Biochemical and cytogenetic studies on the Nucleolus Organizing Regions (NOR) of Man

Summary The hybridization kinetics of DNA with labeled (18s+28s)rRNA from HeLa cells was determined in patients with trisomy 21, healthy probands with normal karyotype and in carriers of a t(DqGq) centric fusion. The results are in, accordance with the saturation values obtained earlier for these probands:Three patients with trisomy 21 showed an increased saturation level. In 2 of these patients the excess of rDNA exceeded the expected value considerably.Three of the investigated translocation carriers t(14q21q) showed significantly reduced saturation values, while results of a fourth proband with a dicentric chromosome t(15q21q) were found to be within the range of normal probands.The heterogeneous results were correlated with the cytogenetic characteristics of the acrocentric chromosomes. It is expected that these differences could be explained on the basis of family analysis.

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Zusammenfassung Hybridisierungskinetiken der DNA mit markierter (18s+28s)rRNA aus HeLa-Zellen wurden ermittelt bei Patienten mit Trisomie 21, gesunden Probanden mit normalem Karyotyp und Trägern einer zentrischen Fusion t(DqGq). Die Ergebnisse bestätigen die bereits früher ermittelten Sättigungswerte von Hybridisierungen bei diesen Probanden:3 Patienten mit Trisomie 21 zeigten erhöhte Sättigungsniveaus. Bei 2 dieser Patienten übersteigt der Überschuß an rDNA den Erwartungswert erheblich.3 der untersuchten Translokationsträger t(14q21q) hatten signifikant erniedrigte Sättigungswerte, während die vierte Probandin mit dem dizentrischen Chromosom t(15q21q) im Normbereich lag.Die unterschiedlichen Befunde werden mit den cytogenetischen Eigenschaften der akrozentrischen Chromosomen in Zusammenhang gebracht. Es wird erwartet, daß diese Unterschiede sich durch Familienuntersuchungen aufklären lassen.

     

Targeting Homologous Recombination in Notch-Driven C. elegans Stem Cell and Human Tumors

Mammalian NOTCH1-4 receptors are all associated with human malignancy, although exact roles remain enigmatic. Here we employ glp-1(ar202), a temperature-sensitive gain-of-function C. elegans NOTCH mutant, to delineate NOTCH-driven tumor responses to radiotherapy. At ≤20°C, glp-1(ar202) is wild-type, whereas at 25°C it forms a germline stem cell⁄progenitor cell tumor reminiscent of human cancer. We identify a NOTCH tumor phenotype in which all tumor cells traffic rapidly to G2⁄M post-irradiation, attempt to repair DNA strand breaks exclusively via homology-driven repair, and when this fails die by mitotic death. Homology-driven repair inactivation is dramatically radiosensitizing. We show that these concepts translate directly to human cancer models.     

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.     

Effect of feeding boxes on the behavior of stereotyping amur tigers (Panthera tigris altaica) in the Zurich Zoo,Zurich, Switzerland

The stereotyped pacing shown by the two Amur tigers in the Zurich Zoo was hypothesized as being caused by permanently frustrated appetitive foraging behavior. Several electrically controlled feeding boxes were installed and access to each box was possible only twice a day for 15 min at semi‐random times. The boxes had to be opened actively by the tigers. Two trials were carried out: one with solitary confinement, and one with paired confinement. During box feeding, the female's stereotyped pacing was significantly reduced from 16% (solitary confinement, conventional feeding) and 7% (paired confinement, conventional feeding) to 1% (solitary confinement) and less than 0.01% (paired confinement) of the daily observed time. The female's sleeping increased significantly in both solitary and paired confinement. The male only showed a significant reduction in stereotyped pacing behavior when kept with the female (conventional feeding: 10%; box feeding: <0.01% of the daily observed time). On days with a box‐feeding regime in paired confinement, the male spent 25% (83 min) of the observed time with active behavior at the feeding boxes. The results support the hypothesis that permanently frustrated appetitive foraging behavior causes stereotyped pacing in adult tigers. Zoo Biol 21:573–584, 2002. © 2002 Wiley‐Liss, Inc.     

Fragility and spiralization anomalies of the chromosomes in three cases, including fraternal twins, with Fanconi's anemia, type Estren-Dameshek

Fraternal twins, offspring of consanguineous parents, developed pancytopenia, the boy at 7, the girl at 12 years of age. A third patient became anemic at 3 years. All three are free of associated malformations. In blood cultures the incidence of chromatid breaks, exchanges, and chromosome-type aberrations was elevated to 24%, 18%, and 28%, respectively. In addition, in a low number of mitotic cells unusual observations, pointing to profound disturbances of chromosome structure, were made. It is suggested that these patients have a genetic defect impairing the normal process of mitotic chromosome condensation and decondensation.     

Unsaturated oligogalacturonic acids are generated by in vitro treatment of pectin with human faecal flora.

Pectins with a degree of esterification (DE) of 95, 66, 34 and 0%, respectively, were incubated in vitro with human faecal flora (pH 7.8). The concentration and composition of oligogalacturonic acids (oligoGalA) generated were determined using high-performance thin-layer chromatography (HPTLC) with UV and colorimetric detection. In the first period of the anaerobic degradation, the pectin macromolecules were fragmented into unsaturated oligoGalA as intermediate products by the action of bacterial pectate lyases. Depending on the incubation time and the DE of pectin, the amount of unsaturated oligoGalA having different degrees of polymerization changed continuously. These oligoGalA were present in the cultures for some hours. Mixtures of unsaturated di-, tri- and tetraGalA were the end products of a pectate lyase action. Later, the oligoGalA disappear as a result of their further fermentation by the gastrointestinal microflora under formation of short-chain fatty acids (SCFA). Low-esterified pectins were depolymerized and fermented faster than the highly esterified by the human faecal flora in vitro. Furthermore, a mixture of unsaturated oligoGalA prepared from pectic acid by the action of pectate lyase from Erwinia carotovora was completely fermented by human faecal flora.