PubMed Health⌕ Search

Biomedical subjects

J M Villar

Publications and source records attributed to J M Villar.

At least 19 recordsLinked to original sources
PubMed1995

Neurogenic cells inhibit the differentiation of cardiogenic cells.

In this study, we present evidence that neurogenic cells inhibit the differentiation of cardiogenic cells. When cells of the entire area pellucida at stage 5 were dissociated and reaggregated, the aggregates differentiated into neural tissues and other structures of any germ layer origin, except for heart tissues, despite the fact that the cardiogenic cells are already committed to differentiate. The phenomenon also occurs from stages 6 to 8, during which cells are in a higher state of commitment. Using combinations of different regions of the area pellucida, it was confirmed that neurogenic cells are responsible for the inhibition of cardiogenic cell differentiation. The inhibition is not species-specific because quail and chick neurogenic cells inhibit each other's cardiogenic cell differentiation. Direct contact between cardiogenic and neurogenic cells seems to be necessary for inhibition because cardiogenic cell differentiation takes place if cardiogenic and neurogenic cells are separated by a porous membrane. Dissociated neural tubes from early stages, but not dissociated telencephalon from 2-day-old chicks, also inhibit cardiogenic cell differentiation. These results suggest that neurogenic cells may sequester molecules necessary for the differentiation of cardiogenic cells rather than produce inhibitory molecules.

Animals↗
PubMed1994

[Massive fecal impaction in a patient with osteogenesis imperfecta].

The case of a 22 year old male with massive faecal impaction and anorectal mechanical stenosis caused by multiples bone fractures and pelvic deformities secondary to imperfect osteogenesis is reported. The patient was treated with subtotal colectomy and permanent colostomy.

Adult↗
PubMed1992

Five-year follow-up evaluation of the noncemented press-fit titanium hip-joint endoprosthesis.

A series of 260 noncemented total hip arthroplasties with a titanium alloy stem and fixation by the Zweymüller press-fit and an Endler polyethylene threaded cup was reviewed in detail. The minimum follow-up period was 48 months and the maximum 72 months, with an average of 60 months. A scale from zero to five points was applied to evaluate pain, mobility, and motion for a total possible accumulation of 15 points. The global results of the different etiologic groups (arthrosis, femoral head necrosis, rheumatoid arthritis, and subcapital hip fractures) have been very good and good (12-15 points) in 67.5% of the cases and fairly good and bad in 32.3%. These results have been better in femoral head necrosis than in arthrosis or rheumatoid arthritis, but not as good in subcapital hip fractures. The age groups below 60 had better results than the above 60 groups. The Singh index higher than 3 was correlated with better-than-average results. The polyethylene cup migrated horizontally (more than 4 mm) in 7.6% of the cases and vertically (more than 5 mm) in 10%. The non-evolutionary cortical remodelation of the femur does not influence the results. Prosthetic stem sinking less than 4 mm has been found in 62% of the cases, from 4 to 9 mm in 21%, and greater than 9 mm in 6%. No alterations with clinical consequences attributable to stress-shielding have been detected.

Adult↗
PubMed1992

Delamination of neuroepithelium and nonneural ectoderm and its relation to the convergence step in chick neurulation.

We have analysed the characteristics of the neuroectoderm-nonneural ectoderm meeting point at several axial levels in relation to the mechanics of neurulation in each level. The results show wide differences at cephalic and somitic levels. At cephalic levels, where convergence plays an important role, the delamination process appears at the beginning of the convergence step. This phenomenon produces a major isolation of the basal lamina, forming a space between this structure and the epithelial sheet in whose basal surface a new basal lamina begins to form. This cavity contains abundant extracellular matrix stained with ruthenium red (RR) and tannic acid (TA), and its increase in volume correlates with the progressive convergence of neural folds. At somitic levels, where the convergence is not important, delamination involves the progressive formation of a half-moon-shaped cavity. This structure appears between a dorsal attachment point, in the tip of neuroectodermal wall, and a ventral attachment point which coincides with the point of bending that determines the bilateral furrow, if it exists. In this small cavity, delamination is not related to an isolation of basal lamina. The RR-staining of the extracellular matrix in this cavity is scarce and the volume increase is smaller than in the cephalic region. These results are discussed in terms of neural fold convergence and neural tube closure.

Animals↗
PubMed1990

Hematological abnormalities in hemophilic patients with human immunodeficiency virus infection.

Hematological abnormalities are common in patients with AIDS or AIDS-related complex. We studied cytological characteristics in peripheral blood and bone marrow samples of 33 hemophilic patients with HIV Infection and in six HIV negatives. The HIV-positive patients presented leukopenia (60.6%), thrombocytopenia (69.9%), and anemia (57.5%). Bone marrow showed abnormalities of maturation in one or more cell lines similar to those described in other HIV-infected groups of patients. These findings were more prominent in megakaryocytes and granulocytic series. Lymphocytosis, plasmocytosis, and increased hemophagocytosis were also common. These alterations do not appear in HIV-negative patients and seem related to a direct effect of HIV on bone marrow cells or to alterations in T-cell regulatory functions.

AIDS-Related Complex↗
PubMed1988

Effects of colchicine- and cytochalasin B-treatment on the intracellular distribution of yolk droplets, lipid bodies, and Golgi apparatus of the chick neuroepithelial cells.

Treatment with colchicine (antimicrotubular agent) and cytochalasin B (antimicrofilamentous agent) has been used to investigate the possible role played by the cytoskeleton in the maintenance of intracellular distribution of yolk droplets, lipid bodies, and Golgi apparatus of the chick neuroepithelial cells. On the one hand, embryos treated with colchicine showed modifications in their distribution patterns of yolk droplets and lipid bodies, which suggests the involvement of the microtubular integrity of neuroepithelial cells in the maintenance of normal distribution patterns. On the other hand, the close relationships between vitelline and lipid inclusions and Golgi apparatus observed in untreated embryos seems to be kept in the embryos treated with colchicine and cytochalasin B. Moreover, from the effects of colchicine on Golgi apparatus position a possible functional role for the microtubular system in the maintenance of Golgi apparatus polarity in the chick neuroepithelial cells can be proposed. The results provided here constitute new information about the cellular mechanisms involved in chick neurulation.

Animals↗
PubMed1988

Scintigraphy with Tc, Ga and In in painful total hip prostheses.

A series of 40 patients were studied, who were operated upon for a painful total hip prosthesis, half of which were infected. In each case, preoperative scintigraphy was performed using Tc99, Ga67 and In111. The images obtained with Tc and Ga were compared with those of In111 and analysed with respect to sensitivity, specificity, accuracy and the predictive value of a positive or negative test. In111 had a predictive value of more than 90% and showed greater reliability in the diagnosis of an infection as the cause of a painful total hip prosthesis.

Bacterial Infections↗
PubMed1988

Stereological study of the early ultrastructural differentiation of chick embryo neuroepithelial cells during neurulation.

The neuroectodermal cells of chick embryos have been analyzed during neurulation by stereological and morphometrical ultrastructural methods in an attempt to describe their cytometric evolution. A profound change of cellular form coefficient was observed which is related to the typical process of columnarization of these cells. At stages 7 and 8, the nucleus appeared round in shape, probably due to a loss of pressure of the vitelline inclusions. In this sense, the volume density of these inclusions falls during this period. There was also a significant increase of the nuclear surface density, the significance of which is discussed on the basis of the nucleo-cytoplasmic interchanges and the differentiation process. At the same time, an increase in the number of mitochondria was observed, which is related to the neural folding process. Simultaneously, the amount of rough endoplasmic reticulum increases, presumably related to the remarkable changes of the embryonic extracellular matrix.

Animals↗
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↗