摘要:

A dual pacemaker model is described which accounts for the variety of types of free‐run lability evident in the locomotor rhythms of the insectHemideina thoracica(Orthoptera: Stenopelmatidae). The model pacemakers, each comprising a linked population of circadian feedback oscillators, interact through unequal mutual coupling. One pacemaker (Y) directly controls the timing of locomotor activity, and the other (X) regulates other rhythms, such as the daily rhythm of cuticle deposition. The evidence on which the model is based includes spontaneous change in period, compression and decompression of active phases (scalloping), rhythm splitting, “day skipping”; and arrhythmicity. The simulations of free‐running activity mirror a number of features of the real data, and hence lend support to this model.

ISSN:0022-1945    

DOI:10.1080/09291019109360114

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0022-1945    

DOI:10.1080/09291019109360115

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Rats exhibit ultradian as well as circadian rhythms in activity. Short‐term activity rhythms appear to result from bouts of feeding‐related behavior interspersed with periods of quiescence. We examined the relationship of activity to feeding in 12 male Long‐Evans derived rats during ad lib and restricted feeding (RF) conditions to determine the effect of RF on both circadian and ultradian activity rhythms. By the end of 20 days of RF all animals exhibited an ultradian periodicity of approximately 12 hours. A twenty‐four hour rhythm in feeding persisted, apparently due to the rats adapting to the diurnal feeding period. General findings were that RF resulted in anticipatory activity prior to feeding and that short‐term activity fluctuations and investigations of the food bin continued during RF even though overall nocturnal activity decreased. The results suggest that male rats of this strain exhibit ultradian activity rhythms that appear to be strongly related to feeding.

ISSN:0022-1945    

DOI:10.1080/09291019109360116

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A very simple and inexpensive device is described allowing continuous, environment independent measurement of the ultradian rhythm period of shoot movement. The ultradian rhythm is monitored by the interruption of a 940 nm light emitting diode generated light beam and a phototransistor. The results show that the period is constant under stable conditions, but is strongly dependent on temperature. Conversely, it is independent of short term (within 1 day) light conditions (presence or absence) and variations of relative humidity.

ISSN:0022-1945    

DOI:10.1080/09291019109360117

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The circadian rhythms of blood pressure (BP) and heart rate (HR) were documented in 30 patients for a 24‐hour period before and during the 24 hours that included unilateral surgery for senile cataract or retinal detachment. The patients were premedicated with diazepam. Anaesthesia was induced at a fixed time (09.00) in all patients with thiopentone, and muscle relaxation was with pancuronium. Maintenance was with enflurane in 15 patients and with fentanyl and droperidol in the rest. Though the intraoperative changes in haemodynamic parameters were dissimilar with the two types of maintenance agents, but both types had a similar effect on the circadian rhythms of blood pressure and heart rate. Whereas preoperatively the BP and HR circadian rhythms were nearly in phase, with their peaks in the late morning to early afternoon, the postoperative rhythms underwent a dissociation to a phase shift in the BP 24‐h pattern. The phase effect may be hypothetically attributed to direct pharmacological actions or to masking effects.

ISSN:0022-1945    

DOI:10.1080/09291019109360118

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Sugar Gliders(Petaurus breviceps)re‐entrain faster after 8‐h delay shifts of an LD 12:12 and an LD 8:16 (31–56:0.3 lux each) than after 8‐h advance shifts of these Zeitgeber cycles. In order to test whether this asymmetric re‐entrainment behavior is related to, or even caused by the phase response characteristics of the circadian system, the phase response of the activity rhythm to short and long light pulses was studied. Short light pulses (15 min of 31–56 lux against a background intensity of 0.3 lux) caused only relatively small delay shifts when applied around the onset, and more pronounced advance shifts when given at the end of the activity time (α). Onset and end of activity shifted by different amounts. Long light pulses produced by 8‐h advances and delays of one single lighttime of an LD 12:12 elicited pronounced phase delays when applied at the beginning of the activity time, but only minor phase advances when given at the posterior part of α. These results indicate that inPetaurus brevicepsthe phase response characteristics to long light pulses exerting parametric effects of light are responsible for the pronounced asymmetry effect in re‐entrainment. Differing phase responses of onset and end of activity point to a two‐oscillator structure of the circadian pacemaker system in this marsupial.

ISSN:0022-1945    

DOI:10.1080/09291019109360119

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Annual variations in trunk kidney and urinary bladder ATPases of domesticated rainbow trout(Oncorhynchus mykiss),reared under natural conditions, were studied throughout 1989.

ISSN:0022-1945    

DOI:10.1080/09291019109360120

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Feeding behavior ofLonchura punctulata,a tropical waxbill, maintained in constant photoperiod (LL) and temperature (27±3° C) conditions was recorded. Food intake exhibited rhythmicity in LL, however with strongly diminished amplitude in some of the phases. These results provide evidence for the participation of an endogenous circadian oscillator in the control of feeding behavior inL. punctulata.

ISSN:0022-1945    

DOI:10.1080/09291019109360121

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0022-1945    

DOI:10.1080/09291019109360113

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor