Biomedical subjects

R Sakamoto

Publications and source records attributed to R Sakamoto.

At least 19 recordsLinked to original sources

PubMed2006

Observation of stable superdense core plasmas in the large helical device.

In reduced recycling discharges in the Large Helical Device, a super dense core plasma develops when a series of pellets are injected. A core region with density as high as 4.5 x 10(20) m(-3) and temperature of 0.85 keV is maintained by an internal diffusion barrier with very high-density gradient. These results may extrapolate to a scenario for fusion ignition at very high density and relatively low temperature in helical devices.

Journal Article↗

PubMed2006

Slow transition of energy transport in high-temperature plasmas.

A new slow transition process for energy transport in magnetically confined plasmas is reported. The slow transition is characterized by the change between two metastable transport conditions characterized by a weak and a strong electron temperature (Te) dependence of normalized heat flux. These two branches are found to merge at the critical gradient. In metastable transport, the derivative of normalized heat flux to the Te gradient, [EQUATION: SEE TEXT], is positive, while it becomes negative during the transition phase. The time for the transition increases as the normalized Te gradient is increased and exceeds the transport time scale characterized by the global energy confinement time.

Journal Article↗

PubMed2006

[Successful surgical management of papillary muscle rupture following acute myocardial infarction in an elderly patient].

Papillary muscle rupture is rare but catastrophic complication of acute myocardial infarction. We report a 91-year-old woman who underwent successful management of papillary muscle rupture following acute myocardial infarction. She was transferred to our hospital because of severe pulmonary edema and cardiogenic shock. Echocardiography revealed severe mitral valve regurgitation due to total rupture of anterolateral papillary muscle. After intubation, intraaortic balloon pumping (IABP) and percutaneous cardiopulmonary support (PCPS) insertion, mitral valve replacement was successfully performed. She was discharged 134 days after operation. In papillary muscle rupture deteriorating hemodynamics, early diagnosis and immediate cardiopulmonary support are required before surgical treatment. She was, to the best of our knowledge, the oldest among the reported cases of successful surgical treatment of papillary muscle rupture in Japan.

Aged, 80 and over↗

PubMed2003

Sawtooth oscillation in current-carrying plasma in the large helical device.

Sawtooth oscillations have been observed in current-carrying helical plasmas by using electron-cyclotron-emission diagnostics in the Large Helical Device. The plasma current, which is driven by neutral beam injection, reduces the beta threshold of the sawtooth oscillation. When the central q value is increased due to the plasma current, the core region crashes, and, when it is decreased, the edge region crashes annularly. Observed rapid mixture of the plasma in the limited region suggests that these sawtooth crashes are reconnection phenomena. Unlike previous experiments, no precursor oscillation has been observed.

Journal Article↗

PubMed2003

Conversion factors for a mobile survey method by car in the Chernobyl area.

Conversion factors for the purpose of mobile survey by car in the Chernobyl area have been evaluated using simulation calculations. In the calculations, the width of road is assumed as being 4 m, 10 m and 20 m and the surrounding area is divided into ten zones contaminated homogeneously by 137Cs with different depth profiles in the ground. The air kerma contribution from all zones to the road is simulated. A conversion factor is calculated by dividing the air kerma rate in typical land-use adjacent to the road by that on the road. Conversion factors in various land uses around the roads are examined. The calculated conversion factors agree with the conversion factors measured in the Chernobyl area within an accuracy of 20%. Further, basic data, needed for composing conversion factors appropriate to other contaminated regions with different depth distributions from the Chernobyl area, are also indicated.

Air Pollutants, Radioactive↗

PubMed2002

Island dynamics in the large-helical-device plasmas.

In the Large Helical Device plasma discharges, the size of an externally imposed island with mode number ( n/m = 1/1) decreases substantially when the plasma is collisionless ( nu(*)< approximately 1) and the beta is finite ( > approximately 0.1%) at the island location. For the collisional plasmas with finite beta, on the other hand, the size of the island increases. However, there is a threshold in terms of the vacuum island size below which the island enlargement is not seen.

