Bimodal Rhythm Research Articles

Circadian rhythms and time measurement in locomotor activity of the scorpion Leiurus quinquestriatus (Buthidae).

The circadian rhythms of locomotor activity of the scorpion Leiurus quinquestriatus were examined under different light-dark cycles and in free-running conditions. The circadian rhythm is bimodal in LD 12:12 with alternating cycles of temperature (35 degrees-25 degrees C) with high intensity (1300 lux) or in LD 12:12 with constant temperature 35 degrees C with 300 lux. In LD 12:12 (1300 lux), in long or in short light spans with constant temperature, the bimodal pattern is slightly changed with the appearance of a third minor peak of activity. In free-running conditions, the bimodal rhythm of locomotor activity persists in DD with T about 24 hr, but in LL the rhythm becomes unimodal with T about 24 hr. Cosinor and power spectrum analysis showed the presence of more than one periodic component. It seems that there is a correlation between the range of light regimens, temperature, light intensity and the coincidence of these components. These components are independently entrained by the environmental light cycle. The mechanism of entrainment of components is discussed.

Circadian pacemaker interferes with sleep onset at specific times each day: role in insomnia.

The human circadian pacemaker modulates our desire and ability to fall asleep at different times of day. To study this circadian component of sleep tendency, we have analyzed the sleep-wake patterns recorded from 15 free-running subjects in whom the sleep-wake cycle spontaneously desynchronized from the circadian rhythm of body temperature. The analysis indicates that the distribution of sleep onsets during free run is bimodal, with one peak at the temperature trough and, contrary to previous reports, a second peak 9-10 h later. Furthermore, there are two consistent zones in the circadian temperature cycle during which normal subjects rarely fall asleep. We hypothesize that this bimodal rhythm of sleep tendency, revealed under free-running conditions, maintains the same fixed phase relation to the circadian temperature cycle during 24-h entrainment. This would imply that normally entrained individuals should experience a peak of sleep tendency in the midafternoon and a zone of minimal sleep tendency approximately 1-3 h before habitual bedtime. Our temporal isolation data thereby account quantitatively for the timing of the afternoon siesta and suggest that malfunctions of the phasing of the circadian pacemaker may underlie the insomnia associated with sleep-scheduling disorders.

Internal coupling of five functions of rabbits exhibiting a bimodal circadian rhythm

Abstract By means of a microcomputer‐assisted, electronic recording system five physiological, circadian rhythms of the rabbit were monitored: locomotor activity, hard faeces excretion, food intake, urine excretion and water intake. During 120 days of continuous light conditions (30 lx) the animals exhibited a free‐running circadian rhythm. After the fading out of aftereffects of the preceding light: dark schedule on day 51 ± 11 the animals ran free with an individually distinct period length of > 24.0 h (τ: 24.48 ± 0.10 (SD) h). Spectral analysis of coherent data of 50–84 days showed that in addition to the circadian period persistent ultradian periods of 6.1, 8.2 and 12.3 h were present. Within each individual the five functions proved to be tightly coupled during the free‐run, during the time of reentrainment and when entrained with the LD 12:12. While during LD 12:12 the animals exhibited a bimodal rhythm, during the free‐run the rhythm was unimodal in all five functions. In one animal a “splitting”; of the free‐running period occurred. Both components ran free with different period length. They fused again after 38 days. The “splitting”; was reflected in all five functions of this animal. The behavioural characteristics of meal duration and ‐frequency, duration of activity and ‐intervals, of water intake and urination did not show significant differences during the conditions of LD 12:12 and LL. The results support Pittendrigh's model of two systems of oscillators, selectively susceptible to the transitions of dark : light and light : dark. Our results suggest that in the rabbit the five functions are governed in common by both oscillator‐systems.

