Electrical pacing in the gastroduodenal junction area of conscious dogs (author's transl)]

To determine whether the electric activities of the stomach and duodenum are related, the gastroduodenal junction area of the stomach of dogs was paced through implanted bipolar silver electrodes. It was found that the pacing rate of the basic electrical rhythm (BER) in the antrum of the stomach could be increased to a maximum of 8.9 cycles/min, without affecting the BER frequency in the duodenum. Conversely when the pacing rate of the BER in the duodenum was increased to a maximum of 24 cycles/min, the BER frequency in the antrum remained unaffected. These results show that the BER in the stomach and duodenum are independent, and imply that the BER cycles in the stomach and duodenum are due to the presence of two independent pace-maker areas.     

The chronopathology of breast pre-cancer

Breast temperatures have been measured by the automated instrumentation called the 'Chronobra' for 16 progesterone cycles in women at normal risk for breast cancer and for 15 cycles in women at high risk for breast cancer. Circatrigintan and circaseptan rhythm parameters have been examined by the single and population mean cosinor technique. In the first analysis there was strong evidence for a loss of the 28-day rhythm and its replacement by a 7-day rhythm (? frequency multiplication). In the more rigorous population mean cosinor method the presence of a phase and frequency synchronized rhythm with a period at or close to 28 days was sustained in the normal-risk subjects and it was confirmed that this rhythm is absent in the high-risk subjects. At tau = 7 days there was no rhythm detected in the normal-risk subjects and only a weak effect (p = 0.07) in the high-risk subjects. In other words, the circaseptan expression was detected in the high-risk breasts but then not in every case. The MESOR of the high-risk cases was highly significantly warmer than in the controls.     

Circadian periodicity in cockroaches altered by high frequency light-dark cycles

Summary The circadian period of the freerunning activity rhythm in the cockroach is systematically altered by high frequency light-dark cycles (HF-LD) according to the ratio of light to dark within each cycle. With a standard 10 min cycle time, brief (e.g., 0.5 min) exposure to light each cycle causes the free-running period to shorten significantly in comparison to its steady-state value in constant darkness. As the ratio of light to dark in HF-LD is increased, the period of the rhythm is progressively lengthened. These findings are discussed in terms of the general proposition that light, applied throughout the circadian cycle, predictably modifies periodicity according to the asymmetrical shape of the circadian phase response curve.Abbreviations LD light-dark cycles in which cycle length is in hours - HF-LD light-dark cycles in which cycle length is in min; period of the activity rhythm; change in period of the activity rhythm - PRC phase response curve - LL constant light     

Circadian organization in cockroaches: Effects of temperature cycles on locomotor activity

The effects of various temperature cycles on the locomotor activity of the cockroach Leucophaea maderae were investigated. While bilateral ablation of the optic lobes abolished the free-running activity rhythm in constant conditions, rhythmicity was exhibited by lobeless animals placed in temperature cycles. The rhythms were driven by cycles as short as 12 h and as long as 48 h without evidence of frequency division or frequency demultiplication. The phase relationship between activity onset and the temperature cycle was dependent on both the relative durations of the “warm” and “cold” phases of the cycles and on the period of the cycle. Computer simulations indicated that these properties of the rhythm can be explained by proposing that activity is controlled by a damped oscillator, located outside the optic lobes, that can be forced by cycles of temperature.     

Entrainment of the circatidal rhythm of the estuarine amphipod Coroph1um volutator (pallas) to non-tidal cycles of inundation and exposure in the laboratory

The endogenous rhythm of swimming activity shown by the estuarine amphipod Corophium volutator (Pallas) has been studied in animals subjected to periodic inundation under controlled laboratory conditions. A rhythm of circatidal frequency which persisted under constant conditions was recorded in animals entrained to cycles of 8-, 12- and 24-h periods, whereas animals entrained to 6-h cycles appeared to follow the entraining regimen directly, although the free running rhythm was less distinct. Cycles of 4-h period failed to induce rhythmicity. The results support the hypothesis that the endogenous oscillator has a circatidal frequency.

The period for which the animals are submerged is important with regard to entrainment but the effective parameters of the imposed regimen are incompletely understood in this respect.     

Slow-wave fluctuations in craniosacral space: hemo-liquorodynamic conception of origin

In the paper, the mechanism of forming of rhythmic slow-wave fluctuations in craniospinal cavity was investigated. In five young healthy persons, at rest and under voluntary respiration arrest test, the bioimpedansograms of head and lumbosacral part of vertebral column were synchronously registered as these recordings reflect the changes of relationships between blood/CSF volumes in cranial and lumbosacral regions, respectively. The recordings were subjected to frequency and spectral computer analysis (PC Macintosh G-4, Chart 5.2. software). The rapid (pulsatile) as well as slow and counter-directed waves (frequency 6-10 cycles/min) of these processes were revealed in cranial and lumbosacral regions. The data obtained suggest the CSF dynamic concept of origin of the craniosacral rhythm. The pulse and slow-frequency oscillations of the cerebral vessels tone initiate corresponding intracranial pressure waves, and the latter are the motivating forces for to-and-fro CSF shifts in caudal direction. This mechanism is accompanied by tonic contractions of lumbar muscles and sacrum movements, and it is manually perceptible as a craniosacral rhythm.     

The entrainment of ventilation frequency to exercise rhythm

To investigate whether ventilation frequency could be entrained to a sub-harmonic of the exercise rhythm, 19 experimentally naive male volunteers were tested during steady state bicycle ergometry and arm cranking under conditions of constant applied workload. Each exercise was performed at two separate ventilatory loads, one within the linear range and the other in the curvilinear range of ventilatory response to exercise. A preferred exercise rhythm was initially adopted (4 min.) followed by forced incremented and decremented rhythm changes each lasting 3 min during a 12 min exercise period. Ventilation, pedal pulse train and heart rate were sampled at 17 Hz on a PDP 11/23 computer. Ratios of limb frequency to dominant respiratory frequency were determined following Fourier analysis of these signals. Data that lay within +/- 0.05 of an integer and half-integer ratio were accepted as indices of entrainment, provided that the observed entrained scores were statistically significant. Ventilation frequency showed a clear, but intermittent tendency to entrain with limb frequency. This tendency was greater during bicycle ergometry, possibly as a consequence of task familiarisation, although both exercise entrainments were independent of workload. No difference between preferred versus varied exercise rhythm was evident, but more entrainment (p less than 0.01) was observed during a decremental change in exercise rhythm. These responses do not appear to support an appreciable role for limb-based afferents in the control of entrainment. The results of this study provide evidence that exercise rhythm has some regulatory role in the control of breathing during moderate rhythmical laboratory-based exercise ergometry.     

Temperature entrainment of the circadian cuticle deposition rhythm in Drosophila melanogaster

The cuticle deposition rhythm, which is observed in the apodeme of the furca in the thorax, is controlled by a peripheral circadian clock in the epidermal cells and entrained to light-dark (LD) cycles via CRYPTOCHROME (CRY) in Drosophila melanogaster. In the present study, we examined the effects of temperature (TC) cycles and the combination of LD and TC cycles on entrainment of the cuticle deposition rhythm. The rhythm was entrained to TC cycles, whose period was 28 h. In T = 21 and 24 h, the rhythm was entrained to TC cycles in some individuals. CRY is not necessary for temperature entrainment of the cuticle deposition rhythm because the rhythm in cry(b) (lacking functional CRY) was entrained to TC cycles. Temperature entrainment of the rhythm was achieved even when the thoraxes or furcae were cultured in vitro, suggesting that the mechanism for temperature entrainment is independent of the central clock in the brain and the site of the thermoreception resides in the epidermal cells. When LD and TC cycles with different periods were applied, the rhythm was entrained to LD cycles with a slight influence of TC cycles. Thus, the LD cycle is a stronger zeitgeber than the TC cycle. The variance of the number of the cuticle layers decreased in the flies kept under LD and TC cycles with the same period in which the thermophase coincided with the photophase. Therefore, we conclude that LD and TC cycles synergistically entrain the rhythm. Synergistic effects of LD and TC cycles on entrainment were also observed even when the thoraxes were cultured in vitro, suggesting that the light and temperature information is integrated within the peripheral circadian system.     

Evidence that photoperiodic, dark time measurement in Pharbitis nil involves a circadian rather than a semidian rhythm

Experiments were carried out to determine whether a semidian (12 h) rhythm in flowering response operates in Pharbitis nil as the basis for photoperiodic time measurement. The effect of 5 min far-red light followed by 85 min dark (FRD) given 4, 8,14 and 22 h before the end of a 48 h photoperiod on night-break timing and critical night length was determined. When given 4 h before the end of a 48 h photoperiod, an interruption with FRD advanced the phase of the circadian rhythm in the night-break inhibition of flowering. In contrast, earlier interruptions of the photoperiod had no effect on the phase of the rhythm. The critical night length was modified by FRD given 4 h (shortened) or 8 h (lengthened) before the end of the photo-period; when given at other times FRD did not alter the critical night length. The results are discussed in relation to the basis for photoperiodic timekeeping, with particular reference to suggestions for the involvement of a semidian rhythm. A circadian model based on the concept of limit cycles is described.     

The Paramecium circadian behavioral rhythm: light phase response curves and entrainment

The population of a ciliate protozoan, Paramecium multimicronucleatum, exhibits a circadian rhythm as measured by the number of the cells traversing an observation point ("traverse frequency," or TF). The present study examined phase shifting of the TF rhythm by administering 2-hr light pulses at different phases of the circadian cycle to cultures free-running in constant darkness (DD). The results were summarized in a phase response curve (PRC), categorized as Type 1. This PRC indicated a relatively narrow phase zone insensitive to the light pulse ("dead zone"). Entrainment of the rhythm to light pulses repeated at 24-hr intervals was also examined, and it was found that the rhythm gradually reached a steady state, following several transient cycles, with the pulses falling at a phase corresponding to the narrow dead zone. Such a steady-state rhythm, with a minimum at approximately 3 hr after the pulse and a maximum at approximately 12 hr after the pulse, was mathematically simulated by superimposing a response function to the pulse on a sinusoidal function representative of the free-running rhythm in DD.     

Sleep, performance, circadian rhythms, and light-dark cycles during two space shuttle flights

Sleep, circadian rhythm, and neurobehavioral performance measures were obtained in five astronauts before, during, and after 16-day or 10-day space missions. In space, scheduled rest-activity cycles were 20-35 min shorter than 24 h. Light-dark cycles were highly variable on the flight deck, and daytime illuminances in other compartments of the spacecraft were very low (5.0-79.4 lx). In space, the amplitude of the body temperature rhythm was reduced and the circadian rhythm of urinary cortisol appeared misaligned relative to the imposed non-24-h sleep-wake schedule. Neurobehavioral performance decrements were observed. Sleep duration, assessed by questionnaires and actigraphy, was only approximately 6.5 h/day. Subjective sleep quality diminished. Polysomnography revealed more wakefulness and less slow-wave sleep during the final third of sleep episodes. Administration of melatonin (0.3 mg) on alternate nights did not improve sleep. After return to earth, rapid eye movement (REM) sleep was markedly increased. Crewmembers on these flights experienced circadian rhythm disturbances, sleep loss, decrements in neurobehavioral performance, and postflight changes in REM sleep.     

Rhythmic settling induced by temperature cycles in continuously-stirred autotrophic cultures of Euglena gracilis (Z strain)

Summary Temperature cycles which produced synchrony of cell division in autotrophic Euglena (preceding paper, Terry and Edmunds, 1970) usually also evoked a cellular settling rhythm. The rhythm was expressed as a recurrent cycle of cell attachment to culture-vessel surfaces, with nearly the same phase angle to each of the different temperature cycles. Attachment occurred in cultures stirred rapidly enough for thorough mixing of the cell suspension, but it was possible to prevent attachment by increased agitation. The settling rhythm was entrained by temperature cycles with periods shorter than the minimum period length required to phase cell division, but the rhythm also persisted with a circadian period at constant temperature in continuous light following entrainment by 12,12 hr temperature cycles. The rhythm appeared in stationary-phase cultures exposed to either cold-synchronizing or heat-synchronizing temperature cycles, and also in growth-phase cultures exposed to cold-synchronizing cycles. The settling rhythm was generally not observable in heat-synchronized growth-phase cultures although it often appeared in the same cultures as they approached the stationary phase.This work is derived from a dissertation submitted to the Department of Biological Sciences of the State University of New York at Stony Brook by OzTerry in partial fulfillment of the requirements for the degree of Doctor of Philosophy. It was supported in part by a National Science Foundation Cooperative Graduate Fellowship to 0. Terry and in part by National Science Foundation research grants GB-4140 and GB-6892 and by State University of New York Research Foundation Grant-in-Aid 31-7150A to L. Edmunds.     

Diurnal rhythm of emergence from pupae in parasitic wasp Trichogramma evanescens Westw. (Insecta: Hymenoptera)

Abstract

Pupal eclosion of Trichogramma evanescens Westw. was studied in different conditions of light‐darkness and temperature fluctuations. The results revealed that under natural light cycles Trichogramma exhibits a distinct rhythm of emergence from pupae. Maximum emergence takes place in the morning. This rhythm persists in constant dim red light and temperature, so it is endogenous in nature. The rhythm can be entrained by artificial 24‐h temperature cycles or by day‐night cycles of light with a very low intensity of illumination (<0.01 lux). Nevertheless a single pulse of bright light or of high temperature is not able to reset the rhythm. The emergence rhythm was also absent if the culture was grown in constant darkness and temperature.     

Quantitative estimation of connection of the heart rate rhythm with motor activity in rat fetuses

In rat fetuses over E17-20 with preserved placental circulation with use of mathematical analysis there were revealed value and character of connections of slow wave oscillations of the heart rhythm with motor activity for 30 min of observation. In the software PowerGraph 3.3.8, normalization and filtration of the studied signals were performed in three frequency diapasons: D1-0.02–0.2 Hz (5–50 s), D2-0.0083-0.02 Hz (50 s-2 min), and D3-0.0017–0.0083 Hz (2–10 min). The EMG curves filtrated by diapasons or piezograms were compared with periodograms in the corresponding diapasons of the heart rhythm variations. In the software “Origin 8.0”, quantitative estimation of the degree of intersystemic interrelations for each frequency diapason was performed by Pearson correlation of coefficient, by the correlation connection value, and by the time shift of maximum of cross-correlation function. It has been established that in the frequency D1, regardless of age, the connection of heart rhythm oscillations with motor activity is expressed weakly. In the frequency diapason D2, the connection in most cases is located in the zone of weak and moderate correlations. In the multiminute diapason (D3), the connection is more pronounced. The number of animals that have a significant value of the correlation connection rises. The fetal motor activity fires in the decasecond diapason in all age groups are accompanied by short-time decelerations of the heart rhythms. In the minute diapason, there is observed a transition from positive connections in E17 and E18 to the negative ones in E19-20. Results of the study are considered in association with age-related changes of ratios of positive and negative oscillations of the heart rhythm change depending on the character of motor activity.     

Circannual prolactin rhythm in intact dogs housed outdoors.

Prolactin (PRL) and progesterone (P4) values were collected from eight intact (4 female, 4 male) mixed-breed dogs housed outdoors for a two-year span. A circannual component was significant for PRL for each dog (P less than 0.01) and the rhythm was validated for the population (P less than 0.004). Females had two estrus periods a year demonstrated by a P4 frequency of 23.5 +/- 0.47 wk. A 6-month component was statistically significant for P4 for three dogs and of borderline statistical significance for the fourth dog. Circannual acrophases yielded a statistically significant population rhythm (P = 0.012), whereas the 6-month component was of borderline statistical significance (P = 0.056). No time-macroscopic relationship between PRL cycles and P4 cycles was seen. These findings are consistent with similar PRL rhythms in non-domestic canids and emphasize the importance of considering seasonal effects when interpreting PRL data.     

Light and temperature entrainment of a locomotor rhythm in honeybees

Abstract. The circadian locomotor (walking) rhythms of forager honeybees (Apis mellifera ligustica L.) were entrained to eight different 24 h light-dark cycles. The phases of activity onset, peak activity, and offset were correlated with the lights-off transition, suggesting lights-off as the primary zeitgeber for the rhythm. Further support for this hypothesis was provided by LD 1:23 experiments, in which entrainment occurred when the light pulse was situated at the end, but not at the beginning, of the subjective photophase. Steady-state entrainment of the locomotor rhythm was achieved with square-wave temperature cycles of 10^oC amplitude under constant dark: most of the activity occurred within the early thermophase. Smaller amplitude temperature cycles yielded relative coordination of the rhythm. Interactions of temperature and light-dark cycles resulted in entrainment patterns different from those elicited in response to either cycle alone or those formed by a simple combination of the two separate responses. Furthermore, temperature cycles having amplitudes insufficient for entrainment of the rhythm nevertheless modified the pattern of entrainment to light - dark cycles, suggesting a synergism of light and temperature effects on the underlying circadian clock system.     

雌性大鼠离体垂体前叶内在促黄体生成激素释放节律性现象

众所周知,下丘脑促性腺激素释放激素以脉冲形式驱使垂体前叶释放促黄体生成激素,但垂体前叶本身彼和ＬＨ的形式却遭忽略。直到Ｍａｒｃｏ Ｇａｍｂａｃｃｉａｎｉ和谢二发现人和大鼠离体垂体的ＬＨ释放呈节律性。本文目的在于进一步证实是否确定存在ＬＨ释放的内在节律。     

Fractal and periodic heart rate dynamics in fetal sheep: comparison of conventional and new measures based on fractal analysis

The physiological significance of spectral and fractal components of spontaneous heart rate (HR) variability in the fetus remains unclear. To examine the relationship between circadian rhythms in different measures of HR variability, R-R interval time series obtained by fetal ECGs were recorded continuously over 24 h in five pregnant sheep at 116-125 days gestation. Conventional measures of short-term (STV) and long-term variability (LTV), low-frequency (LF; 0.025-0.15 cycles/beat) and high-frequency (HF; 0.2-0.5 cycles/beat) spectral powers, the LF-to-HF ratio, and fractal dimension values were calculated from 24-h ECG recordings and quantified every 60 min. STV, LTV, and LF and HF spectral powers were minimal during the day but increased significantly to their highest values at night. We found a significant positive correlation between these measures, whereas the cosinor method showed significant similarity between their circadian rhythm patterns. Fetal R-R intervals also exhibited fractal structures. Fetal HR variability had a fractal structure, which was similar between day and night. These results suggested that the circadian rhythms exhibited by STV and LTV during the day were mainly due to changes in frequency components rather than to fractal components of fetal HR fluctuation.     

Circadian Rhythmicity in Photoperiodic Regulation of Regeneration in Begonia Leaves

The mechanism of photoperiodic regulation of regeneration in Begonia leaves has been studied by the night interruption technique in 24, 48, and 72-h cycles. The response to 30 min red light interruptions in 48 and 72-h cycles indicated a circadian rhythm in red light sensitivity with typical photophile and scotophile phases. In 24-h cycles two types of response patterns were observed. With a main photoperiod of 3 h the usual response pattern with only one light-sensitive phase near the middle of the dark period was found, whereas with 8-h photoperiods two light-sensitive phases were observed as previously reported by Zimmer in Begonia flowering studies (Gartenbauwissenschaft 38: 57, 1973). Reversion studies with FR indicate that the reactions are mediated by phytochrome. The results are discussed in relation to alternative hypotheses for photoperiodic timing.     

Diel profile of behaviour in the smooth newt, Triturus vulgaris (L.): an analysis of environmental cues and endogenous timing

Diel activity in a population of smooth newts during the aquatic period, was compared with rhythmic activity in newts under controlled light-dark and temperature cycles in the laboratory. The light-dark cycle was the primary synchronizer of activity and entrained a bimodal activity rhythm. This rhythm was endogenous and persisted for several cycles under constant conditions. Under natural conditions this rhythm was modified by illumination and temperature to produce a crepuscular activity pattern with a dominant second peak in activity. Diel activity under natural conditions was partitioned into sexual behaviour and feeding. Whereas sexual behaviour was entirely crepuscular, feeding behaviour was nocturnal. Feeding was probably unrelated to the underlying circadian rhythm and was engendered by the diel migration of zooplankton in the ponds. Ascents to the pond surface for air were most frequent during periods of sexual behaviour.