Cation channels,cell volume and the death of an erythrocyte

Similar to a variety of nucleated cells, human erythrocytes activate a non-selective cation channel upon osmotic cell shrinkage. Further stimuli of channel activation include oxidative stress, energy depletion and extracellular removal of Cl^–. The channel is permeable to Ca²⁺ and opening of the channel increases cytosolic [Ca²⁺]. Intriguing evidence points to a role of this channel in the elimination of erythrocytes by apoptosis. Ca²⁺ entering through the cation channel stimulates a scramblase, leading to breakdown of cell membrane phosphatidylserine asymmetry, and stimulates Ca²⁺-sensitive K⁺ channels, thus leading to KCl loss and (further) cell shrinkage. The breakdown of phosphatidylserine asymmetry is evidenced by annexin binding, a typical feature of apoptotic cells. The effects of osmotic shock, oxidative stress and energy depletion on annexin binding are mimicked by the Ca²⁺ ionophore ionomycin (1 µM) and blunted in the nominal absence of extracellular Ca²⁺. Nevertheless, the residual annexin binding points to additional mechanisms involved in the triggering of the scramblase. The exposure of phosphatidylserine at the extracellular face of the cell membrane stimulates phagocytes to engulf the apoptotic erythrocytes. Thus, sustained activation of the cation channels eventually leads to clearance of affected erythrocytes from peripheral blood. Susceptibility to annexin binding is enhanced in several genetic disorders affecting erythrocyte function, such as thalassaemia, sickle-cell disease and glucose-6-phosphate dehydrogenase deficiency. The enhanced vulnerability presumably contributes to the shortened life span of the affected erythrocytes. Beyond their role in the limitation of erythrocyte survival, cation channels may contribute to the triggering of apoptosis in nucleated cells exposed to osmotic shock and/or oxidative stress.     

Ocular counterrolling induced by centrifugation during orbital space flight

During the 1998 Neurolab mission (STS-90), four astronauts were exposed to interaural centripetal accelerations (Gy centrifugation) of 0.5g and 1g during rotation on a centrifuge, both on Earth and during orbital space flight. Subjects were oriented either left-ear out or right-ear out, facing or back to motion. Binocular eye movements were measured in three dimensions using a video technique. On Earth, tangential centrifugation that produces 1g of interaural linear acceleration combines with gravity to tilt the gravitoinertial acceleration (GIA) vector 45° in the roll plane relative to the head vertical, generating a summed vector of 1.4g. Before flight, this elicited mean ocular counterrolling (OCR) of 5.7°. Due to the relative absence of gravity during flight, there was no linear acceleration along the dorsoventral axis of the head. As a result, during in-flight centrifugation, gravitoinertial acceleration was strictly aligned with the centripetal acceleration along the interaural axis. There was a small but significant decrease (mean 10%) in the magnitude of OCR in space (5.1°). The magnitude of OCR during postflight 1g centrifugation was not significantly different from preflight OCR (5.9°). Findings were similar for 0.5g centrifugation, but the OCR magnitude was approximately 60% of that induced by centrifugation at 1g. OCR during pre- and postflight static tilt was not significantly different and was always less than OCR elicited by centrifugation on Earth for an equivalent interaural linear acceleration. In contrast, there was no difference between the OCR generated by in-flight centrifugation and by static tilt on Earth at equivalent interaural linear accelerations. These data support the following conclusions: (1) OCR is generated predominantly in response to interaural linear acceleration; (2) the increased OCR during centrifugation on Earth is a response to the head dorsoventral 1g linear acceleration component, which was absent in microgravity. The dorsoventral linear acceleration could have activated either the otoliths or body-tilt receptors that responded to the larger GIA magnitude (1.4g), to generate the increased OCR during centrifugation on Earth. A striking finding was that magnitude of OCR was maintained throughout and after flight. This is in contrast to most previous postflight OCR studies, which have generally registered decreases in OCR. We postulate that intermittent exposure to artificial gravity, in the form of the centripetal acceleration experienced during centrifugation, acted as a countermeasure to deconditioning of this otolith-ocular orienting reflex during the 16-day mission. Electronic Publication     

Detection and deletion of motion artifacts in electrogastrogram using feature analysis and neural networks

Electrogastrogram is a surface measurement of gastric myoelectrical activity, and electrogastrography has been an attractive method for physiological and pathophysiological studies of the stomach due to its nonivasive nature. Motion artifacts, however, ruin the electrogastrogram (EGG), and make the analysis very difficult and sometimes even impossible. They must be eliminated from EGG signals before analysis. Up to now, this can only be done by visual inspection, which is not only time-consuming but also subjective. In this study, a method using feature analysis and neural networks has been developed to realize automatic detection and elimination of the motion artifacts in EGG recordings by computer. Experiments were conducted to investigate the characteristics of different motion artifacts. Useful features were extracted, and different combinations of the features used as the input of the neural network were compared to obtain the optimal performance for the detection of motion artifacts using the artificial neural network.     

人工组织神经移植物修复狗缺损坐骨神经后腓肠肌的形态观察

目的 了解复合型医用可降解材料制成的人工组织神经移植物辅加神经再生素修复狗坐骨神经缺损后，腓肠肌的形态变化。方法 将人工组织神经移植物连接在狗的坐骨神经缺损30mm处。以自体神经桥接和神经缺损的狗为对照组Ⅰ和Ⅱ。术后6个月时取腓肠肌进行称重、特殊染色和组织化学染色，显微镜下了解腓肠肌的形态变化并进行图像定量分析，同时了解肌纤维的超微结构变化。结果 术后6个月，实验组腓肠肌的萎缩形态指标变化均轻于对照组Ⅱ，而与对照组Ⅰ相似。结论 经人工组织神经移植物修复缺损的坐骨神经后，使腓肠肌又重新获得神经支配，肌肉萎缩明显减轻。     

Time adaptive denoising of single trial event-related potentials in the wavelet domain

We present a new wavelet-based method for single trial analysis of transient and time variant event-related potentials (ERPs). Expecting more accurate filter settings than achieved by other techniques (low-pass filter, a posteriori Wiener filter, time invariant wavelet filter), ERPs were initially balanced in time. By simulation, better filter performance could be established for test signals contaminated with either white noise or isospectral noise. To provide an example of real application, the method was applied to limbic P300 potentials (MTL-P300). As a result, variance of single trial MTL-P300s decreased, without restricting the corresponding mean. The proposed method can be regarded as an alternative for single-trial ERP analysis.     

Blastocoele collapse by micropipetting prior to vitrification gives excellent survival and pregnancy outcomes for human day 5 and 6 expanded blastocysts

BACKGROUND: Manual puncture of the trophectoderm of human blastocysts with a needle before vitrification increases their survival rate, but the embryos take a long time to re-expand. This study examined whether causing human blastocysts to collapse by manual pipetting before vitrification would allow more rapid re-expansion and improve pregnancy rates. METHODS: After embryo transfer in IVF cycles, surplus embryos that developed to the expanded blastocyst stage were placed in cryoprotectant and then artificially shrunk by mechanical pipetting with a fine hand-drawn glass pipette slightly smaller in diameter than the blastocyst. The shrunken embryos were placed in a small volume of vitrification solution and plunged into liquid nitrogen on a cryotop. The blastocysts were thawed by warming and then dilution in 1 mol/l sucrose. RESULTS: Of 49 expanded vitrified blastocysts, 48 (98%) re-expanded within 3 h after warming. Following transfer (48 blastocysts in 28 cycles), 14 women (50%) became clinically pregnant, and the implantation rate was 33% (16/48). Eight healthy babies have been born in six deliveries, and the other eight pregnancies are ongoing. To date, there have been no spontaneous abortions. CONCLUSIONS: The results suggest that artificial shrinkage with pipetting is a simple and effective technique to assist successful cryopreservation of expanded blastocysts by vitrification.     

硅凝胶人工晶体的生物相容性

本文参照国内外有关医用高分子材料的生物学评价试验方法,对国产医用级硅凝胶人工晶体作了系统的生物学评价。结果表明:硅凝胶人工晶体对眼及皮肤无刺激作用、无热原、无毒性、体外溶血率小于5％,对细胞生长有促进作用,长期植入皮下时,随植入时间延长,囊壁厚度逐渐变薄,炎性细胞反应30天基本消失。染色体及骨髓多染红细胞未受影响。因此,可以认为硅凝胶人工晶体有良好的生物相容性。     

Construction and characterization of centric circular and acentric linear chromosomes in fission yeast

Summary Gene disruption and gap repair of chromosomal DNA have been frequently employed techniques in yeast genetics. To extend the possibility of using these gene manipulations for larger genomic regions, we have examined the maximal sizes of chromosomal DNA disrupted or repaired in vivo. Here we report a simple, potentially general, method for selectively deleting a 150 kb region, or gap-filling a 100 kb region, in the fission yeast genome. This enables the generation of acentric linear chromosomes by deletion, or the cloning of large functional centromeric DNAs into circular minichromosomes by gap-filling. The fidelity of the resulting gap-filling is high, judging from partial-digestion mapping of gap-repaired DNAs. By analysing a series of such circular minichromosomes, we conclude that only a part of the repetitive centromeric region, including the central domain, is essential for mitotic and meiotic chromosome segregation. Acentric linear chromosomes, although unstable, could be maintained, indicating that it may be possible to construct an acentric vector for large DNA fragments in this organism.     

模拟股骨置入人工关节扭转与应力松弛蠕变的实验研究

研究了在相同扭矩作用下,正常组股骨和以生物学和骨水泥固定置入人工关节组股骨标本扭转角度,还对正常股骨、生物学固定股骨和骨水泥固定股骨进行应力松弛、蠕变实验,为临床提供生物力学参数。以电子万能试验机对正常对照组、股骨置入人工关节骨水泥固定组、股骨置入人工关节生物学固定组标本进行扭转和粘弹性实验研究。得出了各组标本在相同扭矩下的扭转角度及悬臂弯曲状态下,正常组和置入人工关节组标本应力松弛、蠕变数据和曲线。对实验数据进行归一化处理,得出了正常组和置入人工关节组标本的归一化应力松弛函数,归一化蠕变函数及曲线。表明:骨水泥固定组扭转角比生物学固定组小,说明骨水泥固定有较好的稳定性,其应力松弛、蠕变量丢失小。骨水泥固定组较生物学固定组3600s应力松弛、蠕变量大。     

人工器官的快速成形制造

综述了一种快速成形技术在医学物理模型、可植入假体和组织工程人工器官制造中的应用，并比较了各种快速成形技术在人工器官制造中的优缺点，探讨了人工器官快速成形制造的发展方向。