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991.
Siemens J Zhou S Piskorowski R Nikai T Lumpkin EA Basbaum AI King D Julius D 《Nature》2006,444(7116):208-212
Bites and stings from venomous creatures can produce pain and inflammation as part of their defensive strategy to ward off predators or competitors. Molecules accounting for lethal effects of venoms have been extensively characterized, but less is known about the mechanisms by which they produce pain. Venoms from spiders, snakes, cone snails or scorpions contain a pharmacopoeia of peptide toxins that block receptor or channel activation as a means of producing shock, paralysis or death. We examined whether these venoms also contain toxins that activate (rather than inhibit) excitatory channels on somatosensory neurons to produce a noxious sensation in mammals. Here we show that venom from a tarantula that is native to the West Indies contains three inhibitor cysteine knot (ICK) peptides that target the capsaicin receptor (TRPV1), an excitatory channel expressed by sensory neurons of the pain pathway. In contrast with the predominant role of ICK toxins as channel inhibitors, these previously unknown 'vanillotoxins' function as TRPV1 agonists, providing new tools for understanding mechanisms of TRP channel gating. Some vanillotoxins also inhibit voltage-gated potassium channels, supporting potential similarities between TRP and voltage-gated channel structures. TRP channels can now be included among the targets of peptide toxins, showing that animals, like plants (for example, chilli peppers), avert predators by activating TRP channels on sensory nerve fibres to elicit pain and inflammation. 相似文献
992.
Saturn's largest satellite, Titan, has a massive nitrogen atmosphere containing up to 5 per cent methane near its surface. Photochemistry in the stratosphere would remove the present-day atmospheric methane in a few tens of millions of years. Before the Cassini-Huygens mission arrived at Saturn, widespread liquid methane or mixed hydrocarbon seas hundreds of metres in thickness were proposed as reservoirs from which methane could be resupplied to the atmosphere over geologic time. Titan fly-by observations and ground-based observations rule out the presence of extensive bodies of liquid hydrocarbons at present, which means that methane must be derived from another source over Titan's history. Here we show that episodic outgassing of methane stored as clathrate hydrates within an icy shell above an ammonia-enriched water ocean is the most likely explanation for Titan's atmospheric methane. The other possible explanations all fail because they cannot explain the absence of surface liquid reservoirs and/or the low dissipative state of the interior. On the basis of our models, we predict that future fly-bys should reveal the existence of both a subsurface water ocean and a rocky core, and should detect more cryovolcanic edifices. 相似文献
993.
The Southern Ocean biogeochemical divide 总被引:1,自引:0,他引:1
Modelling studies have demonstrated that the nutrient and carbon cycles in the Southern Ocean play a central role in setting the air-sea balance of CO(2) and global biological production. Box model studies first pointed out that an increase in nutrient utilization in the high latitudes results in a strong decrease in the atmospheric carbon dioxide partial pressure (pCO2). This early research led to two important ideas: high latitude regions are more important in determining atmospheric pCO2 than low latitudes, despite their much smaller area, and nutrient utilization and atmospheric pCO2 are tightly linked. Subsequent general circulation model simulations show that the Southern Ocean is the most important high latitude region in controlling pre-industrial atmospheric CO(2) because it serves as a lid to a larger volume of the deep ocean. Other studies point out the crucial role of the Southern Ocean in the uptake and storage of anthropogenic carbon dioxide and in controlling global biological production. Here we probe the system to determine whether certain regions of the Southern Ocean are more critical than others for air-sea CO(2) balance and the biological export production, by increasing surface nutrient drawdown in an ocean general circulation model. We demonstrate that atmospheric CO(2) and global biological export production are controlled by different regions of the Southern Ocean. The air-sea balance of carbon dioxide is controlled mainly by the biological pump and circulation in the Antarctic deep-water formation region, whereas global export production is controlled mainly by the biological pump and circulation in the Subantarctic intermediate and mode water formation region. The existence of this biogeochemical divide separating the Antarctic from the Subantarctic suggests that it may be possible for climate change or human intervention to modify one of these without greatly altering the other. 相似文献
994.
无公害工业化生产要求制革企业放弃制革工艺中沿用的传统有害物质,采用新方法生产高质量皮革制品。介绍了中俄科研人员用两种不同的方法(涂布法、浸酶法)和两种不同的脱毛酶制剂进行的生皮脱毛试验。试验证明,用酶制剂脱毛效果良好,完全可以替代传统的硫化碱,同时能够改善制革工艺,削弱碱性物质对皮革表面的侵害,减少制革业对水源污染。 相似文献
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李莹 《辽宁师专学报(自然科学版)》2014,(2):20-22
通过对辽阳职业技术学院生物制药专业2010级、2011级学生顶岗实习情况的调查分析,构建"五化三落实"顶岗实习管理机制,提出顶岗实习是培养高技能人才的重要环节,是充分就业的有效途径. 相似文献
999.
黑杨派新无性系研究——Ⅰ、苗期测定 总被引:10,自引:2,他引:8
<正>从I-69杨 ×小叶杨派间杂交 F_1中和从I-69杨×欧洲黑杨种间杂交 F_1中分别 初选出 19个和11个无性系。前者h~2_h= 86.0211%,h~2_d= 85. 1068%,h~2_v= 76.4196%; GCV_h= 15.8371%, GCV_d=17.5931%,GCV_v= 41.7448%。后者h~2_h= 86.6561%, h~2_d=96.6488%, h~2_v=88.0213%; GCV_h=17.0832%,GCV_d=18.8078%, GCV_v=42.9045%。说明从中选择优良无性系是可能的。 苗高、地径和材积三个性状之间的遗传、表型和环境相关系数都是极显著的,表明三个性状中任何一个性状均可作为优良无性系的选择性状。在前述初选的19个和11个无性系中又分别选择了5个和6个无性系,并估算了它们的遗传增益。 相似文献