Sunday, 30 March 2014

Anna-Riitta Fuchs

Anna-Riitta Fuchs (1926-2014)
Anna-Riitta Fuchs was a reproductive endocrinologist whose great interest was the control of parturition. Much of her work centred on the posterior pituitary hormone oxytocin and its receptors in the myometrium.

I first met Anna-Riitta and her husband Fritz at their laboratory in Copenhagen shortly before they relocated to New York. I was a very green graduate student back then but was received with great warmth as they patiently explained their work on parturition in the rabbit. Those were heady times when a great debate was raging about the most important determinant of birth: was it oxytocin release or the withdrawal of progesterone from the placenta?

Anna-Riitta's many achievements include a D.Sc. from the University of Copenhagen and the Carl G. Hartman Award from the Society for the Study of Reproduction. Anna-Riitta was born 1926 in Helsinki and died last week in New York. A full obituary can be found here.

Friday, 21 March 2014

Endogenous retroviruses expressed by ovine trophoblast

Urial Sheep (Ovis vignei)
Wikimedia Commons
Jaagsiekte sheep retrovirus (JSRV) is a nasty pathogen causing lung tumours in sheep. No fewer than 27 JSRV-related endogenous retroviruses (enJSRVs) occur in domestic breeds. Gene capture is an ongoing process and the distribution of enJSRVs has been exploited to test hypotheses about the domestication of sheep (here). For example, the most common variant (enJSRV-18) is absent in ancestral breeds such as the Urial (above) and Mouflon. Although found in goats, enJSRVs are not present in cattle so are much younger than a syncytin recently described by Cornelis et al. for ruminants (here).

Five enJSRVs are capable of transcription and like syncytins (previous post) they have an env gene. Are they then "nascent syncytins" as suggested by Cornelis et al., or do they already subserve a function in the ovine placenta?

A period of blastocyst elongation precedes implantation in sheep and binucleated trophoblast cells first appear then. enJSRV mRNAs are detectable at this stage and later are expressed in binucleate trophoblast cells as well as in the syncytial plaques formed by fusion of those cells with uterine epithelial cells (reviewed here).

Moreover, when antisense oligonucleotides were used to block enJSRV protein production, differentiation of binucleate cells was inhibited (here). The more i read about endogenous retroviruses the more intrigued I become.

Thursday, 6 March 2014

Blood supply to brain and placenta in the capybara

Capybara (Hydrochoeris hydrochaeris)
Wikimedia Commons
The current issue of Science (here) draws attention to recent work on the blood supply to the brain in capybaras. As in other mammals young capybaras have a dual supply from the internal carotid arteries and the basilar artery. At one year of age, however, remodelling of the internal carotid shuts down that source and the basilar artery becomes the sole source of blood to the brain. Research on the underlying mechanisms is being conducted at the Department of Surgery at the Veterinary School in Sao Paulo (here).

The Department is also home to a vibrant research group led by Angelica Miglino with whom it has been my privilege to collaborate on the blood supply to the capybara placenta (here and here).

Placentation in the capybara from Kanashiro et al.
Reprod Biol Endocrinol 2009 (here)
Like other hystricognath rodents, capybaras have a discoid, labyrinthine, haemochorial placenta with an inverted yolk sac that persists to term. An additional feature shared with other hystricognaths is the subplacenta (sub in panel D above). With Claudia Kanashiro we published a detailed study of this structure in the capybara (here). 

It is encouraging to see Science advocate the capybara as a model for stroke. In view of its size - at around 65 kg it is the largest living rodent - it might be useful as a model for fetal physiology. As shown in a previous post on the guinea pig, hystricognaths have precocial young and are in this respect more satisfactory models for gestation than mice and their kin. 

Wednesday, 5 March 2014

Ten thousand birds

Birkhead, Wimpenny and Montgomerie
Princeton University Press 2014 ISBN 978-0-691-15197-7
Because a bird has no placenta, Eggs is how this world they enter (Simon Drew). Yet it would be remiss of me not to mention this lucidly written and lavishly illustrated narrative of the history and philosophy of ornithology.

The opening chapter, "Yesterday's Birds," is a fascinating account of the progression of ideas on the origin of birds, including the influence of the Danish artist and self taught palaeontologist Gerhard Heilmann, who surmised birds evolved from thecodonts (Pseudosuchia). The alternative view of birds as dinosaurs (BAD), promoted in the 1970's, was slow to take hold. A related story concerns the origin of feathers, which were long thought to be highly modified scales but now are seen as a novel evolutionary development. The chapter brings us up to date with feathered but flightless dinosaurs, including superb fossils from China, the colours of fossil feathers and the different type of keratin that distinguish scales from feathers.

One word of caution: despite the title this is not an overview of the various families of birds although it does contain many paintings and photographs to delight the eye of the amateur ornithologist (a group not recognized by the authors to whom ornithologists are scientists and the rest mere bird watchers).