Freeze-substitution and the preservation of diffusible ions

Freeze-substitution of biological material in pure acetone followed by low-temperature embedding in the Lowicryls K11M and HM23 yields stable preparations well suited for sectioning and subsequent morphological and microanalytical studies. Transmission electron microscopy of dry-cut sections shows that diffusible cellular thallium ions (Tl⁺) of Tl⁺-loaded muscle are localized at similar protein sites in freeze-substituted as in frozen-hydrated preparations. A comparison of X-ray micro-analytical data obtained from freeze-dried cryosections and sections of freeze-substituted normal (potassium-containing) muscle shows that K⁺ ion retention in the freeze-substituted sample is highly dependent on the freeze-substitution procedure used; so far, in the best case, about 67% of the cellular K⁺ is retained after freeze-substitution in pure acetone and low-temperature embedding. It is concluded that the retention of diffusible cellular ions is dependent on their interactions with cellular macromolecules during the preparative steps and that ion retention may be increased by further optimizing freeze-substitution and low-temperature embedding.     

Cryoultramicrotomy of muscle: improved preservation and resolution of muscle ultrastructure using negatively stained ultrathin cryosections

Ultrathin sections of rapidly frozen, briefly pre-treated muscle tissue are cut and thereafter are thawed and contrasted using a negative staining technique. The method has provided micrographs in which the in-vivo order in the muscle fibres has been preserved well enough to enable both a more complete interpretation of X-ray diffraction evidence from muscle, and also a gain of new ultrastructural information on aspects of myofibril and myofilament architecture in different types of fibre. Examples here are taken from chicken, rabbit and fish muscles and show both the M-band and the bridge region of the A-band in great detail. To enhance the detail in the original images, one-dimensional (1-D) and 2-D averaging techniques (lateral smearing and step averaging, respectively) are used. Although there is major shrinkage in section thickness to about one-third of its original value, demonstrated here for the first time is the fact that the characteristic A-band lattice planes are preserved in these sections in 3-D. This confirms the usefulness of cryosections not just for 1-D and 2-D image processing, but also for 3-D reconstruction. Thus, in combination with techniques of image processing, cryoultramicrotomy can give the muscle morphologist the detailed data that are needed to match the molecular biologists, biochemists and immunologists in the interpretation of their data about physiological and pathophysiological events in muscle fibres at the macromolecular level.     

提上睑肌缩短法矫正重度上睑下垂疗效分析简

目的：探讨提上睑肌缩短法治疗重度上睑下垂的可行性及疗效,为临床合理治疗提供依据。方法将2011年2月至2012年3月来南昌大学第一附属医院接受手术的26例（32只眼）严重上睑下垂患者,按照不同手术方式分为：提上睑肌缩短术组16例,额肌瓣悬吊术组10例。随访1年,比较提上睑肌缩短术与公认的额肌瓣悬吊术治疗重度上睑下垂的疗效。结果提上睑肌缩短术组术后2只眼欠矫,1只眼过矫,额肌瓣悬吊术组术后1只眼欠矫,1只眼过矫。其余随访1年上睑下垂均得到恢复,无睑内外翻、穹窿结膜脱垂等并发症,且外形美观。2组治愈率分别为85．0％、83．3％,差异无统计学意义（P＞0．05）。结论提上睑肌缩短法治疗严重上睑下垂,在矫正眼睑生理功能和改善外观上均达到满意的效果。     

直线电磁驱动串并联阵列人工肌肉设计研究

在分析动物骨骼肌的结构和运动形式的基础上,设计了基于电磁力的类肌肉肌纤维多肌小节串并联构成的阵列式人工肌肉。首先对构成人工肌肉的驱动器进行了性能对比,而后对类肌小节驱动器电磁场进行了有限元仿真分析,并完成了样机制作、不同负载及不同控制策略的多组开闭环实验测试。通过分析样机实验数据可知,该方案具有响应速度高、体积小、质量小、加速度高等特点。     

Relationships between muscle type and some traits influencing veal colour

The influence of the muscle type on some compositional and qualitative traits of veal was studied in two experiments, each including 20 Friesian-Holstein veal calves. Metabolic type, pigment content, glycolytic potential, buffering capacity and pH (at slaughter and ultimate) were determined on muscles longissimus dorsi, psoas major and triceps brachii caput laterale in experiment 1. Pigment content, glycolytic potential and pH (at 5 h after slaughter and ultimate) were determined in experiment 2. In both experiments, reflectance spectra were obtained from m longissimus dorsi and m psoas major at 3 and 9 days after slaughter. Reflectance at 630 nm, lightness, redness (a) and difference between reflectances at 630 and 580 nm (ΔR) were calculated from the spectra. Muscle type strongly influenced the rate of pH fall and most colour traits. Pigment content, reflectance, a and ΔR were higher in m psoas major than in m longissimus dorsi. The ultimate pH was related to the glycolytic potential but not to the buffering capacity. The relative influence of the pigment content and the rate of pH fall on the colour traits depended on the muscle. Colour of m psoas major was affected to a larger extent by the rate of pH fall than by the pigment content. Conversely, pigment content played the more important role in m longissimus dorsi.     

Glutathione Peroxidase of Fish

Glutathione peroxidase (GSH-Px) activity was detected in the muscle and skin tissues from several fish species. The muscle GSH-Px showed an optimum pH at 8.0 for salmon and 8.5 for carp. Stability of salmon muscle enzyme was enhanced in the presence of reduced glutathione (GSH), but considerably decreased in the presence of tert-butylhydroperoxide. When salmon fillets were stored at -50°C, the GSH-Px activity increased gradually during storage. Fish muscle GSH-Px shows potential for preventing oxidative deterioration in muscle during storage and processing.     

A systematic approach to the discovery of new proteins of ultrastructural interest

A systematic approach to the discovery of new proteins of ultrastructural interest is discussed. It involves the merging of monoclonal antibody technology with immunocytochemical technology, particularly immunoelectron microscopy. In this approach, monoclonal antibodies are raised to a cellular preparation that can be grossly heterogeneous in its protein composition. The hybridoma culture fluids are screened by immunocytochemistry for the ultrastructural localization of their antibodies. Those monoclonal antibodies that show specific ultrastructural localizations of interest are then selected for further investigation. The antigen to which a given monoclonal antibody is directed is then identified by immunoprecipitation and immunoblotting with that antibody. By this approach, two new striated muscle proteins of ultrastructural interest have been discovered and are named zeugmatin and enactin. The former is a protein of over 500 kD localized by immunoelectron microscopy to the Z-bands, the latter of 245 kD localized to the N₁ line of striated muscle.     

Membrane ion channels as physiological targets for local Ca2+ signalling

Ionized calcium plays a central role as a second messenger in a number of physiologically important processes determining smooth muscle function. To regulate a wide range of cellular activities the mechanisms of subcellular calcium signalling should be very diverse. Recent progress in development of visible light-excitable fluorescent dyes with high affinity for Ca²⁺ (such as oregon green 488 BAPTA indicators, fluo-3 and fura red) and confocal laser scanning microscopy provides an opportunity for direct visualization of subcellular Ca²⁺ signalling and reveals that many cell function are regulated by the microenvironment within small regions of the cytoplasm ('local control' concept). Here confocal imaging is used to measure and locate changes in [Ca²⁺]_i on a subcellular level in response to receptor stimulation in visceral myocytes. We show that stimulation of muscarinic receptors in ileal myocytes with carbachol leading to activation of inositol 1,4,5-trisphosphate receptors (IP₃Rs) accelerates the frequency of spontaneous calcium sparks (discharged via ryanodine receptors, RyRs) and gives rise to periodic propagating Ca²⁺ waves oscillating with a frequency similar to that of carbachol-activated cationic current oscillations. Furthermore, by combining the whole-cell patch clamp technique with simultaneous confocal imaging of [Ca²⁺]_i in voltage-clamped vascular myocytes we demonstrate that calcium sparks may lead to the opening of either Ca²⁺-activated Cl⁻ channels or Ca²⁺-activated K⁺ channels, and the discharge of a spontaneous transient inward current (STIC) or a spontaneous transient outward current (STOC), respectively.     

利用变结构系统理论实现人工肌肉的夹持力控制

本文推导了人工肌肉系统的数学模型.探讨了用变结构系统理论实现人工肌肉的夹持力的控制方法,给出了仿真和实验结果.人工肌肉既可以输出力(力矩),又可以调节刚性,是一种在柔顺运动控制中很有应用前途的新型作动器.     

A methodology for muscular isometric endurance and fatigue research

The objective of this study was to develop a reliable statistical method of finding a cut-off point between the endurance section and the fatigue section from a single endurance-fatigue curve of force versus time for extended times. Two age groups (20–29, 50–59 years old) with 10 subjects in each group participated in this study. Two muscle groups (biceps and quadriceps) were tested at five levels of % MVC (20, 40, 60, 80 and 100 % MVC). Subjects were instructed to exert a force and reach a designated % MVC level and maintain that level for as long as possible until asked by the experimenter to stop. Each condition was tested for five minutes. The method developed used the sum of squares technique to find the optimal cut-off point on the curve thus, determining the endurance time. The methodology proved to be useful and reliable. The steps involved along with an example are discussed.