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1
Best, J. "How quickly does light reset the circadian clock." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596605.
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The first experiment used the male Syrian hamster as the subject, as it has good wheel-running rhythms with consistent and robust activity onsets and also a well defined phase delay and advance region of the phase response curve (PRC). In this study, a double light pulse paradigm was used to examine if the clock could reset within 2 h. The second light pulse administered 2 h after an initial pulse was used to map the effects of the first light pulse on the resetting behaviour to determine whether the clock had reset to primary light pulse before receiving the second one. The results obtained in both the phase delay and phase advance portions of the PRC were consistent with the hypothesis that the clock of the Syrian hamster could reset within 2 h of a light pulse. The next experiment investigated whether the immediate early genes (IEGs) are a reliable marker of clock resetting and if they have a role in clock resetting. The same double light pulse paradigm employed in the first experiment was used to ascertain if <I>c-fos</I> and <I>egr-l</I> could be induced to two delaying light pulses. The study revealed that both IEGs were induced to each light pulse demonstrating that the clock could differentiate between the two pulses of light and that the immediate early genes may play a role in phase resetting to light. Having established that the clock of the Syrian hamster was reset in 2 h the outbred mouse was used to ascertain if this rapid resetting is common to other mammalian species. The results obtained using multiple light pulses revealed that the mouse clock is also reset within 2 h, supporting the findings in the Syrian hamster and demonstrating cross-species homology. In addition, investigations on CREB phosphorylation, c-Fos induction and AP-l binding activity revealed that all three transcriptional regulators were induced in response to a light pulse during subjective night and that there was a strong correlation with photic phase resetting of the mammalian clock.
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Dixon, Laura Evelyn. "Investigation of light inputs into plant circadian clocks." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/5266.
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Circadian clocks are biological signalling networks which have a period of ~24 hours under constant environmental conditions. They have been identified in a wide range of organisms, from cyanobacteria to mammals and through the temporal co-ordination of biological processes are believed to increase individual fitness. The mechanisms which generate these self-sustained rhythms, the pathways of entrainment and the target outputs of the clock are all areas of great interest to circadian biologists. The plant circadian clock is believed to comprise of interlocking feedback loops of transcription and translation. The morning MYB-transcription factors CIRCADIAN CLOCK ASSOCIATED 1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY) bind to the promoter of TIMING OF CAB2 1 (TOC1) and repress its expression, as well as their own. As levels of CCA1 and LHY fall, TOC1 is expressed and activates the expression of its repressors. This is a simplified version of the known clock components and the current model contains this core loop as well as an interlocked morning and evening loop, which also incorporates some post-translational modification (Chapter 1). Understanding the plant circadian network and its entrainment are the topics of this thesis. The study has focused on two plant species, the land plant Arabidopsis thaliana and the picoeukaryotic marine algae Ostreococcus tauri. In both of these species light-mediated entrainment of the clock has been investigated (Chapter 8), as well as the core circadian mechanism. In A. thaliana the role of a circadian associated gene, EARLY FLOWERING 3 has been a particular focus for investigation, through both experimentation and mathematical models (Chapters 4 and 5). In O. tauri the responses to light signals have been tested, as have the circadian responses to pharmacological manipulation (Chapters 6, 7 and 8). The work presented identifies a role for ELF3 in the repression of circadian genes and also links it with the regulation of protein stability. Likewise, in O. tauri the regulation of protein stability is identified to be a key mechanism for sustaining circadian rhythms. As well as investigating the clock in plants, certain photoreceptors have been characterised in S. cerevisiae with the aim of linking them to a synthetic oscillator. Together the work presented in this thesis provides evidence for the circadian community to aid with the understanding of circadian rhythms in plants, and possibly other organisms.
3
Bedrosian, Tracy A. "Circadian Disruption by Light at Night: Implications for Mood." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1363097253.
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4
Breda, Carlo. "Temperature and light entrainment of the Drosophila circadian clock." Thesis, University of Leicester, 2010. http://hdl.handle.net/2381/9743.
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Drosophila melanogaster locomotor activity responds to seasonal conditions by modulating the “evening” activity component. During simulated winters of cold temperature and short days an advanced evening locomotor peak occurs with more daytime locomotor activity; on the other hand long photoperiods and warm temperatures give a delay in the evening peak, thereby avoiding a possible desiccation during the hottest times of the day. This pattern of activity is related to a thermosensitive splicing event that occurs in a 3’ intron in the period gene, with a higher level of splicing and earlier accumulation of PERIOD in short days and low temperatures. A mutation in norpA which encodes a phospholipase C, generates a high level of spliced per at warmer temperature, so mutants behave as if it is colder than it actually is. The relation between norpA, per splicing and the circadian neurons has been analysed. Initially, norpA expression has been investigated via in situ hybridisation and immunocytochemistry. norpA transcript has been localised among the clock pacemakers but not NORPA. Subsequently, norpA expression has been knocked-down by RNAi in specific subset of neurons. The resulting locomotor behaviour shows seasonally related effects implicating the photoreceptors, lateral and dorsal clock neurons as structures involved in timing the locomotor behaviour. In parallel, the thermal role of a second PLCβ, plc21C, has been investigated via RNAi among circadian pacemakers. It has been possible to show that plc21C expression in the photoreceptors, lateral and dorsal neurons is required to set different locomotor behaviours at different temperatures, but not via per and tim splicing. Finally, in contrast to reports that the double photoreceptor mutants involving glass and cryptochrome are “circadian blind”, these flies have been observed to entrain to light-dark cycles at moderate temperatures. Candidate orphan G protein coupled receptors have been screened in order to identify a further set of putative circadian-relevant photoreceptors contributing to this residual entrainment in glass60jcryb mutants. In constant light conditions, the RNAi of CG7497 and CG16958 generates rhythmic or arrhythmic flies depending on the genetic background tested.
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Moore, H. A. "Circadian rhythmicity and light sensitivity of the zebrafish brain." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1469451/.
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Light is important for entraining circadian rhythms, which regulate a wide range of biological processes. Zebrafish have directly light responsive tissues (Whitmore et al 2000) and are thus a useful vertebrate model for circadian rhythmicity and light sensitivity. Recent studies show the pineal regulates locomotor rhythms (Li et al 2012). However, there are many unresolved questions concerning the neurobiological basis of the zebrafish clock, such as whether neuronal pacemakers, which drive rhythms in other tissues, are present throughout the brain. In this study, per3-luc zebrafish confirm that both central and peripheral tissues are directly light sensitive and have endogenous circadian rhythmicity. Chromogenic in situ hybridization reveals localised expression of several core zebrafish clock genes, a rhythmic gene, per3, and two light responsive genes, cry1a and per2. Adult brain nuclei with expression include the suprachiasmatic nucleus, periventricular grey zone of the optic tectum, and granular cells of the rhombencephalon. Pilot experiments using high-resolution spatial recording of per3-luc brain slices show some of these regions can display robust rhythmicity in DD. Some of the cells expressing clock genes are neurons, and therefore neurons were further investigated. C-fos, a marker for neuronal activity in mammalian photoreceptors, is upregulated in at least four different responses to light in zebrafish, in different brain nuclei. This suggests the brain contains several types of photosensitive cells, which respond to different lighting conditions. Zebrafish larvae exhibit developmental changes in spatial circadian gene expression of per3 and light induction of c-fos. Finally, the photopigment group of opsins were investigated for their potential role in light entrainment. Exorh was prominent solely in the pineal. Rgr1 was found in numerous nuclei, many of which had shown expression of cry1a, per2 and per3. Overall, this thesis shows that the zebrafish brain is not uniformly light sensitive. Localised regions in the zebrafish brain with strong rhythmicity and light sensitivity are neuronal pacemaker candidates.
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Flyktman, A. (Antti). "Effects of transcranial light on molecules regulating circadian rhythm." Doctoral thesis, Oulun yliopisto, 2018. http://urn.fi/urn:isbn:9789526219592.
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Abstract Light acts as the most important regulating and entraining factor of the mammalian circadian rhythm. This rhythm has evolved to set phases, in which different physiological and behavioral events occur at the right time of the day to synchronize the organism. The mechanism of light transduction via eyes to the brain and its effects on circadian rhythmicity is well known. Yet, it has also been shown that light is able to penetrate the skull bone directly, but it is still unknown, whether transcranial light is able to affect molecules regulating circadian rhythmicity. Monoamines and especially opsins have been shown to act as important regulators in circadian rhythmicity. Both group of molecules can mediate the effects of light on regulation and entrainment. In this thesis, mice and hamsters have been illuminated transcranially and the expression of three different opsins and the concentrations of several monoamines have been measured. The animals were illuminated under anesthesia either just after the onset of the light period or just after the beginning of the dark period. The opsin expression in rodent brain were measured by western blot and the monoamine concentrations from mouse brain, plasma and adrenal gland were measured by HPLC. It was observed that both opsin expression and monoamine concentrations can be influenced by transcranial illumination. The effect varied depending on the studied molecule, tissue and time of illumination. The findings of this study demonstrate that opsins, which are considered to be the most important molecules regulating circadian rhythmicity, can be directly and specifically affected not only via the eyes but also by light illuminated through the skull. Furthermore, monoamine production can be altered in both the central nervous system and the peripheral tissues by transcranial illumination. This thesis demonstrates an alternate pathway for circadian entrainment and regulation by light involving specific molecular mediators such as opsins and monoamines<br>Tiivistelmä Valo on tärkein yksittäinen tekijä nisäkkäiden vuorokausirytmiikassa. Tämä rytmi on kehittynyt ajoittamaan fysiologiset ja käyttäytymiseen perustuvat ilmiöt tapahtumaan oikeaan aikaan vuorokaudesta. Valosignaalin välittyminen silmien kautta aivoihin ja sen vaikutukset vuorokausirytmiikkaan ovat hyvin tunnetut ja paljon tutkitut, mutta vielä on epäselvää, pystyykö kallon läpi annettava valo samaan, vaikka valon on osoitettu pystyvän läpäisemään nisäkkäiden kallon. Monoamiinit ja opsiinit ovat molekyylejä, jotka ovat tärkeässä roolissa vuorokausirytmiikan säätelyssä, ja molempien ilmeneminen on riippuvainen valon määrästä. Tässä väitöskirjassa valotettiin hiirien ja hamstereiden aivoja korvan kautta annettavalla valolla ja mitattiin kolmen eri opsiinin ekspressiota sekä monoamiinien määrää. Eläimiä valotettiin nukutuksessa joko valojakson alussa aamulla tai valojakson päätyttyä illalla. Opsiinien ekspressio aivoissa mitattiin western blot -menetelmällä ja monoamiinien HPLC-menetelmällä. Tuloksista huomattiin, että sekä opsiinien ekspressioon että monoamiinien pitoisuuksiin voidaan vaikuttaa suoraan kallon läpi annettavalla valolla. Valohoidon vaikutus riippui tutkittavasta molekyylistä, kudoksesta ja valohoidon ajankohdasta. Näiden tulosten avulla pystyttiin osoittamaan, että opsiinien, jotka ovat tärkeimpiä molekyylejä vuorokausirytmiikan säätelyssä, määrää voidaan manipuloida myös kallon läpi annettavan valon vaikutuksesta. Lisäksi kallon läpi annettavalla valolla voidaan vaikuttaa monoamiinien pitoisuuksiin sekä keskushermostossa että muissa kudoksissa. Tämä väitöskirja antaa tärkeää tietoa vuorokausirytmiikkaa säätelevistä molekyyleistä ja osoittaa, että niihin pystytään vaikuttamaan myös muuten kuin silmien kautta annettavalla valolla
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Fonken, Laura K. "PHYSIOLOGICAL CONSEQUENCES OF CIRCADIAN DISRUPTION BY NIGHTTIME LIGHT EXPOSURE." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1365165088.
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8
Grandner, Michael Andrew. "Sleep, mood, and circadian responses to bright green light during sleep." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3259050.
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Thesis (Ph. D.)--University of California, San Diego and San Diego State University, 2007.<br>Title from first page of PDF file (viewed June 11, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 108-123).
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Walmsley, Lauren. "Sensory processing in the mouse circadian system." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/sensory-processing-in-the-mouse-circadian-system(bd32ea60-48a8-46d4-b5db-dd83d0326d87).html.
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In order to anticipate the predictable changes in the environment associated with the earth’s rotation, most organisms possess intrinsic biological clocks. To be useful, such clocks require a reliable signal of ‘time’ from the external world. In mammals, light provides the principle source of such information; conveyed to the suprachiasmatic nucleus circadian pacemaker (SCN) either directly from the retina or indirectly via other visual structures such as the thalamic intergeniculate leaflet (IGL). Nonetheless, while the basic pathways supplying sensory information to the clock are well understood, the sensory signals they convey or how these are processed within the circadian system are not. One established view is that circadian entrainment relies on measuring the total amount of environmental illumination. In line with that view, the dense bilateral retinal input to the SCN allows for the possibility that individual neurons could average signals from across the whole visual scene. Here I test this possibility by examining responses to monocular and binocular visual stimuli in the SCN of anaesthetised mice. In fact, these experiments reveal that SCN cells provide information about (at most) irradiance within just one visual hemisphere. As a result, overall light-evoked activity across the SCN is substantially greater when light is distributed evenly across the visual scene when the same amount of light is non-uniformly distributed. Surprisingly then, acute electrophysiological responses of the SCN population do not reflect the total amount of environmental illumination. Another untested suggestion has been that the circadian system might use changes in the spectral composition of light to estimate time of day. Hence, during ‘twilight’, there is a relative enrichment of shortwavelength light, which is detectable as a change in colour to the dichromatic visual system of most mammals. Here I used a ‘silent substitution’ approach to selectively manipulate mouse cone photoreception, revealing a subset of SCN neurons that exhibit spectrally-opponent (blue-yellow) visual responses and are capable of reliably tracking sun position across the day-night transition. I then confirm the importance of this colour discrimination mechanism for circadian entrainment by demonstrating a reliable change in mouse body temperature rhythms when exposed to simulated natural photoperiods with and without simultaneous changes in colour. This identification of chromatic influences on circadian entrainment then raises important new questions such as which SCN cell types process colour signals and do these properties originate in the retina or arise via input from other visual regions? Advances in mouse genetics now offer powerful ways to address these questions. Our original method for studying colour discrimination required transgenic mice with red-shifted cone sensitivity – presenting a barrier to applying this approach alongside other genetic tools. To circumvent this issue I validated a modified approach for manipulating wildtype cone photoreception. Using this approach alongside optogenetic cell-identification I then demonstrate that the thalamic inputs to the SCN are unlikely to provide a major source of chromatic information. To further probe IGL-contributions to SCN visual responses, I next used electrical microstimulation to show that the thalamus provides inhibitory input to both colour and brightness sensitive SCN cells. Using local pharmacological inhibition I then show that thalamic inputs supress specific features of the SCN light response originating with the contralateral retina, including colour discrimination. These data thus provide new insight into the ways that arousal signals reaching the visual thalamus could modulate sensory processing in the SCN. Together then, the work described in this thesis provides important new insight into sensory control of the circadian system and the underlying neural mechanisms.
10
Hanifin, John P. "Circadian, neuroendocrine and neurobehavioral effects of polychromatic light in humans." Thesis, University of Surrey, 2015. http://epubs.surrey.ac.uk/807999/.
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In the last eighteen years there has been the identification of a novel photopigment, melanopsin, and its subsequent localization to human intrinsically photosensitive retinal ganglion cells (ipRGCs). Since melanopsin’s peak sensitivity is in the short wavelength portion of the visible spectrum (from 447 nm to 484 nm), there has been a steady increase in studies investigating the physiological effects of blue light. This thesis examines polychromatic light mixtures of blue light for circadian, neuroendocrine and neurobehavioral effects in humans. White blue-enriched fluorescent lamps were tested at equal photon densities for increased efficacy for melatonin suppression, increased alertness, and circadian phase shifting. Results demonstrated that compared to white fluorescent light, blue-enriched fluorescent light was significantly stronger for suppressing melatonin and resulted in significantly reduced subjective sleepiness. Blue-enriched light, however, was not significantly stronger in eliciting circadian phase-delay or increasing objective measures of alertness. Next, blue-appearing narrowband solid-state light was examined for its ability to acutely suppress nocturnal melatonin as well as enhance cognitive performance and alertness in healthy men and women when compared to dim white lighting. The results demonstrated that narrowband blue solid-state light was significantly stronger for melatonin suppression compared to dim white light. Subjective and objective assessments of alertness, however, were not significantly increased by blue-enriched light exposure. The final study tested the hypothesis that certain combinations of light wavelengths are additive or opponent to the photoreceptor system that mediates the melatonin suppression. The results demonstrated that the melatonin suppression responses to dual narrow bandwidth light combinations were not significantly different from single wavelength exposures. Taken together, the results suggest that melanopsin sensitivity is not the sole consideration for predicting the efficacy of white polychromatic lighting. The different effects of blue light on alertness, circadian phase-shifting and melatonin suppression imply a either a context dependent sensitivity and/or differential involvement of the classical photoreceptors in these light responses.
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Najjar, Raymond. "Non visual photoreception in humans : circadian consequences of spectral modulations of light." Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10110.
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Chez les mammifères dont l’Homme, les rythmes circadiens physiologiques et comportementaux sont régulés par l’horloge centrale, localisée dans les noyaux suprachiasmatiques de l’hypothalamus. Possédant une période endogène proche mais pas exactement de 24 heures, cette horloge est constamment synchronisée à la période terrestre par le cycle lumière-obscurité perçu au niveau de l’oeil. Cette synchronisation entraîne l’expression de rythmes appropriés (hormonaux, veille-sommeil, température corporelle, etc.). Les hypothèses de ma thèse sont : 1- une exposition chronique à un spectre lumineux appauvri en longueurs d’ondes courtes, causée par l’opacification du cristallin chez le sujet âgé ou par l’exposition chronique à des lumières artificielles blanches, est à l’origine d’une altération de la réponse du système circadien à la lumière ; 2- une exposition chronique à un spectre lumineux enrichi en longueurs d’ondes courtes chez le sujet jeune, améliore la synchronisation du système circadien, la vigilance, les performances cognitives et la qualité du sommeil. L’objectif de ma thèse est d‘évaluer ces hypothèses selon deux approches : 1. Une approche physiologique : chez le sujet âgé sain, le brunissement physiologique du cristallin oculaire conduit à une filtration des longueurs d’ondes courtes du spectre lumineux. Cette approche inclus la mise au point et la validation d’un système de mesure de transmittance du cristallin in vivo. Ce système est nécessaire pour quantifier la qualité spectrale de la lumière atteignant la rétine. 2. Une approche artificielle : chez des sujets jeunes exposés de manière chronique (63 jours) à des lumières ambiantes blanches ou enrichies en longueurs d’ondes courtes<br>Physiological and behavioral circadian rhythms in mammals and humans are under the control of a central clock located in the suprachiasmatic nuclei of the hypothalamus. This endogenous clock has a period close to but not exactly 24 hours and therefore needs to be constantly entrained to the 24-h period of the earth, by the light-dark cycle. Light is perceived through the eyes and implicates all the retina’s photoreceptors (rods, cones, melanopsin ganglion cells (ipRGCs)). A properly entrained circadian system leads to an appropriate rhythmic expression of many physiological functions (hormonal secretion, sleep/wake cycles, core body temperature …). My project’s hypotheses are: 1- a chronic exposure to blue deprived light, as occurring in the aged due to lens filtration or under standard indoor lighting, leads to a decreased nonvisual sensitivity to light.; 2- exposure to blue enriched white light in the young subjects enhances non-visual responses to light such as, entrainment of the circadian system, vigilance, mood, sleep quality and cognitive performance. The aim of my thesis is to evaluate these hypotheses using two approaches : 1. A physiological approach: In the aged subject, in whom the ocular crystalline lens specifically filters short wavelength lights, known to be crucial for circadian entrainment. This approach includes the development and clinical validation of a scotopic heterochromatic flicker photometry technique to assess lens transmittance in vivo. This technique is essential to evaluate individual light spectra reaching the retina. 2. An artificial approach: In young subjects chronically exposed (63 days in the Concordia base, Antarctica) solely to standard white or blue enriched white light
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Peters, Jennifer Lynn. "Astrocytes and the circadian clock: roles for calcium, light, and melatonin." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/3872.
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Melatonin is rhythmically synthesized and released by the pineal gland and, in some species, retina during the night and regulates many physiological and behavioral processes in birds and mammals. Chick diencephalic astrocytes express two melatonin receptor subtypes in vitro, and melatonin plays a role in regulating metabolic activity. We examined the role of glial cells in circadian function and asked if melatonin modulated glial functions within the retina and the brain. Calcium waves were potentiated by physiological concentrations of melatonin. Melatonin increased resting calcium levels and reduced gap junctional coupling among astrocytes at these same concentrations. Both mouse and chick diencephalic and telencephalic astrocytes express melatonin receptor protein. Nanomolar melatonin modulated astrocytic calcium waves of the mouse and chick diencephalon but not waves of the telencephalon. Mammalian intercellular calcium waves spread farther than avian calcium waves, and the nature of the spread of the waves differed between telencephalic and diencephalic mammalian astrocytes. These differences in propagation were abolished by melatonin. Using northern analysis, we identified period2, period3, cryptochrome1, cryptochrome2, clock, melanopsin and peropsin within chick diencephalic astrocytes. The clock genes cry1 and, per2 were expressed rhythmically in a LD cycle, but metabolic activity was not rhythmic. When cells were placed in constant darkness and rhythmically administrated melatonin, a robust rhythm in glucose uptake was induced without a coordinated clock gene rhythm, suggesting rhythmic clock gene expression and metabolic activity are separable processes. Melatonin affected visual function as assessed by electroretinogram. Circadian rhythms of a- and b-wave implicit times and amplitudes were observed. Melatonin (1 mg/kg and 100 ng/kg) decreased a- and b-wave amplitudes greater during the night than during the day and it increased a- and b-wave implicit times while 1 ng/kg melatonin had little to no effect over the saline controls. These data indicate that melatonin modulates glial intercellular communication, affects metabolic activity in astrocytes, and may play a role in regulating a day and night functional shift in the retina, at least partially through Müller glial cells. Thus, melatonin can regulate glia function and thereby, affect outputs of the vertebrate biological clock.
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Hurley, Elisabeth. "Effects of early light environment on the photic response of the circadian system." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/effects-of-early-light-environment-on-the-photic-response-of-the-circadian-system(6b32d591-5394-4f1e-a422-7458eb740c2c).html.
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Early light environment has been shown to alter locomotor activity behaviour in adult rats and mice when exposed to constant light (LL), constant darkness (DD) or 12:12 hour light-dark cycles (LD). In particular, exposure to LL during lactation results in an increased ability to cope with exposure to LL as adults, implying that the ability to interpret light information is altered depending on early light environment. Therefore, the aim of this project was to explore how early light environment affects the photic response of the circadian system. The retina forms the first component of the photic response of the circadian system. We wanted to know whether being raised in DD, LD or LL would alter retinal function or structure in adult CD1 (albino) and C57BL/6J (pigmented) mice. We found that in CD1 mice, being raised in LL caused significant retinal damage and a significant reduction in retinal function. In C57BL/6J mice, we saw no such changes, implying that any changes that we see in behaviour would be due to alterations further downstream, such as the suprachiasmatic nucleus (SCN), site of the master circadian clock in the mammalian brain. We next exposed C57BL/6J mice to LL and found that mice raised in DD had significantly longer taus than mice raised in LL, implying that mice raised in DD are more sensitive to light than mice raised in LL.Previous work has shown that early light environment alters neuropeptide and astrocyte expression in the SCN of C57BL/6J mice. Furthermore, early light environment produces opposite behavioural responses in CD1 and C57BL/6J mice when exposed to LD as adults. We therefore examined how neuropeptide and astrocyte expression would be affected by early light environment in CD1 mice and whether this would reflect the differential behavioural response. We found that neuropeptide and astrocyte expression in the SCN seemed to be affected by the level of retinal damage and/or the type and intensity of the light source used. This sensitivity to lighting environment makes CD1 mice unsuitable for further studies on the photic response of the circadian system. Pigmented mice were used for the remainder of this project. The photic response of the circadian system can be quantified using a phase response curve (PRC) which measures behavioural responses to light pulses administered at different times of day. We measured the effect of a light pulse on the delay and advance portion of the PRC and found no differences due to early light environment, implying that the phasic effect of light is not altered by early light environment. Light pulses administered during the subjective night result in the upregulation of SCN intracellular photic signalling pathways. After a light pulse given during the early subjective night, we found no differences in the upregulation of different components of the photic signalling pathway due to early light environment indicating early light environment does not seem to affect the initial photic signalling pathway in the SCN.Finally, recent advances in molecular biology allow for real-time monitoring of clock gene expression in vitro. Using mPer2::luc mice, we monitored in vitro PER2::LUC expression to determine the effects of early light environment on clock gene expression. In the SCN, we found that the amplitude of PER2::LUC expression was significantly reduced in mice raised in DD compared to mice raised in LD and LL. These results suggest that early light environment affects the coupling strength between SCN neurons and this may be the mechanism mediating the changes in behaviour we have measured. In peripheral tissue, we found altered PER2::LUC expression due to early light environment in the heart, lung and spleen, implying that early light environment not only alters behaviour but may also affect heart and lung function and the immune system.
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Itzhacki, Jacobo. "Reward effects of light." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAJ083/document.
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Pour élucider les effets récompensants de la lumière, deux approches expérimentales ont été adoptées. Une étude chez le rongeur diurne Arvicanthis ansorgei indique que le raccourcissement de la longueur du jour avec la diminution de l'intensité lumineuse induit des changements du rythme de l’activité locomotrice, de la quantité de dopamine dans le système de la récompense et sur l'expression du gène Per2 dans le noyau suprachiasmatique. Ces altérations ont été améliorées par l'exposition journalière à des créneaux d’une heure de lumière à la fin du jour. Dans une étude humaine, le bien-être subjectif mesuré par d'échantillonnage de ressentis, a été corrélée avec des mesures de fluctuations lumineuses environnementales chez des participants en bonne santé et des insomniaques. Les résultats ont montré que le bien-être subjectif augmente proportionnellement à l'intensité de la lumière chez de jeunes en bonne santé contrairement à un déficit global en matière d'évaluation hédonique chez les insomniaques. De plus amples études devraient être menées afin d'élucider l'effet des signaux lumineux environnementaux sur les circuits de récompense<br>To elucidate the reward effects of light, two experimental approaches have been adopted. An experiment for the study of the effects of exposure to a winter-like photoperiod on the diurnal rodent Arvicanthis ansorgei indicated that shortened day length with reduced light intensity induces a phase change in locomotor activity, alterations in the dopamine content in reward system structures, and alterations in the Per2 clock gene expression in the suprachiasmatic nucleus. These measures were improved by daily exposure to a one-hour pulse of light at late in the day. In a human model, subjective wellbeing, measured by experience sampling, was correlated with ambient luminosity measurements in participants with insomnia and healthy controls. Results indicated that subjective wellbeing increases with increasing light intensity in healthy young volunteers, in contrast to an overall deficit in reward evaluation in insomniacs. Light exposure should be taken into account as an important factor in determining the quality of life of insomniacs and in depression. Further studies should be conducted to elucidate the effect of ambient light signals on reward circuits
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Deacon, Stephen John. "Manipulation of the human circadian system with bright light and melatonin." Thesis, University of Surrey, 1994. http://epubs.surrey.ac.uk/800041/.
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Herljevic, Mirela. "Effect of light and melatonin on circadian physiology in the elderly." Thesis, University of Surrey, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441870.
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Petrone, L. "Circadian clock and light input system in the sea urchin larva." Thesis, University College London (University of London), 2016. http://discovery.ucl.ac.uk/1503707/.
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A circadian clock is an endogenous time-keeping mechanism that synchronizes several biological processes with local environment. In metazoans the circadian system is driven by a regulatory network of so called ―clock‖ genes interconnected in transcriptional-translational feedback loops that generate rhythmicity at mRNA and protein level. Sea urchin and its molecular tools can facilitate the comprehension of the evolution of the time-keeping mechanism in bilaterians. For this purpose we identified and analysed the expression of orthologous clock genes in the sea urchin larvae. Genome survey identifies almost all canonical clock genes known in protostomes and deuterostomes, with exception of period, indicating that the last common ancestor of all bilaterians already had a complex clock toolkit. Quantitative gene expression data reveal that the circadian clock begins to oscillate consistently in the free-living larva. Sp_vcry and sp_tim mRNA cycle in both light/dark (LD) and free running (DD) conditions; several other genes consistently show oscillation in LD condition only; while, neither sp_clock, nor sp_bmal have rhythmic expression. Interestingly, in-situ hybridization of key sea urchin clock genes together with cell markers (e.g. serotonin) suggest the presence of two types of light perceiving cells in the apical region of the larva: serotoninergic cells expressing sp_dcry and no-serotoninergic cells expressing sp_opsin3.2. Furthermore, functional analysis was performed to discern linkages in the regulatory network of clock genes. In larvae entrained to light/dark cycles, knockdown of sp_dcry induces arrythmicity in the expression of itself, reduction of amplitude of oscillation in sp_vcry, and reduction of amplitude of oscillation and lower levels of expression in sp_tim. Knockdown of sp_opsin3.2 reduces levels of expression of sp_hlf; and sp_vcry knockdown induces arrythmicity in sp_tim. Importantly, our study highlights differences in the architecture and gene regulation of the sea urchin larval circadian clock compared to other metazoan clocks.
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Cissé, Yasmine-marie Nirina Cisse. "Multigenerational effects of pre-conception circadian disruption by light at night." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1512163356982794.
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Evans, Jennifer Anne. "Changing the shape of circadian rhythms with light no brighter than moonlight." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3258782.
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Thesis (Ph. D.)--University of California, San Diego, 2007.<br>Title from first page of PDF file (viewed June 8, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 169-188).
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Edelstein, Kim. "The role of the intergeniculate leaflet in the circadian response to light." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0002/NQ39623.pdf.
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Flynn-Evans, Erin E. "Light perception, circadian rhythm disorders and breast cancer risk in blind women." Thesis, University of Surrey, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520563.
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Krupa, Susanne. "Is the nap zone controlled by a light-sensitive circadian arousal process?" Thesis, University of Ottawa (Canada), 2003. http://hdl.handle.net/10393/29056.
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This study attempts to identify the mechanism of the so-called afternoon nap zone. More specifically, it investigates a recent proposal that the afternoon nap zone represents the point in time after morning awakening when process-S has increased to a sufficiently high level to facilitate sleep onset, while at the same time an SCN-controlled circadian arousal process has not yet risen high enough to reverse this increased sleepiness.
Eight normal male subjects aged 20--30 years, were monitored on two separate occasions under low ambient light (150 lux). Night sleep hours were maintained at 23:00--06:00h. PSG monitoring included EEG (C3-A2, O2-A1), right EOG-M1, left EOG-M2, submental EMG and core body temperature recorded continuously by a combination of the Oxford Medilog 9000 8-channel ambulatory recorder and the Minilogger temperature monitoring system. Following a baseline 24-hour day, bright light stimulation (10,000 lux) was given on two consecutive days either in the evening (20:00--22:00h) or morning (06:00--08:00h) in counter-balanced fashion with a 30 day washout periods between. Other than during a period of bright light stimulation, the level of daytime arousal was assessed every 60 min by quantified EEG spectral power followed by a 10 min duration simple reaction time test.
In the baseline condition both the performance and Q-EEG variables confirmed the presence of a transitory afternoon nap zone as indexed by the timing of poorest performance and of greatest spectral power in a number of Q-EEG measures. Evening bright light treatment phase delayed these nap zone measures. Conversely, morning bright light phase advanced these measures.
The finding that the timing of poorest performance and of the Q-EEG determined nap zone can be phase delayed by evening light and phase advanced by morning light supports the hypothesis tested, as well as supporting the existence of an SCN-dependent circadian arousal system in humans similar to that described by Edgar et al. (1993) in sub-human primates.
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De, Caluwe Joelle. "Modeling the plant circadian clock: a study of light, photoperiodism, and growth." Doctoral thesis, Universite Libre de Bruxelles, 2017. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/251373.
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Le travail présenté dans cette thèse consiste en la création et l'étude des propriétés d'un nouveau modèle computationnel de l'horloge circadienne végétale et de certains processus physiologiques qui en dépendent.L'horloge circadienne est un rythme endogène d'une période d'environ 24 heures que possèdent la plupart des êtres vivants. Il est généré au niveau moléculaire par des boucles de rétroaction transcriptionnelles, traductionnelles et/ou post-traductionnelles. L'horloge permet aux organismes de s'a- dapter à leur environnement. L'horloge des plantes se distingue par un nombre important de composants (gènes et protéines) dont la majorité sont régulés par la lumière.Dans un premier temps, un nouveau modèle computationnel qui combine une structure complexe et hautement interconnectée avec un nombre réduit d'équations et de paramètres est construit. Ce modèle reproduit correctement les profils d'expression des gènes de l'horloge du type sauvage ainsi que les altérations provoquées par une perte de fonction de chacun de ces gènes. Plusieurs extensions modélisant des processus physiologiques dépendant de l'horloge, à savoir la croissance de l'hypocotyle et la régulation de la floraison, sont également testées.Ensuite, la réponse particulièrement complexe de l'horloge végétale à la lumière est explorée en détail afin de déterminer l'utilité de multiples récepteurs lumineux. Pour ce faire, l'entraînement de l'oscillateur par des cycles jour-nuit de durée différente de 24 heures est mesuré et les différents comportements observés (entraînement périodique, quasipériodicité, chaos) sont caractérisés. Les simulations suggèrent que les multiples senseurs lumineux permettent d'allier une grande flexibilité et une résistance aux effets des fluctuations rapides de luminosité, améliorant ainsi l'adaptation des plantes à l'environnement.Enfin, plusieurs hypothèses permettant de rendre compte des différences observées entre l'horloge des racines et celle des feuilles sont explorées, et différents mécanismes de synchronisation entre ces deux oscillateurs sont testés.<br>The circadian clock is an endogenous timekeeper with a period of around 24 hours, found in most living beings, which helps organisms adapt to their environment by anticipating daily and seasonal variations. It originates at the molecular level, from transcriptional-translational feedback loops between a small number of genes.In this thesis, a computational model of the plant circadian oscillator is built based on current knowledge of the underlying genetic network. This network is highly complex and interconnected, but the new model needs only a small number of equations and parameters to accurately predict the expression profiles of the main clock genes in various light conditions, as well as the defects associated with a loss of function in those genes. Clock-regulated processes such as hypocotyl growth and flowering are also reproduced with good accuracy. One of the particularities of the plant clock is a large number of light-sensitive components. A study of the role of those multiple light sensors on the entrainment properties of the clock is presented. It uses the newly built model to subject the clock to a very large range of conditions and generate theoretical light-insensitive mutants. The combination of an intricate oscillator and a multiplicity of light sensors makes the plant clock highly flexible, able to adapt to a wide range of conditions but resistant to the disrupting effects of random fluctuations.Preliminary steps towards a more realistic depiction of the plant clock as multiple interacting oscillators are taken. These include modeling a heterogeneous population by changing parameter values, modifying the model to account for known differences between the clocks of the roots and shoots, and testing possible synchronizing mechanisms between those two organs.<br>Doctorat en Sciences<br>info:eu-repo/semantics/nonPublished
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Amicarelli, Mario Joseph. "THE EFFECTS OF ORAL COCAINE ON THE CIRCADIAN TIMING SYSTEM." Kent State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=kent1406227527.
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Leary, Dagmar Hajkova. "CIRCADIAN PROTEOME CHANGES IN PHOTORECEPTOR OUTER SEGMENTS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1264276011.
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Landry, Glenn J. "Differential effects of constant light on circadian clock resetting by photic and nonphotic stimuli in Syrian hamsters /." Burnaby B.C. : Simon Fraser University, 2006. http://ir.lib.sfu.ca/handle/1892/2623.
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Busza, Ania. "Molecular and Behavioral Analysis of Drosophila Circadian Photoreception and Circadian Thermoreception: A Dissertation." eScholarship@UMMS, 2007. https://escholarship.umassmed.edu/gsbs_diss/343.
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Circadian clocks are biological timekeepers that help maintain an organism’s behavior and physiological state optimally timed to the Earth’s day/night cycle. To do this, these internal pacemakers must accurately keep track of time. Equally importantly, they must be able to adjust their oscillations in response to external time cues to remain properly synchronized with the environment, and correctly anticipate environmental changes. When the internal clock is offset from its surrounding day/night cycle, clinically relevant disruptions develop, ranging from inconveniences such as jet-lag to more severe problems such as sleep disorders or mood disorders. In this work, I have used the fruit fly, Drosophila melanogaster, as a model organism to investigate how light and temperature can synchronize circadian systems.
My initial studies centered on an intracellular photoreceptor, CRYPTOCHROME (CRY). CRY is a blue light photoreceptor previously identified as a major component of the primary light-input pathway into the Drosophila circadian clock. We used molecular techniques to show that after light-activation, CRY binds to the key circadian molecule TIMELESS (TIM). This interaction irreversibly targets TIM, but not CRY, for degradation. Further studies characterizing a newly isolated cry mutant, crym, showed that the carboxyl-terminus of CRY is not necessary for CRY’s ability to impart photic information to the molecular clock. Instead, the C-terminus appears to be necessary for normal CRY stability and protein-protein interactions. Thus, we conclude that in contrast to previous reports on CRYs of other species, where the C-terminal domain was required for transduction of photic information, the C-terminus of DrosophilaCRY has a purely modulatory function.
During the second part of my dissertation work, I focused my studies on circadian thermoreception. While the effects of light in synchronization of the Drosophilaclock to environmental cycles have been extensively characterized, significantly less is known about temperature input pathways into the circadian pacemaker. I have used two approaches to look at how temperature affects the circadian system. First, I conducted a series of behavioral analyses looking at how locomotor rhythms can be phase-shifted in response to temperature cycles. By examining the behavior of genetically ablated flies, we determined that the well-characterized neurons controlling morning and evening surges of activity during light/dark cycles are also implicated in morning and evening behaviors under temperature cycles. However, we also find evidence of cells that contribute to modulating afternoon and evening behavior specifically under temperature cycles. These data contribute to a growing number of studies in the field suggesting that pacemaker cells may play different roles under various environmental conditions. Additionally, we provide data showing that intercellular communication plays an important role in regulating circadian response to temperature cycles. When the morning oscillator is absent or attenuated, the evening cells respond abnormally quickly to temperature cycles. My work thus provides information on the roles of different cell groups during temperature cycles, and suggests that beyond simply synchronizing individual oscillating cells, intercellular network activity may also have a role in modulating proper response to environmental time cues.
Finally, I present some preliminary work looking at effects of temperature on known circadian molecules. Using a combination of in vivo and cell culture techniques, I have found that TIM protein levels decrease at higher temperatures. My cell culture data suggest that this is a proteasome-independent degradation event. As TIM is also a key molecule in the light-input pathway, the stability of TIM proteins may be a key point of integration for light and temperature input pathways. While additional research needs to be conducted to confirm these effects in vivoin wild-type flies, these preliminary results identify a possible avenue for further study.
Taken together, my work has contributed new data on both molecular and neuronal substrates involved in processing light and temperature inputs into the Drosophila circadian clock.
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Quiles, Caroline Luísa. "Iluminação artificial : efeito do fotoperíodo e do espectro de cor sobre os ritmos biológicos e metabolismo." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/163577.
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Objetivo: Avaliar a influencia da iluminação artificial nos ritmos biológicos e metabolismo por meio de dois experimentos em ratos Wistar. O primeiro avalia mudanças de fotoperíodo que mimetizem a sazonalidade; o segundo, a qualidade da iluminação artificial (espectro de cor) no ciclo claro/escuro (LD). Métodos: Experimento1 - Três grupos de animais: Controle (CL; n=6, ciclo LD de 12/12); grupo que inicia com fotoperíodo longo (LP/SP; n=7; LD 16.5:7.5); grupo que inicia com fotoperíodo curto (SP/LP; n=7; LD 7.5:16.5). Os grupos experimentais passaram por 18 dias no fotoperíodo inicial, 17 dias de redução ou aumento gradual do fotoperíodo, 18 dias no fotoperíodo inverso ao que iniciou. Experimento 2 - 36 animais foram mantidos 108 dias em ciclo LD 16:8h, divididos em 2 grupos: Standard Light (SL; n=18), mantidos sob iluminação com espectro de cor padrão (LED, 4000K); e Circadian Light (CL; n=18) com alterações de espectro de cor ao longo do dia (LED, 2700-6500K). Em ambos os estudos, níveis de atividade e temperatura, além de melatonina e corticosterona sérica, foram mensurados. No Experimento 2, além das pesagens semanais, após eutanásia a gordura visceral foi medida. Os parâmetros circadianos foram obtidos por meio da análise de séries temporais. Na análise estatística foram usados os testes paramétricos ou não paramétricos, de acordo com a normalidade dos dados. Resultados: A quantidade de atividade noturna, além dos níveis de corticosterona foram menores no grupo SP/LP (p<0.05). Portanto, os animais demonstraram pior adaptação dos ritmos à transição do fotoperíodo de dia curto para longo (SP/LP). A qualidade de iluminação também influenciou o comportamento animal. O grupo CL apresentou melhores parâmetros rítmicos que o grupo SL, por exemplo, menor intracyclevariability, maior amplitude e quantidade de atividade (p<0.05). Apesar de o peso corporal ter sido similar, o grupo SL apresentou maior quantidade de gordura visceral (p<0.05). Parâmetros rítmicos de atividade correlacionaram com a concentração de melatonina somente no grupo CL, enquanto que parâmetros rítmicos correlacionaram com a concentração de corticosterona principalmente no grupo SL. Conclusões: Nosso estudo reforça a relevância da iluminação como um fator importante na regulação do comportamento e metabolismo, sugerindo que o a iluminação artificial comumente utilizada, sem variação de espectro de cor, é um forte fator facilitador do processo de cronodisrupção e aumento de gordura visceral. Ainda, o sistema de iluminação utilizado frequentemente nos alojamentos experimentais podem ser subótimas para simular o ambiente natural. Apoio: FIPE/HCPA, CNPq, CAPES e Luxion Iluminação.<br>Objective:To evaluate the influence of artificial illumination on biological rhythms and metabolism by two experiments whit Wistar rats. The first one evaluated changes in photoperiod that mimetics seasonality; the second one, the quality of artificial light (color spectrum) on light/dark cycle (LD). Methods: Experiment 1 – Three animal groups: Control (CL; n=6, LD cycle 12/12); group that started with long photoperiod (LP/SP; n = 7; LD 16.5:7.5); group that started with short photoperiod (SP/LP; n=7; LD 7.5:16.5). Experimental groups passed for 18 day in a start photoperiod, 17 days of gradual increase or decrease of photoperiod, 18 days on inverse photoperiod to what start.Experiment 2 – 36 animals were kept for 108 days in a LD cycle of 16:8h, divided in 2 groups: Standard Light (SL; n=18), kept under illumination with standard color spectrum (LED, 4000K); and Circadian Light (CL; n=18) with changes of color spectrum during the day (LED, 2700-6500K). In both studies, activity and temperature levels, as well as serum melatonin and corticosterone, were measured. On Experiment 2, in addition to weekly weighing, after euthanasia the visceral fat was measures. The circadian parameters were obtained by temporal series analyses. In statistical analyses were used parametric or non-parametric tests, according the normality of data. Results:Amount of activity on dark, besides corticosterone levels were lower on SL/LP group (p<0.05). So, animals showed low rhythms adaptation to photoperiod transitions from short to long light (SL/LP). The quality of illumination also influenced in animal behavior. The CL group presented better rhythmic parameters than SL group, for example, low intracycle variability, high amplitude and quantity of activity (p<0.05). Although body weight was similar, SL group presented higher amount of visceral fat (p<0.05). Rhythmic parameters of activity correlated with the melatonin concentration just in CL group, whereas rhythmic parameters correlated whit corticosterone concentration principally in SL group. Conclusions: Our study reinforces the relevance of illumination as an important factor on metabolic and behavioral regulation, suggesting that artificial illumination commonly used, without color spectrum variation, is a strong facilitating factor on the process of chronodisruption and increase of visceral fat. Thus, the illumination system frequently used in experimental accommodation could be suboptimal for to simulate the natural environment. Support:FIPE/HCPA, CNPq, CAPES andLuxionIluminação.
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Vijayakumar, Sarath Ding Jian. "The role of mediators of neuronal plasticity in the circadian regulation of suprachiasmatic nucleus by light." [Greenville, N.C.] : East Carolina University, 2009. http://hdl.handle.net/10342/2215.
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Thesis (Ph.D.)--East Carolina University, 2009.<br>Presented to the faculty of the Department of Physiology. Advisor: Jian Ding. Title from PDF t.p. (viewed June 12, 2010). Includes bibliographical references.
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James, Francine O. "Circadian adaptation to full-time night shift work with bright light intervention regimen." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=31243.
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The primary consequence of night shift work is a misalignment of the endogenous circadian pacemaker with the inverted sleep-wake cycle. This study evaluated the efficacy of a judicious schedule of light exposure on circadian adaptation to night work. Fifteen night shift workers (mean age +/-S.E.M.: 41.8 +/- 1.8 years) were studied for 3 weeks in their work environments under one of two experimental conditions. Treatment group participants underwent an intervention including bright light in the workplace, while control group participants were studied in their habitual light environments. The efficacy of the intervention was evaluated in the laboratory via constant routines. Following the intervention, treatment group subjects displayed a mean phase delay of (+/-S.E.M.) -9.32 +/- 1.06 hours and full entrainment to the night-oriented schedule while control group subjects displayed a phase delay -4.09 +/- 1.94 hours and a partial entrainment (F(1,30) = 11.33, p = 0.002). The results of this study suggest a means of alleviating the difficulties associated with night shift work with control of the overall pattern of light exposure.
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Adewoye, Adeolu Badi. "Genetic architecture and molecular mechanisms underlying light entrainment of the Drosophila circadian clock." Thesis, University of Leicester, 2011. http://hdl.handle.net/2381/10229.
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Despite significant progress in the understanding of how the circadian clock is entrained by light, the genetic architecture and molecular basis of this process are still largely unknown. This study was undertaken to identify biological pathways underlying light entrainment in Drosophila melanogaster. Complementary approaches that combined quantitative trait loci (QTL) mapping, complementation tests, and genome-wide gene expression profiling were used. One hundred and twenty-three recombinant inbred lines (RIL) were assayed for circadian photosensitivity. Composite interval mapping identified a single significant QTL. Quantitative deficiency complementation test refined this QTL interval into two smaller QTLs consisting of 140 candidate genes. Complementation tests with null mutant strains suggested segregating alleles of timeless and cycle may contribute to the variation in light response. In addition, two genes CG9879 and Lilliputian located within the QTL showed a significant differential expression in two RIL that were analysed by microarrays. Interestingly, Lilliputian interacts with several genes such as Shaggy and nejire which have been previously implicated in the circadian clock. Global profiling of gene expression following a light pulse at ZT15 revealed 209 differentially expressed genes in a laboratory strain (Canton-S). These genes are involved in several biological processes, however genes related to signal transduction, gene regulation, glutamate receptor activity, cellular communication and chromatin remodelling were statistically over-represented. RNA interference mediated knockdown further supported the role of these genes in the light response. Notable among these genes were nrv1, Neurofibromin 1, still life and Thor. In addition, the microarray experiments indicated that histone modifications may also play an important role in light entrainment of the clock. Consistently, an aberrant light response was found in various mutants and transgenic strains in which histone acetylation, de-acetylation, and methylation (of DNA and histones) are defective.
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Covington, Michael Fulton. "ELF3 and the light resetting mechanism of the circadian clock in Arabidopsis thaliana /." view abstract or download file of text, 2002. http://wwwlib.umi.com/cr/uoregon/fullcit?p3061940.
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Thapan, Kavita. "The spectral sensitivity of light-induced melatonin suppression in humans." Thesis, University of Surrey, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365184.
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Caddas, Andrew. "Blue Light and Adult Sleep Outcomes." Otterbein University Distinction Theses / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=otbndist1620462993096741.
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Hölbling, Markus. "A HUG OF LIGHT." Thesis, KTH, Ljusdesign, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-297945.
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This project is an elaboration of how luminaire design can provide for fundamental human needs. Visual needs in terms of task performance, orientability and visual comfort; emotional needs in terms of soothing feelings of safeness and cosiness; and biological needs in terms of circadian rhythm and resetting of our biological clock in the morning. These needs are tested through three bedroom scenarios named focus, contemplation and dawn, each with their own demands and desires on lighting qualities. I have submerged into desired lighting qualities and atmosphere in a bedroom context; into how circadian rhythm can be promoted through lighting design; into how the perception of space can be effected through light; into how responsible use of natural resources can be achieved; and finally into what the impact and consequences of the design intervention are. The investigation is performed in a generic bedroom situation without daylight considerations. A prototype has been produced in order to perform observations and measurements. Through the investigation I can state that luminaire design is able to provide for visual, emotional and biological needs. By simultaneously working with light qualities and shape of the luminaire, and having formulated the specific scenarios focus, contemplation and dawn, qualitative observations and experience could be supplemented by quantitative measurements and drive the design process forward towards intended lighting effects, characteristics and impacts on the human body and mind.
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Beauchemin, Kathleen Mary. "Nocturnal psychopathology : sleep, dreaming, mood and light-therapy in bipolar disorder /." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq22949.pdf.
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Tseng, Yu-Yao. "Systems biology of the Neurospora circadian clock and its response to light and temperature." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/systems-biology-of-the-neurospora-circadian-clock-and-its-response-to-light-and-temperature(4680ee43-3f65-4398-bc79-bac70d463e58).html.
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Circadian clocks are internal timekeepers that aid survival by allowing organisms, from photosynthetic cyanobacteria to humans, to anticipate predictable daily changes in the environment and make appropriate adjustments to their cellular biochemistry and behaviour. Whilst many of the molecular cogs and gears of circadian clocks are known, the complex interactions of clock components in time and space that generate a reliable internal measure of external time are still under investigation. Computational modelling has aided our understanding of the molecular mechanisms of circadian clocks, nevertheless it remains a major challenge to integrate the large number of clock components and their interactions into a single, comprehensive model that is able to account for the full breadth of clock properties. An important property of circadian clocks is their ability to maintain a constant period over a range of temperatures. Temperature compensation of circadian period is the least understood characteristic of circadian clocks. To investigate possible mechanisms underlying temperature compensation, I first constructed a comprehensive dynamic model of the Neurospora crassa circadian clock that incorporates its key components and their transcriptional and post-transcriptional regulation. The model is based on a compilation of published and new experimental data and incorporates facets of previously described Neurospora clock models. Light components were also incorporated into the model to test it and to reproduce our knowledge of light response of the clock. Also, experiments were carried out to investigate the unknown mechanisms of light response, such as the molecular mechanisms supporting the correct timing of conidiation after light to dark transfer. The model accounts for a wide range of clock characteristics including: a periodicity of 21.6 hours, persistent oscillation in constant conditions, resetting by brief light pulses, and entrainment to full photoperiods. Next, I carried out robustness tests and response coefficient analysis to identify components that strongly influence the period and amplitude of the molecular oscillations. These data measure the influence of the parameters in the model and were beneficial for making and testing predictions in the model. Thermodynamic properties were then introduced into reactions that experimental observations suggested might be temperature sensitive. This analysis indicated that temperature compensation can be achieved if nuclear localisation of a key clock component, FRQ, decreases with increasing temperature. Experiments have been carried out to validate this hypothesis and simulations were made to explore other possible mechanisms. However, from my experimental data and modelling results, the restriction of FRQ nuclear localisation might not be the only mechanism required to achieve temperature compensation. In conclusion, temperature compensation is most likely a complex property and may involve a combination of multiple mechanisms regulating clock component activity over a range of temperatures.
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Mouland, Josh. "The effect of spatially patterned light on the suprachiasmatic nucleus." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/the-effect-of-spatially-patterned-light-on-the-suprachiasmatic-nucleus(de2b1fff-2058-497e-948a-cc3811ffa39d).html.
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The daily variation in background light intensity (irradiance) can entrain the endogenous clock in the suprachiasmatic nucleus (SCN) to the external environment. The only source of this photic information in mammals is the eye, which is primarily a visual organ. It is therefore highly specialised to detect high frequency spatiotemporal modulations. This together with the adaptation which occurs within the retina could be present difficulties when encoding global irradiance. This raises the question of whether spatial patterns, which are present in our everyday viewing, might affect the ability of the SCN to receive 'true irradiance' signals and entrain to the external environment. My first approach was to determine whether individual SCN cells might receive a 'true irradiance' signal. To this end I mapped and characterised the receptive field properties of SCN neurons using in vivo electrophysiology. Indeed a handful of neurons (full field cells) responded to light anywhere in the visual scene and thus may act as 'irradiance detectors'. However, the vast majority of cells only sampled local radiance from a limited area of the visual scene. Having mapped the receptive field properties it became clear that cells which sampled from a limited area of the visual scene would be sensitive to spatial contrast (patterns). To examine the effect of spatiotemporal contrast on the SCN I examined two SCN outputs: locomotor activity and neuronal firing rates. Although spatiotemporal modulation in light intensity could induce large amplitude oscillations in neuronal activity; the time averaged firing rate and locomotor activity, which are believed to be determined by irradiance, were largely unaffected by spatial patterns. This led to the conclusion that the SCN can multiplex photic information into information regarding irradiance, and spatial information by encoding them under different timescales. Melanopsin has been heralded as the key photopigment for encoding irradiance and entraining the SCN. However such experiments have been only performed using diffuse light stimuli. Here I investigated the role of melanopsin under natural viewing conditions which incorporated spatial patterns. Under such stimuli the SCN response can be almost entirely accounted for by the melanopic irradiance of the stimuli.
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Sassi, Loretta Natasha. "The effect of light applied to the skin on melatonin, circadian phase and sleep /." Title page, contents and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09AR.PS/09ar.pss252.pdf.
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Thind, Raja Mandeep Singh. "BRIEF CONSTANT LIGHT ACCELERATION OF NONPHOTIC CIRCADIAN PHASE SHIFTING AND REENTRAINMENT OF LD CYCLE." Kent State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=kent1270764667.
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Hofer, Sabine. "The circadian system of the cockroach Leucophaea maderae role of the neuropeptide orcokinin and light entrainment = (Das circadiane System der Schabe Leucophaea maderae) /." [S.l. : s.n.], 2004. http://archiv.ub.uni-marburg.de/diss/z2004/0634/.
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Sayer, Tamsin. "Variation in central serotoninergic 5-HT1B function through the light-dark cycle : effect of chronic antidepressant treatment." Thesis, University of Bath, 1994. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239953.
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Alejevski, Faredin. "Photoentrainment of the Drosophila circadian clock through visual system." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS200.
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La rotation de la Terre oblige les organismes vivants à s’adapter aux modifications cycliques de l’environnement, et tout particulièrement aux changements de lumière et de température. Des unicellulaires à l’Homme, la plupart des espèces ont développé des horloges circadiennes, qui leur permettent d’anticiper les transitions jour-nuit. La lumière constitue le signal majeur pour la synchronisation de l’horloge. En cycles jour-nuit, les drosophiles présentent un profil d’activité locomotrice bimodal, avec un premier pic autour de l’aube et le deuxième au crépuscule. Chez cet insecte, la perception de la lumière est assurée à la fois par un système complexe, constitué des yeux composés, des ocelles et de l’eyelet d’Hofbauer-Buchner. Ces organes contiennent des photorécepteurs (PRs) exprimant six protéines photosensibles différentes, les rhodopsines (Rh1 à Rh6). Une septième rhodopsine (Rh7) a été décrite dans quelques neurones de l’horloge cérébrale. La lumière est également perçue directement dans la plupart des neurones d’horloge grâce à une protéine photosensible, le cryptochrome (Cry). Les différentes études du rôle de la lumière sur l’entraînement de l’horloge ont essentiellement porté sur la voie cry-dépendante, en utilisant de courts flashs lumineux pour recaler l’horloge cérébrale. Notre étude s’est intéressée à l’entraînement de l’horloge via les rhodopsines. Quels types de photorécepteur sont impliqués ? Après l’activation de la cascade de phototransduction et la libération de l’histamine par les photorécepteurs, quels neurones, exprimant les récepteurs à l’histamine Ort et Hiscl1, participent à l’entraînement de l’horloge circadienne ? Une première partie présente l’étude de l’implication des 6 rhodopsines dans l’entraînement circadien. Tout d’abord, nous avons mis en évidence la fonction de photorécepteurs spécifiques (exprimant Rh1 ou Rh6) dans la voie NorpA-dépendante (Saint-Charles et al. J Comp Neurol 2016). Nous avons ensuite généré des lignées de drosophiles n’exprimant aucune ou qu’une seule rhodopsine. Sans rhodopsine ni Cry les mouches sont incapables de se synchroniser sur les cycles jour-nuit, quelle que soit l’intensité lumineuse. En lumière faible, l’input pour l’entraînement vient principalement des photorécepteurs exprimant Rh1 et Rh6. En forte lumière, chacune des 6 rhodopsines des différents photorécepteurs est capable d’entrainer l’horloge, Rh1, Rh5 et Rh6 étant les plus efficaces ( Alejevski et al., in prep). Une deuxième partie présente la caractérisation des voies neuronales connectant directement ou indirectement les PRs à l’horloge cérébrale. L’horloge circadienne de mouches mutantes, à la fois pour le cryptochrome et les 2 récepteurs à l’histamine, est « aveugle » alors que les mutantes pour Cry mais possédant l’un ou l’autre récepteur à l’histamine sont capables de se synchroniser sur les cycles de lumière. La ré-expression chez les mutants de Ort ou Hiscl1 dans les neurones d’horloge