GABA_A受体在酒精依赖中作用的研究进展

酒精依赖的产生机制是由特定的GABAA受体亚单位介导的,并且能够影响其它GABAA受体亚单位,使其对一定剂量的酒精敏感。此外酒精还可以通过细胞内信号转导途径影响GABA在大脑不同区域及核团单元的表达。焦虑、抗惊厥、镇静催眠、认知功能障碍等由酒精依赖产生的现象或者机制,均与GABA受体的介导有关。这些机制包括酒精对GABAA受体的直接或间接的作用,以及GABA的合成和释放。因此对GABAA受体功能的研究,将有助于人们关注酒精依赖现象及其治疗手段,为寻找酒精依赖治疗药物和治疗酒精中毒的机制的提供新线索。     

认知负荷对色词Stroop干扰效应的影响

目的:依据负荷理论,认知负荷会导致选择性注意任务中干扰刺激干扰效应的增加.本研究目的在于检验两种类型的认知负荷对色词Stroop干扰效应的影响.方法:实验一通过比较色词Stroop任务与言语工作记忆任务同时进行的双任务区组(高负荷条件)与单任务区组(低负荷条件)来检验认知负荷对构成Stroop干扰效应的语义冲突及反应冲突产生的影响.实验二则通过比较色词Stroop任务与言语工作记忆任务相协调的双任务区组(高负荷条件)与单任务区组(低负荷条件)来操纵认知负荷.结果:实验一的结果显示工作记忆负荷变化对语义冲突及反应冲突均不产生影响.实验二发现虽然在反应时指标上认知负荷与一致性之间未产生显著交互作用,但在错误率指标上两者交互作用达到显著,说明在高认知负荷条件下反应冲突显著增加了.结论:认知负荷对选择性注意任务中干扰刺激干扰效应的影响取决于认知负荷类型及冲突所发生的水平.     

GABAA受体在酒精依赖中作用的研究进展

酒精依赖的产生机制是由特定的GABAA受体亚单位介导的,并且能够影响其它GABAA受体亚单位,使其对一定剂量的酒精敏感.此外酒精还可以通过细胞内信号转导途径影响GABA在大脑不同区域及核团单元的表达.焦虑、抗惊厥、镇静催眠、认知功能障碍等由酒精依赖产生的现象或者机制,均与GABA受体的介导有关.这些机制包括酒精对GABAA受体的直接或间接的作用,以及GABA的合成和释放.因此对GABAA受体功能的研究,将有助于人们关注酒精依赖现象及其治疗手段,为寻找酒精依赖治疗药物和治疗酒精中毒的机制的提供新线索.     

双联抗血小板治疗急性冠脉综合征临床疗效观察

目的:探讨双联抗血小板治疗急性冠脉综合征(ACS)的临床疗效和安全性。方法:60例ACS患者随机分为治疗组和对照组。对照组给予阿司匹林单抗血小板治疗,治疗组采用阿司匹林+氯吡格雷双联抗血小板治疗,治疗3个月后评价临床疗效。结果:治疗组临床疗效总有效率为93.3%,显著高于对照组(76.7%),相比较有显著性差异(P<0.05);治疗后,两组LVEF、CO、E/A显著上升,与治疗前比较均有显著性差异(P<0.05);且治疗组与对照组比较有显著性差异(P<0.05)。结论:阿司匹林和氯吡格雷双联抗血小板药物治疗ACS,可以强化对血小板聚集的抑制,并增强抗栓效果,值得临床应用。     

MECHANISMS OF RAPID PHOTOSYNTHETIC ADAPTATION IN NATURAL PHYTOPLANKTON COMMUNITIES. I. REDISTRIBUTION OF EXCITATION ENERGY BETWEEN PHOTOSYSTEMS I AND II1

An inverse linear relationship between chlorophyll fluorescence yield (R) and light intensity was recorded in the near-surface waters of six lakes (New Zealand, England) of greatly different trophic status and phytoplankton species composition. This surface depression of R values could be removed by incubation of samples in dim light or darkness and was not observed in situ below a threshold irradiance (146 μEin ·m^?2·s^?1 for Lake Taupo, New Zealand). The time course of chlorophyll fluorescence depression and recovery in response to light treatment was measured in samples from Lake Windermere (England). Fluorescence exponentially decreased upon exposure to bright light and the response was 100% (5 m samples) or 83% (dim light-adapted 0 m samples) complete within 2 min. An increase in R values in the dim light occurred after a lag of 60 s and the rate of increase decreased exponentially with time. Full recovery took 15 min or more. Deep (6.5 m) populations from Lake Windermere exhibited large, time-dependent variations in chlorophyll fluorescence over the first 25 s of exposure to 450 nm light, whereas surface populations did not. These data were interpreted in terms of decreased spillover from PSII to PSI with increasing depth, to a minimum at the threshold light intensity below which cells are in light state 1.     

Spatially resolved characterization of biogenic manganese oxide production within a bacterial biofilm

Pseudomonas putida strain MnB1, a biofilm-forming bacterial culture, was used as a model for the study of bacterial Mn oxidation in freshwater and soil environments. The oxidation of aqueous Mn+2 [Mn+2(aq)] by P. putida was characterized by spatially and temporally resolving the oxidation state of Mn in the presence of a bacterial biofilm, using scanning transmission X-ray microscopy (STXM) combined with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at the Mn L2,3 absorption edges. Subsamples were collected from growth flasks containing 0.1 and 1 mM total Mn at 16, 24, 36, and 48 h after inoculation. Immediately after collection, the unprocessed hydrated subsamples were imaged at a 40-nm resolution. Manganese NEXAFS spectra were extracted from X-ray energy sequences of STXM images (stacks) and fit with linear combinations of well-characterized reference spectra to obtain quantitative relative abundances of Mn(II), Mn(III), and Mn(IV). Careful consideration was given to uncertainty in the normalization of the reference spectra, choice of reference compounds, and chemical changes due to radiation damage. The STXM results confirm that Mn+2(aq) was removed from solution by P. putida and was concentrated as Mn(III) and Mn(IV) immediately adjacent to the bacterial cells. The Mn precipitates were completely enveloped by bacterial biofilm material. The distribution of Mn oxidation states was spatially heterogeneous within and between the clusters of bacterial cells. Scanning transmission X-ray microscopy is a promising tool for advancing the study of hydrated interfaces between minerals and bacteria, particularly in cases where the structure of bacterial biofilms needs to be maintained.     

Importance of temporal flow gradients and integrin alphaIIbbeta3 mechanotransduction for shear activation of platelets

Disturbances of blood flow play an important role in promoting platelet activation and arterial thrombus formation in stenosed, injured, atherosclerotic arteries. To date, glycoprotein Ib (GPIb) has been considered the primary platelet mechanosensory receptor, responding to increased shear with enhanced adhesive and signaling function. We demonstrate here that von Willebrand factor-GPIb interaction is inefficient at inducing platelet activation even when platelets are exposed to very high wall shear stresses (60 dyn/cm(2)). Rapid platelet activation under flow was only observed under experimental conditions in which transiently adherent platelets were exposed to sudden accelerations in blood flow. Platelet responsiveness to temporal shear gradients was integrin alpha(IIb)beta(3)-dependent and occurred only on a von Willebrand factor substrate, as platelets forming integrin alpha(IIb)beta(3) adhesive contacts with immobilized fibrinogen were unresponsive to sudden increases in shear. The calcium response induced by temporal shear gradients was distinct from previously identified integrin alpha(IIb)beta(3) calcium responses in terms of its transient nature, its requirement for platelet co-stimulation by the P2Y(1) purinergic ADP receptor, and its dependence on the influx of extracellular calcium. Our studies demonstrate a key role for temporal shear gradients in promoting platelet activation. Moreover, they define for the first time the involvement of P2Y receptors in integrin mechanotransduction.     

Evidence from biosynthetically incorporated strontium and FTIR difference spectroscopy that the C-terminus of the D1 polypeptide of photosystem II does not ligate calcium

Recent FTIR studies have provided evidence that the C-terminal alpha-COO(-) group of the D1 polypeptide at D1-Ala344 is a unidentate ligand of a Mn ion in photosystem II [Chu, H.-A., Hiller, W., and Debus, R. J. (2004) Biochemistry 43, 3152-3166; Kimura, Y., Mizusawa, N., Yamanari, T., Ishii, A., and Ono, T.-A. (2005) J. Biol. Chem. 280, 2078-2083]. However, the FTIR data could not exclude Ca ligation. Furthermore, the recent approximately 3.5 A X-ray crystallographic structural model positions the alpha-COO(-) group of D1-Ala344 near a Ca ion [Ferreira, K. N., Iverson, T. M., Maghlaoui, K., Barber, J., and Iwata, S. (2004) Science 303, 1831-1838]. Therefore, to conclusively establish whether the alpha-COO(-) group of D1-Ala344 ligates Mn or Ca, the symmetric carboxylate stretching mode of the alpha-COO(-) group of D1-Ala344 was identified in the S(2)-minus-S(1) FTIR difference spectrum of PSII particles having Sr substituted for Ca. Cells of the cyanobacterium Synechocystis sp. PCC 6803 were propagated in media having Sr substituted for Ca and containing either l-[1-(13)C]alanine or unlabeled ((12)C) alanine. The S(2)-minus-S(1) FTIR difference spectra of the purified PSII particles show that substituting Sr for Ca alters several carboxylate stretching modes, including some that may correspond to one or more metal ligands, but importantly does not alter the symmetric carboxylate stretching mode of the alpha-COO(-) group of D1-Ala344. In unlabeled PSII particles, this mode appears at approximately 1356 cm(-)(1) in the S(1) state and at either approximately 1337 or approximately 1320 cm(-)(1) in the S(2) state, irrespective of whether the PSII particles contain Ca or Sr. These data are inconsistent with Ca ligation and show, therefore, that the C-terminal alpha-COO(-) group of the D1 polypeptide ligates a Mn ion. These data also show that substituting Ca with the larger Sr ion perturbs other unidentified carboxylate groups, at least one of which may ligate the Mn(4) cluster.