While a female mammal is still in the womb her eggs are already starting to form. They reach a specific stage, called the germinal vesicle, then all growth stops. Pictured is a mouse germinal vesicle with the genetic material (DNA) stained gold in the centre. Adjacent, in orange, are smaller cells that support the egg’s survival. The sphere in the middle is where the egg’s protein-making machinery is normally manufactured but here it is closed down. Suspended in time, the cell stays like this until puberty when sex hormones kick start protein production and the egg starts to mature. The gold-coloured strings-with-blobs that radiate out from the central sphere are also DNA. These structures are unique to this cell type but no one knows what their role is. Chemicals that disrupt them also cause infertility so researchers hope that studying them will eventually lead to new fertility treatments.
Written by Julie Webb
BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.