Elastosonografía mamaria / Breast elastosonography

Elastosonography is a technique that assesses objectively tissue consisteney orhardness. This diagnostic modality adds structural information to the morphological properties displayed by conventional B-mode ultrasound, thus enhancing specificity values, since malignant lesions show elasticity scores significantly higher than those of benign lesions, as recorded in all published studies. Computerized correlation of anatomical elasticity maps before and after external compression on tissues is shown as a colour map projected semitransparently on the B-mode image. Published studies reveal that breast elastography specificity results are consistently higher than those of B-mode ultrasound and its main clinical application is centered on BI-RADS 3 lesions. In this group of probably benign lesions, sonoelastography can single out those lesions that will benefit from an early biopsy due to their elastographic textural features.

La elastosonografía es una técnica que evalúa objetivamente la consistencia o dureza de los tejidos. Esta modalidad diagnóstica añade información estructural a las propiedades morfológicas que nos muestra la ecografía y nos permite alcanzar mejores resultados de especificidad, pues en todos los estudios publicados las lesiones malignas muestran dureza significativamente superior a las lesiones benignas. La correlación computarizada de los mapas anatómicos de elasticidad antes y después de ejercer una compresión externa sobre el tejido, muestra el resultado en escala de color proyectado de modo semitransparente sobre la imagen en modo-B. Los estudios publicados demuestran que la elastosonografía mamaria mejora los valores de especificidad de la ecografía en modo-B y su aplicación clínica fundamental se centra en las lesiones BI-RADS 3. En este grupo de lesiones, probablemente benignas, la elastosonografía permite detectar aquellas que se beneficiarán de una biopsia precoz por sus características elastográficas.

The 12 base pair duplication/insertion alteration could be a regulatory mutation.

A wide array of mutations now numbering more than 200 have been identified in the BRCA1 gene, one of the two breast cancer susceptibility genes identified so far. In addition, there have been several variants described but it is not known if they really represent functionally significant mutations of the BRCA1 gene. We report evidence to show that the duplication/ insertion of 12 base pairs in intron 20 could have a real effect on expression of the BRCA1 gene, although it was also present in 1% of our control population.

Dynamic mosaicism involving an unstable supernumerary der(22) chromosome in cat eye syndrome.

We have studied a girl, her sister and her mother who had a supernumerary marker chromosome in mosaicism. The marker was studied by cytogenetic methods and non-isotopic in situ hybridization with the single D22S9 DNA probe which maps to 22q11. The supernumerary chromosome was derived from a chromosome 22 and it did not present the same morphology in all the cells. At least 5 distinct types of the marker chromosome were detected and some of them were probably derived from each other (dynamic mosaicism). The proposita had an MCA pattern consistent with mild cat eye syndrome, while her sister and her mother had some of the manifestations described in this syndrome. A specific correlation could be established between phenotype and karyotype.

Non-uniform distribution of methylatable CCGG sequences on human chromosomes as shown by in situ methylation.

We carried out in situ methylation of human chromosomes with the HpaII methylase using [3H]methyl-S-adenosyl-L-methionine as the methyl group carrier. Autoradiographs localising [3H]methyl groups show methylatable CCGG sequences in the R-bands as well as in the short arms of the acrocentric chromosomes that include ribosomal DNA. The strongest labelling was observed over a subset of R-bands, including T-bands. Since methylatable CCGG sequences are representative of the unmethylated fraction of DNA, we suggest that differences in the degree of DNA methylation could be involved in the structure and function of chromosomal bands.

Distribution of DYZ2 repetitive sequences on the human Y chromosome.

The distribution of the 2000 copies of the Y-specific repetitive family DYZ2 is controversial since previous reports have mapped these sequences to different sites of the Yqh region. In this work, we have performed non-radioactive in situ hybridization of a cloned DYZ2 fragment at higher stringency conditions on 5-aza-cytidine-enlarged Y chromosomes; the results suggest a non-uniform distribution of these sequences, which are preferentially located at the proximal and distal parts of Yqh, including the C+/Q- heterochromatin at the boundary with the euchromatic region.

Induction of G- and R-banding in human chromosomes by the demethylating agent S-adenosyl-L-homocysteine.

In this report we describe the procedure of growing human lymphocytes with the demethylating agent S-adenosyl-L-homocysteine (SAH). After this treatment, which is not toxic for cell survival, both R- and G-banding were obtained by new experimental procedures: R-bands have been directly demonstrated with the GC-specific fluorochrome chromomycin A3 without the necessity of any AT-specific counterstaining agent; simultaneous G-banding and active nucleolar organizer regions have been obtained by silver impregnation of chromosomes and subsequent Giemsa staining. These results suggest a possible relationship between local differences in DNA methylation and the determination of the banded chromosome structure.

Dodeca satellite: a conserved G+C-rich satellite from the centromeric heterochromatin of Drosophila melanogaster.

To identify sequences from the centromeric region, we have constructed a Drosophila melanogaster yeast artificial chromosome (YAC) library and screened it with purified DNA from the minichromosome Dp(1;f)1187 derived from the X chromosome. We describe the structure of one clone isolated in this way. This YAC is structurally unstable and contains tandemly repeated G+C-rich 11-mer and 12-mer units, which we call dodeca satellite. Most of this satellite is located near the centromere of an autosome. Cross-hybridizing sequences are found in the genomes of organisms as distant as Arabidopsis thaliana and Homo sapiens.

Cytogenetic analysis of a human familial 15p+ marker chromosome.

An extreme variant of a human 15p+ marker chromosome is described in a human family. The short arm of this variant is greatly enriched in ribosomal RNA genes, and there are up to three secondary constrictions potentially active for rRNA transcription. These sites are hypomethylated, whereas the rest of rDNA is highly methylated, as shown by the isoschizomer pair HpaII-MspI. This chromosome variant is similar to others previously described for chromosomes 14 and 22, but some differences have been found after C-banding and after treatments with AluI and Sau3AI.

Longitudinal differentiation of the human Yq heterochromatin as revealed by the restriction enzyme TaqI.

The restriction endonuclease TaqI cleaves DNA at TCGA sites which are very common in human satellite DNAs. However, this enzyme was not used successfully up to now to digest constitutive heterochromatin of human chromosomes, where those highly repetitive DNAs are preferentially located. In this work, we show that TaqI is able to cut and extract DNA from the major heterochromatic regions on chromosomes 1, 9, 15, and 16 which appear as unstained gaps. Yq heterochromatin displays moderate digestion along its entire length but a middle region can be distinguished which is usually more affected. Complete digestion of Yq heterochromatin can be achieved when this block has been previously undercondensed by treating cell cultures with the cytidine analog, 5-azacytidine. Thus, it may be deduced that some factors related to chromatin organization might be involved in the action of TaqI. These results come to reinforce previous data about heterogeneity of Yq heterochromatin, and allow us to subdivide it into three different regions according to their differential response to TaqI digestion.

Visualization of R-bands in human metaphase chromosomes by the restriction endonuclease MseI.

Human metaphase chromosomes were treated with the restriction endonuclease MseI, which cuts DNA at TTAA sequences. This enzyme preferentially cuts and extracts DNA from G-bands and thus is the first restriction endonuclease allowing direct R-band visualization. Specific patterns ranging from R+C-like to C-like banding can be induced, depending on the concentration of the enzyme. At intermediate concentrations, only a subset of R-bands are produced, corresponding to GC-rich bands that are especially resistant to heat denaturation (so-called T-bands). These results suggest that compositional differences between chromosomal regions determine the different rates of cleavage by MseI, not only between R- and G-bands but also among different R-bands.

Cryptic variants of acrocentric human chromosomes as analysed by restriction endonucleases.

Ten phenotypically normal human individuals have been analysed by in situ treatments with restriction endonucleases in order to obtain a better characterization of some cryptic variants of acrocentric chromosomes. Treatments with AluI, NdeII and Sau3AI confirm the existence of two cryptic amplified regions on the short arms of both one chromosome 15 and one chromosome 22, in one female. These amplifications seem to be of different origin involving the nucleolar organizer region of chromosome 15 and the satellite of chromosome 22.

New distinctions between regions of centromeric heterochromatin in human chromosomes by treatments with the isoschizomers NdeII-Sau3AI.

The isoschizomers NdeII-Sau3AI (decreases GATC) have been used to characterize heterochromatic regions in human chromosomes. The findings with NdeII are identical with those previously published with MboI, but the results with Sau3AI provide evidence for new distinctions of centromeric heterochromatin in chromosomes 5 and 6. The results are discussed in relation to the chromatin organization at these regions an the mechanisms of the action of restriction endonucleases.

In situ methylation of human chromosomes with methylase-AluI.

A method for in situ DNA methylation with the prokaryotic methylase AluI has been developed for use on fixed human chromosomes. Incorporation of methyl groups into the chromosomal DNA has been shown by autoradiography using a labeled substrate. The methylation prevents the digestion of chromosomal DNA by AluI, allowing direct visualization of clusters of nonmethylated AGCT targets along the human complement.