Reciprocal behaviour associated with altered homeostasis and photosensitivity of Drosophila clock mutants.

The circadian oscillators of genetically short-period and long-period Drosophila exhibit reciprocal behaviour in four distinct ways: (1) with respect to the dependence of period on temperature, (2) in the change of period during constant darkness after ten days of constant light, (3) in the change of period during the second ten days of darkness as compared with the period during the first ten days, and (4) in the period change resulting from exposure to low-intensity constant light. The homeostatic control of the dependence of period length on temperature is impaired in the mutants as compared with wild-type files. The normal Drosophila pacemaker may comprise two mutually coupled oscillators, whereas the mutants may represent a reduction in activity of one or the other constituent oscillator.

The amplitude of circadian oscillations: temperature dependence, latitudinal clines, and the photoperiodic time measurement.

This paper develops several propositions concerning the lability of the amplitude of Drosophila circadian pacemakers. The first is that the amplitude of the pacemaker's motion, unlike its period, is markedly temperature-dependent. The second is that latitudinal variation in pacemaker amplitude (higher in the north) is responsible for two very different sets of observations on Drosophila circadian systems at successively higher latitudes.

Reciprocal behaviour associated with altered homeostasis and photosensitivity of Drosophila clock mutants.

The circadian oscillators of genetically short-period and long-period Drosophila exhibit reciprocal behaviour in four distinct ways: (1) with respect to the dependence of period on temperature, (2) in the change of period during constant darkness after ten days of constant light, (3) in the change of period during the second ten days of darkness as compared with the period during the first ten days, and (4) in the period change resulting from exposure to low-intensity constant light. The homeostatic control of the dependence of period length on temperature is impaired in the mutants as compared with wild-type flies. The normal Drosophila pacemaker may comprise two mutually coupled oscillators, whereas the mutants may represent a reduction in activity of one or the other constituent oscillator.

Latitudinal clines in the properties of a circadian pacemaker.

The circadian rhythm of eclosion activity and its pacemaker were analyzed in a series of latitudinal races of Drosophila auraria ranging from 34.2 degrees to 42.9 degrees N in Japan.

Temperature dependence and evolutionary adjustment of critical night length in insect photoperiodism.

The photoperiodic responses of Drosophila auraria are shown to involve its circadian system functioning as the "clock" that measures the duration of darkness at night. Attempts at further clarification of this finding were based on the widely held assumption that adaptive adjustment of critical night length is caused by change in the circadian system's entrainment behavior. Three different experimental programs yielded data that are incompatible with this starting premise.

Sleep and activity rhythms in mice: a description of circadian patterns and unexpected disruptions in sleep.

Studies on daily and circadian rhythms in wheel running and electrographically defined wakefulness, NREM sleep, and REM sleep in M. musculus were done to gather data on the temporal distribution of activity and sleep. Generally, peaks in NREM and sleep tended to coincide and to alternate with the coincident peaks of wakefulness and wheel running.

Mutual entrainment of bilaterally distributed circadian pacemaker.

The interactions between the bilaterally distributed components of the circadin system that controls the locomotor activity rhythm of the cockroach Leucophaea maderae were investigated in a series of surgical lesion experiments. Complete excision of one optic lobe (either right or left) or its surgical isolation from the central nervous system had no effect on the animals' ability to free-run in constant darkness nor was there any indication, as judged by postoperative pi values of any difference between left and right lobe pacemakers. However, these surgical procedures consistently resulted in a significant increase in tau over preoperative value while optic nerve section had no effect on tau.

An effect of castration and testosterone replacement on a circadian pacemaker in mice (Mus musculus).

Castration of mice in freerunning conditions (total darkness, DD) causes a reduction of running wheel activity in the beginning of the active period (alpha) and stimulates activity at the end of alpha. Simultaneously, the period (tau) of the freerunning rhythm is increased. Both effects are abolished by implantation of a Silastic capsule from which a physiological dose of testosterone is released at a constant rate.

Circadian oscillations in rodents: a systematic increase of their frequency with age.

The circadian activity rhythms of golden hamsters and two species of deermouse, when released from a light-dark cycle of 12 hours light and 12 hours of darkness into constant darkness, had progressively shorter periods as the animals became older. A possible bearing of this fact on the aging process is briefly outlined.

A test of the hypothesis that D2O affects circadian oscillations by diminishing the apparent temperature.

