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'Circadian Rhythm' in keywords Facet   Publication Year 1984  [X]
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1984[X]
1Author    Margarete Hoffmans-Hohn, W. Olfgang, M. Artin, Klaus BrinkmRequires cookie*
 Title    Multiple Periodicities in the Circadian System of Unicellular Algae  
 Abstract    Three periodicities in the circadian range are observed when m easuring circadian parameters of unicellular organisms in long running experim ents (m ore than 15 days). This is dem onstrated for different organisms (Chlamydomonas, Euglena, C hlorella) and different parameters (auto­ kinesis, extracellular pH, C 0 2-and 0 2-partial pressure). H aving excluded analytical and experimental artefacts {i.e. filter leakage and subpopulation effects), the m ultiple periodicities have to be interpreted in a physiological m odel. The three p eriod icities always exhibit two common features: The locations o f the side peaks are sym m etrical to the m iddle peak and their energy contribution is always the same. W e therefore favour the m odel o f m ultiplicative coupling between the circadian oscillator and a low frequency oscillator m odulating the am plitude o f the circadian rhythm. Since the low frequency rhythm is not correlated to any exogenously running periodicity o f the experim ental surroundings, it is considered as generated by an endogenous oscillator. This shows the existence o f different biological long tim e oscillators in one single cell and contradicts the so-called m aster-clock hypothesis stating that one cell has only one clock related oscillator. 
  Reference    Z. Naturforsch. 39c, 791—8 (1984); received D ecem ber 5 1983/M arch 17 1984 
  Published    1984 
  Keywords    Circadian Rhythm, pH-Rhythm, Chlamydomonas, Euglena, Chlorella 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0791.pdf 
 Identifier    ZNC-1984-39c-0791 
 Volume    39 
2Author    Ken GotoRequires cookie*
 Title    in Lemna  
 Abstract    Biochemical aspects o f circadian rhythms were studied using a long-day duckweed, Lem na gibba G 3 cultured in short day condition (9 h light at 3800 lux follow ed by 15 h darkness), which was transferred in continuous light (LL) at the end (LL 0) o f the last night period. With such a system I have previously reported a rhythm o f affinity for N A D + o f cytoplasm ic N A D -dependent glyceraldehyde 3-phosphate dehydrogenase (C yt-N A D -G P D) 180° out o f phase with that o f affinity for N A D P + o f chloroplastic N A D P -dependent G PD (C h l-N A D P -G P D) and that N A DP+ could increase in vitro the affinity for N A D P + o f C h l-N A D P -G PD . I report here that NA D P+ can decrease in vitro the affinity for N A D + o f C yt-N A D -G P D as well, and furthermore, that the in vivo level o f N A D P + oscillates in phase with the rhythm o f the affinity for N A D P + o f Chl-NADP-GPD. Moreover, I found the existence o f m irror-image circadian rhythms, o f com parable am pli­ tudes, o f in vivo levels o f N A D + + N A D H (total N A D) (with peaks, as the ones o f C yt-N A D -GPD. at LL 0 and 24) and o f N A D P + + N A D P H (total N A D P) (with peaks, as the ones o f Chl-NADP-G PD, at LL 12 and 36). Consequently, a circadian rhythm in the rate o f net in vivo production o f total N A D P (or N A D) m ight be expected 90° in advance o f that in the level o f total NADP (or N A D). Indeed. I found oscillations in the activities o f N A D kinase and o f NA DP phosphatase with peaks occurring, respectively, at LL 6 and at LL 18. Moreover, in vitro treatments with EGTA (a Ca2+-chelator), chlorprom azine and W 7 (both inhibitors o f cal­ modulin) were able to both inhibit N A D kinase from its highest level o f activity to its m inim al one and activate N A D P phosphatase from its lowest level o f activity to its maxim al one. I conclude, therefore, that the in vivo level o f C a2+-calm odulin could oscillate in phase with the rhythm o f N A D kinase activity and induce the mirror-image circadian rhythms o f activities o f NA D kinase and o f NA D P phosphatase. I propose that the control sequence among the several circadian rhythms I studied could start with changes in Ca2+-calm odulin, then proceed through oscillations in N A D kinase and N A D P phosphatase activities, leading to changes in N A D +, N A D P +, and N A D P H levels, which would themselves induce the C hl-N A D P -G PD and C yt-N A D -G P D rhythms. 
  Reference    Z. Naturforsch. 39c, 73 (1984); received June 16/Septem ber 19 1983 
  Published    1984 
  Keywords    Ca2+-Calmodulin, Circadian Rhythms, G lyceraldehyde 3-Phosphate Dehydrogenases (EC 12 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0073.pdf 
 Identifier    ZNC-1984-39c-0073 
 Volume    39 
3Author    T. Kreuels, R. Joerres, W. M. Artin, K. BrinkmannRequires cookie*
 Title    System Analysis of the Circadian Rhythm of Euglena gracilis, II: Masking Effects and Mutual Interactions of Light and Temperature Responses  
 Abstract    Motility o f Euglena gracilis shows free running circadian rhythms. The circadian system is sensitive to light and temperature signals, but it is always m asked by direct responses o f m otility to light (photokinesis) and temperature (therm okinesis). By means o f a com partim ental m odel which defines the interrelations between the pathways o f therm okinesis, photokinesis and the circadian system a unifying view o f effects o f temperature and light input signals is outlined. According to the model, and using double sine input signals the dynam ics o f thermokinesis is described by a differential am plifier with constant gain. Although thermokinesis heavily masks circadian responses to tem perature signals, the lim ited range o f circadian entrainment is indirectly dem onstrated by a lim ited reappearance o f free running circadian oscillations after stopping the tem perature program. Free running circadian oscillations do reappear only after pretreatment with tem perature periods near the circadian eigenperiod. A white mutant lacking photosynthesis is used to investigate the role o f photosynthesis in the signal processing. Although light synchronizes the circadian rhythms o f the white mutant if applied as single input, it does not affect the m otility if applied together with temperature inputs near the circadian eigenperiod. These results indicate frequency dependent m utual interactions between the model compartments. 
  Reference    Z. Naturforsch. 39c, 801—8 (1984); received February 2 2 /April 27 1984 
  Published    1984 
  Keywords    Circadian Rhythm, System Analysis, Euglena gracilis, Masking Temperature Responses 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0801.pdf 
 Identifier    ZNC-1984-39c-0801 
 Volume    39