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排序方式: 共有87条查询结果,搜索用时 15 毫秒
1.
Manabu Sakakibara Carlos Collin Alan Kuzirian Daniel L. Alkon Eliahu Heldman Shigetaka Naito Izja Lederhendler 《Journal of neurochemistry》1987,48(2):405-416
Type B photoreceptors of the nudibranch mollusc Hermissenda crassicornis receive excitatory synaptic potentials (EPSPs) whose frequency is controlled by potential changes of a neighboring cell known as the S optic ganglion cell which is thought to be electrically coupled to the presynaptic source of these EPSPs, the E optic ganglion cell. The frequency of the EPSPs increases when a conditioned stimulus (light) is paired with an unconditioned stimulus (rotation) during acquisition of a Pavlovian conditioned response. The results of the present study are consistent with an adrenergic origin for these EPSPs. Noradrenergic agonists (greater than 100 microM), norepinephrine and clonidine, only slightly depolarize the type B cell but clearly prolong its depolarizing response to light. Serotonin, by contrast, causes hyperpolarization of the type B cell's resting potential as well as after a light step. Clonidine reduces voltage-dependent outward K+ currents (IA, an early current, ICa2+-K+, a late Ca2+-dependent current) that control the type B cell's excitability (and thus its light response and membrane potential). These effects of clonidine are reduced or blocked by the alpha 2-receptor antagonist, yohimbine (0.5 microM), but not the alpha 1-blocker, prazosin. The same yohimbine concentration also blocked depolarizing synaptic excitation of the type B cell in response to depolarization of a simultaneously impaled S optic ganglion cell. Histochemical techniques (both the glyoxylic acid method of de la Torre and Surgeon and the formaldehyde-induced fluorescence or Falck-Hillarp method) demonstrated the presence of a biogenic amine(s) within a single neuron in each optic ganglion as well as three or four cells within the vicinity of previously identified visual interneurons. No serotonergic neurons were found within the optic ganglion or in proximity to visual interneurons. A clonidine-like synaptic effect on type B cells, therefore, could amplify conditioning-specific changes of membrane currents by increasing type B depolarization and possibly, as well, by elevating intracellular second messengers. 相似文献
2.
R.L. Horst B.C. Pramanik T.A. Reinhardt S.-J. Shiuey J.J. Partridge M.R. Uskokovic J.L. Napoli 《Biochemical and biophysical research communications》1982,106(3):1006-1011
23,25-Dihydroxyvitamin D3 was isolated from the plasma of vitamin D3-toxic pigs. An ultraviolet absorbance spectrum confirmed its purity. The configuration of the 23-hydroxyl group was determined to be S by comparison of the natural product with synthetic 23,25- and 23,25-dihydroxyvitamin D3 by high-pressure liquid chromatography. The affinity of both 23,25- and 23,25-dihydroxyvitamin D3 for the plasma vitamin D binding protein was similar to vitamin D3. Thus, with respect to the plasma vitamin D binding protein, 23,25-dihydroxyvitamin D3 is the least potent, naturally-occurring, dihydroxylated vitamin D3 metabolite known. 相似文献
3.
Timothy A. Reinhardt Ronald L. Horst E.Travis Littledike Donald C. Beitz 《Biochemical and biophysical research communications》1982,106(3):1012-1018
1,25-Dihydroxyvitamin D3 [1,25-(OH)2D3] receptor was characterized after partial purification of thymus cytosol by ammonium sulfate fractionation. The 1,25-(OH)2D3 receptor sediments at 3.7S in 5–20% sucrose gradients. The binding of 1,25-(OH)2D3 in thymic cytosol was a saturable process with high affinity (Kd = 0.12?0.48 nM) at 4°C. Competition for 1,25-(OH)2[3H]D3 receptor by nonradioactive analogs demonstrated the affinities of these analogs to be in order; 1,25-(OH)2D3 = 1,24R,25-(OH)3D3 = 1,25S,26-(OH)3D3 = 1,25R,26-(OH)3D3 > 1,25-(OH)2D3-26,23 lactone > 25-OHD3 > 23R,25-(OH)2D3 > 24R,25-(OH)2D3 > 23S,25-(OH)2D3 ? 25-OHD3-26,23 lactone. The receptor bound to DNA cellulose columns in low salt buffer and eluted as a single peak at 0.21 M KCl. These findings provide evidence that the thymus possesses a 1,25-(OH)2D3 receptor with properties indistinguishable from 1,25-(OH)2D3 receptors in other tissues. 相似文献
4.
Cheng Chu Gang Xu Xiaocong Li Zuowei Duan Lihong Tao Hongxia Cai Ming Yang Xinjiang Zhang Bin Chen Yanyu Zheng Hongcan Shi Xiaoyu Li 《Journal of cellular and molecular medicine》2021,25(1):110-119
Shear stress was reported to regulate the expression of AC007362, but its underlying mechanisms remain to be explored. In this study, to isolate endothelial cells of blood vessels, unruptured and ruptured intracranial aneurysm (IA) tissues were collected from IA patients. Subsequently, quantitative real-time PCR (qRT-PCR), Western blot and luciferase assay were performed to investigate the relationships between AC007362, miRNAs-493 and monocyte chemoattractant protein-1 (MCP-1) in human umbilical vein endothelial cells (HUVECs) exposed to shear stress. Reduced representation bisulphite sequencing (RRBS) was performed to assess the level of DNA methylation in AC007362 promoter. Accordingly, AC007362 and MCP-1 were significantly up-regulated while miR-493 was significantly down-regulated in HUVECs exposed to shear stress. AC007362 could suppress the miR-493 expression and elevate the MCP-1 expression, and miR-493 was shown to respectively target AC007362 and MCP-1. Moreover, shear stress in HUVECs led to the down-regulated DNA methyltransferase 1 (DNMT1), as well as the decreased DNA methylation level of AC007362 promoter. Similar results were also observed in ruptured IA tissues when compared with unruptured IA tissues. In conclusion, this study presented a deep insight into the operation of the regulatory network of AC007362, miR-493 and MCP-1 upon shear stress. Under shear stress, the expression of AC007362 was enhanced by the inhibited promoter DNA methylation, while the expression of MCP-1 was enhanced by sponging the expression of miR-493. 相似文献
5.
Masaru Matsumoto 《Archives Of Phytopathology And Plant Protection》2013,46(9):1082-1088
In the present study, characterisation of genotypic variations of Rhizoctonia solani AG-1 IA associated with rice sheath blight by Rep-PCR assay and their structure of the genotypic variations by monitoring vertical and horizontal movements of their populations at a short distance level were investigated in Japanese paddy fields. Differences of the Rep-PCR fingerprintings were observed and distinguished into four genotypic variations referred to as GI, GII, GIII and GIV, respectively. Although similarity index of each genotype showed high levels of homology (85–90%) within the same genotypes, low levels of similarity index (65–70%) were also varied among the comparison of different genotypes. Moreover, diversity of genotypic populations was observed which is consistent with the correlations between the geographical undulations of the paddy fields and the occupation of their genotypic populations, indicating the presence of genotype GI on low lands such as AK1 and also the presence ofgenotype GIV on high lands such as AK4. 相似文献
6.
7.
瞬间外向钾电流(IA)具有快速激活和失活等特征,是动作电位复极化早期外向钾离子电流的主要成分,广泛分布在海马神经元,树突处尤为突出.该电流通过减慢去极化速度和延缓动作电位的产生等作用,调节突触的输入和动作电位的反向传播,从而在信号整合及突触可塑性等过程中扮演重要角色.很多人类疾病,如癫痫性疾病等,和海马神经元的IA电流有关. 相似文献
8.
Pirman NL Milshteyn E Galiano L Hewlett JC Fanucci GE 《Protein science : a publication of the Protein Society》2011,20(1):150-159
Electron paramagnetic resonance (EPR) spectroscopy coupled with site-directed spin labeling (SDSL) is a valuable tool for characterizing the mobility and conformational changes of proteins but has seldom been applied to intrinsically disordered proteins (IDPs). Here, IA3 is used as a model system demonstrating SDSL-EPR characterization of conformational changes in small IDP systems. IA3 has 68 amino acids, is unstructured in solution, and becomes α-helical upon addition of the secondary structural stabilizer 2,2,2-trifluoroethanol (TFE). Two single cysteine substitutions, one in the N-terminus (S14C) and one in the C-terminus (N58C), were generated and labeled with three different nitroxide spin labels. The resultant EPR line shapes of each of the labels were compared and each reported changes in mobility upon addition of TFE. Specifically, the spectral line shape parameters h(+1)/h(0), the local tumbling volume (VL), and the percent change of the h(−1) intensity were utilized to quantitatively monitor TFE-induced conformational changes. The values of h(+1)/h(0) as a function of TFE titration varied in a sigmoidal manner and were fit to a two-state Boltzmann model that provided values for the midpoint of the transition, thus, reporting on the global conformational change of IA3. The other parameters provide site-specific information and show that S14C-SL undergoes a conformational change resulting in more restricted motion than N58C-SL, which is consistent with previously published results obtained by studies using NMR and circular dichroism spectroscopy indicating a higher degree of α-helical propensity of the N-terminal segment of IA3. Overall, the results provide a framework for data analyzes that can be used to study induced unstructured-to-helical conformations in IDPs by SDSL. 相似文献
9.
Depressed energy metabolism and oxidative stress are common features in many pathological situations in the brain, including stroke. In order to investigate astrocytic responses to such stress, we induced metabolic depression in cultured rat astrocytes. Iodoacetate (IA), an inhibitor of the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used and resulted in a rapid inhibition of GAPDH activity. After 1h of GAPDH inhibition the ATP levels started to decrease and were completely abolished at 4h. In parallel, the activity of reactive oxygen species (ROS) was significantly increased, followed by extensive cell death involving flipping of phosphatidylserine and translocation of apoptosis-inducing factor, but not caspase-3 activation. When IA was combined with azide, a respiratory chain complex IV inhibitor, the ATP levels decreased immediately. Interestingly, with azide present, the ROS activity remained low and the astrocytes remained viable even at very low ATP levels. Addition of exogenous ROS-scavengers prevented the IA-induced ROS activity, the ATP levels were maintained and cell death was prevented. Similar protection could be obtained when astrocytes, prior to addition of IA, were incubated with substances known to activate the nuclear factor erythroid 2-related factor 2 (Nrf2)-regulated endogenous antioxidant system. When IA was washed out, after a relatively moderate ATP depression, massive cell death occurred. This was efficiently prevented by addition of azide or ROS scavengers during the IA treatment or by pre-activation of the Nrf2 system. Our results demonstrate that astrocytes in culture can endure and recover from glycolytic inhibition if the ROS activity remained at a low level and suggest that oxidative stress can be an important component for astrocytic cell death following metabolic stress. 相似文献
10.
Alessandra Fierabracci Carla Bizzarri Alessia Palma Annamaria Milillo Emanuele Bellacchio Marco Cappa 《Gene》2012