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Biomedical subjects

S Miyahara

Publications and source records attributed to S Miyahara.

At least 19 recordsLinked to original sources
PubMed2006

Field-induced staggered magnetization and magnetic ordering in Cu2(C5H12N2)2Cl4.

We present a 2D NMR investigation of the gapped spin-1/2 compound Cu2(C5H10N2D2)2Cl4. Our measurements reveal the presence of a magnetic field-induced transverse staggered magnetization (TSM) which persists well below and above the field-induced 3D long-range magnetically ordered (FIMO) phase. The symmetry of this TSM is different from that of the TSM induced by the order parameter of the FIMO phase. Its origin, field dependence, and symmetry can be explained by an intradimer Dzyaloshinskii-Moriya interaction, as shown by DMRG calculations on a spin-1/2 ladder. This leads us to predict that the transition into the FIMO phase is not in the BEC universality class.

Journal Article↗
PubMed2006

Prospective 12-month course of bipolar disorder in out-patients with and without comorbid anxiety disorders.

BACKGROUND: The impact of anxiety disorders has not been well delineated in prospective studies of bipolar disorder. AIMS: To examine the association between anxiety and course of bipolar disorder, as defined by mood episodes, quality of life and role functioning. METHOD: A thousand thousand out-patients with bipolar disorder were followed prospectively for 1 year. RESULTS: A current comorbid anxiety disorder (present in 31.9% of participants) was associated with fewer days well, a lower likelihood of timely recovery from depression, risk of earlier relapse, lower quality of life and diminished role function over I year of prospective study. The negative impact was greater with multiple anxiety disorders. CONCLUSIONS: Anxiety disorders, including those present during relative euthymia, predicted a poorer bipolar course. The detrimental effects of anxiety were not simply a feature of mood state. Treatment studies targeting anxiety disorders will help to clarify the nature of the impact of anxiety on bipolar course.

Adolescent↗
PubMed2005

In vivo evaluation of ocular inflammatory responses in experimental diabetes.

AIMS: Diabetic patients may have abnormal inflammatory reactions to foreign or endogenous stimuli. This study was designed to evaluate inflammatory reactions in the diabetic eye through retinal leucocyte dynamics in the inflamed eyes of diabetic rats. METHODS: Three weeks after diabetes induction in Long-Evans rats, endotoxin induced uveitis was produced by footpad injection of lipopolysaccharide (LPS). After LPS injection, leucocyte behaviour was evaluated in vivo by acridine orange digital fluorography. RESULTS: The number of rolling leucocytes increased in a biphasic manner at 12 hours and 48 hours. The number of leucocytes accumulating in the retina reached a peak at 72 hours. The maximal numbers of rolling and accumulating leucocytes in the diabetic retina decreased by 56.3% (p<0.01) and 46.7% (p<0.0001), respectively, compared with the non-diabetic retina. The levels of mRNA expression of adhesion molecules in the retina, which were upregulated after LPS injection, were also lower in diabetic rats than in non-diabetic rats. CONCLUSION: This study is the first to show that endotoxin induced inflammation is disturbed in the diabetic eye, based on evidence that the leucocyte-endothelial cell interactions stimulated by LPS were suppressed in the diabetic retina. These findings support the theory that ocular inflammatory reactions are impaired in diabetic patients.

Animals↗
PubMed2003

[Irrigation for the post-pneumonectomy empyema infected by methicillin-resistant Staphylococcus aureus without broncho-pleural fistula; report of a successful case].

It has been known that treatments of post-pneumonectomy empyema are difficult. We report a successful case of irrigation for the post-pneumonectomy. The patient was 68-year-old man with advanced lung cancer. He underwent induction chemoradiotherapy following by pneumonectomy of the right side. A few days later after the chest drain was withdrawn, spike fever appeared. Empyema was suspected, so a 28 Fr diameter double lumen chest drain was intubated again. Turbid effusion was discharged through the drain, in which methicillin-resistant staphylococcus aureus (MRSA) was cultured. Irrigation using a lot of saline and acid electrolyzed water started. A month later, irrigator through the drain was looking clear, however, MRSA was cultured so far. After putting minomycine into the irrigator, MRSA died away. This physical and chemical irrigations were effective.

