ISSN:1424-8581    

DOI:10.1159/000130825

出版商:S. Karger AG    

年代:1977

数据来源: Karger

摘要:

The nucleolus organizer regions of domestic sheep (Ovis aries), as shown by silver staining, are located terminally on chromosomes 1, 2, 3, 4, and 25. Significant differences between individuals in the number of Ag-NORs per cell were found. The frequency of involvement of individual chromosome pairs in nucleolar organization was found to be a characteristic of individual animals. Association frequencies of individual chromosomes were accounted for by their frequency of participation in nucleolar organization. No evidence for nonrandom association of chromosome pairs was found.

ISSN:1424-8581    

DOI:10.1159/000130826

出版商:S. Karger AG    

年代:1977

数据来源: Karger

摘要:

The positioning of metaphase chromosomes of the Indian muntjac (Muntiacus muntjak) in the radial metaphase array was investigated using two methods for examining cells. Large numbers of radial metaphase figures were obtained by mitotic shake-off. Treatment with hypotonic solution, fixation, and spreading onto glass slides did not disrupt the radial metaphase configuration of a proportion of the cells. Analysis of 567 cells for the arrangement of six of the seven muntjac chromosomes revealed a random positioning of each chromosome within the radial array. These results were corroborated by results obtained from 101 living cells oriented with microneedles to enable examination of radial metaphases with phase-contrast microscopy.

ISSN:1424-8581    

DOI:10.1159/000130827

出版商:S. Karger AG    

年代:1977

数据来源: Karger

摘要:

Xenopus vestitus possesses 72 chromosomes, whereas in the majority of known Xenopus species there are 2n = 36. During meiosis, 36 bivalents are usually observed at metaphase I and 36 chromosomes at metaphase II. Arranged according to size and centromere position, the chromosomes form the same basic morphologic groups typical of the genus Xenopus. However, the groups are composed of quartets of four similar chromosomes instead of diploid pairs of homologs. The exception to this arrangement involves chromosomes bearing secondary constrictions, which in X. vestitus are represented by two different pairs of homologs, one of which shows, in 39 % of the observed mitoses, somatic association and is, therefore, considered to carry the nucleolar organizer. X. vestitus represents either a case of ancient autotetraploidy or, more likely, one of allotetraploidy of more modern origin.

ISSN:1424-8581    

DOI:10.1159/000130828

出版商:S. Karger AG    

年代:1977

数据来源: Karger

摘要:

Active thymidine incorporation was observed in both parental nuclei in heterokaryons derived via polyethylene glycol-mediated fusion of postreplicative “senescent” human diploid fibroblast-like cells and a thymidine kinase-deficient murine cell line (3T3der-4E). Some increase of the 3H-thymidine labeling index was also apparent in unfused 3T3der-4E cells co-cultivated with senescent cells, consistent with metabolic cooperation. While no human metaphases could be detected in control hybrid preparations, hybrid metaphase figures containing essentially the entire human complement were demonstrated in the fused cultures as early as 24 h after fusion; the morphology of the human chromosome (bi-armed) suggested that the senescent human cells were stimulated to reinitiate replicative DNA synthesis rather than rep

ISSN:1424-8581    

DOI:10.1159/000130829

出版商:S. Karger AG    

年代:1977

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130830

出版商:S. Karger AG    

年代:1977

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130831

出版商:S. Karger AG    

年代:1977

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130832

出版商:S. Karger AG    

年代:1977

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130833

出版商:S. Karger AG    

年代:1977

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130824

出版商:S. Karger AG    

年代:1977

数据来源: Karger