Two Oscillators Might Control the Locomotor Activity Rhythm of the High‐Altitude Himalayan Strain of Drosophila Helvetica

The properties of the pacemaker controlling the adult locomotor activity rhythm of the high‐altitude Himalayan (haH) strain (Hemkund Sahib, 4121 m above sea level) of Drosophila helvetica are strikingly different from those of the low‐altitude Himalayan (laH) strain (Birahi, 1132 m above sea level) of the same species. The haH strain has a unimodal activity pattern with a delayed peak occurring about 4.5 h after lights‐on of the entraining light‐dark (LD) cycle, while the laH strain has a bimodal activity pattern with the morning and evening peaks. It is rather unusual for a wild type strain of any Drosophila species to have a unimodal activity pattern during entrainment as observed in the haH strain. The single activity peak of the haH strain is regarded as a consequence of delayed morning peak merging with the evening one. Three experiments were performed to test this hypothesis. The first experiment examined whether the single activity peak could be dissociated into two components by LD cycles in which photoperiods varied from 10 to 16 h per 24 h. The haH strain again exhibited a unimodal activity pattern with a delayed peak in 10, 12, and 14 h photoperiods but a bimodal activity pattern in 16 h photoperiod. The laH strain had bimodality in 10 and 12 h photoperiods, unimodality in a 14 h photoperiod, but complete arrhythmicity in a 16 h photoperiod.

In the second experiment, the haH flies were transferred from LD 16∶8 to LL at 5 lux to confirm whether the bimodality of this strain in LD 16∶8 cycles was not the result of masking by the long photoperiod of 16 h. Bimodality of the haH strain persisted in LL too; moreover, the morning component free‐ran with period (τ) <24 h, while the evening component free‐ran with τ>24 h. The third experiment examined the LL‐induced splitting of activity peak of the haH strain. Flies were transferred from LD 12∶12 cycles to LL at 0, 1, 5, and 15 lux. The haH strain was rhythmic in LL at 0 and 1 lux with a unimodal activity pattern. It was also rhythmic in LL at 5 lux, but the single activity peak was split into two discrete components; the morning component free‐ran with τ<24 h, while the evening component free‐ran with τ>24 h. This strain, however, was completely arrhythmic in LL at 15 lux. The laH strain was uniformly arrhythmic in LL at all levels of light intensity. These results suggest that the single but late activity component of the haH strain during entrainment appears to be the consequence of merging the delayed morning peak with the evening one as an adaptation to the environmental conditions at the altitude of origin of this strain, where these flies begin activity in the forenoon owing to non‐permissible low temperature in the morning.     

Rhythm-Specific Mutations in Drosophila rajasekari Altered Adult Locomotor Activity Rhythm but Not Eclosion Rhythm

The early and late strains for phase angle difference (Φ) of adult locomotor activity in Drosophila rajasekari were developed by artificial selection; these strains differed in Φ, activity pattern, activity level, free-running period (τ) in constant darkness (DD) and light induced phase shifts from those of the wild type (Joshi, 1998). The present studies were designed to determine whether or not the psi-mutations for adult locomotor activity rhythm had also altered the fundamental properties of the eclosion rhythms in these strains. The circadian rhythms of eclosion have been studied in the wild type, the early and late strains. In contrast to the effects on the locomotor activity rhythms in the early and late strains, the psi-mutations have no apparent effect on the eclosion median in light-dark cycles of 12 : 12 h, on τ in DD, light induced phase shifts or subjective light sensitivity in these strains. Thus the psi-mutations for the adult locomotor activity rhythms in D. rajasekari appear to be rhythm-specific mutations altering the locomotor rhythms but not the eclosion rhythms.     

