Showing papers by "University of Tokyo published in 1987"

Observation of a neutrino burst from the supernova SN1987A.

Abstract: A neutrino burst was observed in the Kamiokande II detector on 23 February, 7:35:35 UT (\ifmmode\pm\else\textpm\fi{}1 min) during a time interval of 13 sec. The signal consisted of 11 electron events of energy 7.5 to 36 MeV, of which the first two point back to the Large Magellanic Cloud with angles 18\ifmmode^\circ\else\textdegree\fi{}\ifmmode\pm\else\textpm\fi{}18\ifmmode^\circ\else\textdegree\fi{} and 15\ifmmode^\circ\else\textdegree\fi{}\ifmmode\pm\else\textpm\fi{}27\ifmmode^\circ\else\textdegree\fi{}.

The βγ subunits of GTP-binding proteins activate the muscarinic K + channel in heart

Abstract: Subunits ofguanine nucleotide regulatory proteins purified from bovine cerebral cortex were used to perfuse the intracellular surface of excised patches of chick embryonic atrial cells. Single-channel current measurements unexpectedly indicate that the βγ, and not the a subunits, are responsible for activating the muscarinic-gated potassium channel.

Heterogeneous catalysis by heteropoly compounds of molybdenum and tungsten

Abstract: Heteropolyanions are polymeric oxoanions which are formed by the condensation of more than two different oxoanions [Eq. (1)l. Polyanions consisting of one kind of oxoanion are called isopolyanions [Eq. (2)]. Acidic elements such as Mo, W, V, Nb, and Ta are present as oxoanions in aqueous solutions and polymerize to form polyanions at low pH. Free acids (or acid forms) of these species are called heteropoly and isopoly acids, respectively. Here, the term “heteropoly compounds” is used for heteropoly acids and their salts.

Maximizing daily canopy photosynthesis with respect to the leaf nitrogen allocation pattern in the canopy.

Abstract: A model of daily canopy photosynthesis was constructed taking light and leaf nitrogen distribution in the canopy into consideration. It was applied to a canopy of Solidago altissima. Both irradiance and nitrogen concentration per unit leaf area decreased exponentially with increasing cumulative leaf area from the top of the canopy. The photosynthetic capacity of a single leaf was evaluated in relation to irradiance and nitrogen concentration. By integration, daily canopy photosynthesis was calculated for various canopy architectures and nitrogen allocation patterns. The optimal pattern of nitrogen distribution that maximizes the canopy photosynthesis was determined. Actual distribution of leaf nitrogen in the canopy was more uniform than the optimal one, but it realized over 20% more photosynthesis than that under uniform distribution and 4.7% less photosynthesis than that under the optimal distribution. Redeployment of leaf nitrogen to the top of the canopy with ageing should be more effective in increasing total canopy photosynthesis in a stand with a dense canopy than in a stand with an open canopy.

Universal conductance fluctuations in metals: Effects of finite temperature, interactions, and magnetic field.

Abstract: The conductance of any metallic sample has been shown to fluctuate as a function of chemical potential, magnetic field, or impurity configuration by an amount of order ${e}^{2}$/h independent of sample size and degree of disorder at zero temperature. We discuss the relationship of these results to other results in the theory of weak and strong localization, and discuss its physical implications. We discuss the physical assumptions underlying the ergodic hypothesis used to relate theory to experiment. We review the zero-temperature theory and provide a detailed discussion of the conductance correlation functions in magnetic field and Fermi energy. We show that the zero-temperature amplitude of the fluctuations is unaffected by electron-electron interactions to lowest order in (${k}_{f}$l${)}^{\mathrm{\ensuremath{-}}1}$, and at finite temperature interactions only enter insofar as they contribute to the inelastic scattering rate. We calculate the effects of finite temperature on both the amplitude of the fluctuations and their scale. We discuss the conditions for dimensional crossover at finite temperature, and the behavior of different experimental measures of the fluctuation amplitude, in order to facilitate quantitative comparisons of experiment and theory.

