Biomedical subjects

M Murayama

Publications and source records attributed to M Murayama.

At least 19 recordsLinked to original sources

PubMed2006

Left ventricular chamber size predicts the race time of Japanese participants in a 100 km ultramarathon.

OBJECTIVE: As a subanalysis of an echocardiographic study performed on 291 Japanese participants in a 100 km ultramarathon, to estimate predictors of race time. METHODS: A total of 247 male participants in a 100 km ultramarathon (age 20-73 years) were examined by echocardiography. Correlations between age, body surface area, monthly running distance, or echocardiographic variables and the race time were examined. RESULTS: According to simple regression analysis, age (r = 0.299, p < 0.0001), monthly running distance (r = -0.388, p < 0.0001), left ventricular end diastolic diameter (r = -0.300, p < 0.0001), and left ventricular end systolic diameter (r = -0.325, p < 0.0001) correlated significantly with the race time. When multiple regression analysis was performed, age (f = 2.364), monthly running distance (f = -0.113), and left ventricular end systolic diameter (f = -2.361) remained significant predictors of the race time. CONCLUSION: Left ventricular diameter predicts the race time for a 100 km ultramarathon, in addition to age and amount of training.

Adult↗

PubMed2003

In situ transmission-electron-microscopy investigation of melting in submicron Al-Si alloy particles under electron-beam irradiation.

In situ heating and electron-beam irradiation in the transmission electron microscope were performed to study melting of submicron Al-11.6 at. % Si particles supported on a C thin film. It was found that electron irradiation could be used to melt the particles, even when the hot-stage sample holder was kept at a much lower temperature ( approximately 125 degrees C) than the initial melting point of the particles. Comparison between the experimentally observed melting behavior and analytical calculations indicate that melting of the submicron Al-Si particles under electron-beam irradiation is caused by a temperature rise due to electron thermal spikes in the particles and poor thermal conduction away from the particles. These results have important implications in transmission electron microscopy studies of nanoparticles supported on thin films or poorly conducting substrates.

Journal Article↗

PubMed2002

Atomic-level observation of disclination dipoles in mechanically milled, nanocrystalline Fe.

Plastic deformation of materials occurs by the motion of defects known as dislocations and disclinations. High-resolution transmission electron microscopy was used to directly reveal the individual dislocations that constitute partial disclination dipoles in nanocrystalline, body-centered cubic iron that had undergone severe plastic deformation by mechanical milling. The mechanisms by which the formation and migration of such partial disclination dipoles during deformation allow crystalline solids to fragment and rotate at the nanometer level are described. Such rearrangements are important basic phenomena that occur during material deformation, and hence, they may be critical in the formation of nanocrystalline metals by mechanical milling and other deformation processes.

Journal Article↗

PubMed2002

Lithium inhibits amyloid secretion in COS7 cells transfected with amyloid precursor protein C100.

To examine the regulation of amyloid secretion in more detail, Abeta sandwich ELISAs with high sensitivity and specificity were developed. Using this technique, we measured Abeta secreted from COS7 cells transiently transfected with APP C100 in the presence of LiCl, a potent glycogen synthase kinase (GSK)-3beta inhibitor. We found that both Abetax-40 and Abetax-42 secretion were reduced by LiCl treatment in a dose-dependent manner. Diminished amyloid secretion was associated with GSK-3beta activity. These results suggest that GSK-3beta might function as a possible mediator for regulating both amyloid deposition and tau pathology in Alzheimer's disease (AD), and that lithium should be re-evaluated as a candidate reagent for preventing AD pathology.

Alzheimer Disease↗

PubMed2001

Alcoholism, ALDH2*2 allele and the A1 allele of the dopamine D2 receptor gene: an association study.

The inactive form of aldehyde dehydrogenase-2 (ALDH2) is regarded as a protective factor against the development of alcoholism, and alcoholics with inactive ALDH2 are considered to be relatively homogeneous. This examination of a possible allelic association of the dopamine D2 receptor (DRD2) gene TaqI A polymorphism failed to detect significant differences between 583 Japanese alcoholics and 295 unrelated Japanese controls, or between alcoholic subjects with different ALDH2 genotypes. Despite the significantly higher frequency of the DRD2 A1 allele in the 207 alcoholics with inactive ALDH2 than in the 376 alcoholics with active ALDH2, multiple logistic regression analysis (controlled for the ALDH2 genotype) revealed no association between the TaqI A polymorphism and alcoholism. Nor did the frequency of the DRD2 TaqI A polymorphism differ in alcoholic subjects grouped by several pertinent clinical characteristics, including severity of alcoholism. Although there remains a possibility that the DRD2 TaqI A polymorphism plays some role in modifying the phenotype of the disease, these results suggest that neither the A1 allele nor the homozygous A1 genotype is associated with alcoholism.