Adenocarcinoma↗
PubMed2002

Magnetic superstructure in the two-dimensional quantum antiferromagnet SrCu2(BO3)2.

We report the observation of magnetic superstructure in a magnetization plateau state of SrCu2(BO3)2, a frustrated quasi-two-dimensional quantum spin system. The Cu and B nuclear magnetic resonance (NMR) spectra at 35 millikelvin indicate an apparently discontinuous phase transition from uniform magnetization to a modulated superstructure near 27 tesla, above which a magnetization plateau at 1/8 of the full saturation has been observed. Comparison of the Cu NMR spectrum and the theoretical analysis of a Heisenberg spin model demonstrates the crystallization of itinerant triplets in the plateau phase within a large rhomboid unit cell (16 spins per layer) showing oscillations of the spin polarization. Thus, we are now in possession of an interesting model system to study a localization transition of strongly interacting quantum particles.

Journal Article↗
PubMed2002

Recurrent palmar dislocation of the distal radioulnar joint. A case report.

Recurrent palmar dislocation of the distal radioulnar joint is not a common injury. We report one case in a 73-year-old female. This injury was incorrectly diagnosed at the first presentation because there has been no distinct deformity at the wrist and extension-flexion was normal. The need for proper physical examination and accurate radiographic positioning is stressed. Distal diaphysis resection combined with distal radioulnar arthrodesis (modified Sauve-Kapandji procedure) was the preferred method of treatment in an old patient. Two years after the injury, the patient was asymptomatic.

Age Factors↗
PubMed2001

Nociceptin/orphanin FQ and [Phe(1)psi(CH2-NH)Gly2]nociceptin(1-13)NH2 modulates the activity of hypothalamic paraventricular nucleus neurons in vitro.

Nociceptin, also known as orphanin FQ (N/OFQ), an endogenous ligand for the orphan opioid receptor-like(1) (ORL(1)) receptor, is moderately expressed in the hypothalamic paraventricular nucleus (PVN) involved in the integrative control of the function of the endocrine and autonomic nervous systems. Our previous study demonstrated that intracerebroventricular administration of N/OFQ elicits an inhibitory action on the function of the cardiovascular and sympathetic nervous systems in conscious rats. However, the effects of N/OFQ on PVN neurons have not been examined. We investigated the effects of N/OFQ on PVN neurons using a whole-cell patch-clamp recording technique in rat brain slices. N/OFQ (30-1000 nM) hyperpolarized membrane potentials in type 1 and type 2 neurons of the PVN classified by the electrophysiological property. [Phe(1)psi(CH2-NH)Gly2]nociceptin(1-13)NH2 (Phepsi) (1-9 microM), a presumed competitive antagonist of the ORL(1) receptor, also hyperpolarized membrane potential in both types of neurons. In voltage clamp studies, N/OFQ (3-3000 nM) activated a K+ current concentration-dependently in 69.7% of PVN neurons with an EC(50) of 72.4+/-12 nM. Phepsi (100-9000 nM) also activated a K+ current with an EC(50) of 818+/-162 nM in PVN neurons, and significantly reduced the amplitude of the N/OFQ-stimulated current. The N/OFQ-induced current was not antagonized by the classical opioid receptor antagonist naloxone and putative antagonist nocistatin. These findings suggest that N/OFQ may have a functional role in the PVN.

Animals↗
PubMed2001

Low-lying magnetic excitation of the Shastry-Sutherland model.

By using perturbation calculation and numerical diagonalization, the low-energy spin dynamics of the Shastry-Sutherland model is investigated with particular attention to the two-particle coherent motion. In addition to spin-singlet- and triplet-bound states, we find novel branches of coherent motion of a bound quintet pair, which are usually unstable because of repulsion. Unusual dispersion observed in neutron-scattering measurements is explained by the present theory. The importance of the effects of phonons is also pointed out.

Journal Article↗
PubMed2001

Long-term enhancement of synaptic transmission induced by veratridine in rat CA3 hippocampal neurons.

