Assessment of double ovulation to halve Xenopus laevis use for eggs

非洲爪趾蛙，非洲爪蛙，因其卵而被许多实验室使用。与许多其他物种的卵不同，青蛙卵(产卵)在普通池塘水中大量产卵，并在另一种卵之外发育。这使它们成为观察胚胎发育和进行实验的理想选择，例如测试组织移植的后果或注入少量DNA(遗传物质)以找出基因如何在活的有机体中发挥作用。非洲爪蛙特别有用，因为它们通常生活在水中，因此全年都可以很容易地饲养在充满水的水箱中。为了让它们产卵(排卵)，研究人员给雌性黑猩猩注射了一种激素。如果在晚上注射，这些青蛙第二天就会把蛋下到水箱里。(这曾被用作临床上的怀孕测试，因为孕妇的尿液中荷尔蒙会升高。)目前，实验室使用非洲爪蛙排卵，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，产卵量只会逐渐下降。这可能反映了青蛙在野外繁殖，那里的青蛙繁殖(雨季)有限。我们已经进行了一些初步实验，以表明每次排卵两次，间隔一周(“双排”)，并在此之前休息三个月，每次排卵产生的数量相似，并不明显少于单次排卵。在这个项目中，我们将测试这种双排卵方案，看看产量数字是否得到可靠的维持。重要的是，为了确保这一过程不会立即或随着时间的推移给动物带来额外的压力，我们将通过跟踪鸡蛋数量和质量(众所周知，生病或其他压力下的动物都会恶化)来评估压力水平，并测量动物在压力条件下释放的应激激素(皮质酮)的水平。如果这些措施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，它们将使实验室使用的动物数量是现在的一半。在全球范围内，Xenopus用户拥有一个强大的社区，新方法被迅速分享。采用双排卵没有任何障碍，我们计划通过Xenbase网站、英国和美国的国家库存中心、培训课程以及在期刊和会议上发布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.