ISSN:1424-8581    

DOI:10.1159/000130834

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

For several years the SEWA mouse ascites tumor has been a carrier of double minute chromosomes (DMs), some 90 % of its cells containing from one to several hundred DMs. In one specific subline of this tumor, the cells with DMs had decreased in frequency to less than 5 % of the cells. At the same time, the stemline chromosome number had increased from 43 to around 50. This was due to the presence, in addition to the ordinary telocentric chromosomes, of a varying number of medium-sized metacentrics. The fact that these chromosomes deviated from ordinary mouse chromosomes in special features, such as median centromeric position, early DNA replication, and complete lack of centromeric heterochromatin, indicates that they represent a new type of chromosome. Their striking agreement with the DMs in many properties makes it tempting to associate their origin with the disappearance of the DMs.

ISSN:1424-8581    

DOI:10.1159/000130836

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Electron micrographs reveal that the Ag-stainable substance is located on the outside of NOR’s or around them but not in the chromosomes themselves. In association figures, the Ag-positive material lies between the acrocentric chromosomes. Light-microscopic studies show that the Ag stainability of the nucleolus in interphase is correlated with the function of the NOR, as seen from inactive and activated lymphocytes. Much more Ag-positive material is seen in prophase than in meta- and anaphase. It starts to increase again in late telophase. In male meiosis the NOR’s remain Ag-positive until pachytene. First and second metaphase figures are negative. Experiments using RNase, TCA, and trypsin indicate that the Ag-stainable substance is an acidic protein. The precipitation of Ag granules in interphase nuclei seen in the electron microscope is greatest over the fibrillar component of the nucleolus. The most likely interpretation is that the Ag-stainable material is a component of ribonucleic protein accumulating around active NOR’s. In mitosis some of this material remains at the NOR’s. In first meiosis it is completely removed before dia

ISSN:1424-8581    

DOI:10.1159/000130837

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Chromosomes with active nucleolus organizer regions (NORs) were identified by combined Q-banding, C-banding (in some cases), and silver staining in mouse cell lines. NOR-bearing chromosomes were overrepresented among the chromosomes involved in Robertsonian translocations in LM(TK-), A9, and RAG cell lines. Usually only one NOR-bearing chromosome was seen in any biarmed chromosome; relatively few contained two NOR-bearing chromosomes. Thus the nucleolus plays an important role, but nucleolar fusion is relatively unimportant, in the origin of Robertsonian translocations in the mouse.

ISSN:1424-8581    

DOI:10.1159/000130838

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

The incorporation of SH-uridine in oogonia and oocytes during meiotic prophase I was studied in three human fetuses 13, 18, and 19 weeks old. Following a 40- or 60-min pulse, intense nuclear and nucleolar labeling was observed in oogonia. During the preleptotene chromosome condensation stage, the heteropycnotic masses were unlabeled, while numerous silver grains were seen on the filaments persisting around these masses. During leptotene, chromosomal and nucleolar RNA synthesis was significant, but less than that in the oogonia. The rate of incorporation declined rapidly during zygotene and fell to a very low level at early pachytene. Throughout pachytene no nucleolar RNA synthesis was observed. Chromosomal RNA synthesis progressively recovered during middle pachytene, was of moderate intensity at late pachytene, and increased again at early diplotene. Nucleolar RNA synthesis was very intense at early diplotene, at the same time as nucleolar size and basophilia increased.

ISSN:1424-8581    

DOI:10.1159/000130839

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

The restriction endonuclease BSu, an isoschizomer of the enzyme HaeIII, cleaves human DNA to yield classes of fragments that are characteristic of the DNA of individuals having a Y chromosome. The fragments concerned are therefore diagnostic of the presence of Y-chromosome DNA and have been studied here with the intention of confirming the origin of various translocations thought, on other grounds, to involve the Y. The absence of the fragments from DNA of a case exhibiting absence of the fluorescent region of Yq suggests that the DNA concerned maps predominantly to Yq. Normal gender in the absence of the BSu fragments indicates that they do not function in sex determination.

