Showing papers by "University of Tsukuba published in 1993"

Maintenance of neuronal glutathione by glial cells.

Abstract: — Glutathione levels in neurons and gllal cells were investigated in a neuronal-glial coculture and in separate cultures. Brain cell suspensions obtained from cerebral hemispheres of fetal rats were cultured, and after 5 days the glutathione content of this cell population, consisting mainly of neurons and astroglial cells, was 23.0 nmol/mg of cell protein, with a significantly high content in glial cells (28.0 nmol/mg of protein) in comparison with neurons (18.8 nmol/mg of protein). When the neurons and glial cells were separated and recultured in fresh medium, neu-ronal glutathione rapidly decreased, whereas glial glutathione remained unchanged. Cysteine is a rate-limiting precursor for glutathione synthesis, and its level was also decreased in neurons, but not in glial cells. Cysteine was taken up rapidly by both neurons and glial cells, but cys-tine was taken up only by glial cells. This accounts for the rapid decrease of glutathione in the cultured neurons, because the culture medium contains cystine, but not cys-teine. It was also found that the cultured glial cells released cysteine into the medium. These results suggest that neurons maintain their glutathione level by taking up cysteine provided by glial cells.

Visible photoluminescence from oxidized Si nanometer-sized spheres: Exciton confinement on a spherical shell.

Abstract: We report strong visible photoluminescence (PL) at room temperature from oxidized Si nanometer-sized spheres with a spherical crystalline Si (c-Si) core and an amorphous ${\mathrm{SiO}}_{2}$ (a-${\mathrm{SiO}}_{2}$) surface layer. The peak energy of the broad PL spectrum is about 1.65 eV, which is independent of the core diameter. We propose a model in which excitons are confined on a spherical shell, an interfacial layer between the c-Si core and the a-${\mathrm{SiO}}_{2}$ surface layer, and in which the exciton confinement enhances the oscillator strength and the PL intensity.

Microstructure and optical properties of free-standing porous silicon films: Size dependence of absorption spectra in Si nanometer-sized crystallites.

Abstract: We have studied the microstructure and optical properties of free-standing porous Si thin films fabricated by electrochemical anodization. Raman-spectroscopy and transmission-electron-microscopy examinations show that Si crystallite spheres with diameters of several nanometers are dispersed in the amorphous phase. The blueshift of the optical-absorption spectrum is observed for decreasing average diameter of the Si crystallites. However, there is no clear size dependence of the peak energy of the broad photoluminescence (PL) spectrum. Spectroscopic analysis strongly suggests that the photogeneration of carriers occurs in the c-Si core, whose band gap is modified by the quantum-confinement effect, while the strong PL comes from the near-surface region of small crystallites.

Contribution of endogenous endothelin-1 to the progression of cardiopulmonary alterations in rats with monocrotaline-induced pulmonary hypertension.

Abstract: Endothelin-1 (ET-1) is known to have potent contractile and proliferative effects on vascular smooth muscle cells and is known to induce myocardial cell hypertrophy. We studied the pathophysiological role of endogenous ET-1 in rats with monocrotaline-induced pulmonary hypertension. Four-week-old rats were given a single subcutaneous injection of 60 mg/kg monocrotaline (MCT rats) or saline (control rats) and were killed after 6, 10, 14, 18, and 25 days. In the MCT rats, right ventricular systolic pressure progressively increased and right ventricular hypertrophy developed in a parallel fashion. The venous plasma ET-1 concentration also progressively increased, and this increase preceded the development of pulmonary hypertension. The isolated pulmonary artery exhibited a significantly weaker response to ET-1 in the MCT rats on day 25 but not on days 6 and 14. In the MCT rats, the expression of prepro ET-1 mRNA as measured by Northern blot analysis significantly increased in the heart on days 18 and 25, whereas it gradually decreased in the lungs. The peptide level of ET-1 in the lungs also significantly decreased in the pulmonary hypertensive stage. The expression of prepro ET-1 mRNA had increased by day 6 only in the kidneys. Continuous infusion of BQ-123, a selective ETA receptor antagonist, by an osmotic minipump (14.3 mg per day per rat for 18 days) significantly inhibited the progression of both pulmonary hypertension (right ventricular systolic pressure, 77.8 +/- 4.2 [mean +/- SEM] mm Hg [n = 10] versus 52.3 +/- 2.4 mm Hg [n = 7]; P < .01) and right ventricular hypertrophy (right ventricle/[left ventricle +/- septum], 0.56 +/- 0.03 [n = 10] versus 0.41 +/- 0.02 [n = 7]; P < .01). Histological examination revealed that BQ-123 also effectively prevented pulmonary arterial medial thickening. The inhibition of right ventricular hypertrophy by BQ-123 may be partly ascribed to the blockade of excessive stimulation of the heart by ET-1, in addition to the prevention of pulmonary hypertension. The present findings suggest that endogenous ET-1 contributes to the progression of cardiopulmonary alterations in rats with MCT-induced pulmonary hypertension.

