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排序方式: 共有3458条查询结果,搜索用时 31 毫秒
31.
T Akema A Chiba T Ikeda Y Nagami F Kimura J Toyoda 《Canadian Metallurgical Quarterly》1997,9(11):849-857
The present study aimed to examine the effect of melatonin on naloxone-induced luteinizing hormone (LH) secretion in ovariectomized estrogen-primed rats. A single intracerebroventricular (i.c.v.) injection of naloxone (mu opioid receptor blocker, 15 micrograms) or an intravenous (i.v.) injection of LH-releasing hormone (LHRH, 50 ng/kg) elicited a transient and significant increase in the serum LH concentration within 10 min. While an i.c.v. injection of 100 ng melatonin by itself did not change the basal LH release, it almost completely inhibited the naloxone-induced LH release. Melatonin (10 ng) also significantly reduced the effect of naloxone. However, an i.c.v. injection of 100 ng melatonin did not affect the LHRH-induced LH release. In separate experiments, the effect of melatonin on naloxone-induced pulsatile LH secretion was studied in estrogen-treated rats. A continuous i.v. infusion of naloxone (20 mg/kg/h) induced LH pulses in rats treated i.c.v. with saline. An i.c.v. administration of 100 ng melatonin, which by itself did not affect basal LH secretion, significantly reduced the frequency, but not the amplitude, of LH pulses induced by the naloxone infusion. These results show that melatonin has a suprapituitary site of action to inhibit naloxone-induced LH release, and suggest that melatonin has an effect in inhibiting the activity of the hypothalamic LHRH pulse generator, either directly or indirectly, in female rats. 相似文献
32.
T Kimura I Hashimoto M Nishikawa JI Fujisawa 《Canadian Metallurgical Quarterly》1996,78(11-12):1075-1080
Human immunodeficiency virus type-1 (HIV-1) Rev acts by inducing the specific nucleocytoplasmic transport of a class of incompletely spliced RNAs that encodes the viral structural proteins. The transfection of HeLa cells with a rev-defective HIV-1 expression plasmid, however, resulted in the export of overexpressed, intron-containing species of viral RNAs, possibly through a default process of nuclear retention. Thus, this system enabled us to directly compare Rev+ and Rev+ cells as to the usage of RRE-containing mRNAs by the cellular translational machinery. Biochemical examination of the transfected cells revealed that although significant levels of gag and env mRNAs were detected in both the presence and absence of Rev, efficient production of viral proteins was strictly dependent on the presence of Rev. A fluorescence in situ hybridisation assay confirmed these findings and provided further evidence that even in the presence of Rev, not all of the viral mRNA was equally translated. At the early phase of RNA export in Rev+ cells, gag mRNA was observed throughout both the cytoplasm and nucleoplasm as uniform fine stippling. In addition, the mRNA formed clusters mainly in the perinuclear region, which were not observed in Rev+ cells. In the presence of Rev, expression of the gag protein was limited to these perinuclear sites where the mRNA accumulated. Subsequent staining of the cytoskeletal proteins demonstrated that in Rev+ cells gag mRNA is colocalized with beta-actin in the sites where the RNA formed clusters. In the absence of Rev, in contrast, the gag mRNA failed to associate with the cytoskeletal proteins. These results suggest that in addition to promoting the emergence of intron-containing RNA from the nucleus, Rev plays an important role in the compartmentation of translation by directing RRE-containing mRNAs to the beta-actin to form the perinuclear clusters at which the synthesis of viral structural proteins begins. 相似文献
33.
The authors state that in the original paper (Kimura, Lu and Kawatani, ibid., vol. 36, p. 653-67, 1991) a lemma on (J,J')-losslessness is not correct. Its stated implications are also not fully correct. They give a counterexample to these claims and show how they can be fixed by strengthening the assumption 相似文献
34.
Nakamura M. Ishihara N. Akazawa Y. Kimura H. 《Solid-State Circuits, IEEE Journal of》1995,30(9):991-997
An instantaneous response CMOS optical-receiver IC is described with wide input dynamic range and high sensitivity. In a TCM (time compression multiplexing)-TDMA (time division multiple access) fiber-optic subscriber system, a receiver should be able to handle burst-data packets with different amplitude. This requires quick response and a wide dynamic range. Instantaneous response is achieved with a new feed-forward auto-bias adjustment technique. In addition, multistaged offset compensation provides a wide dynamic range without any external elements and adjustments. Using these design techniques, an optical receiver IC was fabricated in a standard 0.8-μm CMOS technology. The receiver has a wide dynamic range of more than 25 dB for burst-mode optical input at 29 Mb/s. It has high transimpedance gain of 150 dBΩ and high sensitivity of -42 dBm with stable operation for FET threshold voltage and power supply voltage fluctuation 相似文献
35.
T Yamamura H Matsuzaki K Seo M Kimura T Shinagawa 《Canadian Metallurgical Quarterly》1998,28(11):1175-1178
We report herein the case of a 59-year-old woman who developed a local recurrence of rectal cancer which showed extremely rapid growth. The patient had undergone a curative low anterior resection with total mesoexcision, and was discharged on postoperative day 25 after an uneventful recovery. However, 2 months after the operation, she developed bleeding from the rectum during defecation, the quantity of which gradually increased. A colonoscopy performed during the fifth postoperative month revealed a circular tumor at the suture line. The tumor was unresectable because it had firmly invaded not only the sacrum, but also the right ureter. Despite the administration of 5-fluorouracil and leucovorin, the patient died of cancer 18 months after her initial surgery. Considering that local recurrence of rectal cancer does not usually occur within 1 year after surgery, this case is unusual because the local recurrence developed very early and showed extremely rapid growth, occupying the entire lumen of the rectum by the time it was detected by colonoscopy during the fifth postoperative month. 相似文献
36.
Amorphous specimens of Fe100–x
B
x
were prepared in the range 10 × 35 at % B by a single-roller method. The crystallization process and the boron concentration dependence of the Curie temperature were examined by differential scanning calorimetry, X-ray diffraction, Mössbauer spectroscopy and magnetic measurements. Two-step crystallization was observed in specimens with× < 17: amorphous amorphous + boron-supersaturated b c c phase (-Fe(B)) t-Fe3B +-Fe. A single-Fe(B) phase was not observed. The transition temperature from t-Fe3B to stable (-Fe + t-Fe2B) sensitively depends on the boron content in the alloys. The crystallization temperature (T
x) of the amorphous alloys was almost unchanged for 17 × 31, but increased remarkably at high boron concentrations of× 33, where the decomposition products consisted of t-Fe2B and o-FeB. The Curie temperature (T
c) of the amorphous phase was as low as 480 K at× = 10, increased with increasing boron content up to 820 K and then decreased in the high boron concentration alloys of× > 28. A single-Fe(B) phase was not detected in the as-quenched specimens of× = 8 and 10. The phase coexisted with the o-Fe3B and amorphous phases. The lattice parameter of the phase was 0.28610 nm which was smaller than that of pure iron by 2/1000, indicating the substitutional occupation of boron atoms in the b c c lattice. 相似文献
37.
Rod-shaped BaTiO3 powder particles have been prepared from rod-shaped TiO2 ·nH2O and BaCO3 in molten chloride. The morphology of BaTiO3 particles was studied referring to the effects of the chemical species of the starting titanium compound, amount of chloride, particle size of the titanium compound and reaction conditions, and the preparation condition of rod-shaped BaTiO3 has been determined: i.e., large TiO2 ·nH2O particles were heated at 700°C in molten salt with an equal amount of BaTiO3. This condition was effective in suppressing the formation of BaTiO3 by a solution-precipitation process as well as the deformation of either TiO2 ·nH2O or BaTiO3, which are responsible for the formation of equiaxed BaTiO3 particles. The obtained rod-shaped BaTiO3 particles had a cubic symmetry. Electron diffraction analysis showed that the following topotactic relation is retained; 0 1 0potassium tetratitanate 0 1 0hydrated titania 1 0 0anatase 1 0 0barium titanate 相似文献
38.
Modified quadratic discriminant functions and the application to chinese character recognition 总被引:8,自引:0,他引:8
Kimura F Takashina K Tsuruoka S Miyake Y 《IEEE transactions on pattern analysis and machine intelligence》1987,(1):149-153
Issues in the quadratic discriminant functions (QDF) are discussed and two types of modified quadratic disriminant functions (MQDF1, MQDF2) which are less sensitive to the estimation error of the covariance matrices are proposed. The MQDF1 is a function which employs a kind of a (pseudo) Bayesian estimate of the covariance matrix instead of the maximum likelihood estimate ordinarily used in the QDF. The MQDF2 is a variation of the MQDF1 to save the required computation time and storage. Two discriminant functions were applied to Chinese character recognition to evaluate their effectiveness, and remarkable improvement was observed in their performance. 相似文献
39.
Hai -Hang Li Masafumi Inoue Hiroyuki Nishimura Junya Mizutani Eiji Tsuzuki 《Journal of chemical ecology》1993,19(8):1775-1787
Phenolic compounds have been identified as the most common allelochemicals produced by higher plants. Inhibitions of cinnamic acid, its related phenolic derivatives, and abscisic acid (ABA) on seedling growth and seed germination of lettuce were studied.trans-Cinnamic acid, ando-,m-, andp-coumaric acids inhibited the growth of etiolated seedlings of lettuce at concentrations higher than 10–4 M and seed germination above 10–3 M. Coumarin inhibited seedling growth and seed germination at 10–5 M or above. Chlorogenic acid inhibited seedling growth above 10–4 M, but did not inhibit seed germination at 10–5–5×10–3 M. Low concentrations (below 10–3 M) of caffeic and ferulic acids promoted the elongation of hypocotyls, but higher concentrations (over 10–3 M) inhibited seedling growth and seed germination. These phenolic compounds and abscisic acid had additive inhibitory effects both on seedling growth and seed germination. The inhibition on lettuce was reversed by caffeic and ferulic acids at concentrations lower than 10–3 M except for the inhibition of germination by coumarin. These results suggest that in naturetrans-cinnamic acid,o-, m-, p-coumaric acids, coumarin, and chlorogenic acid inhibit plant growth regardless of their concentration. However, caffeic and ferulic acids can either promote or inhibit plant growth according to their concentration. 相似文献
40.
T. Kimura T. Tokuda Y. Nakada T. Nokajima T. Matsumoto A. Doucet 《Pattern Analysis & Applications》2013,16(1):55-67
Mixture models are ubiquitous in applied science. In many real-world applications, the number of mixture components needs to be estimated from the data. A popular approach consists of using information criteria to perform model selection. Another approach which has become very popular over the past few years consists of using Dirichlet processes mixture (DPM) models. Both approaches are computationally intensive. The use of information criteria requires computing the maximum likelihood parameter estimates for each candidate model whereas DPM are usually trained using Markov chain Monte Carlo (MCMC) or variational Bayes (VB) methods. We propose here original batch and recursive expectation-maximization algorithms to estimate the parameters of DPM. The performance of our algorithms is demonstrated on several applications including image segmentation and image classification tasks. Our algorithms are computationally much more efficient than MCMC and VB and outperform VB on an example. 相似文献