摘要:

The present paper was aimed at establishing the time course for development of the light entrainment mechanism of the ERG. Chronic ERG recordings were obtained from juvenile crayfish during different stages of their ontogenetic development, by measuring (as a phase‐response curve, PRC), the effect produced by single 15‐min. light pulses on the period and phase of the ERG amplitude rhythm. It was found that the circadian rhythm of the ERG appears at relatively early stages of development (4th week after hatching) and that the entrainment mechanism developes after the crayfish has reached 2–5 months of age. The role played by the visual photoreceptors in the expression of the ERG rhythm as well as in its entrainment is discussed.

ISSN:0022-1945    

DOI:10.1080/09291019209360132

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The positive and negative feedback loops in oscillatory reactions provide a basis for obtaining temperature‐compensation in any reaction‐kinetic model of chemical or biological oscillators. The present paper shows that positive and negative feedback reactions play the role of “opposing reactions”; whose existence was suggested by Hastings and Sweeney for more than 30 years ago. The principle is illustrated with the Brusselator model.

ISSN:0022-1945    

DOI:10.1080/09291019209360133

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Locomotor activity (LA) and food intake (FI) were recorded in 12 adult male and 8 female guinea pigs of the inbred strain 2 kept initially under social conditions and later separated. The groups consisted of two, and in one case, of 4 animals. Some animals were regrouped again after separation. In addition, four individual and 4 grouped animals were kept in continuous darkness (DD).

ISSN:0022-1945    

DOI:10.1080/09291019209360134

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

In circadian studies dim red light is often used as a convenient alternative for darkness because it would not affect the pacemaking system. In this study male Wistar rats were first exposed to constant light (LL) for 3 months and next to LD 14:10 cycles of dim red light (> 610 nm; 1 ‐ 5 μWatt/cm2) while recording feeding behaviour. All rats displayed entrainment of the circadian feeding rhythm to the red light cycle. A phase reversal of the LD cycle was followed by a gradual reentrainment over 5–8 weeks via delaying transients.

ISSN:0022-1945    

DOI:10.1080/09291019209360135

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A study of the temporal synergism of serotonergic and dopaminergic activity in the regulation of reproductive seasonality of photosensitive and photorefractory migratory Red headed bunting was undertaken. In experiment 1, groups of birds kept in natural day length (NDL) in their photosensitive phase (April) received daily injections of L‐DOPA (L‐dihydroxyphenylalanine, a dopamine precursor) at 8 and 12 hr after 5‐HTP (5 hydroxytryptophan, a serotonin precursor) administration. One control group received two daily injections of saline. The injections with 12‐hr temporal relation induced early recrudescence and full gonadal growth was achieved much in advance to that of control birds. The applications with 8‐hr temporal relation suppressed the testicular growth initially but later on this effect was eliminated by NDL of May‐June. In Experiment 2, photorefractory birds also received the treatments but the temporal relation of 5‐HTP and L‐DOPA had no effect on the regressed gonads of these birds.

ISSN:0022-1945    

DOI:10.1080/09291019209360136

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Halimedahas been found particularly suitable for studies of long‐distance chloroplast migration by virtue of its coenocytic structure and calcium carbonate skeleton. A circadian rhythm of chloroplast migration inHalimeda distortawas monitored by videography of segment surface pigmentation. In normal 12 h light/12 h dark treatments synchronised with dawn and dusk, the segments were green all day, began to become pale immediately the light was turned off, and then remained almost white for most of the night until beginning to re‐green a few hours before dawn. As a result of that, they were already quite green by the time the light was turned on. In continuous darkness a similar cycle, albeit with reducing amplitude and a period of about 23 hours, was maintained for at least 7 days. However, this cycle differed significantly from the normal one in that the segments did not remain green after the light was not switched on at dawn, but rather began to pale immediately thereafter. Conversely, in continuous light the segments did not become pale at any time. Thus, the rhythmical re‐emergence of the chloroplasts before dawn and their subsequent withdrawal appears to be controlled by an endogenous rhythm which is independent of light. However, light does completely, but reversibly, inhibit the chloroplast withdrawal component of the cycle. This behaviour of the chloroplasts inHalimedais very similar to that in the related alga,Caulerpa, but it is quite different from that in another extensively Studied but unrelated siphonous green alga,Acetabularia, in which the circadian rhythm of chloroplast migration is maintained in continuous light.

ISSN:0022-1945    

DOI:10.1080/09291019209360137

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0022-1945    

DOI:10.1080/09291019209360131

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor