Norihiko L. Okamoto

Suppression by human placental protein 14 of natural killer cell activity

ABSTRACT: Human decidua of early pregnancy contains considerable numbers of CD3− CD56+ natural killer (NK) cells. In this study, two major protein products of the decidua, placental protein 14 (PP14) and placental protein 12 (PP12), were tested for the ability to regulate human NK cell activity. In vitro overnight exposure to PP14 of blood lymphocytes or purified large granular lymphocytes (LGL) resulted in suppression of cytotoxicity against K562 target cells in a 4‐h 51Cr release assay. The NK inhibition was dependent on concentrations of PP14, being detectable at 5 μg/ml and reaching maximum at 50 μg/ml. Manifestation of PP14‐induced NK suppression required 18‐h contact with NK cells. The suppression of NK activity by PP14 was not abolished by indomethacin. In a target binding assay the number of PP14‐treated LGL binding to K562 was comparable to that of untreated ones. By contrast with PP14, PP12 produced no effects on NK cells. These results indicate that PP14 suppresses the function of NK cells, which might be involved in prevention of maternal immune rejection of fetus at the fetomaternal interface.

Temperature dependence of thermal expansion and elastic constants of single crystals of ZrB2 and the suitability of ZrB2 as a substrate for GaN film

Coefficients of thermal expansion (CTE) and elastic constants of single crystals of ZrB2 have been determined in the temperature ranges from room temperature to 1073 K and from room temperature to 1373 K, respectively. The elastic constants of ZrB2 are best characterized by the large value of the Young modulus (as high as 500 GPa) and the small values of the Poisson ratio (0.13–0.15), indicating the high stiffness and hardness and the brittleness, respectively. The values of CTE along the a- and c-axis directions are 6.66×10−6 and 6.93×10−6 K−1, respectively, when averaged over the temperature range from room temperature to 1073 K. The CTE value along the a-axis direction of ZrB2 is only moderately larger than the corresponding value for GaN. This together with the small lattice mismatch along the a-axis direction between ZrB2 and GaN in the heteroepitaxial orientation relationship of (0001)GaN//(0001)ZrB2 and 〈1120〉GaN//〈1120〉ZrB2 indicate that only a small compressive stress develops in the GaN thin-f...

Plastic deformation of polycrystals of Co

The plastic behaviour of Co3(Al,W) polycrystals with the L12 structure has been investigated in compression from 77 to 1273 K. The yield stress exhibits a rapid decrease at low temperatures (up to room temperature) followed by a plateau (up to 950 K), then it increases anomalously with temperature in a narrow temperature range between 950 and 1100 K, followed again by a rapid decrease at high temperatures. Slip is observed to occur exclusively on {111} planes at all temperatures investigated. The rapid decrease in yield stress observed at low temperatures is ascribed to a thermal component of solid-solution hardening that occurs during the motion of APB-coupled dislocations whose core adopts a planar, glissile structure. The anomalous increase in yield stress is consistent with the thermally activated cross-slip of APB-coupled dislocations from (111) to (010), as for many other L12 compounds. Similarities and differences in the deformation behaviour and operating mechanisms among Co3(Al,W) and other L12 compounds, such as Ni3Al and Co3Ti, are discussed.

Lymphocytes stimulate progesterone production by cultured human granulosa luteal cells

After follicular rupture, massive invasion of blood vessels with neovascularization of the developing corpus luteum takes place, providing many chances for direct contact of luteal cells with resident and migrating immune cells. We studied the effects of peripheral blood lymphocytes on progesterone production by human granulosa luteal cells isolated from women undergoing in vitro fertilization. During 6 days of culture, progesterone production by granulosa luteal cells was significantly increased when they were cultured together with autologous or allogenic peripheral blood lymphocytes. This stimulatory effect was also observed on the addition of medium conditioned with peripheral blood lymphocytes and was synergistic with gonadotropin stimulation. The activity was present in the fraction retained by ultrafiltration with a 30,000 molecular weight cutoff filter and was preserved after heating at 56 degrees C for 30 minutes but disappeared after heating at 70 degrees C for 15 minutes. These findings suggest that lymphocytes infiltrating the corpus luteum during early luteinization can stimulate the function of human granulosa luteal cells through the action of some protein-like humoral factor(s) of higher molecular weight than that of previously identified lymphokines and indicate a possible paracrinologic regulatory role for lymphocytes in ovarian function.

Size effect, critical resolved shear stress, stacking fault energy, and solid solution strengthening in the CrMnFeCoNi high-entropy alloy

High-entropy alloys (HEAs) comprise a novel class of scientifically and technologically interesting materials. Among these, equatomic CrMnFeCoNi with the face-centered cubic (FCC) structure is noteworthy because its ductility and strength increase with decreasing temperature while maintaining outstanding fracture toughness at cryogenic temperatures. Here we report for the first time by single-crystal micropillar compression that its bulk room temperature critical resolved shear stress (CRSS) is ~33–43 MPa, ~10 times higher than that of pure nickel. CRSS depends on pillar size with an inverse power-law scaling exponent of –0.63 independent of orientation. Planar ½ < 110 > {111} dislocations dissociate into Shockley partials whose separations range from ~3.5–4.5 nm near the screw orientation to ~5–8 nm near the edge, yielding a stacking fault energy of 30 ± 5 mJ/m2. Dislocations are smoothly curved without any preferred line orientation indicating no significant anisotropy in mobilities of edge and screw segments. The shear-modulus-normalized CRSS of the HEA is not exceptionally high compared to those of certain concentrated binary FCC solid solutions. Its rough magnitude calculated using the Fleischer/Labusch models corresponds to that of a hypothetical binary with the elastic constants of our HEA, solute concentrations of 20–50 at.%, and atomic size misfit of ~4%.

Crystal structure and thermoelectric properties of type-I clathrate compounds in the Ba-Ga-Ge system

The crystal structure and thermoelectric properties of type-I clathrate compounds in the Ba–Ga–Ge system have been investigated as a function of Ga content. The solid solubility of Ga in the type-I clathrate compounds is determined to be X=16 when expressed with the formula of Ba8GaXGe46−X. As the Ga content increases, the crystal structure changes from a superlattice structure to the normal type-I clathrate structure with the transition occurring at X=3.5–5. The density of Ge vacancies in the type-I clathrate phase decreases as the Ga content increases. The absolute values of electrical resistivity and Seebeck coefficient increase, while that of lattice thermal conductivity decreases with the increase in the Ga content. The changes in electrical resistivity and Seebeck coefficient are explained in terms of the number of excess electrons, while the change in lattice thermal conductivity is explained in terms of the extent of the rattling motion of Ba atoms encapsulated in the cage structure.

Effect of In additions on the thermoelectric properties of the type-I clathrate compound Ba8Ga16Ge30

The thermoelectric properties of quaternary type-I clathrate compounds, Ba8Ga16−xInxGe30 (x=0–9), have been investigated as a function of In content and temperature. The substitution of In atoms for Ga atoms leads to a decrease in electrical resistivity, as well as a decrease in thermal conductivity. The decrease in electrical resisitivity is explained in terms of the In occupancy behavior in the 6c sites, whereas the decrease in thermal conductivity in terms of the increased extent of the rattling motion of Ba atoms due to the increased lattice constant. As a result, the value of thermoelectric dimensionless figure of merit (ZT) of Ba8Ga16Ge30 is improved by In substitutions from 0.49 to 1.03 at 670°C when x=6.

Activation of human natural killer cells by the protein-bound polysaccharide PSK independently of interferon and interleukin 2

The protein-bound polysaccharide PSK was tested for the ability to activate human natural killer (NK) cells. When blood lymphocytes and purified CD3-CD16+ large granular lymphocytes (LGL) were treated in vitro overnight with PSK, they demonstrated enhanced NK cell activity against K562. The PSK-activated killer cells also lysed NK-resistant targets and freshly isolated autologous and allogeneic tumor cells. The PSK effect was observed with concentrations that could be obtained in the blood of cancer patients receiving oral administration of PSK. PSK-induced enhancement of NK activity was not abrogated by monoclonal antibodies (mAb) that neutralized interferon (IFN) alpha, IFN gamma, or interleukin-2 (IL-2). In addition, mAb reactive with p55 (alpha chain) or p75 (beta chain) glycoproteins of IL-2 receptors had no effects on PSK-enhanced NK activity even when used simultaneously. These results indicate that the PSK could activate human NK cells independently of IFN and IL-2/IL-2R systems.

Atomic displacement in the CrMnFeCoNi high-entropy alloy – A scaling factor to predict solid solution strengthening

Although metals strengthened by alloying have been used for millennia, models to quantify solid solution strengthening (SSS) were first proposed scarcely seventy years ago. Early models could predict the strengths of only simple alloys such as dilute binaries and not those of compositionally complex alloys because of the difficulty of calculating dislocation-solute interaction energies. Recently, models and theories of SSS have been proposed to tackle complex high-entropy alloys (HEAs). Here we show that the strength at 0 K of a prototypical HEA, CrMnFeCoNi, can be scaled and predicted using the root-mean-square atomic displacement, which can be deduced from X-ray diffraction and first-principles calculations as the isotropic atomic displacement parameter, that is, the average displacements of the constituent atoms from regular lattice positions. We show that our approach can be applied successfully to rationalize SSS in FeCoNi, MnFeCoNi, MnCoNi, MnFeNi, CrCoNi, CrFeCoNi, and CrMnCoNi, which are all medium-entropy subsets of the CrMnFeCoNi HEA.

Studies on T-Lineage Cells in Human Decidua of First Trimester Pregnancies

ABSTRACT: T‐lineage cells in human decidua of early pregnancies were tested for surface markers, proliferative response, interleukin‐2 (IL‐2) production, and natural killer (NK) activity. T‐lineage (CD2+) cells that were obtained from decidua by the use of E‐rosette formation contained fewer CD3+ mature T cells and CD4+ cells than those from the peripheral blood of the same donors, while no differences were seen in the frequencies of CD8+ cells. P55 molecules of IL‐2 receptor (IL‐2R/p55, Tac antigen) were hardly detected on fresh decidual T‐lineage cells, though approximately 20% were positive for HLA‐DR. More than a half of decidual T‐lineage cells expressed CD56 molecules on their surface and killed K562 cells, the prototype target of NK cells, while most of them were negative for CD16 and CD57. Upon stimulation with IL‐2, decidual T‐lineage cells demonstrated dose‐dependent proliferative response. In addition, they were induced to produce high amounts of IL‐2 by stimulation with mitogens but not with alloantigens. These results suggest that human decidua contains high numbers of CD2+3‐CD16+56+ lymphocytes and that this population responds to IL‐2, produces IL‐2 and mediates NK activity.