摘要:

A comparative study of the karyotypes of eight Xenopus species and subspecies possessing a diploid number of 36 chromosomes (X.l. laevis, Xl. petersi, Xl. victorianus, X. borealis, X. gilli, X. fraseri, and X. clivii) was performed. Karyotypes based on the morphology and size of chromosomes differ only by the type and position of secondary constrictions. Some of these constrictions are nucleolar organizers, recognizable by mitotic chromosomal association. By comparing the chromosomes bearing secondary constrictions, an attempt is made to establish the cytotaxonomic relationships. The close relationship between the subspecies X.l. laevis, X.l. petersi, and X.l. victorianus is confirmed; X. borealis, however, is a separate species much nearer to X. muelleri. The karyotype of X. gilli is interpreted as being intermediate to these two groups. X. clivii could be regarded as a species close to the group of X. muelleri. X. fraseri, having a particular type of secondary constriction, is systematically more distant.

ISSN:1424-8581    

DOI:10.1159/000130761

出版商:S. Karger AG    

年代:1977

数据来源: Karger

摘要:

Due to the very limited amount of knowledge available on the cytochemistry and architecture of fish chromosomes, an extensive banding study was carried out on chromosomes of the central mudminnow, Umbra limi. Through the use of fluorescent staining, C-banding, and silver staining, the chromosomes were characterized, and an idiogram was constructed showing the location of C-band heterochromatin, F-bodies, and the nucleolar-organizer regions. G-banding was attempted but was unsuccessful. Results of fluorescent staining with 33258 Hoechst and quinacrine HCl raised some interesting questions concerning the cytochemistry of U. limi chromosomes, as well as the specificity of these stains.

ISSN:1424-8581    

DOI:10.1159/000130762

出版商:S. Karger AG    

年代:1977

数据来源: Karger

摘要:

The chromosome analysis of meiosis in four lemurs, Lemur fulvus fulvus, L. f. collaris, L. f. albocollaris, and L. macaco, and particular hybrid crosses is reported. In metaphase I, trivalents and chain elements were detected and identified with T-banding. The study largely confirms our previous work on mitotic karyotype comparisons in the genus Lemur. The absence of chain multivalents elements in the pachytene stages of hybrid meiosis, where a chain is detected later in diakinesis, may offer evidence on the possible existence of a two-step pairing mechanism in meiotic homolog pairing. Considerations about the role of the chromosome rearrangements in establishing a gametic barrier in speciation are developed.

ISSN:1424-8581    

DOI:10.1159/000130763

出版商:S. Karger AG    

年代:1977

数据来源: Karger

摘要:

Thirty-three rabbit cell lines were established from various fetal tissues of the inbred strain III of the New Zealand rabbit (Oryctolagus cuniculus). None of these lines exhibited senescence during a growth period of more than 2 years. Karyologic studies of most cell lines at 10 to 20 cell-passage intervals revealed that the karyotype stability of the rabbit cells in vitro was correlated with the organs from which the cell lines were derived. Thus, lines derived from cornea, spleen, and kidney tissues usually contained high frequencies of polyploidy in their early passages, whereas most of those derived from lung and skin were found to retain the normal diploid karyotype for much longer periods of time. One line derived from fetal lung tissue, designated Lung 16, remained diploid up to 100 passages. In late passages of the majority of all the lines studied, the cells became pseudodiploid, hyperdiploid, or polyploid. Among the pseudodiploid and the hyperdiploid cell lines, the chromosomal changes followed three basic patterns: (1) a gain of one or more telocentric chromosomes; (2) a loss of one telocentric chromosome plus a metacentric marker chromosome (M); or (3) a gain of a long telocentric marker chromosome with or without changes in the number of telocentric D chromosomes. By the G-banding technique, the telocentric chromosome involved in these three patterns was identified as the D-group chromosome 18 and the M marker chromosome as an isochromosome of 18. These results suggest that chromosomal rearrangement in rabbit cells involving trisomy of 18 may be responsible for the longevity of these cell lines cultured in vitro.

ISSN:1424-8581    

DOI:10.1159/000130764

出版商:S. Karger AG    

年代:1977

数据来源: Karger

摘要:

A small tablet of 5-bromodeoxyuridine (BrdU), implanted subcutaneously in a mouse, provides sustained release of base analog sufficient to effect substitution of DNA throughout an entire replication period. As illustrated by studies of mouse bone-marrow and spleen cells in the presence or absence of cyclophosphamide, this depot method of BrdU administration greatly simplifies in vivo analysis of sister-chromatid-exchange formation.

ISSN:1424-8581    

DOI:10.1159/000130765

出版商:S. Karger AG    

年代:1977

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130766

出版商:S. Karger AG    

年代:1977

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130767

出版商:S. Karger AG    

年代:1977

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130768

出版商:S. Karger AG    

年代:1977

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130769

出版商:S. Karger AG    

年代:1977

数据来源: Karger