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T Haaf

Publications and source records attributed to T Haaf.

136 records · Page 8Linked to original sources
PubMed1985

Evolutionary conservation of fragile sites induced by 5-azacytidine and 5-azadeoxycytidine in man, gorilla, and chimpanzee.

Lymphocyte cultures from man, gorilla, and chimpanzee were treated with 5-azacytidine and 5-azadeoxycytidine. These cytidine analogues induce common fragile sites in the chromosome bands 1q42 and 19q13 of man. A rare fragile site is induced by 5-azadeoxycytidine in the band 1q24. The optimum conditions required for inducing these new fragile sites were determined by a series of experiments. The common fragile site in human chromosome 1q42 also exists in the gorilla and chimpanzee in the homologous band 1p32. The fragile site in human chromosome 19q13 was demonstrated in the gorilla in the homologous chromosome band 20q13. These are the first examples found of evolutionary highly conserved fragile sites in homologous chromosome bands in related primate species. The interaction between 5-azacytidine, 5-azadeoxycytidine, and chromosomal DNA; the evolutionary conservation of genes located within or closely adjacent to the fragile sites in the chromosome 1 of Hominoidea; and the phylogenetic origin of the two new common fragile sites are discussed.

Animals↗
PubMed1984

Satellited Y chromosomes: structure, origin, and clinical significance.

Three cases of inherited satellited Y chromosomes (Yqs) were analysed using several cytogenetic techniques. The cytogenetic data of the 14 cases of Yqs chromosomes described to date were reviewed. All Yqs chromosomes carry an active nucleolus organizer region (NOR) in their long arm and must have developed from translocations involving the short arms of the acrocentric autosomes. The structure of the heterochromatic satellite region in the Yqs chromosomes shows conspicuous inter-familial differences; this permits the reconstruction of the translocations from which the various Yqs were derived. Some causal factors leading to the development of Yqs chromosomes are considered: the specific localization of the four satellite DNAs and highly methylated DNA sequences in the karyotype, and some new experimental data on the spatial arrangement of heterochromatic regions in interphase nuclei. These provide distinct evidence for a preferential involvement of the autosomes 15 and 22 in the translocations with the Y heterochromatin. All clinical reports documenting Yqs males born with malformations were reviewed. It appears that the presence of an extra NOR and NOR-associated heterochromatin in the Yqs chromosomes does not cause any phenotypic abnormalities (as long as the Y euchromatin is intact). The possibility that a Yqs chromosome predisposes to non-disjunction and/or to translocations of other chromosomes is discussed.

Adolescent↗
PubMed1984

5-Azacytidine-induced undercondensations in human chromosomes.

The cytosine analogue 5-azacytidine induces very distinct undercondensations in human chromosomes if applied to lymphocyte cultures. The number of induced undercondensations and their chromosomal localization can be varied by the 5-azacytidine dose and the treatment time. "Pulverized" chromosomes or undercondensations in the G-band-positive chromosome regions are produced with high doses and long treatment times. If applied in low doses during the last hours of culture, 5-azacytidine induces specific undercondensations in the heterochromatin of chromosomes 1, 9, 15, 16, and Y. Optimum conditions required for inducing the various types of undercondensation in the chromosomes were determined. Various examples of the use of 5-azacytidine in the analysis of chromosome rearrangements involving heterochromatic regions are presented.

Azacitidine↗
PubMed1984

Specific silver staining of experimentally undercondensed chromosome regions.

Treatment of human and mouse cell cultures with DNA binding AT-specific compounds and with some base analogues induced distinct undercondensations in several heterochromatic chromosome regions. All those heterochromatic regions undercondensed by AT-specific DNA ligands (distamycin A, DAPI, Hoechst 33258) could be heavily labeled with the silver(Ag)-staining technique; but the heterochromatic regions undercondensed with the cytidine analogue 5-azacytidine were Ag-negative. In metaphase chromosomes from BrdU-treated human cell cultures, the bifilarly substituted chromatids, which show a slight undercondensation, were also Ag-negative. Cytochemical analyses of the Ag-stained undercondensed heterochromatic regions showed that the Ag-stainable material consisted of nonhistone proteins. The mechanism of Ag staining in the undercondensed heterochromatic regions was compared with Ag staining of the nucleolus organizer regions.

Animals↗
PubMed1984

Distamycin A/DAPI bands and the effects of 5-azacytidine on the chromosomes of the chimpanzee, Pan troglodytes.

