PubMed Health⌕ Search

Biomedical subjects

G Stetten

Publications and source records attributed to G Stetten.

At least 73 records · Page 4Linked to original sources
PubMed1988

Clonal evolution in human lymphoblast cultures.

We established lymphoblast cultures from normal females heterozygous for electrophoretic variants of glucose-6-phosphate dehydrogenase (G6PD), and the X-linked markers have permitted us to look at evolution of these cell populations in culture. The established cultures were phenotypically heterozygous at onset, having both of the mosaic cell populations resulting from X chromosome inactivation. However, by the tenth subculture, the population of cells no longer reflected the heterozygous genotype in 50% of the cultures, as only a single G6PD isozyme was expressed. The ultimate cell composition seems to be influenced by the initial composition, by the nature of alleles at heterozygous X-linked loci that may provide a growth advantage (or disadvantage), as well as by stochastic events. Our results show that lymphoblast cultures may not reflect the X-linked phenotype of the cells from which they were derived. The fate of such cultures seems to be evolution toward clonal cell populations.

Cells, Cultured↗
PubMed1986

Translocation of the nucleolus organizer region to the human X chromosome.

We report the unique finding of a satellited X chromosome in a woman with Turner syndrome and a mosaic karyotype 45,X/46,X,mar(X)(sat,QFQ55),var(21)(sat,QFQ55). In PHA-stimulated lymphocytes and in lymphoblast culture, the satellited X chromosome was consistently late replicating. The translocated nucleolus organizer region (NOR) genes in the stalk of the satellite, however, remained transcriptionally active, and an unusual, late-replicating band was seen at the distal end of Xp. Analysis of fibroblast clones containing the satellited X chromosome suggests that the mar(X) is relatively stable.

Adult↗
PubMed1985

Ring chromosome 21: characterization of DNA sequences at sites of breakage and reunion.

We have presented studies of an unusual child with an r21 chromosome who lacks the phenotype of Down syndrome. We have sequenced the region of the breakpoint in the normal DNA fragment and have isolated the abnormal breakpoint fragment as a 7.5-kb EcoRI fragment. We have preliminary evidence localizing the breakpoint to a few hundred base pairs of 21q DNA. Since the child lacks the classical phenotype of Down syndrome, further studies of the DNA distal to the breakpoint on the long arm of chromosome 21 may help us to elucidate "genes" important to the phenotype of Down syndrome.

Base Sequence↗
PubMed1984

Prenatal detection of an unstable ring 21 chromosome.

An unstable ring chromosome 21 detected through prenatal studies was associated at birth with an apparently normal male phenotype. At 14 months of age, examination indicated only minor developmental delay. The majority of cells examined from amniocyte, fibroblast, and lymphocyte cultures contained an asymmetrical dicentric ring 21 chromosome which was larger than a normal chromosome 21. This ring is presumed to be a duplication for most of chromosome 21 and a deletion of part of the terminal regions. The karyotype is described as mos45,XY,-21/46,XY,r(21)(p13q22.3). The child is monosomic for part of the sub-band 21q22.3 in every cell and trisomic for the remainder of the chromosome in most of his cells. The terminal deletion does not appear to have been severely detrimental to the phenotype and the effective trisomy present in many cells studied was insufficient to cause the Down syndrome.

Adult↗
PubMed1983

Prenatal diagnosis using DNA polymorphisms. Report on 95 pregnancies at risk for sickle-cell disease or beta-thalassemia.

DNA polymorphisms are normal inherited variations in DNA that can often be used to document the inheritance of genes that produce disease. In this report we summarize our experience with prenatal diagnosis in 95 pregnancies in which the fetus was at risk for a hemoglobinopathy; the diagnosis was performed with use of DNA polymorphisms located so near the beta-globin gene that they are inherited along with that gene. Of the 95 pregnancies, 57 involved fetuses at risk for sickle-cell anemia, 32 fetuses at risk for beta-thalassemia, and 6 fetuses at risk for other beta-chain hemoglobinopathies. Diagnosis was achieved solely by analysis of DNA polymorphisms in cells recovered by amniocentesis in 82 cases (86 per cent) and was completed by fetoscopy and fetal-blood study in an additional 6 cases (6 per cent). Prenatal diagnosis was proved correct in all 78 cases that have been available for confirmation to date. Our experience demonstrates that DNA polymorphisms can be useful for the prenatal diagnosis of genetic diseases in which the basic defect cannot be directly detected.

Amniocentesis↗
PubMed1982

Amniotic fluid steroid levels. Fetuses with adrenal hyperplasia, 46,XXY fetuses, and normal fetuses.

