摘要:

Rat hepatoma cells amplified for adenosine deaminase (ADA) gene sequences show the amplified DNA on large, homogeneously staining regions (HSRs). The amplified cells are stable in the absence of selection for 12 mo without loss of ADA activity or gene sequences. However, in hybrids formed between an amplified cell line with a prominent HSR and a nonamplified cell line, rapid loss of ADA activity, as well as gene sequences, occurs. Karyotype analyses of the hybrids indicate that the HSR structures are no longer visible in a large percentage of the hybrid metaphase spreads and appear to have been replaced by DNA structures that resemble double minutes. Our data provide evidence that (1) the extent of the breakdown of the HSR in the hybrids may be affected by the presence of an active adenosine kinase or the level of ATP in the cells and (2) additional unidentified factors are present in the hybrids that affect the integrity of the HSR structure. There is no evidence for a specific transacting factor in nonamplified cells that regulates gene amplification.

ISSN:1424-8581    

DOI:10.1159/000132370

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

The karyotypes of European vespertilionid bats are distinguished by only a few, easily detectable differences in their G-banding patterns. Most rearrangements can be identified as Robertsonian translocations. Yet, there are surprising differences in the location of active nucleolus organizer regions (NORs), as revealed by silver staining. The ancestral position of the NOR is considered to be a secondary constriction on chromosome 15, as is the case in the genera Eptesicus, Nyctalus, and Vespertilio and in three of four Pipistrellus species. The remaining genera show multiple NOR sites located on minute short arms close to the centromere. In P. pipistrellus, differences in the location of the NORs correlate with the geographical origin of the animals. Some Myotis species possess NORs on numerous chromosomes and show great interindividual variability. In addition, two sibling species, M. brandtii and M. mystacinus, show completely different NOR locations.

ISSN:1424-8581    

DOI:10.1159/000132371

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Chromosomal banding data on three species of Tatera from Kenya significantly alter the previous hypothesis of relationships between and within the genera Tatera and Gerbillurus based on cladistic analyses and the rule of parsimony (Qumsiyeh, 1986b). Of the many possible hypothetical relationships, the most parsimonious tree showed three homoplasies and allowed the genus Gerbillurus to be paraphyletic. The alternative trees, depicting larger number of homoplasies but with homoplasies restricted to fusion or fission events, were compatible with the morphological data in supporting the monophyly of Gerbillurus. To choose between the hypothesis based on the most parsimonious chromosomal tree and those supported by both morphology and slightly less parsimonious chromosomal trees, we performed an electrophoretic study on this group of gerbils. The conclusions are that the genus Gerbillurus is monophyletic and represents a branch that is closely related to the T. robusta group of Taterillini. The study documents that fissions and fusions must have occurred frequently and that in some cases the same fusions were acquired in two independent lineages in numbers exceeding those that are predicted by strict parsimony. The results raise questions about the validity of systematic conclusions based solely on fusion/fission data and utilizing the parsimony criterion.

ISSN:1424-8581    

DOI:10.1159/000132372

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Vitamin C (vit C) at 2 mM enhanced sister chromatid exchange (SCE) frequencies induced by Thiotepa (THIO) or L-ethionine (L-ETH) in cultured human lymphocytes. However, when vit C was tested at 0.02 mM and 0.2 mM a rather protective effect on SCE rates induced by THIO or L-ETH was identified. Vit C (2 mM) caused a cell division delay in cultures treated with THIO or L-ETH. Division delays caused by THIO or L-ETH were reversed in the presence of 0.02 mM or 0.2 mM vit C. Mitotic indices (Mis) in cultures treated with THIO or L-ETH continued to be suppressed in the presence of 2 mM vit C. However, vit C at 0.02 mM reversed suppression of Mis caused by L-ETH or THIO. These findings illustrate the complexity of the interactions of vit C in biological systems and indicate that with different concentrations vit C can cause or prevent genetic toxicity.

ISSN:1424-8581    

DOI:10.1159/000132373

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Up to the beginning of 1986, some 327 variant Philadelphia translocations were reported in chronic myeloid leukemia. The present study represents an attempt to determine which factors (sex, age, geographic localization, etc.) influence the occurrence and chromosome involvement of these variant Philadelphia (Ph1) translocations. Clinical data indicated that band 9q34 was always rearranged in the variant Ph1 translocations and no difference existed between the hematologic and prognostic features among patients with the standard and the variant translocations. An uneven geographic distribution of the variant Ph1 translocations was found. Whether this was due to populations with different ethnic backgrounds or to environmental factors could not be determined. Twenty-eight bands were shown to be rearranged more frequently than expected (P < 0.05); 27 of them are known to contain a fragile site and/or an oncogene and/or are rearranged more frequently than expected in other malignancies. The chromosomes involved in these variant Ph1 translocations were found to show a very particular geographic distribution, which cannot be explained at present.

ISSN:1424-8581    

DOI:10.1159/000132374

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

By means of double staining with DAPI and chromomycin A3, we show that the chromomeres of human pachytene chromosomes are generally DAPI positive and chromomycin negative, like the G- or Q-bands of mitotic chromosomes. Thus we have demonstrated, using an objective technique not based on morphological comparisons, that chromomeres and G-bands are equivalent. However, terminal chromomeres and the ends of mitotic chromosomes, as well as a few other sites, are chromomycin positive and DAPI negative. The ends of human chromosomes appear, therefore, to contain a distinctive class of GC-rich DNA.

ISSN:1424-8581    

DOI:10.1159/000132375

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

A cow, trisomic for chromosome 22, became pregnant and gave birth to a karyotypically normal and healthy calf. Thus, a second example of reproductive capability in autosomal trisomies in mammals, in addition to trisomy 21 in man, is provided.

ISSN:1424-8581    

DOI:10.1159/000132376

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Studies of the catalase and apolipoprotein A-I genes are pertinent to the understanding of human disease. Not only are these genes involved in acatalasemia and atherosclerosis, respectively, but they are also important gene markers for chromosome 11, deletions of which are involved in the development of Wilms tumor. We have used in situ hybridization to localize these genes to specific bands on chromosome 11. Hybridization with a catalase cDNA yielded a significant number of cells (38%) exhibiting label at band 1 lpl3. A high percentage of metaphase cells (50%) hybridized with a human genomic fragment containing the gene for apolipoprotein A-I displayed labeling at 11q13.

ISSN:1424-8581    

DOI:10.1159/000132377

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

The gene CA2 for the human carbonic anhydrase II isozyme is encoded in band q22 of chromosome 8. These data and supporting evidence predict that the genes for carbonic anhydrase I and III are also physically closely linked in this chromosomal region.

ISSN:1424-8581    

DOI:10.1159/000132378

出版商:S. Karger AG    

年代:1987

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000132379

出版商:S. Karger AG    

年代:1987

数据来源: Karger