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Biomedical subjects

J M Villar

Publications and source records attributed to J M Villar.

At least 37 records · Page 2Linked to original sources
PubMed1988

Organelle distribution in the wedge-, spindle- and inverted wedge-shaped neuroepithelial cells during chick embryo neurulation.

The formation of the neural tube is a morphogenetic process involving cell-shape changes. The activity of the cytoskeletal elements of the neuroepithelial cells and the interkinetic nuclear migration affect the neuroepithelial cell shape in a way that these cells acquire three distinct conformations of wedge-shaped, spindle-shaped and inverted wedge-shaped cells. Each of them is ultrastructurally characterized in this paper with regard to the intracellular distribution of mitochondria, rough endoplasmic reticulum, yolk droplets, lipid bodies and Golgi apparatus. These distribution patterns are analyzed in relation to the role played by the neuroepithelial cells during the successive phases of neural tube formation.

Animals↗
PubMed1987

Ultrastructural analysis of chick embryo blastoderms explanted in vitro in absence of endoderm. Differentiation capacity of mesoderm.

A study of the structural characteristics of stage 5 chick embryo blastoderms, cultured in vitro, was carried out after previous elimination of endoderm to analyse the differentiation capacity of mesoderm. Our results show that only the precardiac mesoderm is determined at this early stage and that it is able to differentiate cardiac tissue in the absence of the endoderm. The ultrastructural characteristics of this tissue are described. However, the degree of differentiation of cardiomyoblasts does not reach the expected level of organization and myofibrillar complexity.

Animals↗
PubMed1987

Scanning electron microscopy of the aggregation of head mesoderm cells from chick embryos.

Head mesoderm cells from chick embryos at different stages of development were dissociated and cultured on plastic coverslips. In all cultures several cellular aggregates were described by means of scanning electron microscopy. Isolated cells present filopodia and lamellipodia. However, when mesoderm cells make contact with one another the filopodial and lamellipodial activity in the contact cellular edge disappear. Thus, the cells into cellular clusters do not present projections. The clusters were circular and bidimensional in character. The scanning electron microscopic observations showed that it is the type 1 variant of "contact inhibition of locomotion" which occurs. By means of these mechanisms the bidimensional aggregates are formed and cellular overlapping is not present. Since the behaviour of the mesoderm cells "in vitro" in some way could be comparable to their behaviour "in situ", the results here observed are discussed in relation to the conduct of mesoderm cells "in vivo".

Animals↗
PubMed1987

Intracellular distribution of yolk droplets, lipid bodies and Golgi apparatus in the chick neuroepithelial cells during neurulation.

Vitelline and lipidic inclusions which are present in the neuroepithelial cells during chick embryo neurulation show a typical intracellular localization in the apical zone of the cell. In the same cellular zone the Golgi apparatus can be seen during the successive stages of neurulation. These patterns of inclusion and organelle polarity during chick embryo neurulation may be related to active consumption of the reserves contained in inclusions during this morphogenetic process. Such an active consumption would imply a close relationship between the vitelline and lipidic inclusions and the Golgi apparatus. On the other hand, the apical position of the Golgi apparatus in the neuroepithelial cells reveals the remarkable apicobasal polarity of these cells which remains unchanged during chick embryo neurulation.

Animals↗
PubMed1987

Stereological analysis of the ultrastructure of the early chick embryo cell types involved in sorting out.

Analysis of the aggregates obtained from the prenodal region of the chick embryo (stage 5) show the existence of three cell types which sorted out. The application of morphometrical and stereological methods show that each of these cell types has a characteristic subcellular organization which is discussed with respect to the cytometrical characteristics of embryonic cells of stage 5. This early ultrastructure of each cell type is presumably related to its state of differentiation and consequently to some of the potential morphogenetic roles.

Animals↗
PubMed1986

Stereological analysis of ultrastructural changes of surrounding tissues to neuroectoderm during chick embryo neurulation.

The cytometric evolution of different subcellular components in the epiblast and the mesoderm of chick embryo during neurulation has been studied with stereological methods. The coefficient of cellular form (CFc) has specific values for each type, the epiblast having a mean CFc of 0.474, while the mesoderm, which has ellipsoidal cells, has a mean CFc of 0.643. The nucleus does not show any change of its coefficient of form although its surface density increases significantly. The proportion of mitochondria, present in the cells of each embryonic layer, remains constant during the 4 stages, being higher in the mesoderm cells (epiblast 3.6%; mesoderm 4.3%). The epiblast cells show a stable vitelline reserve, though the relative proportions of lipid bodies and yolk droplets vary: the volume density of yolk droplets increases from stage 5 (3.1%) to stage 8 (7.7%), while the lipid bodies diminish from 7 to 3.6% during this period. The mesoderm cells undergo a remarkable loss of vitelline volume during the same period. The rough endoplasmic reticulum of each cellular type has a remarkable length density increase, the significance of which is discussed in relation to production of extracellular matrix.

Animals↗
PubMed1986

Effects of cytochalasin B on cell to cell adhesion and cellular shape of embryo mesoderm cells in vitro.

The effects of cytochalasin B on chick embryo mesoderm cells cultured in vitro were studied by scanning electron microscopy. The untreated cells showed numerous filopodia and lamellipodia and they were flattened onto the coverslip. Several cellular clusters were observed in each culture. The treated cells did not show filopodia, they had a rounded shape and cellular clusters were not present on the coverslip. These alterations are discussed on the basis of the actions of cytochalasin B on the micrcfilamentous cytoskeleton and the role proposed for microfilaments in filopodia formation, cellular shape and locomotion. It was observed that the mechanisms of cell to cell adhesion of chick embryo mesoderm cells were not the same as the mechanisms of cell adhesion to artificial substrates.

Animals↗
PubMed1986

Differentiation of chick embryo cardiomyocytes in cellular cultures: influence of the neurogenic ectoderm.

The behaviour and differentiation of cultured precardiac cells in the presence of neurogenic cells were studied by means of light and electron microscopy. Inhibition of the process of cardiac differentiation may be due to cellular contact or some specific factor elaborated in the process of differentiation by the neurogenic cells. Differentiation of cardiomyocytes in vitro may be compatible with the presence and contact of neurogenic cells, since both cell populations appear in the same reaggregate. Diffused substances in the medium of the culture through neurogenic cells do not appear to produce any modifications in cardiac differentiation. These processes were examined and are discussed.

Animals↗
PubMed1985

Evidence of non-early ultrastructural regionalization in the neural epithelium of the chick by stereological methods.

Cell populations of the anterior, medial and posterior regions of the neural epithelium of chick embryo were analyzed by ultrastructural morphometrical and stereological methods. No morphological subcellular differences appear to occur between the cells of these distinct areas, demonstrable by morphometrical and stereological conventional methods. The homogeneity of this cell population in each stage during neurulation is discussed in relation to the induction process.

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