Pen-based haptic virtual environment

Abstract: The development of a pen-based force display and its application to the direct manipulation of a free-form surface are described. A six degree-of-freedom force reflective master manipulator which has a pen-shaped grip has been developed. The system uses two three degree-of-freedom manipulators. Both ends of the pen are connected to these manipulators. The hardware of the force display is small and light-weight. The performance of the force display is exemplified in interactive deformation of a free-form surface. >

Errors in the measurement of cardiac output by thermodilution

Abstract: Cardiac output (CO) determination by thermodilution, which was introduced by Fegler in 1954, has gained wide acceptance in clinical medicine and animal experiments because it has several advantages over other methods with respect to simplicity, accuracy, reproducibility, repeated measurements at short intervals, and because there is no need for blood withdrawal. However, errors in determination of CO by thermodilution may be introduced by technical factors and the patients' pathological conditions. The current review summarizes these issues and provides our recommendations, based on the medical literature published between 1954-1992. To obtain more reproducible and accurate CO values by thermodilution, one should make several determinations (1) by using 10 ml injectate at room temperature for adults and 0.15 ml.kg-1 injectate for infants and children; (2) at evenly spaced intervals of the ventilation cycle; (3) when rapid intravenous fluid administration is discontinued; (4) by observing thermodilution curves so that baseline pulmonary artery temperature drift or the existence of intra- and extracardiac shunts are noticed. Finally, CO determination by thermodilution may be unreliable or impossible in patients with low CO states and tricuspid or pulmonary regurgitation. Since non-invasive CO monitoring has not replaced CO determination by thermodilution, intimate knowledge of this method is crucial for anaesthetists to prevent errors in the management of patients.

Effect of thiol compounds on in vitro development and intracellular glutathione content of bovine embryos.

Abstract: The purpose of this investigation was to determine the effect of beta-mercaptoethanol (beta-ME) and cysteamine, low-molecular-weight thiol compounds, on the development and intracellular glutathione content of bovine embryos obtained by in vitro fertilization of in vitro-matured oocytes. Embryos developed to the 6-8-cell stage after in vitro fertilization were cultured without feeder cells in TCM-199 containing 10% fetal calf serum with or without beta-ME or cysteamine. The percentage of embryos that developed to the blastocyst and hatched blastocyst stages were significantly higher in medium containing beta-ME or cysteamine. Also, total intracellular glutathione levels were higher for embryos cultured in the medium with beta-ME or cysteamine than for those cultured in medium without thiol compounds. Moreover, when buthionine sulfoximine, a specific inhibitor of glutathione synthesis, was added to medium containing thiol compounds, there was a reduction both in the development of embryos to the blastocyst stage and in intracellular glutathione content. These results indicate that the inclusion of low-molecular-weight thiol compounds aids the in vitro development of bovine embryos without feeder cells and that the effect of thiol compounds is mediated through the increase of intracellular glutathione levels.

A mean-absolute deviation-skewness portfolio optimization model

Abstract: It is assumed in the standard portfolio analysis that an investor is risk averse and that his utility is a function of the mean and variance of the rate of the return of the portfolio or can be approximated as such. It turns out, however, that the third moment (skewness) plays an important role if the distribution of the rate of return of assets is asymmetric around the mean. In particular, an investor would prefer a portfolio with larger third moment if the mean and variance are the same. In this paper, we propose a practical scheme to obtain a portfolio with a large third moment under the constraints on the first and second moment. The problem we need to solve is a linear programming problem, so that a large scale model can be optimized without difficulty. It is demonstrated that this model generates a portfolio with a large third moment very quickly.

