Hello everyone,

I am consistently seeing these black specks (see low and higher mag images attached) in unstained sections of fat tissue from Drosophila. Upon referring to the text Hayat (1981), it seems like it has to be OsO4 blacks, especially since it is the only electron-dense thing present. The text refers to some papers that I, unfortunately, do not have access to. It also says to try to fix in the dark to minimize these effects, but I already fix in the dark at 4C overnight.

I only see them in this tissue and am following a pretty routine EM procedure (sodium cacodylate buffer, glut, PFA). I don't see them in images from the literature using the same tissue, but these images are low mag. 

From what I have read so far, it makes sense that they would be present in such a lipid droplet-rich tissue, but any insight would be greatly appreciated. 

Thanks!

-Blanca