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Search Results: 1 - 10 of 4269 matches for " Takashi Okai "
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Oxygen Metabolic Responses of Three Species of Large Benthic Foraminifers with Algal Symbionts to Temperature Stress
Kazuhiko Fujita, Takaaki Okai, Takashi Hosono
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0090304
Abstract: Water temperature affects the physiology of large benthic foraminifers (LBFs) with algal symbionts dwelling in coral reef environments. However, the detailed physiological responses of LBF holobionts to temperature ranges occurring in their habitats are not known. We report net oxygen (O2) production and respiration rates of three LBF holobionts (Baculogypsina sphaerulata and Calcarina gaudichaudii hosting diatom symbionts, and Amphisorus kudakajimensis hosting dinoflagellate symbionts) measured in the laboratory at water temperatures ranging from 5°C to 45°C in 2.5°C or 5°C intervals and with light saturation levels of ~500 μmol m?2 s?1. In addition, the recovery of net O2 production and respiration rates after exposure to temperature stress was assessed. The net O2 production and respiration rates of the three LBF holobionts peaked at ~30°C, indicating their optimal temperature for a short exposure period. At extreme high temperatures (≥40°C), the net O2 production rates of all three LBF holobionts declined to less than zero and the respiration rates slightly decreased, indicating that photosynthesis of algal symbionts was inactivated. At extreme low temperatures (≤10°C for two calcarinid species and ≤5°C for A. kudakajimensis), the net O2 production and respiration rates were near zero, indicating a weakening of holobiont activity. After exposure to extreme high or low temperature, the net O2 production rates did not recover until the following day, whereas the respiration rates recovered rapidly, suggesting that a longer time (days) is required for recovery from damage to the photosystem by temperature stress compared to the respiration system. These results indicate that the oxygen metabolism of LBF holobionts can generally cope well with conditions that fluctuate diurnally and seasonally in their habitats. However, temporal heat and cold stresses with high light levels may induce severe damage to algal symbionts and also damage to host foraminifers.
Effects of Late Preterm Birth on the Incidence of Developmental Delays among Children at 3 Years of Age: A Matched-Pair Case-Control Study  [PDF]
Tomohiro Oba, Junichi Hasegawa, Katsufumi Otsuki, Kazuo Itabashi, Takashi Okai, Akihiko Sekizawa
Open Journal of Obstetrics and Gynecology (OJOG) , 2015, DOI: 10.4236/ojog.2015.54029
Abstract:
Purpose: To investigate the relationship between preterm delivery and developmental outcomes in children born at 34 - 36 weeks of gestation (late preterm period). Methods: This study reviewed the cases of singleton late preterm children and full-term (38 - 40 weeks of gestation) children born at Showa University Hospital. The developmental outcomes at 3 years of age were assessed based on the results of questionnaires sent to the families by mail. In addition, the incidence of developmental delays was compared between the late preterm and full-term children. In the full-term control group, perinatal characteristics (neonatal gender, Apgar score, Cesarean delivery, birth weight < 10th percentile, birth weight < 3rd percentile) were matched with those of the late preterm cases. We compared categorical variables using Fisher’s exact test. For variables with a non-normal distribution, Welch’s t-test was applied. A p-value of <0.05 was considered to be statistically significant. Results: The rate of return of the questionnaires was 25.9% (121) among the cases and 25.8% (163) among the controls. The frequency of developmental delays was 6.6% among the cases, compared with 4.3% among the controls. Conclusions: Matching the perinatal characteristics of the subjects, the frequency of developmental delays was similar between the two groups.
