芦荟维管束的结构与芦荟素积累的相关性

应用半薄切片、组织化学、荧光显微镜观察和薄层层析 (TLC)相结合的方法研究了中华芦荟 (Aloeve-ra L.var.chinensis)、木立芦荟 (Aloe arborescens)叶和茎内维管束的结构及其与芦荟素积累的关系。结果表明 ,木立芦荟叶内维管束和中华芦荟叶内外轮的维管束中有大型韧皮薄壁细胞 ,而木立芦荟茎和中华芦荟叶中内轮维管束无大型韧皮薄壁细胞。组织化学结果表明 ,用醋酸铅处理过的上述材料 ,大型韧皮薄壁细胞内出现沉淀物 ;在荧光显微镜下经蓝光激发 ,大型韧皮薄壁细胞发出桔黄色荧光 ,都显示出芦荟素反应。薄层层析(TLC)结果证明 ,木立芦荟和中华芦荟叶含有大型韧皮薄壁细胞的维管束都含芦荟素 ,而木立芦荟茎及中华芦荟叶中内轮维管束都不含芦荟素。为此 ,维管束中的大型韧皮薄壁细胞与芦荟素的积累密切相关 ,维管束中是否有大型韧皮薄壁细胞可作为判断是否含有芦荟素的解剖学指标。     

Effects of Acetylcholine, Cytochalasin B and Amiprophosmethyl on Phloem Transport in Radish （Raphanus sativas）

We investigated the role of the ＂sieve tube-companion cell complex＂ lining the tube periphery, particularly the microfilament and microtubule, in assisting the pushing of phloem sap flow. We made a simple phloem transport system with a living radish plant, in which the conducting channel was exposed for local treatment with chemicals that are effective in modulating protoplasmic movement （acetylcholine, （ACh） a neurotransmitter in animals and insects; cytochalasin B, （CB） a specific inhibitor of many cellular responses that are mediated by microfilament systems and amiprophos-methyl, （APM） a specific inhibitor of many cellular responses that are mediated by microtubule systems）. Their effects on phloem transport were estimated by two experimental devices： （i） a comparison of changes in the amount of assimilates in terms of carbohydrates and ^14C-labeled photosynthetic production that is left in the leaf blade of treated plants; and （ii） distribution patterns of ^14C-labeled leaf assimilates in the phloem transport system. The results indicate that CB and APM markedly inhibited the transfer of photosynthetic product from leaf to root via the leaf vein, while ACh enhanced the transfer of photosynthetic product in low concentrations （5.0×10^-4 mol/L） but inhibited it in higher concentrations （2.0×10^-3 mol/L） from leaf to root via the leaf vein. Autoradiograph imaging clearly reveals that ACh treatment is more effective than the control, and both CB and APM treatments effectively inhibit the passage of radioactive assimilates. All of the results support the postulation that the peripheral protoplasm in the sieve tube serves not only as a passive semi-permeable membrane, but is also directly involved in phloem transport.     

新疆罂粟属高山罂粟组分类研究

我国有罂粟属植物12种,新疆有10种,其中6种属于高山罂粟组。对新疆高山罂粟组植物的花葶进行了解剖研究,并用扫描电镜观察了花粉形态,结果表明,花葶中维管束的数量及排列方式在各种间存在着差异,可以作为一个鉴定特征。花粉上的小刺密度在放大12000倍时,在有种间存在着明显差异,可分类提供微观佐证。     

流域生态系统服务簇变化及影响因素——以大清河流域为例

生态系统服务簇是多种生态系统服务的组合,是生态系统多功能性中的主导功能表征。识别生态系统服务簇的空间和功能变化及影响因素,可为基于主导功能实施分区管理策略、统筹土地多功能性,进而为整体提升区域生态系统服务提供参考。本研究以大清河流域为例,选取6种生态系统服务（水资源供给服务、粮食供给服务、水源涵养服务、水质净化服务、土壤保持服务、固碳服务）,在乡镇尺度上探讨了生态系统服务簇的变化特征,研究了影响其变化的主要因素。结果表明：（1）依据主导的生态系统服务类型,大清流域可以分为3个生态系统服务簇,生态调节服务簇（B1）,农产品供给服务簇（B2）和人居环境簇（B3）;（2）2000-2015年,生态调节服务簇的空间格局变幅最大,乡镇变化率为19.6%,而农产品供给服务簇和人居环境簇的空间稳定性较强,变化率小于5.0%;生态系统服务簇类型发生转化的区域主要位于服务簇交界处;（3）尽管服务簇在空间上有变化,但生态调节服务簇、农产品供给服务簇和人居环境簇的生态系统服务呈增长趋势,平均增幅高达8.62%;（4）自然本底条件和生态保护政策是驱动生态调节服务簇变化的主要因素,农产品供给和建设用地面积的变化分别是驱动农产品供给服务簇和人居环境簇时空变化的主要因素。该案例研究结果为管理土地多功能属性、整体提升国土空间功能提供了有效的途径。     

The ER ladder is a unique morphological feature of developing mammalian axons

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γ-Aminobutyric Acid and Benzodiazepine Receptor Changes Induced by Unilateral 6-Hydroxydopamine Lesions of the Medial Forebrain Bundle

Quantitative autoradiography was used to ascertain alterations in [3H]muscimol, [3H]flunitrazepam (FLU), [3H]naloxone, [3H]D-alanine-D-leucine-enkephalin (DADL), and [3H]spiroperidol binding in basal ganglia 1 week, 4 weeks, and 5 months after unilateral 6-hydroxydopamine lesions of the medial forebrain bundle (MFB) in the rat. At 1 and 4 weeks following lesions, [3H]spiroperidol binding increased 33% in striatum. At 5 months, [3H]spiroperidol was only nonsignificantly increased above control. At 1 week, [3H]muscimol binding decreased 39% in ipsilateral globus pallidus (GP), but increased 41% and 11% in entopeduncular nucleus (EPN) and substantia nigra pars reticulata (SNr), respectively. At 4 weeks, [3H]muscimol binding was reduced 19% in striatum and 44% in GP and remained enhanced by 32% in both EPN and SNr. These changes in [3H]muscimol binding persisted at 5 months. [3H]FLU binding was altered in the same direction as [3H]muscimol binding; however, changes were slower in onset and became significant (and remained so) only at 4 weeks after lesions. Decreases in [3H]naloxone and [3H]DADL binding were seen in striatum, GP, EPN, and SNr. Scatchard analyses revealed that only receptor numbers were altered. This study provides biochemical evidence for differential regulation of striatal GABAergic output to GP and EPN/SNr.     

Anatomy of non-uniform leaf photosynthesis

Since 1986, non-uniform photosynthesis over the leaf area that may be attributed to patchy stomatal closure, has been an important issue in stress physiology of photosynthesis. In this review, I first outline the gaseous environment within the intercellular spaces, because this is the most fundamental background of this problem. Then, recent studies approaching non-uniform photosynthesis are reviwed. After examining techniques for the detection of non-uniform photosynthesis or non-uniform stomatal aperture, results of the relevant studies are discussed for respective stress factors, seeking causes and consequences of non-uniform photosynthesis. From these, mechanisms responsible for, and consequences of non-uniform photosynthesis, are considered. The problems which should be challenged are also pointed out.Abbreviations A rate of photosynthetic CO₂ fixation (assimilation rate) - ABA abscisic acid - g conductance for CO₂ or H₂O - p_a partial pressure of CO₂ in the ambient air - p_i partial pressure of CO₂ in the intercellular space - p_i p_i estimated by the conventional gas exchange techniques - q_N non-photochemical quenching - q_p photochemical quenching     

The roles of serine and threonine sidechains in ion channels: a modelling study

The ion channel of the nicotinic acetylcholine receptor (nAChR) is believed to be lined by transmembrane M2 helices. A 4-8-12 sequence motif, comprising serine (S) or threonine (T) residues at positions 4, 8 and 12 of M2, is conserved between different members, anion and cation selective, of the nAChR superfamily. Parallel bundles of 4-8-12 motif-containing helices are considered as simplified models of ion channels. The relationship between S and T sidechain conformations and channelion interactions is explored via evaluation of interaction energies of K⁺ and of Cl^– ions with channel models. Energy calculations are used to determine optimal ₂ (C-C\-O-H) values in the presence of K⁺ or Cl^– ions. 4-8-12 motif-containing bundles may form favourable interactions with either cations or anions, dependent upon the ₂ values adopted. Parallel-helix and tilted-helix bundles are considered, as are heteromeric models designed to mimic the Torpedo nAChR. The main conclusion of the study is that conformational flexibility at ₂ enables both S and T residues to form favourable interactions with anions or cations. Consequently, there is apparently no difference between S and T residues in their interactions with permeant ions, which suggests that the presence of T vs. S residues within the 4-8-12 motif is not a major mechanism whereby anion/cation selectivity may be generated. The implications of these studies with respect to more elaborate models of nAChR and related receptors are considered.Abbreviations nAChR, GluR, NMDA-R, 5HT₃-R, GABA_AR, GlyR nicotinic acetylcholine, glutamate, NMDA, 5HT₃, GABA_A and glycine receptors, respectively - PhTx philanthotoxin - M2 second membrane-spanning helix of receptor-channel subunits     

Right bundle branch block pattern after uncomplicated right ventricular outflow tract pacing in a patient with a left sided superior vena cava and corrected tetralogy of Fallot

Usually an electrocardiogram after right ventricular (RV) pacing should yield left bundle branch block (LBBB) pattern. However, the presence of right bundle branch block (RBBB) pattern after pacemaker implantation should alert the physician to a malposition of lead. We report a case of 18-year-old female who underwent dual chamber pacemaker implantation and had RBBB pattern post implantation. Detailed evaluation revealed an uncomplicated right ventricular outflow tract pacing. The possible causes of this abnormal pattern after an uncomplicated RV pacing are also reviewed.     

Structure,function and evolution of the hemerythrin‐like domain superfamily

Hemerythrin‐like proteins have generally been studied for their ability to reversibly bind oxygen through their binuclear nonheme iron centers. However, in recent years, it has become increasingly evident that some members of the hemerythrin‐like superfamily also participate in many other biological processes. For instance, the binuclear nonheme iron site of YtfE, a hemerythrin‐like protein involved in the repair of iron centers in Escherichia coli, catalyzes the reduction of nitric oxide to nitrous oxide, and the human F‐box/LRR‐repeat protein 5, which contains a hemerythrin‐like domain, is involved in intracellular iron homeostasis. Furthermore, structural data on hemerythrin‐like domains from two proteins of unknown function, PF0695 from Pyrococcus furiosus and NMB1532 from Neisseria meningitidis, show that the cation‐binding sites, typical of hemerythrin, can be absent or be occupied by metal ions other than iron. To systematically investigate this functional and structural diversity of the hemerythrin‐like superfamily, we have collected hemerythrin‐like sequences from a database comprising fully sequenced proteomes and generated a cluster map based on their all‐against‐all pairwise sequence similarity. Our results show that the hemerythrin‐like superfamily comprises a large number of protein families which can be classified into three broad groups on the basis of their cation‐coordinating residues: (a) signal‐transduction and oxygen‐carrier hemerythrins (H‐HxxxE‐HxxxH‐HxxxxD); (b) hemerythrin‐like (H‐HxxxE‐H‐HxxxE); and, (c) metazoan F‐box proteins (H‐HExxE‐H‐HxxxE). Interestingly, all but two hemerythrin‐like families exhibit internal sequence and structural symmetry, suggesting that a duplication event may have led to the origin of the hemerythrin domain.