Somites from 9H. H. chick embryos and PC12 cells were co-cultivated in synthetic medium containing N.G.F., which induces the transformation of PC12 cells into neuron-like cells. During the first two days of culture, PC12 cells retained the spherical shape and tended to cluster. Somitic mesoderm cells exhibited a fibroblastic aspect. By the third day, PC12 cells extended long processes resembling nerve fibres which surrounded and penetrated the mesodermic explants. On the 10th day of culture, contractions, limited at first to a few cells were perceptible. Later, the contractions involved large cellular masses. Microscopic observations at 10 days revealed the presence of an increasing number of fusiform mononucleated cells. Later, long and narrow multinucleated elements appeared. Such elements never developed from cultures of only somites. Immunohistochemical observations revealed a desmin positivity in both mononucleated and multinucleated elements characterizing them as myogenic cells that are formed in and because of the presence of PC12 cells which were transformed by N.G.F. into nerve cells. After 10 days of culture, PC12 cells positive to antiserum antidesmin were noted. Desmin positivity of PC12 cells leads to the conclusion that newly-formed muscle cells exert an induction on Pheocromocytoma cells which, as derivatives of the neural crest, have a greater multipotentiality.

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PubMedDate not supplied

"In vitro" expression of the cardiogenic potentiality of chick embryo heart-forming cells.

Chick embryos between final presomitic and 4 somites stage were studied. The subcephalic fold was handly severed from the embryos and cultivated in liquid medium for 7 days. Because of the embryo age, no heart anlage was observed at the moment of dissection. After 4 hours of culture the cells began to migrate from the explants. After 20 hours a very extended migration ring was observed in all of the cultures; in the explants, one or more newformed tubular or spherical masses of cells throbbed rhythmically. Their size and shape were related to the embryos age: from presomitic embryos, irregular clusters appeared, while starting from two somites embryos tubular, vascular-like structures were formed. The cells of the throbbing areas at submicroscopic observation showed organizing myofibrillar apparatus into the cytoplasm; junctional complexes between the cells and gap junctions in course of organization were present in the vascular-like structures. This suggests that very early, in the lateral mesoderm are the presumptive cardiac cells which can develop "in vitro" as myocardic elements even in absence of the interactions that occur during the development "in vitro"; the observed vascular-like structures may be considered as an attempt to form a sort of cardiac primordium "in vitro", and a further step in the expression of the cardiogenic potentiality, involving cell-cell communications. The serial sections of the embryos enhanced that into the cultivated areas, vessels from yolk sac are always present; this suggests that the vascular structures, i.e. the endothelium may be involved in the determination of the myocardic elements.

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PubMedDate not supplied

In vitro expression of n-cadherin adhesion molecule during early cardiac morphogenesis.

The aim of the present study was to investigate, "in vitro", the degree of organogenetic potentiality of the cells of the cardiogenic area during the early developmental stages of the chick embryo. Embryos from between the end of the presomitic stage to the 8 somite stage were studied. The subcephalic fold was cultured in liquid medium for up to 7 days. After 24 hs of culturing, an extended migration ring was observed. In the explants, from 3 somite stage, onwards, beating masses were noted, the shape and size of which suggested a vascular-like structure. Sections of the cultures were processed for the detection of the N-Cadherin adhesion molecule. The observations stated that the diffusion and intensity of expression of this receptor is related to the stage od development of the embryo. Cultures from the presomitic stage to 3 somite stage did not express the molecule. Instead, expression took place in those cultures of embryos at the 3 somite stage, onwards. In the cultures to which the antiserum against N-Cadherin had been to the medium, the formation of vascular-like structures was affected. The changes depended on the age of the embryos. These observations suggest that the expression of the N-Cadherin is related to the potentiality of the presumptive myocardic cells to organize themselves, at least "in vitro", to form a well-defined tridimensional structure. The expression of the adhesion molecule and the potentiality of the cells to build tubular structures were transient features, "in vitro" in our cultures. This suggests that "in vivo" the expression of the N-Cadherin must be aided by factors which, at present, are unidentified.

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