Journal Article↗

PubMed2001

Observation of the "self-healing" of an error field island in the large helical device.

It was observed that the vacuum magnetic island produced by an external error magnetic field in the large helical device shrank in the presence of plasma. This was evidenced by the disappearance of flat regions in the electron temperature profile obtained by Thomson scattering. This island behavior depended on the magnetic configuration in which the plasmas were produced.

Journal Article↗

PubMed2001

Reduction of ion thermal diffusivity associated with the transition of the radial electric field in neutral-beam-heated plasmas in the large helical device.

Recent large helical device experiments revealed that the transition from ion root to electron root occurred for the first time in neutral-beam-heated discharges, where no nonthermal electrons exist. The measured values of the radial electric field were found to be in qualitative agreement with those estimated by neoclassical theory. A clear reduction of ion thermal diffusivity was observed after the mode transition from ion root to electron root as predicted by neoclassical theory when the neoclassical ion loss is more dominant than the anomalous ion loss.

Journal Article↗

PubMed2001

Characterization of secretory type IIA phospholipase A2 (sPLA2-IIA) as a glycyrrhizin (GL)-binding protein and the GL-induced inhibition of the CK-II-mediated stimulation of sPLA2-IIA activity in vitro.

By means of heparin-affinity and glycyrrhizin (GL)-affinity column chromatographies (HPLC), a GL-binding phospholipase A2 (gbPLA2) was selectively purified from the synovial fluids of patients with rheumatoid arthritis. This purified gbPLA2 was identified as a secretory type IIA PLA2 (sPLA2-IIA) since it was crossreacted with anti-sPLA2-IIA serum. The activity of purified sPLA2-IIA was inhibited by glycyrrhetinic acid (GA) and a GA derivative (oGA) in a dose-dependent manner, but it was more sensitive to GA than GL. Furthermore, it was found that (i) purified sPLA2-IIA is phosphorylated by casein kinase II (CK-II) in vitro; (ii) this phosphorylation induces in a significant stimulation of PLA2 activity; and (iii) oGA at one-tenth the concentration of GL inhibits the CK-II-mediated stimulation of sPLA2-IIA activity. These results show that (i) sPLA2-IIA is a GL-binding protein; and (ii) CK-II mediates stimulation of its PLA2 activity in vitro.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2001

Characterization of bovine angiogenin-1 and lactogenin-like protein as glycyrrhizin-binding proteins and their in vitro phosphorylation by C-kinase.

Angiogenin-1 (p15, an angiogenesis inducer with RNase activity) and lactogenin-like protein (p17) isolated from partially purified bovine lactoferrin (bLF) preparations were characterized as glycyrrhizin (GL)-binding proteins (gbPs). As expected, bLF-affinity column chromatography confirmed these two gbPs to be bLF-binding proteins. These two purified gbPs exhibited RNase activities when incubated with poly(C) as a substrate. Both GL and glycyrrhetinic acid (GA) at 100 microM significantly inhibited RNase activities of these two gbPs, both of which functioned as phosphate acceptors of C-kinase in vitro. Phosphorylation of p15 and p17 by C-kinase was inhibited by GA in a dose-dependent manner with the 50% inhibition dose (ID50) of approx. 10 microM, whereas GL required a relatively high dose (300 microM) to inhibit significantly it. A GA derivative (oGA, ID50=approx. 0.3 microM) was found to be a potent inhibitor of the C-kinase-mediated phosphorylation of these two gbPs in vitro. In addition, a possible physiological significance of C-kinase on the physiological interaction between bLF and two bLF-binding proteins (p15 and p17) is noted.

Animals↗

PubMed2001

Inhibitory effect of glycyrrhizin on the phosphorylation and DNA-binding abilities of high mobility group proteins 1 and 2 in vitro.

