes me smile.  Great post, as always, Rajini Rao ~

  32. Norman M. says:

    Now, this is scientific understanding.

  33. Mary T says:

    PS:  Love the poem :-).

  34. Peying Fong says:

    Rajini–check out Segal et al 1996 Am J Physiol Cell Physiol  270: C1843-C1863…images of “snow man” cells prepared from salamander (Ambystoma) renal proximal tubules…they use descriptive terms such as “belt”, “waistband”, “hoop of actin”/”actin-rich hoop”.  The apparent advance was that the reported procedure yields isolated cells which retain their polarity and therefore are suitable for patch-clamping within identifiable membrane domains.

  35. Azlin Bloor says:

    Hey Rajini Rao, have just added you to my circle because I am so impressed with all your posts and would like to see them more! 

  36. Interesting post.

    Is there a video which shows the build process of these structures as a time laps video?

    Rajini Rao It would be interesting to know how these structures get built up.

  37. In molecular biology the simmetry is present. For example, the palindromic sequence in DNA or RNA structure has a true axis of simmetry:



    or repeated sequence as the mirror image:



  38. Rajini Rao says:

    annarita ruberto , that’s a neat example of symmetry!

    I had a post on restriction enzymes recently: https://plus.google.com/+RajiniRao/posts/NvSU1fJdjzm

  39. Rajini Rao

    Thank you for reporting. I will read the post with due care. Your posts are fantastic 🙂

  40. hi rajini what are you doing

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