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排序方式: 共有390条查询结果,搜索用时 15 毫秒
1.
Takahito Yamashita Miki Kawada‐Matsuo Tamaki Katsumata Atsuko Watanabe Yuichi Oogai Yoshihiro Nishitani Shouichi Miyawaki Hitoshi Komatsuzawa 《Microbiology and immunology》2019,63(7):251-260
Streptococcus mutans is a cariogenic bacterium that localizes in the oral cavity. Glycyrrhetinic acid (GRA) is a major component of licorice extract. GRA and several derivatives, including disodium succinoyl glycyrrhetinate (GR‐SU), are known to have anti‐inflammatory effects in humans. In this study, the antimicrobial effect of GRA and its derivatives against the S. mutans UA159 strain were investigated. Minimum inhibitory concentrations (MICs) of GRA and GR‐SU showed antibacterial activity against the S. mutans strain, whereas other tested derivatives did not. Because GR‐SU is more soluble than GRA, GR‐SU was used for further experiments. The antibacterial activity of GR‐SU against 100 S. mutans strains was evaluated and it was found that all strains are susceptible to GR‐SU, with MIC values below 256 µg/mL. A cell viability assay showed that GR‐SU has a bacteriostatic effect on S. mutans cells. As to growth kinetics, sub‐MICs of GR‐SU inhibited growth. The effect of GR‐SU on S. mutans virulence was then investigated. GR‐SU at sub‐MICs suppresses biofilm formation. Additionally, GR‐SU greatly suppresses the pH drop caused by the addition of glucose and glucose‐induced expression of the genes responsible for acid production (ldh and pykF) and tolerance (aguD and atpD). Additionally, expression of enolase, which is responsible for the carbohydrate phosphotransferase system, was not increased in the presence of GR‐SU, indicating that GR‐SU suppresses incorporation of sugars into S. mutans. In conclusion, GR‐SU has antibacterial activity against S. mutans and also decreases S. mutans virulence. 相似文献
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Hideyuki Doi Elena I. Zuykova Eisuke Kikuchi Shuichi Shikano Keiichi Kanou Natalia Yurlova Elena Yadrenkina 《Hydrobiologia》2006,571(1):395-400
We investigated spatial changes in the isotope ratios of the plankton food web in Lake Chany, Siberia, Russia, especially
at an estuarine transition zone of the lake. The δ13C values of particulate organic matter (POM) varied among the sampling sites, and increased with increasing pH of the lake
water. This may reflect a shift by phytoplankton from using CO2 to using bicarbonate for photosynthesis with increasing pH. The δ13C values of zooplankton community also changed at each site along with those of the POM. This was indicative of carbon isotope
changes of plankton food webs between the stations along an environmental gradient. 相似文献
5.
Masamitsu Konno Atsushi Hamabe Shinichiro Hasegawa Hisataka Ogawa Takahito Fukusumi Shimpei Nishikawa Katsuya Ohta Yoshihiro Kano Miyuki Ozaki Yuko Noguchi Daisuke Sakai Toshihiro Kudoh Koichi Kawamoto Hidetoshi Eguchi Taroh Satoh Masahiro Tanemura Hiroaki Nagano Yuichiro Doki Masaki Mori Hideshi Ishii 《Development, growth & differentiation》2013,55(3):309-318
Adipose tissue‐derived mesenchymal stem cells (ADSCs) are multipotent and can differentiate into various cell types, including osteocytes, adipocytes, neural cells, vascular endothelial cells, cardiomyocytes, pancreatic β‐cells, and hepatocytes. Compared with the extraction of other stem cells such as bone marrow‐derived mesenchymal stem cells (BMSCs), that of ADSCs requires minimally invasive techniques. In the field of regenerative medicine, the use of autologous cells is preferable to embryonic stem cells or induced pluripotent stem cells. Therefore, ADSCs are a useful resource for drug screening and regenerative medicine. Here we present the methods and mechanisms underlying the induction of multilineage cells from ADSCs. 相似文献
6.
