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How circadian clocks communicate with each other -- ScienceDaily

The Würzburg researchers found their master and slave theory confirmed by the work of their Chilean colleagues. The researchers in Chile had conducted a number of experiments in which they had artificially slowed down the circadian clocks of Drosophila in various combinations and observed the impact on the hatching behaviour. The results: When both clocks run more slowly, the "hatching rhythm" increases from normally 24 hours to over 27. A similar effect is observed when the peripheral clock continues to run at regular speed and the central clock is slowed down. Vice versa, however -- i.e. normal working central clock and slowed down peripheral clock -- the hatching behaviour remains unchanged at a 24-hour interval. "This is the first comprehensive experimental description of a pathway that links circadian clocks and it shows that the coupled-oscillator model is actually true in certain cases," says Christian Wegener. But he admits that science is still a long way from understanding the exact interactions of the circadian clocks. After all, the recent findings illustrate that the diverse mechanisms are heavily interwoven and provided with feedback loops. So Wegener is certain that "it is not going to be easy."

The Benefits of Exercising Before Breakfast - The New York Times

At the end, the nonexercising group was, to no one’s surprise, super-sized, having packed on an average of more than six pounds. They had also developed insulin resistance — their muscles were no longer responding well to insulin and weren’t pulling sugar (or, more technically, glucose) out of the bloodstream efficiently — and they had begun storing extra fat within and between their muscle cells. Both insulin resistance and fat-marbled muscles are metabolically unhealthy conditions that can be precursors of diabetes. The men who ate breakfast before exercising gained weight, too, although only about half as much as the control group. Like those sedentary big eaters, however, they had become more insulin-resistant and were storing a greater amount of fat in their muscles. Only the group that exercised before breakfast gained almost no weight and showed no signs of insulin resistance. They also burned the fat they were taking in more efficiently. “Our current data,” the study’s authors wrote, “indicate that exercise training in the fasted state is more effective than exercise in the carbohydrate-fed state to stimulate glucose tolerance despite a hypercaloric high-fat diet.”

Why Everything We Know About Salt May Be Wrong - The New York Times

Their urine volumes went up and down in a seven-day cycle. That contradicted all he’d been taught in medical school: There should be no such temporal cycle. In 1994, the Russian space program decided to do a 135-day simulation of life on the Mir space station. Dr. Titze arranged to go to Russia to study urine patterns among the crew members and how these were affected by salt in the diet. A striking finding emerged: a 28-day rhythm in the amount of sodium the cosmonauts’ bodies retained that was not linked to the amount of urine they produced. And the sodium rhythms were much more pronounced than the urine patterns.

Circadian meta rhythm needed for consciouness?

of Surrey and the University of Salzburg, Austria, examined circadian body temperature variations of 18 patients suffering from severe brain injuries and the potential link to consciousness. Circadian rhythms are an approximate 24-hour cycle governed by the body's internal clock and they determine a number of physiological processes in the body including core body temperature, which fluctuates throughout the day. To assess the body temperature of patients, researchers used four external skin sensors to monitor the circadian rhythm, which was found to range between 23.5 hours and 26.3 hours. The level of consciousness of each patient was evaluated through the Coma Recovery Scale-Revised, which among others measures responsiveness to sound or a patient's ability to spontaneously open eyes without or only with stimulation by the examiner. Researchers discovered that patients who scored better on the Coma Recovery Scale-Revised, especially, those patients with a stronger arousal had body temperature patterns that were more closely aligned with a healthy 24-hour rhythm. This finding demonstrates a newly discovered relationship between circadian body temperature variation and the level of consciousness of a patient with severe brain damage. This finding suggests that patient's consciousness levels should be assessed during time windows when their circadian rhythm predicts them to be more responsive. The effects of bright light stimulation on patients with severe brain injuries was also investigated during this study. To measure its effectiveness, eight patients received bright light stimulation, three times per day for one hour over the course of one week. After one week, improvements were found in the level of consciousness of two patients, whose condition improved from vegetative state/unresponsive wakefulness to a minimally conscious state. Interestingly, in these two patients, a shift in their circadian body temperature, closer to a healthy 24-hour rhythm was also recorded. Co-investigator of the paper Dr Nayantara Santhi from the Surrey Sleep Research Centre, University of Surrey, said: "Prior to our study little was known about the circadian rhythms of patients with brain injuries. What we have learnt is that the circadian body temperature holds vital clues to the state of consciousness of patients which could potentially enable doctors to tailor medical treatment more effectively. "Circadian rhythms hold the secret to the workings of the body and we will be looking further into this in future research."

Cellular jetlag seems to favor the development of diabetes -- ScienceDaily

studied pancreatic ɑ- and β- cells that are in charge of the production of insulin and glucagon, two hormones that regulate glucose levels in the blood. They discovered that already at cellular levels, these internal clocks orchestrate the timing of proper hormone secretion, thus optimizing body metabolism by anticipating the rest-activity and feeding-fasting cycles. Their misalignment would thus favor the occurrence of metabolic diseases. Their discovery, to be read in the journal Genes and Development, highlights an essential factor, yet still poorly understood, which may explain diabetes development as a consequence of circadian misalignments of these cellular clocks.

Bad timing is depressing: Disrupting the brain's internal clock causes depressive-like behavior in mice -- ScienceDaily

Inherent circadian clocks help us function throughout the day, by telling us when to sleep, wake and eat, as well as by synchronizing our bodily processes. "It is perhaps not surprising that disruptions of our natural synchronization can have heavy impacts on our physical and mental health," Dr. Landgraf added. However, until now researchers did not know if disturbed circadian rhythms were a cause or consequence of mood disorders. In the new study, a team led by David K. Welsh has shown for the first time a causal relationship between functioning circadian clocks and mood regulation.

Midnight munchies mangle memory: Eating at the wrong time impairs learning, memory -- ScienceDaily

Some genes involved in both the circadian clock and in learning and memory are regulated by a protein called CREB (cAMP response element-binding protein). When CREB is less active, it decreases memory, and may play a role in the onset of Alzheimer's disease. In the mice fed at the wrong time, the total activity of CREB throughout the hippocampus was significantly reduced, with the strongest effects in the day. However, the master pacemaker of the circadian system, the suprachiasmatic nucleus located in the hypothalamus, is unaffected. This leads to desynchrony between the clocks in the different brain regions (misalignment), which the authors suggest underlies the memory impairment. "Modern schedules can lead us to eat around the clock so it is important to understand how the timing of food can impact cogitation" says Professor Christopher Colwell from the Department of Psychiatry and Biobehavioral Sciences at UCLA. "For the first time, we have shown that simply adjusting the time when food is made available alters the molecular clock in the hippocampus and can alter the cognitive performance of mice." Eating at the wrong time also disrupted sleep patterns. The inappropriate feeding schedule resulted in the loss of the normal day/night difference in the amount of sleep although the total time spent asleep over 24 hours was not changed. Sleep became fragmented, with the mice catching up on sleep by grabbing more short naps throughout the day and night.