scholarly journals Biochemistry and physiology of zebrafish photoreceptors

2021 ◽  
Author(s):  
Jingjing Zang ◽  
Stephan C. F. Neuhauss
Keyword(s):  
Synaptic Transmission ◽  
Danio Rerio ◽  
Light Stimulus ◽  
Bright Light ◽  
Model System ◽  
Light Conditions ◽  
Outer Retina ◽  
Visual Transduction ◽  
Rods And Cones ◽  
Biological Signal

AbstractAll vertebrates share a canonical retina with light-sensitive photoreceptors in the outer retina. These photoreceptors are of two kinds: rods and cones, adapted to low and bright light conditions, respectively. They both show a peculiar morphology, with long outer segments, comprised of ordered stacks of disc-shaped membranes. These discs host numerous proteins, many of which contribute to the visual transduction cascade. This pathway converts the light stimulus into a biological signal, ultimately modulating synaptic transmission. Recently, the zebrafish (Danio rerio) has gained popularity for studying the function of vertebrate photoreceptors. In this review, we introduce this model system and its contribution to our understanding of photoreception with a focus on the cone visual transduction cascade.

scholarly journals Fundamentals of circadian entrainment by light

2021 ◽  
Vol 53 (5) ◽  
pp. 377-393
Author(s):  
RG Foster
Keyword(s):  
Ganglion Cells ◽  
Light Exposure ◽  
Bright Light ◽  
Evidence Based ◽  
Retinal Ganglion ◽  
Rods And Cones ◽  
Long Duration ◽  
Lighting Systems ◽  
Short Wavelength Light ◽  
Wavelength Light

Light at dawn and dusk is the key signal for the entrainment of the circadian clock. Light at dusk delays the clock. Light at dawn advances the clock. The threshold for human entrainment requires relatively bright light for a long duration, but the precise irradiance/duration relationships for photoentrainment have yet to be fully defined. Photoentrainment is achieved by a network of photosensitive retinal ganglion cells (pRGCs) which utilise the short-wavelength light-sensitive photopigment, melanopsin. Although rods and cones are not required, they do play a role in photoentrainment, by projecting to and modulating the endogenous photosensitivity of the pRGCs, but in a manner that remains poorly understood. It is also important to emphasise that the age and prior light exposure of an individual will modify the efficacy of entrainment stimuli. Because of the complexity of photoreceptor interactions, attempts to develop evidence-based human centric lighting are not straightforward. We need to study how humans respond to dynamic light exposure in the ‘real world’ where light intensity, duration, spectral quality and the time of exposure vary greatly. Defining these parameters will allow the development of electric lighting systems that will enhance human circadian entrainment.

The use of zebrafish (Danio rerio) as a model system in neurobehavioral toxicology

2004 ◽  
Vol 26 (6) ◽  
pp. 707-708 ◽  
Author(s):  
Frank M. Scalzo ◽  
Edward D. Levin
Keyword(s):  
Danio Rerio ◽  
Model System

scholarly journals A scalable culturing system for the marine annelid Platynereis dumerilii

2019 ◽  
Author(s):  
Emily Kuehn ◽  
Alexander W. Stockinger ◽  
Jerome Girard ◽  
Florian Raible ◽  
B. Duygu Özpolat
Keyword(s):  
Aquatic Organisms ◽  
Model System ◽  
Light Conditions ◽  
Cell Type ◽  
Culture Methods ◽  
Cell Lineages ◽  
Full Life Cycle ◽  
Platynereis Dumerilii ◽  
Culturing Conditions ◽  
And Behavior

ABSTRACTPlatynereis dumerilii is a marine segmented worm (annelid) with externally fertilized embryos and it can be cultured for the full life cycle in the laboratory. The accessibility of embryos and larvae combined with the breadth of the established molecular and functional techniques has made P. dumerilii an attractive model for studying development, cell lineages, cell type evolution, reproduction, regeneration, the nervous system, and behavior. Traditionally, these worms have been kept in rooms dedicated for their culture. This allows for the regulation of temperature and light cycles, which is critical to synchronizing sexual maturation. However, regulating the conditions of a whole room present limitations, especially if experiments require being able to change culturing conditions. Here we present scalable and flexible culture methods that provide ability to control the environmental conditions, and have a multi-purpose culture space. We provide a closed setup shelving design with proper light conditions necessary for P. dumerilii to mature. We also implemented a standardized method of feeding P. dumerilii cultures with powdered spirulina which relieves the ambiguity associated with using frozen spinach, and helps standardize nutrition conditions across experiments and across different labs. By using these methods, we were able to raise mature P. dumerilii, capable of spawning and producing viable embryos for experimentation and replenishing culture populations. These methods will allow for the further accessibility of P. dumerilii as a model system, and they can be adapted for other aquatic organisms.

scholarly journals Response time of an avian prey to a simulated hawk attack is slower in darker conditions, but is independent of hawk colour morph

2019 ◽  
Vol 6 (8) ◽  
pp. 190677 ◽  
Author(s):  
Carina Nebel ◽  
Petra Sumasgutner ◽  
Adrien Pajot ◽  
Arjun Amar
Keyword(s):  
Response Time ◽  
Response Times ◽  
Bright Light ◽  
Light Level ◽  
White Background ◽  
Light Conditions ◽  
Dark Light ◽  
Light Levels ◽  
Columbia Livia ◽  
Colour Morphs

To avoid predation, many species rely on vision to detect predators and initiate an escape response. The ability to detect predators may be lower in darker light conditions or with darker backgrounds. For birds, however, this has never been experimentally tested. We test the hypothesis that the response time of avian prey (feral pigeon Columbia livia f. domestica ) to a simulated hawk attack (taxidermy mounted colour-polymorphic black sparrowhawk Accipiter melanoleucus ) will differ depending on light levels or background colour. We predict that response will be slower under darker conditions, which would translate into higher predation risk. The speed of response of prey in relation to light level or background colour may also interact with the colour of the predator, and this idea underpins a key hypothesis proposed for the maintenance of different colour morphs in polymorphic raptors. We therefore test whether the speed of reaction is influenced by the morph of the hawk (dark/light) in combination with light conditions (dull/bright), or background colours (black/white). We predict slowest responses to morphs under conditions that less contrast with the plumage of the hawk (e.g. light morph under bright light or white background). In support of our first hypothesis, pigeons reacted slower under duller light and with a black background. However, we found no support for the second hypothesis, with response times observed between the hawk-morphs being irrespective of light levels or background colour. Our findings experimentally confirm that birds detect avian predators less efficiently under darker conditions. These conditions, for example, might occur during early mornings or in dense forests, which could lead to changes in anti-predator behaviours. However, our results provide no support that different morphs may be maintained in a population due to differential selective advantages linked to improved hunting efficiencies in different conditions due to crypsis.

Contemporaneous melatonin administration modifies the circadian response to nocturnal bright light stimuli

1997 ◽  
Vol 272 (2) ◽  
pp. R482-R486 ◽  
Author(s):  
A. Cagnacci ◽  
R. Soldani ◽  
S. S. Yen
Keyword(s):  
Light Exposure ◽  
Light Stimulus ◽  
Core Body Temperature ◽  
Bright Light ◽  
Phase Shifts ◽  
Double Blind ◽  
Circadian Phase ◽  
Melatonin Administration ◽  
Baseline Evaluation ◽  
Light Stimuli

We investigated whether the contemporaneous administration of melatonin can modify circadian phase shifts induced by bright light stimuli. After a baseline evaluation, 10 women were exposed for three consecutive nights to a 4-h bright light stimulus (>3,000 lx) initiated at the time of the estimated core body temperature (BT(c)) nadir. Along with light, each woman orally received, randomly and in a double-blind fashion, placebo (n = 5) or melatonin (n = 5; 1 mg 30 min before and 0.75 mg 120 min after the start of light exposure). Daily rhythms were reevaluated at the end of treatment. Bright light phase advanced, by about 90-120 min, BT(c) (P < 0.01), cortisol (P < 0.05), and melatonin (P < 0.01) rhythms. Contemporaneous administration of melatonin antagonized the phase advances of the cortisol and BT(c) rhythms, as well as the melatonin peak and melatonin offset. The phase advance of the melatonin onset was instead enhanced (P < 0.05). Contemporaneous melatonin administration modifies the capability of light to induce circadian phase shifts.

scholarly journals Partitioning of gene expression among zebrafish photoreceptor subtypes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yohey Ogawa ◽  
Joseph C. Corbo
Keyword(s):  
Gene Expression ◽  
Genome Duplication ◽  
Bright Light ◽  
Transcriptional Regulators ◽  
Specific Gene ◽  
Gene Duplications ◽  
Rna Seq ◽  
Rods And Cones ◽  
Molecular Features ◽  
Photoreceptor Development

AbstractVertebrate photoreceptors are categorized into two broad classes, rods and cones, responsible for dim- and bright-light vision, respectively. While many molecular features that distinguish rods and cones are known, gene expression differences among cone subtypes remain poorly understood. Teleost fishes are renowned for the diversity of their photoreceptor systems. Here, we used single-cell RNA-seq to profile adult photoreceptors in zebrafish, a teleost. We found that in addition to the four canonical zebrafish cone types, there exist subpopulations of green and red cones (previously shown to be located in the ventral retina) that express red-shifted opsin paralogs (opn1mw4 or opn1lw1) as well as a unique combination of cone phototransduction genes. Furthermore, the expression of many paralogous phototransduction genes is partitioned among cone subtypes, analogous to the partitioning of the phototransduction paralogs between rods and cones seen across vertebrates. The partitioned cone-gene pairs arose via the teleost-specific whole-genome duplication or later clade-specific gene duplications. We also discovered that cone subtypes express distinct transcriptional regulators, including many factors not previously implicated in photoreceptor development or differentiation. Overall, our work suggests that partitioning of paralogous gene expression via the action of differentially expressed transcriptional regulators enables diversification of cone subtypes in teleosts.

Melatonin Rhythm Observed throughout a Three-Cycle Bright-Light Stimulus Designed to Reset the Human Circadian Pacemaker

1999 ◽  
Vol 14 (3) ◽  
pp. 237-253 ◽  
Author(s):  
Theresa L. Shanahan ◽  
Richard E. Kronauer ◽  
Jeanne F. Duffy ◽  
Gordon H. Williams ◽  
Charles A. Czeisler
Keyword(s):  
Light Stimulus ◽  
Bright Light ◽  
Circadian Pacemaker ◽  
Melatonin Rhythm

Human circadian pacemaker is sensitive to light throughout subjective day without evidence of transients

1997 ◽  
Vol 273 (5) ◽  
pp. R1800-R1809 ◽  
Author(s):  
Megan E. Jewett ◽  
David W. Rimmer ◽  
Jeanne F. Duffy ◽  
Elizabeth B. Klerman ◽  
Richard E. Kronauer ◽  
...  
Keyword(s):  
Steady State ◽  
Response Curve ◽  
Phase Response Curve ◽  
Light Exposure ◽  
Light Stimulus ◽  
Dead Zone ◽  
Bright Light ◽  
Temperature Minimum ◽  
Circadian Pacemaker ◽  
Dim Light

Fifty-six resetting trials were conducted across the subjective day in 43 young men using a three-cycle bright-light (∼10,000 lx) stimulus against a background of very dim light (10–15 lx). The phase-response curve (PRC) to these trials was assessed for the presence of a “dead zone” of photic insensitivity and was compared with another three-cycle PRC that had used a background of ∼150 lx. To assess possible transients after the light stimulus, the trials were divided into 43 steady-state trials, which occurred after several baseline days, and 13 consecutive trials, which occurred immediately after a previous resetting trial. We found that 1) bright light induces phase shifts throughout subjective day with no apparent dead zone; 2) there is no evidence of transients in constant routine assessments of the fitted temperature minimum 1–2 days after completion of the resetting stimulus; and 3) the timing of background room light modulates the resetting response to bright light. These data indicate that the human circadian pacemaker is sensitive to light at virtually all circadian phases, implying that the entire 24-h pattern of light exposure contributes to entrainment.

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