AN AVIFAUNAL STUDY IN KAKAMEGA FOREST, KENYA, WITH PARTICULAR REFERENCE TO SPECIES DIVERSITY, WEIGHT AND MOULT

Summary Mann, Clive F. 1985. An avifaunal study in Kakamega Forest, Kenya, with particular reference to species diversity, weight and moult. Ostrich 56: 236–262. A study of the longevity, species diversity, weight, diurnal activity, moult and breeding of forest birds in western Kenya was undertaken between January 1973 and January 1975. Some results from earlier and later studies are used where relevant. By mist-netting, 964 birds of 66 species were captured. The greatest longevity recorded to date is 19 years 6 months for a Cameroon Sombre Bulbul, Andropadus curvirostcis. Species diversity for different months, and the same month in different years are compared, along with those for different forests, and for non-forest habitats. Weight changes are recorded. Contrary to expectation, more birds were heavier, not lighter, when in moult. A bimodal rhythm of diurnal activity is recorded. The approximate duration of primary moult for 94 individuals of 28 species ranged from 37 to 350 days. The months of egg-l...

Reappearance of electroencephalogram slow waves in extended sleep with delayed bedtime.

A three-part study using prolonged nights of sleep was undertaken to verify Broughton's hypothesis of an approximate 12-h ultradrian rhythm of human slow wave sleep (SWS). Part I consisted of 2 8-h adaptation nights followed by a prolonged 15-h night of sleep with bedtime at midnight. A significant return of SWS occurred 12 h and 32 min after the first appearance of SWS. In part II, after 1 adaptation night, subjects were asked to sleep for 15 h but bedtime was delayed until 0400 h. A two-peak return of SWS was observed with a first significant return at 1228 h and a second significant return at 1745 h (i.e., 13 h and 32 min after the first appearance of SWS). In part III, bedtime was again delayed to 0400 h; but subjects were given 3 nights to adapt before the 15 h extended sleep. A single significant return of SWS was then observed at 1656 h, i.e., 12 h and 24 min after the first appearance with no peaks around 1200 h, thus exhibiting the same pattern as in part I. These results suggest that the return of SWS seen normally between 1200 and 1500 h is relatively well entrenched since it remained present in the extended night following sudden bedtime delay. It appears, moreover, that SWS does follow a bimodal 12-h rhythm, which is seen immediately upon extended delayed sleep and can be fully phase-shifted with habituation.

Diurnal rhythm of activity in the arboreal tarantulaAvicularia avicularia(L.) (Mygalomorphae: Theraphosidae)

Abstract By means of aktograph apparatus, immature specimens of A. avicularia have been shown to be crepuscular, with a weak bimodal rhythm of locomotory activity. The peak at the subjective dusk is more pronounced than the one at the subjective dawn. These spiders are “sit wait”; predators and their activity is limited. They are less active, and have a weaker circadian rhythm, than desert‐dwelling tarantulas. This supports the hypothesis that large desert‐inhabiting arthropods are generally both more active and show more marked rhythmichy than tropical forest species.

Circadian rhythms in accessory sex gland function in the male rat.

Alterations in various parameters of accessory sex gland function were monitored during two separate 24 h periods in adult male rats, and compared to fluctuations in the circulating levels of testosterone, prolactin, corticosterone and LH. Bimodal circadian rhythms in ventral prostate prolactin binding, cytosolic oestrogen binding and seminal vesicle weight could be discerned which appeared to be related to a similar rhythmicity in circulating testosterone levels, but with a phase shift of 3 h. Prostatic membrane bound adenylyl cyclase activities (basal and hormone stimulated) and prostatein concentrations followed different patterns possibly correlated to other endocrine changes.

Hypothalamic α 2- and β-adrenoceptor rhythms are correlated with circadian feeding: evidence from hronic methamphetamine treatment and withdrawal

The circadian regulation of food intake in rats is correlated with a bimodal rhythm of β-adrenoceptor binding in the lateral hypothalamus and a unimodal rhythm of α 2-adrenoceptor binding in the medial hypothalamus. Chronic methampheamine treatment provides evidence for a functional correlation: β-adrenoceptor binding in the lateral hypothalamus is reduced at dusk, together with reduction of food intake; α 2-adrenoceptor binding in the medial hypothalamus is increased at dawn, together with persistent food intake. Longterm changes in these two adrenergic systems are also correlated with homeostasis of food intakke: 24-h mean β-adrenoceptor binding is reduced and α 2-adrenoceptor binding is increased upon methamphetamine withdrawal, when rebound feeding occurs. Corticosterone, although normally coupled to adrenergic mechan isms that regulate feeding, is phase delayed after chronic methamphetamine treatment.

Oviposition rhythm in Drosophila melanogaster is influenced by acetic acid

Fermenting fruit can contain acetic acid, a known attractant for fruit flies. Vinegar food induces a bimodal oviposition rhythm in Drosophila melanogaster, however non-vinegar (control) food induces a unimodal rhythm. The bimodal rhythm has a broad day mode showing variability in onset or pattern and a sharp dusk peak. The day mode may not be coupled to the dusk peak or to the 12L : 12D cycle because some flies show oviposition drifting. The day mode augments at the expense of the dusk mode, the latter diminishing within a few days. The unimodal expression on control food is a single dusk peak. Anticipation in the form of oviposition onset is shown by a few flies several hours before the light-off signal. On control food, a pulse of acetic acid fumes can induce a daytime oviposition. When pulsed twice in the day several hours apart two daytime modes are produced, thus leaving few eggs in the dusk mode. The experiments suggest that the fly is attracted to fruit by odours and oviposit rhythmically of a biological clock. If acetic acid is present in fermenting fruit oviposition is induced, thus overriding the clock.

Human post-mortem pineal enzyme activity.

The synthetic enzymes for melatonin production, serotonin-N-acetyltransferase (SNAT) and hydroxy-indole-O-methyltransferase (HIOMT) were measured in post-mortem pineal organs from eighty-eight men and women. The activity of each enzyme was correlated with age and sex. No difference was seen in either parameter when the maximum or minimum activities were measured in the death time periods of the diurnal rhythm established earlier. However, an annual bimodal rhythm was seen in HIOMT activity with maximal values occurring in January and July and minimum activities in March and October. The SNAT and HIOMT enzymes have previously been shown to be stable when measured in pineal organs held under the usual post-mortem conditions. Pineal HIOMT has also been measured in twenty-one psychotic individuals. Whilst the schizophrenic group showed significantly increased values, the schizophrenic-like group had normal values. The results were not affected by ante-mortem or post-mortem states or by drug treatment. Any clinical interpretation of pineal dysfunction in disease states need not, therefore, take into consideration age, or possible sex, but should be aware of the normal diurnal rhythm as well as the bimodal annual rhythm.

Two peaks in the activity rhythm of cockroaches controlled by one circadian pacemaker

Under certain conditions, circadian locomotor activity of the cockroachesLeucophaea maderae (Fabr.) andBlaberus fuscus (Burm.) exhibits two peaks per cycle. Phase-shifting experiments with split rhythms inL. maderae show an identical reaction in both peaks, revealing a strong coupling. Light pulses evoke either delays or advances dependent on the phase of exposure. Phase shifts of bimodal rhythms fit the shape of the phase response curve derived from unimodal systems. Thus the first peak is decisive while the second one shifts accordingly, remaining in a constant phase angle with the other. The results suggest that the bimodal activity pattern inL. maderae isnot a result of two pacemakers each driving one activity peak, as is generally proposed for splitting. Instead, a unitary oscillator system is postulated which shows identical phase shifting properties when driving either a unimodal activity pattern or two peaks of a bimodal rhythm.

Bimodal oscillation in the oxygen consumption of the isolated tissues of the scorpion Heterometrus fulvipes

Oxygen consumption of hepatopancreas and pedipalpal muscle tissue in the scorpion Heterometrus fulvipes was measured over 24 h periods under LD/12 : 12 and in darkness. Hepatopancreas tissue exhibited a bimodal rhythm in the rate of oxygen consumption under both conditions. The two peak values fell at times of highest and lowest locomotor activity and were 12 h out of phase with each other. Pedipalpal muscle did not show much diel variation although there were two small peaks, coinciding with those of hepatopancreas tissue, and indicating the existence of independent oscillations in individual cells and tissues.

Distribution and environmental synchronization of the marine insect, Halobates robustus , in the Galapagos Islands

The following three aspects of the biology of the marine insect Halobates robustus were studied, during a two week observation period, at several sites in the Galapagos Islands: distribution, aggregation behaviour and rhythmicity of locomotory activity. H. robustus occurred in highest numbers on the water surface at shores fringed with mangroves. The aggregations of H. robustus varied according to their location and density. Copulating adults formed dense, floating aggregations, which tended to be close to rocks or mangroves. Late instar nymphs were less aggregated and, in lagoons (where there was some shelter from direct tidal forces), were furthest from the shore. In two types of habitat (mangrove-fringed, sandy shores and rocky shores) the aggregations of H. robustus showed a pronounced ability to maintain a floating station in relation to the surrounding environment, irrespective of tidal movements (in one case at 34 m from the nearest fixed objects). Evidence of the ability of the aggregations to maintain station on the water surface was also obtained by comparing the movements of H. robustus with those of floating polystyrene particles, which move passively with wind and tide. Laboratory observations and experiments indicated no clear periodicity in locomotory movements throughout a 24 h period. However, the frequency of encounters between individuals showed two daily peaks, post-dawn and pre-dusk, with fewer encounters during the day and only occasional encounters during the night. By shifting the light-dark cycle it was demonstrated that the daily bimodal rhythm of encounters is triggered by dawn and, since it is not maintained in constant light or dark, an 'hour-glass' mechanism is suggested. The contributions of single adults, of copulating pairs and of immature stages to the overall pattern of activity were also determined. Immature stages did not affect the overall rate of encounters significantly and the interactions between single and copulating pairs of adults appear to have been responsible for the bimodal pattern.

Turtle diel activity: Response to different regimes of temperature and photoperiod

1. 1. Painted turtles, Chrysemys picta, spotted turtles, Clemmys guttata, and stinkpots, Sternotherus odoratus, acclimated and tested at 15 and 25°C exhibited a unimodal rhythm of locomotor activity at 15°C and a bimodal rhythm at 25°C. 2. 2. Under cyclic thermal acclimation (15–25°C) Chrysemys and Clemmys demonstrated a unimodal rhythm of activity with a major pre-noon peak and an afternoon minimum coinciding with the peak of the ambient temperature cycle, whereas the activity of Sternotherus was bimodal. 3. 3. Each species showed its strongest diurnal tendency under long photoperiod acclimation (LD 16:08) and its greatest noctrnality under short photoperiod (LD 08:16).

Diel patterns of preferred temperature and locomotor activity in the goldfish Carassius auratus

1. 1. Goldfish thermoregulating in an electronic shuttlebox device exhibited a bimodal (crepuscular) rhythm of locomotor activity (peaks at the beginning and end of the dark period) and a unimodal (nocturnal) peak of preferred temperature during the latter half of the dark period. 2. 2. There was no direct relationship between temperature and activity level within the preferred-temperature range of 26–30°C. 3. 3. The preferred temperature peak (29.7°C) occurred at a time (“pre-dawn”) most conducive to increase in body weight and gonosomatic index in goldfish subjected to an exogenously cycled thermal regime.

Circadian rhythms in catecholamine concentrations in organs of the common goldfish ( Carassius auratus L.)

1. 1. Circadian variations in tissue catecholamine levels were demonstrated in goldfish maintained under standard conditions. 2. 2. Cardiac adrenaline and noradrenaline concentrations exhibited a bimodal rhythm with one peak at 08.00 (2 hr post light onset) and the other at 20.00 (2 hr post dark onset), while the amine levels in the brain and the swimbladder only showed one pronounced maximum at 08.00 (brain) or at midnight (swimbladder) respectively. 3. 3. The biological significance of these findings is discussed with special regard to the activity pattern of the animals.

Changes in the daily rhythm of plasma corticosterone concentration related to seasonal conditions in the white-throated sparrow, Zonotrichia albicollis.

Circadian variations in concentrations of plasma corticosterone were investigated in the white-throated sparrow maintained on short (10-hr) or long (16-hr) daily photoperiods. In addition, the plasma concentrations of corticosterone were determined throughout a day in birds that were in the reproductively photosensitive spring migratory condition, the reproductively photorefractory post nuptial molt condition, and the fall migratory condition. Distinct unimodal rhythms were found in photosensitive birds. The daily rise occurred 12 hr after the offset of light in birds kept on both the short and the long photoperiodic regimens. There was no discernible daily variation in photorefractory birds kept on a 16 hr daily photoperiod and there was a bimodal rhythm in the birds that were in the fall migratory condition. The results are consistent with an hypothesis that assigns an important role to the circadian rhythm of corticosteroid concentration in the photoperiodic mechanism controlling seasonal reproductive and migratory conditions in the white-throated sparrow.

Environmental and Intrinsic Control of Filtering and Feeding Rates in Arctic Daphnia

Filtering and feeding rates of Daphnia middendorffiana at Point Barrow, Alaska were measured as a function of temperature, food density, animal length, and time of day.The functional relationship between feeding rate and food density followed the hyperbolic pattern typical for filter feeders. Daphnia middendorffiana was found to have comparatively high filtering capabilities at its temperature optimum (around 11 C), with filtering rate increasing with length according to the equation F =.458L3.17. The exponent of this equation was found to be a function of temperature, and the coefficient a function of food density.A bimodal diel rhythm in feeding rate was found in this species in experiments where the animals were held under constant conditions. Feeding rates were maximum at 1400 and 2400, the time of day when the temperature cycle in the ponds passes through the mean daily temperature, which is optimum for feeding in D. middendorffiana. Thus the timing of the rhythm may serve to maximize the daily food gathering ability of this species.

Circadian rhythm in acetylcholinesterase activity during aging of the central nervous system

The circadian rhythm of acetylcholinesterase (AChE) activity was investigated in the cerebrum, cerebellum, medulla and optic lobes of rats aged 1 day and 3, 13, 44 and 87 weeks. The rhythm was found to be age-dependent. Animals aged 1 day exhibited a bimodal rhythm in all the four regions of the brain studied. At 3 and 13 weeks the activity was unimodal. The peak occurred during the light-on phase at 3 weeks and during the light-off phase at 13 weeks. At 87 weeks the rhythms in the medulla and cerebrum were similar to those of 44 week animals. By contrast the cerebellum had a bimodal rhythm with peaks at intervals of 12 h. In the optic lobes there was a shift from a bimodal pattern at 44 weeks to a unimodal one at 87 weeks. The times of onset of the light-on and light-off peaks in different regions of the brain differed with age.

Cellular patterns of differing circadian rhythms and levels of RNA synthesis in Drosophila salivary glands

Autoradiographic analysis of 3H-uridine incorporation into cytoplasmic RNA of Drosophila larval salivary glands reveals differing circadian rhythms. Within a salivary gland proximal cells in general show higher levels of 3H-uridine incorporation and a single maximum at 12.00–18.00 hr; distal cells in general exhibit lower incorporation rates and two maxima at 6.00–9.00 and 21 hr. Within a cross section of the distal part of the gland alternating higher and lower 3H-uridine label is observed in adjoining cells in about 40% of 250 sections. Both cell types can be distinguished also by differences in their rhythmic behaviour: the highly labelled cells show a unimodal rhythm with a maximum at 15.00 hr, the weakly labelled cells a bimodal rhythm with maxima at 9.00 and 21.00 hr. The alternation differing cells in cross sections is highly significant at certain times of day (12.00, 3.00 hr) and less significant at other times. A more or less regular spatial distribution of these different physiologic populations is concluded.