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81.
The liver of the neonatal mouse continues to show haematopoietic activity for up to 2 weeks after birth and morphological analysis has shown that this activity becomes focused in discrete haematopoietic colonies by the end of the first week postnatal. Furthermore, each colony contains cells of one haematopoietic lineage only, that is, erythroid, myeloid or pre-B-lymphoid cells. This pattern of differentiation suggests that each colony is derived from a single committed precursor cell, which, if true, would represent the first demonstration of non-mixed haematopoietic colonies in normal development and would provide a useful system for studying the factors affecting the clonal diversity of haematopoietic stem cells and their lineage-committed progeny. Here we have analysed the haematopoietic foci in the liver of neonatal mouse chimaeras, using a newly developed ubiquitous in situ cell marker system which clearly demonstrates the clonal origin of these colonies. 相似文献
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Cloning of a complementary DNA for a protein-tyrosine kinase that specifically phosphorylates a negative regulatory site of p60c-src. 总被引:55,自引:0,他引:55
The protein-tyrosine kinase activity of the proto-oncogene product p60c-src is negatively regulated by the phosphorylation of a tyrosine residue close to the C terminus, tyrosine 527. The phosphorylation might be catalysed by a so-far-unidentified tyrosine kinase, distinct from p60c-src. Recently we purified a protein-tyrosine kinase that specifically phosphorylates tyrosine 527 of p60c-src from neonatal rat brain. We have now confirmed the specificity of this enzyme by using a mutant p60c-src that has a phenylalanine instead of tyrosine 527, and cloned a complementary DNA that encodes the enzyme. The enzyme is similar to kinases of the src family in that it has two conserved regions, Src-homology regions 2 and 3, upstream of a tyrosine kinase domain. The amino-acid identity of each region is no more than 47%, however, and the enzyme lacks phosphorylation sites corresponding to tyrosines 416 and 527 of p60c-src and has no myristylation signal. These results suggest that this protein-tyrosine kinase, which might negatively regulate p60c-src, represents a new type of tyrosine kinase. 相似文献
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V Dhanaraj C G Dealwis C Frazao M Badasso B L Sibanda I J Tickle J B Cooper H P Driessen M Newman C Aguilar 《Nature》1992,357(6378):466-472
X-ray analyses have defined the three-dimensional structures of crystals of mouse and human renins complexed with peptide inhibitors at resolutions of 1.9 and 2.8 A, respectively. The exquisite specificity of renin arises partly from ordered loop regions at the periphery of the binding cleft. Although the pattern of main-chain hydrogen bonding in other aspartic proteinase inhibitor complexes is conserved in renins, differences in the positions of secondary structure elements (particularly helices) also lead to improved specificity in renins for angiotensinogen substrates. 相似文献
86.
Jame J. Cooper 《西北部美国博物学家》2011,45(4)
At Walker Lake, Nevada, tui chub were collected 1975–1977 for analysis of age, growth rate, and food habits. The fork length (FL) – scale radius (SR) relationship was linear and described by the equation FL = 4.44 + 3.17 (SR). Age I, II, III, and IV chub were 116, 176, 218, and 242 mm fork length, respectively. Maximum longevity was six years. The length weight relationship was defined by the log transformed linear equation log weight = - 4.65 + 2.93 (log FL). Chub collected from pelagic regions ate mostly zooplankton, whereas chub collected from littoral areas had a diet of zooplankton and benthic organisms. 相似文献
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Molecular cloning of a new transforming gene from a chemically transformed human cell line 总被引:28,自引:0,他引:28
C S Cooper M Park D G Blair M A Tainsky K Huebner C M Croce G F Vande Woude 《Nature》1984,311(5981):29-33
Molecular cloning of the transforming gene from a chemically transformed human osteosarcoma-derived cell line enables the gene to be mapped to chromosome 7 (7p11.4-7qter) and by this criterion and by direct hybridization to be shown to be unrelated to known oncogenes. 相似文献