大鼠骨髓间质干细胞体外诱导分化为心肌样细胞Cx43通讯连接功能检测

目的： 探讨大鼠骨髓间充质干细胞（MSCs）体外诱导分化为心肌样细胞Cx43的分布与通讯连接功能状态。方法： 取健康SD大鼠骨髓，用5-氮杂胞苷体外诱导培养。取诱导培养2、3、4周的MSCs为Ⅰ、Ⅱ、Ⅲ组，另取急性分离的心肌细胞为对照组，用激光共聚焦技术检测Cx43的分布及平均荧光漂白恢复率。结果： 对Cx43在细胞内分布检测发现，随诱导培养时间的延长，细胞内蛋白颗粒密度逐渐增加；诱导培养4周后MSCs内蛋白颗粒密度与对照组比较无显著差异（63.87±12.43，64.87±12.15，P>0.05）。各组细胞平均荧光漂白率的变化趋势与Cx43分布变化相似，即随诱导培养时间的延长，细胞平均荧光漂白率逐渐增加；Ⅰ、Ⅱ、Ⅲ组及对照组分别为19.59%±6.08%、37.17%±3.84%、46.82%±2.69%、49.71%±5.53%，Ⅲ组与对照组比较无显著差异（P>0.05）。结论： 大鼠MSCs在体外诱导培养4周后已分化为心肌样细胞，其细胞Cx43的分布与通讯连接功能与正常心肌细胞相似。     

Diverse roles of E-cadherin in the morphogenesis of the submandibular gland: insights into the formation of acinar and ductal structures

The formation of acinar and ductal structures during epithelial tissue branching morphogenesis is not well understood. We report that in the mouse submandibular gland (SMG), acinar and ductal cell fates are determined early in embryonic morphogenesis with E-cadherin playing pivotal roles in development. We identified two morphologically distinct cell populations at the single bud stage, destined for different functions. The outer layer of columnar cells with organized E-cadherin junctions expressed the neonatal acinar marker B1 by E13.5, demonstrating their acinar fate. The interior cells initially lacked distinct E-cadherin junctions, but with morphogenesis formed cytokeratin 7 (K7) -positive ductal structures with organized E-cadherin junctions and F-actin filaments. Inhibition of E-cadherin function with either siRNA or function blocking antibody caused extensive apoptosis of ductal cells and aberrantly dilated lumens, providing the first evidence that E-cadherin regulates ductal lumen formation during branching morphogenesis of the salivary gland.     

缝隙连接蛋白在钙离子介导的乳腺癌细胞转移和侵袭中的作用

目的 探讨缝隙接蛋白(Cx)在钙离子介导的乳腺癌细胞转移和侵袭中的作用. 方法 选用不影响细胞生长的缝隙连接蛋白阻断剂,辛醇100μmol/L处理高转移MDA-MB-231细胞和低转移MCF-7细胞.倒置相差显微镜下观察细胞形态,激光扫描共焦显微镜下观察Cx43的位置、微丝纤维的排列和细胞内钙离子浓度变化,划痕和侵袭实验观察细胞的转移情况. 结果 辛醇处理细胞后,细胞的生长状态由大面积片状生长转变为单个或少数几个团状的独立生长;Cx43蛋白的形成和表达位置虽无改变,但相邻细胞间微丝纤维排列的平行同向性显著性降低;MDA-MB-231细胞穿过基底膜成胶和Transwell小室基底面的细胞数显著低于对照组;此外,细胞内钙离子浓度强度显著性降低,钙离子螯合剂(EGTA)处理显著性加剧辛醇对细胞转移和侵袭能力的抑制.但是,上述现象在低转移MCF-7细胞中效果不明显.结论 缝隙连接蛋白阻断剂在干扰乳腺癌细胞Cx功能活性,而不影响Cx形成的情况下,能够显著性抑制高转移乳腺癌的恶性进展和侵袭转移,此机制与细胞内钙离子浓度降低有关.     

Gating of cx46 gap junction hemichannels by calcium and voltage

 Connexin 46 (cx46), when expressed in Xenopus oocytes, not only forms typical gap junction channels between paired cells but also forms open gap junction hemichannels in the plasma membrane of single cells. The gap junction hemichannels share properties with complete gap junction channels in terms of permeability and gating. Here we characterize the gate that closes hemichannels in response to increased calcium concentration with whole-cell and single-channel records. The channels close within a narrow range of extracellular calcium concentrations (1–2 mM) which includes the calcium concentration prevailing in the primary site of cx46 expression, the lens. The effect of calcium on the channels is determined by voltage. A cysteine mutant of cx46, cx46L35C, was used to determine the localization of the gate. Experimental evidence suggests that position 35 is pore lining. The localization protocol tests the accessibility of position 35 for thiol reagents applied extra- or intracellularly to the channel closed by calcium. Channel closure by calcium excluded the thiol reagent from the outside but not from the inside. Consequently, the gate results in a regional closure of the pore and it is located extracellular to the position 35 of cx46. The present data also suggest that the cx46 gap junction hemichannel may exert a physiological function in the lens. Considering the association of calcium with cataract formation, it is feasible that misregulation of cx46 gap junction hemichannels could be a cause for cataract. Received: 30 July 1998 / Received after revision and accepted: 14 September 1998     

胆红素和内毒素联合作用对NRK52E细胞缝隙连接功能的影响

目的: 观察胆红素(BR)和内毒素(LPS)联合作用对肾小管上皮细胞(NRK52E)生长及细胞间缝隙连接(GJ)的影响。方法: 体外培养NRK52E细胞,不同浓度的BR和LPS联合干预,用MTT测量细胞生长;观察它们对生长融合细胞(有GJ形成)和生长未融合细胞(无GJ形成)集落形成的影响;采用细胞荧光免疫示踪法分析细胞间GJ的功能。结果: BR 从17.1 μmol/L增加至 513 μmol/L,可浓度依赖性地增加细胞生长;当BR浓度继续增加时,细胞生长逐渐降低。LPS(10-1 000 μg/L)能浓度依赖性地降低NRK52E细胞生长。 BR和LPS 联合作用下,513 μmol/L BR增加100 μg/L LPS作用下的细胞生长(P<0.05),而684 μmol/L BR降低100 μg/L LPS的细胞生长(P<0.05);513 μmol/L BR能增加100 μg/L LPS作用下GJ传递数目(P<0.05),684 μmol/L BR降低100 μg/L LPS作用下的GJ传递数目。 结论: BR和LPS联合作用时,513 μmol/L BR降低LPS的细胞毒性,684 μmol/L BR增加LPS的细胞毒性,其改变可能是通过细胞间缝隙连接发挥作用的。     

The Renin–Angiotensin System Mediates the Effects of Stretch on Conduction Velocity,Connexin43 Expression,and Redistribution in Intact Ventricle

Effect of Stretch on Conduction and Cx43 . Introduction: In disease states such as heart failure, myocardial infarction, and hypertrophy, changes in the expression and location of Connexin43 (Cx43) occur (Cx43 remodeling), and may predispose to arrhythmias. Stretch may be an important stimulus to Cx43 remodeling; however, it has only been investigated in neonatal cell cultures, which have different physiological properties than adult myocytes. We hypothesized that localized stretch in vivo causes Cx43 remodeling, with associated changes in conduction, mediated by the renin–angiotensin system (RAS). Methods and Results: In an open‐chest canine model, a device was used to stretch part of the right ventricle (RV) by 22% for 6 hours. Activation mapping using a 312‐electrode array was performed before and after stretch. Regional stretch did not change longitudinal conduction velocity (post‐stretch vs baseline: 51.5 ± 5.2 vs 55.3 ± 8.1 cm/s, P = 0.24, n = 11), but significantly reduced transverse conduction velocity (28.7 ± 2.5 vs 35.4 ± 5.4 cm/s, P < 0.01). It also reduced total Cx43 expression, by Western blotting, compared with nonstretched RV of the same animal (86.1 ± 32.2 vs 100 ± 19.4%, P < 0.02, n = 11). Cx43 labeling redistributed to the lateral cell borders. Stretch caused a small but significant increase in the proportion of the dephosphorylated form of Cx43 (stretch 9.95 ± 1.4% vs control 8.74 ± 1.2%, P < 0.05). Olmesartan, an angiotensin II blocker, prevented the stretch‐induced changes in Cx43 levels, localization, and conduction. Conclusion: Myocardial stretch in vivo has opposite effects to that in neonatal myocytes in vitro. Stretch in vivo causes conduction changes associated with Cx43 remodeling that are likely caused by local stretch‐induced activation of the RAS. (J Cardiovasc Electrophysiol, Vol. 21, pp. 1276‐1283, November 2010)     

咬合蛋白在血脑屏障通透性改变中的作用

作为脑微血管内皮细胞紧密连接中的重要跨膜蛋白,咬合蛋白(occludin)在血脑屏障通透性调节和维持方面起着重要作用,其表达异常可使血脑屏障通透性增高.文章就咬合蛋白在血脑屏障紧密连接中的分子组成、功能维持以及在缺氧时脑微血管通透性改变中所起的作用做了综述,以便为深入研究咬合蛋白在血脑屏障通透性改变相关疾病发生机制和药物治疗靶点中的作用提供理论帮助.     

Prior information and oculomotor initiation: the effect of cues in gaps

Eye movements reflect not only an important output of various neural control systems, but also often reflect cognitive processing. For example, saccades are frequently used as a behavioural index of attentional processing. A second important eye movement type, smooth pursuit (SP), has received much less attention in this regard. These two types of eye movement were classically thought of as being separate, but recent results have suggested a closer linkage of their control mechanisms and perhaps their interactions with cognitive processes. Prior information, in the form of cues, alters saccade latency leading to characteristic cueing effects. When the period between the appearance of the cue and the appearance of the saccade target is sufficiently long, the latency of saccades to targets appearing at cued locations is increased. This "inhibition of return" is enhanced by a second type of stimulus manipulation, the early removal of the fixation target a few hundred milliseconds before the target appears (the gap paradigm). In the current experiments, the effect of cues, and interactions between cues and long gaps were investigated. In the main pursuit experiment, and in a separate saccade experiment, subjects were presented with interleaved runs of tasks with and without long gaps (gap duration = 1 s), and with and without cues. In tasks without cues, SP latency was reduced by long gaps (mean reduction 8 ms); unexpectedly, saccade latency for non-cue tasks was increased by long gaps (mean increase 41 ms). In a control experiment with only non-cue tasks, in which SP and saccade gap and non-gap tasks were run together, SP latency was again reduced in gap tasks, while saccade latency was increased, but by much less than in the first experiment. Analysis of individual subjects' data showed that while gaps increased saccade latency in two subjects who had participated in the main experiment (in which cues and gaps had been combined), in two naive subjects long gaps did not affect saccade latency. In the main pursuit experiment, cues had both spatially specific and non-spatially specific (warning) effects on pursuit latency. In non-gap conditions, latency was greater when contralateral cues were presented 250 ms prior to the appearance of the pursuit target, compared to ipsilateral cues, a pattern of effect consistent with inhibition of return. However, this was reversed when cues appeared during a gap--contralateral cues increased while ipsilateral cues decreased latency. For saccades, as expected, in both gap and non-gap conditions, cue effects were consistent with inhibition of return (latency was lower with contralateral cues), and the inhibition of return effect was larger in gap, compared to non-gap conditions. The results suggest that, in appropriate contexts (or as a result of appropriate training), there are distinct inhibitory mechanisms that operate on saccades but not pursuit. What appears to be an inhibition of return effect on pursuit latency when static cues are presented in pursuit tasks, may be better understood as the product of a modulation of mechanisms active in pursuit initiation, perhaps related to motion processing. In contrast to some recent evidence suggesting a close anatomical and functional linkage between pursuit and saccade initiation, the results are consistent with the involvement of a wider range of mechanisms, or a greater degree of flexibility, in programming the initiation of these two oculomotor behaviours.     

Semantic retrieval of spoken words with an obliterated initial phoneme in a sentence context

Perception of a phoneme may occur even when the speech sound is missing (e.g., when an extraneous noise replaces the sound). This phenomenon, called phonemic restoration, has been observed to depend on the type of distortion. It requires a replacing sound that provides acoustic input to the auditory system, since the restoration has not been found when a speech sound was replaced by silence. We examined the brain activation underlying speech processing when the word's initial phoneme was completely replaced by a silent gap. Event-related potentials (ERPs) and reaction times (RTs) were measured as indicators of semantic processing of sentence final words. Slower voice onset times during repetition of the manipulated words as compared to normal words indicated increased difficulty in retrieving their meaning. The N400, which is related to the increased demands of the semantic integration of words, was elicited by less expected words as compared to highly expected ones. For manipulated words, the N400 was elicited at the same latency than for normal words, with respect to the onset of the remaining word fragment. The amplitude of the N400 was not increased, nor did it last longer, thereby indicating successful retrieval of the word's meaning based on the semantic context and remaining phonetic information. Thus, semantic retrieval does not seem to require the word's initial phoneme to be present in a sentence context. The results suggest that both context-driven expectancy (top–down) and stimulus-driven processes (bottom–up) are utilized in word processing and contribute to the overall N400 response.