摘要:

High-resolution flow-cytometric measurements of ethidium bromide/mithramycin-stained human fibroblast cultures reveal discrepancies between fluorescence pulse-height distributions and genome size as a function of cell strain, culture conditions, culture age, and proliferative stage. These discrepancies were quantitatively assessed by (1) evaluation of the variation of the widths of the 2c fluorescence pulse-height histogram peaks, (2) comparisons between sample to standard fluorescence ratios of 45, XO and 49, XXXXY cell strains, and (3) comparison of fluorescence intensities among cell populations of identical genome size but differing degrees of chromatin condensation (mitotic vs. nonmitotic cells of diploid and tetraploid cell strains). As in our previous studies with lymphocytes, our results suggest caution in equating fluorescence intensity with “DNA content” in flow measurements of nonhomogeneous cell populations. Conditions of cell culture and sample preparation must be standardized in order to compare “DNA content” differences by flow techniques. Remaining sources of variation presently limit detection to differences in DNA content of greater

ISSN:1424-8581    

DOI:10.1159/000131553

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

Cells with spontaneously endoreduplicated chromosomes were observed in tonsillar lymphocyte cultures from the second to the seventh day of culture, although at a low frequency. Cell cycle kinetics leading to endoreduplication were examined by the 5-bromodeoxyuridine (BrdU)-acridine orange method. The diplochromosomes showed four fluorescent patterns depending on the period during which BrdU was incorporated into the DNA. The kinetic data also revealed two populations among the cells with endoreduplicated chromosomes: one with a shorter (36 or 48 h) and the other with a longer cell cycle time. The existance of the latter population was shown by the fact that cell without differentially stained chromatids were observed many hours after BrdU addition (up to 120 h). This suggests that some cells with endoreduplicated chromosomes originate from cells arrested in G2.

ISSN:1424-8581    

DOI:10.1159/000131554

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

Chromosome banding patterns obtained by ammoniacal silver staining (Ag-AS) and alkaline Giemsa (CBG) have been analysed in several amphibian species of the genus Odontophrynus from South America. Ag-AS bands were found at secondary constrictions, mainly of chromosomes 4 and 11. The CBG technique revealed centromeric and telomeric constitutive heterochromatin on almost all chromosomes of these species. Moreover, intercalary bands were found at particular sites of several chromosomes. Some inter- and intra-population polymorphisms were found for the Ag-AS and C-banding patterns. The species variability in the number and position of the Ag-AS bands, known to be regions of active ribosomal cistrons, as well as the specific sites of intercalary heterochromatin, are used to discuss the possible evolutionary relationships among these species.

ISSN:1424-8581    

DOI:10.1159/000131555

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

The lymphocytes of a patient with Bloom’s syndrome were examined for chromosome abnormalities. The break points involved in the abnormalities in this patient were found to be nonrandom in their distribution, as was previously described in the literature in another case. It is preliminarily proposed that, in both cases, many more breaks occur in chromosomal areas which replicate their DNA late in the S phase of the cell cycle than would be expected by chance. The particularly severe manifestations of the disease in this patient, including an unusually high percentage of cells with chromosome abnormalities, tend to confirm the suggestion that Bloom’s syndrome may not simply be the result of one structural mutat

ISSN:1424-8581    

DOI:10.1159/000131556

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

Cytological hybridization in situ was used to identify chromosomes carrying DNA sequences homologous to Herpes simplex I (HSV-I) DNA in a HSV-transformed L-cell line. The L-cell karyotype, frequency of chromosome distribution, and possible homology to the normal chromosome complement are given. The major chromosomal sites for transcription of ribosomal RNA (rRNA) were also determined.

ISSN:1424-8581    

DOI:10.1159/000131557

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

Immunochemical methods were used to identify the genetic origin of hypoxanthine phosphoribosyltransferase (HPRT) expressed in heteroploid, HPRT-deficient mouse (A9) cells and Chinese hamster ovary (K627) cells, after these cells were fused with chick embryo erythrocytes and selected for resistance to hypoxanthine-aminopterin-thymidine (HAT) medium. All of the HAT-selected clones produced HPRT activity which was immunoprecipitable by an antiserum specific for chick HPRT, but not by an antiserum specific for mouse and hamster HPRT. Furthermore, the HPRT activity in these clones was electrophoretically indistinguishable from chick liver HPRT and clearly different from mouse liver HPRT. These data provide evidence that the HPRT activity expressed in cell hybrids produced by the fusion of HPRT-negative mammalian cells and chick erythrocytes containing genetically inactive nuclei is indeed coded by the chick HPRT gene and that an avian gene can be stably incorporated and correctly expressed in a mammalian cell.

ISSN:1424-8581    

DOI:10.1159/000131558

出版商:S. Karger AG    

年代:1981

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000131559

出版商:S. Karger AG    

年代:1981

数据来源: Karger