Population of follicles and luteal structures during the oestrous cycle of mares detected by three-dimensional internal structure microscopy.

The research article demonstrates the use of a novel imaging method, three-dimensional internal structure microscopy (3D-ISM), for observing the internal structures of a mare’s ovaries over the course of an oestrous cycle. This technique has made it possible to track changes in the numbers and sizes of follicles and luteal structures, and to correlate these data with hormone levels.

Study Methodology

• The researchers used 3D-ISM to observe the internal structures of equine ovaries. This advanced microscopy involves a computer-controlled slicer, a CCD camera, a laser disc recorder and a PC.
• The researchers focused on the follicles and the corpus luteum (CL), the latter being a transitory endocrine structure involved in the reproductive cycle of mares.
• This allowed them to utilise the segmentation technique to reconstruct three-dimensional images, shedding light on the spatial configuration inside the equine ovary.

Findings and Results

• The main discovery in this study was the presence of many small follicles of less than 10 mm in diameter.
• The researchers were also able to differentiate three types of luteal structures: the corpus haemorragicum (CH), which forms from blood elements in the cavity after ovulation, CL, and the corpus albican (CA).
• They found that the presence of CHs and CL correlated with higher concentrations of progesterone (P(4)) (>1 ng/ml), while CHs were also found at lower P(4) concentrations (<1ng/ml).
• However, CAs were discovered regardless of P(4) level.

Conclusion and Implications

• The findings of the study demonstrated that 3D-ISM allows for detailed observation of ovarian internal structures and aids in determining the stage of the ovarian cycle, supplemented by physiological information.
• These insights acquired through 3D-ISM offer fundamental knowledge that can be applied clinically, improving the understanding of the oestrous cycle in mares.