2013 年 8 月 19 日 13:28 安迪科格伦 种类： SPALAX ehrenbergi 盲鼹鼠 栖息地：如果你碰巧住在地中海东部，那它们就在你脚下的土壤里，潮湿、黑暗又缺氧的地下坑道里。 中东盲鼹鼠将其 20 年的寿命几乎全都匆匆忙忙间花在了缺氧、黑暗还发霉的地下坑道里。但是关于它还有个问题：在近 50 年对这种啮齿动物的研究里居然都没有发现它们会患上癌症。我们最终也可能会将枪口对准这种辗转腾挪躲避肿瘤的技能。 鼹鼠已经成功进化了两次。皮毛是唯一能区分非洲裸鼹鼠和亚洲盲鼹鼠的特征，但这两种动物居然在啮齿类动物完全不同的进化树分支。 在这两种里，属于一个 bathyergids 家族的非洲鼹鼠可能更特殊些。两个非洲品种 - 裸鼹鼠和达马拉兰鼹鼠 - 它们是世界上唯一两种像白蚁般社会化的哺乳动物在：一个的女王一样的雌性产下所有其他成员。 spalacid 家族的亚洲鼹鼠并不遵循这种不寻常的繁殖行为。但它们却和它们的非洲兄弟共享一个特征：它们从来不会患上癌症。事实上，研究人员刚刚发现，即便把中东盲鼹鼠暴露在一些强力致癌化学物质里，它们也不会患癌。实验把 20 只鼹鼠暴露在强力致癌物长达三年，但是只有一只得了肿瘤。 “我们已经证明，无论鼹鼠是年轻还是年老，它们都几乎不可能患上癌症，”以色列海法大学的亚伦 Aaron AVIVI 说。相比之下，大鼠和小鼠暴露于相同的化学品里短短几个月内就会得上肿瘤。 顽强的免疫力 鼹鼠 顽 强免疫力可能的成因是，他们的细胞和组织中含有某种物质可以保护它们甚至免受最强力致癌化学物质的危害。亚伦和他的同事们正试图找出这些物质，从而用新颖有效的方式去和人类癌症相抗衡 - 他们已经有所斩获。 这个团队把从鼹鼠腋下获得的成纤维细胞与人体肝癌和乳腺癌细胞培养在了一起。成纤维细胞迅速杀死了人体癌细胞。所以成纤维细胞分泌的液体里有可能有某种东西可以抗衡癌症。而当他检查实验时，亚伦发现，成纤维细胞和他们的分泌物并不会损害健康的人体细胞。“它只针对癌细胞，”他说。 相比较而言，实验室正常的大鼠、小鼠和另一种被称为刺鼠的啮齿动物其成纤维细胞和分泌物都无力阻止人类癌症细胞的生长。 好粘 ！ 今年早些时候，纽约罗切斯特大学的一个研究小组发现了在非洲裸鼹鼠的体内发现了一种化学物质，这种化学物质似乎可以保护它们免于受到癌症的危害。维拉 Vera Gorbunova 和她的同事们得出的结论是这种化学物质是一种高分子量透明质酸（ HMM –HA ）——鼹鼠通过分泌这种粘性物质来在密闭蜿蜒的地下隧道里穿行。 当维拉用遗传工程手段来处理裸鼹鼠使其不能再分泌 HMM-HA 以后，他们变得极易患癌，这表明该物质是保护他们的关键。 但是亚伦并不确信， HMM-HA 就可以解释他的中东鼹鼠为什么不得癌症。他说，鼹鼠的成纤维细胞提取物里确实含有粘性物质，但是它似乎并不会在动物的天然抗癌能力里发挥关键作用，在实验室中抵抗癌细胞也并不活跃。 维拉说，可能还有一些其他的机制在共同起作用。中东鼹鼠的细胞会分泌另一种被称为β - 干扰素化学物质，它可以杀死癌细胞。但她仍然相信，保护裸鼹鼠和盲鼹鼠的关键化学物质是 HMM-HA 。 亚伦同时还在继续检查其他能杀死癌细胞的化学物质。“我们未来的工作就是去发现鼹鼠的细胞到底分泌了哪种能杀死癌细胞的物质，“他说。 Zoologger: The rat thatdefies powerful carcinogens · Updated 13:28 19 August2013 by Andy Coghlan · For similar stories, visitthe Zoologger and Cancer Topic Guides Zoologger is our weekly column highlighting extraordinary animals – andoccasionally other organisms – from around the world Species: Spalax ehrenbergi Habitat: Dark, suffocating tunnels in damp soildeep beneath you – if you happen to live in the eastern Mediterranean As anti-cancer regimes go, this one isn't going to get many takers. The Middle East blind mole rat spends almost all of its 20years of life hurrying down dark and fusty tunnels full of oxygen-deprived air.But for reasons unknown, it works: in 50 years of research on the rodents, nonehas ever spontaneously developed cancer. We might finally be zeroing in on anexplanation for their tumour-dodging skills. Mole rats are so successful they've evolved twice. Fur might seem be theonly thing distinguishing the naked mole rats of Africa from theblind mole rats of Asia, but the two animalsactually sit on entirely different branches of the rodent evolutionarytree . Of the two groups, the mole rats of Africa,which belong to a family called the bathyergids , are probably the more peculiar. Two African species – the naked mole ratand the Damaraland mole rat – are the only mammals in the world to have optedfor a termite-like eusocial existence: a single queen gives birth to all other colony members. The Asian mole rats – in the spalacid family – do not go in for this kind of unusual breeding behaviour. But theydo share one thing in common with their African doppelgangers: they neverdevelop cancer. In fact, researchers have just discovered that the Middle East blind mole rat will not develop cancer evenwhen it is exposed to some potent cancer-causing chemicals. After three yearsof exposure to one of two powerful carcinogens, only one of the 20 animalsstudied developed any tumours. We've shown that whether the rats are young or old, it's almostimpossible to induce cancer in them, says Aaron Avivi of the University of Haifain Israel.By contrast, rats and mice exposed to the same chemicals developed tumours in amatter of months. Stubbornimmunity A possible implication of the mole rats' stubborn immunity is that theircells and tissues contain substances that protect them even from some of themost powerful cancer-causing chemicals. Avivi and his colleagues are now tryingto identify such substances, in an effort to find new and potent agents tocombat cancer in people – and they are making progress. The team took fibroblast skin cells from the armpits of the rats and grewthem in culture alongside cancer cells, including two types each of human liverand breast cancers. The fibroblasts rapidly killed the human cancer cells. Sodid fluids secreted by the fibroblasts, suggesting that there's something inthere of great value to combat cancer. And when he checked, Avivi found thatthe fibroblasts and their secretions didn't harm healthy human cells. Itwas only cancer cells, he says. As controls, fibroblasts and secretions from normal lab rats, mice, andanother rodent called the spiny mouse were powerless to stop the human cancercells growing. Globbygoo Earlier this year, a research team from the Universityof Rochester in New York identified a chemical in Africannaked mole rats that seems to protect them against developing cancer. Vera Gorbunova and her colleagues concluded that the chemical is high-molecular-masshyaluronan (HMM-HA) – a sticky, globbygoo that the rats secrete to help them slither through tight tunnelsunderground. When Gorbunova genetically engineered naked mole rats so that they couldnot make HMM-HA, they became vulnerable to cancer, suggesting that thesubstance is a key to protecting them. Avivi isn't convinced that HMM-HA can explain why his Middle East mole rats do not get cancer, though. He says that theextracts from their fibroblasts do contain the sticky substance, but that inspalacids it does not seem to play a key role in the animals' naturalresistance to cancer or activity against cancer cells in the lab. Gorbunova says there are some other possible mechanisms. The Middle East mole rat cells might secrete anotherchemical, called beta interferon, which kills cancerous cells. But she remainsconvinced that the key chemical protecting both naked and blind mole rats isHMM-HA. Avivi, meanwhile, is continuing to check for other cancer-killingchemicals that might be responsible. Our future work is to try to findwhat Spalax cells secrete that only interacts with andkills cancer cells, he says. http://www.newscientist.com/article/dn24055-zoologger-the-rat-that-defies-powerful-carcinogens.html
研究组成果介绍：环境温度影响哺乳啮齿动物对后代的投资策略 （王德华） 哺乳期是小型哺乳动物生活史中能量需求最大的一个时期，在这个时期母体的大部分的能量是以乳汁的形式散失的。因此关于哺乳期母体的最大持续能量需求的生理限制因素及其对繁殖性能的影响备受学术界关注。限制动物的最大持续能量摄入的因素很多，学者们提出了中心限制假说 (central limit hypothesis ，能量摄入受消化系统的能力限制 ) 、外周限制假说 (peripheral limit hypothesis ，能量摄入受动物体内消耗能量的系统的限制如乳腺的泌乳能力、肝脏的解毒能力、肌肉的运动能力等等 ) 等等进行机理性解释。散热能力限制假说 (Heat dissipation limit hypothesis) 是近年解释最大持续能量摄入的一个新学说。这个假说认为动物哺乳期的最大持续能量摄入受到母体加工利用食物和泌乳过程中产生的副产物 热量散失能力的限制。也就是说，恒温动物的体温调节受到产热和散热两个方面的影响， 30C 的环境对于恒温动物已经是过热区 （在热中性区的上限或超过了动物的上临界温度点），泌乳过程本身就要产生热量，消化食物也产生热量，哺乳过程（母体与后代密切接触）自然也会限制热量散失。按照这个学说，受到散热能力限制的母体能量摄入会减少，泌乳量降低，乳汁中的脂肪成分减少，从而导致幼体的体重较小（生长发育受到影响）。这个假说迄今仅在实验小鼠中有了一些证据。我们研究组以栖息于内蒙古草原的布氏田鼠 ( Lasiopodomys brandtii ) 的室内繁殖种群为研究对象，在研究组工作积累的基础上，对高温驯化条件下的哺乳布氏田鼠及其幼体的能量收支特征进行了研究。 为了测定哺乳期布氏田鼠最大持续能量收支的生理限制因素，布氏田鼠在分娩当天被随机分为两组：对照组饲养温度为 21 1 C (n=23) ，处理组为 30 1 C (n=23) 。每日测定母体的食物摄入、窝仔总重；在哺乳的第 14-16 天，用双标记水技术 (doubly labeled water, DLW) 测定动物的每日能量消耗 (daily energy expenditure, DEE) 。我们发现：高温条件下，布氏田鼠母体的体重并没有发生补偿性变化，两组动物（ 30C 与 21C ）之间的体重没有差异。 在整个哺乳期，饲养在环境温度为 30C 条件下 的动物，其能量摄入一直低于 21C 组，在哺乳的第 1-14 天内差异显著。在哺乳高峰期， 30C 组动物的食物摄入比 21C 组每天少 3.3 g ，但两组动物对食物的消化效率则表现出差异。两组动物的平均窝仔数也无差异，分娩时 21C 组为 7.3 0.5 ， 30C 组为 7.8 0.4 ；断乳时 21C 组为 6.8 0.5 ， 30C 组为 7.7 0.5 。 但是，在哺乳的第 14-16 天，用双标水技术测定的田鼠母体的每日能量消耗在 21C 组为 105.7 3.8 kJ/day （千焦耳每天），在 30C 组为每天 75.7 2.5 kJ/day （千焦耳每天），两组动物间差异极显著。动物的泌乳量的计算可以通过母体的可代谢能量摄入 (metabolizable energy intake ， MEI) 与每日能量消耗 (DEE) 的差值来估算。计算得知，在 30C 条件下的动物的泌乳量 比 21C 条件下每天 少 23.38 kJ/day （千焦耳每天）。如果窝仔数小于 7 的时候，窝仔总重在两组动物之间没有差异；但当窝仔数大于 7 （包括等于 7 ）的时候，在哺乳第 1-14 天内窝仔总重在两组动物之间差异显著，如在哺乳第 12 天时， 21C 条件下的 窝仔总重在比 30C 条件下 重 15.5 g 。 这些结果表明：如果窝仔数较大，那么布氏田鼠在哺乳高峰期的持续能量摄入对热量散失能力的限制比较敏感，这可能是一个重要的生理限制因素。当窝仔数较小的时候，布氏田鼠母体对散热能力的限制就不是很敏感，其可持续能量摄入可能受到乳腺的泌乳能力等方面的限制。因此，我们还需要在窝仔数小的物种中对这个假说进行进一步的验证，这样我们才会对这个问题有一个比较全面的认识。 那么这个研究结果还有哪些意义呢？ 我们的结果已经说明了：环境温度不同，哺乳母体的泌乳量是不同的，自然对后代生长发育的影响也是不同的。高温环境下，母体的泌乳量减少，后代生长发育慢；相反，在低温环境中，母体的泌乳量多，后代生长发育快。所以，热带地区的妈妈们，哺乳期的泌乳量要少，孩子受委屈；而温度适宜的地区的妈妈们，哺乳期的泌乳量就多，孩子有奶吃。