Veratridine is a neurotoxin that induces persistent activation of sodium channels in excitable cells. We investigated the effects of this toxin on excitatory synaptic transmission in CA3 neurons of juvenile rat hippocampus using whole-cell patch-clamp and field-potential recordings. The population spikes evoked by electrical stimulation of the mossy fiber were gradually enhanced after washout of veratridine (0.3 microM), but they were not enhanced by the co-application of veratridine and an N-methyl-D-aspartate (NMDA) receptor antagonist (D-APV, 30 microM). When a pipette solution contained QX-314 that antagonized the effect of veratridine in the recorded neuron, oscillatory membrane depolarization appeared in the early stage during bath-application of veratridine and gradually decreased in the late stage. After washout of veratridine, however, the oscillatory depolarization was gradually restored and maintained for at least 3 h. This oscillatory depolarization was also abolished by D-APV. We suggest that the activation of NMDA receptors is involved in the veratridine-induced long-lasting enhancement in the excitatory synaptic transmission in rat CA3 hippocampal neurons.

2-Amino-5-phosphonovalerate↗
PubMed2001

Liver injury in acute pancreatitis and mitigation by continuous arterial infusion of an antibiotic via the superior mesenteric artery.

Macrophage-derived inflammatory mediators, such as tumor necrosis factor-alpha (TNF-alpha), have been shown to play a central role in aggravation of acute pancreatitis (AP), but little is known about their roles in liver injury. We investigated the pathogenesis of the liver injury in AP and assessed the efficacy of arterial infusion of an antibiotic via the superior mesenteric artery (SMA). Infusion of saline (group A) or imipenem (group B) was started 6 hours after induction of AP in dogs by intraductal administration of autologous gallbladder bile. The survival rate in group B was significantly improved compared with group A. Serum alanine aminotransferase levels in peripheral blood and endotoxin levels in portal vein blood were both significantly higher at 18 hours in group A than in group B. When hepatocytes and Kupffer cells were isolated at 18 hours and cultured for 24 hours thereafter, there was significant exacerbation of the hepatocyte injury and significantly greater production of TNF-alpha in the coculture of hepatocytes and Kupffer cells in group A, indicating that the Kupffer cells had been activated. By contrast, both of these manifestations were significantly mitigated in group B. These findings suggest that TNF-alpha secreted by endotoxin-activated Kupffer cells contributes to liver injury in AP, and that SMA infusion of an antibiotic mitigates the liver injury by controlling endotoxin translocation.

Alanine Transaminase↗
PubMed2001

Orexin depolarizes rat hypothalamic paraventricular nucleus neurons.

Orexins, also called hypocretins, are newly discovered hypothalamic peptides that are thought to be involved in various physiological functions. In spite of the fact that orexin receptors, especially orexin receptor 2, are abundant in the hypothalamic paraventricular nucleus (PVN), the effects of orexins on PVN neurons remain unknown. Using a whole cell patch-clamp recording technique, we investigated the effects of orexin-B on PVN neurons of rat brain slices. Bath application of orexin-B (0.01-1.0 microM) depolarized 80.8% of type 1 (n = 26) and 79.2% of type 2 neurons tested (n = 24) in the PVN in a concentration-dependent manner. The effects of orexin-B persisted in the presence of TTX (1 microM), indicating that these depolarizing effects were generated postsynaptically. Addition of Cd(2+) (1 mM) to artificial cerebrospinal fluid containing TTX (1 microM) significantly reduced the depolarizing effect in type 2 neurons. These results suggest that orexin-B has excitatory effects on the PVN neurons mediated via a depolarization of the membrane potential.

Animals↗
PubMed2001

An estimation of economic effects of tele-home-care: hospital cost-savings of the elderly.

Tele-home-care (or tele-medicine) is being implemented by the application of multimedia such as CATV and ISDN. In this paper, by focusing on the so-called "social hospitalization of the aged," we carry out an estimation of the extent to which tele-home-care based on multimedia can help in saving the cost of hospitalization of the aged in the future. Estimation consists of the following two parts. First, we estimate the trends of the aged population and their hospital expenses using the regression analysis. Second, we assume that new technology such as multimedia and new medical instruments develop according to a logistic curve. Thus, we estimate the rate of diffusion of CATV and ISDN by logistic curves. Then, by multiplying this number by hospital costs per elderly patient as estimated previously, we have been able to calculate the extent to which hospitalization costs can be saved in the entire economy. Our results indicated that in the year 2050, US$257.3 billion, or nearly 7.4% of total hospitalization costs of the aged could be saved by tele-home-care.

