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Search Results: 1 - 10 of 986 matches for " Yasushi Miyagawa "
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Distribution of Deviation Distance to Alternative Fuel Stations  [PDF]
Masashi Miyagawa
American Journal of Operations Research (AJOR) , 2013, DOI: 10.4236/ajor.2013.33033
Abstract: This paper derives the distribution of the deviation distance to visit an alternative fuel station. Distance is measured as the Euclidean distance on a continuous plane. The distribution explicitly considers the vehicle range and whether the round trip between origin and destination can be made. Three cases are examined: fuel is available at both origin and destination, fuel is available at either origin or destination, and fuel is available at neither origin nor destination. The analytical expressions for the distribution demonstrate how the vehicle range, the shortest distance, and the refueling availability at origin and destination affect the deviation distance. The distribution will thus be useful to estimate the number of vehicles refueled at a station.

Male Infertility and Its Causes in Human
Toshinobu Miyamoto,Akira Tsujimura,Yasushi Miyagawa,Eitetsu Koh,Mikio Namiki,Kazuo Sengoku
Advances in Urology , 2012, DOI: 10.1155/2012/384520
Abstract: Infertility is one of the most serious social problems facing advanced nations. In general, approximate half of all cases of infertility are caused by factors related to the male partner. To date, various treatments have been developed for male infertility and are steadily producing results. However, there is no effective treatment for patients with nonobstructive azoospermia, in which there is an absence of mature sperm in the testes. Although evidence suggests that many patients with male infertility have a genetic predisposition to the condition, the cause has not been elucidated in the vast majority of cases. This paper discusses the environmental factors considered likely to be involved in male infertility and the genes that have been clearly shown to be involved in male infertility in humans, including our recent findings. 1. Introduction One of the most serious social problems facing developed countries today is the declining birth rate, although it is generally not well recognized that the number of infertile couples is on the rise in these countries. While both social (i.e., social progress for women and the resulting increase in the age at which women marry) and environmental (i.e., pollution and global warming) factors are behind part of the increase in the number of patients with infertility, infertility in the male partner contributes to approximately half of all cases. To date, various techniques, such as in vitro fertilization (particularly, intracytoplasmic sperm injection or ICSI) and so-called TESE-ICSI involving the harvesting of sperm from the testes, have been developed for male infertility. Although these methods are steadily producing results, no technique has proven effective for patients with nonobstructive azoospermia, in which there is an absence of mature sperm in the testes. Evidence suggests that many patients with azoospermia have a genetic predisposition to the condition, although the cause has not been elucidated in the vast majority of cases [1]. Conversely, studies using knockout mouse models have recently linked many genes to spermatogenesis, the mechanisms of which are currently being clarified. These animal findings have yet to be shown applicable to most human cases. This is because identifying the affected genes in humans requires a retrograde genetic approach and because the knockout mouse phenotype is not always faithfully reproduced in humans. This paper discusses the environmental factors considered likely to be involved in male infertility and the genes that have been clearly shown to be involved in male
Recent Clinical and Experimental Advances in Atrial Fibrillation
Shigeru Miyagawa,Taichi Sakaguchi,Hiroyuki Nishi,Yasushi Yoshikawa,Satsuki Fukushima,Shunsuke Saito,Yoshiki Sawa
ISRN Cardiology , 2011, DOI: 10.5402/2011/958189
