Friday, 19 September 2014

Reproduction in domestic ruminants

ISBN13: 9781899043637
Every four years there is a conference on reproduction in domestic ruminants. The latest was held this August at Obihiro, which is on Hokkaido, the North Island of Japan. The accompanying book (details here) is a useful collection of reviews covering most aspects of male and female reproductive biology.

The opening chapter Ruminant phylogenetics: a reproductive biological perspective by William J. Silvia is an excellent overview that integrates molecular phylogenetics with morphology including various aspects of placentation.

There are several chapters on placentation including Early placentation and local immune regulation by Kazuhiko Imakawa and colleagues. This deals with transcriptional regulation of IFNT the gene coding for interferon-tau, which is secreted by the trophectoderm at the blastocyst stage and results in maternal regulation of pregnancy. Another topic is syncytins (previous post) in ruminants. In addition, I have contributed a chapter on Evolution of placental structure and function in ruminants.

Previous volumes in this series have appeared under the imprint of the journal Reproduction. Although the current volume conforms to that journal's format, it has been published in book form by Context. As far as I can make out, it is not possible to purchase individual chapters.

Monday, 15 September 2014

Placenta-derived exosomes and the immune response to pregnancy

Placental exosomes at the maternal-fetal interface
Reproduced with permission from Mincheva-Nilsson and Baranov Am J Reprod Immunol 2014
(c) 2014 John Wiley & Sons A/S
Exosomes are tiny vesicles (30-100 nm) released from living cells that facilitate intercellular communication (previous post). Exosomes are assembled by and released from the syncytiotrophoblast of human placenta. They carry molecules that could be of critical importance for suppression of the maternal immune response, which might otherwise cause rejection of the fetal allograft.

A brand new review by Lucia Mincheva-Nilsson and Vladimir Baranov (here) summarizes several mechanisms that might be involved and suggest "the placenta is surrounded by a cloud of exosomes that creates a beneficient and protective mileau for its existence." Among these mechanisms (summarized in the Figure) are reduced NK-cell cytotoxicity (through down regulation of the NKG2D receptor), impaired T-cell signalling, apoptosis of activated lymphocytes and effects mediated by TGF-beta that might include recruitment of regulatory T-cells (previous post).

There is more. The syncytiotrophoblast also releases much larger particles (0.2-2 micrometers) often referred to as STBM (for syncytiotrophoblast-derived microparticles). They are not carefully assembled as are exosomes but resemble a form of cellular debris. Importantly, they are pro-inflammatory with the potential to activate the immune system. Mincheva-Nilsson and Baranov hypothesize that placental exosome production may counterbalance the deleterious effects of STBM. They argue that determination of a normal range for the STBM/exosome ratio should be a research priority as it could lead to development of new diagnostic tools.

Monday, 1 September 2014

The Blakiston line

Thomas Wright Blakiston (1832-91)

Thomas Blakiston spent 23 years in Hakodate, one of the Japanese Treaty Ports opened to foreign trade in 1858. He failed in his original enterprise, to establish a saw mill, but flourished as a merchant. More importantly he made many observations as an ornithologist.

Blakiston was the first to observe that fauna of the northern island of Hokkaido differed from that of Honshu. Thus the Strait of Tsugara formed a zoogeographical barrier of a type similar to the Wallace Line (previous post). It is referred to as the Blakiston Line.

Blakiston's Fish Owl (Bubo blakistoni)
There is a memorial to Thomas Blakiston atop Mount Hakodate. In addition the former British Consulate, now a museum in the historic quarter of Hakodate, commemorates his several contributions. Blakiston's Fish Owl was named in his honour.