Protective effect of lipoproteins containing apoprotein A-I on Cu2+ - catalyzed oxidation of human low density lipoprotein

AbstractTwo apoprotein A-I (apoA-I)-containing lipoproteins, one containing apoA-I and apoA-II (LpA-I/A-II) and the other containing only apoA-I (LpA-I), were examined for their effect on Cu2+-mediated oxidation of low density lipoprotein (LDL). The presence of LpA-I or LpA-I/A-II prevented LDL oxidation when assessed by the electrophoretic mobility, apoprotein B fragmentation and amounts of thiobarbituric acid-reactive substances. The protection of LDL oxidation by these lipoproteins was effective for up to 6 h, with LpA-I being more active than LpA-I/A-II. Results from these in vitro model experiments raise a possibility that LpA-I mayplay a role in protecting LDL from Cu2+ -mediated oxidation

Current Performance and On-Going Improvements of the 8.2 m Subaru Telescope

An overview of the current status of the 8.2 m Subaru Telescope constructed and operated at Mauna Kea, Hawaii, by the National Astronomical Observatory of Japan is presented. The basic design concept and the verified performance of the telescope system are described. Also given are the status of the instrument package offered to the astronomical community, the status of operation, and some of the future plans. The status of the telescope reported in a number of SPIE papers as of the summer of 2002 are incorporated with some updates included as of 2004 February. However, readers are encouraged to check the most updated status of the telescope through the home page, http://subarutelescope.org/index.html, and/or the direct contact with the observatory staff.Comment: 18 pages (17 pages in published version), 29 figures (GIF format), This is the version before the galley proo

Lack of association of genetic variation in chromosome region 15q14-22.1 with type 2 diabetes in a Japanese population

<p>Abstract</p> <p>Background</p> <p>Chromosome 15q14-22.1 has been linked to type 2 diabetes (T2D) and its related traits in Japanese and other populations. The presence of T2D disease susceptibility variant(s) was assessed in the 21.8 Mb region between <it>D15S118 </it>and <it>D15S117 </it>in a Japanese population using a region-wide case-control association test.</p> <p>Methods</p> <p>A two-stage association test was performed using Japanese subjects: The discovery panel (Stage 1) used 372 cases and 360 controls, while an independent replication panel (Stage 2) used 532 cases and 530 controls. A total of 1,317 evenly-spaced, common SNP markers with minor allele frequencies > 0.10 were typed for each stage. Captured genetic variation was examined in HapMap JPT SNPs, and a haplotype-based association test was performed.</p> <p>Results</p> <p>SNP2140 (rs2412747) (<it>C/T</it>) in intron 33 of the ubiquitin protein ligase E3 component n-recognin 1 (<it>UBR1</it>) gene was selected as a landmark SNP based on repeated significant associations in Stage 1 and Stage 2. However, the marginal <it>p </it>value (<it>p </it>= 0.0043 in the allelic test, OR = 1.26, 95% CI = 1.07–1.48 for combined samples) was weak in a single locus or haplotype-based association test. We failed to find any significant SNPs after correcting for multiple testing.</p> <p>Conclusion</p> <p>The two-stage association test did not reveal a strong association between T2D and any common variants on chromosome 15q14-22.1 in 1,794 Japanese subjects. A further association test with a larger sample size and denser SNP markers is required to confirm these observations.</p

Collaborative Action of Brca1 and CtIP in Elimination of Covalent Modifications from Double-Strand Breaks to Facilitate Subsequent Break Repair

Topoisomerase inhibitors such as camptothecin and etoposide are used as anti-cancer drugs and induce double-strand breaks (DSBs) in genomic DNA in cycling cells. These DSBs are often covalently bound with polypeptides at the 3′ and 5′ ends. Such modifications must be eliminated before DSB repair can take place, but it remains elusive which nucleases are involved in this process. Previous studies show that CtIP plays a critical role in the generation of 3′ single-strand overhang at “clean” DSBs, thus initiating homologous recombination (HR)–dependent DSB repair. To analyze the function of CtIP in detail, we conditionally disrupted the CtIP gene in the chicken DT40 cell line. We found that CtIP is essential for cellular proliferation as well as for the formation of 3′ single-strand overhang, similar to what is observed in DT40 cells deficient in the Mre11/Rad50/Nbs1 complex. We also generated DT40 cell line harboring CtIP with an alanine substitution at residue Ser332, which is required for interaction with BRCA1. Although the resulting CtIPS332A/−/− cells exhibited accumulation of RPA and Rad51 upon DNA damage, and were proficient in HR, they showed a marked hypersensitivity to camptothecin and etoposide in comparison with CtIP+/−/− cells. Finally, CtIPS332A/−/−BRCA1−/− and CtIP+/−/−BRCA1−/− showed similar sensitivities to these reagents. Taken together, our data indicate that, in addition to its function in HR, CtIP plays a role in cellular tolerance to topoisomerase inhibitors. We propose that the BRCA1-CtIP complex plays a role in the nuclease-mediated elimination of oligonucleotides covalently bound to polypeptides from DSBs, thereby facilitating subsequent DSB repair

