High-altitude tree growth responses to climate change across the Hindu Kush Himalaya

兴都库什喜马拉雅地区高海拔树木生长对气候变化的响应 高海拔地区快速升温可能导致树木对温度响应更为敏感,而限制高海拔地区树木生长的关键气候因子以及气候变化对树木生长产生多大程度的影响尚不清楚。本研究在兴都库什喜马拉雅地区收集了73 个样点的树轮数据,包括3个优势属的树种(Abies属、Juniperus属和Picea属),样点海拔均在3000 m以上。 将时间动态规整(dynamic time warping)的方法用于建立亚区域年表,以考虑不同站点年表之间变化的同步 性。同时,定量分析了气候因子对树木生长的贡献以及树木生长与气候因子关系的时空动态。研究结果发现,73个站点年表可以聚为3类,且与其所处的生物气候区相对应,即西喜马拉雅地区,中东喜马拉雅地区和藏东南地区。在干旱的西喜马拉雅地区,树木生长与冬、春两季的降水呈正相关关系,而在湿润的藏东南地区,树木生长与冬季温度和春季降水呈正相关关系。树木生长受最低温度的影响最大,特别是冬季温度,其重要性从西到东呈现递增趋势。滑动窗口相关分析表明,在中西喜马拉雅地区,影响树木生长的冬季温度信号在减弱,然而在藏东南地区该信号随着1980年以来的快速升温而增强。本研究结果表明,若该地区升温持续,在西喜马拉雅地区可能会因变暖引起的水分亏缺而造成森林衰退,而在藏东南地区因树木生长得益于变暖而使得森林扩张。     

Intact Histological Characterization of Brain-implanted Microdevices and Surrounding Tissue

Research into the design and utilization of brain-implanted microdevices, such as microelectrode arrays, aims to produce clinically relevant devices that interface chronically with surrounding brain tissue. Tissue surrounding these implants is thought to react to the presence of the devices over time, which includes the formation of an insulating "glial scar" around the devices. However, histological analysis of these tissue changes is typically performed after explanting the device, in a process that can disrupt the morphology of the tissue of interest.Here we demonstrate a protocol in which cortical-implanted devices are collected intact in surrounding rodent brain tissue. We describe how, once perfused with fixative, brains are removed and sliced in such a way as to avoid explanting devices. We outline fluorescent antibody labeling and optical clearing methods useful for producing an informative, yet thick tissue section. Finally, we demonstrate the mounting and imaging of these tissue sections in order to investigate the biological interface around brain-implanted devices.     

Downregulation of mu opioid receptor by RNA interference in the ventral tegmental area reduces ethanol consumption in mice

Pharmacological and genetic studies have implicated the mu opioid receptor (MOR) in the regulation of ethanol intake in animal models and humans. Non-specific antagonists of opioid receptors have been shown to affect ethanol consumption when infused directly into the ventral tegmental area (VTA) of rats. However, administration of MOR-selective antagonists into the VTA has yielded mixed results. We used RNA interference (RNAi) to specifically decrease levels of MOR messenger RNA in the VTA of mice and examined the effect on ethanol consumption in a two-bottle choice paradigm. Mice were injected in the VTA with lentivirus expressing either a small hairpin RNA (shRNA) targeting MOR or a control shRNA. One week after virus injection, mice were examined for ethanol consumption in a two-bottle choice experiment with increasing concentrations of ethanol over the course of 1 month. Expression of an shRNA targeting MOR in the VTA led to a significant reduction in ethanol consumption. These results strengthen the hypothesis that MOR in the VTA is one of the key brain substrates mediating alcohol consumption. The RNAi combined with lentiviral delivery can be used successfully in brain to effect a sustained reduction in expression of specific genes for behavioral analysis.     

青藏高原东缘两处高山树线交错带时空动态及其建群种的生态学特征

热量匮乏是高山树线的主要成因, 在全球变暖趋势下对高山树线及其建群种的生态学过程及特征的研究具有重要意义。该文以青藏高原东缘的折多山和剪子弯山两处高山树线(海拔分别为4 265 m和4 425 m)作为研究对象, 通过设置垂直样带, 同时结合区域温度、降水的长时间序列分析, 探究两处树线的时空动态过程, 并明确了建群种冷杉(Abies spp.)的生态学特征。结果表明: 1)折多山和剪子弯山区域的气温在过去58年均存在显著的上升趋势(分别上升了0.72和0.91 ℃), 而折多山和剪子弯山区域降水均存在微弱的降低趋势。2)折多山的峨眉冷杉(A. fabri)龄级结构呈反J形, 剪子弯山的鳞皮冷杉(A. squamata)龄级结构呈双峰形, 二者种群结构均相对稳定。3)在小尺度上, 种子扩散限制使得两处树线的冷杉聚集分布。在大尺度上, 折多山峨眉冷杉亦呈聚集分布, 而剪子弯山鳞皮冷杉受生长环境以及种内或种间关系的影响呈随机分布。4)两处样地建群树种的树高和基径均随海拔升高而降低, 位于树线交错带上部的冷杉均呈现树高生长大于径向生长的异速生长关系, 而位于样地中、下部位的冷杉大部分呈等速生长关系。5)相比10年前, 折多山和剪子弯山的树线及树种线位置均无明显变化, 剪子弯山鳞皮冷杉种群的树木密度亦无明显变化, 而折多山的树木个体数提高了约25%; 相比20年前, 折多山和剪子弯山的树种线分别上移了50和30 m, 树线位置分别升高了75和40 m, 树木个体数亦明显增加, 分别提高了约220%和100%。树线及其建群种在较大时空尺度上主要受热量的控制, 而在较小时空尺度上受温度及生长环境共同作用的影响。     

