Changes in the Estrous Cycle and Number of Ovulated and Fertilized Ova in Aging Female IVCS Mice

Abstract

IV CS mice (ddN origin) aged 90 days (control) and 180, 210, 240, 270, 300, 330, 360 and 420 days were used for observation of the length of the estrous cycle, and the numbers of ovulated and fertilized ova. The estrous cycle between the ages of 90 and 330 days presented a regular 4-day pattern.Thereafter, regularity of the cycle declined steadily between the ages of 360 and 420 days. All mice over 420 days old exhibited cessation of cyclicity and ultimately persistent diestrus. The average number of ova ovulated in mice aged between 90 and 240 days was consistent (11.8 to 11.4 ova), whereas a steady decline was observed for mice between 270 days old (10.5 ova) and 360 days old (4.8 ova). Ova were not recovered from oviducts of mice aged about 420 days. The average number of fertilized ova (2-cell stage) in mice between 90 and 210 days old showed no significant change(11.5 to 10. 3), whereas the number began to decrease in mice aged between 240 days (8.7 fertilized ova) and 330 days (2.5 fertilized ova). No fertilized ova were recovered from the oviducts of mice around 360 days old. These findings demonstrate that the decline of reproductive activity is initially observed in the number of fertilized ova, followed by a decline in the number of ovulations and finally by loss of the estrous cycle.

Changes of Estrous Cycles with Aging in Female F344/N Rats

“…2: 8, 11, and 14 M groups). Similar aging changes in the cycle length have been reported in outbred strain of rats, e.g., Long-Evans [11,14] or SD [6], and also in inbred or outbred strains of mice [19,30]. It is therefore considered that the disorder of the cycle length prior to the cycle cessation was the first reproductive aging change common to these laboratory rodents.…”

Effect of electromagnetic field exposure on the reproductive system

“…Undoubtedly, reproduction is under control of the nervous system and endocrine system. In female mice, neuroendocrinological alteration was believed to be a prime cause of loss of fertility with aging [45,46]. In female mice exposed to a 20 kHz saw tooth EMF generated from a TV set or PC for 6 weeks after weaning, the estrous cycle was extended [47].…”

Predictive Models of Life Span in Old Female Mice Based on Immune, Redox, and Behavioral Parameters

“…We used ex-reproductive females, given that it better replicates the most frequent situation in human aging. In addition, in ex-reproductive female mice, the cyclicity of the estrous cycle ceases (maintaining the diestrus phase), and because of that, the hormones do not affect the parameters studied in the present work [24].…”