Yonsei Med J.  1973 Dec;14(1):63-90.

Volume Changes During the Preimplantation Stages of Mouse Egg Development

• Chung SO

Abstract

The mouse eggs in the various stages, of the development prior to implantation were collected and measurements were made on both the largest and smallest diameters of the vitellus, inner and outer surface of the zona pellucida. The various stages of development used were ovarian oocytes (germinal vesicle stage), ovulated but unfertilized egg, ovulated and fertilized egg, the 2-cell embryo on the second day of pregnancy, 4-8-cell embryo on the third day of pregnancy and morulablastocyst on the fourth day of pregnancy, A further comparative study on unfertilized and fertilized tubal eggs was made, The time of l2 hours after H.C.G. injection was chosen as the starting point from which to follow the collection of eggs every 3 hours for 24 hours. Since the volume gives a better comparison of size than diameter, the volume of the total eggs, intrazonal cavity, perivitelline space and the various were calculated for the various preimplantation stages of mouse egg. The volume of zona pellucida was also calsulated by subtraction of the volume of the inner zonal cavity from the volume of total egg and compared with the zona pellucida thickness. All calculations were made by computor(CEIR Time-sharing Computor). The diameter and volume of the vitellus in the ovarian oocyte is the largest one of any stage during the preimplantation stages of development, while the total volume of the entire egg as determined from the diameter of outer surface of the zona pellucida of the ovarian cocyte is the smallest one of any stage during development. The diameter and total volume of the entire egg increases from the ovarian oocytes to the first day of pregnancy and then gradually decreases until the third day of pregnancy. An increase in these parameters again takes place on the fourth day of pregnancy. The zona pellucida of the tubal ova is thicker than that of the oocyte, with the zona pellucida of the fertilized egg being definitely thinner when compared with unfertilized eggs. This phenomenon of decreased thickness in fertilized egg may be associated with zona reaction. The perivitelline space between the vitellus and zona pellucida thus formed following ovulation occupied approximately 40 percent of the total volume enclosed by the inner surface of the zona pellucida (intrazonal cavity) in the 1-cell tubal ova. Neither the cause of the rapid accumulation of fluid after ovulation which resulted in the production of the perivitelline space nor the actual time of the formation of the perivitelline space are known. Some possible reasons for the formation or origin of the perivitelline space are discussed. The size and shape of the vitellus undergo compartive reduction during preimplantation stages of development. The possible reason for the reduction of vitelline volume are discussed.

MeSH Terms

Animal
Blastocyst
Embryo/cytology*
Embryo Implantation
Embryo and Fetal Development
Female
Fertilization
Mice
Ovulation
Ovum/cytology
Ovum/growth & development
Temperature
Time Factors