A Direct Comparison between Circadian and Noncircadian Rhythms in Neurospora crassa

A method has been devised for observing both circadian and noncircadian rhythms in a single wild type strain of Neurospora crassa. This method allows a direct comparison of the properties of the two types of rhythm. The circadian rhythm of conidiation always entrains to a light-dark cycle, damps out in constant light, and has a temperature-compensated period length. The noncircadian rhythm of hyphal branching, expressed by the same strain under different environmental conditions, does not entrain to a light-dark cycle, persists in constant light, and its period length is temperature-dependent. These results suggest that the two rhythms have different underlying mechanisms and demonstrate that the differences in the rhythms previously observed in different strains (patch, band, and clock) are not due to genetic differences between these strains but rather are inherent properties of the rhythms themselves.     

Circadian rhythms of oviposition and feeding activity in Japanese quail: effects of cyclic administration of melatonin

The aim of these experiments was to test the effect of a cyclic administration of melatonin, by mimicking the daily rhythm of hormone levels, on the circadian organization of two distinct functions in quail: oviposition and feeding activity. Laying and feeding rhythms under photoperiodic conditions and constant darkness (DD) were investigated. Under DD, where the two rhythms were free running, a daily rhythm of melatonin was administered. In LD 14h:10h, two different individual profiles of laying were established, with stable females laying at the same time each day and delayed females laying progressively later each day. For feeding activity, all birds were clearly synchronized to the photoperiodic cycle. In DD, the laying birds showed a free-running rhythm of oviposition with a period longer than 24 h for both profiles but the delayed profile females had a longer period than stable profile females. In comparison, the free-running period of feeding rhythm of the same birds was shorter than 24 h. A cyclic administration of melatonin had no effect on laying rhythm, which continued to free-run in DD, whereas feeding activity was synchronized as soon as the first cycle of melatonin was administered. From these results, it seems that two different circadian systems drive each of the two types of behavior separately. Melatonin could be the main synchronizer for the temporal control of feeding behavior, but it does not play a part in the control of oviposition in Japanese quail.     

Circadian activity rhythms in cockroaches. 3. The role of endocrine and neural factors

The control of circadian activity rhythms (diurnal rhythms) in insects has been suggested to result by periodic neuroendocrine secretions. More specifically, Harker ('56) claimed that the locomotor rhythm in the cockroach, Periplaneta americana, is timed by a secretory “clock” located in the subesophageal ganglion. Later experiments by Harker indicated that this “clock” function failed unless the retrocerebral organs were left intact; allatectomy was said (no evidence given) to abolish a rhythm. The procedure for demonstrating a “clock” function in the ganglion involved transplanting it from a rhythmic donor into the hemocoel of an arrhythmic host and observing that the host subsequently became rhythmic. This result (without explicit information about the phase of the rhythm) does not warrant the conclusion that the ganglion acts as a clock. Therefore, I have attempted to confirm and extend these important results. Employing techniques essentially identical to Harker's, and using the same species of roach, I have been unable to find any evidence to support the original claim: (1) in 20 test animals, implantation of ganglia from rhythmic donors failed to re-instate a rhythm, and (2) allatectomy (22 cases) or removal of the entire retrocerebral complex (20 cases) did not interfere with the rhythm. The results of another series of experiments show that the cockroach brain is involved in the control of the activity rhythm. When the brain is surgically bisected (mid-sagittal) through the pars intercerebralis, arrhythmic activity patterns are immediately evoked. These continue for many weeks, but in a few cases rhythms ultimately “regenerate”.     

Circadian rhythms of locomotor activity and temperature selection in sleepy lizards, <Emphasis Type="Italic">Tiliqua rugosa</Emphasis>

This study examined whether the daily rhythms of locomotor activity and behavioural thermoregulation that have previously been observed in Australian sleepy lizards (Tiliqua rugosa) under field conditions are true circadian rhythms that persist in constant darkness (DD) and whether these rhythms show similar characteristics. Lizards held on laboratory thermal gradients in the Australian spring under the prevailing 12-hour light : dark (LD) cycle for 14 days displayed robust daily rhythms of behavioural thermoregulation and locomotor activity. In the 13-day period of DD that followed LD, most lizards exhibited free-running circadian rhythms of locomotor activity and behavioural thermoregulation. The predominant activity pattern displayed in LD was unimodal and this was retained in DD. While mean levels of skin temperature and locomotor activity were found to decrease from LD to DD, activity duration remained unchanged. The present results demonstrate for the first time that this species’ daily rhythm of locomotor activity is an endogenous circadian rhythm. Our results also demonstrate a close correlation between the circadian activity and thermoregulatory rhythms in this species indicating that the two rhythms are controlled by the same master oscillator(s). Future examination of seasonal aspects of these rhythms, may, however, cause this hypothesis to be modified.     

