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1.
We isolated several mutants with nucleotide substitutions in alanine tRNA (tRNAAla) that resulted in glutamine tRNA (tRNAGli) acceptor identity in Escherichia coli. These substitutions were in three regions of tRNA structure not previously associated with tRNAGln acceptor identity. Only the phosphate-sugar backbone moieties of these nucleotides interact with the enzyme in the previously determined X-ray crystal structure of the complex between tRNAGln and glutaminyl-tRNA synthetase. We conclude that these sequence-dependent phosphate-sugar backbone interactions contribute to tRNAGln identity, and argue that the interactions help communicate enzyme recognition of the anticodon to the acceptor end of the tRNA and the catalytic center of the enzyme. 相似文献
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Luisa F. Arnedo Francisco D.C. Mendes Karen B. Strier 《American journal of primatology》2010,72(2):122-128
We investigated whether sex differences in spatial dynamics correlate with rates of staccato and neigh vocalizations in northern muriquis (Brachyteles hypoxanthus) at the Reserva Particular do Patrimônio Natural–Feliciano Miguel Abdala, Minas Gerais, Brazil. A total of 2,727 10 min focal subject samples were collected on 32 adult females and 31 adult males between April 2007 and March 2008. Compared with males, females spent a significantly lower proportion of their time in proximity to other group members and gave staccatos at significantly higher rates while feeding, resting, and traveling. Conversely, males emitted neigh vocalizations at significantly higher rates than females when feeding and resting only. Both sexes gave significantly more staccatos when feeding than when they were engaged in other activities, but their respective rates of neighs did not vary across activities. Both females and males emitted staccato vocalizations at significantly higher rates during times of the year when preferred foods were scarce, but no seasonal differences in the rates of neigh vocalizations were observed in either sex. Females and males showed a reduction in the number of neighbors following staccato vocalizations and an increase in the number of neighbors following neigh vocalizations. Our findings of sex differences in the rates of staccato and neigh vocalizations and the effects of these vocalizations on interindividual spacing are consistent with sex differences in spatial dynamics, and confirm the role of vocal communication in mediating spatial associations in this species. Am. J. Primatol. 72:122–128, 2010. © 2009 Wiley‐Liss, Inc. 相似文献
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Fangfang Jiao;Xiaowei Wang;Aiqin Zhang; 《Ecology and evolution》2024,14(4):e11284
In heterostylous plants, short-tongued pollinators are often ineffective/inefficient owing to the limitations imposed by a long corolla tube. However, it is unclear how disassortative pollen transfer is achieved in small flowers. We investigated the pollination pattern and floral morph variation by analyzing heterostylous syndrome, pollinator groups, and pollen deposition after a single visitation in two Limonium myrianthum populations with short-corolla-tubular small flowers. The predominant pollinators in the Hutubi population were pollen-seeking short-tongued syrphids, which can only transfer pollen between high-level sexual organs. In the Xishan population, nectar-seeking short-tongued insects were efficient pollinators with symmetrical disassortative pollen transfer between high- and low-level sexual organs, whereas long-tongued pollinators had a low efficiency between high-level sexual organs due to the low contact probability with the stigma of long-styled flowers (L-morph), which no longer offered the same advantage observed in tubular flowers. Asymmetrical disassortative pollination may cause the female fitness of short-styled (S-morph) individuals in the Hutubi and L-morph individuals in the Xishan population to suffer greater selection pressure and exhibit a higher degree of floral morph variation. Limonium myrianthum exhibits an unusual pollination pattern in which the small flowers with short corolla tubes make it possible for short-tongued insects to become effective pollinators. However, factors such as the position of stigma–anther within the flower, pollinator species and their preference further caused asymmetrical disassortative pollen transfer. Therefore, more factors should be considered when evaluating the effectiveness of short- and long-tongued insects in pollination service. 相似文献
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Spatial learning and memory of laboratory rodents is often assessed via navigational ability in mazes, most popular of which are the water and dry-land (Barnes) mazes. Improved performance over sessions or trials is thought to reflect learning and memory of the escape cage/platform location. Considered less stressful than water mazes, the Barnes maze is a relatively simple design of a circular platform top with several holes equally spaced around the perimeter edge. All but one of the holes are false-bottomed or blind-ending, while one leads to an escape cage. Mildly aversive stimuli (e.g. bright overhead lights) provide motivation to locate the escape cage. Latency to locate the escape cage can be measured during the session; however, additional endpoints typically require video recording. From those video recordings, use of automated tracking software can generate a variety of endpoints that are similar to those produced in water mazes (e.g. distance traveled, velocity/speed, time spent in the correct quadrant, time spent moving/resting, and confirmation of latency). Type of search strategy (i.e. random, serial, or direct) can be categorized as well. Barnes maze construction and testing methodologies can differ for small rodents, such as mice, and large rodents, such as rats. For example, while extra-maze cues are effective for rats, smaller wild rodents may require intra-maze cues with a visual barrier around the maze. Appropriate stimuli must be identified which motivate the rodent to locate the escape cage. Both Barnes and water mazes can be time consuming as 4-7 test trials are typically required to detect improved learning and memory performance (e.g. shorter latencies or path lengths to locate the escape platform or cage) and/or differences between experimental groups. Even so, the Barnes maze is a widely employed behavioral assessment measuring spatial navigational abilities and their potential disruption by genetic, neurobehavioral manipulations, or drug/ toxicant exposure. 相似文献
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Klaus Fichter 《Journal of Industrial Ecology》2002,6(2):25-41
The environmental effects of e‐commerce may be described in terms of first‐, second‐, and third‐order effects. Data for these effects are scarce, partly because research on environmental effects of e‐commerce and e‐business is still in its infancy, although it is evolving very rapidly. Until now, positive environmental consequences of e‐commerce have generally been coincidental. Two crucial questions that must be addressed are (1) How do we improve our understanding and management of the environmental effects of e‐commerce? and (2) Which approaches are best suited to the development of sustainable e‐solutions? Three approaches to developing sustainable e‐commerce solutions are discussed: the extension of environmental performance measurement and management to e‐commerce activities, the use of new cooperative forms of innovation management, and the provision of customer choice. Finally, an outlook on future research demands is presented. The technology itself (information and communication technologies, Internet) does not determine sustainability, but rather its design, use, and regulation does. 相似文献
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生态保护修复是维持和提升生态系统稳定性和可持续性的重要举措。识别生态保护修复优先区并进行有规划的生态保护修复能够达到抑制生态环境退化的目的。以浙江省为研究对象,运用生态系统服务价值计算模型、神经网络自组织映射(SOM)聚类分析法、空间统计、Spearman非参数相关性分析等方法,识别生态系统服务簇,分析生态系统服务簇演化和人类活动强度变化特征,识别生态保护修复优先区,探讨不同生态系统服务价值的权衡/协同关系,提出生态保护修复优先区规划策略。结果表明:(1)2000—2021年浙江省生态系统服务空间分布逐渐趋于均衡,生态系统服务价值总量由7279.73亿元降低至6980.28亿元;(2)2000—2021年浙江省人类活动强度显著增加,呈现由西到东、由南到北的递增趋势;(3)2000—2021年浙江省生态系统服务与人类活动强度变化Moran′s I指数呈现显著负相关性,说明人类活动强度与生态服务价值两者空间上处于相互制约状态;(4)2000—2021年浙江省90县(区)可划分为4类生态系统服务簇,包括:城市中心簇、农业生产簇、核心生态簇和生态保育簇;(5)基于2021年双变量Moran′s I指数聚类结果将研究区划分的5种类型分区作为生态保护修复一级分区,以区域内主导生态系统服务簇作为生态保护修复二级分区划分依据。浙江省生态保护修复优先区划分为4个类型,即面积占比14.83%的生态预防治理区、面积占比19.94%的生态调控建设区、面积占比50.23%的核心生态保护区和面积占比15.00%的生态综合提升区。据此,提出不同类型优先分区实施生态保护修复的规划策略。 相似文献
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SYNOPSIS. The mechanisms of ferritin uptake and digestion differ in bloodstream and culture forms of Trypanosoma brucei. Ferritin enters bloodstream forms from the flagellar pocket by pinocytosis in large spiny-coated vesicles. These vesicles become continuous with straight tubular extensions of a complex, mostly tubular, collecting membrane system where ferritin is concentrated. From the collecting membrane system the tracer enters large digestive vacuoles. Small spiny-coated vesicles, which never contain ferritin, are found in the Golgi region, fusing with the collecting membrane system, and around the flagellar pocket. Acid phosphatase activity is present in some small spiny-coated vesicles which may represent primary lysosomes. This enzymic activity is also found in the flagellar pocket, pinocytotic vesicles, the collecting membrane system, the Golgi (mature face), and digestive vacuoles of bloodstream forms. About 50% of the acid phosphatase activity of blood forms is latent. The remaining nonlatent activity is firmly cell-associated and probably represents activity in the flagellar pocket. The structures involved in ferritin uptake and digestion are larger and more active in the short stumpy than in the long slender bloodstream forms. The short stumpy forms also have more autophagic vacuoles. No pinocytotic large, spiny-coated vesicles or Golgi-derived, small spiny-coated vesicles are seen in culture forms. Ferritin leaves the flagellar pocket of these forms and enters small smooth cisternae located just beneath bulges in the pocket membrane. The tracer then passes through a cisternal collecting membrane network, where it is concentrated, and then into multivesicular bodies. In the culture forms, acid phosphatase activity is localized in the cisternal system, multivesicular bodies, the Golgi (mature face), and small vesicles in the Golgi and cisternal regions. The flagellar pocket has no acid phosphatase activity, and almost all the activity is latent in these forms. The culture forms do not release acid phosphatase into culture medium during 4 days growth. Uptake of ferritin by all forms is almost completely inhibited by low temperature. These differences among the long slender and short stumpy bloodstream forms and culture forms are undoubtedly adaptive and reflect different needs of the parasite in different life cycle stages. 相似文献
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Le Gao Qiuhui Chen Haofan Dong Zhaokun Zhang Tongtong Bao Lixian Wang Fan Yang Xin Wu 《Global Change Biology Bioenergy》2023,15(2):143-153
There is a high level of conservation of tryptophans within the active site architecture of the cellulase family, whereas the function of the four tryptophans in the catalytic domain of Cel7A is unclear. By mutating four tryptophan residues in the catalytic domain of Cel7A from Penicillium piceum (PpCel7A), the binding affinity between PpCel7A and p-nitrophenol-d -cellobioside (pNPC) was reduced as determined by Michaelis–Menten constants, molecular dynamics simulations, and fluorescence spectroscopy. Furthermore, PpCel7A variants showed a reduced level of cellobiohydrolase (CBH) activity against cellulose analogs or natural cellulose. Therefore, it could be concluded four tryptophan residues in Cel7A played a critical role in substrate binding. Mutagenesis results indicated that the W390 stacking interactions at the −2 site played an essential role in facilitating substrate distortion to the −1 site. As soon as the function was altered, the mutation would inevitably affect the catalytic activity against the natural substrate. Interestingly, no clear relationship was found between the CBH activity of PpCel7A variants against pNPC and Avicel. p-Nitrophenol contains many electrophilic groups that may result in overestimation of the binding constant between tryptophan residues and pNPC in comparison with the natural substrate. Consequently, screening improved cellulase using cellulose analogs would divert attention from the target direction for lignocellulose biorefinery. Clarifying mechanism of catalytic diversity on the natural cellulose or cellulose analogs may give better insight into cellulase screening and selecting strategy. 相似文献
