Photosynthetic electron transport and establishment of an associated trans-thylakoid proton electrochemical gradient during development of the wheat leaf

Abstract Photosynthetic electron transport activities and the ability to generate and maintain a trans-thylakoid proton electrochemical gradient were examined during chloroplast development in 4-day-old wheat leaves grown under a diurnal light regime. Polarographic and spectropholometric studies on leaf tissue demonstrated that poorly developed chloroplasls at the leaf base could photo-oxidize water and transfer electrons from photosystem 2 to photosystem 1. The capacity for non-cyclic whole-chain electron transport increased during chloroplast development. Thylakoids isolated from the leaf base, although capable of pumping protons into the inlrathylakoid space, could not maintain a trans-membrane proton electrochemical gradient; this ability developed at later stages of chloroplast biogenesis in the leaf. The implications of these results for the energetics of the developing leaf are discussed.     

Effect of temperature on seed production in the invasive grass Glyceria maxima (Hartm.) Holmb. (Poaceae) in South Africa

Temperature is one of the main factors that determine sexual reproduction in terrestrial and emergent aquatic plant species. The effect of temperature on sexual reproduction and seed production of Glyceria maxima (Hartm.) Holmb. in the southern hemisphere is unknown. Glyceria maxima collections in February 2010 at three isolated infestations in KwaZulu-Natal failed to yield a single seed, only empty panicles. Laboratory experiments showed that vernalisation had no consistent effect on seed production. Field- and laboratory-grown plants produced seeds in the 2010/2011 season, because of having sufficient time at optimum temperatures required for seed production (1 491 and 1 585 hours, respectively), compared to a shorter period (1 352 hours) of suitable temperatures during the 2009/2010 growing season. An inadequate period of optimum temperatures (15–25°C) during seed production resulted in the lack of seeds in the field in the 2009/2010 growing season. This study showed that temperature and duration of exposure thereto during the seed-production period play vital roles in G. maxima sexual reproduction.     

Disturbance affects spatial patterning and stand structure of a tropical rainforest tree

The distribution and spatial patterns of plant populations in natural ecosystems have recently received much attention; yet the impacts of human‐induced disturbances on these patterns and underlying processes remain poorly understood. We used the sub‐canopy tree, Ryparosa kurrangii (Achariaceae), to explore the possible effects of such disturbances on stand structure and spatial patterning in an Australian tropical rainforest. We studied three populations that differed in their extent of habitat modification: anthropogenic disturbance (proximate settlement and roads) and internal damage by an invasive alien species, the feral pig (Sus scrofa). Populations were mapped, characterized, and three size cohorts (seedlings, saplings, trees) were analysed using a suite of spatial point pattern analyses (univariate: Diggle's G and F and Ripley's K; bivariate: Diggle's G and Ripley's K). Ryparosa kurrangii has a typical stand structure for a sub‐canopy tree species, but occurs at high densities locally (>400 stems ha^?1). At all sites, the tree cohort were randomly distributed and saplings were spatially aggregated at distances of up to 2–3 m. Between sites there were distinct differences in the size structure and spatial pattern of seedlings, the cohort most affected by recent habitat modification. That is, the least disturbed site had no aggregation among seedlings, the site with the greatest anthropogenic disturbance had many small, clustered seedlings that were spatially associated with trees, and the site with pig damage had clustered seedlings that had no spatial relationship with trees. We propose that habitat modification by anthropogenic and pig disturbance disrupts seed dispersal and establishment regimes, which leads to altered seedling spatial patterns. These disturbances could have long‐term implications for the population structure and health of R. Kurrangii.     

Isocitrate dehydrogenase 1 R132C mutation occurs exclusively in microsatellite stable colorectal cancers with the CpG island methylator phenotype

The CpG Island Methylator Phenotype (CIMP) is fundamental to an important subset of colorectal cancer; however, its cause is unknown. CIMP is associated with microsatellite instability but is also found in BRAF mutant microsatellite stable cancers that are associated with poor prognosis. The isocitrate dehydrogenase 1 (IDH1) gene causes CIMP in glioma due to an activating mutation that produces the 2-hydroxyglutarate oncometabolite. We therefore examined IDH1 alteration as a potential cause of CIMP in colorectal cancer. The IDH1 mutational hotspot was screened in 86 CIMP-positive and 80 CIMP-negative cancers. The entire coding sequence was examined in 81 CIMP-positive colorectal cancers. Forty-seven cancers varying by CIMP-status and IDH1 mutation status were examined using Illumina 450K DNA methylation microarrays. The R132C IDH1 mutation was detected in 4/166 cancers. All IDH1 mutations were in CIMP cancers that were BRAF mutant and microsatellite stable (4/45, 8.9%). Unsupervised hierarchical cluster analysis identified an IDH1 mutation-like methylation signature in approximately half of the CIMP-positive cancers. IDH1 mutation appears to cause CIMP in a small proportion of BRAF mutant, microsatellite stable colorectal cancers. This study provides a precedent that a single gene mutation may cause CIMP in colorectal cancer, and that this will be associated with a specific epigenetic signature and clinicopathological features.     

奥美拉唑联合法莫替丁治疗反流性食管炎的临床效果分析

目的：观察并分析奥关拉唑联合法莫替丁治疗反流性食管炎的临床效果。方法：选取2008年5月至2012年5月在本院确诊并治疗的反流性食管炎患者45例,随机平均分为三组。联合用药组（15例）：每日早餐前口服20mg奥关拉唑,睡前口服20mg法莫替丁;奥关拉唑组（15例）：每日口服两次奥美拉唑,每次20mg;法莫替丁组（15例）：每日口服两次法莫替丁,每次20mg。每组的治疗时间均为8周。在内镜指导下观察并比较三组患者的胸痛、反酸和烧心等主要病征的改善情况,综合评价三种治疗方法的临床疗效。结果：联合用药组较其他两组获得的疗效更明显,患者的症状得到较好的改善,差异有统计学意义（P〈0．05）。结论：奥美拉唑联合法莫替丁能够有效地抑制胃酸的分泌,对于反流性食管炎的,临床治疗具有良好的效果。     

Theory in motion

Modeling studies are now a significant part of mainstream research in motor control. Novel and classical modeling techniques used in recent work on small and large motor systems illustrate the different roles that models play in furthering our understanding of motor systems. The models presented reveal single neuron short-term memory, unexpected effects of reciprocal inhibition and methods for decoding activity in large populations of neurons.