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Foster RG. Introduction and reflections on the comparative physiology of sleep and circadian rhythms. J Comp Physiol B 2024:10.1007/s00360-024-01567-z. [PMID: 38856727 DOI: 10.1007/s00360-024-01567-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2024] [Accepted: 05/17/2024] [Indexed: 06/11/2024]
Abstract
Circadian rhythms and the sleep/wake cycle allows us, and most life on Earth, to function optimally in a dynamic world, adjusting all aspects of biology to the varied and complex demands imposed by the 24-hour rotation of the Earth upon its axis. A key element in understanding these rhythms, and the success of the field in general, has been because researchers have adopted a comparative approach. Across all taxa, fundamental questions relating to the generation and regulation of sleep and circadian rhythms have been address using biochemical, molecular, cellular, system and computer modelling techniques. Furthermore, findings have been placed into an ecological and evolutionary context. By addressing both the "How" - mechanistic, and "Why" - evolutionary questions in parallel, the field has achieved remarkable successes, including how circadian rhythms are generated and regulated by light. Yet many key questions remain. In this special issue on the Comparative Physiology of Sleep and Circadian Rhythms, celebrating the 100th anniversary of the Journal of Comparative Physiology, important new discoveries are detailed. These findings illustrate the power of comparative physiology to address novel questions and demonstrate that sleep and circadian physiology are embedded within the biological framework of an organism.
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Affiliation(s)
- Russell G Foster
- Sir Jules Thorn Sleep and Circadian Neuroscience Institute (SCNi), Nuffield Department of Clinical Neurosciences, University of Oxford, Dorothy Crowfoot Hodgkin Building, South Parks Road, Oxford, OX1 3QU, UK.
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Betti L, Palego L, Demontis GC, Miraglia F, Giannaccini G. Hydroxyindole- O-methyltransferase (HIOMT) activity in the retina of melatonin-proficient mice. Heliyon 2019; 5:e02417. [PMID: 31687544 PMCID: PMC6819757 DOI: 10.1016/j.heliyon.2019.e02417] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 07/19/2019] [Accepted: 09/02/2019] [Indexed: 01/02/2023] Open
Abstract
Numerous pieces of evidence support the expression by the mammalian retina of Hydroxyindole-O-methyltransferase (HIOMT, EC 2.1.1.4), the enzyme directly responsible for the biosynthesis of the pineal chronobiotic hormone melatonin (MLT). However, conflicting results obtained so far by enzyme-kinetic and immune-detection techniques still make HIOMT presence and relevance in the eye a matter of debate. This work aimed at evaluating unambiguously HIOMT activity in the mouse retina, a valuable model for studying the effects of MLT variations on ocular pathophysiology. Since laboratory mouse strains can bear genetic polymorphisms yielding defective enzymes of MLT biosynthesis, retinas and control pineal glands used in this study were obtained in a MLT-proficient crossing of A/J mice, the A/J/C57BL/10 strain. To improve the radiochemical reference assay, we tested different homogenization procedures coupled with HPLC detection. Concomitantly, we quantified MLT, and its precursor N-acetyl-serotonin (NAS) by HPLC coupled to electrochemical detection in retinas isolated from either light- or dark-adapted mice. Results showed that the standard radio-chemical assay was successful for pineal HIOMT only, whereas specific homogenization buffers and HPLC were required to detect retinal activity, presumably due to interfering methyl-transferases inhibited by NAS. Under present conditions, retinal HIOMT Vmax accounted for by ≈ 40 fmol/h/mg protein, 2.6-hundreds-fold lower than the pineal counterpart, displaying equivalent KMs (≈10 μM). Moreover, NAS and MLT rapidly decreased in light-exposed isolated retinas, corroborating light-sensitive in-situ MLT formation. Conclusively, we measured mouse retinal HIOMT kinetics under basal conditions, a useful result to elucidate the regulatory patterns, the possible impact on eye health, and therapeutic approaches related to this enzyme.