An Experimental Analysis and Comparison of Three Rhythms of Movements in Bean (Phaseolus Vulgaris L.)

Three types of rhythmic movements of Phaseolus vulgaris L. (pole beans) were examined collectively and their characteristics compared. Although the ultradian rhythms of shoot circumnutation and leaf movement, as well as the circadian rhythm of leaf movement, occurred simultaneously, each rhythm could be expressed independently of the other two. Shoot circumnutation and ultradian leaf movements displayed the same period (80 min at 25°C and Q₁₀⋍2), while the period of the circadian leaf movements was not temperature dependent (Q₁₀⋍1). Interaction into the plant between two ultradian rhythms (shoot circumnutation and ultradian leaf movement) with the same period and coexistence in the pulvinus of an ultradian with a circadian rhythm are discussed.     

Circadian rhythm of ERG in Iguana iguana: role of the pineal

In green iguanas, the pineal controls the circadian rhythm of body temperature but not the rhythm of locomotor activity. As part of a program to investigate the characteristics of this multioscillator circadian system, the authors studied the circadian rhythms of the electroretinographic response (ERG) and asked whether the pineal gland is necessary for the expression of this rhythm. ERGs from a total of 24 anesthetized juvenile iguanas were recorded under four different conditions: (a) complete darkness (DD), (b) dim light-dark cycles (dLD), (c) constant dim light (dLL), and (d) pinealectomized in DD. Results demonstrate that the b-wave component of the ERG shows a very clear circadian rhythm in DD and that this rhythm persists in dLL and entrains to dLD cycles. The ERG response is maximally sensitive during the subjective day. Pinealectomy does not abolish the circadian rhythm in ERG, demonstrating that the oscillator responsible for the ERG rhythm is located elsewhere.     

Effects of a Seven‐Day Continuous Infusion of Ropivacaine on Circadian Rhythms in the Rat

The present study was conducted to evaluate the effect of a 7 d continuous infusion of ropivacaine on the 24 h rhythms of body temperature, heart rate, and locomotor activity. After an initial 7 d baseline, rats were randomly divided into two groups of 4 rats each to receive ropivacaine or saline via an osmotic pump for 7 consecutive days. The pumps were removed thereafter and observed during a 7 d recovery span. The studied circadian rhythms were measured by radiotelemetry throughout each of the 7 d periods. An additional group of 4 rats was studied under the same experimental conditions to assess the plasma levels of ropivacaine on days 3 and 8 following pump implantation. Our results indicate that ropivacaine does not induce loss of the circadian rhythms of body temperature, heart rate, or locomotor activity; a prominent period of 24 h was found for all variables in all animals, before, during, and after ropivacaine treatment. However, ropivacaine treatment did modify some characteristics of the rhythms; it increased the MESOR (24 h mean) of the heart rate and locomotor activity rhythms and advanced the acrophase (peak time) of the locomotor activity circadian rhythm. The present study indicates that the circadian rhythms of heart rate and locomotor activity are modified after continuous infusion of ropivacaine, which is of particular interest, given the potential cardiotoxicity of this local anesthetic agent.     

A Circadian Rhythm in Mice that is Unaffected by the Period Mutation at Clock

Circadian rhythms of locomotor behavior were induced in mice using chronic d-amphetamine. The periods of the rhythms at various doses of amphetamine were unaffected by a mutation at the clock locus that lengthens circadian period. Amphetamine-induced rhythms were superimposed on the hostÕs natural circadian rhythm that is driven by the pacemaker in the suprachiasmatic nucleus. The results demonstrate the existence of an alternative mechanism for generating circadian rhythms that does not require the activity of canonical clock genes.     

Effect of change in levels of motor activity and innervation on basic and secondary rhythms of rat heart rate and respiration in ontogenesis

Changes in the heart basic rhythm, its rhythmical variations on periodograms, and level of spontaneos motor activity were studied on offspring of white rats from newborn to 3-week age at transition from the state of active wakefulness to narcosis as well as under conditions of blockade of M-cholinoreceptors with atropine. It is shown that the endogenous rhythmical activity can be regulated not only by a change in frequency of basic rhythms, but also by action on all parameters and properties of their rhythmical variations and secondary rhythms. The changes in power of the heart secondary rhythms exceed considerably the frequency oscillations of basic rhythms during blockade of cholinergic innervation or a change in the motor activity level that affects both the basic rhythm circulation and respiration and their variations--secondary rhythms. The atropine blockade of M-cholinoreceptors at the studied ages changes the heart beating rhythm within the limits of 10% of bradicardia in newborns to tachycardia in the 3-week old animals. At the same time, power of the cardiac rhythm secondary oscillations changes several times. These data indicate that the cholinergic mechanisms play the key role in formation of the secondary rhythms and their correlation with motor activity.     

心肌细胞团搏动的整数倍节律的实验观察

实验报道了心肌细胞团自发性同步化搏动的一类新节律——整数倍节律。这种稳定的节律模式由两种相关的搏动形式的随机交替出现形成,这两种搏动形式中任何一种的出现间期具有整数倍特征。在静息状态和周期1搏动间的随机交替形成0-1整数倍节律,在周期1搏动和周期2搏动之间的随机交替形成l-2整数倍节律。0-1整数倍是居于静息状态和周期1节律之间的节律模式,1-2整数倍是居于周期1节律和周期2节律之间的节律模式,实验所见的节律转迁过程清楚地展示了静息状态、0-1整数倍节律、周期1节律、1-2整数倍节律、周期2节律等顺序地构成的一种“节律谱系”。“节律谱系”的观念可以为认识正常和异常心律的关系和其间的转迁机制提供深刻的理论启示。     

Effects of a seven-day continuous infusion of ropivacaine on circadian rhythms in the rat

The present study was conducted to evaluate the effect of a 7 d continuous infusion of ropivacaine on the 24 h rhythms of body temperature, heart rate, and locomotor activity. After an initial 7 d baseline, rats were randomly divided into two groups of 4 rats each to receive ropivacaine or saline via an osmotic pump for 7 consecutive days. The pumps were removed thereafter and observed during a 7 d recovery span. The studied circadian rhythms were measured by radiotelemetry throughout each of the 7 d periods. An additional group of 4 rats was studied under the same experimental conditions to assess the plasma levels of ropivacaine on days 3 and 8 following pump implantation. Our results indicate that ropivacaine does not induce loss of the circadian rhythms of body temperature, heart rate, or locomotor activity; a prominent period of 24 h was found for all variables in all animals, before, during, and after ropivacaine treatment. However, ropivacaine treatment did modify some characteristics of the rhythms; it increased the MESOR (24 h mean) of the heart rate and locomotor activity rhythms and advanced the acrophase (peak time) of the locomotor activity circadian rhythm. The present study indicates that the circadian rhythms of heart rate and locomotor activity are modified after continuous infusion of ropivacaine, which is of particular interest, given the potential cardiotoxicity of this local anesthetic agent.     

Effect of change in levels of motor activity and innervation on basic and secondary rhythms of rat heart beatings and respiration in ontogenesis

Changes in the heart basic rhythm, its rhythmical variations on periodograms, and level of spontaneous motor activity were studied on offspring of white rats from newborn to 3-week age at transition from the state of active wakefulness to narcosis as well as under conditions of blockade of M-cholinoreceptors with atropine. It is shown that the endogenous rhythmical activity can be regulated not only by a change in frequency of basic rhythms, but also by action on all parameters and properties of their rhythmical variations and secondary rhythms. The changes in power of the heart secondary rhythms exceed considerably the frequency oscillations of basic rhythms during blockade of cholinergic innervation or a change in the motor activity level that affects both the basic rhythm circulation and respiration and their variations—secondary rhythms. The atropine blockade of M-cholinoreceptors at the studied ages changes the heart contraction rhythm within the limits of 10% of bradycardia in newborns to tachycardia in the 3-week old animals. At the same time, power of the cardiac rhythm secondary oscillations changes several times. These data indicate that the cholinergic mechanisms play the key role in formation of the secondary rhythms and their correlation with motor activity.     