Adult↗

PubMed2001

Association between 5HT2A receptor gene promoter region polymorphism and eating disorders in Japanese patients.

BACKGROUND: Evidence from family and twin studies suggests a genetic contribution to the etiology of eating disorders (EDs). Recently, researchers have reported genetic associations between the MspI polymorphism (-1438A/G) of the promoter region of the 5HT2A receptor gene and EDs; however, reports of evidence against these findings make the association controversial. METHODS: The authors examined the prevalence of the -1438A/G polymorphism of the 5HT2A receptor gene among 182 Japanese patients with EDs and 374 normal control subjects. Interactions of the association of this polymorphism with subtypes of anorexia nervosa (AN), bulimia nervosa (BN), and various clinical characteristics were also assessed. RESULTS: In contrast to previous studies reporting elevated A allele frequencies in patients with AN, the G allele had a significantly higher frequency in patients with BN but not in patients with AN, than in control subjects. Examination of the interactions revealed that the presence of the binge eating and/or purging behavior and comorbid borderline personality disorder (BPD) tended to be associated with increased frequency of the G allele. CONCLUSIONS: Though preliminary, these results can be interpreted as suggesting that the G allele of the 5HT2A receptor gene -1438A/G polymorphism may be associated with pathological features that EDs and BPD have in common, especially disinhibition in eating behavior and personality trait.

Adult↗

PubMed2001

Association study of serotonin transporter gene regulatory region polymorphism and alcoholism.

Previous studies have indicated associations between a functional biallelic repetitive element in the 5' regulatory region of the serotonin transporter gene (5-HTTLPR) and alcoholic subjects who have either dissocial personality disorder or severe withdrawal symptoms. To replicate these associations under the hypothesis that genetic polymorphism plays some role in the susceptibility or vulnerability of some subgroup of alcoholics, the associations between alcoholic subjects' genetic polymorphisms, clinical characteristics, and personality traits were examined. This case control study comprised 697 alcoholic and 270 control subjects. A questionnaire focusing on family and social background, history of drinking and alcohol withdrawal, DSM-III-R criteria for the evaluation of psychiatric conditions, and Feighner's criteria for the lifetime diagnosis and assessment of overall severity of alcoholism was administered to 373 alcoholic subjects. Temperament and Character Inventory (TCI) and Sensation Seeking Scale (SSS) were used to evaluate the other 324 alcoholics. The frequency of the homozygous short allele was significantly higher in alcoholic binge drinkers than in nonbinge drinking alcoholics. There were no significant differences in the frequencies of either the 5-HTTLPR genotype or the short vs. long allele in alcoholic and control subjects. The alcoholics' 5-HTTLPR genotype and allele frequencies did not differ significantly by the severity of withdrawal symptoms or by the number of positive Feighner's diagnostic criteria. Although these results indicate an association between 5-HTTLPR and a subgroup of alcoholics characterized by binge drinking, the authors found no differences in SSS and TCI subscale scores for alcoholics with different 5-HTTLPR genotypes. Future studies of the association in other alcoholic population should take into account personality traits.

Alcoholism↗

PubMed2001

Involvement of cyclin dependent kinase5 activator p25 on tau phosphorylation in mouse brain.

P35 or its truncated fragment p25 is required for cyclin dependent kinase (Cdk)5 activation. It has been reported that p25 is accumulated in the brain of Alzheimer's disease (AD) patients and that p25/Cdk5 induces high phosphorylation of tau and apoptosis in cultured neurons (Nature 402 (1999) 615). Our investigation of AD brain did not show specific accumulation of p25. Exposure to Ca ionophore (A23187) at 10(-6) M induced p25 accumulation in rat primary hippocampal neurons, causing neuronal death without showing hyperphosphorylation of tau. Transgenic mice expressing p25 showed the accumulation of p25 but neither hyperphosphorylation of tau nor neuronal death was shown in these mice. The feature of these mice was the progression of cell growth in pituitary gland. These results suggest that overexpression of p25 lead to the activation of cell cycle but not to the direct phosphorylation of tau.

