Changes In Period Length Research Articles

The association of COVID-19 vaccination and menstrual health: A period-tracking app-based cohort study

BackgroundIn initial COVID-19 clinical trials, menstrual health was not formally monitored, yet anecdotal reports of menstruation changes surfaced on social media. This study aims to assess the association between COVID-19 vaccines and menstruation using Clue, a period-tracking application. Study designA survey assessing demographics, menstrual health, stress levels, and COVID-19 vaccination was sent to Clue users between 12/7/2021 and 2/9/2022. Inclusion criteria were (1) 18 years or older (2) currently menstruating (3) not pregnant or breastfeeding since 1/2020. Menstrual data was collected for each participant. Users with cycle lengths more than 90 days were excluded. Cycle lengths were calculated for the 6-month average pre-vaccination (PRIOR), the cycle during which vaccination was administered (DURING), the cycle following DURING (AFTER1), and the cycle following AFTER1 (AFTER2). For periods, individuals were stratified based on whether vaccination was received during their menstrual period (DURING). Period lengths were additionally calculated for the 6-month average pre-vaccination (PRIOR), the first period following vaccination (AFTER1), and the period following AFTER1 (AFTER2). For unvaccinated participants, an index date (4/1/2022) was used to similarly designate menstrual cycles and periods. For each participant, cycle length changes for DURING, AFTER1, and AFTER2 compared to PRIOR were determined. Student’s t-test compared the mean of these changes between vaccinated and unvaccinated groups. ResultsOf 7,559 participants, 6,897 (91 %) were vaccinated. Compared to PRIOR, individuals vaccinated during their menstrual period demonstrated a statistically significant increase in the DURING period length, but not AFTER1 (p = 0.463) and AFTER2 (p = 0.692). No statistically significant changes were observed in period lengths of those vaccinated in between periods or in cycle lengths overall. ConclusionA small but statistically significant change in period length was observed only in individuals vaccinated for COVID-19 during their menstrual period. Providers can better counsel menstruating individuals to reduce vaccine misinformation.

Modeling the crosstalk between the circadian clock and ROS in Neurospora crassa

The circadian clock regulates the expression of clock-controlled genes and adapts to environmental changes. Reactive oxygen species (ROS) also undergo circadian rhythms and have a role in circadian timekeeping. To elucidate crosstalk between ROS and the circadian clock in Neurospora crassa, we build an integrative network model, characterizing the circadian oscillator, ROS system and their interactions. Notably, the (de)phosphorylation and nuclear-cytoplasmic shuttling of clock proteins are modeled in detail. Simulation results quantitatively reproduce the essential features of circadian rhythm (both in constant darkness and under light/dark cycles) and the changes in period length and phase when ROS levels are altered under diverse conditions. This work clarifies the effects of three interactions between ROS and the clock on the circadian rhythm, suggesting that the regulation of WCC activity by protein phosphatase 2A in an O2−-dependent manner plays a predominant role. The functional significance of such modulations is also discussed.

Chemomechanical oscillations with a non-redox non-oscillatory reaction.

Periodic length changes, over 20%, were sustained in a pH-responsive gel by associating the methylene glycol-sulphite OH-producing clock-reaction with variations of the exchange time induced between the core of the gel and a steady chemical environment. This is the first synergistic actuator that operates beyond acid-producing redox reactions.

Inference on periodicity of circadian time series

Estimation of the period length of time-course data from cyclical biological processes, such as those driven by the circadian pacemaker, is crucial for inferring the properties of the biological clock found in many living organisms. We propose a methodology for period estimation based on spectrum resampling (SR) techniques. Simulation studies show that SR is superior and more robust to non-sinusoidal and noisy cycles than a currently used routine based on Fourier approximations. In addition, a simple fit to the oscillations using linear least squares is available, together with a non-parametric test for detecting changes in period length which allows for period estimates with different variances, as frequently encountered in practice. The proposed methods are motivated by and applied to various data examples from chronobiology.

