摘要:

After Christian's hypothesis of a physiological regulation of population numbers, we want to analyze serum gamma‐globulin (immunoglobulin) levels in the common vole from populations of different density. A five‐year study was carried out on voles caught in spring, summer (early‐late), and autumn, in alfalfa fields of northern (low population density) and southern (high density) Poland. The lowest concentration of gamma‐globulins occurred in early summer and the highest in late summer and autumn, especially in a year of the highest density of voles. Sexually nonactive females showed the highest level of gamma‐globulin in late summer especially in less dence northern populations. The increase in the gamma‐globulin levels with age was significant in summer and in autumn (South and North) and more rapid in nonactive females than in nonactive males. The parasitism in comparison to gamma‐globulin level showed the negative correlation in summer and the positive one ‐ in autumn, that suggests the mutual dependence of parasitism and immune response in voles. The pattern of gamma‐globulin level changes as well as the variability of the parameter similar each year in sexually active males and different in females suggest a greater role of females in forming the long‐term cycle of immunological events. The greater variability and maximum level of the fraction in late summer preceded high density in autumn. The seasonal increase in population number as well as greater density on the South might be caused by an intensity of immunologic processes and simultanously higher viability and smaller fertility of vole. It suggests that immunological competency may be a factor regulating the numbers of common voles in natural populations.

ISSN:0022-1945    

DOI:10.1080/09291019109360094

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0022-1945    

DOI:10.1080/09291019109360095

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Experiments examining the photoperiodic effects of various light‐dark cycles unexpectedly demonstrated that light during the subjective night is not necessarily photoinductive to the reproductive system of long day breeders. Feedback lighting (illumination in response to locomotor activity) and a high‐frequency light‐dark cycle with 1 minute (m) of light followed with 1 minute of dark (LD1m:1m) failed to maintain reproductive function in Syrian hamsters despite exposing the animal to 5–6 hours of light per cycle during the subjective night. In an effort to determine why feedback lighting and LD1m:1m do not maintain reproductive function, male Syrian hamsters were exposed to one of the following lighting conditions for ten weeks: a light‐dark cycle with 14 hours of light followed by a 10 hour light‐dark cycle of 1 minute of light followed by 1 minute of dark {LD14:10(1m:1m)}; a cycle of a 14 hour light‐dark cycle of 1 minute of light followed by 1 minute of dark, followed by 10 hours of dark {LD14(1m:1m):10)} ; a light‐dark cycle of 2 hours of light and 21 hours of dark (LD2:21); a light‐dark cycle of 2 hours of light and 22 hours of dark (LD2:22); LD2:21 in conjunction with feedback lighting (LD2:21/FB); LD2:22 in conjunction with feedback lighting (LD2:22/FB); constant dark (DD) or constant light (LL). All hamsters exposed to LD14(1m:1m):10 entrained. Only 7 of 12 hamsters exposed to LD14:10(1m:1m) entrained. This supports previous findings, which suggest that the circadian system has difficulty differentiating between LD1m:1m and LL. Exposure to LD2:22 and DD induced testicular regression, while LL, LD2:21 and LD14(1m:1m):10 maintained reproductive function, as expected. The addition of approximately 5 hours of nocturnal illumination by feedback lighting, however, not only failed to prevent reproductive regression in LD2:22, but attenuated the stimulatory nature of LD2:21. This suggests that feedback lighting is not only not stimulatory, but may be actively inhibitory. Perhaps this is due to a photoinhibitory effect of multi‐transitional nocturnal illumination. This hypothesis is supported by the finding that LD14:10(1m:1m) allows regression, while LD14(1m:1m):10 is stimulatory. These findings also imply that the state of the circadian system is instrumental in the reproductive system's interpretation of a light signal.

ISSN:0022-1945    

DOI:10.1080/09291019109360096

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The present study of the circadian rhythm of locomotor activity during the summer in minks reared in a natural photoperiod showed that under laboratory conditions, this species has an essentially nocturnal behavior. But the relatively extensive activity that occurred in the light phase, as also described in the wild mink, suggests that the photoperiod is not the only factor controlling the circadian cycle. In animals exposed to constant light, the locomotor activity was concentrated in a single phase that shifted forward each day, showing that the period of endogenous rhythm is longer than 24 h under these conditions. An abrupt increase in this period of circadian rhythm was observed in one of the animals exposed to constant light.

ISSN:0022-1945    

DOI:10.1080/09291019109360097

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

An unconventional hypothesis is proposed combining for the first time two different features which are basic for cell metabolism but have been as yet investigated separately: (a) circadian rhythms in enzyme activity, which play a fundamental role in adaptation to the 24h cyclities of environmental cues, and (b) the dynamic character of protein structure which results in continuous shifting between conformational states. Recent data indicate that large time‐scale (hours, circadian) periodicities can thus arise spontaneously in the catalytic characteristics of enzymes in solution, alternating phases of high and low sensitivity to substrate and effectors. The question raises whether conformational oscillators would provide a molecular component of the processes which govern rhythmicity of enzyme activity. This hypothesis also opens a new approach to the study of the temporal organization of enzyme‐enzyme interactions and metabolic channeling, particularly in photoperiodism.

ISSN:0022-1945    

DOI:10.1080/09291019109360098

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

It was previously established that when rabbits have been exposed to 24‐h LD alternations for several weeks, they afterwards exhibit in steady darkness the presence of a programmed rhythm in photic responses of the visual system. In one phase of this rhythm they respond to flashes with “Day Time Potentials”; (D.T.P.’s) while the other phase is characterized by a markedly raised retinal photic sensitivity and a consequent responding with “Night Time Potentials”; (N.T.P.’s). It is also known that these changes of the responses,e.g.of the ERG's , are absent after transection of both cervical sympathetic nerves whereas they can easily be elicited by low‐frequency electrical stimulation of these nerves. From the present experiments it appears that similar D.T.P. ‐ N.T.P. conversions of the ERG's can be induced by highly localized electrical stimuli that are applied at rates of 10 cps or less to either the suprachiasmatic nuclei (SCN's) or to a tract descending caudally from these towards the spinal cord. Such effects of SCN stimulation are absent in rabbits in which the cervical sympathetics have been cut beforehand.

ISSN:0022-1945    

DOI:10.1080/09291019109360099

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The spontaneous sleep‐wakefulness behavior of three infants (one male and two females) from the same parents, normal with respect to pregnancy and delivery, was observed continuously from 2–14 days after birth up to 4 months of life. The infants were allowed to feed and sleep according to their own schedule. One of them supplied another sample of clear freerunning circadian rhythmicity during the first postnatal month. The least square cosine fitting method and the maximal entropy spectral analysis with high spectral resolution revealed the circadian rhythmicity to exist as early as the first week of life. This fact may suggest that the human circadian clock regulating the daily sleep‐wakefulness rhythm is already functional at birth. It was also found that sleep duration depended on the timing of sleep: the first nighttime sleep being the longest, while the sleep during the early morning and the late afternoon was the shortest. These results are discussed with respect to the development of circadian rhythmicity.

ISSN:0022-1945    

DOI:10.1080/09291019109360100

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0022-1945    

DOI:10.1080/09291019109360093

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor