3. Results
The ratio of normal to atretic follicles was significantly reduced at 6 h after irradiation. In the sham-irradiated control ovaries, the primordial follicles might be
degenerated by the gradual, somewhat long-lasting, procedure. In the irradiated ones, however, it happened acutely. Since the degenerating patterns of ovarian primordial,
follicles were diverse in the control mouse, various types of primordial follicles were observed. The normal primordial follicles with two or three flattened granulosa cells
possessed round ooplasmic membrane, clear germinal vesicle, and one or more nucleoli as shown in Fig. 1. Mitochondria were randomly distributed throughout the ooplasm
Ž
. Fig. 1 .
At 6 h after irradiation, the degenerated primordial follicles were considerably increased. Germinal vesicles disappeared, and lipid droplets increased. No more ooplas-
mic membrane was observable. Granulosa cells became round in their shape, and apoptotic cells started to appear. Dark-stained germinal vesicles and apoptotic granulosa
cells were also seen. The ratio of normal to atretic follicles in control group was 62.5. This ratio decreased with time after the irradiation. The ratio was 51.6, 49.0, 11.1 and
Ž .
7.1 at 0, 3, 6 and 12 h, respectively Fig. 2 . The degenerating primordial follicles had Ž .
one of the following characteristics: 1 relatively normal oocyte with apoptotic granu- Ž .
Ž . losa cells, 2 degenerating oocyte with intact granulosa cells, and 3 apoptotic or
pyknotic oocyte and granulosa cells. The primary follicle with a degenerating oocyte was observed. Follicles with apop-
totic or pyknotic granulosa cells and with a relatively intact oocyte increased, similarly Ž
. with those in primordial follicles Fig. 2 . The ratio of normal to atretic follicles in the
Fig. 2. Changes in the ratio of normal to atretic primordial and primary follicles in the control and irradiated mouse ovaries. The irradiation time in the present experiment was 2 h. Time 0 means the end of the
irradiation. The number of mice in each experimental group was five. The ratio decreased steeply at 6 h after irradiation, and decreased further at 12 h after irradiation. Data were expressed as meanSEM. a: significantly
Ž .
different from that of group ‘y2 h’ p- 0.01 .
control mouse ovary was 81.3. This ratio decreased down to 80.0, 75.0, 45.5 and 33.3 at 0, 3, 6 and 12 h after irradiation, respectively.
4. Discussion
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