Showing papers by "Hokkaido University published in 1991"

The structural groups of alkali silicate glasses determined from 29Si MAS-NMR

Abstract: Lithium, sodium and potassium silicate glasses containing 20–56 mol% alkali oxide were investigated by 29 Si nuclear magnetic resonance (MAS-NMR) spectroscopy. In the spectrum of each sample, at least two to four distinct peaks were identified. The distributions of SiO 4 structural units, Q n , where n is the number of bridging oxygen atoms bound to other Si atoms, were determined as a function of composition. The equilibrium constants of the reactions, 2Q n ⇌ Q n −1 + Q n +1 ( n = 3, 2, 1), were determined. The reaction proceeds to the right direction as cationic power of alkali ion ( Z / r ) increases (Li + >Na + >K + ) at the same alkali oxide concentration. The apparent equilibrium constants of the above reactions are discussed along with a proposed thermodynamic model. The 29 Si chemical shifts assigned to each structural unit increase linearly with alkali oxide contents. The slope of these lines decreases as the numbers of attached bridging oxygen (BO) atoms decrease. The average chemical shifts also increase linearly with an increase of alkali content. A close relationship between the average chemical shifts and the theoretical optical basicity was observed.

Abrupt Increase in the Level of Hydrogen Peroxide in Leaves of Winter Wheat Is Caused by Cold Treatment

Abstract: After cold treatment of seedlings of winter wheat (Triticum aestivum L.), levels of hydrogen peroxide in the leaves were measured. The concentration of hydrogen peroxide increased to about three times the control level within a few minutes, and returned to the normal level in 15 to 20 minutes. The elevated level of hydrogen peroxide was found to be equivalent to 1.5 micromoles per gram fresh weight tissues of leaves.

HIV-associated disease of the nervous system: review of nomenclature and proposal for neuropathology-based terminology.

Abstract: Herbert Budka 1, Clayton A. Wiley 2, Paul Kleihues 3, Juan Artigas 4, Arthur K. Asbury 5, Eun-Sook Cho 6, David R. Cornblath 7, Mauro C. Dal Canto 8, Umberto DeGirolami 9, Dennis Dickson 10, Leon G. Epstein 11, Margaret M. Esiri 12, Felice Giangaspero 13, Georg Gosztonyi 14, Francoise Gray 15, John W. Griffin 7, Dominique Henin 16, Yuzo lwasaki 17, Robert S. Janssen '8, Richard T. Johnson 7, Peter L. Lantos 19, William D. Lyman 10, Justin C. McArthur 7, Kazuo Nagashima 20, Nancy Peress 21, Carol K. Petito 22, Richard W. Price 23, Roy H. Rhodes Z4, Marc Rosenblum 25, Gerard Said 26, Francesco Scaravilli 27, Leroy R. Sharer 6, Harry V. Vinters 28

Marginal adaptation of a restorative resin polymerized at reduced rate.

Abstract: — The aim of this study was to investigate the effect of reduced rate of polymerization on the marginal adaptation of a composite resin inserted in dentin cavities treated with a simplified Gluma system. The effect on bonding strength to dentin and compressive strength was also investigated. The light intensity of the polymerization unit was lowered by the use of a transformer, and thus the rate of polymerization of the composite resin. When the resin was irradiated for 30 s at 110 V followed by 30 s at 220 V, the marginal adaptation was significantly improved. This condition resulted in acceptable values of bonding strength to dentin and diametral compressive strength. It is suggested that the reduced rate of polymerization may allow for increased flow of the material, decreasing the contraction stress in the filling.

Cu-ZSM-5 zeolite as highly active catalyst for removal of nitrogen monoxide from emission of diesel engines

Abstract: Experiments were designed to characterize endothelium-dependent relaxation in thoracic aortic rings obtained from streptozotocin-induced diabetic rats. When the degree of the peak relaxation was compared, the endothelium-dependent relaxant responses to acetylcholine, histamine, or ADP in precontracted aortic rings showed that there was no significant difference between diabetic and control vessels. However, the time courses appeared quite different. The endothelium-dependent relaxant responses in diabetic vessels were more transient than those in control vessels. In addition, the rapid fade of the endothelium-dependent responses observed in diabetic vessels was significantly suppressed by pretreatment with superoxide dismutase. Pretreatment with catalase, deferoxamine, allopurinol, or indomethacin did not prevent the rapid fade of the endothelium-dependent relaxation. The endothelium-independent relaxation induced by nitric oxide also faded more quickly in diabetic vessels; this impairment was less pronounced in the presence of superoxide dismutase. These results suggest that the transient nature of the endothelium-dependent relaxation is more marked in diabetic rat aorta as a result of an enhanced accumulation of superoxide anion.