Fetal nucleated cells in maternal peripheral blood : frequency and relationship to gestational age

Abstract: To determine the frequency of fetal nucleated cells in maternal peripheral blood during different stages of pregnancy, 50 primigravidas were investigated by determining the frequency of cells with the Y chromosome using fluorescence in situ hybridization (FISH) of Y-specific repetitive sequences of the DYZ1 family. Polymerase chain reaction (PCR) amplifying the same part of the DYZ1 used as the probe in FISH and a single-copy Y-specific fragment was also carried out for genomic DNA from the same samples. Cells with the hybridization signal were detected by FISH at and after 15 weeks of pregnancy in all pregnant women who gave birth to boys. The ratio of cells with the signal to those without the signal ranged from 1 in 144,000 to 1 in 4,000 with a tendency to increase as the pregnancy advanced. The frequency of fetal cells estimated by the PCR experiments was significantly and positively correlated with that found by FISH. The present study suggests that fetal nucleated cells increase in maternal peripheral blood with advancing gestation, from less than 1 in 100,000 nucleated cells in the first trimester to around 1 in 10,000 at term. These frequencies were much lower than those reported by cytological methods.

Mechanism of the As temperature increase by pre-deformation in thermoelastic alloys

Abstract: The Ti-Ni-Nb shape memory alloys are attracting recent attention for the wide transformation temperature hysteresis, whih is caused by the A s increase due to pre-deformation, since it is suitable for pipe couplings. To find out the origin for the A s increase by pre-deformation, similar investigation was made by tensile tests, electrical resistance measurements, optical microscopy and transmission electron microscopy (TEM), for a Cu-13.8%Al-4.0%Ni (mass%) single cyrstal and Ti-50%Ni and Ti-50.5%Ni(at%) polycrystals, which exhibit the thermoelastic martensitic transformation

Determination of the phylogenetic relationships among Pacific salmonids by using short interspersed elements (SINEs) as temporal landmarks of evolution

Abstract: Several subfamilies of the salmonid Hpa I short interspersed element (SINE) family were isolated from salmonid genomes and were sequenced. For each genomic locus that represented the subfamily, amplification by PCR of the orthologous loci in the 12 fish allowed us to determine the order of branching of the Pacific salmonid species. The deduced phylogeny suggests three evolutionary lines, namely, a line of chum salmon, pink salmon, and kokanee; a line of coho salmon and chinook salmon; and a line of steelhead trout. Our data also support a change in the phylogenetic assignment of steelhead trout from Salmo to Oncorhynchus. We present here an extensive phylogenetic tree constructed from an analysis of differential insertion of SINEs, and we propose that SINE insertion analysis is one of the best available methods for clarifying the order of divergence of closely related species.

Volume haptization

Abstract: The authors describe haptic representation of volume data. Volume visualization is a powerful tool in the field of scientific visualization. However, visual representation of full three-dimensional volume is hard to comprehend because of occlusion. Higher-dimensional and multi-parameter data sets are also difficult to present by visual image. The authors propose methods for presentation of volume data by force sensation. A six degree-of-freedom force reflective master manipulator is used for haptization. The manipulator is combined to real-time visual image of volume data. Methods of haptic representation of scalar, vector, and tensor data are discussed. Recognition performance tests of scalar and multiparameter volume data are examined. >

Identification and Functional Expression of a New Member of the Mammalian Kex2-Like Processing Endoprotease Family: Its Striking Structural Similarity to PACE4.

Abstract: We used the polymerase chain reaction to identify a mouse cDNA which represented a new member of a growing class of mammalian endoproteases homologous to the yeast Kex2 protease involved in the processing of precursor proteins. This cDNA encoded a 915-residue protein, designated as PC6, containing a subtilisin-like catalytic domain closely related to those of other Kex2-like members (furin, PC2, PC1/3, PC4, and PACE4). It exhibited striking sequence similarity to PACE4 and contained similar protein domains, such as the COOH-terminal Cys-rich region. Northern blot analysis revealed that PC6 mRNA, as with furin and PACE4 mRNAs, was expressed in various tissues and cell lines, with the highest level in the intestine. Transfection experiments revealed that PC6 was capable of cleaving precursors at dibasic sites. These observations suggest that PC6 is a candidate for a processing endoprotease responsible for the maturation of gastrointestinal peptides.

