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M Asakawa

Publications and source records attributed to M Asakawa.

At least 19 recordsLinked to original sources
PubMed2006

Anomalous viscosity of an expanding quark-gluon plasma.

We argue that an expanding quark-gluon plasma has an anomalous viscosity, which arises from interactions with dynamically generated color fields. We derive an expression for the anomalous viscosity in the turbulent plasma domain and apply it to the hydrodynamic expansion phase, when the quark-gluon plasma is near equilibrium. The anomalous viscosity dominates over the collisional viscosity for weak coupling and not too late times. This effect may provide an explanation for the apparent "nearly perfect" liquidity of the matter produced in nuclear collisions at the Relativistic Heavy Ion Collider without the assumption that it is a strongly coupled state.

Journal Article↗
PubMed2006

Spontaneous scratching behaviour in DS-Nh mice as a possible model for pruritus in atopic dermatitis.

Itching is one of the major clinical symptoms in atopic dermatitis (AD) and complicates the management of this pathological condition. An animal model of AD-like pruritus would contribute to a better understanding of AD and could lead to the development of safe and effective antipruritic agents. DS non-hair (DS-Nh) mice raised under conventional conditions spontaneously develop pruritus, which is associated with a dermatitis similar to human AD. There is a significant positive correlation between disease severity and the period of scratching behaviour in DS-Nh mice. In the present study, we found that levels of histamine and nerve growth factor (NGF) in serum and/or skin tissue were higher in DS-Nh mice with AD-like dermatitis than in age-matched mice without dermatitis. The histopathological data indicated that nerve fibres extend into and mast cells infiltrate the surrounding area of the skin lesion. NGF production by XB-2 cells, which was derived from mouse keratinocytes, was enhanced by histamine via the H1 receptor. We also found that prolonged treatment with an H1-antagonist was effective against pruritus through depression of the production of NGF, which is thought to be generated by keratinocytes. We conclude that DS-Nh mice can serve as a suitable model for gaining a better understanding of pruritus in AD, and that prolonged treatment with an H1-antagonist may be beneficial in patients with AD-associated pruritus.

Animals↗
PubMed2004

J/psi and eta(c) in the deconfined plasma from lattice QCD.

Analyzing correlation functions of charmonia at finite temperature (T) on 32(3)x(32-96) anisotropic lattices by the maximum entropy method (MEM), we find that J/psi and eta(c) survive as distinct resonances in the plasma even up to T approximately 1.6T(c) and that they eventually dissociate between 1.6T(c) and 1.9T(c) (T(c) is the critical temperature of deconfinement). This suggests that the deconfined plasma is nonperturbative enough to hold heavy-quark bound states. The importance of having a sufficient number of temporal data points in MEM analyses is also emphasized.

Journal Article↗
PubMed2003

Distribution of anxiogenic-induced c-Fos in the forebrain regions of developing rats.

An anxiogenic or a pharmacological stressor, N-methyl-beta-carboline-3-carboxamide (FG-7142), (20 mg/kg, intraperitoneally injected) induced a dense nuclear c-Fos-like immunoreactivity in the pyriform cortex, cingulate and retrosplenial cortex, layers II-VI of the neocortex, lateral habenula, lateral septum, paraventricular nucleus of the thalamus, striatum, central and medial nucleus of the amygdala, but a sparse c-Fos immunostaining in the hippocampus and layer I of the neocortex in the forebrain of 56-day-old rats. Among these regions, the 8-day-old rats expressed much fewer c-Fos-positive cells in the neocortex, lateral habenula, lateral septum and medial nucleus of the amygdala than the young adult rats following the FG-7142 injection. These differences in the regional distribution of a neuronal activity marker, c-Fos, could reflect the postnatal development of neuronal populations or neuron circuits involved in stress and/or emotional response in the forebrain.

Aging↗
PubMed2003

DS-Nh as an experimental model of atopic dermatitis induced by Staphylococcus aureus producing staphylococcal enterotoxin C.

DS-Nh mice raised under conventional conditions spontaneously develop dermatitis similar to human atopic dermatitis (AD), which is associated with staphylococcal infection. In the present study, we show that Staphylococcus aureus producing staphylococcus exotoxin C (SEC) was recovered from the culture of the skin lesions of DS-Nh mice with AD-like dermatitis and that the serum levels of anti-SEC antibodies from these mice were elevated. We describe here how to promote experimental AD by epicutaneous injection with SEC-producing S. aureus to DS-Nh mice. In order to assess the role of SEC in the pathogenesis of AD, the mitogenic activity, TCRBV repertoire analysis and the production of IL-4 and IFN-gamma from spleen mononuclear cells (MNC) from DS-Nh stimulated by SEC were compared with those due to SEA, SEB and TSST. The weakest was the mitogenic activity of SEC, and higher IL-4 responses and lower IFN-gamma responses to SEC showed correlation with TCRBV8S2-positive T cells, which were selectively stimulated by SEC. We also demonstrate that SEC-producing S. aureus was able to survive in DS-Nh after intradermal injection. These results suggest a possible role for SEC in the pathogenesis of AD through host-S. aureus relationships.