ne restaure pas l’entraînement, suggérant ainsi l’absence de connexions directes entre les PRs histaminergiques et les neurones d’horloge. Nos expériences de sauvetage comportemental mettent en évidence des connexions fonctionnelles entre certains interneurones Ort des lobes optiques et les neurones d’horloge. En revanche et de façon inattendue, nous n’observons d’entraînement circadien que lorsque nous ré-exprimons Hiscl1 dans les seuls PRs Rh6. Nos résultats révèlent que les photorécepteurs interviennent dans l’entraînement à la fois comme photorécepteurs et comme interneurones, cibles d’input histaminergique, rappelant ainsi le double rôle des cellules ganglionnaires de la rétine exprimant la mélanopsine chez les mammifères (Alejevski et al. Nat Commun, in revision)<br>The rotation of the earth forces living organisms to adapt to its cyclic environment, in particular light and temperature changes. From unicellular organisms to humans, almost all species have evolved circadian clocks, which allow them to anticipate day-night transitions and use light as the most powerful synchronizing cue. In light-dark cycles, D. melanogaster flies display a bimodal locomotor activity with peaks around dawn and dusk. To perceive light, Drosophila has evolved a complex visual system, composed of compound eyes, ocelli and Hofbauer-Buchner eyelet. These organs contain photoreceptors (PRs) expressing six different light receptors named rhodopsins (Rh1 to Rh6). In addition, one rhodopsin (Rh7) is found in some of the clock neurons in the brain. Most of the clock cells also express another type of light receptor, Cryptochrome (Cry). Most studies about clock entrainment by light have focused on the Cry-dependent light input, which allows short light pulses to reset the brain clock. The present thesis focuses on the entrainment of the brain clock through rhodopsins. In photoreceptors, rhodopsins capture photons and activate a transduction cascade, where a key player is the phospholipase C (PLC) encoded by norpA. Mutants deficient for Cry and NorpA do not synchronize at low light intensity but still entrain with high light, indicating that an unknown NorpA-independent pathway is also used by the clock. Light induces a depolarization of the PRs, which release histamine as a neurotransmitter, but their role in circadian entrainment is unknown. Which type of rhodopsine-expressing photoreceptors are implicated? After the phototransduction cascade activation and the release of histamine from the photoreceptors, which downstream neurons expressing the histamine-gated chloride channels Ort and Hiscl1 (whose function has been studied in the visual behavior) are involved in the circadian entrainment? The first part of the thesis was to study the function of the 6 PR rhodopsins in circadian entrainment. I first contributed to studying the function of the specific photoreceptors in the NorpA-dependent pathway (Saint-Charles et al. J Comp Neurol 2016). Then, we generated genotypes having either none or only one of the six PR rhodopsins. Mutants with no Cry and none of the 6 PR rhodopsins could not synchronize with light-dark (LD) cycles (low light or high light). In low light, Rh1 and Rh6 were the main light input for entrainment. In high-light, each one of the 6 PR rhodopsins can provide entrainment, with Rh1, Rh5 and Rh6 being the most efficient (Alejevski et al., in prep).The second part of the work was to identify the neuronal pathways that connect the PRs to the brain circadian clock. Flies deficient for Cry and the two histamine receptors are circadianly blind, whereas Cry mutants having either Ort or Hiscl1 are able to entrain. Thus, each one of the two receptors supports circadian entrainment. Rescuing Ort or Hiscl1 in the clock cells could not restore entrainment, indicating that there is no direct histaminergic connection between PRs and clock neurons. Our rescue experiments revealed several pathways in otic lobes that rely on Ort-expressing interneurons to entrain the clock. In contrast and unexpectedly, we observed that the expression of Hiscl1 in PRs but not in interneurons was involved in circadian entrainment. In fact, only Hiscl1 expression in Rh6 PRs mediates entrainment. Our work thus reveals Rh6-expressing PRs as both photoreceptors and histamine-receiving interneurons in the rhodopsin-dependent entrainment pathway, which recalls the role of melanopsin-expressing retinal ganglion cells in the mammalian retina (Alejevski et al. Nat Commun, in revision)
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Cao, Ruifeng. "Mammalian Target of Rapamycin Signaling and the Suprachiasmatic Circadian Clock." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1290199441.
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Nitschke, Silvia [Verfasser]. "Novel roles for cytokinin in the responses to high light and circadian stress / Silvia Nitschke." Berlin : Freie Universität Berlin, 2015. http://d-nb.info/1068810017/34.
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Nakahira, Yoichi. "Circadian Clock-Regulated Transcription of the psbD Light-Responsive Promoter (psbD LRP) in Wheat Chloroplasts." Kyoto University, 1998. http://hdl.handle.net/2433/182388.
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Kyoto University (京都大学)<br>0048<br>新制・課程博士<br>博士(人間・環境学)<br>甲第7534号<br>人博第48号<br>10||158(吉田南総合図書館)<br>新制||人||11(附属図書館)<br>UT51-98-W278<br>京都大学大学院人間・環境学研究科人間・環境学専攻<br>(主査)教授 豊島 喜則, 教授 丸山 圭蔵, 教授 竹安 邦夫, 教授 藤堂 剛<br>学位規則第4条第1項該当
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Coleman, Georgia. "Effects of postnatal light environment on the development of the mouse stress system." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/effects-of-postnatal-light-environment-on-the-development-of-the-mouse-stress-system(1cb0bdca-3aaa-4d92-879c-98131575aff2).html.
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The postnatal period is a critical time for development where external influences can help shape the long-term structure and function of the brain. Adverse experiences or stressors during the postnatal period, such as abuse or neglect, can have huge consequences on the long term function, health and susceptibility to disease. One environmental factor, whose importance is becoming increasingly more recognised for normal development, is light. Abnormal light during the first three weeks of life has been shown to have long term effects on the circadian system of rodents. On the other hand, the effects of abnormal light during the postnatal period on the stress system have yet been relatively unexplored. Therefore the aim of this thesis was to assess if altered postnatal light environment, such as that a preterm baby might be exposed to, has any long-term effects on the stress system. Mice were raised under constant light (LL), constant darkness (DD) or a normal 12:12hr light:dark cycle (LD) for the first three weeks of life from postnatal day (P)1 up until P21. From P21, all mice were then housed in LD conditions and the stress system was assessed by looking at several different levels of the HPA axis including neuropeptide expression in the brain, body and adrenal weight, and plasma corticosterone levels under both basal and stressed conditions. Learning and memory, anxiety-like behaviour and circadian output rhythms were also evaluated. Finally, mother-pup behaviour and maternal HPA axis were assessed to see if maternal care was changed by altered postnatal light. Both LL and DD rearing caused changes in the HPA axis of offspring with LL raised mice showing alterations in neuropeptide and glucocorticoid receptor expression in the brain. Postnatal DD resulted in a blunted corticosterone response to a stressor in females but had no effect in males. In terms of behaviour, LL raised mice had increased depressive-like behaviour. In contrast, postnatal light appears to have no effect on learning and memory or anxiety behaviour. When we looked at circadian output rhythms, we found that LL rearing appears to confer resilience to the rhythm disrupting effects of LL later on in life as seen by the maintenance of locomotor activity, body temperature and plasma corticosterone rhythms in LL. Maternal care and maternal stress systems appeared unaltered under the different postnatal light environments suggesting that the changes we see in the offspring are attributed to mechanisms other than alterations in maternal care.
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Svanberg, Mira. "The right light at the right time for bipolar patients. An exploratory study of light environments for patients with bipolar disease in behavioral health clinics." Thesis, KTH, Ljusdesign, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-297963.
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Research has showed that different light scenarios have a profound effect on hospitalized bipolar patients. Different light situations decrease the hospital stay for patients during both manic and depressive episodes. Nevertheless, a field study carried out during this thesis work of two arbitrary patient rooms in Swedish behavioral health clinics showed no incorporation of this knowledge in the light design of the rooms. Both patient rooms had insufficient light levels both in terms of circadian recommendations and perceived brightness. Hence this thesis suggests an improved light design for patient rooms housing bipolar patients. The basis of the improved design is to incorporate a dynamic, circadian lighting that varies depending on the patient's need and diagnosed episode.
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Gropp, Claire-Marie [Verfasser]. "Regulation of Melanopsin and PACAP mRNA by Light, Circadian and Sleep Homeostatic Processes / Claire-Marie Gropp." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2014. http://d-nb.info/1052530117/34.
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Ohnmeiss, Amanda Sara. "ANALYSIS OF LIGHT-INDUCED IMMEDIATE-EARLY GENE EXPRESSION IN THE SUPRACHIASMATIC NUCLEUS." Kent State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=kent1247680456.
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