摘要:

XX/XY chimerism has been studied in the liver of 22 presumptive freemartin fetuses and in 12 male cotwins of multiple pregnancies, at an age of 39 to 62 days post-insemination. At these stages, the majority of the liver cells are hematopoietic cells. In these fetuses, the degree of chimerism varies from 0% to 55 %. Except for one case, the cells of the host predominate, i.e., the percentage of XY cells in freemartins is less than 50 % and is of the same order of magnitude as the number of XX cells in the male twin. According to several authors, freemartins and their male twins, when studied postnatally, possess the same percentage of XY (or XX) blood cells (variations from 1 % to almost 100%). These data suggest that the degree of chimerism of blood cells might change during development. If this is so, it seems unwarranted to compare chimerism in postnatal freemartins with the sex anomalies which appeared at an early fetal stage. The first signs of freemartinism (inhibition of gonadal growth and regression of the upper part of the Müllerian ducts) appear after day 48. In 15 freemartin fetuses of 49 to 62 days of age, the degree of inhibition of the left ovary and of the upper Müllerian ducts was compared with the percentage of XY cells present in the liver. The degree of inhibition of the ovarian volume and of the diameter of the upper Müllerian ducts was evaluated by reference to regression lines which had been previously calculated for a larger number of freemartins of the same age. There is no correlation between the percentage of XY cells and the degree of inhibition of the ovaries or of the Müllerian du

ISSN:1424-8581    

DOI:10.1159/000130179

出版商:S. Karger AG    

年代:1972

数据来源: Karger

摘要:

Asynchronous centromere division, i.e., variation in the distance between sister centromeres in the same cell, has been observed in bone-marrow cells of the Chinese hamster (2n = 22). The cells were harvested with brief hypotonic treatment but without colchicine. In each of 20 cells, the chromosomes were arranged in a sequence according to decreasing intercentromeric distance, i.e., the distance between sister centromeres. The 20 sequences exhibited a significant degree of concordance, permitting the construction of a best-estimate or overall sequence. There appears to be the same sequence among the chromosomes of each haploid set, although the two homologs of each pair ranked, on the average, 7.6 positions apart. The data on the X and Y chromosomes, which are morphologically distinguishable, indicate that the intercentromeric distance of the X is significantly larger than that of the Y. The concordance could be either an artifact of the harvest procedure (hypotonic treatment, flattening, etc.) or a result of the chromosomes dividing in a sequence at the onset of anaphase. These alternatives are discussed along with the relation of the findings to such chromosome characteristics as length and the time of DNA replication.

ISSN:1424-8581    

DOI:10.1159/000130180

出版商:S. Karger AG    

年代:1972

数据来源: Karger

摘要:

Banding patterns of human chromosomes obtained with various new techniques-quinacrine mustard staining, staining after heating, and staining after proteolytic digestion —are compared. Depending on the technique, the same band may be stained or not, but the sequence of the bands is identical with all technique

ISSN:1424-8581    

DOI:10.1159/000130181

出版商:S. Karger AG    

年代:1972

数据来源: Karger

摘要:

Some of the immediate and long-term effects of UV irradiation (2537 Å) on human fibroblasts have been studied by measuring the DNA content of individual nuclei and examining metaphase chromosomes in the irradiated population for up to 18 days. Time-lapse cinematography was used to demonstrate that irradiation of diploid human fibroblasts during a wave of DNA synthesis causes rapid radiation death in a proportion of cells and severe reduction in mitotic activity. Measurement of the DNA content by a spectrophotometric method of individual nuclei remaining attached to the substrate 28 and 52 h after irradiation showed that cells with high DNA values accumulate in the irradiated population. However, significant numbers of giant cells were not maintained in the surviving population. Metaphases sampled up to 31 h after UV irradiation contained predominantly chromatid deletions. Exchange aberrations were less frequent and were not found in cells sampled up to 10 h after irradiation. UV had no immediately apparent effect on mitotic chromosomes, even at high doses. None of the surviving cultures contained a significant number of cells with stable translocations or polyploidy

ISSN:1424-8581    

DOI:10.1159/000130183

出版商:S. Karger AG    

年代:1972

数据来源: Karger

摘要:

Two similar pericentric inversions of chromosome 9 are transmitted in two unrelated families, each of which includes a consanguineous marriage. In both instances the inverted segment comprises the centromere region and the proximal part of the long arm, including the secondary constriction. The inverted chromosome was found in one homozygote and in three heterozygotes of the six karyotyped individuals of one family; in the second family, three of five karyotyped individuals were heterozygotes. The health problems of the propositi are apparently not associated with their chromosomal constitution.

ISSN:1424-8581    

DOI:10.1159/000130182

出版商:S. Karger AG    

年代:1972

数据来源: Karger