Hannah Peters

The duration of the premeiotic DNA synthesis in mouse oocytes

Abstract The duration of the premeiotic DNA synthesis in oocytes of mouse embryos has been determined using a specific DNA precursor (tritiated thymidine) and autoradiography. The duration of the premeiotic S period in mouse oocytes is considerably longer than the S period in mammalian somatic cells, but in good agreement with the duration of the premeiotic S period in primary spermatocytes of the mouse [5]. Three different methods were used. The mean value of the duration of the premeiotic S period was determined by two of the methods to be 10.5 hr and 12 hr respectively. The maximum duration of premeiotic S + G2 was determined by the last method and was found to be 14 hr. G2 seems to be very short, its minimum value being less than half an hour. Some crude estimations of the duration of the early stages of the first meiotic prophase were made. Leptotene lasts from 3 to 6 hr and zygotene from 12 to 40 hr. The minimum duration of pachytene is more than 60 hr.

Effect of Irradiation in Infancy on the Fertility of Female Mice

Studies were made on the effects of a single dose of 20 r of x radiation to mice at different ages during infancy on the reproductive performance in an attempt to establish whether there is a variation in the physiological response of the ovary to radiation given early in life. A marked variation was found. The greatest sensitivity was found at the end of the third week at which time irradiation with 20 r of x rays impairs all reproductive functions markedly and reduces the total reproductive capacity to 1.4% of the normal. (P.C.H.)

FOLLICULAR DEVELOPMENT IN OVARIES OF CHILDREN WITH DOWN'S SYNDROME

ABSTRACT. Ovaries of children with Downs syndrome were examined histologically in order to determine in what way the ovarian development differed from the normal. Twenty‐six specimens obtained at autopsy at various ages between birth and 14½ years were available and compared with ovaries from normal children of similar ages. All ovaries from normal children were characterized by active follicle growth. The ovaries of the children with Downs syndrome, however, showed absence or retardation of follicle growth. Furthermore the number as well as the size of the antral follicles differed from those in the normal ovary. The decrease of the number of small follicles occurs earlier in life in the ovaries of children with Downs syndrome than in the control. The possible relationship between an abnormal ovarian growth pattern and hormonal imbalance is discussed.

The development of mouse ovaries after low-dose irradiation at birth.

SummaryA single dose of 20 r of x-rays given to mice at birth influences the development of their ovaries considerably. The effect becomes evident a few hours after radiation, and the damage can be traced in the infantile and pre-pubertal ovaries and in the organs of young mature animals. The immediate damage seems to be due to the marked radiation sensitivity of oocytes in pachytene, i.e. the pre-stationary stage of meiotic prophase, in which many of the oocytes still are on the day of birth in the ‘Street’ mouse. Oocytes in pachytene disappear quickly after radiation, whereas oocytes already in the stationary phase of meiosis at the time of radiation seem more resistant to immediate damage. Although irradiated animals start to ovulate at about the same age as normal animals and produce morphologically normal ova soon after they reach maturity, histological analysis reveals already marked degeneration and destruction of parts of the ovary at that time.

Unusual incorporation of tritiated thymidine into early diplotene oocytes of mice

Abstract After a single injection of 3HTdR into mice shortly after birth a few labelled oocytes were observed. These were all in early diplotene, a stage of meiotic prophase in which no normal chromosome replication takes place. Several possibilities to explain this phenomenon are discussed including abnormal DNA synthesis during degeneration and DNA repair after some kind of damage or as a step in the process of genetic recombination. The first possibility is considered to be the most likely. The mechanism underlying this DNA synthesis is not known.

Lactation Period in Indian Women: Duration of Amenorrhea and Vaginal and Cervical Cytology

An investigation was undertaken to determine the time of the reappearance of menstruation in lactating women in India and the vaginal and cervical cytology during the lactation period. 272 lactating women seen as patients in a birth control clinic in Bombay made up the study sample. 15% of the women nursing babies 1-4 months old were menstruating as were 33% of those nursing infants between 5-8 months 57% of those nursing babies 9-12 months old 55% of those nursing babies 13-18 months old and 81% of those nursing babies older than 18 months. Only 1/3 of the women menstruated by the end of 8 months and just over 1/2 of them by the time the child was 1 year old. The lactation amenorrhea was longer in Indian women than that reported in women in the U.S. and Europe. Vaginal smears were taken in the postpartum period and compared with smears taken from the exocervix. From the smears it was determined that the cervical mucosa reacts less sensitively to hormone stimulation than the vaginal epithelium. Since the vaginal mucosa is more sensitive to the ovarian hormones than the endometrium and the exocervix is less sensitive than the vagina it would seem that the cervical smear would give a better indication of the functional state of the endometrium in the lactation period.

Ovarian development and fertility of the progeny of mice irradiated before mating.

Bagg mice were irradiated with 300 R x-ray ( F0 mice), and mated immediately afterward. The development of the ovaries and the fertility of their female offspring ( F1) was investigated. The ovaries of the F1 mice showed early signs of aging but the number of oocytes was not altered. The fertility of the F1 mice was different from the normal. The F1 mice produced more young than the control animals. The mortality rate was higher in the F1 mice, many dying with mature embryos in utero, apparently unable to give birth. It is reasoned that the observed changes are probably not due to genetic damage but rather to an altered maternal hormonal milieu initiated by radiation of the F0 animal.

The Fertility of Mice After Androgen Injection in Early Infancy

Androgen treatment during the critical neonatal period in themouse leads to a marked change in the evolution of the reproductive performance. Though ovulation occurs in most animals in the early mature period, 25% of the androgenized mice are sterile. The mice that prove to be fertile do not develop young after the first insemination apparently due to a faulty maternal milieu caused by a temporary incompetence of the endometrium. The total reproduction capacity is reduced by more than half. The fertility span of the androgenized mice is shortened due to the late appearance of first litters and the early onset of secondary sterility. The early failure of the uterus to support developing embryos and thereby initiating the end of reproduction suggests an early aging of the uterus.

FOLLICULAR ATRESIA IN THE INFANT HUMAN OVARY

The pattern of follicular atresia was studied in nine ovaries from children between the ages 3 months and 8 years. Atretic follicles were found among follicles at all stages of development. The percentage of follicles with signs of atresia became larger as the size of the follicles increased. Only 2% of small follicles (Type 3b) showed signs of atresia, while all follicles greater than 1 mm in diameter (Type 8) were atretic. In follicles of Type 5 and larger, four stages of atresia, which represent consecutive stages of a single atretic process, were defined. The beginning of atresia was characterized by the presence of pyknotic granulosa cells. As atresia progressed, the granulosa layer disappeared, the oocyte became necrotic, the follicle collapsed and the theca cells became hypertrophied. The oocyte can degenerate in several ways: it can be penetrated by cells, the nucleus can become pyknotic or it may complete meiotic prophase. It is suggested that the last event is only possible after the oocyte has reached its full size and has completed RNA synthesis.

Intrauterine Gonadal Development**Presented in part at a symposium, “The Hypo-thalamic-Pituitary-Gonadal Axis,” held at the Royal Society of Medicine, February 25 and 26, 1975, London, England.

This review article summarizes the intrauterine gonadal development and differentiation of both male and female human embryos and fetuses. It describes in detail (1) the organization of the indifferent gonad and its seeding by the extra-gonadal germ cells, (2) the development of the duct systems before sex differentiation, and (3) the controlling mechanism of differentiation of the ovaries and testes. Timetable for the development of the human male and female reproductive systems have been compiled from the literature.