摘要:

Eighty-four specimens of Oryzomys subflavus, collected in the State of Pernambuco, Brazil, were studied. A Robertsonian chromosome polymorphism, characterized by a varying diploid number of 50, 49, 48, and 46, was found. All the specimens showed a chromosome arm number of 56. G-banding patterns in somatic cells allowed identification of the chromosome pairs (2, 3, 5, and 7) involved in centric fusion. C-banding revealed the presence of constitutive heterochromatin near the centromere the X chromosome and those of the autosomes. The Y chromosome presented a large heterochromatic block in the distal portion of its long arm.

ISSN:1424-8581    

DOI:10.1159/000131623

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

Approximately 100 human fibroblast-like cell lines derived from the upper arms of members of the Baltimore Longitudinal Study have been deposited in the Aging Cell Bank at the Institute for Medical Research, Camden, N.J. These cell lines were derived from individuals ranging from 29 to 96 years in age. The in vitro lifespan of each culture has been estimated by the distribution of colony sizes. The availability of cell lines of known proliferative potential from donors of various ages should provide an important new resource for cellular aging studies.

ISSN:1424-8581    

DOI:10.1159/000131624

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

Selective silver staining demonstrated that autosomal bivalents containing transcriptively active nucleolar organizers associated with the sex vesicle during pachytene of mouse spermatocytes. Later in pachytene, the nucleolar organizers covered the portion of the sex vesicle furthest from the attachment to the nuclear envelope. Hybridization in situ revealed the presence of rDNA in the silver-positive material. The nucleolus, formed from an autosomal bivalent, exhibited a large fibrillar center surrounded by an electron-opaque fibrillar zone. The nucleolar association with the sex vesicle was studied at early, middle, and late pachytene by hybridization in situ, NOR silver staining, and electron microscopy. These observations enabled us to further define the relationships of the nucleolar components with the X-Y pair.

ISSN:1424-8581    

DOI:10.1159/000131625

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

We have utilized a panel of Chinese hamster × mouse somatic cell hybrids segregating mouse chromosomes to assign a gene for arylsulfatase A (ARSA) to mouse chromosome 15. Considering our previous assignment of a gene for diaphorase-1 (DIAl) to the same mouse chromosome, we have evidence for another syntenic relationship that has been conserved, since the homologous loci for human ARSA and DIAl are both located on human chromosome 22. Because MMU 15 and HSA 22 are quite dissimilar in size and banding patterns, we have attempted to identify the conserved portion by regional mapping of human DIAl and ARSA using somatic cell hybrids segregating a human chromosome translocation t(15;22)(q14;q13.31). The results assign human DIAl and ARSA to the distal sub-band of 22q13 (region 22q13.31→qter). The locus for mitochondrial aconitase (ACO2) has been separated by the breakpoint from DIAl and ARSA and is located more proximal

ISSN:1424-8581    

DOI:10.1159/000131626

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

A standard chromomere map of the Chinese hamster autosomes at pachytene has been prepared and presented. Comparison of bands on somatic chromosomes and chromomeres on meiotic chromosomes revealed a close correspondence between the two. Chromosome contraction from prophase to metaphase at mitosis and early to late pachytene at meiosis lead, due to coalescence, to the recognition of decreasing numbers of bands and chromomeres. As expected, a greater number of chromomeres could be recognized at pachytene than could Giemsa- and Quinacrine-positive bands at somatic metaphase.

ISSN:1424-8581    

DOI:10.1159/000131627

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

High-resolution replication banding was performed to (1) delineate at the prometaphase level small interstitial deletions of chromosome 13 in two unrelated patients with retinoblastoma (Rb) and (2) study the influence of these deletions in the replication autonomy of the regions involved. The present study indicates that, in spite of the fact that break points separate (split) bands ql4 and q21 in different segments, these deletions do not produce a position effect or alteration in the replication behavior of the abnormal chromosome 13’s. Each segment in the deleted chromosomes replicates with a chronology and pattern identical to the normal homolog’s. The present data also indicate that metaphase bands are not only autonomous foci of replication but that they can be further divided into subunits of replication which correspond to sub-bands observed in more elongated prometaphase chromosomes. Our results strongly suggest that prometaphase sub-bands represent units of chromatid organization and replicat

ISSN:1424-8581    

DOI:10.1159/000131628

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

The chromosome complement of metaphase II oocytes matured by different methods was determined. These oocytes were collected from young and old Swiss-Webster random bred and CBA inbred mice. The results from the two strains were remarkably similar. Superovulation caused no increase in aneuploidy frequencies; however, in vitro maturation resulted in increased hyperploidy rates for oocytes from younger females of both strains. Of the six possible comparisons regarding a maternal age effect, there were no significant increases in hyperploidy. The absence of a maternal age effect on the first meiotic division of oocytes, while such an effect does exist for mid-gestation mouse fetuses, suggests that the maternal age effect on aneuploidy may be due to a decreased ability to select against (abort) aneuploid embryos/fetuses as a function of increasing maternal age.

ISSN:1424-8581    

DOI:10.1159/000131629

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

Chromosomes from cultured fibroblasts of two Pacific porpoise species, Stenella attenuata and S. longirostris and one Atlantic species, S. dubia, were compared to test the feasibility of using variation in constitutive heterochromatin and other chromosomal characteristics for analyses of population relationships and defining stocks of endangered porpoises. The G-band karyotypes of the three species were identical except for minor band differences resulting from heterochromatin variation. The nucleolar organizer regions (NORs) were located on the same two pairs of acrocentric chromosomes in all three species, although individual variation occurred in the number of active NORs present. Differences in the distribution and amount of C-band heterochromatin were observed between the three species. Stenella attenuata and S. dubia were very similar in C-band pattern, while S. longirostris was distinctly different. Conspicuous heteromorphism between the C-heterochromatin of the homologs of several pairs of chromosomes was noted in all individuals examined. In addition, variation in the amount of heterochromatin was observed between the four S. attenuata individuals studied. Of the chromosomal characteristics studied, only C-heterochromatin variation holds promise for distinguishing interspecific populations of porpoises. The final decision regarding the feasibility of using C-band heterochromatin to distinguish interspecific populations of porpoises must await comparison of morphologically differing populations within what is currently regarded as a single species.

ISSN:1424-8581    

DOI:10.1159/000131630

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

The method described here has the advantage of presenting a clear image of both chromosomes and silver grains. Chromosomes are stained through the emulsion with Hoechst 33258. As two different sources of light are employed—epi-ultraviolet illumination and transmitted visible light—a separate photographic record of each optical plane can be obtained of chromosomes, silver grains, and chromosomes and grains toget

ISSN:1424-8581    

DOI:10.1159/000131631

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

Dispersed cells of the gonads of newborn rats reaggregate histotypically in rotation culture. Ovarian cells form follicles, while testicular cells organize tubuli. When testis cell supernatant is added to ovarian cells, they form tubulus-like structures. This effect is impeded by simultaneous addition of monoclonal anti-H-Y antibody. It is concluded that H-Y antigen is the active factor of testis cell supernatant that induces sex-reversal of ovarian cells in vitro. The reverse experiment, i.e., exposure of testicular cells to anti-H-Y antiserum, does not result in the organization of follicular structures. These findings are consistent with the view that H-Y antigen is involved in testis differentiation by inducing testis cell-specific functions, rather than by cross-linking cells.

ISSN:1424-8581    

DOI:10.1159/000131632

出版商:S. Karger AG    

年代:1981

数据来源: Karger