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N Fargeix

Publications and source records attributed to N Fargeix.

At least 19 recordsLinked to original sources
PubMed1990

Expression and distribution of carbohydrate sequences in chick germ cells: a comparative study with lectins and the NC-1/HNK-1 monoclonal antibody.

The expression of end-chain sugar residues and of oligosaccharidic sequences has been investigated in chick germ cells at critical stages during the migration, proliferation and sexual differentiation of these cells. Fluorescent lectins and indirect immunofluorescence studies using the NC-1/HNK-1 monoclonal antibody indicate a remarkable control of glycosylation during germ cell embryonal life. Besides a retained expression of glucose/mannose residues, it was found that alpha- and beta-galactose residues, N-acetyllactosamine and N-N' diacetylchitobiose sequences as well as the sulfated trisaccharidic NC-1 epitope were detectable in a stage-specific pattern. Present at a very high density in the cytoplasm and on the surface of the early germ cells at premigrative and migratory stages, the staining for these carbohydrate sequences gradually disappeared when the germ cells settled and proliferated in the developing gonadal primordia. The disaccharide Gal beta 1----3 Gal NAc was exclusively detected in migrating PGCs. In sexualized gonads, acetyllactosamine and/or diacetylchitobiose were similarly reexpressed in both oogonia and spermatogonia. Spermatogonia displayed beta-galactose residues and a high immunoreactivity with the NC1 Mab, indicating modulations in PGC glycosylations related to the acquisition of sexual phenotypes. In addition NC-1 was found to be expressed in the somatic component of the undifferentiated gonad and in the testis interstitial gland.

Animals↗
PubMed1983

Distribution of polyanionic sites in the developing gonads and the dorsal mesentery of the chick embryo.

The distribution of glycoconjugates was investigated in the embryonic trunk mesoderm used as a substrate by migrating primordial germ cells (PGCs) by means of ultrastructural cytochemistry. In both mesentery and developing gonads polyanionic sites were abundant in epithelial and mesenchymal cell coats, basal laminae, and extracellular matrices (ECM). In the latter, polyanions distributed on microfibrils and granules were associated with collagen fibers, forming an entangled network. No preferential association of this fibrillo-granular material with PGCs was observed, suggesting that polyanions present in ECM likely act by promoting inflation of the extracellular spaces rather than by providing mechanical guides for the moving cells.

Animals↗
PubMed1981

Early sequential development in avian gonads. An ultrastructural study using selective glycogen labeling in the germ cells.

The early development of chick embryo gonads was studied by light and transmission electron microscopy and by cytochemical detection of glycogen in primordial germ cells (PGC's). The sequential events are presented from day 2 to day 5 (stages 14 to 27), together with the ultrastructural characteristics of the various cell populations. This study attempts to contribute data on the controversial origin of the avian gonadal medulla. It is shown that the main part of the primitive medulla arises from the association of the proliferating germinal epithelium (GE) and epithelioid cords (formed early from the condensed splanchnopleural mesenchyme); later deep cords, probably developed from the intermediate mesoderm mesenchyme, join the medulla. The process of mesenchymal condensation is described (cells aggregated by dense plaques and membrane anchorages, deposits of fibrillar extracellular material around the cords) together with ultrastructural changes in the GE basal lamina, which is progressively pushed back then disorganized. The study of the morphological relationships between the PGC's and the somatic cells has been facilitated by glycogen labeling in the former. Whereas the PGC's settled in the germinal epithelia do not display any junctional complex with the epithelial cells up to stage 26, those which are migrating through the dorsal mesentery and in the deep gonadal mesenchyme are associated to fibroblast-like somatic cells by dense plaques. The cytological characteristics of migrating PGC's (polymorphism, pseudopodia and filopodia, paucity of microfilaments, high alpha-glycogen particle content) have been described. In addition, the cell pattern in mesodermal tissues is thought well-suited to PGC invasion owing to a wide extracellular compartment, distributed in the mesenchyme and the early epithelium, and to discontinuities in the basal lamina.

Animals↗
PubMed1980

[Germ cells of the bird embryo: early localization, migration and colonization of gonadal anlagen].

Several experimental and morphological papers are analyzed concerning germ cell origin, migration and proliferation within sexually undifferentiated gonads. The germ material which is first localized in both anterior and posterior halves of the unincubated blastoderm assembles in the anterior area only at the beginning of incubation. In gonads the germinal population does not depend on the initial quantity of germ cells in the early blastoderm: its value seems to be determined by the somatic cells of the gonadal stroma. During the migratory phase, it is suggested that regulated interactions occur between the glycoconjugates of the moving germ cells and the physico-chemical characteristics of the extracellular matrices acting as substrates for the movement.

Animals↗
PubMed1977

[Establishing of an asymmetry index in the germ cell distribution between the genital ridges in the Hubbard chick embryo].

Germ cell numberings inside the gonadic anlages of Hubbard chick embryos allowed us to display these following events: From stage 23 to stage 26, the germ cell number obviously increases. It is for this period that an asymmetry index number, specific for the Hubbard strain is got, thanks to a decreasing in the number of gonocytes colonizing the right gonad epithelium. It is for the same period that the medulla differentiates and becomes populated with gonocytes. Such simultaneous events allow us to suppose that the gonadic colonization might result from some interactions between the germinal epithelium and the underlying mesenchyme.

Animals↗
PubMed1976

[Germinal population of gonads in some chimerical embryos obtained by connecting pieces of japanese quail and domestic chick blastoderms (author's transl)].

The experimental realization of chemerical embryos (Martin's13 technic) permits a quantitative appreciation of the modalities of the colonization of quail gonads by chick germ cells. Results clearly show that nature and origin of the somatic part of the gonad areas settle the characters of the genital ridges populating, and specially the specific index of asymmetry expressed by the percentage of PGC colonizing the right gonad.

Animals↗
PubMed1976

[Regulation of the number of gonocytes in the genital ridges of duck embryos after partial destruction of the initial stock of germ cells].

X rays irradiation of anterior or posterior halves of Duck blastoderms at the non incubated stage is followed by a decrease of the number of germ cells in the germinal crescent at the stage of 10 somites. However, after 6 days of incubation, the genital ridges of such embryos contain the same number of gonocytes as those of normal embryos. A regulation of the number of gonocytes occures at the level of the genital ridges.

Age Factors↗
PubMed1976

[Quantitative aspects of the colonization of the gonads by germ cells in the quail embryo (Coturnix coturnix japonical)].

A quantitative analysis made on quail embryos coming from 13 isolated parent-couples reveals some significative variations of a genetic origin, between some of the offspring studied: the differences observed concern both the quantitative importance of the colonization of gonads by germ cells and the asymmetrical distribution of PGGs (primordial germ cells) between the two genital ridges. The chronological study of the colonization in the quail shows, as in both the duck and the chick, two periods of rapid and regular increase of the number of gonadic PGC, at stages from 13 to 18 and from 24 to 30 of Hamburger & Hamilton. The distribution of germ cells between the two genital ridges is, at the beginning of the colonization, not very asymmetrical. Between stages 18 and 24 the asymmetry increases and remains stable so that the mean value of D% (percentage of the number of PGC contained in the right gonad) from that moment on is equal to 29-34%. This value is specific for the quail embryo.

Animals↗