Calcium imaging of epileptiform events with single‐cell resolution

Epileptic discharges propagate through apparently normal circuits, although it is still unclear how this recruitment takes place. To understand the role of different classes of neurons in neocortical epilepsy, we have developed a novel imaging assay that detects which neurons participate in epileptiform discharges. Using calcium imaging of neuronal populations during bicuculline‐induced spontaneous epileptiform events in slices from juvenile mouse somatosensory cortex, we find that fast calcium transients correlate with epileptiform field potentials and intracellular depolarizing shifts and can be used as an optical signature that a given neuron has participated in an epileptiform event. Our results demonstrate a novel method to characterize epileptiform events with single‐cell resolution. In addition, our data are consistent with an important role for layer 5 in generating neocortical seizures and indicate that subgroups of neurons are particularly prone to epileptiform recruitment. © 2001 John Wiley & Sons, Inc. J Neurobiol 48: 215–227, 2001     

A refined method of quantifying deceleration capacity index for heart rate variability analysis

Background

Phase-rectified signal averaging (PRSA) was often applied to assess the cardiac vagal modulation. Despite its broad use, this method suffers from the confounding effects of anomalous variants of sinus rhythm. This study aimed to improve the original PRSA method in deceleration capacity (DC) quantification.

Methods

The refined deceleration capacity (DC_ref) was calculated by excluding from non-vagally mediated abnormal variants of sinus rhythms. Holter recordings from 202 healthy subjects and 51 patients with end-stage renal disease (ESRD) have been used for validity. The DC_ref was compared to original DC (DC_org) by the area under receiver operating characteristic curve.

Results

Experimental results demonstrate that the original and refined DCs calculated from 24-h, 2-h, and 30-min Holter recordings are significantly lower in patients with ESRD than those in the healthy group. In receiver operating characteristic curve analysis, the DC_ref provides better performance than the DC_org in distinguishing between the patients with ESRD and healthy control subjects. Furthermore, the refined PRSA technique enhances the low frequency and attenuates high frequency components for spectral analysis in ESRD patients.

Conclusions

The DC_ref appears to reduce the influence of non-vagally mediated abnormal variants of sinus rhythm and highlighting the pathological influence. DC_ref, especially assessed from short-term electrocardiography recordings, may be complementary to existing autonomic function assessment, risk stratification, and efficacy prediction strategies.

     

Influence of ammonium and nitrate supply on growth,nitrate reductase activity and N-use efficiency in a natural hybrid pine and its parents

Aims Selection of tree species with a high capacity to assimilate N and efficiently utilize N resources would facilitate the success of initial tree seedling establishment in infertile soils. The preference for N forms was tested using three pine species (Pinus densata, Pinus tabuliformis and Pinus yunnanensis). Pinus densata is a natural diploid hybrid between P. tabuliformis and P. yunnanensis .Methods Seedlings of three pine species were supplied with nitrate-N, ammonium-N (at two different pH regimes) or combined ammonium and nitrate as a nitrogen source in perlite culture in a controlled environment.Important findings Seedlings of P. densata had higher total biomass and net photosynthesis when supplied with nitrate-N and ammonium nitrate than with ammonium-N. In parental species, total biomass and net photosynthesis for P. yunnanensis seedlings was higher in ammonium-N than in nitrate-N, whereas the other parental species P. tabuliformis had the highest total biomass among species for all treatments except ammonium with CaCO 3. Most morphological traits in P. densata seedlings were intermediate between its two parental species. However, N-use efficiency and photosynthetic N-use efficiency of P. densata significantly exceeded both parents when supplied with nitrate-N and ammonium nitrate. The results suggested that the diploid hybrid tree species P. densata has a preference for nitrate and is not well adapted to ammonium-N as a sole nitrogen source regardless of the growth medium pH. Based on changes in environmental conditions, such as predicted future temperature increases in high altitude areas associated with climate change, P. densata is likely to be increasingly competitive and have wide adaptation in high altitude regions.     

矮嵩草草甸主要植物不同器官对氮素的吸收及分配特征研究

以高寒矮嵩草(Kobresia humilis)草甸7个主要植物种为研究对象,利用15 N同位素标记技术,通过分析不同器官对氮素的吸收及分配特征,揭示主要植物种在群落中的生态适应性、竞争力和地位。结果显示:(1)矮嵩草的叶和茎、垂穗披碱草(Elymus nutans)的叶,以及双柱头藨草(Scirpus distigmaticus)和鹅绒委陵菜(Potentilla anserina)的叶、茎、根均偏好累积硝态氮,早熟禾(Poa annua)的穗和叶以及甘肃马先蒿(Pedicularis kansuensis)和短穗兔耳草(Lagotis brachystachya)的根均偏好积累铵态氮。(2)矮嵩草对吸收的甘氨酸和硝态氮主要分配于叶中,铵态氮分配于茎中;双柱头藨草对吸收的甘氨酸和硝态氮主要分配于茎中,铵态氮分配于叶中;垂穗披碱草和早熟禾对吸收的硝态氮和铵态氮主要分配于叶中;垂穗披碱草对吸收的甘氨酸主要分配于根中,而早熟禾将较多的甘氨酸分配到穗中;甘肃马先蒿对吸收的硝态氮主要分配于叶中,铵态氮分配于根中;鹅绒委陵菜对吸收的甘氨酸、硝态氮和铵态氮主要分配于叶中;短穗兔耳草对吸收的甘氨酸主要分配于叶中,硝态氮和铵态氮主要分配于根中。(3)在牧草生长盛期,矮嵩草草甸土壤的有机氮和无机氮主要贡献于甘肃马先蒿的花、早熟禾的穗、垂穗披碱草的根和鹅绒委陵菜的茎叶。研究表明,高寒矮嵩草草甸主要植物不同器官对氮素的吸收及分配呈现多元化特征,因不同植物种的生物学特性和生态适应习性而异。     

青藏高原高寒草甸3种植物对模拟增温的生理生化响应

采用国际冻原计划(ITEX)模拟增温对植物影响的研究方法,将开项式生长室(OTC)按不同直径设置5个增温梯度,并按其直径从小到大的顺序依次标记为A、B、C、D、E 5个处理,研究了增温效应对青藏高原高寒草甸3种植物生理生化特性的影响。研究表明:（1） A~E 5个增温处理使OTC内部气温依次比对照升高了2.68 ℃、1.57 ℃、1.20 ℃、1.07 ℃ 和0.69 ℃,土壤温度依次比对照升高了1.74 ℃、1.06 ℃、0.80 ℃、0.60 ℃和0.30 ℃。（2）增温对3种植物的叶绿素含量、可溶性糖含量、可溶性蛋白含量、SOD活性、谷胱甘肽等生理生化特性产生了一系列的影响,3种植物对增温效应的响应也不尽相同。（3）增温对青藏高原3种植物生理生化特性的影响明显且复杂,适度增温0.69 ℃~1.07 ℃（D、E处理）对3种植物生理生化特性在总体上表现为正效应。     

