Search PubMed⌕ Search

Biomedical subjects

R Karhu

Publications and source records attributed to R Karhu.

40 records · Page 3Linked to original sources
PubMed1995

Comparative genomic hybridization in clinical cytogenetics.

We report the results of applying comparative genomic hybridization (CGH) in a cytogenetic service laboratory for (1) determination of the origin of extra and missing chromosomal material in intricate cases of unbalanced aberrations and (2) detection of common prenatal numerical chromosome aberrations. A total of 11 fetal samples were analyzed. Seven cases of complex unbalanced aberrations that could not be identified reliably by conventional cytogenetics were successfully resolved by CGH analysis. CGH results were validated by using FISH with chromosome-specific probes. Four cases representing common prenatal numerical aberrations (trisomy 21, 18, and 13 and monosomy X) were also successfully diagnosed by CGH. We conclude that CGH is a powerful adjunct to traditional cytogenetic techniques that makes it possible to solve clinical cases of intricate unbalanced aberrations in a single hybridization. CGH may also be a useful adjunct to screen for euchromatic involvement in marker chromosomes. Further technical development may render CGH applicable for routine aberration screening.

Chromosome Aberrations↗
PubMed1994

Increased copy number at 20q13 in breast cancer: defining the critical region and exclusion of candidate genes.

Studies by comparative genomic hybridization have indicated that a major new locus for DNA amplification in breast cancer is 20q13 and suggested that this genetic event is associated with aggressive clinical behavior. We used interphase fluorescence in situ hybridization with anonymous cosmid probes and gene-specific P1 clones to determine the minimal common region of increased copy number and to study involvement of known genes at 20q13. Based on high-level copy number increases (3 to 10-fold) found with one or more probes in 5 of 14 (35%) breast cancer cell lines and in 3 of 36 (8%) primary tumors, the critical region was narrowed to approximately 1.5 megabases at 20q13.2 defined by fractional length pter values 0.81-0.84. Previously known genes were excluded as candidates, implying that this chromosomal region harbors a novel oncogene that contributes to the malignant progression of breast cancer.

Breast Neoplasms↗
PubMed1994

High resolution mapping using fluorescence in situ hybridization to extended DNA fibers prepared from agarose-embedded cells.

Fluorescence in situ hybridization (FISH) and pulse field gel electrophoresis (PFGE) are essential techniques in physical mapping and in positional cloning. We present a technique that utilizes agarose-embedded high molecular weight DNA prepared for PFGE as a target for FISH. The agarose blocks are melted, and the DNA is extended on a poly-L-lysine-coated microscope slide. The resulting DNA fibers appear on the slide as long straight strands and are a suitable target for high resolution FISH mapping as demonstrated here with cosmid and plasmid hybridizations.

Chromosome Mapping↗