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An Elasto-Plastic Model of Avian Gastrulation #1

An Elasto-Plastic Model of Avian Gastrulation

Vincent Fleury

Organogenesis 2:1, 6-16, January/February/March 2005

The motions observed during avian gastrulation may be simply interpreted in terms of elasto-plastic flow of sheets. Such a model allows one to calculate the flow map inside the blastodisc, hence the evolution of its shape. In addition, the model predicts that there exists a region of high stress oriented radially from the caudal pole towards the center of the blastodisc, with a tensile component oriented orthoradially. If the stress generated by cellular motion is enough to provoke a crack in the extra cellular matrix, then mesoderm ingression proceeds through a “streak” (the primitive streak) oriented from the caudal pole inwards, which relieves the stress while it creates the three germ layers. The model predicts that crack opening is next followed by crack retreat (primitive streak retreat), as mesoderm ingression continues. As mesoderm ingression proceeds around the area pellucida, similar phenomena in the anterior pole may contribute to formation of the embryo. This gives a mechanical description of avian gastrulation which complements the biochemical approach. In addition, the model provides a simple explanation to the shape of the embryo at very early stages, and possibly an explanation of the entry point of the vitteline arteries into the mesoderm.

As the paper is freely available from Organogenesis, I’ll assume that the pdf is on your desktop1 and thus limit quotes at minima.

It’s time to have a closer look at this paper about which Fleury made such a fuzz and often cited as a peer-reviewed part of his theory. Peer-reviewed it is, certainly, and Jamie Davies assured me that it was reviewed properly. But I will focus on a first time to the fact that it presents a set of hypotheses that require experimental validation prior to any use as a support to any theory. Recently, Fleury asserted that there are only two hypotheses:

Especially the article which you discuss with Prof. Davies contains only two true hypothesis, namely

first : that the blastula is much wider than thick, a fact well established (the “sheets” of the blastula being about a hundred times wider than thick,).

The second hypothesis is that there exists a contraction area in the shape of a crescent or sickle. I, of course, did not invent out of nothing the existence of this. It is the well known Koller-Rauber sickle. These are the only hypothesis of the model, and they are based on wet biology, as you say.

The use of the word hypothesis to describe facts, the ratio of dimensions of the blastodisk and the Kohler’s sickle, a well distinguishable feature, is absolutely inappropriate. And it cast shadow to the set of assumptions that need to be supported by data before the proposed model could be considered as validated. Some of them it may be easy to prove correct, others certainly need sophisticated experimental settings to be tested and probably a few ones are in contradiction with already available data.

When I first read it (Jan 2007) I found it interesting as a description of cell movements during gastrulation and commented that with some more work to connect it to the cells’ properties it could evolve to something much more interesting. The reaction wasn’t what I would call friendly and the exchanges rapidly diverged toward general considerations on the role of genes and their products, chemical organizers and genetic determinism; the paper pes se was set aside and I didn’t gave it more attention, as Fleury had posted a lot of supplementary material in his website.

Following Davies e-mail contact, I read it again, this time more critically, with the main intend to evaluate not the mathematical part of the model but the premises upon which it is built. Mathematical models must be tightly connected to physical reality to present some interest.

The very first thing that came up is the description of gastrulation (p6, §2):

It requires a huge cellular motion which has the shape of two vortices converging towards the posterior pole an along the antero-posterior (AP) axis

So, the model is based on the presence of two vortices, schematically presented at fig 2. Later, Fleury presented us four vortices, each causing the budding necessary to form a limb. But this late hypothesis, implicating four vortices, isn’t presented in this paper. I haven’t see it in another of Fleury’s papers; so it goes as unpublished, not yet peer-reviewed, as well as unsupported by data.

1 – The pdf is « copy/paste » and « print » protected. MacUsers may find convenient to display it using Skim, a handy freeware fro displaying and annotating pdf files, which bypass both limitations; Select and -N to transfert in a new annotation box, then -C. -P is direct.


18 Réponses

  1. completely non sensical

    you are making a fool out of yourself, you should really consider stoppiong all that
    you completely mistake hypothesis of a physical model and predictions, general observations and accurate predictions etc.

