Crosslinking reactions of 4-amino-6-oxo-2-vinylpyrimidine with guanine derivatives and structural analysis of the adducts

DNA interstrand crosslinks (ICLs) are the primary mechanism for the cytotoxic activity of many clinical anticancer drugs, and numerous strategies for forming ICLs have been developed. One such method is using crosslink-forming oligonucleotides (CFOs). In this study, we designed a 4-amino-6-oxo-2-vinylpyrimidine (AOVP) derivative with an acyclic spacer to react selectively with guanine. The AOVP CFO exhibited selective crosslinking reactivity with guanine and thymine in DNA, and with guanine in RNA. These crosslinking reactions with guanine were accelerated in the presence of CoCl₂, NiCl₂, ZnCl₂ and MnCl₂. In addition, we demonstrated that the AOVP CFO was reactive toward 8-oxoguanine opposite AOVP in the duplex DNA. The structural analysis of each guanine and 8-oxoguanine adduct in the duplex DNA was investigated by high-resolution NMR. The results suggested that AOVP reacts at the N2 amine in guanine and at the N1 or N2 amines in 8-oxoguanine in the duplex DNA. This study demonstrated the first direct determination of the adduct structure in duplex DNA without enzyme digestion.     

Fast DNA Interstrand Cross-Linking Reaction by 6-Vinylpurine

Oligonucleotides that incorporate a reactive moiety to form an interstrand cross-link have been widely studied for their potential toward inhibiting gene expression or as basic tools for chemical biology studies. The 6-vinylpurine (2) newly designed in the current study serves well as a new purine-base moiety for increasing cross-link reactivity to target cytosine. Thus, oligonucleotides containing 6-vinylpurine exhibit a more selective and much smoother DNA cross-linking ability to cytosine than the oligonucleotide analogs derived from 2-amino-6-vinylpurine (1) previously explored.     

In Vitro Experimental Study for the Determination of Cellular Axial Strain Threshold and Preferential Axial Strain from Cell Orientation Behavior in a Non-uniform Deformation Field

Cells within connective tissues are routinely subjected to a wide range of non-uniform mechanical loads that regulate many cell behaviors. In the present study, the relationship between cell orientation angle and strain value of the membrane was comprehensively investigated using an inhomogeneous strain field. Additionally, the cellular axial strain threshold, which corresponds to the launching of cell reorientation response, was elucidated. Human bone marrow mesenchymal stem cells were used for these experiments. In this study, an inhomogeneous strain distribution was easily created by removing one side holes of an elastic chamber in a commonly used uniaxial stretching device. The strains of 2D stretched membranes were quantified on a position-by-position basis using the digital image correlation method. The normal strain in the direction of stretch was changed continuously from 2.0 to 15.0 %. A 3D histogram of the cell frequency, which was correlated with the cell orientation angle and normal strain of the membrane, made it possible to determine the axial strain threshold accurately. The value of the axial strain threshold was 4.4 ± 0.3 %, which was reasonable compared with previous studies based on cyclic uniaxial stretch stimulation (homogeneous strain field). Additionally, preferential axial strain of cells, which was a cell property firstly introduced, was also achieved and the value was ?2.0 ± 0.1 %. This study is novel in three respects: (i) it precisely and easily determined the axial strain threshold of cells; (ii) it is the first to suggest preferential axial strain of cells; and (iii) it methodically investigated cell behavior in an inhomogeneous strain field.     

Correction to: Food conditions,competitive regime,and female social relationships in Japanese macaques: within-population variation on Yakushima

Primates - In our published paper (Hanya et al. 2008), we found an error in a figure described in the     

Relationship between sleep problems and dangerous driving behaviors in Japanese short-haul commercial truck drivers: a cross-sectional survey using digital tachograph data

Sleep and Biological Rhythms - The aim of the study was to examine the relationship between sleep problems and objective driving behaviors of short-haul commercial truck drivers in Japan. One...     