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小鼠自主活动实验中的评价指标 总被引:2,自引:2,他引:2
目的为神经精神药物研究中动物自主活动评价提供科学客观、规范灵敏的指标评价体系。方法选用经典的镇静药物力月西、兴奋药咖啡因,以及镇静安神临床疗效肯定的中药远志及人参,研究对小鼠水平自主活动指标,包括周边区、中央区及总区域的运动、静息状态等评价指标的影响。结果总路程、平均速度、运动总时间、周边区运动路程、周边区运动时间与小鼠的兴奋状态成同向变化,静息总时间、周边区静息时间与小鼠的兴奋状态成反向变化。以上7个指标能准确、有效的评价小鼠的行为学改变。结论总路程、平均速度、运动总时间、周边区运动路程、周边区运动时间、静息总时间、周边区静息时间为评价小鼠自主活动客观灵敏的有效指标。 相似文献
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Takashi Yokota Reiji Masuda Nobuaki Arai Hiromichi Mitamura Yasushi Mitsunaga Hiroyuki Takeuchi Tatsuo Tsuzaki 《Hydrobiologia》2007,582(1):109-120
The behavior of wild and hatchery-reared red tilefish Branchiostegus japonicus was analyzed using two different methods: video observation and acoustic telemetry tracking. In the laboratory, digging and
swimming activity of seven wild and five hatchery-reared fish were recorded for 2–4 days in an experimental aquarium and related
to changes in light intensity. The activity of wild individuals increased with light intensity, while hatchery-reared individuals
were active during both day and night. In the field, 18 wild and 9 hatchery-reared fish were released and tracked using an
acoustic telemetry system during the winter and the summer in Maizuru Bay, Kyoto (Japan). Seven wild and three hatchery-reared
fish settled within 2 km of the release point for 21–200 days whilst 11 wild and 6 hatchery-reared fish were detected in the
central part of the bay within 13 days. The settled fish demonstrated a diel pattern of behavior; most of them probably stayed
outside their burrows in the daytime but inside their burrows during the nighttime. During the winter wild fish tended to
stay near the release site for longer periods than the hatchery-reared fish. However, in summer the hatchery-reared fish tended
to remain close to the release site for longer than the wild fish. Based on these two experiments, we suggest that the activity
of wild red tilefish respond to changes in low levels of light intensity (0–0.1 μmol m−2 s−1) at dawn and display a diel behavior. Hatchery-reared fish may differ from wild fish with regard to their behavior, response
to water temperature and light conditions.
Electronic supplementary material Supplementary material is available for this article at and accessible for authorized users 相似文献
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Ruirui Chen Mehmet Senbayram Sergey Blagodatsky Olga Myachina Klaus Dittert Xiangui Lin Evgenia Blagodatskaya Yakov Kuzyakov 《Global Change Biology》2014,20(7):2356-2367
The increasing input of anthropogenically derived nitrogen (N) to ecosystems raises a crucial question: how does available N modify the decomposer community and thus affects the mineralization of soil organic matter (SOM). Moreover, N input modifies the priming effect (PE), that is, the effect of fresh organics on the microbial decomposition of SOM. We studied the interactive effects of C and N on SOM mineralization (by natural 13C labelling adding C4‐sucrose or C4‐maize straw to C3‐soil) in relation to microbial growth kinetics and to the activities of five hydrolytic enzymes. This encompasses the groups of parameters governing two mechanisms of priming effects – microbial N mining and stoichiometric decomposition theories. In sole C treatments, positive PE was accompanied by a decrease in specific microbial growth rates, confirming a greater contribution of K‐strategists to the decomposition of native SOM. Sucrose addition with N significantly accelerated mineralization of native SOM, whereas mineral N added with plant residues accelerated decomposition of plant residues. This supports the microbial mining theory in terms of N limitation. Sucrose addition with N was accompanied by accelerated microbial growth, increased activities of β‐glucosidase and cellobiohydrolase, and decreased activities of xylanase and leucine amino peptidase. This indicated an increased contribution of r‐strategists to the PE and to decomposition of cellulose but the decreased hemicellulolytic and proteolytic activities. Thus, the acceleration of the C cycle was primed by exogenous organic C and was controlled by N. This confirms the stoichiometric decomposition theory. Both K‐ and r‐strategists were beneficial for priming effects, with an increasing contribution of K‐selected species under N limitation. Thus, the priming phenomenon described in ‘microbial N mining’ theory can be ascribed to K‐strategists. In contrast, ‘stoichiometric decomposition’ theory, that is, accelerated OM mineralization due to balanced microbial growth, is explained by domination of r‐strategists. 相似文献
