Cellular and nuclear volume of primitive red blood cells in digynic and diandric triploid and control diploid mouse embryos.

ABSTRACT

It has long been known that a relationship exists between ploidy and cellular and nuclear volume. This has been observed in amphibia and plants, and more recently in postimplantation tetraploid mouse embryos. We wished to establish whether a similar relationship exists in digynic and diandric triploid mouse embryos, as well as establishing whether the cellular or nuclear volume of primitive nucleated red blood cells of these two classes of triploids were the same. Spontaneously occurring digynic triploid embryos isolated from LT/Sv strain female mice result from the fertilisation of primary oocytes. These embryos develop to the forelimb-bud stage but invariably possess neural tube and cardiac abnormalities. Diandric triploid embryos were also analysed, and were produced experimentally by standard micromanipulatory techniques. They have a relatively normal morphology, and can survive up to the forelimb--bud stage. Primitive red blood cellular and nuclear volume was analysed in serially sectioned digynic and diandric triploid and in developmentally matched diploid control embryos isolated both as littermates of triploid embryos from LT/Sv strain mice, and from other genetically dissimilar diploid controls. The triploid and diploid embryos were analysed between 8-8.5 and 10-10.5 days of gestation, respectively. The cellular and nuclear volumes of the primitive red blood cells in the digynic and diandric triploid embryos were not significantly different, though they were significantly greater than comparable measurements for diploid embryos. We have therefore confirmed that a predictable relationship exists between cellular and nuclear volume and ploidy in the material analysed. The red blood cellular volume in triploid and diploid embryos increased in a predictable way over time, while their nuclear volume decreased in a predictable way over the same time period. A similar relationship has previously been observed when the nucleated red blood cells of diploid and tetraploid embryos were analysed morphometrically.