Effect of Exercise on Photoperiod-Regulated Hypothalamic Gene Expression and Peripheral Hormones in the Seasonal Dwarf Hamster Phodopus sungorus

Acknowledgments: Many thanks to Dana Wilson, Susan Hay, David Brown and Vivienne Buchan at RINH, Siegrid Hilken and Esther Lipokatic-Takacs at UVMH for the excellent technical support and advice provided. Many thanks are due to Claus Mayer of Biomathematics, Statistics Scotland for assistance with the statistical analysis of data. Author Contributions: Conceived and designed the experiments: IP SS FS PB. Performed the experiments: IP RD FS. Analyzed the data: IP RD FS SS PB. Wrote the paper: PB SS FS IP.Peer reviewedPublisher PD

Enhancing Purity of Single Photons in Parametric Down-Conversion through Simultaneous Pump Beam and Crystal Domain Engineering

Spontaneous parametric down-conversion (SPDC) has shown great promise in the generation of pure and indistinguishable single photons. Photon pairs produced in bulk crystals are highly correlated in terms of transverse space and frequency. These correlations limit the indistinguishability of photons and result in inefficient photon sources. Domain-engineered crystals with a Gaussian nonlinear response have been explored to minimize spectral correlations. Here, we study the impact of such domain engineering on spatial correlations of generated photons. We show that crystals with a Gaussian nonlinear response reduce the spatial correlations between photons. However, the Gaussian nonlinear response is not sufficient to fully eliminate the spatial correlations. Therefore, the development of a comprehensive method to minimize these correlations remains an open challenge. Our solution to this problem involves simultaneous engineering of the pump beam and crystal. We achieve purity of single-photon state up to 99 \% without any spatial filtering. Our findings provide valuable insights into the spatial waveform generated in structured SPDC crystals, with implications for applications such as Boson Sampling

Generalized description of the spatio-temporal biphoton State in spontaneous parametric down-conversion

Spontaneous parametric down-conversion (SPDC) is a widely used source for photonic entanglement. Years of focused research have led to a solid understanding of the process, but a cohesive analytical description of the paraxial biphoton state has yet to be achieved. We derive a general expression for the spatio-temporal biphoton state that applies universally across common experimental settings and correctly describes the non-separability of spatial and spectral modes. We formulate a criterion on how to decrease the coupling of the spatial from the spectral degree of freedom by taking into account the Gouy phase of interacting beams. This work provides new insights into the role of the Gouy phase in SPDC, and also into the preparation of engineered entangled states for multidimensional quantum information processing

Orchestration of gene expression across the seasons : Hypothalamic gene expression in natural photoperiod throughout the year in the Siberian hamster

Acknowledgements Funding for work in the laboratory of PB was supported by Scottish Government Rural and Environment Science and Analytical Services Division, BBSRC (grant BB/M001504/1), British Society for Neuroendocrinology (research visit grant to IP). Work in the laboratory of SS was supported by a grant from the DFG (Ste 331/8-1). We thank Siegried Hilken, Marianne Brüning, Dr. Esther Lipokatic-Takacs and Dr. Frank Scherbarth at UVMH for technical assistance. We thank Graham Horgan of Bioinformatics, Statistics Scotland for assistance with some of statistical tests.Peer reviewedPublisher PD

Impaired daily glucocorticoid rhythm in <i>Per1</i>^<i>Brd</i> mice

Biological clocks have evolved in all kinds of organisms in order to anticipate and adjust to the daily light–dark cycle. Within the last decade, the molecular machinery underlying the circadian system was unraveled. In the present study, the impact of the loss of the Per1 or Per2 genes, key components of the core clock oscillator, on body mass, food and water intake, glucose metabolism, and hypothalamic-pituitary-adrenal axis, was investigated in the Per1 and Per2 mouse models. The results reveal that the lack of Per1 but not Per2 has severe consequences for the regulation of these parameters. Specifically, in Per1 animals, we found an impaired daily glucocorticoid rhythm, with markedly elevated levels during the day compared to control animals. In addition, Per1 mice showed significant differences in body mass as well as food and water intake. Although the Per1 are lighter than wildtype mice, food and water intake per gram body mass is elevated. In addition, the Per1 mice exhibit an increased glucose metabolism after i.p. injection with glucose. In conclusion, our study presents first evidence for a link between an altered metabolism in Per1 and Per2 deficient mice, which in the case of the Per1 animals might be due to an impaired corticosterone rhythm

Torpeur et mesure du temps (incidence de l'hypothermie contrôlée sur le système circadien de deux espèces de hamsters)

