Modeling the Influence of Synaptic Plasticity on After-effects

2019 ◽  
Vol 34 (6) ◽  
pp. 645-657
Author(s):  
Semra Foster ◽  
Tom Christiansen ◽  
Michael C. Antle
Keyword(s):  
Mathematical Model ◽  
Synaptic Plasticity ◽  
Circadian Rhythms ◽  
Weighted Average ◽  
Cycle Period ◽  
Circadian Period ◽  
After Effects ◽  
A Cell ◽  
Free Running ◽  
And Behavior

While circadian rhythms in physiology and behavior demonstrate remarkable day-to-day precision, they are also able to exhibit plasticity in a variety of parameters and under a variety of conditions. After-effects are one type of plasticity in which exposure to non–24-h light-dark cycles (T-cycles) will alter the animal’s free-running rhythm in subsequent constant conditions. We use a mathematical model to explore whether the concept of synaptic plasticity can explain the observation of after-effects. In this model, the SCN is composed of a set of individual oscillators randomly selected from a normally distributed population. Each cell receives input from a defined set of oscillators, and the overall period of a cell is a weighted average of its own period and that of its inputs. The influence that an input has on its target’s period is determined by the proximity of the input cell’s period to the imposed T-cycle period, such that cells with periods near T will have greater influence. Such an arrangement is able to duplicate the phenomenon of after-effects, with relatively few inputs per cell (~4-5) being required. When the variability of periods between oscillators is low, the system is quite robust and results in minimal after-effects, while systems with greater between-cell variability exhibit greater magnitude after-effects. T-cycles that produce maximal after-effects have periods within ~2.5 to 3 h of the population period. Overall, this model demonstrates that synaptic plasticity in the SCN network could contribute to plasticity of the circadian period.

scholarly journals Is the cell division cycle gated by a circadian clock? The case of Chlamydomonas reinhardtii.

1995 ◽  
Vol 129 (4) ◽  
pp. 1061-1069 ◽  
Author(s):  
K Goto ◽  
C H Johnson
Keyword(s):  
Cell Division ◽  
Circadian Clock ◽  
Chlamydomonas Reinhardtii ◽  
Cell Division Cycle ◽  
Circadian Rhythmicity ◽  
Circadian Period ◽  
Circadian Oscillators ◽  
A Cell ◽  
Free Running

Circadian oscillators are known to regulate the timing of cell division in many organisms. In the case of Chlamydomonas reinhardtii, however, this conclusion has been challenged by several investigators. We have reexamined this issue and find that the division behavior of Chlamydomonas meets all the criteria for circadian rhythmicity: persistence of a cell division rhythm (a) with a period of approximately 24 h under free-running conditions, (b) that is temperature compensated, and (c) which can entrain to light/dark signals. In addition, a mutation that lengthens the circadian period of the phototactic rhythm similarly affects the cell division rhythm. We conclude that a circadian mechanism determines the timing of cell division in Chlamydomonas reinhardtii.

Circadian activity of the white sucker, Catostomus commersoni: comparison of individual and shoaling fish

1980 ◽  
Vol 58 (8) ◽  
pp. 1399-1403 ◽  
Author(s):  
Martin Kavaliers
Keyword(s):  
Locomotor Activity ◽  
Circadian Rhythms ◽  
Social Organization ◽  
Constant Darkness ◽  
White Sucker ◽  
Circadian Period ◽  
Circadian Activity ◽  
Catostomus Commersoni ◽  
Free Running ◽  
Precise Version

Individual and shoaling white suckers, Catostomus commersoni, displayed free running circadian rhythms of locomotor activity under conditions of constant darkness and temperature. The circadian activity of shoals was different from that of single fish. The activity of single fish was rhythmic initially with a period of less than 24 h, but became arrhythmic after 15–30 days. Shoals of white suckers had a less variable circadian period that was greater than 24 h, and showed no evidence of arrhythmicity. The circadian activity of shoals is determined by its behavioural and social organization; it is not simply a more precise version of the activity of single fish.

scholarly journals Dissociation of Per1 and Bmal1 circadian rhythms in the suprachiasmatic nucleus in parallel with behavioral outputs

2017 ◽  
Vol 114 (18) ◽  
pp. E3699-E3708 ◽  
Author(s):  
Daisuke Ono ◽  
Sato Honma ◽  
Yoshihiro Nakajima ◽  
Shigeru Kuroda ◽  
Ryosuke Enoki ◽  
...  
Keyword(s):  
Circadian Rhythms ◽  
Suprachiasmatic Nucleus ◽  
Clock Genes ◽  
Behavioral Rhythm ◽  
Calcium Indicator ◽  
Intracellular Ca ◽  
Regional Specificity ◽  
Free Running ◽  
Activity Onset ◽  
And Behavior

The temporal order of physiology and behavior in mammals is primarily regulated by the circadian pacemaker located in the hypothalamic suprachiasmatic nucleus (SCN). Taking advantage of bioluminescence reporters, we monitored the circadian rhythms of the expression of clock genes Per1 and Bmal1 in the SCN of freely moving mice and found that the rate of phase shifts induced by a single light pulse was different in the two rhythms. The Per1-luc rhythm was phase-delayed instantaneously by the light presented at the subjective evening in parallel with the activity onset of behavioral rhythm, whereas the Bmal1-ELuc rhythm was phase-delayed gradually, similar to the activity offset. The dissociation was confirmed in cultured SCN slices of mice carrying both Per1-luc and Bmal1-ELuc reporters. The two rhythms in a single SCN slice showed significantly different periods in a long-term (3 wk) culture and were internally desynchronized. Regional specificity in the SCN was not detected for the period of Per1-luc and Bmal1-ELuc rhythms. Furthermore, neither is synchronized with circadian intracellular Ca2+ rhythms monitored by a calcium indicator, GCaMP6s, or with firing rhythms monitored on a multielectrode array dish, although the coupling between the circadian firing and Ca2+ rhythms persisted during culture. These findings indicate that the expressions of two key clock genes, Per1 and Bmal1, in the SCN are regulated in such a way that they may adopt different phases and free-running periods relative to each other and are respectively associated with the expression of activity onset and offset.

Behavioral and neurochemical sources of variability of circadian period and phase: studies of circadian rhythms of npy−/− mice

2007 ◽  
Vol 292 (3) ◽  
pp. R1306-R1314 ◽  
Author(s):  
Mary Harrington ◽  
Penny Molyneux ◽  
Stephanie Soscia ◽  
Cheruba Prabakar ◽  
Judy McKinley-Brewer ◽  
...  
Keyword(s):  
Locomotor Activity ◽  
Circadian Rhythms ◽  
Activity Patterns ◽  
Circadian Period ◽  
Running Wheel ◽  
Clock Period ◽  
A Value ◽  
Free Running ◽  
The Mean ◽  
Delayed Phase

The cycle length or period of the free-running rhythm is a key characteristic of circadian rhythms. In this study we verify prior reports that locomotor activity patterns and running wheel access can alter the circadian period, and we report that these treatments also increase variability of the circadian period between animals. We demonstrate that the loss of a neurochemical, neuropeptide Y (NPY), abolishes these influences and reduces the interindividual variability in clock period. These behavioral and environmental influences, from daily distribution of peak locomotor activity and from access to a running wheel, both act to push the mean circadian period to a value < 24 h. Magnitude of light-induced resetting is altered as well. When photoperiod was abruptly changed from a 18:6-h light-dark cycle (LD18:6) to LD6:18, mice deficient in NPY were slower to respond to the change in photoperiod by redistribution of their activity within the prolonged dark and eventually adopted a delayed phase angle of entrainment compared with controls. These results support the hypothesis that nonphotic influences on circadian period serve a useful function when animals must respond to abruptly changing photoperiods and point to the NPYergic pathway from the intergeniculate leaflet innervating the suprachiasmatic nucleus as a circuit mediating these effects.

scholarly journals On the optimal control of coronavirus (2019-nCov) mathematical model; a numerical approach

2020 ◽  
Vol 2020 (1) ◽  
Author(s):  
N. H. Sweilam ◽  
S. M. Al-Mekhlafi ◽  
A. O. Albalawi ◽  
D. Baleanu
Keyword(s):  
Mathematical Model ◽  
Optimal Control ◽  
Weighted Average ◽  
Necessary Optimality Conditions ◽  
Numerical Approach ◽  
Population Number ◽  
Infected People ◽  
The Stability ◽  
Novel Coronavirus ◽  
Theoretical Results

Abstract In this paper, a novel coronavirus (2019-nCov) mathematical model with modified parameters is presented. This model consists of six nonlinear fractional order differential equations. Optimal control of the suggested model is the main objective of this work. Two control variables are presented in this model to minimize the population number of infected and asymptotically infected people. Necessary optimality conditions are derived. The Grünwald–Letnikov nonstandard weighted average finite difference method is constructed for simulating the proposed optimal control system. The stability of the proposed method is proved. In order to validate the theoretical results, numerical simulations and comparative studies are given.

scholarly journals Shared Components of the FRQ-Less Oscillator and TOR Pathway Maintain Rhythmicity in Neurospora

2021 ◽  
pp. 074873042199994
Author(s):  
Rosa Eskandari ◽  
Lalanthi Ratnayake ◽  
Patricia L. Lakin-Thomas
Keyword(s):  
Circadian Rhythms ◽  
Clock Genes ◽  
Nutrient Sensing ◽  
Mass Spectrometry Analysis ◽  
Growth Responses ◽  
Tor Pathway ◽  
Spectrometry Analysis ◽  
Binding Partner ◽  
Binding Partners ◽  
Free Running

Molecular models for the endogenous oscillators that drive circadian rhythms in eukaryotes center on rhythmic transcription/translation of a small number of “clock genes.” Although substantial evidence supports the concept that negative and positive transcription/translation feedback loops (TTFLs) are responsible for regulating the expression of these clock genes, certain rhythms in the filamentous fungus Neurospora crassa continue even when clock genes ( frq, wc-1, and wc-2) are not rhythmically expressed. Identification of the rhythmic processes operating outside of the TTFL has been a major unresolved area in circadian biology. Our lab previously identified a mutation ( vta) that abolishes FRQ-less rhythmicity of the conidiation rhythm and also affects rhythmicity when FRQ is functional. Further studies identified the vta gene product as a component of the TOR (Target of Rapamycin) nutrient-sensing pathway that is conserved in eukaryotes. We now report the discovery of TOR pathway components including GTR2 (homologous to the yeast protein Gtr2, and RAG C/D in mammals) as binding partners of VTA through co-immunoprecipitation (IP) and mass spectrometry analysis using a VTA-FLAG strain. Reciprocal IP with GTR2-FLAG found VTA as a binding partner. A Δ gtr2 strain was deficient in growth responses to amino acids. Free-running conidiation rhythms in a FRQ-less strain were abolished in Δ gtr2. Entrainment of a FRQ-less strain to cycles of heat pulses demonstrated that Δ gtr2 is defective in entrainment. In all of these assays, Δ gtr2 is similar to Δ vta. In addition, expression of GTR2 protein was found to be rhythmic across two circadian cycles, and functional VTA was required for GTR2 rhythmicity. FRQ protein exhibited the expected rhythm in the presence of GTR2 but the rhythmic level of FRQ dampened in the absence of GTR2. These results establish association of VTA with GTR2, and their role in maintaining functional circadian rhythms through the TOR pathway.

Restricted food access and light-dark: impact of conflicting zeitgebers on circadian rhythms of the rabbit

1993 ◽  
Vol 264 (4) ◽  
pp. R708-R715 ◽  
Author(s):  
B. Jilge ◽  
H. Stahle
Keyword(s):  
Circadian Rhythms ◽  
Phase Difference ◽  
Food Access ◽  
Activity Rhythm ◽  
Light Period ◽  
The Other ◽  
Behavioral Rhythms ◽  
Activity Component ◽  
Common Control ◽  
Free Running

Free-running circadian rhythms of rabbits were exposed to a 11:55-11:55-h light-dark (LD) schedule. After complete entrainment (63 +/- 22 days), the predominantly nocturnally active rabbits were exposed to an additional zeitgeber, restricted food access (RF), which was imposed during the light period. In five animals RF had the same period (T) as the LD cycle (23:50 h), and in five other animals TRF was 24:10 h. At a period of 23:50 h for both zeitgebers, the rhythms of four animals were stably entrained to RF, while in one animal a component of the rhythm broke away from RF and entrained to the LD zeitgeber. In animals exposed to zeitgebers of different periods most of the activity rhythm also entrained to RF, but 20 +/- 7% of the activity entrained to the LD zeitgeber. The light-entrained activity component merged with the RF component when the zeitgebers crossed, and decomposition occurred when the phase difference exceeded 4-6 h. The results indicate that two circadian oscillator systems exist in the rabbit, one entrained by light-dark cycles and the other by feeding-fasting cycles. Both exert common control over a number of overt behavioral rhythms.

Sign in / Sign up

Export Citation Format

Share Document