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Affiliation(s)
- Laura Betti
- Department of Pharmacy, Via Bonanno 6, University of Pisa, 56126 Pisa, Italy
- Corresponding author.
| | - Lionella Palego
- Department of Clinical and Experimental Medicine, Via Savi 10, University of Pisa, 56126 Pisa, Italy
- Corresponding author.
| | - Gian Carlo Demontis
- Department of Pharmacy, Via Bonanno 6, University of Pisa, 56126 Pisa, Italy
| | - Fabiana Miraglia
- Department of Pharmacy, Via Bonanno 6, University of Pisa, 56126 Pisa, Italy
| | - Gino Giannaccini
- Department of Pharmacy, Via Bonanno 6, University of Pisa, 56126 Pisa, Italy
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Wang J, Yoo HS, Obrochta KM, Huang P, Napoli JL. Quantitation of retinaldehyde in small biological samples using ultrahigh-performance liquid chromatography tandem mass spectrometry. Anal Biochem 2015; 484:162-8. [PMID: 26045160 DOI: 10.1016/j.ab.2015.05.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Accepted: 05/26/2015] [Indexed: 12/24/2022]
Abstract
We report an ultrahigh-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method to quantify all-trans-retinal in biological samples of limited size (15-35mg), which is especially advantageous for use with adipose. To facilitate recovery, retinal and the internal standard 3,4-didehydroretinal were derivatized in situ into their O-ethyloximes. UHPLC resolution combined with high sensitivity and specificity of MS/MS allowed quantification of retinal-O-ethyloximes with a 5-fmol lower limit of detection and a linear range from 5fmol to 1pmol. This assay revealed that extraocular concentrations of retinal range from approximately 2 to 40pmol/g in multiple tissues-the same range as all-trans-retinoic acid. All-trans-retinoic acid has high affinity (kd⩽0.4nM) for its nuclear receptors (RARα, -β, and -γ), whereas retinal has low (if any) affinity for these receptors, making it unlikely that these retinal concentrations would activate RAR. We also show that the copious amount of vitamin A used in chow diets increases retinal in adipose depots 2- to 5-fold relative to levels in adipose of mice fed a vitamin A-sufficient diet, as recommended for laboratory rodents. This assay also is proficient for quantifying conversion of retinol into retinal in vitro and, therefore, provides an efficient method to study metabolism of retinol in vivo and in vitro.
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Affiliation(s)
- Jinshan Wang
- Graduate Program in Metabolic Biology, Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Hong Sik Yoo
- Graduate Program in Metabolic Biology, Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Kristin M Obrochta
- Graduate Program in Metabolic Biology, Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Priscilla Huang
- Graduate Program in Metabolic Biology, Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Joseph L Napoli
- Graduate Program in Metabolic Biology, Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720, USA.
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Peirson SN, Halford S, Foster RG. The evolution of irradiance detection: melanopsin and the non-visual opsins. Philos Trans R Soc Lond B Biol Sci 2009; 364:2849-65. [PMID: 19720649 PMCID: PMC2781857 DOI: 10.1098/rstb.2009.0050] [Citation(s) in RCA: 174] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Circadian rhythms are endogenous 24 h cycles that persist in the absence of external time cues. These rhythms provide an internal representation of day length and optimize physiology and behaviour to the varying demands of the solar cycle. These clocks require daily adjustment to local time and the primary time cue (zeitgeber) used by most vertebrates is the daily change in the amount of environmental light (irradiance) at dawn and dusk, a process termed photoentrainment. Attempts to understand the photoreceptor mechanisms mediating non-image-forming responses to light, such as photoentrainment, have resulted in the discovery of a remarkable array of different photoreceptors and photopigment families, all of which appear to use a basic opsin/vitamin A-based photopigment biochemistry. In non-mammalian vertebrates, specialized photoreceptors are located within the pineal complex, deep brain and dermal melanophores. There is also strong evidence in fish and amphibians for the direct photic regulation of circadian clocks in multiple tissues. By contrast, mammals possess only ocular photoreceptors. However, in addition to the image-forming rods and cones of the retina, there exists a third photoreceptor system based on a subset of melanopsin-expressing photosensitive retinal ganglion cells (pRGCs). In this review, we discuss the range of vertebrate photoreceptors and their opsin photopigments, describe the melanopsin/pRGC system in some detail and then finally consider the molecular evolution and sensory ecology of these non-image-forming photoreceptor systems.
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Affiliation(s)
- Stuart N Peirson
- Nuffield Laboratory of Ophthalmology, University of Oxford, The John Radcliffe Hospital, Headley Way, Headington, Oxford OX3 9DU, UK
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Morin LP, Allen CN. The circadian visual system, 2005. ACTA ACUST UNITED AC 2006; 51:1-60. [PMID: 16337005 DOI: 10.1016/j.brainresrev.2005.08.003] [Citation(s) in RCA: 306] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2005] [Revised: 07/19/2005] [Accepted: 08/09/2005] [Indexed: 11/17/2022]
Abstract
The primary mammalian circadian clock resides in the suprachiasmatic nucleus (SCN), a recipient of dense retinohypothalamic innervation. In its most basic form, the circadian rhythm system is part of the greater visual system. A secondary component of the circadian visual system is the retinorecipient intergeniculate leaflet (IGL) which has connections to many parts of the brain, including efferents converging on targets of the SCN. The IGL also provides a major input to the SCN, with a third major SCN afferent projection arriving from the median raphe nucleus. The last decade has seen a blossoming of research into the anatomy and function of the visual, geniculohypothalamic and midbrain serotonergic systems modulating circadian rhythmicity in a variety of species. There has also been a substantial and simultaneous elaboration of knowledge about the intrinsic structure of the SCN. Many of the developments have been driven by molecular biological investigation of the circadian clock and the molecular tools are enabling novel understanding of regional function within the SCN. The present discussion is an extension of the material covered by the 1994 review, "The Circadian Visual System."
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Affiliation(s)
- L P Morin
- Department of Psychiatry and Graduate Program in Neuroscience, Stony Brook University, Stony Brook, NY 11794, USA.
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Tefsen B, Geurtsen J, Beckers F, Tommassen J, de Cock H. Lipopolysaccharide Transport to the Bacterial Outer Membrane in Spheroplasts. J Biol Chem 2005; 280:4504-9. [PMID: 15576375 DOI: 10.1074/jbc.m409259200] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mechanism of lipopolysaccharide (LPS) transport in Gram-negative bacteria from the inner membrane to the outer membrane is largely unknown. Here, we investigated the possibility that LPS transport proceeds via a soluble intermediate associated with a periplasmic chaperone analogous to the Lol-dependent transport mechanism of lipoproteins. Whereas newly synthesized lipoproteins could be released from spheroplasts of Escherichia coli upon addition of a periplasmic extract containing LolA, de novo synthesized LPS was not released. We demonstrate that LPS synthesized de novo in spheroplasts co-fractionated with the outer membranes and that this co-fractionation was dependent on the presence in the spheroplasts of a functional MsbA protein, the protein responsible for the flip-flop of LPS across the inner membrane. The outer membrane localization of the LPS was confirmed by its modification by the outer membrane enzyme CrcA (PagP). We conclude that a substantial amount of LPS was translocated to the outer membrane in spheroplasts, suggesting that transport proceeds via contact sites between the two membranes. In contrast to LPS, de novo synthesized phospholipids were not transported to the outer membrane in spheroplasts. Apparently, LPS and phospholipids have different requirements for their transport to the outer membrane.
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Affiliation(s)
- Boris Tefsen
- Department of Molecular Microbiology and Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
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Ghosh S, Salvador-Silva M, Coca-Prados M. The bovine iris-ciliary epithelium expresses components of rod phototransduction. Neurosci Lett 2005; 370:7-12. [PMID: 15489008 DOI: 10.1016/j.neulet.2004.07.026] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2004] [Revised: 07/12/2004] [Accepted: 07/14/2004] [Indexed: 10/26/2022]
Abstract
Earlier studies have documented that the iris in lower vertebrates is photosensitive. In the present work, we examined whether the bovine iris which exhibits a common embryonic origin with the ocular ciliary epithelium and the neural retina, expresses components of phototransduction. By Northern blot and RT-PCR amplification we detected in the iris, rhodopsin, rhodopsin kinase and arrestin transcripts and DNA products, respectively, of the same size as in the retina. By Western blot, antibodies to rhodopsin, rhodopsin kinase and arrestin detected low levels of protein with similar molecular masses as in the retina. Transient transfections of bovine iris cells in vitro with rhodopsin promoter-luciferase-reporter constructs (p130-Luc, p176-Luc, 1225-Luc and p2000-Luc) containing proximal and distal promoter elements led to a significant stimulation of promoter activity over the basal activity. In particular, the construct p225-Luc containing proximal promoter elements upstream of the transcription start site (-225 to +70 bp) led to 3.1-fold stimulation of activity over p176-Luc, 2.1-fold over p130 or p2000-Luc and 190-fold over the basal activity. These results suggested that the bovine iris cells contain factors that could either stimulate or attenuate rhodopsin transcription. The data also supported the view that components associated with non-visual phototransduction are expressed in extraretinal sites including the ciliary epithelium and the iris.
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Affiliation(s)
- Sikha Ghosh
- Department of Ophthalmology and Visual Science, Yale University School of Medicine, 330 Cedar St., New Haven, CT 06510, USA
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Peirson SN, Thompson S, Hankins MW, Foster RG. Mammalian photoentrainment: results, methods, and approaches. Methods Enzymol 2005; 393:697-726. [PMID: 15817320 DOI: 10.1016/s0076-6879(05)93037-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Research on circadian biology over the past decade has paid increasing attention to the photoreceptor mechanisms that align the molecular clock to the 24-h light/dark cycle, and some of the results to emerge are surprising. For example, the rods and cones within the mammalian eye are not required for entrainment. A population of directly light-sensitive ganglion cells exists within the retina and acts as brightness detectors. This article provides a brief history of the discovery of these novel ocular photoreceptors and then describes the methods that have been used to study the photopigments mediating these responses to light. Photopigment characterization has traditionally been based on a number of complementary approaches, but one of the most useful techniques has been action spectroscopy. A photopigment has a discrete absorbance spectrum, which describes the probability of photons being absorbed as a function of wavelength, and the magnitude of any light-dependent response depends on the number of photons absorbed by the photopigment. Thus, a description of the spectral sensitivity profile (action spectrum) of any light-dependent response must, by necessity, match absorbance spectra of the photopigment mediating the response. We provide a step-by-step approach to conducting action spectra, including the construction of irradiance response curves, the calculation of relative spectral sensitivities, and photopigment template fitting, and discuss the underlying assumptions behind this approach. We then illustrate action spectrum methodologies by an in-depth analysis of action spectra obtained from rodless/coneless (rd/rd cl) mice and discuss, for the first time, the full implications of these findings.
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Affiliation(s)
- Stuart N Peirson
- Department of Visual Neuroscience, Imperial College, Charing Cross Hospital, London W6 8RF, United Kingdom
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Ekström P, Meissl H. Evolution of photosensory pineal organs in new light: the fate of neuroendocrine photoreceptors. Philos Trans R Soc Lond B Biol Sci 2004; 358:1679-700. [PMID: 14561326 PMCID: PMC1693265 DOI: 10.1098/rstb.2003.1303] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Pineal evolution is envisaged as a gradual transformation of pinealocytes (a gradual regression of pinealocyte sensory capacity within a particular cell line), the so-called sensory cell line of the pineal organ. In most non-mammals the pineal organ is a directly photosensory organ, while the pineal organ of mammals (epiphysis cerebri) is a non-sensory neuroendocrine organ under photoperiod control. The phylogenetic transformation of the pineal organ is reflected in the morphology and physiology of the main parenchymal cell type, the pinealocyte. In anamniotes, pinealocytes with retinal cone photoreceptor-like characteristics predominate, whereas in sauropsids so-called rudimentary photoreceptors predominate. These have well-developed secretory characteristics, and have been interpreted as intermediaries between the anamniote pineal photoreceptors and the mammalian non-sensory pinealocytes. We have re-examined the original studies on which the gradual transformation hypothesis of pineal evolution is based, and found that the evidence for this model of pineal evolution is ambiguous. In the light of recent advances in the understanding of neural development mechanisms, we propose a new hypothesis of pineal evolution, in which the old notion 'gradual regression within the sensory cell line' should be replaced with 'changes in fate restriction within the neural lineage of the pineal field'.
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Affiliation(s)
- Peter Ekström
- Institute of Cell and Organism Biology, Zoology Building, Lund University, Helgonavägen 3, S-223 62 Lund, Sweden.
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