Showing papers by "University of Tsukuba published in 1990"

Cloning of a cDNA encoding a non-isopeptide-selective subtype of the endothelin receptor.

Abstract: ENDOTHELIN-1 was initially identified as a 21-residue potent vasoconstrictor peptide produced by vascular endothelial cells, but was subsequently found to have many effects on both vascular and non-vascular tissues1,2. The discovery of three isopeptides of the endothelin family3, ET-1, ET-2 and ET-3, each possessing a diverse set of pharmacological activities of different potency, suggested the existence of several different endothelin receptor subtypes3–7. Endothelins may elicit biological responses by various signal-transduction mechanisms, including the G protein-coupled activation of phospholipase C and the activation of voltage-dependent Ca2+ channels8–10. Thus, different subtypes of the endothelin receptor may use different signal-transduction mechanisms. Here we report the cloning of a complementary DNA encoding one subtype belonging to the superf amily of G protein-coupled receptors. COS-7 cells transfected with the cDNA express specific and high-affinity binding sites for endothelins, responding to binding by the production of inositol phosphates and a transient increase in the concentration of intracellular free Ca2+. The three endothelin isopeptides are roughly equipotent in displacing 125I-labelled ET-1 binding and causing Ca2+ mobilization. A messenger RNA corresponding to the cDNA is detected in many rat tissues including the brain, kidney and lung but not in vascular smooth muscle cells. These results indicate that this cDNA encodes a 'nonselective' subtype of the receptor which is different from the vascular smooth muscle receptor.

Antiferromagnetic Spin Fluctuations and Superconductivity in Two-Dimensional Metals —A Possible Model for High Tc Oxides

Abstract: Spin fluctuations in antiferromagnetic and nearly antiferromagnetic two dimensional (square lattice) itinerant electron systems, as a possible model for high T c superconductors, are investigated by using the self-consistent renormalization theory. The electrical resistivity and the nuclear spin relaxation rate due to the spin fluctuations in the normal state are calculated. The results in the nearly antiferromagnetic regime as applied to high T c oxides seem to explain the experimental results both in their temperature dependence and in their orders of magnitudes. By using the same spin fluctuations we discuss superconductivity due to the spin fluctuation mechanism within a weak coupling theory. The order parameter is shown to have B 1 g or A 2 g symmetry and the critical temperature is evaluated to be of the right order of magnitude.

Artificial reality with force-feedback: development of desktop virtual space with compact master manipulator

Abstract: A new configuration of Human Interface for "artificial reality" is discussed. This paper describes a method of implementing force-feedback in a virtual space manipulation system. The system is composed of two subsystems, a real-time graphic display system and a tactile input device with reaction force generator. A specialized graphics computer (Stardent TITAN) provides a realtime image of the virtual space. A 9 degree-of-freedom manipulator has been developed as a tactile input device. The manipulator applies reaction forces to the fingers and palm of the operator. The generated forces are calculated from a solid model of the virtual space. The performance of the system is exemplified in manipulation of virtual solid objects such as a mockup for industrial design and a 3D animated character.

Application of the micropipette technique to the measurement of cultured porcine aortic endothelial cell viscoelastic properties.

Abstract: The viscoelastic deformation of porcine aortic endothelial cells grown under static culture conditions was measured using the micropipette technique. Experiments were conducted both for control cells (mechanically or trypsin detached from the substrate) and for cells in which cytoskeletal elements were disrupted by cytochalasin B or colchicine. The time course of the aspirated length into the pipette was measured after applying a stepwise increase in aspiration pressure. To analyze the data, a standard linear viscoelastic half-space model of the endothelial cell was used. The aspirated length was expressed as an exponential function of time. The actin microfilaments were found to be the major cytoskeletal component determining the viscoelastic response of endothelial cells grown in static culture.

The variability of critical shear stress, friction angle, and grain protrusion in water-worked sediments

Abstract: The erodibility of a grain on a rough bed is controlled by, among other factors, its relative projection above the mean bed, its exposure relative to upstream grains, and its friction angle. Here we report direct measurements of friction angles, grain projection and exposure, and small-scale topographic structure on a variety of water-worked mixed-grain sediment surfaces. Using a simple analytical model of the force balance on individual grains, we calculate the distribution of critical shear stress for idealized spherical grains on the measured bed topography. The friction angle, projection, and exposure of single grain sizes vary widely from point to point within a given bed surface; the variability within a single surface often exceeds the difference between the mean values of disparate surfaces. As a result, the critical shear stress for a given grain size on a sediment surface is characterized by a probability distribution, rather than a single value. On a given bed, the crtitical shear stress distributions of different grain sizes have similar lower bounds, but above their lower tails they diverge rapidly, with smaller grains having substantially higher median critical shear stresses. Large numbers of fines, trapp.ed within pockets on the bed or shielded by upstream grains, are effectively lost to the flow. Our calculations suggest that critical shear stress, as conventionally measured, is defined by the most erodible grains, entrained during transient shear stress excursions associated with the turbulent flow; this implies a physical basis for the indeterminacy of initial motion. These observations suggest that transport rate/shear stress relationships may be controlled, in part, by the increasing numbers of grains that become available for entrainment as mean shear stress increases. They also suggest that bed textures and grain size distributions may be controlled, within the constraints of an imposed shear stress and sediment supply regime, by the influence of each size fraction on the erodibility of other grain sizes present on the bed.

Mesodermal induction in early amphibian embryos by activin A (erythroid differentiation factor)

Abstract: Recently the mesoderm-inducing effects of the transforming growth factor β (TGF-β) family of proteins have been widely examined. In an attemt to elucidate the functions of these proteins, porcine inhibin A and activin A (erythroid differentiation factor; EDF) were examined. Treatment of explants with activin A led to differentiation of mesodermal derivatives such as mesenchyme, notochord, blood cells and muscle, but inhibin A had a much lesser effect. The mesodermal differentiation induced by activin A was also comfirmed by analyses using a polyclonal antibody against muscle myosin. By indirect immunofluorescence analysis, the differentiation of muscle blocks was observed in the activin-A-treated explants, whereas no differentiation was observed in inhibin-A-treated and control explants. These findings confirm that this protein of the TGF-β family has mesoderm-inducing ability.

Endothelin: A novel peptide in the posterior pituitary system

Abstract: Endothelin (ET), originally characterized as a 21-residue vasoconstrictor peptide from endothelial cells, is present in the porcine spinal cord and may act as a neuropeptide. Endothelin-like immunoreactivity has now been demonstrated by immunohistochemistry in the paraventricular and supraoptic nuclear neurons and their terminals in the posterior pituitary of the pig and the rat. The presence of ET in the porcine hypothalamus was confirmed by reversed-phase high-pressure liquid chromatography and radioimmunoassay. Moreover, in situ hybridization demonstrated ET messenger RNA in porcine paraventricular nuclear neurons. Endothelin-like immunoreactive products in the posterior pituitary of the rat were depleted by water deprivation, suggesting a release of ET under physiological conditions. These findings indicate that ET is synthesized in the posterior pituitary system and may be involved in neurosecretory functions.

Less body fat accumulation in rats fed a safflower oil diet than in rats fed a beef tallow diet.

Abstract: The effects on body fat accumulation of long-term feeding of high fat diets of differing fatty acid composition were studied in rats. The rats were meal-fed isoenergetic diets based on safflower oil or beef tallow for 4 mo. Each diet was freshly prepared every day throughout the experimental period. Oxygen consumption and carbon dioxide production for 6 h after meals were measured between the 50th and 54th d of the experimental period. Oxygen consumption for 3 h after meals was significantly greater in the safflower oil diet group than in the beef tallow diet group, indicating greater diet-induced thermogenesis in the former group. From the assessment of respiratory quotient, the fat oxidation rate was also higher in the former. After the experimental period (4 mo), body fat accumulation was significantly less in the rats fed safflower oil. This difference was, at least in part, ascribed to increased diet-induced thermogenesis and fat oxidation. Serum triacylglycerol level was markedly lower in the rats fed safflower oil than in those fed beef tallow. The lipoprotein lipase activities in heart and soleus muscle after meals appeared to be higher in the former than in the latter. These results suggest that the consumption of the safflower oil diet increased lipoprotein lipase activity in heart and skeletal muscle, resulting in the elevation of fat oxidation rate and the depression of serum triacylglycerol level.

Rietveld analysis of the modulated structure in the superconducting oxide Bi2(Sr,Ca)3Cu2O8+x.

