GROWTH, ELECTROCHEMICAL DEPOSITION, MORPHOGENESIS, JELLYFISH, CHICKEN, DEVELOPMENT, GASTRULATION, DENDRITES FRACTALS

Vincent FLEURY

Directeur de recherches au CNRS, HDR

version française, cliquer sur Alexandre

“Writing in English is the most ingenious torture ever devised for sins committed in previous lives. The English reading public explains the reason why.” James Joyce.

Alexandre à Aristote, salut. Je n'approuve pas que tu aies donné au public tes traités. En quoi donc serions-nous supérieurs au reste des hommes, si les sciences que tu nous as enseignées deviennent communes à tous les hommes". (Cité in Alexandre le Grand, Joël Schmidt, Folio (2009).

Vincent Fleury

A reply.

An interview.

A virtual course.

London,

Westminster, December 2009.

"I believe that animals are descended from at most only four or five progenitors, and plants from an equal or lesser number", Charles Darwin.

A Press release on the web-site The European Physical Journal (July 2011)

SEE LOTS OF BEAUTIFUL IMAGES

By clicking here, you access a gallery of scientific images, including very rare scans of historical books.

GALLERY OF ARTICLES

By clicking here you access a gallery of recent articles about vertebrate development [complete list :Publications].

SEE LOTS OF EMBRYOS

By clicking here, you access a gallery of embryo slides and all corresponding MOVIES. I have designed a set up for simultaneous ventral and dorsal movie of embryo development (chicken case). Many films are double dorso-ventral views. The movies span almost all stages between onset of movements and a recognizable vertebrate

SEE LOTS OF VORTICES

By clicking here you access a gallery of vortices in embryos.

All movies both dorsal and ventral movies obtained after rinsing away the yolk can be viewed at the "See Lots of Embryos page".

The lighter side:

"We've been watching cells move (or not move) in embryos for a long, long time. There are no vortices of cell movement centering around the navel. Period.[...] This is complete nonsense, of course; while cells certainly move in interesting ways, the movement is not sufficient explanation of the phenomena, and it's definitely not true that you can describe development as occurring from the navel outwards."

Prof. Paul Zachary Myers, Associate professor, University of Minnesota, Morris.

Please notice the hilarious "of course".

On going research : in vivo time-lapse imaging of vortex flow forming the limb fields in a tetrapod embryo

Here especially, tracking of tissue flow by PIV technique, in vivo, in a chicken embryo (the blue cross is the last point, the green dots the subsequent positions superimposed on the final plate, with 5 minutes interval). One witnesses the vortex flow which forms the navel in the constricted area, the hips and hindlimbs territories in the rotational (vortex) recirculation of the tissue is quite conspicuous. Of course, the flow starts much earlier, and ends much later. This is just a window of experimental time (about 3 hours). Meanwhile the central folds forming the back bone extend caudally to form the tail bud, and cranially to form the head. There is no scalar field of chemotactant which satisfies this vector field. The pattern is due to the conservation law of hydrodynamics (div (V)=0, associated to the fact that cell number is conservative). Earlier and later stages available, cell tracks Will be put online after processing of the data. The low resolution films provided here are at the 0.33 scale from the initial data.

click to animate

click to animate

The lighter side :

"People who know the least are the ones who are the most confident about how much they know"

- the same PZ Myers

"All you have to do is ignore all the evidence and invent a non-existent danger, and people will believe anything you say"

- the same PZ Myers (about the opponents to the swine flue vaccine)

Velocity field of the presumptive hindlimb plate.

Velocity field during formation of the navel (stagnation point)

Press release
THEME 1:BRAIN DEVELOPMENT
THEME 2:FORMATION OF BLOOD VESSELS
THEME 3 :FORMATION OF INTERNAL ORGANS
THEME 4 :FORMATION OF FINGERS AND FIBRED STRUCTURES
THEME 5 :STUDY OF DEVELOPMENT BY SHADOWGRAPH
THEME 6 :STUDY OF DEVELOPMENT BY SHG
THEME 7 :STUDY OF THE JELLYFISH AURELIA AURITA
THEME 8 :MATHEMATICAL DETAILS
THEME 9 :THE ORIGIN OF TETRAPODS
THEME 10 :PROBLEMS IN THE "I'am too busy" LIST
Improve your french :MY THREE BOOKS ON MORPHOGENESIS

UNDERGRAD SCIENCE PROJECT 1 Topic N° 1

UNDERGRAD SCIENCE PROJECT 2 Topic N° 2

Animations accompanying my book "De l'oeuf à l'éternité (from egg to eternity)"

Color plates of "De l'oeuf à l'éternité"

Summary of my theory of evolution

The scanning air puff tonometer

FAQ on my theory

SEE LOTS OF BEAUTIFUL IMAGES podcasts of radio interviews

A lecture at institut Cochin including sound and image.

A lecture at the IRISA in this lecture I explain by the end how cell orientation defines an arrow of evolution.

A lecture at the Institute of Pure and Applied Maths de UCLA le powerpoint is here, and the sound there .

A lecture in the workshop "chaos et déterminations" the powerpoint is here , and the sound there (please be patient, the file is 50Mo).

A lecture at the Ecole Normale Supérieure de Cachan, in the workshop "colloque Modélisation en physiologie", entitled, "How many parameters to fit an elephant" (my guess is 4).

Poster announcing my talk at the Institut de Mécanique des Fluides de Toulouse, entitled "Hydrodynamic effects in animal morphogenesis from embryogenesis to evolution (or : does evolution follow a streamline?)".