ISSN:1424-8581    

DOI:10.1159/000130840

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Chain and ring chromosome configurations were detected in a small percentage of the lymphocytes of a patient suffering from Thiberge-Weissenbach syndrome. Precise recognition of the chromosomes involved in the rearrangements did not indicate a systematic order of end-to-end fusions. A relationship between these configurations and the chromosome arrangement in the interphase nucleus is possible.

ISSN:1424-8581    

DOI:10.1159/000130841

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Chromosome analysis using G-banding was carried out on cells from 65 males and 102 females of all ages from a random sample of the population. The frequency of aneuploid cells showed a significant increase with age in both sexes, and in females the increase in hypodiploidy and hyperdiploidy was more marked than in males, and involved a high proportion of cells that had lost or gained an X chromosome, 45, X cells being much more common than 47, XXX cells. In females, the occurrence of a “fragment” of an X chromosome also correlated with increasing age, and this “fragment” appears to be an X chromosome that has simply divided prematurely at the centromere. The effects of time in culture and of repeating cultures of blood samples from the same individual on proportions of abnormal cells of various types were also investigated, and the results are discussed in the light of findings from several other “ageing

ISSN:1424-8581    

DOI:10.1159/000130842

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

A study of the chromosomes of 14,069 consecutive liveborn infants revealed 11 infants with balanced reciprocal and 13 with balanced Robertsonian translocations. A detailed physical assessment revealed no increase in major or minor malformations over control infants except for an increase in frequency of upslanting palpebral fissures and some possible minor dermatoglyphic changes. A preliminary psychologic assessment of six heterozygotes and 11 controls at 6 years of age revealed no detectable differences. The results of detailed family studies revealed only one child with an unbalanced karyotype, suggesting that where families are ascertained at random through balanced translocation heterozygotes, the frequency of children with unbalanced karyotypes is low in both the t(DqDq) and reciprocal translocation families. Fetal wastage was shown to be slightly increased in reciprocal but not in Robertsonian translocation families. In both the reciprocal and Robertsonian translocation families the segregation ratio for the translocation was not significantly different from 1:1. A significant excess of males was found among reciprocal but not among Robertsonian translocation heterozygotes. A study of the chromosomes involved in 60 reciprocal translocations ascertained at random by conventional staining in the present and two other series suggested that chromosome 11 and perhaps 13 were involved significantly more frequently than might have been expected by chance. However, with the possible exception of band ll(ql3), no “hot” spots for chromosome breakage were observed in these series. Breaks were, however, found to occur significantly more frequently in pale fluorescent, light-staining than in bright fluorescent, dark-staining bands. The importance of these findings in genetic counselling is discus

ISSN:1424-8581    

DOI:10.1159/000130843

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Blood lymphocytes from a boy with Bloom’s syndrome and a man with a mild form of xeroderma pigmentosum were examined for their response to UV-irradiation, as measured by the levels of induced unscheduled DNA synthesis, and to X-irradiation, as measured by chromosome aberrations. Although the individual with Bloom’s syndrome showed facial skin sensitivity to sunlight, his lymphocytes showed a normal response in unscheduled DNA synthesis. In contrast, cells from the individual with xeroderma pigmentosum showed a 50 % reduction in the amount of unscheduled DNA synthesis following UV exposure. Cytogenetic studies on PHA-stimulated Bloom’s syndrome lymphocytes revealed a typical increase in the incidence of aberrations. Many of the Bloom’s cells showed breakages located at the centromere and equal, symmetrical chromatid interchanges involving homologous chromosomes; these aberrations were not produced in control cells cultured in serum from the Bloom’s syndrome patient. In contrast, the frequency of spontaneous aberration in xeroderma pigmentosum lymphocytes was similar to that in controls. G1 cells from both patients were exposed to a range of X-ray doses, and it was shown that neither cell type differed from controls in the incidence of induced chromosome-type aberrations. The significance of these findings is

ISSN:1424-8581    

DOI:10.1159/000130844

出版商:S. Karger AG    

年代:1978

数据来源: Karger