The clock genes Period 2 and Cryptochrome 2 differentially balance bone formation

Background: Clock genes and their protein products regulate circadian rhythms in mammals but have also been implicated in various physiological processes, including bone formation. Osteoblasts build new mineralized bone whereas osteoclasts degrade it thereby balancing bone formation. To evaluate the contribution of clock components in this process, we investigated mice mutant in clock genes for a bone volume phenotype. Methodology/Principal Findings: We found that Per2Brdm1 mutant mice as well as mice lacking Cry2-/- displayed significantly increased bone volume at 12 weeks of age, when bone turnover is high. Per2Brdm1 mutant mice showed alterations in parameters specific for osteoblasts whereas mice lacking Cry2-/- displayed changes in osteoclast specific parameters. Interestingly, inactivation of both Per2 and Cry2 genes leads to normal bone volume as observed in wild type animals. Importantly, osteoclast parameters affected due to the lack of Cry2, remained at the level seen in the Cry2-/- mutants despite the simultaneous inactivation of Per2. Conclusions/Significance: This indicates that Cry2 and Per2 affect distinct pathways in the regulation of bone volume with Cry2 influencing mostly the osteoclastic cellular component of bone and Per2 acting on osteoblast parameters

The HEV Ventilator

HEV is a low-cost, versatile, high-quality ventilator, which has been designed in response to the COVID-19 pandemic. The ventilator is intended to be used both in and out of hospital intensive care units, and for both invasive and non-invasive ventilation. The hardware can be complemented with an external turbine for use in regions where compressed air supplies are not reliably available. The standard modes provided include PC-A/C(Pressure Assist Control),PC-A/C-PRVC(Pressure Regulated Volume Control), PC-PSV (Pressure Support Ventilation) and CPAP (Continuous Positive airway pressure). HEV is designed to support remote training and post market surveillance via a web interface and data logging to complement the standard touch screen operation, making it suitable for a wide range of geographical deployment. The HEV design places emphasis on the quality of the pressure curves and the reactivity of the trigger, delivering a global performance which will be applicable to ventilator needs beyond theCOVID-19 pandemic. This article describes the conceptual design and presents the prototype units together with their performance evaluation.Comment: 34 pages, 18 figures, Extended version of the article submitted to PNA

The cost of a specific immune response in young guinea pigs

Pilorz V, Jackel M, Knudsen K, Trillmich F. The cost of a specific immune response in young guinea pigs. PHYSIOLOGY & BEHAVIOR. 2005;85(2):205-211.The specific immune system is a protective mechanism that detects infection and fights it by production of antibodies. Newborns are especially susceptible to infections because their immune system is not yet as fully developed as that of adults. This has been well established in altricial mammals. Fighting infection is associated with costs (metabolic rate, protein synthesis) potentially affecting other developmental processes. We investigated the specific immune response in a precocial mammal, by testing the response of 3 and 7 day old young guinea pigs (Cavia aperea f. porcellus) against a non-pathogenic antigen (KLH) and determined the effect of the immune response on growth and metabolic rate. Challenged young produced a substantial specific immune response (IgG). The efficiency of the immune response was almost identical in 3 and 7 day old young, but lower than in adult females. Antibody titres achieved by actively immunised young pups were as high as titres transferred transplacentally by mothers immunised on day 40 and 47 of pregnancy. In comparison to a control group, the immune response did not influence growth and metabolic rate measured on day 4 after each immune challenge and was not reflected by changes in hematocrit value. We discuss whether the weaker immune response of pups is caused by reduced allocation of limited resources in growing young or by the immature immune system of young animals. (c) 2005 Elsevier Inc. All rights reserved

Melanopsin Regulates Both Sleep-Promoting and Arousal-Promoting Responses to Light

