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排序方式: 共有6842条查询结果,搜索用时 15 毫秒
61.
肝细胞生长因子mRNA在成年小鼠和人胎儿不同器官中的表达 总被引:2,自引:0,他引:2
本实验从成年小鼠和胎龄4-5月的人胎儿不同器官中分离总RNA。经斑点印迹分析显示,肝细胞生长因子(HGF)mRNA在成年KM小鼠多种器官中表达,其表达水平由高到低依次为:肺、肝、肾、卵巢、睾丸、大脑和胃;在脾、心、骨髓、小肠和骨骼肌组织中以HGFmRNA。在胎龄4-5月的人胎儿中,HGFmRNA表达水平由高到低依次为:大脑、肝、腮腺、胃、小肠、肾、心和骨骼肌;肺和脾组织为阴性。由此可见,HGF在成 相似文献
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63.
Regulation of GABAB receptors by histamine and neuronal activity in the isolated spinal cord of neonatal opossum in culture. 总被引:1,自引:0,他引:1
D J Zou J M Treherne R R Stewart N R Saunders J G Nicholls 《Proceedings. Biological sciences / The Royal Society》1991,246(1315):77-82
The aim of these experiments has been to analyse the properties of receptors for the transmitter gamma-aminobutyric acid (GABA) in developing mammalian nervous system. Changes in responses of GABAB receptors have been measured after alterations of the chemical environment and the level of electrical activity. We have previously shown that when the central nervous system (CNS) of the new-born opossum, Monodelphis domestica, is cultured for three to five days in the presence of histidine, inhibition by baclofen, a GABAB agonist, disappears (Stewart et al. 1991). We have now investigated whether histidine acts indirectly by way of conversion to histamine. As with histidine, culture with 150 microM histamine for five days virtually abolished the inhibition by baclofen. The effects of histidine, as well as histamine, were blocked by mepyramine, a histamine H1-receptor antagonist, and by ranitidine, an H2-antagonist. Tetrodotoxin (TTX), which blocks all electrical activity, protected preparations from the action of histidine but not histamine. Our results suggest that histidine is converted to histamine, which reduces the efficacy of GABAB agonists. We conclude that, in the developing mammalian CNS, transmitter levels and electrical activity can selectively influence the properties of receptors. 相似文献
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本文首次研究了田菁蛋白胨一般化学成份、氨基酸组份、肽链平均长度、微量元素、维生素以及红外、紫外光谱等。本文还将田菁蛋白胨氨基酸、红外光谱等和英国大豆蛋白胨作了比较。研究结果附图表于后。 相似文献
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67.
A new method for estimating gross phosphorus mineralization and immobilization rates in soils 总被引:7,自引:1,他引:6
Phosphorus availability in soils is controlled by both the sizes of P pools and the transformation rates among these pools. Rates of gross P mineralization and immobilization are poorly known due to the limitations of available analytical techniques. We developed a new method to estimate P transformation rates in three forest soils and one grassland soil representing an Alfisol, an Ultisol, and Andisol, and a Mollisol. Three treatments were applied to each soil in order to separate the processes of mineral P solubilization, organic P mineralization, and solution P immobilization. One set of soils was retained as control, a second set was irradiated with -rays to stop microbial immobilization, and a third was irradiated and then autoclaved, also stop phosphatase activity. All three sets of samples were then incubated with anion exchange resin bags under aerobic conditions. Differences in resin P among the three treatments were used to estimate gross P mineralization and immobilization rates. Autoclaving did not affect resin-extractable P in any of the soils. Radiation did not alter resin-extractable P in the forest soils but increased resin-extractable P in the grassland soil. This increase was corrected in the calculation of potential P transformation rates. Effects of radiation on phosphatase activity varied with soils but was within 30% of the original values. Rates of P gross mineralization and immobilization ranged from 0.6–3.8 and 0–4.3 mg kg-soil-1 d-1, respectively, for the four soils. The net rates of solubilization of mineral P in the grassland soil were 7–10 times higher than the rates in forest soils. Mineralization of organic P contributed from 20–60% of total available P in the acid forest soils compared with 6% in the grassland soil, suggesting that the P mineralization processes are more important in controlling P availability in these forest ecosystems. This new method does not require an assumption of equilibrium among P pools, and is safer and simpler in operation than isotopic techniques. 相似文献
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F T Greenaway C Y O'Gara J M Marchena J W Poku J G Urtiaga Y Zou 《Archives of biochemistry and biophysics》1991,285(2):291-296
The carbonyl cofactor of bovine plasma amine oxidase (EC 1.4.3.6), recently shown to be 6-hydroxydopa (also known as topa), has been spin labeled to the extent of one label per enzyme dimer molecule, using 4-amino-2,2,6,6-tetramethylpiperidine-N-oxyl (4-amino-TEMPO) and 4-hydrazino-TEMPO followed by reduction with borohydride. By studying the EPR spectra of the labeled enzyme, it has been deduced that there is no magnetic interaction between the copper and the spin label, and that the spin label is at least 1.3 nm distant from the copper(II) ion in the resting enzyme. The bound label is strongly immobilized, is in a sterically constricted environment, and is not accessible to small anions. Removal of the copper does not alter the EPR spectrum of the label. The results are similar to results for porcine plasma amine oxidase, and show that the copper is not close to, and does not directly interact with, the topa-bound substrate. 相似文献
70.
龟纹瓢虫幼虫的食物搜索行为 总被引:10,自引:1,他引:9
本试验采用Nakamuta(1982)装置研究龟纹瓢虫Propylea japonica(Thunberg)幼虫的食饵搜索行为,结果表明:1.五种刺激均能激发搜索行为由广域型转换为地域集中型;2.摄食时间与GUT呈正相关;3.摄食的最后一个食饵大小决定GUT的长短;4.摄食后0—15秒的搜索速度小、弯曲角度大. 相似文献