Molecular cloning and charcterization of rat estrogen receptor cDNA

Abstract: A cDNA clone of rat uterus estrogen receptor (ER) has been isolated and sequenced. This clone contains a complete open reading frame encoding 600 amino acid residues which is 5 and 11 amino acids larger than the corresponding molecules of human and chicken, respectively. The molecular weight of this protein is calculated to be 67,029. When this clone was ligated to the pSV2 vector and transfected into COS7 cells, a protein was produced that had the same affinity to estrogen as rat uterus ER. This sequence shows 88% homology with human ER; 528 amino acids are identical and 14 amino acids are conservative substitutions. The comparison of rat, human and chicken ER sequences indicate the presence of three highly conserved regions suggesting that these regions play important roles in ER function. The putative DNA-binding domain is completely identical in rat, human and chicken. The C-terminal half region which is thought to be the estrogen binding domain is also highly conserved and is rich in hydrophobic amino acid residues. Southern blot analysis of genomic DNA with ER cDNA as a probe has shown that related sequences are present in the genome.

A novel putative tyrosine kinase receptor encoded by the eph gene

Abstract: Growth factors and their receptors are involved in the regulation of cell proliferation and also play a key role in oncogenesis. In this study, a novel putative kinase receptor gene, termed eph, has been identified and characterized by molecular cloning. Its primary structure is similar to that of tyrosine kinase receptors thus far cloned and includes a cysteine-rich region in the extracellular domain. However, other features of the sequence distinguish the eph gene product from known receptors with tyrosine kinase activity. Thus the eph protein may define a new class of these molecules. The eph gene is overexpressed in several human carcinomas, suggesting that this gene may be involved in the neoplastic process of some tumors.

Interaction of ascorbate and alpha-tocopherol.

Abstract: Vitamins C and E function as water-soluble and lipid-soluble chain-breaking antioxidants, respectively, and protect lipids, proteins, and membranes from oxidative damage. Vitamin C scavenges oxygen radicals in the aqueous phase, whereas vitamin E scavenges oxygen radicals within the membranes. Vitamin C regenerates vitamin E by reducing vitamin E radicals formed when vitamin E scavenges the oxygen radicals. This interaction between vitamin C and vitamin E radicals can take place not only in homogeneous solutions but also in liposomal membrane systems where vitamins C and E reside separately outside and within the membranes respectively, and vitamin C can act as a synergist.

Existence of solutions for Schrödinger evolution equations

Abstract: We study the existence, uniqueness and regularity of the solution of the initial value problem for the time dependent Schrodinger equationi∂u/∂t=(−1/2)Δu+V(t,x)u,u(0)=u 0. We provide sufficient conditions onV(t,x) such that the equation generates a unique unitary propagatorU(t,s) and such thatU(t,s)u 0eC 1(ℝ,L 2) ∩C 0(ℝH 2(ℝ n )) foru 0eH 2(ℝ n ). The conditions are general enough to accommodate moving singularities of type ∣x∣−2+ɛ(n≧4) or ∣x∣−n/2+ɛ(n≧3).

Synaptic modification of parallel fibre-Purkinje cell transmission in in vitro guinea-pig cerebellar slices.

Abstract: 1. Synaptic transmission from parallel fibres to Purkinje cells and its modification by paired stimulation of parallel fibres and climbing fibres were studied in in vitro slices of the cerebellum obtained from guinea-pigs. 2. Intracellular recordings were made from Purkinje cells, mainly from dendrites in the middle third of the molecular layer, but also, in a few cases, from somata. Climbing fibres were activated by stimulation of the white matter, while parallel fibres were stimulated with an electrode placed near the pial surface of the molecular layer. 3. Stimulation of the white matter elicited antidromic spikes, all-or-none climbing fibre responses, disynaptic responses through mossy fibres and parallel fibres, and trisynaptic responses through inhibitory interneurones. Climbing fibre responses were often followed by a small plateau potential, usually less than 2-3 mV in amplitude and less than 100 ms in duration, followed by a slow hyperpolarization which reached its peak in several seconds. Inhibitory inputs to Purkinje cells were blocked with picrotoxin for the experiments described below. 4. Stimulation of the superficial molecular layer with currents less than 50 microA produced graded parallel fibre-mediated excitatory postsynaptic potentials (e.p.s.p.s) ranging from 4 to 8 mV in peak amplitude. 5. Conjunctive stimulation of climbing fibres and parallel fibres at 4 Hz for 25 s induced depression of parallel fibre-mediated e.p.s.p.s in Purkinje cells, both in the peak amplitudes and in the slopes. The depression was about 30% on average and lasted for more than 50 min. 6. No such depression occurred when the intensity of the white matter stimulation was set just subthreshold for the climbing fibre innervating the Purkinje cell under study. Instead, the parallel fibre-mediated e.p.s.p.s were moderately potentiated for a period ranging from 10 to 50 min. Repetitive stimulation of the climbing fibre alone did not affect parallel fibre-mediated e.p.s.p.s. 7. Immediately after the conjunctive stimulation or the repetitive stimulation of climbing fibres alone, a transient hyperpolarization which lasted for several minutes was seen. Its time course was similar to that of the hyperpolarization following a climbing fibre response. Except for this, there were no associated changes in the membrane potential, the input resistance, or the magnitudes of climbing fibre responses in any of the cases mentioned in 5 and 6 above.