凋落物和根系输入对南亚热带季风常绿阔叶林土壤养分的影响

植被凋落物和根系输入在调节森林土壤元素生物地球化学循环中扮演着关键作用。目前仍然不清楚凋落物和根系输入对热带原始林土壤主要元素含量的调控作用。针对该研究现状,以中国南亚热带季风常绿阔叶林为研究对象,通过开展凋落物与根系输入改变的控制试验（6个处理,每处理4次重复：对照、凋落物加倍、凋落物去除、断根、断根+凋落物加倍、断根+去除凋落物）,探讨了凋落物和断根处理对土壤可溶性离子、土壤酸中和能力（ANC）和阳离子交换量（CEC）的短期影响。凋落物与根系处理半年后的结果显示：（1）凋落物去除与加倍处理都显著增加了0-40 cm土壤NO₃^-含量,并且凋落物去除效应大于添加效应;去除凋落物增加了表层土壤（0-20 cm） Ca²⁺、Mg²⁺、Na⁺的含量。（2）断根处理显著增加0-40 cm土壤NO₃^-和表层土壤Ca²⁺、Mg²⁺含量。（3）断根和去除凋落物交互处理显著增加了0-40 cm土壤NO₃^-和表层土壤Ca²⁺、Mg²⁺、K⁺含量,产生了叠加效应。（4）凋落物和断根处理并没有改变土壤pH,但降低了土壤酸中和能力（除凋落物加倍外）,其降低的原因主要与阳离子交换量的降低和NO₃^-含量的增加有关。这些结果表明,土壤养分离子的可利用性（尤其是NO₃^-和Ca²⁺、Mg²⁺）和酸缓冲能力对凋落物和根系输入改变响应敏感,森林植物及其凋落物对土壤养分保留和缓冲性能具有重要调节作用。在人为干扰和气候变化加剧背景下,该研究可为森林生态系统可持续管理提供重要的理论参考。此外,植被凋落物和根系输入改变引起的长期生态学效应仍值得进一步关注。     

WASH inhibits autophagy through suppression of Beclin 1 ubiquitination

Autophagy degrades cytoplasmic proteins and organelles to recycle cellular components that are required for cell survival and tissue homeostasis. However, it is not clear how autophagy is regulated in mammalian cells. WASH (Wiskott–Aldrich syndrome protein (WASP) and SCAR homologue) plays an essential role in endosomal sorting through facilitating tubule fission via Arp2/3 activation. Here, we demonstrate a novel function of WASH in modulation of autophagy. We show that WASH deficiency causes early embryonic lethality and extensive autophagy of mouse embryos. WASH inhibits vacuolar protein sorting (Vps)34 kinase activity and autophagy induction. We identified that WASH is a new interactor of Beclin 1. Beclin 1 is ubiquitinated at lysine 437 through lysine 63 linkage in cells undergoing autophagy. Ambra1 is an E3 ligase for lysine 63‐linked ubiquitination of Beclin 1 that is required for starvation‐induced autophagy. The lysine 437 ubiquitination of Beclin 1 enhances the association with Vps34 to promote Vps34 activity. WASH can suppress Beclin 1 ubiquitination to inactivate Vps34 activity leading to suppression of autophagy.     

春性甘蓝型油菜BnFY34基因的克隆及序列分析

春性甘蓝型油菜杂交种由于发育期较长,极大地限制了该油菜在高寒地区的推广。为了从春性特早熟甘蓝型油菜中筛选出苗期和蕾期差异表达的基因,该研究以春性特早熟甘蓝型油菜为材料,利用cDNA-AFLP技术筛选出1个春性特早熟甘蓝型油菜苗期特异表达的基因片段,并采用RACE技术成功分离克隆了该基因,命名为BnFY34。通过对该基因的测序和生物信息学分析,发现该基因序列大小为455 bp,包含完整的开放阅读框(ORF),编码一个由71个氨基酸残基组成的蛋白,推测的蛋白质分子量为8.04 kD,理论等电点为10.25,其三级结构中含有3个α螺旋,不含β折叠。同时,将BnFY34基因与甘蓝型油菜基因组序列进行比对,结果显示BnFY34基因位于C4染色体上,由3个外显子和2个内含子组成。另外,通过对该基因与其他植物同源基因的亲缘关系进行了分析,结果表明BnFY34基因与芸薹属植物属于同一亚族,并且与甘蓝型油菜中已报到的未诠释基因XM_013837282.1的相似度达100%,其功能有待进一步研究。该研究结果对春油菜产量和品质的早熟转基因育种具有重要意义。