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91.
Condensed and dispersed chromatin fractions were isolated from human placental nuclei. The DNA of each fraction was purified and characterised by isopycnic centrifugation, thermal fractionation on hydroxylapatite (HAP) and sequence complexity studies. The DNAs had identical buoyant densities in neutral CsCl (1.698 g/cm3) and similar melting profiles on HAP. Analytical ultracentrifugation in Ag+-Cs2SO4, however, showed that satellite DNAs were present in the condensed fraction DNA (DNAC) but were not visible in the dispersed fraction DNA (DNAD). In addition, DNAC was found to be enriched in highly reiterated sequences (20% reassociated by C0t 10?3) which can be correlated with the presence of satellite DNAs, whereas DNAD contained only 3% of these fast reassociating sequences. In contrast DNAD contained 30% intermediate sequences (reassociating between C0t 10?3 and C0t 100) which represent only 10% of DNAC. The reassociated highly repeated sequences of DNAC showed the presence of two components in both CsCl density gradients and HAP thermal elution studies. This suggests that either there are sequence relationships resulting in partial mismatching between the different highly repeated DNA sequences in this fraction, or that highly repeated sequences are associated with less repetitious DNA. The results are discussed in terms of possible differences in genetic activity between the chromatin fractions. 相似文献
92.
R S Jones 《BMJ (Clinical research ed.)》1981,282(6280):1914-1916
93.
The isolation and characterization of an alkylating-agent-sensitive yeast mutant, ngs1 总被引:4,自引:0,他引:4
We have isolated and characterized a mutant of baker's yeast, Saccharomyces cerevisiae, carrying the new mutation, ngs1, which is sensitive to the toxic effects of monofunctional alkylating agents, but normal with respect to 254-nm ultraviolet light sensitivity. ngs1 mutants exhibited more or less normal reversion frequencies for his1-7 and ilv1-92 induced by each of these mutagens. The various sensitivities associated with ngs1 cosegregated and have been shown to be the result of a lesion in a single nuclear gene. Extracts of ngs1 and NGS1+ strains contained approximately equal levels of an activity that removes 3-methyladenine (3MA) and 7-methylguanine (7MG) from DNA in vitro. The mutation also depressed sporulation. 相似文献
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97.
Techniques are described for capturing and marking redtail monkeys (Cercopithecus ascanius). An air-powered darting rifle and syringe darts loaded with a Ketamine-Rompun mixture were used for capture. Ketamine was used for maintaining anesthesia. Monkeys were darted 48 times and captured 27 times. In 24 of the 27 captures, the monkeys were released unharmed. Adult males were marked with radiotransmitters attached to collars of nylon webbing. Females received nylon webbing collars with colorcoded plastic washers for identification. 相似文献
98.
D. J. Jones 《BMJ (Clinical research ed.)》1992,305(6853):575-577
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100.
Francis G. Spinale Rupak Mukherjee Juozas A. Zavadzkas Christine N. Koval Shenikqua Bouges Robert E. Stroud Lawrence W. Dobrucki Albert J. Sinusas 《The Journal of biological chemistry》2010,285(39):30316-30327
The membrane type-1 matrix metalloproteinase (MT1-MMP) is a unique member of the MMP family, but induction patterns and consequences of MT1-MMP overexpression (MT1-MMPexp), in a left ventricular (LV) remodeling process such as myocardial infarction (MI), have not been explored. MT1-MMP promoter activity (murine luciferase reporter) increased 20-fold at 3 days and 50-fold at 14 days post-MI. MI was then induced in mice with cardiac restricted MT1-MMPexp (n = 58) and wild type (WT, n = 60). Post-MI survival was reduced (67% versus 46%, p < 0.05), and LV ejection fraction was lower in the post-MI MT1-MMPexp mice compared with WT (41 ± 2 versus 32 ± 2%,p < 0.05). In the post-MI MT1-MMPexp mice, LV myocardial MMP activity, as assessed by radiotracer uptake, and MT1-MMP-specific proteolytic activity using a specific fluorogenic assay were both increased by 2-fold. LV collagen content was increased by nearly 2-fold in the post-MI MT1-MMPexp compared with WT. Using a validated fluorogenic construct, it was discovered that MT1-MMP proteolytically processed the pro-fibrotic molecule, latency-associated transforming growth factor-1 binding protein (LTBP-1), and MT1-MMP-specific LTBP-1 proteolytic activity was increased by 4-fold in the post-MI MT1-MMPexp group. Early and persistent MT1-MMP promoter activity occurred post-MI, and increased myocardial MT1-MMP levels resulted in poor survival, worsening of LV function, and significant fibrosis. A molecular mechanism for the adverse LV matrix remodeling with MT1-MMP induction is increased processing of pro-fibrotic signaling molecules. Thus, a proteolytically diverse portfolio exists for MT1-MMP within the myocardium and likely plays a mechanistic role in adverse LV remodeling. 相似文献