Structural disjoining potential for grain boundary premelting and grain coalescence from molecular-dynamics simulations

We describe a molecular dynamics framework for the direct calculation of the short-ranged structural forces underlying grain-boundary premelting and grain-coalescence in solidification. The method is applied in a comparative study of (i) a Sigma 9 120 degress twist and (ii) a Sigma 9 {411} symmetric tilt boundary in a classical embedded-atom model of elemental Ni. Although both boundaries feature highly disordered structures near the melting point, the nature of the temperature dependence of the width of the disordered regions in these boundaries is qualitatively different. The former boundary displays behavior consistent with a logarithmically diverging premelted layer thickness as the melting temperature is approached from below, while the latter displays behavior featuring a finite grain-boundary width at the melting point. It is demonstrated that both types of behavior can be quantitatively described within a sharp-interface thermodynamic formalism involving a width-dependent interfacial free energy, referred to as the disjoining potential. The disjoining potential for boundary (i) is calculated to display a monotonic exponential dependence on width, while that of boundary (ii) features a weak attractive minimum. The results of this work are discussed in relation to recent simulation and theoretical studies of the thermodynamic forces underlying grain-boundary premelting.Comment: 24 pages, 8 figures, 1 tabl

A swollen phase observed between the liquid-crystalline phase and the interdigitated phase induced by pressure and/or adding ethanol in DPPC aqueous solution

A swollen phase, in which the mean repeat distance of lipid bilayers is larger than the other phases, is found between the liquid-crystalline phase and the interdigitated gel phase in DPPC aqueous solution. Temperature, pressure and ethanol concentration dependences of the structure were investigated by small-angle neutron scattering, and a bending rigidity of lipid bilayers was by neutron spin echo. The nature of the swollen phase is similar to the anomalous swelling reported previously. However, the temperature dependence of the mean repeat distance and the bending rigidity of lipid bilayers are different. This phase could be a precursor to the interdigitated gel phase induced by pressure and/or adding ethanol.Comment: 7 pages, 6 figure

Identification of CD93 expression on hematopoietic stem cells in human neonatal umbilical cord blood cells

臍帯血由来造血幹細胞表面上のCD93の発現を我々が開発したCD93モノクローナル抗体(mNI-11)、既存のCD34抗体、CD45抗体を組み合わせたフローサイトメトリー法で解析した。その結果、臍帯血由来造血幹細胞(CD34+細胞およびCD34+CD45dim+細胞)表面上にはCD93が発現していることが分かった。以上の結果は、CD93が未熟な造血幹細胞の新たな細胞表面マーカーに成り得ると共に、造血幹細胞におけるCD93の免疫学的な機能解析に非常に有益な情報と考えられる。Human CD93 is a heavily O-glycosylated type I transmembrane protein consisting of unique C-type lectin domains (CTLDs) containing glycoprotein. CD93 is mainly expressed on myeloid cells (monocytes and granulocytes) and endothelial cells. However, the expression patterns of CD93 on various other kinds of cells are not well understood. In this study, we found that CD93 was recognized by a CD93 monoclonal antibody (mAb) (mNI-11) that was established in our laboratories and was expressed on a broad hematopoietic stem cell population (CD34+ cells) from human neonatal umbilical cord blood cells (UCBCs), as shown using a two-color flow cytometric analysis. In addition, the CD93 recognized by mNI-11 was also expressed on a narrow hematopoietic stem cell population(CD34+CD45dim+ cells) in which the non-specific reactivity of CD34 mAb from human neonatal UCBCs was excluded using a three-color flow cytometric analysis. Taken together, these results provide the first evidence concerning the identification of CD93 expression on hematopoietic stem cells. These cell populations (CD34+CD93+ and CD34+CD45dim+CD93+ cells) in human neonatal UCBCs are thought to have an important role in cell biology, transplantation, and immature/mature immune responses

[原著］Genetic influence of HLA-DR on longevity in Okinawan people

Okinawa is well-known as one of the longevity areas in the world and the population rate of centenarians is higher by far than that of the whole of Japan. However, only few reports have used genetic approaches to explain Okinawan long lifespan. In this study, we analyzed human luekocyte antigen (HLA) both in phenotyping and in genotyping for the same subjects of Okinawan centenarians and normal adults for the purpose of clarifying one of the primary genetic factors in major histo-compatibility complex (MHC) region genes associated with longevity. Eighty-six healthy centenarians and 142 normal adults in Okinawa were studied. For HLA phenotyping, 14 antigen specificities on DR locus were typed according to the standard microdroplet lymphocyte cytotoxicity test, and for genotyping 27 alleles on DRBl were typed by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method based on the digestion of PCR-amplified DNAs with allele specific enzymes. In the present study, DR1 was found to be high in centenarians in phenotyping (P=0.029, RR=5.779), which was similar in genotypeing (DRB1^*0101: P=0.030, RR=5.779), but both results were not significantly different at Pc level. However, DRB1^*1401 (P=0.00103, Pc=0.028, RR-3.456) was significantly high. These data suggest that several alleles of HLA-DRB1, such as DRB1^*1401, favourably relate to longevity.論文http://purl.org/coar/resource_type/c_650

Major histocompatibility complex (Mhc) class Ib gene duplications, organization and expression patterns in mouse strain C57BL/6

<p>Abstract</p> <p>Background</p> <p>The mouse has more than 30 <it>Major histocompatibility complex </it>(<it>Mhc</it>) class Ib genes, most of which exist in the <it>H2 </it>region of chromosome 17 in distinct gene clusters. Although recent progress in <it>Mhc </it>research has revealed the unique roles of several <it>Mhc </it>class Ib genes in the immune and non-immune systems, the functions of many class Ib genes have still to be elucidated. To better understand the roles of class Ib molecules, we have characterized their gene duplication, organization and expression patterns within the <it>H2 </it>region of the mouse strain C57BL/6.</p> <p>Results</p> <p>The genomic organization of the <it>H2-Q</it>, -<it>T </it>and -<it>M </it>regions was analyzed and 21 transcribed <it>Mhc </it>class Ib genes were identified within these regions. Dot-plot and phylogenetic analyses implied that the genes were generated by monogenic and/or multigenic duplicated events. To investigate the adult tissue, embryonic and placental expressions of these genes, we performed RT-PCR gene expression profiling using gene-specific primers. Both tissue-wide and tissue-specific gene expression patterns were obtained that suggest that the variations in the gene expression may depend on the genomic location of the duplicated genes as well as locus specific mechanisms. The genes located in the <it>H2-T </it>region at the centromeric end of the cluster were expressed more widely than those at the telomeric end, which showed tissue-restricted expression in spite of nucleotide sequence similarities among gene paralogs.</p> <p>Conclusion</p> <p>Duplicated <it>Mhc </it>class Ib genes located in the <it>H2-Q</it>, -<it>T </it>and -<it>M </it>regions are differentially expressed in a variety of developing and adult tissues. Our findings form the basis for further functional validation studies of the <it>Mhc </it>class Ib gene expression profiles in specific tissues, such as the brain. The duplicated gene expression results in combination with the genome analysis suggest the possibility of long-range regulation of <it>H2-T </it>gene expression and/or important, but as yet unidentified nucleotide changes in the promoter or enhancer regions of the genes. Since the <it>Mhc </it>genomic region has diversified among mouse strains, it should be a useful model region for comparative analyses of the relationships between duplicated gene organization, evolution and the regulation of expression patterns.</p

Single nucleotide polymorphism detection by polymerase chain reaction-restriction fragment length polymorphism

ArticleNATURE PROTOCOLS. 2(11): 2857-2864 (2007)journal articl