Among other functions, the Notch signaling pathway contributes to the development of somites [4] in animals. It involves a cell signaling mechanism with a wide range of functions, including cellular differentiation [5], and the formation of the embryonic structures (embryogenesis [6]). All multicellular animals use Notch signaling, which is involved in the development, maintenance, and regenera...

The segmental plate mesoderm of snapping turtle embryos (Chelydra serpentina) was examined with stereoscanning electron microscopy imaging. A metameric pattern was detected along the entire length of the segmental plates. This pattern consisted of a tandem sequence of mesodermal units, called somitomeres. Each somitomere was oval to cubic in shape and the processes of the constituent mesodermal...

Pax3 is a member of the paired-box-containing transcription factors. It is expressed in the developing somites, dorsal spinal cord, mesencephalon and neural crest derivatives. Several loss-of-function mutations are correlated with the Splotch phenotype in mice and Waardenburg syndrome in humans. Malformations include a lack of muscle in the limb, a failure of neural tube closure and dysgenesis ...

It has been shown by using the quail/chick chimera system that Hox gene expression in the hindbrain is influenced by positional signals arising from the environment. In order to decipher the pathway that leads to Hox gene induction, we have investigated whether a Hox gene regulator, the leucine zipper transcription factor MafB/Kr, is itself transcriptionally regulated by the environmental signa...

In avian embryos, somites constitute the morphological unit of the metameric pattern. Somites are epithelia formed from a mesenchyme, the segmental plate, and are subsequently reorganized into dermatome, myotome, and sclerotome. In this study, we used somitogenesis as a basis to examine tissue remodeling during early vertebrate morphogenesis. Particular emphasis was put on the distribution and ...

Previous experimental evidence suggested that the avian segmental pattern is already specified in the apparently unsegmented paraxial (segmental plate) mesoderm, but is susceptible to modification and reconstitution. We explored capacities of embryos to alter the specified pattern and restore it after disruption. In control experiments, right segmental plates of chicken or Japanese quail embryo...

The intrasomitic changes in cell arrangement which accompany somite rotation during somitogenesis in Xenopus laevis were analysed with the scanning electron microscope (SEM). Longitudinal, horizontal fractures of whole embryos were examined at various dorsoventral levels of stage-22 to -24 embryos. Observations of the gross morphological features of somitogenesis, and the cellular changes which...

This paper describes development of a three somites earthworm type mobile inspection robot which is able to move in long pipes. We have many small diameter pipes which are gas or water pipes for individual or corporate houses and boilers or hot water pipes for industries. They are settled in the ground horizontally or in the narrow spaces vertically and some of them are covered by casings or ha...

Chick embryos were treated in ovo and in vitro with L-phenylalanine from the intermediate streak stage (Hamburger & Hamilton stage 3, 12-13 h of incubation) to the 7-somite stage (H & H stage 9, 29-33 h of incubation). Treatment in ovo resulted in a large number of embryos developing somite blocks, i.e. imperfectly segmented somites. In embryos treated at an early developmental stage (12-21 h o...

Most of the enteric nervous system derives from the "vagal" neural crest, lying at the level of somites 1-7, which invades the digestive tract rostro-caudally from the foregut to the hindgut. Little is known about the initial phase of this colonization, which brings enteric precursors into the foregut. Here we show that the "vagal crest" subsumes two populations of enteric precursors with contr...