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Physical Factors
Published in Michael J. Kennish, Ecology of Estuaries Physical and Chemical Aspects, 2019
The ability of organisms to measure time physiologically stems from a biological clock mechanism which couples environmental and physiological rhythms.111 The biological clock of an organism may be coupled with photoperiodicity, thereby generating a strong timing mechanism.80 The manifestation of a biological clock can be detected in the growth patterns of a diverse group of organisms, perhaps most notably among the Bivalvia.4,112
A Review of the Problem of Alcoholism in Siberia
Published in Bernard Segal, Caesar Korolenko, Addictive Disorders in Arctic Climates, 2014
C. P. Korolenko, N. L. Botchkareva
The influence of continental and extracontinental climates are combined with considerable oscillations of atmospheric pressure, and in the far north the situation is aggravated by unusual photoperiodicity (periods of polar nights and days). Climatic conditions are also significantly affected by industrial and municipal pollution. These climatic factors, when linked with the psychological aspects of living in extreme conditions (e.g., the impact on sensory processes and different forms of hyperstimulation), together with an increase in lifespan, all contribute to create high levels of stress.
Comparative Anatomy and Physiology of the Mammalian Eye
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
In addition to nutritional deficiencies, the retina is also sensitive to toxic injury. Zinc pryidinethione, an antifungal and antibacterial agent used as an antidandruff agent in shampoo, has been demonstrated to result in injury to the tapetum lucidum with a resultant retinitis, retinal hemorrhage, retinal detachment, and blindness in cats and dogs.146 The lesions were not present in the nontapetal region of affected eyes. 6-Aminonicotinamide, a potent nicotinamide antagonist, results in vacuolation of the RPE and outer plexiform layer in rabbits.147,148 The anticancer agent, adriamycin, has been shown to be both cardio- and retinotoxic, likely through the formation of lipid peroxides.142 Metal ions, especially iron, are toxic to the retina.142 The phenothiazine and quinolines compounds are also toxic to the retina, possibly by disrupting the rod outer segments and resulting in the accumulation of visual pigment in the RPE.149,150 Urethane results in a toxic retinopathy in pigmented rats.141 In addition, compounds such as ethambutol, diphenylthiocarbazone, hydroxypyridinethione, naphthalene, chloroquine, and numerous others, have been demonstrated to result in degeneration of the photoreceptors or ganglion cells.149 Low illumination for a prolonged period (photic injury) or intense illumination for a short period (mechanical injury) are also damaging to the retina.151 Phototoxicity is influenced by the spectral wavelength of the light, the intensity of the light, and the photoperiodicity.152 It also appears to be influenced by the light intensity under which the animal was raised.153 This has importance in the laboratory animal environment, as inappropriate levels of illumination can result in retinal damage that could be confused with a toxic insult. It would appear that albino rats are more susceptible to phototoxic injury than other laboratory animals.152 One study indicates that the threshold to phototoxic damage appears to be 1.3 log units greater than the light intensity under which the animal was raised.153 Attention must also be paid to the illumination at various areas of the room, for example, the difference in light intensity between the top and bottom row of cages.
Early menarche in visually impaired girls: evidence and hypothesis of light-dark cycle disruption and blindness effect on puberty onset
Published in Chronobiology International, 2022
Jorge A. Barrero, Ismena Mockus
Photoperiodicity integrates a physiological response to changes in the regular pattern of the light-dark cycle. Therefore it is understood as an important evolutionary mechanism that has allowed mammals to adapt to the variations in day and night length during different seasons of the year (Oster et al. 2002). Still, evidence for photoperiodic behavior in humans is inconclusive; it has been observed that the reproductive patterning could be affected by daylight exposure (Bronson 2004), yet this photosensitive regulation appears to have attenuated over time (Wehr 2001). Photoperiodism conveys information from the light-dark cycle and photic influx via neuroendocrine signals that converge on melatonin secretion in the pineal gland (Arendt and Middleton 2018; Gorman 2020). The photoperiodic modulation of the HPG axis has been largely attributed to this neurohormone (Bellastella et al. 2014), and while melatonin has shown to be a potential neuromodulator involved in various aspects of female reproduction, its effect on puberty timing remains somewhat unclear (Boafo et al. 2019; Olcese 2020).
Daytime and season do not affect reinforcement learning capacity in a response time adjustment task
Published in Chronobiology International, 2021
Sina Kohne, Luise Reimers, Malika Müller, Esther K. Diekhof
Meyer et al. (2016) investigated seasonal influences on performance in a working memory and sustained attention task in healthy young adults and could not detect measurable behavioral effects, just as we could not find any relation between season and behavior. However, Meyer and colleagues could demonstrate neurophysiological changes with season. Working memory provoked a maximum response (inter alia in thalamus, prefrontal and frontopolar areas) around autumn and a minimum around spring. For the attention task, the greatest activity (inter alia in the thalamus, amygdala, frontal areas and hippocampus) was found around summer and it was reduced during the winter. Furthermore, neural activity in this task was closely related to photoperiodicity (Meyer et al. 2016). In addition to that, an impairment of the hippocampal long-term potentiation, learning and memory during simulated short days compared to long days was observed in male white-footed mice (Walton et al. 2011). This indicated that the impairment was mediated by photoperiod and the diminishing impact of melatonin on long-term potentiation and cognition (Walton et al. 2011). It may be assumed that season and probably photoperiod might have an influence on neurophysiological processing of various cognitive operations, which may not necessarily be measurable in behavior.
Biological variables influencing the estimation of reference limits
Published in Scandinavian Journal of Clinical and Laboratory Investigation, 2018
Mustafa K. Özçürümez, Rainer Haeckel
Table 2 of the supplement gives a representative overview of further measurands with reported seasonal effects on within-subject variation. These differences partly resemble the annual cycle of day and night length. Annual photoperiodicity is one of the strongest seasonal synchronizers and subsumes timing, duration, intensity and spectral composition of light exposure as well as the contrast between daily light intensities and dark periods [98]. Pineal gland triggered mediators modulate primordial biological processes that determine seasonal variations of biochemical functions as well as behavioural patterns [99]. The majority of these processes is driven by the hypothalamic-pituitary-adrenal axis and controls basic body functions such as stress and immune response, digestion, mood and emotions, sexuality, and energy balance. Thus, all measurands coupled to these processes may potentially be influenced by photoperiodicity.