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Seasons and Photoperiodism
Published in Sue Binkley, Biological Clocks, 2020
A response of an organism to the changes in day and night length is a photoperiodic response. The rationale that is offered is that there are adaptive advantages in being able to anticipate and make best use of the advantages, particularly of spring and summer for raising young, and to avoid the harsh winter conditions.
Eating Disorders and Treatment
Published in Emily Crews Splane, Neil E. Rowland, Anaya Mitra, Psychology of Eating, 2019
Emily Crews Splane, Neil E. Rowland, Anaya Mitra
This model is not only task-related but, because birds are seasonal breeders, will be associated with specific day length (photoperiod) indicative of the season. If animals show physiological and behavioral changes in different seasons, they are said to be photoperiodic. There are other photoperiod-related changes in food intake. Many species eat less in the winter when days are short and lose substantial body weight (e.g., 20%; Iverson & Turner, 1974), and, like the incubating birds, this occurs even in captivity when food is readily available. In the natural environment, food tends to be less abundant during the winter, and expending large amounts of energy in unsuccessful foraging is a poor survival strategy. The physiological suppression of hunger then has an adaptive function. Another example is in rutting deer (Yoccoz et al., 2002): The males lose 10% to 15% of their body weight during rutting season, even though there is plenty of grass around; in contrast, females do not lose weight.
Gonadotropins in the Male
Published in Paul V. Malven, Mammalian Neuroendocrinology, 2019
Photoperiod is the environmental factor that has the greatest influence on male reproduction, and this influence differs among species. In long-day breeding species such as the hamster, the testes atrophy when the animal is exposed to short photoperiods. As discussed in Chapter 10, this effect is mediated by pineal secretion of melatonin and is closely related to the endogenous free-running circadian rhythm. As little as 1 sec of light occurring 8 h after the end of a once daily 6-h period of light could entrain the circadian rhythm of locomotor activity equivalent to a 14-h photoperiod and prevent the testes atrophy usually observed in 6-h photoperiods (Earnest and Turek, 1983).
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
Puberty is a stage that mirrors the complex network of neuroendocrine interactions which determine the onset of sexual maturity. Early in this period of somatic growth and reproductive development, the hypothalamic-pituitary-gonadal (HPG) axis activation is triggered by hypothalamic stimuli which, in turn, respond to an intricate regulation by a wide range of modulatory neuropeptides (Naulé et al. 2021). In females, menarche occurs in the late stages of HPG axis activation and is often relied upon as a marker to estimate pubertal development initiation (Hoyt et al. 2020; Huang et al. 2009). It has been well established that the exposure to oscillating environmental stimuli is associated with specific patterns in the frequency of appearance of the first menstrual cycle (Canelón and Boland 2020). More precisely, a higher occurrence of menarche has been observed during winter (December-January) and autumn (August-September); seasons in which daylight hours are relatively short (Albright et al. 1990; Valenzuela et al. 1991). Although evidence is sparse, these studies suggest that the photoperiod could somehow influence puberty timing in humans (Matchock et al. 2004; Ubuka and Tsutsui 2019; Yokoya and Terada 2021).
Sex differences in the response to circadian disruption in diurnal sand rats
Published in Chronobiology International, 2022
Carmel Bilu, Noga Kronfeld-Schor, Paul Zimmet, Haim Einat
Mixed ANOVA with sex and photoperiod as main factors and “sink” as repeated measure factors indicated a significant effect for sex [F(1,29) = 4.51, p = .04], a significant effect for photoperiod [F(1,29) = 10.43, p = .003], and a significant effect for sink [F(1,29) = 34.29, p < .001]. Considering the significant effect of sink, we separately analyzed each sink with a two-way ANOVA with photoperiod and sex as main factors. Two-way ANOVA showed a significant effect for sex [F(1,29) = 4.5, p = .043] and photoperiod [F(1,29) = 11.61, p = .002], with no interaction [F(1,29) = 0.11, p = .74], on the time to sink 1. Post-hoc analysis indicated that the effect of photoperiod is demonstrated both in males (Males-NP vs. Males-SP, p = .014) and in females (Females-NP vs. Females-SP, p = .034). For the time to sink 2, two-way ANOVA showed a significant effect for photoperiod [F(1,29) = 8.46, p = .007], a near significant effect for sex [F(1,29) = 4.12, p = .052], and no interaction [F(1,29) = 1.78, p = .19]. Interestingly, post-hoc analysis indicated that the effect of photoperiod is demonstrated only in males (Males-NP vs. Males-SP, p = .006) but not in females (Females-NP vs. Females-SP, p = .27) (Figure 8).
Perinatal photoperiod and childhood cancer: pooled results from 182,856 individuals in the international childhood cancer cohort consortium (I4C)
Published in Chronobiology International, 2020
Philip Lewis, Martin Hellmich, Lin Fritschi, Gabriella Tikellis, Peter Morfeld, J. Valérie Groß, Russell G. Foster, Ora Paltiel, Mark A. Klebanoff, Jean Golding, Sjurdur Olsen, Per Magnus, Anne-Louise Ponsonby, Martha S. Linet, Mary H. Ward, Neil Caporaso, Terence Dwyer, Thomas C. Erren
Regarding the hypothesized PLICCS mechanism, inability to account for circulating circadian factors or “temporal information” provided via breast milk may be considered a limitation. Although some I4C cohorts collected breastfeeding information, there was insufficient detail on timing across all cohorts for respective analyses. Similarly, it is unknown whether mothers took medication with possible effects on the fetal circadian system (e.g. melatonin). Additionally, this study assumes sufficient photoperiod information reaches the developing circadian systems of each fetus/infant on a sufficient number of days (brief exposures of mothers to natural light in the mornings and evenings and even through windows can be expected to suffice) (Simonneaux 2011). Furthermore, we assume most pregnant women in the third trimester and mothers with newborns no more than 3 months old base their “schedules” around the daily photoperiod for the majority of the time windows of interest. That we observe a significant association between perinatal photoperiod and childhood cancer, and consider other factors less likely to be driving the association (for reasons outlined above), is in line with this rationale. Importantly, natural photoperiod impacts on the circadian time structure of individuals can be observed in ecological studies despite the presence of artificial light (Roenneberg et al. 2007; Shochat et al. 2019). This is likely due to the higher intensity of daylight being of greater zeitgeber strength (Duffy et al. 1996). In a similar fashion, natural photoperiod can be a co-causal agent in the current study.