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Freeruns
Published in Sue Binkley, Biological Clocks, 2020
In contrast, when a diurnal animal, such as the house sparrow, is placed in constant light (LL), its activity lasts longer (e.g. activity time, alpha = 17 hours) and its rest period is reduced in comparison to house sparrows in DD (e.g. activity time, alpha = 8 hours). Thus a nine-hour difference in activity time can be produced by light!
Sleep Disorders
Published in Divya Vohora, The Third Histamine Receptor, 2008
Jonathan E. Shelton, Timothy W. Lovenberg, Christine Dugovic
Thus, the sleep/wake cycle is predominantly regulated by the integration of two mechanisms: Process S (homeostatic) and Process C (circadian). The circadian component influences sleep by integrating it to the time of day and behaves like an endogenous clock that can run in the presence or absence of external cues. The homeostatic component is related to the duration of wake [19,28]. Therefore, the longer an individual is awake, the higher the sleep drive. The accumulation or dissipation of sleep pressure resides in the interaction between the two components. For a diurnal species, Process S accrues during the day and diminishes during the rest period. The circadian Process C for sleep propensity, however, obtains its peak during the latter portion of the night. Thus, the diurnal animal will experience the onset of sleep when the greatest separation between Processes S and C occurs.
Contrast adaptation
Published in Pablo Artal, Handbook of Visual Optics, 2017
Because the light sensitivity of humans rods is similar to the one of nocturnal mammals (also our rods can respond to a single photon), the only way for nocturnal animals to increase their CS at night is to increase retinal illuminance. This is achieved by lowering the aperture stop, that is, the ratio of focal length to pupil size (Figure 21.6). For instance, a barn owl has an aperture stop of less than 1, and a diurnal animal like a chameleon has an aperture stop of about 5. The ratio of retinal illuminance in both types of eyes is determined by the ratio of the squares of the two aperture stops, 1/25. Accordingly, the retinal image is 25 times brighter in the owl compared to the chameleon. Young children may have an aperture stop of around 2 (anterior focal length 16.7 mm, pupil size 8 mm), which means that their retinal image is only about four times darker than in an owl. Since CS rises with the square root of luminance in dim light, retinal illuminance can explain a difference in CS of a factor of 2. However, it was found that nocturnal mammals, like cat and owl, have about a six times higher CS at low light levels (Pasternak and Merigan 1981; Orlowski et al. 2012) than human subjects, and the difference cannot be fully explained only by optics. Cats and dogs have developed highly reflective layers behind the photoreceptors, the tapetum lucidum, to increase the chance that photons can be absorbed in a second pass. It has been calculated that the tapetum increases light sensitivity (and thereby CS) by further 29%. Because reflected photons are more scattered, this may be at the cost of visual acuity.
Effect of Long-term Anti-VEGF Treatment on Viability and Function of RPE Cells
Published in Current Eye Research, 2022
Anna Brinkmann, Katrin Winkelmann, Tom Käckenmeister, Johann Roider, Alexa Klettner
In our study, we have evaluated the long-term effect of VEGF antagonists on primary porcine RPE cells. Primary porcine RPE cells are an excellent model for adult human RPE cells.38 Of all non-primate eyes, the porcine eye is the most similar to the human eye. Both the bulbus and the retina are of similar size and function.39 Moreover, the pig is a diurnal animal with a high content of cones and a high cone density streak for higher acuity vision, similar to humans but in contrast to mice.40,41 Porcine RPE cells resemble human RPE cells, e.g., they show a similar polarization and can develop similar barrier properties, (and in contrast to mice they express the same proteins for tight junctions, claudin-19), which makes them an excellent model for adult human RPE.40,42,43 As they can be prepared from slaughterhouse waste, their use contributes to the 3 R principle (reduction, replacement and refinement of animal experimentation).44 Furthermore, due to their high availability and standardized supply, variation due to donor age and post mortem time can be avoided.45,46
Daily rhythms after vaccination on specific and non-specific responses in Nile tilapia (Oreochromis niloticus)
Published in Chronobiology International, 2018
Bartira Guerra-Santos, José Fernando López-Olmeda, Denise Soledade Peixoto Pereira, Cristóbal Espinossa Ruiz, Francisco Javier Sánchez-Vázquez, María Ángeles Esteban, Robson Bahia Cerqueira, Rodrigo Fortes-Silva
Despite expressing daily variation, blood cells rhythm could be affected for several reasons in fish. According to Wang et al. (1994), increased fish activity can induce a bigger globular cell volume, which could also result in an increase in the HCT. Since tilapia is mostly a diurnal animal (Toguyeni et al. 1997), greater locomotor activity is expected to occur in the daytime and to coincide with the highest values in the HCT. Some hematological parameters showed a definite rhythm in the vaccinated group, which could be expected considering the complexity of the immune system and the metabolism of every defense cell. Many immune cells depend on biochemical responses for daily operations. Nucleated cells, for example, require glucose to operate. In this case, glucose availability could also be rhythmic and directly influence cellular metabolism by causing a daily rhythmic effect or not. As RBC are dependent on glycolysis for ATP synthesis, O’Neill and Reddy (2011) observed two cycles of circadian oscillation of ATP in humans, which supports the idea that the observed cycles are metabolic in origin. It should be noted that glucose also displayed daily rhythms in fish (López-Olmeda and Sánchez-Vázquez 2009) which could, in turn, also influence the rhythms in some of the parameters analyzed in the present study. Summarizing, for all evaluated parameters the interaction effect between time and treatment depended on the ZT. This results agree with a study of dietary yeast β-glucan and alginic acid to determine the combined effects of immunostimulation and time in sea bass (Dicentrarchus labrax) (Bagni et al. 2005), which revealed a similar pattern of interactions at different sampling times. This interaction between time and infection challenge on the hematological and immunological response is uncertain and may be species-dependent in fish (Paixão et al. 2017).
Red white and blue – bright light effects in a diurnal rodent model for seasonal affective disorder
Published in Chronobiology International, 2019
Carmel Bilu, Haim Einat, Katy Tal-Krivisky, Joseph Mizrahi, Vicktoria Vishnevskia-Dai, Galila Agam, Noga Kronfeld-Schor
Our own and others previous studies already demonstrated the effects of bright white light in a diurnal animal model (Ashkenazy et al. 2009; Deats et al. 2015; Krivisky et al. 2012). The added value of the current study is the demonstration of equal effects obtained with blue light, but not red light, further supporting the notion that ipRGC are critical in these effects since these cells are most sensitive to blue light (Hattar et al. 2002) and since application of only blue but not red light resulted in antidepressant-like effects.