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- ItemOut of the lab and into the bathroom: Evening short-term exposure to conventional light suppresses melatonin and increases alertness perception(Basel : MDPI AG, 2013) Wahnschaffe, A.; Haedel, S.; Rodenbeck, A.; Stoll, C.; Rudolph, H.; Kozakov, R.; Schoepp, H.; Kunz, D.Life in 24-h society relies on the use of artificial light at night that might disrupt synchronization of the endogenous circadian timing system to the solar day. This could have a negative impact on sleep-wake patterns and psychiatric symptoms. The aim of the study was to investigate the influence of evening light emitted by domestic and work place lamps in a naturalistic setting on melatonin levels and alertness in humans. Healthy subjects (6 male, 3 female, 22-33 years) were exposed to constant dim light (<10 lx) for six evenings from 7:00 p.m. to midnight. On evenings 2 through 6, 1 h before habitual bedtime, they were also exposed to light emitted by 5 different conventional lamps for 30 min. Exposure to yellow light did not alter the increase of melatonin in saliva compared to dim light baseline during (38 ± 27 pg/mL vs. 39 ± 23 pg/mL) and after light exposure (39 ± 22 pg/mL vs. 44 ± 26 pg/mL). In contrast, lighting conditions including blue components reduced melatonin increase significantly both during (office daylight white: 25 ± 16 pg/mL, bathroom daylight white: 24 ± 10 pg/mL, Planon warm white: 26 ± 14 pg/mL, hall daylight white: 22 ± 14 pg/mL) and after light exposure (office daylight white: 25 ± 15 pg/mL, bathroom daylight white: 23 ± 9 pg/mL, Planon warm white: 24 ± 13 pg/mL, hall daylight white: 22 ± 26 pg/mL). Subjective alertness was significantly increased after exposure to three of the lighting conditions which included blue spectral components in their spectra. Evening exposure to conventional lamps in an everyday setting influences melatonin excretion and alertness perception within 30 min.
- ItemCardio-respiratory coordination increases during sleep apnea(San Francisco, CA : Public Library of Science (PLoS), 2014) Riedl, M.; MĂ¼ller, A.; Kraemer, J.F.; Penzel, T.; Kurths, J.; Wessel, N.Cardiovascular diseases are the main source of morbidity and mortality in the United States with costs of more than $170 billion. Repetitive respiratory disorders during sleep are assumed to be a major cause of these diseases. Therefore, the understanding of the cardio-respiratory regulation during these events is of high public interest. One of the governing mechanisms is the mutual influence of the cardiac and respiratory oscillations on their respective onsets, the cardiorespiratory coordination (CRC). We analyze this mechanism based on nocturnal measurements of 27 males suffering from obstructive sleep apnea syndrome. Here we find, by using an advanced analysis technique, the coordigram, not only that the occurrence of CRC is significantly more frequent during respiratory sleep disturbances than in normal respiration (p-value<10-51) but also more frequent after these events (p-value<10-15). Especially, the latter finding contradicts the common assumption that spontaneous CRC can only be observed in epochs of relaxed conditions, while our newly discovered epochs of CRC after disturbances are characterized by high autonomic stress. Our findings on the connection between CRC and the appearance of sleep-disordered events require a substantial extension of the current understanding of obstructive sleep apneas and hypopneas.
- ItemOrder patterns networks (orpan) - A method to estimate time-evolving functional connectivity from multivariate time series(Lausanne : Frontiers Research Foundation, 2012) Schinkel, S.; Zamora-LĂ³pez, G.; Dimigen, O.; Sommer, W.; Kurths, J.Complex networks provide an excellent framework for studying the function of the human brain activity. Yet estimating functional networks from measured signals is not trivial, especially if the data is non-stationary and noisy as it is often the case with physiological recordings. In this article we propose a method that uses the local rank structure of the data to define functional links in terms of identical rank structures. The method yields temporal sequences of networks which permits to trace the evolution of the functional connectivity during the time course of the observation. We demonstrate the potentials of this approach with model data as well as with experimental data from an electrophysiological study on language processing.
- ItemInsulin adsorption to catheter materials used for intensive insulin therapy in critically ill patients: Polyethylene versus polyurethane - possible cause of variation in glucose control?(Sharjah : Bentham Science Publishers B.V., 2014) Ley, S.C.; Ammann, J.; Herder, C.; Dickhaus, T.; Hartmann, M.; Kindgen-Milles, D.Introduction: Restoring and maintaining normoglycemia by intensified insulin therapy in critically ill patients is a matter of ongoing debate since the risk of hypoglycemia may outweigh positive effects on morbidity and mortality. In this context, adsorption of insulin to different catheter materials may contribute to instability of glucose control. We studied the adsorption of insulin to different tubing materials in vitro and the effects on glycemic control in vivo. Materials and Methods: In vitro experiments: A syringe pump was filled with 50 IU insulin diluted to 50 ml saline. A flow of 2 ml/h was perfused through polyethylene (PET) or polyurethane (PUR) tubing. Insulin concentrations were measured at the end of the tube for 24 hours using Bradford's protein assay. In vivo study: In a randomized double-blinded cross-over design, 10 intensive care patients received insulin via PET and PUR tubes for 24 hours each, targeting blood glucose levels of 80-150 mg/dl. We measured blood glucose levels, the insulin dose required to maintain target levels, and serum insulin and C-peptide levels. Results: In vitro experiments: After the start of the insulin infusion, only 20% (median, IQR 20-27) (PET) and 22% (IQR 16-27) (PUR) of the prepared insulin concentration were measured at the end of the 2 meter tubing. Using PET, after one hour infusion the concentration increased to 34% (IQR 29-36) and did not increase significantly during the next 24 hours (39% (IQR 39-40)). Using PUR, higher concentrations were detected than for PET at every measurement from 1 hour (82% (IQR 70-86)) to 24 hours (79% (IQR 64-87)). In vivo study: Glycemic control was effective and not different between groups. Significantly higher volumes of insulin solution had to be infused with PET compared to PUR (median PET 70.0 (IQR 56-82) ml vs. PUR 42 (IQR 31-63) ml; p=0.0015). Serum insulin concentrations did not decrease significantly one hour after changing to PET or PUR tubing. Conclusion: Polyurethane tubing systems allow application of insulin with significantly lower adsorption rates than polyethylene tubing systems. As a consequence, less insulin solution has to be infused to patients for effective blood glucose control. Tubing material of the insulin infusion may be crucial for safe and effective glycemic control in critically ill patients.
- ItemLiver Dysfunction and Phosphatidylinositol-3-Kinase Signalling in Early Sepsis: Experimental Studies in Rodent Models of Peritonitis(San Francisco, CA : Public Library of Science, 2012) Recknagel, P.; Gonnert, F.A.; Westermann, M.; Lambeck, S.; Lupp, A.; Rudiger, A.; Dyson, A.; CarrĂ©, J.E.; Kortgen, A.; Krafft, C.; Popp, J.; Sponholz, C.; Fuhrmann, V.; Hilger, I.; Claus, R.A.; Riedemann, N.C.; Wetzker, R.; Singer, M.; Trauner, M.; Bauer, M.Background: Hepatic dysfunction and jaundice are traditionally viewed as late features of sepsis and portend poor outcomes. We hypothesized that changes in liver function occur early in the onset of sepsis, yet pass undetected by standard laboratory tests. Methods and Findings: In a long-term rat model of faecal peritonitis, biotransformation and hepatobiliary transport were impaired, depending on subsequent disease severity, as early as 6 h after peritoneal contamination. Phosphatidylinositol-3-kinase (PI3K) signalling was simultaneously induced at this time point. At 15 h there was hepatocellular accumulation of bilirubin, bile acids, and xenobiotics, with disturbed bile acid conjugation and drug metabolism. Cholestasis was preceded by disruption of the bile acid and organic anion transport machinery at the canalicular pole. Inhibitors of PI3K partially prevented cytokine-induced loss of villi in cultured HepG2 cells. Notably, mice lacking the PI3Kγ gene were protected against cholestasis and impaired bile acid conjugation. This was partially confirmed by an increase in plasma bile acids (e.g., chenodeoxycholic acid [CDCA] and taurodeoxycholic acid [TDCA]) observed in 48 patients on the day severe sepsis was diagnosed; unlike bilirubin (area under the receiver-operating curve: 0.59), these bile acids predicted 28-d mortality with high sensitivity and specificity (area under the receiver-operating curve: CDCA: 0.77; TDCA: 0.72; CDCA+TDCA: 0.87). Conclusions: Liver dysfunction is an early and commonplace event in the rat model of sepsis studied here; PI3K signalling seems to play a crucial role. All aspects of hepatic biotransformation are affected, with severity relating to subsequent prognosis. Detected changes significantly precede conventional markers and are reflected by early alterations in plasma bile acids. These observations carry important implications for the diagnosis of liver dysfunction and pharmacotherapy in the critically ill. Further clinical work is necessary to extend these concepts into clinical practice. Please see later in the article for the Editors' Summary.