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Biomedical subjects

A M Vagner-Capodano

Publications and source records attributed to A M Vagner-Capodano.

At least 37 records · Page 2Linked to original sources
PubMed1985

Three-dimensional analysis of fibrillar centers and associated chromatin in the nucleolus of human oocytes in primordial follicles.

The intranucleolar localization of fibrillar centers and their relationships with nucleolus-associated chromatin were determined in stereopairs of human oocyte nucleoli obtained by computer reconstruction of serial sections. This study showed that there was no numerical relationship between the number of fibrillar centers and the number of chromosomal NORs. The three-dimensional reconstruction demonstrated that the majority of fibrillar centers was directly connected with the nucleolus-associated chromatin.

Adult↗
PubMed1984

The relationships between ribosomal genes and fibrillar centers in thyroid cells cultivated in vitro.

Despite the fact that the fibrillar centers of the nucleolus and the chromosomal nucleolar organisers (NORs) are similarly stained with the NOR-silver technique, there remain some questions about the identification of fibrillar centers as NORs. The distinct delineation of the fibrillar centers in porcine thyroid cells allowed us to determine whether there was a numerical equivalence or correlation between fibrillar centers and NORs. Hybridization in situ and silver staining performed on pig chromosomes showed that pairs 8 and 10 contained rDNA sites. Silver staining of thyroid cells in electron microscopy showed that the fibrillar centers and their surrounding layer of dense fibrils were the sites of silver deposit. Chromatin fibers were demonstrated within the fibrillar centers through the aid of the osmiumammine reaction and with the oxidized diaminobenzidine technique. It was observed that in cultured thyroid cells the fibrillar centers could be identified in the light microscope as argyrophilic spherules, and easily counted. The number of fibrillar centers was variable according to culture conditions. In cells cultured for 5 hr, the mean number of fibrillar centers was 1.7. After 5 days of culture, the number of fibrillar centers increased, reaching a mean value of 5.93. When thyroid cells were stimulated with thyrotropin, the number of fibrillar centers again increased to a mean value of 7.54. These results demonstrate that the relationship between fibrillar centers and NORs is not a simple proportionality: the number of fibrillar centers increases with increased cellular activity. These data imply that in active cells each NOR may pass through several fibrillar centers.

Animals↗
PubMed1984

[Localization of ribosomal genes and nucleolar activity in lymphocytes of swine (Sus scrofa domestica) stimulated by phytohemagglutinins].

The Pig chromosomes that contain rDNA sites displayed a polymorphism in the distribution of the genes among the nucleolar organizers located on pairs Nos. 8 and 10. Two, or more often three, active sites were observed in the chromosomes of lymphocytes stimulated with phytohemagglutinin. Only 5% of the metaphases showed a 4th small active site. At the onset of stimulation most cells contained one-two nucleoli; four nucleoli were never observed. After prolonged stimulation, the number of nuclei containing three nucleoli increased. A 4th small nucleolus appeared in a few cells, presumably formed by activation of the smallest rDNA site.

Animals↗
PubMed1982

[The bone marrow karyotype in refractory anemia and preleukemia].

The term preleukemia may be used to refer to patients with acquired chronic cytopenias (refractory anemia with an excess of blast cells, refractory sideroblastic idiopathic anemia, or others idiopathic refractory cytopenias) who develop acute myeloid leukemia (AML) months or years later. In these syndromes, an abnormal bone marrow karyotype is found in about 50% cases, like in de novo AML. These abnormalities are similar to those observed in AML (mostly +8, -7, -5 or 5q-). The translocations t(8;21) and t(15;17) are never observed in preleukemia. Correlations exist between hematological data and cytogenetic features namely, in the 5q- syndrome. Thus in preleukemia the cytogenetic analysis is a valuable diagnostic method. At the present time, the prognostic value of the bone marrow karyotype is not clearly established but in single chromosome deletions (5q-, 20q-) the acute transformation is rare or delayed. At the opposite, evolution of the karyotype is generally regarded as a progression to high malignancy.