Animals↗
PubMed2002

Hymenolepis pseudodiminuta Tenora et al. 1994 from Apodemus speciosus and H. diminuta: a comparison of experimental infections in rats.

The successful maintenance of Hymenolepis pseudodiminuta, isolated from Apodemus speciosus, is described for the first time. In the laboratory, the flour beetle, Tribolium confusum, and F344 rats could serve as intermediate and definitive hosts, respectively. In single worm infections with H. pseudodiminuta, which were carried in two groups of rats, adult worms were recovered from eight and seven out of ten rats, respectively, while Hymenolepis diminuta was found in all of ten rats 6 weeks after inoculation. The worm weight of H. pseudodiminuta in rats was significantly lower than that of H. diminuta. The egg output of H. pseudodiminuta occurred significantly earlier than that of H. diminuta. The number of eggs in the faeces of H. diminuta-infected rats was approximately twofold higher than the number in the faeces of H. pseudodiminuta-infected rats throughout the course of the infection. Mucosal mast cells in rats infected with H. pseudodiminuta were significantly more common than in rats infected with H. diminuta. No detectable IgE antibodies were found in the uninfected and H. diminuta-infected rat groups; however total IgE was detected in H. pseudodiminuta-infected rats but the concentrations were variable between individuals.

Animals↗
PubMed2001

Seroprevalence of Borna disease virus in domestic animals in Xinjiang, China.

To investigate the animals infected with Borna disease virus (BDV) in Xinjiang, China, we examined for BDV antibodies in the sera from groups of 20 horses, sheep and cattle, and from 165 wild rodents (18 species) by ELISA and immunoblot. The serological study disclosed the presence of antibodies to both BDV-p24 and -p40 in the horses (20%) and sheep (25%), whereas no apparent positive reaction was detected either in cattle or rodents. The results suggested that BDV is prevalent in horses and sheep in the district investigated.

Animals↗
PubMed2001

Doppler-shifted cyclotron absorption of electron Bernstein waves via N( parallel)-upshift in a Tokamak plasma.

Extraordinary (X) waves are perpendicularly injected for electron Bernstein (B) wave heating into an Ohmically heated plasma from the inboard side in the WT-3 tokamak. Measurements show that absorption does not take place at the electron cyclotron resonance layer nor the upper hybrid resonance layer, but does happen midway between them. This is consistent with the ray tracing prediction, i.e., the poloidal field and poloidal inhomogeneity of toroidal field lead the B waves to have a large parallel refractive index N( parallel) (>1), and the B waves are damped away via the Doppler-shifted cyclotron resonance.

Journal Article↗
PubMed2001

Purification and identification of N-glycolylneuraminic acid (Neu5Gc) from the holothuroidea Gumi, Cucumaria echinata.

N-Glycolylneuraminic acid (Neu5Gc), precious sialic acid which could not be synthesized by a chemical method, occurrs in the body of holothuroidea, Gumi Cucumaria echinata. Gumi contains 85% of total sialic acid, as Neu5Gc, in the body. Neu5Gc was purified from dry powder of the body using Dowex 1-x8 (HCOO* form) anion exchange chromatography after mild acid hydrolysis with 0.1 N trifluoroacetic acid. Using GC-MS and 1H-NMR spectroscopy, the purified Neu5Gc was correctly identified to be Neu5Gc. The purity of Neu5Gc was more than 99%. This is the first report of purification and identification of Neu5Gc from holothuroidea by using anion exchange chromatography, GC-MS, and 1H-NMR.

Animals↗
PubMed2001

Anthracycline-induced cardiomyopathies evaluated by tissue Doppler tracking system and strain rate imaging.