Aged↗
PubMed2000

Effects of repeated stress on expression of interleukin-6 (IL-6) and IL-6 receptor mRNAs in rat hypothalamus and midbrain.

We examined the effects of single and repeated stress on the expression of interleukin-6 (IL-6) and IL-6 receptor (IL-6R) mRNAs in the rat midbrain and hypothalamus using reverse transcriptase-polymerase chain reaction (RT-PCR). Following a single episode of restraint stress for 4 hours (1R) or 4 hours per day on two (2R) or three (3R) consecutive days, the hypothalamus and midbrain were removed immediately and the levels of IL-6 and IL-6R mRNAs in both regions were determined. Regional differences in stress-related changes in mRNA levels were noted. The expression of IL-6 mRNA in the hypothalamus did not change in 1R group but decreased in 2R and 3R groups. The expression of IL-6R mRNA in the same region significantly diminished in all groups. In the midbrain, the expression of IL-6 mRNA increased in 1R group and decreased in 2R and 3R, while the expression of IL-6R mRNA significantly diminished in 1R and 3R groups but was not different from control in 2R group. Our findings indicate that repeated stress in rats produce changes in IL-6 and IL-6R mRNAs in the midbrain and hypothalamus that are different than those of a single stress episode.

Animals↗
PubMed1999

Effects of restraint stress on alpha(1) adrenoceptor mRNA expression in the hypothalamus and midbrain of the rat.

We examined the effects of restraint stress on alpha(1) adrenoceptor mRNA expression in the rat brain using reverse transcriptase-polymerase chain reaction (RT-PCR). After rats had been restrained for 10, 30, 60, 120 or 240 min, the hypothalamus and midbrain were removed immediately and alpha(1) adrenoceptor mRNA levels in these regions were determined by RT-PCR. Blood samples were also collected for simultaneous measurement of serum adrenocorticotropic hormone (ACTH) and corticosterone. Restraint stress resulted in a variety of changes in the hypothalamus and midbrain. In the hypothalamus, 30 and 60 min of stress resulted in a significant fall in the level of alpha(1) adrenoceptor mRNA relative to the control. This was associated with a rise in serum ACTH and corticosterone. In the midbrain, significant elevation of alpha(1) adrenoceptor mRNA was noted after 60, 120 and 240 min of restraint stress. Our findings indicated that the influence of restraint stress on alpha(1) adrenoceptor mRNA level in the hypothalamus is different to that of the midbrain region in rats.

Adrenocorticotropic Hormone↗
PubMed1999

Effects of single and repeated stresses on the expression of mRNA for alpha1-adrenoceptors in the rat hypothalamus and midbrain.

We examined the effects of single or repeated stress on the expression of mRNA for alpha1-adrenoceptors in the rat hypothalamus and midbrain using the reverse transcriptase-polymerase chain reaction (RT-PCR). Single stress significantly increased the mRNA level for alpha1-adrenoceptors in the midbrain, but had no effect on mRNA levels in the hypothalamus. Repeated stress significantly decreased mRNA levels for alpha1-adrenoceptors in both regions.

Animals↗
PubMed1999

Hepatocellular carcinoma complicated by gastrointestinal hemorrhage caused by direct tumor invasion of stomach.

A 65-year-old man with multiple hepatocellular carcinoma (HCC) underwent intra-hepato-arterial chemotherapy (IHAC) through an implantable port over a period of 10 months after transcatheter arterial embolization (TAE) had been performed three times. TAE was performed twice more, and radiotherapy (total dose, 30 Gy; given over a 3-week period) was given for progressive disease in the lateral segment of the liver. Three months after the radiotherapy had finished, the patient suddenly developed melena. Diagnostic imaging revealed gastrointestinal (GI) hemorrhage from HCC invading the stomach, and total gastrectomy and lateral segmentectomy of the liver were performed because the bleeding could not be controlled. The resected specimen disclosed a centrally necrotic tumor that had invaded the lesser gastric curvature and perforated into the lumen. Pathology examination revealed that the HCC had expansively invaded the gastric mucosa, resulting in exposure in the lumen. The possible mechanisms of direct GI invasion by HCC are briefly discussed, with a review of the literature. GI bleeding secondary to involvement by HCC is rare. The enteric radiation injury seems to have been largely responsible for the GI bleeding in this patient.

Aged↗