Ultradian and Infradian Rhythms in the Dynamic of Testosterone Concentration in the Serum of the White-Breasted Hedgehog Erinaceus roumanicus

A time for sex: circadian regulation of mammalian sexual and reproductive function

The circadian clock regulates physiological and biochemical processes in nearly every species. Sexual and reproductive behaviors are two processes controlled by the circadian timing system. Evidence supporting the importance of proper clock function on fertility comes from several lines of work demonstrating that misalignment of biological rhythms or disrupted function of the body's master clock, such as occurs from repeated shift work or chronic jet lag, negatively impacts reproduction by interfering with both male and female fertility. Along these lines, dysregulation of clock genes leads to impairments in fertility within mammals, and disruption of circadian clock timing negatively impacts sex hormone levels and semen quality in males, and it leads to ovulatory deficiencies in females. Here, we review the current understanding of the circadian modulation of both male and female reproductive hormones-from animal models to humans. Further, we discuss neural circuits within the hypothalamus that may regulate circadian changes in mammalian sexual behavior and reproduction, and we explore how knowledge of such circuits in animal models may help to improve human sexual function, fertility, and reproduction.

Autonomic Nervous System Adaptation and Circadian Rhythm Disturbances of the Cardiovascular System in a Ground-Based Murine Model of Spaceflight

Whether in real or simulated microgravity, Humans or animals, the kinetics of cardiovascular adaptation and its regulation by the autonomic nervous system (ANS) remain controversial. In this study, we used hindlimb unloading (HU) in 10 conscious mice. Blood pressure (BP), heart rate (HR), temperature, and locomotor activity were continuously monitored with radio-telemetry, during 3 days of control, 5 days of HU, and 2 days of recovery. Six additional mice were used to assess core temperature. ANS activity was indirectly determined by analyzing both heart rate variability (HRV) and baroreflex sensitivity (BRS). Our study showed that HU induced an initial bradycardia, accompanied by an increase in vagal activity markers of HRV and BRS, together with a decrease in water intake, indicating the early adaptation to fluid redistribution. During HU, BRS was reduced; temperature and BP circadian rhythms were altered, showing a loss in day/night differences, a decrease in cycle amplitude, a drop in core body temperature, and an increase in day BP suggestive of a rise in sympathetic activity. Reloading induced resting tachycardia and a decrease in BP, vagal activity, and BRS. In addition to cardiovascular deconditioning, HU induces disruption in day/night rhythmicity of locomotor activity, temperature, and BP.

Dental biorhythm is associated with adolescent weight gain

Background

Evidence of a long-period biological rhythm present in mammalian hard tissue relates to species average body mass. Studies have just begun to investigate the role of this biorhythm in human physiology.

Methods

The biorhythm is calculated from naturally exfoliated primary molars for 61 adolescents. We determine if the timing relates to longitudinal measures of their weight, height, lower leg length and body mass collected over 14 months between September 2019 to October 2020. We use univariate and multivariate statistical analyses to isolate and identify relationships with the biorhythm.

Results

Participants with a faster biorhythm typically weigh less each month and gain significantly less weight and mass over 14-months, relative to those with a slower biorhythm. The biorhythm relates to sex differences in weight gain.

Conclusions

We identify a previously unknown factor that associates with the rapid change in body size that accompanies human adolescence. Our findings provide a basis from which to explore novel relationships between the biorhythm and weight-related health risks.

A Scoping Review of the Diurnal Variation in the Intensity of Neuropathic Pain

BACKGROUND

Recent studies have suggested that neuropathic pain exhibits a daily diurnal pattern, with peak levels usually occurring in the late afternoon to evening and the trough in the morning hours, although literature on this topic has been sparse. This scoping review examines current evidence on the chronobiology of neuropathic pain both in animal models and in humans with neuropathic pain.

METHODS

A literature search was conducted in major medical databases for relevant articles on the chronobiology of neuropathic pain both in animal models and in humans with neuropathic pain. Data extracted included details of specific animal models or specific neuropathic pain conditions in humans, methods and timing of assessing pain severity, and specific findings of diurnal variation in pain intensity or its surrogate markers.

RESULTS

Thirteen animal and eight human studies published between 1976 and 2020 were included in the analysis. Seven of the 13 animal studies reported specific diurnal variation in pain intensity, with five of the seven studies reporting a trend toward increased sensitivity to mechanical allodynia or thermal hyperalgesia in the late light to dark phase. All eight studies in human subjects reported a diurnal variation in the intensity of neuropathic pain, where there was an increase in pain intensity through the day with peaks in the late evening and early night hours.

CONCLUSIONS

Studies included in this review demonstrated a diurnal variation in the pattern of neuropathic pain that is distinct from the pattern for nociceptive pain. These findings have implications for potential therapeutic strategies for neuropathic pain.

About 4-day rhythm of proliferative activity of fibroblast-like cell cultures isn't endogenous and don't depend from the variations of Earth's magnetic field

A study of the 4-day rhythm of the proliferative activity of the embryonic fibroblast-like cells in the logarithmic growth phase was carried out. It was shown that in cell cultures obtained on different days from embryos of different ages, the phase of the 4-day rhythm coincides. In vitro the maxima of the proliferative activity were consistent with the minima of the motor activity of mice. Freezing the culture for 2 or 6 days does not cause a shift in the phase of the 4-day rhythm of cell proliferative activity compare with the unfreezing culture. That indicates the existence of an external synchronizer, which determines the 4-day infradian rhythm of the proliferative activity of embryonic cells. Then we daily thawed samples of single L929 culture of mice fibroblast-like cells for 22 and 17 days and researched the dynamics of its proliferative activity. We also showed 4-day rhythm of the simultaneous increase in the number of cells for all thawed samples. Taking into account that deep freezing of a culture leads to the cessation of all life processes, the fact we obtained indicates an exogenous mechanism of the formation of about a 4-day rhythm of the proliferative activity of cell culture. Variations of the Earth's magnetic field could be one of the external synchronizers of the infradian rhythm. We studied the increase in number of L929 cell in conditions of a magnetic permalloy screen and showed that the magnetic shielding no affect the parameters of the infradian rhythm of L929 cell proliferative activity. So further searches of the external synchronizers are need.

Infradian 4-Day Rhythm of Proliferative Activity of L-929 Mouse Fibroblast Culture in the Logarithmic Growth Phase Is Exogenous

We studied the dynamic of proliferative activity of cultured mouse transformed fibroblast-like L-929 cells in the logarithmic growth phase. During a long period (December 5-23, 2020), we revealed a 4-day rhythm of daily increase in the number of L-929 cells with an amplitude not lower than in a culture of embryonic fibroblast-like cells. Hence, the formation of the 4-day rhythm is not associated with the molecular mechanisms of inhibition of proliferation, which are absent in transformed cells. Daily thawing of samples of one culture over 17 days showed the presence of a 4-day rhythm synchronous between all thawed samples and the control cell culture. As deep freezing leads to the cessation of all life processes in cells, the formation of a 4-day rhythm of proliferative activity of cell culture is determined by an exogenous mechanism.

European space agency's hibernation (torpor) strategy for deep space missions: Linking biology to engineering

Long-duration space missions to Mars will impose extreme stresses of physical and psychological nature on the crew, as well as significant logistical and technical challenges for life support and transportation. Main challenges include optimising overall mass and maintaining crew physical and mental health. These key scopes have been taken up as the baseline for a study by the European Space Agency (ESA) using its Concurrent Design Facility (CDF). It focussed on the biology of hibernation in reducing metabolism and hence stress, and its links to the infrastructure and life support. We concluded that torpor of crew members can reduce the payload with respect to oxygen, food and water but will require monitoring and artificial intelligence (AI) assisted monitoring of the crew. These studies additionally offer new potential applications for patient care on Earth. Keywords: Space flight, concurrent design facility, metabolic reduction.