OBJECTIVES: Anthracycline cardiotoxicity is known to occur from the subendocardial side of the left ventricular wall. Recent advances of tissue Doppler echocardiography may allow the evaluation of anthracycline cardiotoxicity by dividing the left ventricular wall into the subendocardial half and subepicardial half. The present study assessed the feasibility using the tissue Doppler echo tracking system (M-mode) and myocardial strain rate imaging (B-mode) to noninvasively detect anthracycline cardiotoxicity. METHODS: The tissue Doppler echo tracking system (M-mode) was used to measure systolic thickening of the subendocardial layer (delta Endo), subepicardial layer (delta Epi), and whole wall (delta Total) of the left ventricular posterior wall in 41 normal subjects and three groups of patients receiving anthracycline: 34 patients in the low dose group, 19 in the middle dose group, and 12 in the high dose group. Strain rate is the spatial gradient of local velocities, reflecting local compression and expansion rates not affected by overall heart motion. Myocardial strain rate imaging (B-mode) was used in 25 normal subjects, 9 patients in the low dose group, and 10 patients in the high dose group. The ratio of peak systolic strain rate of subendocardium to that of subepicardium (peak strain rate endo/epi), and the ratio of integrated strain rate during ejection time of subendocardium to that of subepicardium (integrated strain rate endo/epi) were measured. RESULTS: Tissue Doppler echo tracking system (M-mode) measurement of delta Endo/delta Epi showed the most distinct difference and the least overlap of the data between normal subjects and patients, whereas delta Total failed to show significant differences. Myocardial strain rate imaging (B-mode) measurement of integrated strain rate endo/epi showed the most distinct difference and the least overlap of the data between normal subjects and patients, but ejection fraction failed to show statistically significant differences. CONCLUSIONS: These methods are highly sensitive tools for monitoring anthracycline cardiotoxicity.

Anthracyclines↗
PubMed2001

[A case of choroidal hemangioma with bullous exudative retinal detachment treated successfully by transpupillary thermotherapy].

BACKGROUND: Choroidal hemangioma associated with bullous retinal detachment may be difficult to treat, due to varying results with conventional laser photocoagulation, radiotherapy, or surgical drainage. Here we report on a case of extensive bullous retinal detachment secondary to circumscribed choroidal hemangioma that was resolved after combined treatment with vitrectomy, silicone oil tamponade, and transpupillary thermotherapy. CASE: A 29-year-old woman presented with a large choroidal hemangioma in her right eye associated with serous retinal detachment. The tumor measured 8 disc diameters in size and was located in the inferotemporal macula, abutting the fovea. RESULTS: Laser photocoagulation of the tumor was unsuccessful in inducing absorption of subretinal fluid. Because of progressive bullous retinal detachment, surgery was performed consisting of external drainage of subretinal fluid, vitrectomy, endolaser photocoagulation of the tumor, and silicone oil tamponade. The silicone oil was removed four weeks postoperatively at which time almost complete resolution of the retinal detachment was observed. However, retinal detachment recurred eight weeks later, and transpupillary thermotherapy was then applied to the tumor. By four weeks after transpupillary thermotherapy, total reabsorption of subretinal fluid, visual acuity improvement, and decreased height of the choroidal hemangioma were noted. CONCLUSION: Transpupillary thermotherapy is an effective treatment for serous retinal detachment associated with choroidal hemangioma.

Adult↗
PubMed2001

[Cardiac hypertrophy and calcium signaling].

Numerous studies have implicated intracellular Ca(2+) as a signal for cardiac hypertrophy. It has recently been reported that the calcium-dependent phosphatase calcineurin plays a critical role in the development of cardiac hypertrophy. It is also reported that cyclosporin A and FK506, calcineurin inhibitors, inhibit the development of cardiac hypertrophy. Inhibiting the calcineurin activity may be of potential benefit for prevention of cardiac hypertrophy and heart failure.

English Abstract↗
PubMed2000

Peroxisome proliferator-activated receptor activators inhibit lipopolysaccharide-induced tumor necrosis factor-alpha expression in neonatal rat cardiac myocytes.

Peroxisome proliferator-activated receptors (PPARs) are transcription factors belonging to the nuclear receptor superfamily. Recently, PPAR activators have been shown to inhibit the production of proinflammatory cytokines in macrophages or vascular smooth muscle cells. It has been reported that tumor necrosis factor-alpha (TNF-alpha) expression is elevated in the failing heart and that TNF-alpha has a negative inotropic effect on cardiac myocytes. Therefore, we examined the effects of PPARalpha and PPARgamma activators on expression of TNF-alpha in neonatal rat cardiac myocytes. Northern blot analysis revealed expression of PPARalpha and PPARgamma mRNA in cardiac myocytes. Immunofluorescent staining demonstrated that both PPARalpha and PPARgamma were expressed in the nuclei of cells. When cardiac myocytes were transfected with PPAR responsive element (PPRE)-luciferase reporter plasmid, both PPARalpha and PPARgamma activators increased the promoter activity. Cardiomyocytes were stimulated with lipopolysaccharide (LPS), and the levels of TNF-alpha in the medium were measured by ELISA. After exposure to LPS, the levels of TNF-alpha significantly increased. However, pretreatment of myocytes with PPARalpha or PPARgamma activators decreased LPS-induced expression of TNF-alpha in the medium. Both PPARalpha and PPARgamma activators also inhibited LPS-induced increase in TNF-alpha mRNA in myocytes. In addition, electrophoretic mobility shift assays demonstrated that PPAR activators reduced LPS-induced nuclear factor-kappaB activation. These results suggest that both PPARalpha and PPARgamma activators inhibit cardiac expression of TNF-alpha in part by antagonizing nuclear factor-kappaB activity and that treatment with PPAR activators may lead to improvement in congestive heart failure.