Aged↗

PubMed2001

New insights on how metals disrupt amyloid beta-aggregation and their effects on amyloid-beta cytotoxicity.

Amyloid-beta protein (A beta) aggregates in the brain to form senile plaques. By using thioflavin T, a dye that specifically binds to fibrillar structures, we found that metals such as Zn(II) and Cu(II) normally inhibit amyloid beta-aggregation. Another method for detecting A beta, which does not distinguish the types of aggregates, showed that these metals induce a non-beta-sheeted aggregation, as reported previously. Secondary structural analysis and microscopic studies revealed that metals induced A beta to make non-fibrillar aggregates by disrupting beta-sheet formation. These non-fibrillar A beta aggregates displayed much weaker Congo Red birefringence, and in separate cell culture experiments, were less toxic than self beta-aggregates, as demonstrated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay. The toxicity of soluble A beta was enhanced in the presence of Cu(II), which suggests the previously hypothesized role of A beta in generating oxidative stress. Finally, under an acidic condition, similar to that in the inflammation associated with senile plaques, beta-aggregation was robustly facilitated at one specific concentration of Zn(II) in the presence of heparin. However, because a higher concentration of Zn(II) virtually abolished this abnormal phenomenon, and at normal pH any concentrations strongly inhibit beta-aggregation and its associated cytotoxicity, including its anti-oxidative nature we suggest that Zn(II) has an overall protective effect against beta-amyloid toxicity.

Amyloid beta-Peptides↗

PubMed2001

Three-year follow-up of patients with right bundle branch block and ST segment elevation in the right precordial leads: Japanese Registry of Brugada Syndrome. Idiopathic Ventricular Fibrillation Investigators.

OBJECTIVES: We sought to determine the prevalence of right bundle branch block (RBBB) and ST segment elevation in the working Japanese population, as well as the event rate during a three-year prospective follow-up period. BACKGROUND: A poor prognosis of RBBB and ST segment elevation has been reported in Europe and South America, even in asymptomatic patients; however, a large population of asymptomatic patients with sporadic RBBB and ST segment elevation has not been studied. METHODS: Ten thousand 12-lead electrocardiograms (ECGs) were obtained during annual check-ups of working adults in the Tokyo area. This three-year prospective follow-up study consisted of 105 patients, including 20 with ventricular fibrillation, 18 with syncope and 67 who were asymptomatic. They were registered from 46 institutions in Japan. RESULTS: The prevalence of ECG abnormalities in working adults was 0.16%. A coved-type ST segment elevation was related to a history of cardiac events, and 18% of registered patients had PR prolongation and 9.5% had left-axis deviation. The cumulative cardiac event-free rate was 67.6% in the symptomatic group and 93.4% in the asymptomatic group (p = 0.0004) after three years. CONCLUSIONS: The recurrence rate of cardiac events in symptomatic patients was similar to that reported previously, but it was very low in sporadic asymptomatic patients. The ECG findings may help us to select patients for further examination and more accurate evaluation of their prognoses.

Adult↗

PubMed2001

Formation of filamentous tau aggregations in transgenic mice expressing V337M human tau.

Formation of neurofibrillary tangles (NFTs) is the most common feature in several neurodegenerative diseases, including Alzheimer's disease (AD). Here we report the formation of filamentous tau aggregations having a beta-sheet structure in transgenic mice expressing mutant human tau. These mice contain a tau gene with a mutation of the frontotemporal dementia parkinsonism (FTDP-17) type, in which valine is substituted with methionine residue 337. The aggregation of tau in these transgenic mice satisfies all histological criteria used to identify NFTs common to human neurodegenerative diseases. These mice, therefore, provide a preclinical model for the testing of therapeutic drugs for the treatment of neurodegenerative disorders that exhibit NFTs.

Animals↗

PubMed2001

Telementoring and teleproctoring.

