排序方式: 共有47条查询结果,搜索用时 546 毫秒
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Loss of the Lkb1 tumour suppressor provokes intestinal polyposis but resistance to transformation 总被引:18,自引:0,他引:18
Bardeesy N Sinha M Hezel AF Signoretti S Hathaway NA Sharpless NE Loda M Carrasco DR DePinho RA 《Nature》2002,419(6903):162-167
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A. K. Sinha 《Cellular and molecular life sciences : CMLS》1967,23(11):889-895
Conclusion Somatic heterochromatization of the opossum,D. virginiana, was studied from prophase and tritiated thymidine-labeled metaphase chromosome preparations. In both sexes of this mammal, a number of prophase autosomes and the sex chromosomes were observed displaying deeply stained condensed areas. These chromosomal areas were interpreted as evidence for heterochromatization. The extent of heterochromatization in the opossum was found much greater in certain autosomes than either theX orY chromosome alone. This assertion that some opossum autosomes possess more heterochromatin than the sex chromosomes was supported by data collected on the terminal labeling patterns of the chromosomes. Metaphase autoradiographs prepared from cultured leucocytes of the animals unequivocally suggested that certain opossum autosomes completed replication later than the sex chromosomes. If one assumes that there is heterochromatin in the autosomes, as the evidence suggests, then it merely becomes a question as to what block of heterochromatin replicates last — a phenomenon that is probably size dependent.
Supported in part by Baylor University College of Medicine General Research Grant (No. P-13) and grants from the James Picker Foundation and the Texas Heart Association. The auther wishes to thank Dr.W. Hill for his help at the vivarium and MissMarion Gay and MissShirley Powell for technical assistance. The editorial assistance of MissMarilyn Morningstar is also appreciated. 相似文献
Résumé L'héterochromatisation somatique de l'opossum (Didelphys virginiana) a été étudiée sur des préparations de chromosomes aux stades de la prophase et de la métaphase, la thymidine ayant été utilisée comme marqueur. Dans les 2 sexes de ce mammifère de nombreux autosomes et les chromosomes sexuels montrent, à la prophase, des plages denses fortement colorées. Ces plages chromosomiales ont été interprétées comme un signe évident d'héterochromatisation. L'héterochromatisation est beaucoup plus accentuée dans certains autosomes que dans les chromosomesX ouY. Les autoradiographies de stades métaphasiques dans des préparations effectuées de leucocytes en cultures suggèrent d'une façon non équivoque que certains autosomes de l'opossum achèvent leur réplication plus tardivement que les chromosomes sexuels. Si l'on assume que l'héterochromatine est présente dans les autosomes, comme le démontrent nos observations, il semble évident que l'héterochromatine autosomale a un rôle significatif dans le développement.
Supported in part by Baylor University College of Medicine General Research Grant (No. P-13) and grants from the James Picker Foundation and the Texas Heart Association. The auther wishes to thank Dr.W. Hill for his help at the vivarium and MissMarion Gay and MissShirley Powell for technical assistance. The editorial assistance of MissMarilyn Morningstar is also appreciated. 相似文献
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A. K. Sinha 《Cellular and molecular life sciences : CMLS》1978,34(8):1029-1030
Summary Food-perception ability ofAulacophora foveicollis is adversely affected by bilateral antennectomy, but remains unaffected by unilateral antennectomy. 相似文献
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Evidence from three-dimensional seismic reflectivity images for enhanced melt supply beneath mid-ocean-ridge discontinuities 总被引:1,自引:0,他引:1
Kent GM Singh SC Harding AJ Sinha MC Orcutt JA Barton PJ White RS Bazin S Hobbs RW Tong CH Pye JW 《Nature》2000,406(6796):614-618
Quantifying the melt distribution and crustal structure across ridge-axis discontinuities is essential for understanding the relationship between magmatic, tectonic and petrologic segmentation of mid-ocean-ridge spreading centres. The geometry and continuity of magma bodies beneath features such as overlapping spreading centres can strongly influence the composition of erupted lavas and may give insight into the underlying pattern of mantle flow. Here we present three-dimensional images of seismic reflectivity beneath a mid-ocean ridge to investigate the nature of melt distribution across a ridge-axis discontinuity. Reflectivity slices through the 9 degrees 03' N overlapping spreading centre on East Pacific Rise suggest that it has a robust magma supply, with melt bodies underlying both limbs and ponding of melt beneath large areas of the overlap basin. The geometry of melt distribution beneath this offset is inconsistent with large-scale, crustal redistribution of melt away from centres of upwelling. The complex distribution of melt seems instead to be caused by a combination of vertical melt transport from the underlying mantle and subsequent focusing of melt beneath a magma freezing boundary in the mid-crust. 相似文献