We tested the hypothesis that acute hypoxia may alter the circadian pattern of body temperature in adult humans. Six healthy subjects were studied in normoxia, hypoxia (approximately 13% inspired O(2)), and again normoxia, each session lasting >24 h and spaced a few days apart, with a constant routine protocol of sustained wakefulness and minimal activity. Some parameters (e.g., tympanic and abdominal temperatures, heart rate) were recorded continuously; others (e.g., oxygen consumption and pulmonary ventilation) were monitored for approximately 10 min every 2 h. The amplitudes of the circadian oscillation of tympanic, abdominal, and calf skin temperatures were reduced in hypoxia, averaging, respectively, 61%, 80% and 50% of the normoxic amplitude. Oxygen consumption and pulmonary ventilation, which presented a circadian pattern in normoxia, had no longer significant oscillations during hypoxia, whereas the opposite was the case for heart rate and diastolic pressure. Therefore, acute hypoxia can disturb the normal circadian patterns and, specifically, depress those of body temperature. These effects, qualitatively similar to those observed in chronically hypoxic animals and humans, could contribute to sleep disturbances at high altitude.

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Epidemiological studies have linked high consumption of meat with major age-related diseases including cardiovascular diseases. Abnormal postprandial increases in plasma lipids after a meat meal have been hypothesized among the pathogenetic mechanisms. However, it is still unknown if the postprandial serum derived after a normal meat meal is able to affect endothelial function, and if the type of meat and the age of the donors are critical factors. Here, we show the effects of postprandial sera derived from healthy adults and elderly volunteers who consumed meat meals on human coronary artery endothelial cell (HCAEC) oxidative stress, gene expression, DNA damage, and cellular senescence. We observed that a single exposure to postprandial serum induces a slight increase in ROS that is associated with modulation of gene expression pathways related to oxidative stress response and metabolism. The postprandial-induced increase in ROS is not associated with a measurable DNA oxidative damage. However, repeated exposure to postprandial serum induces an acceleration of cellular senescence. Taking into account the deleterious role of cellular senescence in age-related vascular diseases, the results suggest a new mechanism by which excessive meat consumption and time spent in postprandial state may affect health status during aging.

Objective: Cellular senescence is a phenotypic state characterized by stable cell-cycle arrest, enhanced lysosomal activity, and the secretion of inflammatory molecules and matrix degrading enzymes. Senescence has been implicated in osteoarthritis (OA) pathophysiology; however, the mechanisms that drive senescence induction in cartilage and other joint tissues are unknown. While numerous physiological signals are capable of initiating the senescence phenotype, one emerging theme is that growth-arrested cells convert to senescence in response to sustained mitogenic stimulation. The goal of this study was to develop an in vitro articular cartilage explant model to investigate the mechanisms of senescence induction.Design: This study utilized healthy articular cartilage derived from cadaveric equine stifles and human ankles.Explants were irradiated or treated with palbociclib to initiate cell cycle arrest, and mitogenic stimulation was provided by serum-containing medium (horse) and the inclusion of growth factors (human). The primary readout of senescence was a quantitative flow cytometry assay to detect senescence-associated ꞵ galactosidase activity (SA-ꞵ-gal).Results: Irradiation of equine explants caused 25.39% of cells to express high levels of SA-ꞵ-gal, as compared to 3.82% in control explants (p=0.0031). For human cartilage, explants that received both mitogenic stimulation and cell cycle arrest showed increased rates of senescence induction as compared to baseline control (7.16% vs. 2.34% SA-ꞵ-gal high, p=0.0007).Conclusions: Treatment of cartilage explants with mitogenic stimuli in the context of cell-cycle arrest reliably induces high levels of SA-β gal activity, which provides a physiologically relevant model system to investigate the mechanisms of senescence induction. Introduction:Osteoarthritis (OA) is a disease characterized by joint pain and progressive degradation of articular cartilage and other tissues of the joint 1,2 . As the most common chronic disease of the articular joint, OA produces a substantial burden on society and the economy 3,4 . Despite increasing knowledge about factors contributing to the progression of OA, there are no approved disease-modifying therapies 5 , leading to high rates of total joint replacement 6 . Risk factors for OA include obesity, joint injury, and genetic predisposition, with the most dominant risk factor being aging 7,8 . Cellular senescence has been described as a key phenotype associated with aging 9 , and there is mounting evidence that the accumulation of senescent cells in the joint during both aging and in response to injury contributes to the development of OA 10-14 . Senescent chondrocytes likely contribute to tissue degradation by producing pro-inflammatory and matrix-degrading molecules known collectively as the senescence-associated secretory phenotype (SASP) 15,16 . Significant advances have begun to unravel the role of senescence in OA and the therapeutic implications of such findings, including the potential for senolytic therapy as a potential di...