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In mammals, the Golgi complex is structured in the form of a continuous membranous system composed of stacks connected by tubular bridges, the “Golgi ribbon”. At the onset of mitosis, the Golgi complex undergoes a multi-step fragmentation process that is required for its correct partition into the dividing cells. Regulation of Golgi fragmentation and cell cycle progression appear to be precisely coordinated. Here, we review recent studies that are revealing the fundamental mechanisms, the molecular players and the biological significance of the mitotic inheritance of the Golgi complex in mammalian cells. 相似文献
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The α9β1 integrin is a multifunctional receptor that interacts with a variety of ligands including vascular cell adhesion molecule 1, tenascin-C, and osteopontin. A 2.3-kb truncated form of α9 integrin subunit cDNA was identified by searching the Medline database. This splice variant, which we called the short form of α9 integrin (SFα9), encodes a 632-aa isoform lacking transmembrane and cytoplasmic domains, and its authentic expression was verified by PCR and Western blotting. SFα9 is expressed on the cell surface but cannot bind ligand in the absence of the full-length α9 subunit. Over-expression of SFα9 in cells expressing full-length α9 promotes α9-dependent cell adhesion. This promoting effect of SFα9 requires the authentic cytoplasmic domain of the co-expressed full-length α9 subunit. Thus, SFα9 is a novel functional modulator of α9β1 integrin by inside-out signaling. 相似文献
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The particular compositions of the intracellular membrane organelles rely on the proteins and lipids received frequently through membrane trafficking. The delivery of these molecules is driven by the membrane-bound organelles known as transport carriers (TCs). Advanced microscopy approaches have revealed that TC morphology ranges from small vesicles to complex tubular membrane structures. These tubular TCs (TTCs) support effectively both sorting and transport events within the biosynthetic and endocytic pathways, while a coherent picture of the processes that define the formation and further fate of TTCs is still missing. Here, we present an overview of the mechanisms operating during the TTC life cycle, as well as of the emerging role of tubular carriers in different intracellular transport routes. 相似文献
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The identification of proteins aberrantly expressed in malignant B-cells can potentially be used to develop new diagnostic, prognostic or therapeutic targets. Proteomic studies of B-cell malignancies have made significant progress, but further studies are needed to increase our coverage of the B-cell malignant proteome. To achieve this goal we stress the advantages of using sub-cellular fractionation, protein separation, quantitation and affinity purification techniques to identify hitherto unidentified signalling and regulatory proteins. For example, proteomic analysis of B-cell plasma membranes isolated from patients with mantle cell lymphoma (MCL) identified the voltage-gated proton channel (HVCN1,[1]). This protein has now been characterised as a key modulator of B-cell receptor (BCR) signalling and abrogation of HVCN1 function could have a role in the treatment of B-cell malignancies dependent on maintained BCR signalling [2]. Similarly, proteomic studies on cell lysates from prognostic subtypes of CLL, distinguished by the absence (UM-CLL) or presence (M-CLL) of somatic hypermutation of the immunoglobulin heavy chain locus identified nucleophosmin 1 (NMP1) as a potential prognostic marker [3,4]. Thus, targeted proteomic analysis on selected organelles or sub-cellular compartments can identify novel proteins with unexpected localisation or function in malignant B-cells that could be developed for clinical purposes. 相似文献