  2. Let me make a fool of … 🙂
    Don’t need your concerns, I would appreciate your apologizes

    And it would be finished since January 2007 if you didn’t acted as an [beep] 🙂

    Have you read the latest news about the PS?

    Clearly incompatible with some models, isn’t it?

  3. I make sense of it: your four vortices fantasy you didn’t dared to submit for publication, Davies consider the « paper » you published as an heterodox hypothetical starting point for further discussions not a mechanism as he put it, and your accurate predictions are neither accurate or predictions IMHO.

    What [beep] could stand for OldC? a… or i…?

  4. That’s true, you didn’t said a single word about L2/R2 Fleury.

    Dropped the idea maybe? That would be good news!

  5. shrug of shoulders:

    « Clearly incompatible with some models, isn’t it? »

    yes sure, as stated in the paper, incompatible with morphogenes, thanks.

    About L2/R2? Still alive, and revolving nicely. The saddle point of L2 R2?

    I sent you several times the references.

    Are you really scientists?? Mrs Agathi, or whoever you are, do you exist at all?

  6. Oh, sorry I forgot, the 4 vortices are in the organogenesis paper, if you can read,a nd also in the Phys Rev paper. The saddle point was experimentally evidenced by Weijer and Chuia only afterwards.

    I have no time to waste with you, please stop sending e-mails around, especially anonymous, Mrs Agathi, that does not give a good image of science and scientists.

  7. the 4 vortices are in the organogenesis paper, if you can read

    Oh, where exactly?

    And more important, do you have images available of L2/R2? Not the saddle point, please, try to read what is requested correctly for once, the 2 supplementary vortices you term L2/R2.

    If don’t have time to spend leave us alone. You said you would do so at least 8 months ago, back at Sur-la-Toile. Remember?

    “Clearly incompatible with some models, isn’t it?”
    yes sure, as stated in the paper, incompatible with morphogenes, thanks.

    You really believe that the paper from Voiculescu et al. « The amniote primitive streak is defined by epithelial cell intercalation before gastrulation » is compatible with your model and incompatible with morphogenes?

  8. completely ridiculous, nonsensical, wrong, defamatory etc.

    if you cannot even spot the four vortices in Fig 6 of the paper « An elasto plastic model of avian gastrulation » you have nothing to do in science and your pseudo review of my paper is just nothing

    see also fig 1 of the phys rev Paper 73 061907, 2006Nguyen Lenoble Eichman and Fleury dynamics of vascular branching morphogenesis, the effect of blood and tissue flow.

    « And more important, do you have images available of L2/R2? Not the saddle point, please, try to read what is requested correctly for once, the 2 supplementary vortices you term L2/R2 »

    completely ridiculous

    If you do not understand that away from a saddle point four revolving domains correspond to domains of + – + – vorticity you have nothing to do in science. Also : the four domains ( four, yes) correspond eventually, after twisting etc. to the 4 limbs. If you do not understand the logic, you have nothing to do in science.This is why eventually the chirality of arms is left (arm) right (arm) left (leg) right (leg)

    Yes the chirality of the right leg, is a left arm chirality. Did you know that? Just think about it without anger. That’s really cool.

    By the way I notice that you now admit that there is a saddle point after stating so many times that it was in my imagination. Please put here the figure 2 of the paper,

    Cheng Cui, Xuesong Yang, Manli Chuai, James A. Glazier and Cornelis J. Weijer,Developmental Biology Volume 284, Issue 1, 1 August 2005, Pages 37-47,

    I gave you already many times this reference. Then change all the posts about these facts, and go to hide somewhere.

    This is a serious business, you know : try to make a saddle point, now, with chemicals…

    « You really believe that the paper from Voiculescu et al. “The amniote primitive streak is defined by epithelial cell intercalation before gastrulation” is compatible with your model and incompatible with morphogenes? »

    yes, the fluid flow is not an « analogy » you do not understand scientific concepts. One cannot escape writing Newton’s law in thin shells, as I do, for the displacement of cells. It is not a « hypothesis ». it is a model, i.e. the mathematical modelling of a physical situation, based on simplifying assumptions (thin blastula, contracting sickle, by the way, you now seem to state that these are « facts » not hypothesis, ok, so my model is based on facts, I agree) and fundamental laws of nature. V=grad C is not a fundamental law of nature, whatever C. You have to integrate the pulling forc e of each and every cell in the thin shell (blastula). That’s what the paper is about. The expression ot the fluid flow which I use is just the correct writing of Newton’s law for cells exerting forces in thin shells you cannot get that from gowing up gradients of chemical, whatever gradients. That is even discussed in Weijer’s papers.