Abstract: The modulated structure of the high-${\mathit{T}}_{\mathit{c}}$ superconductor ${\mathrm{Bi}}_{2}$(Sr,Ca${)}_{3}$${\mathrm{Cu}}_{2}$${\mathrm{O}}_{8+\mathit{x}}$ was analyzed with a newly developed Rietveld refinement program for modulated structures. The structure refinement was made by the simultaneous refinement method using x-ray and time-of-flight neutron-diffraction data. It has a one-dimensionally modulated structure with N Bbmb/11\ifmmode\bar\else\textasciimacron\fi{}1, a=5.3957(3), b=5.3971(3), c=30.649(1) \AA{}, and k=0.2118(1)${\mathbf{b}}^{\mathrm{*}}$. Atoms in Bi-O, Sr-O, Cu-O, and Ca layers are all greatly displaced from their average positions. In particular Bi atoms are displaced mainly along the b axis, forming Bi-condensed and Bi-dilute regions. The characteristic feature of the structure is the existence of extra oxygens, giving x=1.0, in the Bi-dilute region of the Bi-O layer. Bi has a distorted rocksalt-type oxygen coordination with four short Bi-O bonds in the Bi-condensed region and a deformed square pyramidal coordination with five Bi-O bonds in the Bi-dilute region. The apical oxygen of a ${\mathrm{CuO}}_{5}$ pyramid, which joins Cu to Bi, moves along with Bi, distorting the pyramid considerably.

Impact of Indian Monsoon on the Coupled Atmosphere)Ocean System in the Tropical Pacific

Abstract: This study addresses the relationship between the Indian summer monsoon (ISM) and the coupled atmosphere/ocean system in the tropical Pacific on the interannual time scales. High positive correlations are found between ISM rainfall and both mixed layer sea water temperature (SWT) and sea surface temperature (SST) anomalies of the tropical western Pacific in the following winter. Negative correlations between ISM rainfall and SST in the central/eastern Pacific also appear to be most significant in the following winter. These parameters are correlated with each other mainly on a biennial time scale. Lag-correlations between the zonal wind and SST along the the equatorial Pacific show that the westerly (easterly) surface wind stress anomalies over the central/western Pacific are greatly responsible for the formation of negative (positive) SST/SWT anomalies in the western Pacific and positive (negative) SST/SWT anomalies in the central/eastern Pacific. Furthermore, it is evidenced that these lagcorrelations are physically based on the anomalies in the large-scale convection over the Asian monsoon region and the associated east-west circulation over the tropical Pacific, which first appear during the Indian summer monsoon season and evolve during the following autumn and winter. These results strongly suggest that the Asian summer monsoon may have an active, rather than a passive, role on the interannual variability, including the ENSO events, of the coupled atmosphere/ocean system over the tropical Pacific.

Soliton Lattice Modulation of Incommensurate Spin Density Wave in Two Dimensional Hubbard Model -A Mean Field Study-

Abstract: Spatially modulated magnetic phases are investigated within the mean field theory for an itinerant electron model, i.e. the Hubbard model on a two-dimensional square lattice. By numerically diagonalizing the Hamiltonian for finite-size systems under a periodic boundary condition, we examine relative stability and physical properties of several possible magnetic states. When the electron fillings are nearly half-full, the diagonally or vertically modulated spin density wave (SDW) state is stabilized over the uniform antiferromagnetic state and a crossover from the vertical to the diagonal states appears. The diagonal or vertical stripe state is characterized by the presence of the midgap band due to the soliton lattice formation inside the main SDW gap, being an insulator. The wave length λ SDW is linearly proportional to the excess carrier concentration. Excess carriers are accommodated in the form of the soliton lattice, forming a charge density wave whose wave length is λ SDW /2.

Uptake of Glutamate and Cystine in C‐6 Glioma Cells and in Cultured Astrocytes

Abstract: The uptake of glutamate in rat glioma C-6 cells and cultured astrocytes derived from rat cerebral hemispheres was found to be mediated by a Na(+)-dependent and a Na(+)-independent system. The Na(+)-dependent system was inhibited by aspartate and was consistent with the commonly occurring system designated system X-AG. The Na(+)-independent system was inhibited by cystine and was consistent with system x-c described in various types of cells in the periphery. It was also found that quisqualate selectively and competitively interfered with the Na(+)-independent glutamate uptake. In C-6 cells, the glutamate uptake via systems X-AG and x-c accounted for approximately 35% and 55% of the total uptake, respectively, at 0.05 mM glutamate. In cultured astrocytes, the glutamate uptake via system X-AG was very potent, whereas the uptake via system xc- was relatively weak and its contribution to the total uptake of glutamate seemed almost negligible. However, in both C-6 cells and astrocytes, system xc- was necessary for the uptake of cystine, another substrate of system xc-. Cystine in the culture medium was an essential precursor of glutathione, and the inhibition of the cystine uptake by excess glutamate as a competitor led to a severe deficiency in glutathione, followed by cell degeneration.

Endothelin receptor is coupled to phospholipase C via a pertussis toxin-insensitive guanine nucleotide-binding regulatory protein in vascular smooth muscle cells.

Abstract: The mechanisms of endothelin-1 (ET) actions were investigated in cultured rat aortic vascular smooth muscle A-10 cells. The A-10 cells have a single class of high affinity binding sites for ET with an apparent Mr of 65,000-75,000 on SDS-PAGE. Stimulation of cells with ET induces mobilization of Ca2+ from both intra- and extracellular pools to produce a biphasic increase in cytoplasmic free Ca2+ concentration. ET increases cellular levels of inositol trisphosphate and 1,2-diacylglycerol, indicating activation of phospholipase C by ET. ET stimulates production of inositol phosphates in membranes prepared from A-10 cells in the presence of guanosine 5'-O-(thiotriphosphate) (GTP gamma S), but not in its absence. Further, specific binding of 125I-labeled ET to A-10 cell membranes is shown to be inhibited by GTP gamma S in a dose-dependent manner. Treatment of A-10 cells with pertussis toxin induces ADP-ribosylation of a 41,000-D membrane protein but fails to block the ET-induced increases in inositol phosphate production and Ca2+ mobilization. These results indicate that the receptor for ET is coupled to phospholipase C via a guanine nucleotide-binding regulatory protein which is distinct from the pertussis toxin substrate in A-10 cells.

Cu3N thin film for a new light recording media

Abstract: Copper nitride thin films were prepared by using the ion-assisted deposition in which accelerated nitrogen ions were irradiated during the deposition of copper metal. The degree of nitrification of the film was controlled by changing the ion current density. The reflection coefficient of the prepared copper nitride films decreased with the increase of the ion current density. The reflection coefficient was about 30% at 780 nm wavelength, and it recovered to 70% after the film was heated at 300°C. The preliminary experiment of write-once optical recording of this film was carried out, and the viability of its practical use in new media was confirmed.

Flume experiments on the alignment of transverse, oblique, and longitudinal dunes in directionally varying flows

Abstract: For more than a century geologists have wondered why some bedforms are orientated roughly transverse to flow, whereas others are parallel or oblique to flow. This problem of bedform alignment was studied experimentally using subaqueous dunes on a 3–6-m-diameter sand-covered turntable on the floor of a 4-m-wide flume. In each experiment, two flow directions (relative to the bed) were produced by alternating the turntable between two orientations. The turntable was held in each orientation for a short time relative to the reconstitution time of the bedforms; the resulting bedforms were in equilibrium with the time-averaged conditions of the bimodal flows. Dune alignment was studied for five divergence angles (the angle between the two flow directions): 45°, 67–5°, 90°, 112–5° and 135°. The flow depth during all experiments was approximately 30 cm; mean velocity was approximately 50 cm s-1 and mean grain diameter was 0–6 mm. Each experiment continued for 30–75 min, during which time the flume flow was steady and the turntable position changed every 2 min. At the end of each experiment, water was slowly drained from the flume and dune alignment was measured. Transverse dunes (defined relative to the resultant transport direction) were created when the divergence angle was 45° and 67–5°, and longitudinal dunes were created when the divergence angle was 135°. At intermediate divergence angles, dunes with both orientations were produced, but transverse dunes were dominant at 90°, and longitudinal dunes were dominant at 112–5°. One experiment was conducted with a divergence angle of 135° and with unequal amounts of transport in the two flow directions. This was achieved by changing the orientation of the turntable at unequal time intervals, thereby causing the amount of transport to be unequal in the two directions. The dunes formed during this experiment were oblique to the resultant transport direction. These experimental dunes follow the same rule of alignment as wind ripples studied in previous turntable experiments. In both sets of experiments, the bedforms developed with the orientation having the maximum gross bedform-normal transport (the orientation at which the sum of the bedform-normal components of the two transport vectors reaches its maximum value). In other words, the bedforms develop with an orientation that is as transverse as possible to the two flows. In those cases where the two flows diverge by more than 90° and transport equal amounts of sand, bedforms that are as transverse as possible to the two separate flows will be parallel to the resultant of the two flow vectors. Although such bedforms have been defined by previous work as longitudinal bedforms, they are intrinsically the same kind of bedform as transverse bedforms.

