The dissociated solution from PMSG antigen-antibody complex by heating were investigated on the biological and immunological activity in vitro. When the dissociated solution of its complex were injected into immature female mice, performance of hemorrhagic follicles and corpora lutea formation reaction, and increase of uterine wet weight were observed. The precipitin reaction of the dissociated solution was positive.

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[in Japanese]

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In the rat and the mouse, it is said that a luteal phase after the post-partum ovulation may persist throughout lactation and the cyclical activity of estrus is not resumed until the litter is weaned.
Long & Evans (1922) reported the estrus of the rat recurs somewhat more tardily when the litter is large (after the litter is weaned).
Crew & Mirskaia(1930) reported that the ovulation during lactation of the albino mouse (the litter size: 48) appeared in a few case during 21 days post-partum.
Greenwald (1958) and Atkinson & Leathem (1946) reported that the estrus and ovulation during lactation of the Swiss albino mouse (the litter size: 6) did not appeared except in a few case during 21 days post-partum.
Authers examined the vaginal smears of lactating IVCS strain mice in the various litter size.
The results obtained are as follows:
1) In the vaginal smear collected during the lactation of the maternal IVCS strain mice (the litter size: the appearance of stage with cornified cells were observed between the 12th and the 16th days post-partum (Table 1).
2) When the litter size were small, the estrous cycles with cornified cells were often observed.during the lactation of the IVCS strain mice (Fig. 1).
3) Spontaneous ovulations of mother during the lactation were confirmed by the observation of ova in tubal ampulla on the days of appearance of the stage with cornified cells in the IVCS strain mice (Fig. 3).
4) On the night of the proestrous stage (the previous day of stage with cornified cells) appeared in some period during lactation, the maternal mice which were mated with normal male became pregnant the same as in the normal mice.
Accordingly, the relationship between lactation and appearance of estrus in IVCS strain mice seems to be evident.
5) Average body weight of the suckling mice in this experiment showed the curve in the standard IVCS strain mice (Fig. 2).
6) The appearance of the stage with cornified cells in some period during lactation were observed not only in the IVCS strain mice but also in C3H strain mice.
But the day of appearance of the one in C3H strain mice was later compared with that in IVCS strain mice.

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The present study was attempted to elucidate the mechanism and the process of zona shedding by rat blastocyst.
The animals were killed between 9:00 and 17:30 hours on day 5 pregnancy (the day on which the spermatozoa were observed in the smear was designed the first day of gestation), A total of 761 blastocysts were recovered: 444 were zona encased, 316 were zona free and 23 were half-way out of the zona shedding including the various case of the process in the zona shedding.
Shedding of the zona pellucida begins early (9:00 A.M.) on the 5 th days of pregnancy. By 14:00 P.M., about sixty percent of blastocysts were zona free and 90 percent of blastocysts recovered were denuded by 17:30.
From the observation morphological changes in the zona before, during and after shedding, it was considered that the blastocyst can escape from its zona pellucida by way of either the embryonic or the abembryonic pole. The mechanisms of the zona shedding was disscussed.

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[in Japanese]

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