An improved and highly standardised transformation procedure allows efficient production of single and multiple targeted gene-knockouts in a moss,<Emphasis Type="Italic"> Physcomitrella patens</Emphasis>

The moss Physcomitrella patens is the only land plant known to date with highly efficient homologous recombination in its nuclear DNA, making it a unique model for plant functional genomics approaches. For high-throughput production of knockout plants, a robust transformation system based on polyethylene glycol-mediated transfection of protoplasts was developed and optimised. Both the DNA conformation and pre-culture of plants used for protoplast isolation significantly affected transformation efficiencies. Employing a newly developed PCR high-throughput method, the gene-targeting efficiency in more than 1,000 plants transformed with different cDNA-based knockout constructs was determined and analysed with regard to the length and intron/exon structure of the homologous gene locus. Different targeting constructs, each containing an identical selectable marker gene, were applied as batch DNA in a single transformation experiment and resulted in double-knockout plants. Thus, the fast and efficient generation of multiple targeted gene-knockouts is now feasible in Physcomitrella.Communicated by U. Kück     

ATP敏感性钾通道P266T突变对离子通道特性的影响

目的： 通过通道蛋白特定位点(P266T)突变,观察对ATP敏感性钾通道电生理特性的影响。 方法: 将Kir6.2及其突变子P266T的cDNA导入人胚肾细胞，表达ATP敏感性钾通道，用膜片钳方法研究K_ATP电生理特性。 结果: K_ATP(P266T)开放能力是野生型的2倍; K_ATP(P266T)密度仅是野生型20%; K_ATP(P266T)对ATP敏感性降低;对pH敏感性增高。 结论: K_ATP特定位点(P266T)突变可改变K_ATP电生理特性。     

Potassium kinetics and its relationship with ventilation during repeated bouts of exercise in women

The purpose of this study was to determine the electrolyte concentration changes in arterial plasma from high-intensity repeated bouts of cycling exercise in well-trained females and to determine the relationships between arterial plasma lactate, potassium (K⁺), bicarbonate (HCO₃⁻), and pH with minute ventilation. Fourteen female subjects (mean age = 27 ± 4 years; mean height = 170 ± 7 cm; mean weight = 62 ± 7 kg; maximal oxygen uptake = 50 ± 6 ml/kg/min) were recruited to perform 3 × 5 min bouts of exercise at 236 ± 27 W with 10 min recovery between each set. Minute ventilation, arterial plasma lactate, potassium, calcium, chloride, and sodium ion concentrations were measured a minute 0, 1, 2, 3, 4, 5 of each set and midway through recovery (21 sampling points total per subject). The results showed that the strongest relationship was between arterial plasma K⁺ concentration and minute ventilation (r ² = 0.91), and, that arterial plasma lactate mirrored both arterial plasma HCO₃⁻ and pH. In conclusion, this study demonstrates that women exhibit similar electrolyte responses as reported elsewhere in men, and support the idea that K⁺ may partly contribute to controlling ventilation during high-intensity exercise and recovery.     

线粒体ATP敏感性钾通道参与超极化停搏的心肌保护作用

目的：探讨线粒体ATP敏感性钾通道（mitoKATP）开放在超极化停搏心肌保护中的作用机制。方法:将SD大鼠随机分为对照组（Control）、去极化停搏组（D）、超极化停搏组（H）、5-羟葵酸(5-HD) +去极化停搏组（5HD+D）、5-HD+超极化停搏组（5HD+H），每组8例。建立Langendorff灌注模型，平衡20 min，以不同方式停搏40 min，再灌注30 min，对比观察：(1)不同时间血流动力学变化；(2)再灌注末取心肌并分离、制备线粒体，电镜观察超微结构的变化。(3)平衡末、再灌注末线粒体活性氧的产生。结果: (1)各组再灌注末大鼠心脏功能明显低于平衡末, 心肌线粒体超微结构均遭受不同程度损伤，左室发展压（LVDP）、左室舒张末压（LVEDP）、率压双乘积（DP）、冠脉流量（CF）有显著差异（P<0.01）；（2）超极化停博组再灌注末心脏功能指标LVDP、LVEDP、DP、CF明显优于去极化停博组、5-HD+超极化停搏组、5-HD+去极化停搏组、对照组（P<0.01），电镜示：心肌、线粒体超微结构遭受的损伤较轻; (3)超极化停博组再灌注末心肌线粒体活性氧产生率低于对照组与其它3组（P<0.01）。结论:(1)超极化停搏能明显改善再灌注后心功能，保护心肌、线粒体超微结构，减少活性氧生成；(2)mitoKATP的早期开放参与超极化停搏，其作用可能通过保护再灌注后的线粒体呼吸功能，减轻线粒体的氧化损伤，为再灌注心肌提供较好的能量供应，从而使缺血再灌注后的心脏收缩功能得到一定恢复。     

N-Terminal deletions of rKv1.4 channels affect the voltage dependence of channel availability

Rat Kv1.4 potassium channels undergo rapid inactivation, which is mediated by the N-terminal structure of the polypeptide. This inactivation can be removed by N-terminal deletion of about 20 residues. However, more substantial deletion (e.g. 37 residues) restores inactivation suggesting a second inactivating domain [Kondoh et al. J Biol Chem 272:19333–19338, 1997]. Here we provide evidence that this inactivation shares all properties with N-type inactivation. Pore mutations, which are supposed to affect C-type inactivation, have no effect. In addition, the redox regulation of inactivation, which is typical for Kv1.4 channels, can be conferred to the inactivation of the deleted constructs by incorporation of an N-terminal cysteine residue. The most remarkable feature of this secondary inactivation is the existence of two components in the steady-state voltage dependence of inactivation. For mutant rKv1.4Δ2–37 about 90% of the channels only activate when the holding membrane potential is more negative than about –120 mV; the remaining 10% show the typical threshold at –60 mV. Mutagenesis of the truncated channel affected the relative amplitudes of these two components, but not the voltage dependence. The results suggest that the secondary ball structures of rKv1.4 channels interact with the protein structures responsible for activation. Received: 3 February 1999 / Accepted: 15 March 1999     

Role of different types of potassium channels and peroxisome proliferator-activated receptors γ in the antidepressant-like activity of bis selenide in the mouse tail suspension test

In the present study we investigated the role of potassium (K(+)) channels and peroxisome proliferator-activated receptor gamma (PPARγ) in the antidepressant-like effect of bis selenide in the mouse tail suspension test (TST). Intracerebroventricular (i.c.v.) pretreatment with tetraethyl ammonium (TEA, a non-specific inhibitor of K(+) channels, 25 pg/site), glibenclamide (an ATP-sensitive K(+) channel inhibitor, 0.5 pg/site), charybdotoxin (a large and intermediate conductance calcium-activated K(+) channel inhibitor, 25 pg/site) or apamin (a small-conductance calcium-activated K(+) channel inhibitor, 10 pg/site) produced a synergistic action with a sub effective dose of bis selenide (0.1 mg/kg, per oral--p.o.). Picrotoxin (1 mg/kg, intraperitoneally--i.p.) pretreatment did not prevent the reduction in immobility time elicited by bis selenide (1 mg/kg, p.o.) in the TST. The reduction in the immobility time elicited by an effective dose of bis selenide (1 mg/kg, p.o.) was prevented by the pretreatment of mice with cromakalim, minoxidil (K(+) channel openers, 10 μg/site, i.c.v.) and GW 9662 (a PPARγ antagonist, 10 μg/site, i.c.v.). The findings clearly suggest that an acute oral dose of bis selenide produced an antidepressant-like effect in the mouse TST by a mechanism that involves the K(+) channels and PPARγ receptors.     

新疆维、汉两民族健康人群KCNE1基因多态性分布

目的 研究心肌钾离子通道β亚单位基因(potassium voltage-gated channel,Isk-related family,member 1,KCNE1)标签SNP rs2834497和rs4817656在新疆维吾尔族和汉族健康人群中的分布情况。方法选择新疆地区409名维吾尔族和406名汉族,均为健康人群,采用等位基因特异性PCR(allele-spocific polymerase chain reaction,AS-PCR)方法进行基因分型。结果 ①rs2834497三种基因型AA型、AG型和GG型在维吾尔族人群中的分布频率分别为：65.5％、29.8％和4.6％;在汉族人群中的分布频率分别为：55.4％、36.9％和7.6％,两组基因型分布比较有统计学意义(x2= 9.92,P＜0.01);②rs4817656三种基因型CC型、CT型和TT型在维吾尔族人群中的分布频率分别为：26.4％、53.5％和20.0％;在汉族人群中的分布频率分别为：22.2％、49.0％和28.8％。两组基因型分布比较有统计学意义(x2=8.74,P＜0.05);③rs4817656和rs2834497共构建4个单体型,其中CG和TA单体型在维族中的分布明显高于汉族(x2= 37.83,P＜0.01;x2=4.13,P＜0.05),TG单体型在汉族中的分布明显高于维族(x2= 30.77,P＜0.01)。结论 KCNE1基因标签SNP rs2834497和rs4817656在新疆汉族和维吾尔族健康人群中的分布差异具有统计学意义。     

肾病综合征大鼠模型的建立及酶酚酸酯对其作用的实验研究

目的：研究酶酚酸酯（ＭＭＦ）对大鼠肾病综合征的治疗作用。为临床应用提供依据。方法：经尾静脉一次性注射阿霉素,构建大鼠肾病综合征动物模型。观察ＭＭＦ对大鼠肾病综合征血、尿生化指标、淋巴细胞电压依赖性钾通道及肾脏组织学改变的影响。并与强的松进行对照研究。结果：注射阿霉素１４ｄ。大鼠肾病综合征模型建立。模型鼠表现外周Ｔ淋巴细胞电压依赖性钾通道电流增强。ＭＭＦ治疗可使大鼠尿蛋白和血尿素氮明显下降。血白蛋白上升。肾脏病理显示足突无明显融合。疗效明显优于强的松治疗组。结论：在阿霉素诱导的大鼠肾病综合征模型的形成中,细胞免疫参与了其发病,ＭＭＦ能明显改善模型鼠的肾功能并减轻肾脏组织形态学损害。且疗效优于强的松。     

Firing properties and dendrotoxin-sensitive sustained potassium current in vestibular nuclei neurons of the hatchling chick

To understand the emergence of excitability in vestibular nuclei neurons, we performed patch-clamp recordings on brain slices to characterize the firing pattern on depolarization and the underlying currents in principal cells of the chick tangential nucleus. This study, on 0- to 3-day-old hatchlings, distinguishes electrophysiologically one main group of principal cells based on their response to depolarizing current pulses (300-400 ms) in current-clamp recordings. This group (90%; n=29) displayed nonaccommodating, repetitive firing on depolarization. The remaining cells fired one action potential at the beginning of the current pulse and then accommodated. In voltage-clamp recordings, a low-threshold, sustained, dendrotoxin-sensitive (DTX; 200 nM) potassium current, I(DS), was identified in both cell groups. In the repetitively firing principal cells, the mean proportion of the DTX-sensitive sustained current contributing to the total outward current was less than 20%. This percentage is significantly less than that reported (45%) in a previous study performed in late chick embryos (E16), in which most of the cells (83%; n=89) were accommodating neurons. Tonic firing is an important electrophysiological feature characterizing most mature, second-order vestibular neurons, since it allows the neurons to process signals from behaviorally relevant inputs. Accordingly, this study contributes toward defining the emergence of the mature pattern of neuronal excitability and the ionic currents involved.