Animals↗
PubMed2000

Fluctuation probes of quark deconfinement

The size of the average fluctuations of net baryon number and electric charge in a finite volume of hadronic matter differs widely between the confined and deconfined phases. These differences may be exploited as indicators of the formation of a quark-gluon plasma in relativistic heavy-ion collisions, because fluctuations created in the initial state survive until freeze-out due to the rapid expansion of the hot fireball.

Journal Article↗
PubMed2000

Paralytic toxins in a ribbon worm Cephalothrix species (Nemertean) adherent to cultured oysters in Hiroshima Bay, Hiroshima Prefecture, Japan.

In 1998, during the surveillance of the toxicity of various marine fouling organisms in Hiroshima Bay, Hiroshima Prefecture, Japan, specimens of the ribbon worm, "himomushi" Cephalothrix sp. (Nemertean) adherent to the shells of cultured oysters hanging onto floating culture rafts were found to contain toxins which showed strong paralytic action in mice throughout the survey period, February to May. The maximum toxicity (as tetrodotoxin, TTX) was 14,734 MU/g whole body. Attempts were made to identify the paralytic toxins in this worm. The "himomushi" toxin (HMT) was extracted from the worm with 80% methanol acidified with acetic acid and the extract defatted with dichloromethane. The aqueous layer was chromatographed on activated charcoal and the unbound and bound toxic fractions were analyzed by high-performance liquid chromatography and gas chromatography-mass spectrometry. It was rather unexpectedly revealed from these results that HMT was comprised of TTX, 4-epiTTX, anhydroTTX and three unidentified toxins. To our knowledge, this is the first report of the occurrence of toxic organisms, containing a high concentration of TTX, adherent to cultured bivalves such as oysters.

Animals↗
PubMed2000

Viral mutation accelerated by nitric oxide production during infection in vivo.

Nitric oxide (NO), superoxide (O(2)(-)), and their reaction product peroxynitrite (ONOO(-)) are generated in excess during a host's response against viral infection, and contribute to viral pathogenesis by promoting oxidative stress and tissue injury. Here we demonstrate that NO and peroxynitrite greatly accelerates the mutation of Sendai virus (SeV), a nonsegmented negative-strand RNA virus, by using green fluorescent protein (GFP) inserted into and expressed by a recombinant SeV (GFP-SeV) as an indicator for mutation. GFP-SeV mutation frequencies were much higher in the wild-type mice than in those lacking inducible NO synthase, suggesting that mutation of the virus in vivo is NO dependent. High levels of NO and NO-mediated oxidative stress were induced by GFP-SeV infection in the lung of the wild-type mice, but not in the iNOS-deficient mice, as evidenced by electron spin resonance spectroscopy and immunohistochemical analysis for nitrotyrosine formation as well as histopathological examination. Furthermore, peroxynitrite, an NO-derived reactive nitrogen intermediate, enhanced viral mutation in vitro. These results indicate that the oxidative stress induced by NO produced during the natural course of viral infection increases mutation, expands the quasispecies spectrum, and facilitates evolution of RNA viruses.

Animals↗
PubMed2000

A cytoplasmic RNA vector derived from nontransmissible Sendai virus with efficient gene transfer and expression.

We have recovered a virion from defective cDNA of Sendai virus (SeV) that is capable of self-replication but incapable of transmissible-virion production. This virion delivers and expresses foreign genes in infected cells, and this is the first report of a gene expression vector derived from a defective viral genome of the Paramyxoviridae. First, functional ribonucleoprotein complexes (RNPs) were recovered from SeV cloned cDNA defective in the F (envelope fusion protein) gene, in the presence of plasmids expressing nucleocapsid protein and viral RNA polymerase. Then the RNPs were transfected to the cells inducibly expressing F protein. Virion-like particles thus obtained had a titer of 0.5 x 10(8) to 1. 0 x 10(8) cell infectious units/ml and contained F-defective RNA genome. This defective vector amplified specifically in an F-expressing packaging cell line in a trypsin-dependent manner but did not spread to F-nonexpressing cells. This vector infected and expressed an enhanced green fluorescent protein reporter gene in various types of animal and human cells, including nondividing cells, with high efficiency. These results suggest that this vector has great potential for use in human gene therapy and vaccine delivery systems.

Animals↗