Circadian regulation of reproduction: From gamete to offspring

P01326625; Grants: GNT0519315Few challenges are more critical to the survival of a species than reproduction. To ensure reproductive success, myriad aspects of physiology and behaviour need to be tightly orchestrated within the animal, as well as timed appropriately with the external environment. This is accomplished through an endogenous circadian timing system generated at the cellular level through a series of interlocked transcription/translation feedback loops, leading to the overt expression of circadian rhythms. These expression patterns are found throughout the body, and are intimately interwoven with both the timing and function of the reproductive process. In this review we highlight the many aspects of reproductive physiology in which circadian rhythms are known to play a role, including regulation of the estrus cycle, the LH surge and ovulation, the production and maturation of sperm and the timing of insemination and fertilisation. We will also describe roles for circadian rhythms in support of the preimplantation embryo in the oviduct, implantation/placentation, as well as the control of parturition and early postnatal life. There are several key differences in physiology between humans and the model systems used for the study of circadian disruption, and these challenges to interpretation will be discussed as part of this review.M.J. Boden, T.J. Varcoe, D.J. Kennawa

Dimer models from mirror symmetry and quivering amoebae

Dimer models are 2-dimensional combinatorial systems that have been shown to encode the gauge groups, matter content and tree-level superpotential of the world-volume quiver gauge theories obtained by placing D3-branes at the tip of a singular toric Calabi-Yau cone. In particular the dimer graph is dual to the quiver graph. However, the string theoretic explanation of this was unclear. In this paper we use mirror symmetry to shed light on this: the dimer models live on a T^2 subspace of the T^3 fiber that is involved in mirror symmetry and is wrapped by D6-branes. These D6-branes are mirror to the D3-branes at the singular point, and geometrically encode the same quiver theory on their world-volume

Are the proposed benefits of melatonin-rich foods too hard to swallow?

Published online: 15 May 2015Melatonin has been proposed as a potent anti-oxidant and its presence in many plants and foods has been suggested to be beneficial for health. Indeed, the concentrations of melatonin in blood, and the melatonin metabolite 6 sulphatoxymelatonin in urine, have been found to increase significantly after ingestion of melatonin rich foods. In this review the studies have been critically evaluated in light of the reported plant melatonin concentrations and our knowledge of pharmacokinetics of orally administered pure melatonin. In the case of studies involving measurement of plasma melatonin following ingestion of beer or fruits the reported increases in melatonin are not consistent with the amount of melatonin ingested. Similarly the amount of melatonin metabolite excreted following ingestion of melatonin rich foods greatly exceed the amount ingested. It is concluded that studies reporting the appearance of melatonin in blood and its metabolites in urine following ingestion of melatonin rich foods are flawed. While there may be health benefits for certain foods it is difficult to accept that they are due to their low melatonin content.David J Kennawa