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"Clocks "
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The different faces of time in physics
Time in physics has several faces and in an important sense, is not really a thing at all. This paper examines a number of the features of time in physics with particular emphasis on the role of clocks in relativistic physics.
Journal Article
The circadian clock and metabolic homeostasis: entangled networks
The circadian clock exerts an important role in systemic homeostasis as it acts a keeper of time for the organism. The synchrony between the daily challenges imposed by the environment needs to be aligned with biological processes and with the internal circadian clock. In this review, it is provided an in-depth view of the molecular functioning of the circadian molecular clock, how this system is organized, and how central and peripheral clocks communicate with each other. In this sense, we provide an overview of the neuro-hormonal factors controlled by the central clock and how they affect peripheral tissues. We also evaluate signals released by peripheral organs and their effects in the central clock and other brain areas. Additionally, we evaluate a possible communication between peripheral tissues as a novel layer of circadian organization by reviewing recent studies in the literature. In the last section, we analyze how the circadian clock can modulate intracellular and tissue-dependent processes of metabolic organs. Taken altogether, the goal of this review is to provide a systemic and integrative view of the molecular clock function and organization with an emphasis in metabolic tissues.
Journal Article
The beauty of time
Franًcois Chaille presents the most beautiful timepieces from the Middle Ages to the present. Lavishly illustrated, 'The Beauty of Time' contains a selection of nearly 200 wonders - from mechanical and pendulum clocks to pocket and wristwatches. The timepieces are annotated by an expert horology historian and accompanied by a text that elucidates the cultural and artistic contexts in which they were created. As a counterpoint to the timepieces, extensive reproductions of artistic masterpieces provide perspective regarding the technical advances of each period and demonstrate the evolution of aesthetic tastes over time.
Book
Stabilization of heterochromatin by CLOCK promotes stem cell rejuvenation and cartilage regeneration
Accumulating evidence indicates an association between the circadian clock and the aging process. However, it remains elusive whether the deregulation of circadian clock proteins underlies stem cell aging and whether they are targetable for the alleviation of aging-associated syndromes. Here, we identified a transcription factor-independent role of CLOCK, a core component of the molecular circadian clock machinery, in counteracting human mesenchymal stem cell (hMSC) decay. CLOCK expression was decreased during hMSC aging. In addition, CLOCK deficiency accelerated hMSC senescence, whereas the overexpression of CLOCK, even as a transcriptionally inactive form, rejuvenated physiologically and pathologically aged hMSCs. Mechanistic studies revealed that CLOCK formed complexes with nuclear lamina proteins and KAP1, thus maintaining heterochromatin architecture and stabilizing repetitive genomic sequences. Finally, gene therapy with lentiviral vectors encoding CLOCK promoted cartilage regeneration and attenuated age-related articular degeneration in mice. These findings demonstrate a noncanonical role of CLOCK in stabilizing heterochromatin, promoting tissue regeneration, and mitigating aging-associated chronic diseases.
Journal Article
I know about telling time
\"Telling time using an analog clock is an important step for young learners, and an early standard of Common Core math, and this straightforward text and accompanying photographs guide readers in mastery of that fundamental skill. Final questions aid in evaluating what they've learned\"--Provided by publisher.
Book
Effects of short-chain fatty acid-butyrate supplementation on expression of circadian-clock genes, sleep quality, and inflammation in patients with active ulcerative colitis: a double-blind randomized controlled trial
Background
The regulation of the circadian clock genes, which coordinate the activity of the immune system, is disturbed in inflammatory bowel disease (IBD). Emerging evidence suggests that butyrate, a short-chain fatty acid produced by the gut microbiota is involved in the regulation of inflammatory responses as well as circadian-clock genes. This study was conducted to investigate the effects of sodium-butyrate supplementation on the expression of circadian-clock genes, inflammation, sleep and life quality in active ulcerative colitis (UC) patients.
Methods
In the current randomized placebo-controlled trial, 36 active UC patients were randomly divided to receive sodium-butyrate (600 mg/kg) or placebo for 12-weeks. In this study the expression of circadian clock genes (CRY1, CRY2, PER1, PER2, BMAl1 and CLOCK) were assessed by real time polymerase chain reaction (qPCR) in whole blood. Gene expression changes were presented as fold changes in expression (2^-ΔΔCT) relative to the baseline. The faecal calprotectin and serum level of high-sensitivity C-reactive protein (hs-CRP) were assessed by enzyme-linked immunosorbent assay method (ELIZA). Moreover, the sleep quality and IBD quality of life (QoL) were assessed by Pittsburgh sleep quality index (PSQI) and inflammatory bowel disease questionnaire-9 (IBDQ-9) respectively before and after the intervention.
Results
The results showed that sodium-butyrate supplementation in comparison with placebo significantly decreased the level of calprotectin (-133.82 ± 155.62 vs. 51.58 ± 95.57,
P
-value < 0.001) and hs-CRP (-0.36 (-1.57, -0.05) vs. 0.48 (-0.09-4.77),
P
-value < 0.001) and upregulated the fold change expression of CRY1 (2.22 ± 1.59 vs. 0.63 ± 0.49,
P
-value < 0.001), CRY2 (2.15 ± 1.26 vs. 0.93 ± 0.80,
P
-value = 0.001), PER1 (1.86 ± 1.77 vs. 0.65 ± 0.48,
P
-value = 0.005), BMAL1 (1.85 ± 0.97 vs. 0.86 ± 0.63,
P
-value = 0.003). Also, sodium-butyrate caused an improvement in the sleep quality (PSQI score: -2.94 ± 3.50 vs. 1.16 ± 3.61,
P
-value < 0.001) and QoL (IBDQ-9: 17.00 ± 11.36 vs. -3.50 ± 6.87,
P
-value < 0.001).
Conclusion
Butyrate may be an effective adjunct treatment for active UC patients by reducing biomarkers of inflammation, upregulation of circadian-clock genes and improving sleep quality and QoL.
Journal Article
Telling time
\"A young boy learns to tell time on digital and analog clocks as he impatiently waits for a friend to come over to play.\"-- Provided by publisher.
Book
The Circadian Clock, Nutritional Signals and Reproduction: A Close Relationship
The circadian rhythm, which is necessary for reproduction, is controlled by clock genes. In the mouse uterus, the oscillation of the circadian clock gene has been observed. The transcription of the core clock gene period (Per) and cryptochrome (Cry) is activated by the heterodimer of the transcription factor circadian locomotor output cycles kaput (Clock) and brain and muscle Arnt-like protein-1 (Bmal1). By binding to E-box sequences in the promoters of Per1/2 and Cry1/2 genes, the CLOCK-BMAL1 heterodimer promotes the transcription of these genes. Per1/2 and Cry1/2 form a complex with the Clock/Bmal1 heterodimer and inactivate its transcriptional activities. Endometrial BMAL1 expression levels are lower in human recurrent-miscarriage sufferers. Additionally, it was shown that the presence of BMAL1-depleted decidual cells prevents trophoblast invasion, highlighting the importance of the endometrial clock throughout pregnancy. It is widely known that hormone synthesis is disturbed and sterility develops in Bmal1-deficient mice. Recently, we discovered that animals with uterus-specific Bmal1 loss also had poor placental development, and these mice also had intrauterine fetal death. Furthermore, it was shown that time-restricted feeding controlled the uterine clock’s circadian rhythm. The uterine clock system may be a possibility for pregnancy complications, according to these results. We summarize the most recent research on the close connection between the circadian clock and reproduction in this review.
Journal Article