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Biomedical subjects

E Fukushima

Publications and source records attributed to E Fukushima.

At least 19 recordsLinked to original sources
PubMed2001

Improved salt tolerance of transgenic tobacco expressing apoplastic yeast-derived invertase.

We investigated the salt tolerance of transgenic tobacco, in which yeast invertase is expressed in the apoplastic (Apo-Inv) spaces. Whereas photosynthetic activities in wild-type tobacco in light were inhibited under salt stress, transgenic Apo-Inv tobacco maintained constant photosynthetic activities. The physical appearance of plants under salt stress also indicates that yeast invertase expression in the apoplastic space is beneficial for inducing salt tolerance. Apo-Inv tobacco had a much higher osmotic pressure increase in the cell sap than did wild-type tobacco under this type of stress. The physiological importance of sucrose metabolism under salt stress is discussed.

Chloroplasts↗
PubMed2001

Acute epiglottitis: a review of 80 patients.

We reviewed 80 patients admitted to our hospital who were diagnosed with acute epiglottitis between January 1995 and March 1999, and their clinical features, evolution and treatments were analysed. No sexual predominance was found, and there was no patient younger than 16 years of age. The patient fatality rate was 1.3 per cent, and the hospitalization period was markedly longer than those of other reports.

Acute Disease↗
PubMed2000

Pulsed gradient spin echo nuclear magnetic resonance imaging of diffusion in granular flow

We derive the formalism to obtain spatial distributions of collisional correlation times for macroscopic particles undergoing granular flow from pulsed gradient spin echo nuclear magnetic resonance diffusion data. This is demonstrated with an example of axial motion in the shear flow regime of a 3D granular flow in a horizontal rotating cylinder at one rotation rate.

Journal Article↗
PubMed2000

Thermally polarized (1)H NMR microimaging studies of liquid and gas flow in monolithic catalysts

The feasibility of gas flow imaging in moderately high magnetic fields employing thermally polarized gases at atmospheric pressures is demonstrated experimentally. Two-dimensional spatial maps of flow velocity distributions for acetylene, propane, and butane flowing along the transport channels of shaped monolithic alumina catalysts were obtained at 7 T by (1)H NMR, with true in-plane resolution of 400 &mgr;m and reasonable detection times. The resolution is shown to be limited by the echo attenuation due to rapid molecular diffusion in the imaging gradients of magnetic field. All gas flow images exhibit flow patterns that are not fully developed, in agreement with the range of Reynolds numbers (190-570) and the length of the sample used in gas flow experiments. The flow maps reveal the highly nonuniform spatial distribution of shear rates within the monolith channels of square cross-section, the kind of information essential for evaluation and improvement of the efficiency of mass transfer in shaped catalysts. The water flow images were obtained at lower Re numbers for comparison. These images demonstrate the transformation of a transient flow pattern observed closer to the inflow edge of a monolith into a fully developed one further downstream. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Imaging obstructed ventilation with NMR using inert fluorinated gases.

We partially obstructed the left bronchi of rats and imaged an inert insoluble gas, SF(6), in the lungs with NMR using a technique that clearly differentiates obstructed and normal ventilation. When the inhaled fraction of O(2) is high, SF(6) concentrates dramatically in regions of the lung with low ventilation-to-perfusion ratios (VA/Q); therefore, these regions are brighter in an image than where VA/Q values are normal or high. A second image, made when the inhaled fraction of O(2) is low, serves as a reference because the SF(6) fraction is nearly uniform, regardless of VA/Q. The quotient of the first and second images displays the low-VA/Q regions and is corrected for other causes of brightness variation. The technique may provide sufficient quantification of VA/Q to be a useful research tool. The noise in the quotient image is described by the probability density function for the quotient of two normal random variables. When the signal-to-noise ratio of the denominator image is >10, the signal-to-noise ratio of the quotient image is similar to that of the parent images and decreases with pixel value.

Animals↗
PubMed1998

Imaging lungs using inert fluorinated gases.

Rat lungs were imaged by 19F projection MRI of hexafluoroethane, mixed with 20% oxygen to form the inhaled gas. The 3D image had 700 microm resolution, and the data took 4.3 h to acquire. Free induction decays were collected in the presence of steady magnetic field gradients in 686 different directions. To take advantage of fast relaxation (T1 = 5.9 +/- 0.2 ms), the repetition time was 5 ms. To eliminate signal loss from magnetic field inhomogeneities, data were collected within 2 ms of spin excitation (from 80 micros to 2 ms after the 42-micros pi/2 pulses). The singular value decomposition of the transform from frequency to time domain was used to obtain projections despite the absence of data during and immediately after the RF pulses. Inert fluorinated gas imaging may be less expensive than polarized noble gas imaging and is appropriate for imaging steady-state rather than transient gas concentrations.

Animals↗
PubMed1998

A programmable pre-emphasis system.