    You say that you are not going to review the mathematics, so then drop altogether this review, you do not have the level to review this paper, and make again a fool out of yourself.

    your comment about the stress is irrelevant (flow=stress, antagonist flow= maximum deformation at the center where V=0)

    your comment about a pseudo 3rd hypothesis is irrelevant, it is part of the second

    « If don’t have time to spend leave us alone. You said you would do so at least 8 months ago, back at Sur-la-Toile. Remember? »

    Sure I have no time to spend with losers like you, but you indeed kept on for months to piling up stupid statements and defamations on this site, and also the other, not even mentionning this hilarious Agathi who scorns me with such stupid statements as 31415 is not of the order of 50000.

    If you continue I will have no other means than sue you. You send emails around to my boss the editor of organogenesis etc. making a fool out of yourself. I already told you many times to stop, in your own interest, you are jeopardizing more and more your own scientific reputation, while I am busy working on new results in this topic, which, by the way, is not a topic in which you have ever produced anything.
    Sure I will leave you alone. But please put this as a right of reply to your bullshit.

    By the way, and to put an end to all this, I am not a creationnist and all the undestatements and accusations of creationnism found on this site are defamatory and just bullshit.
    You know perfectly well that I happened fortuitously to discover UIP and Staune after discussing with him and you. I went to give a lecture to the UIP because he kindly invited me to do so, I never met him again and have no ties whatsoever with Templeton foundation etc.
    All your allegations are defamatory, and will be submitted soon to a lawyer for consideration. You are not allowed to state such things on a web site.
    Even if you wish I were a creationnist, wishful thinking in these matters is defamatory.

    Law gives you 3 days to post this as a right of reply.

    This was posted on october 18th 23 03 french time.

  9. Let’s see:

    a) you don’t want to help by saying where exactly the four vortices are shown, mentioned in « An Elasto-Plastic… » Not kind of you. But I do understand, the last time you tried to show them you produced an horrible mistake.
    Let me help you with: « It requires a huge cellular motion which has the shape of two vortices converging towards the posterior pole an along the antero-posterior (AP) ». Remember? You wrote that!

    b) you think it is ridiculous for someone to ask for evidence of the assumption that L2/R2 form; your simulations are in amathematical space where the circular border of the blastodisk is absent, isn’t it? It’s involvement on the potential impairment on the completion of the L2/R2 is not discussed. And no wet biology data about their existence neither.
    Now, if it is ridiculous to ask for evidence from a scientist about his claims, then let me be the ridiculous one!

    c-1) mails to your superiors were to be sure if they endorse your points of view, published on your personal webspace allowed by the university; they shut it down, so I suppose they weren’t OK with the content. I remind you that I offered to help you to set-up a personal space. I do help people on the other side, especially when I consider interesting that what they prone must be exposed to help others make an informed opinion about them. On the past I helped Denyse O’Leary to recover data form her scratched blog template.

    c-2) Jamie Davies contacted me, I didn’t had the time to contact him! But it was nice to learn that he doesn’t consider your model as a proven mechanism. So, I’m not the only one. And it is not correct from you to go around in public fora and say that this is a bit of your theory published. Theories are build on validated models.

    c-3) your level of attention is so low that you haven’t see that comments are free 🙂 Learn to read and understand, that couldn’t harm you (that’s a general remark). Your current status plays you tricks.

    d) never said you are a creationist, but I do said (and when you will be able to read correctly you will find it) that you have acquaintances with creationists and I mentioned UIP and Jean Staune as such. And this is true and documented. But where have you see that you could have ties with John Templeton Foundation? Who said that? Where did he said so? And in what basis? More important, what have I to do with that assertion? If nothing, why do you mention that here?

    e) if you think you are unable to discuss science and you prefer lawsuits that will make part of my point. Else, try to reply to questions about your model, not saying « should be » but showing « how it is ».

