Localization of the K+ lock-In and the Ba2+ binding sites in a voltage-gated calcium-modulated channel. Implications for survival of K+ permeability.

Using Ba2+ as a probe, we performed a detailed characterization of an external K+ binding site located in the pore of a large conductance Ca2+-activated K+ (BKCa) channel from skeletal muscle incorporated into planar lipid bilayers. Internal Ba2+ blocks BKCa channels and decreasing external K+ using a K+ chelator, (+)-18-Crown-6-tetracarboxylic acid, dramatically reduces the duration of the Ba2+-blocked events. Average Ba2+ dwell time changes from 10 s at 10 mM external K+ to 100 ms in the limit of very low [K+]. Using a model where external K+ binds to a site hindering the exit of Ba2+ toward the external side (Neyton, J., and C. Miller. 1988. J. Gen. Physiol. 92:549-568), we calculated a dissociation constant of 2.7 mircoM for K) at this lock-in site. We also found that BK(Ca) channels enter into a long-lasting nonconductive state when the external [K+] is reduced below 4 microM using the crown ether. Channel activity can be recovered by adding K+, Rb+, Cs+, or NH4+ to the external solution. These results suggest that the BK(Ca) channel stability in solutions of very low [K+] is due to K+ binding to a site having a very high affinity. Occupancy of this site by K+ avoids the channel conductance collapse and the exit of Ba2+ toward the external side. External tetraethylammonium also reduced the Ba2+ off rate and impeded the channel from entering into the long-lasting nonconductive state. This effect requires the presence of external K+. It is explained in terms of a model in which the conduction pore contains Ba2+, K+, and tetraethylammonium simultaneously, with the K+ binding site located internal to the tetraethylammonium site. Altogether, these results and the known potassium channel structure (Doyle, D.A., J.M. Cabral, R.A. Pfuetzner, A. Kuo, J.M. Gulbis, S.L. Cohen, B.T. Chait, and R. MacKinnon. 1998. Science. 280:69-77) imply that the lock-in site and the Ba2+ sites are the external and internal ion sites of the selectivity filter, respectively.     

植物分枝模型

从生物体总是最有效地利用物质的思想出发,对植物分枝形状建立了一个数学模型,该模型认为,当主干与侧枝的截面积之间存在类似平行四边形法则的关系时,分枝的体积取极小值。该模型揭示植物分枝形态不仅符合力学平衡的原则,在进化上也有显著生物学意义。     

Use of Growth Indices in Markov Chain Models for Crop Yield Forecasting

An improved Markov chain model has been developed for forecasting of sugarcane yields in which growth indices of biometrical characters based on data from two stages simultaneously have been utilised. Comparisons were also made with the models in use viz. the regression model and the first order Markov chain model.     

生态贫困视角下的贫困县多维贫困综合度量

作为国家扶贫开发决策实施的重要单元,贫困县贫困程度及其致贫原因的识别和评估是国家“精准扶贫”战略实施的前提和保障.本文从生态贫困的视角,设计了顾及自然环境-经济-社会可持续协调发展的县级别多维贫困度量指标体系,构建基于贫困指数-最小方差模型(PI-MVM)的县级多维贫困度量模型,以6个连片特困区的249个县为典型研究区,系统揭示片区-县级层面上的贫困程度、致贫原因及其空间分布特征.结果显示: 各片区的综合贫困程度由北向南逐渐加重,各片区县存在“从北向南、从东到西,贫困程度逐渐加重”的趋势;乌蒙片区西部、秦巴片区西北部各县贫困程度的高-高聚集现象突出;秦巴中南部以及乌蒙片区受自然环境因素影响较大,贫困程度较深.一般致贫型片区县较多,主导致贫型片区县聚集在贫困程度较低的片区;经济因素对贫困的缓解作用逐渐下降,自然环境、社会发展因素的影响逐渐明显.研究结果可以更加精准地全面把握贫困县的贫困区划特征,为指导研究区早日脱贫提供辅助决策技术支撑.     

Recent developments in the production and applications of bacterial cellulose fibers and nanocrystals

Cellulosic nanomaterials provide a novel and sustainable platform for the production of high performance materials enabled by nanotechnology. Bacterial cellulose (BC) is a highly crystalline material and contains pure cellulose without lignin and hemicellulose. BC offers an opportunity to provide control of the products’ properties in-situ, via specific BC production methods and culture conditions. The BC potential in advanced material applications are hindered by a limited knowledge of optimal BC production conditions, efficient process scale-up, separation methods, and purification methods. There is a growing body of work on the production of bacterial cellulose nanocrystals (BCNs) from BC fibers. However, there is limited information regarding the effect of BC fibers’ characteristics on the production of nanocrystals. This review describes developments in BC and BCNs production methods and factors affecting their yield and physical characteristics.     

Temporal-spatial distribution,environmental significance and release risks of phosphorus in the sediments of a tropical mountain’s deep drinking water reservoir in southeastern China

In this study, the fractionation and distribution of phosphorus (P) in the core sediments of the Shanmei reservoir were investigated by using the chemical extraction method in directions for the first time in order to understand its bio-availability, adsorption characteristics, potential release and environmental significance. The results of the study showed that P in the sediments mainly consisted of inorganic phosphorus (IP) and that IP mainly consisted of non-apatite phosphorus (NAIP). The horizontal and temporal distributions of the P fractions were different from each other, but the vertical distribution was similar, which indicated a trend of stabilization after falling. The content of total phosphorus (TP), IP, organic phosphorus (OP), NAIP, apatite phosphorus (AP), and bio-available phosphorus (BAP) in the sediments during the three seasons ranged from 193.85 to 1664.05 mg·kg^?1, 126.90 to 1127.70 mg·kg^?1, 43.74 to 669.29 mg·kg^?1, 57.62 to 937.07 mg·kg^?1, 32.58 to 250.71 mg·kg^?1, and 41.06 to 871.82 mg·kg^?1, respectively. NAIP contents in the sediments accounted for more than 50% of TP. Using an analysis from three aspects, the eutrophication risk index (ERI) could be used to assess the potential release of P in the sediments, and there was a high release risk of P in the sediments in the Shanmei reservoir.     

连续股神经阻滞联合帕瑞昔布对全膝置换患者术后镇痛效果观察

目的:探讨连续股神经阻滞(CFNB)联合帕瑞昔布对全膝关节置换术(TKA)患者术后镇痛效果。方法:选择2015年1月至2016年12月间我院行择期单侧TKA治疗的患者100例,按照随机数字表法分为对照组和研究组,每组各50例。两组患者术后分别接受CFNB和CFNB联合帕瑞昔布镇痛,镇痛时间2 d。观察两组患者术后6 h、12 h、24 h、48 h静息状态和运动状态视觉模拟疼痛评分(VAS)以及术后不良反应发生率。并于术前1 d、术后1 d、2 d、3 d应用美国特种外科医院膝关节评分表(HSS)评定两组患者膝关节功能。结果:术后6 h、12 h、24 h、48 h研究组患者静息状态VAS评分和运动状态VAS评分显著低于对照组患者(P0.05)。两组恶心/呕吐、呼吸抑制、导管相关问题、尿潴留发生率比较无统计学差异(P0.05)。两组患者术前1d HSS评分比较无统计学差异(P0.05),术后1 d、术后2 d、术后3 d两组患者HSS评分均较术前1 d显著升高,且研究组患者HSS评分显著高于对照组(P0.05)。结论:CFNB联合帕瑞昔布具有镇痛效果好、安全可靠的优点,应用TKA术后镇痛有利于患者早期进行膝关节功能锻炼,值得临床推广。     

七氟醚联合骶管阻滞麻醉对小儿疝气手术的麻醉效果分析

目的:观察七氟醚联合骶管阻滞麻醉对小儿疝气手术的麻醉效果。方法:选取80例行腹股沟疝气手术患儿,按随机数字表法分为两组,对照组(39例)静脉注射氯胺酮,观察组(41例)先吸入8%七氟醚,然后进行骶管阻滞麻醉,通过观察并记录两组患儿生命体征、麻醉诱导时间、苏醒时间、手术麻醉时间、苏醒期躁动评分(Pediatric anesthesia emergence delirium,PAED)和麻醉诱导期合作量表(Induction Compliance Checklist,ICC)及麻醉期间不良反应情况,评价七氟醚联合骶管阻滞麻醉对小儿疝气手术的麻醉效果。结果:两组切皮后T1、T2时心率(HR)、平均动脉压(MAP)水平均高于T0时的值(P0.05),两组切皮后T1、T2时组间HR、MAP水平相比,无统计学差异(P0.05)。两组切皮后T3时HR、MAP水平基本恢复到T0时的水平。两组切皮前后4个时间点的血氧饱和度(Sp O2)相比,无统计学差异(P0.05)。观察组患儿麻醉诱导时间,苏醒时间均明显短于对照组患儿(P0.05),两组术中麻醉持续时间相比,无统计学差异(P0.05),均能达到期望麻醉时间,观察组患儿PAED评分和ICC评分均低于对照组患儿(P0.05),不良反应组间比较无统计学差异(P0.05)。结论:七氟醚联合骶管阻滞麻醉对小儿疝气手术具有良好的麻醉效果,麻醉诱导快,苏醒快,小儿配合度高,术后躁动少,值得临床推广使用。     

血浆D-二聚体、纤维蛋白原水平与骨创伤患者创伤程度的相关性

目的:分析骨创伤患者的血浆D-二聚体、纤维蛋白原水平及其与创伤程度的相关性。方法:收集2015年1月至2016年1月我院收治的骨创伤患者180例作为观察组,选择同期接受体检的健康者100例作为对照组。动态监测两组受检者入院后第1、3、6、10 d的血浆D-二聚(DD)和纤维蛋白原(FIB)的水平,并分析DD和FIB水平与骨创伤程度的相关性。结果:入院后第1、3、6、10 d,观察组的FIB和DD水平均出现下降趋势,但均显著高于对照组,差异具有统计学意义(P0.05)。重度创伤组和中度创伤组患者的FIB水平显著高于轻度创伤组,且重度创伤组FIB水平显著高于中度创伤组,组间比较差异均具有统计学差异(P0.05)。从入院第1 d至10 d,3组患者的FIB水平均出现显著降低(P0.05)。轻度创伤组患者的DD水平最低,其次是中度创伤组,重度创伤组最高,组间比较差异均具有统计学差异(P0.05)。从入院第1 d至10 d,3组患者的DD水平均出现显著降低(P0.05)。此骨创伤患者创伤严重程度与FIB和DD的水平均呈现出显著正相关关系(r=0.64,P=0.003;r=0.71,P=0.002)。结论:骨创伤患者的血浆FIB和DD水平显著高于健康人,与创伤程度呈显著正相关,可能作为骨创伤患者病情程度和预后评估的生物指标。     

连续股神经阻滞与静脉自控镇痛对全膝关节置换术后患者凝血功能的影响

目的:比较连续股神经阻滞(CFNB)与静脉自控镇痛(PCIA)在全膝关节置换术中的应用效果及对患者凝血功能的影响。方法:选取2014年1月至2015年12月间我院行单侧全膝关节置换术的患者80例,按照随机数字表法分为CFNB组和PCIA组,每组各40例,两组患者分别接受CFNB和PCIA治疗。观察两组患者术后6 h、12 h、24 h、48 h视觉模拟疼痛评分(VAS),两组患者分别于麻醉前(T1)、术毕(T2)、术后1 d(T3)、术后2 d(T4)进行血栓弹力图检查,观察两组凝血功能变化。并于术后随访1年,比较两组患者膝关节功能。结果:术后6 h、12 h、24 h、48 h CFNB组患者VAS评分显著低于PCIA组患者(P0.05)。T2、T3、T4时点CFNB组患者凝血反应时间(R)、血凝块形成时间(K)较T1升高,血凝块聚合形成速率(α角)、血凝块最大振幅(MA)较T1降低,PCIA组患者R、K较T1降低,α角、MA较T1升高,T2、T3、T4时点CFNB组患者R、K高于PCIA组患者,α角、MA低于PCIA组患者,差异均有统计学意义(P0.05)。两组患者术后均完成1年的随访,两组患者KSS评分、膝关节最大屈曲度、膝关节最大伸直度比较无统计学差异(P0.05)。结论:CFNB对于全膝关节置换术术后患者镇痛效果优于PCIA,有利于改善患者凝血功能,不影响术后患者膝关节功能的恢复。