Leonor Parreira

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It is believed that the 3-dimensional organization of centromeric heterochromatin in interphase may be of functional relevance as an epigenetic mechanism for the regulation of gene expression. Accordingly, a likely possibility is that the centromeres that spatially associate into the heterochromatic structures (chromocenters) observed in the G1 phase of the(More)
Notch signaling is known to differentially affect the development of lymphoid B and T cell lineages, but it remains unclear whether such effects are specifically dependent on distinct Notch ligands. Using a cell coculture assay we observed that the Notch ligand Delta-1 completely inhibits the differentiation of human hematopoietic progenitors into the B(More)
The mechanisms whereby chromosomal translocations are consistently associated with specific tumor types are largely unknown. A generally accepted hypothesis is that the physical proximity of the involved chromosomal regions may be one important factor in the genesis of these phenomena. Accordingly, a likely possibility is that such a proximity may occur in(More)
Deletions within chromosome 6 (6q25 to 6qter) are the most consistent structural change observed in salivary gland carcinomas. To better define the location of these deletions we investigated loss of heterozygosity (LOH) for 23 polymorphic markers within 19 salivary gland carcinomas covering several histological subtypes. LOH was observed in 47% of tumors,(More)
The three-dimensional positioning of immunoglobulin (Ig) genes within the nucleus of human cells was investigated using in situ hybridization and confocal microscopy. The visualization of heavy and light chain genes in B-lymphoid cells showed that the three Ig genes are differentially and nonrandomly distributed in different nuclear subvolumes: the κ genes(More)
Aims-To directly visualise immunoglobulin (Ig) heavy (H) and light chain genes (kappa and lambda) in metaphase chromosomes and interphase nuclei of normal and malignant lymphocytes using small genomic probes targeted to intragenic sequences.Methods-Cytogenetic preparations from phytohaemagglutinin stimulated lymphocytes, B-chronic lymphocytic leukaemia(More)
At present several lines of evidence indicate that the nucleus is functionally compartmentalized into discrete structures with defined properties. For instance, it is well established that the molecular machines involved in replication, transcription, and RNA processing assemble into morphological entities but it remains unclear whether these correspond to(More)
OBJECTIVE The results obtained in 43 patients using direct intraoperative radiofrequency catheter ablation, as an alternative to surgical incisions, to perform atrial fibrillation surgery, are presented. METHODS Forty-three patients with ages ranging from 43 to 74 years (x = 59), with chronic atrial fibrillation with an average duration 6+/-5 years were(More)
We carried out cytogenetic analysis in 23 patients with Ph-positive chronic granulocytic leukemia in blast crisis. In all cases the type of blast cell was characterized by cytochemistry, immunologic markers, and ultrastructural studies. Twelve cases were classified as myeloid transformation, six as lymphoid, two as mixed (lymphoid and myeloid), and two were(More)
It is believed that two important factors in the genesis of reciprocal chromosomal translocations in malignant cells are the physical proximity of the involved regions and local structural features of the chromatin fiber that make them more susceptible to breakage and rearrangement. In this work we sought to investigate whether PML-RARA fusion transcripts,(More)