Chromosome number distribution and cellular DNA content in colorectal adenomas from polyposis and nonpolyposis patients

Ploidy analyses of colorectal adenomas were performed by combined flow cytometric DNA analysis of unfixed isolated nuclei and direct chromosome preparation after Colcemid incubation for 9-20 hours. Ten of 18 adenomas from nonpolyposis patients and 4 of 13 adenomas from patients with familial adenomatous polyposis yielded a mean of 25 countable metaphases (range 7-44) per tumor. Of 343 metaphases, only 38% had 46 chromosomes, and 62% were nondiploid. All but one adenoma had diploid or peridiploid modes in the range of 46-50 chromosomes. One adenoma was hyperploid, with a mode of 74 chromosomes and a correspondingly increased nuclear DNA content. In another two adenomas, the DNA analyses showed small hyperploid populations constituting 6% and 2% of the cells. The most striking difference between the DNA analyses and chromosome number distributions was that 13% of all metaphases were hyperploid with chromosome numbers outside the perimodal range but, except in one adenoma, without indication in the DNA histogram of corresponding hyperploid cell populations. We propose that these aberrant metaphases indicate an early acquired genetic instability of the neoplastic epithelium, which may be instrumental in generation of hyperploid, invasive clones, which constitute most colorectal carcinomas.     

Smooth muscle differentiation in cultured human breast gland stromal cells

We analyzed in cultures from the human breast the potential of stromal cells resembling fibroblasts to undergo smooth muscle differentiation. The cellular components of the breast tissue from 10 biopsies were disaggregated by collagenase digestion and further purified by differential centrifugation into suspensions of single cells and intact blood vessels. These two fractions of stromal cells were plated in culture and their phenotypic traits analyzed within 24 hours. During this time, the blood vessel fraction gave rise to stromal cells with smooth muscle differentiation as judged immunocytochemically using monoclonal antibodies to alpha-/gamma-muscle actins, to alpha-smooth muscle actin, to type IV collagen, and to laminin. Furthermore, the cells of this fraction resembled smooth muscle cells based on 2D gel electrophoresis and immunoblotting determination of isoactin content. After 24 hours in culture, the single-cell fraction consisted of an almost pure population of cells not exhibiting smooth muscle differentiation but rather resembling fibroblasts. Maintenance of fibroblast-like cells without smooth muscle differentiation was possible for more than 14 days on chemically defined medium. These cells remained quiescent, as measured by cell quantification and immunoreactivity to the proliferation-associated antigen, Ki-67. Growth of these cells could be stimulated by adding serum at any time during the experimental period. Single-cell fractions from seven biopsies were allowed to grow exponentially in the presence of serum for up to 10 days, and the kinetics of smooth muscle differentiation were monitored immunocytochemically and biochemically. These experiments showed that alpha-smooth muscle actin synthesis was induced in 10 to 80% of the fibroblast-like cells after 4 to 11 days in culture. Both the final number of alpha-smooth muscle actin-positive cells and the onset of synthesis varied with the initial seeding density. Dose-response experiments (at constant cell density) revealed that serum exerted maximal effect at concentrations above 10%. It was therefore concluded that elements of smooth muscle differentiation may arise in non-smooth muscle stromal cells taken directly from human breast tissue.     

Androgen receptor YAC transgenic mice carrying CAG 45 alleles show trinucleotide repeat instability

X-linked spinal and bulbar muscular atrophy (SBMA) is caused by a CAG repeat expansion in the first exon of the androgen receptor (AR) gene. Disease-associated alleles (37-66 CAGs) change in length when transmitted from parents to offspring, with a significantly greater tendency to shift size when inherited paternally. As transgenic mice carrying human AR cDNAs with 45 and 66 CAG repeats do not display repeat instability, we attempted to model trinucleotide repeat instability by generating transgenic mice with yeast artificial chromosomes (YACs) carrying AR CAG repeat expansions in their genomic context. Studies of independent lines of AR YAC transgenic mice with CAG 45 alleles reveal intergenerational instability at an overall rate of approximately 10%. We also find that the 45 CAG repeat tracts are significantly more unstable with maternal transmission and as the transmitting mother ages. Of all the CAG/CTG repeat transgenic mice produced to date the AR YAC CAG 45 mice are unstable with the smallest trinucleotide repeat mutations, suggesting that the length threshold for repeat instability in the mouse may be lowered by including the appropriate flanking human DNA sequences. By sequence-tagged site content analysis and long range mapping we determined that one unstable transgenic line has integrated an approximately 70 kb segment of the AR locus due to fragmentation of the AR YAC. Identification of the cis - acting elements that permit CAG tract instability and the trans -acting factors that modulate repeat instability in the AR YAC CAG 45 mice may provide insights into the molecular basis of trinucleotide repeat instability in humans.      

Ensemble noise and current relaxation analysis of K+ current in single isolated salivary acinar cells from rat

The K⁺ channel in rat parotid gland acinar cells were investigated by ensemble current noise analysis in single isolated cells employing the giga-seal whole cell current recording mode. Sets of 20–40 identical de- and hyperpolarization voltage steps were applied and the resultant current records were processed by computer to obtain the mean and the variance of the current. The time-course of the mean current could be fitted by the sum of two exponentials, suggesting a 3-state model. The simplest plausible hypothesis is a model with one open and two closed states. Assuming this model, the relationship between the variance (₂) and the mean current (I) could be fitted by the function ₂/I=i–I/N. The estimated single channeli/V-relations were similar to those taken from single channel current recordings, and the size of the population of channels per cell (N) was 76±26 (n=12). The validity of the model was tested by a successful simulation of the time-course of the variance.     

Congenital malformation of the feet with low body height

Among 75 members of a Danish family, 12 were found with a syndrome not previously described. Clinically, the syndrome consists of low body height and rigid flat feet, with weight-bearing pain in the feet. Radiologically, the deformation of the feet is a medial synostosis between the talus and the calcaneus combined with ankle joint dysplasia. The cause of the syndrome is most probably an autosomal dominant gene with complete penetrance. No linkage was found of the gene to 18 marker genes.     

Ring chromosome 22 and neurofibromatosis

Variable constitutional mosaicism, mos45,XY,-22/46,XY,-22,+mar/46,XY,-22,+r(22)/47,XY,-22,+r(22)+mar/ 47, XY,-22,+r(22)*2, was found in PHA-stimulated peripheral blood, in a lymphoblastoid cell line and in cultured skin fibroblasts from a mentally retarded patient with neurofibromatosis. Both the ring chromosome and the small extra marker chromosome stained positively by in situ hybridization with a chromosome 14/22-specific alphoid repeat probe. DNA dosage analysis showed constitutional loss of one copy of the arylsulfatase A gene (ARSA), consistent with its terminal location on 22q. There was no evidence of constitutional loss of D22S1 or D22S28 which flank the neurofibromatosis type 2 (NF2) locus. Analysis of two DNA samples from a skin neurofibroma indicated retainment of two copies of D22S1, whereas the results were ambiguous with respect to tumor-specific loss of one copy of D22S28. It is suggested that the development of neurofibromatosis of unclear type in two r(22) carriers might be associated with somatic mutation of the NF2 locus due to instability of the ring chromosome(s), and in analogy, that somatic mutation of either NF1 or NF2 may account for some cases of neurofibromatosis which do not meet the criteria of either NF1 or NF2. The occurrence of seminoma in the proband may be fortuitous, but could also be due to the presence of a seminoma-associated locus on chromosome 22.