MRI systems often use magnetic field gradient and shim pulse-shaping networks (pre-emphasis) to correct for magnetic field distortions caused by eddy currents. A pre-emphasis system that uses up to 16 fixed resistor-capacitor (RC) time constants per channel with programmable amplitude coefficients is described. The magnetic fields induced by the pre-emphasis RC time constants serve as a set of basis functions for compensating eddy-current fields induced by the gradient set. The resultant time-varying magnetic field gradient accurately reflects the gradient specified by the pulse programmer. Reductions in eddy-current fields are demonstrated for actively shielded and unshielded gradient sets.

Artifacts↗
PubMed1997

Diffusion imaging with hyperpolarized 3He Gas

We used MRI of hyperpolarized 3He to demonstrate some novel aspects of gas diffusion. Two different techniques were used. First, a slice was burned into a one-dimensional image by inverting the spins in the slice and diffusion was studied by measuring the magnetization as it filled the depleted slice. A diffusion coefficient was determined by the fit of these data. Second, one-dimensional diffusion images were made using a Stejskal-Tanner PGSE method. This was done with and without a temperature gradient present, showing that the effect of temperature can be dynamically monitored by such diffusion images. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗
PubMed1997

NMR measurements of flow profiles in a coarse bed of packed spheres.

The velocity profiles of water flowing in a circular pipe filled with coarse, uniform, spherical beads, as well as the evolution of velocity profiles from clear flow into the bed of beads and visa versa, were measured by nuclear magnetic resonance (NMR) imaging using the phase-encoding method. Corrections for partial-volume effects were necessary in order to obtain accurate flow parameters. Phase errors due, for example, to electrical eddy currents induced by switching gradients, were minimized by the use of a static reference sample. For a tube diameter that is eight times the particle diameter, the flow reaches a steady state condition within one bead diameter into the packed bed after having a parabolic velocity profile only 1.5 tube diameters before encountering the bed. Within the packed bed, there are velocity spikes up to 16 times the average velocity in the unobstructed part of the pipe. The velocity distribution in the packed bed has a maximum that approaches the average velocity in the bed for increasing slice thickness along the flow. This distribution decreases exponentially with increasing velocity on the high-velocity side of the maximum. Even at modest flows, where velocity is steady upstream of the packed bed as well as in the bed, unsteady flow is detected downstream of the beads.

Humans↗
PubMed1996

Velocity distribution of slow fluid flows in Bentheimer sandstone: an NMRI and propagator study.

This work addresses the special problems of measuring flow velocity distributions in rock by NMR methods. Specifically, these problems are to measure very slow flows as well as flows in the presence of background magnetic field gradients caused by heterogeneities of the rock. We modify a stimulated echo sequence for use in diffusion measurements, in order to maximize velocity sensitivity and minimize background gradient effects. Accurate velocity images of Soltrol 220 oil in sandstone were made for flow velocities up to around 0.04 mm/s with an imager that does not have echo-planar capability. Accurate velocity distributions by the propagator method can be obtained even with stimulated echo delays of 1.9 T1 by phase cycling combined with suitable crusher gradients.

Geological Phenomena↗
PubMed1992

Purification and characterization of phosphofructokinase in bovine parotid gland.

1. Phosphofructokinase (PFK) was purified from bovine parotid gland to 750-fold with the specific activity of 67.5 units/mg protein by Cibacron Blue F3GA affinity chromatography, and TSK DEAE-5PW ion-exchange and TSK G4000SW size exclusion chromatographies on HPLC. 2. On gel-filtration, molecular weight of the native PFK was estimated to 400,000. 3. PFK was a heterotetramer composed of three kinds of subunit with molecular weights of 92,000 (C-type), 88,000 (M-type) and 86,000 (L-type), by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Densitometrically, relative amounts of C-, M- and L-type subunit were 1:1:2. 4. Under the physiological conditions of fructose 6-phosphate (Fru-6-P) and ATP concentrations and pH, PFK activity was suppressed and hardly detectable. 5. Fru-6-P relieved PFK from the ATP inhibition. 6. Fructose 2,6-bisphosphate (Fru-2,6-P2) and AMP activated PFK with a reduction of S0.5 for Fru-6-P and subunit cooperativity. Fru-2,6-P2 was more effective than AMP.

Adenosine Monophosphate↗
PubMed1990

Velocity imaging of slow coherent flows using stimulated echoes.

We measure the velocity distribution of slow fluid flow in model systems using stimulated echoes and velocity phase encoding. We show velocity images of slow coherent flow with velocities of the order of 0.1 mm/s which is slower than can be obtained by the bolus-tracking method. The eddy current errors were compensated by phase correction.

Humans↗
PubMed1990

Training-induced skeletal muscle adaptations are independent of systemic adaptations.

