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Recently amplified Alu family members share a common parental Alu sequence. 总被引:18,自引:1,他引:17
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Three of the most recently inserted primate Alu family members are exceptionally closely related. Therefore, one, or a few, Alu family members are dominating the amplification process and the vast majority are not actively involved in retroposition. Although individual Alu family members are not under any apparent evolutionary constraint, the sequences of these active members are being moderately conserved. 相似文献
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M A Gama-Sosa V A Slagel R W Trewyn R Oxenhandler K C Kuo C W Gehrke M Ehrlich 《Nucleic acids research》1983,11(19):6883-6894
The over-all 5-methylcytosine (m5C) content of DNA from normal tissues varies considerably in a tissue-specific manner. By high-performance liquid chromatography, we have examined the m5C contents of enzymatic digests of DNA from 103 human tumors including benign, primary malignant and secondary malignant neoplasms. The diversity and large number of these tumor samples allowed us to compare the range of DNA methylation levels from neoplastic tissues to that of normal tissues from humans. Most of the metastatic neoplasms had significantly lower genomic m5C contents than did most of the benign neoplasms or normal tissues. The percentage of primary malignancies with hypomethylated DNA was intermediate between those of metastases and benign neoplasms. These findings might reflect an involvement of extensive demethylation of DNA in tumor progression. Such demethylation could be a source of the continually generated cellular diversity associated with cancer. 相似文献
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Slagel V; Flemington E; Traina-Dorge V; Bradshaw H; Deininger P 《Molecular biology and evolution》1987,4(1):19-29
Thirteen and 10 sequences of the Alu family of repeated DNA elements found
within the human thymidine kinase and beta-tubulin genes, respectively,
were compared. These genes have approximately five times the expected
density of Alu family members. The consensus sequence that could be drawn
from these 23 Alu family members would differ slightly from others drawn
from random Alu family sequences but only at very heterogeneous positions.
The different Alu family members do show different pairwise percentage
identities, with approximately 15% (7 of 48 Alu family members analyzed) of
them clearly representing a separate subfamily of sequences. This analysis
also confirms the species- specific differences between human and the
prosimian Galago crassicaudatus Alu family members. These data are
consistent with both the origin of these sequences in primates less than
65-70 Myr ago and amplification since that time to their present 500,000
copies. The data do not show any special relationships among densely
clustered Alu family members.
相似文献
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Venneti S Lopresti BJ Wang G Slagel SL Mason NS Mathis CA Fischer ML Larsen NJ Mortimer AD Hastings TG Smith AD Zigmond MJ Suhara T Higuchi M Wiley CA 《Journal of neurochemistry》2007,102(6):2118-2131
Activated microglia are an important feature of many neurological diseases and can be imaged in vivo using 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxamide (PK11195), a ligand that binds the peripheral benzodiazepine receptor (PBR). N-(2,5-dimethoxybenzyl)-N-(5-fluoro-2-phenoxyphenyl) acetamide (DAA1106) is a new PBR-specific ligand that has been reported to bind to PBR with higher affinity compared with PK11195. We hypothesized that this high-affinity binding of DAA1106 to PBR will enable better delineation of microglia in vivo using positron emission tomography. [(3)H]DAA1106 showed higher binding affinity compared with [(3)H](R)-PK11195 in brain tissue derived from normal rats and the rats injected intrastriatally with 6-hydroxydopamine or lipopolysaccharide at the site of the lesion. Immunohistochemistry combined with autoradiography in brain tissues as well as correlation analyses showed that increased [(3)H]DAA1106 binding corresponded mainly to activated microglia. Finally, ex vivo autoradiography and positron emission tomography imaging in vivo showed greater retention of [(11)C]DAA1106 compared with [(11)C](R)-PK11195 in animals injected with either lipopolysaccaride or 6-hydroxydopamine at the site of lesion. These results indicate that DAA1106 binds with higher affinity to microglia in rat models of neuroinflammation when compared with PK11195, suggesting that [(11)C]DAA1106 may represent a significant improvement over [(11)C](R)-PK11195 for in vivo imaging of activated microglia in human neuroinflammatory disorders. 相似文献
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Lipid composition of human glial tumour and adjacent brain 总被引:2,自引:2,他引:0
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Miguel A. Gama-Sosa Rose Marie Midgett Valerie A. Slagel Sherwood Githens Kenneth C. Kuo Charles W. Gehrke Melanie Ehrlich 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1983,740(2):212-219
The only naturally occurring modified base in vertebrate DNA is 5-methylcytosine. Using a precise high-performance liquid chromatographic analysis of DNA enzymatically digested to deoxynucleosides, we have shown that rats, mice and four types of monkey display tissue-specific as well as species-specific differences in the extent of methylation of their cytosine residues. Several similarities in the patterns of tissue-specific DNA methylation in these mammals and in the previously studied human samples were observed. Compared to most other types of DNA examined, brain and thymus DNAs were hypermethylated, which suggests that this hypermethylation is a determinant or a necessary byproduct of mammalian differentiation. In all of the studied rodents and primates, the highly repeated DNA sequence fraction was more methylated than the moderately repetitive or single copy fractions. The tissue-specific differences in overall DNA methylation showed no correlation with what is known about average cell turnover rates nor with the percentage of the genome that is transcribed. Liver regeneration in the rat following partial hepatectomy did not detectably alter 5-methylcytosine levels in liver DNA. A considerable increase in the extent of methylation of total liver DNA was observed during normal development of the rat. The latter phenomenon may be due to a major change in the cellular composition of the liver. 相似文献
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