The period (tau) of a circadian pacemaker in the cockroach Leucophaea maderae is a nonmonotonic function of temperature. The slope of the curve (tau as a function of temperature) is negative at 20 degrees and positive at 30 degrees . When these insects are deuterated at 20 degrees and 30 degrees the period (tau) of the pacemaker lengthens in both cases, although there is a marked temperature dependence of D(2)O action.

On the very rapid enhancement by D2O of the temperature-tolerance of adult Drosophila.

Deuterium oxide, D(2)O, increases the temperature-tolerance of Drosophila pseudoobscura when it is administered to adult flies as a sucrose solution. The effect is very rapidly exerted; it is detected within 10 min after the flies have a brief (10 min) opportunity to drink. This increased resistance to heat-death surely implies an increased resistance of macromolecules to thermal denaturation.

General homeostasis of the frequency of circadian oscillations.

Some well-defined statistical regularities characterize the change in period (tau) of cockroach circadian oscillations subjected to a large temperature step. These are explainable in terms of the well-known temperature-compensation (homeostasis) of tau of circadian oscillations. The same regularities are detectable in published data on the effect of several other variables affecting several other circadian oscillations.

A differential effect of heavy water on temperature-dependent and temperature-compensated aspects of circadian system of Drosophila pseudoobscura.

D(2)O is the only "chemical" agent that consistently affects the frequency of circadian oscillations: its effect is now known to be so widespread and predictable that its action merits closer study as a potential clue to the currently obscure concrete nature of circadian oscillators. The great diversity of D(2)O effects on biological systems in general is briefly reviewed and the need for rejectable hypotheses concerning the action of D(2)O on circadian clocks is stressed because current speculation on its action yields "predictions" expected from almost any hypothesis. We consider the hypothesis that it "diminishes the apparent temperature" of the cell and proceed to test this by examining the effect of D(2)O on temperature-dependent and temperature-compensated aspects of the circadian system in Drosophila.

Circadian surfaces and the diversity of possible roles of circadian organization in photoperiodic induction.

It is an established fact that circadian rhythmicity is often somehow involved in the physiology of photoperiodic induction. It is shown, however, that there are three possible ways in which such rhythmicity could be involved. For the most part available data are inadequate to discriminate among these three roles, only one of which is covered by "Bünning's Hypothesis.

Circadian systems: longevity as a function of circadian resonance in Drosophila melanogaster.

Drosophila melanogaster, which had been reared under standard conditions (25 degrees and a 24-hr light/dark cycle involving 12 hr of light) were exposed, on the first day of adult life, to four environments (all at 25 degrees ) as follows: (i) a 24-hr day consisting of 12 hr light and 12 hr dark; (ii) a 21-hr day (10.5 hr light, 10.5 hr dark); (iii) a 27-hr day (13.

Circadian systems, VI. Photoperiodic time measurement in Pectinophora gossypiella.

Diapause (100% incidence) occurs in the moth Pectinophora gossypiella when it is exposed to 24-hour light/dark cycles involving 12 hours of red light (600 nm); only 2% occurs when the photoperiod is extended to 14 hours, again with 600-nm light. This wavelength fails to synchronize all the known circadian oscillations of the moth. These observations appear, therefore, to constitute positive evidence that the photoperiodic time measurement is not mediated by a circadian oscillation.

Circadian systems. V. The driving oscillation and the temporal sequence of development.

A circadian oscillation (in the brain) of Drosophila spp. acts as a gating device restricting the emergence behavior of the adult to a limited fraction of each 24-hour cycle defined by that oscillator, but the oscillation does not gate intermediate steps of pupal development. Unlike the emergence act, such intermediate events in development occur at fixed times after prepupa formation and are totally independent of the phase of the ongoing oscillator that gates emergence behavior.

Circadian oscillation controlling hatching: its ontogeny during embryogenesis of a moth.

Populations of eggs of the moth Pectinophora gossypiella develop a circadian rhythm of hatching activity under certain circumstances. This rhythm derives from circadian oscillations in each egg, which can be initiated or made synchronous by steps or pulses of either light or temperature, but only if these signals are administered after the midpoint of embryogenesis. Correlations between the development of the oscillation, appearance of a pigment, sensitivity to photoperiodic induction, and a possible effect of light on growth rate are discussed.