Transition of f electron nature from itinerant to localized: Metamagnetic transition in CeRu2Si2 studied via the de Haas-van Alphen effect.

Abstract: We report the measurements of the de Haas--van Alphen (dHvA) effect for field ranges below and above the metamagnetic transition field (${\mathit{H}}_{\mathit{m}}$) in ${\mathrm{CeRu}}_{2}$${\mathrm{Si}}_{2}$. The dHvA frequency branches and the effective masses ranging from 1.5${\mathit{m}}_{0}$ to 120${\mathit{m}}_{0}$ observed below ${\mathit{H}}_{\mathit{m}}$ agree with the predictions of the itinerant f electron model, whereas those above ${\mathit{H}}_{\mathit{m}}$ can be explained well with the localized f electron model. All the dHvA frequencies change abruptly around ${\mathit{H}}_{\mathit{m}}$. The effective masses decrease considerably around ${\mathit{H}}_{\mathit{m}}$ and then continue to decrease with increasing field.

Cystine uptake and glutathione level in fetal brain cells in primary culture and in suspension.

Abstract: — The glutathione level and the factors affecting this level were investigated in fetal rat brain cells in a primary culture. Early in the culture, the glutathione level of the brain cells decreased, but after 5 h it began to increase. This increase was not observed in a cystine-free medium and was prevented by excess glutamate. Cystine was taken up in freshly isolated brain cell suspensions, and its rate increased during the culture. The cystine uptake was mediated by a Na+-independent, glutamate-sensitive route previously found in various types of cells and designated as system x−c. The uptake of cystine is a crucial factor in maintaining the glutathione level of the cells under culture, because it provides cysteine for the cells for glutathione synthesis. Cysteine was undetectable in the medium before the culture, but it appeared, though at a very low level, when the brain cells were cultured there. The source of this cysteine was the cystine in the medium. Presumably the decrease in the glutathione level of the cells in the early stage of the culture resulted from the fact that the medium did not contain cysteine. The enhancement of the cystine uptake during culture may constitute a protective mechanism against the oxidative stress to which the cultured cells are exposed. Regulation of the glutathione level in fetal brain cells in vivo by the transport of cystine and cysteine is discussed.

Low-frequency Raman scattering from CdS microcrystals embedded in a germanium dioxide glass matrix.

Abstract: We report here results from experiments on low-frequency Raman scattering from CdS microcrystals of various sizes embedded in a germanium dioxide glass matrix. We observed peaks in the low-frequency region in the tail parts of the Rayleigh lines and we found that the frequencies of these peaks were proportional to the inverse microcrystal diameters and that the size dependences of the peak shifts agreed fairly well with the calculated results based on Lamb's theory. Furthermore, we found that these Raman-scattering spectra had the characteristic polarization properties. Our results show that the observed low-frequency Raman scattering originates from confined acoustic vibrations of a spherical CdS microcrystal.

Presence of mitochondrial large ribosomal RNA outside mitochondria in germ plasm of Drosophila melanogaster

Abstract: Mitochondrial large ribosomal RNA (mtlrRNA) has been identified as a cytoplasmic factor that induces pole cell formation in embryos whose ability to form a germ line has been abolished by treatment with ultraviolet light. In situ hybridization analyses reveal that mtlrRNA is enriched in germ plasm and is tightly associated with polar granules, the distinctive organelles of germ plasm, which supports the idea that mtlrRNA functions in pole cell formation. This suggests that a product from the mitochondrial genome, along with nuclear products, participates in a key event in embryonic development: determination of the germ line.

Localization of T lymphocytes and macrophages expressing IL-1, IL-2 receptor, IL-6 and TNF in human aortic intima. Role of cell-mediated immunity in human atherogenesis.

