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11.
12.
Gonad-stimulating substance, a hormonal peptide released from the nervous system of starfishes, acts on the ovary to produce 1-methyladenine, an inducer of oocyte maturation. Addition of methionine to the incubation mixture of ovarian fragments and gonad-stimulating substance enhanced the production of 1-methyladenine, whereas ethionine inhibited it. Incubation of ovarian tissue with methionine alone failed to produce 1-methyladenine. Use of a radioactive label showed that methionine is a methyl donor in the biosynthesis of 1-methyladenine, suggesting that gonad-stimulating substance is involved in the methylation process. 相似文献
13.
Noguchi T Nakamura T Kimura M Zolensky ME Tanaka M Hashimoto T Konno M Nakato A Ogami T Fujimura A Abe M Yada T Mukai T Ueno M Okada T Shirai K Ishibashi Y Okazaki R 《Science (New York, N.Y.)》2011,333(6046):1121-1125
The reflectance spectra of the most abundant meteorites, ordinary chondrites, are different from those of the abundant S-type (mnemonic for siliceous) asteroids. This discrepancy has been thought to be due to space weathering, which is an alteration of the surfaces of airless bodies exposed to the space environment. Here we report evidence of space weathering on particles returned from the S-type asteroid 25143 Itokawa by the Hayabusa spacecraft. Surface modification was found in 5 out of 10 particles, which varies depending on mineral species. Sulfur-bearing Fe-rich nanoparticles exist in a thin (5 to 15 nanometers) surface layer on olivine, low-Ca pyroxene, and plagioclase, which is suggestive of vapor deposition. Sulfur-free Fe-rich nanoparticles exist deeper inside (<60 nanometers) ferromagnesian silicates. Their texture suggests formation by metamictization and in situ reduction of Fe(2+). 相似文献
14.
Ebihara M Sekimoto S Shirai N Hamajima Y Yamamoto M Kumagai K Oura Y Ireland TR Kitajima F Nagao K Nakamura T Naraoka H Noguchi T Okazaki R Tsuchiyama A Uesugi M Yurimoto H Zolensky ME Abe M Fujimura A Mukai T Yada Y 《Science (New York, N.Y.)》2011,333(6046):1119-1121
A single grain (~3 micrograms) returned by the Hayabusa spacecraft was analyzed by neutron activation analysis. This grain is mainly composed of olivine with minor amounts of plagioclase, troilite, and metal. Our results establish that the Itokawa sample has similar chemical characteristics (iron/scandium and nickel/cobalt ratios) to chondrites, confirming that this grain is extraterrestrial in origin and has primitive chemical compositions. Estimated iridium/nickel and iridium/cobalt ratios for metal in the Itokawa samples are about five times lower than CI carbonaceous chondrite values. A similar depletion of iridium was observed in chondrule metals of ordinary chondrites. These metals must have condensed from the nebular where refractory siderophile elements already condensed and were segregated. 相似文献
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16.
Sato T Takada M Shibuya H Shirai W Matsuo K 《Journal of veterinary medicine. A, Physiology, pathology, clinical medicine》2004,51(1):23-26
'Granular cell' tumor observed in the malar subcutis of a Djungarian hamster was examined to determine its cellular origin. Histologically, the tumor consisted of a solid growth of oval or spindle-shaped large cells with abundant cytoplasm filled with eosinophilic granules that were periodic acid-Schiff-positive and diastase-resistant. Immunohistochemically, the tumor cells were positive to anti-vimentin and anti-desmin antibodies and a few cells showed positivity to anti-actin antibody as well. They did not react to myoglobin, S-100 protein, and glial fibrillary acidic protein (GFAP). Electron microscopic studies revealed that the tumor cells had pinocytotic vesicles, dense plaque and microfilaments. The first granular cell variant of myogenic tumor reported here in Djungarian hamsters was differentiated from granular cell tumor of Schwann cell origin. 相似文献
17.
Okada T Shirai K Yamamoto Y Arai T Ogawa K Hosono K Kato M 《Science (New York, N.Y.)》2006,312(5778):1338-1341
X-ray fluorescence spectrometry of asteroid 25143 Itokawa was performed by the x-ray spectrometer onboard Hayabusa during the first touchdown on 19 November 2005. We selected those data observed during relatively enhanced solar activity and determined average elemental mass ratios of Mg/Si = 0.78 +/- 0.09 and Al/Si = 0.07 +/- 0.03. Our preliminary results suggest that Itokawa has a composition consistent with that of ordinary chondrites, but primitive achondrites cannot be ruled out. Among ordinary chondrites, LL- or L-chondrites appear to be more likely than H-chondrites. No substantial regional difference was found on the asteroid surface, indicating its homogeneity in composition. 相似文献
18.
Kaji N Okuno A Ohno-Ichiki K Oki H Ishizawa H Shirai M Asai F 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2012,74(9):1185-1189
Plasma profiles of glucose, insulin and lipids were examined in the male WBN/Kob-Lepr(fa) (fa/fa) rat, a new model of type 2 diabetes (T2D), in comparison with age-matched original male WBN/Kob (lean) rats. The fa/fa rats developed hypertriglycemia, obesity and hyperglycemia from 5, 7, and 9 weeks of age, respectively. Plasma insulin levels in fa/fa rats were significantly higher than those in lean rats at 5 weeks of age, but after 11 weeks of age gradually declined to the levels in lean rats. HOMA-IR, a measure of insulin resistance status, showed that fa/fa rats had insulin resistance. The fa/fa rat has the potential to become an important animal model of T2D with obesity. 相似文献
19.
20.
Surveys of beni-zuwai crab were conducted to clarify the bathymetric distribution and fecundity of beni-zuwai crab populations
without the effects of bias due to fisheries. The results were compared with previous ones obtained at the heavily exploited
Yamato Bank. Two sites in the northern part of the Sea of Japan, off southwest Hokkaido (200–2500 m deep) and West-Tsugaru
Basin (300–1900 m deep), both of which are experiencing low exploitation levels, were surveyed in August to September, 2007.
There was an abundance of morphologically immature crabs of both sexes in the depth range 1800–2100 m, and a few occurred
at depths >2200 m. Immature crabs of <40 mm carapace width were found to migrate downslope to depths of 1800–2100 m and then
to migrate upslope during molting for males and after maturity molting for females. Although data were lacking for depths
>2000 m at the West-Tsugaru Basin, these relationships were significant for the pooled data of both localities, and they were
similar to the results at the Yamato Bank. Clutch fullness of ovigerous females was negatively correlated with depth, which
indicates that the low clutch fullness was not induced by fisheries, although the similar phenomenon observed at the Yamato
Bank had previously been considered to be due to fishery effects. 相似文献