The physiological correlation between glycyrrhizin (GL) and high mobility group proteins I and 2 (HMG1/2) and the inhibitory effect of GL on their phosphorylation by three protein kinases (CK-I, CK-II and PKC) were investigated biochemically in vitro. It was found that GL binds directly to HMG1/2, because (i) HMG1/2 have a high affinity with a GL-affinity column; and (ii) GL induces the conformational changes in HMG1/2. Both purified HMG1/2 functioned as phosphate acceptors for these two protein kinases (CK-I and PKC), but not phosphorylated by CK-II. Phosphorylation of HMG1/2 by two protein kinases (CK-I and PKC) was completely inhibited by a glycyrrhetinic acid derivative (oGA) at one-tenth the concentration of GL. Also, the DNA-binding abilities of HNG1/2 were reduced by GL in a dose-dependent manner. These results show that the binding of GL to HMG1/2 results in the inhibition of their physiological activities (DNA-binding ability and phosphorylation by PKC or CK-I) in vitro. The GL-induced inhibition of the physiological activities of HMG1/2 may be involved in the anti-inflammatory effect of GL in vivo.

Animals↗

PubMed2000

Smad7 selectively interferes with different pathways of activin signaling and inhibits erythroid leukemia cell differentiation.

Smad family proteins are essential for transforming growth factor beta (TGF-beta) signal mediation downstream of a heteromeric complex of the type I and type II receptor serine/threonine kinases. A distant family member, Smad7, is expressed in most mammalian tissues and cells and prevents TGF-beta signaling. In this study, we examined the physiologic role of Smad7 in mediating the effects of activin, a member of the TGF-beta superfamily of peptides that functions in a number of processes, including blood-cell development. We report here that Smad7 expression is specifically absent in particular hematopoietic cells that respond to activin by differentiating into the erythroid lineage and that ectopic production of Smad7 causes mouse erythroid leukemia (F5-5) cells to become resistant to activin induction of erythroid differentiation. When coexpressed with type I activin receptor ActR-I or ActR-IB in concert with type II receptor ActR-II, Smad7 efficiently reduced an early transcriptional response mediated by ActR-I but had only a minimal effect on the response mediated by ActR-IB. In the presence of Smad7, overexpression of an activated form of ActR-IB, but not of an activated form of ActR-I, induced F5-5 cells to differentiate. These results suggest that Smad7 selectively interferes with the ActR-I pathway in activin signal transduction. The findings also indicate the existence of a novel activity of Smad7 that inhibits erythroid differentiation by blocking intracellular signaling of activin.

3T3 Cells↗

PubMed2000

Energy confinement time and heat transport in initial neutral beam heated plasmas on the large helical device

The confinement characteristics of large net-current-free plasmas heated by neutral-beam injection have been investigated in the Large Helical Device (LHD). A systematic enhancement in energy-confinement times from the scaling derived from the medium-sized heliotron/torsatron experiments have been observed, which is attributed to the edge pedestal. The core confinement is scaled with the Bohm term divided by the square root of the gyro radii. The comparative analysis using a dimensionally similar discharge in the Compact Helical System indicates gyro-Bohm dependence in the core and transport improvement in the edge region of LHD plasmas.

Journal Article↗

PubMed2000

Reverse geometry contact lens wear after photorefractive keratectomy, radial keratotomy, or penetrating keratoplasty.

PURPOSE: To determine if a super diffusion coefficient of lens/lens thickness (Dk/L) reverse geometry gas permeable (steep peripheral and flatter central curve) contact lenses can be successfully worn after excimer photorefractive keratectomy (PRK), radial keratotomy (RK), or penetrating keratoplasty (PK). METHODS: Patients with residual ametropia after PRK, RK, or PK were fitted with reverse geometry lenses (Plateau lens in SF-P material; Menicon USA, Inc, Clovis, CA, U.S.A.). Contact lens fit characteristics and comfort were assessed. Lens centration, visual quality, and ocular surface status were graded and visual acuity charted. RESULTS: Thirteen eyes of 11 patients were fitted; eight eyes with PRK, one eye with RK, and four eyes with PK previously performed. The mean follow up of the patients was six months. The visual acuity prior to lenses ranged from 6/12 to counting fingers, and the acuity with lenses ranged from 6/6 to 6/30. Eight of the 11 patients wore the lenses the whole day without problems; 3 patients discontinued lens wear due to discomfort or unsatisfactory vision. CONCLUSIONS: The combination of super Dk/L and reverse geometry lenses facilitate lens wear and is associated with good visual acuity.