Anemia, Aplastic↗
PubMed1977

Effect of actinomycin D on the quail oocyte nucleolus during meiotic prophase I.

Actinomycine D alters profoundly the distribution of the nucleolar constituents in the quail oocyte at prophase I of meiosis. As a consequence of nucleolar segregation, the normally existing relations between the nucleolus fibrillar centers and the microchromosomes are ruptured. The relations between the fibrillar center and the dense fibrills which surround it remain intact, suggesting that they constitute together a functional unit.

Animals↗
PubMed1976

Chromosomal constitution of nucleolus-associated chromatin in man.

Use of specific stains permits analysis of the frequency of nucleolus-associated heterochromatin in chromosomes 1 and 9 from human fibroblasts. In 81 per cent of interphase nuclei the heterochromatic segment of both No. 1 chromosomes is associated with the nucleolus, while in 19 per cent only one heterochromatic segment shows such an association with the other occupying a random position in the nucleoplasm. The nucleolar association of chromosome 9 heterochromatin is less constant: in 42.3 per cent of the nuclei both segments are associated with the nucleolus, in 39 per cent of the nuclei only one heterochromatic segment presents such an association, and in 18.7 per cent neither of the two heterochromatic segments is in nucleolar association. In 6 per cent of the cells, one or two chromosome 9 heterochromatic segments are in contact with the nuclear membrane. In situ hybridization using tritium-labeled 28S and 18S RNA shows that in the interphase nucleus the acrocentric short arms, carriers of ribosomal cistrons, are associated with the nucleolus. These observations demonstrate the complexity of the nucleolus-associated chromatin which, in addition to segments of chromosomes 1, 9, 13, 14, 15, 21, 22, may include the Y chromosome. They also confirm that the nucleolus constitutes one of the orientation points determining the relative localization of chromosomes in the interphase nucleus.

Cell Nucleolus↗
PubMed1976

Cytochemical study of pseudoisocyanine stained human chromosomes.

Human meiotic and mitotic chromosomes were studied with N-N' diethyl pseudoisocyanine stain. Following methylation and oxydation, the staining allowed microscopic observation of slides with both monochromatic light and fluorescence. In addition, stained preparations can be permanently conserved. Preceeded by diverse methods of chromosome denaturation or 5-BUDR incorporation, PIC lends itself to a large number of banding techniques. Cytochemical study of stained chromosomes demonstrated a certain PIC affinity for DNA although tests performed do not exclude the possibility of PIC reaction with certain proteins.

Chromatin↗
PubMed1975

[Location of nucleolar organizers in somatic nuclei of newly-formed ovary of Japanese quail (Coturnix coturnix japonica)].

The localization of nucleolar organizers has been studied in the nuclei of the somatic cells of one-day-old quail ovaries with in situ hybridization techniques. In these cells the nucleolus apparatus has a chromocentre formed by heterochromatin and small nucleoli typified by cytochemical and ultrastructural characteristics, associated at the periphery of the chromocentre. After hybridization wtih [3H] rRNA (28 S-18 S) and histoautoradiography, levels of radioactivity are detected only on the nucleoli, and not located on the chromocentre. In the interphasic nuclei of these cells, the ribosomal cistrons are intricated with nucleolus ribonucleoproteins.

Animals↗
PubMed1975

[Study of human chromosomes using fluorescence technics].

Fluorescent techniques permitted us to draw up a system of banding of human chromosomes, using quinacrine derivatives. This procedure may be used to measure the density of the chromosomes. Recently, other techniques which use various fluorochromes after denaturation, have been developed. The latter, which use acridine orange, give remarkably reliable and reproducible results. These techniques are particularly useful for the analysis of structural changes in the chromosomes. Their use is illustrated by a certain number of observations where they permitted the authors to determine the type of structural change and identify the chromosomes involved. The method of constitution and significance of the fluorescent bands is very controversial. It is not clearly known whether the fluorochromes combine with DNA or with protein bound to the latter. In spite of this uncertainty, the existence of heterogeneity in the structure of the chromatids at the metaphase provides new information for the understanding of chromosome organisation.

Acridines↗