    Well, my 10 min for dloale are gone, answering an irrelevant non informative comment 😦
    So #3 not ’till Monday. It’s a nice one.

  10. a) you don’t want to help by saying where exactly the four vortices are shown,

    the answer to that was clear enough:

    « if you cannot even spot the four vortices in Fig 6 of the paper “An elasto plastic model of avian gastrulation” you have nothing to do in science and your pseudo review of my paper is just nothing »

    if you do not understand that two dipoles head on generate 4 vortices, as shown in Fig 6 of that paper,

    your brain is off

    If your fingers are not, please put here the figure in question, I give you permission.

    I also asked you to put the figure of the saddle point, but you did not do it. Please do.

    please continue your comments, I will dedicate my time to science and to analyzing the legal aspects of this.

    [snip by owner] Please remember that anything legal about the content of this blog should be communicated by letter, in greek, addressed to the postal address provided at the « About » page. Comments irrelevant to the post will be simply snipped out.

  11. Now, come on Fleury, we are looking for cellular flow L2/R2, producing vortices that induce limbs budding, remember?

    From your paper:

    Figure 6. The stream lines with symmetrical forces, oriented face to face. These model the attractive (contractile) effect of Kohler’s sickle. (A) depicts schematically the situation. (B) shows the stream lines for two centers of forces (one on each side, top and bottom, located at -R/10 and +R/10). (C) shows the streamlines for six aligned centers of forces modeling Kohler’s sickle as a line of pulling agents (located at ±R/30, ±2R/30, ±R/10).

    You can’t just say that this is the same thing untill you have prove that the schema of fig. 6 correspond to the physical reality of the embryo and even then you have to show if there are vortices formed at the caudal end of the blastodisk.

    You should be able to understand that.

  12. how ridiculous.

    please just put the figure 6 of my paper
    and then the figure of the saddle point observed and described by Weijer and co workers (and the legend, that would be cool)

    you spend your time speaking of scientific denialism, and that sort of crap, please, just put those two images and the references, and that’s all

    then you go hide somewhere and stop all that, all this is just useless, these two figures should put an end to all that

    anyone of your readers will be able to judge for him(her) self

    [snip by owner]

    My trouble is that if I file a police « plainte » as we say in france, it will be much worse for her to have done that anonymously.

    Also, you live in Bordeaux, I guess, and have a blog on dloale, would you please tell me why on earth should I go through Greece to sue you?

    We meet in court.

    Good bye.


  13. Fig 6 commented later today here, on your screens 🙂
    (tomorrow I’ll be busy)

    The editorial address of the blog is in Athens/Greece, I’m sorry, this have nothing to do with my personal address.

  14. […] octobre 21, 2007 par Oldcola Following Fleury’s appreciation i’m a bad bad biologist, the worst he ever met, and probably vortex-blind, unable to see vortices where there are […]

  15. Αντώνης Βεκρής Τμώλου 1616233 ΒύρωναςΑθήναHellas

    Αντώνης Βεκρής reads Antoine Vekris

    If I understand well, you say that you are allowed to write whatever vomit about anyone in english, to be broadcasted worldwide instantaneously by internet, while anyone who disagrees should send a complaint in greek to you, in Greece, by slow mail.

    Oh, so you do find some interest in slow mail, when it suits you.

    How hilarious.

  16. It’s not that it suits me, but a paper-letter can be presented to a tribunal and you have to write down exactly what disturbs you, give a list, with justifications if any.

    The Greek take is more for the « fair use », which is not recognized by the french law on intellectual property. Much more convenient when it comes to cite abstracts and present images from copyrighted material.

    Now, as I already said, try to keep it science related commenting or I’ll snip out more and more ’till you understand what this blog is for: scientific discussion.

  17. Oh, one more remark. Read your comments, full of injurious language, and wrong accusations, then take a few seconds to think about it: who’s vomiting?

    And now, for something completely different: talk us about science.

  18. […] #1 of my discussion on EPMAG I pointed to the fact that in the introduction only two vortices are […]

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