Adult↗

PubMed1999

Incidence of Haemophilus influenzae in the throats of healthy infants with different feeding methods.

BACKGROUND: Haemophilus influenzae is the major cause of otitis media and lower respiratory tract infection in childhood. In the presence of human milk, which contains numerous host defense factors, Haemophilus influenzae may be inhibited in attaching to and colonizing pharyngeal cells. We investigated the incidence of H. influenzae in the throats of 162 healthy infants with different feeding methods: 70 breast-fed, 49 mixed-fed and 43 formula-fed infants. METHODS AND RESULTS: Haemophilus influenzae was identified using standard microbiological procedures and the API NH system. The incidence of H. influenzae in breast-fed infants, mixed-fed infants and formula-fed infants was 0, 0 and 7.0% respectively. CONCLUSION: The results suggest that the colonization of H. influenzae in the throat was inhibited by the presence of breast milk.

Bacterial Adhesion↗

PubMed1999

Electrophysiological properties of the left atrium evaluated by coronary sinus pacing in patients with atrial fibrillation.

Repetitive atrial firing (RAF), marked fragmentation of atrial activity (FAA), and interatrial conduction delay (CD) have been shown to be electrophysiological features of the atrium in patients with atrial fibrillation (AF). Moreover, it has been observed that atrial extrastimuli are more likely to induce AF when delivered from the right atrial appendage (RAA) than from the distal coronary sinus (CSd). We examined the electrophysiological properties of the atrial muscle by CS and RAA stimulation in patients with paroxysmal AF. Patients were divided into two groups: group I, consisting of 18 patients with clinical paroxysmal AF; and group II, consisting of 22 patients with various cardiac arrhythmias in which the substrate does not exist in the atrium. In group I, the following values of electrophysiological parameters of the atrium indicated that AF was more likely to be induced during RAA pacing than CSd pacing: atrial effective refractory period (RAA vs CSd: 201 +/- 28 ms vs 240 +/- 35 ms, P < 0.001), RAF zone (16 +/- 25 ms vs 0 +/- 0 ms, P < 0.03), FAA zone (38 +/- 37 ms vs 5 +/- 19 ms, P < 0.01), maximum interatrial conduction time (144 +/- 19 ms vs 93 +/- 19 ms, P < 0.0001) and CD zone (53 +/- 21 ms vs 9 +/- 18 ms, P < 0.0001). The values of the electrophysiological parameters of the atrium evaluated by CSd pacing in group I patients were not significantly different from those in group II patients. In conclusion, when coronary sinus stimulation is performed, electrophysiological properties of the atrium in patients with AF show a significant decrease in atrial vulnerability compared to stimulation from RAA and also show similar values to those in patients without AF. It might be suggested that the left posterior or posterolateral atrium is electrophysiologically stable even in patients with paroxysmal AF.

Adult↗

PubMed1998

[Abnormalities of electrocardiographic P wave morphology and the relationship to electrophysiological parameters of the atrium in patients with idiopathic paroxysmal atrial fibrillation].

