Morphological and ultrastructural changes occurring during degeneration ofgoat preantral follicles preserved in vitro

The present work has investigated the morphological and ultrastructural cha nges occurring during degeneration of goat preantral follicles preserved in vitro and showed quantitative data about the distribution of follicular de generation types in the control and after preservation in coconut water sol ution or Braun-Collins solution at different temperatures (4, 20 or 39 degr eesC) and incubation times (4, 12 or 24 h). At the slaughterhouse, the pair of ovaries of each animal was divided into 19 fragments. One ovarian fragm ent was immediately fixed (control: Time 0). The other 18 fragments were ra ndomly distributed in tubes containing 2 ml of coconut water or Braun-Colli ns solution at 4, 20 or 39 degreesC and stored for 4, 12 or 24 h. Normal pr eantral follicles exhibited a healthy oocyte surrounded by one or more well -organized layers of granulosa cells. The ooplasm contained numerous rounde d or elongated mitochondria with continuous mitochondrial membranes. Golgi complexes were rare. Both smooth and rough endoplasmic reticulum were obser ved, either as isolated aggre gations or complex associations with mitochon dria and vesicles. Degenerated preantral follicles in the control tissue e, exhibited pycnotic nuclei of the oocyte, vacuolated ooplasm and normal gran ulosa cells. This kind of degeneration also predominated significantly (P < 0.05) after preservation at 4 degreesC. In contrast, after preservation at 20 or 39 degreesC a significant predominance (P < 0.05) of preantral folli cles showing a retracted oocyte and swollen granulosa cells was observed. T hese follicles showed large irregularity of the oocyte and nuclear outlines . The ooplasm exhibited moderate proliferation of the endoplasmic reticulum and mitochondria showed disappearance of most of the cristae and damage to the mitochondrial membrane. Some follicles had numerous vacuoles in the oo plasm. Granulosa cells were spread and a low density of organelles was obse rved. The alterations in follicular structure progressed with an increase o f tc temperature from 20 to 39 degreesC as well as with an increase of the incubation time from 4 to 12, or 24 h. In conclusion, the present study sho ws for the first time that initial proliferation of the endoplasmic reticul um and damage to mitochondria are the first signs of degeneration in goat p reantral follicles during storage in vitro. (C) 2001 Published by Elsevier Science B.V.