Abstract: Atrial fibrillation (AF) is the most common arrhythmia in clinical settings (Fuster et al., 2001), and it is often associated with congestive heart diseases (Issac et al., 2007). Many studies in both laboratory and clinical settings have sought to analyze the mechanisms of AF, develop treatments based on these mechanisms, and examine atrial remodeling in chronic AF. The aim of this paper is to analyze recent findings regarding the atrial remodeling that occurs in AF. In particular, we will describe the electrical and structural changes that involve atrial myocytes and the extracellular matrix. We will also describe the general classification and basic pathophysiology of AF and its surgical treatments. 1. Classification of AF The joint American College of Cardiology/American Heart Association/European Society of Cardiology proposed a classification system for AF to simplify its heterogeneous clinical aspects and clarify its clinical states [1]. Patients are initially classified as having a “first detected episode of AF,” when AF is confirmed by clinicians. If a patient has two or more episodes, the AF is classified as recurrent. Recurrent AF is designated as paroxysmal or persistent. Paroxysmal AF is an episode that generally continues for 7 or fewer days and terminates on its own. Persistent AF usually continues for more than 7 days without self-terminating and requires clinicians to terminate it using pharmacological treatment or electrical cardioversion to restore the sinus rhythm. Permanent AF is a situation in which the sinus rhythm cannot be sustained after cardioversion, and further medical efforts are required to restore it. 2. Pathophysiology of AF 2.1. The Basic Mechanisms of AF Many researchers agree that inflammation [2], neurohormonal disorders [3], cardiovascular diseases such as valvular diseases [4], diabetes, hypertension, congestive heart failure, myocardial infarction [5], and genetic factors [6] are “modulating factors” that can induce AF. Classically, AF mechanisms are described by the concept of atrial ectopic foci [7], which fire spontaneously in the atrium, a single reentry circuit, or multiple reentry circuits [8, 9]. The surgical maze procedure is designed to block the multiple reentry circuits and create an isolated electrical lesion in the atrium [10]. Haissaguerre et al. reported that triggers located in the pulmonary veins initiate most cases of paroxysmal AF [7], while in some cases the trigger, such as a venous remnant in the left atrium (LA) and superior vena cavae, occurs outside the pulmonary vein. This finding supports
Genetic Variation in the Testis-Specific HASPIN Gene Encoding a Serine/Threonine Protein Kinase in Infertile Japanese Males  [PDF]
Hiromitsu Tanaka, Akira Tsujimura, Yasushi Miyagawa, Dakyo Oh, Damin Choi, Morimasa Wada, Hiromi Nishimura, Yoshitake Nishimune
Advances in Sexual Medicine (ASM) , 2016, DOI: 10.4236/asm.2016.63003
Abstract: HASPIN is a serine/threonine protein kinase predominantly expressed during spermatogenesis and localized in the nucleus. The HASPIN gene is conserved from yeast to mammals and plants. To investigate any possible associations between HASPIN polymorphisms and impaired spermatogenesis in Japanese males, we screened for mutations in the HASPIN coding sequence (CDS) using DNA from 282 sterile male patients and 262 fertile male volunteers. Polymorphisms were found at 10 positions within the HASPIN CDS. Among these 10 polymorphisms, 5 were found only in the infertile group, 3 of which were nonsynonymous. These polymorphisms found only in the infertile patients may be a cause of male infertility and thus valuable candidates for further study of this condition.
From bench to bedside, work in cell-based myocardial regeneration therapy  [PDF]
Shigeru Miyagawa, Yoshiki Sawa
Journal of Biomedical Science and Engineering (JBiSE) , 2014, DOI: 10.4236/jbise.2014.72012
Abstract:

In clinical cellular cardiomyoplasty, bone marrow cells and myoblasts are introduced mainly to ischemic cardiomyopathy tissue via several cell delivery systems, such as needle injection or catheter. These clinical studies have demonstrated the safety and feasibility of this technique, but its effectiveness for treating heart failure, especially in the long term, is still under discussion. Neither of these cell types can differentiate into cardiomyocytes; rather, they improve the failing heart mainly by the paracrine effects of some cytokines, such as Hepatocyte growth factor (HGF) and Vascular endothelial growth factor (VEGF). Thus, many researchers have a great interest in stem cells, which exist in bone marrow, circulating blood, atrium, and adipose tissue, and can differentiate into cardiomyocytes. Although several stem cells with the potential to differentiate into various cell types have been reported, few can differentiate into cardiomyocytes. Moreover, beating cells that can demonstrate synchronized contraction with native cardiomyocytes are critical for the complete repair of severe heart failure. Therefore, stem cells with a high differentiation capacity should be explored for the goal of completely repairing severely damaged myocardium. In this review, we summarize the clinical protocols and basic experiments for cellular cardiomyoplasty using bone marrow cells, myoblasts, and other stem cells.