In 39 patients with idiopathic paroxysmal atrial fibrillation (PAF group), the incidence of the abnormal P wave morphology (prolonged P wave and mitral P in lead II and increased P terminal force in lead V1: PTF V1) was examined, and the relationships to the electrophysiologic findings of the atrial muscle were investigated. The control group consisted of 42 patients with various cardiac arrhythmias other than sick sinus syndrome. P wave duration was significantly longer in the PAF group than in the control group (112 +/- 12 vs 98 +/- 10 msec, p < 0.0001). PTF V1 was greater in the PAF group than in the control group (0.051 +/- 0.018 vs 0.028 +/- 0.010 msec, p < 0.0001). P mitrale occurred in only 5 patients (12%) in the control group as compared to 25 patients in the PAF group (64%, p < 0.0001). The longest duration of the right atrial electrograms was longer in the PAF group than in the control group (101 +/- 17 vs 85 +/- 10 msec, p < 0.0001), as was the maximal number of the fragmented deflections (8.0 +/- 2.5 vs 5.8 +/- 1.4, p < 0.0001). Repetitive atrial firing zone and also fragmented atrial activity zone were longer in the PAF group than in the control group (34 +/- 24 vs 12 +/- 19 msec, p < 0.02 and 47 +/- 27 vs 24 +/- 19 msec, p < 0.001, respectively). Interatrial conduction delay zone was longer in the PAF group than in the control group (55 +/- 25 vs 38 +/- 18 msec, p < 0.001). P wave duration and PTF V1 had significant and/or borderline correlations with the longest duration of the right atrial electrocardiograms (r = 0.75, p < 0.0001 and r = 0.68, p < 0.0001, respectively), and the maximal number of its fragmented defections (r = 0.50, p < 0.002 and r = 0.40, p < 0.05, respectively). Furthermore, P wave duration had a correlation with the repetitive atrial firing zone (r = 0.55, p < 0.01). Prolonged P wave duration and increased PTF V1 are electrocardiographic indicators for the coexistence of electrophysiologic abnormalities in patients with idiopathic paroxysmal atrial fibrillation.

Adult↗

PubMed1996

Liver function and morphology after resuscitation from severe hemorrhagic shock with hemoglobin solutions or autologous blood.

OBJECTIVE: To test the effects of three hemoglobin solutions on liver function and hepatic morphology after resuscitation from severe hemorrhagic shock. DESIGN: Prospective study. SETTING: Laboratory. SUBJECTS: Thirty-three beagle dogs. INTERVENTION: Hemorrhagic shock was induced in anesthetized dogs by removal of blood at a rate of 2 mL/kg/min until systolic blood pressure (BP) reached 50 mm Hg. BP was maintained at this level 2 hrs by further withdrawing 5 to 10 mL aliquots whenever BP increased > 50 mm Hg. Resuscitation was then initiated with autologous whole blood (n = 7), 4% pyridoxalated-hemoglobin-polyoxyethylene conjugate (4% PHP [n = 6]), 8% pyridoxalated-hemoglobin-polyoxyethylene conjugate (8% PHP [n = 9], or 8% stroma-free hemoglobin (n = 7). Four dogs were managed identically but were not resuscitated. Gross necropsy and histologic examination of the liver were performed on all dogs after 7 days, or earlier if death occurred. MEASUREMENTS AND MAIN RESULTS: In vitro interferences of PHP and stroma-free hemoglobin with liver function tests were determined and recommendations for interpretation of results from blood samples containing PHP and stroma-free hemoglobin were made. Blood was collected before, during, and after resuscitation from hemorrhagic shock. The dogs were then awakened and survivors were monitored daily with blood sampling until they were killed and necropsy was performed. After 7 days, the survival rate following hemorrhagic shock was 100% for whole blood and 4% PHP, 86% for stroma-free hemoglobin, and 33% for 8% PHP. Of the resuscitated dogs not surviving 7 days, all but one died within 27 hrs from coagulopathy. All dogs not resuscitated died within 1.75 hrs after 2 hrs of shock. Bilirubin, alkaline phosphatase, and lactic dehydrogenase concentrations could not be measured due to interferences of stroma-free hemoglobin and PHP. Aspartate (AST) and alanine (ALT) aminotransferase concentrations could be measured after dilution to overcome the interferences. Significant increases in AST and ALT values in all groups 24 hrs after resuscitation were attributed to hypoxic hepatocellular damage associated with the severity of the shock model rather than to the resuscitation fluid. Liver histology showed no changes attributed to toxic damage of hepatocytes in dogs resuscitated with stroma-free hemoglobin or PHP. However, changes, were less severe in dogs resuscitated with 4% PHP than in other groups. CONCLUSION: Morphologic studies at necropsy and liver function tests in dogs receiving hemoglobin solutions, compared with autologous blood, support the conclusion that the PHP and stroma-free hemoglobin solutions tested did not produce hepatic toxicity when used as resuscitation fluids in this model of severe shock.

Acute Disease↗