Immunolocalization of zona pellucida antigens in the ovarian follicle of dogs, cats, horses and elephants.

The study focuses on comparing the location of immunoreactive pig egg coat (pZP) proteins using antibodies in the ovaries of dogs, cats, horses, and elephants.

Methodology

• The researchers carried out the study using formalin and glutaraldehyde for light and transmission electron microscopy (TEM) respectively. These chemicals were used to fix ovarian sections of the dog, cat, horse, and elephant under investigation.
• The fixed ovarian sections were then exposed to antibodies which were produced against highly purified pZP. The patterns resulting from the staining were determined with the use of diaminobenzidine (DAB) at the light level.

Results

• The patterns from the dog indicated intense staining around the perimeter of the ZP and the oolemma (membrane surrounding the egg) and slightly less staining throughout the width of the ZP. It was also observed that dog follicles containing more than one egg presented eggs in the same or different developmental stages.
• The cat ovarian sections demonstrated uniform staining of the ZP.
• Olympian findings demonstrated consistent staining of the ZP, ooplasm (cytoplasm of a cell), and granulosa cells (cells lining the follicle).
• The elephant sections demonstrated the staining of the ZP with mass staining at the oolemma, as well as staining of the ooplasm.
• In all the species subjected to study, the staining of ZP wasn’t visible until the differentiation of the granulosa cells. The ovarian tissue showed no staining with the control, normal rabbit serum in each of these cases.

Immunogold Staining and Follicle Characterization

• The distinct patterns of ZP staining were further evaluated using TEM and immunogold staining. This high-resolution analysis showed that the immunogold-linked anti-pZP antibodies stained the ZP in all species.
• Staining of the organelles within the cell cytoplasm suggested that secretion of ZP originates from the egg cell in dogs and cats.
• Lastly, researchers also took measurements of follicles and the ZP which allowed accurate characterization of the follicle stage.

In conclusion, the study suggests that in all four species, the ZP is recognized by anti-pZP antibodies. There is also early evidence to suggest that the origin of ZP proteins could potentially be the egg cells.