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

Abstract

The present work has investigated the morphological and ultrastructural changes occurring during degeneration of goat preantral follicles preserved in vitro and showed quantitative data about the distribution of follicular degeneration types in the control and after preservation in coconut water solution or Braun-Collins solution at different temperatures (4, 20 or 39°C) 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 fragment was immediately fixed (control: Time 0). The other 18 fragments were randomly distributed in tubes containing 2 ml of coconut water or Braun-Collins solution at 4, 20 or 39°C and stored for 4, 12 or 24 h. Normal preantral follicles exhibited a healthy oocyte surrounded by one or more well-organized layers of granulosa cells. The ooplasm contained numerous rounded or elongated mitochondria with continuous mitochondrial membranes. Golgi complexes were rare. Both smooth and rough endoplasmic reticulum were observed, either as isolated aggregations or complex associations with mitochondria and vesicles. Degenerated preantral follicles in the control tissue exhibited pycnotic nuclei of the oocyte, vacuolated ooplasm and normal granulosa cells. This kind of degeneration also predominated significantly (P<0.05) after preservation at 4°C. In contrast, after preservation at 20 or 39°C a significant predominance (P<0.05) of preantral follicles showing a retracted oocyte and swollen granulosa cells was observed. These 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 ooplasm. Granulosa cells were spread and a low density of organelles was observed. The alterations in follicular structure progressed with an increase of temperature from 20 to 39°C as well as with an increase of the incubation time from 4 to 12, or 24 h. In conclusion, the present study shows for the first time that initial proliferation of the endoplasmic reticulum and damage to mitochondria are the first signs of degeneration in goat preantral follicles during storage in vitro.

Short-term preservation of canine preantral follicles: Effects of temperature, medium and time

“…Silva et al (2001) observed that the damage to mitochondria is one of the first signs of degeneration in goat preantral follicles during storage in vitro. Ischemia impairs cellular energetic metabolism which decreases the activity of the Na+/K+-ATPase pump with a gain in sodium (Bonz et al, 1998).…”

Degeneration rate of preantral follicles in the ovaries of goats

“…These vacuoles represent endoplasmic reticulum swelling (Hay et al, 1976), or altered mitochondria (Fuku et al, 1995). Silva et al (2001) reported that mitochondria exhibiting extensive swelling and disappearance of most of cristae as well as endoplasmic reticulum enlarged in volume are the first sign of degeneration in preantral follicles. The low density of granulosa cells recorded in Type 2 degenerated follicles may be due to their enlarged volume.…”

“…After fixation, specimens were rinsed in the buffer and post-fixed in 1% osmium tetroxide, 0.8% potassium ferricyanide and 5 mM CaCl2 in a 0.1 M sodium cacodylate buffer (Silva et al, 2001). Subsequently, the samples were dehydrated in acetone and embedded in Spurr's epoxy resin.…”

Degeneration rate of goat primordial follicles maintained in TCM 199 or PBS at different temperatures and incubation times

“…According DRIANCOURT & THUEL (1998) the oocyte is the first cell within the follicle to be affected by atresia, and whether oocyte atresia is related to oocyte defects or to an improper dialogue between the oocyte and its surrounding granulosa cells remains unclear. In addition, we show in previous study that the oocyte of goat preantral follicles were more sensitive to degeneration than granulosa cells (SILVA et al, 2001). In contrast, in both solutions after preservation at 39 o C for 12h and 24h, there were significantly higher percentage of primordial follicles with degenerated oocyte and granulosa cells, i.e., Type 2 degeneration.…”