Genetics of Endometrial Cancers
Tsuyoshi Okuda,Akihiko Sekizawa,Yuditiya Purwosunu,Masaaki Nagatsuka,Miki Morioka,Masaki Hayashi,Takashi Okai
Obstetrics and Gynecology International , 2010, DOI: 10.1155/2010/984013
Abstract: Endometrial cancers exhibit a different mechanism of tumorigenesis and progression depending on histopathological and clinical types. The most frequently altered gene in estrogen-dependent endometrioid endometrial carcinoma tumors is PTEN. Microsatellite instability is another important genetic event in this type of tumor. In contrast, p53 mutations or Her2/neu overexpression are more frequent in non-endometrioid tumors. On the other hand, it is possible that the clear cell type may arise from a unique pathway which appears similar to the ovarian clear cell carcinoma. K-ras mutations are detected in approximately 15%–30% of endometrioid carcinomas, are unrelated to the existence of endometrial hyperplasia. A -catenin mutation was detected in about 20% of endometrioid carcinomas, but is rare in serous carcinoma. Telomere shortening is another important type of genomic instability observed in endometrial cancer. Only non-endometrioid endometrial carcinoma tumors were significantly associated with critical telomere shortening in the adjacent morphologically normal epithelium. Lynch syndrome, which is an autosomal dominantly inherited disorder of cancer susceptibility and is characterized by a MSH2/MSH6 protein complex deficiency, is associated with the development of non-endometrioid carcinomas. 1. Introduction Endometrial cancer is the most common cancer of the female reproductive tract with 150,000 new cases diagnosed annually worldwide. Approximately 90% of endometrial cancers are sporadic, and the remaining 10% are hereditary. Bokhman have generally categorized endometrial cancer into two broad groups of tumors using both clinical and histopathological variables: estrogen-dependent endometrioid endometrial carcinomas (EECs), or type I, and non-endometrioid endometrial carcinomas (NEECs), or type II tumors (Table 1) [1]. It should be noted that this model is not strict, and only a minority of endometrial cancer may exhibit shared characteristics. For example, mixed serous and endometrioid tumors are being increasingly recognized. Approximately 70% to 80% of new cases are classified as EECs, and other 10% to 20% are designated as NEEC tumors [1]. EECs are strongly associated with the estrogen-related pathway and arise in association with unopposed estrogen stimulation [2]. In contrast, NEECs are unrelated to the estrogen pathways and arise in the background of atrophic endometrium [3]. EECs typically occur in premenopausal and younger postmenopausal women and are usually low-grade and have a favorable outcome, whereas NEECs occur in older postmenopausal
Comparison in gene expression of secretory human endometrium using laser microdissection
Atsushi Yanaihara, Yukiko Otsuka, Shinji Iwasaki, Keiko Koide, Tadateru Aida, Takashi Okai
Reproductive Biology and Endocrinology , 2004, DOI: 10.1186/1477-7827-2-66
Abstract: The epithelial and stromal areas were microdissected from the human endometrium during the secretory phase. RNA was extracted and amplified by PCR. Macroarray analysis of nearly 1000 human genes was carried out in this study. Some genes identified by macroarray analysis were verified using real-time PCR.In this study, changes in expression <2.5-fold in three samples were excluded. A total of 28 genes displayed changes in expression from array data. Fifteen genes were strongly expressed in the epithelial areas, while 13 genes were strongly expressed in the stromal areas. The strongly expressed genes in the epithelial areas with a changes >5-fold were WAP four-disulfide core domain 2 (44.1 fold), matrix metalloproteinase 7 (40.1 fold), homeo box B5 (19.8 fold), msh homeo box homolog (18.8 fold), homeo box B7 (12.7 fold) and protein kinase C, theta (6.4 fold). On the other hand, decorin (55.6 fold), discoidin domain receptor member 2 (17.3 fold), tissue inhibitor of metalloproteinase 1 (9 fold), ribosomal protein S3A (6.3 fold), and tyrosine kinase with immunoglobulin and epidermal growth factor homology domains (5.2 fold) were strongly expressed in the stromal areas. WAP four-disulfide core domain 2 (19.4 fold), matrix metalloproteinase 7 (9.7-fold), decorin (16.3-fold) and tissue inhibitor of metalloproteinase 1 (7.2-fold) were verified by real-time PCR.Some of the genes we identified with differential expression are related to the immune system. These results are telling us the new information for understanding the secretory human endometrium.Many studies have sought to understand the mechanism of implantation. Recently, the rate of pregnancy in the in vitro fertilization and embryo transfer (IVF-ET) cycle has declined, and this has been attributed to a decrease in the rate of implantation.The recently developed laser microdissection method has gained widespread use throughout the research field. Information about cells can be determined without contamination by usi
4-dimensional dilaton black holes with cosmological constant
Tadashi Okai
Physics , 1994,
Abstract: Static and spherically symmetric black hole solutions with non-zero cosmological constant are investigated. A formal power series solution is found. It is proved that the number of regular horizons is less than or equal to 2 for positive cosmological constant and is less than or equal to 1 for negative cosmological constant. This shows a striking contrast to the fact that the Reissner-Nordstr{\o}m-de Sitter black hole with positive cosmological horizon has 3 regular horizons.
Mass Formulae of 4-Dimensional Dilaton Black Holes
Tadashi Okai
Physics , 1993, DOI: 10.1088/0264-9381/11/2/012
Abstract: Integral and differential mass formulae of 4-dimensional stationary and axisymmetric Einstein-Maxwell-dilaton systems are derived. The total mass (energy) of these systems are expressed in terms of other physical quantities such as electric charge of the black hole suitably modified due to the existence of the dilaton field. It is shown that when we vary slightly the fields (metric of the spacetime $g_{\mu\nu}$, $U(1)-$gauge potential $A_{\mu}$, and dilaton $\phi$) in such a way as they obey classical equations of motion, the variation of the dilaton does not contribute explicitly to the variation of the total mass, but contributes only through the variation of the electric charge of the black hole.
Global structure and thermodynamic property of the 4-dimensional twisted Kerr solution
Tadashi OKAI
Physics , 1994, DOI: 10.1143/PTP.92.47
Abstract: Rotating stringy black hole solutions with non-vanishing dilaton $\phi$, antisymmetric tensor $B_{\mu\nu}$, and $U(1)$ gauge field $A_{\mu}$ are investigated. Both Boyer-Lindquist-like and Kerr-Schild-like coordinate are constructed. The latter is utilised to construct the analytically extended spacetime. The global structure of the resulting extended spacetime is almost identical to that of the Kerr. In carrying out the analytic extension, the radial coordinate should be suitably chosen so that we can avoid singularity caused by the twisting. The thermodynamic property of the stringy black hole is examined through the injection of test bodies into the black hole. It is shown that one cannot change a black hole configuration into a naked singularity by way of throwing test bodies into the black hole. The global $O(2,3)$ symmetry and the preservation of the asymptotic flatness are discussed. When we impose stationarity, axisymmetry, and asymptotic flatness, there is no other twisting than the one pointed out by A.Sen\cite{sen}. All the other elements of $O(2,3)$ either break the asymptotic flatness, or cause only coordinate transformations and gives no physical change.
Extent of Awareness of Birth Control Methods and Their Use by Women in a Peri-Urban Area of Accra, Ghana  [PDF]
Kwabena Asomanin Anaman, Joana Okailey Aku Okai
Modern Economy (ME) , 2016, DOI: 10.4236/me.2016.71005
Abstract: The rapid population growth and economic expansion in Ghana over the last decade have made the management of its population increasingly important necessitating detailed confidential studies on use of birth control methods. This paper reports a highly confidential survey-based study undertaken to assess the extent of awareness of and factors influencing the use of birth control methods among 120 women aged between 15 and 49 years, in their reproductive lifespan, at Abokobi, a suburb of Accra, Ghana. The analysis showed that age was the main factor responsible for the general level of awareness of birth control methods. The use of birth control methods was positively related to the level of awareness of birth control methods, being in a current sexual relationship, and the number of children that the woman had. Students were less likely to use birth control methods than non-students suggesting the need for more recognition of abstinence as an alternative birth control method.
Enhancement of the superconducting transition temperature of MgB2 by proximity effect of d0 ferromagnet
Takashi Uchino,Kazuyuki Takahashi,Yuki Uenaka,Haruka Soma,Yu Kato,Mitsunobu Okai,Kanako Kodama,Katsuya Ueno,Takafumi Nakagawa,Kumihiro Genji,Takahiro Sakurai,Hitoshi Ohta
Physics , 2013,
Abstract: Heterostructures of superconducting and ferromagnetic materials are of fundamental interest because of the mutual interaction of antagonistic kinds of ordering at the S-F interface. Normally, the superconducting transition temperature Tc should be strongly suppressed at the S-F interface owing to the penetration of Cooper pairs into the ferromagnetic side. Nevertheless, constructive interactions between S and F orders have been suggested to occur via the modification of ferromagnetic order by the superconducting state. This may induce an inhomogeneous magnetic state, often called a cryptoferromagnetic state, and the relevant domain wall effect, which will lead to a local decrease of the pair-breaking parameter. However, the domain wall effect, even if it exists, is quite subtle from the experimental view point and is normally difficult to observe. Here we show that the defect-related d0 ferromagnetism in MgO and the superconductivity in MgB2 do not antagonize, but rather enhance the superconducting transition temperature Tc to any significant degree. We found in superconducting MgB2-d0 ferromagnetic MgO composites that the superconducting transition proceeds in two steps. The first at the S-F interface, between 110-120 K, then in the rest of the bulk at 39 K, which is the Tc of single phase MgB2 superconductor. Moreover, the additional transition emerges at 60 K at the S-F interface especially in the ferromagnetic side, showing a spin-glass-like magnetic state. Our findings reveal that the proximity effect in the superconductor-d0 ferromagnet heterostructures will provide the knowledge and basis to enhance the Tc value of the existing superconductors.
High Ethanol Production by Marine-Derived Yeasts-Saccharomyces cerevisiae under Stress Pressures  [PDF]
Naoto Urano, Ayaka Shirao, Masahiko Okai, Masami Ishida
Advances in Microbiology (AiM) , 2017, DOI: 10.4236/aim.2017.75029
Abstract: For practical applications of bioethanol, the uses of both highly concentrated biomass materials and their effective fermentation by yeasts are indispensable in order to produce ethanol at low costs. However, as the saccharified products of those biomass generally contain abundant sugars, the yeasts are affected by the compounds and are inclined to decrease their physiological activities. In the process of fermentation, ethanol is gradually produced by the yeasts in the culture; the concentrated metabolic product also damages itself, and inhibition of the fermentation frequently occurs. The application of yeasts with high fermentative activities under stress pressures such as sugars and ethanol is thus desired for bioethanol production. In this study, various types of high-fermentative yeasts under stress pressures were isolated mainly from coastal waters in Japan and characterized. All yeast strains with high fermentative activities under 20% v/v ethanol were found to be Saccharomyces cerevisiae. The HK21 strain isolated from Tokyo Bay and identified as S. cerevisiae had the highest fermentation activity under 30% w/v sorbitol and under 20% v/v ethanol, and it produced approx. 70 g/l (9% v/v) ethanol from the 15% w/v glucose solution at 25 oC within 5 days.
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