Regulation of mitochondrial dynamics and distribution by synapse position and neuronal activity in the axon

Proper distribution of axonal mitochondria is critical for multiple neuronal functions. To understand the underlying mechanisms for population behavior, quantitative characterisation of elemental dynamics on multiple time scales is required. Here we investigated the stability and transport of axonal mitochondria using live‐cell imaging of cultured mouse hippocampal neurons. We first characterised the long‐term stability of stationary mitochondria. At a given moment, about 10% of the mitochondria were in a state of transport and the remaining 90% were stationary. Among these stationary mitochondria, 40% of them remained in the same position over several days. The rest of the mitochondria transited to mobile state stochastically and this process could be detected and quantitatively analysed by time‐lapse imaging with intervals of 30 min. The stability of axonal mitochondria increased from 2 to 3 weeks in culture, was decreased by tetrodotoxin treatment, and was higher near synapses. Stationary mitochondria should be generated by pause of moving mitochondria and subsequent stabilisation. Therefore, we next analysed pause events of moving mitochondria by repetitive imaging at 0.3 Hz. We found that the probability of transient pause increased with field stimulation, decreased with tetrodotoxin treatment, and was higher near synapses. Finally, by combining parameters obtained from time‐lapse imaging with different time scales, we could estimate transition rates between different mitochondrial states. The analyses suggested specific developmental regulation in the probability of paused mitochondria to transit into stationary state. These findings indicate that multiple mitochondrial behaviors, especially those regulated by neuronal activity and synapse location, determine their distribution in the axon.     

Cysteine residues 87 and 320 in the amino terminal domain of NMDA receptor GluN2A govern its homodimerization but do not influence GluN2A/GluN1 heteromeric assembly

N-Methyl-D-aspartate receptors（NMDARs） play a central role in various physiological and pathological processes in the central nervous system.And they are commonly composed of four subunits,two GluN1 subunits and two GluN2 or GluN3 subunits.The different subunit compositions make NMDARs a heterogeneous population with distinct electrophysiological and pharmacological properties and thus with different abilities to conduct neuronal activities.The subunit composition,assembly process,and final structure of assembled NMDARs have been studied for years but no consensus has been achieved.In this study,we investigated the role of the amino terminal domain（ATD） of GluN2A in regulating NMDAR assembly.The ATD of GluN2A was first expressed in heterogeneous cells and the homodimer formation was investigated by fluorescent resonance energy transfer and non-reducing SDS- PAGE electrophoresis.Each of the three cysteine residues located in the ATD was mutated into alanine,and the homodimerization of the ATD or GluN2A,as well as the heteromeric assembly of NMDARs was assessed by non-reducing SDS- PAGE electrophoresis,co-immunoprecipitation and immunocytochemistry.We found that two cysteine residues,C87 and C320,in the ATD of the GluN2A subunit were required for the formation of disulfide bonds and GluN2A ATD homodimers.Furthermore,the disruption of GluN2A ATD domain dimerization had no influence on the assembly and surface expression of NMDARs.These results suggest that the two ATD domains of GluN2A are structurally adjacent in fully-assembled NMDARs.However,unlike GluN1,the homomerization of the ATD domain of GluN2A is not required for the assembly of NMDARs,implying that GluN2A and GluN1 play unequal roles in NMDAR assembly.     

Sensory outcomes of the anterior tongue after lingual nerve repair in oropharyngeal cancer

Primary treatment of oropharyngeal cancer often involves surgical resection and reconstruction of the affected area. However, during base of tongue reconstruction the lingual nerve is often severed on one or both sides, affecting sensation in the preserved tissue of the anterior tongue. The loss of specific tongue sensations could negatively affect a person's oral function and quality of life. The aim of this study was to explore the effects of different types of lingual nerve intervention on sensory function for patients with base of tongue cancer as compared to healthy, age-matched adults. Subjects included 30 patients who had undergone primary oropharyngeal reconstruction with a radial forearm free-flap and 30 matched controls. Sensations tested were temperature, two-point discrimination, light touch, taste, oral stereognosis and texture on the anterior two-thirds of the tongue. Results indicated that type of surgical nerve repair may not have a significant impact on overall sensory outcomes, providing mixed results for either nerve repair technique. Sensations for the nonoperated tongue side and operated side with lingual nerve intact were comparable to matched controls, with mixed outcomes for nerve repair. The poorest sensory outcomes were observed in patients with the lingual nerve severed, while all patients with lingual nerve intervention exhibited deteriorated taste sensation on the affected tongue side. Overall, patients in this study who had undergone oropharyngeal reconstruction with lingual nerve intervention exhibited decreased levels of sensation on the operated tongue side, with minimal differences between types of lingual nerve repair.     

932名武汉市民对生命维持治疗的态度现状及影响因素分析

目的探讨武汉市民对生命维持治疗的态度,分析其影响因素。方法采用便利抽样法,2018年6月—2019年1月抽取武汉成年市民932名,采用一般资料调查表及生命维持治疗调查表对其进行调查,采用二分类Logistic回归分析生命维持治疗态度的影响因素。结果932名市民中,600名(64.4%)听说过生命维持治疗,842名(90.3%)在假设病情严重或陷入昏迷时拒绝接受这些治疗。二分类Logistic回归分析显示,未患绝症(OR=2.153,P<0.001)的市民倾向于接受生命维持治疗,年龄越大(50~59岁:OR=0.472,P=0.028;≥60岁:OR=0.402,P=0.013)、大专及以上学历(OR=0.526,P=0.009)、患有绝症(OR=0.542,P=0.037)的市民越倾向于拒绝生命维持治疗。结论本研究中64.4%市民听说过生命维持治疗,90.3%倾向于拒绝生命维持治疗,年龄、教育程度、是否患绝症是对生命维持治疗态度的主要影响因素。建议加强对生命维持治疗局限性的宣教,以帮助市民理解其本质,做出理性选择,提高生命质量。     

手术治疗儿童硬脊膜囊末端囊肿样膨出的疗效

目的观察手术治疗儿童硬脊膜囊末端囊肿样膨出的疗效。方法2015年1月至2021年1月苏州大学附属儿童医院神经外科采用手术治疗11例儿童硬脊膜囊末端囊肿样膨出患者,其中8例行终丝离断+椎管内囊肿切除+硬脊膜囊末端缺损修补术,2例仅行终丝切断手术,1例行终丝离断+囊壁部分切除+囊腔脂肪填塞术。回顾性观察患儿术后的临床及影像学改善情况。结果11例患儿术后无一例发生感染及脑脊液漏等并发症。术后随访3个月至5年4个月(中位数为3年6个月),无一例患儿出现新发神经功能缺损症状;4例术前出现症状的患儿术后3例原有症状明显改善。术后3~6个月复查MRI,所有患儿均可见终丝离断;行硬膜囊远端瘘口修补的8例患儿,术后MRI显示骶管囊肿基本消失;行终丝离断+囊壁部分切除+囊腔脂肪填塞术的1例患儿,术后MRI显示囊肿为填塞脂肪组织代替。3例术前出现脊髓远端和终丝中央管极度扩张的患儿,术后MRI显示扩张明显改善。结论采用手术治疗儿童硬脊膜囊末端囊肿样膨出,手术安全;可改善患儿的临床症状和影像学情况。     

急性心肌梗死恢复期V1导联P波终末电势与左室舒张功能的相关性研究

目的  探讨急性心肌梗死（AMI）患者恢复期心电图V1导联P波终末电势（Ptfv1）与左心室舒张功能的相关性。方法  选择78例AMI后6周左右[（41.76±4.28）d]心电图Ptfv1≤-40 mm/s的患者为观察组,以及同期86例心电图Ptfv1>-40 mm/s的AMI患者为对照组。比较两组间超声心动图左房内径（LAD）、左室舒张期直径（LVDd）、左室等容舒张时间（LVRT）、二尖瓣舒张早期流速峰值（E）、二尖瓣舒张晚期流速峰值（A）、左心室射血分数（LVEF）、组织多普勒舒张早期二尖瓣环水平心肌速率峰值（E''）、E/A及E/E''等。结果  观察组LVDd、LAD、LVRT增大（P <0.05）,观察组LVEF减低（P <0.01）,观察组中E/A值降低（P <0.025）,观察组E及E''峰值减小（P <0.05）,E/E''值増高（P <0.05）,观察组E''<9 cm/s、E/E''>8及15的例数增多（P <0.05）。结论  在AMI恢复期患者中,Ptfv1值异常反映左心室舒张功能减退。测量Ptfv1是简单易行的初步评估左室舒张功能方法。

