(81) Probably because the presumptive mesenchyme cells
, but not the presumptive muscle cells, abut on endodermal cells expressing Fgf9/16/ 20, Twist-r.
The antibodies used were produced originally for primary mesenchyme cells
(PMCs) that were early larval skeletogenic cells, but they were also useful for the immunohistochemistry of skeletogenic cells in later larvae and adult rudiments.
Therefore, fetal mouse UGS mesenchyme cells
provide an informative model of endocrine control of prostate development.
Some of these embryos remained normal at the mid-blastula 2 stage (category 0), whereas others exhibited anomalies: inhibition of hatching, precocious appearance of mesenchyme cells
in the blastocele, and extrusion of some cells to the perivitelline space (Figure 7C, 8A).
The origin of spicule-forming cells in a 'primitive' sea urchin (Eucidaris trihuloides) which appears to lack primary mesenchyme cells
. Development 103: 305-315.
Seven days after bisection (28 days after fertilization), the aggregation of mesenchyme cells
(described above) seen in the anterior portions of the larvae appeared to be involved in development of a new pair of coelomic pouches that evaginated from the anterior portion of the newly formed "digestive tube" (Fig.
In these embryos, unlike the embryos of regular echinoids, secondary mesenchyme cells
did not seem to exert the force to pull up the archenteron toward the inner surface of the apical plate.
The larval gut was filled with mesenchyme cells
, and opened posteriorly via the blastopore (Fig.
The sea urchin Brachyury gene (HpTa) is transiently expressed in the lineage of secondary mesenchyme cells
: first in the vegetal plate of the mesenchyme blastula, extending to the tip of the invaginating archenteron, and finally in the secondary mesenchyme cells
at the late-gastrula stage (16).
These studies have demonstrated that about 300 bp of sequence upstream of the transcription initiation site of SpHE and SpAN are each sufficient to drive expression of a [Beta]-galactosidase reporter in the correct nonvegetal pattern - i.e., expression of the transgene is never observed in primary mesenchyme cells
(PMCs) derived from the vegetal micromeres.
Expression of SUM-1 in the intact embryo precedes overt myogenic differentiation of the secondary mesenchyme cells
as determined by RNAse protection analyses using riboprobes to SUM-1 and myosin heavy chain (MHC) and labeling of cells by indirect immunofluorescence (4, 5).