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PubMed1984

Relationship between phenolamines and catecholamines during rat brain embryonic development in vivo and in vitro.

p-Octopamine and phenylethanolamine are present in the embryonic rat brain earlier than catecholamines. These phenolamines are localized mainly in the hypothalamus, where the level of p-octopamine is very high. The parallel developmental study of the activities of dopamine beta-hydroxylase, 3,4-dihydroxyphenylalanine decarboxylase, tyrosine hydroxylase, and monoamine oxidase shows that phenolamines are present in significant amounts in the hypothalamus until tyrosine hydroxylase and monoamine oxidase become catalytically active. The culture of embryonic hypothalamus at different ages shows that no tyrosine hydroxylase and monoamine oxidase activities can be detected if the tissue is cultured before 15 days. This clearly indicates that all the enzymes related to catecholamine biosynthesis are not triggered at the same time during the development of the rat brain. These results are discussed on the basis of the physiological importance of phenolamines in mammals and of the use of the developing rat brain as a model for the study of the onset of the catecholaminergic system and the decline of the octopamine.

Animals↗
PubMed2000

Expression of amelogenins in developing embryonic and neonatal rat teeth.

OBJECTIVE: Tooth enamel is formed by ameloblasts, which are derived from epitheliums and secrete an extracellular matrix containing a complex arrangement of protein components. The epithelial component, referred to as the enamel organ, contains a layer of cells that secrete an organic matrix that biomineralizes to become tooth enamel. Adjacent ectomesenchyme cells differentiate to become dentinproducing odontoblasts. These two mineralized matrices form the crown of the vertebrate tooth. Therefore, amelogenins play a critical role in tooth enamel formation. We have examined the expression patterns and tissue distribution of amelogenins in their developmental stages in order to build a foundation for further study. METHODS: Amelogenin expression patterns and tissue distribution in developing teeth of embryonic (E17E19) and neonatal (1 to 9 days old) Wistar rats were examined by immunohistochemistry. RESULTS: Positive immunostaining for amelogenin was first observed in the late embryonic stage, E18. The highest level of amelogenin was noted in neonatal secretary ameloblasts, fully engaged in enamel matrix deposition (3 to 5 days old). After that, amelogenin expression continued at a lower level (6, 7, 8 days old). There was no amelogenin staining observed in the maturation stage of development (9 days old). CONCLUSIONS: Amelogenin expression occurs as early as the polarization stage of pre-ameloblasts. Amelogenin was also expressed, but at a low level, in post-secretary stages of amelogenesis. Odontoblasts did not contain detectable amelogenin.

Ameloblasts↗
PubMed2005

Essential role for Galpha13 in endothelial cells during embryonic development.

Toward identifying the roles of protease-activated receptor-1 (PAR1) and other G protein-coupled receptors important for vascular development, we investigated the role of Galpha13 in endothelial cells in the mouse embryo. LacZ inserted into Galpha13 exon 1 was highly expressed in endothelial cells at midgestation. Endothelial-specific Galpha13 knockout embryos died at embryonic days 9.5-11.5 and resembled the PAR1 knockout. Restoration of Galpha13 expression in endothelial cells by use of a Tie2 promoter-driven Galpha13 transgene rescued development of endothelial-specific Galpha13 knockout embryos as well the embryonic day 9.5 vascular phenotype in Galpha13 conventional knockouts; transgene-positive Galpha13-/- embryos developed for several days beyond their transgene-negative Galpha13-/- littermates and then manifested a previously uncharacterized phenotype that included intracranial bleeding and exencephaly. Taken together, our results suggest a critical role for Galpha13 in endothelial cells during vascular development, place Galpha13 as a candidate mediator of PAR1 signaling in this process, and reveal roles for Galpha13 in other cell types in the mammalian embryo.

Alleles↗
PubMed1991

Embryonic development and incidence of aneuploidy in two rabbit strains of different fecundity.

The correlation between strain fecundity and (i) development and (ii) rate of aneuploidy was studied in rabbit preimplantation embryos obtained from 2 strains of different fecundity. Embryos were investigated at Days 3-6 (preimplantation development) or Days 2, 4 and 6 post coitum (aneuploidy). Embryonic size and cell proliferation varied on the days of investigation, but with no consistent tendency in favour of one strain. The incidence of aneuploidy did not differ significantly between embryos from the 2 strains (P greater than 0.05). The multifactorially determined criterion of prolificacy was not selectively correlated with overall differences in embryonic preimplantation growth and rate of aneuploidy.

Aneuploidy↗
PubMed1998

Embryonic development of the Drosophila brain. I. Pattern of pioneer tracts.

The neuropile of the late embryonic Drosophila brain can be subdivided into a vertical component (cervical connective), a transverse component (supraesophageal commissure), and a horizontal component for which we propose the term protocerebral connective. The core of each neuropile component is formed by numerous axon fascicles, the trajectory of which follows an invariant pattern. In the present study we have used an antibody against the adhesion molecule Fasciclin II (FasII) that is expressed in a large number of early differentiating neurons of the Drosophila embryo to follow the development of the axon tracts of the brain. The FasII antigen appears on the surface of clusters of neuronal somata prior to axon outgrowth. These clusters, for which we propose the term fibre tract founder clusters, are laid out in a linear pattern that forms an almost uninterrupted longitudinal track reaching from the ventral nerve cord to the "tip" of the brain. After expressing FasII on their soma, neurons of the fibre tract founder clusters extend axons that grow along the surface of the founder clusters and form a simple system of pioneer tracts for each of the components of the brain neuropile. We have reconstructed the FasII-positive fibre tract founder clusters and their axons from optical sections and generated digital 3-D models that illustrate the spatial relationships of the pioneer tracts. Three fibre tract founder clusters, D/T, P1, and P3m, pioneer the cervical connective. P21 and P2m form a transverse track that pioneers the supraesophageal commissure. P4m and P41/P51/VP5m form two tracts that pioneer a medial and a lateral component of the protocerebral connective, respectively. Because FasII expression continues uninterruptedly into the larval period when the "rudiments" of many parts of the adult neuropile are readily identifiable, it was possible to assign several of the embryonic pioneer tracts to definitive neuropile components, including the median bundle, antennocerebral tract, mushroom body, and posterior optic tract.

Age Factors↗
PubMed2000

Pancreatic pattern of expression of thyrotropin-releasing hormone during rat embryonic development.

In rodents, the first insulin-producing cells appear in the pancreas at mid-gestation around embryonic day 11 (E11). However, on the basis of various features, such as morphology or hormonal coexpression, it is apparent that these initial insulin-expressing cells are different from those that develop after E15. In the present study, the pancreatic expression of both thyrotropin-releasing hormone (TRH) mRNA and insulin was studied during embryonic and fetal life. We report here that in the rat, while insulin mRNA is detected in the pancreas as early as E12, TRH mRNA cannot be detected before E16. At that stage and later on during fetal and early postnatal life, TRH mRNA is detected in insulin-producing cells, no signal being detected in other endocrine cell types or in exocrine tissue. It was also noted, by means of triple staining performed at E17, that the expression of TRH mRNA was restricted to insulin-expressing cells negative for glucagon, whereas the few insulin-expressing cells present at that stage, which coexpress insulin and glucagon, did not express TRH mRNA. Taken together, these data indicate that TRH is a marker of insulin-expressing cells, which develop after E15.

Animals↗
PubMed1996

Noncytopathogenic and cytopathogenic bovine viral diarrhea-mucosal disease viruses do not affect in vitro embryonic development into the blastocyst stage.

Bovine oocytes enclosed within follicular epithelial (FE) cells were exposed to noncytopathogenic or cytopathogenic strains of bovine viral diarrhea-mucosal disease virus (BVD-MDV). After culture at 39 degrees C in humidified air with 5 percent CO2 for 24 h, the oocytes matured and then in vitro fertilization was performed. Some of the fertilized oocytes developed into blastocysts from day 8 to day 10 (day 1: date of insemination), and the rate of development to blastocysts was the same as for the unexposed control oocytes. In the developmental medium, each strain of BVD-MDV was present at 10(3) to 10(6) TCID (50)/0.25 ml from day 3 to day 10, respectively and the virus was isolated from the FE cells at high titers and from the embryos at low titers on day 10. BVD-MDV antigen was detected in the cytoplasm of the FE cells by indirect immunofluorescence. These findings indicate that BVD-MDV replicates well in FE cells. The results of this study suggest that BVD-MDV replication in cells around embryos has no effect on bovine embryo development.

Animals↗