Ovarian germline stem cells in the teleost fish, medaka (Oryzias latipes)

In the mammalian testis germline stem cells keep producing many sperms, while there is no direct evidence for the presence of germline stem cells in the ovary. It is widely accepted in mammals that the mature oocytes are supplied from a pool of primordial follicles in the adult ovary. In other vertebrates, such as fish, however, there has been no investigation on the mechanism underlying the high egg-producing ability. In this review, we introduce the recently identified ovarian germline stem cells and the surrounding unique structure in teleost fish, medaka (Oryzias latipes) [Nakamura S et al. Science. 2010; 328: 1561-1563]. We also discuss about the expression and function of sox9 that characterizes this unique structure.     

Homoeologous relationship of rye chromosome arms as detected with wheat PLUG markers

Based on the similarity in gene structure between rice and wheat, the polymerase chain reaction (PCR)-based landmark unique gene (PLUG) system enabled us to design primer sets that amplify wheat genic sequences including introns. From the previously reported wheat PLUG markers, we chose 144 markers that are distributed on different chromosomes and in known chromosomal regions (bins) to obtain rye-specific PCR-based markers. We conducted PCR with the 144 primer sets and the template of the Imperial rye genomic DNA and found that 131 (91.0 %) primer sets successfully amplified PCR products. Of the 131 PLUG markers, 110 (76.4 %) markers showed rye-specific PCR amplification with or without restriction enzyme digestion. We assigned 79 of the 110 markers to seven rye chromosomes (1R to 7R) using seven wheat–rye (cv. Imperial) chromosome addition and substitution lines: 12 to 1R, 8 to 2R, 11 to 3R, 8 to 4R, 16 to 5R, 12 to 6R, and 12 to 7R. Furthermore, we located their positions on the short or long (L) chromosome arm, using 13 Imperial rye telosomic lines of common wheat (except for 3RL). Referring to the chromosome bin locations of the 79 PLUG markers in wheat, we deduced the syntenic relationships between rye and wheat chromosomes. We also discussed chromosomal rearrangements in the rye genome with reference to the cytologically visible chromosomal gaps.     

Protection by α-tocopherol of the repair of photosystem II during photoinhibition in Synechocystis sp. PCC 6803

α-Tocopherol is a lipophilic antioxidant that is an efficient scavenger of singlet oxygen. We investigated the role of α-tocopherol in the protection of photosystem II (PSII) from photoinhibition using a mutant of the cyanobacterium Synechocystis sp. PCC 6803 that is deficient in the biosynthesis of α-tocopherol. The activity of PSII in mutant cells was more sensitive to inactivation by strong light than that in wild-type cells, indicating that lack of α-tocopherol enhances the extent of photoinhibition. However, the rate of photodamage to PSII, as measured in the presence of chloramphenicol, which blocks the repair of PSII, did not differ between the two lines of cells. By contrast, the repair of PSII from photodamage was suppressed in mutant cells. Addition of α-tocopherol to cultures of mutant cells returned the extent of photoinhibition to that in wild-type cells, without any effect on photodamage. The synthesis de novo of various proteins, including the D1 protein that plays a central role in the repair of PSII, was suppressed in mutant cells under strong light. These observations suggest that α-tocopherol promotes the repair of photodamaged PSII by protecting the synthesis de novo of the proteins that are required for recovery from inhibition by singlet oxygen.     

Differential heavy metal sensitivity in seven algal species from the NIES culture collection based on delayed fluorescence assays

Seafloor massive sulfide (SMS) deposits are the target of available metallic resources. The toxic impacts of leachable metals from hydrothermal ore by mining operations in marine environments are a concern. However, ecotoxicological knowledge about marine algae, and particularly open ocean species, is still limited. Here, we evaluated the toxic effects of three leachable metals (i.e. Zn, Cu, and Pb) on seven marine algae, including cyanobacteria and eukaryotes, by a delayed fluorescence method. Cyanobacterial Synechococcus and Cyanobium species were sensitive to Zn and Cu, while eukaryotic algae showed various responses to heavy metal species. The prasinophycean Bathycoccus prasinos NIES‐2670 was sensitive to all metal species; this strain is a potential test strain to detect the leachable metals. A co‐culture experiment showed that the impact on community structure varies depending on leachable metal species. This study demonstrates that surveys across multiple taxonomic groups are necessary to assess the impact of SMS‐mining operations on marine ecosystems as a whole.