Biomedical subjects

L Pardanaud

Publications and source records attributed to L Pardanaud.

22 records · Page 2Linked to original sources

PubMed1989

Complementary patterns of expression of c-ets 1, c-myb and c-myc in the blood-forming system of the chick embryo.

We have used in situ hybridization to study the spatial and temporal distribution of the transcription of three cellular oncogenes encoding DNA-binding proteins, c-ets 1, c-myb and c-myc during the development of the chick embryo. c-ets 1 mRNA expression appears linked to the mesodermal lineage and is strongly expressed in early endothelia; it subsequently becomes restricted to small vessel endothelia. Hemopoietic cells in extraembryonic blood islands at E2 express c-ets 1, while intraembryonic hemopoietic cells in aortic clusters (E3) and paraaortic foci (E6) express c-myb. c-myc transcripts are detected in cells undergoing hemopoiesis in both these extraembryonic and intraembryonic sites. Outside the blood-forming system, c-myc is transcribed in a large variety of cells; c-ets 1 displays tissue-specific expression in groups of mesodermal cells engaged in morphogenetic processes and appears excluded from all epithelia; finally the expression of c-myb is the most tightly linked to hemopoietic cells. In any case, it is clear that these three oncogenes display complementary expression in endothelial and hemopoietic cells where their patterns are modulated in relationship to multiplication and differentiation.

Animals↗

PubMed1988

Early haemopoietic stem cells in the avian embryo.

Using 'yolk sac chimaeras', we have previously demonstrated that stem cells, destined to colonize haemopoietic organs other than the yolk sac, arise in the embryo proper. We have now investigated the emergence and potentialities of these cells in vivo and in vitro. The in vivo approach consisted of interspecies grafting between quail and chick embryos. The cell progeny from the grafts was detected by means of QH1, a monoclonal antibody specific for the quail haemangioblastic lineage. When grafted into the dorsal mesentery of the chick embryo, which is a haemopoietic microenvironment, the region of the aorta from E3-E4 quail embryos generated large haemopoietic foci. When associated with a chick attractive thymic rudiment, cells left the quail aorta, entered this rudiment and underwent lymphopoiesis. Cell suspensions prepared from 40-50 chick aortae, seeded in appropriate semi-solid media, yielded macrophage, granulocyte or erythrocyte clones. These colony forming cells were two to eight times more frequent than in cell preparations from hatchling bone marrow. By contrast, cells prepared from the whole embryonic body deprived of the aorta were not clonogenic. By interspecies grafting of somatopleural (ectoderm + mesoderm, e.g. limb bud) or splanchnopleural rudiments (endoderm + mesoderm, e.g. lung, pancreas, intestine), the endothelial lining of blood vessels was shown to arise by two entirely different processes according to the rudiment considered: angiogenesis, i.e. invasion by extrinsic endothelial cells, in the limb bud, and vasculogenesis, i.e. in situ emergence of endothelial cells, in internal organs. The spleen, which first develops as a continuum to the pancreatic mesoderm, acquires its endothelial network by vasculogenesis, and is colonized by extrinsic haemopoietic stem cells. Granulopoietic cells in the pancreas and accessory cells in the lung are also extrinsic. Thus, in the case of endomesodermal rudiments, interspecies grafting reveals separate origins of endothelial and haemopoietic cells.

Animals↗

PubMed1987

Early germ cell segregation and distribution in the quail blastodisc.

The distribution and number of primordial germ cells has been analyzed in quail blastodiscs from the incubated state to the 13-somite stage, treated in toto with monoclonal antibody QH1. Some cells were already positive in unincubated blastulas some 18 h earlier than described with other markers in previous studies of avian development. The number of PGCs increased from 2-3 in the unincubated state to more than 100 at the early primitive streak stage. During following stages their numbers did not increase significantly. At first these cells were isolated, thereafter they often assembled in small groups and progressively gathered into Swift's crescent. It is concluded that PGCs begin segregating in birds at the blastula stage and that they multiply until the primitive streak stage.

Animals↗

PubMed1987

Vasculogenesis in the early quail blastodisc as studied with a monoclonal antibody recognizing endothelial cells.

QH1, a monoclonal antibody that recognizes quail endothelial and haemopoietic cells, was applied to quail blastodiscs in toto, in order to analyse by immunofluorescence the emergence of the vascular tree. The first endothelial cells were detected in the area opaca at the headfold stage and in the area pellucida at the 1-somite stage. Single cells then interconnected progressively, especially in the anterior intestinal portal and along the somites building up the linings of the heart and dorsal aortas. This study demonstrates that endothelial cells differentiate as single entities 4 h earlier in development than hitherto detected and that the vascular network forms secondarily. The horseshoe shape of the extraembryonic area vasculosa is also a secondary acquisition. A nonvascularized area persists until later (at least the 14-somite stage) in the region of the regressing primitive streak.

Animals↗