L influence des saisons est extrêmement marquée au niveau des hautes latitudes du globe, avec des variations des conditions environnementales très prononcées. Les Mammifères vivant dans de telles conditions drastiques, ont développés différentes formes d hibernation (ou torpeur) pour réduire les coûts métaboliques pendant ces périodes rudes lorsque les ressources énergétiques se font rares. Les Mammifères hibernants comme le Hamster d Europe (Cricetus cricetus), dont la température corporelle (Tb) diminue pendant plusieurs jours pour atteindre des niveaux voisins de la température ambiante (Ta), peuvent ainsi préserver au maximum leurs réserves d énergie. Au contraire, quelques petits Mammifères comme le Hamster de Djungarie (Phodopus sungorus) montrent des hypothermies journalières de moindre amplitude. Ils utilisent les quelques heures de leur temps de repos circadien pour effectuer avec précision des hypothermies contrôlées, et diminuer leur Tb jusqu à un seuil minimal de 15 C. De telles Tb basses qui se prolongent, peuvent avoir des conséquences sur l activité du système nerveux central (SNC). Il est donc crucial que l intégralité fonctionnelle du SNC soit maintenue, ainsi, la limitation de la durée d hypothermie permet un réveil régulier à des Tas basses. Pendant la torpeur, un des systèmes régulateurs importants serait le système circadien, car il réagit à la photopériode et synchronise les phénomènes internes sur une base de temps circadienne. Dans ce travail de thèse, nous avons pu montrer, pour la première fois, que la machinerie moléculaire de l horloge biologique endogène reste active pendant la torpeur chez le Hamster de Djungarie mais une chute de la Tb diminue l amplitude de l expression des gènes de l horloge biologique circadienne. La diminution de l expression des protéines pendant l hypothermie, induirait une diminution du rétrocontrôle de la transcription pendant et après une période de torpeur. Pour mieux comprendre les changements d expression de ces gènes, nous avons déterminé par microdialyse trans-pineal les sécrétions de mélatonine (hormone reflétant l activité de la principale sortie de l horloge ), pendant une longue durée. Cette méthode, qui a été adaptée pour la première fois au Hamster de Djungarie (animal de petite taille), s avère être un bon outil pour étudier les signaux saisonniers comme la mélatonine chez les animaux hibernants. Pendant l hibernation du Hamster d Europe, la diminution de la Tb atteint ~8 C pendant quelques jours dans nos conditions expérimentales. A basse température, nous n avons pas pu observer de rythme de l expression des gènes de l horloge biologique ce qui indiquerait dans ces conditions un arrêt des oscillations. A partir de nos résultats, nous avons conclu que l horloge circadienne semble compenser les effets d une diminution de la Tb dans un large gradient mais au delà d un certain seuil de température les oscillations sont arrêtées.Seasonal influences become increasingly important at high latitudes, where variations in external conditions are most pronounced. Mammals living in such drastic conditions have developed different forms of torpor to reduce metabolic costs in harsh periods when energy is rare. Deep hibernators like the European hamster (Cricetus cricetus) regularly decrease their body temperature (Tb) for several days to temperatures approaching ambient temperature (Ta) and thereby save a maximum of energy. In contrast some small mammals like the Djungarian hamster (Phodopus sungorus) undergo shallower bouts of daily torpor. Induced by short photoperiod they spontaneously use their daily resting time for only a few hours of precisely timed hypothermia during which their body temperature decreases to minimum 15C. Invariably low Tbs go along with a depression of CNS activity. Nevertheless it is crucial that functional integrity is maintained, which is why systems of vital importance during hypothermia are supposed to remain active at those low Tbs. One of the important keys during torpor is believed to be the circadian system. It measures photoperiod and thereby determines the onset of the torpor season and moreover synchronizes internal processes on a circadian basis. In this thesis we could for the first time demonstrate that the clock s molecular machinery is still active during daily torpor in Djungarian hamsters. Alterations in phase and amplitude of clock gene expression rhythms however, point to temperature sensitivity. Decrease in protein expression during hypothermia, hence a decreased feedback might be responsible for transcriptional alterations during and after a torpor bout. To more precisely investigate phase changes seen in gene expression, we set up a long term microdialysis experiment to continuously measure melatonin, a well defined clock output, in vivo directly in the pineal gland. This method could for the first time be adapted to the very small Djungarian hamster and provides a good tool to study a circadian signal like melatonin in a seasonally heterothermic animal. During deep hibernation in European hamsters that decreased their Tb for several days to ~8C in our experimental conditions, we could not observe any rhythmic clock gene expression and thereby show that the clock stops oscillating at those low temperatures. We conclude from our data, that the circadian clock seems to be temperature compensated in a wide temperature range but once a certain low temperature is reached, oscillation is no longer possible.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceGermanyFRD

Restoration of circadian rhythmicity in circadian clock-deficient mice in constant light

In mammals, circadian rhythms in behavior and physiology are controlled by a central pacemaker, the SCN, and subordinated clocks throughout the body. On the molecular level, these clocks are based on transcriptional/translational feedback loops involving a set of clock genes that regulate their own transcription. Among the components driving the mammalian circadian clock are the Period 1 and 2 (Per1 and Per2) and Cryptochrome 1 and 2 (Cry1 and Cry2) genes. In the present study, the authors characterize the behavioral and molecular rhythms of Per2/Cry1 double mutant mice under 3 different lighting conditions. In an LD cycle, the activity of these animals is masked by light, while in DD, the mutants lose circadian rhythmicity but exhibit strong ultradian rhythms. In LL of higher intensity, circadian rhythms are restored on the behavioral level with a drastically shortened endogenous period. Furthermore, both in the SCN and in the periphery, clock gene rhythms are restored. Based on these observations and also on the fact that light-mediated induction of Per gene expression is preserved in these mutants, the authors propose a mechanism by which endogenous ultradian rhythms may relay timed light exposure to the SCN, leading to a reinitiation of self-sustained circadian rhythms in LL