Ultradian rhythms and the lux-gene reporter system

'Noisy' bioluminescence of an unstirred and exposed-to-air microculture of lux -gene fused Escherichia coli was interpreted, assuming two oscillatory processes: cyclic induction of the lac promoter, resulting in oscillatory reporter lux -gene expression, and oscillatory respiration in the culture. Biological support for the theoretical argument, that two rhythms can interact in cells to produce additional rhythms, is provided. These results, along with previously obtained data on oscillatory bioluminescence, indicate the deterministic nature of observed noise-like fluctuations and promising perspectives of lux gene reporter systems in investigations of ultradian rhythm.     

Ultradian rhythms in renal excretion in dogs

Urine flow, urinary osmolality, concentrations of sodium and potassium were measured every 10 min for 24 hours in 6 female dogs, whose sleep-wake stages were monitored electrographically. Experiments were conducted under hydration and progressive dehydration conditions. Visual examination and spectral analysis revealed significant diurnal ultradian rhythms of about 200 min/cycle in urine flow, which were out of phase with similar rhythms in osmolality in different hydratory conditions. Diurnal rhythms with similar characteristics were found in urinary potassium only in the hydration condition. Sodium excretions did not show consistent rhythmic patterns. No consistent rhythms were found in nocturnal urine parameters in different hydratory conditions. The variations in renal activities were related to the dogs' diurnal ultradian sleep-wake cycle, urine volume increased and osmolality decreased during diurnal waking episodes, and conversely volume decreased and osmolality increased during the diurnal sleep episodes.     

Circahoralian (Ultradian) metabolic rhythms

This review presents data concerning metabolic rhythms with periods close to one hour (20 to 120 min): their occurrence, biochemical organization, nature, and significance for adaptations and age-related changes of cells and organs. Circahoralian (ultradian) rhythms have been detected for cell mass and size, protein synthesis, enzyme activities, concentration of ATP and hormones, cell respiration, and cytoplasm pH. Rhythms have been observed in bacteria, yeasts, and protozoa, as well as in many cells of metazoans, including mammals, in vivo and in cell cultures. In cell populations, the rhythms are organized by direct cell-cell communication. The biochemical mechanism involves membrane signal factors and cytoplasmic processes resulting in synchronization of individual oscillations to a common rhythm. Phosphorylation of proteins is the key process of coordination of protein synthesis and enzyme activity kinetics. The fractal nature of circahoralian rhythms is discussed as well as the involvement of these rhythms in adaptations of the cells and organs. Senescent decrease in rhythm amplitudes and correspondingly in cell-cell communication has been observed. The possibility of remodeling these changes through the intercellular medium has been predicted and experimentally shown. Perspectives for studies of the organizers and disorganizers of cell-cell communication in the intercellular medium along with appropriate receptors are discussed with special emphasis on aging and pathology. One perspective can be more precise definition of the range of normal biochemical and physiological state with the goal of correction of cellular functions.     

Ultradian and asymmetric rhythms of hemispheric processing speed

Daily changes in cognitive performance have been documented, both in time of day/effect paradigm studies and in time-isolation studies. However, in both types of studies, phenomena such as the “post-lunch dip” have been found that were difficult to explain in terms of theoretical backgrounds. These phenomena may suggest ultradian rhythms in cognitive performance. A number of studies have also shown ultradian and asymmetric rhythms in activity indices of the brain hemispheres. The aim of this study was to test three hypotheses: the first two assumed that there is a significant ultradian frequency in a component of the endogenous rhythm of processing speed, and the third assumed that the ultradian endogenous rhythms of the processing speed (encoding and recognition) of stimuli addressed to the left brain hemisphere differ in period length from those addressed to right hemisphere. During a 24 h constant-routine experiment, the memory performance of 30 participants was measured eight times (every 2.5-3 h), starting at 06:30 h. Parallel sets of words and pictures were shown to subjects in a random order in either the left or the right visual field on a computer screen. The participants pressed one of two buttons in response to the picture or word, or when answering a question concerning the meaning of a presented stimulus. Cosinor analysis was applied to individual time series data. Two significant ultradian components were found in a majority of the time series. Dominant periods were analyzed using three factor ANOVA. The results showed an asymmetry between both hemispheres in the frequency of ultradian rhythms in encoding speed.     

Ultradian rhythms in processing speed of laterally exposed words and pictures

The study was designed to find out the cerebral hemispheres oscillations in stimuli processing during the 24-hour period of wakefulness in isolated subjects remaining in a monotonous environment. Stimuli processing speed from the 24-hour constant routine periods (06.00-06.00 h) of a larger experiment were analysed for the purpose of this paper. Parallel sets of words and pictures were exposed laterally using a purpose-designed computer program. The subjects reacted to pictures or words by pressing appropriate buttons. The significant dominant ultradian rhythms (around 4 h) in the processing speed of words addressed to the right hemisphere were found and of pictures addressed to the left hemisphere. Longer significant dominant periodicities (around 12 h) appeared in the processing speed of words addressed to the left hemisphere and of pictures (around 8 h) addressed to the right hemisphere. Ultradian rhythmicity of the central nervous system functioning is suggested.     

Ultradian circa 112 hours rhythms: A multioscillatory system

Recent research has demonstrated rhythms in physiologic, behavioral, and endocrine processes with periodicity similar to that of the sleep REM-NONREM cycles. These findings confirm that part of Kleitman's Basic Rest-Activity (BRAC) hypothesis which predicted about $\text{1}\text{1}\text{2}\text{hour}$ cycles in waking levels of arousal. In contrast, however, with the BRAC model, which viewed the waking rhythms as fragments of the same oscillatory system controlling the REM-NONREM cycles, the accumulated data suggest that ultradian 90–100 min rhythms are generated by a multi-oscillatory system. It is hypothesized that the diverse ultradian variations in behavioral, physiologic and endocrine subsystems may play a role in the adaptation of group living animals to their environment.     

Ultradian respiratory rhythms in groups of Sprague-Dawley rats of both sexes

Spectral analysis of the carbon dioxide emitted in controlled environmental conditions (temperature: 20-21 degrees C; humidity: 50-60%; lighting: 150 lux in LD12-12; background noise: 70 dB), by groups of 14 month old Sprague Dawleys, shows ultradian respiratory rates with periods of a 107-72 minute range for males and 107-45 minute for females. Moreover, VCO2 related to body weight is higher in females than in males.     

Ultradian and circadian rhythms of sleep-wake and food-intake behavior during early infancy

The early development of sleep-wake and food-intake rhythms in human infants is reviewed. The development of a 24h day-night rhythm contains two observable developmental processes: the alterations in the periodic structure of behavior (decreased ultradian, increased circadian components) and the process of synchronization to external time (entrainment). The authors present the results of their studies involving 26 German children and compare them with previous investigations. In their research, it became evident that, during the first weeks of life, the time pattern of sleep-wake and food-intake behavior is characterized by different ultradian periodicities, ranging from 2h to 8h. In the course of further ontogenesis, the share of ultradian rhythms in the sleep-wake behavior decreases, while it remains dominant for food-intake behavior. The circadian component is established as early as the first weeks of life and increases in the months that follow. Besides, the authors' study supports the notion of broad interindividual variation in ultradian rhythms and in the development of a day-night rhythm. Examples of free-running rhythms of sleep-wake and food-intake behavior by various authors are strong indicators of the endogenous nature of the circadian rhythms in infants and show that the internal clock is already functioning at birth. It is still uncertain when the process of synchronization to external and social time cues begins and how differences in the maturation of perceptive organs affect the importance of time cues for the entrainment. Prepartally, the physiological maternal entrainment factors and mother-fetus interactions may be most important; during the first weeks of life, the social time cues gain importance, while light acts as a dominant “zeitgeber” at a later time only.     

A clockwork mollusc: Ultradian rhythms in bivalve activity revealed by digital photography

Time-lapse digital images can be acquired and archived using web-cameras, allowing non-invasive analysis of behavior patterns of bivalve molluscs at ultradian (sub-daily) time-scales over long intervals. These records can be analyzed directly by a human operator or through properly calibrated image analysis software. Preliminary results using species of marine and freshwater bivalves identify several ultradian biological rhythms of similar duration. Wavelet analysis indicates strong periodicity in mantle and siphon activity in the 3 to 7 min range, with longer duration shell contraction periods at 60-90 min. The recurrence of these rhythms among marine and freshwater bivalve species maintained under constant (but differing) conditions suggests the influence of common intrinsic drivers (chemico-physical mechanisms or biological clocks). Sub-daily growth increments preserved in the shells of rapidly growing bivalve species are potentially related to these biological rhythms, with implications for shell growth, biomineralization, and the temporal resolution of paleoclimate proxy data.     

Differential shaping of EEG theta rhythms

Heart rate, EEG, frontal EMG, and forearm EMG were recorded in 20 subjects for 3 baseline, 8 feedback, and 2 postbaseline sessions in order to compare two biofeedback methods of teaching subjects to increase theta EEG activity. Subjects were divided into high- and low-EMG groups. Five high-EMG subjects, and 5 low-EMG subjects then received 8 sessions of strictly theta feedback. The remaining 10 subjects, 5 from the high-EMG group, and 5 from the low-EMG group, received a “graduated” training which involved shaping the target response. This procedure consisted of 4 initial sessions of EMG feedback, followed by a second phase consisting of 4 sessions of theta feedback. Results showed a clear relationship between subjects' baseline frontal EMG levels and the effect of the training methods. Although subjects with high-EMG baseline increased their theta output only with the two-phase training, subjects with low-EMG baseline levels performed better when given theta feedback only. This result shows not only that amounts of theta can be reliably increased, but that training techniques should be adapted to the physiological characteristics of the individual—in this case, baseline levels of frontal EMG levels.     

Changes in EEG rhythms during verbal and visual-image thinking

General and local characteristics of EEG activation were studied in frontal, central, temporal and occipital areas of the left and right cerebral hemispheres in 20 adult subjects during execution of various mental tasks. The analysis of the changes of five main EEG rhythms (delta, theta, alpha, beta-1 and beta-2) showed that EEG power decrease in alpha- and beta-frequency ranges is a reliable and sensitive index of brain activation at thinking. On this basis EEG activation mosaics are described at carrying out of each task and its systemic changes at transition from one type of task to another one, depending on their psychological structure--modality and complexity.     

Circadian rhythms during cycling exercise and finger-tapping task

The aim of this study was to follow the circadian fluctuation of the spontaneous pedal rate and the motor spontaneous tempo (MST) in a sample of highly trained cyclists. Ten subjects performed five test sessions at various times of day. During each test session, subjects were required to perform (i) a finger-tapping task, in order to set the MST and (ii) a submaximal exercise on a cycle ergometer for 15 min at 50% of their W_max. For this exercise, pedal rate was freely chosen. Spontaneous pedal rate and heart rate (HR) were measured continuously.

The results demonstrated a circadian variation for mean oral temperature, HR, and MST. Under submaximal exercise conditions, HR showed no significant time-of-day influence although spontaneous pedal rate changed significantly throughout the day. Circadian rhythm of oral temperature and pedal rate were strongly correlated. Moreover, a significant positive correlation was found between MST and pedal rate. Both parameters may be controlled by a common brain oscillator. MST, rest HR, and pedal rate changes follow the rhythm of internal temperature, which is considered to be the major marker in chronobiology, therefore, if there is a relation between MST and pedal rate, we cannot rule out partial dependence of both parameters on body temperature.