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Author (up) Kujanik, S.; Mikulecky, M. url  doi
openurl 
  Title Circadian and ultradian extrasystole rhythms in healthy individuals at elevated versus lowland altitudes Type Journal Article
  Year 2010 Publication International Journal of Biometeorology Abbreviated Journal Int J Biometeorol  
  Volume 54 Issue 5 Pages 531-538  
  Keywords Human Health; Acclimatization/physiology; Aged; *Altitude; Anoxia/etiology; Cardiac Complexes, Premature/*physiopathology; Circadian Rhythm/*physiology; Electrocardiography, Ambulatory; Heart Rate/*physiology; Humans; Male; Middle Aged; Reference Values; Time Factors  
  Abstract We defined chronobiologic norms for supraventricular and ventricular single extrasystoles (SV and VE, respectively) in healthy older males in lowland areas. The study was extended to higher altitudes, where hypobaric hypoxia was expected to increase extrasystole frequency, while perhaps not changing rhythmicity. In healthy men (lowland n = 37, altitude n = 22), aged 49-72 years, mean numbers of SVs and VEs were counted over a 24-h period. Cosinor regression was used to test the 24-h rhythm and its 2nd-10th harmonics. The resulting approximating function for either extrasystole type includes its point, 95% confidence interval of the mean, and 95% tolerance for single measurement estimates. Separate hourly differences (delta) between altitude and lowland (n = 59) were also analysed. Hourly means were significantly higher in the mountains versus lowland, by +0.8 beats/h on average for SVs, and by +0.9 beats/h for VEs. A relatively rich chronogram for VEs in mountains versus lowland exists. Delta VEs clearly display a 24-h component and its 2nd, 3rd, 4th and 7th harmonics. This results in significantly higher accumulation of VEs around 8.00 a.m., 11.00 a.m. and 3.00 p.m. in the mountains. The increase in extrasystole occurrence in the mountains is probably caused by higher hypobaric hypoxia and resulting sympathetic drive. Healthy men at elevated altitudes show circadian and several ultradian rhythms of single VEs dependent on the hypoxia level. This new methodological approach--evaluating the differences between two locations using delta values--promises to provide deeper insight into the occurrence of premature beats.  
  Address Dept of Physiology, Faculty of Medicine, Pavol Jozef Safarik University, Trieda SNP 1, 040 66 Kosice, Slovak Republic. stefan.kujanik@upjs.sk  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0020-7128 ISBN Medium  
  Area Expedition Conference  
  Notes PMID:20195873 Approved no  
  Call Number LoNNe @ kagoburian @ Serial 774  
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Author (up) Li, Y.; Ma, W.; Kang, Q.; Qiao, L.; Tang, D.; Qiu, J.; Zhang, Q.; Li, H. url  doi
openurl 
  Title Night or darkness, which intensifies the feeling of fear? Type Journal Article
  Year 2015 Publication International Journal of Psychophysiology : Official Journal of the International Organization of Psychophysiology Abbreviated Journal Int J Psychophysiol  
  Volume 97 Issue 1 Pages 46–57  
  Keywords Human Health; Circadian rhythm; Dark; Heart rate; Nighttime fear; Sensory modality; Skin conductance  
  Abstract Nighttime fear is a phenomenon in which people feel more afraid of threats at night. Despite the vast amount of psychological research on nighttime fear, previous researchers have not accurately distinguished between “night” and “darkness”, both of which play important roles in nighttime fear. We collected physiological (skin conductance response and heart rate) and psychological (self-report) data simultaneously to investigate the effects of “night” and “darkness” on fearful feelings and whether these effects were moderated by the mode of stimulus delivery (i.e., visual or auditory). Specifically, two tasks were employed in which time (day vs. night), illumination (light vs. darkness) and stimulus type (fearful vs. neutral) were manipulated. Participants (n=128) were exposed to visual and auditory oddball tasks consisting of fearful and neutral stimuli. The results indicated that there were significant increases in fear responses at night, and the difference between day and night was significant for fear stimuli but not for neutral events. Furthermore, these effects were consistent over different sensory modalities (visual and auditory). The results of this study underscore the importance of the day-night cycle in fear-related information processing and suggest that further attention needs to be paid to the influence of the biological circadian rhythm on these processes. The current findings could inform a deeper understanding of anxiety and fear-related disorders, and thus, we invite future studies to illuminate the underlying neurobiological mechanisms therein.  
  Address Institute of Brain Function and Psychological Science, Shenzhen University, Shenzhen, 518060, P. R. China  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0167-8760 ISBN Medium  
  Area Expedition Conference  
  Notes PMID:25957698 Approved no  
  Call Number LoNNe @ christopher.kyba @ Serial 1168  
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Author (up) Ruger, M.; Gordijn, M.C.M.; Beersma, D.G.M.; de Vries, B.; Daan, S. url  doi
openurl 
  Title Time-of-day-dependent effects of bright light exposure on human psychophysiology: comparison of daytime and nighttime exposure Type Journal Article
  Year 2006 Publication American Journal of Physiology. Regulatory, Integrative and Comparative Physiology Abbreviated Journal Am J Physiol Regul Integr Comp Physiol  
  Volume 290 Issue 5 Pages R1413-20  
  Keywords Human Health; Adult; Body Temperature/*physiology; Circadian Rhythm/*physiology; Fatigue/*physiopathology; Heart Rate/*physiology; Humans; Hydrocortisone/*blood; *Light; Sleep Stages/*physiology  
  Abstract Bright light can influence human psychophysiology instantaneously by inducing endocrine (suppression of melatonin, increasing cortisol levels), other physiological changes (enhancement of core body temperature), and psychological changes (reduction of sleepiness, increase of alertness). Its broad range of action is reflected in the wide field of applications, ranging from optimizing a work environment to treating depressed patients. For optimally applying bright light and understanding its mechanism, it is crucial to know whether its effects depend on the time of day. In this paper, we report the effects of bright light given at two different times of day on psychological and physiological parameters. Twenty-four subjects participated in two experiments (n = 12 each). All subjects were nonsmoking, healthy young males (18-30 yr). In both experiments, subjects were exposed to either bright light (5,000 lux) or dim light <10 lux (control condition) either between 12:00 P.M. and 4:00 P.M. (experiment A) or between midnight and 4:00 A.M. (experiment B). Hourly measurements included salivary cortisol concentrations, electrocardiogram, sleepiness (Karolinska Sleepiness Scale), fatigue, and energy ratings (Visual Analog Scale). Core body temperature was measured continuously throughout the experiments. Bright light had a time-dependent effect on heart rate and core body temperature; i.e., bright light exposure at night, but not in daytime, increased heart rate and enhanced core body temperature. It had no significant effect at all on cortisol. The effect of bright light on the psychological variables was time independent, since nighttime and daytime bright light reduced sleepiness and fatigue significantly and similarly.  
  Address Department of Chronobiology, University of Groningen, The Netherlands. Melanie.Rueger@med.nyu.edu  
  Corporate Author Thesis  
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  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0363-6119 ISBN Medium  
  Area Expedition Conference  
  Notes PMID:16373441 Approved no  
  Call Number LoNNe @ kagoburian @ Serial 801  
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