Abstract: Recent observations have demonstrated the presence of activated T lymphocytes and macrophages in human atherosclerotic lesions. Cells found within these lesions produce cytokines that alter vascular homeostasis in a manner that promotes atherogenesis. To elucidate the role of these immunocompetent cells in human atherosclerosis, the localization of various cytokines with an analysis of immunophenotypic features of the cellular infiltrates was studied in normal aortas from children; and in later phases of the disease (including fatty streaks and fibrous or atheromatous plaques). Semi-quantitative analysis of cytokine-expressing cells was also investigated with serial sectioning. In 4 of 9 young subjects, the grossly normal aorta contained relatively cell-rich areas which were located preferentially around the ostia of intercostal arteries and were composed of isolated or layered T lymphocytes and macrophages. In these prelesional areas, interleukin-1 (IL-1), IL-2 receptor (IL-2R) and tumour necrosis factor (TNF) were detected in the cytoplasm of the infiltrating cells, whereas no detectable reactivity was noted for IL-2, IL-6, interferon-γ (IFN-γ) or lymphotoxin (LT). In fatty streaks and full-grown atheromas including “cap” and “shoulder” regions, various numbers of T lymphocytes, macrophages and macrophage foam cells were present. In these lesion areas, especially where the cellular infiltrates were numerous, macrophage foam cells and smooth muscle cells expressed not only IL-1 and TNF but also IL-6. The ratio of IL-2R positive cells showed a tendency to decrease with advance of the disease process. Electron-microscopic examination of lesion areas demonstrated ultrastructural aspects of the cognate cellto-cell interaction, as shown by the direct apposition of lymphocytes to macrophages or macrophage foam cells. These results suggest that a specific in situ, cell mediated hypersensitivity plays a pivotal role in the nascent as well as the progression stages of human atherosclerosis.

Identification, cDNA Cloning, and Gene Expression of Soluble Starch Synthase in Rice (Oryza sativa L.) Immature Seeds

Abstract: Three forms of soluble starch synthase were resolved by anion-exchange chromatography of soluble extracts from immature rice (Oryza sativa L.) seeds, and each of these forms was further purified by affinity chromatograph. The 55-, 57-, and 57-kD proteins in the three preparations were identified as candidates for soluble starch synthase by western blot analysis using an antiserum against rice granule-bound starch synthase. It is interesting that the amino-terminal amino acid sequence was identical among the three proteins, except that the 55-kD protein lacked eight amino acids at the amino terminus. Thus, these three proteins are products of the same gene. The cDNA clones coding for this protein have been isolated from an immature rice seed library in lambda gt11 using synthetic oligonucleotides as probes. The deduced amino acid sequence of this protein contains a lysine-X-glycine-glycine consensus sequence for the ADP-glucose-binding site of starch and glycogen synthases. Therefore, we conclude that this protein corresponds to a form of soluble starch synthase in immature rice seeds. The precursor of the enzyme contains 626 amino acids, including a 113-residue transit peptide at the amino terminus. The mature form of soluble starch synthase shares a significant but low sequence identity with rice granule-bound starch synthase and Escherichia coli glycogen synthase. However, several regions, including the substrate-binding site, are highly conserved among these three enzymes. Blot hybridization analysis demonstrates that the gene encoding soluble starch synthase is a single-copy gene in the rice genome and is expressed in both leaves and immature seeds. These results suggest that soluble and granule-bound starch synthases play distinct roles in starch biosynthesis of plant.

Acrogranin, an acrosomal cysteine-rich glycoprotein, is the precursor of the growth-modulating peptides, granulins, and epithelins, and is expressed in somatic as well as male germ cells

Abstract: Spermatogenesis is a unique system of differentiation involving cellular remodeling and the biogenesis of sperm-specific organelles. To study the biogenesis of one such organelle, the acrosome, we have been examining the gene expression, biosynthesis, and targeting of specific acrosomal proteins during mammalian spermatogenesis. An acrosomal marker that we recently purified and began characterizing is acrogranin, a 67,000-molecular-weight glycoprotein originally isolated from guinea pig testes. This glycoprotein is detected in pachytene spermatocytes and is found later in the acrosomes of developing spermatids and sperm. Immunoblotting of several tissues and immunofluorescent localization in frozen sections of guinea pig testes suggested that acrogranin was a germ cell-specific glycoprotein that was expressed meiotically and post-meiotically. However, Northern blot analysis demonstrated that the mRNA for acrogranin was ubiquitously expressed in all guinea pig and mouse tissues examined. Furthermore, the primary structures of guinea pig and mouse acrogranins, deduced from the cDNA sequences, reveal that this glycoprotein is a cysteine-rich molecule with a motif that is tandemly repeated seven times, very similar to that of the human epithelin/granulin precursor. We conclude that guinea pig and mouse acrogranins are homologues of the precursor of the human and rat epithelin/granulin peptides previously demonstrated to have growth-modulating properties. © 1993 Wiley-Liss, Inc.