The chromosomes of the chimpanzee were stained with distamycin A/DAPI, which labels specific C-bands. Bright distamycin A/DAPI fluorescence was found in the heterochromatic regions of chromosomes 6, 11, 14 to 16, 18 to 20, and 23 and the Y. Lymphocyte cultures from chimpanzees were treated with low doses of 5-azacytidine during the last hours of culture. This cytosine analog induces highly distinct undercondensations in 28 heterochromatic regions of 19 chromosomes. These 5-azacytidine-sensitive regions are predominantly located in the terminal C-bands of the chromosomes. In vitro treatment with 5-azacytidine also preserves into the metaphase stage somatic pairings between the 5-azacytidine-sensitive heterochromatic regions in interphase nuclei. The homologies and differences regarding the chromosomal localization of distamycin A/DAPI-bright C-bands, 5-azacytidine-sensitive heterochromatin, 5-methylcytosine-rich DNA sequences, and satellite DNAs in the chimpanzee and man are discussed.

Animals↗
PubMed1983

Chromosome banding in Amphibia. VIII. An unusual XY/XX-sex chromosome system in Gastrotheca riobambae (Anura, Hylidae).

The mitotic and meiotic chromosomes of the marsupial frog Gastrotheca riobambae were analysed with various banding techniques. The karyotype of this species is distinguished by considerable amounts of constitutive heterochromatin and unusual, heteromorphic XY sex chromosomes. The Y chromosome is considerably larger than the X chromosome and almost completely heterochromatic. The analysis of the banding patterns obtained with GC- and AT-base-pair-specific fluorochromes shows that the constitutive heterochromatin in the Y chromosome consists of at least three different structural categories. The only nucleolus organizer region (NOR) of the karyotype is localized in the short arm of the X chromosome. This causes a sex-specific difference in the number of NOR: female animals have two NORs in diploid cells, male animals one. No cytological indications were found for the inactivation of one of the two X chromosomes in the female cells. In male meiosis, the heteromorphic sex chromosomes form a characteristic sex-bivalent by pairing their telomeres in an end-to-end arrangement. The significance of the XY/XX sex chromosomes of G. riobambae for the study of X-linked genes in Amphibia, the evolution of sex chromosomes and their specific DNA sequences, and the significance of the meiotic process of sex chromosomes are discussed.

Animals↗
PubMed1983

A direct demonstration of somatically paired heterochromatin of human chromosomes.

Human lymphocyte cultures were treated with different concentrations of 5-azacytidine for various lengths of time. This cytosine analog induces very distinct undercondensation in the heterochromatin of chromosomes 1, 9, 15, 16, and Y if applied in low doses during the last hours of culture. These regions are further distinguished by their intense distamycin A/DAPI-staining and highly methylated DNA. In interphase nuclei, these heterochromatic regions are frequently somatically paired. These somatic pairings are preserved up to the metaphase stage in the 5-azacytidine-treated cultures and are thus susceptible to direct analysis. The specific effect of 5-azacytidine on the heterochromatin of these chromosomes, its conserving effect on somatic pairing, and some of the consequences of the somatic pairing on the development of human chromosome aberrations are discussed.

Adult↗
PubMedDate not supplied

Chromosome heteromorphisms in the gorilla karyotype. Analyses with distamycin A/DAPI, quinacrine and 5-azacytidine.

The chromosomes of one male and three female gorillas were extensively studied with various regional banding methods. The chromosomes were stained with the fluorescent dyes quinacrine mustard and distamycin A/DAPI (DA/DAPI), which label different subsets of heterochromatin in the chromosome complement. Furthermore, lymphocyte cultures were treated with the cytidine analog 5-azacytidine (5-azaC). The 5-azaC-induced undercondensations were found in most of the DA/DAPI-bands as well as in many telomeric C-bands. The karyotype of the gorilla exhibits a considerable number of heterochromatin variants. Of the different types of heteromorphisms noted, the most striking is that involving the short arm regions of chromosomes 12 to 16 and 23 (satellite stalk regions) and the paracentromeric heterochromatin of chromosomes 17 and 18. There also are numerous heteromorphic C-bands localized in the telomeric regions of homologous chromosome arms. In comparison, only few heteromorphisms occur between C-bands in the centromeric and pericentromeric regions of homologs. Finally, a variability in the fluorescence intensity of quinacrine-bright satellites in the short arms of chromosomes 12 to 16, 22, and 23 is observed.

Animals↗
PubMedDate not supplied

Chromatin bodies in multidrug resistant hybrid cells have centromeres and originate from homogeneously staining regions.

Antikinetochore antibodies from patients with the CREST syndrome of scleroderma were used as probes to study homogeneously staining regions (HSRs) in multidrug resistant (MDR) mouse tumor cells, and chromatin bodies (CBs) in MDR mouse-hamster hybrid cells. In one mouse tumor line the C-band positive HSR showed antigenic properties and displayed many weekly fluorescent spots, i.e. it contained kinetochore proteins. The immunofluorescence pattern of the HSR could also be observed in interphase nuclei. The C-band positive CBs of the hybrid cells had active centromeres, as shown by double kinetochore spots. These results support our hypothesis that CBs originate from C-band positive HSRs.

Animals↗