Concentrations of testosterone, androstenedione, dehydroepiandrosterone (DHA), DHA sulfate (DHAS), progesterone, 17 alpha-hydroxyprogesterone (17-OHP), and hydrocortisone were determined in amniotic fluid obtained at amniocentesis or at elective cesarean section. Male fetuses had significantly higher concentrations of testosterone and androstenedione than female fetuses had between 15 and 21 weeks of gestation but not near term (36 to 40 weeks). In both sexes, progesterone and 17-OHP concentrations fell and DHA, DHAS, and hydrocortisone concentrations increased significantly with advancing gestational age. Amniotic fluid 17-OHP, testosterone, DHA, and androstenedione levels from female fetuses with congenital adrenal hyperplasia (CAH) were more elevated in the second trimester than in the third. Three female fetuses at risk for CAH, but not affected, had normal steroid concentrations. Steroid concentrations from two fetuses with Klinefelter's syndrome were not abnormal.

Adrenal Hyperplasia, Congenital↗
PubMed1976

33258 Hoechst enhancement of the photosensitivity of bromodeoxyuridine-substituted cells.

Cells that have incorporated 5-bromodeoxyuridine (BrdU) into their DNA become extremely sensitive to photoinduced killing after treatment with the dye, 33258 Hoechst. Under appropriate conditions the dye increases the efficiency of killing by a factor of approximately 10(4). This enhanced photosensitivity suggests that the combination of BrdU, dye, and light can be used to select conditional lethal mutants.

Benzimidazoles↗
PubMed1976

Spectral studies on 33258 Hoechst and related bisbenzimidazole dyes useful for fluorescent detection of deoxyribonucleic acid synthesis.

Absorption, fluroescence and circular dichroism measrements on 33258 Hoechst-deoxyribonucleic acid (DNA) complexes are consistent with the existence of two types of dye-binding interactions. One type, which persists at elevated solution ionic strength, is highly specific for adenine-thymine-rich DNA. Dye bound under this condition exhibits efficient fluorescence and strong optical activity. A less specific, largely electrostatic interaction is associated with less intense fluorescence and weaker optical activity. The fluorescence of 33258 Hoechst and several other bisbenzimidazole dyes is less when bound to poly(deoxyadenylate-5-bromodeoxyuridylate) than when bound to poly(deoxyadenlyate-deoxythymidylate). Quenching of 33258 Hoechst fluorescence can also be used to detect biosynthetic incorporation of 5-bromodeoxyuridine into the DNA of living cells. This property of 33258 Hoechst should allow fluorescence-activated cell and chromosome sorting according to the extent of DNA synthesis, providing a bridge between biochemical and cytologic analyses of processes related to DNA replication.

Animals↗
PubMed1975

Induction by alkylating agents of sister chromatid exchanges and chromatid breaks in Fanconi's anemia.

Sister chromatid exchanges, which may reflect chromosome repair in response to certain types of DNA damage, provide a means of investigating the increased chromosome fragility characteristic of Fanconi's anemia. By a recently developed technique using 33258 Hoechst and 5-bromodeoxyuridine, it was observed that the baseline frequency of sister chromatid exchanges in phytohemagglutinin-stimulated lymphocytes from four males with Fanconi's anemia differed little from that of normal lymphocytes. However, addition of the bifunctional alkylating agent mitomycin C (0.01 or 0.03 mug/ml) to the Fanconi's anemia cells during culture induces less than half of the increase in exchanges found in identically treated normal lymphocytes. This reduced increment in exchanges in accompanied by a partial suppression of mitosis and a marked increase in chromatid breaks and rearrangements. Many of these events occur at sites of incomplete chromatid interchange. The increase in sister chromatid exchanges induced in Fanconi's anemia lymphocytes by the monofunctional alkylating agent ethylmethane sulfonate (0.25 mg/ml) was slightly less than that in normal cells. Lymphocytes from two sets of parents of the patients with Fanconi's anemia exhibited a normal response to alkylating agents, while dermal fibroblasts from two different patients with Fanconi's anemia reacted to mitomycin C with an increase in chromatid breaks, but a nearly normal increment of sister chromatid exchanges. The results suggest that chromosomal breaks and rearrangements in Fanconi's anemia lymphocytes may result from a defect in a form of repair of DNA damage.

Alkylating Agents↗
PubMed1975

Recent developments in the detection of deoxyribonucleic acid synthesis by 33258 Hoechst fluorescence.

A number of applications of the detection of deoxyribonucleic acid synthesis by fluorescence microscopy are illustrated. These include (a) the analysis of sister chromatid exchanges and sister chromatid segregation at mitosis, (b) the location of chromosome regions containing deoxyribonucleic acid with an asymmetric distribution of thymine residues between polynucleotide chains and (c) the detection of late replicating regions in metaphase chromosomes. The suppression of 33258 Hoechst fluorescence by 5-bromodeoxyuridine incorporated biosynthetically into interphase nuclei is demonstrated both in fixed cytologic preparations and in unfixed cultured cells. Many of the cytologic observations described might form a basis for future biochemical studies.

Animals↗