Superoxide dismutase recovers altered endothelium-dependent relaxation in diabetic rat aorta.

Abstract: Experiments were designed to characterize endothelium-dependent relaxation in thoracic aortic rings obtained from streptozotocin-induced diabetic rats. When the degree of the peak relaxation was compared, the endothelium-dependent relaxant responses to acetylcholine, histamine, or ADP in precontracted aortic rings showed that there was no significant difference between diabetic and control vessels. However, the time courses appeared quite different. The endothelium-dependent relaxant responses in diabetic vessels were more transient than those in control vessels. In addition, the rapid fade of the endothelium-dependent responses observed in diabetic vessels was significantly suppressed by pretreatment with superoxide dismutase. Pretreatment with catalase, deferoxamine, allopurinol, or indomethacin did not prevent the rapid fade of the endothelium-dependent relaxation. The endothelium-independent relaxation induced by nitric oxide also faded more quickly in diabetic vessels; this impairment was less pronounced in the presence of superoxide dismutase. These results suggest that the transient nature of the endothelium-dependent relaxation is more marked in diabetic rat aorta as a result of an enhanced accumulation of superoxide anion.

Spontaneous hepatic copper accumulation in Long-Evans Cinnamon rats with hereditary hepatitis. A model of Wilson's disease.

Abstract: Long-Evans Cinnamon (LEC) rats, an inbred strain of a mutant rat isolated from Long-Evans rats, develop hereditary hepatitis. To elucidate the role of copper metabolism in the development of the hepatitis in LEC rats, we examined the copper concentration in the tissues and serum levels of copper and ceruloplasmin. Copper concentration in the liver of LEC rats was over 40 times that of normal Long-Evans Agouti (LEA) rats, while the serum ceruloplasmin and copper concentrations in LEC rats decreased significantly. The hepatocytes of LEC rats show steatosis in cytoplasm and pleomorphism of mitochondria, resembling the histologic features of the liver in Wilson's disease. These findings suggest that the hereditary hepatitis in LEC rats is closely associated with copper toxicity, and may be dealing with a rat form of Wilson's disease. Thus the LEC rats will provide a unique and useful animal model for clarifying the mechanism and for developing treatment strategies for Wilson's disease and other abnormal copper metabolism in humans.

Bio-speckle phenomena and their application to the evaluation of blood flow

Abstract: The study of time-varying speckle phenomena observed in light-fields scattered from living objects is reviewed. The laser speckles produced from living objects may be called ‘bio-speckles’ and fluctuate temporally due to various physiological movements such as blood flow. The time-varying properties of the bio-speckles are experimentally investigated from the analyses of the power spectrum and the autocorrelation function. Based on the knowledge of dynamic bio-speckles, some methods are introduced for evaluating blood flow in the skin surface, internal organs, and ocular fundus. The experimental results show that the degree of blood flow is reflected sensitively by the time-varying properties of the bio-speckles and this can be utilized for monitoring the blood flow.

An Epstein-Barr virus-producer line Akata: Establishment of the cell line and analysis of viral DNA

Abstract: An Epstein-Barr virus (EBV)-producer line, designated Akata, was established from a Japanese patient with Burkitt's lymphoma. The Akata line possessed the Burkitt's-type chromosome translocation, t(8q- ; 14q+), and was derived from the tumor cell. Akata cells produced a large quantity of transforming virus upon treatment of cells with anti-immunoglobulin antibodies (Takada, 1984). Southern blot analysis of viral DNA indicated that the Akata EBV is nondefective and more representative of wild-type viruses. Akata cells should be useful as a source of EBV.

Secretion of acid phosphatase by the roots of several crop species under phosphorus-deficient conditions

Abstract: Nine crop species (rice, wheat, soybean, lupin, azuki bean, sugar beet, tomato, cabbage and radish.) were grown in phosphorus-sufficient and phosphorus-deficient nutrient solutions. Then, the activities of acid phosphatase secreted by the roots for 24 h and of that eluted by 100 mM NaCl were investigated. Both activities of acid phosphatase increased under low phosphorus conditions in all the crop species. The activity of acid phosphatase secreted by the roots under phosphorus-deficient conditions was remarkably high in lupin and tomato, high in cabbage and radish, moderate in soybean and sugar beet, and low in wheat and azuki bean. The increased rates of activity of acid phosphatase (on a root dry weight basis) secreted under phosphorus-deficient conditions when compared with those under phosphorus-sufficient conditions ranged from 1.5 times in azuki bean to 19.9 times in lupin. The activity of acid phosphatase in the NaCl eluates was also higher in all the crop species under phosphorus-deficien...

Redistribution of carbon and nitrogen compounds from the shoot to the harvesting organs during maturation in field crops

Abstract: The present paper alms at determining how carbon (C) and nitrogen (N) compounds are redistributed from leaves to harvesting organs during maturation in several major field crops. In order to illustrate these processes in the case of C and N compounds, 6 major crops in Hokkaido were grown and compared during maturation. The results obtained were as follows. 1) The N-redistribution rate during maturation was in the order of wheat, soybean and potato > maize > rice. The percentage of distributed nitrogen among the different nitrogenous fractions in leaves and stems was remained constant during maturation, suggesting that each nitrogen compound was equally decomposed. 2) The composition of protein amino acids was similar regardless of organs or crops. The composition of free amino acids differed widely among organs and crops, and differed from that of protein amino acids. Therefore during the translocation of amino acids from leaves to harvesting organs through stems, the composition of free amino ac...

Effects of phosphorothioate and 2-amino groups in hammerhead ribozymes on cleavage rates and Mg2+ binding.

Abstract: Mg2+ is important for the RNase activity of the hammerhead ribozyme. To investigate the binding properties of Mg2+ to the hammerhead ribozyme, cleavage rates and CD spectra for substrates containing inosine or guanosine at the cleavage site were measured. The 2-amino group of this guanosine interfered with the rate of the cleavage reaction and did not affect the amount of Mg2+ bound to the hammerhead RNA. The kinetics and CD spectra for chemically synthesized oligoribonucleotides with a Sp or Rp phosphorothioate diester bond at the cleavage site indicated that 1 mol of Mg2+ binds to the pro-R oxygen of phosphate. The binding constant for Mg2+ was about 10(4) M-1, which represents outer-sphere complexation. The hammerhead ribozyme catalyzes the cleavage reaction via an in-line pathway. This mechanism has been proved for RNA cleavage by RNase A by using a modified oligonucleotide that has an Sp phosphorothionate bond at the cleavage site. From these results, we present the reaction pathway and a model for Mg2+ binding to the hammerhead ribozyme.

Biomechanical analysis of rehabilitation in the standing position.

Abstract: Biomechanical analysis of the two-dimensional models composed from roentgenographic pictures and electromyographic analysis of the shear force exerted on the tibia during standing on both legs were conducted in 21 young adult males. The simultaneous contraction of the quadriceps and hamstrings was observed in all electromyograms. Amplitude observed on electromyograms of the hamstrings increased as the trunk flexion angle increased. The calculated average values of shear force were negative at every knee flexion angle (negative value means posteriorly directed force). As the trunk flexion angle increased, posterior drawer force increased at knee flexion angles of 30 degrees and 60 degrees. The simultaneous contraction of the quadriceps and the hamstrings was considered to be the main factor that influenced these results. Standing on both legs with knee and trunk flexion was considered to be applicable in the early stages after anterior cruciate ligament reconstruction.

Vapor Diffusional Growth of Free-Falling Snow Crystals between -3 and -23°C

Abstract: The characteristics of snow crystal growth by vapor diffusion at water saturation and in free fall were quantitatively investigated in a vertical supercooled cloud tunnel for periods up to 30 min at temperatures from -3 to -23*. The results obtained are as follows: 1) the basic growth habits were plates (>-4.0*), columns (-4.0--8.1*), plates (-8.1--22.4*) and columns (<-22.4*), respectively. At about -5.5, -12, -14 .5, -16.5 and -18*, crystal shapes were enhanced with time; 2) for an isometric crystal, the slope of a log-log plot between the crystal mass and the growth time showed the Maxwellian value of 1.5. The mass growth rate of a shape-enhanced crystal was larger than that of the isometric crystal, indicating more effective vapor transfer on the former; 3) in the case of shape-enhanced planar crystals grown at around -12, -14.5 and -16.5*, ventilation effects became recognizable, whereas the effect was not evident for needle crystals grown at about -5.5*. This suggests that the characteristic length of the flow field even around a needle crystal is along the a-axis. The ventilation effect became significant when the Reynolds number exceeded about 2 (sector) and 5 (dendrite); 4) linear relationships between the drag coefficient and the Reynolds number were found in log-log plots.