Impact of microRNA Expression in Human Atrial Tissue in Patients with Atrial Fibrillation Undergoing Cardiac Surgery
Hiroyuki Nishi, Taichi Sakaguchi, Shigeru Miyagawa, Yasushi Yoshikawa, Satsuki Fukushima, Shunsuke Saito, Takayoshi Ueno, Toru Kuratani, Yoshiki Sawa
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0073397
Abstract: Background Although microRNA (miRNA) regulates initiation and/or progression of atrial fibrillation (AF) in canine AF models, the underlying mechanism in humans remains unclear. We speculated that certain miRNAs in atrial tissue are related to AF, and evaluated the relationship of miRNA expression in human atrial tissue in cardiac surgery patients. Methods Right atrial tissues from 29 patients undergoing cardiovascular surgery were divided into 3 groups [A: chronic AF or unsuccessful maze, n=6; B: successful maze, n=10; C: sinus rhythm (SR) n=13]. miRNA expression was determined using high density microarrays and with Reverse transcriptase-polymerase chain reaction (RT-PCR). Fibrosis was examined using Masson trichrome staining. Results miRNA microarray analysis showed elevated miRNA-21, miRNA-23b, miRNA-199b, and miRNA-208b in AF as compared to SR groups. RT-PCR showed elevated miRNA-21 (1.9-fold) and miRNA-208b (4.2-fold) in AF as compared to the SR groups. miRNA-21 expression increased from Group C to A (A: 2.1-fold, B: 1.8-fold, C: 1.0-fold). Fibrosis increased from C to A (A: 43.0±12.9%, B: 21.3±6.1%, C: 11.9±3.1%). Percent fibrosis and miRNA-21 expression were correlated (r=0.508, p<0.05). The plasma levels of miRNA-21 in AF patients was significantly decreased as compared to the healthy volunteers (p<0.05). Conclusion The expression of miRNA-21 in human atrial tissue was found to be related to atrial fibrosis and might affect AF occurrence, indicating its usefulness as a biomarker for cardiac surgery management.
Effects of Pitavastatin on the Intima-Media Thickness of the Carotid Artery in Patients with Ischemic Stroke: The Pitavastatin Efficacy Study on Surrogate Markers and Imaging for Stroke (PESSMIST)  [PDF]
Yasushi Shibata
World Journal of Neuroscience (WJNS) , 2014, DOI: 10.4236/wjns.2014.44034
Abstract:

Pitavastatin is a strong statin that was developed in Japan. The clinical impact of pitavastatin treatment in patients with ischemic stroke has not been reported. We conducted a prospective, open label, clinical case-control study to determine the secondary preventive effects of pitavastatin for patients with cerebral infarction and hyperlipidemia. The pitavastatin group included 20 Japanese patients diagnosed with cerebral infarction and hyperlipidemia without previous statin intake. The control group included 22 patients diagnosed with cerebral infarction without hyperlipidemia. The pitavastatin group of patients received 2 mg of pitavastatin once a day after dinner. The mean age of the patients was 69.3 and 75.5 years for the pitavastatin and control groups, respectively, and the age of the pitavastatin group was significantly younger than that of the control group (P < 0.05). The serum TCho and LDL-C levels significantly decreased two months after the initiation of pitavastatin treatment. The mean and maximum intima-media thickness (IMT) also decreased after the initiation of pitavastatin. The mean and maximum IMT did not show any significant changes in the control group. The change of IMT %/year was less than zero for the pitavastatin group, and was almost zero or higher for the control group. Pitavastatin showed beneficial effects by improving the surrogate makers of stroke. These surrogate makers were effective to evaluate the efficacy of pitavastatin to prevent secondary stroke. Although a prospective randomized study is required to elucidate the long-term effects of pitavastatin, the current study suggests that pitavastatin may be effective to prevent secondary stroke in patients with stroke and hyperlipidemia.

