Determination of left–right patterning of the mouse embryo by artificial nodal flow

Nature ◽  
2002 ◽  
Vol 418 (6893) ◽  
pp. 96-99 ◽  
Author(s):  
Shigenori Nonaka ◽  
Hidetaka Shiratori ◽  
Yukio Saijoh ◽  
Hiroshi Hamada
Keyword(s):  
Mouse Embryo ◽  
Nodal Flow

Retinoic acid is required in the mouse embryo for left-right asymmetry determination and heart morphogenesis

Development ◽  
1999 ◽  
Vol 126 (12) ◽  
pp. 2589-2596 ◽  
Author(s):  
C. Chazaud ◽  
P. Chambon ◽  
P. Dolle
Keyword(s):  
Retinoic Acid ◽  
Vitamin A ◽  
Mouse Embryo ◽  
Time Course ◽  
Retinoic Acid Receptor ◽  
Mouse Embryos ◽  
Anteroposterior Patterning ◽  
Heart Looping ◽  
Left Right Asymmetry

Determination of the left-right position (situs) of visceral organs involves lefty, nodal and Pitx2 genes that are specifically expressed on the left side of the embryo. We demonstrate that the expression of these genes is prevented by the addition of a retinoic acid receptor pan-antagonist to cultured headfold stage mouse embryos, whereas addition of excess retinoic acid leads to their symmetrical expression. Interestingly, both treatments lead to randomization of heart looping and to defects in heart anteroposterior patterning. A time course analysis indicates that only the newly formed mesoderm at the headfold-presomite stage is competent for these retinoid effects. We conclude that retinoic acid, the active derivative of vitamin A, is essential for heart situs determination and morphogenesis.

Mode and determination of the initial contraction stage in the mouse embryo heart

2005 ◽  
Vol 211 (2) ◽  
pp. 95-100 ◽  
Author(s):  
Kiyomasa Nishii ◽  
Yosaburo Shibata
Keyword(s):  
Mouse Embryo ◽  
Embryo Heart ◽  
Contraction Stage

Sonic hedgehog controls epaxial muscle determination through Myf5 activation

Development ◽  
1999 ◽  
Vol 126 (18) ◽  
pp. 4053-4063 ◽  
Author(s):  
A.G. Borycki ◽  
B. Brunk ◽  
S. Tajbakhsh ◽  
M. Buckingham ◽  
C. Chiang ◽  
...  
Keyword(s):  
Sonic Hedgehog ◽  
Neural Tube ◽  
Mouse Embryo ◽  
Body Wall ◽  
Presomitic Mesoderm ◽  
Dorsal Neural Tube ◽  
Body Wall Muscles ◽  
Myogenic Progenitor Cells ◽  
Epaxial Muscle

Sonic hedgehog (Shh), produced by the notochord and floor plate, is proposed to function as an inductive and trophic signal that controls somite and neural tube patterning and differentiation. To investigate Shh functions during somite myogenesis in the mouse embryo, we have analyzed the expression of the myogenic determination genes, Myf5 and MyoD, and other regulatory genes in somites of Shh null embryos and in explants of presomitic mesoderm from wild-type and Myf5 null embryos. Our findings establish that Shh has an essential inductive function in the early activation of the myogenic determination genes, Myf5 and MyoD, in the epaxial somite cells that give rise to the progenitors of the deep back muscles. Shh is not required for the activation of Myf5 and MyoD at any of the other sites of myogenesis in the mouse embryo, including the hypaxial dermomyotomal cells that give rise to the abdominal and body wall muscles, or the myogenic progenitor cells that form the limb and head muscles. Shh also functions in somites to establish and maintain the medio-lateral boundaries of epaxial and hypaxial gene expression. Myf5, and not MyoD, is the target of Shh signaling in the epaxial dermomyotome, as MyoD activation by recombinant Shh protein in presomitic mesoderm explants is defective in Myf5 null embryos. In further support of the inductive function of Shh in epaxial myogenesis, we show that Shh is not essential for the survival or the proliferation of epaxial myogenic progenitors. However, Shh is required specifically for the survival of sclerotomal cells in the ventral somite as well as for the survival of ventral and dorsal neural tube cells. We conclude, therefore, that Shh has multiple functions in the somite, including inductive functions in the activation of Myf5, leading to the determination of epaxial dermomyotomal cells to myogenesis, as well as trophic functions in the maintenance of cell survival in the sclerotome and adjacent neural tube.

scholarly journals Gastrulation in the mouse: Growth and regionalization of the epiblast

Development ◽  
1977 ◽  
Vol 42 (1) ◽  
pp. 293-303 ◽  
Author(s):  
M. H. L. Snow
Keyword(s):  
Mouse Embryo ◽  
Rapid Growth ◽  
Generation Time ◽  
Primitive Streak ◽  
Small Region ◽  
Cell Generation ◽  
Cell Numbers ◽  
Proliferative Zone ◽  
The Mean

Histological determination of cell numbers in the mouse embryo between 4½ and 7½ days post coitum show that growth during this period, in which gastrulation occurs, is not uniform. Prior to primitive streak formation mean cell generation time is about 9 h. Co-incidental with the appearance of the primitive streak the embryo enters a period of rapid growth, lasting about 24 h, during which the mean cell generation time must be about 5 h in order to account for the increase in cell numbers. A more detailed study, in which variations in mitotic activity in different regions of the embryo have been analysed, has identified a small region, the so-called ‘proliferative zone’, constituting about 10% of the whole epiblast, in which cell generation time may average as little as 2–3 h over a 24 h period. The cell generation time for other epiblast regions is estimated at about 6·5 h. It is calculated that the proliferative zone, in the 24 h period commencing with primitive streak formation, could generate about half the cells in the 7½-day embryo. The topographical consequences of such a rapidly expanding region in the embryo are discussed in the light of other, circumstantial evidence, and it is postulated that the cells generated in the PZ may constitute the ectoderm of later stage embryos.

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

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