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Paul Pevet - One of the best experts on this subject based on the ideXlab platform.
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melatonin independent photoperiodic entrainment of the circannual tsh rhythm in the pars tuberalis of the European Hamster
Journal of Biological Rhythms, 2018Co-Authors: Cristina Saenz De Miera, Stefanie Monecke, Paul Pevet, Valerie Simonneaux, Dominique SagecioccaAbstract:Adaptation of biological rhythms to a seasonal environment in circannual mammals is achieved via the synchronization of intrinsic circannual rhythms to the external year by photoperiod. In mammals, the photoperiodic information is integrated to seasonal physiology via the pineal hormone melatonin regulation of pars tuberalis (PT) TSHβ expression and its downstream control of hypothalamic dio2 gene expression. In the circannual European Hamster, however, photoperiodic entrainment of the circannual clock is possible in pinealectomized animals. The present study explores whether the TSHβ expression in the PT and the downstream hypothalamic pathways are regulated by photoperiod in European Hamsters in the absence of melatonin. All animals were kept on an accelerated photoperiodic regime, which compressed the natural year to a 6-month cycle. Sham-operated European Hamsters and half of the pinealectomized European Hamsters entrained their annual cycle in reproduction, body weight, and activity pattern to this c...
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melatonin independent photoperiodic entrainment of the circannual tsh rhythm in the pars tuberalis of the European Hamster
Journal of Biological Rhythms, 2018Co-Authors: Cristina Saenz De Miera, Stefanie Monecke, Paul Pevet, Valerie Simonneaux, Dominique SagecioccaAbstract:Adaptation of biological rhythms to a seasonal environment in circannual mammals is achieved via the synchronization of intrinsic circannual rhythms to the external year by photoperiod. In mammals, the photoperiodic information is integrated to seasonal physiology via the pineal hormone melatonin regulation of pars tuberalis (PT) TSHβ expression and its downstream control of hypothalamic dio2 gene expression. In the circannual European Hamster, however, photoperiodic entrainment of the circannual clock is possible in pinealectomized animals. The present study explores whether the TSHβ expression in the PT and the downstream hypothalamic pathways are regulated by photoperiod in European Hamsters in the absence of melatonin. All animals were kept on an accelerated photoperiodic regime, which compressed the natural year to a 6-month cycle. Sham-operated European Hamsters and half of the pinealectomized European Hamsters entrained their annual cycle in reproduction, body weight, and activity pattern to this cycle, whereas the other half of the pinealectomized animals followed only each second cycle. In all animals, PT TSHβ and hypothalamic dio2 expressions were higher in Hamsters displaying a summer physiological state than in those in winter state. Moreover, in agreement with their seasonal state, reproductive animals (summer state) showed higher expression of rfrp and lower expression of kiss1-genes encoding central regulators of the reproductive axis-than those animals in reproductive quiescence (winter state), indicating the hypothalamic integration of the photoperiodic signal even in pinealectomized animals. The appropriate occurrence of a well-characterized activity pattern indicative of a so-called sensitive phase to short photoperiod suggested that the SCN constructs the melatonin-independent photoperiodic message. This message is sufficient to entrain the circannual rhythm in TSHβ expression in the PT and the downstream hypothalamic neuroendocrine pathway through a yet unknown pathway. These results reinforce the hypothesis that the PT is the site for the integration of circannual and photoperiodic information.
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how maize monoculture and increasing winter rainfall have brought the hibernating European Hamster to the verge of extinction
Scientific Reports, 2016Co-Authors: Mathilde L. Tissier, Yves Handrich, Paul Pevet, Jeanpatrice Robin, Mathieu Weitten, Charlotte KourkgyAbstract:Over the last decades, climate change and agricultural intensification have been identified as two major phenomena negatively affecting biodiversity. However, little is known about their effects on the life-history traits of hibernating species living in agro-ecosystems. The European Hamster (Cricetus cricetus), once a common rodent on agricultural land, is now on the verge of extinction in France. Despite the implemented measures for its protection, populations are still in sharp decline but the reasons for it remain unclear. To investigate how environmental change has affected this hibernating rodent, we used a data set based on 1468 recordings of Hamster body mass at emergence from hibernation from 1937 to 2014. We reveal the adverse effects of increasing winter rainfall and maize monoculture intensification on the body mass of wild Hamsters. Given the links that exist between body mass, reproductive success and population dynamics in mammals, these results are of particular importance to understand the decline of this species. In view of the rates of maize monoculture intensification and the predicted increase in winter rainfall, it is of the utmost importance to improve land management in Western Europe to avoid the extinction of this species.
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the circannual clock in the European Hamster how is it synchronized by photoperiodic changes
2014Co-Authors: Stefanie Monecke, Franziska Wollnik, Paul PevetAbstract:In a seasonal environment, mammals time their reproductive phase so that the offspring are born in spring and summer. Two strategies have evolved to ensure accurate seasonal timing of reproduction, but both share a common Zeitgeber, the seasonal changes in photoperiod. The reproductive axis might be directly controlled, as in photoperiodic species, which require photoperiodic input to show seasonal changes in reproductive competence. In contrast, in circannual species photoperiodic changes act indirectly, namely, on an endogenous circannual clock that then times reproduction. This circannual clock generates self-sustained rhythms with a period length of about 1 year, and photoperiodic information is only needed to synchronize these rhythms. Concerning the mechanism that imparts the photoperiodic message internally, so far no differences between photoperiodic and circannual mammals have been reported. Recent results however, strongly suggest that the circannual European Hamster (Cricetus cricetus) uses a fundamentally different mechanism than photoperiodic species. In the latter, photoperiod induces a change in the reproductive state via a melatonin-dependent pathway, whereas the circannual clock of the European Hamsters can be synchronized via a melatonin-independent pathway. Instead, a circadian mechanism based on a specific organizational state is involved. Juvenile European Hamsters use probably both pathways: the melatonin-dependent photoperiodic pathway for the short-term timing in the year of birth and the melatonin-independent circannual pathway for long-term timing of the seasonal events in the next year.
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Photoperiod can entrain circannual rhythms in pinealectomized European Hamsters.
Journal of Biological Rhythms, 2013Co-Authors: Stefanie Monecke, Dominique Sage-ciocca, Franziska Wollnik, Paul PevetAbstract:In mammals, the pineal hormone melatonin is thought to be essential to process environmental photoperiodic information. In this study, we demonstrate in a circannual species, the European Hamster Cricetus cricetus, the existence of a melatonin-independent second pathway. In 4 physiological parameters (reproduction, body weight, activity pattern, body temperature), a large majority of pinealectomized European Hamsters were entrained to an accelerated photoperiodic regime. It compressed the natural variations in the photoperiod to a 6-month cycle, which allowed us to record up to 6 complete physiological cycles during the life span of the individuals. We show further that whether a pinealectomized animal is able to entrain to changes in the photoperiod is influenced by the season of pinealectomy. The results do not disprove that melatonin is capable of entraining a circannual rhythm, but they show clearly that melatonin is not necessary, demonstrating another melatonin-independent pathway for circannual ent...
Stefanie Monecke - One of the best experts on this subject based on the ideXlab platform.
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Asymmetric Control of Short Day Response in European Hamsters
Journal of Biological Rhythms, 2020Co-Authors: Stefanie Monecke, A Malan, Franziska WollnikAbstract:The European Hamster (Cricetus cricetus) is a circannual species in which the synchronization of the circannual cycle to the natural year occurs during 2 annual phases of sensitivity. Around the summer solstice, the animals are sensitive to a shortening of photoperiod. During this sensitive phase, pronounced changes in circadian output parameters are observed, indicating a different functional state of the circadian system. This special state is assumed to be necessary to develop the extreme sensitivity to short day length in European Hamsters during this phase. In natural conditions, the animals are able to recognize the shortening of photoperiod already in mid-July, when the photoperiod is reduced only by 30 min. To investigate the short-day response in sensitive European Hamsters on the basis of the 2-coupled oscillator model of Pittendrigh and Daan (1976), daily activity and the reproductive state of European Hamsters were recorded after an asymmetrical reduction of photoperiod from long (LD 16:08) to short (LD 08:16) photoperiods. The activity pattern of the animals showed an immediate response to the short photoperiod at the day of transfer when the night was extended only into the evening, but there was a significant delay in the response time when the night was extended into the morning. Thus, the evening oscillator E is more important in inducing the photoperiodic response than the morning oscillator M. Moreover, the broad intragroup variation in the latter conditions strongly suggests that the changes in the activity pattern were endogenously induced and that the animals were not able to recognize a lengthening of the night into the morning. Gonadal regression started in both groups 3 weeks after the change in the activity pattern, indicating that this process is initiated when the circadian system has received the short-day signal either through changes in photoperiod or through the circannual clock.
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melatonin independent photoperiodic entrainment of the circannual tsh rhythm in the pars tuberalis of the European Hamster
Journal of Biological Rhythms, 2018Co-Authors: Cristina Saenz De Miera, Stefanie Monecke, Paul Pevet, Valerie Simonneaux, Dominique SagecioccaAbstract:Adaptation of biological rhythms to a seasonal environment in circannual mammals is achieved via the synchronization of intrinsic circannual rhythms to the external year by photoperiod. In mammals, the photoperiodic information is integrated to seasonal physiology via the pineal hormone melatonin regulation of pars tuberalis (PT) TSHβ expression and its downstream control of hypothalamic dio2 gene expression. In the circannual European Hamster, however, photoperiodic entrainment of the circannual clock is possible in pinealectomized animals. The present study explores whether the TSHβ expression in the PT and the downstream hypothalamic pathways are regulated by photoperiod in European Hamsters in the absence of melatonin. All animals were kept on an accelerated photoperiodic regime, which compressed the natural year to a 6-month cycle. Sham-operated European Hamsters and half of the pinealectomized European Hamsters entrained their annual cycle in reproduction, body weight, and activity pattern to this c...
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melatonin independent photoperiodic entrainment of the circannual tsh rhythm in the pars tuberalis of the European Hamster
Journal of Biological Rhythms, 2018Co-Authors: Cristina Saenz De Miera, Stefanie Monecke, Paul Pevet, Valerie Simonneaux, Dominique SagecioccaAbstract:Adaptation of biological rhythms to a seasonal environment in circannual mammals is achieved via the synchronization of intrinsic circannual rhythms to the external year by photoperiod. In mammals, the photoperiodic information is integrated to seasonal physiology via the pineal hormone melatonin regulation of pars tuberalis (PT) TSHβ expression and its downstream control of hypothalamic dio2 gene expression. In the circannual European Hamster, however, photoperiodic entrainment of the circannual clock is possible in pinealectomized animals. The present study explores whether the TSHβ expression in the PT and the downstream hypothalamic pathways are regulated by photoperiod in European Hamsters in the absence of melatonin. All animals were kept on an accelerated photoperiodic regime, which compressed the natural year to a 6-month cycle. Sham-operated European Hamsters and half of the pinealectomized European Hamsters entrained their annual cycle in reproduction, body weight, and activity pattern to this cycle, whereas the other half of the pinealectomized animals followed only each second cycle. In all animals, PT TSHβ and hypothalamic dio2 expressions were higher in Hamsters displaying a summer physiological state than in those in winter state. Moreover, in agreement with their seasonal state, reproductive animals (summer state) showed higher expression of rfrp and lower expression of kiss1-genes encoding central regulators of the reproductive axis-than those animals in reproductive quiescence (winter state), indicating the hypothalamic integration of the photoperiodic signal even in pinealectomized animals. The appropriate occurrence of a well-characterized activity pattern indicative of a so-called sensitive phase to short photoperiod suggested that the SCN constructs the melatonin-independent photoperiodic message. This message is sufficient to entrain the circannual rhythm in TSHβ expression in the PT and the downstream hypothalamic neuroendocrine pathway through a yet unknown pathway. These results reinforce the hypothesis that the PT is the site for the integration of circannual and photoperiodic information.
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dramatic global decrease in the range and reproduction rate of the European Hamster cricetus cricetus
Endangered Species Research, 2016Co-Authors: Alexey V Surov, Agata Banaszek, Pavel L Bogomolov, Natalia Yu Feoktistova, Stefanie MoneckeAbstract:Although the European Hamster is probably the fastest-declining Eurasian mammal, its IUCN Red List status is still Least Concern. In addition to the huge distribution area, this categorization is based on the assumptions (1) that the decline affects only Western Europe, where (2) modern agriculture has led to (3) an increase in the mortality of the species. Since mortalityreducing protection measures in Western Europe have been unable to stop the decline, we reviewed the literature from 1765 to the present and reappraised the situation. We found support for none of these assumptions. The species has also vanished from more than 75% of its range in Central and Eastern Europe. In 48 of 85 Russian, Belarussian, Ukrainian and Moldovan provinces, its relative occurrence has decreased. It is now rare in 42 provinces and extinct in 8. Mortality has not increased, but the reproduction rate has shrunk since 1954 throughout the distribution area. Today the reproduction rate is only 23% of that between 1914 and 1935. Taking into account the mortality of this prey species, 1 female today raises only 0.5 females for next year’s reproduction. The extra polation of the literature data points to an extinction of the species between 2020 and 2038. We strongly recommend (1) changing the status of the European Hamster on the IUCN Red List from Least Concern at least to Vulnerable or even Endangered and (2) supporting scientific research on the reproduction of European Hamsters as a protection measure. Global threats such as climate change, light pollution or (in the past) fur trapping are more likely to be the ultimate reason for the decline of this species than modern agriculture.
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the circannual clock in the European Hamster how is it synchronized by photoperiodic changes
2014Co-Authors: Stefanie Monecke, Franziska Wollnik, Paul PevetAbstract:In a seasonal environment, mammals time their reproductive phase so that the offspring are born in spring and summer. Two strategies have evolved to ensure accurate seasonal timing of reproduction, but both share a common Zeitgeber, the seasonal changes in photoperiod. The reproductive axis might be directly controlled, as in photoperiodic species, which require photoperiodic input to show seasonal changes in reproductive competence. In contrast, in circannual species photoperiodic changes act indirectly, namely, on an endogenous circannual clock that then times reproduction. This circannual clock generates self-sustained rhythms with a period length of about 1 year, and photoperiodic information is only needed to synchronize these rhythms. Concerning the mechanism that imparts the photoperiodic message internally, so far no differences between photoperiodic and circannual mammals have been reported. Recent results however, strongly suggest that the circannual European Hamster (Cricetus cricetus) uses a fundamentally different mechanism than photoperiodic species. In the latter, photoperiod induces a change in the reproductive state via a melatonin-dependent pathway, whereas the circannual clock of the European Hamsters can be synchronized via a melatonin-independent pathway. Instead, a circadian mechanism based on a specific organizational state is involved. Juvenile European Hamsters use probably both pathways: the melatonin-dependent photoperiodic pathway for the short-term timing in the year of birth and the melatonin-independent circannual pathway for long-term timing of the seasonal events in the next year.
M Massonpevet - One of the best experts on this subject based on the ideXlab platform.
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effect of photoperiod on the thyroid stimulating hormone neuroendocrine system in the European Hamster cricetus cricetus
Journal of Neuroendocrinology, 2010Co-Authors: M Massonpevet, Hugues Dardente, E A Hanon, Kevin William Routledge, Peter J Morgan, David G HazleriggAbstract:Recent studies have characterised a retrograde mechanism whereby the pineal hormone melatonin acts in the pars tuberalis (PT) of the pituitary gland to control thyroid hormone action in the hypothalamus, leading to changes in seasonal reproductive function. This involves the release of thyroid-stimulating hormone (TSH) from PT that activates type II deiodinase (DIO2) gene expression in hypothalamic ependymal cells, locally generating biologically active T3, and thus triggering a neuroendocrine cascade. In the present study, we investigated whether a similar regulatory mechanism operates in the European Hamster. This species utilises both melatonin signalling and a circannual timer to time the seasonal reproductive cycle. We found that expression of βTSH RNA in the PT was markedly increased under long compared to short photoperiod, whereas TSH receptor expression was localised in the ependymal cells lining the third ventricle, and in the PT, where its expression varied with time and photoperiod. In the ependymal cells at the base of the third ventricle, DIO2 and type III deiodinase (DIO3) expression was reciprocally regulated, with DIO2 activated under long and repressed under short photoperiod, and the reverse case for DIO3. These data are consistent with recent observations in sheep, and suggest that the PT TSH third ventricle-ependymal cell relay plays a conserved role in initiating the photoperiodic response in both long- and short-day breeding mammals.
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circannual phase response curves to short and long photoperiod in the European Hamster
Journal of Biological Rhythms, 2009Co-Authors: Stefanie Monecke, M Massonpevet, Michel Saboureau, Daniel Bonn, A Malan, Paul PevetAbstract:This study investigated in male e uropean Hamsters (Cricetus cricetus) whether entrainment of circannual rhythms follows the principles of the non- parametric entrainment model. In 2 experiments the times of the year when long (LP) or short photoperiod (SP) are able to synchronize the reproductive cycle were determined, by recording phase response curves (PRCs). A total of 28 groups of 10 Hamsters were synchronized by SP, before being subjected to 2 converse experiments: a) 14 groups were transferred to constant LP, only inter- rupted by SP for 1 month (SP - pulse), the pulse being increasingly delayed between groups by 2 weeks or 1 month steps; and b) the remaining 14 groups stayed in constant SP interrupted by LP for 1 month (LP - pulse) at different phases of the cycle. In a 3rd experiment 5 groups of 10 e uropean Hamsters were subjected to constant LP interrupted by 1-month SP-pulses in regular non-365-day zeitgeber intervals (circannual T-cycles) differing between groups (c). The reproductive state was checked every 2 or 4 weeks. The PRCs revealed that an SP - pulse had a very strong phase-resetting capability of -180° to at least +81° in subjective summer (a). During subjective winter when the animals hibernate, a SP - pulse had only weak effectiveness (a) whereas an LP - pulse advanced the circannual clock by up to +41° (b). In the latter conditions a further advance of up to +156° was achieved by the decrease in photoperiod at the return to SP conditions, which terminated the reproductive phase already after 4 to 5 weeks. In different circannual T-cycles the animals entrained for at least 2 cycles (c). In conclusion, 1) the circannual rhythm of e uropean Hamsters can be entrained by one photoperiodic signal per cycle, 2) the decrease in photoperiod is most impor- tant for its synchronization, and 3) as in circadian clocks the resetting of circan- nual clocks follows the principles of the nonparametric entrainment model.
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the circadian clock stops ticking during deep hibernation in the European Hamster
Proceedings of the National Academy of Sciences of the United States of America, 2007Co-Authors: Florent G Revel, M Massonpevet, Hugues Dardente, Valerie Simonneaux, Michel Saboureau, Annika Herwig, Marielaure Garidou, Jerome S Menet, Paul PevetAbstract:Hibernation is a fascinating, yet enigmatic, physiological phenomenon during which body temperature and metabolism are reduced to save energy. During the harsh season, this strategy allows substantial energy saving by reducing body temperature and metabolism. Accordingly, biological processes are considerably slowed down and reduced to a minimum. However, the persistence of a temperature-compensated, functional biological clock in hibernating mammals has long been debated. Here, we show that the master circadian clock no longer displays 24-h molecular oscillations in hibernating European Hamsters. The clock genes Per1, Per2, and Bmal1 and the clock-controlled gene arginine vasopressin were constantly expressed in the suprachiasmatic nucleus during deep torpor, as assessed by radioactive in situ hybridization. Finally, the melatonin rhythm-generating enzyme, arylalkylamine N-acetyltransferase, whose rhythmic expression in the pineal gland is controlled by the master circadian clock, no longer exhibits day/night changes of expression but constantly elevated mRNA levels over 24 h. Overall, these data provide strong evidence that in the European Hamster the molecular circadian clock is arrested during hibernation and stops delivering rhythmic output signals.
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seasonal variations of clock gene expression in the suprachiasmatic nuclei and pars tuberalis of the European Hamster cricetus cricetus
European Journal of Neuroscience, 2007Co-Authors: Benjamin B Tournier, Paul Pevet, M Massonpevet, Hugues Dardente, B Vivienroels, Valerie Simonneaux, Patrick VuillezAbstract:In mammals, day length (photoperiod) is read and encoded in the main circadian clock, the suprachiasmatic nuclei (SCN). In turn, the SCN control the seasonal rhythmicity of various physiological processes, in particular the secretion pattern of the pineal hormone melatonin. This hormone then operates as an essential mediator for the control of seasonal physiological functions on some tissues, especially the pars tuberalis (PT). In the European Hamster, both hormonal (melatonin) and behavioral (locomotor activity) rhythms are strongly affected by season, making this species an interesting model to investigate the impact of the seasonal variations of the environment. The direct (on SCN) and indirect (via melatonin on PT) effect of natural short and long photoperiod was investigated on the daily expression of clock genes, these being expressed in both tissues. In the SCN, photoperiod altered the expression of all clock genes studied. In short photoperiod, whereas Clock mRNA levels were reduced, Bmal1 expression became arrhythmic, probably resulting in the observed dramatic reduction in the rhythm of Avp expression. In the PT, Per1 and Rev-erbalpha expressions were anchored to dawn in both photoperiods. The daily profiles of Cry1 mRNA were not concordant with the daily variations in plasma melatonin although we confirmed that Cry1 expression is regulated by an acute melatonin injection in the Hamster PT. The putative role of such seasonal-dependent changes in clock gene expression on the control of seasonal functions is discussed.
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mt1 melatonin receptor mrna expressing cells in the pars tuberalis of the European Hamster effect of photoperiod
Journal of Neuroendocrinology, 2003Co-Authors: Hugues Dardente, Paul Pevet, Paul Klosen, M MassonpevetAbstract:Melatonin, secreted only during the night by the pineal gland, transduces the photoperiodic message to the organism. One important target for the hormone is the pars tuberalis (PT) of the adenohypophysis which displays a very high number of melatonin binding sites in mammals and is implicated in the seasonal regulation of prolactin secretion. To gain insight into the mechanism by which the melatonin signal is decoded in the PT, we studied the effect of photoperiod on the PT cells expressing the MT1 melatonin receptor in a highly photoperiodic species, the European Hamster. Recently, we showed that, in the rat, the MT1 receptor mRNA is expressed in PT-specific cells characterized by their expression of β-thyroid stimulating hormone (β-TSH) along with the α-glycoprotein subunit (a-GSU). As the cellular composition of the PT shows variability among species, we first identified the cell type expressing the MT1 receptor in the European Hamster by combining immunocytochemistry and nonradioactive in situ hybridization for the MT1 receptor mRNA. Our results show that, in the European Hamster, as in the rat, the MT1 receptor is only expressed by the PT-specific-cells, β-TSH and α-GSU positive. In a second step, we analysed the effects of photoperiod on the MT1 mRNA, and on β-TSH and α-GSU both at the mRNA and protein levels. Our data show that, compared to long photoperiod, short photoperiod induces a dramatic decrease of MT1, β-TSH and α-GSU expression. Protein levels of p-TSH and α-GSU were also dramatically reduced in short photoperiod. Together, our data suggest that melatonin exerts its seasonal effects in the PT by signalling to PT specific-cells through the MT1 receptor subtype.
B Canguilhem - One of the best experts on this subject based on the ideXlab platform.
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circannual reproductive rhythm in the European Hamster cricetus cricetus demonstration of the existence of an annual phase of sensitivity to short photoperiod
Journal of Pineal Research, 1999Co-Authors: Michel Saboureau, B Canguilhem, M Massonpevet, Paul PevetAbstract:: In the European Hamster (Cricetus cricetus) short photoperiod (SP) is responsible for the transition between the breeding and the resting season and data obtained previously suggest that a circannual “clock” drives the annual rhythm of reproduction. This hypothesis implies the existence of a SP-sensitive phase of the circannual system that occurs independently of the photoperiodic regime perceived by the animals after their arousal from hibernation at the end of March. In control animals kept outside, testicular atrophy occurs in August. When the animals were transferred from outdoors to controlled SP conditions (LD 10:14 and ambient temperature Ta = 18 ± 2°C), immediately (Group II) or 2, 4, 6 wk after capture (Groups IV, V, VI, respectively), sexual arrest occurs at the same time between mid-June and mid-July. In the other groups, transfer from outdoors to SP either after 6, 8, 10, 12 or 14 wk (Groups VI, VII, IX, X, XI, respectively) after capture, is followed directly within 4 wk by the gonadal atrophy. When SP was applied from the beginning of August (Group XII) gonadal atrophy was observed after only 2 wk. In this last group, however, the rapid involution is the consequence of the already initiated decline in sexual activity induced by the short daylengths from July. When comparing the effect of SP in two different ambient temperatures (Ta: 18 ± 2°C vs 7 ± 2°C), immediately (Groups II vs III), 8 (Groups VII vs VIII) or 16 (Groups XII vs XIII) wk after capture, it appears that low temperature does not affect the physiological process described above. In the European Hamster, after the gonadal regrowth at the end of hibernation, the animals do not need to experience increasing long days to react against SP. Gonadal inhibition is induced when, following our hypothesis, SP coincides with an endogenous period of sensitivity that extends from mid-May to at least July-August. The present findings complement and extend earlier evidence to support the existence of an endogenous circannual control of seasonal reproduction in the European Hamster.
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Photoperiodic Control of the Seasonal Variations in the Daily Pattern of Melatonin Synthesis in the European Hamster, Cricetus cricetus
Annals of the New York Academy of Sciences, 1998Co-Authors: Berthe Vivien-roels, B Canguilhem, Bruno Pitrosky, M Zitouni, A Malan, Daniel Bonn, Paul PevetAbstract:Nocturnal patterns of pineal melatonin concentrations were measured at hourly intervals in the European Hamster, Cricetus cricetus, maintained under different natural or experimental environmental conditions. There were pronounced variations in the night peak of pineal melatonin both in the duration and the amplitude of the melatonin peak and in the onset and decline of melatonin synthesis. The duration of the melatonin peak increased proportionnally with increased dark period. The amplitude increased abruptly from LD 16/8 to LD 15/9 and remained constant in all other photoperiods. The onset of synthesis started 6:00 hours after the onset of darkness in LD 16/8, 15/9, and 14/10, while it started 4:00 hours after dark onset in shorter photoperiods (LD 12/12 and 10/14). This result is opposite to that observed in the rat. The decline of synthesis was delayed as darkness increased and was directly related to lights on in long photoperiods, while it was endogenous in short photoperiods. Temperature, under a long photoperiod, also seems to be implicated in the regulation of the amplitude of themelatonin peak. r 1997 Academic Press Many species living in temperate regions use photoperiodic information to regulate their annual cycles of reproduction. Photoperiod is conveyed to the central nervous system via the daily pattern of melatonin synthesis and secretion (Goldman, 1983; Hoffmann, 1985; Reiter, 1987a; Pevet, 1988). Natural or experimental photoperiodic changes alter the duration of melatonin synthesis in many species (ref. in Hoffmann et al., 1985; Illnerova, 1986; Vivien-Roels et al., 1988; Pevet et al., 1991) and in most mammals the duration of the nocturnal peak of melatonin secretion is proportional to the duration of the dark period. Melatonin infusions into pinealectomized sheep or Hamsters can reproduce the effects of either a short or a long photoperiod (Carter and Goldman, 1983; Bittman and Karsch, 1983; Pitrosky et al., 1991). These results have led to the ‘‘duration hypothesis,’’ according to which photoperiodic information is conveyed to the central nervous system by the duration of the nocturnal peak of melatonin (Bartness et al., 1983). Nevertheless, it is now increasingly evident that seasonal changes in the daily pattern of melatonin secretion aremore complex than a simple change in the duration of the night peak (Pevet et al., 1991, 1995; Reiter, 1987b). The changes may also affect the amplitude of the melatonin rhythm or its phase with respect to the light–dark cycle (Pevet et al., 1995; Vivien-Roels, 1996). 1 To whom correspondence should be addressed at URA-CNRS 1332 ‘‘Neurobiologie des fonctions rythmiques et saisonnieres,’’ Laboratoire de Zoologie, Universite Louis Pasteur, 12 rue de l’Universite, 67000 Strasbourg, France. Fax: (33) 388.24.04.61. E-mail: vivien@neurochem.u-strasbg.fr. General and Comparative Endocrinology 106, 85–94 (1997) Article No. GC966853
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environmental control of the seasonal variations in the daily pattern of melatonin synthesis in the European Hamster cricetus cricetus
General and Comparative Endocrinology, 1997Co-Authors: B Vivienroels, B Canguilhem, Bruno Pitrosky, M Zitouni, A Malan, Daniel Bonn, Paul PevetAbstract:Abstract Nocturnal patterns of pineal melatonin concentrations were measured at hourly intervals in the European Hamster, Cricetus cricetus, maintained under different natural or experimental environmental conditions. There were pronounced variations in the night peak of pineal melatonin both in the duration and the amplitude of the melatonin peak and in the onset and decline of melatonin synthesis. The duration of the melatonin peak increased proportionnally with increased dark period. The amplitude increased abruptly from LD 16/8 to LD 15/9 and remained constant in all other photoperiods. The onset of synthesis started 6:00 hours after the onset of darkness in LD 16/8, 15/9, and 14/10, while it started 4:00 hours after dark onset in shorter photoperiods (LD 12/12 and 10/14). This result is opposite to that observed in the rat. The decline of synthesis was delayed as darkness increased and was directly related to lights on in long photoperiods, while it was endogenous in short photoperiods. Temperature, under a long photoperiod, also seems to be implicated in the regulation of the amplitude of the melatonin peak.
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are the annual reproductive and body weight rhythms in the male European Hamster cricetus cricetus dependent upon a photoperiodically entrained circannual clock
Journal of Pineal Research, 1994Co-Authors: M Massonpevet, B Canguilhem, Michel Saboureau, Daniel Bonn, F Naimi, Paul PevetAbstract:Masson-Pevet M, Naimi F, Canguilhem B, Saboureau M, Bonn D, Pevet P. Are the annual reproductive and body weight rhythms in the male European Hamster (Cricetus cricetus) dependent upon a photoperodically entrained circannual clock? J. Pineal Res. 1994; 17:151–163. Abstract Most or the data obtained so far on the European Hamster (Cricetus cricetus) suggest direct photoperiodically driven seasonal changes in sexual activity and body weight. The results of the present long-term study support the hypothesis that these annual changes are the expression of photoperiodically driven endogenous circannual rhythms. When subjected following capture (April-May) to constant conditions of long photoperiod (LP) and constant temperature a large number of the European Hamsters present, in September-December, complete gonadal atrophy associated with a decrease in body weight. A sexual reactivation as well as an increase in body weight are observed in the same animals between January and April. Of the six animals that survived long enough, two only presented partial gonadal atrophy during the second year. These observations clearly demonstrate that the decline in sexual activity in subjective autumn does not require a decrease in photoperiod, at least in the first year. Theoretically, the observed rhythms, if circannual in nature, would be generated by a self-sustained annual oscillator (circannual clock) able to function in the absence of a photoperiodic input. Pinealectomy makes animals unable to detect or measure photoperiodic information. Of the six European Hamsters tested (pinealectomized in June and then kept continuously under LP), five showed clear annual rhythms in body weight and reproductive capacities for two consecutive years. Clearly endogenous annual rhythms were expressed in these conditions. To be entrained to a 1-year period, such a circannual clock should, however, be able to react to either LP and/or to short-photoperiod (SP), at least at certain periods of the annual cycle. In animals exposed to LP in August or October, after gondal atrophy had been established by exposure to natural SP, gonadal regrowth started in December or January, about 2 to 3 months earlier than in animals kept outside or in experimental SP. With the same experimental conditions, exactly the same results were obtained in pinealectomized animals; thus stimulatory effect of LP or LP-induced phase advance of the circannual clock can be excluded. The absence of the SP information would then induce such reaction. In animals kept under constant LP and temperature following capture, however, pinealectomy in January—when all animals are sexually active—induces gonadal atrophy within 4 weeks. This clearly demonstrates that LP is stimulatory at this time of the subjective year.
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search for rhythmicity during hibernation in the European Hamster
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 1994Co-Authors: B Canguilhem, Paul Pevet, M Massonpevet, R Kirsch, A Malan, P Nobelis, Le J MinorAbstract:Temporal patterns of hibernation were studied by continuous monitoring of body temperature by radiotelemetry over 6 months in European Hamsters, Cricetus cricetus, at constant temperature and photoperiod. Entrances into hibernation occurred mostly at the end of the night (0000–0800 hours), while arousals were randomly distributed between day and night. This is at variance with a control of bout duration by a clock with a period of 24 h. Consequently, the timing of entrances implies a phase-resetting of the circadian clock on each arousal. Persistence of circadian rhythmicity with a period different from 24 h during deep hibernation was investigated examining whether the durations of torpor bouts were integer multiples of a constant period. A non-parametric version of the classical contingency test of periodicity was developed for this purpose. Periods ranging from 21 to 29 h were tested. Nine animals out of ten showed at least one significant period in this range (P<0.01), either below 24 h (21.8±0.5 h, n=4) or above (27.3±0.5 h, n=7). However, we have found a theoretical model of bout durations for which the contingency test of periodicity sometimes gives false significant results. This indicates that the power of the test is weak. With this reservation our results suggest that a circadian oscillator controls the duration of a bout of hibernation, which would occur after an integer, but variable and possibly temperature-dependent number of cycles.
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melatonin independent photoperiodic entrainment of the circannual tsh rhythm in the pars tuberalis of the European Hamster
Journal of Biological Rhythms, 2018Co-Authors: Cristina Saenz De Miera, Stefanie Monecke, Paul Pevet, Valerie Simonneaux, Dominique SagecioccaAbstract:Adaptation of biological rhythms to a seasonal environment in circannual mammals is achieved via the synchronization of intrinsic circannual rhythms to the external year by photoperiod. In mammals, the photoperiodic information is integrated to seasonal physiology via the pineal hormone melatonin regulation of pars tuberalis (PT) TSHβ expression and its downstream control of hypothalamic dio2 gene expression. In the circannual European Hamster, however, photoperiodic entrainment of the circannual clock is possible in pinealectomized animals. The present study explores whether the TSHβ expression in the PT and the downstream hypothalamic pathways are regulated by photoperiod in European Hamsters in the absence of melatonin. All animals were kept on an accelerated photoperiodic regime, which compressed the natural year to a 6-month cycle. Sham-operated European Hamsters and half of the pinealectomized European Hamsters entrained their annual cycle in reproduction, body weight, and activity pattern to this c...
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melatonin independent photoperiodic entrainment of the circannual tsh rhythm in the pars tuberalis of the European Hamster
Journal of Biological Rhythms, 2018Co-Authors: Cristina Saenz De Miera, Stefanie Monecke, Paul Pevet, Valerie Simonneaux, Dominique SagecioccaAbstract:Adaptation of biological rhythms to a seasonal environment in circannual mammals is achieved via the synchronization of intrinsic circannual rhythms to the external year by photoperiod. In mammals, the photoperiodic information is integrated to seasonal physiology via the pineal hormone melatonin regulation of pars tuberalis (PT) TSHβ expression and its downstream control of hypothalamic dio2 gene expression. In the circannual European Hamster, however, photoperiodic entrainment of the circannual clock is possible in pinealectomized animals. The present study explores whether the TSHβ expression in the PT and the downstream hypothalamic pathways are regulated by photoperiod in European Hamsters in the absence of melatonin. All animals were kept on an accelerated photoperiodic regime, which compressed the natural year to a 6-month cycle. Sham-operated European Hamsters and half of the pinealectomized European Hamsters entrained their annual cycle in reproduction, body weight, and activity pattern to this cycle, whereas the other half of the pinealectomized animals followed only each second cycle. In all animals, PT TSHβ and hypothalamic dio2 expressions were higher in Hamsters displaying a summer physiological state than in those in winter state. Moreover, in agreement with their seasonal state, reproductive animals (summer state) showed higher expression of rfrp and lower expression of kiss1-genes encoding central regulators of the reproductive axis-than those animals in reproductive quiescence (winter state), indicating the hypothalamic integration of the photoperiodic signal even in pinealectomized animals. The appropriate occurrence of a well-characterized activity pattern indicative of a so-called sensitive phase to short photoperiod suggested that the SCN constructs the melatonin-independent photoperiodic message. This message is sufficient to entrain the circannual rhythm in TSHβ expression in the PT and the downstream hypothalamic neuroendocrine pathway through a yet unknown pathway. These results reinforce the hypothesis that the PT is the site for the integration of circannual and photoperiodic information.
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the circadian clock stops ticking during deep hibernation in the European Hamster
Proceedings of the National Academy of Sciences of the United States of America, 2007Co-Authors: Florent G Revel, M Massonpevet, Hugues Dardente, Valerie Simonneaux, Michel Saboureau, Annika Herwig, Marielaure Garidou, Jerome S Menet, Paul PevetAbstract:Hibernation is a fascinating, yet enigmatic, physiological phenomenon during which body temperature and metabolism are reduced to save energy. During the harsh season, this strategy allows substantial energy saving by reducing body temperature and metabolism. Accordingly, biological processes are considerably slowed down and reduced to a minimum. However, the persistence of a temperature-compensated, functional biological clock in hibernating mammals has long been debated. Here, we show that the master circadian clock no longer displays 24-h molecular oscillations in hibernating European Hamsters. The clock genes Per1, Per2, and Bmal1 and the clock-controlled gene arginine vasopressin were constantly expressed in the suprachiasmatic nucleus during deep torpor, as assessed by radioactive in situ hybridization. Finally, the melatonin rhythm-generating enzyme, arylalkylamine N-acetyltransferase, whose rhythmic expression in the pineal gland is controlled by the master circadian clock, no longer exhibits day/night changes of expression but constantly elevated mRNA levels over 24 h. Overall, these data provide strong evidence that in the European Hamster the molecular circadian clock is arrested during hibernation and stops delivering rhythmic output signals.
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seasonal variations of clock gene expression in the suprachiasmatic nuclei and pars tuberalis of the European Hamster cricetus cricetus
European Journal of Neuroscience, 2007Co-Authors: Benjamin B Tournier, Paul Pevet, M Massonpevet, Hugues Dardente, B Vivienroels, Valerie Simonneaux, Patrick VuillezAbstract:In mammals, day length (photoperiod) is read and encoded in the main circadian clock, the suprachiasmatic nuclei (SCN). In turn, the SCN control the seasonal rhythmicity of various physiological processes, in particular the secretion pattern of the pineal hormone melatonin. This hormone then operates as an essential mediator for the control of seasonal physiological functions on some tissues, especially the pars tuberalis (PT). In the European Hamster, both hormonal (melatonin) and behavioral (locomotor activity) rhythms are strongly affected by season, making this species an interesting model to investigate the impact of the seasonal variations of the environment. The direct (on SCN) and indirect (via melatonin on PT) effect of natural short and long photoperiod was investigated on the daily expression of clock genes, these being expressed in both tissues. In the SCN, photoperiod altered the expression of all clock genes studied. In short photoperiod, whereas Clock mRNA levels were reduced, Bmal1 expression became arrhythmic, probably resulting in the observed dramatic reduction in the rhythm of Avp expression. In the PT, Per1 and Rev-erbalpha expressions were anchored to dawn in both photoperiods. The daily profiles of Cry1 mRNA were not concordant with the daily variations in plasma melatonin although we confirmed that Cry1 expression is regulated by an acute melatonin injection in the Hamster PT. The putative role of such seasonal-dependent changes in clock gene expression on the control of seasonal functions is discussed.
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mechanisms regulating the marked seasonal variation in melatonin synthesis in the European Hamster pineal gland
American Journal of Physiology-regulatory Integrative and Comparative Physiology, 2003Co-Authors: Marielaure Garidou, Paul Pevet, B Vivienroels, Jesus M Miguez, Valerie SimonneauxAbstract:Like many wild species, the European Hamster (Cricetus cricetus) adapts to the marked seasonal changes in its environment, namely by hibernation and inhibition of sexual activity in winter. These annual functions are driven by the variation in the environmental factors (light, temperature) that are transmitted to the body through large variations in the duration and amplitude of the nocturnal melatonin rhythm. Here we report that the seasonal variation in melatonin synthesis is mainly driven by arylalkylamine N-acetyltransferase gene transcription and enzyme activation. This, however, does not exclude participation of hydroxyindole-O-methyltransferase, which may relay environmental temperature information. The in vivo experiments show that norepinephrine stimulates melatonin synthesis, this effect being gated at night. The possibility that the variation in pineal metabolism depends on a seasonal change in the suprachiasmatic nuclei clock circadian activity that is transmitted by norepinephrine is discussed.