The effect of the cag pathogenicity island on binding of Helicobacter pylori to gastric epithelial cells and the subsequent induction of apoptosis

BACKGROUND: Helicobacter pylori infection leads to gastritis, peptic ulcer, and gastric cancer, in part due to epithelial damage following bacteria binding to the epithelium. Infection with cag pathogenicity island (PAI) bearing strains of H. pylori is associated with increased gastric inflammation and a higher incidence of gastroduodenal diseases. It is now known that various effector molecules are injected into host epithelial cells via a type IV secretion apparatus, resulting in cytoskeletal changes and chemokine secretion. Whether binding of bacteria and subsequent apoptosis of gastric epithelial cells are altered by cag PAI status was examined in this study. METHODS: AGS, Kato III, and N87 human gastric epithelial cell lines were incubated with cag PAI-positive or cag PAI-negative strains of H. pylori in the presence or absence of clarithromycin. Binding was evaluated by flow cytometry and scanning electron microscopy. Apoptosis was assessed by detection of DNA degradation and ELISA detection of exposed histone residues. RESULTS: cag PAI-negative strains bound to gastric epithelial cells to the same extent as cag PAI-positive strains. Both cag PAI-positive and cag PAI-negative strains induced apoptosis. However, cag PAI-positive strains induced higher levels of DNA degradation. Incubation with clarithromycin inactivated H. pylori but did not affect binding. However, pretreatment with clarithromycin decreased infection-induced apoptosis. CONCLUSIONS: cag PAI status did not affect binding of bacteria to gastric epithelial cells but cag PAI-positive H. pylori induced apoptosis more rapidly than cag PAI-negative mutant strains, suggesting that H. pylori binding and subsequent apoptosis are differentially regulated with regard to bacterial properties.     

Calcium oscillations trigger focal adhesion disassembly in human U87 astrocytoma cells

Integrin-associated intracellular Ca(2+) oscillations modulate cell migration, probably by controlling integrin-mediated release of the cell rear during migration. Focal adhesion kinase (FAK), via its tyrosine phosphorylation activity, plays a key role in integrin signaling. In human U87 astrocytoma cells, expression of the dominant negative FAK-related non-kinase domain (FRNK) inhibits the Ca(2+)-sensitive component of serum-dependent migration. We investigated how integrin-associated Ca(2+) signaling might be coupled to focal adhesion (FA) dynamics by visualizing the effects of Ca(2+) spikes on FAs using green fluorescent protein (GFP)-tagged FAK and FRNK. We report that Ca(2+) spikes are temporally correlated with movement and disassembly of FAs, but not their formation. FRNK transfection did not affect generation of Ca(2+) spikes, although cell morphology was altered, with fewer FAs of larger size and having a more peripheral localization being observed. Larger sized FAs in FRNK-transfected cells were not disassembled by Ca(2+) spikes, providing a possible explanation for impaired Ca(2+)-dependent migration in these cells. Stress fiber end movements initiated by Ca(2+) spikes were visualized using GFP-tagged myosin light chain kinase (MLCK). Ca(2+)-associated movements of stress fiber ends and FAs had similar kinetics, suggesting that stress fibers and FAs move in a coordinated fashion. This indicates that increases in Ca(2+) likely trigger disassembly of adhesive structures that involves disruption of integrin-extracellular matrix interactions, supporting a key role for Ca(2+)-sensitive inside-out signaling in cell migration. A rapid increase in tyrosine phosphorylation of FAK was found in response to an elevation in Ca(2+) induced by thapsigargin, and we propose that this represents the initial triggering event linking Ca(2+) signaling and FA dynamics to cell motility.     

Grapevine fanleaf virus replication occurs on endoplasmic reticulum-derived membranes

Infection by Grapevine fanleaf nepovirus (GFLV), a bipartite RNA virus of positive polarity belonging to the Comoviridae family, causes extensive cytopathic modifications of the host endomembrane system that eventually culminate in the formation of a perinuclear "viral compartment." We identified by immunoconfocal microscopy this compartment as the site of virus replication since it contained the RNA1-encoded proteins necessary for replication, newly synthesized viral RNA, and double-stranded replicative forms. In addition, by using transgenic T-BY2 protoplasts expressing green fluorescent protein in the endoplasmic reticulum (ER) or in the Golgi apparatus (GA), we could directly show that GFLV replication induced a depletion of the cortical ER, together with a condensation and redistribution of ER-derived membranes, to generate the viral compartment. Brefeldin A, a drug known to inhibit vesicle trafficking between the GA and the ER, was found to inhibit GFLV replication. Cerulenin, a drug inhibiting de novo synthesis of phospholipids, also inhibited GFLV replication. These observations imply that GFLV replication depends both on ER-derived membrane recruitment and on de novo lipid synthesis. In contrast to proteins involved in viral replication, the 2B movement protein and, to a lesser extent, the 2C coat protein were not confined to the viral compartment but were transported toward the cell periphery, a finding consistent with their role in cell-to-cell movement of virus particles.