Telemedicine has previously been defined as "live two-way interactive video communication between a physician and a patient and/or another physician, where all participants are able to see and hear one another much like a face to face encounter." This concept has gained recent notoriety because of the great advances in telecommunications and the potential future increased cost-effectiveness associated with its utilization. We have developed a telementoring deployment protocol that can be effectively used to introduce a student to telementoring processes. The strict protocol uses military commands to facilitate smooth information transfer. The use of a concept called tactical information deployment provides the surgeon with rapid access to reference information in the operating suite. Multimedia interactive CD-ROMs, with digitized movie clips, illustrations, sound bits, and the latest academic review of the literature arm the surgeon with a database that establishes an unprecedented clinical adaptive capability (CAC). The availability of this information is invaluable to surgeons in their initial advanced laparoscopic procedural efforts. Telementoring simulator opportunities are included to acclimate the participant to the process. If the process seems comprehensive, it is meant to be. This is a high-risk situation, and a patient's welfare is on the line. If this concept is to reach its maximal healthcare delivery potential, responsible and academically credible training programs should be established with directional guidelines.

Computer-Assisted Instruction↗

PubMed2001

Effects of prolonged strenuous exercise on plasma levels of atrial natriuretic peptide and brain natriuretic peptide in healthy men.

BACKGROUND: Now that marathon racing is growing in popularity, many thousands of enthusiastic athletes are participating in various ultramarathons all over the world each year. However, it remains controversial whether such a sport contributes to the promotion of health. The occurrence of transient cardiac dysfunction and irreversible myocardial injury has been reported in association with such exercise in healthy individuals. Brain natriuretic peptide (BNP) is a cardiac hormone, as is atrial natriuretic peptide (ANP), and its measurement has been widely used for clinical evaluation of cardiac dysfunction. However, little is known about the response of plasma BNP to prolonged strenuous exercise. We hypothesized that confirmation of minimal cardiac dysfunction or myocardial injury may be made by measurements of plasma BNP. METHODS: Levels of plasma ANP, BNP, catecholamines, blood lactate, and serum cardiac troponin T (cTnT) were determined before and after a 100-km ultramarathon in 10 healthy men to examine the effects of the exercise on levels of ANP and BNP and correlations between the natriuretic peptides and cTnT as a marker for myocardial damage. RESULTS: Whereas all variables significantly increased after the race, increased levels of ANP and BNP were most strongly correlated with increases in cTnT levels. The cTnT level after the race was greater than the upper reference limit in 9 of 10 men. CONCLUSIONS: Such exercise significantly increased ANP and BNP levels in healthy men, and the increases could be partially attributed to myocardial damage during the race.

Adult↗

PubMed2001

Functional relevance of human adh polymorphism.

This article represents the proceedings of a symposium at the 2000 ISBRA Meeting in Yokohama, Japan. The chairs were C. J. Peter Eriksson and Tatsushige Fukunaga. The presentations were (1) 4-Methylpyrazole as a tool in the investigation of the role of ADH in the actions of alcohol in humans, by Taisto Sarkola and C. J. Peter Eriksson; (2) ADH2 polymorphism and flushing in Asian populations, by Wei J. Chen, C. C. Chen, J. M. Ju, and Andrew T. A. Cheng; (3) Role of ADH3 genotypes in the acute effects of alcohol in a Finnish population, by Hidetaka Yamamoto, Kathrin Kohlenberg-Müller, and C. J. Peter Eriksson; (4) Clinical characteristics and disease course of alcoholics with different ADH2 genotypes, by Mitsuru Kimura, Masanobu Murayama, Sachio Matsushita, Haruo Kashima, and Susumu Higuchi; (5) ADH2 polymorphism, alcohol drinking, and birth defects, by Lucinda Carr, D. Viljoen, L. Brooke, T. Stewart, T. Foroud, J. Su, and Ting-Kai Li; and (6) ADH genotypes and alcohol use in Europeans, by John B. Whitfield.

Adult↗

PubMed2001

Congenital giant aneurysm of the left atrial appendage mimicking pericardial absence case report.

A 25-year-old man was found to have an abnormal cardiac contour on a chest radiograph, and was referred. Transesophageal echocardiography suggested herniation of the left atrial appendage (LAA) through a gap in the pericardium, and magnetic resonance imaging indicated congenital partial absence of the pericardium. Cardiac dysfunction was caused by compression from the enlarged left atrium and thrombi were thought to be present in the appendage, so surgery was performed. The intraoperative diagnosis was congenital LAA aneurysm. Although distinguishing between congenital LAA aneurysm and congenital absence of the pericardium is reported to be possible with magnetic resonance imaging, we were unable to so in this case.