Reciprocal Interaction of the Circadian Clock with the Iron Homeostasis Network in Arabidopsis

In plants, iron (Fe) uptake and homeostasis are critical for survival, and these processes are tightly regulated at the transcriptional and posttranscriptional levels. Circadian clocks are endogenous oscillating mechanisms that allow an organism to anticipate environmental changes to coordinate biological processes both with one another and with the environmental day/night cycle. The plant circadian clock controls many physiological processes through rhythmic expression of transcripts. In this study, we examined the expression of three Fe homeostasis genes (IRON REGULATED TRANSPORTER1 [IRT1], BASIC HELIX LOOP HELIX39, and FERRITIN1) in Arabidopsis (Arabidopsis thaliana) using promoter:LUCIFERASE transgenic lines. Each of these promoters showed circadian regulation of transcription. The circadian clock monitors a number of clock outputs and uses these outputs as inputs to modulate clock function. We show that this is also true for Fe status. Fe deficiency results in a lengthened circadian period. We interrogated mutants impaired in the Fe homeostasis response, including irt1-1, which lacks the major high-affinity Fe transporter, and fit-2, which lacks Fe deficiency-induced TRANSCRIPTION FACTOR1, a basic helix-loop-helix transcription factor necessary for induction of the Fe deficiency response. Both mutants exhibit symptoms of Fe deficiency, including lengthened circadian period. To determine which components are involved in this cross talk between the circadian and Fe homeostasis networks, we tested clock- or Fe homeostasis-related mutants. Mutants defective in specific clock gene components were resistant to the change in period length under different Fe conditions observed in the wild type, suggesting that these mutants are impaired in cross talk between Fe homeostasis and the circadian clock.

Distinct Roles of DBHS Family Members in the Circadian Transcriptional Feedback Loop

Factors interacting with core circadian clock components are essential to achieve transcriptional feedback necessary for metazoan clocks. Here, we show that all three members of the Drosophila behavior human splicing (DBHS) family of RNA-binding proteins play a role in the mammalian circadian oscillator, abrogating or altering clock function when overexpressed or depleted in cells. Although these proteins are members of so-called nuclear paraspeckles, depletion of paraspeckles themselves via silencing of the structural noncoding RNA (ncRNA) Neat1 did not affect overall clock function, suggesting that paraspeckles are not required for DBHS-mediated circadian effects. Instead, we show that the proteins bound to circadian promoter DNA in a fashion that required the PERIOD (PER) proteins and potently repressed E-box-mediated transcription but not cytomegalovirus (CMV) promoter-mediated transcription when they were exogenously recruited. Nevertheless, mice with one or both copies of these genes deleted show only small changes in period length or clock gene expression in vivo. Data from transient transfections show that each of these proteins can either repress or activate, depending on the context. Taken together, our data suggest that all of the DBHS family members serve overlapping or redundant roles as transcriptional cofactors at circadian clock-regulated genes.

The nature of lemming cycles on Wrangel: an island without small mustelids

Lemming cycles are a key process in the functioning of tundra ecosystems. Although it is agreed that trophic interactions are important in causing the cycles, the actual mechanism is disputed. Some researchers attribute a major role to predation by small mustelids such as stoats and least weasels. Here we present a 40-year time series of lemming dynamics from Wrangel Island and show statistically that lemmings do exhibit population cycles in the absence of small mustelids. The observed density fluctuations differed, however, from those observed elsewhere, with long cycles and possibly higher densities of lemmings during the low phase. These differences in the shape of the population cycles may be related to the unique species assemblage of Wrangel Island, where arctic foxes are the only year-round resident lemming predator, and to the high diversity of landscapes, microclimatic conditions, and plants on the island. Both spectral analysis and wavelet analysis show a change in period length from five years in the 1970s to nearly eight years in the 1990s and 2000s. This change in dynamics coincides with reports of dampening or fading out of lemming cycles that have been observed in several regions of the Arctic in recent decades. As in the other cases, the changed lemming dynamics on Wrangel Island may be related to ground icing in winter, which could delay peak years.

Ultra-fast in vivo x-ray microtomography of blowfly wingbeat

Ultra-fast in vivo x-ray microtomography of blowfly wingbeat

Period-robust repetitive model predictive control

Repetitive model predictive control (RMPC) incorporates the idea of repetitive control (RC) into the basic formulation of model predictive control (MPC) to enable the user to take full advantage of the constraint handling, multivariable control features of MPC in controlling a periodic process. The RMPC achieves perfect asymptotic setpoint tracking/disturbance rejection in periodic processes, provided that the period length used in the control formulation matches the actual period of the reference/disturbance signal exactly. Even a small mismatch between the actual period of the process and the controller period can deteriorate the RMPCs performance significantly. The period mismatch can occur either from an inaccurate estimation of the actual frequency of disturbance due to resolution limit or from trying to force the controller period to be an integer multiple of the sampling time. For such cases, an extension of RMPC called “period-robust” repetitive model predictive control (pr-RMPC) is proposed. It is based on the idea of using weighted, multiple memory loops in RC, such that small changes in period length do not diminish the tracking/rejection properties by much. Simulation results show that, in case of a slight period mismatch, pr-RMPC achieves significant improvement over the standard RMPC in rejecting periodic disturbances.

LdpA: a component of the circadian clock senses redox state of the cell

The endogenous 24-h (circadian) rhythms exhibited by the cyanobacterium Synechococcus elongatus PCC 7942 and other organisms are entrained by a variety of environmental factors. In cyanobacteria, the mechanism that transduces environmental input signals to the central oscillator of the clock is not known. An earlier study identified ldpA as a gene involved in light-dependent modulation of the circadian period, and a candidate member of a clock-entraining input pathway. Here, we report that the LdpA protein is sensitive to the redox state of the cell and exhibits electron paramagnetic resonance spectra consistent with the presence of two Fe4S4 clusters. Moreover, LdpA copurifies with proteins previously shown to be integral parts of the circadian mechanism. We also demonstrate that LdpA affects both the absolute level and light-dependent variation in abundance of CikA, a key input pathway component. The data suggest a novel input pathway to the circadian oscillator in which LdpA is a component of the clock protein complex that senses the redox state of a cell.

Effects of length oscillation on the subsequent force development in swine tracheal smooth muscle.

It has been shown that deep inspiration (DI) taken before application of bronchoconstricting stimuli causes a reduction in the subsequent bronchoconstriction; a fast DI has a greater inhibitory effect than a slow DI. We hypothesize that periodic length changes imposed on a relaxed airway smooth muscle (ASM) would attenuate subsequent bronchoconstriction by disrupting the organization of the contractile apparatus, and this could be an important mechanism for the observed bronchoprotective effect of DI and tidal breathing. Length oscillations of different amplitude, frequency, and duration were applied to a relaxed muscle. The effects of such perturbations on force development were then assessed. Results show that oscillations reduce the subsequent force generation and that the magnitude of force reduction is proportional to amplitude and duration of the length oscillation. After the oscillation, isometric force recovered to the preoscillation level in a series of isometric contractions, and the rate of recovery was facilitated by frequent stimulation. The in vitro behavior of ASM found in this study could account for the observed temporary reduction in bronchoconstriction subsequent to a DI.

Regulation of muscle stiffness during periodic length changes in the isolated abdomen of the hermit crab.

Reflex activation of the ventral superficial muscles (VSM) in the abdomen of the hermit crab, Pagurus pollicarus, was studied using sinusoidal and stochastic longitudinal vibration of the muscle while recording the length and force of the muscle and the spike times of three exciter motoneurons. In the absence of vibration, the interspike interval histograms of the two larger motoneurons were bimodal; cutting sensory nerves containing most of the mechanoreceptor input removed the short interval peak in the histogram, indicating that the receptors are important in maintaining tonic firing. Vibration of the muscle evoked a reflex increase in motoneuron frequency that habituated after an initial peak but remained above control levels for the duration of stimulation. Motoneuron frequency increased with root mean square (rms) stimulus amplitude. Average stiffness during stimulation was about two times the stiffness of passive muscle. The reflex did not alter muscle dynamics. Estimated transfer functions were calculated from the fast Fourier transform of length and force signals. Coherence was >0.9 for the frequency range of 3-35 Hz. Stiffness magnitude gradually increased over this range in both reflex activated and passive muscle; phase was between 10 and 20 degrees. Reflex stiffness decreased with increasing stimulus amplitudes, but at larger amplitudes, this decrease was much less pronounced; in this range stiffness was regulated by the reflex. The sinusoidal frequency at which reflex bursts were elicited was approximately 6 Hz, consistent with previous measurements using ramp stretch. During reflex excitation, there was an increase in amplitude of the short interval peak in the interspike interval histogram; this was reduced when the majority of afferent pathways was removed. A phase histogram of motoneuron firing during sinusoidal vibration had a peak at approximately 110 ms, also suggesting that an important component of the reflex is via direct projections from the mechanoreceptors. These results are consistent with the hypothesis that a robust feedforward regulation of abdominal stiffness during continuous disturbances is achieved by mechanoreceptors signalling the absolute value of changing forces; habituation of the reflex, its high-threshold for low frequency disturbances and the activation kinetics of the muscle further modify reflex dynamics.

Involvement of the circadian system in photoperiodic termination of diapause in the spider mite Tetranychus urticae

In the spider mite Tetranychus urticae, both diapause induction and diapause termination are under photoperiodic control. Resonance experiments with three strains from different localities in Europe revealed the involvement of the circadian system in the photoperiodic termination of diapause. In all strains the τ-value of the rhythm involved in diapause termination appeared to be shorter than that of the rhythm involved in diapause induction. This may be caused by a change in period length of a circadian oscillator involved in both induction and termination of diapause, or it may indicate that different circadian oscillators affect diapause induction and diapause termination in the spider mite. In previous experiments it has been demonstrated that the photoperiodic clock controlling diapause termination is most probably the same as the one controlling diapause induction. In eight strains of the spider mite, originating from widely different localities in Europe, the critical nightlengths for diapause induction and diapause termination appeared to be identical. Apparently some change occurs in the circadian system between diapause induction and diapause termination, without a concurrent change in photoperiodic time measurement. This makes it unlikely that the oscillator(s) involved in diapause induction and termination would constitute the photoperiodic clock. The results are interpreted according to the so-called non-clock or resonance hypothesis for the involvement of the circadian system in photoperiodic phenomena. Temperature appeared to affect the resonance rhythm of diapause termination differently in different strains of the spider mite: in two strains the rhythm appeared to be temperature compensated, in two other strains it was not. In two strains of the spider mite, originating from the same latitude, critical nightlength appeared to be the same, whereas the period of the rhythm involved in diapause termination differed from 1–3 h among the strains, depending on temperature. These results do not provide evidence in favour of a circadian-based photoperiodic clock in T. urticae. Another effect of temperature was found on the appearance of the different resonance peaks: temperature had little effect on the time course of appearance of the first peak (at nights shorter than the critical nightlength), but subsequent peaks (at nights longer than the critical nightlength) developed faster at higher temperature. This suggests that the mechanism of diapause termination in regimes with nights shorter than the critical nightlength is different from that with nights longer than the critical nightlength. The first represents the photoperiodic response proper, controlled by the photoperiodic clock at nightlengths around the critical nightlength, whereas the latter is most probably a ‘resonance’ effect, revealing the influence of the circadian system on the expression of the photoperiodic response in extended nights. The above effect of temperature therefore also appears to corroborate the non-clock hypothesis for photoperiodic time measurement in the spider mite.

Mathematical model of blood flow in a coronary capillary

The coronary capillary flow is analyzed theoretically based on continuum mechanics. The capillary is a long, elastic, and permeable vessel loaded externally by tissue pressure, and it is subject to possible periodic length changes, together with adjacent myocytes. Capillary flow is driven by arteriolar-venular pressure difference. Ultrafiltration due to transmural hydrostatic and osmotic gradients is included, and consideration of mass conservation leads to a nonlinear flow equation. The results show that under physiological conditions ultrafiltration is of minor importance, and the analysis predicts regional differences in capillary flow. In regions with high tissue pressure (subendocardium), capillaries undergo significant periodic volume changes, giving rise to intramyocardial pumping. In those regions, capillary wall elasticity is of major importance. In regions with low tissue pressure (subepicardium), the possible periodic capillary length changes are predominant. The predicted flow patterns are in good qualitative agreement with measured epicardial phasic flow. In conclusion, the methodological advantage of a distributive analysis is demonstrated by its ability to elucidate and evaluate the role of flow determinants and their complex interactions.

Hypothalamic circuits and circadian rhythms: Effects of knife cuts vary with their placement within the suprachiasmatic area

The suprachiasmatic nucleus (SCN) of the hypothalamus and its efferent projections are necessary for the generation of circadian rhythms. To further investigate the role of SCN connections in the generation of behavioral rhythms, intact and blinded-castrated male rats housed in constant conditions were given horizontal knife cuts aimed dorsal to the SCN, or sham surgery. Rhythms of locomotor activity and drinking behavior were monitored using a microcomputer. Cuts that spared the SCN failed to abolish rhythms. Effects of cuts that damaged the SCN ranged from changes in period length of the rhythms to abolition of drinking rhythms. These and previous results indicate that connections between the SCN and the paraventricular nucleus of the hypothalamus are not necessary for the expression of behavioral rhythms.

Seasonal effects on the freerunning rhythm of circadian activity of longnose dace (Rhinichthys cataractae)

Freerunning circadian rhythms of locomotor activity in individual longnose dace sampled from a population at 41°N latitude were recorded under constant darkness throughout the year. There was an annual cycle in the length of the circadian period, with maximum and minimum lengths of mean period of 23.6 and 21.6 h recorded during summer (June) and winter (December), respectively. These annual changes in period length may have resulted from seasonal changes in entrainment by natural light-dark cycles and their ‘after-effects’ on endogenous circadian rhythms. The possibility of an endogenous circannual rhythm was also considered.

An Interpretation of the Effects of Fiber Length and Calcium on the Mechanical Properties of Insect Flight Muscle

Insect fibrillar flight muscle has many properties in common with vertebrate skeletal muscle. However, it is not capable of the constant velocity shortening at constant load which is the mechanical characteristic of vertebrate striated muscles, but is adapted to produce rapid oscillatory contractions of small amplitude. Consequently, the classical type of mechanical study, involving the measurement of force-velocity diagrams and the fitting of a hyperbola to them, is not suitable for investigations of the properties of insect flight muscle. Instead, periodic length changes must be used. The result of forcing a sinusoidal length change of low amplitude on insect flight muscle is that, over a certain range of frequencies, the resulting sinusoidal tension changes lag behind the length changes (Machin and Pringle, 1960; Jewell and Ruügg, 1966). It is this delay which allows the muscle to deliver work continuously to a resonant load without neural control. One possible way of...

Dynamic characteristics of stretch reflex using force inputs.

Dynamic characteristics of stretch reflex using force inputs.A Berthoz, W J Roberts, and N P RosenthalA Berthoz, W J Roberts, and N P RosenthalPublished Online:01 Jul 1971https://doi.org/10.1152/jn.1971.34.4.612MoreSectionsPDF (1 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByRegulation of Muscle Stiffness During Periodic Length Changes in the Isolated Abdomen of the Hermit CrabWilliam D. Chapple1 September 1997 | Journal of Neurophysiology, Vol. 78, No. 3Dynamics of human ankle stiffness: Variation with mean ankle torqueJournal of Biomechanics, Vol. 15, No. 10Dynamics of human ankle stiffness: Variation with displacement amplitudeJournal of Biomechanics, Vol. 15, No. 10 More from this issue > Volume 34Issue 4July 1971Pages 612-9 https://doi.org/10.1152/jn.1971.34.4.612PubMed5114093History Published online 1 July 1971 Published in print 1 July 1971 Metrics

The error arising from circadian frequency changes in the determination of phase displacements

Phase shifts (Δϕ) are commonly measured without considering the cue's phase position (ϕs). The normally adopted methods for measuring phase shifts give errorless results only when there is no change in period length (Δσ). Very often, however, both phase shifts and changes in period length occur together. The magnitude of the error is then a function of the magnitude ofΔσ and the distance between the points of measurement and the cue's phase position. (The basic hypothesis is thatΔσ is effected immediately after the cue.) Methods for calculating and eliminating the error are given.

Comparative studies in avian persistent rhythms: spontaneous change in period length

1. 1. The persistent activity rhythms of four birds (a Towhee, a Grosbeak and two House Sparrows) were studied for periods up to 4 months. 2. 2. One of the House Sparrows was found to possess a “statistical activity-rhythm” which persisted after the over, circadian rhythm abruptly disappeared. 3. 3. The study emphasizes and compares “spontaneous” changes in the period length of circadian rhythms. Such changes commonly occurred in three of the four birds. 4. 4. The “spontaneous changes” are explained as abrupt alteration in the physiological make-up of the birds, resulting in a sudden change in their sensitivity to the constant conditions in which they were maintained.