An endonuclease activity of Escherichia coli that specifically removes 8-hydroxyguanine residues from DNA.

Abstract: An enzyme that specifically removes an 8-hydroxyguanine (8-OH-Gua) residue in DNA has been purified from Escherichia coli. To assay the enzymatic activity, a synthetic double-stranded DNA (dsDNA) containing 8-OH-Gua at a defined position was used as substrate. The substrate DNA was simultaneously cleaved at 2 sites, i.e., the phosphodiester bonds 5′ and 3′ to 8-OH-Gua, leaving a phosphate at each of the neibhboring deoxynucleosides. The cleavage was observed only in dsDNA, but not with single-stranded DNA containing 8-OH-Gua. This enzyme showed almost no activity on DNAs containing other kinds of modified bases such as 8-hydroxyadenine, O6-methylguanine and N7-methylguanine. Also DNAs containing mismatches (A/G or C/T) were not cleaved. Studies on several other properties of this enzyme indicate that it differs from endonucleases previously isolated from E. coli, indicating that is likely to be an endonuclease which specifically recognizes 8-OH-Gua in dsDNA.

Serotonergic measures in suicide brain: 5-HT1A binding sites in frontal cortex of suicide victims.

Abstract: The density of 5-HT1A binding using3H-8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) as binding ligand, was studied in human frontal cortex of suicide victims and normal controls who died due to medical disease or accidentally. There was no difference in the maximum number of binding site (Bmax) or Kd (an inverse measure of affinity) of 5-HT1A receptor binding sites between normal controls and the entire group of suicide victims. However, nonviolent suicides had significantly higher Bmax (22—25%) compared to both controls and violent suicides. A negative correlation between age and Bmax of 5-HT1A binding sites was found in male controls but not in female controls or suicide victims. This relationship was less apparent among the male controls over age 60.

Asymmetric hydroboration of styrenes catalyzed by cationic chiral phosphine-rhodium(I) complexes

Abstract: Reaction of styrene with catecholborane in the presence of 1 mol % of a cationic phosphine-rhodium catalyst prepared in situ from [Rh(COD)2]BF4 and 1,4-bis(diphenyl-phosphino)butane proceeded regioselectively to give, after oxidation, 1-phenylethanol in a quantitative yield. The regioselectivity forming benzylic alcohols was also observed in the reaction of substituted styrenes. Use of (R)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (BINAP) as a chiral ligand for the rhodium-catalyzed hydroboration of substituted styrenes (ArCHCH2) gave optically active (R)-1-arylethanols (ArCH(OH)Me) in high yields. The enantiomeric purities of the alcohols are 96% ee, 94% ee, 91% ee, 85% ee, 89% ee, and 82% ee for Ar = Ph, 4-MeC6H4,4-ClC6H4, 3-Cl6H4, 4-MeOC6H4, and 2-MeOC6H4, respectively.

Neutron-diffraction investigation of the intramolecular structure of a water molecule in the liquid phase at high temperatures

Abstract: Time-of-flight neutron diffraction measurements were carried out on pure liquid water in the high-Q region and at high temperatures between 25 and 200°C. The observed data at high scattering angle ...

Identification of 1,4-dihydropyridine binding regions within the alpha 1 subunit of skeletal muscle Ca2+ channels by photoaffinity labeling with diazipine.

Abstract: To identify regions that are involved in the formation of the dihydropyridine receptor site of skeletal muscle L-type Ca2+ channels, the alpha 1 subunit of the channel complex was specifically labeled with the 1,4-dihydropyridine-receptor-selective photoaffinity probe [3H]diazipine. Photoaffinity-labeled regions were identified by probing labeled proteolytic fragments with several anti-peptide antibodies recognizing different segments of the alpha 1 sequence. Forty to 50% of the alpha 1-associated [3H]diazipine label was contained in the tryptic fragment between Arg-988 and Ala-1023 derived from the loop between segments S5 and S6 in domain III. This region corresponds to a portion of the channel that is believed to contribute to formation of the transmembrane pore. Twenty to 30% of the labeling occurred in a V8 protease fragment between Glu-1349 and Trp-1391. This fragment contains transmembrane segment S6 of domain IV and has previously been shown to form part of the drug receptor for phenylalkylamine Ca2+ antagonists. Our data suggest that the dihydropyridine receptor is formed by close apposition of two discontinuous regions of the alpha 1 subunit sequence in domains III and IV. In light of previous work localizing this receptor site to the extracellular surface of the lipid bilayer, it is proposed that amino acid residues at the extracellular surface in the loop connecting segments IIIS5 and IIIS6 and at the extracellular end of segment IVS6 contribute to formation of the dihydropyridine receptor site.

Simultaneous measurement of changes in length of the cruciate ligaments during knee motion

Abstract: The changes in length of electrolyte-in-rubber strain-gauge transducers implanted along the fibers of the anterior (ACL) and posterior (PCL) cruciate ligaments of the human anatomic specimen knees were measured simultaneously and continuously during knee motion. In unconstrained flexion and extension of the knee, all transducers in the ACL showed the maximum shortening peak at about 30 degrees flexion. After this, the length of the transducers in the anterior bundle increased, whereas those in the posterior bundle remained shortened. Transducers in the anterior and posterior bundles of the PCL, on the other hand, showed maximum lengthening peaks at approximately 50 degrees and 0 degrees flexion, respectively. The middle bundle of the PCL showed a smaller change. When simulated quadriceps forces were applied, the transducers in the ACL lengthened and those in the PCL shortened. At more than 90 degrees, however, the changes in length decreased. After cutting the ACL, the quadriceps force increased the shortening of the PCL.

Transient intermediates in the folding of dihydrofolate reductase as detected by far-ultraviolet circular dichroism spectroscopy.

Abstract: The kinetics of the reversible folding and unfolding of Escherichia coli dihydrofolate reductase have been studied by stopped-flow circular dichroism in the peptide region at pH 7.8 and 15 degrees C. The reactions were induced by concentration jumps of a denaturant, urea. The method can detect various intermediates transiently populated in the reactions although the equilibrium unfolding of the protein is apparently approximated by a two-state reaction. The results can be summarized as follows. (1) From transient circular dichroism spectra measured as soon as the refolding is started, a substantial amount of secondary structure is formed in the burst phase, i.e., within the dead time of stopped-flow mixing (18 ms). (2) The kinetics from this burst-phase intermediate to the native state are multiphasic, consisting of five phases designated as tau 1, tau 2, tau 3, tau 4, and tau 5 in increasing order of the reaction rate. Measurements of the kinetics at various wavelengths have provided kinetic difference circular dichroism spectra for the individual phases. (3) The tau 5 phase shows a kinetic difference spectrum consistent with an exciton contribution of two aromatic residues in the peptide CD region. The absence of the tau 5 phase in a mutant protein, in which Trp 74 is replaced by leucine, suggests that Trp 74 is involved in the exciton pair and that the tau 5 phase reflects the formation of a hydrophobic cluster around Trp 74. From the similarity of the kinetic difference spectrum to the difference between the native spectra of the mutant and wild-type proteins, it appears that Trp 47 is the partner in the exciton pair and that the structure formed in the tau 5 phase persists during the later stages of folding. (4) The later stages of folding show kinetic difference spectra that can be interpreted by rearrangement of secondary structure, particularly the central beta sheet of the protein. The pairwise similarities in the spectrum between the tau 3 and tau 4 phases, and between the tau 1 and tau 2 phases, also suggest the presence of two parallel folding channels for refolding. (5) The unfolding kinetics show three to four phases and are interpreted in terms of the presence of multiple native species. The total ellipticity change in kinetic unfolding reaction, however, agrees with the ellipticity difference between the native and unfolding states, indicating the absence of the burst phase in unfolding.(ABSTRACT TRUNCATED AT 400 WORDS)

A blind mobility aid modeled after echolocation of bats

Abstract: A new model of a mobility and for the blind was designed using a microprocessor and ultrasonic devices. This mobility and was evaluated based on psychophysical experiments. In this model, a downswept frequency-modulated (FM) ultrasound signal is emitted from a transmitting array with broad directional characteristics in order to detect obstacles. The ultrasound reflections from the obstacles are picked up by a two-channel receiver. The frequency of the emitted ultrasound is swept from 70 to 40 kHz within 1 ms, so it has almost the same characteristics as the ultrasound a bat produces for echolocation. The frequency of the reflected ultrasound wave is downconverted by about 50:1 by using a microcomputer with analog-to-digital and digital-to-analog converters. These audible waves are then presented binaurally through earphones. In this method obstacles may be perceived as localized sound images corresponding to the direction and the size of the obstacles. From the results of psychophysical experiments, it was found that downswept FM ultrasound was superior to other ultrasonic schemes for the recognition of small obstacles. With it a blind person can recognize a 1-mm-diameter wire. It was also proved that the blind could discriminate between several obstacles at the same time without any virtual images. This mobility aid is very effective at detecting small obstacles placed in front of the head. >