Publications

Agenda

Tél, Fax, e-mail
Postal address
A course at UPS done in 2003 Some complementary information A file about blood vessels on the site of Futura-sciences (a french scientific information portal)
The study of morphogenesis is a branch of physics, or of biology, which studies how forms appear and develop. Of course, there exits in principle a bottomless quantity of forms, and these are not all of interest for physicists (many are abstract mathematical forms, for example, others are so contingent that there is no general law for them, others, like a telephone, are merely artefacts).

Morphogenesis has blossomed in France since the 80's, thanks to the pioneering work of such scientists as Yves Couder, Pierre Pelcé, and others. They conceived mathematical tools which allow one to tackle the "evolution" (in a physicists sense) of free boundaries during time. Morphogenetic problems are difficult in that even if the dynamics of a system is known, one has to understand the final outcome of a moving boundary without a priori about the final story.

Until recently, science tried to explain the emergence of forms by "theories", which, when looked ind etail, reveal that they actually make the assumption of what they try to prove. Two examples of this logical inconsistency are the legs of insects and the limb buds of tetrapods. The legs of insects are telescopic tubes with several tubular segments. This pattern originates in the concentric rings of cels called imaginl disks, located along the presumptive body of an insecct. Most work on inscet appendages actually assume that the "buds" of insect appendages are made of concetric rings, which will grow out as telescopic tubes. Therefore, current work on insect appendages, including genetic analyses, study minor stretch effects on appendages, rather than the origin of this pattern, in the first place.

Another example closer to human development is that of limb buds. Current genetic models of limb growth describe in some detail the pools of signaling molecules (such as SHH or Wnt) n the limb bud, in order to explain the pattern formation of limbs. However, the true question is rather : what is the origin of the limb bud, in the first place.

It seems therefore that many current views fall short of explaining development, because they actually already assume the pattern of growth when assuming the boundary conditions of their problem.

The true challenge of conemporary science is to treta forms as "free" mathematical objects, and to see the forms appear by themselves much like crystals cristallize out of vapor. These forms are emergent outcomes of simple pattern forming rules, of physical nature. For this approach, one cannot be satisfied with statements like "there exists a gene of ...".

I have myself contributed to this field by studying experimental systems, and proposing a few simple physical models of pattern formation. In the field of blood vessel formation, I have studied and modeled the mechanical aspects of self-organization of vessel trees. Actually, all these aspects may boil down to a single model, which would hopefully contain all the visco-elastic deformations of branching, elastic, tubes, during development. Shear stress inside the tubes, and tissue expansion, viewed as a slow creep flow, suffice to explain in detail the establishment of the vascular tree, including the position of veins with respect to arteries. Biomechanical self-organizaton is truly crucial for the formation of a well functioning vascular tree.

One interesting case, both fundamentally, and practical, is that of the umbilical chord and of the placenta. It is well known that there exists a set of joined arteries and veins in the umbilcal chord, it is less well known that this pairing of arteries and veins continues in the entire placenta, and in th entire body. We have explained this feature recently in my lab with several of my co-workers. This required a fine study of mechanical properties of the tissue in between arteris and veins. For this purpose I designed a scanning air puff tonometer.

I also suggested some time ago, a relationship between plant formation, and crystal shape. Indeed, plants tend to form stemms, and elongated fruits, with often a fusoid or lenticular shape. I have suggested, together with Tomoko Watanabe that this tendecy is related to the equilibrium of fibers inside plant shapes. In this situation, the pattern of fibers should stabilize, or "select" specific directions, selected by the anisotropy of the mechanical parameters, itself related to the pattern of fiber singularities. For example, it is an obvious observation that fibers on animal darts or plant pins, are aligned towards the apex. It is not so easy to explain why. This model explains qualitatively the formation of specific axis of growth, and the relationship with the form of, say, lemons or turnips. This also explains the difference bewteen biological growth and crystal growth. (In crystals, the crystalline, atomistic organization is long ranged while in biological stuff, the orientational order is local). I believe this model also applies to the outgrowth of insect appendages. Along the body of insects, appendages grow by telescoping out a planar form composed of concentric rings (the imaginal disks). Physics provides a straightforward explanation to this phenomenon.

I have also worked for some time on morphogenesis of glands, kidney and lungs. I have suggested a possible evolutionary explanation for their origin. I have shown together with David Warburton's lab in Los Angeles, that pressure inside the lumen of these glands played a major role in regulating important gnetic pathways (FGF10, SPROUTY, etc.) (USC) This work was mainly done by my former phD student Mathieu Unbekandt, who is now in Jamie Davies lab in Edinburgh (Scotland), and has joined the kidstemm project.

Some of my recent work deals with fingerprints, and the form of fingers

Now, my main excitement these days, is with the origin of the tetrapods, and especially of humans. I have proposed a mechanogenetic synthesis of development which explains very naturally, how a round ovocyte may be scaled up into a tetrapod, with a head, limbs and tail. This form is actually the attractor of a hyperbolic flow, occuring during gastrulation. One needs to treat a problem of vortex collision, to find how limbs are positionned in these animals.

The evolution of the human skull can be treated with the same physics by observing that there exists a vortex ring in the head, associated to the winding of the brain above the eye orbits and around the ear duct. This kind of physics explains qualitatively the observations of Mme Dambricourt-Malassé about the evolution of the human head between apes and humans (it is the forward winding of a vortex ring).

In the course of these studies, I have designed a new instrument, a scanning air puff tonometer, which is able to map dot by dot the elastic properties of (flat) living stuff, in vivo, by gently blowing air through a micro pipette. This is akin to the tonometer used by optometrists to measure the intra-ocular pressure (for glaucoma).

I have been the advisor of Marcus Dejmek (defended 2002), of Mathieu Unbekandt (2006), of Alia Al-Kilani (2009), and of Thi-Hanh Nguyen.

I also happen to write novels, and a few litterary articles.

The quotation of this page : "Illusion is deceptive, but reality is even worse"

Frédéric Dard.