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Biomedical subjects

T Oshima

Publications and source records attributed to T Oshima.

At least 613 records · Page 34Linked to original sources
PubMed1976

CD spectra of 5-methyl-2-thiouridine in tRNA-Met-f from an extreme thermophile.

5-Methyl-2-thiouridine (S) in tRNA-Met-f from an extreme thermophile is located in the TpsiC region, replacing T, and has a positive CD band centered at 310 nm. Upon heating, the profiles of the change in this band were similar to the UV melting profiles of the change monitored at 260 nm. This strongly suggests a close relation between heat denaturation of the tRNA and the conformation of the S base. Oligonucleotides containing S showed negative CD bands at 320-330 nm, like the monomer S itself, but when the 3'-2/5 fragment containing S formed a complex with the complementary 5'-3/5 fragment, a positive CD band appeared at 310 nm. These results suggest that combination of the TpsiC loop containing S with the hU loop is necessary for the positive band of S at 310 nm. S may serve to strengthen the association of the TpsiC loop with the hU loop in tRNA of the thermophile.

Bacteria↗
PubMed1976

Studies on an alpha-amylase from a thermophilic bacterium. I. Purification and characterization.

An amylase-producing thermophilic bacterium was isolated from a Japanese hot spring. The thermophilic cells were gram-negative, nonsporulating, nonpigmented rods and were motile with flagella. Alpha-Amylase [EC 3.2.1.1) purified from the thermophile was studied. The enzyme was more heat-stable than the corresponding enzymes from mesophilic sources, and 50% loss of activity was observed after incubation for 1 hr at 90 degrees. The thermophilic enzyme resembled the corresponding mesophilic enzymes in many respects, such as kinetic parameters, physicochemical properties, and amino acid composition. The molecular weight of the enzyme was 50,000 and the enzyme contained 2 moles of half-cystine residues per mole of protein, but there were no disulfide crosslinkages. The alpha-helix content of the enzyme was estimated to be about 20% from CD spectra, a value similar to those of other alpha-amylases. The isoelectric point of the enzyme was at pH 9.2.

Amino Acids↗
PubMed1976

Protein synthesis in a cell-free system from an extreme thermophile. Effects of preincubation in the cold on polyuridylic acid-dependent polyphenylalanine synthesis at high temperature.

1. It was found that preincubation of the reaction mixture in the cold enhanced polyuridylic acid-directed polyphenylalanine synthesis by a cell-free extract of Thermus thermophilus HB8 at high temperature. 2. The effect of preincubation was most marked at 10-25 degrees in the presence of 20 mM Mg2+. Preincubation at 65 degrees failed to stimulate the incorporation. 3. The presence of phenylalanyl-tRNA, polyuridylic acid, and ribosomes was essential for preincubation in the cold to be effective. 4. A ternary complex of amino acyl-tRNA, polyuridylic acid, and a ribosome formed at low temperature was isolated by CPG-10 column chromatography; the isolated complex initiated polyphenylalanine synthesis effectively at high temperature. 5. The amount of the ternary complex formed depends on the preincubation time and the concentration of Mg2+. Since the amount of the complex correlated positively to the rate of polyphenylalanine synthesis at high temperature, the effectiveness of preincubation in the cold is presumably due to the formation of the ternary complex of phenylalanyl-tRNA, polyuridylic acid, and a ribosome.

Bacteria↗
PubMed1976

Synthesis of various phosphodiesters and phosphomonoesters with ribonuclease N.

1. 3'-Guanylyl-ethanol, 3'-guanylyl-propanol, and 3'-guanylyl-alpha-glycerol were synthesized by ribonuclease N1 [EC 3.1.4.8] using guanosine 2',3'-cyclic phosphate as a phosphate donor and various alcohols as phosphate acceptors. The yields of these phosphodiesters were 15%, 13.5%, 38.2%, respectively, with respect to phosphate donor under the optimum conditions. No phosphodiester was synthesized when 2-propanol was used as a phosphate acceptor. Thus, primary alcoholic hydroxyl groups may be regarded as the preferred phosphate acceptor. 2. 3'-Guanylyl-glucose and 3'-guanylyl-ribose were synthesized using glucose and ribose as phosphate acceptors. Under the optimum conditions, the yields of guanylyl-glucose amounted to 52.0%, while that of guanylyl-ribose was much lower. The guanylyl-glucose can be regarded as 3'-guanylyl-6-glucopyranose, based on the results of periodate oxidation. 3. Neither hydroxyamino acids (serine and threonine) nor N-acetylserinamide could be phosphorylated under the conditions used for the above phosphorylations. 4. 3'-Guanylyl-glycerol obtained as above was hydrolyzed by snake venon phosphodiesterase to produce glycerol 3-phosphate. The latter consisted of L-glycerol 3-phosphate (ca 17%) and the D-isomer (ca. 83%). Ribonuclease N1 thus catalyzes an asymmetric synthesis.

1-Propanol↗
PubMed1976

New device for automatic recording and processing AV transmission intervals of the heart.

The principle and construction of a device made for the purpose of displaying the interrelationship between two sets of cardiac intervals is described. Electrical signals derived from the atrium and ventricle of the experimental animal are fed to the input of the device where a special switch and an integrated circuit logic gate select the two sets of cardiac intervals to be measured, e.g., AA and VV or AA and AV intervals. These intervals are converted into electrical square pulses having voltages proportional to the respective intervals. Besides simply comparing the two cardiac intervals by recording them simultaneously against time, the interrelationship of the two is displayed in an X-Y configuration on-line on a cathode-ray oscilloscope. This latter method, if used only for the occasionally induced premature excitations with varied coupling time, facilitates the measurement of the functional refractory periods for atrioventricular conduction. The mode of operation of the device is presented with examples of experiments.

