Differentiation of endodermal tissues in homografts of primitive ectoderm from two-layered rat embryonic shields

Formation of Cytoskeletal Elements During Mouse Embryogenesis

“…We should like to comment on the remarkable structural similarity of apical organization in proximal endoderm cells of stages as early as days 6-8 of embryogenesis with the typical architecture of absorptive cells of distal regions of the small intestine, prominently ileum, of neonatal rats. Our results suggest that (i) proximal endoderm cells are highly differentiated in their ultrastucture [see also 42, 661, (ii) special features of epithelial cells of the neonatal ileum are already established very early in foetal life and (iii) the proximal endoderm before primitive streak formation may represent precursor cells to the definitive ileum of the small intestine, unlike other definitive endodermal cells of the foetus which are widely believed to be derived from embryonic ectoderm [compare 42, [67][68][69]. From numerous studies on processes of protein uptake and intracellular distribution in the intestine of newly born mammals it has been concluded that the 'apical endocytic complex' and its associated particle-covered membranes are engaged in protein absorption and endocytotic uptake, apparently in a rather non-selective mode [53-55,581. In the same studies a role in protein or particle storage, perhaps with some lysosome-like degradative activity, has been suggested for the large supranuclear vacuoles of ileal cells of newborn mammals [53][54][55]58,70,71].…”

Developmental differences in the ossification process of the human corpus and ramus mandibulae

“…The cartilaginous and skeletal elements of the mandibular arch are formed from cells derived from the embryonic neural crest (Johnston, 1966;Le Lievre, 1971Noden, 19781, which migrate to the mandibular arch (Hall, 1980). This migration has been documented in fish (Jollie, 1971;Berkovitz and Moore, 1974) and is believed, on the basis of circumstantial evidence, to occur in mammals (Levak-Svajger and Svajger, 1971). In the chick embryo, these ectomesenchymal cells are able to form cartilage before reaching the mandibular arch, apparently because of their previous interaction with the cranial ectoderm (Epperlein, 1974;Corsin, 1975;Tyler and Hall, 1976;Hall and Tremaine, 1979;Atchley and Hall, 1991).…”

“…The medial one is similar in appearance to the initial connective tissue hand of the mandibula and rested on the laterosuperior aspect of the cartilago mandibularis. x 10. the neural crest (Hammond and Yntema, 1964;Johnston, 1966;Jollie, 1971;Le Lievre, 1971Levak-Svajger and Svajger, 1971; Berkovitz and Moore, 1974;Le Lievre and Le Douarin, 1975;Noden, 1978). In the chick embryo, these cells are able to form cartilage before they reach the mandibular arch (Hammond and Yntema, 1964;Johnston, 1966;Le Lievre, 1974;Le Lievre and Le Douarin, 19751, possibly as a result of their previous interaction with the cranial ectoderm (Epperlein, 1974;Corsin, 1975;Tyler and Hall, 1976;Hall and Tremaine, 1979;Atchley and Hall, 1991).…”

Physiology and Genetics of Reproduction

“…In the rat (Levak-Svajger et ai., 1969;Levak-Svajger and Svajger, 1971; Skreb, personal communication), it was found that endoderm taken from a two-layered egg cylinder (871 days post conception) fails to grow under these conditions, but ectoderm from the same embryo gives rise not only to ectodermal derivatives but also to mesodermal and endodermal derivatives. This observation raises the question of whether the endoderm covering the egg cylinder at this stage contributes to the definitive endoderm of the fetus.…”