Human CSF-1: molecular cloning and expression of 4-kb cDNA encoding the human urinary protein.

Abstract: A 4-kilobase complementary DNA (cDNA) encoding human macrophage-specific colony-stimulating factor (CSF-1) was isolated. When introduced into mammalian cells, this cDNA directs the expression of CSF-1 that is structurally and functionally indistinguishable from the natural human urinary CSF-1. Direct structural analysis of both the recombinant CSF-1 and the purified human urinary protein revealed that these species contain a sequence of at least 40 amino acids at their carboxyl termini which are not found in the coding region of a 1.6-kilobase CSF-1 cDNA that was previously described. These results demonstrate that the human CSF-1 gene can be expressed to yield at least two different messenger RNA species that encode distinct but related forms of CSF-1.

Expression of bacterial chloramphenicol acetyltransferase gene in tobacco plants mediated by TMV-RNA.

Abstract: We have constructed three tobacco mosaic virus (TMV) cDNA derivatives by modification of the full-length cDNA clone from which infectious TMV-RNA can be transcribed in vitro A coatless TMV construct lacks most of the coat protein gene and chimeric TMV constructs retain the bacterial chloramphenicol acetyltransferase (CAT) gene in place of the coat protein gene When in vitro transcripts from these cDNA derivatives were inoculated on the local lesion tobacco plants, TMV-specific lesions were produced In the case of the TMV-CAT chimeras, however, the lesions were small compared to those of wild-type TMV and those produced by transcript derived from the coatless construct Northern blot analysis of RNA extracted from the inoculated leaves of the systemic host plants revealed replication of the derivative genomic RNAs and production of their own subgenomic RNAs corresponding to the coat protein mRNA The TMV-CAT chimeras produced biologically active CAT in the inoculated leaves of the systemic host CAT activity increased at least until 2 weeks post-inoculation and was approximately 01 units/mg of tissue at 10 days post-inoculation Thus, TMV-RNA may be utilized as a new plant expression vector

Nitrogen use efficiency in instantaneous and daily photosynthesis of leaves in the canopy of a Solidago altissima stand

Abstract: Photosynthetic capacity was measured on detached leaves sampled in a canopy of Solidago altissima L. Non-rectangular hyperbola fitted the light response curve of photosynthesis and significant correlations were observed between leaf nitrogen per unit area and four parameters which characterize the light-response curve. Using regressions of the parameters on leaf nitrogen, a model of leaf photosynthesis was constructed which gave the relationships between leaf nitrogen, photon flux density (PFD) and photosynthesis. Curvilinear relations were obtained between leaf nitrogen and photosynthetic rate on both an instantaneous and a daily basis. Nitrogen use efficiency (NUE, photosynthesis per unit leaf nitrogen) was calculated against leaf nitrogen under varying PFDs. The optimum nitrogen content per unit leaf area that maximizes NUE shifted to higher values with increasing PFD. Field measurements of PFD showed high positive correlations between the distribution of leaf nitrogen in the canopy and relative PFD. The predicted optimum leaf nitrogen content for each level in the canopy, to achieve maximized NUE during a clear day, was close to the actual nitrogen distribution as found through sampling.

Serum pepsinogens as a screening test of extensive chronic gastritis.

Abstract: The serum level of pepsinogen I (PG I) and pepsinogen II (PG II), and the PG I/PG II ratio were compared with the surface area of the fundic mucosa, as determined endoscopically by the Congo red staining method. Reduction in the area of the fundic mucosa due to gastritis was associated with stepwise reduction in the PG I levels and the PG I/PG II ratios. Reduction in the area of the fundic mucosa was also associated with decreases in the basal acid output, maximal acid output (MAO), the basal pepsin output and the stimulated pepsin output. The best sensitivity and specificity levels for the diagnosis of normal mucosa and severe gastritis were obtained with the PG I/PG II ratio and the MAO. A retrospective study of 58 patients with gastric cancer and 162 cancer-free patients showed that a PG I/PG II ratio identified 86.2% of all carcinomas and 87.5% of early carcinomas. Although this test gave a positive rate of 36% among the cancer-susceptible age group controls, its use would lower the cost of mass screening by targeting a smaller test population.

Diesel-exhaust particulates inoculated by the intranasal route have an adjuvant activity for IgE production in mice

Abstract: Our previous study indicated that the IgE antibody responses in mice immunized with intraperitonela injection of the antigens mixed with diesel-exhaust particulates (DEP) were higher than those in the animals immunized with the antigens alone. We examined the adjuvant activity of DEP inoculated by the intranasal route, i.e., the natural entrance of DEP. In 3-week interval immunization, the IgE antibody responses in mice immunized with intranasal inoculation of ovalbumin (OA) mixed with DEP were higher than responses in the animals immunized with OA alone. DEP had an adjuvant activity for anti-OA IgE antibody production, even in a small dose such as 1 μg administered with a 3-week interval. Also in 1-week interval immunization the enhancing effect of DEP on anti-OA IgE antibody production was demonstrated when mice were immunized with intranasal inoculation of OA and DEP. The possibility cannot be excluded that DEP, which are kept buoyant in the environmental atmosphere of urban districts, may exert an adjuvant activity for IgE antibody production after being inhaled into the human body and have some relation to the mechanism of the outbreak of allergic rhinitis caused by pollens in Japan.

Effect of fructo‐oligosaccharides on intestinal microflora

Abstract: Fructo-oligosaccharides are widely distributed in plants such as onions, asparagus, wheat etc., and obtained from sucrose by the action of fructosyltransferase. They are not hydrolyzed by human digestive enzymes, but are utilized by intestinal bacteria such as bifidobacteria. Bacteroides fragilis group, peptostreptococci and klebsiellae. In the experiment with 23 patients (73 +/- 9 years old), improvement of fecal microflora was observed by oral administration of fructo-oligosaccharides 8 g per day for two weeks: the population of bifidobacteria in feces increased about 10 times compared before the administration; average pH of stool showed 0.3 lower than that before administration.

Quisqualate receptors are specifically involved in cerebellar synaptic plasticity

Abstract: Long-term modification of transmission efficacy at synapses is the cellular basis of memory and learning. A special type of synaptic plasticity in the cerebellum was postulated theoretically, and has since been verified. Each cerebellar Purkinje cell (PC) receives two distinct excitatory inputs, one from parallel fibres (PFs) and the other from a climbing fibre (CF). When these two types of inputs are conjunctively activated, PF-PC transmission undergoes long-term depression (LTD). Accumulated evidence suggests that LTD plays a role in the motor learning processes of the cerebellum. At the molecular level, LTD appears to be caused by desensitization of receptor molecules in PC dendrites towards the PF neurotransmitter, presumably L-glutamate (Glu). Glu receptors are heterogeneous and can be divided into several subtypes. In this study, we compared the potency of several Glu agonists in inducing LTD and found a highly selective dependency of LTD on the quisqualate(QA)-selective subtype of Glu receptors.

Function of the 30 kd protein of tobacco mosaic virus: involvement in cell-to-cell movement and dispensability for replication.

Abstract: We have investigated the function of the 30 kd protein of tobacco mosaic virus (TMV) by a reverse genetics approach. First, a point mutation of TMV Ls1 (a temperature-sensitive mutant defective in cell-to-cell movement), that causes an amino acid substitution in the 30 kd protein, was introduced into the parent strain, TMV L. The generated mutant showed the same phenotype as TMV Ls1, and therefore the one-base substitution in the 30 kd protein gene adequately explains the defectiveness of TMV Ls1. Next, four kinds of frame-shift mutants were constructed, whose mutations are located at three different positions of the 30 kd protein gene. All the frame-shift mutants were replication-competent in protoplasts but none showed infectivity on tobacco plants. From these observations the 30 kd protein was confirmed to be involved in cell-to-cell movement. To clarify that the 30 kd protein is not necessary for replication, two kinds of deletion mutants were constructed; one lacking most of the 30 kd protein gene and the other lacking both the 30 kd and coat protein genes. Both mutants replicated in protoplasts and the former still produced the subgenomic mRNA for the coat protein. These results clearly showed that the 30 kd protein, as well as the coat protein, is dispensable for replication and that no cis-acting element for replication is located in their coding sequences. It is also suggested that the signal for coat protein mRNA synthesis may be located within about 100 nucleotides upstream of the initiation codon of the coat protein gene.