     

Thalamocortical and the dual pattern of corticothalamic projections of the posterior parietal cortex in macaque monkeys

The corticothalamic projection includes a main, modulatory projection from cortical layer VI terminating with small endings whereas a less numerous, driving projection from layer V forms giant endings. Such dual pattern of corticothalamic projections is well established in rodents and cats for many cortical areas. In non-human primates (monkeys), it has been reported for the primary sensory cortices (A1, V1, S1), the motor and premotor cortical areas and, in the parietal lobe, also for area 7. The present study aimed first at refining the cytoarchitecture parcellation of area 5 into the sub-areas PE and PEa and, second, establishing whether area 5 also exhibits this dual pattern of corticothalamic projection and what is its precise topography. To this aim, the tracer biotinylated dextran amine (BDA) was injected in area PE in one monkey and in area PEa in a second monkey. Area PE sends a major projection terminating with small endings to the thalamic lateral posterior nucleus (LP), ventral posterior lateral nucleus (VPL), medial pulvinar (PuM) and, but fewer, to ventral lateral posterior nucleus, dorsal division (VLpd), central lateral nucleus (CL) and center median nucleus (CM), whereas giant endings formed restricted terminal fields in LP, VPL and PuM. For area PEa, the corticothalamic projection formed by small endings was found mainly in LP, VPL, anterior pulvinar (PuA), lateral pulvinar (PuL), PuM and, to a lesser extent, in ventral posterior inferior nucleus (VPI), CL, mediodorsal nucleus (MD) and CM. Giant endings originating from area PEa formed restricted terminal fields in LP, VPL, PuA, PuM, MD and PuL. Furthermore, the origin of the thalamocortical projections to areas PE and PEa was established, exhibiting clusters of neurons in the same thalamic nuclei as above, in other words predominantly in the caudal thalamus. Via the giant endings CT projection, areas PE and PEa may send feedforward, transthalamic projections to remote cortical areas in the parietal, temporal and frontal lobes contributing to polysensory and sensorimotor integration, relevant for visual guidance of reaching movements for instance.     

Increased oxidative stress is associated with balanced increases in hepatocyte apoptosis and proliferation in glycerol-3-phosphate acyltransferase-1 deficient mice

The absence of mouse mitochondrial glycerol-3-phosphate acyltransferase-1 (Gpat1-/-) increases the amount of arachidonate in liver phospholipids and increases beta-hydroxybutyrate and acyl-carnitines, suggesting an elevated rate of liver fatty acid oxidation. We asked whether these alterations might increase reactive oxygen species (ROS), apoptosis, or hepatocyte proliferation. Compared to wildtype controls, liver mitochondria from Gpat1-/- mice showed a 20% increase in the rate of ROS production and a markedly increased sensitivity to the induction of the mitochondrial permeability transition. Mitochondrial phosphatidylethanolamine and phosphatidylcholine from Gpat1-/- liver contained 21% and 67% more arachidonate, respectively, than wildtype controls, and higher amounts of 4-hydroxynonenal, a product of arachidonate peroxidation. Oxidative stress was associated with an increase in apoptosis, and with 3-fold and 15-fold higher TUNEL positive cells in liver from young and old Gpat1-/- mice, respectively, compared to age-matched controls. Compared to controls, bromodeoxyuridine labeling was 50% and 7-fold higher in livers from young and old Gpat1-/- mice, respectively, but fewer glutathione-S-transferase positive cells were present. Thus, Gpat1-/- liver exhibits increased oxidative stress and sensitivity of the mitochondrial permeability transition pore, and a balanced increase in apoptosis and proliferation.