Animals↗
PubMed1975

The mode of synaptic linkage in the cerebro-ponto-cerebellar pathway of the cat. I. Responses in the brachium pontis.

Cerebrally-induced responses of pontine nuclei cells (PN cells) were studied in cats anesthetized with pentobarbitone sodium and with the midbrain transected bilaterally sparing only the cerebral penuncles. After stimulating the subcortical white matter, the internal capsule or the cerebral peduncle, mass potentials were recorded from the cut end of fibres in the brachium pontis (BP) and in the pyramid at the level of the trapezoid body. These potentials were regarded as indicating, respectively, the size of an output volley of PN cells and the size of its causative input volley through the pyramidal tract. BP responses consisted of short- and long-latency potentials which were caused by fast and slow conducting pyramidal tract volleys, respectively. The input-output relations for fast component responses took a characteristic S-shaped form resembling those obtained from the monosynaptic spinal reflex. The input-output relations for slow component responses were almost linear. Both fast and slow BP responses were remarkably potentiated after single or relatively brief repetitive peduncular stimulation, but were depressed after long-lasting high-frequency activation. During repetitive stimulation with varied frequencies, fast and slow BP responses showed different patterns of frequency-dependence of their amplitudes. These results suggest the existence of two separate transmission lines with different properties in cerebro-ponto-cerebellar pathways.

Animals↗
PubMed1975

The mode of synaptic linkage in the cerebro-ponto-cerebellar pathway of the cat. II. Responses of single cells in the pontine nuclei.

Extracellular and intracellular recordings were made from single cells in the pontine nuclei (PN) of the cat. PN cells were identified by antidromic invasion from the cerebellum by stimulating either the brachium pontis (BP) or the white matter near the cerebellar nuclei. The cerebrally-induced impulses excited PN cells postsynaptically with a monosynaptic latency. Both fast and slow conducting cortical fibres contributed to the corticopontine excitation, so that the latency varied over a wide range. Measurements of the latencies for antidromic and corticopontine excitation and of the distances between stimulated sites permitted the calcuation of conduction velocities of PN cell axons and of their cortical input fibres. PN cells with fast conducting axons received convergence from both fast and slow cortical fibres, whereas PN cells with slow axons were innervated only by slow cortical fibres. The majority of PN cells were also excited by stimulating the medullary pyramid through collaterals of the pyramidal tract. Evidence of abundant pyramidal collaterals was provided by the collision technique. The functional role of the PN is discussed in connection with the cerebro-cerebellar loop circuits.

Animals↗
PubMed1975

Isolation and characterization of a bacteriophage infectious to an extreme thermophile, Thermus thermophilus HB8.

A bacteriophage (phiYS40) infectious to an extreme thermophile, Thermus thermophilus HB8, was isolated and characterized. phiYS40 grows over the temperature range of 56 to 78 C, and the optimum growth temperature is about 65 C. The phage had a latent period of 80 min and a burst size of about 80 at 65 C. The phage has a hexagonal head 0.125 mum in diameter, a tail 0.178 mum long and 0.027 mum wide, a base plate and tail fibers. The phage is thermostable in broth but rather unstable in a buffer containing 10 mM Tris, 10 mM MgCl2, pH 7.5. The addition of Casamino Acids (1 percent), polypeptone (0.8 percent), yeast extract (0.4 percent), NaCl (0.1 M) or spermidine (1 mM) to the buffer restores the thermostability of phiYS40 to the same degree as in broth. The phage is also thermostable in water of the hot spring from which this phage was isolated. The nucleic acid of PhiYS40 is a double-stranded DNA and has a molecular weight of 1.36 X 10-8. The guanine plus cytosine content of the DNA was determined to be about 35 percent from chemical determinations, buoyant density (1.693 g/cm-3 in CsCl), and melting temperature (83.5 C in 0.15 M NaCl plus 0.015 M sodium citrate).

Bacteria↗
PubMed1975

Effects of beta blockers on cardiac function and myocardial oxygen consumption in the isolated supported heart preparation of the dog.

Effects of 2 different types of beta blockers, CS-359 and practolol, on mechanical performance and myocardial oxygen consumption (MVO2) in the isovolumic contraction of the isolated, blood-perfused canine heart with a support dog were studied. Two dose levels of the beta blockers were given intravenously to the support dog, one of which was enough to produce a significant beta adrenergic blocking action and other of which was a higher dose to reveal a direct depressant action on the isolated heart. CS-359 in the lower dose produced significant decreases in heart rate (HR), peak ventricular systolic pressure (peak VSP), and peak dp/dt while practolol caused no change in these parameters. The HR of the support dog was significantly decreased to the same degree in the lower dose of respective blocker. In the higher dose CS-359 decreased all parameters more definitely whereas practolol diminished peak VSP and peak dp/dt but did not significantly HR. MVO2 was decreased dose-relatedly by CS-359, but not affected significantly by practolol. From the analysis of relationships of MVO2 to peak VSP and HR in the isolated heart it is concluded that the effective reduction in MVO2 by CS-359 resulted mainly from a reduction in the peak VSP in the lower dose and additional decrease in HR in the higher dose of CS-359.

Adrenergic beta-Antagonists↗