Pseudorapidity distributions of charged particles produced in $\bar{p}p$ interactions at $\sqrt{s} = 630$ GeV and 1800 GeV

Abstract: We present measurements of the pseudo-rapidity (η) distribution of charged particles (dNch/dη) produced within |η|≤ 3.5 in proton-antiproton collisions at s= of 630 and 1800 GeV. We measure dNch/dη at η = 0 to be 3.18±0.05(stat)±0.10(sys) at 630 GeV, and 3.95±0.02(stat)±0.13(sys) at 1800 GeV. Many systematic errors in the ratio of dNch dη at the two energies cancel, and we measure 1.26±0.01±0.04 for the ratio of dNch/dη at 1800 GeV to that at 630 GeV within |η|≤ 3. Comparing to lower energy data, we observe an increase faster than In(s) in dNch dη at η=0

Extracellular Accumulation of Mannosylerythritol Lipids by a Strain of Candida antarctica

Abstract: A yeast strain, isolated from the exudate of a tree, accumulated biosurfactants abundantly when grown on soybean oil as the sole carbon source. The biosurfactants were found to be a mixture of 4 mannosylerythritol lipids, including two new mannosylerythritol lipids as major components. The major components, which amounted to about 80% of the total lipids, were determined to be 4-O-(di-O-acetyl-di-O-alkanoyl-β-d-mannopyranosyl)-erythritol and 4-O-(mono-O-acetyl-di-O-alkanoyl-β-d-mannopyranosyl)-erythritol. The yeast strain was identified as Candida antarctica (Goto et al.) Kurtzman et al.

Helical phase dependent action of CRP: effect of the distance between the CRP site and the −35 region on promoter activity

Abstract: A plasmid carrying a CRP-dependent promoter fused to the lac structural genes was manipulated to construct a set of spacing mutants that have varying lengths between the CRP binding site and the -35 region. The lengths of the spacer were changed over 45 bp by inserting or deleting nucleotides. DNase I footprinting analysis revealed that the spacer length did not affect the binding of cAMP-CRP to the CRP site. The effect of the spacer length on transcription activation by cAMP-CRP was tested in vivo by beta-galactosidase and quantitative S1 assays with crp+ and delta crp cells harboring plasmids. Insertions or deletions of non-integral helical turns, which displace the CRP site onto the opposite face of DNA helix compared to the original promoter, eliminated completely the activation of transcription. In contrast, changing the spacer length by integral helical turns allowed the promoter to respond to CRP, although the degree of activation varied with the length of the spacer. We conclude that stereospecific positioning of CRP and RNA polymerase on the DNA helix is strictly required for CRP action. The data support a model that CRP stimulates transcription by directly contacting RNA polymerase.

Lepidodinium viride gen. et sp. nov. (gymnodinaiales, dinophyta), a green dinoflagellate with a chlorophyll a- and b-containing endosymbiont1,2

Abstract: A further description of the green dinoflagellate, strain Y-100, with a chlorophyll a- and b-containing endosymbiont is given with special emphasis on the morphology of the host cell. The host dinoflagellate cell is unarmored and has a gymnodinoid overall appearance. The theca or amphiesma basically consists of the outer membrane and flattened thecal vesicles in which no thecal plates are developed. Unusual hand basket-shaped scales cover the entire cell surface together with a layer of mucilaginous material. These findings suggest that the organism is a new member of the Gymnodiniaceae (Gymnodiniales). We propose the name Lepidodinium viride gen. et sp. nov. The ultrasturcture of the host cell is typical of the dinoflagellates; however, the organism has 1) an unusual cytoplasmic projection that may be a homologue of the peduncle, 2) a single membrane-bounded body containing membranous sheets, closely situated next to the endosymbiont, and 3) an electron opaque network-forming appendage surrounding the transverse flagellum. Name of these features have been found in other dinoflagellates.