Diversity of biological rhythm and food web stability

How ecosystem biodiversity is maintained remains a persistent question in the field of ecology. Here, I present a new coexistence theory, i.e. diversity of biological rhythm. Circadian, circalunar and circannual rhythms, which control short- and long-term activities, are identified as universal phenomena in organisms. Analysis of a theoretical food web with diel, monthly and annual cycles in foraging activity for each organism shows that diverse biological cycles play key roles in maintaining complex communities. Each biological rhythm does not have a strong stabilizing effect independently but enhances community persistence when combined with other rhythms. Biological rhythms also mitigate inherent destabilization tendencies caused by food web complexity. Temporal weak interactions due to hybridity of multiple activity cycles play a key role toward coexistence. Polyrhythmic changes in biological activities in response to the Earth''s rotation may be a key factor in maintaining biological communities.     

Development and relationships of locomotor, feeding, and oxygen consumption rhythms in house crickets

ABSTRACT. Locomotor, feeding, drinking, and oxygen consumption rhythms in adult virgin Acheta domesticus L. all appear to peak in the first half of the scotophase, be entrained cophasically by a LD 14:10 h cycle, have a lights-off Zeitgeber and persist in LL with a π c. 25 h for the locomotor rhythm and c. 23 h for the oxygen consumption rhythm. There is no evidence of these rhythms in last instar larvae. The onset of the locomotor rhythm requires 3 days at 30°C but 5–7 days at 25–28°C after the final ecdysis in virgins, indicating a temperature related development of the locomotor rhythm. Oxygen consumption rhythms are lacking in 2-day-old virgins but present in 8-day-old virgins. Feeding rhythms can be recorded in virgins as young as 2 days (before locomotor rhythm developed). Both oxygen consumption and locomotor rhythms persist during starvation. The results suggest that a central brain oscillator drives both feeding and locomotor rhythms independently, but that the oxygen consumption rhythm is derived from the metabolic demands associated with the other rhythms.     

Lack of circadian rhythmicity of rat fetal intestinal enzymes as compared to the dams

The 24-hr activity patterns of intestinal maltase, lactase, leucylnaphthylamine hydrolyzing activity, γ-glutamyltransferase, and alkaline phosphatase were determined in pregnant rats maintained on a 12-12 light-dark cycle, with feeding during the dark period (1800-0600 hr, EST). The activities of these enzymes plus those of lysosomal maltase and lactase were followed during the same time period in 19- to 20-day-old fetuses. The activity patterns in the dams followed circadian rhythms, with peak activities occurring during the feeding-dark period. These rhythms are similar to the feeding schedule-cued rhythms observed in male rats and, therefore, are assumed to be feeding schedule cued also. In the fetuses, which obtained nutrients through the placenta, the activities increased in a somewhat nonlinear manner throughout the entire 24-hr period, but did not display a defined rhythm. It is concluded that endogenous intestinal enzyme rhythms do not exist in utero, and that oral and/or intermittent feeding is necessary for these rhythms to occur.     

Suprachiasmatic nuclear lesions eliminate circadian rhythms of drinking and activity, but not of body temperature, in male rats

Male Long-Evans rats were maintained in light proof cabinets while drinking, activity, and telemetered body temperature (Tb) data were collected. After suprachiasmatic nuclear (SCN) lesions, the rats were exposed to a 12:12 light-dark cycle, a 6-hr delay in the lighting cycle, and constant dark. Lesions that abolished the drinking and activity rhythms did not eliminate the Tb rhythm. However, the amplitude, phase, and free-running period of the Tb rhythm were altered. Lesions that only partially damaged the SCN had similar, though lesser effects. In some cases, Tb rhythms remained normal, activity rhythms were only temporarily disrupted, and drinking rhythms were eliminated in the same animals. These results support the conclusion that Tb can remain rhythmic after lesions that permanently or temporarily disrupt other circadian rhythms. Of the three rhythms, it appears that drinking rhythms are most easily and Tb rhythms least easily disrupted by SCN lesions.     

Egg-laying rhythm in <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

Extensive research has been carried out to understand how circadian clocks regulate various physiological processes in organisms. The discovery of clock genes and the molecular clockwork has helped researchers to understand the possible role of these genes in regulating various metabolic processes. In Drosophila melanogaster, many studies have shown that the basic architecture of circadian clocks is multi-oscillatory. In nature, different neuronal subgroups in the brain of D. melanogaster have been demonstrated to control different circadian behavioural rhythms or different aspects of the same circadian rhythm. Among the circadian phenomena that have been studied so far in Drosophila, the egg-laying rhythm is unique, and relatively less explored. Unlike most other circadian rhythms, the egg-laying rhythm is rhythmic under constant light conditions, and the endogenous or free-running period of the rhythm is greater than those of most other rhythms. Although the clock genes and neurons required for the persistence of adult emergence and activity/rest rhythms have been studied extensively, those underlying the circadian egg-laying rhythm still remain largely unknown. In this review, we discuss our current understanding of the circadian egg-laying rhythm in D. melanogaster, and the possible molecular and physiological mechanisms that control the rhythmic output of the egg-laying process.     

Co-ordinating interneurones of the locust which convey two patterns of motor commands: their connexions with flight motoneurones.

1. Some flight motoneurones receive two superimposed rhythms of depolarizing synaptic potentials when the locust is not flying; a slow rhythm which is invariably linked to the expiratory phase of ventilation, and a fast rhythm with a period of about 50 ms which is similar to the wingbeat period in flight. 2. By recording simultaneously from groups of motoneurones, the synaptic potentials which underly these rhythms have been revealed in 30 flight motoneurones in the three thoracic ganglia. The inputs occur in elevator motoneurones and some depressors but are of lower amplitude in the latter. The inputs have not been found in leg motoneurones. 3. The rhythmic depolarizations are usually subthreshold but sum with sensory inputs to evoke spikes in flight motoneurones at intervals equal to or multiples of the wingbeat period in flight. 4. Both rhythms originate in the metathoracic ganglion and are mediated by the same interneurones. They can be adequately explained by supposing that there are two symmetrical interneurones which each make widespread connexions with left and right flight motoneurones in the three ganglia. 5. The slow rhythm is coded in the overall burst of interneurone spikes during expiration and the fast rhythm in the interval between the spikes of a burst.     

Circadian Locomotor Rhythms in Mice with Targeted Disruption of the Gene for the Carbon Monoxide Synthesizing Enzyme,Heme Oxygenase-2

Carbon monoxide (CO), generated in neurons by the enzyme heme oxygenase-2 (HO2), is postulated to be a gaseous signaling molecule in the mammalian brain. Because of the recent evidence suggesting an important role of another endogenously produced gas, nitric oxide (NO), in entrainment of circadian rhythms in mammals, we hypothesized that CO may also be involved in regulating these rhythms. Consistent with this idea, others have found a circadian rhythm of heme turnover and CO synthesis can be induced by bright light. Furthermore, HO2 is co-localized with guanylyl cyclase, the putative target of CO, throughout the brain, with high amounts of staining in the suprachiasmatic nucleus (SCN) of the hypothalamus. The goal of the present study was to evaluate the role of CO in photic entrainment in wild-type and HO2 deficient mice. HO2–/– mice did not display any abnormalities in circadian rhythmicity. Entrainment to a light–dark cycle, the ability to phase delay locomotor activity after a four hour phase shift in photoperiod, and the period of the free running rhythm (t) were similar between HO2–/– and wild-type mice. Taken together, these data suggest that CO does not play a major role in regulating circadian activity rhythms in mice.     

Structure of autorhythmical activity of contractile systems

In the autorhythmical activity underlying many visceral and in early ontogenesis also somatomotor systems, three kinds of rhythms are to be distinguished: basic, reflecting activity of individual organs and of systems of organs, the secondary ones representing result of the frequency and amplitude modulation of the basic rhythms, and the rhythmical periodic activity whose distinguishing feature is alternation of the activity and rest phases. Each kind has principally different frequency characteristics, different organization and localization of sources. The frequency of basic rhythms is determined by the generator inserted into the system. It serves an individual characteristics of the current state of function of the organ, the degree of maturity of its motor apparatus. The secondary rhythm and the rhythm of the periodic activity cycles are provided by oscillatory processes common to the whole organism. Universality of these rhythms promotes integration of functions.