当然这只是一个启示了，在啮齿动物身上的结果是否适合于人类，还需要相关的研究和调查。如果真有这种影响的的话，全球气候变化（无论变暖还是变冷），对于人类的健康影响是很大的，尤其是对于哺乳的妈妈和孩子们的健康的影响，不能不引起我们的重视。即使对人类没有很大的影响，对大自然中的动物们的影响是不可置疑的。不管气候怎么变化，野生动物（生物）的衣食住行、生儿育女等都会受到重要的影响，这与政治无关。 我们这个结果发表在《实验生物学杂志》上【 Wu SH, Zhang LN, JR Speakman and Wang DH 2009 Limits to sustained energy intake. XI. A test of the heat dissipation limitation hypothesis in lactating Brandts voles ( Lasiopodomys brandtii ). Journal of Experimental Biology 212, 3455-3465.】 （王德华 2010.1.6 ） 英文介绍： Ambient temperature affects maternal investment strategies in lactating Brandts voles The maximum rate of sustained energy intake (SusEI) may limit reproductive effort, thermoregulatory capability and other aspects of an animals energy expenditure. Consequently, factors that limit SusEI are of interest. The heat dissipation limitation hypothesis suggests that maximum SusEI during lactation is limited by the capacity to dissipate body heat generated as a byproduct of processing food and producing milk. In the present study, we tested the heat dissipation limitation hypothesis in lactating Brandts voles ( Lasiopodomys brandtii ). Female voles were mated and pregnant at 21(1) C. A random sample of animals was transferred into a hot room 30(1) C on the day of parturition. The energy intake of lactating voles at 30C was always lower than that at 21C . At peak lactation food intake was 3.3 ? g ? / day lower at 30C than at 21C . There was no significant difference in digestibility. With similar mean litter sizes (7.260.46 pups at 21C and 7.780.39 pups at 30C at the beginning of parturition, 6.830.51 pups at 21C and 7.730.50 pups at 30C at weaning), the milk energy output of mothers, evaluated from the difference between metabolizable energy intake and daily energy expenditure measured by doubly labelled water, at 30C was 23.3 ? kJ ? day1 lower than that at 21C on days 1416 of lactation. As for reproductive performance, there was a difference in the response to the higher temperature between mothers raising large and those raising small litters. For small litters (7) there was no significant change in litter mass, but for large litters ( 7) there was a significant decrease at the higher temperature. On average, in larger litters the pups were 15.5 ? g heavier on day 12 of lactation when raised at 21C . Our data from Brandts voles support the suggestion that SusEI at peak lactation is limited by heat dissipation capacity, particularly for those voles raising large litters. In smaller litters the peripheral limitation hypothesis may be more relevant. The importance of heat dissipation limits in species raising exclusively small litters needs to be investigated.
标签: 啮齿动物