Optimum-Welfare and Maximum-Revenue Tariffs in Vertically Related Markets  [PDF]
Yasushi Kawabata
Modern Economy (ME) , 2014, DOI: 10.4236/me.2014.55055
Abstract:

This paper compares the optimum-welfare tariffs with the maximum-revenue tariffs in a model of vertically related markets characterized by Cournot competition. It shows that the optimum-welfare tariff on the intermediate good exceeds the maximum-revenue tariff if the home intermediate-good firm is much more cost-competitive than the foreign intermediate-good firm. Further, the optimum-welfare tariff on the final good exceeds the maximum-revenue tariff if the home intermediate-good firm is significantly inefficient compared to the foreign intermediate-good firm. It is less likely that the optimum-welfare tariffs on the intermediate and the final good, respectively, exceed the maximum-revenue tariffs on the intermediate and the final good in the presence of vertical trade structures than in their absence.

A Single Nucleotide Polymorphism within the Novel Sex-Linked Testis-Specific Retrotransposed PGAM4 Gene Influences Human Male Fertility
Hidenobu Okuda, Akira Tsujimura, Shinji Irie, Keisuke Yamamoto, Shinichiro Fukuhara, Yasuhiro Matsuoka, Tetsuya Takao, Yasushi Miyagawa, Norio Nonomura, Morimasa Wada, Hiromitsu Tanaka
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0035195
Abstract: Background The development of novel fertilization treatments, including in vitro fertilization and intracytoplasmic injection, has made pregnancy possible regardless of the level of activity of the spermatozoa; however, the etiology of male-factor infertility is poorly understood. Multiple studies, primarily through the use of transgenic animals, have contributed to a list of candidate genes that may affect male infertility in humans. We examined single nucleotide polymorphisms (SNPs) as a cause of male infertility in an analysis of spermatogenesis-specific genes. Methods and Finding We carried out the prevalence of SNPs in the coding region of phosphoglycerate mutase 4 (PGAM4) on the X chromosome by the direct sequencing of PCR-amplified DNA from male patients. Using RT-PCR and western blot analyses, we identified that PGAM4 is a functional retrogene that is expressed predominantly in the testes and is associated with male infertility. PGAM4 is expressed in post-meiotic stages, including spermatids and spermatozoa in the testes, and the principal piece of the flagellum and acrosome in ejaculated spermatozoa. A case-control study revealed that 4.5% of infertile patients carry the G75C polymorphism, which causes an amino acid substitution in the encoded protein. Furthermore, an assay for enzymatic activity demonstrated that this polymorphism decreases the enzyme’s activity both in vitro and in vivo. Conclusion These results suggest that PGAM4, an X-linked retrogene, is a fundamental gene in human male reproduction and may escape meiotic sex chromosome inactivation. These findings provide fresh insight into elucidating the mechanisms of male infertility.
Analytic properties of generalized Mordell-Tornheim type of multiple zeta-functions and L-functions
Takashi Miyagawa
Mathematics , 2015,
Abstract: Analytic properties of three types of multiple zeta functions, that is, the Euler-Zagier type, the Mordell-Tornheim type and the Apostol-Vu type have been studied by a lot of authors. In particular, in the study of multiple zeta functions of the Apostol-Vu type, a generalized multiple zeta function, including both the Euler-Zagier type and the Apostol-Vu type, was introduced.In this paper, similarly we consider generalized multiple zeta-functions and $ L $-functions, which include both the Euler-Zagier type and the Mordell-Tornheim type as special cases.We prove the meromorphic continuation to the multi-dimensional complex space, and give the results on possible singularities.
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