Non-stationary time series and the robustness of circadian rhythms

Refinetti, Roberto

doi:10.1016/j.jtbi.2003.11.032

Cited by 150 publications

(117 citation statements)

References 34 publications

(35 reference statements)

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“…Also, there is very little change if the averaging is done over a small subset of the days in the dataset. For the T c profile, that is a reflection of the exceptional robustness (Refinetti, 2003) of the circadian rhythms observed in cattle (Piccione et al, 2003), which was found to be more robust than that of any mammalian species previously studied.…”

Section: Resultsmentioning

confidence: 90%

Absence of a causal relationship between environmental and body temperature in dairy cows (Bos taurus) under moderate climatic conditions

Verwoerd

Wellby

Barrell

2006

Journal of Thermal Biology

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Abstract1. Continuous body temperature records from dairy cows for 46 days of summer and contemporary data for climate temperature humidity index (THI) were analysed, 2. A large component of the body temperature data was not explained by changes in THI.3. Outside a normal range of values (above 72 for THI and 39.05 o C for body temperature), there was evidence of a causal relationship with a time delay of about 120 minutes.4. Both variables had a prominent circadian component, but these were more likely to be due to common and/or independent causes than to any direct relationship.

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Section: Resultsmentioning

confidence: 90%

Absence of a causal relationship between environmental and body temperature in dairy cows (Bos taurus) under moderate climatic conditions

Verwoerd

Wellby

Barrell

2006

Journal of Thermal Biology

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“…Each time series was analyzed by cosinor rhythmometry (Nelson et al, 1979;Refinetti et al, 2007) to identify four rhythmic parameters: mesor (mean level), amplitude (half the range of oscillation), acrophase (time of peak), and robustness (strength of rhythmicity, herewith denoted by the lower-case Greek latter ρ). The cosinor procedure assigns 100% robustness only to time series that are perfectly sinusoidal; however, natural biological noise always reduces the robustness of circadian rhythms, keeping it below 100% (Refinetti, 2004), and the strength of rhythmicity can be estimated by the cosinor procedure even when the wave form of the rhythm is not sinusoidal (Refinetti et al, 2007).…”

Section: Discussionmentioning

confidence: 99%

Daily rhythms of physiological parameters in the dromedary camel under natural and laboratory conditions

Alhaidary

Abdoun

Samara

et al. 2016

Research in Veterinary Science

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See next page for additional authorsThis is an author-produced, peer-reviewed version of this article. © 2016, Elsevier. Licensed under the Creative Commons NonCommercial-NoDerivs 4.0 license. Details regarding the use of this work can be found at: http://creativecommons.org/licenses/by-nc-nd/4.0/. Abstract Camels are well adapted to hot arid environments and can contribute significantly to the economy of developing countries in arid regions of the world. Full understanding of the physiology of camels requires understanding of the internal temporal order of the body, as reflected in daily or circadian rhythms. In the current study, we investigated the daily rhythmicity of 20 physiological variables in camels exposed to natural oscillations of ambient temperature in a desert environment and compared the daily temporal courses of the variables. We also studied the rhythm of core body temperature under experimental conditions with constant ambient temperature in the presence and absence of a light-dark cycle. The obtained results indicated that different physiological variables exhibit different degrees of daily rhythmicity and reach their daily peaks at different times of the day, starting with plasma cholesterol, which peaks 24 minutes after midnight, and ending with plasma calcium, which peaks 3 hours before midnight.Furthermore, the rhythm of core body temperature persisted in the absence of environmental rhythmicity, thus confirming its endogenous nature. The observed delay in the acrophase of core body temperature rhythm under constant conditions suggests that the circadian period is longer than 24 hours. Further studies with more refined experimental manipulation of different variables are needed to fully elucidate the causal network of circadian rhythms in dromedary camels.

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“…For each parameter, the mean level of each rhythm was computed as the arithmetic mean of all values in the data set (9 data points), the amplitude of a rhythm was calculated as half the range of oscillation, which in its turn was computed as the difference between the peak and trough. Rhythm robustness was computed as a percentage of the maximal score attained by the chi-square periodogram statistic for ideal data sets of comparable size and 24 h periodicity (Refinetti, 2004). Robustness greater than 15% is above the noise level and indicates statistically significant rhythmicity.…”

Section: Discussionmentioning

confidence: 99%

Circadian rhythms of redox states and total locomotor activity in dairy cattle

Giannetto¹,

Fazio²,

Assenza³

et al. 2010

CZECH J ANIM SCI

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ABSTRACT:We want to study the circadian rhythm of dROMs and anti-oxidative power in dairy cattle during dry period and the possible involvement of the circadian organization of rest/activity cycles in the fluctuation of redox state. For this purpose we recorded TLA in five clinically healthy Bruna Italian dairy cattle by means of an actigraphy-based data logger, Actiwatch-Mini ® . Blood samples were collected every 3 hours over a 48-hour period for the assessment of free radicals (dROMs) and the antioxidant power: antioxidant barrier (Oxy-ads) and thiol-antioxidant barrier (SHp). All animals were in the same productive period (dry) and they were housed in the same stable under natural photoperiod and ambient temperature. One-way repeated measure ANOVA was used to determine a statistical significant effect of time on the studied parameters. A trigonometric statistical model was applied to characterize the main rhythmic parameters according to the single cosinor procedure. A significant effect of time on all studied parameters was observed. They showed a diurnal acrophase and different degrees of robustness of rhythms. In conclusion, we can claim that there is a synergism between the dROM circadian rhythm and the circadian rhythm of anti-oxidative power. These rhythms do not have any implication for the issue of causation with the TLA circadian rhythms.

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Non-stationary time series and the robustness of circadian rhythms

Cited by 150 publications

References 34 publications

Absence of a causal relationship between environmental and body temperature in dairy cows (Bos taurus) under moderate climatic conditions

Absence of a causal relationship between environmental and body temperature in dairy cows (Bos taurus) under moderate climatic conditions

Daily rhythms of physiological parameters in the dromedary camel under natural and laboratory conditions

Circadian rhythms of redox states and total locomotor activity in dairy cattle

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