Mitochondrial gene in the nuclear genome induces reproductive barrier in rice

Hybrid incompatibility in F₁ hybrids or later generations is often observed as sterility or inviability. This incompatibility acts as postzygotic reproductive isolation, which results in the irreversible divergence of species. Here, we show that the reciprocal loss of duplicated genes encoding mitochondrial ribosomal protein L27 causes hybrid pollen sterility in F₁ hybrids of the cultivated rice Oryza sativa and its wild relative O. glumaepatula. Functional analysis revealed that this gene is essential for the later stage of pollen development, and distribution analysis suggests that the gene duplication occurred before the divergence of the AA genome species. On the basis of these results, we discuss the possible contribution of the “founder effect” in establishing this reproductive barrier.     

The effects of 2,3-butanedione monoxime (BDM) on the force-velocity relation in single muscle fibres of the frog

The effects of 2,3-butanedione monoxime (BDM) on the forcevelocity relaion were studied in single fibres from the anterior tibialis muscle of Rana temporaria (2.2 μm sarcomere length, temperature 1.9-2.4 d?C). BDM (1.0 and 1.8 mM) suppressed the maximum tetanic force (P_o) and the maximum speed of shortening (V_max), and increased the main curvature of the force-velocity relation. The biphasic shape of the forcevelocity curve was maintained well in the presence of BDM, but the interrelation between the two portions of the forcevelocity relation was significantly changed. Caffeine (0.5 mM) added in the presence of BDM increased the initial rate of rise of force during twitch and tetanus, increased the twitch amplitude, but did not affect the maximum tetanic force. The latter finding suggests that the contractile system was fully activated during tetanus in the presence of BDM. The results support the view that BDM affects the cross-bridge function by exerting a direct action upon the contractile apparatus. The decrease in tetanic force and the change of the force-velocity relation induced by BDM may be interpreted to show that a larger fraction of the attached cross-bridges is in a state of low force production under the influence of BDM. This view is further supported by the observation that the instantaneous stiffness of the muscle fibre is reduced proportionally less by BDM than the tetanic force.     

Use of thin filament reconstituted muscle fibres to probe the mechanism of force generation

The technique of selective removal of the thin filament by gelsolin in bovine cardiac muscle fibres, and reconstitution of the thin filament from isolated proteins is reviewed, and papers that used reconstituted preparations are discussed. By comparing the results obtained in the absence/presence of regulatory proteins tropomyosin (Tm) and troponin (Tn), it is concluded that the role of Tm and Tn in force generation is not only to expose the binding site of actin to myosin, but also to modify actin for better stereospecific and hydrophobic interaction with myosin. This conclusion is further supported by experiments that used a truncated Tm mutant and the temperature study of reconstituted fibres. The conclusion is consistent with the hypothesis that there are three states in the thin filament: blocked state, closed state, and open state. Tm is the major player to produce these effects, with Tn playing the role of Ca²⁺ sensing and signal transmission mechanism. Experiments that changed the number of negative charges at the N-terminal finger of actin demonstrates that this part of actin is essential to promote the strong interaction between actin and myosin molecules, in addition to the well-known weak interaction that positions the myosin head at the active site of actin prior to force generation.     

Myosin-based contraction is not necessary for cardiac c-looping in the chick embryo

During the initial phase of cardiac looping, known as c-looping, the heart bends and twists into a c-shaped tube with the convex outer curvature normally directed toward the right side of the embryo. Despite intensive study for more than 80 years, the biophysical mechanisms that drive and regulate looping remain poorly understood, although some investigators have speculated that differential cytoskeletal contraction supplies the driving force for c-looping. The purpose of this investigation was to test this hypothesis. To inhibit contraction, embryonic chick hearts at stages 10-12 (10-16 somites, 33-48 h) were exposed to the myosin inhibitors 2,3-butanedione monoxime (BDM), ML-7, Y-27632, and blebbistatin. Experiments were conducted in both whole embryo culture and, to focus on bending alone, isolated heart culture. Measurements of heart stiffness and phosphorylation of the myosin regulatory light chains showed that BDM, Y-27632, and blebbistatin significantly reduced myocardial contractility, while ML-7 had a lesser effect. None of these drugs significantly affected looping during the studied stages. These results suggest that active contraction is not required for normal c-looping of the embryonic chick heart between stages 10 and 12.     

含BDM及钙心脏保存液保存离体鼠心

目的研究含二乙酰—肟（２，３－ｂｕｔａｎｅｄｉｏｎｅｍｏｎｏｘｉｍｅ，ＢＤＭ）及Ｃａ２＋的Ｅｕｒｏ－Ｃｏｌｉｎｓ晶体保存液对离体鼠心脏的保存作用。方法采用离体工作心模型，观察保存前后鼠心的心功能、心率、肌酸磷酸激酶释放及超微结构的变化。结果含ＢＤＭ及Ｃａ２＋保存液保存的鼠心其左心室收缩压（ＬＶＳＰ），左室压力变化最大速率（ＬＶ±ｄｐ／ｄｔｍａｘ）及心率（ＨＲ）与对照组无显著性差异，肌酸磷酸激酶释放及超微结构也显示细胞损伤程度轻于普通保存组。结论ＢＤＭ及Ｃａ２＋可增加心脏冠脉流量，改善心脏功能恢复，减轻细胞损伤程度     

阿法骨化醇对绝经后妇女骨密度及骨转换标志物的影响

目的探讨阿法骨化醇对绝经后妇女骨密度及骨转换标志物的影响。方法选择2009年9月至2011年12月在本院更年期门诊经骨密度（BDM）测量诊断为骨量减少或骨质疏松症,年龄在55～75岁之间的67例绝经后女性为观察对象,随机分为试验组36例,对照组31例。试验组口服氨基酸螯合钙1 000mg/d,阿法骨化醇0.25μg/次,一天两次;对照组口服氨基酸螯合钙1 000mg/d。两组均连续服药48周。两组治疗前、后采用双能X线吸收法测定股骨颈、大粗隆、Ward三角区及腰椎L2-4骨密度;同时采用酶联免疫法检测血清骨碱性磷酸酶（BALP）、抗酒石酸酸性磷酸酶（TRACP）、25羟维生素D3[25-（OH）D3]结果治疗前试验组与对照组间股骨颈、大粗隆、Ward三角区及L2-4骨密度差异均无统计学意义（P〉0.05）。试验组各部位BMD治疗后均有显著增加（P〈0.05）,而对照组治疗前后仅L2-4有显著增加（P〈0.05）。治疗后试验组与对照组各部位BMD差异均有统计学意义（P〈0.05）。血清BALP、TRACP及25-（OH）D3水平治疗前试验组与对照组间比较,差异均无统计学意义（P〉0.05）,治疗后组间比较差异均有统计学意义（P〈0.05）。试验组治疗前血清BALP、TRACP及25-（OH）D3水平分别为（26.52±6.07）μg/L、（2.84±0.97）U/L、（53.91±19.04）nmol/L,治疗后分别为（21.85±5.96）μg/L、（2.37±0.88）U/L、（57.87±19.24）nmol/L,BALP、TRACP均呈显著降低,25-（OH）D3有显著升高（P〈0.05）;对照组治疗前后各骨代谢指标改变差异无统计学意义（P〉0.05）。结论阿法骨化醇可用于绝经后骨质疏松症的治疗,可增加骨密度、降低骨转换,对治疗骨质疏松症有理论依据和临床意义。     

2,3-Butanedione monoxime (BDM) decreases sarcoplasmic reticulum Ca content by stimulating Ca release in isolated rat ventricular myocytes

 The effects of 2,3-butanedione monoxime (BDM) were examined using rat ventricular myocytes loaded with Indo-1 to measure the intracellular Ca concentration ([Ca²⁺]_i). BDM (10 mM) produced a transient increase of the systolic Ca transient with no steady-state effect on its magnitude. This transient increase was more marked when BDM was applied after having decreased the external Ca concentration from 1 to 0.1 mM. There was a transient increase of resting [Ca²⁺]_i in both quiescent and electrically stimulated cells. Prior application of BDM decreased the rise of [Ca²⁺]_i produced by caffeine. In voltage-clamped cells the rise of [Ca²⁺]_i produced by BDM was accompanied by a transient inward current attributed to the electrogenic Na-Ca exchange. The amount of Ca lost from the cell upon application of 10 mM BDM could be estimated either from the integral of the BDM-evoked current or from the reduction of the integral of a caffeine-evoked current and corresponded to about 50% of the sarcoplasmic reticulum (s.r.) Ca content. The decrease of s.r. Ca content and the transient potentiation of the systolic Ca transient suggest that BDM acts by stimulating Ca-induced Ca release. These effects must be allowed for when using BDM. Received: 27 March 1998 / Received after revision: 12 May 1998 / Accepted: 13 May 1998     

2,3‐Butanedione monoxime increases speed of relaxation in single muscle fibres of frog

The effects of 2,3‐butanedione monoxime (BDM) on intracellular Ca²⁺ transient and cross‐bridge function were studied in frog single fibres from the anterior tibialis muscle of Rana temporaria (sarcomere length, 2.2 μm; temperature, 2–4 °C). The fluorescent dye fluo‐3 was used to monitor the intracellular free calcium concentration ([Ca²⁺]_i) during isometric contractions. BDM (1–5 mM ) reduced the amplitude of the Ca²⁺ transient during twitches, but this effect was too small to explain the marked inhibition of BDM on twitch force. [Ca²⁺]_i reached at the end of 1‐s tetanic stimulation was not significantly affected by BDM (1.0 and 1.8 mM ) while the maximum tetanic tension was substantially reduced. The rate of relaxation during isometric tetanus was increased by BDM whereas the rate of decay of the Ca²⁺ transient was reduced in the presence of BDM. The results strongly suggest that BDM, under the experimental conditions used, mainly affects the contractile machinery resulting in altered performance of the cross‐bridges. These effects of BDM were evaluated in terms of the cross‐bridge model of 17 which was fitted to the experimental force–velocity data in the presence and absence of BDM.     

Effects of vanadate, phosphate and 2,3-butanedione monoxime (BDM) on skinned molluscan catch muscle

The effects of orthovanadate (V_i), inorganic phosphate (P_i) and 2,3-butanedione monoxime (BDM) on tension, force transients and the catch state (passive tension maintenance) were investigated in saponin-skinned fibre bundles of the anterior byssus retractor muscle (ABRM) of the bivalve mollusc Mytilus edulis at pH 6.7. During maximal Ca²⁺ activation isometric force was depressed by V_i (0.03–10 mM), P_i (10 mM) and BDM (50 mM). Force transients following quick stretches (0.1–0.3% of fibre length) were accelerated substantially by 1 mM V_i, 10 mM P_i or 50 mM BDM. These compounds also accelerated force responses in experiments in which ATP was released rapidly from caged ATP by flash photolysis at both pCa 4.7 (force rise) and at pCa>8 (force decline). The effects on the catch state were investigated in two types of experiments: (1) Ca²⁺ removal after maximal Ca²⁺ activation and (2) rapid ATP release during high-force rigor at pCa>8. In both cases rapid relaxation was followed by slow relaxation (slower than 2% of initial force per min). This later slow relaxation (catch) was insensitive to V_i (1–10 mM), P_i (10 mM) and BDM (50 mM) but was accelerated by 0.12 mM cAMP. Complete relaxation to almost zero force was attained by changing pH from 6.7 to 7.7 (pCa>8). We conclude that catch depends on cAMP- and pH-sensitive structures linking the myofilaments and not on the force-generating actomyosin cross-bridges that are sensitive to V_i, P_i and BDM.     

联合应用阿仑膦酸钠及替勃龙对围绝经期及绝经后妇女骨质疏松症的疗效观察

目的评价联合应用阿仑膦酸钠及替勃龙对围绝经期及绝经后妇女骨质疏松症的影响。方法征集2008年7月~2010年12月妇科更年期门诊骨量减少或骨质疏松症的围绝经期及绝经后患者77例,随机分为两组,实验组:口服阿仑磷酸钠70mg每周1次+替勃龙2.5mg每日1次+复方氨基酸鳌合钙1000mg每日1次;对照组:口服复方氨基酸鳌合钙1000mg每日1次。两组均连续服药48周。治疗前、后采用双能X线吸收法测定腰锥1-4节(L1-L4)、股骨颈、大粗隆及Ward′s三角区骨密度(BMD);同时抽血清检测FSH及E2水平。结果两组在治疗48周后临床疼痛等症状均明显改善与好转,有效率分别为89.19%和63.64%,有显著差异(P<0.05);试验组股骨颈、大粗隆、Ward′s三角区及平均骨密度均较治疗前显著提高(P<0.05),两者增幅为0.81%、1.05%、1.64%和0.89%;试验组能有效降低FSH和升高E2水平,与治疗前相比,差异均有显著性(P<0.05);治疗后两组相比,两者改变率差异均有显著性(P<0.05)。结论联合应用阿仑膦酸钠及替勃龙在治疗围绝经期及绝经后妇女骨质疏松症效果良好。