<div><p>Light plays a critical role in the regulation of numerous aspects of physiology and behaviour, including the entrainment of circadian rhythms and the regulation of sleep. These responses involve melanopsin (OPN4)-expressing photosensitive retinal ganglion cells (pRGCs) in addition to rods and cones. Nocturnal light exposure in rodents has been shown to result in rapid sleep induction, in which melanopsin plays a key role. However, studies have also shown that light exposure can result in elevated corticosterone, a response that is not compatible with sleep. To investigate these contradictory findings and to dissect the relative contribution of pRGCs and rods/cones, we assessed the effects of light of different wavelengths on behaviourally defined sleep. Here, we show that blue light (470 nm) causes behavioural arousal, elevating corticosterone and delaying sleep onset. By contrast, green light (530 nm) produces rapid sleep induction. Compared to wildtype mice, these responses are altered in melanopsin-deficient mice (<i>Opn4</i>^<i>-/-</i>), resulting in enhanced sleep in response to blue light but delayed sleep induction in response to green or white light. We go on to show that blue light evokes higher <i>Fos</i> induction in the SCN compared to the sleep-promoting ventrolateral preoptic area (VLPO), whereas green light produced greater responses in the VLPO. Collectively, our data demonstrates that nocturnal light exposure can have either an arousal- or sleep-promoting effect, and that these responses are melanopsin-mediated via different neural pathways with different spectral sensitivities. These findings raise important questions relating to how artificial light may alter behaviour in both the work and domestic setting.</p></div

Wavelength-dependent effects on behavioural light aversion.

<p>(<b>A</b>) Mice entrained to an LD12:12 cycle were exposed to 405 nm (violet), 470 nm (blue), and 530 nm (green) light at ZT14 in a light/dark box for 10 min. (<b>B</b>) In the first 1 min of the test, mice spent significantly more time in the hidden zone under blue light compared to violet, green, or control (dark) conditions. One-way repeated measures ANOVA for light condition, F_(3.25) = 20.696, <i>p</i> ≤ 0.001. Post hoc Tukey dark versus violet <i>p</i> = 0.006, dark versus blue <i>p</i> = 0.021, dark versus green <i>p</i> ≤ 0.001, blue versus violet <i>p</i> ≤ 0.001, blue versus green <i>p</i> ≤ 0.001. (<b>C</b>) In the following 9 min, mice exposed to blue light continued to spend more time in the hidden zone compared to violet or green light. One-way repeated measures ANOVA light condition over time 2–-10 mins, F_(3,25) = 11.721, <i>p</i> ≤ 0.001. Post hoc Tukey dark versus violet <i>p</i> = 0.635, dark versus blue <i>p</i> = 0.021, dark versus green <i>p</i> = 0.635, violet versus blue <i>p</i> ≤ 0.001, blue versus green <i>p</i> ≤ 0.001. (<b>D</b>) <i>Opn4</i>^<i>-/-</i> mice (open bars) showed different responses to both blue and green light. In the first minute of the test, in comparison with wildtype mice, <i>Opn4</i>^<i>-/-</i> mice spent less time in the hidden zone in response to blue light. However, <i>Opn4</i>^<i>-/-</i> animals spent more time in the hidden zone compared with wildtype under green light. Two-way repeated measures ANOVA for light condition and genotype, light condition x genotype interaction F_(1,26) = 20.585, <i>p</i> ≤ 0.001. Post hoc Tukey wildtype versus <i>Opn4</i>^<i>-/-</i> blue <i>p</i> = 0.010, green <i>p</i> = 0.001. (<b>E</b>) Whilst the attenuated response to blue light in <i>Opn4</i>^<i>-/-</i> mice persisted over the remaining time course of the test (one-way repeated measures ANOVA for effect of genotype over time, F_(1.13) = 14.376, <i>p</i> = 0.002), no difference was observed between wildtype and <i>Opn4</i>^<i>-/-</i> mice under green light (one-way repeated measures ANOVA for effect of genotype over time, F_(1.13) = 0.26, <i>p</i> = 0.617). <i>Opn4</i>^<i>-/-</i> mice showed no statistical difference in responses to wavelength in the first minute or whole time of the test (one-way repeated measures ANOVA for effect time over wavelength F_(9,81) = 0.976 <i>p</i> = 0.466). Histograms reflect mean percentage ± SEM of time spent in the dark box of the light dark box during the 10 min trial (<i>n</i> = 6–-10/group wildtype, <i>n</i> = 4–-10 <i>Opn4</i>^<i>-/-</i>). Significant differences indicated by *** <i>p</i> ≤ 0.001, ** <i>p</i> ≤ 0.01, * <i>p</i> ≤ 0.05, NS = not significant. The data used to make this figure can be found in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002482#pbio.1002482.s003" target="_blank">S3 Data</a>.</p

Molecular responses to light in SCN and VLPO are wavelength-dependent.

<p>A <i>Fos</i> induction in response to a 30 min light pulse was studied in wildtype mice exposed to blue or green light in both the SCN and VLPO (two-way ANOVA for wavelength x brain region interaction F_(2,31) = 10.968 <i>p</i> ≤ 0.001). Mice exposed to blue light show greater <i>Fos</i> induction in the SCN compared with green light (posthoc Tukey dark versus blue <i>p</i> = 0.001, dark versus green <i>p</i> = 0.035, blue versus green <i>p</i> = 0.008). By contrast, in the VLPO, a greater response to green light than blue light was observed (dark versus blue <i>p</i> = 0.880, dark versus green <i>p</i> = 0.015). As a control, <i>Gal</i> induction was also studied, showing no induction in the SCN but significant induction in the VLPO (two-way ANOVA for wavelength and x brain region interaction F_(2,30) = 3.774 <i>p</i> = 0.035). This response was only evident in response to green light (posthoc Tukey dark versus blue <i>p</i> = 0.742, dark versus green <i>p</i> = 0.011, blue versus green <i>p</i> = 0.003). Histograms show mean ± SEM, <i>n</i> = 5–8/group. Significant differences indicated by *** <i>p</i> ≤ 0.001, ** <i>p</i> ≤0.01, * <i>p</i> ≤0.05, NS = not significant. The data used to make this figure can be found in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002482#pbio.1002482.s006" target="_blank">S6 Data</a>.</p

Wavelength-dependent effects of light on sleep are abolished in melanopsin-deficient (<i>Opn4</i>^<i>-/-</i>) mice.

<p>(<b>A–C</b>) Sleep induction in response to violet (<b>A</b>), blue (<b>B</b>) and green (<b>C</b>) light. Sleep was studied in <i>Opn4</i>^<i>-/-</i> mice (open symbols, <i>n</i> = 6–10/group) and compared with wildtype mice (WT, solid symbols). (<b>D</b>) In comparison with wildtype mice, <i>Opn4</i>^<i>-/-</i> mice show delayed sleep onset in response to green and violet light but advanced sleep onset in response to blue light. Two-way ANOVA for wavelength and genotype, wavelength x genotype interaction F_(2,43) = 12.143, <i>p</i> ≤ 0.001. Posthoc Tukey wildtype versus <i>Opn4</i>^<i>-/-</i> violet <i>p</i> = 0.011, blue <i>p</i> = 0.013, green <i>p</i> ≤ 0.001. Comparison of <i>Opn4</i>^<i>-/-</i> responses in sleep induction as well as duration show no statistical differences due to wavelength. (<b>E</b>) However, in comparison to wildtype mice <i>Opn4</i>^<i>-/-</i> mice exposed to green and violet light show reduced sleep duration. Two-way ANOVA for wavelength and genotype, wavelength x genotype interaction F_(2.44) = 5.142, <i>p</i> = 0.010, posthoc Tukey wildtype versus <i>Opn4</i>^<i>-/-</i> violet <i>p</i> = 0.017, blue <i>p</i> = 0.259, green <i>p</i> = 0.003. Despite the difference in sleep onset under blue light in <i>Opn4</i>^<i>-/-</i> and wildtype mice, there was no difference in sleep duration. Solid horizontal bars illustrate light pulse duration from ZT14 until ZT15. Data plotted as mean ± SEM. Significant differences indicated by *** <i>p</i> ≤ 0.001, ** <i>p</i> ≤ 0.01, * <i>p</i> ≤ 0.05, NS = not significant. The data used to make this figure can be found in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002482#pbio.1002482.s002" target="_blank">S2 Data</a>.</p