摘要:

Metaphase chromosomes from cultured blood cells of female, male, and hermaphroditic European eels were analyzed. In addition, both gonads from each of the specimens were examined microscopically to ensure correct sexing. The karyological investigation revealed that in some of the specimens a heteromorphic chromosome pair was present. This heteromorphism appeared in both sexes and in the hermaphrodite. C-banding and silver nitrate staining demonstrated that the heteromorphism was due to quantitative differences in constitutive heterochromatin and nucleolar organizing regions in the short arm of chromosome 8. In G-banded preparations it was demonstrated that, except for the heteromorphism mentioned, the karyotypes from both sexes and the hermaphrodite were identical. With the G-band technique it was also easily demonstrated that both the largest metacentric (No. 1) and the smallest metacentric (No. 11) had homologs. Therefore, in contrast to some earlier reports which claimed that these two chromosomes were a heteromorphic pair of sex chromosomes, it is concluded that Anguilla anguilla has no heteromorphic sex chromosomes. The implication of these findings are discussed in relation to the many reports of strongly skewed sex ratios found in commercial eel farms. It is tentatively hypothesized that sex determination in A. anguilla may be metagamic and that sex inversion may occur in this species.

ISSN:1424-8581    

DOI:10.1159/000131981

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

The native Chinese hamster DHFR gene was localized to 2pter^-ql4 using a combination of somatic cell hybrid technology and molecular techniques. In addition, PGD, ENOJ, and DTS, qter. Localization of PGM1 to this region was confirmed. The relationship of the site of the native DHFR gene to the location of the homogeneously staining region in methotrexate-resistant cells is discusse

ISSN:1424-8581    

DOI:10.1159/000131982

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

The ability on nonhematopoietic cells to proliferate in vitro without attachment to a solid surface (anchorage independence) is known to be highly correlated with their ability to form tumors in nude mice. Transformed cells in vitro frequently also show less organization of the intracellular actin-containing microfilament bundles and less cell-surface fibronectin compared to normal cells. We have examined whether the loss of the anchorage requirement for growth is related to either of these structural changes in the cellular cytoskeleton. Our approach was to select a series of subclones from a nontransformed Syrian hamster fibroblast line, 8, for the acquisition of either anchorage independence in vitro or tumorigenicity in nude mice. These subclones were then examined for concomitant changes in the cytoskeletal structures. We found that anchorage independence, decreased actin cable organization, and tumorigenicity in nude mice were coordinately induced in both the in vitro- and in vivo-selected subclones, whereas the loss of fibronectin was not consistently co-induced with these three markers. These results suggest that the transformation-associated decrease in actin cable organization in this type of cell enhances the ability to grow without anchorage in vitro and to form tumors in vivo.

ISSN:1424-8581    

DOI:10.1159/000131983

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

BrdU-substituted chromosomes of Don cells were differentially stained with ammoniacal silver carbonate and analyzed by electron microscopy. The results obtained led us to the following conclusions: (1) the differential impregnation of BrdU-substituted chromatids with silver is mainly due to a preferential extraction of non-histone proteins caused by UV-irradiation and incubation in SSC at 55 °C prior to silver staining; (2) the core-like structures detected after silver staining may well represent an artifact due to the effects of severe hypotonic pre-treatment on chromatin dispersion; (3) in each sister-chromatid exchange, the border of exchange clearly defines the course of DNA fibers within the chromatid. This border of exchange tends to run perpendicular to the chromosome axis but may vary slightly depending on the degree of chromosome condensation

