Assessment of double ovulation to halve Xenopus laevis use for eggs

非洲爪趾蛙（Xenopus laevis）因其卵而被用于许多实验室。与许多其他物种的卵不同，青蛙的卵（卵）是大量产卵的，并且在普通的池塘水里在其他卵的外面发育。这使得它们成为观察胚胎发育和做实验的理想选择，比如测试组织移植的结果，或者注射少量的DNA（遗传物质）来发现基因在生物体中是如何工作的。爪蟾特别有用，因为它们通常生活在水中，所以可以全年轻松地放在装满水的水箱里。为了让它们产卵（排卵），研究人员给雌性注射了一种激素。如果在晚上注射，青蛙第二天就会在水箱里产卵。（这曾经被临床用作妊娠试验，因为这种激素在孕妇的尿液中会升高。）目前，实验室使用爪蟾让青蛙排卵，然后让它们休息三个月（“单次排卵”）。然而，尽管不是常规的，但实验表明，一只青蛙可以在几周内每周排卵，卵子的数量只是逐渐下降。这可能反映了青蛙在野外繁殖的情况，那里的青蛙繁殖有限（雨季）。我们进行了一些试点实验，表明女性两次排卵，间隔一周（“两次排卵”），在重复之前休息三个月，每次排卵产生的数字与单次排卵相似，并不明显少于单次排卵。在这个项目中，我们将测试这种双重排卵制度，看看产量是否能可靠地维持。重要的是，为了确保这个过程不会对动物造成额外的压力，无论是立即还是随着时间的推移，我们将通过跟踪鸡蛋的数量和质量来评估压力水平（众所周知，对于生病或受到其他压力的动物来说，鸡蛋的数量和质量都会恶化），并测量动物在压力条件下释放的压力激素（皮质酮）的水平。如果这些测量结果表明，鸡蛋产量保持不变，而对动物的压力或伤害很少或没有增加，他们将允许实验室使用比现在少一半的动物。在世界范围内，Xenopus用户有一个强大的社区，新的方法被迅速分享。采用双排卵没有障碍，我们计划通过Xenbase网站、英国和美国国家库存中心的成熟渠道、培训课程以及在期刊和会议上发表我们的数据和方法来传播我们的结果。

The African claw-toed frog, Xenopus laevis, is used in many laboratories because of its eggs. Unlike the eggs of many other species, frog eggs (spawn) are laid in large numbers and develop outside the other in ordinary pond water. This makes them ideal for observing embryonic development and doing experiments such as testing the consequences of a tissue graft or injecting small amounts of DNA (genetic material) to find out how genes work in a living organism. Xenopus frogs are particularly useful because they normally live in water and so can be kept easily in water-filled tanks all year round. To get them to lay eggs (ovulate) researchers inject the females with a hormone. If injected in the evening, the frogs lay eggs into the tank the following day. (This used to be used clinically as a pregnancy test since the hormone is elevated in a pregnant woman's urine.) Currently, labs using Xenopus ovulate frogs and then rest them for three months ("single ovulation"). However, although not routine, experiments have shown that a frog can be ovulated weekly over several weeks with only gradual decline in the number of eggs produced. This may reflect breeding in the wild where frogs have a limited breeding (rainy) season. We have conducted some pilot experiments to show that ovulating females two times, a week apart ("double ovulation") with three month's rest before this is repeated, yields similar numbers per ovulation that are not obviously less than single ovulation. In this project we will test this double ovulation regime to see if yield numbers are reliably maintained. Importantly, to ensure that the procedure does not cause additional stress to the animals, either immediately or over time, we will assess stress levels by tracking egg numbers and quality (which are both known to deteriorate for sick or otherwise stressed animals) and measure levels of a stress-hormone (corticosterone) that is released by the animals under stressful conditions. If these measures show that egg yields hold up with little or no increase in stress or harm to the animals, they will allow labs to use half as many animals as they do now. Worldwide, Xenopus users have a strong community and new methods are rapidly shared. There are no barriers to take-up of double ovulation, and we plan to disseminate our results using proven channels of the Xenbase website, national Stock Centres in the UK and USA and through training courses, as well as publication of our data and methods in journals and conferences.