摘要:

Stable, self‐sustaining oscillations respond to a stimulus in very complicated ways; but they typically regulate back to normal oscillation with only a phase shift remaining to distinguish the disturbed oscillator from an undistrubed control. The new phase (latent, if not immediately expressed, at the moment the stimulus ends) depends on an old phase and a stimulus magnitude. Graphed, this dependence typically resembles one turn of a screw surface, repeated periodically along both the old phase axis and the new phase axis. This 3‐dimensional graph summarizes pictorially several “rules of phase control”. Their range of application seems to include several biologically interesting rhythms.

ISSN:0022-1945    

DOI:10.1080/09291017709359540

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

1.Circadian adaptation phenomena were investigated in the visual system of the scorpionAndroctonus australisL. by ERG‐recordings with implanted electrodes during long‐time experiments.2.In constant darkness, the median eyes change their sensitivity endogenously, under the control of a circadian oscillator. The period of this rhythm is composed of a subjective day‐state, and of a subjective night‐state having a sensitivity level about 3 log units higher than that of the day‐state.3.In the lateral eyes, circadian sensitivity oscillations range over only about 0.3 log unit. Compared with the synchronous oscillations in the median eyes, these changes in sensitivity are negligable. During the sensitive night‐state, the lateral eyes are about 1 log unit more sensitive than the median eyes.4.The time courses of the changes in sensitivity are almost symmetrical during the transition phases from day‐state to night‐state and from night‐state to day‐state. The slope of this transition differs in different animals and may last 2 to 3 hours.5.In a wide but not complete range, the time course of the transition period, e.g. from day‐state to night‐state, is sufficient to compensate for the diminishing light during dusk.6.The possible influence of the circadian adaptation of the median eyes, over the information processing of Zeitgeber stimuli, are calculated from experimental data. The consequences of these results and of the physiological differences between the lateral and the median ryes are discussed with respect to their significance in the entrainment of the scorpion's circadian rhythm.

ISSN:0022-1945    

DOI:10.1080/09291017709359541

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

The results of aktograph experiments suggest that S.gregariais primarily day‐active although its circadian clock can, to some extent, be synchronized by changes in both light and temperature. Low temperatures exert a threshold effect on activity. The nycthemeral rhythm of the desert locust is feeble in LD 12:12, even with fluctuating temperatures. This, is probably of adaptive significance. It certainly accords with the plastic and opportune nature of locust behaviour, upon which survival depends under the unpredictable conditions of the desert climate. For the insect must always be ready to exploit temporary and irregular amelorations of its harsh, arid environment. The desert locust, therefore, cannot afford to adopt rigid rhythms or behaviour patterns that might cause it to lose the benefits of a chance shower or to miss the temporary appearance of green grass. It is argued that the persistence of a rhythm fora short while could be due to an endogenous ‘clock’ or to an exogenous periodicity that continues briefly in constant conditions. It has been shown experimentally, however, that although locusts do not exhibit a marked periodicity under field conditions they, nevertheless, possess good circadian ‘clocks’ whose disclosure can be elicited by subjecting the insects to unnatural light‐dark régimes.

ISSN:0022-1945    

DOI:10.1080/09291017709359542

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Talorchestia quoyana, a sand beach amphipod, shows a rhythm of locomotor activity controlled by a circadian clock and an inhibitory circatidal clock. This article reports on an investigation of the entrainment of the circadian dock to skeleton photoperiods. Four important mathematical models for circadian rhythms are examined with respect to the results of the entrainment experiments and to predictions from the phase response curve forTalorchestia. Significant differences between the models are described, and properties of circadian rhythms not accounted for by present models are outlined.

ISSN:0022-1945    

DOI:10.1080/09291017709359543

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Adult male albino rats were acclimated to shortened light/dark (L/D) photoperiods (L/D:1/4/23 3/4 or L/D.2/22) concurrently with rats maintained in a L/D: 14/10 photoperiodic cycle. The activity and rhythmicity of pineal serotonin N‐acetyl‐transferase (NAT) was examined in the rats maintained in the shortened photoperiod at 4‐hr intervals for 24 hrs and compared to pineal NAT activity in rats maintained in a L/D:14/10 photoperiod. The results indicate that NAT activity exhibits a refractory period to darkness. During the refractory period the pineal NAT activity is approximately coincident with the period of minimal NAT activity exhibited by rats during the light period in a L/D:14/10 photoperiod. At the end of the refractory period there exists a dramatic rise in NAT activity reaching a peak at 04.00 hr which is 110–130 fold greater than the level during either the light phase or the refractory period. This zenith of NAT activity in rats maintained in shortened photoperiods is approximately 2 fold greater than the NAT activity peak exhibited by rats in the L/D:14/10 photoperiod which exhibits a 50–60 fold increase greater than daytime levels. Since NAT is believed to be the rate limiting enzyme in the formation of melatonin in the pineal gland, the findings imply an increase in the amount of melatonin synthesized in pineals of rats maintained in a short photoperiod. Suppression of reproduction in animals maintained in short photoperiods may be related to the increased melatonin formed as a result of increased pineal NAT activity.

ISSN:0022-1945    

DOI:10.1080/09291017709359544

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

A very distinct annual cycle of activity, as judged from nuclear volume changes, has been found in glandular cells of the pars tuberalis of the hypophysis and neurons in the nucleus tuberis hypothalami of adult green frogs(Rana esculenta). The changes are very similar at both sites, a single maximum in April and a single minimum in September being observed. Ependymal tanycy tes of the region which was investigated showed only very moderate activity changes. No sex differences were found with regard to the character of the cycle and the amplitude of changes. Only quantitative differences in absolute nuclear volume were found between the two sexes.

ISSN:0022-1945    

DOI:10.1080/09291017709359545

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

The diurnal feeding pattern of rabbits has been analysed using a shifting phase analysis correlation. Measurements of feed intake were made at regular intervals (hourly) throughout a’ cycle (24 hrs). Measurements were repeated 8 days later at exactly the same times, then again after retarding the lighting cycle by 6 hrs. The data for any cycle are compared with another by calculating correlation coefficients comparing the measurements during one cycle with those at the corresponding times during another. The data for the second cycle were all moved forward by one hour and a new correlation coefficient calculated. This process was repeated until a shift of 24 hrs was obtained.

ISSN:0022-1945    

DOI:10.1080/09291017709359546

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

A method of analysing rhythmic biological data is presented utilising a curve fitting technique based on solutions of the Volterra Integro‐Differential Equation (VIDE). The technique involves the use of difference equations and the method of moments as the fitting criterion. It is conjectured that combinations of the VIDE can provide a more meaningful fit for such data than does harmonic analysis. The (generating, inhibiting and heredity) parameters of the VIDE may be related to the true biological mechanisms and thus may give the biologist opportunities to understand the underlying processes. A practical example is presented to illustrate the merits and limitations of the method.

ISSN:0022-1945    

DOI:10.1080/09291017709359547

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

ISSN:0022-1945    

DOI:10.1080/09291017709359539

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor