Electrophysiological properties of the propafenone-analogue GE 68 (1-[3-(phenylethyl)-2-benzofuryl]-2-(propylamino)-ethanol) in isolated preparations and ventricular myocytes of guinea-pig hearts

GE 68 ((Rac.)-1-[3-(Phenylethyl)-2-benzofuryl]-2-(propylamino)-ethanol hydrochloride) is structurally related to propafenone, and exerts negative inotropic and negative chronotropic effects similar to the parent drug, but lacks any β-adrenoceptor blocking activity contrary to propafenone. Thus, the electrophysiological effects of GE 68 were studied in papillary muscles, left atria, Purkinje fibres, sinoatrial nodes and ventricular myocytes of the guinea-pig heart with the intracellular microelectrode technique and the patch-clamp technique in the cell-attached mode. The decrease of the maximum upstroke velocity (V˙_max) by GE 68 (1 to 10 μM) was use- and frequency-dependent. V˙_max recovered from the use-dependent block with a time constant of 4.1 ± 0.6 s. In papillary muscles and Purkinje fibres action potential duration was shortened, while it was prolonged in left atria and sinoatrial nodes. Half-maximal steady-state inactivation of the sodium channels was shifted to more negative membrane potentials (control: –91.5 ± 0.8 mV, 10 μM GE 68: –97.9 ± 2.5 mV). The peak of the current-voltage relationship and the reversal potential were not changed by GE 68. The amplitude of the unitary current remained unaltered, while open state probability was decreased. The most striking effect of GE 68 was an increase of the number of sweeps without single channel openings (1 μM: 2 fold, 10 μM: 6 fold). GE 68 also caused a decrease of the mean open times, and an increase of the mean closed times in unmodified and pronase-modified sodium channels. Besides the lack of β-adrenoceptor blocking activity, data present a faster recovery from the use-dependent block by GE 68 and a lower affinity to inactivated sodium channels compared to the reference drug propafenone, as well as differences in the effect on single channel kinetics. Received: 25 July 1996 / Accepted: 14 October 1996     

PPARδ基因多态与有氧能力及训练敏感性的关联研究

目的探讨过氧化物酶体增殖物激活受体δ(PPARδ)基因第四外显子的单核苷酸多态(C294T)是否与有氧运动能力及训练敏感性相关联。方法对102名中国北方地区汉族男性青年进行为期18周的耐力训练(每次5000米、每周3次)。强度以个体通气无氧阈(VT)对应的心率(HRVT)为标准,前10周采用95%通气无氧阈对应的心率(HRVT±3),后8周采用105%通气无氧阈对应的心率(HRVT±3)。递增负荷运动实验测定受试者训练前后VO2max及相关指标和跑节省化时的心率(HR)、通气量(VE)和摄氧量(VO2)。采用限制性片断长度多态(PCR-RFLP)法测定PPARδ基因C294T位点。结果三种基因型的分布频率分别为CC基因型9人(0.09)、CT基因型37人(0.36)和TT基因型56人(0.55),符合Hardy-Weinberg平衡。按基因型分组后,CC基因型训练前的VO2max相对值显著性高于CT基因型和TT基因型(P<0.05);携带不同基因型群体的VO2max、跑节省化测试中的各项指标的变化率无显著性差异(P>0.05)。结论PPARδ基因第四外显子的单核苷酸C294T多态与VO2max相对值的初始值相关联,但与有氧耐力训练效果不关联。     

Characterization of sports by the Vo2 dynamics of athletes in response to sinusoidal work load

The purpose of this study was to evaluate the specificity of maximal oxygen uptake (Vo_2max) and the dynamic response of oxygen uptake (Vo₂) to sinusoidal work load in distance runners and in American-football players. Sinusoidal work load during ergometer cycling was carried from 30 W to 60% to Vo_2max(60% Vo_2max) for a 2 min period. Vo₂ was measured by the breath-by-breath method. The subjects were 10 distance runners (DRs), 10 American-football players (AFPs), and 11 untrained men (UTM). Mean Vo_2max was 64.4 mL kg^-1 min^-1 in the DRs, 53.1 mL kg^-1 min^-1 in the AFPs and 47.3 mL kg^-1 min^-1 in the UTM. The fundamental amplitudes ofthe Vo₂ response, nomalized by dividing by steady state Vo₂ at 60% Vo_2max were similar in the AFPs (20.3%) and the UTM (19.5%), and both were significantly less than in the DRs (25.5%). Phase shift to work load expressed in degrees was similar in the AFPs (87.7d?) and UTM (88.0d?), but significantly greater than in the DRs (80.4d?). HR dynamics in all three groups were similar to a dynamic Vo₂ response. These findings suggest that development of the dynamic Vo₂ response and higher Vo_2max in the AFPs there is no improvement in the dynamic Vo₂ response. The results of the present study demonstrate that athletes participating in different sports have characteristic dynamic Vo₂ responses during cycling exercise.     

Muscular fatigue and rate of tension development

Summary The effects of long-term fatigue upon maximal force and peak rate of tension development (PRTD) (dF/dt max) are studied in man (elbow flexors), in the rat (pseudo-isolated gastrocnemius muscle) and in the frog (isolated sartorius muscle). The muscles are fatigued by voluntary anisometric anisotonic contractions against an elastic resistance in man, and by maximal tetanic contractions in the frog and the rat. In man, the excitation level of the muscle is controlled by the integrated surface EMG of the biceps brachii. In the animals, the muscles are stimulated by a neurostimulator. The PRTD and the maximal isometric force are measured during fatigue tests.In man, frog and rat, the maximal voluntary isometric torque or the maximal force and the PRTD decrease initially more or less rapidly according to the power developed during the fatigue process, and then less rapidly. The relationship between PRTD and maximal force is linear in the animals and curvilinear in man.The variations of maximal force and PRTD are discussed in relation to the level of excitation of the muscles and of the composition in different motor units types and their spatio-temporal recruitment. From a biomechanical point of view, it seems necessary to study the behavior of the series elastic component during the evolution of long term fatigue.     

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??Objective??To study the influence of the inlay on the stress of the remained tooth tissue??three-dimensional finite element is used to analyse stress distributions of the tooth endured different MOD inlay restore at different remaining buccal wall thickness. Methods??Using ANSYS Workbench 15.0 software to established 3d finite element model of mandibular first molar restored by all-ceramic inlay restoration with designed MOD cavities. Analyzing the influences of different remaining buccal wall thickness to the stress distribution and tendency of the teeth. Results??Different remaining buccal wall thickness of the tooth tissue on the stress level had a certain influence??the lowest stress level was the remaining buccal wall thickness of 2 mm. The stress level of occlusal coverage restoration was higher than inlay restoration. Conclusion??The study found that different remaining buccal wall thickness of the tooth tissue on the stress level have a certain influence??try to keep healthy dentine??avoid enamel without foundation is effective means of inlay restoration reducing the risk of tooth fracture. Remaining more tooth tissue is not suggested to restore occlusal coverage.     

CEREC全瓷冠在后牙种植修复中的初步研究

目的：初步观察CEREC系统制作的全瓷冠在后牙种植修复中临床效果。方法：选取15颗后牙单颗种植体,使用CEREC 3椅旁系统制作全瓷冠,修复6个月后复查,患者填写修复体满意度调查表,同时依照改良的USPHS标准对修复体进行评价。结果：在就诊时间和次数上满意度达100%,在费用上满意度为20%为最低,总体满意度86.7%。CEREC全瓷冠边缘适合性和质地达到了A标准的100%,外形和颜色匹配达到了A标准的93.3%。结论：CEREC全瓷冠在后牙种植修复短期临床效果较好,长期效果有待于进一步观察,此外应注意临床适应证的选择。     

心室按需性起搏对无氧阈和最大氧耗量影响

采用活动平板和心肺运动试验的方法，评定VVI起搏患者无氧阈和最大氧耗量。受试者40例，分为2组。病窦（SSS）组24人，年龄52．3±10．1岁。三度房室传导阻滞（Ⅲ°A-VB）组16人，年龄53．7±10．7岁。试验仪器包括Case-15活动平板心电图和CPX／MAX心肺运动试验系统。SSS组有8人运动未达到无氧阈，Ⅲ°A-VB组有9人运动未达到无氧阈。SSS组无氧阈的做功53．7±16．3W／min，氧耗量18．25±3．66ml／kg／min；Ⅲ°A-VB组无氧阈时的做功21．7±14．4W／min，氧耗量6．58±1．71ml／kg／min。极量运动时，SSS组的最大氧耗量26．20±8．33ml／kg／min，最大做功110±20W／min。Ⅲ°A－VB组最大氧耗量17．38±4．48ml／kg／min，最大做功886±16W／min。SSS组能够承受7METS的最大运动负荷。Ⅲ°A-VB组的最大运动负荷5METS。在进行康复训练时，SSS患者开始康复训练的运动强度5METS。Ⅲ°A-VB阻滞病人的康复训练应从2METS开始。     

两种粘结剂对Cerec3D全瓷冠抗折强度的实验研究

目的:探讨Cerec 3D全瓷冠粘结后冠抗折强度。方法:选择无龋坏上颌前磨牙40颗分为1、2、3、4组,完成Cerec全瓷冠,分别用Variolink N+硅烷偶联剂,Variolink N,Bisco Choice2TM+硅烷偶联剂,Bisco Choice2TM粘结。4°C 0.9%氯化钠液中保存24 h后,用万能力学试验机测试其冠最大抗折强度,记录数据;在体式显微镜下观察粘结破坏形式。采用SPSS 17.0软件包比较冠抗折强度和粘结破坏形式。结果:Variolink N+硅烷偶联剂组冠抗折强度最高。结论:双重固化树脂粘结系统是牙科长石质陶瓷粘结的理想选择,可获得较高抗折强度。硅烷偶联剂可增强全瓷冠抗折强度。