ISSN:1424-8581    

DOI:10.1159/000131984

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Is(7;l)40H was found in the daughter of a male mouse given spermatozoal X-irradiation. It is a non-inverted insertion of about half of chromosome 7 into chromosome 1, generating a long somatic marker chromosome. Breakpoints are in bands IB, 7B1, and 7F1; linkage tests show that these breakpoints are about midway between fz and In on the 1, and 0.2 units distal to ru-2 and 12 units proximal to fr on the 7. Female carriers had litters of about one-third normal size and showed some decline in length of reproductive life. Males were sterile, with testis weights only 30% of normal and with abrupt cessation of spermatogenesis in pachytene at stage IV of the seminiferous epithelial cycle. Positive sex-vesicle contact with the insertional configuration was found in only 40% of pachytene spermatocytes, which suggested that other factors may be involved in the spermatogonial breakdown. In oocytes at metaphase I 76% of insertion configurations were multivalent, because of one or more chiasmata in the inserted segment, as were 79% of synaptonemal complex configurations in male pachytenes. Karyotyping at 12.5 to 14.5 days of gestation showed that all embryos with duplications of the inserted segment were exencephalic, and the only example of a corresponding deficiency was retarded. Analysis of the consequences of heterozygosity for the insertion shows that the insertion length should be correlated with the frequency of unbalanced offspring and thus with the amount of F1lethality. The genetic length of 36 cM estimated in this way from data on liveborn offspring is in reasonable agreement with estimates from cytological measurements and meiotic configurations but rather higher than that from linkage tests.

ISSN:1424-8581    

DOI:10.1159/000131985

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

This study describes the sequence of centromere separation in the Chinese hamster genome and the lack of any effect of Colcemid on this sequence. Analysis of bone marrow cells using sequential Giemsa staining and Q-banding established the sequence of centromere separation in cells derived from four Colcemid-treated and three untreated animals. Treatment of the data by use of the ANOVA test showed that the sequences established in the Colcemidtreated group did not differ from those in the untreated animals. The sequence of centromere separation in the Chinese hamster, as expressed by the pooled data from all seven animals, is chromosomes 1 and 2, followed by 3, 4, X, Y, 8, 9, 10, 5, 6, and 7.

ISSN:1424-8581    

DOI:10.1159/000131986

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Human cells transformed in vitro by SV40 rarely form tumors in nude mice. We examined whether these cells as a group are inherently nontumorigenic or whether they are potentially tumorigenic but rejected by the athymic host, possibly by nonspecific immune mechanisms. SV80 and NG8 are SV40-transformed human cell lines that express all of the transformed properties, including anchorage-independent growth, but do not form tumors in adult nude mice after injection of as many as 108 cells. Both the SV80 and NG8 cell lines have SV40-specific transplantation antigens which crossreact with those present on SV40-transformed (but tumorigenic) rodent cells. We found that SV80 cells, though not NG8 cells, induce progressively growing lethal tumors if the cells are injected repeatedly into neonatal nude mice. Somatic cell hybrids between SV80 or NG8 cells and a highly tumorigenic cell line derived from a human tumor continue to express the virus-induced antigens and fail to form tumors in adult nude mice. These results strongly suggest that at least for some SV40-transformed human cells, the failure to form tumors in nude mice may be due to their expression of virusinduced transplantation antigens rather than the absence of tumorigenic potential.

ISSN:1424-8581    

DOI:10.1159/000131987

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Chromosomal analysis of two species of African finches of the genus Pytilia has been carried out using both G- and C-banding. The karyotypes of these two species were found to differ radically, not only from each other, but also from those of other species in the family Estrildidae. The differences are due to paracentric and pericentric inversions and to tandem fusions. However, not all of the karyotypic differences can be explained by conventional mechanisms. These results are discussed in relation to the role of karyotypic rearrangement in avian evolution and the conversion of microchromosomes to macrochromosomes.

ISSN:1424-8581    

DOI:10.1159/000131988

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

The DNA replication patterns of eight cases of X isochromosomes, five idic(X) and three i(Xq), were studied. R-banded prometaphases and metaphases from lymphocyte cultures after synchronization with methotrexate and incorporation of 5-bromodeoxyuridine were analyzed. No significant differences in the frequency of metaphases with symmetric and asymmetric replication patterns between dicentric and monocentric isochromosomes were found. Furthermore the distribution of the frequencies of R-positive bands was similar and comparable to that of the normal late-replicating X. Our data suggest that the DNA replication pattern of Xq isochromosomes is not correlated with the mechanism of their origin.

ISSN:1424-8581    

DOI:10.1159/000131989

出版商:S. Karger AG    

年代:1983

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000131990

出版商:S. Karger AG    

年代:1983

数据来源: Karger