Histochemical localization of glycogen in preimplantation and implantation stages of young and senescent golden hamsters

Summary. Eggs obtained from young and senescent golden hamsters at \m=1/2\to 3\m=1/2\days of pregnancy were tested for glycogen using the PAS technique. The staining intensity was greatest in one-cell embryos, and decreased with subsequent cellular divisions up to the late blastocyst stage. Zygotes examined from senescent animals after 2 days ofpregnancy consistently exhibited a developmental stage approximately 12 hr earlier than embryos obtained from younger animals. Microphotometric measurements of PAS-stained blastocysts at comparable stages from young and senescent animals revealed no statistical difference in glycogen content. Embryos from young and senescent hamsters embedded in situ in glycol methacrylate were examined for glycogen using the PAS tech-nique at 3\m=1/2\to 5\m=1/2\days of pregnancy. Glycogen in most older animals from 4 to 5 days of pregnancy paralleled that found in younger animals 12 hr earlier. At 5\m=1/2\days, glycogen deposits surrounding implantations in senescent uteri were less than those found in younger uteri at 5 days of pregnancy. A few implantations from senescent females at this stage of pregnancy were completely devoid ofglycogen, except for deposits in the myometrium. The smaller quantities of stored uterine glycogen and a reduced uterine circulation may be responsible for the increased fetal resorptions noted in senescent hamsters at later stages of gestation