[PDF] Development And Temporal Timing Of Torpor In Siberian Hamsters Phodopus Sungorus eBook

Author : Annika Herwig
Publisher :
Page : 130 pages
File Size : 46,56 MB
Release : 2007
Category :
ISBN :

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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 15°C. 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 ~8°C 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..

Author : James Olcese
Publisher : Springer Science & Business Media
Page : 465 pages
File Size : 46,43 MB
Release : 2006-04-11
Category : Medical
ISBN : 030646814X

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In the forty years since melatonin's isolation and characterization, a large and multifaceted database has accrued. This book documents the diverse research contributions of most of the major laboratories in the field of melatonin research, as presented in a special conference to mark the 40 year anniversary of the isolation and chemical identification of this hormone. In addition, many chapters by younger scientists provide an exciting glimpse of where melatonin research is heading in the future.

Author : Randy J. Nelson
Publisher : Springer Nature
Page : 463 pages
File Size : 21,53 MB
Release : 2022-11-29
Category : Medical
ISBN : 3031129709

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Behavioral neuroendocrinologists are interested in the interactions between hormones and behaviors. This unique book tracks the development of behavioral neuroendocrinology from the first recognized paper in the field by Arnold Berthold in 1849 to the major contributors of the past century. It traces the history and development of the field by exploring the women and men who conducted the studies that revealed these hormone-behavioral relationships. Most chapters are written by the individuals who knew these pioneers best, and describe their stories and discuss the ways in which their work has shaped the field. Now is the perfect time for this book. The field is burgeoning and interest in the development of theoretical perspectives is thriving. Moreover, although this field was dominated by men early on, it has become a field with near sexual parity among its faculty, society membership, and leadership, and thus serves as an example of equitable science, training, and advocacy.