Neurons and glia of the enteric nervous system (ENS) are constantly subject to mechanical stress stemming from contractions of the gut wall or pressure of the bolus, both in adulthood and during embryonic development. Because it is known that mechanical forces can have long reaching effects on neural growth, we investigate here how contractions of the circular smooth muscle of the gut impact morphogenesis of the developing fetal ENS, in chicken and mouse embryos. We find that the number of enteric ganglia is fixed early in development and that subsequent ENS morphogenesis consists in the anisotropic expansion of a hexagonal honeycomb (chicken) or a square (mouse) lattice, without de-novo ganglion formation. We image the deformations of the ENS during spontaneous myogenic motility and show that circular smooth muscle contractile waves induce longitudinal strain on the ENS network; we rationalize this behavior by mechanical finite element modeling of the incompressible gut wall. We find that the longitudinal anisotropy of the ENS vanishes when contractile waves are suppressed in organ culture, showing that these contractile forces play a key role in sculpting the developing ENS. We conclude by summarizing different key events in the fetal development of the ENS and the role played by mechanics in the morphogenesis of this unique nerve network.

Smooth muscle-lined organs like the gut, the ureter, and the fallopian tubes transport matter by generating traveling contractile waves. Intestinal peristalsis is characterized by rhythmic trains of shallow, low-amplitude myogenic waves and high-amplitude, lumenobliterating neurogenic waves. In this paper, we develop a simple analytical Poiseuille-flow model to predict the flow rates induced by these different contractions as a function of all relevant wave parameters, and compare them to a numerical fluid-solid finite element model. We rationalize experimentally observed bolus to-and-fro motion induced by shallow myogenic waves. We show that occluding waves induce considerable bolus mixing due to an upstream vortex. We then investigate the hydrodynamics induced by two waves propagating either in the same direction (colinear) or in opposite directions, as happens in the digestive tract. For colinear waves, we find that the bolus reflux is maximal at a distance between successive myogenic waves close to the one observed physiologically. Colliding waves create a high pressure region that gives rise to rapid fluid flow, high shear stress, and radial mixing upon annihilation. Our paper provides fundamental insight on the fluid dynamics (reflux, propulsion, and mixing) generated by different contraction patterns of the intestine.

This paper deals with the implementation of a simple algorithm for automatic brain tumor segmentation. Brain tumor is commonly diagnosed by Computer tomography and Magnetic Resonance Imaging in clinical treatment. The paper uses Simple Linear Iterative Clustering (SLIC) to segment brain images according to their spatial and color proximities. The ratio of the mean and variance of the image pixels are determined in order to obtain an optimum threshold value. Region merging after thresholding was carried out. The final output image was an image with tumor sections circled out. The segmentation adheres to boundaries and the procedure is fast and reproducible.