Relationship between diet and sex of offspring.

描述（由申请人提供）：在哺乳动物中，改变母亲所吃食物的质量或数量是否会使出生后代的性别比例发生偏差，这一点存在相当大的争议。在最初的实验中，我们比较了来自NIH Swiss和CF 1远交系小鼠的幼崽的性别比例，这些小鼠喂食了两种脂肪含量不同的营养全面的饮食。第一种是低总甘油三酯但高碳水化合物（LF，低脂饮食），而第二种提供了60%的热量作为猪油（VHF，非常高的脂肪）。饮食对产仔数和妊娠期长度没有影响，但高脂肪饮食的母亲生下的儿子比女儿多得多，而且男性偏好的婴儿比例惊人，而低脂肪饮食的情况正好相反。性别比偏斜与饮食有关，与母体体重无关。然而，年龄是一个重要的变量。只有成熟的小鼠在第一次怀孕时提供的性别比例因饮食而高度偏斜。第一个目标将是产生关于饮食的性质和时间与性别比例之间关系的信息。其目标是：1）当小鼠在受孕前和妊娠早期仅在有限的时间段内提供饮食时，跟踪幼鼠的性别比; 2）通过测试具有不同遗传背景的几种近交系小鼠来确认观察结果的普遍性，长期目标是分析性别偏向现象的遗传基础; 3）测试增加饮食中n-3不饱和脂肪酸的量是否会影响后代的性别比例，如对人类的建议; 4）确定减少VHF饮食小鼠的热量摄入是否会导致幼崽性别比例的向下调整。第二个目标是确定繁殖雌性动物性别比例的偏斜何时发生，并了解可能的机制。这些实验将显示Y精子在到达VHF小鼠生殖道中的卵母细胞方面是否比X精子具有某些优势，同样，X精子在LF小鼠中是否具有某些优势。我们将测试是否在受精后而不是受精前根据性别选择孕体，如果是这样，选择过程是发生在着床前还是着床后。最后，我们将检查实验饮食是否引起血清激素，血液电解质和代谢物的变化，以及生殖道环境的改变，以这种方式，一种性别的概念可能有一个在子宫内的竞争优势。我们的观察结果可能对控制人类生育力产生重大影响，提供了一种根据喂养方式调整一系列实验室和农场动物后代性别的实用方法，并进一步证明了哺乳动物性别分配过程存在争议，这取决于食物资源的可用性和质量。

DESCRIPTION (provided by applicant): There is considerable controversy whether in mammals altering the quality or quantity of food eaten by the mother can bias the sex ratio of offspring born. In initial experiments we compared the sex ratio of pups from NIH Swiss and CF 1 outbred mice fed two nutritionally complete diets that differed in their content of fat. The first was low in total triglyceride but high in carbohydrate (LF, low fat diet), while the second provided 60% of the calories as lard (VHF, very high fat). The diets had no effect on either litter size or gestation length, but mothers on high fat produced many more sons than daughters and a striking proportion of male-biased litters, while the reverse was true on the low fat diet. The sex ratio skewing correlated with diet and was independent of maternal weight. Age was an important variable, however. Only mature mice provided sex ratios that were highly skewed by diet at first pregnancy. The first goal will be to generate information on the relationship between the nature and timing of the diet and sex ratio. The aims will be to; 1) follow sex ratios of pups when mice are provided the diets only for a limited period during the period preceding conception and during early pregnancy; 2) confirm the generality of the observations by testing several inbred strains of mouse with different genetic backgrounds with the long term goal of analyzing the genetic basis of the sex biasing phenomenon; 3) test whether increasing the amount of n-3 unsaturated fatty acids in the diet influences sex ratio of offspring, as has been suggested for humans; 4) determine whether reducing the caloric intake of mice on the VHF diet causes a downwards readjustment of the sex ratio of pups. A second goal will be to determine when the skewing in sex ratios in bred females occurs and to understand what mechanisms might be responsible. The experiments will show whether Y-sperm have some advantage over X-sperm in either reaching or fertilizing oocytes in the reproductive tract of VHF mice, and, likewise, whether X-sperm have some advantage in LF mice. We shall test whether conceptuses are selected according to sex after fertilization rather than before, and, if so, whether the selection process occurs prior to or subsequent to implantation. Finally, we shall examine whether the experimental diets cause changes in serum hormones, blood electrolytes and metabolites, and alterations in the reproductive tract environment in such a manner that conceptuses of one sex might have an in utero competitive advantage over the other. Our observations could have major implications for control of human fertility, provide a practical way of adjusting the sex of progeny for a range of laboratory and farm animals according to how they are fed, and lend further credence for the controversial existence of a process of sex allocation in mammals that depends on the availability and quality of food resources.