摘要:

Mature male Djungarian hamsters(Phodopus sungorus)were placed in individual light‐tight, sound attenuated chambers and exposed to one of four lighting conditions for a duration of approximately seven weeks. The four lighting conditions were: constant light (LL); constant dark (DD); feedback lighting (LDFB: a condition that illuminates the cage in response to locomotor activity); or a feedback lighting neighbor control (LDFBNC: the animal receives the same light pattern as a paired animal in feedback lighting, but has no control over it). Exposure of hamsters to LL or LDFBproduced significantly and similarly longer free‐running periods of the locomotor activity rhythm than exposure of animals to DD. Hamsters exposed to LDFBNCdid not free‐run or entrain, but rather displayed “relative coordination”;. The paired testes and sex accessory glands weights suggest that in the Djungarian hamster, LL and LDFBexposed animals maintained reproductive function, whereas DD exposed animals did not. Animals exposed to LDFB NChad intermediate paired testes weights. Since several previous studies have demonstrated that short pulses of light, which are coincident with the subjective night, are photostimulatory, it is not surprising that LDFBmaintained reproductive function in the mature Djungarian hamster. Feedback lighting, however, has been shown to be an insufficient stimulus to maintain reproductive function of mature male and female Syrian hamsters, and to the reproductive maturation of immature Djungarian hamsters. The results suggest that there may be slight, but significant differences in the way these two species interpret photoperiod. as well as a developmental change in the photoperiodic response of Djungarian hamsters.

ISSN:0022-1945    

DOI:10.1080/09291019009360021

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Interrelationship between age and heart rate, spectral parameters of heart rate variability, peak frequency of mid‐frequency heart rate fluctuations, respiratory rate and coherence coefficient was investigated in normotensive healthy volunteers. Thereafter these parameters were correlated with each other in a young subject group to eliminate the effect of age. The peak frequency of mid‐frequency heart rate fluctuations was significantly inversely related to age. The overall heart rate variability (0.01‐.05 Hz) was reduced with aging due to the diminution of power spectral densities in the mid‐frequency (0.05–0.15 Hz) and respiration related frequency band (heart rate spectral power around the mean respiratory rate). In the young subject group total power was positively related to the power of the discrete spectral components. The respiratory rate was inversely related to mid‐frequency and respiration related frequency components of heart rate variability. Our results appear to support on the one hand the hypothesis of age‐related alterations in the autonomic cardiovascular control mechanisms. On the other hand our data show significant correlations between spectral parameters of heart rate variability and respiration, which should be taken into consideration in the interpretation of heart rate power spectra in spontaneously breathing subjects.

ISSN:0022-1945    

DOI:10.1080/09291019009360022

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Free acetylcholinesterase activity in whole homogenate of the brain stem was assessed every 4 hours over a 48 hour period occurring in the last lunar quarter, studied every month of the year, using the Ellman's spectrophotometric method. At the same time locomotor activity was registered in experimental animals. The annual course of acetylcholinesterase activity and locomotor activity revealed a cyclic occurrence of the maximal values (every 6 months). Therefore it can be concluded that locomotor activity and acetylcholinesterase activity in the mouse brain stem are changed by the time of the year.

ISSN:0022-1945    

DOI:10.1080/09291019009360023

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

We computed the coherence function between simultaneously recorded endogenous skeletal muscle vibrations (vibromyogram, VMG) and electro‐cortical oscillations (electroencephalogram, EEG) in man in order to demonstrate a functional coupling of these signals. For detection of transient changes in coupling strength a novel computerized technique for calculation of the ‘running’ coherence was developed. High coherence values indicated a deterministic relationship between VMG and EEG. Cyclic variation in coherence with periods of 20–70 sec (mean value of 40 sec +/‐ 9 SD) demonstrated an ordered temporal pattern of changes in coupling strength between brain and muscle rhythms. The data suggest the existence of a common rhythm generator involving various oscillating structures, which may simultaneously drive supraspinal cortical and spinal segmental CNS activity. The same source may in part also be responsible for some autonomic rhythms. Models explaining the cyclic variation in VMG‐EEG coherence and a clinical concept of temporal disorder as ‘disease’ are discussed.

ISSN:0022-1945    

DOI:10.1080/09291019009360024

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Actograms of domestic cats were obtained in two settings, in a large animal colony where there were many cats and people, and in isolation in sound‐attenuating rooms. For the four cats that were studied in individual isolation, freeruns were obtained in constant dark, and then recordings of sounds from the animal colony were presented once a day at the same time for eight hours. Entrainment by the colony sounds was demonstrated in three of the four cats. The cats in the main colony exhibited a nocturnal pattern of entrainment to the LD cycles. The humans, present during the L phase, induced a prominent band of activity on the actogram. Because both LD cycles and laboratory routines have separate and independent capabilities of entraining the circadian system, Zeitgebers for the cat may be typically complex and diverse so that all temporal aspects of the environment are exploited.

ISSN:0022-1945    

DOI:10.1080/09291019009360025

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Seasonal changes on gill ATPases activities of domesticated rainbow trout(Salmo gairdneri), reared under natural conditions, were studied during 1988.

ISSN:0022-1945    

DOI:10.1080/09291019009360026

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Extended periods of growth under continuous light (> 10 generations) effectively removed the normally strong circadian controls on the growth ofChlamydomonas reinhardii.Selection‐synchronized cultures of such organisms showed the cell cycle time to be 20h and there was no detectable circadian rhythm in chlorophyll a accumulation. However, an ultradian rhythm of period length 55 min in the level of chlorophyll a similar to that previously reported for LD cultures was still observed. These results provide further evidence for the importance of intracellular timing independent of environmental influences.

ISSN:0022-1945    

DOI:10.1080/09291019009360027

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0022-1945    

DOI:10.1080/09291019009360020

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor