Localization of the circadian pacemakers of Hemideina thoracica (Orthoptera; Stenopelmatidae).

The location of the circadian pacemakers of the orthopteran Hemideina thoracica (White) has been investigated through observation of the effects of surgical removal of brain tissues (principally optic lobes and tracts) on free-running and entrained locomotor rhythms. Bilobectomy and severance of optic tracts invariably resulted in arrhythmicity, whereas rhythmicity was sustained following unilateral lobectomy, generally with increases in the free-running period (FRP) and decreases in both the active-phase lengths and activity-to-rest ratios of the rhythm. Bilobectomized subjects could be entrained by temperature cycles, but exhibited no transients or residual rhythmicity, indicating that temperature brought about a direct response or masking effect. These results support the hypothesis that the circadian locomotor pacemakers of Hemideina are located within each optic lobe, and that there are no extraoptic centers for the control of the timing of locomotor activity. Although confirmation of the pacemaker role of the optic lobes requires transplantation of the tissues, the conclusion may be drawn by inference from other studies (e.g., Leucophaea maderae--Page, 1983; Gryllus bimaculatus--Tomioka and Chiba, 1986). Light entrainment continued after surgical binding and blackening of the compound eyes and ocelli, supporting the view that direct illumination of neural tissue through the cuticle may be one possible pathway for light entrainment.

Ultradian rhythms in Desmodium.

The leaves of Desmodium gyrans (L.F.) DC show circadian movements in the terminal and ultradian movements of the lateral leaflets. The movements are due to swelling and shrinking of motor cells in special organs. The anatomy of these pulvini is described for the lateral leaflets. Data from electrophysiological recordings using microelectrodes inserted into the lateral pulvini, together with treatments that affect the proton pumps and ion channels, have been used to develop a physiological model of the ultradian leaflet movement. It explains the oscillations in the motor cells as being due to a change between a pump state and depolarization. During the pump state, ions are taken up, causing water influx and swelling of the motor cells. Depolarization causes loss of ions and water efflux (the motor cells shrink). The roles of calcium and the phosphatidyl inositol signal chain are discussed on the basis of experiments using chemical agents that affect these processes. Since calcium oscillations are known to occur in organisms in both time and space, an attempt has been made to simulate the situation in Desmodium pulvini by a model of specially coupled oscillators. Effects of different other treatments of the lateral pulvini are discussed. Oscillations in the minute range seem to be more common and some might be related to turgor regulation and ion uptake comparable to the situation in Desmodium. The ultradian control of the lateral pulvini and the circadian control of the terminal pulvini are apparently based on different mechanisms.

Circadian activity rhythm of the house fly continues after optic tract severance and lobectomy.

Under constant conditions, locomotor activity in about 50% of 63 adult Musca domestica continued to be rhythmic after bilateral severance of optic tracts or bilateral lobectomy. Apparently, the optic lobes of Musca do not contain the oscillator for rhythmic control of locomotor activity as has been proposed for other insects. In 20% of the individuals, several circadian components of activity rhythms were found after operation indicating a role of the optic lobes in the coupling of oscillators. The remaining 30% of the flies with severed optic tracts appeared to be arrhythmic. Most of these flies had vacuolized tissue in the central brain. However, disruption of rhythmicity did not correlate with a common pattern of degeneration. Therefore no conclusions can be drawn as to the localization of the circadian control of locomotor activity in the brain. Flies showing an arrhythmic activity pattern could still be synchronized by LD cycles. Activity did not occur solely during the light period as is the case in controls; but was phase delayed by about 6 hr towards the dark period. Since all flies with severed optic tracts could be synchronized by LD cycles, Musca domestica must possess extraocular photoreceptors.

Effects of tetraethylammoniumchloride (TEA), vanadate, and alkali ions on the lateral leaflet movement rhythm of Desmodium motorium (Houtt.) Merr.

The period (approximately 3-5 min) of the ultradian rhythm of the lateral leaflet movement of Desmodium motorium is strongly lengthened (less than or equal to 30-40%) by the K+ channel blocker tetraethylammoniumchloride (20, 30, and 40 mM) and vanadate (0.5 and 1 mM), which is an effective inhibitor of the plasma membrane-bound H+ pump. The alkali ions K+, Na+, Rb+, and Cs+ (10-40 mM) shorten the period only slightly (less than or equal to 10-15%). Li+ (5-30 mM), however, increases the period of the leaflet rhythm drastically (less than or equal to 80%). We concluded that the plasmalemma-H(+)-ATPase-driven K+ transport through K+ channels is an essential component of the ultradian oscillator of Desmodium, as has been proposed for the circadian oscillator.

The National Human Activity Pattern Survey (NHAPS): a resource for assessing exposure to environmental pollutants.

Because human activities impact the timing, location, and degree of pollutant exposure, they play a key role in explaining exposure variation. This fact has motivated the collection of activity pattern data for their specific use in exposure assessments. The largest of these recent efforts is the National Human Activity Pattern Survey (NHAPS), a 2-year probability-based telephone survey (n=9386) of exposure-related human activities in the United States (U.S.) sponsored by the U.S. Environmental Protection Agency (EPA). The primary purpose of NHAPS was to provide comprehensive and current exposure information over broad geographical and temporal scales, particularly for use in probabilistic population exposure models. NHAPS was conducted on a virtually daily basis from late September 1992 through September 1994 by the University of Maryland's Survey Research Center using a computer-assisted telephone interview instrument (CATI) to collect 24-h retrospective diaries and answers to a number of personal and exposure-related questions from each respondent. The resulting diary records contain beginning and ending times for each distinct combination of location and activity occurring on the diary day (i.e., each microenvironment). Between 340 and 1713 respondents of all ages were interviewed in each of the 10 EPA regions across the 48 contiguous states. Interviews were completed in 63% of the households contacted. NHAPS respondents reported spending an average of 87% of their time in enclosed buildings and about 6% of their time in enclosed vehicles. These proportions are fairly constant across the various regions of the U.S. and Canada and for the California population between the late 1980s, when the California Air Resources Board (CARB) sponsored a state-wide activity pattern study, and the mid-1990s, when NHAPS was conducted. However, the number of people exposed to environmental tobacco smoke (ETS) in California seems to have decreased over the same time period, where exposure is determined by the reported time spent with a smoker. In both California and the entire nation, the most time spent exposed to ETS was reported to take place in residential locations.

Evidences for circadian rhythmicity in the per0 mutant of Drosophila melanogaster.

per0 Mutants of Drosophila melanogaster which are exposed to light-dark cycles (LD) with different Zeitgeber period (T) have a limited range of entrainment. Entrained flies show a characteristic phase relationship of activity to the LD which depends on the period of the driving cycle as expected by oscillator theory. Both facts are taken as evidence that per. possesses endogenous oscillators and that the per gene product is not concerned with central clock structures but rather might be responsible for the mutual coupling between the individual oscillators in a multioscillatory system controlling locomotor activity.

Chronobiology of lithium--studies on healthy, middle-aged women.

3 women aged 37, 44 and 53 years were examined in a long term study (4-5 months) with and without lithium carbonate medication. The subjective condition and complaints of the subjects were recorded. The body temperature was measured each night with a rectal probe and the data analysed using TIMESDIA-program. During the lithium medication, deterioration in the subjects well-being, and somatic disturbances can occur. At the same time variations in the circadian course of the body temperature were demonstrated. In addition to the 24-hour period, longer and shorter periods appear. Based on a chronobiological model a possible dissociation of the oscillator controlling body temperature is suggested.

Circadian locomotor activity of Musca flies: recording method and effects of 10 Hz square-wave electric fields.

Musca domestica flies that were exposed to a uniform vertical 10 Hz electric square-wave field of 1 kVm(-1) changed the period length of their circadian locomotor activity rhythm. Under constant conditions, the clock of short-period flies was slowed down by the field, whereas the clock of long-period flies either was affected only scarcely (experiments at about 19 degrees C) or ran faster (experiments at 25 degrees C). If the field was applied for only 12 h daily, then 30-40 percent of the flies were synchronized. Thus, the field could function as a weak "Zeitgeber" (synchronizer). If the field was increased to 10 kVm(-1), then 50-70 percent of the flies were synchronized. Flies avoided becoming active around the onset of the 12 h period of exposure to a 10 Hz field. The results of these experiments are discussed with respect to similar experiments by Wever on the effects of exposure to a 10 Hz field on the circadian system of man.

[The effects of lithium ions on circadian rhythms (author's transl)]. / Wirkung von Lithium-Ionen auf zirkadiane Rhythmen

Lithium ions lengthen the critical dark period in short-day plants, increase the period length of circadian rhythms in Kalanchoe plants, in the rodent Meriones and influence the activity rhythm of birds. In the case of the Kalanchoe rhythm, mainly the process of the petal opening is affected.

Effect of a putative antidepressant, Rolipram, on the circadian running wheel activity of a day-active chipmunk, Eutamias sibiricus.

Siberian chipmunks (Eutamias sibiricus) were kept individually in small cages attached to a running wheel. Under continuous illumination of two different light intensities (0.4-0.9 lux and 400-1200 lux) the influence of Rolipram, a putative new antidepressant, on the period length tau was tested. Under both conditions Rolipram caused a lengthening of tau, a decrease of activity time alpha and an increase of rest time delta, resulting in a decrease of the alpha/delta ratio. These effects of Rolipram could be due to a slowing down of the circadian oscillatory system or an influence on the sensitivity towards light.

Period lengthening of human circadian rhythms by lithium carbonate, a prophylactic for depressive disorders.

The effect of lithium carbonate on the circadian system of man was studied. Four out of eight volunteers living without time cues in isolated huts in the arctic showed a lengthening of the periods of the body temperature rhythm, activity rhythm, and sleep/wakefulness rhythm by c. 1 h. Four of the participants did not show a change in the periods between the placebo and lithium ingestion phases. Two subjects who did not receive lithium salt showed internal desynchronization between the temperature rhythm and the sleep/wakefulness rhythm. Extreme isolation in bunkers is not necessary to allow free running of the circadian system in man. The sleep/wakefulness rhythm, which is very easy to record, was a reliable indicator of the circadian system in the internally-synchronized state.

Free-running human circadian rhythms in Svalbard.

The body temperature, activity-rest time, electrolytes of urine samples and mood was measured in two persons a 19 day period under continuous light conditions in the arctic (vicinity of Ny Alesund, Svalbard-Spitsbergen). For temperature recording a new thermoprobe and a portable printer was used. Possible week Zeitgeber of the 24 hour day did not synchronize the circadian system, since circadian rhythms of about 26 hours were found. These results open up the possibility to study effects of drugs on the circadian system of humans under Svalbard conditions.

Effects of cAMP, theophylline, imidazole, and 4-(3,4-dimethoxybenzyl)-2-imidazolidone on the leaf movement rhythm of Trifolium repens-a test of the cAMP-hypothesis of circadian rhythms.

The period length of the leaf movement rhythm of Trifolium repens L. is lengthened by continuously offered cAMP (0.5-1.0 mol m(-3)) and theophylline (0.5-4 mol m(-3)). At the higher concentrations this effect is more pronounced and the rhythm damps out faster. Imidazole (0.5 and 1 mol m(-3)) has no effect on the period length; however, after 5 mol m(-3) the rhythm is abolished. Offered as 4 h pulses the resulting phase response curves for cAMP and imidazole are similar and show delays of up to 4 h during the day position of the leaves. Theophylline pulses lead to delays of up to 5 h during closure and advances of up to 3 h during opening. No phase shift is brought about by 4-(3,4-dimethoxybenzyl)-2-imidazolidone. The results do not support the cAMP-model of the circadian clock which has been proposed by Cummings (J. theor. Biol. 55, 455-470; 1975). The effect of the substances tested could, however, be based upon influences on the transport of Ca(2+).

Further evidence for period lengthening effect of Li+ on circadian rhythms.

The period length of the activity rhythm of the cockroach Leucophaea maderae is increased by a LiCl solution of 100 mol m-3 offered as drinking water by about 1%.

Temperature sensitive events between photoreceptor and circadian clock?

The phase shifting action of low temperature pulses of 6 degrees C and 2 h duration administered to the various phases of the Drosophila pseudoobscura circadian rhythm and the action of light pulses given 30 min after the beginning of these low temperature pulses have been investigated. The phase response curve obtained from experiments with light pulses during low temperature cannot be explained on the basis of a straightforward and sequential phase shifting of the oscillation by the various transitions in the pulses. The response curve, after the slight phase shifting action of the temperature pulses is corrected for, resembles the standard phase response curve4 for light pulses (at 20 degrees C) in its wave form but not in its time course. Our curve is shifted in time in a manner that indicates that the light pulses accompanying the low temperature pulses arrived at phase points 1.5 h later than the actual phases at which they were given. We attribute this delay to a slowing down of the information that is apparently transmitted by a process that is temperature dependent.

Circadian course of body temperature and the excretion of MHPG and VMA in a patient with bipolar depression.

A 38-year old woman with a bipolar affective disorder was examined for 10 days during a serious retarded depression phase and for 10 days during the subsequent symptom -free interval. During depression the MHPG-excretion showed a significantly shorter circadian periodicity of 20.5 hours, whereas the periodicity of body temperature and VMA amounted to 24 hours. During the symptom-free interval the circadian periodicity of all parameters was 24 hours. These results indicated that the depression phase of a bipolar affective disorder in this patient is related to a desynchronization of central NA function with peripheral NA activity and body temperature.

Influence of lithium ions on human circadian rhythms.

Lithium carbonate lengthens the circadian period of body temperature and sleep-wakefulness in humans under temporal isolation (arctic conditions in Svalbard, 79 degrees N) in two out of four groups.

Effect of lithium carbonate on circadian periodicity in humans.

Five groups of two volunteers lived during four weeks under arctic summer conditions (Spitsbergen) isolated in huts, without time information. They received lithium carbonate or placebo. All showed free-run of their circadian temperature and activity/rest rhythms with periods longer than 24 hours. Under lithium carbonate, a period-lengthening effect can be shown. This could help to understand theprophylactic effect of lithium salts in manic-depressive episodes.