Adult↗

PubMed2001

Time- and subunit-dependent differential mRNA expression of L-type Ca2+ channel during progression of right ventricular hypertrophy.

To clarify the molecular basis for changes in L-type calcium channel (VLCC) density in ventricular hypertrophy, we analyzed the mRNA expression of all the subunits including the main subunit alpha1c and auxiliary subunits (alpha2delta, beta2 and beta3) composing VLCC in rat right ventricular hypertrophy (RVH) induced by monocrotaline injection. To test the hypothesis that the expression of each subunit might change differently during progression of RVH, leading to an altered electrophysiologic outcome for VLCC, we investigated the ratio of the mRNA level of each auxiliary subunit to the main subunit. After monocrotaline injection, alpha1c mRNA showed a transient decrease on the 14th day and thereafter significantly increased to reach approximately 1.8 fold that of the control level on the 21st day. The auxiliary subunit alpha2delta mRNA showed a pattern similar to that of alpha1c. The beta3 mRNA increased rapidly after monocrotaline injection and increased approximately 4.1 fold. On the other hand, beta2 mRNA showed no significant changes. Accordingly, only the mRNA ratio of beta3 to alpha1c showed a significant increase among the auxiliary subunits after the monocrotaline injection. The ratio increased to a maximum of approximately 5.7 fold on the 14th day and thereafter decreased. These results suggest that VLCC density may be modified not only by alpha1c but also by its auxiliary subunit expression in ventricular hypertrophy, and provide a clue for understanding the controversial electrophysiologic results on VLCC density in hypertrophied hearts.

Animals↗

PubMed2001

Assessment of reflection pulse wave in patients with cardiomyopathy: evaluation of noninvasive measurement of wave intensity.

OBJECTIVE: We assessed the reflection pressure wave using noninvasive measurement of wave intensity (WI) in patients with cardiomyopathy. METHODS AND RESULTS: Subjects included 8 patients with hypertrophic cardiomyopathy (HCM group) and 10 patients with dilated cardiomyopathy (DCM group). Twelve healthy subjects were used as a control group. By using a combined Doppler and echo-tracking system, changes in vascular diameter (dD) and blood flow velocity (dV) were recorded simultaneously at the common carotid artery and dD x dV was measured as WI. In the components of WI, the positive component of early systolic phase (FE) and the negative component following FE (B) were significantly reduced in the DCM group. There was a significant positive correlation between FE and B in all 3 groups. The appearance time of B was significantly shorter in the HCM group and significantly longer in the DCM group compared with the control group. CONCLUSIONS: It was suggested that the value of the reflection pressure wave was influenced by the left ventricular contractility, and that the effect of the reflection pressure wave appeared earlier in patients with HCM and later in patients with DCM compared with the control subjects.

Blood Flow Velocity↗

PubMed2001

[Successful non-surgical treatment of acute coronary syndrome involving the left main coronary trunk in four elderly patients].

We encountered 4 patients aged over 80 with acute coronary syndrome involving the left main coronary trunk (LMT) who obtained a successful outcome by non-surgical management. CASE 1: An 80-year-old women suffered acute myocardial infarction. A coronary stent was placed at the orifice of the LMT for dilatation of severe 90% stenosis. Cardiac function was markedly improved after treatment during the chronic period. CASE 2: An 81-year-old man who developed non-sustained ventricular tachycardia. Coronary angiography demonstrated severe stenosis with haziness of the LMT. Intra-aortic balloon pumping was performed for one whole day after the attack and the follow-up study performed one month later revealed that the stenosis was markedly diminished to an insignificant grade without residual ischemia. CASE 3: An 81-year-old man developed acute inferior wall infarction with a background of severe triple vessel disease accompanied by an LMT lesion. Coronary stents were placed at three sites, i.e., the right coronary, LMT, and left anterior descending branch. Though initial treatment was successful, this patient died due to severe arrhythmia. Patients in who CABG is strongly indicated due to LMT lesion complicated with multiple organ disorders will increase as the population of the aged continues to increase in Japan. We obtained satisfactory results by intensive intense non-surgical management including PTCA. From our experience, adequate selection of therapeutic regimens for individual patients is important to improve the long-term prognosis as well as the immediate outcome in the acute stage.

Aged↗