Genetic Evidence for Single-Strand Lesions Initiating Nbs1-Dependent Homologous Recombination in Diversification of Ig V in Chicken B Lymphocytes

Homologous recombination (HR) is initiated by DNA double-strand breaks (DSB). However, it remains unclear whether single-strand lesions also initiate HR in genomic DNA. Chicken B lymphocytes diversify their Immunoglobulin (Ig) V genes through HR (Ig gene conversion) and non-templated hypermutation. Both types of Ig V diversification are initiated by AID-dependent abasic-site formation. Abasic sites stall replication, resulting in the formation of single-stranded gaps. These gaps can be filled by error-prone DNA polymerases, resulting in hypermutation. However, it is unclear whether these single-strand gaps can also initiate Ig gene conversion without being first converted to DSBs. The Mre11-Rad50-Nbs1 (MRN) complex, which produces 3′ single-strand overhangs, promotes the initiation of DSB-induced HR in yeast. We show that a DT40 line expressing only a truncated form of Nbs1 (Nbs1p70) exhibits defective HR-dependent DSB repair, and a significant reduction in the rate—though not the fidelity—of Ig gene conversion. Interestingly, this defective gene conversion was restored to wild type levels by overproduction of Escherichia coli SbcB, a 3′ to 5′ single-strand–specific exonuclease, without affecting DSB repair. Conversely, overexpression of chicken Exo1 increased the efficiency of DSB-induced gene-targeting more than 10-fold, with no effect on Ig gene conversion. These results suggest that Ig gene conversion may be initiated by single-strand gaps rather than by DSBs, and, like SbcB, the MRN complex in DT40 may convert AID-induced lesions into single-strand gaps suitable for triggering HR. In summary, Ig gene conversion and hypermutation may share a common substrate—single-stranded gaps. Genetic analysis of the two types of Ig V diversification in DT40 provides a unique opportunity to gain insight into the molecular mechanisms underlying the filling of gaps that arise as a consequence of replication blocks at abasic sites, by HR and error-prone polymerases

Tensile Creep Behavior of Single-Crystal High-Entropy Superalloy at Intermediate Temperature

In this study, we investigated the creep deformation mechanism of a single-crystal high-entropy superalloy (HESA) with the spherical &gamma;&prime; precipitates at 760 &deg;C. Before the creep tests, long-term aging tests at 760 &deg;C without load were conducted, which showed Ostwald ripening of the secondary &gamma;&prime; precipitates up to 50 h. The creep tests revealed that in the range of 500 and 600 MPa at 760 &deg;C, the creep deformation mechanism of HESA was independent of applied stress in both the primary and secondary creep regions. The deformation mechanism of HESA was further investigated under the condition of 760 &deg;C and 520 MPa by performing creep interrupted tests and microstructural analysis. Scanning electron microscope observation showed elongated &gamma;&prime; precipitates along the applied stress axis near the ruptured surface. This could have been caused by the multi-slip around &lt;100&gt; preceded by the lattice rotation into &lt;100&gt; along the tensile axis, which was confirmed by the electron backscatter diffraction analysis. Transmission electron microscope observation of the creep interrupted and ruptured specimens showed bypass and climb motion of dislocations in the 2-h interrupted, shearing of the &gamma;&prime; precipitates by the paired straight dislocations in the 50-h interrupted, and shearing of the &gamma;&prime; precipitates by both the straight and the curved paired dislocations in the ruptured specimens, respectively. The secondary &gamma;&prime; precipitates do not affect creep behavior as long as the deformation mechanism is a bypass and climb motion of dislocations