Kaori Yoneyama Xiaonan Xie Takaya Kisugi Takahito Nomura Koichi Yoneyama 《Planta》2013,238(5):885-894
Strigolactones (SLs) are essential host recognition signals for both root parasitic plants and arbuscular mycorrhizal fungi, and SLs or their metabolites function as a novel class of plant hormones regulating shoot and root architecture. Our previous study indicated that nitrogen (N) deficiency as well as phosphorus (P) deficiency in sorghum enhanced root content and exudation of 5-deoxystrigol, one of the major SLs produced by sorghum. In the present study, we examined how N and P fertilization affects SL production and exudation in sorghum plants subjected to short- (5 days) or long-term (10 days) N or P deficiency and demonstrated their common and distinct features. The root contents and exudation of SLs in the N- or P-deficient sorghum plants grown for 6, 12 or 24 h with or without N or P fertilization were quantified by LC–MS/MS. In general, without fertilization, root contents and exudation of SLs stayed at similar levels at 6 and 12 h and then significantly increased at 24 h. The production of SLs responded more quickly to P fertilization than the secretion of SLs, while regulation of SL secretion began earlier after N fertilization. It is suggested that sorghum plants regulate SL production and exudation when they are subjected to nutrient deficiencies depending on the type of nutrient and degree of deficiency. 相似文献
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Takahito Tamai Osamu Yamaguchi Shungo Hikoso Toshihiro Takeda Manabu Taneike Takafumi Oka Jota Oyabu Tomokazu Murakawa Hiroyuki Nakayama Yoshihiro Uno Kyoji Horie Kazuhiko Nishida Nahum Sonenberg Ajay M. Shah Junji Takeda Issei Komuro Kinya Otsu 《The Journal of biological chemistry》2013,288(14):10176-10187
Cardiomyocytes proliferate during fetal life but lose their ability to proliferate soon after birth and further increases in cardiac mass are achieved through an increase in cell size or hypertrophy. Mammalian target of rapamycin complex 1 (mTORC1) is critical for cell growth and proliferation. Rheb (Ras homologue enriched in brain) is one of the most important upstream regulators of mTORC1. Here, we attempted to clarify the role of Rheb in the heart using cardiac-specific Rheb-deficient mice (Rheb−/−). Rheb−/− mice died from postnatal day 8 to 10. The heart-to-body weight ratio, an index of cardiomyocyte hypertrophy, in Rheb−/− was lower than that in the control (Rheb+/+) at postnatal day 8. The cell surface area of cardiomyocytes isolated from the mouse hearts increased from postnatal days 5 to 8 in Rheb+/+ mice but not in Rheb−/− mice. Ultrastructural analysis indicated that sarcomere maturation was impaired in Rheb−/− hearts during the neonatal period. Rheb−/− hearts exhibited no difference in the phosphorylation level of S6 or 4E-BP1, downstream of mTORC1 at postnatal day 3 but showed attenuation at postnatal day 5 or 8 compared with the control. Polysome analysis revealed that the mRNA translation activity decreased in Rheb−/− hearts at postnatal day 8. Furthermore, ablation of eukaryotic initiation factor 4E-binding protein 1 in Rheb−/− mice improved mRNA translation, cardiac hypertrophic growth, sarcomere maturation, and survival. Thus, Rheb-dependent mTORC1 activation becomes essential for cardiomyocyte hypertrophic growth after early postnatal period. 相似文献
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Toshio Saito Takahito Kohama Kenjiro Ui Shugo Watabe 《Comparative biochemistry and physiology. Part D, Genomics & proteomics》2006,1(1):158
The objective of this investigation was to study the distribution of tetrodotoxin (TTX) in the xanthid crab (Atergatis floridus) found in the coastal waters of Kanagawa and Wakayama Prefectures of Japan using mouse assay methods. We used 32 crab samples (18 males and 14 females) and toxicity was analyzed on 13 parts of the body of each sample. The muscle of chelipeds was found to be toxic in all the samples with a wide range of toxicity (5–237 MU/g), whereas the toxicity in the muscle of the cephalothorax was found to be non-toxic (below detectable limit) in all the samples [Narita, H., Watanabe, K., Baba, K., Ohgami, H., Ai, T.K., Igarashi, Y., Nara, M., Noguchi, T., Hashimoto, K., 1987. The toxicity of digestive gland of trampet shells inhabiting the coast of Shizuoka Prefecture. J. Food Hyg. Soc. Jpn. 28, 115–118.]. Further investigation of different parts of the chelipeds indicated that the muscle of the palm and carpus are usually toxic and that of merus and ischium are almost non-toxic. Toxicity of the muscles of palm ranged between 7 and 52 MU/g, whereas toxicity of the muscle of ischium was below detectable limit. Results from our study indicate clear contrast in the distribution of tetrodotoxin in muscles of different parts of the xanthid crabs, plausibly due to some inherent physiological mechanism. Further investigation is necessary to understand the mechanism responsible for such contrast. 相似文献
10.
Yasmin Akhtar Ikkei Shikano & Murray B. Isman 《Entomologia Experimentalis et Applicata》2009,132(3):275-282
We have previously determined that larval feeding experience with a feeding/oviposition deterrent modified the feeding responses of larvae and oviposition responses of subsequent moths. These behavioural changes were attributed to learning, but the possibility of chemical legacy could not be ruled out. In the present study, we have topically applied a feeding/oviposition deterrent plant extract from Hoodia gordonii (Masson) Sweet ex Decne (Asclepiadaceae) to larvae, pupae, and adults of Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae) to determine whether the feeding response of larvae and oviposition response of subsequent female moths is similarly modified by chemicals applied to the external surface of the insect. Our results indicate that traces of the extract that may be present internally or externally on the larvae do not reduce the feeding deterrent response of larvae. Furthermore, traces of the extract in or on larvae, pupae, or adult moths did not alter oviposition choice of female moths, leading us to discount the role of experience through topical application in this study. The fact that feeding/oviposition choice was only influenced by prior feeding experience of the larvae and not by topical administration suggests that habituation via sensory stimulation through mouthpart chemosensilla is likely a central phenomenon. Continuous exposure of adult moths to the extract over a period of 7 days did not affect the oviposition response of the female moths, ruling out the role of adult experience on host-plant selection in T. ni . To the best of our knowledge, this is the first study to examine the role of experience via topical application of chemicals onto all life stages of the insect except the egg. Chemical legacy may not be playing a role in influencing the oviposition choices of female T. ni moths. 相似文献