Towards a Characterization of the Locomotor Activity Rhythm of the Supralittoral Isopod Tylos europaeus

Freshly collected samples of Tylos europaeus from Korba beach (northeast of Tunisia) were housed in an environmental cabinet at controlled temperature (18°C?±?.5°C) and photoperiod. Locomotor activity was recorded under two photoperiodic regimens by infrared actography every 20?min by multichannel data loggers. One regimen simulated the natural light-dark cycle on the day of collection, whereas the second imposed a state of continuous darkness on all individuals. Under entraining conditions, the animals displayed rhythmic activity, in phase with the period of darkness, whereas in continuous darkness these isopods exhibited a strong endogenous rhythm with circadian and semidiurnal components at mean periods of τ (h:min)?=?25:09?±?01:02?h and τ?=?12:32?±?00:26?h, respectively. Under free-running conditions, this endogenous rhythm showed significant intraspecific variability. (Author correspondence: bohli.dhouha@gmail.com)     

Cyclic Presence and Absence of Conspecifics Alters Circadian Clock Phase But Does Not Entrain the Locomotor Activity Rhythm of the Fruit Fly Drosophila melanogaster

Circadian clocks use a wide range of environmental cues, including cycles of light, temperature, food, and social interactions, to fine-tune rhythms in behavior and physiology. Although social cues have been shown to influence circadian clocks of a variety of organisms including the fruit fly Drosophila melanogaster, their mechanism of action is still unclear. Here, the authors report the results of their study aimed at investigating if daily cycles of presence and absence (PA) of conspecific male visitors are able to entrain the circadian locomotor activity rhythm of male hosts living under constant darkness (DD). The results suggest that PA cycles may not be able to entrain circadian locomotor activity rhythms of Drosophila. The outcome does not change when male hosts are presented with female visitors, suggesting that PA cycles of either sex may not be effective in bringing about stable entrainment of circadian clocks in D. melanogaster. However, in hosts whose clock phase has already been set by light/dark (LD) cycles, daily PA cycles of visitors can cause measurable change in the phase of subsequent free-running rhythms, provided that their circadian clocks are labile. Thus, the findings of this study suggest that D. melanogaster males may not be using cyclic social cues as their primary zeitgeber (time cue) for entrainment of circadian clocks, although social cues are capable of altering the phase of their circadian rhythms. (Author correspondence: vsharma@jncasr.ac.in, vksharmas@gmail.com)     

Seasonal Variation in the Orcadian Rhythm of Pulmonary Function in Stable Astthmatic Children who have Nearly Outgrown their Asthma

To study whether nocturnal bronchial obstruction changes during the year, we assessed the circadian FEV₁ variation during four consecutive seasons in 20 children (12 boys; aged 9–12 years) with episodic asthma who were outgrowing their asthma. FEV₁ was determined every 4 h between 10:00 and 10:00 during two consecutive days. The last six FEV₁ values were submitted to cosinor and coefficient of variation (CV) analyses. The seasonal means (SD) in the group 24 h percent predicted FEV₁ was 85.5 (11.4), 81.2 (10.6), 86.0 (11.6), and 82.2 (14.0)% during spring, summer, autumn, and winter, respectively. The difference between the summer and autumn FEV₁ values was statistically significant (p < 0.05). The mean (SD) of the circadian amplitude values was 4.1 (4.3), 6.0 (3.8), 4.9 (3.4), and 7.2 (4.1)% during spring, summer, autumn, and winter, respectively. The difference in amplitude between the spring and winter and between the autumn and winter values was statistically significant (p<0.05). CV values of 48 of the 80 (60%) circadian FEV, time series exceeded the average CV of 5% observed in non-asthmatic children studied in our laboratory. There was an unequal distribution during the year in elevated CV values; 6, 17, 10, and 15 of the high CV values occurred, respectively, in the spring, summer, autumn, and winter. These results suggest that nocturnal bronchial obstruction may change seasonally in terms of severity and amplitude in children who have nearly outgrown their asthma. (Chronobiology International, 13(4), 295–303, 1996)     

Entrainment Properties of the Locomotor Activity Rhythm of Drosophila melanogaster Under Different Photoperiodic Regimens

In this paper we report the results of an experiment to assess how closely repeated brief light pulses (LPs) mimic the effects of 12:12 h light/dark (LD) cycles (PPc). The locomotor activity rhythm of individual fruit flies from a laboratory population of Drosophila melanogaster was monitored under four different photoperiodic regimens, created using 12 h of light and 12 h of darkness or brief light pulses (LPs). The phase relationship (Ψ) and the stability (precision) of the locomotor activity rhythm during entrainment were estimated in order to compare the state of the circadian clocks under the four different photoperiodic regimens. The flies (n = 72) were subjected to four different LD cycles: (i) 12 h of light and 12 h of darkness (complete photoperiod, PPc); (ii) a single brief LP of 15 min duration presented close to the onset of activity (SLP-1); (iii) a single brief LP of 15 min duration administered close to the offset of activity (SLP-2); and (iv) two brief LPs administered 12 h apart (skeleton photoperiod, PPs). The locomotor activity rhythm of the flies was first monitored under constant darkness (DD) for about 10 days and then under the four different photoperiodic regimens for about 10 days, and finally in DD for the remainder of the experiment. The Ψ of the locomotor activity rhythm and its precision under PPc and PPs did not differ significantly, but they were significantly different from the SLP-1 and SLP-2 conditions. The results provide interesting insights into photoentrainment mechanisms of circadian clocks in D. melanogaster, and suggest that skeleton photoperiods, but not single brief LPs, mimic the actions of complete photoperiods.     

Effect of Light Intensity on the Oviposition Rhythm of the Altitudinal Strains of Drosophila Ananassae

The sensitivity of the circadian photoreceptors mediating entrainment of the eclosion rhythm and phase shifts of oviposition rhythm of the high altitude (HA) strain of Drosophila ananassae originating from Badrinath (5123 m above sea level) in the Himalayas was compared with the low altitude (LA) strain from Firozpur (179 m above sea level). Reduced photic sensitivity of the HA strain is regarded as the result of natural selection, which led to the weakening of the coupling mechanism between the circadian pacemaker and light at the high altitude of origin. The present study was designed to determine whether or not the photic entrainment of the oviposition rhythm of the HA strain of D. ananassae is also altered by the high altitude of its origin, and the results are compared with those of the LA strain. The effects of light intensity on the phase angle difference (Ψ), degree of rhythmicity (R), the percent oviposition in photophase, the threshold light intensity (i.e., the intensity at which stable entrainment occurred), and the saturation light intensity (i.e., the intensity beyond which the values of Ψ or amplitude of rhythm remained unaltered) were determined. Entrainment was studied in light–dark cycles in which the light intensity of 12 h of photophase varied from 1 to 1000 lux, and complete darkness prevailed in all scotophases. The oviposition rhythm of the HA strain was arrhythmic from 1 to 90 lux, weakly rhythmic at 95 lux, but rhythmic at or above 100 lux, while that of the LA strain was weakly rhythmic at 1 lux but rhythmic at or above 2 lux. Oviposition of the HA strain occurred mostly in the photophase, while that of the LA strain occurred in the scotophase; as a result, the oviposition medians of the HA strain were around the subjective forenoons while those of the LA strain were around the subjective evenings. The percent of oviposition in photophase increased from 68 to 98 in the HA strain and from 5 to 33 in the LA strain as light intensity increased from 1 to 1000 lux. In the HA strain, the Ψ values were significantly less and values of R and percent oviposition in photophase were significantly more than those of the LA strain at each level of light intensity. Threshold and saturation intensities for Ψ were 100 and 700 lux, respectively, for the HA strain, but just 2 and 45 lux, respectively, for the LA strain. The saturation intensity for R was 650 and 700 lux for the HA and LA strains, respectively. These results extend the confirmation that the reduced photic sensitivity of the HA strain might have been acquired through natural selection in response to environmental conditions at the high altitude of its origin.     

Assaying Locomotor Activity to Study Circadian Rhythms and Sleep Parameters in Drosophila

Most life forms exhibit daily rhythms in cellular, physiological and behavioral phenomena that are driven by endogenous circadian (≡24 hr) pacemakers or clocks. Malfunctions in the human circadian system are associated with numerous diseases or disorders. Much progress towards our understanding of the mechanisms underlying circadian rhythms has emerged from genetic screens whereby an easily measured behavioral rhythm is used as a read-out of clock function. Studies using Drosophila have made seminal contributions to our understanding of the cellular and biochemical bases underlying circadian rhythms. The standard circadian behavioral read-out measured in Drosophila is locomotor activity. In general, the monitoring system involves specially designed devices that can measure the locomotor movement of Drosophila. These devices are housed in environmentally controlled incubators located in a darkroom and are based on using the interruption of a beam of infrared light to record the locomotor activity of individual flies contained inside small tubes. When measured over many days, Drosophila exhibit daily cycles of activity and inactivity, a behavioral rhythm that is governed by the animal''s endogenous circadian system. The overall procedure has been simplified with the advent of commercially available locomotor activity monitoring devices and the development of software programs for data analysis. We use the system from Trikinetics Inc., which is the procedure described here and is currently the most popular system used worldwide. More recently, the same monitoring devices have been used to study sleep behavior in Drosophila. Because the daily wake-sleep cycles of many flies can be measured simultaneously and only 1 to 2 weeks worth of continuous locomotor activity data is usually sufficient, this system is ideal for large-scale screens to identify Drosophila manifesting altered circadian or sleep properties.     

Timekeeping Through Social Contacts: Social Synchronization of Circadian Locomotor Activity Rhythm in the Carpenter Ant Camponotus paria

In ant colonies a large proportion of individuals remain inside nests for most of their lives and come out only when necessary. It is not clear how, in a nest of several thousand individuals, information about local time is communicated among members of the colony. Central to this seem to be circadian clocks, which have an intrinsic ability to keep track of local time by entraining to environmental light-dark, temperature, and social cycles. Here, the authors report the results of their study aimed at understanding the role of cyclic social interactions in circadian timekeeping of a day-active species of carpenter ant Camponotus paria. The authors found that daily social interactions with visitors (worker ants) was able to synchronize the circadian locomotor activity rhythm of host worker ants and queens, in one-on-one (pair-wise) and multi-individual (group-wise) interactions. Interestingly, the outcome of cyclic social interactions was context specific; when visitor workers socially interacted with host workers one-on-one, host workers considered the time of interaction as subjective day, but when visitor workers interacted with a group of workers and queens, the hosts considered the time of interaction as subjective night. These results can be taken to suggest that members of the ant species C. paria keep track of local time by socially interacting with workers (foragers) who shuttle in and out of the colony in search of food. (Author correspondence: vsharma@jncasr.ac.in)     

Effects of Photophase and Altitude on Oviposition Rhythm of the Himalayan Strains of Drosophila Ananassae

The effects of varying photophase and altitude of origin on the phase angle difference (Ψ) of the circadian rhythm of oviposition during entrainment to light‐dark (LD) cycles and the aftereffects of such photophases on the period of the free‐running rhythm (τ) in constant darkness (DD) were evaluated in two Himalayan strains of Drosophila ananassae, the high‐altitude (HA) strain from Badrinath (5,123 m above sea level=ASL) and the low‐altitude (LA) strain from Firozpur (179 m ASL). The Ψ (i.e., the hours from lights‐on of the LD cycle to oviposition median) of both strains was determined in LD cycles in which the photophase at 100 lux varied from 6 to 18 h/24 h. The HA strain was entrained by all LD cycles except the one with 6 h photophase in which it was weakly rhythmic, but the LA strain was entrained by only three LD cycles with photophases of 10, 12, and 14 h, but photophases of 6, 8, 16, and 18 h rendered it arrhythmic. Lights‐off transition of LD cycles was the phase‐determining signal for both strains as oviposition medians of the HA strain occurred～6 h prior to lights‐off, while those of the LA strain occurred～1 h after lights‐off. The Ψ of the HA strain increased from～2 h in 8 h photophase to～11 h in 18 h photophase, while that of the LA strain increased from～11 h in 10 h photophase to～15 h in 14 h photophase. The aftereffects of photophase of the prior entraining LD cycles on τ in DD were determined by transferring flies from LD cycles to DD. The τ of the HA strain increased from～19 to～25 h when transferred to DD from LD 8:16 and LD 18:6 cycles, respectively, whereas the τ of the LA strain increased from～26 to～28 h when transferred to DD from LD 10:14 and LD 14:10 cycles, respectively. Thus, these results demonstrate that the photophases of entraining LD cycles and the altitude of origin affected several parameters of entrainment and the period of the free‐running rhythm of these strains.     

Crab Clockwork: The Case for Interactive Circatidal and Circadian Oscillators Controlling Rhythmic Locomotor Activity of Carcinus Maenas

The circalunidian hypothesis that tidal rhythms in coastal animals are controlled by two lunar-day (c. 24.8 h) oscillators coupled in antiphase is challenged. Rhythmic locomotor activity patterns of the shore crab Carcinus maenas, and probably of some other species too, are more economically explained by interacting circadian (c. 24 h) and true circatidal (c. 12.4 h) physiological oscillators. A testable hypothesis is proposed that combines a circadian promotor and a circatidal inhibitor of locomotor activity.     

Social Interactions and the Circadian Rhythm in Locomotor Activity in the Cockroach Leucophaea maderae

The role of social interactions in entrainment has not been extensively studied in the invertebrates. Leucophaea maderae is a gregarious species of cockroach that exhibits extensive social interactions. Social interactions associated with copulation between the sexes have been shown to be regulated by the circadian system. We show here that social interactions between males are also under circadian control. We examined the question of whether or not these rhythmic social contacts could function as zeitgebers capable of regulating circadian phase and period. Animals initially in phase that were housed as groups or pairs of single sex or mixed sex in constant darkness for 2–7 weeks were found to drift out of phase. Their behavior was not significantly different from individual animals maintained in isolation. Further, animals that were initially out of phase by 12 h housed as groups or pairs were not significantly different in phase from animals that were isolated. The results show the circadian clocks of cockroaches are remarkably insensitive to the extensive social interactions that occur between individuals.     

结节乳头体在小鼠运动和摄食中的作用及机制研究

目的:探讨结节乳头体在小鼠运动和摄食中的作用及机制。方法:选择雄性ddy小鼠,180-200 g,通过单侧植入电极损毁TMN-E2区。采用荧光金逆行追踪方法检测小鼠Me5与TMN之间的神经纤维联系;采用免疫组化方法检测小鼠TMN中组氨酸脱羧酶(HDC)免疫反应阳性细胞数;采用旷场试验箱记录小鼠全天、夜间以及白天的自主活动和摄食摄水;采用PCR检测小鼠穹窿周和下丘脑外侧区的orexin m RNA的表达。结果:荧光金逆行追踪实验显示小鼠Me5可向TMN-E2发出神经纤维投射。单侧TMN损毁,两侧TMN中HDC反应阳性细胞显著减少(P0.05),且损毁侧比未损毁侧HDC免疫反应阳性细胞数减少(P0.05)。TMN损毁对小鼠24 h自主活动和摄食摄水无明显影响。单侧TMN损毁,小鼠从暗期到光期的自主活动和摄食摄水显著减少(P0.05)。单侧TMN损毁,小鼠正常昼夜活动摄食节律无显著改变。单侧TMN损毁,小鼠穹隆周和下丘脑外侧区白天的orexin m RNA表达显著减少(P0.05)。结论:Me5与TMN之间存在神经通路,该通路可能通过调节穹隆周区或下丘脑外侧区的orexin神经元的激活从而调控摄食及相关行为的昼夜节律。     

An Investigation of Natural Genetic Variation in the Circadian System of Drosophila melanogaster: Rhythm Characteristics and Methods of Quantification

Variation in four characteristics of the circadian locomotor activity rhythm was investigated in 24 true-breeding strains of Drosophila melanogaster with a view to establishing methods of phenotypic measurement sufficiently robust to allow subsequent biometric analysis. Between them, these strains formed a representative sample of the genetic variability of a natural population. Period, phase, definition (the degree to which a rhythmic signal was obscured by noise), and rhythm waveform were all found to vary continuously among the strains, although within each strain the rhythm phenotype was remarkably consistent. Each characteristic was found to be sufficiently robust to permit objective measurement using several different methods of quantification, which were then compared.     

An Investigation of Natural Genetic Variation in the Circadian System of Drosophila melanogaster: Rhythm Characteristics and Methods of Quantification

Variation in four characteristics of the circadian locomotor activity rhythm was investigated in 24 true-breeding strains of Drosophila melanogaster with a view to establishing methods of phenotypic measurement sufficiently robust to allow subsequent biometric analysis. Between them, these strains formed a representative sample of the genetic variability of a natural population. Period, phase, definition (the degree to which a rhythmic signal was obscured by noise), and rhythm waveform were all found to vary continuously among the strains, although within each strain the rhythm phenotype was remarkably consistent. Each characteristic was found to be sufficiently robust to permit objective measurement using several different methods of quantification, which were then compared.     

影响野生型Canton S果蝇睡眠时间的相关生理因素

目的探讨影响果蝇睡眠时间的相关生理因素。方法选择野生型CantonS果蝇为实验对象,利用果蝇活动监测系统(DAMS),以5min为单位自动统计一次果蝇活动次数,若5min内活动次数为零,认为果蝇处于睡眠状态,计为果蝇的睡眠时间,累积计算果蝇24h睡眠总时间为指标,分别观察了日龄(7日龄)相同,而性别不同和性别(雌性)相同,而日龄(2,7,12,17,22,27和32日龄)不同果蝇的24h睡眠总时间。结果①同一日龄(7日龄)不同性别的果蝇之间白天(12h)及夜间(12h)平均睡眠时间的长短存在着显著差异。雌果蝇白天(12h)平均睡眠时间短于雄果蝇,而夜间(12h)平均睡眠时间长于雄果蝇。雌果蝇白天(12h)平均睡眠时间显著短于夜间平均睡眠时间(P0.05);而雄果蝇白天(12h)平均睡眠时间与夜间(12h)平均睡眠时间基本持平。②同一性别(雌性)不同日龄的果蝇,随着日龄的增加,其白天(12h)平均睡眠时间有逐渐缩短的趋势,27日龄的果蝇睡眠时间减少相对明显,32日龄果蝇的睡眠时间有所恢复,相互之间存在着显著差异(P0.05)。夜间(12h)平均睡眠时间有逐渐延长的趋势,27日龄果蝇的夜间平均睡眠时间有所减少,32日龄果蝇的夜间平均睡眠时间相对有所恢复,相互之间存在着显著差异(P0.05)。结论性别与日龄等生理因素对果蝇24h睡眠时间有显著的影响。     

The Expression of Locomotor Orcadian Rhythm in Female German Cockroach, Blattella Germanica (L.)

Fifteen percent of intact female German cockroaches (n = 13), Blattella germanica (L.) (Dictyoptera: Blattellidae), had weak free-running locomotor rhythmicity under 28°C and constant darkness conditions. However, 86% of ovariectomized females (n = 14) showed a strong free-running rhythm under the same conditions with a circadian period of 23.60 ± 0.15 h, similar to the male's period of 23.45±0.03 h. In addition, the locomotory activities occurred mainly during the subjective night under DD conditions as was the case in males. These results indicated that female locomotion was under the control of a circadian oscillator, which was masked by the existence of ovaries. This internal masking effect could be removed by the existence of males, but females had no effect on the locomotor pattern of another female. Since the male failed to entrain female locomotion, its role as a zeitgeber was excluded. That the locomotory pattern of the females still coincided with their reproductive cycle when exposed to male odor suggests that exposure to a male only partially removed the internal masking effects.     

Alterations of Locomotor Activity Rhythm and Sleep Parameters in Patients With Advanced Glaucoma

The aim of this study was to evaluate the effect of advanced glaucoma on locomotor activity rhythms and related sleep parameters. Nine normal subjects and nine age-matched patients with bilateral advanced primary open-angle glaucoma, >10 yrs since diagnosis, were included in this observational, prospective, case-control study. Patients were required to record the timing and duration of their sleep and daily activities, and wore an actigraph on the wrist of the nondominant arm for 20 d. Activity rhythm period, MESOR (24-h time-series mean), amplitude (one-half peak-to-trough variation), and acrophase (peak time), plus long sleep episodes during the wake state, sleep duration, efficiency, and latency, as well as mean activity score, wake minutes, and mean wake episodes during the sleep interval were assessed in controls and glaucomatous patients. Glaucomatous patients exhibited significant decrease in nighttime sleep efficiency, and significant increase in the mean activity score, wake minutes, and mean wake episode during the night. These results suggest that alterations of circadian physiology could be a risk to the quality of life of patients with glaucoma. (Author correspondence: ruthr@fmed.uba.ar)