Saturday, 20 April 2013

Placentation in the American moles

Eastern American Mole (Scalopus aquaticus) Wikimedia Commons

Harland Mossman was an astute observer. When he reported that the Eastern mole (seen above) had a diffuse epitheliochorial placenta, people took notice. It was 40 years before the evidence was laid out (here) and ever since it has been controversial.

MalassinĂ© and Leiser (here) examined the placenta of the European mole (Talpa europaea) and found it was endotheliochorial. A recent study of a related species (T. occidentalis) (here) arrived at the same result.

So do European and American moles differ in their placentation? A side by side comparison of electron micrographs (found here) opens the possibility that different labels were given to analagous structures.

The Prasad thesis

M.R.N Prasad Wikimedia Commons

Mossman had quite a collection of American mole placentas and entrusted them to a graduate student M.R.N. Prasad. But is clear from Prasad's 1958 thesis and from the annotated versions of an unpublished manuscript that his findings did not support Mossman's interpretation. The story is told in detail elsewhere (here). Prasad was a Fulbright scholar and later had a distinguished career as a reproductive endocrinologist and WHO expert. The Indian National Science Academy has a Professor MRN Prasad Memorial Lecture.

Prasad claimed the initial stages of placentation were invasive with loss of the uterine epithelium. This was at odds with Mossman's theoretical framework. Later in development, however, Prasad found signs of a re-establishment of the uterine epithelium. The placenta of Scalopus started off endotheliochorial (as later described for Talpa) but reverted to epitheliochorial. This interesting interpretation cries for re-examination using more sophisticated methods than were available to Prasad.

No comments:

Post a Comment