To isolate the peripheral adaptations to training, five normal subjects exercised the nondominant (ND) wrist flexors for 41 +/- 11 days, maintaining an exercise intensity below the threshold required for cardiovascular adaptations. Before and after training, intracellular pH and the ratio of inorganic phosphate to phosphocreatine (Pi/PCr) were measured by 31P magnetic resonance spectroscopy. Also maximal O2 consumption (VO2 max), muscle mass, and forearm blood flow were determined by graded systemic exercise, magnetic resonance imaging, and venous occlusion plethysmography, respectively. Blood flow, Pi/PCr, and pH were measured in both forearms at rest and during submaximal wrist flexion at 5, 23, and 46 J/min. Training did not affect VO2 max, exercise blood flow, or muscle mass. Resting pH, Pi/PCr, and blood flow were also unchanged. After training, the ND forearm demonstrated significantly lower Pi/PCr at 23 and 46 J/min. Endurance, measured as the number of contractions to exhaustion, also was increased significantly (63%) after training in the ND forearm. We conclude that 1) forearm training results in a lower Pi/PCr at identical submaximal work loads; 2) this improvement is independent of changes in VO2 max, muscle mass, or limb blood flow; and 3) these differences are associated with improved endurance and may reflect improved oxidative capacity of skeletal muscle.

Adaptation, Physiological↗
PubMed1990

Skeletal muscle response to exercise training in congestive heart failure.

To examine the ability of the skeletal muscle of congestive heart failure (CHF) patients to adapt to chronic exercise, five patients performed localized nondominant wrist flexor training for 28 d. Inorganic phosphate (Pi) and phosphocreatine (PCr) were monitored by magnetic resonance spectroscopy in both forearms at rest and during submaximal wrist flexion exercise at 6, 12, 24, and 36 J.min-1 before and after exercise training. Simultaneous measurements of limb blood flow were made by plethysmography at 12, 24, and 36 J.min-1. Forearm muscle mass and endurance were measured by magnetic resonance imaging and wrist flexion exercise before and after training. The Pi/PCr ratio and pH were calculated from the measured Pi and PCr. Exercise cardiac output, heart rate, plasma norepinephrine, and lactate measured during training were not elevated above resting values, confirming that training was localized to the forearm flexor muscles. After training, muscle bioenergetics, as assessed by the slope of the regression line relating Pi/PCr to submaximal workloads, were improved in the trained forearm of each patient, although muscle mass, limb blood flow, and pH were unchanged. Forearm endurance increased by greater than 260% after training. In the dominant untrained forearm, none of the measured indices were affected. We conclude that localized forearm exercise training in CHF patients improves muscle energetics at submaximal workloads in the trained muscle, an effect which is independent of muscle mass, limb blood flow, or a central cardiovascular response during training. These findings indicate that peripheral muscle metabolic and functional abnormalities in CHF can be improved without altering cardiac performance.

Aged↗
PubMed1989

Forearm metabolic asymmetry detected by 31P-NMR during submaximal exercise.

This study evaluated the relationship of skeletal muscle energy metabolism to forearm blood flow and muscle mass in the dominant (D) and nondominant (ND) forearms of normal subjects. 31P-Magnetic resonance spectroscopy was used to determine intracellular pH and the ratio of inorganic phosphate to phosphocreatine (Pi/PCr), an index of energy metabolism. Forearm blood flow and muscle mass were measured by venous occlusion plethysmography and magnetic resonance imaging, respectively. Metabolic measurements and flow were determined at rest and during submaximal exercise in both forearms. After a warm-up period, six normal right-handed male subjects performed 7.5 min of wrist flexion exercise in the magnet (1 contraction every 5 s), first with the ND forearm and then with the D forearm, at 23, 46, and 69 J/min. At rest, there were no differences between forearms in Pi/PCr or pH. However, at each work load the D forearm demonstrated significantly lower Pi/PCr and higher pH than the ND forearm. Blood flow was not significantly different between the forearms at rest or during exercise. Because these subjects were not engaged in unilateral arm training, we conclude that 1) Pi/PCr is lower and pH is higher in the D compared with the ND forearm in normal subjects during submaximal exercise, 2) these differences are independent of muscle mass and blood flow, and 3) the cumulative effect of long-term, low-level daily activity provides an adequate training stimulus for muscular metabolic adaptations.

Adult↗
PubMed1988

Fructose 2,6-bisphosphate-dependent regulation of phosphofructokinase in rat submandibular gland.

1. Regulation of phosphofructokinase in rat submandibular gland was non-Michaelis-Menten type at physiological pH. 2. At pH 7.3, ATP played a dual role on phosphofructokinase acting as a substrate and inhibitor at high concentration of ATP. 3. The activator of phosphofructokinase was present in cytosol fraction, and its properties were resemble to those of fructose 2,6-bisphosphate. 4. Both the activator and authentic fructose 2,6-bisphosphate relieved the inhibition of phosphofructokinase by ATP, and increased the affinity for fructose 6-phosphate. 5. Concentration of fructose 2,6-bisphosphate in rat submandibular gland was 8.22 nmol/g tissue, and which was about the half of that in liver. 6. Phosphofructokinase in rat submandibular gland was found to be regulated synergistically by ATP, fructose 6-phosphate and fructose 2,6-bisphosphate.

Adenosine Triphosphate↗
PubMed1986

Rapid average-flow velocity measurement by NMR.

We describe an NMR method to make a quick determination of average fluid velocity by monitoring the change in phase of the magnetization during a transient signal. We give an example utilizing the second Carr-Purcell-Meiboom-Gill echo in which we measured the velocity of water up to 54 cm/s where each velocity was determined by data taken over 2.5 ms.

Humans↗