We reviewed the banded karyotypes of 24 human neuroblastomas and cell lines to identify any consistent chromosomal abnormalities. Six of the 10 primary tumors and one of the 14 cell lines were studied at this institution. Of the 24 neuroblastomas karyotyped, 20 were near-diploid, one was near-triploid, and 3 were near-tetraploid. One primary tumor had a diploid karyotype without numerical or st...

Two human colon carcinoma cell lines derived from the same tumor specimen were characterized. The cell lines, COLO 320 and COLO 321 , have amine precursor uptake and decarbox ylation cell properties, such as ectopic production of norepi nephrine, epinephrine, serotonin, adrenocorticotropic hor mone, and parathyroid hormone. The cells were morphologi cally different from most colon cell lines. D...

Amplification of the MYCN gene is a characteristic feature of many neuroblastomas and is correlated with aggressive tumor growth. Amplicons containing this gene form either double minutes (dmins) or homogeneously staining regions (HSRs). To study the nuclear topology of these tumor-specific and transcriptionally active chromatin structures in comparison to chromosome territories, we performed f...

A plasmid bearing both a replication initiation region and a matrix attachment region is spontaneously amplified in transfected mammalian cells and generates plasmid repeats in the extrachromosomal double minutes (DMs) or the chromosomal homogeneously staining region (HSR). Generally, the repeat sequences are subject to repeat-induced gene silencing, the mechanism of which remains to be elucida...

Heterochromatin is critical for genome integrity, and recent studies have suggested the importance of transcription in heterochromatin for maintaining its silent state. We previously developed a method to generate a large homogeneously staining region (HSR) composed of tandem plasmid sequences in human cells that showed typical heterochromatin characteristics. In this study, we examined transcr...

A methotrexate (MTX)-resistant murine lymphoblastoid cell line has been obtained by serial passage in increasing concentrations of MTX which is greater than 100,000-fold resistant to MTX (L5178YR) and has dihydrofolate reductase (DHFR) levels 300-fold higher than the parental line. The L5178YR cell line synthesizes approximately 10-11% of its total soluble cell protein as DHFR regardless of gro...

Let T be an edge weighted tree, let dT (u, v) be the sum of the weights of the edges on the path from u to v in T , and let dmin and dmax be two nonnegative real numbers such that dmin ≤ dmax. Then a pairwise compatibility graph of T for dmin and dmax is a graph G = (V,E), where each vertex u′ ∈ V corresponds to a leaf u of T and there is an edge (u′, v′) ∈ E if and only if dmin ≤ dT (u, v) ≤ d...